A battery repair circuit

Abstract

The present invention relates to a battery charging circuit, and discloses a battery repair circuit, which circuit includes a multi-tap transformer, an input rectification module, a current mode controller module, a PWM signal generation module, a positive pulse branch, and a negative pulse branch; wherein, the positive pulse branch and the negative pulse branch are respectively connected to a tap of the secondary coil of the multi-tap transformer, and the center tap of the coil between the taps connected by the positive pulse branch and the negative pulse branch is grounded. The current mode controller module controls the magnitude of the main current in the primary coil circuit according to the feedback signal and the main current signal, and further controls the voltage magnitudes on the positive and negative pulse branches; meanwhile, the PWM signal generation module generates two PWM signals to respectively drive the positive pulse branch and the negative pulse branch to work, so that the voltages output by the positive and negative pulse branches are more stable and controllable. Therefore, by outputting corresponding pulses through the positive and negative pulse branches, the present invention can improve the activity of lithium ions during the charging process and achieve the repair of the battery.

Description

Technical Field

[0001] The present invention relates to battery charging circuit technology, and particularly to a battery repair circuit. Background Art

[0002] For lithium battery charging, whether it is constant voltage charging or constant current charging, during the charging process, as the inertia of lithium ions gradually increases, lithium ions will adhere and crystallize. When the crystallization of lithium ions is severe, spikes will be generated, which will scratch the electrode diaphragm during migration, causing irreversible damage to the battery and affecting the battery life. Therefore, it is necessary to design a circuit that can repair the battery during the charging process. Summary of the Invention

[0003] In view of the above deficiencies of the prior art, the purpose of the present invention is to design a circuit that can repair the battery during the charging process.

[0004] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0005] A battery repair circuit, which includes:

[0006] A multi-tap transformer;

[0007] An input rectification module;

[0008] A current mode controller module;

[0009] A PWM signal generation module;

[0010] A positive pulse branch and a negative pulse branch;

[0011] Wherein, the input rectification module is used to rectify the input mains power and connect the rectified mains power to the first tap of the primary coil of the multi-tap transformer, and form a primary coil loop;

[0012] The current mode controller module is used to control the magnitude of the main current of the primary coil loop according to the feedback signal and the main current signal;

[0013] The positive pulse branch and the negative pulse branch are respectively connected to a tap of the secondary coil of the multi-tap transformer, and the center tap of the coil between the taps connected by the positive pulse branch and the negative pulse branch is grounded;

[0014] The PWM signal generation module is used to generate two PWM signals to drive the positive pulse branch and the negative pulse branch to work respectively.

[0015] According to a specific embodiment, in the battery repair circuit of the present invention, the current mode controller module includes a current mode controller chip, a first optocoupler, and a first field effect transistor; wherein, the feedback signal is input to the feedback input terminal of the current mode controller chip through the first optocoupler, and the main current signal is input to the main current input terminal of the current mode controller chip; the gate of the first field effect transistor is connected to the drive output terminal of the current mode controller chip, its drain is connected to the primary coil circuit, its source is grounded through a resistor, and the connection point between the source of the first field effect transistor and this resistor serves as the sampling point of the main current signal.

[0016] Further, the current mode controller module further includes a first diode and an RC resonance circuit; wherein, the drain of the first field effect transistor is connected to the anode of the first diode, and the cathode of the first diode is connected to the first tap of the primary coil of the multi-tap transformer through the RC resonance circuit.

[0017] Still further, the current mode controller module further includes a first capacitor and a second capacitor; wherein, one end of the first capacitor is connected to the drain of the first field effect transistor, the other end of it is connected to one end of the second capacitor, and the other end of the second capacitor is connected to the source of the first field effect transistor.

[0018] According to a specific embodiment, in the battery repair circuit of the present invention, the positive pulse branch and the negative pulse branch have the same circuit structure; wherein, the positive pulse branch or the negative pulse branch includes: a field effect transistor A, a field effect transistor B, an inductor, and a fast turn-off control circuit; moreover, the source of the field effect transistor A is connected to the tap of the secondary coil of the multi-tap transformer, its gate is connected to the drive output terminal of the fast turn-off control circuit, and its drain is connected to the drain of the field effect transistor B through the inductor; the gate of the field effect transistor B is connected to a PWM signal output terminal of the PWM signal generation module, and its source outputs a positive pulse signal or a negative pulse signal through a resistor.

