The Kynix Blog

What is a Laser Diode?A laser diode (injection laser diode, or diode laser) is a semiconductor device that can generate laser light, emitting a narrow light containing a single color, which is similar to a light-emitting diode (LED). The three conditions for generating laser light are: achieving particle number inversion, meeting threshold conditions and resonance conditions. Since laser diodes are extremely electrostatic sensitive, they should be used with care to prevent static electricity. They can be divided into homojunction laser, single heterojunction (SH) laser, double heterojunction (DH) laser and quantum well (QW) laser according to the different PN junction materials.Topics Covered in this GuideLaser Diode Tech Guide in 2021What is a Laser Diode?Laser Diode SpecificationsLaser Diode CharacteristicsLaser Diode ApplicationsHow Does a Laser Diode Work?What is the Laser Diode Symbol?What are the types of Laser Diode?Laser Diode Using TipsHow to Test a Laser Diode?How to Make a Laser Diode?How to Power a Laser Diode?How to Build a Laser Diode Driver Circuit?How to Wire a Laser Diode?How to Select the Right Laser Diode?How to Drive Pulse Laser Diode?What is Power Source of 532 Laser Diode?What is the Difference between Laser Diode(LD) and LED?What is the Wavelength Range of a Laser Diode?Is Diode Laser Permanent?Is LED a Laser Light?How Long do Diode Lasers Last?Can an LED be Used as a Laser?What are the Advantages of Using Laser Diode Instead of an LED?What is the Disadvantage of Laser?FAQsLaser Diode Specifications(1) Wavelength– It is the laser tube working wavelength, including 635nm, 650nm, 670nm, 690nm, 780nm, 810nm, 860nm, 980nm, etc, used for photoelectric switch laser.(2) Threshold Current– The current at which the laser tube starts to generate laser oscillation. For general low-power laser tubes, the value is about tens of mA, and the threshold current of laser tubes with multi-quantum well structure can be as low as 10mA or less.(3) Operating Current– It is the drive current that laser tube to achieve the rated output power, which is more important for the design and commissioning of the laser drive circuit.(4) Vertical Divergence Angle– It is the open angle that the laser diode's light-emitting band in the direction of the vertical PN junction, generally in the 15˚ ~ 40˚ or so.(5) Horizontal Divergence Angle– It is open angle that the laser diode's light-emitting band in the parallel direction with the PN junction, generally in 6˚ ~ 10˚ or so.(6) Monitoring Current– It is the current flowing on the PIN tube when the laser tube is at rated output power. Laser Diode CharacteristicsThe basic structure of the semiconductor laser diode is shown in the figure. A pair of parallel planes perpendicular to the PN junction surface form the Fabry-Perot resonant cavity, they can be the solution surface of the semiconductor crystal, but also can be polished plane. The remaining two sides are relatively rough to eliminate the laser action in other directions than the main direction. In addition, lasers consist of three main components: a lasing medium (solid, liquid or gas), a stimulating energy source (pump) and an optical resonator.Figure 1. Semiconductor Laser Diode StructureOne of the characteristics of laser diodes is the ability to modulate the intensity of their output light directly from current. Because the relationship between output optical power and input current is mostly linear, laser diodes can use analog or digital current to directly modulate the output light intensity, no need for expensive modulators, which makes the diode more economical to use.The most important characteristic of a diode is its unidirectional conductivity, and laser diodes, as one of the diode types, have the same features. In a circuit, current can only flow in from the positive terminal of the diode and out from the negative terminal. The following are specific descriptions.1) Forward FeatureIn electronic circuits, the diode conducts when the positive terminal of the diode is connected to the high potential terminal and the negative terminal to the low potential terminal. In terms of this connection, it called forward bias. In addition, when the forward voltage applied to both ends of the diode is very small, the diode still cannot conduct and the forward current flowing through is very small. Only when the forward voltage reaches a certain value (this value is called the "threshold voltage", about 0.2V for germanium tubes and 0.6V for silicon tubes), the diode can conduct. After it, the voltage across the diode remains basically unchanged (about 0.3V for germanium and 0.7V for silicon diode), which is called the "forward voltage drop".2) Reverse FeatureIn electronic circuits, the positive terminal of the diode is connected to the low potential terminal, and the negative terminal is connected to the high potential terminal. When there is almost no current flowing through the tube, the diode is in the cutoff state. This connection called reverse bias. Diode in reverse bias, there will still be a weak reverse current flow through, called leakage current. When the reverse voltage across the diode increases to a certain value, the reverse current will increase sharply, the diode will lose its unidirectional conductive characteristics, this state is called diode breakdown. Laser diode injection current must be greater than the critical current density, which is related to the temperature of the contact surface and indirectly affects the tube performance, to meet the residence reversal conditions and emit laser. When operating at high temperatures, the critical current increases, reducing efficiency and even damaging the component. Laser Diode ApplicationsAs the most common type of laser products, laser diodes have the advantages of high efficiency, small size and long life, but their low output power (generally less than 2mW), poor linearity and monochromaticity are not good for cable TV system applications, because they cannot transmit multi-channel and high-performance analog signals. Based on the advantages of laser diodes, they play a important role in many applications areas. For example, in the return module of bi-directional optical receivers, uplink transmission generally uses quantum well laser diodes as the light source. Also it is widely used in the computer on the CD-ROM drive, laser printer in the print head, bar code scanner, laser ranging, laser medical, optical communications, laser indication and other small power optoelectronic equipment. The lighting, laser surgery, laser welding and laser weapons and other high-power equipment have laser diodes too.Compared with LEDs, With different light source, lasers are more powerful and operate at faster speeds than LEDs, and they can also transmit light farther with fewer errors. They are also much more expensive than LEDs.Figure 2. Laser DiodeHow Does a Laser Diode Work?Light Emitting PrincipleLight emission in semiconductors is usually caused by carrier complexation. When a positive voltage is applied to the PN junction, it will weaken the PN junction barrier, forcing electrons to be injected into the P region from the N region, and holes to be injected into the N region from the P region. These non-equilibrium electrons and holes injected near the PN junction will be compounded, thus emitting photons of wavelength λ with the following equation.λ=hc/EgWhere: h - Planck's constant, c - speed of light, Eg - band gap width of the semiconductor.The above luminescence phenomenon due to the spontaneous compounding of electrons and holes is called spontaneous radiation. When the spontaneous radiation generated by the photon through the semiconductor, once the electron-hole pair has been emitted near, it can excite the two composite to generate new photons. This photon has been induced to excite the carrier compound and issued a new photon known as excited radiation.If the injection current is large enough, a carrier distribution opposite to the thermal equilibrium state will be formed, that is, the particle number reversal. When the carrier within the active layer in the case of a large number of inversion, a small amount of spontaneous radiation generated by the photons due to the resonant cavity two end reflect and then have induction radiation, resulting in frequency-selective resonance positive feedback, or a gain for a frequency. When the gain is greater than the absorption loss, a coherent light with good spectral lines can be issued from the PN junction, that is, the laser.How Laser Diodes Work?As for Laser diode light-emitting principle, the P-N junction in a laser diode is formed by two doped GaAs layers. It has two flat-ended structures, parallel to a end (highly reflective surface) and a partial reflection. Laser diodes emit coherent light in which all the waves are at the same frequency and phase. The wavelength of the light to be emitted is exactly related to the length of the junction. When the P-N junction is forward biased by an external voltage, the electrons move through the junction and recombine as in a normal diode. When the electrons are compounded with holes, photons are released. These photons hit the atoms, causing more photons to be released. As the forward bias current increases, more electrons enter the depletion region and cause more photons to be emitted. Eventually, some of the photons randomly drifting in the depletion region strike the reflecting surface vertically, thus reflecting back along their original path. The reflected photons are again reflected back from the other end of the junction. This movement of photons from one end to the other is continuous several times. During the photon motion, more atoms release more photons due to the avalanche effect. This process of reflection and production of more and more photons produces a very intense laser beam.Each photon produced in the emission process explained above is identical to the other photons in terms of energy level, phase relationship and frequency. Thus, the emission process gives a laser beam of a single wavelength. To produce a laser beam, the current in the laser diode must be made to exceed a certain threshold level. Currents below the threshold level force the diode to behave as an LED, emitting incoherent light. What is the Laser Diode Symbol?The laser diode symbol used is often the same one used for light emitting diodes in circuit diagrams. It uses the basic semiconductor diode symbol with arrows indicating the generation and emanation of light.Figure 3. Laser Diode Symbol What are the types of Laser Diode?There are several types of laser diodes:✔️Quantum well lasers✔️Quantum cascade lasers✔️External-cavity diode lasers✔️Interband cascade lasers✔️Separate confinement heterostructure lasers✔️DHL (double heterostructure lasers)✔️DFB-LD (distributed feedback laser diode)✔️DBR-LD (distributed bragg reflector laser)✔️FBG (FBG laser diodes laser diodes)✔️VCSEL ( vertical-cavity surface-emitting laser)✔️VECSEL(vertical-external-cavity surface-emitting-laser)✔️MOEMS-LD (micro-opto-electro-mechanical systems laser diode) Laser Diode Using Tips1) laser diode emitted laser light may cause harm to the human eyes. When using, don’t directly watch the light source. It requires warning signs.2) The device needs a suitable drive power supply, the instantaneous reverse current should not exceed 2uA, and the reverse voltage should not exceed 3V. In the power supply on and off, to prevent inrush current. When testing the drive circuit with an oscilloscope, disconnect the power supply and then connect the oscilloscope probe, if the probe is tested under power on, the inrush current may damage the device.3) The device should be stored or worked in a clean environment.4) Working at higher temperatures will increase the threshold current, lower conversion frequency and accelerate the aging of the device. When adjusting the amount of light input, use the optical power meter to detect to prevent exceeding the large rated output.5) The output power works higher than the specified parameters, which will accelerate the aging of the components.The following measures can be taken to slow down device aging.    