A bidirectional speed control circuit for a DC brushed motor with overcurrent protection function

Abstract

The present invention discloses a bidirectional speed control circuit for a DC brushed motor with overcurrent protection function, which includes fifteen resistors, a comparator, two relays, an NMOS transistor, an optocoupler, five triodes, four capacitors and five diodes. The PWM control signal is connected to the control terminal of the NMOS transistor through the optocoupler, the current is sampled through the first resistor and converted into a voltage and then connected to the comparator. The comparator determines whether it exceeds the limit. If it exceeds the limit, the interlock circuit designed based on the triode is triggered to cut off the HVC1 voltage to achieve overcurrent protection. The advantages are that it can replace the drive control board or the dedicated integrated drive chip provided by the DC brushed motor manufacturer for speed control, reduces the cost requirements of the product, improves the flexibility of product application, and has an overcurrent protection function, which can avoid the DC brushed motor from being burned out due to overcurrent. There is no need to additionally set a software detection method or a dedicated chip for overcurrent detection of the DC brushed motor, and the reliability is high and the cost is low.

Description

Technical Field

[0001] The present invention relates to a two-way speed control circuit for a DC brushed motor, and more particularly to a two-way speed control circuit for a DC brushed motor with an overcurrent protection function. Background Art

[0002] In a series of products such as medical DR, there are a large number of applications for controlling the movement position of components using DC brushed motors with different powers. Currently, DC brushed motors usually use drive control boards provided by DC brushed motor manufacturers or dedicated integrated drive chips for speed control, which greatly limits the cost requirements of products and the flexibility of applications. Due to the relatively complex mechanical structure of these products, there is a high probability of causing the DC brushed motor to stall and an overcurrent problem, which may further cause the DC brushed motor to burn out. To avoid the DC brushed motor from burning out due to overcurrent, currently, the overcurrent detection of the DC brushed motor is mainly carried out by using software detection methods or dedicated chip detection methods. However, the former has low reliability, while the latter has high reliability but also high cost. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a two-way speed control circuit for a DC brushed motor with an overcurrent protection function. This two-way speed control circuit for a DC brushed motor can replace the drive control board provided by the DC brushed motor manufacturer or the dedicated integrated drive chip for speed control, reducing the cost requirements of the product, improving the flexibility of product applications, and having an overcurrent protection function, which can avoid the DC brushed motor from burning out due to overcurrent. There is no need to additionally set up software detection methods or dedicated chips for the overcurrent detection of the DC brushed motor, with high reliability and low cost.

[0004] The technical solution adopted by the present invention to solve the above technical problems is as follows: A bidirectional speed control circuit for a DC brushed motor with overcurrent protection function, comprising a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a comparator, a first relay, a second relay, an NMOS transistor, an optocoupler, a first triode, a second triode, a third triode, a fourth triode, a fifth triode, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode, a third diode, a fourth diode and a fifth diode. The first diode is a freewheeling diode, the second diode is a common cathode diode, the third diode, the fourth diode and the fifth diode are all light-emitting diodes. The third triode is a PNP type triode, and the first triode, the second triode, the fourth triode and the fifth triode are all NPN type triodes. The comparator has a non-inverting input terminal, an inverting input terminal, a positive voltage terminal, a negative voltage terminal and an output terminal. The first relay and the second relay each include a coil and a switch. The switches of the first relay and the second relay each have a common terminal and two connection terminals;

