Discharge system and discharge method for a brushless direct current motor

Abstract

The application relates to the field of brushless direct-current motors, in particular to a discharging system and a discharging method of a brushless direct-current motor, which comprise an H-bridge driving module, a voltage division detection module, a discharging module and a comparator U1; the output end NO and the output end S0 of the H-bridge driving module are electrically connected with the positive and negative poles of the motor respectively; the detection voltage Vdiv output by the voltage division detection module is input to the same-phase input end of the comparator U1, the external reference voltage Vref is input to the reverse input end of the comparator U1, the output end of the comparator U1 is electrically connected with the control end of the discharging module, the H-bridge driving module drives the motor to work, the voltage division detection module detects the power supply voltage in real time, the comparator U1 compares the detection voltage Vdiv with the reference voltage Vref, when the detection voltage Vdiv exceeds the reference voltage Vref, the discharging module is controlled to be turned on, the power supply voltage is rapidly discharged, the power supply voltage is reduced to a safe level, and the driving chip is protected.

Description

Technical Field

[0001] This invention relates to the field of brushless DC motors, and more specifically to a discharge system and discharge method for a brushless DC motor. Background Technology

[0002] A brushless DC motor is a modern drive device that combines the ease of control of a DC motor with the high efficiency of an AC motor. Its core principle is to use an electronic commutator to replace traditional brushes and mechanical commutators, achieving periodic switching of the current direction to drive the rotor to rotate continuously. This design fundamentally eliminates sparks, noise, and maintenance requirements caused by brush wear, significantly improving motor lifespan and reliability while reducing electromagnetic interference, making it particularly outstanding in precision control scenarios. Structurally, it typically consists of three parts: a stator, a rotor, and a position sensor. The stator windings use a three-phase or multi-phase distribution, and an inverter converts DC power to AC power for drive. The rotor often uses permanent magnets to enhance magnetic field efficiency. The position sensor monitors the rotor angle in real time and feeds it back to the control circuit, ensuring precise synchronization between current switching and rotor position, forming a closed-loop control system.

[0003] Combined with appendix Figure 1 , attached Figure 1 This is a schematic diagram of the high-side P-type MOSFET output of an H-bridge. When the motor enters the commutation region, the brushless DC motor coil generates a reverse electromotive force (EMF), which is superimposed on the power supply voltage VDD through the parasitic body diode Db. In other words, this reverse EMF voltage passes through the output terminal NO or SO of the H-bridge, to the drain of the high-side P-type MOSFET, then to the N-well, to the body contact, and finally to the power supply voltage VDD for superposition. When this voltage is high, there is a risk of damaging the driver chip. Summary of the Invention

[0004] The purpose of this invention is to provide a discharge system and method for a brushless DC motor, which aims to improve the problem of the reverse electromotive force generated during the commutation process of the motor, which affects the power supply voltage.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A discharge system for a brushless DC motor includes an H-bridge drive module, a voltage divider detection module, a discharge module, and a comparator U1. The power input terminals of the H-bridge drive module, the voltage divider detection module, and the discharge module are all electrically connected to the power supply VDD.

[0007] The output terminals NO and S0 of the H-bridge drive module are electrically connected to the positive and negative poles of the motor, respectively; the voltage divider detection module outputs the detection voltage Vdiv to the non-inverting input terminal of the comparator U1, and the external reference voltage Vref is input to the inverting input terminal of the comparator U1. The output terminal of the comparator U1 is electrically connected to the control terminal of the discharge module and controls the conduction and shutdown of the discharge module.

[0008] Furthermore, the comparator U1 is a hysteresis comparator U1.

[0009] Furthermore, the H-bridge drive module includes MOSFETs P1, P2, N1, and N2.

