Motor control method and circuit

Abstract

The invention relates to a motor control method and circuit, and the method comprises the steps: detecting the current of a motor in real time based on a sine wave current envelope area method, and obtaining a current scalar; and calculating a current difference value between the current scalar value and a preset current scalar threshold value, outputting a motor control signal according to the current difference value, the current scalar value and a previous current scalar value, and driving the motor to operate according to the motor control signal. According to the method, the current of the motor is detected in real time based on a sine wave current envelope area method, the problems of measurement errors and control response lag caused by current waveform distortion can be solved, and therefore accurate current value detection and higher response speed can be obtained; besides, in the motor control process, a motor control signal is obtained according to the current difference value, the current current scalar value and the previous current scalar value, and the motor can be controlled to operate stably and smoothly.

Description

Technical Field

[0001] The present invention relates to the field of motor control, and in particular to a motor control method and circuit. Background Art

[0002] There are more and more applications of remote control / automatic control of three-phase motors in unattended production. In order to avoid equipment damage caused by overcurrent / overload / phase loss / load short circuit during the operation of three-phase motors, it is urgent to realize dynamic real-time monitoring and control of the working process of three-phase motors. Real-time current detection is a key function of closed-loop control and motor protection during the working process of the motor. Using real-time current monitoring, the motor control system can obtain key instantaneous information, such as motor torque (based on motor current), motor power, or short circuit information. In general current detection methods, the motor current will be distorted due to current / voltage waveform distortion or changes in load characteristics during motor startup and operation, resulting in sudden changes in current detection values. However, since these data are real, the problem of data error caused by waveform distortion cannot be solved by ordinary hardware or software filtering. Software filtering will cause slow response of protection action, resulting in delayed and inaccurate motor control action. In addition, the existing motor control is achieved by judging whether the current detection value exceeds the preset current threshold. Since the current detection value will change suddenly, the motor will not run smoothly during the motor control process. Summary of the invention

[0003] The present invention provides a motor control method and circuit to solve at least one of the above technical problems. The technical solution of the present invention to solve the above technical problems is as follows: A motor control method, comprising:

[0004] S1, based on the sine wave current envelope area method, the motor current is detected in real time to obtain the current current scalar value;

[0005] S2, calculating the current difference between the current scalar value and the preset current scalar threshold, and outputting a motor control signal according to the current difference, the current current scalar value and the previous current scalar value, and driving the motor to operate according to the motor control signal.

[0006] Based on the above technical solution, the present invention can also be improved as follows.

[0007] Further, the S1 is specifically:

[0008] Sampling the working current of the motor in real time to obtain a current sampling value;

[0009] Directively rectifying the current sampling value to obtain a current rectification value;

[0010] Sampling the rectified current value using a sine wave envelope to obtain a voltage signal based on the sine wave envelope;

[0011] Performing anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal;

[0012] Amplifying the voltage filter signal and performing signal drive and holding processing to obtain a current sinusoidal wave envelope signal;

[0013] The current sinusoidal wave envelope signal is subjected to sampling and quantization processing based on the area integration of the sinusoidal wave envelope line to obtain the current current scalar value.

[0014] Furthermore, the method for sampling the working current of the motor is isolated sampling; and the method for performing sampling and quantization processing on the current sine wave envelope amplified signal based on the sine wave envelope area integration is DMA method.

[0015] Further, the S2 is specifically:

[0016] Calculating a current difference between the current scalar value and a preset current scalar threshold value;

[0017] Comparing the current current scalar value with the previous current scalar value to obtain a comparison signal;

[0018] Performing state latch processing on the comparison signal to obtain a latch signal;

[0019] The latch signal and the current difference are processed to obtain the motor control signal, and the motor is driven to operate according to the motor control signal.

[0020] Based on the above motor control method, the present invention also provides a motor control circuit.

[0021] A motor control circuit, comprising:

[0022] A current detection circuit is used to detect the working current of the motor in real time based on the sinusoidal current envelope area method to obtain the current current scalar value;

[0023] a control circuit for calculating a current difference between the current scalar value and a preset current scalar threshold, and outputting a motor control signal according to the current difference, the current scalar value and a previous current scalar value;

[0024] The driving circuit is used to drive the motor to operate according to the motor control signal.

