The Kynix Components

I IntroductionThe LM393 is a dual voltage comparator. this means that it accepts 2 inputs for comparison.The output load resistance of LM393 comparator can be connected to any power supply voltage within the allowable power supply voltage range, and is not limited by the voltage value of the Vcc terminal. This output can be used as a simple open circuit to ground SPS (when the load resistor is not used), the sink current of the output part is limited by the β value of the driver and the device that can be obtained. When the limit current (16mA) is reached, the output transistor will exit and the output voltage will rise quickly.In this blog, we will discuss 3 ways to use the LM393 comparator to build circuits, including: Infrared Obstacle Avoidance Module, Ni-Cd Battery Charger, and PWM Modulation Circuit.LM393 images are for reference only.Figure 1. LM393 ComparatorCatalogI IntroductionII LM393 Based Infrared Obstacle Avoidance Module2.1 Module Description2.2 Description of Module Parameters2.3 Module Interface DescriptionIII LM393 Ni-Cd Battery ChargerIV LM393 PWM Modulation CircuitOrdering & QuantityII LM393 Based Infrared Obstacle Avoidance ModuleFigure 2. LM393 Infrared Obstacle Avoidance Module2.1 Module DescriptionThe sensor module has strong adaptability to ambient light. It has a pair of infrared emitting and receiving tubes. The transmitting tube emits infrared rays of a frequency. When it encounters an obstacle (reflecting surface) in the detection direction, it will be reflected back and received by the receiving tube.After the received infrared light is processed by the comparator circuit, the green indicator light will light up, and the signal output interface outputs a digital signal (a low-level signal). The detection distance can be adjusted by the potentiometer knob. The effective distance range is 2-30cm, and the operating voltage It is 3.3V-5V.The detection distance of the sensor can be adjusted by a potentiometer, which has the characteristics of small interference, easy assembly and convenient use. It can be widely used in many situations such as robot obstacle avoidance, obstacle avoidance trolley, pipeline counting and black and white line tracking.2.2 Description of Module ParametersWhen the module detects an obstacle signal in front, the green indicator on the circuit board lights up, and the OUT port continuously outputs a low-level signal. The detection distance of this module is 2～30cm, and the detection angle is 35°. In addition, the detection distance can be adjusted by the potentiometer: By adjusting the potentiometer clockwise, the detection distance increases; By adjusting the potentiometer counterclockwise, the detection distance decreases;The sensor is active infrared reflection detection, so the reflectivity and shape of the target is the key to the detection distance. Among them, the black detection distance is small and the white is large; the distance of small areas is small, and the distance of large areas is large;The output port OUT of the sensor module can be directly connected to the IO port of the single-chip microcomputer, or it can directly drive a 5V relay; connection mode: VCC-VCC; GND-GND; OUT-IO;The LM393 comparator has the characteristics of stable operation;3-5V DC power supply can be used to power the module. When the power is turned on, the red power indicator lights;has 3mm screw holes for easy fixing and installation;Circuit board size: 3.2CM*1.4CM;The module has adjusted the threshold comparison voltage through the potentiometer. Unless under special circumstances, please do not adjust the potentiometer at will.2.3 Module Interface Description VCC external 3.3V-5V voltage (can be directly connected to 5v microcontroller and 3.3v microcontroller); Connect GND externally to GND; OUT small board digital output interface (0 and 1); The working current is within 10ma;Barrier sensor module as shown in Figure 3.Figure 3. Infrared Reflective Sensor ModuleIII LM393 Ni-Cd Battery ChargerThe cost-effective nickel-cadmium battery charger formed by LM393 comparator is shown in Figure 4, which has the following characteristics:Figure 4. Nickel-Cadmium Battery ChargerConstant current charging is interspersed with large current discharge. The constant current charging current is about 300mA, and the discharge current increases as the battery voltage increases. When the battery is nearly full, the discharge current reaches 400mA. Charge for 1.5 seconds and discharge for 0.5 seconds at intervals. After the high current charging is completed, there is about 5mA trickle charging.The battery voltage is detected during discharge. Because the voltage during charging is always higher than the voltage during discharging. If there is an error between the detection and the actual working state of the battery during charging, the detection can more reflect the capacity of the battery when discharging.The number of rechargeable batteries can be 1 to 4. For 500mAh nickel-cadmium batteries, the charging time is about 2 hours, which can meet the general needs.IV LM393 PWM Modulation CircuitWe know that PWM generally requires a sawtooth wave and a control voltage to be compared with a comparator to obtain a PWM pulse. The comparator 2 of LM393 votage comparator will be used as a PWM comparator, whose non-inverting input end is the control voltage input end, and the inverting input end is the sawtooth wave input end. The output terminal (pin 7) is used as the output terminal to send the PWM dimming signal to the IRN pin of the IRS2540/1 via the isolation diode VD.The LM393 circuit of PWM Modulation is shown in Figure 5 below.Figure 5. PWM Modulation CircuitThe generation of the sawtooth wave is realized by the comparator 1 of LM393. If you do not look at the capacitor C1, the comparator 1 is a multivibrator with a square wave output. In order to obtain the sawtooth wave, a capacitor C1 is connected in parallel with the COM end of the output end of the comparator 1.This is actually the charging process of the output terminals R1 and C1 of the comparator 1. If the capacitance of this capacitor is large enough, but because the charging of C1 requires R1, and the discharge of C1 is the output transistor of the comparator, then the rise and fall of the voltage at the output of the comparator will be asymmetric, which will form an oscillating sawtooth wave.Figure 6. Oscillating Sawtooth WaveDue to the VBUS application of the power supply of the circuit in the figure, it needs to be stepped down with RS, and the voltage regulation of VD2 and the power supply bypass capacitors C3 and C4 are required. After reading the blog, have you better understand LM393? If you are also interested in how to DIY your solar tracking car by using LM393 , you may wish to browse right here right now!Finally, if you have any questions about LM393, please do not hesitate to leave a message in the comment section below!