[0010] The source of MOSFET P1 and the source of MOSFET P2 are both electrically connected to the power supply VDD. The drain of MOSFET P1 is electrically connected to the drain of MOSFET N1 and serves as the output terminal NO, which is electrically connected to the positive terminal of the motor. The drain of MOSFET P2 is electrically connected to the drain of MOSFET N2 and serves as the output terminal SO, which is electrically connected to the negative terminal of the motor.

[0011] The motor driver chip outputs a drive signal NOdriverH to the gate of MOSFET P1, and a drive signal SOdriverH to the gate of MOSFET P2; the motor driver chip outputs a drive signal NOdriverL to the gate of MOSFET N1, and a drive signal SOdriverL to the gate of MOSFET N2.

[0012] The sources of both MOS transistor N1 and MOS transistor N2 are grounded.

[0013] Furthermore, both MOS transistors P1 and P2 are PMOS transistors, and both MOS transistors N1 and N2 are NMOS transistors.

[0014] Furthermore, the voltage divider detection module includes resistors R1 and R2. One end of resistor R1 is electrically connected to the power supply VDD, and the other end of resistor R1 is electrically connected to one end of resistor R2. The module outputs the detection voltage Vdiv to the non-inverting input of comparator U1.

[0015] The other end of the resistor R2 is grounded.

[0016] Furthermore, the discharge module includes a MOS transistor N3, the drain of which is electrically connected to the power supply VDD, and the output of the comparator U1 is electrically connected to the gate of the MOS transistor N3.

[0017] The source of the MOS transistor N3 is grounded.

[0018] To achieve the above object, the present invention adopts the following technical solutions:

[0019] A discharge method, applying the discharge system of the brushless DC motor, includes the following steps:

[0020] S01. Set the warning threshold A, the reference voltage Vref, and the secondary protection threshold C;

[0021] S02. When the detected voltage Vdiv > A, the internal warning flag of the comparator U1 is set. The motor drive chip receives the warning information, controls the maximum allowable duty cycle of the PWM signal to decrease from 100% to 80%, and shortens the dead time from the standard Dns to D / 2ns;

[0022] S03. When the detected voltage Vdiv > Vref, the comparator U1 controls the discharge module to conduct. The motor drive chip controls the low-side N-type field-effect transistor to conduct alternately every 10ns, limits the duty cycle of all PWM signals to below 50%, and controls all commutation moments to be advanced by 5°;

[0023] S04. When the detected voltage Vdiv > C, the motor drive chip controls the high-side P-type field-effect transistors to turn off simultaneously and controls the low-side N-type field-effect transistors to turn on simultaneously.

[0024] Further, step S01 further includes setting the exit thresholds a, b, and c;

[0025] It further includes the following steps:

[0026] S021. When the detected voltage Vdiv < a and lasts for 10 μs, then it operates normally.

[0027] Further, it further includes the following steps:

[0028] S031. When the detected voltage Vdiv < b and lasts for 50 μs, then return to step S02.

[0029] Further, it further includes the following steps:

[0030] S041. When the detected voltage Vdiv < c and lasts for 100 μs, then return to step S03, otherwise perform step S042;

[0031] S042. When the detected voltage Vdiv > C and lasts for 10 ms, then shut down.

[0032] After adopting the above technical solutions, compared with the background technology, the present invention has the following advantages:

[0033] 1. The H-bridge drive module drives the motor to work. The voltage divider detection module detects the power supply voltage in real time. The comparator U1 compares the detected voltage Vdiv with the reference voltage Vref. When the detected voltage Vdiv exceeds the reference voltage Vref, the discharge module is turned on to quickly discharge the power supply voltage, so that the power supply voltage drops to a safe level, thus protecting the drive chip.