[0025] Based on the above technical solution, the present invention can also be improved as follows.

[0026] Furthermore, the current detection circuit comprises:

[0027] A current sampling module, which is used to sample the working current of the motor in real time to obtain a current sampling value;

[0028] A directional rectification module, used for performing directional rectification on the current sampling value to obtain a current rectification value;

[0029] A sine wave envelope sampling module, which is used to perform sine wave envelope sampling on the current rectified value to obtain a voltage signal based on the sine wave envelope;

[0030] an anti-aliasing filtering module, which is used to perform anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal;

[0031] an amplification and signal drive holding module, which is used to amplify the voltage filter signal and perform signal drive holding processing to obtain a current sinusoidal wave envelope signal;

[0032] The ADC module is used to perform sampling and quantization processing on the current sine wave envelope signal based on the area integration of the sine wave envelope line to obtain the current current scalar value.

[0033] Furthermore, the current sampling module is specifically a current transformer; and the directional rectification module is specifically a bridge rectification circuit.

[0034] Furthermore, the sine wave envelope sampling module includes:

[0035] A sampling resistor, one end of which is connected to an output end of the directional rectifier module, and the other end of which is connected to another output end of the directional rectifier module and is grounded;

[0036] The anti-aliasing filtering module comprises:

[0037] A first capacitor connected in parallel with the sampling resistor;

[0038] A common cathode bidirectional voltage regulator tube, connected in parallel with the first capacitor;

[0039] A first resistor, connected to one end of the sampling resistor;

[0040] A second capacitor, one end of which is connected to the other end of the first resistor, and the other end of which is grounded;

[0041] The amplification and signal drive holding module includes:

[0042] A first operational amplifier, wherein a non-inverting input terminal is connected to the other end of the first resistor, an inverting input terminal is grounded through a second resistor, an inverting input terminal is further connected to an output terminal thereof through a third resistor and a third capacitor connected in parallel, a ground terminal is grounded, and a power supply terminal is connected to a power supply and grounded through a fourth capacitor;

[0043] A second operational amplifier, wherein a non-inverting input terminal is connected to the output terminal of the first operational amplifier, an inverting input terminal is connected to the output terminal thereof, and the output terminal outputs the current sine wave envelope signal;

[0044] A voltage regulator tube, wherein the cathode is connected to the output terminal of the second operational amplifier, and the anode is grounded.

[0045] Furthermore, the control circuit comprises:

[0046] A subtractor, one input end of which is connected to the current detection circuit, and the other input end of which is connected to a preset current scalar threshold, for calculating a current difference between the current scalar value and the preset current scalar threshold;

[0047] A signal delayer, the input end of which is connected to the current detection circuit, and the output end of which is used to output the previous current scalar value at the current sampling moment;

[0048] A comparator, whose inverting input terminal is connected to the current detection circuit, and whose non-inverting input terminal is connected to the output terminal of the signal delayer, is used to compare the current current scalar value with the previous current scalar value to obtain a comparison signal;

[0049] A state latch module, connected to the comparator, for performing state latch processing on the comparison signal to obtain a latch signal;

[0050] The motor driver has two input ends respectively connected to the state latch module and the output end of the subtractor, and is used to process the latch signal and the current difference to obtain the motor control signal, and drive the motor to operate according to the motor control signal.

[0051] Further, the state latch module includes:

[0052] The first transistor, the emitter is connected to the power supply,

[0053] a fifth resistor, one end of which is connected to the collector of the first transistor, and the other end of which is grounded via a fifth capacitor;

[0054] a seventh diode, an anode of which is connected to the other end of the fifth resistor, and a cathode of which is connected to the inverting input end of the comparator;

[0055] a sixth resistor, one end of which is connected to the emitter of the first transistor;

[0056] a seventh resistor, one end of which is connected to the base of the first transistor, and the other end of which is connected to the other end of the sixth resistor;

[0057] an eighth diode, an anode of which is connected to the other end of the seventh resistor, and a cathode of which is connected to the output end of the comparator;

[0058] The second transistor has a base connected to the anode of the eighth diode, an emitter connected to the output end of the comparator, and a collector connected to an input end of the motor driver.

