The Kynix Blog - General electronic semiconductor

Schematic Diagrams CLC П-Filter 1. Working Principle a. When the positive pulse is input, C1 is charged first, the charging current is ic1, and meanwhile, reaching the peak voltage of pulse. The inductor L also has a linearly increasing current, and the magnetic energy is stored in L. With the increase of the current, more and more magnetic energy is stored, and the capacitor C2 is charged with voltage through inductor L (the charge current is ic2), the voltage of C2 is basically equal to the voltage on C1, in addition, the current IRL in load RL is also supplied by input pulse. b. When the input positive pulse disappearing, the current of the load RL is supplied by two channels: one is -ic2 provided by the C2 discharge, the other is converted from the magnetic energy stored by the inductor L, in other words, L connects with C1 to provide current -ic1. The current in the loaded RL is equal to the sum of the discharge currents of the two capacitors, that is IL=-(ic2+ ic1). c. For DC, C1 and C2 in CLC filter are equivalent to open circuit, and the inductance of inductor L to DC component is zero, which is equivalent to short circuit, so DC component can pass through inductor L1 smoothly. d. For AC: capacitors have a large capacity equivalent to short circuit, while inductors are sensitive to various sinusoidal waves, so AC components can not be removed or fewer passed. 2. Advantages High output DC voltage, sometimes the highest peak voltage can reach the rectangular wave. It is suitable for large load current, the output voltage pulsation is small. 3. Disadvantages It is used in the power supply without voltage regulator, and its load capacity is poor. 4. Application CLC filter is usually used in switching power supply of pulse-amplitude modulation. The larger the capacitance and inductance, the better the filtering. DLC Filiter 1. Working Principle a. When the secondary winding of the transformer is up positive and down negative, because the output voltage of the secondary winding of the transformer is positive and negative alternating rectangular wave, so the negative half cycle is removed from the D1 rectifier, the positive half cycle passes through the D1 rectifier, the magnetic energy is stored when current flowing through the inductance L. This current is partly charged for C1, and another is for load RL, at the same time, D2 off. b. When the inputting positive pulse disappears, the self-inductance voltage generated by the secondary winding of the transformer is up negative and down positive, so the rectifier D1 cut off. The filter has no input voltage, and the current supply of the load RL consists of two parts. One is the magnetic energy stored in the inductor converted to electric energy, the current direction is the same as the original current, and forms the circuit current iL through the fly-wheel diode D2; the other is -ic1 provides by the provided by C1 discharge. 2. The output DC voltage of the DLC filter is the average of the input rectangular wave value. 3. DLC filter is usually used in the pulse-width switching power supply. The output of the DLC needs a parallel resistor to the ground, commonly called "release resistor", in general, 30-50mA current is enough. CRC П-Filiter 1. Working Principle a. The output voltage of the rectifier is filtered by C1 capacitor at first, filtering out most of the AC components. And the voltage after C1 is added to the RC filter circuit composed of RL and C2, then the AC component is further filtered by capacitor C2. b. There is almost no inductance in the small capacitor C1, also its capacitive reactance is very small, so the high frequency interference component is easily filtered to the ground, that is to say, the filter effect of high frequency AC interference is better. c. The capacitance capacity is large (C2>C1), the low-frequency AC component flows through C2, so the effect of low-frequency AC interference filtering is better. d. The resistor has voltage drop and power loss effect on AC and DC, so CRC is only used for low load current. Product Recommendation KY53-ZJYS51R5-4PT-01 KY53-CM3032V201R-00 KY53-B39871B3762Z810

 The heat sink has a thermal conductor that carries heat away from the device into fins that provide a large surface area for the heat to dissipate throughout the rest of the components, thus cooling both the heat sink and processor. Both a heat sink and a radiator require airflow and, therefore, both have fans built-in. At present, the main failure form of electronic equipment is thermal failure. According to statistics, 55% of failure of electronic equipment is caused by temperature exceeding the rated value. With the increase of temperature, the failure rate of electronic equipment increases exponentially. Therefore, the thermal design of power devices is most important in the structural design of electronic equipment, which directly determines the success of the products. Good thermal design is the basis for the stable and reliable operation of the equipment. Electronics Thermal Heatsink Design Tutorial CatalogI. Main Parameters of Thermal PropertiesII. Thermal Design of Power DeviceIII. Heat Dissipation CalculationIV. Calculation ExampleV. Selection of RadiatorVI. ConclusionFAQ I. Main Parameters of Thermal Properties The thermal stress of the power device can come from the inside of the device or from the outside of the device. If the heat dissipation capacity of the device is limited, the consumption of power will lead to the rise of temperature and junction temperature in the active region of the chip inside the device, reducing the reliability of the device lower and making the device unable to work safely. The main parameters to characterize the thermal capacity of power devices are junction temperature and thermal resistance. The active region of the device can be the PN junction region of the junction device (such as a transistor), the channel region of the field-effect device, the diffused resistor, or the thin film resistance of the integrated circuit, and so on.  When the junction temperature Tj is higher than the ambient temperature Ta, the heat through the temperature difference to form a diffusive heat flow, which is emitted from the chip through the tube shell, and the heat emitted increases with the increase of the temperature difference (Tj-Ta).  In order to ensure that the device can work properly for a long time, an allowable maximum junction temperature Tj max has been made. Tj max is determined by chip materials, packaging materials, and reliability of devices. The heat dissipation ability of power devices is usually characterized by thermal resistance, called Rt. The larger the thermal resistance is, the worse the heat dissipation ability is. Thermal resistance is also divided into internal thermal resistance and external thermal resistance.  Internal thermal resistance is the inherent thermal resistance of the device itself, which is related to the thermal conductivity, thickness, and cross-sectional area of the tube core, shell material, and processing technology, while external thermal resistance is related to the form of tube package. Generally speaking, the larger the shell area, the smaller the external thermal resistance. The external thermal resistance of the metal shell is obviously lower than that of the plastic. When the power consumption reaches a certain level, the junction temperature of the device goes up and the reliability of the system decreases. In order to improve the reliability, the thermal design of the power device should be carried out.  II. Thermal Design of Power Device The thermal design of the power device is mainly to prevent thermal failure caused by overheating or alternating temperature. It can be divided into the thermal design of the internal chip, thermal design of the package, thermal design of the tube, and thermal design in practical use. For general power devices, only the thermal design of the device's interior, package, and the tube should be considered. But when the power consumption is high, the appropriate radiator should be installed, through which the heat can be effectively dissipated to ensure the device works normally and reliably within the safe junction temperature.   III. Heat Dissipation CalculationThe most commonly used heat dissipation method is to install the power device on the radiator, using the radiator to disperse the heat into the surrounding, if necessary, to add the fan to strengthen the heat dissipation with a certain wind speed.  