IntroductionThe LM393 comparator can be regarded as equivalent to the most popular version of the LM358 operational amplifier. Although any operational amplifier can be used as a voltage comparator, the LM393 comparator proves its advantage by providing an open collector output to make it suitable for driving loads.The output transistor can drive loads up to 50V and 50mA and is suitable for driving most TTL, MOS and RTL loads. The transistor can also isolate the load from the system ground.This Vedio Introduces LM393 Dual Comparator with Open Collector Output from Integrated CircuitCatalogIntroductionCAD CAE SymbolsDocument and MediaECCN UNSPSCLM393 Pin Configuration and FunctionsPopularity by RegionBasic ParametersProduct ManufacturerFeaturesProduct RangeAdvantagesAlternative ModelsFunctional Block Diagram Ordering & QuantityDocument and MediaComponent DatasheetLM393 DatasheetApplication NotesApplication Design Guidelines for LM393LM393 Pin Configuration and FunctionsThe LM393 datasheet provided above is for your reference, so that you can understand the physical dimensions of all packages in more detail. The configuration of all 8 pins and the function of each pin are as follows:The function of LM393 pins are as follows:Basic ParametersNumber of channels2Output typeOpen-collectorPropagation delay time 1.3 µsVs (Max)36 VVs (Min)2 VVos (offset voltage @ 25 C) (Max)5 mVIq per channel (Typ)0.225 mAInput bias current (+/-) (Max)50 nARail-to-railOutRatingCatalogOperating temperature range 0℃ to 70℃FeaturesStandard comparatorVICR (Max)34.5 VVICR (Min)0 VApprox. price1ku | 0.06 US$FeaturesImproved specifications of B-version– Maximum rating: up to 38 V– ESD rating (HBM): 2k V– Low input offset: 0.37 mV– Low input bias current: 3.5 nA– Low supply-current: 200 µA per comparator– Faster response time of 1 µsec– Extended temperature range for LM393B– Available in tiny 2 x 2mm WSON packageB-version is drop-in replacement for LM293,LM393 and LM2903, A and V versionsCommon-mode input voltage range includesgroundDifferential input voltage range equal to maximumrated supply voltage: ±38 VLow output saturation voltageOutput compatible with TTL, MOS, and CMOSAdvantagesVacuum robotSingle phase UPSServer PSUCordless power toolWireless InfrastructureApplicancesBuilding AutomationFactory automation & controlMotor drivesInfotainment & clusterFunctional Block DiagramCAD CAE SymbolsPackagePinsDownloadPDIP (P)8View optionsSO (PS)8View optionsSOIC (D)8View optionsTSSOP (PW)8View optionsVSSOP (DGK)8View optionsECCN UNSPSCDescriptionValueECCN CodeEAR99HTS Code8542.39.00.01Popularity by RegionProduct ManufacturerTexas Instruments Inc. (TI) is an American technology company that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. Its headquarters are in Dallas, Texas, United States. TI is one of the top ten semiconductor companies worldwide, based on sales volume. Texas Instruments's focus is on developing analog chips and embedded processors, which accounts for more than 80% of their revenue. TI also produces TI digital light processing (DLP) technology and education technology products including calculators, microcontrollers and multi-core processors. To date, TI has more than 43,000 patents worldwide.Product RangeDevicesBoardsDeveloper ToolsARM ® PROCESSORSAUTOMOTIVE PRODUCTSIDENTIFICATION & SECURITYKinetis Cortex®-M MicrocontrollersIn-Vehicle NetworkNFCLPC Cortex-M MicrocontrollersMicrocontrollers and ProcessorsRFIDAlternative ModelsLM741LM358LM339LM324  After reading the blog, have you better understand LM393? If you are also interested in how to DIY your solar tracking car by using LM393 , you may wish to browse right here right now!Finally, if you have any questions about LM393, please do not hesitate to leave a message in the comment section below!