[0019] Further, the fast turn-off control circuit includes a fast turn-off controller chip, a zener diode, a resistor, and a capacitor; wherein, the drive end of the fast turn-off controller chip is respectively connected to one end of the capacitor and the cathode of the zener diode; the gate of the field effect transistor A is respectively connected to the other end of the capacitor, one end of the resistor, and the anode of the zener diode; the other end of the resistor is connected to the source of the field effect transistor A.

[0020] According to a specific embodiment, the battery repair circuit of the present invention further includes a lock signal sampling circuit, and the lock signal sampling circuit inputs the lock signal it collects into the lock input end of the current mode controller chip through a second optocoupler; wherein,

[0021] The lock signal sampling circuit includes a first voltage regulator diode and two resistors connected in series. The cathode of the first voltage regulator diode is connected to the drain of the field effect transistor A, and its anode is grounded through two resistors connected in series, and the connection point of the two resistors serves as the sampling point of the lock signal.

[0022] According to a specific embodiment, the battery repair circuit of the present invention further includes a feedback signal sampling circuit for collecting feedback signals; and the feedback signal sampling circuit includes: a voltage reference chip, a first to a sixth resistor, and a third to a fifth capacitor; wherein,

[0023] One end of the first resistor is connected to the drain of the field effect transistor A, and the other end is connected to the first input end of the first optocoupler; one end of the second resistor is connected to the drain of the field effect transistor B, and the other end is sequentially connected to the second input end of the first optocoupler through the third resistor and the third capacitor; the connection point of the second resistor and the third resistor is grounded through the fourth resistor, and this connection point is connected to the reference input end of the voltage reference chip; the anode of the voltage reference chip is grounded, and its cathode is connected to the second input end of the first optocoupler; one end of the fifth resistor is connected to the first input end of the first optocoupler, and the other end is connected to the second input end of the first optocoupler; one end of the fourth capacitor is connected to the second input end of the first optocoupler, and the other end is grounded; the fifth capacitor and the sixth resistor are connected in series and then connected in parallel across the second resistor.

[0024] According to a specific embodiment, the battery repair circuit of the present invention further includes a first power supply circuit for supplying power to the fast turn-off controller chip; and the first power supply circuit includes: a second diode, a seventh resistor, a sixth capacitor, and a seventh capacitor; wherein, the anode of the second diode is connected to a tap of the secondary coil of the multi-tap transformer, and its cathode is connected to one end of the seventh resistor; the other end of the seventh resistor is connected to the power supply input end of the fast turn-off controller chip; the sixth capacitor and the seventh capacitor are connected in parallel, and one end is connected to the power supply input end of the fast turn-off controller chip, and the other end is respectively connected to another tap of the secondary coil of the multi-tap transformer and the reference input end of the fast turn-off controller chip.

[0025] According to a specific embodiment, in the battery repair circuit of the present invention, the PWM signal generation module includes a microcontroller, a digital potentiometer, a first amplifier A, a first amplifier B, a second amplifier A, and a second amplifier B; wherein, the microcontroller is connected to the digital potentiometer, the digital potentiometer is respectively connected to the first amplifier A and the first amplifier B, the second amplifier A is connected to the first amplifier A, the second amplifier B is connected to the first amplifier B, and moreover, two input terminals of the second amplifier A are respectively connected to both ends of the output resistor of the positive pulse branch, two input terminals of the second amplifier B are respectively connected to both ends of the output resistor of the negative pulse branch, the first amplifier A outputs a PWM signal to the positive pulse branch, and the first amplifier B outputs a PWM signal to the negative pulse branch.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The battery repair circuit of the present invention includes a multi-tap transformer, an input rectification module, a current mode controller module, a PWM signal generation module, a positive pulse branch, and a negative pulse branch; wherein, the positive pulse branch and the negative pulse branch are respectively connected to a tap of the secondary coil of the multi-tap transformer, and the center tap of the coil between the taps connected by the positive pulse branch and the negative pulse branch is grounded. The current mode controller module controls the magnitude of the main current in the primary coil circuit according to the feedback signal and the main current signal, and further controls the voltage magnitudes on the positive and negative pulse branches; at the same time, the PWM signal generation module generates two PWM signals to respectively drive the positive pulse branch and the negative pulse branch to work, so that the voltages output by the positive and negative pulse branches are more stable and controllable. Therefore, by outputting corresponding pulses through the positive and negative pulse branches, the present invention can improve the activity of lithium ions during the charging process and achieve the repair of the battery.