a. Driving the laser diode with a DC constant current source.    b. Connect a current limiting resistor in series with a bypass capacitor to the laser diode circuit.    c. Since an increase in the temperature of the laser diode will increase the current flowing through it, the heat dissipation measures must be applied to ensure that the device operates within a certain temperature range.(4) To avoid the laser diode breakdown due to withstand excessive reverse voltage, it can be connected in reverse parallel on both ends of the fast silicon diode.(6) The machine needs to be fully dissipated or used under cooling conditions to prevent high temperature use. The output wavelength of the laser is affected by the operating current and heat dissipation, to maintain good heat dissipation conditions and reduce the temperature of the tube core when working.7) Diodes are electrostatic sensitive devices, to take appropriate anti-static measures.Figure 4. Injection Laser DiodeHow to Test a Laser Diode?a. Resistance measurement methodRemove the laser diode, use a multimeter R × 1k or R × 10k file to measure its positive and negative resistances. If normal, the forward resistance value is between 20~40kΩ, and the reverse resistance value is ∞ (infinity). If the measured forward resistance value has exceeded 50kΩ, it means that the performance of the laser diode has declined. If the measured forward resistance value is greater than 90kΩ, it means that the diode has been seriously aged, can no longer be used.b. Current measurement methodUse a multimeter to measure the voltage drop across the load resistor in the laser diode drive circuit, and then estimate the current value flowing through the tube according to Ohm's law. When the current exceeds 100mA, if the laser power potentiometer is adjusted, and no significant change in current, the laser diode can be judged to be seriously aged. If the current increases sharply and out of control, it means that the optical resonant cavity of the laser diode has been damaged.c. Pins DetectionThe laser diode has three pins: LD transmitter, PD receiver, LD-N common1) To distinguish between LD and PD. Use R × 1k block to measure the resistances of laser diode three pins. If a resistance value between the two pins reaches a few thousand ohms, at this time, the black pen is connected to the end of the PD anode, the red pen is connected to the pin for the common terminal, the remaining pin for the LD cathode, so as to distinguish the PD part (bc part of the figure) and LD part ( This distinguishes the PD part (bc part of the figure) and the LD part (ab part of the figure).2) Detect the PD part. PD part of the laser diode is essentially a photosensitive diode, using a multimeter test method is as follows: R × 1k block to measure its resistance, if the forward resistance of a few thousand ohms, the reverse resistance is infinite, it initially indicates that the PD part is good. If the forward resistance is 0 or infinity, it shows that the PD part has been bad. If the reverse resistance is not infinity, it means that the PD part has reverse leakage and the tube quality has become poor.3) Detect the LD part. Use the multimeter R × 1k block to measure the forward resistance of the LD part, that is, the black pen connected to the common terminal b, red pen connected to the a, the forward resistance should be between 10kΩ ~ 30kΩ, the reverse resistance should be infinity. If the measured forward resistance value is greater than 55kΩ, the reverse resistance value of 100kΩ or less, indicating that the LD part has been seriously aging, so the use of the effect will become worse. How to Make a Laser Diode?Step 1: Before made a laser diode, you should clear somethings firstly, including safety equipment, procedures, training in place, as well as disposal etc. Step 2: Build a working laser yourself you start with buying the diode. then you need a lens , and a heat sink , and a powersupply that won't blow it (they're very sensitive) .... all these components are on online, and that's quiet a tricky job ...much easier and cheaper to buy an assembled laser.Step 3: Spend a couple of pounds to purchase a laser pointer, and pull the diode & circuit out of that.Step 4: Don't power it up when it's direction is not firmly fixed away from your eyes, from anyone's eyes , and there might be reflective surfaces on the beam path nearby. Pay attention, do it legally where you are. How to Power a Laser Diode?Laser diodes are operated in forward conduction mode within a specified current range that is optimal for lasing operation, because they are current-driven devices. Laser diode power supplies can operate in one of two modes, constant current (CC) and automatic power control (APC). Most, but certainly not all, smaller laser diodes (5.6- and 9-mm packages) are operated in APC mode. For APC operation, the power supply must have a photodiode mounted inside the laser diode package. How to Build a Laser Diode Driver Circuit?Firstly, you should know that a laser diode driver circuit is a circuit which is used to limit the current and then supplies to the laser diode, and then follow the below steps:Step 1: Have a project with laser diode.Step 2: Find out all the useful parts and their parameters from your project.Step 3. Build the circuits according to the related project schematic.Step 4. Connect the Laser Diode and test it. How to Wire a Laser Diode?According to unidirectional conductivity, laser diodes only allow current to flow in one direction, and they're always polarized. First look at the positive and negative poles of the diode, and then the positive potential is connected to the anode of the diode, and the negative potential is connected to the cathode of the diode. How to Select the Right Laser Diode?Choose a laser diode for your application according to the following steps:Step 1: Turn application requirements into laser parametersStep 2: Selecting the laser typeStep 3: Selecting the laser materialStep 4: Make your final chart and go searching How to Drive Pulse Laser Diode?Laser Diode Driver is to provide current to the laser diode. With the amount of current controlled by the user or some automatic apparatus, you can drive a pulse laser diode. In addition, a laser driver can only regulate the current as long as the laser voltage stays within certain limits, so you should have a check the circuit parameters to select a proper diode driver. What is Power Source of 532 Laser Diode?Check the following table to find out the power source of 532 laser diode:532nm Green Laser DiodePowerPackageDescription0.004WTO-Can- Integrated Photodiode- Compact Size0.005WTurn-Key Module- Compact Size- Long Lifetime0.01WTurn-Key Module- Fiber-Coupled Output- Integrated Photodiode0.1WTO-Can- Integrated Photodiode- Compact Size0.2WTO-Can- Integrated Photodiode- Mode-Hop Supression0.4WButterfly- Integrated Photodiode- Integrated Heater0.5WButterfly- Internal Heater- Integrated PhotodiodeWhat is the Difference between Laser Diode(LD) and LED?LDs and LEDs both emit photons to produce light, but both of them have many differences according to the following table:ParametersLDLEDWorking PrincipleStimulated emissionSpontaneous emissionOmnidirectional emissionFull FormLight Amplification by Stimulated Emission of RadiationLight Emitting DiodeResponseFast response in comparison to LEDSlow responseDriving CurrentRanges from 5 to 40mARanges from 50 to 100mANature of Emitted LightCoherent and MonochromaticIncoherent and consists of various colors.Junction Area during ManufacturingNarrow and small JunctionWide Junction AreaBandwidth RangeRanges from 1MHz to 2MHZRange from10 to 50THzPower to light Conversion EfficiencyApprox 70 %Approx 30%Numerical Aperture of the obtained Light BeamExtremely low as compared to LEDs.Higher in LEDsCostHigh cost and thus used in the specific application.Low cost and thus economicalWhat is the Wavelength Range of a Laser Diode?Diode lasers deliver wavelengths ranging from 810 to 1064 nm. Diode lasers are compact and portable solid-state units. They are used strictly for soft tissue procedures and penetrate 2 to 3 mm or more into soft tissue, depending on the wavelength and tissue biotype. Is Diode Laser Permanent?Diode lasers use a single wavelength of light that has a high abruption rate in melanin. As the melanin heats up it destroys the root and blood flow to the follicle disabling the hair growth permanently. ... Diode lasers deliver high frequency, low fluence pulses and can be safely used on all skin types. Is LED a Laser Light?LEDs typically last longer than lasers, while lasers are faster. ... LEDs have a higher output with wider bandwidths, meaning that they can produce a broad range of less-concentrated light. Lasers have a lesser output and a small bandwidth, produced with a tiny pinpoint of light. How Long do Diode Lasers Last?Typical lifetime of laser diode modules are 25,000 to 50,000 hours. If the laser diode temperature continues to rise exceeding the maximum operating temperature, the diode can be catastrophically damaged or the long term performance may degrade significantly. Can an LED be Used as a Laser?The LED and laser emit light in a relatively narrow range of wavelengths. However, lasers put all their energy in a single wavelength, which emits from a tiny spot. LEDs spread the energy over more wavelengths and send that light from a larger spot into wide cone. What are the Advantages of Using Laser Diode Instead of an LED?It produces a very intense beam of light or infrared radiation which is having following properties. Laser diode used in optical fiber systems are made of gallium arsenide phosphide. The laser having size of grain of sand can produce power output of about 10 mWatt. ON/OFF switching speed of laser is faster than LED. What is the Disadvantage of Laser?Following are the drawbacks or disadvantages of Laser:It is expensive and hence more expenditure to the patients requiring laser based treatments.It is costly to maintain and hence more cost to doctors and hospital management. Increases complexity and duration of the treatment based on laser devices or equipments. FAQs1. Why do we prefer GaAs for laser diode?GaAs advantagesGaAs devices are relatively insensitive to overheating, owing to their wider energy band gap, and they also tend to create less noise (disturbance in an electrical signal) in electronic circuits than silicon devices, especially at high frequencies. 2. What is the advantage of laser over LED?The output power of a 1 watt LED can be < 100 milliwatts. Besides dramatic differences in total output, the laser also offers a significant advantage in terms of how usable that power is to the optical system. Specifically, the laser is a point source of coherent light that produces a well-behaved beam. 3. Why is laser light monochromatic?Monochromatic Laser LightThe light from a laser typically comes from one atomic transition with a single precise wavelength. So the laser light has a single spectral color and is almost the purest monochromatic light available. 4. What happens if the laser diode is forward biased?Forward bias injects charges into the junction, causing spontaneous emission of photons. When the diode is forward-biased, charges are injected into the active area of the junction, while electrons and holes recombine in the junction, creating spontaneous emission of photons. 5. Is a laser diode an LED?Light-emitting diodes (LEDs), like laser diodes, generate radiation via electrical current injection into a junction. LED light comes from spontaneous emission, whereas laser diode light arises from stimulated emission. Thus, LEDs generally have lower output powers and omnidirectional emission.

