An isolated all-digital brushed motor driving circuit

Abstract

The application discloses an isolated full-digital brush motor driving circuit, mainly comprising: a power filtering and converting circuit, which is used for converting input working voltage into voltage required by an isolation circuit and a control driving circuit; the isolation circuit, which is used for amplifying an input signal, and outputting through optical coupling isolation, and controlling motor running state through optical coupling output, realizing the function of controlling three states by one lead; the control driving circuit, which controls and drives motor stop, forward rotation and reverse rotation according to the signal output by the isolation circuit, and is composed of a dead zone circuit formed by a gate driving chip through a full-digital CMOS circuit to form a driving signal, and then outputting to a rear-stage H-bridge signal after shaping by a rear-stage waveform shaping circuit to realize control driving. The application can satisfy wide voltage working range, anti-power interference, over-current protection and other functions, and adopts full-digital CMOS circuit, so that the application has strong anti-interference ability, good temperature stability and low cost.

Description

Technical Field

[0001] This invention relates to an isolated, fully digital brushed motor drive circuit, belonging to the field of motor control technology. Background Technology

[0002] DC brushed motors possess advantages such as simple structure, long development history, mature technology, fast response speed, high starting torque, stable operation, high control precision, low operating cost, and convenient maintenance, leading to their widespread application since their introduction. For a motor to operate normally, the drive circuit is an indispensable component. With the widespread application of motors across various industries, the functions of drive circuits have become increasingly complex. A key challenge we need to address is how to achieve a drive circuit that features a simple input signal, a wider input voltage range, and integrated high output current, strong anti-interference capability, and overcurrent protection. Summary of the Invention

[0003] The purpose of this invention is to provide an isolated fully digital brushed motor drive circuit to solve several problems, such as the small voltage input range of the drive circuit, weak anti-interference ability, and the servo motor deviation caused by the different power-on sequence of the motor start / stop and servo motor control power supply and the power supply.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] This invention provides an isolated, fully digital brushed motor drive circuit, comprising:

[0006] Power supply filtering and conversion circuit, used to convert the input working voltage into the voltage required by the isolation circuit and control drive circuit;

[0007] An isolation circuit is used to amplify the input signal and output it via optocoupler isolation, as well as to control the motor's operating state through the optocoupler output; the motor's operating state includes forward rotation, reverse rotation, and stop.

[0008] The control drive circuit is used to generate a pre-drive signal with dead time from the input signal that is isolated by optocouplers, and then generate a drive signal through the gate drive chip to drive the motor to run.

[0009] The overcurrent protection circuit is used to collect the motor's operating current and control the motor to stop when the current is too high.

[0010] Furthermore, the power supply filtering and conversion circuit includes:

[0011] The power conversion unit is used to convert the input operating voltage into the voltage required by the isolation circuit and control drive circuit.

[0012] The power filtering unit uses a Class I multilayer ceramic capacitor to filter the voltage converted by the power conversion unit.

[0013] Furthermore, the isolation circuit includes a signal processing unit and an isolation unit.

[0014] The signal processing unit is amplifier U1, which is used to amplify the input signal;

[0015] The isolation unit uses two optocouplers N3 and N4. The amplifier U1 outputs a lead that splits into two paths: one path outputs to the A terminal of optocoupler N3, and the other path outputs to the C terminal of optocoupler N4. The C terminal of optocoupler N3 and the A terminal of optocoupler N4 are connected to signal ground.

[0016] The output signal after optocoupler isolation is fed back to the control drive circuit.

[0017] Furthermore, the two V's of the optocoupler N3 and optocoupler N4 O The output level determines the motor's three states: forward rotation, reverse rotation, and stop.

[0018] When the input signal is high, the V of optocoupler N3... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the motor is in the forward rotation state;

[0019] When the input signal is low, when the V of optocoupler N3 is low. O The output terminal outputs a low level, and the V of optocoupler N4... O When the output terminal outputs a high level, the motor is in reverse rotation; and when the V of optocoupler N3 is high... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the motor is in reverse rotation.