[0028] 2. In the battery repair circuit of the present invention, the positive pulse branch or the negative pulse branch includes: a field effect transistor A, a field effect transistor B, an inductor, and a fast turn-off control circuit; moreover, the source electrode of the field effect transistor A is connected to the tap of the secondary coil of the multi-tap transformer, its gate electrode is connected to the drive output terminal of the fast turn-off control circuit, and its drain electrode is connected to the drain electrode of the field effect transistor B through the inductor; the gate electrode of the field effect transistor B is connected to a PWM signal output terminal of the PWM signal generation module, and its source electrode outputs a positive pulse signal or a negative pulse signal through a resistor. Therefore, by adopting the fast turn-off control circuit, the present invention can control the on / off of the positive and negative pulse branches when a voltage abnormality occurs.

[0029] 3. The battery repair circuit of the present invention further includes a feedback signal sampling circuit, which respectively samples the drain voltages of field effect transistors A and B in the positive pulse branch, and uses the voltage regulation function of the voltage reference chip to provide a stable feedback signal for the current mode controller chip, so as to more accurately control the magnitude of the main current in the primary coil circuit, and further control the voltage magnitudes on the positive and negative pulse branches.

[0030] 4. In the battery repair circuit of the present invention, the PWM signal generation module includes a microcontroller, a digital potentiometer, a first amplifier A, a first amplifier B, a second amplifier A, and a second amplifier B; moreover, by collecting the voltages across the output resistors of the positive and negative pulse branches and performing operational amplification processing, the PWM signals input to the positive and negative pulse branches are adjusted accordingly, so as to optimize the pulses output by the positive and negative pulse branches. Description of the Drawings

[0031] Figure 1 is a schematic structural diagram of the battery repair circuit of the present invention;

[0032] Figure 2 is a schematic circuit diagram of the primary coil circuit of the present invention;

[0033] Figure 3 is a circuit diagram of the positive and negative pulse branches of the present invention;

[0034] Figure 4 is a circuit diagram of the feedback signal sampling circuit of the present invention;

[0035] Figure 5 is a schematic circuit diagram of the PWM signal generation module of the present invention. Detailed Embodiments

[0036] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] As Figure 1 shown, the battery repair circuit of the present invention includes: a multi-tap transformer, an input rectification module, a current mode controller module, a PWM signal generation module, a positive pulse branch, and a negative pulse branch.

[0038] Among them, the input rectification module is used to rectify the input mains power, and connect the rectified mains power to the first tap of the primary coil of the multi-tap transformer, and form a primary coil circuit; the current mode controller module is used to control the magnitude of the main current in the primary coil circuit according to the feedback signal and the main current signal.

[0039] The positive pulse branch and the negative pulse branch are respectively connected to a tap of the secondary coil of the multi-tap transformer, and the center tap of the coil between the taps to which the positive pulse branch and the negative pulse branch are connected is grounded.

[0040] The PWM signal generation module is used to generate two PWM signals to drive the positive pulse branch and the negative pulse branch to work respectively.

[0041] As Figure 2 As shown, in the battery repair circuit of the present invention, the current mode controller module includes a current mode controller chip U1, a first optocoupler P2, and a first field effect transistor Q7. Among them, the feedback signal is input to the feedback input terminal FB of the current mode controller chip through the first optocoupler P2, and the main current signal is input to the main current input terminal CS of the current mode controller chip; the gate of the first field effect transistor Q7 is connected to the drive output terminal DRV of the current mode controller chip, its drain is connected to the primary coil circuit, its source is grounded through a resistor R50, and the connection point of the source of the first field effect transistor Q7 and this resistor is used as the sampling point of the main current signal.

[0042] During implementation, the current mode controller module further includes a first diode D8 and an RC resonance circuit; among them, the drain of the first field effect transistor Q7 is connected to the anode of the first diode D8, and the cathode of the first diode D8 is connected to the first tap of the primary coil of the multi-tap transformer T1 through the RC resonance circuit. Moreover, the RC resonance circuit is composed of a capacitor C20, a resistor R38, and a resistor R39, and the resistor R38 and the resistor R39 are connected in series and then in parallel with the capacitor C20.