I DescriptionWhat is LM5117? LM5117 is a synchronous step-down controller produced by TI. It is widely used in communications and automotive electronics. It can be used as a core control device for low-voltage and high-power DC stabilized power supplies with high stability and anti-interference. In this bolg, we introduces the design process of a 5V/3A step-down DC switching power supply with LM5117 chip that has the features of high efficiency and low ripple.In this blog, the specific method of circuit parameter design and debugging process is given, which is of great help for you to learn the design of DC switching power supply.CatalogI DescriptionII IntroductionIII Synchronous Step-down Circuit Design3.1 Design Goal and Block Diagram3.2 Main Circuit Design3.3 Control Circuit Design3.4 Design of Inductance3.5 Design of Current Sampling ResistorIV Test ResultsV ConclusionOrdering & QuantityII IntroductionWhat are the advantages of DC-DC converter? As a secondary power supply, DC-DC converters have the advantages of small size, light weight, high efficiency, and cost-effective, and have been widely used in machinery, communications, automobiles and other fields.And why do we choose LM5117 as the core device circuit? That is because, the circuit designed with LM5117 as the core device has the characteristics of stable operation, high efficiency and low output ripple, that reduces the overall loss of the low-voltage working circuit. In addition, the value of LM3117 is that, LM5117 can also be used in step-up and step-down low-voltage high-power DC regulated power supplies, which is of great significance to the development of automotive electronics.III Synchronous Step-down Circuit Design3.1 Design Goal and Block DiagramOur design goal here, is to build a step-down DC switching power supply:Input voltage: 16 VOutput voltage: 5 VMaximum output current: 3 AConversion efficiency: over 85%Output voltage ripple factor: less than 50 mVWhen the output current Io changes from full load Iomax to light load 0.2 Iomax, the load regulation rate is less than 5%.　　Figure 1. Block DiagramAs shown in Figure 1, the composition of the switching power supply circuit is as follows:A switch main circuitAn input and output filter circuitAPWM wave control circuitAcurrent and voltage feedback circuitSwitch circuit uses the classic buck step-down circuit modelPWM wave control circuit is composed of LM5117Output filter circuit is composed of a π-type filter circuit3.2 Main Circuit DesignFigure 2. Main CircuitAs shown in Figure 2, the composition of the main circuit as follows:Capacitors C1~C4Inductors L1~L2Switching tubes Q1~Q2Sampling resistor R1Among them, C1 and C2 constitute the input filter circuit, L1 has the function of energy storage and wave smoothing, and C3, C4 and L2 constitute the π-type filter circuit, which is beneficial to reduce the output voltage ripple.3.3 Control Circuit DesignAs shown in Figure 3, the circuit switching frequency is programmed by R11 (that is, RT resistance). At 230 KHz, the product design is small in size and high in efficiency, which is a compromise solution. When the switching frequency is set to 230 KHz, RT=21.6 K is obtained from the relationship between the switching frequency and RT resistance, and the standard value of 20 K is selected for RT.In terms of voltage feedback, it is formed by connecting VR1 and R10 in series, collecting the output voltage to the FB pin in real time, and comparing with the reference voltage (0.8 V) inside the LM5117 chip to adjust the output PWM width, so that the output voltage reaches a stable value.What about the current detection feedback? We have adopted the method of series sampling resistor. The R7 resistor is connected to the high side of the current detection resistor. The high side voltage signal is proportional to the current. It is transmitted to the CS pin and amplified by the amplifier, and then compared with the error amplifier voltage to adjust the output pulse width to achieve the purpose of controlling the output current peak value.Figure 3. Control Circuit3.4 Design of InductanceThe inductance value is calculated by formula (1) to obtain 13 μH. In the following formula, we take the inductance as the standard value of 10 μHIn the above formula:VOUT is the nominal output voltageIPP (MAX) is the maximum ripple currentfSW is the switching frequencyVIN (MAX) is the maximum input voltage.3.5 Design of Current Sampling ResistorIn order to obtain the required output power, we should select the appropriate resistance value of the current sampling resistor Rs. But...What if we don’t?Too high?  The required output power will not be achieved; Too low?  Excessive peak current will be cuased, large circuit loss, and possible damage to the components.In the above formula:IOUT(MAX)is the maximum output current capability, which is 130% of 3 A;K is the relationship coefficient between RRAMP and CRAMP that simulates the positive efficiency inductor current ramp.(Here, we select k=1, just aiming to control the sub-harmonic oscillation and realize the single Cycle damping )IPP is the peak-to-peak ripple current value of the inductor.　Calculated by formula (3), we can learn that the inductor peak-to-peak ripple current value at the minimum input voltage is 1.37 A.Calculated by formula (4), we can learn that the magnitude of the sampling resistor is 9.3 mΩ, and the constantan wire of 10 mΩ is actually used in the design.IV Test ResultsInput voltage: 0 VOutput voltage is 5.02 V when the output is loaded with 1.65 ΩInput current: 12 ACircuit efficiency: 2%When the load becomes 8.3 Ω, the output current is 0.61 A, and the test load adjustment rate is 1%.Figure 4 below shows the driving waveform of the switch tube:The two columns of waveforms are complementary, and the dead time is adaptive. The high-side drive waveform is shown in the first waveform, and the low-side drive waveform is shown in the second waveform. Due to the bootstrap circuit, the high-side drive waveform voltage is greater than the low-side drive voltage.　　Figure 4. Driving WaveformV ConclusionFrom the experimental test data and waveform, we can infer that the output voltage, power efficiency, load regulation rate, and voltage ripple of this circuit design all meet the design requirements!Consequently, we can conclude from the above analysis that switching regulated power supply with LM5117 as the core device has the features of stable operation, high efficiency and low ripple, and this is the reason why LM5117 has been widely used in the field of automotive electronics. After reading the blog, have you better understand LM5117?  Finally, if you have any questions about LM5117, please do not hesitate to leave a message in the comment section below!