[0005] One end of the first resistor is connected to one end of the first capacitor, the other end of the first resistor and one end of the second resistor are connected to the source of the NMOS tube, the other end of the second resistor, the other end of the first capacitor, and one end of the third resistor are connected to the non-inverting end of the comparator, the inverting end of the comparator, one end of the fourth resistor, one end of the fifth resistor, and one end of the second capacitor are connected, the other end of the fifth resistor is connected to the other end of the third resistor and the connection end thereof is connected to a voltage HVre, the other end of the fourth resistor and the other end of the second capacitor are connected to the negative voltage end of the comparator and the connection end thereof is connected to a voltage HND , the positive voltage of the comparator is connected to one end of the third capacitor and its connection end is connected to the voltage HVC, the other end of the third capacitor is connected to the voltage HND, the output end of the comparator, one end of the sixth resistor and the base of the first transistor are connected, the other end of the sixth resistor is connected to the voltage HVC, the emitter of the first transistor, one end of the fourth capacitor, one end of the seventh resistor and the emitter of the second transistor are connected and the connection end is connected to the voltage HND, the collector of the second transistor is connected to one end of the eighth resistor, the other end of the eighth resistor is connected to the base of the third transistor, the collector of the first transistor, the fourth capacitor and the emitter of the seventh resistor are connected to the emitter of the second transistor ..., the collector of the eighth resistor and the base of the third transistor are connected to the collector of the first transistor, the fourth capacitor and the emitter of the seventh resistor. The other end of the capacitor, the other end of the seventh resistor, the base of the second transistor, one end of the ninth resistor and one end of the tenth resistor are connected, the other end of the ninth resistor is connected to the collector of the third transistor and its connection end is connected to the voltage HVC1, the other end of the tenth resistor is connected to the overcurrent recovery signal OCR for releasing the overcurrent protection state, the emitter of the third transistor is connected to the voltage HVC, the gate of the NMOS tube, one end of the fifteenth resistor and the emitter of the optocoupler are connected, the other end of the fifteenth resistor is connected to the voltage HND, the collector of the optocoupler is connected to the voltage HVC1, the cathode of the optocoupler is grounded, the anode of the optocoupler and the One end of the fourteenth resistor is connected, the other end of the fourteenth resistor is the third input terminal K3 of the DC brush motor bidirectional speed regulation control circuit, one end of the twelfth resistor is the first input terminal K1 of the DC brush motor bidirectional speed regulation control circuit, the other end of the twelfth resistor is connected to the anode of the third diode, the cathode of the third diode is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor, one end of the coil of the first relay and an anode of the second diode are connected, the other end of the coil of the first relay is connected to the cathode of the second diode and the connection end thereof is connected to the voltage VDD,The other anode of the second diode, one end of the coil of the second relay, and the collector of the fifth triode are connected. The other end of the coil of the second relay is connected to the voltage VDD. The emitter of the fifth triode is grounded. The base of the fifth triode is connected to the cathode of the fourth diode. The anode of the fourth diode is connected to one end of the thirteenth resistor. The other end of the thirteenth resistor is the second input terminal K2 of the DC brush motor bidirectional speed control circuit. The first connection terminal of the switch of the first relay, the first connection terminal of the switch of the second relay, the anode of the first diode, one end of the eleventh resistor, and the drain of the NMOS transistor are connected. The second connection terminal of the switch of the first relay, the second connection terminal of the switch of the second relay, the cathode of the first diode, and the anode of the fifth diode are connected and their connection terminal is connected to the voltage HVD. The cathode of the fifth diode is connected to the other end of the eleventh resistor. The common terminal of the switch of the first relay is the positive output terminal M+ of the DC brush motor bidirectional speed control circuit. The common terminal of the switch of the second relay is the negative output terminal M- of the DC brush motor bidirectional speed control circuit;

[0006] The voltage HVre provides a bias voltage for the comparator. The voltage HVC1 provides a speed control voltage for the DC brush motor bidirectional speed control circuit. The voltage VDD provides a direction control voltage for the DC brush motor bidirectional speed control circuit. The voltage HVC provides an overcurrent protection control voltage for the DC brush motor bidirectional speed control circuit. The voltage HVD provides a drive voltage for the DC brush motor bidirectional speed control circuit. The voltage HND is a ground voltage. The third input terminal K3 of the DC brush motor bidirectional speed control circuit is used to connect a PWM control signal for controlling the motor speed. The first input terminal K1 of the DC brush motor bidirectional speed control circuit is used to connect a motor forward movement direction control voltage. The second input terminal K2 of the DC brush motor bidirectional speed control circuit is used to connect a motor reverse movement direction control voltage. The positive output terminal M+ of the DC brush motor bidirectional speed control circuit is used to connect the positive voltage terminal of the motor. The negative output terminal M- of the DC brush motor bidirectional speed control circuit is used to connect the negative voltage terminal of the motor.

