Current limiting protection control system and method for motor drive circuit

Abstract

The present invention relates to a current limiting protection control system and method for a motor drive circuit. The system includes a current sampling circuit, a current-to-voltage circuit, a comparator, a reference voltage providing circuit, a digital latch and two AND gates. The current sampling circuit is respectively connected to the motor drive circuit and the current-to-voltage circuit, the current-to-voltage circuit is connected to the inverting input terminal of the comparator, the output terminal of the reference voltage providing circuit is connected to the non-inverting input terminal of the comparator, the output terminal of the comparator is connected to the input terminal of the digital latch, the clock terminal of the digital latch is used to receive a clock signal, the output terminal of the digital latch is connected to the first input terminal of the two AND gates, the second input terminal of the two AND gates is used to receive an input control signal, and the output terminal of the two AND gates is connected to the motor drive circuit. The current limiting protection control system and method for the motor drive circuit of the present invention can limit the current of the motor under the premise of avoiding the generation of low-frequency noise, and avoid the motor current being too large and burning the motor.

Description

Technical Field

[0001] The present invention relates to the field of motor driving, and more specifically to a current limiting protection control system and method for a motor driving circuit. Background Art

[0002] When the motor starts, the voltage on the coil includes the voltage V on the coil internal resistance r r =r*I, voltage on coil inductance L Motor coil back electromotive force E m =Bvl three parts, where parameter I is the motor coil current, B is the motor magnetic field strength, v is the motor speed, and l is a parameter related to the coil length. When the motor starts, the rotor speed v is relatively low, then the motor coil back electromotive force E m It is relatively small, so the voltage drop of the power supply is mainly on the inductance of the motor coil and the internal resistance of the coil, so the motor current will increase rapidly. If there is no current limiting circuit, a large current spike will be formed, and the excessive current will burn the chip; and if the motor current is quickly reduced during a large current spike, a large voltage will be formed at both ends of the coil due to the effect of the inductance. When the voltage generated on the coil is higher than the withstand voltage of the H-bridge output tube, it will break down the components in the circuit and damage the chip. When selecting the starting current limiting value, the force driving the motor to rotate is F=BIl; the force F driving the motor is proportional to the current I flowing through the coil, so if you want the motor to run quickly, you need a large current. In summary, the input current limiting value needs to be a suitable value.

[0003] When the motor is running, the voltage drop on the coil also includes the voltage drop on the coil internal resistance, the voltage drop on the coil inductance and the back electromotive force. When the motor rotates at high speed, the output current may be too large due to various abnormal conditions. The large current will form a backlash on the power supply voltage during the commutation period, causing a large fluctuation in the power supply voltage, thereby affecting the normal operation of the entire chip and the working performance of the motor. Therefore, a current limiting circuit is required to protect the chip during the startup and operation stages.