[0043] In addition, the current mode controller module further includes a first capacitor C21 and a second capacitor C23; among them, one end of the first capacitor C21 is connected to the drain of the first field effect transistor Q7, the other end of it is connected to one end of the second capacitor C23, and the other end of the second capacitor C23 is connected to the source of the first field effect transistor Q7.

[0044] As Figure 3As shown, in the battery repair circuit of the present invention, the positive pulse branch and the negative pulse branch have the same circuit structure. Among them, the positive pulse branch or the negative pulse branch includes: a field effect transistor A, a field effect transistor B, an inductor, and a fast turn-off control circuit; moreover, the source of the field effect transistor A is connected to the tap of the secondary coil of the multi-tap transformer, its gate is connected to the drive output terminal of the fast turn-off control circuit, and its drain is connected to the drain of the field effect transistor B through the inductor; the gate of the field effect transistor B is connected to a PWM signal output terminal of the PWM signal generation module, and its source outputs a positive pulse signal or a negative pulse signal through a resistor.

[0045] Specifically, in the positive pulse branch, the field effect transistor Q2 is the field effect transistor A, the field effect transistor Q6 is the field effect transistor B. The source of the field effect transistor Q2 is connected to the tap of the secondary coil of the multi-tap transformer T1, its gate is connected to the drive output terminal of the fast turn-off control circuit, and its drain is connected to the drain of the field effect transistor Q6 through the inductor L2; the gate of the field effect transistor Q6 is connected to a PWM signal output terminal of the PWM signal generation module, and its source outputs a positive pulse signal or a negative pulse signal through a resistor R28.

[0046] Among them, the fast turn-off control circuit includes a fast turn-off controller chip Q4, a zener diode D2, a resistor R3, and a capacitor C4. Among them, the drive terminal VG of the fast turn-off controller chip Q4 is respectively connected to one end of the capacitor C4 and the cathode of the zener diode D2; the gate of the field effect transistor Q2 is respectively connected to the other end of the capacitor C4, one end of the resistor R3, and the anode of the zener diode D2; the other end of the resistor R3 is connected to the source of the field effect transistor Q2.

[0047] Again, Figure 3 As shown, the battery repair circuit of the present invention further includes a first power supply circuit for supplying power to the fast turn-off controller chips Q4 and Q3; moreover, the first power supply circuit includes: a second diode D10, a seventh resistor R34, a sixth capacitor C40, and a seventh capacitor C41.

[0048] Among them, the anode of the second diode D10 is connected to a tap of the secondary coil of the multi-tap transformer T1, its cathode is connected to one end of the seventh resistor R34; the other end of the seventh resistor R34 is connected to the power supply input terminal VDD of the fast turn-off controller chips Q4 and Q3; the sixth capacitor C40 and the seventh capacitor C41 are connected in parallel, one end is connected to the power supply input terminal VDD of the fast turn-off controller chip, and the other end is respectively connected to another tap of the secondary coil of the multi-tap transformer T1 and the reference input terminal VSS of the fast turn-off controller chip.

[0049] Again, Figure 1 andFigure 3 As shown, the battery repair circuit of the present invention further includes a latch signal sampling circuit, and the latch signal sampling circuit inputs the latch signal it collects to the latch input terminal LATCH of the current mode controller chip U1 through the second optocoupler P1.

[0050] Moreover, the latch signal sampling circuit includes a first voltage regulator diode D11 and two resistors R41 and R53 connected in series. The cathode of the first voltage regulator diode D11 is connected to the drain of the field effect transistor Q2, and its anode is grounded through the two resistors R41 and R53 connected in series, and the connection point P2 - 817 of the two resistors serves as the sampling point of the latch signal.

[0051] As Figure 3 and Figure 4 shown, the battery repair circuit of the present invention further includes a feedback signal sampling circuit for collecting feedback signals; moreover, the feedback signal sampling circuit includes: a voltage reference chip U2, a first to sixth resistor, and a third to fifth capacitor.

