Current sampling circuit for driving direct current motor to rotate forwards and backwards based on H bridge

Abstract

The utility model relates to the technical field of circuits, and belongs to a current sampling circuit for driving a direct current motor to rotate positively and negatively based on an H bridge, which is characterized by comprising an H bridge motor driving circuit and a high-precision operational amplifier proportion amplifying circuit, and the high-precision operational amplifier proportion amplifying circuit comprises an operational amplifier. The high-precision operational amplifier proportion amplifying circuit is connected with an input voltage positive clamping protection circuit and an input voltage negative clamping protection circuit which are used for protecting an operational amplifier, the H-bridge motor driving circuit is connected with a control unit MCU, and the control unit MCU comprises a voltage signal feedback end. And the voltage signal feedback end is connected with an output voltage clamping protection circuit of the protection control unit MCU. According to the utility model, the voltage signal can be amplified, the current sampling precision can be improved, the material cost can be reduced, the space can be saved, the heating problem caused by the series connection of a current sampling resistor in the H-bridge driving circuit can be solved, the resistance of a loop in the H-bridge driving circuit can be reduced, and the sampling efficiency of the circuit can be improved; the stability of the circuit is improved, and normal work of electronic components in the circuit is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, and belongs to a current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation. Background Art

[0002] At present, the current sampling circuit of the H-bridge driven DC motor mostly adopts the current sensor solution, that is, the Hall sensor and silicon steel sheet. This solution is costly and bulky, and is not suitable for controllers with small size, high power density and low cost. Others will use the current sampling resistor plus high-precision operational amplifier solution. When the current passes through the current sampling resistor, it will generate heat and reduce the efficiency of the controller. Improper selection of the current sampling resistor may also cause the resistor to burn out and the controller to fail to work.

[0003] Therefore, in order to solve the above problems, how to design a current sampling circuit based on H-bridge driving the DC motor forward and reverse rotation is a technical problem that needs to be solved urgently in the industry. Utility Model Content

[0004] The utility model provides a current sampling circuit based on H-bridge driven forward and reverse rotation of a DC motor, which can effectively solve the problems in the background technology.

[0005] In order to achieve the above object, the utility model provides the following implementation scheme:

[0006] The present application provides a current sampling circuit based on H-bridge driven forward and reverse rotation of a DC motor, characterized in that it includes an H-bridge motor driving circuit and a high-precision operational amplifier proportional amplification circuit, the high-precision operational amplifier proportional amplification circuit includes an operational amplifier, the high-precision operational amplifier proportional amplification circuit is connected to an input voltage positive clamping protection circuit and an input voltage negative clamping protection circuit for protecting the operational amplifier, the H-bridge motor driving circuit is connected to a control unit MCU, the control unit MCU includes a voltage signal feedback terminal, and the voltage signal feedback terminal is connected to an output voltage clamping protection circuit for protecting the control unit MCU.

[0007] Further, the H-bridge motor drive circuit includes four NMOS tubes Q6, Q7, Q8, Q9 and a DC motor, the DC motor includes a connection terminal M1 and a connection terminal M2, the D pole of the NMOS tube Q6 is connected to the positive pole of the power supply, the S pole of the NMOS tube Q7 is connected to the negative pole of the power supply, the S pole of the NMOS tube Q6 and the D pole of the NMOS tube Q7 are both connected to the connection terminal M1, the D pole of the NMOS tube Q8 is connected to the positive pole of the power supply, the S pole of the NMOS tube Q9 is connected to the negative pole of the power supply, and the S pole of the NMOS tube Q8 and the D pole of the NMOS tube Q9 are both connected to the connection terminal M2.

[0008] Furthermore, the control unit MCU includes pulse width modulation signal terminals PWM1, PWM2, PWM3, and PWM4, the pulse width modulation signal terminal PWM1 is connected to the G pole of the NMOS tube Q6, the pulse width modulation signal terminal PWM2 is connected to the G pole of the NMOS tube Q7, the pulse width modulation signal terminal PWM3 is connected to the G pole of the NMOS tube Q8, and the pulse width modulation signal terminal PWM4 is connected to the G pole of the NMOS tube Q9.