Flow cold water cooling plate is also used in some large power devices, which has a better heat dissipation effect. Heat dissipation calculation is to determine the appropriate heat dissipation measures and radiators through calculation under certain working conditions. There is a certain thermal resistance in the heat transfer process. The thermal resistance from the core of the device to the bottom is Rjc, between the bottom and the radiator is Rcs, a radiator that spreads heat into the surrounding is Rsa, the total resistance is Rja=Rjc+Rcs+Rsa.  If the maximum power loss of the device is Pd, and the permitted junction temperature of the device is Tj, ambient temperature is Ta, the reasonable total thermal resistance Rja can be obtained by the following formula.Rja ≤(Tj-Ta)/Pd The thermal resistance of the maximum allowable Rsa is: Rsa ≤(Tj-Ta)/Pd-(Rjc+Rcs) For design consideration, Tj is generally set to 125℃, Ta=40℃ ~ 60℃ generally used in the case of bad ambient temperature. The size of Rjc depends on the size of the core and the package structure, which can be found from the parameter list. Rcs size depends on the installation technology and device packaging. If the device adopts heat conducting grease or heat transfer pad, installing with the radiator, the typical value of Rcs is 0. 1 ℃/W / ~ 0. 2 ℃/W; If the bottom surface of the device is not insulated and additional mica insulation is required, the Rcs can reach 1 ℃/W. Pd is the maximum power loss calculated according to the working conditions of different devices. In this way, Rsa can be calculated to select an appropriate radiator. IV. Calculation ExampleA power operational amplifier PA02 as low-frequency power amplifier, the device is 8-pin and TO-3 metal shell package. The operating conditions are as follows: the operating voltage Vs is 18 V, the load impedance RL is 4Ω, the ambient temperature is 40 ℃, and the natural cooling is adopted. According to the data of PA02: the typical value of static current Iq is 27mA, the maximum value is 40mA, and the typical value of Rjc (from tube core to shell) is 2.4 ℃/W, and the maximum value is 2.6 ℃/W. The power consumption of the device is Pd=Pdq+ Pdout(Pdq is the internal power consumption and Pdout is the output power consumption). The calculation is as follows: Pdq=Iq(Vs+|-Vs|)  Pdout=Vs2/(4RL)  Iq=37mA                                                                                 Pd=Iq(Vs+|-Vs|)＋Vs2/(4 RL)                                                                                     =0.037×(18+18)＋182/(4×4)                                                                                     =21.6 W Radiator thermal resistance: Rsa ≤(Tj-Ta)/Pd-(Rjc+Rcs) Tj=125℃, Ta=40℃, Rjc=2.6℃/W, Rcs=0.2℃/W(PA02 installed directly on radiator with heat conductive grease in the middle) Substitute the above data into the formula to get Rsa≤ (125-40)/21.6-(2.6+0.2)≤ 1.135℃/W The thermal resistance HSO4 in natural convection is 0. 95 ℃/W, which can meet the requirement of heat dissipation. V. Selection of RadiatorRadiators are generally standard parts, but also provide customization. The surface of the radiator is treated by electrophoretic coating or black oxygen polarization, which aims to improve heat dissipation and insulation performance.  In natural cooling can be increased by 10%~15%, in ventilation cooling can be increased by 3%, and electrophoretic coating can withstand pressure 500V~800V. The heat resistance of different types of radiators in different heat dissipation conditions is given by the radiator manufacturers. The radiator is used to control the temperature of the power device, especially the junction temperature (Tj), making is lower than the safe junction temperature of the power device, so as to improve the reliability of the power device.  Conventional radiators tend to be standardized, serialized, universal, and new products develop towards low thermal resistance, multifunction, small volume, lightweight, and suitable for automatic production and installation.  The internal thermal resistance of various power devices is different and the difference of contact surface and installation torque will lead to the thermal-resistance difference between the contracts.  The main factor of selecting a radiator is the heat resistance Rtf. Under different environmental conditions, the heat dissipation of power devices is also different. Therefore, environmental factors, the matching between radiator and power device, and the volume and quality of the whole electronic equipment should be taken into account in selecting the appropriate radiator. First of all, according to the performance parameters and environmental parameters of the power device in normal operation, calculate whether the junction temperature of the power device is within the safe condition, determine whether it is necessary to install the radiator, and calculate the corresponding thermal resistance of the radiator if it needs to be installed.  The junction temperature of the power device is recalculated to determine whether the junction temperature of the power device is within the range of safe junction temperature, so as to judge whether the selected radiator meets the requirements. For the radiator that meets the requirements, the optimum design should be carried out according to the actual engineering requirements.   VI. ConclusionThrough the analysis and calculation of the heating principle of the power device, it can guide the design of the heat dissipation mode and the selection of the radiator, ensure the power device work in the safe temperature range, reduce the quality problem, and improve the reliability of the electronic products.  The reliability of electronic equipment is also related to the components, structure, assembly, process, processing quality, and so on. In practical engineering applications, feedback data should be obtained through various tests to perfect the design and further improve the reliability of electronic equipment. FAQ 1. What is a heat sink and how does it work?A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature. 2. What is a heat sink used for?A heat sink is a component that increases the heat flow away from a hot device. It accomplishes this task by increasing the device's working surface area and the amount of low-temperature fluid that moves across its enlarged surface area. 3. Does a heat sink need a fan?Most heatsinks have denser fins, which requires a fan to be mounted directly on the cooler. If your heatsink has heat pipes (copper tubes running through the fins), then it's most likely designed to be used with a fan. It's simple to test whether or not a heatsink can safely be run without a fan on it. 4. What material dissipates heat the best?Thermal conductivity is the measure of a metal's ability to conduct heat. What this means is that that the metal acts to cool temperatures, through a process of dissipation. The metals with the highest thermal conductivity are copper and aluminium. The lowest are steel and bronze. 5. How many types of heat sinks are there?The Two Major Heat Sink Categories. All heat sinks can be broken down into two major categories… active and passive. 6. What is the difference between active and passive heat sinks?An active heat sink has a fan attached to it, to actively pull heat away from the heat sink and chip that lies underneath it. A passive heat sink is just a heat sink, a piece of flat metal with fins on top that directs heat away from the chip set it is installed on. 7. Which is better heat sink or fan?Generally though, with good airflow provided by the fan heatsinks can often be a lot smaller. The only benefit to a heatsink-only arrangement is less noise. ... Out of preference you want the heatsink fins to be standing upwards so that hot air can immediately rise off of it and cool air be pulled in. 8. What is the difference between a heatsink and a CPU fan?The heatsink draws the heat away from the CPU, and the fan ensures a steady stream of air for the heatsink to pass the heat to. However, there is more to selecting a heatsink and fan than just looking for a good price or one that looks cool. 9. What is the difference between a heat sink and a heat pipe?Vapor chambers are most often used to spread heat to a local heat sink, whereas heat pipes are generally better for moving heat to a remote sink. ... If you need a heat sink that's minimally 10 times, but usually closer to 20 times, the area of the heat source, consider vapor chambers. 10. How is a heat sink attached to an electrical component?A heat sink is a mechanical component that is attached to an electrical component for the sake of transferring heat from the electrical component into the surrounding environment. This environment is most commonly air, but it can also be other fluids, such as water or coolant. 

