CN111682811A - A DC motor control circuit and a DC motor control system - Google Patents

Abstract

Embodiments of the present invention relate to the technical field of motor control, and provide a DC motor control circuit and a DC motor control system. It includes: a controller for sending a PWM signal; a speed control circuit, which is electrically connected to the controller and used to respond to the PWM signal to generate a drive power, which is proportional to the duty cycle of the PWM signal; an H-bridge drive circuit, It is electrically connected to the speed regulation control circuit for driving the DC motor to work according to the driving power supply, and the driving power supply is proportional to the speed of the DC motor; the overcurrent protection circuit is electrically connected to the H bridge driving circuit and the speed regulation control circuit, and is used for When it is detected that the driving current flowing through the DC motor is greater than or equal to the threshold current, the speed regulation control circuit is triggered to reduce the driving power; Operating Voltage. The embodiments of the present invention can improve the safety and reliability of the DC motor control circuit.

Description

A DC motor control circuit and a DC motor control system

【Technical field】

Embodiments of the present invention relate to the technical field of motor control, and in particular, to a DC motor control circuit and a DC motor control system.

【Background technique】

At present, the H-bridge drive circuit is mostly used to control the operation of the DC motor. The H-bridge drive circuit is electrically connected to the controller, and the duty ratio of the PWM signal output by the controller is used to modulate the target switch base or gate of the H-bridge drive circuit. Bias, thereby changing the on-time of the target switch tube to obtain the driving power, so as to realize the forward or reverse speed regulation of the DC motor. However, in the process of switching the working state of the target switch tube, it may affect the modulation of the PWM signal, resulting in a decrease in the reliability of the driving power supply, and in the process of DC motor speed regulation, the driving power supply is constant. When the driving current of the DC motor is greater than or equal to the threshold current, it may cause safety hazards such as circuit fire.

[Content of the invention]

The embodiments of the present invention aim to provide a safe and reliable DC motor control circuit and a DC motor control system.

In order to solve the above-mentioned technical problems, the embodiments of the present invention provide the following technical solutions:

An embodiment of the present invention provides a DC motor control circuit, including:

Controller, used to send PWM signal;

a speed regulation control circuit, electrically connected to the controller, for generating a driving power supply in response to the PWM signal, and the driving power supply is proportional to the duty ratio of the PWM signal;

The H-bridge drive circuit is electrically connected to the speed regulation control circuit, and is used for driving the DC motor to work according to the drive power source, and the drive power source is proportional to the rotational speed of the DC motor;

an overcurrent protection circuit, which is electrically connected to the H-bridge drive circuit and the speed control circuit respectively, and is used for sending the speed control to the speed control when it is detected that the drive current flowing through the DC motor is greater than or equal to a threshold current a circuit sends a protection signal to cause the speed control circuit to reduce the drive power; and,

a rotational speed detection circuit, which is electrically connected to the H-bridge drive circuit and the controller, respectively, for sampling the working voltage of the DC motor and sending the working voltage to the controller, so that the controller controls the The speed control circuit adjusts the drive power.

Optionally, the speed regulation control circuit includes:

charging circuit;

A startup circuit, which is electrically connected to the controller and the charging circuit respectively, is used to control an external power supply to charge the charging circuit and provide all the necessary power for the H-bridge driving circuit when the PWM signal is at a high level. The driving power supply, when the PWM signal is at a low level, controls the external power supply to stop charging the charging circuit, so that the charging circuit discharges to provide the driving power for the H-bridge driving circuit.

Optionally, the startup circuit includes a first resistor, a second resistor, an NPN transistor, a third resistor, a fourth resistor, and a PNP transistor;

One end of the first resistor is used to receive the PWM signal, and the other end of the first resistor is electrically connected to one end of the second resistor, the base of the NPN transistor and the overcurrent protection circuit; The other end of the second resistor is grounded; the emitter of the NPN triode is grounded, and the collector of the NPN triode is electrically connected to one end of the third resistor; the other end of the third resistor is connected to the fourth resistor One end of the resistor is electrically connected to the base of the PNP triode; the other end of the fourth resistor is electrically connected to the emitter of the PNP triode for receiving external power; the collector of the PNP triode is connected to the charging circuit electrical connection.