[0007] Compared with the prior art, the advantages of the present invention are as follows: a bidirectional speed control circuit for a DC brushed motor with overcurrent protection function is constructed by a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a comparator, a first relay, a second relay, an NMOS transistor, an optocoupler, a first triode, a second triode, a third triode, a fourth triode, a fifth triode, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode, a third diode, a fourth diode, and a fifth diode. The PWM control signal is connected to the control terminal of the NMOS transistor through the optocoupler to achieve simple and reliable speed control, and it can replace the drive control board or the dedicated integrated drive chip provided by the DC brushed motor manufacturer. The current is sampled through the first resistor, converted into a voltage and then connected to the comparator. The comparator determines whether the current exceeds the limit. If it exceeds the limit, it triggers an interlock circuit based on triodes composed of the first triode, the second triode, the third triode, the seventh resistor, the eighth resistor, the ninth resistor, the tenth resistor, and the fourth capacitor to cut off the HVC1 voltage and achieve overcurrent protection. Therefore, the present invention can replace the drive control board or the dedicated integrated drive chip provided by the DC brushed motor manufacturer for speed control, reduce the cost requirements of the product, improve the flexibility of product application, and has an overcurrent protection function, which can prevent the DC brushed motor from burning out due to overcurrent. There is no need to additionally set a software detection method or a dedicated chip for overcurrent detection of the DC brushed motor, and the reliability is high and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a circuit diagram of the bidirectional speed control circuit for a DC brushed motor with overcurrent protection function of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0009] The present invention will be further described in detail below with reference to the embodiments in the drawings.