IntroductionⅠ What is the Backlit Keyboard? 1.1 Advantages of the Backlit Keyboard 1.2 Disadvantages  of the Backlit KeyboardⅡ How to Enable and Disable a Backlit KeyboardⅢ Compact Backlit Keyboard w/Force Sensing Resistor (USB) (Black) | SLK-79-FSR-USB by iKey    3.1 How Does a Force Sensing Resistor (FSR) Work?    3.2 How do Force Sensing Resistors Measure Force?    3.3 How do You Calibrate a Force Sensing Resistor?    3.4 How are Force Sensing Resistors Made?    3.5 Matrix or Single-Point Force Sensing Resistors    3.6 How are Force Sensing Resistors Used?Ⅳ Factors to Consider Before Purchasing a Backlit Keyboard    4.1 Price    4.2 Increased Power Usage    4.3 Brightness    4.4 RGBⅤ How Much does a Backlit Gaming Keyboard Cost?Ⅵ Frequently Asked Questions about Backlit KeyboardIntroductionThe term "backlit keyboard" refers to a keyboard that has a light beneath the keys. In low-light situations, the backlight illuminates the letters and symbols on the keys to make them visible. Because the print on the keys is semi-transparent, the light will pass through it like a window. Read this article to learn how to choose a backlit keyboard quickly.Video: Backlight KeyboardsⅠ What is the Backlit Keyboard?A backlit keyboard, also known as an illuminated keyboard or a backlit gaming keyboard, is one that has lights inside it. The lights illuminate the area behind and around the keys, making them visible in low-light or dark settings. For energy efficiency and increased brightness, the light source is typically made up of mini LED light bulbs. Backlit gaming keyboards are popular among computer gamers, but they can also be used for general computing tasks. G.SKILL 's multicolor backlit gaming keyboard is shown below. 1.1 Advantages of the Backlit KeyboardThe distinction between a backlit keyboard and a regular keyboard is that the backlit keyboards can be used in the dark because they are illuminated from behind the keys.The characters associated with each key on regular boards are simply printed on and do not light up. Backlit keyboards  are therefore the most versatile option.You may have one or more colors depending on the keyboard supplier and model.A colorful backlit keyboard is a way to go for the gamer or the person who wants to add a little flair to their computer hardware setup.While these keyboards do have a more youthful feel to them, they are suitable for anyone who is young at heart.In general, the F and J keys have raised lines on them if you look at your keyboard (you may have to feel your keyboard).It's supposed to help you navigate the board even when the lighting isn't ideal.To work properly, you must, of course, know how to type efficiently and not just with your pointer finger (aka index finger).Some argue that efficient backlighting is the answer.Laptops with lights can be both functional and attractive.Learn more about illuminated keyboards as the ultimate gaming, editing, or programming accessory. 1.2 Disadvantages of the Backlit KeyboardFigure 1 Backlit keyboardThey cost more than other types of keyboards. Most models with key lighting start around $800 and rise from there - sometimes dramatically.Illuminated keyboards use more energy than standard keyboards. It can drain your battery faster if it is not plugged in and charging.Ⅱ How to Enable a Backlit KeyboardTouching the keys or across the edge of the keyboard usually activates the backlit feature. When the keys or keyboard edges are not touched, the lights automatically turn off after a short period of time. Turning off the lights automatically helps to conserve battery energy, extending battery performance between charges.Backlit keyboards for laptops and desktop computers may also include special keys or FN keys for permanently turning the backlight on and off, as well as the ability to change the color. The special or FN key to press on a keyboard varies depending on the manufacturer of the keyboard or laptop.In the Windows Mobility Center, most new PC laptops allow you to change the backlighting on the keyboard. On Dell laptops, this is frequently Fn+F10 or simply F10. Fn+Spacebar is the hidden key for adjusting the backlit keyboard  on Lenovo laptops.Ⅲ Compact Backlit Keyboard w/Force Sensing Resistor (USB) (Black) | SLK-79-FSR-USB by iKeyThe SLK-79-FSR-M keyboard was created for mobile applications that require a small footprint. The SLK-79-FSR-M, which includes an integrated force sensing resistor pointing gadget with dual left-click capability, packs a lot of power into a small package. The SLK-79-FSR-M includes backlit keys for working in low-light environments. The SLK-79-FSR-M, like the other iKey keyboards, has sealed industrial silicone rubber keypads and sturdy ABS polycarbonate cases.Features:12 Keys for FunctionPointing Device With Integrated Force Sensing ResistorKeyboard with Red BacklightConfigurations for USB and PS/2 are available. 3.1 How Does a Force Sensing Resistor (FSR) Work?In recent years, printed, thin, and flexible sensors have created quite a stir in the design engineering community. This is largely due to the proliferation of smart, lightweight, and energy-efficient technologies that have become ingrained in our daily lives. Naturally, when designing these small but powerful devices and products, the embedded components that make them game-changers should share the same characteristics.Force sensing resistors (also known as printed force sensors or force-sensitive resistors) are a large and expanding class of embedded components, with many new sensor types introduced in recent years. Force sensing resistors    , on the other hand, are not a new technology. For decades, force-sensing resistors have been used as an embedded component.3.2 How do Force Sensing Resistors Measure Force?Most engineers know that the formula for force is an object's mass multiplied by its acceleration (or, F=M*A) or applied pressure multiplied by contact zone (F=P*Area). Newtons (N), pound-force (lbf), and other engineering units are used to represent "F" in these equations.Figure 2: When a force sensing resistor is applied, the conductance response as a function of force is linear.Pressure sensor resistors are not pre-calibrated to correlate a force reading to a known technology unit on their own. The force measurement result captured by a force sensing resistor. On the other hand, can be correlated to the applied force via a calibration procedure.Piezoresistive sensing technology is a force-sensing resistor, This means that they are passive elements that serve as variable resistors in an electrical circuit. As illustrated in Figure 1, when the sensor is unloaded, it has a high resistance (on the order of Megaohms (M)) that decreases as force is applied (usually on the order of Kiloohms (K)). When the inverse of resistance (conductance) is considered, the thermal conduction response as a function of force is linear within the sensor's specified force range.3.3 How do You Calibrate a Force Sensing Resistor?Force sensing resistors  can really be calibrated with as few as two-to-three known loads due to their resistance/conductance linear relationship.Furthermore, if the circuit is built with adjustable components, the sensor's sensitivity can indeed be adjusted for optimal performance in the specific force range.3.4 How are Force Sensing Resistors Made?A semi-conductive material – or semi-conductive ink – is sandwiched between two thin substrates to form force-sensing resistors. As illustrated in Figure 3, there are two types of force sensing resistor technologies: Shunt Mode and Thru Mode.Figure 3:  The differences between shunt and thru mode force sensing resistor technologies.Force sensing resistors  in the shunt mode are polymer thick-film devices made up of two membranes separated by a thin air gap. One membrane contains two sets of interdigitated traces that are electronically isolated from one another, while the other is coated with a special textured, resistive ink.Thru mode force-sensing resistors  are flexible printed circuits with two outer substrates of polyester film. Above and below a pressure-sensitive layer, silver circles with traces are positioned, followed by a conductive polymer. The two layers of the substrate are laminated together with an adhesive layer. 3.5 Matrix or Single-Point Force Sensing ResistorsFigure 4: Examples of different force sensitive resistor technologies.ForceSensing resistors  can be configured as single-point force sensors or as a matrix array to capture pressure distribution over a large area. Pressure mapping technology refers to the use of force-sensing resistor  matrices.Tekscan's FlexiForceTM sensors are a type of thru mode force-sensing resistor. This technology's flexibility, combined with its operating capabilities and ability to operate on simple circuitry, makes it an excellent choice for embedding into smart devices with limited space and power. FlexiForce sensors are also extremely adaptable. Size, shape,  electrical termination, electrical termination, sensitivity,  and operating temperature can all be customized to meet the needs of your application. 3.6 How are Force Sensing Resistors Used?While there are new applications for force-sensing resistor technology every day, the majority of them fall into one of four categories:Detecting or measuring the rate at which a force changes.Detecting or measuring a change in force relative to another object.Touch and/or contact detectionDetecting force thresholds to initiate some kind of action (e.g., IoT applications)This short video gives you a better visual understanding of the various applications for force sensing resistors, specifically FlexiForce force sensing resistors.Are you interested in purchasing force sensing resistors? Ⅳ Factors to Consider Before Purchasing a Backlit KeyboardBefore purchasing a system with a backlit keyboard, you should think about a few things. The following sections go over each of them:4.1 PriceBacklit keyboard laptops are significantly more expensive than those without. As a result, it is recommended that you only invest in a feature if you are certain that it will benefit you and improve your user experience. It is recommended that you skip this feature if you rarely use your computer in dimly lit environments or if you can type without looking. 4.2 Increased Power UsageYour battery  percentage will quickly be depleted by backlit keyboard  s. As a result, if you value durability over aesthetics, you should avoid purchasing a laptop with a backlit keyboard,  However, if you don't mind having your system plugged in the majority of the time, the reduced battery  life shouldn't be a big deal. Furthermore, if you purchase a laptop with a backlit keyboard.  you can turn the feature on or off according to your needs.4.3  BrightnessOne of the main benefits of purchasing a laptop with a backlit keyboard  is the ability to use your system effectively in dimly lit environments. As a result, you should make sure that the backlit keyboard on your laptop is bright enough to meet your needs.4.4  RGBIf you're convinced that a backlit keyboard is a must-have feature for your ideal laptop, then go for the best that the market has to offer. When purchasing a laptop with a backlit keyboard, make sure that the keyboard can switch between different color ranges to effectively adapt to your surroundings.Ⅴ How Much does a Backlit Gaming Keyboard Cost?Gaming keyboards with backlighting are more expensive than standard keyboards, costing around $90 or more. They come in both wired and wireless versions. Wireless models require batteries to operate and may include a USB cable for charging the batteries by plugging the keyboard into the computer.Backlit gaming keyboards are made by a variety of companies, the most popular of which are Corsair, G.SKILL, Logitech, and RAZER.Ⅵ Frequently Asked Questions about Backlit Keyboard6.1 Are there wireless backlit keyboards?These keyboards are wireless and have backlit keys together. ... With backlit keys you are able to work in dark or dim light surroundings whereas wireless connectivity allows you to get free of all wires. Wireless keyboards mostly use bluetooth and are battery powered.6.2 Does backlit keyboard drain battery?Powering the keyboard backlights is a lesser drain on the battery, but there's a built-in setting that I recently learned about that turns off the keyboard backlights after a period of inactivity too.6.3 Does LED keyboard consume more power?There is no difference between the amount of energy/electricity usage a light up/LED keyboard will use compared to a non-light/non-LED up keyboard.6.4 Can you buy a backlit keyboard?Keyboards do come in a variety of different sizes, configurations, and builds, but these don't influence whether the keyboard has a backlight. Both membrane keyboards and mechanical keyboards may be built with backlights. Also, backlights are integrated into both desktop keyboards and laptop keyboards.6.5 Does Microsoft make a backlit keyboard?Yes, it does!all Surface Laptop 3 models come with the same three levels of the backlit keyboard. You can control the backlit on the Surface Laptop 3 keyboard by pressing the F1 media key (Next to Esc key). 1st Press: Activate backlight at level 1 (min). 2nd Press: Activate backlight at level 2 (medium).6.6 Does the surface laptop 2 have a backlit keyboard?Surface Laptop 2 keyboard and trackpadThe Surface Laptop 2 features a full-sized chicklet style keyboard with 1.5 mm of travel (versus 1.3 mm in Surface Pro 6) and three-stages of backlighting.6.7 Does HP laptop have backlit keyboard?Many HP laptops have backlit keyboards, some just a single color, others with what's known as RGB lighting, that can be customized to show different colors.6.8 Does ASUS have backlit keyboard?Here you can learn more about ASUS keyboard hotkeys introduction. For part of Notebook models, backlit function key is F3 and F4 key . If they are available, they can enable the backlit by pressing FN and F4 keys (FN+F4 keys) at the same time. ... For Gaming Notebook models, it's generally on Up and Down keys.6.9 How do I make my laptop keyboard glow?Also, depending on your computer model, your PC may be configured to control the backlit keyboard via the F9 or F11 button rather than the F5 button. Practice the same simultaneous Fn + F11 operation to turn on a backlight keyboard light.

