Circuit system for cycle-by-cycle current protection control, motor control circuit and brushless direct current motor

Abstract

The utility model provides a circuit system for performing current protection control cycle by cycle, the circuit system comprises an over-current protection unit and an unlocking unit, the over-current protection unit comprises a sampling circuit and a first comparator, the unlocking unit comprises a second comparator, and a signal of an out-phase input end of the second comparator is based on a PWM signal. The PWM signal is a signal input to a power switch of a motor driving circuit, a signal of an in-phase input end of the second comparator comes from an output end of the overcurrent protection unit, an output end of the second comparator is connected to the overcurrent protection unit through a trigger circuit, the trigger circuit comprises a first diode D1, a second diode D2, a third diode D3 and a fourth diode D3, the positive electrode of the first diode D1 is connected with the in-phase end A + of the first comparator and the first triode Q1, the base electrode of the first diode D1 is connected with the output end of the second comparator, the collector electrode of the first diode D1 is connected with the negative electrode of the first diode D1, and the emitter electrode of the first diode D1 is connected with the output end of the first comparator. The utility model further provides a motor control circuit and a brushless direct current motor.

Description

TECHNICAL FIELD

[0001] The present application relates to control of motor drive circuit, and more particularly, to a technique of performing current protection control cycle by cycle. BACKGROUND

[0002] A brushless direct current motor (BLDC) usually adopts a bridge circuit. During operation, once a power device is misdirected on, it can cause upper and lower tubes to be broken down. Therefore, when designing a voltage drive circuit, an overcurrent protection module needs to be added, and when a large current flows through the circuit, the switching device is turned off, and at the beginning of the next PWM cycle, the switching device resumes operation.

[0003] In the prior art, the overcurrent protection design scheme is mostly to determine whether the current is too large through a micro control unit (MCU), and when the current is too large, the MCU implements a shutdown operation through a PWM. When the MCU is down or runaway, the MCU needs at least 1 second to reset, and at this time, misdirected on can cause the switching device to be damaged.

[0004] Therefore, it is necessary to propose an improved overcurrent protection circuit. CONTENT OF THE INVENTION

[0005] According to an aspect of the present application, a circuit system for performing current protection control cycle by cycle is provided to at least solve at least one of the above problems.

[0006] The circuit system for performing current protection control cycle by cycle according to the first aspect of the present application comprises an overcurrent protection unit and an unlocking unit, the overcurrent protection unit comprises a sampling circuit and a first comparator, the unlocking unit comprises a second comparator, a signal at an opposite-phase input end of the second comparator is based on a PWM signal, the PWM signal is a signal input to a power switch of a motor drive circuit, a signal at a same-phase input end of the second comparator is from an output end of the overcurrent protection unit, and an output end of the second comparator is connected to the overcurrent protection unit via a trigger circuit, wherein the trigger circuit comprises: a first diode D1, a positive electrode of the first diode D1 is connected to a same-phase end A+ of the first comparator; a first triode Q1, a base electrode of the first triode Q1 is connected to the output end of the second comparator, a collector electrode of the first triode Q1 is connected to a negative electrode of the first diode D1, and an emitter electrode of the first triode Q1 is connected to an output end of the first comparator.

[0007] According to the circuit system of the first aspect, optionally or additionally, the circuit system further comprises: a clamping diode, a positive electrode of the clamping diode is connected to the power switch of the motor drive circuit to receive the PWM signal, and a negative electrode of the clamping diode is connected to an output end of the first comparator.

[0008] According to the circuit system of the first aspect, optionally or additionally, the PWM signal comprises a first PWM signal for controlling the first power switch, a second PWM signal for controlling the second power switch, and a third PWM signal for controlling the third power switch; and the clamping diode comprises three diodes respectively for receiving the first PWM signal, the second PWM signal, and the third PWM signal.