Optionally, the charging circuit includes an inductor and a first capacitor;

One end of the inductor is electrically connected to the collector of the PNP triode, and the other end of the inductor is electrically connected to the positive electrode of the first capacitor for outputting the driving power; the negative electrode of the first capacitor is grounded.

Optionally, the speed regulation control circuit further includes a freewheeling circuit, the freewheeling circuit is electrically connected between the start-up circuit and the charging circuit, for when the PWM signal is at a low level, the When the start-up circuit controls the external power supply to stop charging the charging circuit, the back electromotive force generated by the charging circuit is subjected to freewheeling processing.

Optionally, the freewheeling circuit includes a first diode and a second diode;

The cathode of the first diode is electrically connected to the emitter of the PNP triode, the anode of the first diode is connected to the collector of the PNP triode, one end of the inductor and the second diode The cathode of the tube is electrically connected; the anode of the second diode is grounded.

Optionally, the overcurrent protection circuit includes:

a first sampling circuit, electrically connected to the H-bridge drive circuit, for sampling the drive current flowing through the DC motor to generate a sampling voltage;

a switch circuit, which is electrically connected to the first sampling circuit and the speed regulation control circuit respectively, and is used for biasing the PWM signal as the The low level of the protection signal causes the speed control circuit to reduce the drive power.

Optionally, the first sampling circuit includes a fifth resistor, a second capacitor and a sixth resistor;

One end of the fifth resistor is electrically connected to the H-bridge drive circuit, and the other end of the fifth resistor is electrically connected to one end of the second capacitor, one end of the sixth resistor and the switch circuit; The other end of the second capacitor is grounded; the other end of the sixth resistor is grounded.

Optionally, the rotational speed detection circuit includes a seventh resistor, an eighth resistor and a third capacitor;

One end of the seventh resistor is electrically connected to the H-bridge drive circuit and one end of the eighth resistor, and the other end of the seventh resistor is grounded; the other end of the eighth resistor is connected to the third capacitor. One end is electrically connected to the controller; the other end of the third capacitor is grounded. The embodiment of the present invention also provides a DC motor control system, including:

DC;

The DC motor control circuit according to any one of the above, wherein the DC motor control circuit is electrically connected to the DC motor.

The beneficial effects of the present invention are: compared with the prior art, the embodiment of the present invention provides a DC motor control circuit and a DC motor control system, through which the speed regulation control circuit responds to the PWM signal sent by the controller to generate a driving power supply to drive the The power supply is proportional to the duty cycle of the PWM signal. The H-bridge drive circuit drives the DC motor to work according to the drive power. The drive power is proportional to the speed of the DC motor. When the overcurrent protection circuit detects that the drive current flowing through the DC motor is greater than When the current is equal to or equal to the threshold value, a protection signal is sent to the speed control circuit, so that the speed control circuit reduces the driving power. Therefore, in the embodiment of the present invention, the PWM signal is converted into a driving power source through the speed regulation control circuit to directly drive the DC motor, and when the overcurrent protection circuit detects that the driving current flowing through the DC motor is greater than or equal to the threshold current, the regulation is adjusted. The high-speed control circuit reduces the drive power to achieve instant hardware protection, thereby improving the safety and reliability of the DC motor control circuit.

【Description of drawings】

One or more embodiments are exemplified by the pictures in the corresponding drawings, and these exemplifications do not constitute limitations of the embodiments, and elements with the same reference numerals in the drawings are denoted as similar elements, Unless otherwise stated, the figures in the accompanying drawings do not constitute a scale limitation.

1 is a schematic diagram of a circuit structure of a DC motor control system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of the circuit structure of one of the DC motor control circuits provided in an embodiment of the present invention;

FIG. 3 is a schematic diagram of the circuit structure of one of the DC motor control circuits provided in an embodiment of the present invention;

4 is a schematic diagram of circuit connection of a speed regulation control circuit according to an embodiment of the present invention;

5 is a schematic diagram of circuit connection of an H-bridge drive circuit provided by an embodiment of the present invention;

6 is a schematic diagram of circuit connection of an overcurrent protection circuit provided by an embodiment of the present invention;

FIG. 7 is a schematic diagram of circuit connection of a rotational speed detection circuit according to an embodiment of the present invention.

【Detailed ways】

In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is referred to as being "connected" to another element, it can be directly connected to the other element, or one or more intervening elements may be present therebetween. Furthermore, the terms "first," "second," etc. are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the technical field of the present invention. The terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not used to limit the present invention. As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict with each other.

