Motor driver and heat dissipation system thereof

Abstract

The invention provides a motor driver and a heat dissipation system thereof. The motor driver comprises a driving board, and the driving board is provided with a motor driving circuit, a temperature detection circuit, a power supply circuit and a main control chip. The power supply circuit is connected with the motor driving circuit and the main control chip and provides a working power supply; the motor driving circuit comprises a driving chip and MOS tubes, the input end of the driving chip is connected with the PWM output end of the main control chip, the output end of the driving chip is connected with the grid electrodes of the MOS tubes, and the drain electrode of the lower MOS tube and the source electrode of the upper MOS tube are connected into a motor three-phase driving loop; the temperature detection circuit comprises a thermistor which is arranged on the driving board and is connected in series with the fixed resistor to form a voltage division circuit, and a voltage division node is connected to an ADC interface of the main control chip; the main control chip collects voltage values at the two ends of the thermistor through the ADC interface and calculates a temperature value according to the collected voltage values; and when the temperature value exceeds a set threshold value, the main control chip stops outputting the PWM signal to the driving chip so that the motor stops rotating.

Description

Technical Field

[0001] This invention relates to the field of motor driver heat dissipation technology, specifically to a motor driver and its heat dissipation system. Background Technology

[0002] Currently, with the development of technology, modern motor drive systems require higher output power and smaller size, leading to a significant increase in the switching frequency and current density of power devices (such as MOSFETs), and a sharp rise in heat loss per unit area. Excessive heat loss results in a significant reduction in the performance and operating time of the motor drive board, especially in high-power-density, high-frequency switching applications. Therefore, heat dissipation technology for the motor drive board is crucial to ensuring motor reliability and long-term stable operation. Thus, effective temperature control and management per unit area of ​​the drive board are necessary.

[0003] Therefore, the existing technology currently has the following technical problems: 1. Unable to monitor the status under high current or high temperature conditions; 2. Overheating of high-power devices on the driver board can cause MOS losses, leading to reduced efficiency or malfunction. 3. High temperatures in the power supply section of the driver board can cause the DC-DC power chip to burn out, electrolytic capacitors to age faster, and the power supply voltage to fluctuate greatly, affecting the accuracy of the drive signal. 4. The high temperature radiated from the driver board to the main chip will accelerate the wear and tear of the main chip.

[0004] Patent document CN202840493U discloses an overheat protection circuit for a motor, controller, and its power drive module. This overheat protection circuit includes a first resistor and a second resistor connected in series. The first end of the first resistor is connected to a DC power supply, and the second end of the second resistor is grounded. The connection point between the first and second resistors is connected to the control terminal of a switching device. One of the first and second resistors is a thermistor. The first output terminal of the switching device outputs a level signal to the control module, and the second output terminal of the switching device is grounded. The controller includes a control module, a power drive module, etc., and the power drive module is equipped with the aforementioned overheat protection circuit. The motor has a stator and a rotor, and is equipped with the aforementioned controller. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of this invention. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the purpose of this invention is to provide a motor driver and its heat dissipation system.

[0006] The heat dissipation system for a motor driver according to the present invention includes: a driver board, wherein a motor drive circuit, a temperature detection circuit, a power supply circuit and a main control chip are disposed on the driver board; The power supply circuit is connected to the motor drive circuit and the main control chip, and provides working power. The motor drive circuit includes a driver chip and a MOSFET. The input terminal of the driver chip is connected to the PWM output terminal of the main control chip, and the output terminal of the driver chip is connected to the gate of the MOSFET. The drain of the lower MOSFET and the source of the upper MOSFET are connected to the three-phase drive circuit of the motor. The temperature detection circuit includes a thermistor, which is located on the driver board at the position with the maximum current and the highest temperature rise, and is connected in series with a fixed resistor to form a voltage divider circuit. The voltage divider node is connected to the ADC interface of the main control chip. The main control chip acquires the voltage value across the thermistor through the ADC interface and calculates the temperature value based on the acquired voltage value. When the temperature value exceeds a set threshold, the main control chip stops outputting PWM signals to the drive chip, thereby stopping the motor from rotating.