[0004] like Figure 1As shown, in a conventional current limiting scheme, a current limiting protection circuit is connected to a motor driving circuit, the motor driving circuit includes an H-bridge circuit 101 and a transistor driving circuit 102, the H-bridge circuit 101 includes a first transistor M1, a second transistor M2, a third transistor M3 and a fourth transistor M4, the drain of the first transistor M1 and the drain of the second transistor M2 are both connected to a power supply, the source of the first transistor M1 is connected to the drain of the third transistor M3, the source of the third transistor M3 and the source of the fourth transistor are both grounded, the drain of the fourth transistor M4 is connected to the source of the second transistor M2, and the motor 1 The two ends of the transistor driving circuit 103 are respectively connected to the source of the first transistor M1 and the source of the second transistor M2, and the four output ends of the transistor driving circuit 102 are respectively connected to the gate of the first transistor M1, the gate of the second transistor M2, the gate of the third transistor M3 and the gate of the fourth transistor M4. The transistor driving circuit 102 is used to output a signal for controlling the first transistor M1, the second transistor M2, the third transistor M3 and the fourth transistor M4 according to an input control signal. By controlling the opening or closing of the first to fourth transistors by the transistor driving circuit 102, the operation of the motor 103 can be controlled. The current limiting protection circuit includes a fifth transistor M5, a sixth transistor M6, a current-to-voltage circuit 201, a reference voltage providing circuit 202, a comparator 203 and two AND gates 204, the source of the fifth transistor M5 is connected to the source of the first transistor M1, the gate of the fifth transistor M5 is connected to the gate of the first transistor M1, the drain of the fifth transistor M5 is connected to the first input terminal of the current-to-voltage circuit 201, the source of the sixth transistor M6 is connected to the source of the second transistor M2, the gate of the sixth transistor M6 is connected to the gate of the second transistor M2, and the drain of the sixth transistor M5 is connected to the first input terminal of the current-to-voltage circuit 201. The drain of the transistor M6 is connected to the second input terminal of the current-to-voltage circuit 201, the output terminal of the current-to-voltage circuit 201 is connected to the inverting input terminal of the comparator 203, the output terminal of the reference voltage providing circuit 202 is connected to the non-inverting input terminal of the comparator 203, the output terminal of the comparator 203 is respectively connected to the input terminal of the reference voltage providing circuit 202 and the first input terminal of the second AND gate 204, the second input terminal of the second AND gate 204 is used to receive an input control signal PWM_in, and the output terminal of the second AND gate 204 is connected to the input terminal of the transistor driving circuit 102.

[0005] During the operation of the motor, the fifth transistor M5 and the sixth transistor M6 are used to sample the current flowing through the motor 103 to obtain the sampled current. The current-to-voltage circuit 201 is used to convert the sampled current into a sampled voltage. The sampled voltage is compared with the reference voltage output by the reference voltage providing circuit 202 through the comparator 203. When the sampled current is greater than the upper limit of the current limit value, the corresponding sampled voltage is greater than the high reference voltage. The comparator 203 outputs a low-level current control signal Limit_current. The current control signal Limit_current output by the comparator 203 controls the reference voltage. The circuit 202 is provided to output a low reference voltage to form a hysteresis comparator; the current control signal Limit_current output by the comparator 203 causes the control signal PWM_out output by the second AND gate 204 to become a low level. After the low level signal is input into the transistor driving circuit 102, the transistor will be controlled to be turned off, so that the current (i.e., the sampling current) flowing through the motor 103 gradually decreases. When the sampling current is lower than the lower limit of the current limit value, the comparator 203 outputs a high level signal. At this time, the control signal PWM_out output by the second AND gate 204 is the same as PWM_in, and the motor driving circuit enters a normal control state.

[0006] The traditional current limiting method uses the hysteresis comparison method, with the upper limit of hysteresis being Limit_H and the lower limit being Limit_L. This method has two problems. When the hysteresis is too small, the interference caused by the motor rotation and power supply fluctuation will frequently trigger the current limiting and frequently release the current limiting, which will cause the H-bridge transistors to switch irregularly and quickly, causing rotation disorder and affecting the motor performance. When the hysteresis is too large, if the current limiting time is too long, the entire PWM (pulse width modulation) modulation cycle may be cut off by the current control signal Limit_current, which will generate a new modulation frequency lower than the original PWM. When the new modulation frequency is lower than 20kHz, the human ear can hear abnormal sounds. Summary of the invention

[0007] The purpose of the present invention is to provide a current limiting protection control system and method for a motor drive circuit, so as to limit the current flowing through the motor within a specified range while avoiding the generation of low-frequency noise, so as to avoid the motor being burned out due to excessive current.