IntroductionIn order to solve the problem of transient distortion, the typical application circuit of LM3886 power amplifier is changed to the current negative feedback type. The current sample flowing through the speaker voice coil is fed back to the power amplifier input terminal via resistance, and the loudspeaker system is also included in the feedback system.CatalogIntroductionCatalogI Typical power amplifier circuitII Improved Power Amplifier CircuitOrdering & QuantityI Typical power amplifier circuitThe power amplifier circuit made of LM3886 consists of two parts: pre-amplifier and power amplifier. The preamplifier consists of an integrated operational amplifier NE5534, which provides a voltage gain of about 5 times. The power amplifier is composed of LM3886, which provides a voltage gain of about 10 times. Therefore, the full power output can be achieved by inputting about 0.5V signal at the input end. Figure 1 only shows the LM3886 dual power supply circuit, which can also work in a single power supply. Considering from the aspect of sound quality, the audio amplifier circuit generally does not use single power supply, but dual power supply.Figure 1. typical power amplifier circuitThe typical application circuit of LM3886 adopts the traditional negative voltage feedback mode. Negative voltage feedback can improve the frequency characteristics of power amplifier and reduce nonlinear distortion, but the sound is lack of strength. As the volume increases, the low frequency will become tight, dry and hard, and the distortion will increase. At the same time, the high frequency becomes sharp and harsh, and the music and its definition are greatly reduced. This is the so-called Transient Intermodulation Distortion. The transient intermodulation distortion is mainly caused by the introduction of deep negative feedback. Voltage type negative feedback is effective to improve the nonlinear distortion of power amplifier, but it can not take into account the transient distortion at the same time.II Improved Power Amplifier CircuitThe improved circuit is shown in Figure 2. The low-frequency spectral gain of power amplifier is determined by the ratio of R3 and R4. C3 and R5 determine the high-frequency gain of power amplifier. Due to the large capacitance reactance of C3 at low frequency, the current feedback is terminated at low frequency, while the high frequency is improved by current negative feedback. The result is that the total bandwidth is improved and the transient distortion is greatly reduced. The selection of feedback components should be based on the impedance and inductance of the loudspeaker, so that the low-frequency gain is 2-3 times of the high-frequency gain. Former power amplifiers often designed the frequency characteristics to be flat, which did not achieve good sound effects. In order to improve the sound effect of the power amplifier, we should use the negative feedback circuit to consciously increase the low frequency gain to achieve the best effect, which also meets the requirements of the large dynamic sound effect of today's home theater.Figure 2. schematic diagram of power amplifier circuitThe sound effect of this machine is excellent. The low frequency extension is increased and it is flexible. The high frequency is clear and smooth. The resolution is greatly improved, and the metallic sound is completely disappeared. Even if the volume was doubled, no significant distortion was heard.

I DescriptionThis blog introduces the design of a lithium battery backup power control board based on LM393, which is simple, stable, reliable, and low-cost. It can directly output the mains voltage when there is mains power, and continuously monitor the mains voltage. Not only can this design automatically turn on the inverter within 10 ms after the mains power is off, but it also has a power management function: when the internal lithium battery voltage is lower than the set value, it will automatically charge.This Vedio introduces How Does LM393 WorksCatalogI DescriptionII Design and Working Principle2.1 Design2.2 Working PrincipleIII TestIV ConclsionOrdering & QuantityII Design and Working PrincipleThe details of LM393 based lithium battery backup circuit are as follows:2.1 Design2.1.1 Mains Power FailureWhen there is no mains power input, the control panel will turn on the inverter and output 220V AC within 10 ms of the mains power failure.2.1.2 Charging ManagementFigure 1. Function DiagramWhen there is mains input, the control board first shuts down the inverter output and switches to the mains output; then enters the charging management state (due to the feature of the lithium battery protection board, the protection board stops charging after overcharge protection. When the battery voltage When it drops to the overcharge recovery value or below, it will automatically resume charging. When there is mains input for a long time, the lithium battery charger will be repeatedly charged, which will affect the life of the lithium battery). When the lithium battery is fully charged, it will stop charging. When it drops to a certain level (this parameter is lower than the overcharge recovery value of the lithium battery protection board, the specific parameter value is adjustable) and then resume charging until it is fully charged, and repeat the above process.2.2 Working PrincipleAccording to the design requirements, the principle design of this control board is divided into two parts: lithium battery voltage detection and control, and mains voltage detection and control.The main voltage comparison part of the control board uses the dual voltage comparator integrated chip LM393. LM393 integrates 2 independent comparators, its operating power supply voltage range is wide, it can work for 2～36V when single power input, and ±1～±18V when dual power input. In addition, its current consumption is small, only 0.8mA.And what is the pinout of LM393? We can take a look at Figure 2 below:Pins 3 ,5 are the non-inverting input terminals of the two comparators respectively;Pins 2, 6 are the inverting input terminals of the two comparators respectively;Pins 1,7 are the corresponding output terminals of the two comparators respectively.Figure 2. LM393 PinoutWhen used as a basic comparison circuit, if the voltage at the non-inverting input terminal is greater than the voltage at the inverting input terminal, the corresponding output terminal outputs a high level, and vice versa. For example, when U5>U6, U7 outputs high level; when U5<U6, U7 outputs low level.2.2.1 Lithium Battery Voltage Detection and ControlLithium battery voltage detection control is shown in Figure 3.