Introduction RF power amplifier is an important part of various wireless transmitters. In the front-end circuit of the transmitter, the power of the RF signal generated by the modulation oscillator circuit is very small, and it needs to go through a series of amplification-buffer stage, intermediate amplification stage, and final power amplification stage to obtain enough RF power before feeding. In order to obtain a sufficiently large RF output power, a RF power amplifier must be used. RF Power Amplifier Design: The Basics Catalog Introduction Ⅰ Requirements of RF Power Amplifier Ⅱ Types of Power Amplifier in Use Ⅲ Parameters of RF Power Amplifier Design Ⅳ Key Feature: Non-Linearity 4.1 Nonlinear Characteristics 4.2 Influence of Nonlinear Characteristics Ⅴ FAQ Ⅰ Requirements of RF Power Amplifier With the vigorous development of modern digital mobile communication technology, users have more requirements on the performance of wireless communication equipment. To achieve stable and high-speed data transmission in various environments is one of the main goals of future mobile communication system researchers. The RF power amplifier is the last stage of the transmitter. It amplifies the modulated frequency band signal to the required power, ensuring that the receiver in the coverage area can receive a satisfactory signal level, but it cannot interfere too much with the communication of adjacent channels, and meanwhile try to keep the amplified high-power signal without distortion. The requirements of these different aspects make the users of power amplifiers have to consider many factors in all aspects. So you should get a full knowledge of RF power amplifiers. Figure 1. Classic RF Power Amplifier Circuit Ⅱ Types of Power Amplifier in Use What are the main types of RF amplifiers for such an important device?1) According to the operating frequency bandsAccording to the working frequency band, it can be divided into narrowband RF power amplifier and broadband RF power amplifier. The former generally uses frequency selective networks as load circuits, such as LC resonant circuits. The latter does not use the frequency selection network as the load loop, but employs the transmission line with a wide frequency response as the load.2) According to the network propertiesAccording to the nature of the matching network, power amplifiers can be divided into non-resonant power amplifiers and resonant power amplifiers. The matching network of the non-resonant power amplifier is a non-resonant system, such as high-frequency transformers, transmission line transformers and other non-resonant systems, and its load properties are purely resistive, where this is also called reactance properties.3) According to current conduction angleBased on it, RF power amplifiers can be divided into class A, AB, B, C, D, E and so on. The differences between these categories can be seen in the following table: Classification Conduction Angle Efficiency Linearity Application Class A Θ=360° ≤30% Very good Small Signal Low Power Amplification Class B Θ=180° ≤60% Lower than class A For High Power Class C Θ<180° About 60% Nonlinear amplifier For High Power Class AB 180°<Θ<360° 30%~60% Better than class B Small signal works in class A, large signal works in class B Class D Work in switch mode 80% Very good, only good for low frequencies Switch mode amplifier Class E Work in switch mode 90% Completely nonlinear amp Switch mode amplifier In the classification of amplifiers, we often talk about amplifiers of class A to E according to the conduction angle. Class A power amplifier is a linear amplifier, its response to the sine-wave  input is a sine-wave output, generally without distortion amplification, and the output frequency is the same as the input frequency. Since class A amplifiers do not require additional filtering circuitry, their packages can be small and cost less. The output of a class B amplifier is a half sine wave of the input, resulting in half-wave distortion, which produces many harmonics. The output power and efficiency of the class C working state are the highest among these working states, and most of the amplifiers used for radio frequency work in the class C. Figure 2. Class A Amplifier Load Curve   Ⅲ Parameters of RF Power Amplifier Design RF power amplifiers are electronic circuits that comprehensively consider issues such as output power, excitation level, power consumption, distortion, efficiency, size and weight. In the transmitting system, the output power of the RF power amplifier can be as small as mW and as large as several kW, but this refers to the output power of the final power amplifier. In order to achieve high power output, the last stage must have a sufficiently high excitation power level. At the same time, it has other important indicators, as follows:1) Operating FrequencyGenerally speaking, it refers to the linear operating frequency range of the amplifier. If the frequency starts at DC, the amplifier is considered to be a DC amplifier.2) GainThe working gain is the main indicator to measure the amplification ability of the amplifier. Here it is defined as the ratio of the power delivered to the load by the amplifier output port to the power actually delivered by the signal source to the amplifier input port.Gain flatness refers to the variation range of amplifier gain in the entire operating frequency band under a certain temperature, and is also a main indicator of the amplifier. Figure 3. Output Power and 1dB Compression Point (P1dB) Referring to the Figure 3, when the input power exceeds a certain amount, the gain of the transistor begins to decrease, and the end result is that the output power saturates. When the gain of the amplifier deviates from a constant or is 1dB lower than other small signal gains, this point is the famous 1dB compression point (P1dB). Generally speaking, the power capacity of an amplifier is expressed by the 1dB compression point.3) EfficientSince the power amplifier is a power component, it needs to consume the supply current. Therefore, the efficiency of the power amplifier is extremely important to the efficiency of the whole system. Power efficiency is the ratio of the RF output power of the amplifier to the DC power supplied to the transistors.ηp=RF Output Power/DC Input Power4) Intermodulation Distortion (IMD)Intermodulation distortion refers to the mixed components of two or more input signals with different frequencies passing through a power amplifier. This is due to the nonlinear nature of the amplifier. Among them, because the third-order intermodulation product is very close to the fundamental signal, it has the greatest influence, so the third-order intermodulation is the most important consideration for the related products. The lower the third-order intermodulation product, the better.5) Third-order Intermodulation Cut-off Point (IP3)The intersection point of the extension line of the fundamental wave signal output power and the extension line of the third-order intermodulation in Fig is called the third-order intermodulation cut-off point, which is represented by the symbol IP3. It is also an important indicator of nonlinearity. When the output power is constant, the greater the output power of the third-order intermodulation cut-off point, the better the linearity of the power amplifier.6) Dynamic RangeThe dynamic range of a power amplifier generally refers to the difference between the minimum detectable signal and the maximum input power in the linear operating region. Naturally, this value must be as large as possible.7) Harmonic DistortionWhen the input signal increases to a certain level, the power amplifier will generate a series of harmonics due to its work in the nonlinear region. For high-power amplifier systems, filters are generally required to reduce harmonics below 60dBc.8) Input/Output VSWR (Voltage Standing Wave Ratio)This is also a very important indicator of how well the amplifier matches the overall system. The deterioration of the input-output ratio will lead to the deterioration of the gain fluctuation and group delay of the system. However, it is difficult to design a power amplifier with a high VSWR. In general systems, the input VSWR of the power amplifier is required to be lower than 2:1.The main technical indicators of RF power amplifiers are output power and efficiency. Therefore how to improve them is the core of the design goals of RF power amplifiers. Usually in the RF power amplifier, the fundamental frequency or a certain harmonic can be selected by the LC resonant circuit to achieve distortion-free amplification. In addition to this, the harmonic components in the output should be as small as possible to avoid interference with other channels. Figure 4. Increase the Power of the RF Input Signal Ⅳ Key Feature: Non-Linearity In an ideal amplifier, the output signal should faithfully reflect the input signal, that is, the waveform should be the same. But in fact, for many reasons, the input signal cannot be exactly the same waveform as the input signal, which is called amplifier distortion.Amplifier distortion mainly includes frequency distortion (linear distortion) and waveform distortion (non-linear distortion). The former mainly refers to the difference in gain and delay of the amplifier for different frequency components; the latter refers to the same frequency, the output signal and the input signal are not linear. Frequency distortion is represented by spectral changes in the frequency domain, while nonlinear distortion is represented by changes in the time-domain waveform. Non-linear distortion is different from frequency distortion mainly because a large number of new frequency components are generated. The nonlinear distortion of the power amplifier is mainly discussed here. 4.1 Nonlinear Characteristics From the small-signal model and input characteristic curve of an ideal transistor, it can be seen that the transistor amplifier itself is not an ideal linear device, and at the same time, due to the influence of parasitic parameters, the linearity is further reduced. But within a certain power range, the transistor can be regarded as linear amplification. For power amplifier designers, how to obtain higher output power and improve linearity is the key.For a transistor amplifier, its volt-ampere characteristics can be described as follows: A power series expansion can be used to describe the volt-ampere characteristics of the device: In the formula, an(n=0,1,2,3,…) is a coefficient related to the circuit characteristics. Usually, the larger the n, the smaller the value of the coefficient an. When the nonlinear device in the circuit is represented by a power series, the number of series terms taken depends entirely on the magnitude of the signal amplitude and the required precision. 4.2 Influence of Nonlinear Characteristics The influence of the nonlinear characteristics of the device on the amplifier can be discussed in two cases. One is when there is only one signal at the input end, and the other is when the input end has one to two other signals in addition to the useful signal.🔺Only one signal at the inputLet the signal at the input end be , and substitute it into formula 2, at this time there is When the amplitude of the input signal is large and the effect of the cubic term must be considered, the fundamental frequency signal obtained from formula 2 is: Figure 5. 1dB Compression Point (PA) A3 in formula 3 is usually a negative value, that is, y1(t) decreases as the input signal amplitude increases, a phenomenon called gain compression.The "1dB compression point" is often used in engineering to measure the linear performance of the device. The 1dB compression point is defined as the input signal power P1dB that reduces the gain by 1dB from the linear gain. As shown in Figure 5. According to the definition of 1dB compression point and formula 3, we can get 🔺Two signals at the input.The signal amplified at the input end of the amplifier is generally not a single tone signal, but a spectral signal composed of a certain bandwidth. Due to the nonlinearity of the device, a large number of combined interference frequency components other than the useful signal will be generated at the output end. In addition, the combined frequency components of two or more interfering signals may also cause interference to the useful signal. Have an assumption: Substitute into formula 1, where It can be seen from the above formula that the fundamental frequency components of ω1 and ω2 are generated by the first and third power terms: A total of multiple frequency components are generated: ω1 , ω2 , ω1 ± ω2, 2ω1 - ω2, 2ω2 - ω1 , 3ω1 - 2ω2, 3ω2 - 2ω1.The difference frequency 2ω1 - ω2, 2ω2 - ω1 in the combined frequency is generated by the cubic term. The combination of these two signal frequencies is just within the sideband range of the signal frequency, which may cause interference to adjacent channels, and is one of the main indicators of transmission signal. Figure 6. Intermodulation Signal Interference This interference is caused by the mutual modulation of the two signals, so it is called intermodulation interference. At the same time, it is generated by a cubic term, so it is also called third-order intermodulation interference in engineering.When the third-order intermodulation interference is an important indicator of the communication machine, it is often measured by the intermodulation distortion ratio IMR and the third-order intermodulation blocking point IP3 in engineering. IMR is defined as the ratio of the amplitude of the third-order intermodulation product to the amplitude of the fundamental signal at a certain input amplitude. Definition of IP3: When the third-order intermodulation component increases to be equal to the fundamental frequency component, the receiver cannot receive normally, so there is a . Figure 7. Third-order Intermodulation Blocking Point 🔺Sideband Signals Figure 8. Sideband Signals and the Spectrum In fact, most of the sideband signals are generated outside the bandwidth after the useful signals of different frequencies within the bandwidth are modulated with each other. That is, the sideband signal rises faster than the in-band signal, and the spectral mask in the above figure becomes more and more flat. The increase of sideband signals will cause interference to adjacent channels, so the IEEE 802.11 protocol has strict requirements on the spectrum template, as shown in the Figure 9. Figure 9. DSSS Signal Modulation Spectral Mask Figure 10. OFDM 20MHz Bandwidth Signal Spectral Mask For the power amplifier, its nonlinear characteristics will increase the sideband of the modulated signal, and the sideband amplitude is not easily suppressed by other networks such as filters, and it is easy to cause design difficulties. Therefore, when choosing a PA, not only should pay attention to the maximum linear output that it can achieve, but also whether it can meet the sideband spectrum requirements at this output power.🔺Other Effects of NonlinearityIn addition to the previously mentioned gain drop, which generates a large number of harmonic components, as well as third-order intermodulation and sidebands, nonlinearity can also cause signal and EVM to deteriorate, etc.   Ⅴ FAQ 1. What is RF power amplifier?A radio frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal. 2. How does RF power amplifier work?An RF amplifier is actually a tuned amplifier that enables the input signal of broadcast or transmitted information to control an output signal. The RF amplifier uses frequency-determining networks to convert the input signal into an output signal that will provide the required response at a given frequency. 3. What is the most efficient class of RF power amplifier?Class C AmplifierThe Class C Amplifier design has the greatest efficiency but the poorest linearity of the classes of amplifiers mentioned here. The previous classes, A, B and AB are considered linear amplifiers, as the output signals amplitude and phase are linearly related to the input signals amplitude and phase. 4. How do I choose an RF power amplifier?Considerations When Choosing An RF Power Amplifier:Gain.Operating Frequency.Output Power Level.Efficiency.Linearity.Mismatch Tolerance.Noise Level. 5. What are the advantages of RF amplifier?Following are the RF Amplifier advantages:The RF amplifier offers greater gain i.e. better sensitivity. It offers better selectivity and hence it has ability to select wanted signals from multiple input signals at the RF receiver. 6. What are the different types of RF amplifiers?Amplifier TypesBroadband AmplifiersGain Block AmplifiersLog AmplifiersVariable Gain AmplifiersLow Noise AmplifiersCoaxial and Waveguide Power AmplifiersLinear AmplifiersBi-Directional Amplifiers 7. What is RF amplifier circuit?A radio frequency power amplifier (RF power amplifier) is a type of electronic circuit that converts a low-power radio-frequency signal into a higher power signal. 8. Is Class D amplifier better than a class AB?The most common audio power amplifier operates in the Class-AB mode. It provides the greatest amount of output power with the least amount of distortion. ... Class-D amplifiers are switches that are more efficient and produce less heat than their Class-AB equivalents. 9. What are RF amplifiers used for?Whenever people need to magnify a radio frequency signal into a higher power signal, the RF amplifier plays a pivotal role. They are used in commercial and defense avionics, space and deep space, electronic warfare, naval applications, mobile internet, satellite communication, and wireless communications. 10. Which amplifier is used in RF amplifier?RF power amplifiers using LDMOS (laterally diffused MOSFET) are the most widely used power semiconductor devices in wireless telecommunication networks, particularly mobile networks. LDMOS-based RF power amplifiers are widely used in digital mobile networks such as 2G, 3G, and 4G.