[0008] Based on the above purpose, on one hand, the present invention provides a current limiting protection control system for a motor drive circuit, including a current sampling circuit, a current-to-voltage circuit, a comparator, a reference voltage providing circuit, a digital latch and two AND gates, wherein the current sampling circuit is respectively connected to the motor drive circuit and the current-to-voltage circuit, the current-to-voltage circuit is connected to the inverting input terminal of the comparator, the output terminal of the reference voltage providing circuit is connected to the non-inverting input terminal of the comparator, the output terminal of the comparator is connected to the input terminal of the digital latch, the clock terminal of the digital latch is used to receive a clock signal, the output terminal of the digital latch is connected to the first input terminal of the two AND gates, and the second input terminal of the two AND gates is used to receive an input control signal. The output ends of the two AND gates are connected to the motor drive circuit; the current sampling circuit is used to sample the current flowing through the motor in the motor drive circuit to obtain a sampled current; the current-to-voltage circuit is used to convert the sampled current into a sampled voltage; the reference voltage providing circuit is used to input a reference voltage to the non-phase input end of the comparator, the comparator is used to output a current control signal according to the reference voltage and the sampled voltage, and the digital latch is used to update the output signal to the current control signal when a rising edge appears in the clock signal; the two AND gates are used to output an output control signal according to the input control signal and the output signal of the digital latch, so as to control the motor drive circuit through the output control signal.

[0009] Further, the motor drive circuit includes an H-bridge circuit and a transistor drive circuit, the H-bridge circuit includes a first transistor, a second transistor, a third transistor and a fourth transistor, the drain of the first transistor and the drain of the second transistor are both connected to a power supply, the source of the first transistor is connected to the drain of the third transistor, the source of the third transistor and the source of the fourth transistor are both grounded, the drain of the fourth transistor is connected to the source of the second transistor, the two ends of the motor are respectively connected to the source of the first transistor and the source of the second transistor, the four output ends of the transistor drive circuit are respectively connected to the gate of the first transistor, the gate of the second transistor, the gate of the third transistor and the gate of the fourth transistor, the transistor drive circuit is used to control the opening or closing of the first transistor, the second transistor, the third transistor and the fourth transistor according to the input signal; the current sampling circuit is connected to the H-bridge circuit, and the output ends of the two AND gates are connected to the transistor drive circuit.

[0010] Furthermore, the current sampling circuit includes a fifth transistor and a sixth transistor, the source of the fifth transistor is connected to the source of the first transistor, the gate of the fifth transistor is connected to the gate of the first transistor, the drain of the fifth transistor is connected to the first input terminal of the current-to-voltage circuit, the source of the sixth transistor is connected to the source of the second transistor, the gate of the sixth transistor is connected to the gate of the second transistor, and the drain of the sixth transistor is connected to the second input terminal of the current-to-voltage circuit.

[0011] Furthermore, the system also includes a trimming circuit, which is connected to the current-to-voltage circuit and is used to trim the current-to-voltage circuit to adjust the current-to-voltage conversion coefficient of the current-to-voltage circuit.

[0012] Furthermore, the reference voltage providing circuit includes a bandgap reference circuit and a voltage divider circuit connected to each other, the bandgap reference circuit is used to generate a bandgap reference voltage, and the voltage divider circuit is used to divide the bandgap reference voltage to output a bandgap reference voltage of a desired ratio as a reference voltage.

[0013] Furthermore, the system also includes a reference voltage adjustment circuit, which is connected to the input end of the reference voltage providing circuit and is used to adjust the magnitude of the reference voltage output by the reference voltage providing circuit.

[0014] Further, the digital latch is a D flip-flop; the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor and the sixth transistor are all NMOS transistors.

[0015] Another aspect of the present invention provides a current limiting protection control method for a motor drive circuit, comprising:

[0016] Provide a current limiting protection control system for a motor drive circuit as described above;

[0017] The current flowing through the motor is sampled by a current sampling circuit to obtain a sampled current, and the sampled current is transmitted to a current-to-voltage circuit;

[0018] The sampling current is converted into a sampling voltage through a current-to-voltage circuit, and the sampling voltage is transmitted to the inverting input terminal of the comparator;

[0019] Inputting a reference voltage to the positive input terminal of the comparator through a reference voltage providing circuit;

[0020] The comparator compares the sampled voltage with the reference voltage, outputs a current control signal, and inputs the current control signal into the input terminal of the digital latch;

[0021] Input a preset clock signal into the clock terminal of the digital latch, so that when the rising edge of the clock signal arrives, the digital latch transmits the current control signal to the output terminal of the digital latch, and inputs the current control signal into the first input terminal of the second AND gate through the digital latch;

[0022] The preset input control signal is input into the second input terminal of the two AND gates, so that the two AND gates output an output control signal according to the current control signal and the input control signal, and the output control signal is output to the transistor drive circuit; the transistor drive circuit controls the motor drive circuit according to the output control signal.