Please refer to FIG. 1 , which is a schematic diagram of a circuit structure of a DC motor control system according to an embodiment of the present invention. As shown in FIG. 1 , the DC motor control system 300 includes the DC motor 200 and the DC motor control circuit 100 described in any of the following embodiments. The DC motor control circuit 100 is electrically connected to the DC motor 200 for controlling the operation of the DC motor 200 . .

Please refer to FIG. 2 , which is a schematic diagram of a circuit structure of one of the DC motor control circuits provided by the embodiments of the present invention. As shown in FIG. 2 , the DC motor control circuit 100 includes a controller 10 , a speed regulation control circuit 20 , an H-bridge drive circuit 30 , an overcurrent protection circuit 40 and a rotational speed detection circuit 50 .

The controller 10 is used to send the PWM signal.

In the embodiment of the present invention, the controller 10 includes an AD sampling port and several IO ports, the AD sampling port is used to collect the working voltage of the DC motor 200 (the AD port shown in FIG. 7 ), and the several IO ports include It is used to output PWM signal, DR1 level signal and DR2 level signal (as shown in Figure 4 and Figure 5). The PWM signal controls the on-off of the switching device of the inverter circuit, so that the output terminal gets a series of pulses of equal amplitude, and these pulses are used to replace the sine wave or the required waveform. Therefore, the PWM signal is a digital signal, specifically a repetitive pulse sequence of on or off. By controlling the ratio of on (ON) or off (OFF), PWM signals with different duty ratios can be obtained.

In the embodiment of the present invention, the controller 10 includes a single-chip microcomputer, and the single-chip microcomputer may adopt a 51 series, an Arduino series, an STM32 series, and the like. In some embodiments, the controller 10 may also be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), an ARM (Acorn RISC Machine) or other programmable Logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of these; may also be any conventional processor, controller, microcontroller, or state machine; may also be implemented as a combination of computing devices, for example, A combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

The speed control circuit 20 is electrically connected to the controller 10, and is used for generating a driving power in response to the PWM signal, and the driving power is proportional to the duty ratio of the PWM signal.

Please also refer to FIG. 3 , the speed control circuit 20 includes a charging circuit 201 and a start-up circuit 202 .

As shown in FIG. 4 , the charging circuit 201 includes an inductor L1 and a first capacitor C1 . One end of the inductor L1 is electrically connected to the collector Q2 of the PNP transistor, and the other end of the inductor L1 is electrically connected to the positive electrode of the first capacitor C1 for outputting the driving power V2; the negative electrode of the first capacitor C1 is grounded.

The start-up circuit 202 is electrically connected to the controller 10 and the charging circuit 201 respectively, and is used to control the external power supply to charge the charging circuit 201 and provide the driving power for the H-bridge drive circuit 30 when the PWM signal is at a high level. When the PWM signal is at a low level When the level is high, the external power supply is controlled to stop charging the charging circuit 201 , so that the charging circuit 201 discharges to provide the driving power for the H-bridge driving circuit 30 .

As shown in FIG. 4 , the startup circuit includes a first resistor R1 , a second resistor R2 , an NPN transistor Q1 , a third resistor R3 , a fourth resistor R4 and a PNP transistor Q2 . One end of the first resistor R1 is used to receive the PWM signal, and the other end of the first resistor R1 is electrically connected to one end of the second resistor R2, the base of the NPN transistor Q1 and the overcurrent protection circuit 40 (through the The network port P and the overcurrent protection circuit 40, the network port P is the connection node of the first resistor R1, the second resistor R2 and the NPN transistor Q1); the other end of the second resistor R2 is grounded; the emitter of the NPN transistor Q1 is grounded, and the NPN The collector of the transistor Q1 is electrically connected to one end of the third resistor R3; the other end of the third resistor R3 is electrically connected to one end of the fourth resistor R4 and the base of the PNP transistor Q2; the other end of the fourth resistor R4 is electrically connected to the PNP transistor Q2 The emitter is electrically connected to receive the external power supply V1; the collector of the PNP transistor Q2 is electrically connected to the charging circuit 201 (ie, one end of the inductor L1).