Many engineers who have not used the switching power supply may have some worry about it, such as the PCB layout, the parameter and type selection of components, and so on. In fact, as long as you understand the basic principle, the use of switching power supply design is very convenient. In today's article, we will introduce you to some basic knowledge of switch-mode power supply, along with some experience sharing when using the switch-mode power supply. SMPS Tutorial: Switch Mode Power Supplies and Power Conversion  Catalog I. What is the Switch Mode Power SupplyII. How to Debug the Switching Power Supply Circuit?III. What Needs to Be Grounded?3.1 Definition of Grounding3.2 Grounding Mode3.3 How is the Signal of the Single Board Grounded?3.4 How Do the Single Board Interface Devices   Grounding?3.5 How to Grounding the Shield Layer?IV. Introduction of Signal Backflow and TranspartitionV. Should Analog Separate from the Digital , and How?FAQ I. What is the Switch Mode Power Supply  A switch-mode power supply usually consists of a controller and an output part. Some controllers integrate MOSFET into the chip, which makes it easier to use and simplify the PCB design, but the flexibility of components is weakened. The switching controller is actually a closed-loop feedback control system, so there is a sampling circuit of output-voltage feedback and a feedback-loop control circuit. Therefore, this part of the design is to ensure an accurate sampling circuit and to control the feedback depth, because if the feedback loop response is too slow, it will have a great impact on the transient response-ability. The output parts include output capacitance, output inductor, MOSFET, and so on. The selection of these devices is basically to balance the performance need and cost. For example, the high switching frequency can use small inductance (which means small package and low cost), but a high switching frequency will increase interference and the switching loss of MOSFET, result in reducing efficiency and increasing cost. Lower switching frequency has the opposite effect. The selection of Rds_on parameters of MOSFET and the ESR for output capacitance is also very important. ESR is small can reduce output ripple, but the cost of the capacitor will increase. And It is important to note that switching power controllers can not be well driven with too much MOSFET. In general, suppliers of switching power supply controllers will provide specific formulas and usage options for engineers. Figure. 1 Switch Mode Power Supply Circuit   II. How to Debug the Switching Power Supply Circuit? （1）The output of the power supply circuit is installed to the board through the low resistance and high power resistor, so that the power circuit can be debugged first before welding resistance, avoiding the influence of the latter circuit.  （2）The switching controller is a closed-loop system. If the output deterioration beyond the range that the closed-loop can control, the switching power supply will work improperly. This situation requires careful examination of feedback and sampling circuits. Especially, if the output capacitance with a large ESR, lots of ripple of power supply will be produced, which will also affect the operation of switching power supply.  III. What Needs to Be Grounded? At the very start, the introduction of grounding technology is a protective measure to prevent lightning strikes on electric power or electronic equipment. The purpose is to introduce lightning current through the lightning rod to the earth to protect buildings. And meanwhile, grounding is also an effective way to protect personal safety.  When the phase line touches the shell of the equipment causing by some reason (such as poor insulation of the wire, line aging, etc.), there will be a dangerous voltage in the shell of the equipment. Having grounding, the resulting fault current will flow to the earth, thus it plays a protective role.  For example, in communication systems, the interconnection of signals between a large number of devices requires each device to have a point as a reference, and with the complication of electronic equipment, the signal frequency is becoming higher and higher, therefore, grounding design as special attention paid to the electromagnetic compatibility problems such as mutual interference between signals.  In addition, improper grounding will seriously affect the reliability and stability of system operation. Recently, the concept of "grounding" has also been introduced into high-speed signal backflow technology.  3.1  Definition of GroundingIn the modern concept of grounding, for line engineers, the term usually means "reference point for line voltage"; for system designers, it is often a cabinet or frame; for electrical engineers, it is a green and safe ground line or a wire connected to the earth. A more general definition is that "grounding is the low impedance channel which the current returns its source." Noting that the points are "low impedance" and "channel".  3.2  Grounding ModeThere are many ways of grounding: single-point grounding, multi-point grounding, and mixed type of grounding. Single-point grounding is divided into a series of single-point grounding and parallel single-point grounding. In general, single-point grounding is used in simple circuits, and low frequency (f10MHz) circuits use multipoint grounding or multilayer (complete a ground plane layer).  3.3   How is the Signal of the Single Board Grounded?For the general device, the near ground is the best. After adopting the multilayer design with a complete ground plane, the grounding of the general signal is very easy. The basic principle is to ensure the continuity of the line, reduce the number of holes, approach the ground plane or the power plane, etc. 3.4  How Do the Single Board Interface Devices  Grounding?Some veneers will have external input-output interfaces, such as serial port connectors, RJ45 connectors, etc. If their grounding is not well designed, it will also affect normal operation, such as error codes, packet loss, etc. And it will become an external source of electromagnetic interference sending the noise out. In general, a single interface grounding will be made, and the signal is connected by a thin wire connection, string 0 ohms, or small resistance. Thin lines can be used to block signal ground noise. At the same time, the interface and the interface power filter should also be considered seriously.  3.5  How to Grounding the Shield Layer? The shielding layer of cables is connected to the interface grounding instead of the signal grounding, because there are various noises on the signal grounding. If the shield layer is connected to the signal ground, the noise voltage will drive the common-mode current to interfere outward along the shield layer. Therefore, the poorly designed cable is generally the maximum noise output source of electromagnetic interference. Of course, the interface ground should keep clean. IV. Introduction of Signal Backflow and TranspartitionFor an electronic signal, it needs to find a way with the lowest impedance to return current to the ground, so how to deal with the signal backflow becomes very important. First, according to the formula, we can know that the radiation intensity is proportional to the area of the loop. Specifically, the longer the path the return is, the bigger the ring is formed, and the greater the external radiation interference is, thus the power-circuit flow back and signal loop area should as small as possible when design PCB. Second, for a high-speed signal, providing a good signal backflow can guarantee its signal quality. Because the characteristic impedance of the transmission line on the PCB is generally calculated by reference to the ground (or power layer), if there is a continuous ground plane near the high-speed line, the impedance of this line can be kept continuous, and if there is no ground reference near the section line, the impedance will change and the signal will be affected as well. Therefore, the high-speed lines should be distributed to the layer near the ground plane, or they should be walked in parallel next to each other, to shield interference and provide backflow nearly.  