[0020] When there is no input signal, optocouplers N3 and N4 have no output signal, and the motor is in a stopped state.

[0021] Furthermore, the output terminals of the optocouplers N3 and N4 are provided with pull-up resistors; the input terminal C of the optocouplers N3 and N4 is provided with pull-down resistors.

[0022] Furthermore, the control drive circuit includes a pre-drive unit and a drive unit;

[0023] The pre-drive unit includes: a dead-zone generation circuit, a pre-drive chip, and a subsequent waveform shaping and filtering circuit; the optocoupler output signal is input to the dead-zone generation circuit, and after passing through the dead-zone generation circuit, it is given to the pre-drive chip to form a pre-drive signal output;

[0024] The dead zone generation circuit includes an RC differentiating circuit, a Schmitt trigger, and a diode asymmetric delay circuit. The outputs of the optocouplers N3 and N4 are connected to terminals 1 and 13 of the Schmitt trigger N8.

[0025] The subsequent waveform shaping and filtering circuit consists of a 555 timer. It uses the unidirectional conduction of diodes and the filtering function of capacitors to shape the original pulse signal into a standard square wave signal.

[0026] The driving unit consists of a MOSFET and peripheral processing circuitry; when the G terminal of the MOSFET is high, the MOSFET is turned on, and vice versa.

[0027] The MOSFET is switched on and off according to the pre-drive signal output by the pre-drive chip, so as to realize the forward rotation, reverse rotation and stop of the motor.

[0028] Furthermore, the overcurrent protection circuit includes:

[0029] The current acquisition unit uses a sampling resistor. One end of the sampling resistor is connected to the source of the MOSFET, and the other end is connected to the power ground. The sampling resistor is used to acquire the current during the operation of the motor.

[0030] The feedback comparison unit uses comparator N4 to compare currents and control the motor to stop after overcurrent.

[0031] Furthermore, the positive terminal 3 of the comparator N4 is connected to the sampling current SENSE terminal, and the negative terminal 2 is connected to the comparison current.

[0032] When the positive terminal of comparator N4 is greater than the negative terminal, the output of comparator N4 is a high level SD. SD is connected to the output terminals of optocouplers N3 and N4, and pins 1 and 13 of Schmitt trigger N8. When pins 1 and 13 of Schmitt trigger N8 receive a high level signal, the motor stops.

[0033] When the positive terminal of comparator N4 is less than the negative terminal, the output of comparator N4 is low level SD. Pins 1 and 13 of Schmitt trigger N8 receive the pre-drive signal from the normal output of optocouplers N3 and N4, controlling the motor to rotate forward or backward.

[0034] Furthermore, a current-limiting resistor is provided on the negative terminal 2 pin side of the comparator N4.

[0035] The beneficial effects achieved by this invention are as follows:

[0036] This invention relates to an isolated, fully digital brushed motor drive circuit that can meet the requirements of a wide voltage operating range, power supply interference resistance, and overcurrent protection. It also employs a fully digital CMOS circuit, offering strong anti-interference capabilities, good temperature stability, and low cost. The isolation circuit of this invention controls three states through a single lead, resolving the issue of servo motor deviation caused by different power-on sequences between the servo motor control power supply and the main power supply. Furthermore, it utilizes a thick-film hybrid integrated circuit based on LTCC (Low-Temperature Ceramic Capacitor) technology to meet the requirements for system miniaturization. Attached Figure Description

[0037] Figure 1 This is a circuit block diagram of an isolated all-digital brushed motor drive circuit according to the present invention;

[0038] Figure 2 This is a circuit diagram of the isolation unit of an isolated all-digital brushed motor drive circuit according to the present invention;

[0039] Figure 3 This is a dead zone generation circuit diagram of an isolated all-digital brushed motor pre-drive circuit according to the present invention;

[0040] Figure 4 This is a waveform shaping and filtering circuit diagram of the post-stage of the isolated all-digital brushed motor pre-drive circuit of the present invention;

[0041] Figure 5 This is a circuit diagram of the drive unit of an isolated all-digital brushed motor drive circuit according to the present invention.