[0010] Embodiment: As Figure 1As shown, a bidirectional speed control circuit for a DC brushed motor with overcurrent protection function includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a comparator U1A, a first relay, a second relay, an NMOS transistor M1, an optocoupler U2, a first triode Q1, a second triode Q2, a third triode Q3, a fourth triode Q4, a fifth triode Q5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, and a fifth diode D5. The first diode D1 is a freewheeling diode, the second diode D2 is a common cathode diode, the third diode D3, the fourth diode D4, and the fifth diode D5 are all light-emitting diodes, the third triode Q3 is a PNP-type triode, and the first triode Q1, the second triode Q2, the fourth triode Q4, and the fifth triode Q5 are all NPN-type triodes. The comparator U1A has a non-inverting terminal, an inverting terminal, a positive voltage terminal, a negative voltage terminal, and an output terminal. The first relay and the second relay each include a coil and a switch, and the switches of the first relay and the second relay each have a common terminal and two connection terminals; one end of the first resistor R1 is connected to one end of the first capacitor C1, the other end of the first resistor R1, one end of the second resistor R2, and the source of the NMOS transistor M1 are connected, the other end of the second resistor R2, the other end of the first capacitor C1, one end of the third resistor R3, and the non-inverting terminal of the comparator U1A are connected, the inverting terminal of the comparator U1A, one end of the fourth resistor R4, one end of the fifth resistor R5, and one end of the second capacitor C2 are connected, the other end of the fifth resistor R5 is connected to the other end of the third resistor R3 and its connection terminal is connected to the voltage HVre, the other end of the fourth resistor R4, the other end of the second capacitor C2, and the negative voltage terminal of the comparator U1A are connected and its connection terminal is connected to the voltage HND, the positive voltage of the comparator U1A is connected to one end of the third capacitor C3 and its connection terminal is connected to the voltage HVC, the other end of the third capacitor C3 is connected to the voltage HND, the output terminal of the comparator U1A, one end of the sixth resistor R6, and the base of the first triode Q1 are connected, the other end of the sixth resistor R6 is connected to the voltage HVC, the emitter of the first triode Q1, one end of the fourth capacitor C4, one end of the seventh resistor R7, and the emitter of the second triode Q2 are connected and its connection terminal is connected to the voltage HND, the collector of the second triode Q2 is connected to one end of the eighth resistor R8, the other end of the eighth resistor R8 is connected to the base of the third triode Q3, the collector of the first triode Q1, the other end of the fourth capacitor C4, the other end of the seventh resistor R7, the base of the second triode Q2, one end of the ninth resistor R9, and one end of the tenth resistor R10 are connected,The other end of the ninth resistor R9 is connected to the collector of the third transistor Q3 and its connection end is connected to the voltage HVC1, the other end of the tenth resistor R10 is connected to the overcurrent recovery signal OCR for releasing the overcurrent protection state, the emitter of the third transistor Q3 is connected to the voltage HVC, the gate of the NMOS tube M1, one end of the fifteenth resistor R15 and the emitter of the optocoupler U2 are connected, the other end of the fifteenth resistor R15 is connected to the voltage HND, the collector of the optocoupler U2 is connected to the voltage HVC1, the cathode of the optocoupler U2 is grounded, the anode of the optocoupler U2 is connected to one end of the fourteenth resistor R14, the other end of the fourteenth resistor R14 is the third input terminal K3 of the DC brush motor bidirectional speed regulation control circuit, and one end of the twelfth resistor R12 is the DC brush motor bidirectional speed regulation control circuit. The first input terminal K1 of the motor bidirectional speed control circuit, the other end of the twelfth resistor R12 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the base of the fourth transistor Q4, the emitter of the fourth transistor Q4 is grounded, the collector of the fourth transistor Q4, one end of the coil of the first relay and an anode of the second diode D2 are connected, the other end of the coil of the first relay is connected to the cathode of the second diode D2 and the connection end thereof is connected to the voltage VDD, the other anode of the second diode D2, one end of the coil of the second relay and the collector of the fifth transistor Q5 are connected, the other end of the coil of the second relay is connected to the voltage VDD, the emitter of the fifth transistor Q5 is grounded, the base of the fifth transistor Q5 and the fourth The cathode of the diode D4 is connected, the anode of the fourth diode D4 is connected to one end of the thirteenth resistor R13, the other end of the thirteenth resistor R13 is the second input terminal K2 of the DC brush motor bidirectional speed control circuit, the first connection end of the switch of the first relay, the first connection end of the switch of the second relay, the anode of the first diode D1, one end of the eleventh resistor R11 and the drain of the NMOS tube M1 are connected, the second connection end of the switch of the first relay, the second connection end of the switch of the second relay, the cathode of the first diode D1 and the anode of the fifth diode D5 are connected and the connection ends thereof are connected to the voltage HVD, the cathode of the fifth diode D5 and the other end of the eleventh resistor R11 are connected, and the common end of the switch of the first relay is connected to the common end of the switch of the first relay. It is the positive output terminal M+ of the bidirectional speed control circuit of the brushed DC motor, and the common terminal of the switch of the second relay is the negative output terminal M- of the bidirectional speed control circuit of the brushed DC motor; the voltage HVre provides a bias voltage for the comparator U1A, the voltage HVC1 provides a speed control voltage for the bidirectional speed control circuit of the brushed DC motor, the voltage VDD provides a direction control voltage for the bidirectional speed control circuit of the brushed DC motor, the voltage HVC provides an overcurrent protection control voltage for the bidirectional speed control circuit of the brushed DC motor, the voltage HVD provides a driving voltage for the bidirectional speed control circuit of the brushed DC motor, and the voltage HND is a ground voltage; the third input terminal K3 of the bidirectional speed control circuit of the brushed DC motor is used to access the PWM control signal for controlling the motor speed,The first input terminal K1 of the DC brushed motor two-way speed control circuit is used to connect the control voltage for the forward movement direction of the motor. The second input terminal K2 of the DC brushed motor two-way speed control circuit is used to connect the control voltage for the reverse movement direction of the motor. The positive output terminal M+ of the DC brushed motor two-way speed control circuit is used to connect the positive voltage terminal of the motor. The negative output terminal M- of the DC brushed motor two-way speed control circuit is used to connect the negative voltage terminal of the motor.,