Third, do not divide wires when having power supply in wiring way, this is because the signal backflow path across different power layers will be longer, and be vulnerable to interference. For low-speed signals, it is not strictly required that, because the resulting interference signal can not be concerned about. But for high-speed signals should be checked carefully, do not cross as far as possible, you can adjust the power part of the wire. (this is for multiple power supplies on multilayer boards).  V. Should Analog Separate from the Digital , and How? Whether analog signal or digital signal should return to the ground. Because the digital signal changes quickly and the noise caused by the digital signal will be very large, if analog and digital mixing, the noise will affect the analog signal.  In general, the grounding of analog and digital processing must be separated, then connected by a thin line, or a single point. The general idea is to try to block the noise from the digital ground to the analog ground. But it is not a very strict requirement that analog and digital ground must be separated, if the analog section near the digital ground is still very clean, they can be combined. FAQ 1. What are the 3 types of power supply?There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages. 2. What is meant by switch mode power supply?A switch mode power supply is a power converter that utilises switching devices such as MOSFETs that continuously turn on and off at high frequency; and energy storage devices such as the capacitors and inductors to supply power during the non-conduction state of the switching device. 3.What are the advantages and disadvantages of switch mode power supply?Advantages & disadvantages of switch mode power supply (SMPS)a. The switch mode power supply has a smaller in size.b. The SMPS has light weight.c. It has a better power efficiency typically 60 to 70 percent.d. It has a strong anti interference.e. SMPS has wide output range.f. Low heat generation in SMPS. 4. What is a DC switching power supply?A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor. 5. What is the difference between a switching power supply and a linear power supply?Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges. 6. Do I need a switching power supply?The switching power supply implies higher efficiency due to the high switching frequency, enabling it to use a smaller, less-costly high-frequency transformer as well as lighter, less-costly filter components. Switching power supplies contain more overall components, therefore are usually more expensive. 7. Is a switching power supply regulated?A switch mode power supply regulates an output voltage with pulse width modulation (PWM). This process creates high-frequency noise but it provides a high-efficiency rating in a small form factor. ... The low DC voltage is finally converted into a steady DC output with another set of diodes, capacitors, and inductors. 8. How do I know if my power supply is regulated?You can generally stick one probe into the middle of the connector, and hold the other against the outside. With a few exceptions, the middle is positive, so use the red lead there, and use the black lead on the outside shell. Regulated supplies, without any load, should measure very close to the target voltage of 12v. 9. Can I use a switching power supply to drive a DC motor?A simple unregulated analog power supply may be easier and be able to supply the large starting under load current more that the switching one. DC motors are not too fussy about the supply, and will usually run quite well on unfiltered DC. 10. Are switch mode power supplies any good?Switch mode power supplies, SMPS provide improved efficiency & space saving over traditional linear supplies, but care has to be taken to ensure noise on the output is low. Switch mode power supplies are widely used because of the advantages they offer in terms of size, weight, cost, efficiency and overall performance. You May Also LikeSwitching Power Supply Guide: Protection CircuitSwitching Power Supply Tutorial: 4V～16VSwitched Mode Power Supply Tutorial: Principles & Functions of SMPS Circuits

With the development of science and technology, electronic products are changing with each passing day. Also, electronic assembly technology is facing challenges. Following the development of electronic technology, people work harder to make innovations in electronic assembly technology.  And in this context, a flexible circuit board invented used which made of the thin-and-flexible polymer film. It can complete the application of surface mounting technology and bend without affecting the normal circuit operation.  Clear Flexible Printed Circuit Catalog I. Brief IntroductionII. Five Main Materials for Flexible Circuit Board2.1 Insulating Firm2.2 Bonding Sheet2.3 Copper Foil2.4 Overburden2.5 Reinforcement PlateFAQ I. Brief Introduction Today's flexible electrons are all made of SMT technology, so they are thin and exquisite with insulation thickness of fewer than 25 μm. It can be bent arbitrarily and rolled into a cylinder. And it makes full use of three-dimensional volume. It breaks the stereotype of the traditional area of use and creates the ability to make full use of the shape of the volume, which can significantly enhance the effective density of use in the length of the conductor currently routinely used per unit area, forming a high-density assembly. In recent years, flexible circuit technology has been applied in various fields, such as radio communication, computer, and automobile electronic equipment. Unlike in the past, flexible circuits have been used as substitutes for rigid cables, and they have been used as substitutes for rigid circuits and printed circuit boards (PCB) in applications where thin or three-dimensional circuits are required. In order to meet the requirements of rigid and flexible applications, it is combined flexible circuit technology in the rigid circuit board, making flexible circuit board used widely. The functions of the flexible circuit board can be divided into four categories, including the lead line, printed circuit, connector, and IntegraTIon of FuncTIon, which covers the computer, Computer peripheral auxiliary system, civil electrical appliances and cars, and other areas. For different applications, the material of the flexible circuit board should select carefully. And the followings are some rules of the five main materials of the flexible circuit board.  II. Five Main Materials for Flexible Circuit Board 2.1 Insulating FirmThe insulating film is flexible and can be used as the insulation carrier of the circuit board to form the basic layer of the circuit. When selecting the flexible dielectric film, the heat resistance, overlay, thickness, mechanical properties and electrical properties of the material should be tested.  Insulation film is usually available on the market, the most common is polyimide and polyester materials. Of all the flexible circuit manufacturers in the United States, nearly 80% use polyimide film as the material for flexible circuits, and about 20% use polyester film. Because polyimide material is nonflammable, stable geometry, high anti-tear, and able to withstand high temperature during welding. 2.2 Bonding Sheet It is made up of two insulating films coated with adhesive, the ability is gluing the film to the foil, and the film to the film in the flexible circuit, In order to provide mechanical support and eliminate stress during insertion of components and connectors. It also can provide protection and electrical insulation. Different types of adhesive sheets can be used for different film substrates, such as polyester bonding sheets and polyimide bonding sheets are different, for example, the polyimide substrate has epoxy resin and acrylic acid. 2.3 Copper FoilCopper foil is a conductor layer that is coated on the insulating substrate and then selectively etched to form a conductive line. The vast majority of this copper foil is rolled copper foil or electrolytic copper foil. The ductility and bending resistance of the rolled copper foil is better than that of the electrolytic copper foil.  The elongation of the rolled copper foil is 20%~45% and the electrolytic copper foil is 4%~40%. The commonly used thickness of copper foil is 35um (1oz), also they have 18um (O.5oz), 70um (2oz), or even 105um (30z). According to different applications, we have to choose different forms of copper foil.  