[0042] Figure 6 This is a circuit diagram of the current acquisition unit of an isolated all-digital brushed motor drive circuit according to the present invention.

[0043] Figure 7 This is a circuit diagram of the feedback comparison unit of an isolated all-digital brushed motor drive circuit according to the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0045] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0046] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0047] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0048] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0049] It should be emphasized here that the step markers mentioned below are not a limitation on the order of the steps, but should be understood as meaning that the steps can be executed in the order mentioned in the embodiments, or in a different order than in the embodiments, or several steps can be executed simultaneously.

[0050] like Figure 1 As shown, the present invention provides an isolated fully digital brushed motor drive circuit, including a power supply filtering and conversion circuit, an isolation circuit, a control drive circuit, and an overcurrent protection circuit.

[0051] In this invention, the power filtering and conversion circuit includes a power conversion unit and a power filtering unit. The input operating voltage is converted into the voltage required by the isolation circuit and the control drive circuit by the power conversion unit, and then the power filtering unit supplies power to each circuit unit.

[0052] The power conversion unit primarily adjusts the output voltage by regulating the resistance values ​​of resistors R5 and R8. The adjustment formula is: V OUT The input voltage range is 7.5V~100V, and the output voltage can be adjusted automatically according to the formula. The power filter unit composed of C3, C5, C30, and C6 uses Class I multilayer ceramic chip capacitors, which have a low temperature coefficient, ensuring minimal temperature drift during delay and a more stable output voltage for the voltage conversion chip. These capacitors are used in the isolation circuit to prevent power fluctuations and output noise, ensuring smoother circuit operation.

[0053] like Figure 2 As shown, the isolation circuit includes a signal processing unit and an isolation unit, mainly composed of amplifier U1 and two optocouplers N3 and N4. Amplifier U1 amplifies the input signal and improves signal quality. Amplifier U1 outputs a lead that splits into two paths: one outputs to terminal A of optocoupler N3, and the other outputs to terminal C of optocoupler N4. Terminal C of optocoupler N3 and terminal A of optocoupler N4 are connected to signal ground. The output signal after optocoupler isolation is fed back to the subsequent pre-drive unit to generate a pre-drive signal. In this way, the function of controlling forward, reverse, and stop states with a single lead is realized, solving the problem of servo motor deviation caused by different power-on sequences of the servo motor control power supply and the power supply.

[0054] In this invention, the three states of forward rotation, reverse rotation, and stop rotation are determined by the two V-type terminals of optocoupler N3 and optocoupler N4. O The output voltage level is determined by the input signal. When the input signal is high, the V of optocoupler N3... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the servo motor is in forward rotation; when the input signal is low, and the V of the optocoupler N3 is low, the servo motor rotates forward. O The output terminal outputs a low level, and the V of optocoupler N4... OWhen the output terminal outputs a high level, the servo motor is in reverse rotation; when the V of optocoupler N3 is high... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the servo motor is in reverse rotation; when there is no input signal, optocouplers N3 and N4 have no output signal, and the servo motor is in a stopped state.

[0055] Furthermore, pull-up resistors R25 and R19 are provided at the output terminals of optocouplers N3 and N4, and pull-down resistors R40 and R42 are provided at the input terminal C to prevent the device pins from being in a floating state.

[0056] After being isolated by optocouplers, the input signal reaches the all-digital CMOS circuit to generate a pre-drive signal with a dead zone, which then reaches the gate driver chip to generate a drive signal, and the drive circuit works.

[0057] The control drive circuit includes a pre-drive unit and a drive unit.

[0058] The pre-drive unit mainly consists of a dead-time generation circuit, a pre-drive chip, and a subsequent waveform shaping and filtering circuit.

[0059] The optocoupler output signal is input to the dead-time generation circuit. After passing through the dead-time generation circuit, it is sent to the pre-drive chip to form a pre-drive signal output, which drives the motor to different states.