[0009] According to the circuit system of the first aspect, optionally or additionally, the unlocking unit further comprises a second transistor, a base of the second transistor is connected to the PWM signal via a resistor, an emitter of the second transistor is grounded and connected to an inverting input of the second comparator via a capacitor, and a collector of the second transistor is connected to the voltage dividing circuit.

[0010] According to the second aspect of the present application, a circuit system for current protection control on a cycle-by-cycle basis is provided, which can comprise: an overcurrent protection unit comprising a sampling circuit and a clamping circuit connected to the sampling circuit, the overcurrent protection unit being configured to cause the clamping circuit to clamp a PWM signal input to a motor drive circuit at a low level when a current of the sampling circuit is greater than a current threshold, so as to turn off a power switch of the motor drive circuit; a triggering unit having an output end connected to an output end of the overcurrent protection unit and being configured to lock an off state of the power switch; an unlocking unit comprising a second comparator, a signal of an inverting input of the second comparator being based on the PWM signal and a signal of a non-inverting input of the second comparator being from an output end of the overcurrent protection unit, an output end of the unlocking unit being connected to the triggering unit; the unlocking unit being configured to, in a next PWM cycle after the power switch is turned off, unlock the overcurrent protection unit through the triggering unit and cause the triggering unit to remain in a state of unlocking the overcurrent protection unit until the current of the sampling circuit is greater than the current threshold again.

[0011] According to the circuit system of the first aspect, optionally or additionally, the PWM signal comprises a first PWM signal for controlling the first power switch, a second PWM signal for controlling the second power switch, and a third PWM signal for controlling the third power switch; and the clamping diode comprises three diodes respectively for receiving the first PWM signal, the second PWM signal, and the third PWM signal.

[0012] According to the circuit system of the first aspect, optionally or additionally, the triggering unit comprises a first diode and a first transistor, a positive electrode of the first diode is connected to a non-inverting input of the first comparator, a negative electrode of the first diode is connected to a collector of the first transistor, an emitter of the first transistor is connected to an output end of the first comparator, and a base of the first transistor is connected to an output end of the unlocking unit.

[0013] Optionally or additionally, the unlocking unit further comprises a second triode, a base of the second triode is connected with the PWM signal via a resistor, an emitter of the second triode is grounded and connected with an inverting input of the second comparator via a capacitor, a collector of the second triode is connected with the voltage dividing circuit, and an output of the second comparator is connected with the triggering unit.

[0014] Optionally or additionally, the PWM signal comprises a first

[0015] PWM signal, a second PWM signal and a third PWM signal, each of the PWM signals controls a power switch.

[0016] According to another aspect of the present application, there is also provided a motor control circuit comprising any one of the circuit systems as described above. The motor is for example a brushless direct current motor.

[0017] According to still another aspect of the present application, there is also provided a brushless direct current motor comprising any one of the circuit systems as described above. BRIEF DESCRIPTION OF DRAWINGS

[0018] The present application will become more fully understood from the detailed description given herein below, and accompanied by the accompanying drawings, wherein the same reference numerals indicate the same elements throughout various views of the drawings, and wherein:

[0019] Figure 1 Fig. 1 schematically illustrates a structure of a circuit system for performing current protection control on a cycle-by-cycle basis according to an example of the present application;

[0020] Figure 2 Fig. 1 schematically illustrates a structure of a circuit system for performing current protection control on a cycle-by-cycle basis according to an example of the present application; DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the accompanying drawings for a clear and complete description of the embodiments of the present application. It should be noted that the described embodiments are only some of the embodiments of the technical solutions of the present application but not all. All other embodiments obtained by those of ordinary skill in the art based on the embodiments described in the present application document without any creative labor are also covered by the protection scope of the present application.