In some embodiments, please refer to FIG. 3 again, the speed control circuit 20 further includes a freewheeling circuit 203, and the freewheeling circuit 203 is electrically connected between the startup circuit 202 and the charging circuit 201 for when the PWM signal is at a low level , when the startup circuit 202 controls the external power supply to stop charging the charging circuit 201 , the back electromotive force generated by the charging circuit 201 is subjected to a freewheeling process.

As shown in FIG. 4 , the freewheeling circuit 203 includes a first diode D1 and a second diode D2. The cathode of the first diode D1 is electrically connected to the emitter of the PNP transistor Q2, and the anode of the first diode D1 is electrically connected to the collector of the PNP transistor Q2, one end of the inductor L1 and the cathode of the second diode D2. Connect; the anode of the second diode D2 is grounded.

In summary, the working process of the speed control circuit 20 is as follows:

(1) Receive the PWM signal sent by the controller 10. When the PWM signal is at a high level, the high level signal reaches the base of the NPN transistor Q1 through the first resistor R1, which satisfies the conduction condition of the NPN transistor Q1. The NPN transistor Q1 conducts On, the collector voltage of the NPN transistor Q1 is pulled down. At this time, the conduction condition of the PNP transistor Q2 is satisfied, the PNP transistor Q2 is turned on, and the external power supply V1 passes through the emitter of the PNP transistor Q2, the collector of the PNP transistor Q2, and the inductor. L1 , charges the first capacitor C1 and supplies power to the H-bridge driving circuit 30 .

(2) When the PWM signal is at a low level, the low-level signal reaches the base of the NPN transistor Q1 through the first resistor R1, which does not satisfy the conduction condition of the NPN transistor Q1, and the NPN transistor Q1 is turned off. At this time, the PNP transistor is not satisfied. The conduction condition of Q2, the PNP transistor Q2 is turned off. At this time, the first capacitor C1 is discharged, so that the stored energy supplies power to the H-bridge driving circuit 30 . At the same time, due to the characteristic that the current passing through the inductor cannot abruptly change, the reverse electromotive force generated by the inductor L1 freewheels through the first diode D1 and the second diode D2 to protect the PNP transistor Q2 from breakdown.

(3) Steps (1) and (2) are repeated according to the cycle change of the PWM signal, the speed control circuit 20 converts the external power supply V1 into the driving power supply V2, and the size of the driving power supply V2 is proportional to the duty ratio of the PWM signal , the larger the duty cycle of the PWM signal, the larger the drive power V2 output by the speed control circuit 20, the smaller the duty cycle of the PWM signal, the smaller the drive power V2 output by the speed control circuit 20.

The H-bridge driving circuit 30 is electrically connected to the speed regulation control circuit 20 for driving the DC motor 200 to work according to the driving power source, and the driving power source is proportional to the rotation speed of the DC motor 200 .

As shown in FIG. 5, the H-bridge drive circuit 30 includes a PMOS transistor TR1, a PMOS transistor TR2, an NMOS transistor TR3, an NMOS transistor TR4, a resistor R51, a resistor R52, an NPN transistor Q51, a resistor R53, a resistor R54, a resistor R55, a resistor R56, NPN transistor Q52, resistor R57, resistor R58, resistor R59, resistor R60, resistor R61 and resistor R62.

The source of the PMOS transistor TR1 is electrically connected to one end of the resistor R54, the source of the PMOS transistor TR2, one end of the resistor R58 and the speed control circuit 20 for receiving the driving power V2, and the drain of the PMOS transistor TR1 is connected to the NMOS transistor. The drain of TR3 and the positive pole M+ of the DC motor 200 are electrically connected, the gate of the PMOS transistor TR1 is electrically connected to the other end of the resistor R54 and one end of the resistor R53; the drain of the PMOS transistor TR2 is electrically connected to the drain of the NMOS transistor TR4 and the DC motor The negative electrode M- of 200 is electrically connected, the gate of the PMOS transistor TR2 is electrically connected to the other end of the resistor R58 and one end of the resistor R57; the source electrode of the NMOS transistor TR3 is electrically connected to the source electrode of the NMOS transistor TR4, and is connected to the network port IU through the network port. The overcurrent protection circuit 40 is electrically connected to the rotational speed detection circuit 50, the gate of the NMOS transistor TR3 is electrically connected to one end of the resistor R59 and one end of the resistor R60; the gate of the NMOS transistor TR4 is electrically connected to one end of the resistor R61 and one end of the resistor R62 One end of the resistor R51 is electrically connected to the controller 10 for receiving the DR1 level signal, and the other end of the resistor R51 is electrically connected to one end of the resistor R52 and the base of the NPN transistor Q51; the other end of the resistor R52 is grounded; the NPN transistor Q51 The emitter is grounded, the collector of the NPN transistor Q51 is electrically connected to the other end of the resistor R53; one end of the resistor R55 is electrically connected to the controller 10 for receiving the DR2 level signal, the other end of the resistor R55 is connected to one end of the resistor R56 and The base of the NPN transistor Q52 is electrically connected; the other end of the resistor R56 is grounded; the emitter of the NPN transistor Q52 is grounded, and the collector of the NPN transistor Q52 is electrically connected to the other end of the resistor R57; the other end of the resistor R59 is connected to the other end of the resistor R61 Electrical connection; the other end of the resistor R60 is grounded; the other end of the resistor R62 is grounded.