[0007] Preferably, the temperature detection circuit includes a thermistor RT1, which is connected in series with a resistor R1 between the power supply VCC and ground; The ADC interface of the main control chip is connected to the connection point of RT1 and R1. By acquiring the voltage value at this point and applying the formula... The voltage value U is calculated, and then the current temperature value is calculated based on the relationship between the resistance of the thermistor RT1 and the temperature. It also includes an internal temperature detection circuit for the motor, which is connected to a linear thermistor RT2 via interface J1, and RT2 is placed inside the motor. The main control chip acquires the voltage of RT2 through the ADC interface and uses the formula... Calculate the voltage value, and then calculate the internal temperature of the motor based on the resistance-temperature characteristics of the thermistor RT2.

[0008] Preferably, the motor drive circuit includes a driver chip and three MOSFETs Q1 and Q2. The PWM signal input terminal of the driver chip is connected to the PWM output terminal of the main control chip, and the output terminal of the driver chip is connected to the gate of MOSFETs Q1 and Q2 through gate resistors R1 and R3, respectively. The drain and source of MOSFETs Q1 and Q2 are connected to the three-phase motor drive circuit. By controlling the conduction state of Q1 and Q2, the direction of the three-phase current is changed, thereby driving the motor to run.

[0009] Preferably, the main control chip has a dead time between 100ns and 2us to prevent the upper and lower MOS transistors from being turned on simultaneously; the gate resistors R1 and R3 are used to suppress high-frequency oscillations.

[0010] Preferably, in the PCB layout of the driver board, heat dissipation holes are provided at the pads of high-power devices and devices with large heat generation; high-current traces use solid copper foil and adopt a multi-layer copper pouring method; power supply wiring is short and thick to avoid forming loops.

[0011] Preferably, the power supply circuit includes a DC-DC power module and filter capacitors C1 to C5, with the capacitance values ​​of the filter capacitors differing by two orders of magnitude. C1 to C3 are used to filter out high-frequency interference, and C4 to C5 are used to filter out low-frequency interference. The filter capacitors are arranged close to the power chip, with the capacitors having lower capacitance values ​​being closer to the chip pins.

[0012] Preferably, the power supply circuit further includes a TVS diode D3, which is connected in parallel at the power output terminal to clamp voltage fluctuations; and a diode D1 connected in series in the power input circuit for reverse connection protection.

[0013] Preferably, a heat dissipation pad is attached to the drive board, and the heat dissipation pad is tightly attached to the motor rear cover, so that heat is conducted to the external environment through the motor rear cover.

[0014] Preferably, the power supply section and the drive circuit section are arranged separately on the PCB layout; the heat-generating devices are distributed and close to the edge of the PCB board, which facilitates connection with heat sinks or heat-conducting structural components.