[0022] Figure 1A structure diagram of the circuit system for current protection control in each cycle according to the example of the present application is shown. In the example of the present application, "in each cycle" refers to the cycle of a pulse width modulation (PWM) signal, which is a signal input to a power switch of a motor drive circuit, such as a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0023] As shown in Figure 1 The circuit system for current protection control in each cycle includes an overcurrent protection unit 10, a trigger unit 12, and an unlock unit 14. The output of the overcurrent protection unit 10 is connected to a drive circuit 20, which is a drive circuit of a brushless direct current motor (BLDC). The trigger unit 12 is connected to the overcurrent protection unit 10 and the unlock unit 14, respectively. The input of the unlock unit 14 is connected to the output of the overcurrent protection unit 10 and a PWM signal input to the drive circuit 20. In the example, "connected" can be direct connection or indirect connection, for example, the trigger unit 12 is connected to the output of the overcurrent protection unit 10 through a connection terminal, which can be directly connected to the output or indirectly connected to the output through a resistor or other electrical elements.

[0024] According to the example of the present application, in each cycle of the PWM signal input to the drive circuit 20, the overcurrent protection unit 10 detects the current of the drive circuit 20, for example, through a sampling circuit. When the detected current is greater than a current threshold, that is, overcurrent, the overcurrent protection unit 10 clamps the level of the PWM signal to a low level to forcibly turn off the power switch of the drive circuit 20, thereby avoiding damage to the circuit due to overcurrent.

[0025] After the trigger unit 12 forcibly turns off the power switch of the drive circuit 20, it locks the off state of the power switch until the unlock unit 14 unlocks the off state in the next cycle of the PWM signal. After the unlock unit 14 performs the unlocking action, the trigger unit 12 returns to the waiting trigger state as in the initial state, so that the overcurrent protection unit 10 remains normal operation until overcurrent occurs again.

[0026] As an example, the overcurrent protection unit 10 includes a sampling circuit 100, a clamping circuit 102. The sampling circuit 100 is grounded at one end, and the ungrounded end is connected to the clamping circuit 102. The clamping circuit 102 clamps the PWM signal input to the motor drive circuit to a low level when the sampling current of the sampling circuit is greater than the current threshold, so that the power switch controlled by the PWM signal cannot be turned on due to the low level, i.e. is forced off. In some specific examples, the sampling circuit 100 includes a sampling resistor Rs, and the current flows through the sampling resistor Rs, i.e. overcurrent, that is, in this specific example, the current threshold is 0 ampere, and once the current of the sampling resistor Rs changes from zero to non-zero, it is considered that the sampled current is greater than the current threshold.

[0027] As an example, the unlocking unit 14 includes a second comparator 140, the voltage at the non-inverting input of the second comparator 140 is based on the PWM signal, and the signal at the inverting input of the second comparator 140 comes from the output of the overcurrent protection module 10. The output of the unlocking unit 14 is connected to the trigger unit 12. The unlocking unit 14 is configured to unlock the lock state of the forced off state of the power switch by the trigger unit 12 when the next PWM period arrives after the power switch is turned off.

[0028] PWM period arrives after the power switch is turned off.

[0029] In the examples of the present application, the inverting input is also referred to as the inverting terminal, and the inverting input is also referred to as the inverting terminal.

[0030] Figure 2 is a structural schematic diagram of a circuit system for performing current protection control on a cycle-by-cycle basis according to some specific examples of the present application. The circuit system is one specific example of the circuit system described above in conjunction with Figure 1

[0031] As shown in Figure 2 , in this example, the overcurrent protection unit includes a sampling circuit and a clamping circuit. The clamping circuit includes a first comparator U1A, the non-inverting terminal A- of the first comparator U1A is connected to the ungrounded end of the sampling circuit, and the inverting terminal A+ is connected to the trigger unit. The output of the first comparator U1A is connected to the output of three diodes. In this example, the drive circuit includes three PWM signals, namely a first PWM signal PWM1, a second PWM signal