When the DR1 level signal is high and the DR2 level signal is low, the high level signal reaches the base of the NPN transistor Q51 through the resistor R51, which satisfies the conduction condition of the NPN transistor Q51, the NPN transistor Q51 is turned on, and the NPN The collector voltage of the transistor Q51 is pulled down, the gate of the PMOS transistor TR1 is low voltage, which satisfies the conduction condition of the PMOS transistor TR1, and the PMOS transistor TR1 is turned on; at the same time, the high-level signal reaches the gate of the NMOS transistor TR4 through the resistor R61. It meets the conduction condition of the NMOS transistor TR4, and the NMOS transistor TR4 is turned on; the low-level signal reaches the base of the NPN transistor Q52 through the resistor R55, which does not meet the conduction condition of the NPN transistor Q52, and the NPN transistor Q52 is turned off, which does not satisfy the PMOS At the same time, the low-level signal reaches the gate of the NMOS transistor TR3 through the resistor R59, which does not meet the conduction condition of the NMOS transistor TR3, and the NMOS transistor TR3 is turned off. Therefore, the driving power supply V2 passes through The PMOS transistor TR1, the positive pole M+ of the DC motor 200, the negative pole M- of the DC motor 200, and the NMOS transistor TR4 reach the ground, and the DC motor 200 rotates forward.

When the DR1 level signal is low level and the DR2 level signal is high level, the low level signal reaches the base of the NPN transistor Q51 through the resistor R51, which does not meet the conduction condition of the NPN transistor Q51. The NPN transistor Q51 is turned off and does not If the conduction condition of the PMOS transistor TR1 is satisfied, the PMOS transistor TR1 is turned off; at the same time, the low-level signal reaches the gate of the NMOS transistor TR4 through the resistor R61, and the conduction condition of the NMOS transistor TR4 is not satisfied, and the NMOS transistor TR4 is turned off; the high-level signal After the resistor R55 reaches the base of the NPN transistor Q52, the conduction condition of the NPN transistor Q52 is satisfied, the NPN transistor Q52 is turned on, the collector voltage of the NPN transistor Q52 is pulled down, and the gate voltage of the PMOS transistor TR2 is a low voltage, which satisfies the PMOS transistor. The conduction condition of the tube TR2, the PMOS tube TR2 is turned on; at the same time, the low-level signal reaches the gate of the NMOS tube TR3 through the resistor R59, which satisfies the conduction condition of the NMOS tube TR3, and the NMOS tube TR3 is turned on. Therefore, the driving power supply V2 After the PMOS transistor TR2, the negative pole M- of the DC motor 200, the positive pole M+ of the DC motor 200, and the NMOS transistor TR3 reach the ground, the DC motor 200 is reversed.

To sum up, in the process of forward or reverse rotation of the DC motor 200, the size of the driving power supply V2 is proportional to the rotation speed of the DC motor 200. The larger the driving power supply V2 is, the faster the rotation speed of the DC motor 200 is, and the smaller the driving power supply V2 is. , the speed of the DC motor 200 is slower. Therefore, the rotation speed of the DC motor 200 is related to the duty ratio of the PWM signal, but the PWM signal does not directly participate in the speed regulation process of the DC motor 200, which prevents the PWM signal from directly acting on the H-bridge driving circuit 30. The problem of unreliable drive power for output caused by shutdown.