(1) Power SupplyThe power supply of the control part is taken from the lithium battery of the backup power supply, and the voltage of the control board is 12V DC. Because the lithium battery in this design is 48V, its voltage range is 32V to 54.6V, which is higher than the large input voltage required by the stabilizer block 7812. Therefore, in order to protect the voltage regulator block 7812, we need to connect a 20 V voltage regulator tube in series at the input to step down. Here, diode D5 acts as reverse voltage protection(2) Voltage ComparisonThe power management adopts the comparator LM393, the sampling voltage of the lithium battery is divided by resistors R11 and R12, and then input to the non-inverting input of LM393. The reference voltage divides 12V through the resistor R4 and the potentiometer, and then enters the inverting input of LM393.When the sampling voltage U1 is higher than the reference voltage U2, the output terminal corresponding to LM393 outputs a high level, the transistor 9012 is turned off, the relay does not operate, and the inverter stops working.When the sampling voltage U1 is lower than the reference voltage U2, the output terminal corresponding to LM393 outputs a low level, the transistor 9012 is turned on, the relay acts, and the inverter is turned on. The reference voltage can be adjusted according to the actual parameters through the potentiometer R5.Figure 3. LM393 Lithium Battery Voltage Detection and Control(3) Hysteresis Comparator CircuitIn a single-limit comparator, if the input signal Uin has a slight interference near the threshold, the output voltage will produce corresponding jitter (fluctuation). For example, in the design of lithium battery voltage detection, if the sampling voltage of the lithium battery fluctuates near the target voltage (see Figure 3), the voltage of U1 is higher than the voltage of U2, and the output of the comparator should output a high level. However, if the U1 voltage or U2 voltage fluctuates slightly at this time, the transistor 9012 is likely to be turned on and off frequently at this time, and the control output will be very unstable. Then how to overcome this shortcoming? We can introduce positive feedback in the design (that is, the way of hardware to achieve return difference). If we need to fix a trip point at a certain reference voltage value, we can insert a non-linear element (such as a crystal diode) in the positive feedback circuit. By using the unidirectional conductivity of the diode (in Figure 2, D10 diode 1N4148), the above requirements can be achieved.2.2.2 Mains Voltage Detection and ControlThe description of the mains voltage detection control part is shown in Figure 4.(1) Power Supply PartThe power supply part uses the same power supply DC 12 V as the lithium battery voltage detection and control part.(2) Mains Voltage DetectionTaking into account the cost of the mains voltage detection part, this design abandons the traditional transformer or voltage transformer detection method, and uses two optocoupler chips PC817 to detect the mains. PC817 is a commonly used linear optocoupler, which is often used in functional circuits that require more precision. When an electrical signal is applied to the input end, the light emitter emits light and illuminates the light receiver. The light receiver is turned on after receiving the light, and generates a photocurrent output from the output end, thus realizing the "electricity-optical-electricity" conversion. This conversion is often applied to various civil industrial products such as switching power supplies, UPS, adapters, etc.Figure 4. LM393 Mains Voltage Detection and ControlTake AC 220V as an example. In order to protect the optocoupler, we use a 1MΩ resistor in the design to limit the current of the optocoupler emitter. The optocoupler chips U1 and U2 are respectively turned on under the action of alternating current, and cooperate with the capacitor C6 to ensure that the voltage of the non-inverting input terminal U3 is greater than the inverting input terminal U4 under the condition of normal mains input. The optocoupler chip used in this design can also be used for electrical isolation between the control board and the mains.When there is mains power:LM393's non-inverting input terminal U3 voltage is DC 12VInverting input terminal U4 voltage is 9V (R2, R10 divided voltage)The corresponding output terminal is highThe transistor 9014 is turned onThe relay operatesThe normally closed point is openThere is output between mains voltageWhen there is no mains power:The voltage at the non-inverting input terminal U3 of LM393 is DC 0VThe voltage at the inverting input terminal U4 is 9VThe corresponding output terminal is low levelThe transistor 9014 is cut offThe relay does not operateThe normally closed point is closedThe inverter outputs 220V.III TestAfter testing, this control circuit meets the design requirements: when there is mains power supply, it outputs mains voltage, and automatically converts to backup power supply within 10ms in the case of mains power failure, and has good charging management functions, as shown in Figure 5 and Figure 6.Figure 5. Lithium Battery Voltage Detection Waveform Figure 6. Mains Voltage Detection WaveformIn practical applications, MOS tubes and triacs can also be used to replace the relays in the voltage detection and control part of the lithium battery and the relays in the mains voltage detection and control part to achieve the control output.IV ConclsionThis control board is designed according to the characteristics of the lithium battery backup power supply that is gradually popularized at present. It has the advantages of strong anti-interference and low cost, and has strong market promotion value.In subsequent designs, we can also add protection functions such as battery under-voltage protection, short-circuit protection, overload protection, over-voltage protection, and over-temperature protection according to user requirements to continuously improve the product. After reading the blog, have you better understand LM393?Finally, if you have any questions about LM393, please do not hesitate to leave a message in the comment section below!