[0032] PWM2, and a third PWM signal PWM3. The first PWM signal PWM1, the second

[0033] ​The PWM signal PWM2, the third PWM signal PWM3 are input to the control terminals of the first power switch MOS1, the second power switch MOS2, the third power switch MOS3 of the driving circuit. In this example, three clamping diodes are provided, which are diodes D3, D4 and D5. The negative terminals of the three diodes D3, D4 and D5 are connected to the output terminal of the first comparator U1A, and the positive terminals are connected to the control terminals of the power switches, respectively. For example, the positive terminal of the diode D3 is connected to the control terminal of the first power switch MOS1, the positive terminal of the diode D4 is connected to the control terminal of the second power switch MOS2, and the positive terminal of the diode D5 is connected to the control terminal of the third power switch MOS3, which also makes the positive terminal of the diode D3 receive the first PWM signal, the positive terminal of the diode D4 receive the second PWM signal, and the positive terminal of the diode D5 receive the third PWM signal.

[0034] As an example, the power switches are Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), and the control terminals are gates of the MOSFETs, so that each PWM signal is input to the gate of the corresponding MOSFET.

[0035] As an example, the power switches are Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), and the control terminals are gates of the MOSFETs, so that each PWM signal is input to the gate of the corresponding MOSFET.

[0036] Further, the sampling circuit includes a sampling resistor Rs connected to the inverting terminal A- of the first comparator U1A through the resistor R2, and the other terminal of the sampling resistor Rs is grounded.

[0037] The trigger unit includes a first diode D1 and a first transistor Q1, which are referred to as diode D1 and transistor Q1 hereinafter, respectively. The positive terminal of the diode D1 is connected to the non-inverting terminal A+ of the first comparator U1A, and at the same time, the positive terminal is connected between the resistors R3 and R4, the other terminal of the resistor R4 is grounded, and the other terminal of the resistor R3 is connected to a high voltage Vlevel. The voltage level marked as Vlevel in the drawings of the present application is a high voltage equal to, for example, 3.3 volts. It should be understood that the actual circuit diagram connection is more complex, and for the sake of brevity, the wiring between electronic components is not fully shown here, and the same voltage or input is marked with the same symbol. The control terminal of the transistor Q1, i.e. the base, is connected to the output terminal of the unlocking unit; the collector is connected to the negative terminal of the diode D1; and the emitter is connected to the output terminal of the first comparator U1A.

[0038] The unlocking unit includes a second comparator U1B and a second transistor Q2, which is referred to as transistor Q2 hereinafter. The first PWM signal PWM1, the second PWM signal PWM2, the third PWM signal PWM3 are input to the control terminals of the first power switch MOS1, the second power switch MOS2, the third power switch MOS3 of the driving circuit. In this example, three clamping diodes are provided, which are diodes D3, D4 and D5. The negative terminals of the three diodes D3, D4 and D5 are connected to the output terminal of the first comparator U1A, and the positive terminals are connected to the control terminals of the power switches, respectively. For example, the positive terminal of the diode D3 is connected to the control terminal of the first power switch MOS1, the positive terminal of the diode D4 is connected to the control terminal of the second power switch MOS2, and the positive terminal of the diode D5 is connected to the control terminal of the third power switch MOS3, which also makes the positive terminal of the diode D3 receive the first PWM signal, the positive terminal of the diode D4 receive the second PWM signal, and the positive terminal of the diode D5 receive the third PWM signal.

[0039] PWM signals PWM2 and PWM3 are connected to the base of transistor Q2 through resistors R10, R11, and R12, respectively. Therefore, whenever any one of PWM1, PWM2, or PWM3 flips from low to high, the base of transistor Q2 is at a high level, thus turning Q2 on. The emitter of transistor Q2 is grounded, and its collector is connected to the non-inverting input B- of the second comparator U1B. Simultaneously, the collector of transistor Q2 is also connected to voltage divider resistors R14 and R13, with one end of resistor R14 grounded and the other end of resistor R13 connected to a high level Vlevel. The non-inverting input B- of the second comparator U1B is connected to the emitter of Q2 through a capacitor, ensuring that the voltage at the non-inverting input B- of the second comparator U1B is 0 volts when transistor Q2 is on. The non-inverting input B+ of the second comparator U1B is connected to the output of the first comparator U1A via resistor R7. Furthermore, the non-inverting input B+ of the second comparator U1B is also connected to the voltage level Vlevel via resistor R8. The output of the second comparator U1B is connected to the base of diode Q1.