[0011] In this embodiment, the voltages HVre, HND, HVC, HVC1, VDD, and HVD are determined according to the actual circuit parameters. The control voltage for the forward movement direction of the motor connected to the first input terminal K1 of the DC brushed motor two-way speed control circuit is used to control the forward rotation of the motor. The control voltage for the reverse movement direction of the motor connected to the second input terminal K2 of the DC brushed motor two-way speed control circuit is used to control the reverse rotation of the motor.

[0012] When using the DC brushed motor two-way speed control circuit with overcurrent protection function of the present invention to control the motor, connect the positive output terminal M+ of the DC brushed motor two-way speed control circuit of the present invention to the positive voltage terminal of the motor, and the negative output terminal M- to the negative voltage terminal of the motor.

[0013] If it is necessary to control the forward rotation of the motor, connect the control voltage for the forward movement direction of the motor to the first input terminal K1 of the bidirectional speed control circuit for the DC brushed motor, leave the second input terminal K2 of the bidirectional speed control circuit for the DC brushed motor floating, and connect the PWM control signal for controlling the motor speed to the third input terminal K3 of the bidirectional speed control circuit for the DC brushed motor. At this time, a high-level signal is connected to the first input terminal K1 of the bidirectional speed control circuit for the DC brushed motor, the fourth triode Q4 conducts, the level at the CR1 terminal is pulled low, the first relay conducts, the second connection terminal of the first relay conducts with the common terminal, the positive output terminal M+ of the bidirectional speed control circuit for the DC brushed motor is connected to the voltage HVD, a low-level signal is connected to the second input terminal K2 of the bidirectional speed control circuit for the DC brushed motor, the fifth triode Q5 does not conduct, the first connection terminal and the common terminal of the second relay conduct, the negative output terminal M- of the bidirectional speed control circuit for the DC brushed motor is connected to the D pole of the NMOS transistor M1, the third input terminal K3 of the bidirectional speed control circuit for the DC brushed motor is connected to the PWM control signal for controlling the motor speed, the high-level signal of the PWM control signal controls the optocoupler to conduct through the third input terminal K3, the NMOS transistor M1 is conducted, the D pole of the NMOS transistor M1 is pulled low, and the current flows from the positive output terminal M+ to the negative output terminal M- of the bidirectional speed control circuit for the DC brushed motor, realizing the forward rotation of the DC brushed motor. The speed regulation function is realized by controlling the duty cycle of the PWM control signal. The motor current flows into the first resistor R1, is converted from current to voltage and then connected to the non-inverting input terminal of the comparator U1A. When the voltage at the non-inverting input terminal of the comparator U1A exceeds the voltage threshold at the inverting input terminal, the comparator U1A outputs a high level, the first triode Q1 conducts, the second triode Q2 cuts off, the third triode Q3 cuts off, the voltage HVC1 is pulled low, and the NMOS transistor M1 is disconnected, realizing overcurrent protection. During this process, the speed of the DC brushed motor is related to the duty cycle of the PWM control signal for controlling the motor speed connected to the third input terminal K3 of the bidirectional speed control circuit for the DC brushed motor. The larger the duty cycle, the higher the speed; the smaller the duty cycle, the lower the speed.