[0015] The motor driver provided according to the present invention includes a heat dissipation system for the motor driver.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) By placing thermistors at high current and high temperature rise points on the driver board and collecting their resistance values ​​through ADC to calculate the temperature for monitoring and management, the technical problem of not being able to monitor the state at high current and high temperature rise points is solved, and the technical effect of real-time monitoring of driver board temperature and triggering over-temperature protection is achieved to avoid the chip burning due to excessive temperature. (2) By adding heat dissipation holes at the pads of high-power devices in the PCB layout, using solid copper foil and multi-layer copper foil at high current locations, making the power supply wiring short and thick and avoiding loops, and selecting an inductor with a saturation current three times the output current, the technical problem of high-power devices (such as MOS) on the driver board being overheated and causing losses, resulting in reduced efficiency or failure to work was solved, and the technical effect of effectively reducing the temperature of MOS, power chips, capacitors and inductors was achieved. (3) By separating the power supply section from the drive circuit section, adding heat dissipation holes, optimizing wiring, selecting ceramic capacitors, and reducing power supply ripple, the technical problems of high temperature in the power supply section of the drive board causing DC-DC power chip burnout, accelerated aging of electrolytic capacitors, and large voltage fluctuations affecting the accuracy of drive signals have been solved, thus achieving the technical effect of improving the reliability and stability of the power supply section. (4) By adopting a distributed layout of heat-generating devices in the PCB layout, the technical problem of high temperature radiation from the driver board to the main chip (MCU) and its accelerated wear is solved, and the technical effect of low temperature rise of the main chip and unaffected by the temperature rise of other components is achieved. (5) By adjusting the switching frequency of the PWM drive parameters, setting the dead time (100ns to 2us), and adding a resistor to the gate of the MOSFET, the technical problem of overheating damage caused by switching losses and shoot-through between the upper and lower transistors was solved, achieving the technical effects of reducing switching losses, preventing MOSFET breakdown, and reducing temperature rise. (6) By placing a thermistor inside the motor and connecting it to the ADC port of the MCU on the driver board for temperature monitoring, the technical problem of not being able to directly monitor the overheating inside the motor is solved, and the technical effect of real-time monitoring of motor temperature and triggering over-temperature protection is achieved to prevent the motor from being damaged due to excessive temperature is achieved. (7) By attaching heat dissipation pads to the drive board and using the design of the motor back cover to make them fit the pads, the technical problem of local heat accumulation on the drive board that cannot be dissipated quickly is solved, and the technical effect of increasing heat dissipation capacity and reducing local temperature is achieved. (8) By adding large-capacity electrolytic capacitors and ceramic capacitors at the power input terminal, installing TVS diodes to clamp the voltage at the output terminal, and using diodes to achieve reverse connection protection, the technical problems of large interference at the power input terminal, large output fluctuations, and possible damage to the chip by reverse connection are solved, and the technical effect of improving the stability and anti-interference capability of the power system is achieved. Attached Figure Description

[0017] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is the schematic diagram of the motor drive board. Figure 2 This is a circuit diagram illustrating the temperature management principle of a PCB board. Figure 3 This is a circuit diagram illustrating the principle of motor temperature management. Figure 4a and Figure 4b The schematic diagram for adding a capacitor at the power output terminal; Figure 5a and Figure 5b This is a schematic diagram of a circuit with a capacitor added at the power input terminal. Figure 6 This is the overall layout diagram. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0019] Example The present invention provides a heat dissipation system for a motor driver, comprising: a driver board, wherein the driver board is provided with a motor drive circuit, a temperature detection circuit, a power supply circuit and a main control chip; The power supply circuit is connected to the motor drive circuit and the main control chip, and provides working power. The motor drive circuit includes a drive chip and a MOSFET. The input terminal of the drive chip is connected to the PWM output terminal of the main control chip, and the output terminal of the drive chip is connected to the gate of the MOSFET. The drain and source of the upper MOSFET of the lower MOSFET are connected to the three-phase drive circuit of the motor. The temperature detection circuit includes a thermistor, which is located on the driver board at the position with the maximum current and the highest temperature rise, and is connected in series with a fixed resistor to form a voltage divider circuit. The voltage divider node is connected to the ADC interface of the main control chip. The main control chip acquires the voltage value across the thermistor through the ADC interface and calculates the temperature value based on the acquired voltage value. When the temperature value exceeds a set threshold, the main control chip stops outputting PWM signals to the drive chip, thereby stopping the motor from rotating.

[0020] The temperature detection circuit includes a thermistor RT1, which is connected in series with a resistor R1 between the power supply VCC and ground. The ADC interface of the main control chip is connected to the connection point of RT1 and R1. By acquiring the voltage value at this point and applying the formula... The voltage value U is calculated, and then the current temperature value is calculated based on the relationship between the resistance of the thermistor RT1 and the temperature. It also includes an internal temperature detection circuit for the motor, which is connected to a linear thermistor RT2 via interface J1, and RT2 is placed inside the motor. The main control chip acquires the voltage of RT2 through the ADC interface and uses the formula... Calculate the voltage value, and then calculate the internal temperature of the motor based on the resistance-temperature characteristics of the thermistor RT2.