[0052] One end of the first resistor R47 is connected to the drain of the field effect transistor Q2, and the other end is connected to the first input terminal of the first optocoupler P2; one end of the second resistor R45 is connected to the drain of the field effect transistor Q6, and the other end is sequentially connected to the second input terminal of the first optocoupler P2 through the third resistor R17 and the third capacitor C25; the connection point of the second resistor R45 and the third resistor R17 is grounded through the fourth resistor R46, and this connection point is connected to the reference input terminal of the voltage reference chip U1; the anode of the voltage reference chip U1 is grounded, and its cathode is connected to the second input terminal of the first optocoupler P2; one end of the fifth resistor R5 is connected to the first input terminal of the first optocoupler P2, and the other end is connected to the second input terminal of the first optocoupler P2; one end of the fourth capacitor C26 is connected to the second input terminal of the first optocoupler P2, and the other end is grounded; the fifth capacitor C24 and the sixth resistor R33 are connected in series and then connected in parallel on the second resistor R45.

[0053] As Figure 5 shown, in the battery repair circuit of the present invention, the PWM signal generation module includes a microcontroller (not shown in the figure), a digital potentiometer U10, a first amplifier A, a first amplifier B, a second amplifier A, and a second amplifier B. Specifically, the first amplifier A and the first amplifier B are integrated operational amplifiers U9 and U8; the second amplifier A and the second amplifier B are integrated operational amplifiers U7 and U6.

[0054] Among them, the microcontroller is connected to the digital potentiometer U10, and sends its signals MCPCS, MCPCLK, and MCPDATA to the CS terminal, SCK terminal, and SI terminal of the digital potentiometer U10 respectively; the digital potentiometer U10 is respectively connected to the integrated operational amplifier U9 and the integrated operational amplifier U8, and outputs the RW signal output from its PW0 terminal to the INB+ terminals of the integrated operational amplifier U9 and the integrated operational amplifier U8; the integrated operational amplifier U7 is connected to the integrated operational amplifier U9, and the integrated operational amplifier U6 is connected to the integrated operational amplifier U8. Moreover, the two input terminals of the integrated operational amplifier U7 are respectively connected to both ends of the output resistor R28 of the positive pulse branch, and the two input terminals of the integrated operational amplifier U6 are respectively connected to both ends of the output resistor R27 of the negative pulse branch. The integrated operational amplifier U9 outputs a PWM signal to the positive pulse branch, and the integrated operational amplifier U8 outputs a PWM signal to the negative pulse branch.

Claims

1. A battery repair circuit, characterized in that, Comprising: Multi-tap transformer; Input rectifier module; Current mode controller module; PWM signal generation module; Positive pulse branch, and negative pulse branch; Wherein, the input rectifier module is used to rectify the input mains power, and connect the rectified mains power to the first tap of the primary coil of the multi-tap transformer, and form a primary coil loop; The current mode controller module is used to control the magnitude of the main current of the primary coil loop according to the feedback signal and the main current signal; The positive pulse branch and the negative pulse branch are respectively connected to a tap of the secondary coil of the multi-tap transformer, and the center tap of the coil between the taps connected by the positive pulse branch and the negative pulse branch is grounded; The PWM signal generation module is used to generate two PWM signals to respectively drive the positive pulse branch and the negative pulse branch to work; Wherein, the current mode controller module includes a current mode controller chip, a first optocoupler and a first field effect transistor; wherein, the feedback signal is input to the feedback input terminal of the current mode controller chip through the first optocoupler, and the main current signal is input to the main current input terminal of the current mode controller chip; the gate of the first field effect transistor is connected to the drive output terminal of the current mode controller chip, its drain is connected to the primary coil loop, its source is grounded through a resistor, and the connection point of the source of the first field effect transistor and this resistor is used as the sampling point of the main current signal; The current mode controller module further includes a first diode and an RC resonance circuit; wherein, the drain of the first field effect transistor is connected to the anode of the first diode, and the cathode of the first diode is connected to the first tap of the primary coil of the multi-tap transformer through the RC resonance circuit; The positive pulse branch and the negative pulse branch have the same circuit structure; wherein, the positive pulse branch or the negative pulse branch includes: field effect transistor A, field effect transistor B, inductor, fast turn-off control circuit; moreover, the source of field effect transistor A is connected to the tap of the secondary coil of the multi-tap transformer, its gate is connected to the drive output terminal of the fast turn-off control circuit, its drain is connected to the drain of field effect transistor B through the inductor; the gate of field effect transistor B is connected to a PWM signal output terminal of the PWM signal generation module, and its source outputs a positive pulse signal or a negative pulse signal through a resistor.