[0060] like Figure 3 As shown, the outputs of optocouplers N3 and N4 are connected to terminals 1 and 13 of Schmitt trigger N8. The dead-time generation circuit mainly consists of RC differentiation, Schmitt shaping, and diode asymmetric delay. It has fast conduction, strong anti-interference ability, good temperature stability, and low cost.

[0061] like Figure 4 As shown, the subsequent waveform shaping and filtering circuit consists of a 555 timer. Utilizing the unidirectional conduction of diodes and the filtering function of capacitors, it shapes the original pulse signal from the previous stage, which has slow edges, glitches, jitter, and unstable amplitude, into a standard square wave signal with steep edges, stable amplitude, and no glitches, thus enhancing its anti-interference capability.

[0062] like Figure 5 As shown, the drive unit mainly consists of MOSFETs and peripheral processing circuitry. When the gate (G) terminal of the MOSFET is high, the MOSFET is turned on; conversely, it is turned off. The MOSFET's on / off state is controlled by the pre-drive signals V1G, V2G, V3G, and V4G output from the pre-drive chip, thus controlling the motor's forward, reverse, and stop rotation. When the input signal is high, the V gate of optocoupler N3... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the servo motor is in forward rotation; when the input signal is low, and the V of the optocoupler N3 is low, the servo motor rotates forward. OThe output terminal outputs a low level, and the V of optocoupler N4... O When the output terminal outputs a high level, the servo motor is in reverse rotation; when the V of optocoupler N3 is high... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the servo motor is in reverse rotation; when there is no input signal, optocouplers N3 and N4 have no output signal, and the servo motor is in a stopped state.

[0063] The overcurrent protection circuit includes a current acquisition unit and a feedback comparison unit.

[0064] like Figure 6 As shown, the current acquisition unit mainly consists of a sampling resistor. One end of the sampling resistor is connected to the source (S) of the MOSFET, and the other end is connected to power ground to obtain the current during motor operation. The sampling resistor is an ultra-low resistance precision chip resistor, which features high power, high accuracy, and good temperature coefficient, ensuring the accuracy of current acquisition.

[0065] like Figure 7 As shown, the feedback comparison unit mainly consists of voltage divider resistors, filter capacitors, etc. It uses comparator N4 to compare currents and control the output signal after overcurrent. Pin 3 of the positive terminal of comparator N4 is connected to the current acquisition (SENSE) terminal, and pin 2 of the negative terminal is connected to the current comparison (SENSE) terminal. When the positive terminal of the comparator is greater than the negative terminal, the comparator output is high (SD). SD is connected to the output terminals of optocouplers N3 and N4, and pins 1 and 13 of N8. When pins 1 and 13 of N8 receive a high-level signal, the motor stops. When the positive terminal of the comparator is less than the negative terminal, the comparator output is low (SD). Pins 1 and 13 of N8 receive the pre-drive signal from the normal output of optocouplers N3 and N4, controlling the motor to rotate forward or backward.

[0066] Furthermore, a current-limiting resistor R22 is provided on the negative terminal 2 side of comparator N4, and the comparison current can be adjusted by adjusting the resistance value of R22.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An isolated, fully digital brushed motor drive circuit, characterized in that, include: Power supply filtering and conversion circuit, used to convert the input working voltage into the voltage required by the isolation circuit and control drive circuit; An isolation circuit is used to amplify the input signal and output it via optocoupler isolation, as well as to control the motor's operating state through the optocoupler output; the motor's operating state includes forward rotation, reverse rotation, and stop. The control drive circuit is used to generate a pre-drive signal with dead time from the input signal that is isolated by optocouplers, and then generate a drive signal through the gate drive chip to drive the motor to run. The overcurrent protection circuit is used to collect the motor's operating current and control the motor to stop when the current is too high.

2. The isolated fully digital brushed motor drive circuit according to claim 1, characterized in that, The power filtering and conversion circuit includes: The power conversion unit is used to convert the input operating voltage into the voltage required by the isolation circuit and control drive circuit. The power filtering unit uses a Class I multilayer ceramic capacitor to filter the voltage converted by the power conversion unit.