[0021] The motor drive circuit includes a driver chip and three MOSFETs Q1 and Q2. The PWM signal input terminal of the driver chip is connected to the PWM output terminal of the main control chip. The output terminal of the driver chip is connected to the gate of MOSFETs Q1 and Q2 through gate resistors R1 and R3, respectively. The drain and source terminals of MOSFETs Q1 and Q2 are connected to the three-phase motor drive circuit. By controlling the conduction state of Q1 and Q2, the direction of the three-phase current is changed, thereby driving the motor to run.

[0022] The main control chip has a dead time set between 100ns and 2us to prevent the upper and lower MOS transistors from being turned on simultaneously; the gate resistors R1 and R3 are used to suppress high-frequency oscillations.

[0023] In the PCB layout of the driver board, heat dissipation holes are provided at the pads of high-power devices and devices with large heat generation; high-current traces use solid copper foil and multi-layer copper pouring; power supply wiring is short and thick to avoid forming loops.

[0024] The power supply circuit includes a DC-DC power module and filter capacitors C1 to C5. The capacitance values ​​of the filter capacitors differ by two orders of magnitude. C1 to C3 are used to filter out high-frequency interference, and C4 to C5 are used to filter out low-frequency interference. The filter capacitors are arranged close to the power chip, and the capacitors with lower capacitance values ​​are closer to the chip pins.

[0025] The power supply circuit also includes a TVS diode D3, which is connected in parallel at the power output terminal to clamp voltage fluctuations; and a diode D1 connected in series in the power input circuit for reverse connection protection.

[0026] Adjust the switching frequency and optimize the PWM drive parameters to reduce switching losses.

[0027] When laying out the PCB, add heat dissipation holes at the pads of high-power devices and devices with large heat generation and high current. Use solid copper foil and multi-layer copper plating for high current areas. The power supply wiring should be short and thick to avoid creating loops. Distribute heat-generating devices to avoid placing all high-temperature devices in a small area. Place heat-generating devices as close as possible to the edge of the PCB board to facilitate connection with heat sinks and thermal conductive structures.

[0028] When designing the schematic, ensure the MOSFET operates under normal power consumption and avoids operating under extreme conditions to reduce temperature rise. When selecting MOSFETs, choose models with low on-resistance, low temperature rise, and higher temperature resistance.

[0029] Ceramic capacitors are selected for the power supply section; in the design of the DC-DC power module, power ripple is reduced and power supply spikes are avoided.

[0030] Heat dissipation pads are applied to areas with high temperature rise and high power. The design of the motor rear cover allows the heat dissipation pads to fit into the rear cover, increasing heat dissipation capacity.

[0031] Figure 1 Explanation: The high and low level inputs of the PWM wave from the driver chip generate drive signals, controlling the conduction of Q1 and Q2. This changes the direction of the three-phase current, creating a changing magnetic field that causes the rotor to move and the motor to rotate. This circuit schematic is for the U-phase drive circuit; the V-phase and W-phase circuits are similar. Simultaneously, it is necessary to detect the U, V, and W-phase currents of the motor. In this schematic, R6 acts as a current sampling resistor. The current flowing into and out of R6 is input to the operational amplifier, and the output of the operational amplifier is sent to the ADC port of the MCU. Calculate the line current.

[0032] The motor drive section is a high-power section, especially Q1 and Q2. Because the motor is driven by controlling the switching of Q1 and Q2, a large current will flow through this section, which requires a better heat dissipation solution.