[0034] 2. Set a warning threshold A and a secondary protection threshold C. When the warning threshold A is reached, reduce the duty cycle and shorten the dead time to decrease the conduction time of the body diode and suppress the superposition of power supply voltage. When the reference voltage Vref is reached, activate the discharge module to discharge the power supply voltage, control the low-side N-type MOSFET to alternately conduct every 10ns to provide a freewheeling path for the current, form an equivalent resistance, generate a small braking torque, and perform fine control of the motor. Limit the duty cycle of all PWM signals to below 50% and advance all commutation times by 5° to make the back EMF phase lead and reduce voltage superposition. When the secondary protection threshold C is reached, indicating severe overvoltage, turn off the high-side P-type MOSFET and turn on the low-side N-type MOSFET to short-circuit the motor coil, quickly consume motor energy, and generate a large braking torque. Attached Figure Description

[0035] Figure 1 A schematic diagram of the high-side P-type field-effect transistor output of an H-bridge;

[0036] Figure 2 This is a block diagram of the discharge method for the brushless DC motor described in this invention;

[0037] Figure 3 This is a circuit diagram of the discharge system of the brushless DC motor described in this invention;

[0038] Figure 4 This is a schematic diagram of the voltage and current waveforms at key nodes during motor commutation.

[0039] Figure 5 This is a simulation diagram of the discharge system of the brushless DC motor described in this invention. Detailed Implementation

[0040] 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 accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] Additionally, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are all based on the orientation or positional relationship shown in the accompanying drawings. They are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element of the present invention must have a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0042] When an element is referred to as being "fixed to," "set on," or "contained on" another element, it can be directly on or indirectly on that other element. When an element is referred to as being "connected to," it can be directly connected to or indirectly connected to that other element.

[0043] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Example

[0044] Please refer to Figure 1-5 As shown, this embodiment provides a discharge system for a brushless DC motor, including an H-bridge drive module, a voltage divider detection module, a discharge module, and a comparator U1. The power input terminals of the H-bridge drive module, the voltage divider detection module, and the discharge module are all electrically connected to the power supply VDD. The output terminals NO and S0 of the H-bridge drive module are electrically connected to the positive and negative terminals of the motor, respectively. The voltage divider detection module outputs a detection voltage Vdiv to the non-inverting input terminal of the comparator U1, and an external reference voltage Vref is input to the inverting input terminal of the comparator U1. The output terminal of the comparator U1 is electrically connected to the control terminal of the discharge module and controls the on and off states of the discharge module.

[0045] Please refer to Figure 2 As shown, this embodiment also discloses a discharge method using the above-mentioned brushless DC motor discharge system, specifically including the following steps:

[0046] S01. Set the early warning threshold A, the reference voltage Vref, and the secondary protection threshold C;

[0047] S02. When the detected voltage Vdiv>A, the internal warning flag of comparator U1 is set, the motor drive chip receives the warning information, and controls the maximum allowable duty cycle of the PWM signal to drop from 100% to 80%, shortening the dead time from the standard Dns to D / 2ns;

[0048] S03. When the detected voltage Vdiv > Vref, the comparator U1 controls the discharge module to conduct, and the motor drive chip controls the low-side N-type field-effect transistor to conduct alternately every 10 ns, limiting the duty cycle of all PWM signals to less than 50%, and controlling all commutation times to be advanced by 5°;

[0049] S04. When the detected voltage Vdiv > C, the motor drive chip controls the high-side P-type field-effect transistor to turn off simultaneously and controls the low-side N-type field-effect transistor to turn on simultaneously.

[0050] The H-bridge drive module drives the motor to work. The voltage division detection module detects the power supply voltage in real time. The comparator U1 compares the detected voltage Vdiv with the reference voltage Vref. When the detected voltage Vdiv exceeds the reference voltage Vref, it controls the discharge module to conduct and discharges the power supply voltage quickly, causing the power supply voltage to drop to a safe level, playing a role in protecting the drive chip.