If only to replace wires and connectors, and to reduce manufacturing time and cost, the best choice is electrolytic copper foil. The electrolytic copper foil will increase the weight of copper to level the load capacity of the current, thus obtaining the suitable width of the copper sheet. 2.4 OverburdenThe brand, Novaclad, created by Sheldahl, applies the vacuum metal spraying technology which is a patent. It is a technology that applying a thin layer of pure copper to the surface of a polyimide film, then electroplating into a specific thickness to form the substrate of Novaclad. The base material is used in Novaflex, a flexible circuit without adhesive. After all the circuits have been made, a layer of Novaflex insulation is applied. The Novaflex is designed to work under harsh conditions, and Novaflex without adhesive provides better flexibility, chemical resistance, high-temperature properties, and maximum heat dissipation properties. 2.5 Reinforcement PlateThe reinforced plate to the local position of the flexible plate plays the role of super supporting and strengthening the flexible film substrate, which is convenient for the connection, fixation, or other functions of the PCB. According to different needs, the reinforcement board materials commonly use polyester, polyimide sheet, epoxy fiberglass cloth plate, phenolic-aldehyde paper board, steel plate, aluminum plate, etc.  FAQ 1.What is a flexible circuit board?A flexible printed circuit board features a combination of several printed circuits as well as components that are positioned on a flexible substrate. These circuit boards are also known as flex circuit boards, flex PCBs, flex circuits, or flexible printed circuits. 2. What is flex circuit used for?Flex circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring. A common application of flex circuits is in computer keyboards; most keyboards use flex circuits for the switch matrix. 3. What are flexible circuit boards made of?Flexible circuits are thin, light-weight electrical circuits that conform to small spaces and contoured shapes. They consist of conductive strips of metal, usually copper, encapsulated with an insulating dielectric material made of polyimide or a solder mask. 4. Where are flexible PCBS used?a. Automobiles.b. Consumer electronics including smartphones, SLR cameras and camcorders,c. Medical systems and devices such as heart monitors, pacemakers and the bionic knee.d. Motion systems.e. GPS systems.f. Aerospace and avionics systems. 5. When was the first flex printed circuit made?From early applications during World War II to the present, growth and proliferation for flex circuits and flexible printed circuit boards continues exponentially. A flexible circuit in its purest form is a vast array of conductors bonded to a thin dielectric film. 6. What are the advantages and disadvantages of flexible circuit boards?The advantages of the flexible circuit board are mainly high assembly density, which can save the connection of redundant cables, in addition, it has good bendability, high flexibility, small size, simple structure, and convenient installation.Disadvantages of flexible circuit boards: 1. High initial cost 2. Difficult to change and repair 3. Size limited 4. Improper operation and easy damage, etc. 7. What do flexible circuit boards and rigid circuit boards mean?a.  Flexible circuit boards are used more in digital products. The difference between it and the rigid circuit board is that the substrate of the circuit board is different. As the name implies, the board can be bent and softer.b. "Multilayer board" and "double-sided board" mainly refer to the number of sides of wiring on the circuit board. Above 2 layers are multi-layer boards.From the perspective of the process flow, the multilayer board needs to be processed by the inner layer map, and the outer layer can be processed after being pressed. The processing flow of the outer layer is basically the same as the processing flow of the double-sided board. 8. What is the temperature resistance of fpc flexible circuit boards?FPC flexible circuit board can withstand high temperature of 280 degrees, about 1 hour. However, the recommended temperature for normal use is not less than -20 and not higher than 80. 9. With flexible circuit boards, why pcb hard printed circuit boards are still not eliminated?For PCBs that need to use plug-in components, only rigid boards can be used, which is what you call rigid boards; for many PCBs with stress requirements, only rigid boards can be used. The cost of flexible boards is currently much higher than rigid boards, more than doubled. And the straight-through rate of rigid boards is higher than that of flexible boards 10.Classification of flexible circuit boards?According to the combination of base material and copper foil, flexible circuit boards can be divided into two types: flexible boards with glue and flexible boards without glue. Among them, the price of the glueless flexible board is much higher than that of the glued flexible board, but its flexibility, the bonding force of the copper foil and the substrate, and the flatness of the pad are also better than the glued flexible board. You May Also LikeSwitching Power Supply Tutorial: 4V～16VWhat is A MCU’s internal Structure: Single Chip Micro-ComputerPCB Wring Tutorial: A/D converterMonitoring Technology in Communication Power Supply: Application GuideDIY CommunityDIY Flxible Printed CircuitsMake Flexible Circuit Boards Using A 3D Printer

  This technical article will introduce 10 common problems you might encounter with when apply inverter in your project.     What is Inverter? This video explains what inverter is and which inverter you need in your project.   1. Leakage Circuit Breakers are Prone to Tripping When Using Variable-Frequency Drive. The output waveform of the ac drive contains higher harmonic, and the leakage current will be generated between the motor and the cable between the inverter and the motor, what’s more, the leakage current is much larger than that of the motor driven by the power frequency.   The leakage current at the output side of the inverter is about three times that of the power frequency operation, in addition, adding the leakage current of the motor. The operation current of the selected leakage protector should be 10 times greater than that of the leakage current at the power frequency.    2. The Temperature Rise of the Motor Higher Than That of the Power Frequency When the AC Drive is Used. The output voltage waveform of the inverter is not sinusoid wave, but distorted wave, the motor current under rating torque is about 10% more than the power frequency, so the temperature rise is slightly higher than the power frequency.   3. How to Adjust Torque Boost. A. When the torque boost setting is too high and the load is very small, the current will increase due to the magnetic flux saturation of the motor core, and the variable-frequency drive may run overcurrent protection. Therefore, in order to improve the motor efficiency, the setting should be reduced when the load is lightened.   B. For heavy load, the voltage drop loss caused by stator winding and motor cable can be compensated by increasing the torque-boost setting value.   4. Carrier Frequency and How to Adjust It. A. The output voltage of the SPWM converter is a series of pulses whose pulse frequency is equal to the carrier frequency.   B. In the current of the motor, there is a strong harmonic component of the carrier frequency, which will cause the oscillation of the iron core of the motor and emit noise. If the frequency of the noise is equal to the inherent oscillation frequency of the motor core, the noise will increase. In order to reduce it, the frequency inverter can adjust the carrier frequency in a certain range to avoid the resonance frequency of the noise.   C. Harmonic component of carrier frequency has strong radiation, which will cause electromagnetic interference to external electronic equipment.   D. From the point of view of improving the current waveform, the higher the carrier frequency, the smoother the current waveform. However, the electromagnetic interference to the outside is also stronger.   