[0033] There are three points to note regarding heat dissipation in this part: (1) To reduce the heat generated by the power consumption of the MOSFET itself, it is important to pay attention to the MOSFET's turn-on threshold. The gate voltage should be higher than the threshold voltage, and gate resistors R1 and R3 should be added to suppress high-frequency oscillations. (2) In PWM wave modulation, an excessively high carrier frequency will increase the switching loss of the MOSFET, leading to an increase in temperature. Therefore, it is necessary to balance the maximum carrier frequency of the MOSFET itself with the carrier frequency in PWM wave modulation to reduce switching losses. In addition, by setting a dead time, it is necessary to prevent the upper and lower MOSFETs from turning on at the same time and breaking down the MOSFET. Insufficient dead time will cause the device to overheat and be damaged. The dead time is generally between 100ns and 2us. (3) When laying out the PCB, it is necessary to drill more heat dissipation holes to isolate the ground of this high-power part and prevent signal interference and heat conduction to other components, which will cause thermal damage. Solid copper sheets should be used, with multiple layers of copper, and placed as close as possible to the edge of the PCB board to facilitate connection with heat sinks and heat-conducting structural components.

[0034] Figure 2 Note: This schematic diagram is for PCB temperature management. The change in the resistance of thermistor RT1 affects the voltage division of RT1. The voltage divided by RT1 is then transmitted to the MCU via the MCU's ADC port, and the result is calculated using the formula... The voltage divider is calculated, and based on the performance of the selected thermistor (the relationship between resistance and temperature rise; different thermistor models have different performance characteristics), when the calculated result is greater than or equal to 100 degrees Celsius, the MCU stops sending PWM waves to the driver chip, thereby stopping the motor from rotating and preventing damage to components due to overheating. If using our host computer, the temperature threshold can be set to a maximum of 100 degrees Celsius (meaning it can be set to stop the motor from rotating when the temperature reaches 80 degrees Celsius). In the driver board, the thermistor should be placed at the point where the board temperature is highest, that is, next to the switching MOS, in order to better detect the temperature of the board.

[0035] Figure 3 Note: This schematic diagram is for motor temperature management. A linear thermistor (denoted as RT2 in this text) is connected via interface J1 and sealed inside the motor. Changing the resistance of RT2 affects its voltage division. The voltage divided by RT2 is transmitted to the MCU through the MCU's ADC port, and then processed using the formula... The voltage divider is calculated, and based on the performance of the selected thermistor (the relationship between resistance and temperature rise; different thermistor models have different performance characteristics), when the calculated result is greater than or equal to 100 degrees Celsius, the MCU stops sending PWM waves to the driver chip, thereby stopping the motor from rotating and preventing damage to components due to overheating. If using our host computer, the temperature threshold can be set to a maximum of 100 degrees Celsius (meaning it can be set to stop the motor from rotating when the temperature reaches 80 degrees Celsius).

[0036] Figure 4a and Figure 4b Note: Capacitors (C1-C5) should also be added to the output of the DC-DC power supply chip for filtering (the capacitance values ​​generally differ by a power of 2, filtering high-frequency interference (C1-C3) and low-frequency interference (C4-C5) respectively). When the power input and output voltage difference is low, a linear regulator LDO (U2) should be selected to reduce power supply ripple. In the PCB layout, the power supply section has a large current, so it should be laid out separately from the drive circuit section, with more heat dissipation holes. Solid copper foil should be used in high-current areas, with multiple layers of copper plating. The power supply wiring should be short and thick to avoid creating loops. The filter capacitors should be placed as close as possible to the power supply chip, and the capacitors with lower capacitance values ​​should be placed closer to the chip pins than those with higher capacitance values. In addition, D3 is a TVS diode, which can effectively clamp voltage output fluctuations, protect the chips and components connected to the next stage, and also improve the anti-interference capability of the power supply system. D1 is a diode, which provides reverse connection protection to prevent the chip from being damaged by reverse voltage.

[0037] Figure 5a and Figure 5b Note: For the power supply section, a large-capacity capacitor (electrolytic capacitor or ceramic capacitor) needs to be added at the power input terminal in the schematic diagram.

[0038] Figure 6 This is the overall layout diagram.