IntroductionAs one type of relays, reed relays use an electromagnetic coil to control one or more flexible ferromagnetic metal reed switches directly. It is composed only by the contacts themselves that triggers the conduction in the secondary circuit. Reed relay switches can be used as magnetic proximity switches or relays, which are smaller in size, higher in speed and longer in working life than general mechanical switches. Here, let's explore this special relay.What is a Reed Relay? Characteristics IntroductionCatalogIntroductionⅠ A Special Relay: Reed RelayⅡ Structure Comparison: Relay vs Reed RelayⅢ Reed Relay CharacteristicsⅣ What is a Reed Relay Used For?Ⅰ A Special Relay: Reed RelayIn electronic circuits, relays are the switches which close and open the circuits contacts electronically as well as electromechanically. When the relay coil is energized or de-energized, it plays the role of automatic regulation, safety protection and circuit conversion. Relays are available with two main types. As everyone knows, relays are divided into mechanical relays and semiconductor relays.Figure 1. Mechanical Relay vs Semiconductor RelayOn the insulation detection circuit of BMS, we often use a device called PhotoMOS, which is used to switch the Wheatstone bridge. Actually, it is a semiconductor relay.Figure 2. PhotoMOS AQV258For example, AQV258 is a model we often choose.PhotoMOS is a semiconductor relay with LED as input and MOSFET as output, but we are not mainly discussing PhotoMOS today.In recent years, another device has appeared on the insulation detection circuit, which is called Reed Relay Switch, Reed Switch, Reed Relays, etc. It is also used for the switch of the Wheatstone bridge arm. Ⅱ Structure Comparison: Relay vs Reed RelayReed relay is a kind of mechanical relays, but its structure is different from the traditional electromagnetic relay. The traditional electromagnetic relay is an electrical relay that uses the suction force generated by the circuit in the input circuit between the electromagnet core and the armature to work. This kind of relay is large in size, slow in action, and limited in life, but it is reliable. With the development of electronic appliances in the direction of miniaturization, new requirements have been put forward for relays. In this case, reed relays can meet the needs of this development in many aspects.Figure 3. Electromagnetic Relay StructureThe reed relay is composed of two parts: a reed switch and a coil. Compared with other types of relays, it is more compact and has higher energy efficiency. The following describes its structure and principle in detail.As shown in the figure below, the magnetic reed switch consists of two magnetic reeds, which are sealed inside a glass tube. The two magnetic reeds have a contact overlap area at the middle end of the glass tube, and has a small gap. The inside of the glass tube is filled with inert gas, such as nitrogen, to prevent oxidation. In order to improve the strength of electrical breakdown, the inside of the glass tube can also be evacuated.Figure 4. Reed Relay StructureThe magnetic reed body is made of nickel-iron alloy, and the surface of the contact overlap area of the two magnetic reeds is plated with hard metals such as rhodium or ruthenium to play a role in wear resistance. Placing the magnetic reed switch in a magnetic field, when the two magnetic reeds are magnetized into opposite polarities, they generate attractive force, and the contact overcomes the elastic force to connect. Similarly, when the magnetic field disappears, the contact is pulled away without magnetic force.In order to allow the reed switch to be closed or opened by human control, the coil is wound on the surface of the glass tube, and the coil is energized, thus forming an electromagnet, which generates a magnetic field for the reed switch to act.Figure 5. Relay CoilTherefore, as a circuit switch device controlled by a magnetic field signal, the reed switch can be used as a sensor for counting and limiting (in the security system, it is mainly used for the production of door and window magnets). It is widely used in various communication devices. In practical applications, permanent magnets are usually used to control whether the two metal pieces are connected or not, so they are also called magnetic relay.What’s more, the more turns the coil has, the less current reed relay switch needs to work. The relationship between the number of turns and the working voltage is restricted by the following factors: the wire diameter of the coil, the number of turns, the resistivity of the conductor, and the size of the reed contact.In theory, the working principle of the reed relay is like a switch: when the permanent magnet is close to the reed switch or the magnetic field formed by the coil winding on the reed switch magnetizes the reed, the contact part of the reed will be attracted by the magnetic force. When the attractive force is greater than the elastic force of the reed, the normally open contact will attract and close; when the magnetic force is reduced to a certain extent, the contact is opened by the elastic force of the reed.Figure 6. Reed Relay Magnetic FieldThe lifespan of reed switches is shorter than that of semiconductor switches, but much longer than general electromagnetic relays. The following figure shows the operating parameters of a certain type of reed switch, which can be switched on and off millions of times.Figure 7. Life Test DataThe reason for using the reed relay in the bridge method is that it has higher insulation and withstand voltage regardless of the load end or input/output. Ⅲ Reed Relay Characteristics1) High reliabilityThe failure rate of general relays is set at 50ppm, so in order to meet this requirement, the quality level of reed switches is much higher than this standard. So far, there has not been any electromechanical device that can achieve this level of quality.2) High securityReed relay switch has excellent insulation properties. Its insulation resistance can reach up to 1015Ω, that is, its leakage current only has 10-15A. Such extremely low leakage levels are widely used in medical electronic equipment, such as probes inserted into the human body or cardiac pacemakers, because these equipment require no leakage current close to the heart, even if the current is microampere or submicroampere, which will change the electrical properties of key parts of the heart.3) High adaptabilityThe reed sensor is sealed. Because the switch components is airtightly sealed in an inert gas, it will not contact the external environment, so it can work in almost any environment without being sensitive to humidity and not affected by the outside world. At the same time, the reed switch has no special requirements for the ambient temperature and has a wide temperature adaptability. The typical working temperature range can be from -50℃ to +150℃, and no special additional conditions, restrictions or costs are required.4) Long lifespanBecause the reed switch is a wear-free component and does not use a sliding component, there will be no worn metals, ensuring practically unlimited mechanical service life. At the same time, because the contact made of inert precious metal rhodium has a high melting point, it can reduce the loss of arc power generation on the contact surface, so it is more resistant to wear and can maintain a longer working life. General reed switches can work up to a million times under low-level loads (less than 5V and lower at 10mA).5) Small sizeThe reed relay switch can be installed in a limited space and is very suitable for miniaturized equipment.6) Superior electrical performanceReed relay switches have a series of excellent electrical properties. For example, their contacts have extremely low on-resistance when they are turned on, typically as low as 50mΩ. In addition, their direct switching signals can range from a few nanovolts to thousands of volts, and the current ranges from micro An to An, etc.7) High speed operationSince each movable component has only a very small weight, the operating speed is very high, making the reed switch a part that can be used in transistor circuits or integrated circuits.Ⅳ What is a Reed Relay Used For?Reed relay switches have been widely used in many fields of automatic control systems, such as machinery, automobiles, electronics, electric power, petroleum, chemical industry, office automation, communications and other engineering. For example, in the military field, high-voltage reed relays are related to national defense components for modern weapons and equipment. Frequently Asked Questions about Reed Relay Basics and Uses1. What is a reed relay used for?Reed Relays are ideally used for switching applications requiring low and stable contact resistance, low capacitance, high insulation resistance, long life and small size. 2. What is the difference between relay and reed relay?A relay switch is composed of an electromagnet that actuates a high power switch made of two metallic contacts. ... A reed switch is composed only by the contacts themselves that triggers the conduction in the secondary circuit. 3. Why is reed relay used in a switching circuit?The reed relay consists of a switch with magnetic contacts that move under the influence of an external magnetic or the induced field from its solenoid. They have faster switching speed compared to the electromechanical ones but their switching current and voltage is lower mainly because of its contacts thickness. 4. What is required to operate a reed relay in a switching circuit?The coil surrounds the reed switch and generates the axial magnetic field needed to close the reed contacts. 5. Where is a reed switch used?Reed switches are used in fluid level sensors for brake fluid reservoirs and to monitor motor oil levels. They are also used in speed sensors for engine control and power steering. Automatic door locks, air bags, parking brakes, seat, door, and hood proximity sensors also utilize reed switches.