[0009] Furthermore, the input voltage positive clamping protection circuit includes a plurality of resistors R5, R12 and a Schottky diode D1, one end of the resistor R5 is connected to pin 1 of the Schottky diode D1, the other end of the resistor R5 is connected to the DC motor connection terminal M1, one end of the resistor R12 is connected to pin 2 of the Schottky diode D1, the other end of the resistor R12 is connected to the DC motor connection terminal M2, and pin 3 of the Schottky diode D1 is connected to a 5V voltage.

[0010] Furthermore, the input voltage negative clamping protection circuit includes resistors R6, R13, capacitors C2, C3 and diodes D2, D3. One end of the resistor R6 is connected to the resistor R5, the other end of the resistor R6 is connected to the cathode of the diode D2, the anode of the diode D2 is connected to the reference ground GND, the capacitor C2 is connected in parallel to both ends of the diode D2, one end of the resistor R13 is connected to the resistor R12, the other end of the resistor R13 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the reference ground GND, and the capacitor C3 is connected in parallel to both ends of the diode D3.

[0011] Furthermore, the high-precision operational amplifier proportional amplification circuit also includes resistors R1 and R8, the operational amplifier includes operational amplifiers U1A and U1B, the inverting input terminal of the operational amplifier U1A is connected to the negative pole of the power supply through a plurality of resistors, the positive input terminal of the operational amplifier U1A is connected to the reference ground GND through a plurality of resistors, the resistor R1 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1A, the resistor R6 is connected to one end of the diode D2 and is connected to the positive input terminal of the operational amplifier U1A, the positive input terminal of the power supply of the operational amplifier U1A is connected to a 12V voltage and a capacitor C1, the capacitor C1 is connected to the reference ground GND, the negative input terminal of the power supply of the operational amplifier U1A is connected to the reference ground GND, the inverting input terminal of the operational amplifier U1B is connected to the negative pole of the power supply through a plurality of resistors, the positive input terminal of the operational amplifier U1B is connected to the reference ground GND through a plurality of resistors, the resistor R8 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1B, and the resistor R13 is connected to one end of the diode D3 and is connected to the positive input terminal of the operational amplifier U1B.

[0012] Further, the output voltage clamping protection circuit includes a low-pass filter composed of R15 and C4, a low-pass filter composed of R16 and C5, resistors R4, R11 and Schottky diode D4, one end of the resistor R4 is connected to the output end of the operational amplifier U1A, the other end of the resistor R4 is connected to one end of the resistor R15, the other end of the resistor R15 is connected to the capacitor C4, the capacitor C4 is connected to the reference ground GND, one end of the resistor R11 is connected to the output end of the operational amplifier U1B, the other end of the resistor R11 is connected to one end of the resistor R16, the other end of the resistor R16 is connected to the capacitor C5, the capacitor C4 is connected to the reference ground GND, pin 1 of the Schottky diode D4 is connected between the resistor R4 and the resistor R15, pin 3 of the Schottky diode D4 is connected between the resistor R11 and the resistor R16, and pin 2 of the Schottky diode D4 is connected to a 5V voltage.

[0013] Furthermore, the control unit MCU also includes voltage signal feedback terminals M1_AI and M2_AI. The voltage signal feedback terminal M1_AI is connected to one end of the resistor R15 connected to the capacitor C4, and the voltage signal feedback terminal M2_AI is connected to one end of the resistor R16 connected to the capacitor C5.

[0014] Compared with the prior art, the utility model provides a current sampling circuit based on H-bridge driving DC motor forward and reverse rotation, which has the following beneficial effects:

[0015] The utility model realizes the forward and reverse rotation of the motor through the H-bridge motor driving circuit, and can amplify the voltage signal through the high-precision operational amplifier proportional amplifier circuit, thereby improving the current sampling accuracy. The accuracy of the current sampling circuit can replace the finished current sensor, and the internal resistance after the NMOS is turned on replaces the current sampling resistor, thereby reducing the material cost, saving space, solving the heating problem caused by the series current sampling resistor in the H-bridge driving circuit, and reducing the resistance of the loop in the H-bridge driving circuit, thereby improving the operating efficiency of the controller. In addition, a corresponding protection circuit is also provided to improve the stability of the circuit and ensure the normal operation of the electronic components in the circuit.