[0023] Furthermore, the method further comprises:

[0024] The current-to-voltage circuit is trimmed by a trimming circuit to adjust the current-to-voltage conversion coefficient of the current-to-voltage circuit.

[0025] Furthermore, the method further comprises:

[0026] The reference voltage output by the reference voltage providing circuit is adjusted by the reference voltage adjusting circuit.

[0027] The current limiting protection control system and method of the motor drive circuit of the embodiment of the present invention samples the current flowing through the motor through a current sampling circuit. When the sampled current exceeds a preset current limiting value, the current control signal output by the comparator will flip. When the rising edge of the clock signal arrives, the digital latch and the two AND gates modulate the input control signal. The modulated output control signal will control the upper tube of the H-bridge circuit to turn off through the transistor drive circuit, thereby reducing the motor current and achieving current limiting protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A circuit diagram of an existing motor drive circuit and a current limiting protection circuit;

[0029] Figure 2 A schematic diagram of the structure of a current limiting protection control system for a motor drive circuit according to an embodiment of the present invention;

[0030] Figure 3 It is a timing waveform diagram of each signal of the existing current limiting protection circuit;

[0031] Figure 4 A timing waveform diagram of each signal of a current limiting protection control system of a motor drive circuit according to an embodiment of the present invention;

[0032] Figure 5 The figure is a flow chart of a current limiting protection control method of a motor drive circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0034] like Figure 2 As shown, the present invention provides a current limiting protection control system for a motor drive circuit, which is used to limit the current of the motor drive circuit to play a protective role. The structure of the motor drive circuit is the same as that of the prior art and is not repeated here; the current limiting protection control system includes a current sampling circuit, a current-to-voltage circuit 301, a comparator 303, a reference voltage providing circuit 304, a digital latch 305 and two AND gates 306. The current sampling circuit is connected to the H-bridge circuit and the current-to-voltage circuit 301 respectively, and the current-to-voltage circuit 301 is also connected to the inverting gate of the comparator 303. The output end of the reference voltage providing circuit 304 is connected to the non-phase input end of the comparator 303, the output end of the comparator 303 is connected to the input end of the digital latch 305, the clock end of the digital latch 305 is connected to a clock signal CLK, the output end of the digital latch 305 is connected to the first input end of the second AND gate 306, the second input end of the second AND gate 306 is connected to the input control signal PWM_in input by, for example, an external signal source, and the output end of the second AND gate 306 is connected to the input end of the transistor driving circuit 102. The current sampling circuit is used to sample the current I_out flowing through the motor 103 to obtain the sampled current. The current-to-voltage circuit 301 is used to convert the sampled current into a sampled voltage and output the sampled voltage to the inverting output terminal of the comparator 303. The reference voltage providing circuit 304 is used to input a reference voltage to the non-phase input terminal of the comparator 303. The comparator 303 outputs a current control signal Limit_current according to the sampled voltage and the reference voltage. The digital latch 305 is used to update the output signal to the current control signal Limit_current when a rising edge appears in the clock signal CLK. The two AND gates 306 are used to output a PWM_out signal (i.e., an output control signal) according to the input control signal PWM_in and the output signal of the digital latch 305. The output control signal PWM_out controls the H-bridge circuit 101 through the transistor driving circuit 102 to achieve current limiting protection.

[0035] In some embodiments, the current sampling circuit may include a fifth transistor M5 and a sixth transistor M6, the source of the fifth transistor M5 is connected to the source of the first transistor M1, the gate of the fifth transistor M5 is connected to the gate of the first transistor M1, the drain of the fifth transistor M5 is connected to the first input terminal of the current-to-voltage circuit 201, the source of the sixth transistor M6 is connected to the source of the second transistor M2, the gate of the sixth transistor M6 is connected to the gate of the second transistor M2, and the drain of the sixth transistor M6 is connected to the second input terminal of the current-to-voltage circuit 201.