The overcurrent protection circuit 40 is electrically connected to the H-bridge drive circuit 30 and the speed control circuit 20 respectively, and is used to send a protection signal to the speed control circuit 20 when it is detected that the drive current flowing through the DC motor 200 is greater than or equal to the threshold current , so that the speed control circuit 20 reduces the driving power.

As shown in FIG. 3 , the overcurrent protection circuit 40 includes a first sampling circuit 401 and a switch circuit 402 .

The first sampling circuit 401 is electrically connected to the H-bridge driving circuit 30, and is used for sampling the driving current flowing through the DC motor 200 to generate a sampling voltage.

As shown in FIG. 6 , the first sampling circuit 401 includes a fifth resistor R5 , a second capacitor C2 and a sixth resistor R6 . One end of the fifth resistor R5 is electrically connected to the H-bridge drive circuit 30 (ie, the network port IU shown in FIG. 4 ), and the other end of the fifth resistor R5 is connected to one end of the second capacitor C2, one end of the sixth resistor R6 and The switch circuit 402 is electrically connected; the other end of the second capacitor C2 is grounded; the other end of the sixth resistor R6 is grounded.

The switch circuit 402 is electrically connected to the first sampling circuit 401 and the speed regulation control circuit 20 respectively, and is used to bias the PWM signal to a low level as a protection signal when the sampling voltage is greater than the voltage turn-on threshold, so that the regulation The speed control circuit 20 reduces the drive power.

As shown in FIG. 6 , the switch circuit 402 includes an NPN transistor Q3, the base of the NPN transistor Q3 is electrically connected to the other end of the fifth resistor R5, one end of the second capacitor C2 and one end of the sixth resistor R6, and the emission of the NPN transistor Q3 The pole is grounded, and the collector of the NPN transistor Q3 is electrically connected to the speed control circuit 20 (ie, the network port P shown in FIG. 4 ).

To sum up, the working process of the overcurrent protection circuit 40 is as follows:

(1) Assuming that the threshold current of the DC motor 200 is Im and the on-voltage of the base of the NPN transistor Q3 is VB, when the DC motor 200 works normally, the driving current of the DC motor 200 is less than the threshold current Im, and the driving current of the DC motor 200 The sampling voltage is generated through the fifth resistor R5, the second capacitor C2 and the sixth resistor R6, and acts on the base of the NPN transistor Q3. At this time, the sampling voltage is less than the conduction voltage VB of the base of the NPN transistor Q3, which does not satisfy the conduction condition of the NPN transistor Q3, the NPN transistor Q3 is turned off, and the overcurrent protection circuit 40 does not work.

(2) When the DC motor 200 is abnormal (such as a bridge arm short circuit, a short circuit of the DC motor 200, etc.), the driving current of the DC motor 200 is greater than or equal to the threshold current Im, and the driving current of the DC motor 200 passes through the fifth resistor R5, the first The second capacitor C2 and the sixth resistor R6 generate the sampling voltage. At this time, the sampling voltage is greater than or equal to the conduction voltage VB of the base of the NPN transistor Q3, which satisfies the conduction condition of the NPN transistor Q3, the NPN transistor Q3 is turned on, and the overcurrent protection circuit 40 operates. Specifically, when the NPN transistor Q3 is turned on, the voltage of the conductive collector of the NPN transistor Q3 is pulled down, and the base input of the NPN transistor Q1 is biased to a low level through the network port P, so that the speed control circuit 20 cannot After receiving the PWM signal, the driving power V2 output by the speed control circuit 20 is lowered.

(3) When the driving power V2 drops to the point that the driving current of the DC motor 200 is less than the threshold current Im again, repeat the above step (1), the overcurrent protection circuit 40 does not work, so that the speed control circuit 20 can normally receive the PWM signal again , and then make the drive power V2 output by the speed control circuit 20 rise, when the drive power V2 rises to make the sampling voltage greater than or equal to the conduction voltage VB of the base of the NPN transistor Q3, repeat the above step (2), overcurrent The protection circuit 40 operates.

It should be noted that the above process is the current amplification process of the NPN transistor Q3, and finally the drive current of the H-bridge drive circuit 30 (that is, the drive current flowing through the DC motor 200) is equal to the threshold current Im, so that the drive current does not exceed the threshold current. Im, in order to achieve the purpose of protecting the H-bridge driving circuit 30, thereby improving the safety of the DC motor control circuit 100.