[0016] It solves the problems of high cost, large size, severe resistance heating, and low controller efficiency.

[0017] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a circuit diagram of a current sampling circuit for driving a DC motor forward and reverse based on an H-bridge according to the utility model;

[0019] Figure 2 This is the H-bridge motor driving circuit diagram of the utility model;

[0020] Figure 3 This is a schematic diagram of the control unit MCU of the utility model;

[0021] Figure 4 This is a schematic diagram of an input voltage positive clamping protection circuit of the utility model;

[0022] Figure 5 It is a schematic diagram of a high-precision operational amplifier proportional amplification circuit and an input voltage negative clamp protection circuit of the utility model;

[0023] Figure 6 This is a schematic diagram of the output voltage clamping protection circuit of the utility model;

[0024] Figure 7 It is a simulation curve diagram of the utility model. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model is further described in detail below through the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the utility model and are not used to limit the scope of the utility model. In addition, in the following description, the description of the known structure and technology is omitted to avoid unnecessary confusion of the concept of the utility model.

[0026] See also Figure 1-6 A current sampling circuit based on H-bridge driving of a DC motor for forward and reverse rotation, comprising an H-bridge motor driving circuit and a high-precision operational amplifier proportional amplification circuit, wherein the high-precision operational amplifier proportional amplification circuit includes an operational amplifier, and the high-precision operational amplifier proportional amplification circuit is connected to an input voltage positive clamping protection circuit and an input voltage negative clamping protection circuit for protecting the operational amplifier, and the H-bridge motor driving circuit is connected to a control unit MCU, and the control unit MCU includes a voltage signal feedback terminal, and the voltage signal feedback terminal is connected to an output voltage clamping protection circuit for protecting the control unit MCU.

[0027] Specifically, see Figure 2 The H-bridge motor driving circuit includes four NMOS tubes Q6, Q7, Q8, Q9 and a DC motor, wherein the DC motor includes a connection terminal M1 and a connection terminal M2, a D pole of the NMOS tube Q6 is connected to the positive pole of the power supply, an S pole of the NMOS tube Q7 is connected to the negative pole of the power supply, an S pole of the NMOS tube Q6 and a D pole of the NMOS tube Q7 are both connected to the connection terminal M1, a D pole of the NMOS tube Q8 is connected to the positive pole of the power supply, an S pole of the NMOS tube Q9 is connected to the negative pole of the power supply, and an S pole of the NMOS tube Q8 and a D pole of the NMOS tube Q9 are both connected to the connection terminal M2.

[0028] Specifically, see Figure 2-3 The control unit MCU includes pulse width modulation signal terminals PWM1, PWM2, PWM3, and PWM4. The pulse width modulation signal terminal PWM1 is connected to the G pole of the NMOS tube Q6, the pulse width modulation signal terminal PWM2 is connected to the G pole of the NMOS tube Q7, the pulse width modulation signal terminal PWM3 is connected to the G pole of the NMOS tube Q8, and the pulse width modulation signal terminal PWM4 is connected to the G pole of the NMOS tube Q9.

[0029] Specifically, see Figure 4 The input voltage positive clamping protection circuit includes a plurality of resistors R5, R12 and a Schottky diode D1. One end of the resistor R5 is connected to pin 1 of the Schottky diode D1, and the other end of the resistor R5 is connected to the DC motor connection terminal M1. One end of the resistor R12 is connected to pin 2 of the Schottky diode D1, and the other end of the resistor R12 is connected to the DC motor connection terminal M2. Pin 3 of the Schottky diode D1 is connected to a 5V voltage.

[0030] Specifically, see Figure 5 The input voltage negative clamp protection circuit includes resistors R6, R13, capacitors C2, C3 and diodes D2, D3. One end of the resistor R6 is connected to the resistor R5, the other end of the resistor R6 is connected to the cathode of the diode D2, the anode of the diode D2 is connected to the reference ground GND, the capacitor C2 is connected in parallel to both ends of the diode D2, one end of the resistor R13 is connected to the resistor R12, the other end of the resistor R13 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the reference ground GND, and the capacitor C3 is connected in parallel to both ends of the diode D3.