[0051] And set the warning threshold A and the secondary protection threshold C. When the warning threshold A is reached, reduce the duty cycle and shorten the dead time, reduce the conduction time of the body diode, and suppress the superimposition of the power supply voltage. When the reference voltage Vref is reached, turn on the discharge module to discharge the power supply voltage, control the low-side N-type field-effect transistor to conduct alternately every 10 ns, provide a freewheeling path for the current, form an equivalent resistance, generate a small braking torque, and perform fine control on the motor; limit the duty cycle of all PWM signals to less than 50%, and control all commutation times to be advanced by 5°, making the back electromotive force phase lead and reducing voltage superimposition. When the secondary protection threshold C is reached, it indicates severe overvoltage, turn off the high-side P-type field-effect transistor, turn on the low-side N-type field-effect transistor, short-circuit the motor coil, quickly consume the motor energy, and generate a large braking torque.

[0052] Specifically, step S01 further includes setting the exit threshold a, exit threshold b, and exit threshold c;

[0053] The discharge protection method further includes the following steps. S021. When the detected voltage Vdiv < a and lasts for 10 μs, then operate normally.

[0054] S031. When the detected voltage Vdiv < b and lasts for 50 μs, then return to step S02.

[0055] S041. When the detected voltage Vdiv < c and lasts for 100 μs, then return to step S03, otherwise perform step S042;

[0056] S042. When the detected voltage Vdiv > C and lasts for 10 ms, then shut down.

[0057] In this embodiment, the exit thresholds a, b, and c are less than the warning threshold A, the reference voltage Vref, and the secondary protection threshold C, respectively. Setting smaller exit thresholds at different stages ensures a stable decrease in power supply voltage, avoiding frequent on / off control of the discharge module. Furthermore, setting a longer duration at each stage further guarantees that the power supply voltage remains consistently below the preset threshold.

[0058] Comparator U1 is a hysteresis comparator. It ensures that the discharge module is only turned off when the power supply voltage drops to a lower point to prevent oscillation.

[0059] Please refer to Figure 3 As shown, the H-bridge driver module includes MOSFETs P1, P2, N1, and N2. The sources of MOSFETs P1 and P2 are electrically connected to the power supply VDD. The drain of MOSFET P1 is electrically connected to the drain of MOSFET N1 and serves as the output terminal NO, electrically connected to the positive terminal of the motor. The drain of MOSFET P2 is electrically connected to the drain of MOSFET N2 and serves as the output terminal SO, electrically connected to the negative terminal of the motor. The motor driver chip outputs a drive signal NOdriverH to the gate of MOSFET P1 and a drive signal SOdriverH to the gate of MOSFET P2. The motor driver chip outputs a drive signal NOdriverL to the gate of MOSFET N1 and a drive signal SOdriverL to the gate of MOSFET N2. The sources of MOSFETs N1 and N2 are both grounded. In this embodiment, MOSFETs P1 and P2 are PMOS transistors, and MOSFETs N1 and N2 are NMOS transistors.

[0060] The voltage divider detection module includes resistors R1 and R2. One end of resistor R1 is electrically connected to the power supply VDD, and the other end of resistor R1 is electrically connected to one end of resistor R2, outputting the detection voltage Vdiv to the non-inverting input of comparator U1. The other end of resistor R2 is grounded.

[0061] The discharge module includes a MOSFET N3, the drain of which is electrically connected to the power supply VDD, and the output of comparator U1 is electrically connected to the gate of MOSFET N3. The source of MOSFET N3 is grounded. In this embodiment, MOSFET N3 is an NMOS transistor.

[0062] In this embodiment, resistor R1 has a resistance of 200kΩ, and resistor R2 has a resistance of 66.7kΩ; comparator U1 has a hysteresis width of 50mV, a warning threshold A of 1.235V, a reference voltage Vref of 1.25V, and a secondary protection threshold C of 1.3125V. Exit threshold a is 1.23V; exit threshold b is 1.24V; and exit threshold c is 1.3V. Similarly, other resistor values ​​and different voltage levels for warning threshold A, reference voltage Vref, secondary protection threshold C, exit threshold a, exit threshold b, and exit threshold c can be set; D is 100ns.