The rotational speed detection circuit 50 is electrically connected to the H-bridge driving circuit and the controller, respectively, for sampling the operating voltage of the DC motor 200 and sending the operating voltage to the controller 10 , so that the controller 10 controls the speed control circuit 20 to adjust the driving power.

As shown in FIG. 7 , the rotational speed detection circuit 50 includes a seventh resistor R7 , an eighth resistor R8 and a third capacitor C3 . One end of the seventh resistor R7 is electrically connected to the H-bridge drive circuit 30 and one end of the eighth resistor R8, and the other end of the seventh resistor R7 is grounded; the other end of the eighth resistor R8 is connected to one end of the third capacitor C3 and the controller 10 is electrically connected; the other end of the third capacitor C3 is grounded.

The seventh resistor R7 is a sampling resistor, and the resistance value of the seventh resistor R7 is equal to VB/Im. The eighth resistor R8 and the third capacitor C3 form a filter circuit, which performs noise reduction filtering on the working voltage sampled by the seventh resistor R7, and sends it to the AD sampling port of the controller 10. The controller 10 works according to the sampling of the rotational speed detection circuit 50. The voltage and the preset voltage are used to calculate the target duty cycle of the PWM signal, so that the speed control circuit 20 adjusts the drive power according to the target duty cycle.

To sum up, the working process of the rotational speed detection circuit 50 is as follows:

(1) When the DC motor 200 is working normally, the driving current flowing through the DC motor 200 is less than the threshold current Im, and the working voltage of the DC motor 200 sampled by the seventh resistor R7 is filtered through the eighth resistor R8 and the third capacitor C3 Then, it is sent to the controller 10, and the controller 10 calculates the difference between the working voltage of the DC motor 200 sampled by the seventh resistor R7 and the preset voltage, and adjusts the duty cycle of the PWM signal output by the controller 10 according to the result of the difference calculation. until the working voltage of the DC motor 200 sampled by the rotational speed detection circuit 50 reaches within the allowable deviation of the preset voltage, so as to achieve the purpose of speed regulation of the DC motor 200 .

(2) When the DC motor 200 is abnormal, the driving current flowing through the DC motor 200 is greater than or equal to the threshold current Im, and the working voltage of the DC motor 200 sampled by the seventh resistor R7 is filtered through the eighth resistor R8 and the third capacitor C3 After processing, it is sent to the controller 10. At this time, the working voltage is greater than or equal to the turn-on voltage VB of the base of the NPN transistor Q3, and the controller 10 controls the PWM signal to be low to achieve the purpose of software-controlled overcurrent protection, and further The safety of the DC motor control circuit 100 is improved.

The embodiment of the present invention provides a DC motor control circuit. The speed regulation control circuit responds to a PWM signal sent by a controller to generate a driving power supply. The driving power supply is proportional to the duty cycle of the PWM signal. The H-bridge driving circuit responds to the driving power supply The DC motor is driven to work, and the driving power is proportional to the speed of the DC motor. When the overcurrent protection circuit detects that the driving current flowing through the DC motor is greater than or equal to the threshold current, it sends a protection signal to the speed control circuit to make the speed control control The circuit reduces the drive power. Therefore, in the embodiment of the present invention, the PWM signal is converted into a driving power source through the speed regulation control circuit to directly drive the DC motor, and when the overcurrent protection circuit detects that the driving current flowing through the DC motor is greater than or equal to the threshold current, the regulation is adjusted. The high-speed control circuit reduces the drive power to achieve instant hardware protection, thereby improving the safety and reliability of the DC motor control circuit.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, The steps may be carried out in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity; although the invention has been The skilled person should understand that it is still possible to modify the technical solutions recorded in the foregoing embodiments, or to perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the implementation of the present invention. scope of technical solutions.

Claims (10)

1. A dc motor control circuit, comprising:

a controller for transmitting a PWM signal;

the speed regulation control circuit is electrically connected with the controller and used for responding to the PWM signal and generating a driving power supply, and the driving power supply and the duty ratio of the PWM signal are in a direct proportion relation;

the H-bridge driving circuit is electrically connected with the speed regulation control circuit and used for driving the direct current motor to work according to the driving power supply, and the driving power supply is in direct proportion to the rotating speed of the direct current motor;

the overcurrent protection circuit is respectively electrically connected with the H-bridge drive circuit and the speed regulation control circuit and is used for sending a protection signal to the speed regulation control circuit when detecting that the drive current flowing through the direct current motor is greater than or equal to a threshold current, so that the speed regulation control circuit reduces the drive power supply; and the number of the first and second groups,

and the rotating speed detection circuit is respectively electrically connected with the H-bridge driving circuit and the controller and is used for sampling the working voltage of the direct current motor and sending the working voltage to the controller, so that the controller controls the speed regulation control circuit to regulate the driving power supply.