[0036] The size of the fifth transistor M5 is proportional to the size of the first transistor M1, and the size of the sixth transistor M6 is proportional to the size of the second transistor M2. According to the MOS tube linear region current formula Wherein, μ is the mobility, which is the electron mobility in NMOS tube and the hole mobility in PMOS tube; C OX is the gate oxide capacitance per unit area; W / L is the width-to-length ratio of the transistor; V GS is the transistor gate-source voltage; V TH is the transistor threshold voltage; V DS is the transistor drain-source voltage; when the fifth transistor M5 and the first transistor M1 both operate in the linear region and ensure that their V GS With V DS Etc., the currents of the two transistors are proportional to their width-to-length ratios, so the fifth transistor M5 can replicate the current of the first transistor M1 in the ratio of (W / L)5 / (W / L)1, that is, the sampling current is proportional to I_out; similarly, the sixth transistor M6 can replicate the current of the second transistor M2 in the ratio of (W / L)6 / (W / L)2.

[0037] In some embodiments, the first to sixth transistors are all NMOS transistors (ie, N-type metal-oxide semiconductor transistors).

[0038] In some embodiments, the current-to-voltage circuit 301 may include one or more resistors. After the sampling current flows through the resistor, the voltage of the resistor can be collected as the sampling voltage. Since V=I*R, where R is the resistance value of the resistor (i.e., the current-to-voltage conversion coefficient), the sampling current is proportional to the sampling voltage; similarly, the current flowing through the motor 103 is also proportional to the sampling voltage.

[0039] The current limiting protection control system may also include a trimming circuit 302, which is connected to the current-to-voltage circuit 301 and is used to trim the current-to-voltage circuit 301 so that it outputs a fixed sampling voltage under a specific sampling current. Since there are deviations in the chip manufacturing process, the resistance value of the current-to-voltage circuit 301 may also have deviations. The trimming circuit 301 can change the series-parallel connection mode of the resistors in the current-to-voltage circuit 301 through trimming to change its resistance value, so that it outputs a fixed sampling voltage under a specific sampling current.

[0040] In some embodiments, the reference voltage providing circuit 304 may include a bandgap reference circuit and a voltage divider circuit. The bandgap reference circuit is used to generate a bandgap reference voltage that varies very little with temperature within a certain range. Under a certain power supply voltage, the bandgap reference voltage is independent of the power supply voltage. The voltage divider circuit is used to divide the bandgap reference voltage to output a bandgap reference voltage of a desired ratio as a reference voltage.

[0041] In some embodiments, the current limiting protection control system may further include a reference voltage adjustment circuit 307, which is connected to the input end of the reference voltage providing circuit 304 and is used to adjust the magnitude of the reference voltage output by the reference voltage providing circuit 304. By changing the value of the reference voltage, the current limiting value of the current limiting protection control system can be changed. The reference voltage adjustment circuit 307 may be a logic circuit, which controls the switch in the voltage divider circuit by outputting a logic signal to control the magnitude of the voltage divider output by the voltage divider circuit, thereby changing the magnitude of the reference voltage output by the voltage divider circuit, and ultimately changing the current limiting value of the current limiting protection control system. For example, during the startup phase of the motor 103, the reference voltage adjustment circuit 307 can enable the reference voltage providing circuit 304 to output a first reference voltage, and during the normal operation phase of the motor 103, the reference voltage providing circuit 304 can output a second reference voltage. The first reference voltage can be set to be greater than the second reference voltage, so that the current limiting value of the motor 103 during the startup phase is greater than the current limiting value during the normal operation phase. In this way, the motor 103 can have a larger current during the startup phase, which facilitates the rapid start-up of the motor 103. During normal operation, the current of the motor 103 can be reduced to avoid burning out the chip.