[0014] If it is necessary to control the reverse rotation of the motor, the first input terminal K1 of the DC brushed motor two-way speed control circuit is left floating, and the control voltage for the reverse movement direction of the motor is connected to the second input terminal K2 of the DC brushed motor two-way speed control circuit. The PWM control signal for controlling the motor speed is connected to the third input terminal K3 of the DC brushed motor two-way speed control circuit. At this time, a high-level signal is connected to the second input terminal K2 of the DC brushed motor two-way speed control circuit, and the fifth triode Q5 conducts, pulling down the level of the CR2 terminal, and the second relay conducts. The second connection terminal of the second relay conducts with the common terminal, and the negative output terminal M- of the brushed motor two-way speed control circuit is connected to the voltage HVD. A low-level signal is connected to the first input terminal K1 of the DC brushed motor two-way speed control circuit, and the fourth triode Q4 does not conduct. The first connection terminal and the common terminal of the first relay conduct. The positive output terminal M+ of the DC brushed motor two-way speed control circuit is connected to the D pole of the NMOS transistor M1. The PWM control signal for controlling the motor speed is connected to the third input terminal K3 of the DC brushed motor two-way speed control circuit. The high-level signal of the PWM control signal controls the optocoupler to conduct through the third input terminal K3, turning on the NMOS transistor M1, pulling down the D pole of the NMOS transistor M1, and the current flows from the negative output terminal M- to the positive output terminal M+ of the DC brushed motor two-way speed control circuit, realizing the reverse rotation of the motor. The speed regulation function is realized by controlling the duty cycle of the PWM control signal. The motor current flows into the first resistor R1, and after being converted from current to voltage, it is connected to the non-inverting input terminal of the U1 comparator. When the voltage at the non-inverting input terminal of the comparator U1A exceeds the voltage threshold at the inverting input terminal, the comparator U1A outputs a high level, the first triode Q1 conducts, the second triode Q2 cuts off, the third triode Q3 cuts off, the HVC1 voltage is pulled down, and the NMOS transistor M1 is turned off, realizing overcurrent protection. During this process, the rotational speed of the DC brushed motor is related to the duty cycle of the PWM control signal for controlling the motor speed connected to the third input terminal K3 of the DC brushed motor two-way speed control circuit. The larger the duty cycle, the higher the speed; the smaller the duty cycle, the lower the speed.