CategoryⅠ IntroductionⅡ Electronic Ballast Circuit Diagram Research Application 2.1 Overview 2.2 Circuit Structure of High-Performance Electronic Ballast       2.2.1 Power Factor Correction Circuit       2.2.2 Inverter Circuit       2.2.3 Lamp Circuit Network       2.2.4 Control Circuit2.3 High-Performance Electronic Ballast Dedicated Integrated Controller of ML4830 Series       2.3.1 Introduction to ML4831/32 Function       2.3.2 The Improvement of the Internal Function of ML48332.4 High-performance Electronic Ballast Built by ML4833Ⅲ FAQ Ⅰ IntroductionIn the 1970s, a worldwide energy crisis emerged. The urgency of energy conservation has led many companies to focus on energy-saving light sources and electronic ballasts for fluorescent lamps. With the rapid development of semiconductor technology, various high-return power switching devices are emerging, which provide conditions for the development of electronic ballasts. In the late 1970s, foreign manufacturers took the lead in launching the first generation of electronic ballasts, which was a major innovation in the history of lighting development. Because it has many advantages such as energy-saving, it has aroused great concern and interest around the world. It is considered to be an ideal product to replace the inductance ballast. Later, some well-known enterprises have invested considerable manpower and material resources to carry out higher-level research and development. Due to the rapid advancement of microelectronics technology, the development of electronic ballasts to high performance and high reliability has been promoted. Many semiconductor companies have introduced a series of products for dedicated power switching devices and control ICs. In 1984, Siemens developed an active power factor correction IC such as the TPA4812 with a power factor of 0.99. Subsequently, some companies have successively launched integrated electronic ballasts. In 1989, Finland's Hell Valley Company successfully launched electronically adjustable ballast monolithic integrated circuit ballasts. Electronic ballasts have been promoted and applied throughout the world, especially in developed countries. Figure 1. BallastChina's research and development of electronic ballasts started late, the technology is not advanced, early understanding of the difficulty and complexity of this product is insufficient, the development of special semiconductor devices has not kept up, the quality of products has not passed, and the market is extremely irregular. A large number of low-priced inferior goods were thrown to the market, causing losses to consumers and seriously damaging the image of electronic ballasts.  In the late 1990s, due to the rapid development and improvement of production levels, from circuit design to electronic components, the products entered a relatively mature stage, and high-quality products entered the construction project. The implementation of China's green lighting project paved the way for the promotion and application of electronic ballasts. Knowledge of Electronic Ballast for Fluorescent Lamps and Germicidal Lamps The electronic ballast is an electronic control device that uses a semiconductor electronic component to convert a direct current or low frequency alternating current voltage into a high frequency alternating current voltage, and drives a light source such as a low pressure gas discharge lamp (sterilization lamp) or a tungsten halogen lamp. The most widely used is the electronic ballast for fluorescent lamps. Due to the adoption of modern soft-switching inverter technology and advanced active power factor correction technology and electronic filtering measures, the electronic ballast has good electromagnetic compatibility and reduces the self-loss of the ballast. Ⅱ Electronic Ballast Circuit Diagram Research Application2.1 OverviewOn October 1, 1997, China's "Green Lighting Project" was officially launched. This is a major decision and measure in the field of lighting technology, which has a huge impact on China's energy, electric light source and lighting technology, and even environmental protection. As an important target of the "green lighting project", China will replace the incandescent lamp with an integrated energy-saving lamp composed of electronic ballasts and compact fluorescent lamps and promote more than 300 million energy-saving lamp, forming the terminal's ability to save 22 billion kWh, which is equivalent to saving about 49-63 billion yuan electricity construction funds. In addition to saving electricity, it can actually reduce social expenditures by 30-40 billion yuan. According to relevant experts from the Ministry of Information Industry, under the same luminous flux conditions, energy-saving lamps can save 80% of energy compared with incandescent lamps, and the cost of purchasing energy-saving lamps can be recovered in the 8-10 months of electricity savings. The use of electronic energy-saving lamps in ordinary households, enterprises and institutions, hotels, restaurants, and commercial systems is more cost-effective than incandescent lamps. However, the old-fashioned inductance ballasts currently working at the industrial frequency generally have the disadvantages of high energy consumption, low efficiency, large volume, and large amount of copper needed. Therefore, the state has set a policy which is to replace traditional inductance ballasts with high frequency electronic ballasts. Currently, some electronic ballasts have appeared on the market, and Table 1 lists the performance comparison of these electronic ballasts. According to the International Electrotechnical Commission standard IEC929 and China's professional standard ZBK74012-90, the electronic ballast should be used in "normal conditions, the lamp should be activated, but it does not cause damage to the lamp performance"; "The shortest time to apply the cathode preheating voltage should not be less than 0.4s" and "the crest factor of the open circuit voltage shall not exceed 1.8; during the minimum warm-up period, no extremely narrow voltage peaks that do not affect the rms value shall be generated", etc.  As listed in table 1, except for high grade electronic ballasts, they are unqualified products. In particular, as early as 1982, the International Electrotechnical Commission (IEC) developed a standard called “interference of household equipment and similar electrical equipment to the power supply system”, namely the IEC555-2 standard. In 1987, Europe also developed a similar EN60555-2 standard. Both standards strictly limit the power factor of the equipment to be close to 1, and it also clearly stated that, all products that do not meet the standards are not allowed to be sold. In view of the great harm caused by the low power factor, it is very important and necessary to impose regulations on the power factor of electronic equipment and products that must be close to 1. Figure 2. Brief Comparison of Low, Medium and High Grade Electronic Ballasts We believe that the high-performance electronic ballast should be a product that has both power factor correction and lamp filament preheating, lighting adjustment and lamp circuit protection, and is fully compliant with IEC555-2 and similar standards. The basic principles of the circuit structure and power factor correction circuit that must be provided for high-performance electronic ballasts are briefly discussed in this article. The integrated controllers for electronic ballasts ML4831, ML4832, ML4833 and high-performance electronic ballast circuits composed of them are highlighted. 2.2 Circuit Structure of High Performance Electronic BallastThe RFI and EMI filters in the figure filter out conducted RF interference and electromagnetic interference from the grid, while obstructing the conducted RF and electromagnetic interference generated by the ballast circuit from entering the grid. The bridge rectifier circuit converts the input AC to DC. The power factor correction circuit acts to improve the input AC current waveform, ensuring that the input current is sinusoidal and in phase with the input voltage, achieving a power factor close to or equal to one.  The inverter circuit completes the conversion of the DC high voltage to the high-frequency AC, and finally transmits the input power to the fluorescent tube through the lamp circuit network. In addition to transmitting electrical power, the lamp network will also perform preheating of the fluorescent filament, sampling and feedback of the lamp operating state signal. The feedback signal of the working state of the lamp is taken from the power factor correction circuit and the dimming signal, and processed by the control circuit to obtain the driving pulse of the switching device in the correct inverter circuit. 2.2.1 Power Factor Correction CircuitThe power factor of the system is defined as PF=γcosφ1 In the formula, γ=I1/IRMS, which is the ratio of the fundamental rms value of the input current to the rms value of the input total current and is also called the distortion factor of the current. φ1 is the phase shift angle of the fundamental current and voltage. If the input voltage of the system has no phase shift (ie, the system is purely resistive) and there is no harmonic component (ie DF=1), the PF of the system must be one. Unfortunately, the input rectification filter units that most of the current devices connect with the power frequency grid are composed of uncontrolled diodes and large-capacity electrolytic capacitors. The instantaneous value of the current on the grid side is quite high (generally about 2 to 3 times that of IRMS), the duration is very short (usually no more than 4ms), and it is severely non-sinusoidal, so the PF of the system is much lower than 1.  The power factor correction is aimed at the drawbacks of the traditional uncontrolled rectifier circuit, and adopts corresponding circuit measures. While increasing the DF value of the system, the phase shift of the input fundamental current and voltage is minimized, and finally the target with the PF value equal to 1 is achieved. As a boost-type active power factor correction circuit commonly used in electronic ballasts, the control circuit uses the input voltage signal as a reference, and the product of the input current and the output voltage signal is used as a modulation source to obtain a sinusoidal pulse width modulation (SPWM) signal to the step-up DC/DC power conversion circuit to adjust the on/off time ratio of the power switch. In the end, a stable DC high voltage is obtained.  The power switching device in the step-up power conversion circuit is driven by the SPWM signal outputted by the control circuit to turn on and off at a high speed, thereby ensuring that the current waveform flowing through the inductor connected in series with the rectifier bridge is a sine wave, and is in phase with the input voltage. Thus, the distortion factors γ=1 and φ1=0 of the system input current are obtained, that is, cosφ1=1, and the system power factor is 1. 2.2.2 Inverter CircuitThe most important function of the inverter circuit is to convert the high-voltage direct current outputted by the power factor correction circuit into a high-frequency alternating current for the fluorescent lamp. The power MOSFET push-pull tubes (V1 and V2) are alternately turned on and off under the driving pulse with a duty cycle of 50%, and is commutated when the current crosses zero in the parallel resonant loop of the power transformer primary inductance and capacitance thus to realize zero voltage switching(ZVS) and perform chopping on high voltage DC. The zero-voltage switching eliminates switching losses associated with output capacitance and parasitic capacitance charging of MOSFET tube, and the gate drive charge is minimal, which helps reduce gate losses.  Since the high frequency AC obtained by the secondary coupling of the power transformer is directly fed to the lamp network, there is no phase shift between the lamp current (ie, secondary current of the power transformer) and the output current of the inverter circuit (ie, primary current of the power transformer). Considering that the total impedance of the lamp network is reduced at high frequencies, and the negative resistance characteristic of the fluorescent lamp itself, it can be found that as the lamp current decreases (corresponding to the weakening of the light intensity of the lamp), the output current of the inverter circuit will increase. 2.2.3 Lamp Circuit NetworkThe lamp circuit network not only needs to deliver the high-frequency AC power to the lamp tube to complete the efficient conversion of electricity and light, but it also needs to implement functions such as filament warm-up, lamp current detection feedback, and auxiliary power supply for the entire electronic ballast system.  The power transformer primary T is connected to the inverter circuit, and the lamp current is directly transmitted to the lamp through the capacitor, and the secondary winding supplies the lamp with filament current for preheating and maintaining the operation. The current transformer TA performs detection and sensing of the lamp current, and sends a signal about the operation of the lamp to the control circuit at any time by the change of the lamp current. The control circuit can judge the light intensity of the lamp according to the magnitude of the lamp current (even including the disconnection and short circuit of the lamp), and then send corresponding control signals to the inverter circuit. 