[0042] In some embodiments, the digital latch 305 can be a D flip-flop, which includes a clock terminal, a D input terminal, and two Q output terminals and ~Q terminals with opposite logic signals. Only when the clock signal CLK at the clock terminal has a rising edge logic signal jump, the logic signal at the D input terminal will be transmitted to the Q output terminal. At other times, no matter how the logic signal at the D input terminal changes, the logic signal at the Q output terminal will not change. The output terminal of the comparator 303 is connected to the D input terminal, and the first input terminal of the second AND gate 306 is connected to the Q output terminal.

[0043] The working principle of the current limiting protection control system of the present invention is as follows:

[0044] When the sampling voltage is less than the reference voltage, the current control signal Limit_current output by the comparator 303 is at a high level. When the clock signal CLK is at a rising edge, the digital latch 305 transmits the current control signal Limit_current at the input end to the output end, that is, the digital latch 305 outputs a high level. At this time, the output control signal PWM_out is the same as the external input control signal PWM_in, that is, the external input control signal PWM_in performs normal pulse control on the H bridge; when the current I_out flowing through the motor 103 gradually increases, the sampling voltage will also increase. When the sampling voltage gradually increases, the sampling voltage will increase. When it gradually increases to be greater than the reference voltage, the current control signal Limit_current output by the comparator 303 will change from a high level to a low level. When the rising edge of the clock signal CLK arrives, the digital latch 305 will update the output signal to a low level. The low level signal will set the input control signal PWM_in to a low level, so that the output control signal PWM_out becomes a low level. After the low level output control signal PWM_out is input to the transistor driving circuit 102, the transistor driving circuit 102 will turn off the upper tube of the H bridge, that is, the first transistor M1 and the second transistor M2, thereby reducing the motor current I_out and realizing current limiting protection.

[0045] like Figure 3 As shown, in the traditional current limiting protection circuit, when the motor current I_out reaches Limit_H, the current control signal Limit_current becomes low. When Limit_current is low, PWM_out is low, so that the upper tube in the H-bridge circuit 101 is turned off, and the motor current I_out decreases until the current is detected at the beginning of the next modulation cycle. When the motor current I_out is still above Limit_L, a modulation cycle is closed; when a new modulation cycle starts and the motor current I_out is detected to be reduced to Limit_L, the current control signal Limit_current becomes high, and the current limiting is released. After the current limiting is released, PWM_in is the same as PWM_out. The problem with this method is that when the maximum current limiting value is far from the minimum current limiting value, the PWM_out signal will lose the complete PWM_in cycle relative to the PWM_in signal, which will reduce the PWM_out frequency (the period of PWM_out is 2T, which is twice that of PWM_in). When PWM_out is lower than 20kHz, electromagnetic noise that can be heard by the human ear may be generated.

[0046] like Figure 4As shown, in the current limiting protection control system of the present invention, the high-frequency clock signal CLK is used to modulate the current control signal Limit_current, and the current control signal Limit_current is updated to the output end of the digital latch 305 at each rising edge of the clock signal CLK. When the motor current I_out is greater than the current limiting value I_limit, the sampling voltage is greater than the reference voltage, and the current control signal Limit_current is low level. When the rising edge of the clock signal CLK arrives, the output of the digital latch 305 is low level, so that PWM_out also becomes low level, and the upper tube of the H-bridge circuit 101 is turned off, so that the motor current I_out is reduced; when I_out is less than the current limiting value I_limit, the current control signal Limit_current becomes high level. When the rising edge of the clock signal CLK arrives, the output of the digital latch 305 also becomes high level, so that PWM_out and PWM_in are the same, thereby driving the motor to operate normally. Because when I_out is greater than I_limit, the clock signal CLK will modulate the PWM_out signal to a higher frequency, which can not only avoid the generation of low-frequency signals, but also effectively reduce the duty cycle of PWM_out, resulting in a better current limiting effect.