E. The higher the carrier frequency is, the less the motor noise is, but the greater the switching loss of power device is, the more serious the frequency converter is. The lower the carrier frequency, the greater the motor noise, and the switching loss of the inverter is lower too.   5. DC Brake (1) It is used to control the precise parking of some equipments, to avoid "crawling" at low speed, and to start the function at the time of shutdown.   (2) Since the frequency conversion speed control system always starts from the lowest frequency, if the motor starts with a certain speed, and the frequency converter does not set the speed tracking function, the overcurrent or overvoltage will appear.   6. Should the Rating Frequency of the Load Motor be the Same as That of the Motor? This function parameter:  the fundamental frequency   A. If the fundamental frequency is set below the rated frequency of the motor, the motor voltage will increase, and the output voltage will increase will lead to the increase of the magnetic flux of the motor, making the saturation of the flux, the distortion of the exciting current, and the occurrence of a very large peak current. As a result, the converter tripped because of overcurrent.   B. If the fundamental frequency is higher than the rated frequency of the motor, the voltage and load capacity of the motor will decrease.   Difference Compensation Depending on the magnitude of the load current, the output frequency of the ac drive (internal improvement, actual display constant) is appropriately increased to compensate for the increase in the rotational difference due to the increase in the load.   7. AVR Function When the power network voltage drops, the reference frequency is reduced automatically and the flux K*U/F is constant, so as to ensure the load capacity of the motor unchanged.   Kinds of Common Load: 1)Constant Torque Load Although the rotational speed is different, resistance torque load is basically constant. The output power is proportional to the rotational speed, like the belt conveyer.   2)Constant Power Load Although the rotational speed is different, load power is basically constant. The output torque is proportional to the rotational speed. Like a winding device, such as a thin film or sheet.   3)Square Load The resistance torque load is proportional to the square of the rotational speed. Such as fans and pumps.     8. Frequency Control of Several Special Motors (1) Wound Rotor Asynchronous Motor The rotor winding of a wound rotor asynchronous motor is a set of star-schema three-phase windings. The end points of the three-phase windings are connected to the three collector rings, through it to collect the brush and the external resistor (starting or adjusting speed).   After adopting the frequency converter to adjust the speed, the rotor winding does not need to connect the resistor, so the terminal of the three-phase winding can be connected directly with the wire.   (2) Magnetic Brake Motor It is composed of ordinary motor and magnetic brake. The motor and the magnetic brake are connected to the power supply at the same time, and the armature of the electromagnet is absorbed, which makes the motor rotor rotate freely.   After cutting off the power supply, the excitation winding of the brake powers off and the rotor stops quickly. The excitation winding circuit of the electromagnet should be connected to the input side of the frequency converter after adopting the frequency converter, and turned on at the same time as motor.   9. Capacity Selection of a Single Inverter with Multiple Motors.  A. Simultaneous Start-up The rated current of the inverter should be greater than the sum of the maximum operating current of several motors.   B. Starting Time in Turn The rated current of the converter shall be greater than the sum of the rated current of the motor other than the maximum motor plus the seven-times rated current of the maximum motor.     10. Interference Mode and Treatment of Inverter Propagation Mode 1) Radiatedradiated Interference  2) Conducted Interference   Anti-jamming Measures Interference signals propagating by radiation are weakened mainly by wiring and shielding the radioactive sources and the interfered lines.   For the interference signal propagating through the circuit, the filter, reactor or magnetic ring are added to the input and output side of the inverter.   The Specific Methods and Precautions are as Follows:   (1) Signal lines and power lines should be vertically crossed or slotted separately. (2) Do not use different metal wires to connect to each other. (3) Shielding tube (layer) should be reliably grounded and ensure continuous and reliable grounding across the whole length. (4) Twisted-pair shielded cables should be used in signal circuits. (5) Grounding contacts of the shield layer should away from the frequency converter as far as possible, and separated from the connecting location of the frequency converter. (6) The magnetic ring can be used on the input power line and output line of the inverter. The method is as follows: the input line goes around four times in the same direction and the output line around three times in the same direction with magnetic rings. When winding the wire, the magnetic rings should close the frequency converter as far as possible. 7) Shielding and other anti-interference measures, such as the temperature control of injection molding machine, can be taken for the equipment.   FAQ   1. What does an inverter do? Inverters are also called AC Drives, or VFD (variable frequency drive). They are electronic devices that can turn DC (Direct Current) to AC (Alternating Current). It is also responsible for controlling speed and torque for electric motors.   2. What is the purpose and function of an inverter? An inverter converts the DC electricity from sources such as batteries or fuel cells to AC electricity. The electricity can be at any required voltage; in particular it can operate AC equipment designed for mains operation, or rectified to produce DC at any desired voltage.   3. What is inverter and how it works? The first thing to keep in mind when it comes to enriching your understanding of the internal structure of an inverter device, is that the converter circuit converts alternating current (AC) coming from the power source into direct current (DC), and the inverter circuit changes the converted direct current (DC) back into alternating current (AC). They work as a set.    4. Does inverter really save electricity? An inverter is energy saving technology that eliminates wasted operation in air conditioners by efficiently controlling motor speed. ... Compared to non-inverter type air conditioners, air conditioners with inverters have less power loss and can save in energy.   5. What can you plug into an inverter? A power inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few.   6. How many hours can an inverter last? Usually, you can expect your inverter battery to last anywhere from 5 to 10 hours when it is fully charged. Most inverters show an estimated as soon as they start powering the appliances.   7. How many watts inverter do I need for home? Peak output is the wattage that an inverter can supply for short periods of time when the demand spikes, while continuous output is the limit for normal operation. If your devices draw a combined total of 600 watts, then you need to buy an inverter that has a continuous output rating of 600 watts   8. Is UPS and inverter same? The UPS is the electric device that has a rectifier for providing the backup power to the system whereas the inverter converts DC into AC. The main function of the UPS is to store the electric supply whereas the inverter converts the AC power into DC power.   9. Where should I install an inverter in my house? To install the inverter, place the inverter assembly on top of the main housing chassis in such a way that the inverter faces forward. Remember to remove power at the electricity board meter of the home.   10. What size inverter do I need to run a laptop? Volts (120) x Amps = Watts. For example if your DVD player draws 100 watts and your laptop another 100 watts, a minimum 300-watt inverter is recommended. If the item is motor driven, it requires additional start-up (surge) wattage (typically 2-3 times the continuous wattage required) to start the device.   