2.2.4 Control CircuitThe control circuit for high-performance electronic ballasts should have a series of functions including power factor correction, lighting adjustment, light-on preheating, lamp disconnection alarm, and lamp restart program control. At present, some integrated circuit controllers for electronic ballasts appearing in the domestic and international device market are mostly based on PFC control, with appropriate addition of lamp control functions, or implementation of lamp control by external circuits. It is worth mentioning that the ML4830/31/32/33 series products can be said to be integrated controllers for high-performance electronic ballasts. 2.3 High-Performance Electronic Ballast Dedicated Integrated Controller of ML4830 SeriesML4830/31/32/33 are integrated circuit controllers developed by American Micro Linear Corporation for high-performance electronic ballasts. The first generation ML4830 has been eliminated; the second generation ML4831 is manufactured by bipolar integrated circuit technology; the third generation ML4832 uses Bicmos process to replace the original bipolar process, the circuit bias current is greatly reduced, and the consumption is greatly reduced. The fourth-generation ML4833 not only adopts the Bicmos process but also has a major improvement in the internal structure, so the function is enhanced and the performance is better. Although these devices can use the functional block diagram of figure 3, the internal structure of ML4831 and ML4832 and the internal structure of ML4833 are respectively shown in figure 4 and figure 5. Figure 3. Functional Block Diagram of ML4831, 32, 33  Figure 4. Internal Block Diagram of ML4831, 32  Figure 5. Internal Structure Block Diagram of ML4833 2.3.1 Introduction to ML4831/32 FunctionThe ML4831/32 is composed of a continuous current type boosting power factor correction stage controlled by an average current. It has a dedicated control circuit for electronic ballasts with various ballast control links. Lamp start-up and restart timing can be achieved by using external circuit components to provide a wide range of control over different types of lamps. The ballast link uses an additional programmable method of frequency modulation and adjustment of the frequency range of the voltage-controlled oscillator to control the lamp power, so it is suitable for various types of output networks. The gain modulator in the ML4831/32 is highly immune to interference caused by switching high-power switching devices. The output of the gain modulator appears as a reference to the current error amplifier at the inverting input of the amplifier. Isine is the current drawn from the AC input; UEA is the output of the error amplifier (pin 1). The output of the gain modulator is limited to 1V. The PWM regulator in the PFC control section compensates for the positive voltage generated by the multiplier output through the negative voltage developed across the pin 4 sense resistor. At the same time, the power MOSFET is protected against high-speed current transients by weekly current limiting. Once the voltage at pin 4 is below 1V, the PWM cycle is terminated immediately. The overvoltage protection (OVP) terminal (pin 18) of the ML4831/32 is used to protect the power circuit from high voltage damage when the lamp is suddenly disconnected. The OVP take-off point can be set by directly tapping the voltage divider resistor to the high-voltage DC bus. As long as the voltage at pin 18 exceeds 2.75V, the power factor correction (PFC) transistor will be turned off and the ballast operation can continue.  The threshold of the OVP should be set to a value that the power device can operate safely, but is not too low to affect the operation of the boost power conversion link. The internal operational transconductance amplifier performs PFC voltage feedback, current sensing and loop amplification. The transconductance amplifier is designed with a low signal forward transconductance so that a large value resistor can be used as a load and a small (<1μF) ceramic capacitor for AC coupling in the compensation network. The compensation network can take the form of figure 6, introducing a zero point and a pole at frequencies fz and fP, respectively: fZ=1/2πR1C1fP=1/2πR1C2 It is noted that the DC-to-ground path and the output of the transconductance amplifier may be out of tune, and the offset error voltage value reflected at the input is determined by uos=iO/gm. Capacitor C1 in figure 6 is used to block DC and minimize the adverse effects of offset. All of the operational transconductance amplifiers in the ML4831/32 incorporate a Slew Rate enhancement to improve recovery under circuit power-up and transient response conditions because the transconductance amplifier changes from a small transconductance state to a large transconductance state. The response to large signals is essentially non-linear. Figure 6. Compensation Network for Transconductance Amplifier The ML4831/32 controls the output power of the lamp by frequency modulation of the non-overlapping conduction of the power switch tube in the inverter part of the ballast circuit. That is to say, during the discharge of oscillation timing capacitor CT, the output of both ballast power tubes is low. The frequency range of the voltage controlled oscillator (VCO) in the device is controlled by the output of the LFB amplifier (pin 6). As the lamp current decreases, the voltage at pin 6 rises, causing the CT charging current to drop, thus causing the oscillation frequency of the oscillator to become lower. Because the ballast output network attenuates high frequencies, the power fed to the lamp increases accordingly. In general, the frequency of the oscillator can be calculated as follows: fosc=1/（tchg＋tdis） Attention: A zero charge current occurs when LFBOUT (pin 6) is high level. Typically, the charge current varies with the two inputs to the oscillator: One is the output of the warm-up timer, and the other is the output of the lamp feedback amplifier (pin 6). During the warm-up phase, the charging current is fixed at a value of Ichg (preheat) = 2.5 / Rset (3). During normal operation, the charging current varies with the voltage of pin 6 from 0 to UOH. When the voltage at pin 6 is zero, the oscillator frequency is lowest and the lamp power is maximum. The discharge current is much larger than the current flowing through the timing resistor RT. For example, when the discharge current is 5 mA, the discharge time is：  tdis ≈ 490 × CT. The ML4831/32 also includes a parallel regulator that limits the UCC voltage to 13.5V. When the UCC is 0.7V lower than 13.5V, the quiescent current of the device will be less than 1.7mA, and the output will be turned off, allowing the device to be started directly using the resistor attached to the rectified AC bus. In addition, because the ML4831/32 contains a temperature sensing function, the ballast operation is stopped as soon as the junction temperature of the device exceeds 120 °C. In order to better utilize the internal sensing function without using an external sensor, the position of the ML4831/32 must be carefully determined on the ballast's circuit board to ensure that the device can properly transfer the operating temperature of the ballast. The chip temperature of ML4831/32 can usually be estimated by the following formula:  Tj=65TA/PD(°C/W) It is worth noting that fully and reasonably using the sensing function inside the device is useful for reducing the total cost of the ballast. The starting scheme of the device is specifically designed for the ML4831/32 in accordance with the principle of ensuring the longest lamp life and minimizing the ballast heating. Figure 7(a) contains a starting scheme including preheating of the filament and sudden breaking of the lamp. When the ballast is energized, the time that the voltage on the CX rises from 0.7V to 3.4V is called the warm-up time of the filament.  During this time, the oscillator's charging current Ichg = 2.5/Rset, the oscillator produces a very high frequency, but does not produce a voltage sufficient to start the lamp. After the filament is preheated, the frequency of the inverter circuit drops to a minimum, and a high voltage is generated to start the lamp. If the voltage of the inverter circuit does not jump when the lamp should start to work, the lamp feedback voltage entering pin 9 will rise above Uref, the CX charging current will be bypassed, and the inverter circuit will stop working until CX drops to a 1.2V threshold by RX discharge. Stopping the inverter circuit in this way can avoid the failure of the lamp to start or the inverter circuit to overheat when it is disconnected from the socket.  In general, it is better to choose a large resistance RX to make this period longer. When CX reaches the 6.8V threshold, the oscillator will turn off LFBOUT, so the lamp will be driven to full power, then dimmed, and the potential of the CX pin is clamped at approximately 7.5V. The whole process is shown in the waveform of figure 7(b). Figure 7. Lamp Start Preheat and Interrupt Timing Scheme and Its Waveform 2.3.2 The Improvement of the Internal Function of ML4833The ML4833 is a modified version of the ML4831/32. In addition to the full functionality of the ML4831/32 described above, the most prominent improvement is in the power factor correction section. The power factor correction part of the ML4833 is a step-up type PFC control circuit for peak current sensing. This form of circuit only requires voltage loop compensation, which is simpler than the ML4831/32 with average current control mode circuit. It consists of a voltage error amplifier, a current sense amplifier without compensation, an integrator, a comparator, and a logic control circuit.  In the boost type power conversion part, the correction of the power factor is performed by the current sensing resistor to output the sensing voltage and the current flowing through, and the duty ratio is adjusted by comparing the integrated voltage signal of the error amplifier with the voltage across the Rsense. The control timing of the duty ratio is as shown in figure 8. Considering that all of the high-performance electronic ballast integrated control chips of Micro-Linearity are packaged in 18-pin DIP or SOIC packages, the improvement of the device structure will inevitably bring about changes in the internal functional frame and external pin functions. Figure 8. PEC Link and Duty Cycle Control of ML4833 2.4 High-performance Electronic Ballast Built by ML4833Figure 9 shows the complete circuit diagram of a high-performance electronic ballast built by ML4833. The circuit is a typical AC/DC/AC structure: the RFI suppression filter circuit is added to the input terminal, the booster active power factor correction circuit is composed of AC/DC in the front stage, and the high-frequency inverter circuit is composed of DC/AC in the rear stage. A closed-loop is formed through T5, VD11, R23 and pin 8 of the control to make the system works stably. Figure 9. Complete Circuit Diagram of High-performance Eectronic Ballast Built with ML4833  Ⅲ FAQ1. What is the use of electronic ballast?An electronic ballast will convert power frequency to a very high frequency to initialize the gas discharge process in Fluorescent Lamps – by controlling the voltage across the lamp and current through the lamp. 2. What is the output voltage of an electronic ballast?This unit operates off the AC mains with a voltage of 230 Volts and voltages generated within the unit can reach 600 to 800 Volts. 3. What is inside an electronic ballast?Lighting ballasts generate an initial high voltage to start the arc that excites the gases in fluorescent and HID lamps and makes them shine. ... Lighting ballasts for fluorescent light bulbs and HID lamps made before 1980 may contain polychlorinated biphenyls (PCBs). 4. How do you make an electronic ballast for tube light?An electrical ballast is nothing but a simple high current, mains voltage inductor made by winding number of turns of copper wire over the laminated iron core. Basically, as we all know a fluorescent tube requires a high initial current thrust to ignite and make the electrons flow connect in between its end filaments. 5. How do you wire an electronic ballast?Connect the ballast to the power from the breaker panel by wiring the black wire from the breaker panel to the black wire on the ballast, using a wire nut. Connect the white wire from the breaker to the white wire from the ballast. 6. What's the difference between electronic and magnetic ballast?A magnetic ballast uses coiled wire and creates magnetic fields to transform voltage. ... An electronic ballast uses solid-state components to transform voltage. It also changes the frequency of the power from 60 HZ to 20,000 HZ or higher depending on the ballast. 7. How do you test an electronic ballast with a multimeter?Insert one probe of the multimeter into the wire connector holding the white wires together. Touch the remaining probe to the ends of the blue, red and yellow wires leading from the ballast. Depending on the ballast, you may have only red and blue wires. 8. Are electronic ballasts non-linear loads?Rectified input, switching power supplies and electronic lighting ballasts are the most common single-phase non-linear loads. 9. Which is not the advantage of electronic ballast?Electronic ballasts are more efficient and more compact in size and weight. They also provide the ability for continuous power adjustment in different settings. A disadvantage is that power fluctuations may cause a failure but this can be offset by adding a buffer capacitor. The operation of the ballasts generates heat. 10. Can you repair an electronic ballast?I eventually replaced the 2 switching transistors in this ballast as well and it worked. So the next time you have a problem with an electronic ballast from a fluorescent fitting open it and check before buying a new one. They can be expensive and more often than not they can be repaired. 