Claims

1. A bidirectional speed control circuit for a DC brushed motor with overcurrent protection function, comprising a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a comparator, a first relay, a second relay, an NMOS transistor, an optocoupler, a first triode, a second triode, a third triode, a fourth triode, a fifth triode, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first diode, a second diode, a third diode, a fourth diode and a fifth diode. The first diode is a freewheeling diode, the second diode is a common cathode diode, the third diode, the fourth diode and the fifth diode are all light-emitting diodes. The third triode is a PNP type triode, and the first triode, the second triode, the fourth triode and the fifth triode are all NPN type triodes. The comparator has a non-inverting input terminal, an inverting input terminal, a positive voltage terminal, a negative voltage terminal and an output terminal. The first relay and the second relay each include a coil and a switch. The switches of the first relay and the second relay each have a common terminal and two connection terminals; One end of the first resistor is connected to one end of the first capacitor, the other end of the first resistor and one end of the second resistor are connected to the source of the NMOS tube, the other end of the second resistor, the other end of the first capacitor, and one end of the third resistor are connected to the non-inverting end of the comparator, the inverting end of the comparator, one end of the fourth resistor, one end of the fifth resistor, and one end of the second capacitor are connected, the other end of the fifth resistor is connected to the other end of the third resistor and the connection end thereof is connected to a voltage HVre, the other end of the fourth resistor and the other end of the second capacitor are connected to the negative voltage end of the comparator and the connection end thereof is connected to a voltage HND , the positive voltage of the comparator is connected to one end of the third capacitor and its connection end is connected to the voltage HVC, the other end of the third capacitor is connected to the voltage HND, the output end of the comparator, one end of the sixth resistor and the base of the first transistor are connected, the other end of the sixth resistor is connected to the voltage HVC, the emitter of the first transistor, one end of the fourth capacitor, one end of the seventh resistor and the emitter of the second transistor are connected and the connection end is connected to the voltage HND, the collector of the second transistor is connected to one end of the eighth resistor, the other end of the eighth resistor is connected to the base of the third transistor, the collector of the first transistor, the fourth capacitor and the emitter of the seventh resistor are connected to the emitter of the second transistor ..., the collector of the eighth resistor and the base of the third transistor are connected to the collector of the first transistor, the fourth capacitor and the emitter of the seventh resistor. The other end of the capacitor, the other end of the seventh resistor, the base of the second transistor, one end of the ninth resistor and one end of the tenth resistor are connected, the other end of the ninth resistor is connected to the collector of the third transistor and its connection end is connected to the voltage HVC1, the other end of the tenth resistor is connected to the overcurrent recovery signal OCR for releasing the overcurrent protection state, the emitter of the third transistor is connected to the voltage HVC, the gate of the NMOS tube, one end of the fifteenth resistor and the emitter of the optocoupler are connected, the other end of the fifteenth resistor is connected to the voltage HND, the collector of the optocoupler is connected to the voltage HVC1, the cathode of the optocoupler is grounded, the anode of the optocoupler and the One end of the fourteenth resistor is connected, the other end of the fourteenth resistor is the third input terminal K3 of the DC brush motor bidirectional speed regulation control circuit, one end of the twelfth resistor is the first input terminal K1 of the DC brush motor bidirectional speed regulation control circuit, the other end of the twelfth resistor is connected to the anode of the third diode, the cathode of the third diode is connected to the base of the fourth transistor, the emitter of the fourth transistor is grounded, the collector of the fourth transistor, one end of the coil of the first relay and an anode of the second diode are connected, the other end of the coil of the first relay is connected to the cathode of the second diode and the connection end thereof is connected to the voltage VDD,The other anode of the second diode, one end of the coil of the second relay, and the collector of the fifth triode are connected. The other end of the coil of the second relay is connected to the voltage VDD. The emitter of the fifth triode is grounded. The base of the fifth triode is connected to the cathode of the fourth diode. The anode of the fourth diode is connected to one end of the thirteenth resistor. The other end of the thirteenth resistor is the second input terminal K2 of the DC brushed motor two-way speed control circuit. The first connection terminal of the switch of the first relay, the first connection terminal of the switch of the second relay, the anode of the first diode, one end of the eleventh resistor, and the drain of the NMOS transistor are connected. The second connection terminal of the switch of the first relay, the second connection terminal of the switch of the second relay, the cathode of the first diode, and the anode of the fifth diode are connected and their connection terminal is connected to the voltage HVD. The cathode of the fifth diode is connected to the other end of the eleventh resistor. The common terminal of the switch of the first relay is the positive output terminal M+ of the DC brushed motor two-way speed control circuit. The common terminal of the switch of the second relay is the negative output terminal M- of the DC brushed motor two-way speed control circuit; The voltage HVre provides a bias voltage for the comparator. The voltage HVC1 provides a speed control voltage for the DC brushed motor two-way speed control circuit. The voltage VDD provides a direction control voltage for the DC brushed motor two-way speed control circuit. The voltage HVC provides an overcurrent protection control voltage for the DC brushed motor two-way speed control circuit. The voltage HVD provides a drive voltage for the DC brushed motor two-way speed control circuit. The voltage HND is a ground voltage. The third input terminal K3 of the DC brushed motor two-way speed control circuit is used to connect a PWM control signal for controlling the motor speed. The first input terminal K1 of the DC brushed motor two-way speed control circuit is used to connect a motor forward movement direction control voltage. The second input terminal K2 of the DC brushed motor two-way speed control circuit is used to connect a motor reverse movement direction control voltage. The positive output terminal M+ of the DC brushed motor two-way speed control circuit is used to connect the positive voltage terminal of the motor. The negative output terminal M- of the DC brushed motor two-way speed control circuit is used to connect the negative voltage terminal of the motor.

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