I. IntroductionTDA7294 is a very innovative DMOS high-power integrated amplifier circuit launched by the famous European SGS-THOMSON STMicroelectronics to mainland China in the 1990s. It sweeps away the raw, cold, and hard tones of the previous  linear integrated power amplifiers and thick film integration, and is widely used in the HI-FI field: such as home theater, active speakers, etc. The design of this chip focuses on tone, and has the advantages of bipolar signal processing circuit and power MOS. It has the characteristics of high voltage resistance, low noise, low distortion, and very affinity for replaying sound; and has a silent standby function, short-circuit current and overheat protection functions to make its performance more perfect. This article will introduce several power amplifier circuit designs based on TDA7294.CatalogI. IntroductionII.OCL CircuitIII. BTL CircuitIV. Constant Current Power AmplifierV. Hi-Fi Integrated Power AmplifierVI. Active Subwoofer Amplifier Adds Standby FunctionVII. High Fidelity Power AmplifierVIII. Class AB Power AmplifierIX. Two-channel Power AmplifierX.100W Power Amplifier CircuitOrdering & QuantityII. OCL CircuitThe OCL circuit diagram is shown in Figure 1. This circuit is a dual-channel 70W power amplifier composed of two TDA7294. There are few external components and simple circuit. When the power supply voltage is ±35V, 70W continuous output power can be obtained on an 8 ohm load. It is very suitable for playback in an environment below 30 square meters. If the speaker impedance is less than 8 ohms, the power supply voltage should be reduced accordingly.Figure 1 OCL Circuit DiagramIII. BTL CircuitThe BTL circuit is shown in Figure 2. It uses two TDA7294 bridges to form a BTL power amplifier circuit. The output power can reach more than 150W. It is suitable for places that require high power such as dance halls. 4 TDA7294 are required for stereo. When the power supply voltage is ±25V, a continuous output power of 150W can be obtained on an 8 ohm load. When the power supply is ±35V, a continuous output power of 180W can be obtained on a 16 ohm load. When use TDA7294 as BTL power amplifier, the load must not be less than 8 ohms.Figure 2 BTL Circuit DiagramIV. Constant Current Power Amplifier This power amplifier circuit is somewhat different from the previous two structures. Its feedback circuit is current sampling, voltage summation and negative feedback. This kind of circuit structure is the constant current power amplifier that people often say. The specific analysis of the circuit will not be detailed, only the more prominent advantages compared with the traditional constant voltage power amplifier will be introduced.(1) The output current of the power amplifier has nothing to do with the load impedance. Even if the load is short-circuited, it will not cause the amplifier to overheat.(2) The output power increases with the increase of load impedance. Pushing the speaker load within a certain power reserve can ensure the bass strength and high frequency resolution of the original music signal.(3) The force acting on the voice coil of the speaker only depends on the current. The use of fluid-controlled oscillation to promote the speaker must be faster than the voltage-controlled oscillation, so that the input and output impedance of the speaker vibration system can be easily matched.The constant current power amplifier circuit is actually a controlled current source controlled by the input signal voltage. Its internal feedback circuit is current sampling, voltage summing negative feedback, and it has the characteristics of high input and output impedance. The input impedance is high, which is exactly what the previous stage constant voltage amplifier circuit needs, which is beneficial for the signal voltage to be sent to the input end of the power amplifier without loss. The high output impedance can reduce the shunt of the internal resistance to the signal, which is conducive to adding the output signal current to the load.In Figure 3, the power supply voltage is selected as ±35V, and its magnification is determined by the ratio of the speaker to R6.Figure 3 Constant current power amplifier circuit diagramV. Hi-Fi Integrated Power Amplifier The famous European SGS-THOMSON STMicroelectronics has launched a Hi-Fi high-power DMOS integrated amplifier circuit TDA7294. The circuit is shown in Figure 4. It integrates the best design of modern power amplifier circuit, combines the advantages of bipolar signal processing circuit and power MOS, has the characteristics of low noise and low distortion; standby and mute circuit completely eliminates the impact noise caused by power on and off, and eliminates speaker protection circuit overheating, short-circuit current protection and other functions make its performance more excellent. This device is suitable for home theater and Hi-Fi amplifiers. The main parameters are: VS (power supply voltage) ±10～±40V (maximum voltage without signal ±50V); Io (peak output current) 10A; Po (RMS continuous output power) 70W when vs=±35V 8Ω; vs= 70W when ±27V 4Ω; (effective value of music output power) 100W when VS=±38V 8Ω; 100W when VS=±29V 4Ω.Figure 4 Hi-Fi Integrated Power Amplifier Circuit DiagramThe closed-loop gain of the circuit in Figure 4 is 30dB. Increasing R3 can increase the gain, and vice versa, but the amplifier gain should be ≥24dB. The amplifier has the best performance when R1=R3. R7, C4 and R5+R6, C3 determine the standby and mute time constants. The larger the value, the