[0031] Specifically, see Figure 5The high-precision operational amplifier proportional amplification circuit also includes resistors R1 and R8. The operational amplifier includes operational amplifiers U1A and U1B. The inverting input terminal of the operational amplifier U1A is connected to the negative electrode of the power supply through a plurality of resistors. The positive input terminal of the operational amplifier U1A is connected to the reference ground GND through a plurality of resistors. The resistor R1 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1A. The resistor R6 is connected to one end of the diode D2 and the positive input terminal of the operational amplifier U1A. The positive input terminal of the power supply of the operational amplifier U1A is connected to a 12V voltage and a capacitor C1. The capacitor C1 is connected to the reference ground GND. The negative input terminal of the power supply of the operational amplifier U1A is connected to the reference ground GND. The inverting input terminal of the operational amplifier U1B is connected to the negative electrode of the power supply through a plurality of resistors. The positive input terminal of the operational amplifier U1B is connected to the reference ground GND through a plurality of resistors. The resistor R8 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1B. The resistor R13 is connected to one end of the diode D3 and the positive input terminal of the operational amplifier U1B.

[0032] Specifically, see Figure 6 The output voltage clamping protection circuit includes a low-pass filter composed of R15 and C4, a low-pass filter composed of R16 and C5, resistors R4, R11 and Schottky diode D4, one end of the resistor R4 is connected to the output end of the operational amplifier U1A, the other end of the resistor R4 is connected to one end of the resistor R15, the other end of the resistor R15 is connected to the capacitor C4, the capacitor C4 is connected to the reference ground GND, one end of the resistor R11 is connected to the output end of the operational amplifier U1B, the other end of the resistor R11 is connected to one end of the resistor R16, the other end of the resistor R16 is connected to the capacitor C5, the capacitor C4 is connected to the reference ground GND, pin 1 of the Schottky diode D4 is connected between the resistor R4 and the resistor R15, pin 3 of the Schottky diode D4 is connected between the resistor R11 and the resistor R16, and pin 2 of the Schottky diode D4 is connected to a 5V voltage.

[0033] Specifically, see Figure 3 , Figure 6 The control unit MCU also includes voltage signal feedback terminals M1_AI and M2_AI. The voltage signal feedback terminal M1_AI is connected to one end of the resistor R15 connected to the capacitor C4, and the voltage signal feedback terminal M2_AI is connected to one end of the resistor R16 connected to the capacitor C5.

[0034] Embodiment 1:

[0035] The H-bridge motor drive circuit includes four NMOS tubes, namely Q6, Q7, Q8, and Q9, and two NMOS tubes form a half bridge. The DC motor includes a connection terminal M1 and a connection terminal M2, the D pole of Q6 is connected to the positive pole of the power supply, the S pole of Q7 is connected to the negative pole of the power supply, the S pole of Q6 and the D pole of Q7 are both connected to the connection terminal M1, the D pole of Q8 is connected to the positive pole of the power supply, the S pole of Q9 is connected to the negative pole of the power supply, and the S pole of Q8 and the D pole of Q9 are both connected to the connection terminal M2.

[0036] The control unit MCU controls the conduction signal of the MOS tube, and is respectively provided with four pulse width modulation signal terminals PWM1, PWM2, PWM3 and PWM4. The pulse width modulation signal terminal PWM1 is connected to the G pole of the NMOS tube Q6, the pulse width modulation signal terminal PWM2 is connected to the G pole of the NMOS tube Q7, the pulse width modulation signal terminal PWM3 is connected to the G pole of the NMOS tube Q8, and the pulse width modulation signal terminal PWM4 is connected to the G pole of the NMOS tube Q9.

[0037] During the H-bridge driving process, Q8 is turned on, Q9 is turned off, Q6 and Q7 cannot be turned on at the same time, Q8 and Q9 cannot be turned on at the same time, and after Q8 is turned on, the source S and drain D of Q8 are approximately connected together, so a voltage close to B+ will appear at the M2 end. When a voltage close to B+ appears at M2, the R9 resistor limits the current, and the positive electrode voltage of the D1 Schottky diode is greater than the negative electrode, and then the diode is turned on, clamping the B+ voltage at 5.3V to prevent the input voltage from being too high and damaging the operational amplifier.