[0059] The beneficial effects of the present invention are as follows: a motor control method and circuit of the present invention detects the current of the motor in real time based on the sinusoidal current envelope area method, which can overcome the measurement error and control response lag caused by the current waveform distortion, thereby obtaining accurate current value detection and faster response speed; in addition, the present invention takes into account the current difference between the current current scalar value and the preset current scalar threshold, the current current scalar value and the previous current scalar value in the process of motor control, and the motor control signal obtained according to the current difference, the current current scalar value and the previous current scalar value can control the motor to run smoothly. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A flow chart of a motor control method of the present invention;

[0061] Figure 2 A structural block diagram of a motor control circuit of the present invention;

[0062] Figure 3 It is the structural block diagram of the current detection circuit;

[0063] Figure 4 is the circuit schematic diagram of the current detection circuit;

[0064] Figure 5 It is the structural block diagram of the control circuit;

[0065] Figure 6 This is the circuit schematic diagram of the control circuit. DETAILED DESCRIPTION

[0066] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0067] like Figure 1 As shown, a motor control method includes:

[0068] S1, based on the sine wave current envelope area method, the motor current is detected in real time to obtain the current current scalar value;

[0069] S2, calculating the current difference between the current scalar value and the preset current scalar threshold, and outputting a motor control signal according to the current difference, the current current scalar value and the previous current scalar value, and driving the motor to operate according to the motor control signal.

[0070] In some embodiments, S1 specifically includes:

[0071] Sampling the working current of the motor in real time to obtain a current sampling value;

[0072] Directively rectifying the current sampling value to obtain a current rectification value;

[0073] Sampling the rectified current value using a sine wave envelope to obtain a voltage signal based on the sine wave envelope;

[0074] Performing anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal;

[0075] Amplifying the voltage filter signal and performing signal drive and holding processing to obtain a current sinusoidal wave envelope signal;

[0076] The current sinusoidal wave envelope signal is subjected to sampling and quantization processing based on the area integration of the sinusoidal wave envelope line to obtain the current current scalar value.

[0077] Specifically, the present invention realizes real-time detection of motor current based on the sinusoidal current envelope area method through real-time sampling, directional rectification, sinusoidal wave envelope sampling, anti-aliasing filtering, amplification and signal drive hold processing, and sampling quantization processing. It can overcome the measurement error caused by current waveform distortion and has sensitive measurement response.

[0078] In some real-time examples, the method for sampling the working current of the motor is isolated sampling; the method for sampling and quantizing the current sine wave envelope amplified signal based on the sine wave envelope area integration is DMA.

[0079] Specifically, the working current of the motor is isolated and sampled, which has the advantages of strong and weak current isolation, high sensitivity, good dynamic characteristics and high safety; the DMA method is used to sample and quantize the current sinusoidal wave envelope amplified signal based on the area integration of the sinusoidal wave envelope, which can meet the real-time requirements.

[0080] In some real-time examples, S2 is specifically:

[0081] Calculating a current difference between the current scalar value and a preset current scalar threshold value;

[0082] Comparing the current current scalar value with the previous current scalar value to obtain a comparison signal;

[0083] Performing state latch processing on the comparison signal to obtain a latch signal;

[0084] The latch signal and the current difference are processed to obtain the motor control signal, and the motor is driven to operate according to the motor control signal.

[0085] Specifically, in the process of motor control, the present invention takes into account the current difference between the current current scalar value and the preset current scalar threshold, the current current scalar value and the previous current scalar value. The motor control signal obtained according to the current difference, the current current scalar value and the previous current scalar value can control the motor to run smoothly.

[0086] Based on the above motor control method, the present invention also provides a motor control circuit.

[0087] like Figure 2 As shown, a motor control circuit comprises:

[0088] A current detection circuit is used to detect the working current of the motor in real time based on the sinusoidal current envelope area method to obtain the current current scalar value;

[0089] A control circuit is used to calculate the current difference between the current scalar value and a preset current scalar threshold, output a motor control signal according to the current difference, the current current scalar value and the previous current scalar value, and drive the motor to operate according to the motor control signal.