2. The battery repair circuit according to claim 1, characterized in that, The current mode controller module further includes a first capacitor and a second capacitor; wherein, one end of the first capacitor is connected to the drain of the first field effect transistor, the other end of it is connected to one end of the second capacitor, and the other end of the second capacitor is connected to the source of the first field effect transistor.

3. The battery repair circuit according to claim 1, wherein, The fast turn-off control circuit includes a fast turn-off controller chip, a voltage stabilizing diode, a resistor, and a capacitor; wherein, the driving end of the fast turn-off controller chip is respectively connected to one end of the capacitor and the cathode of the voltage stabilizing diode; the gate of the field effect transistor A is respectively connected to the other end of the capacitor, one end of the resistor, and the anode of the voltage stabilizing diode; the other end of the resistor is connected to the source of the field effect transistor A.

4. The battery repair circuit according to claim 1, wherein, It further includes a blocking signal sampling circuit, and moreover, the blocking signal sampling circuit inputs the blocking signal it collects into the blocking input end of the current mode controller chip through a second optocoupler; wherein, The blocking signal sampling circuit includes a first voltage stabilizing diode and two resistors connected in series. The cathode of the first voltage stabilizing diode is connected to the drain of the field effect transistor A, and its anode is grounded through two resistors connected in series, and the connection point of the two resistors serves as the sampling point of the blocking signal.

5. The battery repair circuit according to claim 1, wherein, It further includes a feedback signal sampling circuit for collecting feedback signals; and the feedback signal sampling circuit includes: a voltage reference chip, a first to sixth resistor, a third to fifth capacitor; wherein, One end of the first resistor is connected to the drain of the field effect transistor A, and the other end is connected to the first input end of the first optocoupler; one end of the second resistor is connected to the drain of the field effect transistor B, and the other end is sequentially connected to the second input end of the first optocoupler through the third resistor and the third capacitor; the connection point of the second resistor and the third resistor is grounded through the fourth resistor, and this connection point is connected to the reference input end of the voltage reference chip; the anode of the voltage reference chip is grounded, and its cathode is connected to the second input end of the first optocoupler; one end of the fifth resistor is connected to the first input end of the first optocoupler, and the other end is connected to the second input end of the first optocoupler; one end of the fourth capacitor is connected to the second input end of the first optocoupler, and the other end is grounded; the fifth capacitor and the sixth resistor are connected in series and then connected in parallel to the second resistor.

6. The battery repair circuit according to claim 3, wherein, It further includes a first power supply circuit for supplying power to the fast turn-off controller chip; and moreover, the first power supply circuit includes: a second diode, a seventh resistor, a sixth capacitor, and a seventh capacitor; wherein, the anode of the second diode is connected to a tap of the secondary coil of the multi-tap transformer, and its cathode is connected to one end of the seventh resistor; the other end of the seventh resistor is connected to the power supply input end of the fast turn-off controller chip; the sixth capacitor and the seventh capacitor are connected in parallel, one end is connected to the power supply input end of the fast turn-off controller chip, and the other end is respectively connected to another tap of the secondary coil of the multi-tap transformer and the reference input end of the fast turn-off controller chip.

7. The battery repair circuit according to any one of claims 2 to 6, characterized in that, The PWM signal generation module includes a microcontroller, a digital potentiometer, a first amplifier A, a first amplifier B, a second amplifier A, and a second amplifier B. Among them, the microcontroller is connected to the digital potentiometer, the digital potentiometer is respectively connected to the first amplifier A and the first amplifier B, the second amplifier A is connected to the first amplifier A, and the second amplifier B is connected to the first amplifier B. Moreover, the two input terminals of the second amplifier A are respectively connected to both ends of the output resistor of the positive pulse branch, the two input terminals of the second amplifier B are respectively connected to both ends of the output resistor of the negative pulse branch, the first amplifier A outputs a PWM signal to the positive pulse branch, and the first amplifier B outputs a PWM signal to the negative pulse branch.

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