[0040] In combination Figure 2 The specific example described also includes resistors R1, R5, and R6, one end of which is connected to the voltage level Vlevel, and the other end is connected to the out-of-phase input terminal A- of the first comparator U1A, the output terminal of the first comparator U1A, and the output terminal of the second comparator U1B, respectively.

[0041] The following combination Figure 2 The process of controlling the power switch is further explained. In the initial state of the circuit, the voltage at the non-inverting input A- of the first comparator U1A is lower than the voltage at the non-inverting input A+, and the output signal Aout (hereinafter referred to as output Aout) of the first comparator U1A is H, where H represents a high voltage as indicated by the signal. In the initial state, the voltage at the non-inverting input B+ of the second comparator U1B is higher than the voltage at the non-inverting input B-, and the output Bout of the second comparator U1B is H. In a specific example, the high voltage is 3.3 volts. Under the combined effect of the three PWM signals, the voltage of B+ varies between 0V and 2.5V. As long as one of the three PWM signals is high, the base voltage of diode Q2 in the unlocking unit is high, causing diode Q2 to conduct, and the non-inverting input B- of the second comparator U1B remains at 0V. In the initial state, the voltage at both the base and emitter of transistor Q1 in the triggering unit is H, and it is in a ready-to-trigger state.

[0042] When the over-current occurs but the over-current protection is not triggered, the PWM is in H state and the MOSFET is turned on. The first PWM signal PWM1, the second PWM signal PWM2 and the third PWM signal PWM3 are kept at 0V by the transistor Q2. At this time, the voltage at the inverting terminal B- of the second comparator U1B is less than the voltage at the non-inverting terminal B+ of the second comparator U1B, and the output Bout of the second comparator U1B is H, so the diode Q1 is still in the state of waiting to be triggered.

[0043] The current flowing through the sampling resistor Rs causes the voltage at the inverting terminal A- of the first comparator U1A to be higher than the voltage at the non-inverting terminal A+ of the first comparator U1A, and the output Aout of the first comparator U1A is thus changed to L, where L represents low voltage in the present context. When Aout is L, the diodes D3, D4 and D5 clamp the first PWM signal PWM1, the second PWM signal PWM2 and the third PWM signal PWM3 respectively to low voltage, so the MOSFET cannot be driven to work, and the MOSFET is thus forcibly turned off.

[0044] When Aout is L, the voltage at the emitter of the diode Q1 is low, and the voltage difference at the base of the diode Q1 caused by the resistor R6 causes the diode Q1 to be triggered to be turned on, so the current is transmitted to the output of the first comparator U1A via the resistor R3, the diode D1 and the transistor Q1. At this time, the non-inverting terminal A+ of the first comparator U1A is clamped to low voltage by the diode D1. Therefore, although the current of the sampling resistor Rs disappears after the MOSFET is turned off, the state of the first comparator U1A is still that the voltage at the inverting terminal A- is higher than the voltage at the non-inverting terminal A+, so Aout is still L. This causes the state of the MOSFET being forcibly turned off to be locked, that is, the MOSFET is kept in the state of being forcibly turned off.

[0045] When the PWM signal jumps from H to L, the MOSFET is still in the state of being turned off, and at this time, the voltage at the non-inverting terminal B+ of the second comparator U1B is less than the voltage at the inverting terminal B- of the second comparator U1B, so the output Bout of the second comparator U1B is L, and the diode Q1 changes from being turned on to being turned off because the voltage at the base is lowered to L, so the lock of the state of the MOSFET being forcibly turned off is released.