11. What are the types of inverter? There are 3 major types of inverters - sine wave (sometimes referred to as a "true" or "pure" sine wave), modified sine wave (actually a modified square wave), and square wave.   12. How long will a 12V battery last with an inverter? For example: 12V 100Ah battery will be able to power 1000W inverter for ~30 minutes, 12V 200Ah battery will be able to power 2000W inverter for ~30 minutes, etc.   13. Is inverter An gate? An Inverter is a Logic Gate that has only one Input, it outputs the opposite Logic State of its Input. The Inverter is also called NOT Gate.   14. What is the disadvantage of inverter AC? If an inverter AC has lower capacity than requirement, the compressor runs at higher speeds for longer duration of time thereby increasing power consumption. On the other hand, if an inverter AC has higher capacity than heat load, it will run for short cycles and render the room over cooled and uncomfortable.   15. What is the difference between Eco mode and UPS mode in an inverter? In eco-mode the load is normally powered by the bypass path, allowing raw mains power to supply the load, and the UPS inverter is engaged only when the utility mains fails. In eco-mode the UPS inverter operates in a “standby” mode. In principle, this is a simple change in the control software of the UPS. You May Also Like About Operational Amplifier LM358: 24 Classical Circuits Switching Power Supply Guide: Protection Circuit Simplify Current Monitoring by Using Diode | Power Supply Negative End A Complete Guide to Solid State Drive (SSD)

    Circuit protection is a frequently discussed topic, and the various types of circuit protection differ due to the various problems in the circuit. Short-circuit, overload, grounding, and lightning strikes are the most common faults in power supply systems. To ensure the safe and dependable operation of the power supply system, protection devices must be installed to monitor the working conditions of the power supply system, detect faults in time, and cut off the power supply of the faulty equipment, preventing the accident from spreading. In general, the protection circuit is made up of various relays, signal indicating devices, and other components. This blog provides an in-depth discussion on several circuit protections. Below is an introduction video about short circuit protection. DIY Short Circuit (Overcurrent) Protection   Catalog   I Introduction to circuit protection II Switching power principle and characteristics      2.1 Operational principle of switching power      2.2 Characteristic of switching power III DC Switching power supply protection      3.1 Overcurrent protection circuit      3.2 Overvoltage protection circuit      3.3 Soft start protection circuit        3.4 Overheat protection circuit IV Conclusion FAQ   I Introdcution to circuit protection The operation of electronic equipment can not be separated from electricity, so DC switching power supply which can control the electricity is playing a more and more important role. And it has entered various fields of electronics and electrical equipment: SPC exchange, communication, electronic testing equipment power supply and controlling equipment power supply, which are widely used DC switching power supply.  Meanwhile, with the development of many high-tech technologies, including high-frequency switching technology, soft-switching technology, power factor correction technology, synchronous rectifier technology, intelligent technology, surface installation technology, etc., switching power supply technology is constantly innovating. This provides a wide range of development for DC switching power supply.  DC current diagram   But the circuit is complex to control in the switching power supply, the transistor and the integrated device have poor resistance to electricity and thermal shock, which brings great inconvenience to the user in the process of using. In order to protect the safety of switching power supply itself and load, the overheat protection, over-current protection, over-voltage protection and soft start protection circuit are designed according to the principle and characteristics of DC switching power supply.   II Switching power principle and characteristics 2.1 Operational principle of switching power DC switching power supply is composed of input part, power conversion part, output part and control part. The power conversion part is the core of the switching power supply. It performs conversion which needed for the output on the high-frequency and unstable DC. It is mainly composed of switching transistor and high frequency transformer. Figure 1. DC Switching power supply principle Figure 1 shows the schematic diagram and equivalent schematic block diagram of DC switching power supply, which is composed of full wave rectifier, switching tube V, excitation signal, fly-wheel diode Vp, energy storage inductance and filter capacitance C. In fact, the core part of DC switching power supply is a DC transformer. 2.2 Characteristic of switching power   In order to meet the needs of users, the world's major switching power supply manufacturers are committed to the simultaneous development of new and highly intelligent components, especially by reducing the loss of the secondary rectifier. In order to improve the magnetic properties under high frequency and high magnetic flux density, power ferrite (Mn-Zn) materials have been developed. At the same time, the application of SMT technology in the field of switching power supplies has also made considerable progress. The components are arranged on both sides of the circuit board to ensure that the switching power supply is light, small and thin. Therefore, high frequency, high reliability, low power consumption, low noise, anti-interference and modularization are the development trends of DC switching power supplies. However, DC switching power supplies also have disadvantages. The DC switching power supply switch has serious interference, and its ability to adapt to harsh environments and sudden failures is weak. There is still a certain gap in microelectronics technology in developing countries. Specifically, the production technology of resistors and capacitors and the technology of magnetic materials are compared with those of some technologically advanced countries. Therefore, the manufacture of DC switching power supplies is very difficult. In most parts of the world, maintenance is difficult and the cost is high. III DC Switching power supply protection Based on the characteristics of DC switching power supply and the actual electrical condition, in order to make DC switching power supply work safely and reliably in bad environment and sudden fault, this paper designs a variety of protection circuits according to different conditions. 3.1 Overcurrent protection circuit   Figure 2. Input Overcurrent protection circuit In DC switching power supply circuit, in order to avoid short circuit and overflow damage to protect the regulator tube in the circuit, the basic method is that, when the output current exceeds a certain value, the regulator tube is in the reverse bias state, thus the circuit current is cut off automatically. As shown in Fig. 2, the over-current protection circuit consists of transistor BG2 and divider resistor R4, R5. When the circuit works normally, the base potential of BG2 is lower than that of emitter through the partial voltage interaction between R4 and R5, and the emitter junction bears reverse voltage. So the BG2 is in the cutoff state (equivalent to open circuit), which is used to stabilize the voltage. But the voltage stabilizing circuit has no effect. When the circuit is short circuit, the output voltage is zero and the emitter of BG2 is equivalent to grounding, then the BG2 is in the state of saturation conduction (equivalent to short circuit), so that the regulator tube BG1 base and emitter are close to short circuit, and in the cut-off state, the circuit current is cut off to achieve the purpose of protection.   