[0038] PWM3 controls Q8 to turn on. When Q8 is turned off, the current of the DC motor will not change suddenly. Due to the inductance of the DC motor, it will continue to flow. When the current passes through the body diode of Q9, M2 will have a negative voltage. When M2 has a negative voltage, the R9 resistor and R11 will limit the current. After the positive electrode voltage of the D5 Schottky diode is greater than the negative electrode, the diode will turn on and clamp the voltage at -0.1V to prevent the input voltage from being too low to damage the operational amplifier.

[0039] Embodiment 2:

[0040] The high-precision op amp proportional amplifier circuit includes operational amplifiers U1A and U1B and resistors R1 and R8. The DC motor connection terminal M1 inputs the voltage V, and after voltage division, the voltage at the op amp 3pin is = , due to the virtual short and virtual break characteristics of the op amp, the voltage of the op amp 2pin is = , and finally get the output voltage = .

[0041] Furthermore, R1=R7, R2=R5, R3=R6, and the simplified formula equals the output voltage .

[0042] Furthermore, the DC motor connection terminal M2 input voltage V, after voltage division, the voltage to the op amp 5pin = , due to the virtual short and virtual break characteristics of the op amp, the voltage of the op amp 2pin is = , and finally get the output voltage = .

[0043] Furthermore, R9=R12, R10=R13, R8=R14, and the simplified formula equals the output voltage .

[0044] Furthermore, the output voltage clamping protection circuit includes a low-pass filter composed of R15 and C4, a low-pass filter composed of R16 and C5, resistors R4, R11 and Schottky diode D4. When the input voltage exceeds the safety voltage, the positive electrode voltage of Schottky diode D4 is greater than the negative electrode and then it is turned on to clamp. The low-pass filter can filter out high-frequency interference, and the cut-off frequency f= .

[0045] Furthermore, when the DC motor rotates forward: the relationship between the motor current and the op amp output sampling voltage is: Vout = .

[0046] Furthermore, when the DC motor reverses: the relationship between the motor current and the op amp output sampling voltage is: Vout = .

[0047] Embodiment three:

[0048] R2=R5=R9=R12=30KΩ, R3=R6=R10=R13=100Ω, R1=R7=R8=R14=100KΩ, MOS tube Rdson=3mΩ, the DC motor rotates forward.

[0049] According to the second embodiment, the simulation results are obtained. Figure 4 : Current output 103A, the operational amplifier output voltage M2_AI voltage signal feedback value is 1.04V, the current sampling accuracy is accurate to 1%, the operational amplifier U1A positive input terminal voltage alternates between B+ voltage and negative voltage, and the curve in the figure is the waveform that appears when the protection circuit clamps the DC motor M1 terminal voltage.

[0050] The above description is only a preferred embodiment of the present invention, and the printed data cable is not intended to limit the present invention. Any modification, equivalent replacement or improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation, characterized in that: It comprises an H-bridge motor drive circuit and a high-precision operational amplifier proportional amplification circuit, wherein the high-precision operational amplifier proportional amplification circuit comprises an operational amplifier, the high-precision operational amplifier proportional amplification circuit is connected to an input voltage positive clamping protection circuit and an input voltage negative clamping protection circuit for protecting the operational amplifier, the H-bridge motor drive circuit is connected to a control unit MCU, the control unit MCU comprises a voltage signal feedback terminal, and the voltage signal feedback terminal is connected to an output voltage clamping protection circuit for protecting the control unit MCU.

2. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 1, characterized in that: The H-bridge motor driving circuit includes four NMOS tubes Q6, Q7, Q8, Q9 and a DC motor, wherein the DC motor includes a connection terminal M1 and a connection terminal M2, the D pole of the NMOS tube Q6 is connected to the positive pole of the power supply, the S pole of the NMOS tube Q7 is connected to the negative pole of the power supply, the S pole of the NMOS tube Q6 and the D pole of the NMOS tube Q7 are both connected to the connection terminal M1, the D pole of the NMOS tube Q8 is connected to the positive pole of the power supply, the S pole of the NMOS tube Q9 is connected to the negative pole of the power supply, and the S pole of the NMOS tube Q8 and the D pole of the NMOS tube Q9 are both connected to the connection terminal M2.

3. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 2, characterized in that: The control unit MCU includes pulse width modulation signal terminals PWM1, PWM2, PWM3, and PWM4. The pulse width modulation signal terminal PWM1 is connected to the G pole of the NMOS tube Q6, the pulse width modulation signal terminal PWM2 is connected to the G pole of the NMOS tube Q7, the pulse width modulation signal terminal PWM3 is connected to the G pole of the NMOS tube Q8, and the pulse width modulation signal terminal PWM4 is connected to the G pole of the NMOS tube Q9.

4. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 2, characterized in that: The input voltage positive clamping protection circuit includes several resistors R5, R12 and a Schottky diode D1. One end of the resistor R5 is connected to pin 1 of the Schottky diode D1, and the other end of the resistor R5 is connected to the DC motor connection terminal M1. One end of the resistor R12 is connected to pin 2 of the Schottky diode D1, and the other end of the resistor R12 is connected to the DC motor connection terminal M2. Pin 3 of the Schottky diode D1 is connected to a 5V voltage.

5. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 4, characterized in that: The input voltage negative clamp protection circuit includes resistors R6, R13, capacitors C2, C3 and diodes D2, D3. One end of the resistor R6 is connected to the resistor R5, the other end of the resistor R6 is connected to the cathode of the diode D2, the anode of the diode D2 is connected to the reference ground GND, the capacitor C2 is connected in parallel to both ends of the diode D2, one end of the resistor R13 is connected to the resistor R12, the other end of the resistor R13 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the reference ground GND, and the capacitor C3 is connected in parallel to both ends of the diode D3.

6. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 5, characterized in that: The high-precision operational amplifier proportional amplification circuit also includes resistors R1 and R8. The operational amplifier includes operational amplifiers U1A and U1B. The inverting input terminal of the operational amplifier U1A is connected to the negative electrode of the power supply through a plurality of resistors. The positive input terminal of the operational amplifier U1A is connected to the reference ground GND through a plurality of resistors. The resistor R1 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1A. The resistor R6 is connected to one end of the diode D2 and is connected to the positive input terminal of the operational amplifier U1A. The positive input terminal of the power supply of the operational amplifier U1A is connected to a 12V voltage and a capacitor C1. The capacitor C1 is connected to the reference ground GND. The negative input terminal of the power supply of the operational amplifier U1A is connected to the reference ground GND. The inverting input terminal of the operational amplifier U1B is connected to the negative electrode of the power supply through a plurality of resistors. The positive input terminal of the operational amplifier U1B is connected to the reference ground GND through a plurality of resistors. The resistor R8 is connected in parallel between the inverting input terminal and the output terminal of the operational amplifier U1B. The resistor R13 is connected to one end of the diode D3 and is connected to the positive input terminal of the operational amplifier U1B.

7. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 6, characterized in that: The output voltage clamping protection circuit includes a low-pass filter composed of R15 and C4, a low-pass filter composed of R16 and C5, resistors R4, R11 and Schottky diode D4, one end of the resistor R4 is connected to the output end of the operational amplifier U1A, the other end of the resistor R4 is connected to one end of the resistor R15, the other end of the resistor R15 is connected to the capacitor C4, the capacitor C4 is connected to the reference ground GND, one end of the resistor R11 is connected to the output end of the operational amplifier U1B, the other end of the resistor R11 is connected to one end of the resistor R16, the other end of the resistor R16 is connected to the capacitor C5, pin 1 of the Schottky diode D4 is connected between the resistor R4 and the resistor R15, pin 3 of the Schottky diode D4 is connected between the resistor R11 and the resistor R16, and pin 2 of the Schottky diode D4 is connected to a 5V voltage.

8. A current sampling circuit based on H-bridge driving a DC motor for forward and reverse rotation as claimed in claim 7, characterized in that: The control unit MCU further includes voltage signal feedback terminals M1_AI and M2_AI. The voltage signal feedback terminal M1_AI is connected to one end of the resistor R15 connected to the capacitor C4. The voltage signal feedback terminal M2_AI is connected to one end of the resistor R16 connected to the capacitor C5.

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