[0046] After diode Q1 is off, the voltage of the non-inverting terminal A+ of the first comparator U1A is again greater than the voltage of the inverting terminal A-, so that the output Aout of the first comparator U1A becomes H. For the unlocking unit, as long as the PWM signal is high, the diode Q2 is in the on state, so that the inverting terminal B- of the second comparator U1B is L, which is less than the voltage of the non-inverting terminal B+, so that Bout is H, and the diode Q1 again enters the state of being triggered by H at the base and H at the emitter. Thus, as long as there is current flowing through the sampling resistor Rs when the PWM signal is high, the PWM signal is clamped to the low level and the MOSFET is forcibly turned off and kept in the off state, and then the state is changed by the unlocking unit in the next PWM cycle, so that the circuit enters the normal working state until the overcurrent condition occurs again.

[0047] According to the example of the application, the circuit system for performing current protection control cycle by cycle, through the sampling circuit, in a more specific example, through the sampling resistor, determines whether overcurrent occurs, and in the case of overcurrent, forcibly turns off the power switch of the motor driving circuit through the change of the output of the comparator, thereby avoiding damage to the circuit due to overcurrent. Further, unlike the conventional technology, which only focuses on triggering overcurrent protection to turn off the power switch, in the example of the application, the locking of the power switch is unlocked in time after the implementation of the turn-off operation, thereby avoiding affecting the normal operation of the driving circuit. Furthermore, according to the example of the application, after the locking of the power switch is unlocked, the trigger unit will again enter the standby state, maintaining the normal operation of the circuit to guide the arrival of the next overcurrent state.

[0048] With the circuit system for performing current protection control cycle by cycle according to the example of the application, overcurrent is detected in each PWM cycle, and if overcurrent occurs, the power switch is forcibly turned off, and the power switch is unlocked in the next cycle; then a new PWM cycle is entered, overcurrent is detected, and in the case of overcurrent, the process of turning off and unlocking is repeated, and so on. During the operation of the motor, overcurrent detection and protection of the driving circuit are performed cycle by cycle.

[0049] In addition, the circuit system for performing current protection control cycle by cycle according to the example of the application uses hardware circuits, such as comparators, diodes, transistors and other electronic components, and the entire process is based on the voltage change of the electronic components when overcurrent occurs to implement protection, unlocking and other processes. Compared with overcurrent protection implemented by software or software combined in a micro control unit (MCU), the situation that overcurrent protection cannot be implemented due to software failure, MCU failure and other reasons is reduced. In addition, in the example of the application, the hardware circuit generally uses discrete components, has low cost and high compatibility.

[0050] According to examples of the present application, there is also provided a motor control circuit. The motor control circuit comprises any of the circuitry for cycle-by-cycle current protection control as described above in connection with the figures. As an example, the motor is a brushless DC motor.

[0051] According to examples of the present application, there is also provided a brushless DC motor. The brushless DC motor comprises any of the circuitry for cycle-by-cycle current protection control as described above in connection with the figures.

[0052] The technical features in the various embodiments of the present application can be combined with each other without departing from the spirit of the present application and without conflicting with each other, to form new embodiments. Although specific embodiments of the present application have been shown and described in detail in order to explain the principles of the present application, it should be understood that the present application can be implemented in other ways without departing from such principles.