3. The isolated fully digital brushed motor drive circuit according to claim 1, characterized in that, The isolation circuit includes a signal processing unit and an isolation unit. The signal processing unit is amplifier U1, which is used to amplify the input signal; The isolation unit uses two optocouplers N3 and N4. The amplifier U1 outputs a lead that splits into two paths: one path outputs to the A terminal of optocoupler N3, and the other path outputs to the C terminal of optocoupler N4. The C terminal of optocoupler N3 and the A terminal of optocoupler N4 are connected to signal ground. The output signal after optocoupler isolation is fed back to the control drive circuit.

4. The isolated fully digital brushed motor drive circuit according to claim 3, characterized in that, The two V of the optocoupler N3 and optocoupler N4 O The output level determines the motor's three states: forward rotation, reverse rotation, and stop. When the input signal is high, the V of optocoupler N3... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the motor is in the forward rotation state; When the input signal is low, when the V of optocoupler N3 is low. O The output terminal outputs a low level, and the V of optocoupler N4... O When the output terminal outputs a high level, the motor is in reverse rotation; and when the V of optocoupler N3 is high... O The output terminal outputs a high level, and the V of optocoupler N4... O When the output terminal outputs a low level, the motor is in reverse rotation. When there is no input signal, optocouplers N3 and N4 have no output signal, and the motor is in a stopped state.

5. The isolated all-digital brushed motor drive circuit according to claim 3, characterized in that, The output terminals of optocouplers N3 and N4 are equipped with pull-up resistors; the input terminal C of optocouplers N3 and N4 is equipped with pull-down resistors.

6. The isolated all-digital brushed motor drive circuit according to claim 3, characterized in that, The control drive circuit includes a pre-drive unit and a drive unit; The pre-drive unit includes: a dead-zone generation circuit, a pre-drive chip, and a subsequent waveform shaping and filtering circuit; the optocoupler output signal is input to the dead-zone generation circuit, and after passing through the dead-zone generation circuit, it is given to the pre-drive chip to form a pre-drive signal output; The dead zone generation circuit includes an RC differentiating circuit, a Schmitt trigger, and a diode asymmetric delay circuit. The outputs of the optocouplers N3 and N4 are connected to terminals 1 and 13 of the Schmitt trigger N8. The subsequent waveform shaping and filtering circuit consists of a 555 timer. It uses the unidirectional conduction of diodes and the filtering function of capacitors to shape the original pulse signal into a standard square wave signal. The driving unit consists of a MOSFET and peripheral processing circuitry; when the G terminal of the MOSFET is high, the MOSFET is turned on, and vice versa. The MOSFET is switched on and off according to the pre-drive signal output by the pre-drive chip, so as to realize the forward rotation, reverse rotation and stop of the motor.

7. The isolated all-digital brushed motor drive circuit according to claim 6, characterized in that, The overcurrent protection circuit includes: The current acquisition unit uses a sampling resistor. One end of the sampling resistor is connected to the source of the MOSFET, and the other end is connected to the power ground. The sampling resistor is used to acquire the current during the operation of the motor. The feedback comparison unit uses comparator N4 to compare currents and control the motor to stop after overcurrent.

8. The isolated fully digital brushed motor drive circuit according to claim 7, characterized in that, The positive terminal 3 of the comparator N4 is connected to the current sampling SENSE terminal, and the negative terminal 2 is connected to the current comparison current. When the positive terminal of comparator N4 is greater than the negative terminal, the output of comparator N4 is a high level SD. SD is connected to the output terminals of optocouplers N3 and N4, and pins 1 and 13 of Schmitt trigger N8. When pins 1 and 13 of Schmitt trigger N8 receive a high level signal, the motor stops. When the positive terminal of comparator N4 is less than the negative terminal, the output of comparator N4 is low level SD. Pins 1 and 13 of Schmitt trigger N8 receive the pre-drive signal from the normal output of optocouplers N3 and N4, controlling the motor to rotate forward or backward.

9. The isolated all-digital brushed motor drive circuit according to claim 8, characterized in that, A current-limiting resistor is provided on the negative terminal 2 pin side of the comparator N4.

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