[0047] The current limiting protection control system of the motor drive circuit of the embodiment of the present invention samples the current flowing through the motor 103 through the current sampling circuit. When the sampled current exceeds the preset current limiting value, the current control signal output by the comparator 303 will be flipped. When the rising edge of the clock signal arrives, the digital latch 305 and the two AND gates 306 modulate the input control signal. The modulated output control signal will control the upper tube of the H-bridge circuit 101 to turn off through the transistor drive circuit 102, thereby reducing the motor current and realizing current limiting protection.

[0048] like Figure 5 As shown, another embodiment of the present invention provides a current limiting protection control method for a motor drive circuit, which includes the following steps:

[0049] S410: providing a current limiting protection control system for the motor drive circuit of the above embodiment;

[0050] S420: sampling the current flowing through the motor through the current sampling circuit to obtain the sampled current, and transmitting the sampled current to the current-to-voltage circuit 301;

[0051] S430: converting the sampled current into a sampled voltage through the current-to-voltage circuit 301, and transmitting the sampled voltage to the inverting input terminal of the comparator 303;

[0052] S440: Inputting a reference voltage to the positive input terminal of the comparator 303 through the reference voltage providing circuit 304;

[0053] S450: The comparator 303 compares the sampled voltage with the reference voltage and outputs a current control signal, and inputs the current control signal into the input terminal of the digital latch 305;

[0054] S460: Input the preset clock signal CLK to the clock terminal of the digital latch 305, so that the digital latch 305 transmits the current control signal to the output terminal of the digital latch 305 when the rising edge of the clock signal CLK arrives, and inputs the current control signal to the first input terminal of the second AND gate 306 through the digital latch 305;

[0055] S470: Input the preset input control signal PWM_in to the second input terminal of the second AND gate 306, so that the second AND gate 306 outputs an output control signal PWM_out according to the current control signal and the input control signal, and outputs the output control signal to the transistor driving circuit 102; the transistor driving circuit 102 controls the H-bridge circuit 101 according to the output control signal PWM_out to achieve current limiting protection.

[0056] The current limiting protection control method of the motor drive circuit of the embodiment of the present invention samples the current flowing through the motor 103 through the current sampling circuit. When the sampled current exceeds the preset current limiting value, the current control signal output by the comparator 303 will be flipped. When the rising edge of the clock signal arrives, the digital latch 305 and the two AND gates 306 modulate the input control signal. The modulated output control signal will control the upper tube of the H-bridge circuit 101 to turn off through the transistor drive circuit 102, thereby reducing the motor current and realizing current limiting protection.

[0057] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A current limiting protection control system for a motor drive circuit, characterized in that: It includes a current sampling circuit, a current-to-voltage circuit, a comparator, a reference voltage providing circuit, a digital latch and two AND gates, wherein the current sampling circuit is respectively connected to the motor driving circuit and the current-to-voltage circuit, the current-to-voltage circuit is connected to the inverting input terminal of the comparator, the output terminal of the reference voltage providing circuit is connected to the non-inverting input terminal of the comparator, the output terminal of the comparator is connected to the input terminal of the digital latch, the clock terminal of the digital latch is used to receive a clock signal, the output terminal of the digital latch is connected to the first input terminal of the two AND gates, the second input terminal of the two AND gates is used to receive an input control signal, and the output terminal of the two AND gates is connected to the motor driving circuit; the current sampling circuit is used to sample the current flowing through the motor in the motor driving circuit to obtain the sampled current; the current-to-voltage circuit is used to convert the sampled current into a sampled voltage; The reference voltage providing circuit is used to input a reference voltage to the non-phase input terminal of the comparator, the comparator is used to output a current control signal according to the reference voltage and the sampling voltage, and the digital latch is used to update the output signal to the current control signal when a rising edge occurs in the clock signal; the two AND gates are used to output an output control signal according to the input control signal and the output signal of the digital latch, so as to control the motor drive circuit through the output control signal.