CatalogIntroductionⅠ CR123A Battery Basics    1.1 What is a CR2 Battery?    1.2 CR2 Battery Features and SpecificationsⅡ CR2 Lithium Battery Replacement    2.1 CR2 Batteries Cross Reference Chart    2.2 CR2 Battery Chemistry    2.3 Rechargeable CR2 Battery Replacement    2.4 15270 ChemistriesⅢ 11 Safety Precautions to Take While Using the CR2 Battery?Ⅳ Best CR2 Battery For Everyday ElectronicsⅤ FAQ    5.1  Are CR2 Batteries Rechargeable?    5.2  How Long does the CR2 Battery Last?    5.3 What Battery is Equivalent to the CR2 Battery?    5.4 Are CR2 Batteries the Same as CR123A?    5.5 Are C2 and CR2 Batteries the Same?    5.6 What Uses the CR2 Battery?    5.7 Where to Buy the CR2 Battery?    5.8 Is the Energizer 123 the Same as CR2?    5.9 What Warnings Should I Consider While Using Lithium Batteries Such As Lithium-Ion 15270?IntroductionThe CR2 battery, which is found in cameras,weapon-mounted lights, golf rangefinders, EDC flashlights, and security devices, is revered around the world. A standard cylindrical lithium battery is referred to as a CR2. This is the type of battery used in cameras (such as the CR2). This is due to their small size, which makes them ideal for electronic devices on the go. A CR2 lithium battery's shelf life is determined by its model and manufacturer. The Energizer brand, for example, puts more strain on its batteries than other brands, ensuring comparative endurance under extreme conditions.Ⅰ CR2 Battery Basics1.1 What is a CR2 Battery? CR2 battery and Pad replacementThe CR2 battery is a cylindrical lithium cell with measurements of 27mm x 15.6mm. In simple terms, the CR2 battery resembles a smaller version of a D Cell Battery, or, to put it another way, a can. These batteries can be used in a wide range of situations. They're commonly found in cameras that require a high-capacity lithium battery, as well as in a variety of industrial applications. Because of its numerous applications, this battery is extremely popular and, as a result, can be difficult to locate. Panasonic, Duracell, and Energizer are just a few of the big and small brands that make them. This article will provide you with all of the information you need to know about the CR2 battery.CR2 lithium battery1.2 CR2 Battery Features and SpecificationsThe CR2 battery has a nominal voltage of 3.0 volts and a cutoff voltage of 2.0 volts. It is a non-rechargeable lithium battery.The CR2 battery has a diameter of 15.6 mm and a height of 27 mm (1.063 inches). The CR2 battery typically has a capacity of 800 to 850 mAh, though this varies depending on the device's cutoff voltage and drain conditions (current strength, temperature, and similar).Many manufacturers use the standard CR2 label but add a letter or two to emphasize the brand, for example, when labeling their batteries.The 1CR2, DL-CR2, DLCR2, 5046LC, CR15H270, EL1CR2, KCR2, and other CR2 battery equivalents are commonly used.Manganese-dioxide lithium 15.6 x 27 mm non-rechargeable cylindrical batteries are the most common, with carbon-monofluoride lithium 15.6 x 27 mm non-rechargeable cylindrical batteries ('BR2 battery') being extremely rare.The shelf life of CR2 batteries varies depending on the model and brand, but it is typically 3+ years, with some brands having 10+ year shelf lives, making them ideal for standby or emergency devices (panic lights, EDC flashlights, medical equipment, etc.).CR2 batteries are fairly common, and most reputable brands offer them, so finding good ones from online shops and stores should not be a problem.CR2 Battery Nominal Voltage:3 VoltsCR2 Capacity (Lithium)≈  800 mAhCR2 Operating Temperature:-40°C – 60°C CR2 Height:27.0 mmCR2 Width (Diameter):15.60  mmCR2 Chemistry:Lithium Manganese Dioxide (Li/MnO2                                                  Technical Specifications Of The CR2 BatteryⅡ CR2 Lithium Battery Replacement2.1 CR2 Batteries Cross Reference ChartThe table below compares and contrasts the most important characteristics of several popular CR2 battery models.A nominal voltage of 3.0 volts, a cutoff voltage of 2.0 volts, and a very low self-discharge rate are all included in the chart.Also, while the 'official' operating temperature range is usually between -40°C and +70°C, it is important to remember that the performance of these batteries is temperature-dependent, and they perform best at room temperatures (20-25°C), with temperatures between -10°C and 50°C being avoided if at all possible.BatteryCapacityDischarge CurrentsDatasheetEnergizer CR2800 mAh, 100Ω @21°C down to 2.0V1000 mA max. continuous1200 mA, 3s/7s, @21°C, 760 cycles, down to 1.8V1800 mA, 3s/7s, @21°C, 400 cycles, down to 1.8V2500 mA max. pulseEnergizer CR2GP CR2800 mAh, @10 mA @23°C down to 1.8V10 mA continuous900 mA, 3s/27s, @23°C, 900 cycles, down to 1.6VGP CR2Panasonic CR2850 mAh20 mA continuous900 mA, 3s/27s, @20°C, 1000 cycles, down to 1.8VPanasonic CR2Varta CR2850 mAh, @20mA @20°C down to 2.0V20 mA continuous900 mA, 3s/27s, @25°C, 900 cycles, down to 1.5VVarta CR2As can be seen, the CR2 battery can easily deliver continuous currents of 10-20 mA.They are, however, exceptional high-discharge performers, with the best models capable of 900-1000 cycles (3 seconds ON, 27 seconds OFF) at 1.5-1.8 volts at room temperature.Some manufacturers (such as Energizer in this chart) stress their batteries even more by testing them with 3s/7s cycles; even under such conditions, Energizer CR2 batteries have an actual capacity of 760 mAh (down to 1.8V), which is very similar to the nominal capacity of 800 mAh (down to 2.0V).CR2 batteries are commonly used in high-drain devices such as cameras, range finders, compact EDC flashlights, and similar devices due to their performance.2.2 CR2 Battery ChemistryThe 3v CR2 battery that measures 27mm in length and 15.6mm in width (diameter). Lithium, alkaline, and Li-Ion batteries are used in its technology. Due to the general manganese oxide in its positive electrode and the spiral nature of its polar plate, it has a very high discharge rate.A Positive Temperature Coefficient (PTC) safety device is also built into the battery to limit current during short circuit conditions.Part NumberCR2Chemical SystemLithium / Manganese Dioxide (Li/MnO2)Typical Lithium content0.28 gramsNominal voltage (Open circuit voltage)3.0VTypical capacity800mAH (to 2.0volts, rated at 100 ohms at 21℃)Nominal capacity850mAHContinuous drain (standard discharge current)20mADimensions15.6 mm (max diameter) 27.0 mm (max height)Typical Weight11.0gTypical volume5.2 cm3Temperature rangeDischarge: -40℃ to 60℃ Storage: -40℃ to 75℃Maximum continuous discharge current1000 mA continuous (2500 mA pulse)Maximum reverse charge2 µA2.3 Rechargeable CR2 Battery ReplacementA few letters can be added to CR2 to emphasize the brand on the label in some cases. 1CR2, KCR2, DLCR2, and other equivalents are possible.The 15270 (or RCR2) is commonly referred to as the "rechargeable CR2." It's a rechargeable lithium-ion battery with a single prismatic cell and a one-parallel, one-series configuration.In comparison to primary CR2 models, it is slightly smaller (15 by 26.6mm). It can be charged multiple times without experiencing the "lazy battery effect."Other technical characteristics are:Voltage: 3.7V (nominal)Capacity nominal: 450 mAhStandard: 0.2C, continuous: 1C Constant discharge current0 to 45°C for charging; -20 to 60°C for dischargeApproximate cell weight: 20 g2.4 15270 ChemistriesThe most common chemistries are lithium manganese oxide (LiMn2O4) and lithium iron phosphate (LiFePO4).The battery on the 15270 is protected from overheating and overcharging by a built-in Battery Management System (BMS). As a result, a "protected" 15270 battery has a capacity of 400-600 mAh.The non-rechargeable CR2 and the 15270 are fully compatible thanks to a BMS that reduces the output voltage to 3.0V.Rechargeable 15270s have a reputation for lasting longer, providing better value for money, and outperforming their primary CR2 counterpart.Ⅲ 11 Safety Precautions to Take While Using the CR2 Battery?The CR2 battery is designed to be explosion-proof. However, due to the explosive nature of lithium metal and organic electrolytes within the product packaging, special instructions must be followed.1Do not light the batteries on fire. They are prone to catching fire.2Do not charge anything.3Avoid short-circuiting.4Do not attempt to disassemble.5Avoid exposing batteries to extreme temperatures, including direct sunlight. 30°C is the recommended storage temperature. Temperatures above 45°C should be avoided. Temperatures below -40°C also deform the plastic parts and may cause leakage.6Avoid storing the batteries in places with high humidity. To avoid self-discharge due to corrosion or a decrease in insulation, storage humidity should not exceed 70%.7KEEP BATTERIES OUT OF THE REACH OF CHILDREN. If a child swallows a battery, seek medical attention immediately.8Never mix old and new batteries or batteries from different series.9Do not use a wire to connect the negative and positive electrodes. Carry batteries separately from metallic objects such as necklaces, coins, and so on.10Never use an ultrasonic wave washer to clean the battery.11Always follow the instructions on the package for safe usage.Ⅳ Best CR2 Battery For Everyday ElectronicsThe Energizer CR2 lithium battery is ideal for use in commonplace electronics. It will always provide a consistent source of power to any device. The 800 mAh rating ensures that this battery can power a device for extended periods.These batteries are not only powerful but also very durable and have very long battery life. They also slowly discharge power to the device. Have the ability to retain power for up to ten years when stored. Perfect for cameras, CD players, and portable speakers.Ⅴ FAQ5.1 Are CR2 Batteries Rechargeable?Most CR2 batteries cannot be recharged, but some can. Typically, the label of a CR2 battery will indicate whether or not the battery is rechargeable. Rechargeable batteries are also referred to as "secondary batteries," whereas non-rechargeable or single-use CR2 batteries are referred to as "primary batteries." It is critical to determine whether a CR2 battery is a "primary battery" or a "secondary battery." Attempting to recharge a non-rechargeable battery (particularly a lithium battery) can result in a fire, explosion, or the destruction of your charger/device. Even when using a high-quality rechargeable battery, it is critical to use the proper charger to avoid problems. Using the wrong or incompatible charger for your CR2 battery can cause the battery to malfunction or stop working entirely.5.2 How Long does the CR2 Battery Last?The lifespan of a CR2 battery is heavily dependent on the battery's manufacturing quality and application. Assuming the battery is new and purchased from a reputable source, there is still a wide range of service life available depending on usage. A CR2 battery may last less than a month for a frequent application that requires a large amount of energy, such as a high lumen flashlight. With the right conditions, the service life of a more passive application, such as a home security alarm panel, can be over a year. Essentially, how long your CR2 battery will last is determined by what you require it to do.5.3 What Battery Is Equivalent to the CR2 Battery?DLCR2, KCR2, ECR2 1CR2, and 5046LC could be direct replacements and equivalents for the CR2 battery. All of these batteries are direct replacements for the CR2 battery and are classified as primary or non-rechargeable batteries. The 15270 and 15266 batteries are rechargeable or secondary versions of the CR2. These rechargeable CR2 batteries have a slightly lower capacity (lower mAh) than non-rechargeable versions, but they will still fit in and power the same devices. The non-rechargeable version has a longer single-use life, but the rechargeable CR2 battery saves you money over time.5.4 Are CR2 Batteries the Same as CR123A?The CR2 battery is not interchangeable with the CR123A battery. Because the CR2 battery is slightly shorter than the CR123A battery, it will not fit in the majority of applications that require a CR123A battery. Furthermore, the CR123A battery will deliver approximately 50% more output than the CR2 battery, implying that even if you were able to seat a CR2 battery into a CR123A device, it would not be able to deliver the full power required, and your device would either function poorly or not at all. These batteries do have some similarities, such as the fact that they are both made of lithium manganese dioxide and are both 3-volt batteries.5.5 Are C2 and CR2 Batteries the same?The CR2 battery is not commonly referred to as a C2, but some small manufacturers do sell batteries labeled C2 that are identical to the CR2. The CR2 battery is typically designated by the majority of major manufacturers. In addition, certain retail packaging for C cell batteries may cause some confusion. Some retail packs of two C batteries may have C 2 written on the top of the packaging. This does not imply that it is the same as a C2 (CR2) battery, but rather that there are two C cell batteries in the pack.5.6 What Uses the CR2 Battery?Military, industrial, medical, and consumer applications are all possible with the CR2 battery. The CR2 battery is used in weapon lights,  laser designators, optics, laser rangefinders, and communications devices in the military. Alarm batteries and power for various instruments are medical applications for the CR2 battery. Lights, alarms, cameras, and memory backup applications are just a few examples of industrial and consumer uses.5.7 Where to buy the CR2 Battery?CR2 batteries are extremely popular and common. This means that these batteries are made by a wide range of manufacturers and sold by a wide range of retailers. It is important to remember that not all CR2 batteries are created equal, and not all retailers are equally committed to quality. To avoid low-quality or, worse, counterfeit batteries, it is critical to purchase your batteries from a highly reputable retailer that sells only the highest quality brands.5.8  Is the Energizer 123 the Same as CR2?No, it isn't.The Energizer 123 (or CR123) battery is 34.5mm long, while the CR2 is only 27mm long. As a result, even though both claim a voltage of 3V, the CR123 cannot be used in place of the CR2.5.9 What Warnings Should I Consider While Using Lithium Batteries Such As Lithium-Ion 15270?Before the first use, fully charge the battery.Charge the battery frequently and with high-quality chargers. When charging, Do not leave it unattended.Avoid storing your Li-ion battery fully charged for extended periods.Keep it cool and dry, away from heat.Insert a Li-ion battery gently. Use no force.