2. The dc motor control circuit of claim 1, wherein the speed regulation control circuit comprises:

a charging circuit;

and the starting circuit is respectively electrically connected with the controller and the charging circuit and used for controlling an external power supply to charge the charging circuit and provide the driving power supply for the H-bridge driving circuit when the PWM signal is at a high level, and controlling the external power supply to stop charging the charging circuit when the PWM signal is at a low level so that the charging circuit discharges to provide the driving power supply for the H-bridge driving circuit.

3. The dc motor control circuit of claim 2, wherein the start-up circuit comprises a first resistor, a second resistor, an NPN transistor, a third resistor, a fourth resistor, and a PNP transistor;

one end of the first resistor is used for receiving the PWM signal, and the other end of the first resistor is electrically connected with one end of the second resistor, the base electrode of the NPN triode and the overcurrent protection circuit; the other end of the second resistor is grounded; an emitting electrode of the NPN triode is grounded, and a collector electrode of the NPN triode is electrically connected with one end of the third resistor; the other end of the third resistor is electrically connected with one end of the fourth resistor and the base electrode of the PNP triode; the other end of the fourth resistor is electrically connected with an emitting electrode of the PNP triode and used for receiving an external power supply; and the collector electrode of the PNP triode is electrically connected with the charging circuit.

4. The dc motor control circuit of claim 3, wherein the charging circuit comprises an inductor and a first capacitor;

one end of the inductor is electrically connected with the collector of the PNP triode, and the other end of the inductor is electrically connected with the positive electrode of the first capacitor and used for outputting the driving power supply; and the negative electrode of the first capacitor is grounded.

5. The DC motor control circuit of claim 4, wherein the speed control circuit further comprises a free-wheeling circuit electrically connected between the start-up circuit and the charging circuit, for controlling the start-up circuit to stop charging the charging circuit when the external power supply stops charging the charging circuit when the PWM signal is at a low level, and performing free-wheeling processing on the back electromotive force generated by the charging circuit.

6. The dc motor control circuit of claim 5, wherein the freewheel circuit includes a first diode and a second diode;

the cathode of the first diode is electrically connected with the emitting electrode of the PNP triode, and the anode of the first diode is electrically connected with the collector electrode of the PNP triode, one end of the inductor and the cathode of the second diode; the anode of the second diode is grounded.

7. The direct current motor control circuit according to any one of claims 1 to 6, wherein the overcurrent protection circuit comprises:

the first sampling circuit is electrically connected with the H-bridge driving circuit and is used for sampling the driving current flowing through the direct current motor and generating sampling voltage;

and the switching circuit is respectively electrically connected with the first sampling circuit and the speed regulation control circuit and is used for biasing the PWM signal at a low level serving as the protection signal when the sampling voltage is greater than a voltage conduction threshold value, so that the speed regulation control circuit reduces the driving power supply.

8. The dc motor control circuit of claim 7, wherein the first sampling circuit comprises a fifth resistor, a second capacitor, and a sixth resistor;

one end of the fifth resistor is electrically connected with the H-bridge driving circuit, and the other end of the fifth resistor is electrically connected with one end of the second capacitor, one end of the sixth resistor and the switch circuit; the other end of the second capacitor is grounded; the other end of the sixth resistor is grounded.

9. The direct current motor control circuit according to any one of claims 1 to 6, wherein the rotation speed detection circuit includes a seventh resistor, an eighth resistor, and a third capacitor;

one end of the seventh resistor is electrically connected with the H-bridge driving circuit and one end of the eighth resistor, and the other end of the seventh resistor is grounded; the other end of the eighth resistor is electrically connected with one end of the third capacitor and the controller; the other end of the third capacitor is grounded.

10. A dc motor control system, comprising:

a direct current motor;

the dc motor control circuit of any of claims 1 to 9, electrically connected to the dc motor.

Images