[0039] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A heat dissipation system for a motor driver, characterized by, The utility model relates to a kind of motor drive board, including: Drive board, motor drive circuit, temperature detection circuit, power supply circuit and main control chip are arranged on the drive board; The power supply circuit is connected with the motor drive circuit and the main control chip, and provides working power supply; The motor drive circuit includes drive chip and MOS tube, the input end of the drive chip is connected with the PWM output end of the main control chip, the output end of the drive chip is connected with the gate of the MOS tube, and the drain of lower MOS tube and the source of upper MOS tube are connected in motor three-phase drive loop; The temperature detection circuit includes thermistor, the thermistor is arranged at the position of maximum current and highest temperature rise on drive board, and forms voltage division circuit in series with fixed resistance, and the voltage division node is connected to the ADC interface of the main control chip; The main control chip collects the voltage value between the thermistor by ADC interface, and calculates temperature value according to the collected voltage value; When the temperature value exceeds the set threshold, the main control chip stops outputting PWM signal to the drive chip, so that the motor stops rotating.

2. The heat dissipation system of an electric motor drive according to claim 1, wherein, The temperature detection circuit includes a thermistor RT1 connected in series with a resistor R1 between a power supply VCC and ground. The ADC interface of the master chip is connected to the connection point of RT1 and R1, the voltage value of the point is collected, and the voltage value U is calculated according to the formula The current temperature value is calculated according to the corresponding relationship between the resistance value of the thermistor RT1 and the temperature. It also includes a motor internal temperature detection circuit connected to a linear thermistor RT2 through an interface J1, and the RT2 is placed inside the motor. The master chip collects the voltage of RT2 through the ADC interface, and calculates the voltage value through the formula and then calculates the internal temperature of the motor according to the resistance-temperature characteristic of the thermistor RT2.

3. The heat dissipation system of an electric motor drive according to claim 1, wherein, The motor drive circuit includes three paths of drive chip and MOS tubes Q1 and Q2, the PWM signal input end of the drive chip is connected to the PWM output end of the main control chip, and the output end of the drive chip is connected to the gate of the MOS tubes Q1 and Q2 through gate resistors R1 and R3, respectively. The drain and source of the MOS tubes Q1 and Q2 are connected to a three-phase motor drive loop, and by controlling the conduction state of Q1 and Q2 in three phases, the direction of three-phase current is changed to drive the motor to operate.

4. The heat dissipation system of an electric motor drive according to claim 3, wherein, The main control chip sets a dead time between 100 ns and 2 us to prevent the upper and lower MOS tubes from being turned on at the same time, and the gate resistors R1 and R3 are used to suppress high-frequency oscillation.

5. The heat dissipation system of an electric motor drive according to claim 1, wherein, In the PCB layout of the drive board, heat dissipation holes are provided at the pads of high-power devices and devices with large heat generation, solid copper is used for large current wiring, and multiple layers of copper are used.

6. The heat dissipation system of an electric motor drive according to claim 1, wherein, The power supply circuit includes a DC-DC power supply module and filter capacitors C1-C5, and the capacitance values of the filter capacitors differ by two orders of magnitude. C1-C3 are used to filter out high-frequency interference, and C4-C5 are used to filter out low-frequency interference. The filter capacitors are arranged close to the power supply chip, and the lower the capacitance value, the closer to the chip pin.

7. The heat dissipation system of an electric motor drive according to claim 6, wherein, The power supply circuit also includes a TVS diode D3 connected in parallel at the power supply output end to clamp voltage fluctuations, and a diode D1 connected in series in the power supply input loop for reverse connection protection.

8. The heat dissipation system of an electric motor drive according to claim 1, wherein, A heat dissipation pad is attached to the drive board, which is tightly attached to the motor rear cover to conduct heat to the external environment through the motor rear cover.

9. The heat dissipation system of an electric motor drive according to claim 1, wherein, The power supply part and the drive circuit part are arranged separately in the PCB layout, and the heat generating devices are dispersed and arranged close to the edge of the PCB board, which is convenient for connection with the heat sink or heat conduction structural member.

10. An electric motor drive, characterized by A heat dissipation system comprising the motor driver of any one of claims 1 to 9.

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