longer the time.When the control terminal is connected to low potential ground, it is mute and standby; when the control terminal is connected to VS, because (R5+R6)> R7, pin ⑩ rises to a higher potential than pin ⑨, and turns to a low potential first when shutting down, which makes the standby and shutdown processes go on in a silent state, ensuring that the amplifier is turned on and off without noise.Figure 5 BTL Power amplifier finished boardFor high-power professional applications fileds such as dance halls, you can choose the BTL power amplifier finished board shown in Figure 5. Both TDA7294 are equipped with their own professional radiators. When vs=±25V8Ω, the maximum continuous output power reaches 150W; when ±35V 16Ω, The maximum continuous output power reaches 170W.We used TDA7294 standard application circuit and Marantz PM80 and YAMAHAA-592 to make a listening comparison. The former is a mid-priced Hi-Fi machine with a Class A, Class A and B status switch, and the latter is a 439.16 dollars class with Ac -3 input AV power amplifier, audio source is music fax E60CD, speaker is Tanner No. 5.It turns out that the sound orientation of TDA7294 has a distinctive European style, soft, mellow, delicate, and full of bouncing feeling. It is similar to the Marantz PM-80 in Class A and B status, but the sound field of PM-80 is deeper when working in pure Class A. Compared with YAMAHA A-592, the difference is larger. The low frequency of A-592 seems to be slightly improved. It sounds powerful, but it is harder and the lines are blurry. TDA7294 is sweet and natural, with higher resolution, really like landscape painting done with splashes of ink and fine-brush flowers and birds (a technique of chinese ink-painting), each has its infinite charm. VI.Active Subwoofer Amplifier Adds Standby Function This circuit is an improvement on the audio circuit using the integrated circuit TDA7294. The circuit diagram is shown in Figure 6. TDA729410 pin has a mute function. When the external DC provides high level, the integrated block is in the working state; when the low level is applied, the integrated block is in the cut-off state. At this time, the circuit consumes little power and IC1 14 pin has no output, that is, "standby "form. The general circuit is to provide a high level to pin 10 to make it in the conducting state, in fact, the development of this pin function can meet some special work requirements. This circuit is based on this to increase the standby function of the active subwoofer power amplifier, and its circuit is reliable and responsive.Figure 6 Active subwoofer amplifier adds standby function circuit diagramVII. High Fidelity Power Amplifier The circuit is shown in Figure 7. The drive stage adopts TDA7294. The internal drive stage and output stage of the chip use field effect tubes, which are powered by ±40V, and the output power can reach 70W (RL=8Ω; THD=0.005%). It has a delicate tone and an excellent sense of hearing. Power output VT1, VT2 adopts Shanken high-power pair tube 2SA1394, 2SC3858.The circuit principle is as follows: The signal is input to the TDA7294 non-inverting input pin ③ through C1 and R1. R7 and R3, C3, C4 of IC pin ② form a negative feedback network, the closed loop gain of this amplifier is about 34 times. The ⑨ and ⑩ pins are the standby and mute terminals respectively. Since the RC network time constant of the ⑩ pin is larger than that of the ⑨ pin, the switching machines are all performed under mute satge, avoiding the switching impact sound, and C7 is a bootstrap capacitor.Figure 7 High-fidelity power amplifier promoted by TDA7294Production points:(1) Insulating mica sheets should be added between the metal cap and the heat sink of TDA7294 (the metal cap is connected to the pin ⑧).(2) The power transformer uses ring-shaped 300W double 20V, four 50V/10000μF filter capacitors, two 50V/100μF, and two 100V/0.1μF. The power supply part should be tested separately, first without connecting the power amplifier, measure whether the positive and negative output voltage of the power supply are symmetrical, the error should be within 0.6V.(3) When testing the machine, for safety reasons, you should first use a lower voltage test (such as ±25V) without adding a signal, and measure the DC voltage of the output terminal to the ground. Normally, it should be within 20mV.(4) R8, R9, R10, D1 form the final bias circuit. This bias makes the output tubes VT1 and VT2 not cut off during operation, so the quiescent current can be small (about 5mA).(5) The power tube should be strictly matched (within 3%) and genuine products should be selected. The output resistance R14 is a 5W non-inductive type, and the inductor L is formed by tightly winding 10 turns on R14 with a diameter of 1.5mm enameled wire. TDA7294 uses 60mmTimes, 85mmTimes, 20mm 12-slot heat sink, and the output pair tube needs a professional heat sink. The sections with high current on the printed board need to be tin-rolled, which is extremely beneficial for the transparency and strength of the sound.Figure 8 Power amplifier PCB promoted by TDA7294VIII. Class AB Power Amplifier TDA7294 integrated circuit can be used as a high-fidelity audio class AB power amplifier. It can drive 4 ohm or 8 ohm speakers, and when connected to an 8 ohm speaker, it will provide 50 watts of output power and 0.1% THD.Figure 9 Class AB power amplifier circuit diagram You must install a large enough radiator for TDA7294. Pin 10 is a mute input, and pin 9 provides a standby mode. Mute should always occur when