Claims

1. Circuitry for cycle-by-cycle current protection control, the circuitry comprising an overcurrent protection unit and an unlock unit, the overcurrent protection unit comprising a sampling circuit and a first comparator, the unlock unit comprising a second comparator, characterized in that, The signal of the non-inverting input end of the second comparator is based on a PWM signal, the PWM signal being a signal input to a power switch of a motor drive circuit, the signal of the inverting input end of the second comparator being from an output end of the overcurrent protection unit, and the output end of the second comparator being connected to the overcurrent protection unit via a trigger circuit, wherein the trigger circuit comprises: a first diode D1, a positive electrode of which is connected to the inverting input end of the first comparator, a first transistor Q1, a base electrode of which is connected to the output end of the second comparator, a collector electrode of which is connected to a negative electrode of the first diode D1, and an emitter electrode of which is connected to the output end of the first comparator.

2. The circuitry of claim 1, wherein, The circuit system further comprises: a clamping diode, a positive electrode of which is connected to the power switch of the motor drive circuit to receive the PWM signal, and a negative electrode of which is connected to the output end of the first comparator.

3. The circuitry of claim 2, wherein, The PWM signal comprises a first PWM signal for controlling a first power switch, a second PWM signal for controlling a second power switch, and a third PWM signal for controlling a third power switch, and the clamping diode comprises three diodes respectively for receiving the first PWM signal, the second PWM signal, and the third PWM signal.

4. The circuitry of any one of claims 1 to 3, wherein, The unlocking unit further comprises a second transistor, a base electrode of which is connected to the PWM signal via a resistor, an emitter electrode of which is grounded and connected to the non-inverting input end of the second comparator through a capacitor, and a collector electrode of which is connected to a voltage dividing circuit.

5. Circuitry for cycle-by-cycle current protection control, characterized in that The circuit system comprises: an overcurrent protection unit comprising a sampling circuit and a clamping circuit connected to the sampling circuit, the overcurrent protection unit being configured to cause the clamping circuit to clamp a PWM signal input to a motor drive circuit at a low level to turn off a power switch of the motor drive circuit when a current of the sampling circuit is greater than a current threshold value; a trigger unit, an output end of which is connected to an output end of the overcurrent protection unit and is configured to lock a turned-off state of the power switch; an unlocking unit comprising a second comparator, a signal of a non-inverting input end of the second comparator being based on the PWM signal and a signal of an inverting input end of the second comparator being from an output end of the overcurrent protection unit, and an output end of the unlocking unit being connected to the trigger unit, the unlocking unit being configured to, in a next PWM period after the power switch is turned off, unlock the overcurrent protection unit through the trigger unit and keep the trigger unit in a state of unlocking the overcurrent protection unit until the current of the sampling circuit is greater than the current threshold value again.

6. The circuitry of claim 5, wherein, The clamping circuit comprises: a first comparator, a non-inverting input end of the first comparator being connected to a non-grounded end of the sampling circuit; a diode, a positive electrode of which is connected to a control end of the power switch for receiving the PWM signal, and a negative electrode of which is connected to an output end of the first comparator.

7. The circuitry of claim 6, wherein, The trigger unit comprises a first diode and a first triode, the anode of the first diode is connected to the non-inverting input of the first comparator, the cathode of the first diode is connected to the collector of the first triode, the emitter of the first triode is connected to the output of the first comparator, and the base of the first triode is connected to the output of the unlock unit.

8. The circuitry of claim 6, wherein, The unlock unit further comprises a second triode, the base of the second triode is connected to the PWM signal via a resistor, the emitter of the second triode is grounded and connected to the inverting input of the second comparator via a capacitor, the collector of the second triode is connected to a voltage dividing circuit, and the output of the second comparator is connected to the trigger unit.

9. Circuitry according to any one of claims 6 to 8, characterised in that, The PWM signal comprises a first PWM signal, a second PWM signal and a third PWM signal, each of the PWM signals controls a power switch.

10. An electric motor control circuit, characterized by The motor control circuit comprises the circuit system according to any one of claims 1 to 9.

11. The motor control circuit of claim 10, wherein, The motor is a brushless direct current motor.

12. A brushless DC motor, characterized by The brushless direct current motor comprises the circuit system according to any one of claims 1 to 9.

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