3.2 Overvoltage protection circuit The overvoltage protection of switching regulator in DC switching power supply includes input overvoltage protection and output overvoltage protection. If the voltage of the unstabilized DC power supply (such as batteries and rectifiers) used by the switching regulator is too high, it will cause the switching regulator to fail to work properly and even damage the internal devices. Therefore, it is necessary to use the input overvoltage protection circuit in the switching power supply. Fig. 3 is a protection circuit composed of transistors and relays, in which the voltage of the input DC power supply is higher than the breakdown voltage of the zener diode, at this condition, current flows through resistor R, making diode T conducts. Following these electrical actions, relay operates and common closed contact disconnected, inputting current. The polarity protection circuit of the input power supply can be combined with the input overvoltage protection to form the polarity protection identification and overvoltage protection circuit. Figure 3. Input overvoltage protection circuit 3.3 Soft start protection circuit The circuit of switching power supply is complex, the input end of switching regulator is usually connected with small inductance and large-capacitance input filter. At start-up instant, the filter capacitor flows through a large surge current that can be several times the normal input current. Such a large surge current melts the contacts of the normal power switch or the relay and melts the input fuse. In addition, surge current can also damage capacitors, shorten their life, cause premature damage. To this end, a current-limiting resistance should be connected in the circuit, through this current-limiting resistance to charge the capacitor. In order not to consume too much power by the current limiting resistance, and avoid affecting the normal operation of the switching regulator, therefore a relay is used to connect it automatically after the transient process is finished, which makes the DC power supply directly to the switching regulator. This is called the "soft start" circuit of DC switching power supply. Figure 4. Soft start-up protection circuit When the power supply is switched on, capacitor C is charged by input voltage through rectifier bridge (D1 ~ D4) and current-limiting resistance R1 to limit the surge current. The inverter works normally when the capacitor C is charged to about 80% rated voltage. The trigger signal of thyristor is generated by auxiliary winding of main transformer, which makes thyristor switch on and short circuit current-limiting resistance R1, and the switching power supply is in normal operation state. In order to improve the accuracy of the delay time and prevent the relay operation from shaking and oscillating. The delay circuit can replace the RC delay circuit by the circuit shown in figure 4(b). 3.4 Overheat protection circuit The high integration and light weight of switching regulator in DC switching power supply greatly increase the power density per unit volume, so if the internal components of the power supply do not have a corresponding increase in the temperature of its working environment, it will inevitably make the circuit performance damaged and components life service shortened prematurely. Therefore, overheating protection circuit should be installed in high power DC switching power supply. Figure 5. Overtemperature protection circuit In this paper, the temperature relay is used to detect the internal temperature of the power supply device. When the inside of the power supply device is overheated, the temperature relay operates, which makes the alarm circuit of the whole machine in the state of alarm and realizes the protection of the overheating of the power supply.  As shown in Fig. 5 (a), the P type control gate thermal thyristor is placed near the power switch transistor in the protection circuit. According to the characteristics of the TT102 (the on-on temperature of the device is determined by the Rr value, the larger the Rr is, The lower the conduction temperature), when the temperature of the power tube or the temperature inside the device exceeds the allowable value, the thermal thyristor is switched on and the LED is lighting to give an alarm. If cooperate with photoelectric coupler which can make whole machine alarm circuit operation, protecting switch power supply.  The circuit can also be designed as shown in Fig. 5 (b) to protect the power transistor from overheating. The base current of the switching transister is bypassed by the TT201 of the N type control gate thermal thyristor, and the switch tube is cut off, also the collector current is cut off, and the overheating is prevented. IV Conclusion This blog mainly discusses various protection methods of internal devices in DC switching power supply, and introduces some concrete circuits. For a given DC switching power supply, it is very important for the security and reliability of the power supply device whether the protection circuit is perfect and set up to work necessarily. Because the protection scheme and circuit structure of switching power supply are diverse, reasonable protection scheme and circuit structure should be chosen for specific power supply devices. In practical application, several protection methods are usually used to form a perfect protection system to ensure the normal operation of DC switching power supply.   FAQ   1. What is the purpose of circuit protection? The basic goals of circuit protection are to 1) localize and isolate the condition or fault and 2) prevent and minimize any unnecessary power loss. There are several types of abnormal conditions that may occur throughout a building's life, in which an electrical system must be designed to correct or overcome.   2. What protective devices are used in circuits? Fuses, MCBs, RCDs, and RCBOs are all devices used to protect users and equipment from fault conditions in an electrical circuit by isolating the electrical supply.   3. How do you protect a circuit design? The most basic device is a fuse, a type of low resistance resistor that acts as a sacrificial device to provide over current protection, of either the load or source circuit. A fuse protects the circuit, but once it's utilized, it's kaput.   4. What are the two main circuit protection devices? The two types of circuit protection devices discussed in this chapter are fuses and circuit breakers. A fuse is the simplest circuit protection device. It derives its name from the Latin word "fusus," meaning "to melt." Fuses have been used almost from the beginning of the use of electricity.   5. What is a DC switching power supply? A Switching DC power supply (also known as switch mode power supply) regulates the output voltage through a process called pulse width modulation (PWM). The PWM process generates some high frequency noise, but enables the switching power supplies to be built with very high power efficiency and small form factor.   6. What are the differences between linear DC power supply and switching power supply? Linear power supplies deliver DC by passing the primary AC voltage through a transformer and then filtering it to remove the AC component. Switching power supplies feature higher efficiencies, lighter weight, longer hold up times, and the ability to handle wider input voltage ranges.   7. Can I use a switching power supply to drive a DC motor? A simple unregulated analog power supply may be easier and be able to supply the large starting under load current more that the switching one. DC motors are not too fussy about the supply, and will usually run quite well on unfiltered DC.   8. Do I need a switching power supply? The switching power supply implies higher efficiency due to the high switching frequency, enabling it to use a smaller, less-costly high-frequency transformer as well as lighter, less-costly filter components. Switching power supplies contain more overall components, therefore are usually more expensive.   9. What are the 3 types of power supply? There are three subsets of regulated power supplies: linear, switched, and battery-based. Of the three basic regulated power supply designs, linear is the least complicated system, but switched and battery power have their advantages.   10. What is a switching mode power supply used for? Switched-mode power supplies are used to power a wide variety of equipment such as computers, sensitive electronics, battery-operated devices and other equipment requiring high efficiency.