selecting standby mode. The IC has internal thermal protection, which causes mute reduction at 145°C, and the amplifier enters standby at 150°C. The TDA7294 integrated circuit heat sink is internally connected to the negative power rail. If the module is installed in a grounded metal enclosure, then the IC must be insulated from the heat sink. If not, the negative power rail will be shorted to ground.IX. Two-channel Power Amplifier TDA7294 high-power integrated circuit IC is specially designed for assembling high-performance audio amplifiers. Two TDA7294 pieces can be used to make a powerful dual-channel high-fidelity power amplifier. The circuit principle is shown in Figure 10. The overall circuit is composed of two TDA7294 core components, and the periphery includes some resistors and capacitors.The circuits of the two channels are almost identical in design. They all use the standard circuit officially released by TDA7294, connected to a non-inverting amplifier circuit, with a voltage gain of 30.5dB, an output power of up to 70W per channel, and a dual power supply symmetrical power supply voltage ± 35V. Among them, Cl5 and Cl6 are input coupling capacitors. 0.47μF is used in the original circuit. Here, if you increase it to 1μF, you can improve the low-frequency response of the circuit. It is recommended to use polypropylene special audio capacitors, such as WIMA's MKT4 series capacitors, it can greatly improve the sound resolution.R3 and R4 are input resistances, which determine the input impedance of TDA7294 in the in-phase amplification state. Here, 22kΩ is relatively moderate. Too large a value can reduce the burden on the front-end signal source, but it may affect the stability of TDA7294 and make the output midpoint voltage drift increased, too small value will affect the response ability to low frequency.The theoretical value of the feedback resistors R7 and R8 should be equal to the input resistors R3 and R4, which can ensure the bias current balance of the TDA7294 input differential circuit and reduce signal distortion. The feedback ground resistance R5, R6 cooperates with R7, R8 to set the circuit gain. Here, the feedback DC blocking capacitors Cl3 and Cl4 are used to form AC negative feedback, inhibit DC voltage output, and protect the speaker.Figure 10 Two-channel power amplifier circuit diagramTDA7294 has a start mute function, and cooperates with an external circuit to achieve a non-impact sound effect when the power is turned on and off. R9, R1O, R11, Rl2, Cl7, Cl8 and VD5, VD6 in the schematic diagram form an external mute control circuit. Delay the energization of pins 9 and 10 of TDA7294 to achieve the function of soft start.The power supply rectifier filter circuit is also very simple. The full bridge rectifier circuit is composed of 4 European speed rectifier diodes VD1-VD4. Capacitors C1 and C2 are the main filter capacitors. Large-capacity and high-current audio filter capacitors are required, such as ELNA's FORAUDIO series or BHCAerovox industrial grade capacitors.DesignPCB is generally a bottleneck in amateur production, so that many excellent schematic diagrams have not been transformed into finished PCBs that can be actually assembled. Here, the popular Protel99se design software is used to draw the printed circuit board against the schematic diagram 10, as shown in Figure 11. The 2mm thick FR-4 board-based double-sided PCB is used, and the copper foil is thickened to 70mm, which is suitable for high current power amplifiers.The whole PCB trace adopts one-point grounding method, which effectively eliminates ground wire interference noise. In some high-current traces, tin plating is also adopted to increase the additional current carrying capacity. The power input and power output structure uses high-current screw terminals to ensure sufficient over-current capability and durability of repeated wiring.Figure 11 Printed circuit boardX.100W Power Amplifier CircuitFigure 12 100W power amplifier circuit diagram composed of TDA7294Figure 12 is a 100W power amplifier composed of a monolithic audio power amplifier integrated circuit TDA7294. TDA7294 includes pre-op amplifier, final power amplifier, temperature protection, short circuit protection, mute control and other circuits. The final stage adopts bipolar DMOS power transistor, which has the characteristics of high output power, bandwidth, low distortion, and good versatility.The integrated circuit also has perfect anti-overload, anti-short circuit and temperature protection circuit functions. When the chip temperature is too high, it automatically cuts off the audio signal to protect the chip from burningThe power amplifier circuit composed of TDA7294 has the characteristics of simple peripheral circuit and easy production. The circuit input impedance is 20k, the input sensitivity is 750mV, the voltage gain is 32dB, the power supply voltage range is ±(25～40)V, and the quiescent current is 50mA. When the load impedance is 8Ω, the output power is 100W; when the load impedance is 4Ω, the output power can reach 180W.In actual production, TDA7294 should be equipped with enough heat sinks. The supporting power circuit should have sufficient capacity. If you need to increase the circuit voltage gain, you can appropriately change the ratio of R3 to R2, voltage gain A=201g(R3/R2)(dB). However, it is not advisable to one-sidedly pursue the voltage gain of this stage. Excessive voltage gain can easily cause circuit self-excitation. The solution is to increase the voltage gain of the pre-stage.