2. The current limiting protection control system of the motor drive circuit according to claim 1, characterized in that: The motor drive circuit includes an H-bridge circuit and a transistor drive circuit. The H-bridge circuit includes a first transistor, a second transistor, a third transistor and a fourth transistor. The drain of the first transistor and the drain of the second transistor are both connected to a power supply, the source of the first transistor is connected to the drain of the third transistor, the source of the third transistor and the source of the fourth transistor are both grounded, the drain of the fourth transistor is connected to the source of the second transistor, the two ends of the motor are respectively connected to the source of the first transistor and the source of the second transistor, the four output ends of the transistor drive circuit are respectively connected to the gate of the first transistor, the gate of the second transistor, the gate of the third transistor and the gate of the fourth transistor, and the transistor drive circuit is used to control the opening or closing of the first transistor, the second transistor, the third transistor and the fourth transistor according to an input signal; the current sampling circuit is connected to the H-bridge circuit, and the output ends of the two AND gates are connected to the transistor drive circuit.

3. The current limiting protection control system of the motor drive circuit according to claim 2, characterized in that: The current sampling circuit includes a fifth transistor and a sixth transistor, the source of the fifth transistor is connected to the source of the first transistor, the gate of the fifth transistor is connected to the gate of the first transistor, the drain of the fifth transistor is connected to the first input end of the current-to-voltage circuit, the source of the sixth transistor is connected to the source of the second transistor, the gate of the sixth transistor is connected to the gate of the second transistor, and the drain of the sixth transistor is connected to the second input end of the current-to-voltage circuit.

4. The current limiting protection control system of the motor drive circuit according to claim 1, characterized in that: It also includes a trimming circuit, which is connected to the current-to-voltage circuit and is used to trim the current-to-voltage circuit to adjust the current-to-voltage conversion coefficient of the current-to-voltage circuit.

5. The current limiting protection control system of the motor drive circuit according to claim 1, characterized in that: The reference voltage providing circuit includes a bandgap reference circuit and a voltage divider circuit connected to each other, the bandgap reference circuit is used to generate a bandgap reference voltage, and the voltage divider circuit is used to divide the bandgap reference voltage to output a bandgap reference voltage of a desired ratio as a reference voltage.

6. The current limiting protection control system of the motor drive circuit according to claim 1, characterized in that: It also includes a reference voltage adjustment circuit, which is connected to the input end of the reference voltage providing circuit and is used to adjust the magnitude of the reference voltage output by the reference voltage providing circuit.

7. The current limiting protection control system of the motor drive circuit according to claim 3, characterized in that: The digital latch is a D flip-flop; the first transistor, the second transistor, the third transistor, the fourth transistor, the fifth transistor and the sixth transistor are all NMOS transistors.

8. A current limiting protection control method for a motor drive circuit, characterized in that: include: Provided is a current limiting protection control system for a motor drive circuit according to any one of claims 1 to 7; The current flowing through the motor is sampled by a current sampling circuit to obtain a sampled current, and the sampled current is transmitted to a current-to-voltage circuit; The sampling current is converted into a sampling voltage through a current-to-voltage circuit, and the sampling voltage is transmitted to the inverting input terminal of the comparator; Inputting a reference voltage to the positive input terminal of the comparator through a reference voltage providing circuit; The comparator compares the sampled voltage with the reference voltage, outputs a current control signal, and inputs the current control signal into the input terminal of the digital latch; Input a preset clock signal into the clock terminal of the digital latch, so that when the rising edge of the clock signal arrives, the digital latch transmits the current control signal to the output terminal of the digital latch, and inputs the current control signal into the first input terminal of the second AND gate through the digital latch; Inputting a preset input control signal into the second input terminal of the two AND gates, so that the two AND gates output an output control signal according to the current control signal and the input control signal, and outputting the output control signal to the transistor driving circuit; The transistor driving circuit controls the motor driving circuit according to the output control signal.

9. The current limiting protection control method of the motor drive circuit according to claim 8, characterized in that: Also includes: The current-to-voltage circuit is trimmed by a trimming circuit to adjust the current-to-voltage conversion coefficient of the current-to-voltage circuit.

10. The current limiting protection control method of the motor drive circuit according to claim 8, characterized in that: Also includes: The reference voltage output by the reference voltage providing circuit is adjusted by the reference voltage adjusting circuit.

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