[0090] like Figure 3 As shown, the current detection circuit includes:

[0091] A current sampling module, which is used to sample the working current of the motor in real time to obtain a current sampling value;

[0092] A directional rectification module, used for performing directional rectification on the current sampling value to obtain a current rectification value;

[0093] A sine wave envelope sampling module, which is used to perform sine wave envelope sampling on the current rectified value to obtain a voltage signal based on the sine wave envelope;

[0094] an anti-aliasing filtering module, which is used to perform anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal;

[0095] an amplification and signal drive holding module, which is used to amplify the voltage filter signal and perform signal drive holding processing to obtain a current sinusoidal wave envelope signal;

[0096] The ADC module is used to perform sampling and quantization processing on the current sine wave envelope signal based on the area integration of the sine wave envelope line to obtain the current current scalar value.

[0097] like Figure 4 As shown, the current sampling module is specifically a current transformer CT; the directional rectification module is specifically a bridge rectifier circuit, which is composed of Figure 4The first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are shown.

[0098] Specifically, the current sampling module uses a small-volume miniature current transformer CT with an accuracy of 0.1. Its basic principle is to use the electromagnetic induction effect to sense the magnetic field strength generated by the working current of the motor, and then convert it into a 0-20mA current output. Using a current transformer CT for current testing has the advantages of strong and weak electrical isolation, high sensitivity, good dynamic characteristics, and high safety. The voltage level of the miniature current transformer CT used in this embodiment is 0.66KV, the insulation resistance is normally greater than 1000MΩ, the withstand voltage reaches 3KV / 50Hz / 1min, and the operating temperature is: -40℃~+85℃, which can meet the needs of motor current monitoring conditions. The range of this miniature current transformer CT is 2000:1, corresponding to the primary / secondary current of: 30A:15mA. That is, when a 20KW power motor is working normally, the maximum output current of the miniature current transformer CT does not exceed 15mA, and this maximum working current value is used as the current scalar threshold during processing.

[0099] like Figure 4 As shown, the sine wave envelope sampling module includes:

[0100] A sampling resistor R0, one end of which is connected to an output end of the directional rectifier module, and the other end of which is connected to another output end of the directional rectifier module and is grounded;

[0101] The anti-aliasing filtering module comprises:

[0102] A first capacitor C1 is connected in parallel with the sampling resistor R0;

[0103] A common cathode bidirectional voltage regulator D5 is connected in parallel with the first capacitor C1;

[0104] A first resistor R1, connected to one end of the sampling resistor R0;

[0105] A second capacitor C2, one end of which is connected to the other end of the first resistor R1, and the other end of which is grounded;

[0106] The amplification and signal drive holding module includes:

[0107] A first operational amplifier A1, a non-inverting input terminal connected to the other end of the first resistor R1, an inverting input terminal connected to ground via a second resistor R2, an inverting input terminal connected to an output terminal via a third resistor R3 and a third capacitor C3 connected in parallel, a ground terminal connected to ground, a power supply terminal connected to a power supply VDD and connected to ground via a fourth capacitor C4;

[0108] A second operational amplifier A2, having a non-inverting input terminal connected to the output terminal of the first operational amplifier A1, an inverting input terminal connected to its output terminal, and an output terminal outputting the current sine wave envelope signal;

[0109] The voltage regulator tube D6 has a cathode connected to the output end of the second operational amplifier A2 and an anode connected to the ground.

[0110] Specifically, the directional rectification module, the sine wave envelope sampling module, the anti-aliasing filter module, the amplification and signal drive holding module are used to condition the output signal of the current transformer CT. According to the calculation that the maximum working current of the external motor is 30A and the maximum detection current is 15mA, the directional rectification module performs directional rectification, and the maximum voltage signal of 0.5V is obtained on the sampling resistor R0. After filtering by the anti-aliasing filter module, it is amplified by 2 times by the amplification and signal drive holding module, and the emitter follower is used as the signal drive to maintain the peak-to-peak value of 1Vpp sine wave envelope signal. The conditioning is now completed.

[0111] The ADC module samples the sinusoidal envelope signal of the sampling current through DMA, performs area integration operation, and obtains the scalar of the corresponding working current of the motor.

[0112] like Figure 5 As shown, the control circuit includes:

[0113] A subtractor, one input end of which is connected to the current detection circuit, and the other input end of which is connected to a preset current scalar threshold, for calculating a current difference between the current scalar value and the preset current scalar threshold;

[0114] A signal delayer, the input end of which is connected to the current detection circuit, and the output end of which is used to output the previous current scalar value at the current sampling moment;

[0115] A comparator, whose inverting input terminal is connected to the current detection circuit, and whose non-inverting input terminal is connected to the output terminal of the signal delayer, is used to compare the current current scalar value with the previous current scalar value to obtain a comparison signal;

[0116] A state latch module, connected to the comparator, for performing state latch processing on the comparison signal to obtain a latch signal;

[0117] The motor driver has two input ends connected to the state latch module and the output end of the subtractor respectively, and is used to process the latch signal and the current difference to obtain the motor control signal, and drive the motor to operate according to the motor control signal.

[0118] Specifically, the comparator compares the current scalar value and the previous current scalar value to obtain the changing trend of the motor current. The state latch module is used to latch the changing trend of the motor current to obtain a latch signal, which is combined with the current difference to determine the motor control signal. This can avoid the phenomenon of intermittent operation of the motor due to overcurrent, thereby ensuring smooth operation of the motor.

[0119] like Figure 6 As shown, A3 represents the comparator, and a fourth resistor R is connected between the non-inverting input terminal and the output terminal of the comparator A3;

[0120] The state latch module comprises:

[0121] The first transistor Q1, the emitter is connected to the power supply VDD,

[0122] a fifth resistor R5, one end of which is connected to the collector of the first transistor Q1, and the other end of which is grounded via a fifth capacitor C5;

[0123] a seventh diode D7, an anode of which is connected to the other end of the fifth resistor R5, and a cathode of which is connected to the inverting input end of the comparator A3;

[0124] a sixth resistor R6, one end of which is connected to the emitter of the first transistor Q1;

[0125] a seventh resistor R7, one end of which is connected to the base of the first transistor Q1, and the other end of which is connected to the other end of the sixth resistor R6;

[0126] an eighth diode D8, an anode of which is connected to the other end of the seventh resistor R7, and a cathode of which is connected to the output end of the comparator A3;

[0127] The second transistor Q2 has a base connected to the anode of the eighth diode D8, an emitter connected to the output end of the comparator A3, and a collector connected to an input end of the motor driver.

[0128] A motor control method and circuit of the present invention detects the current of the motor in real time based on the sinusoidal current envelope area method, which can overcome the measurement error and control response lag caused by the current waveform distortion, thereby obtaining accurate current value detection and faster response speed; in addition, during the motor control process, the present invention takes into account the current difference between the current scalar value and the preset current scalar threshold, the current current scalar value and the previous current scalar value, and the motor control signal obtained according to the current difference, the current current scalar value and the previous current scalar value can control the motor to run smoothly.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A motor control method, characterized in that: include: S1, based on the sine wave current envelope area method, the motor current is detected in real time to obtain the current current scalar value; S2, calculating the current difference between the current scalar value and the preset current scalar threshold, and outputting a motor control signal according to the current difference, the current current scalar value and the previous current scalar value, and driving the motor to operate according to the motor control signal.

2. The motor control method according to claim 1, characterized in that: The S1 is specifically: Sampling the working current of the motor in real time to obtain a current sampling value; Directively rectifying the current sampling value to obtain a current rectification value; Sampling the rectified current value using a sine wave envelope to obtain a voltage signal based on the sine wave envelope; Performing anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal; Amplifying the voltage filter signal and performing signal drive and holding processing to obtain a current sinusoidal wave envelope signal; The current sinusoidal wave envelope signal is subjected to sampling and quantization processing based on the area integration of the sinusoidal wave envelope line to obtain the current current scalar value.

3. The motor control method according to claim 2, characterized in that: The method for sampling the working current of the motor is isolated sampling; the method for performing sampling and quantization processing on the current sine wave envelope amplified signal based on the sine wave envelope area integration is DMA method.

4. The motor control method according to claim 1, characterized in that: The S2 is specifically: Calculating a current difference between the current scalar value and a preset current scalar threshold value; Comparing the current current scalar value with the previous current scalar value to obtain a comparison signal; Performing state latch processing on the comparison signal to obtain a latch signal; The latch signal and the current difference are processed to obtain the motor control signal, and the motor is driven to operate according to the motor control signal.

5. A motor control circuit, characterized in that: include: A current detection circuit is used to detect the working current of the motor in real time based on the sinusoidal current envelope area method to obtain the current current scalar value; A control circuit is used to calculate the current difference between the current scalar value and a preset current scalar threshold, output a motor control signal according to the current difference, the current current scalar value and the previous current scalar value, and drive the motor to operate according to the motor control signal.

6. The motor control circuit according to claim 5, characterized in that: The current detection circuit comprises: A current sampling module, which is used to sample the working current of the motor in real time to obtain a current sampling value; A directional rectification module, used for performing directional rectification on the current sampling value to obtain a current rectification value; A sine wave envelope sampling module, which is used to perform sine wave envelope sampling on the current rectified value to obtain a voltage signal based on the sine wave envelope; an anti-aliasing filtering module, which is used to perform anti-aliasing filtering on the voltage signal to obtain a voltage filtering signal; an amplification and signal drive holding module, which is used to amplify the voltage filter signal and perform signal drive holding processing to obtain a current sinusoidal wave envelope signal; The ADC module is used to perform sampling and quantization processing on the current sine wave envelope signal based on the area integration of the sine wave envelope line to obtain the current current scalar value.

7. The motor control circuit according to claim 6, characterized in that: The current sampling module is specifically a current transformer; the directional rectification module is specifically a bridge rectification circuit.

8. The motor control circuit according to claim 6, characterized in that: The sine wave envelope sampling module comprises: A sampling resistor, one end of which is connected to an output end of the directional rectifier module, and the other end of which is connected to another output end of the directional rectifier module and is grounded; The anti-aliasing filtering module comprises: A first capacitor connected in parallel with the sampling resistor; A common cathode bidirectional voltage regulator tube, connected in parallel with the first capacitor; A first resistor, connected to one end of the sampling resistor; A second capacitor, one end of which is connected to the other end of the first resistor, and the other end of which is grounded; The amplification and signal drive holding module includes: A first operational amplifier, wherein a non-inverting input terminal is connected to the other end of the first resistor, an inverting input terminal is grounded through a second resistor, an inverting input terminal is further connected to an output terminal thereof through a third resistor and a third capacitor connected in parallel, a ground terminal is grounded, and a power supply terminal is connected to a power supply and grounded through a fourth capacitor; A second operational amplifier, wherein a non-inverting input terminal is connected to the output terminal of the first operational amplifier, an inverting input terminal is connected to the output terminal thereof, and the output terminal outputs the current sine wave envelope signal; A voltage regulator tube, wherein the cathode is connected to the output terminal of the second operational amplifier, and the anode is grounded.

9. The motor control circuit according to claim 6, characterized in that: The control circuit comprises: A subtractor, one input end of which is connected to the current detection circuit, and the other input end of which is connected to a preset current scalar threshold, for calculating a current difference between the current scalar value and the preset current scalar threshold; A signal delayer, the input end of which is connected to the current detection circuit, and the output end of which is used to output the previous current scalar value at the current sampling moment; A comparator, whose inverting input terminal is connected to the current detection circuit, and whose non-inverting input terminal is connected to the output terminal of the signal delayer, is used to compare the current current scalar value with the previous current scalar value to obtain a comparison signal; A state latch module, connected to the comparator, for performing state latch processing on the comparison signal to obtain a latch signal; The motor driver has two input ends respectively connected to the state latch module and the output end of the subtractor, and is used to process the latch signal and the current difference to obtain the motor control signal, and drive the motor to operate according to the motor control signal.

10. The motor control circuit according to claim 9, characterized in that: The state latch module comprises: The first transistor, the emitter is connected to the power supply, a fifth resistor, one end of which is connected to the collector of the first transistor, and the other end of which is grounded via a fifth capacitor; a seventh diode, an anode of which is connected to the other end of the fifth resistor, and a cathode of which is connected to the inverting input end of the comparator; a sixth resistor, one end of which is connected to the emitter of the first transistor; a seventh resistor, one end of which is connected to the base of the first transistor, and the other end of which is connected to the other end of the sixth resistor; an eighth diode, an anode of which is connected to the other end of the seventh resistor, and a cathode of which is connected to the output end of the comparator; The second transistor has a base connected to the anode of the eighth diode, an emitter connected to the output end of the comparator, and a collector connected to an input end of the motor driver.

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