[0063] Furthermore, the motor drive chip monitors and detects the rate of change of voltage Vdiv in real time. When dV / dt > 100V / μs, it is identified as external interference. MOSFETs P1, P2, N1, and N2 are turned off for 5μs, allowing the interference to be absorbed by the external input capacitor, thus improving the accuracy of the discharge action.

[0064] Please refer to the appendix. Figure 4 , attached Figure 4 This is a schematic diagram of the voltage and current waveforms at key nodes during motor commutation, provided by Appendix Figure 4 It can be seen that during the commutation of NO and SO, when the directional induced electromotive force generated is superimposed on the power supply voltage VDD and exceeds ΔV, the MOSFET N3 is started to discharge, and the discharge current is Idis, which makes the power supply voltage VDD drop to a safe level.

[0065] Please refer to the appendix. Figure 5 , attached Figure 5 This is a simulation diagram of the discharge system and discharge method of the brushless DC motor disclosed in this embodiment, provided by Appendix Figure 5 It can be seen that the power supply voltage VDD is set to 5V, the coil inductance of the brushless DC motor is 5 millihenries, and the parasitic resistance is 3 ohms; where vdd! is the power supply voltage, SO and NO are the output terminals of the H-bridge, and i1 is the coil current of the brushless DC motor. From this simulation diagram, it can be seen that the voltage of vdd! is limited to 5.15V, which is a safe and reliable voltage range.

[0066] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for discharging a brushless DC motor, characterized in that, It includes an H-bridge driver module, a voltage divider detection module, a discharge module, and a comparator U1. The power input terminals of the H-bridge driver module, the voltage divider detection module, and the discharge module are all electrically connected to the power supply VDD. The output terminals NO and S0 of the H-bridge drive module are electrically connected to the positive and negative poles of the motor, respectively; the voltage divider detection module outputs the detection voltage Vdiv to the non-inverting input terminal of the comparator U1, and the external reference voltage Vref is input to the inverting input terminal of the comparator U1; the output terminal of the comparator U1 is electrically connected to the control terminal of the discharge module and controls the conduction and shutdown of the discharge module. Includes the following steps, S01. Set the early warning threshold A, the reference voltage Vref, and the secondary protection threshold C; S02. When the detected voltage Vdiv>A, the internal warning flag of comparator U1 is set, the motor drive chip receives the warning information, and controls the maximum allowable duty cycle of the PWM signal to drop from 100% to 80%, shortening the dead time from the standard Dns to D / 2ns; S03. When the detected voltage Vdiv>Vref, the comparator U1 controls the discharge module to turn on, and the motor drive chip controls the low-side N-type field-effect transistor to turn on alternately every 10ns, limiting the duty cycle of all PWM signals to below 50% and controlling all commutation times to be advanced by 5°. S04. When the detected voltage Vdiv>C, the motor drive chip controls the high-side P-type field-effect transistor to turn off simultaneously and controls the low-side N-type field-effect transistor to turn on simultaneously.

2. The discharge method for a brushless DC motor according to claim 1, characterized in that: The comparator U1 is a hysteresis comparator U1.

3. The discharge method for a brushless DC motor according to claim 1, characterized in that: The H-bridge drive module includes MOSFET P1, MOSFET P2, MOSFET N1 and MOSFET N2; The source of MOSFET P1 and the source of MOSFET P2 are both electrically connected to the power supply VDD. The drain of MOSFET P1 is electrically connected to the drain of MOSFET N1 and serves as the output terminal NO, which is electrically connected to the positive terminal of the motor. The drain of MOSFET P2 is electrically connected to the drain of MOSFET N2 and serves as the output terminal SO, which is electrically connected to the negative terminal of the motor. The motor driver chip outputs a drive signal NOdriverH to the gate of MOSFET P1, and a drive signal SOdriverH to the gate of MOSFET P2; the motor driver chip outputs a drive signal NOdriverL to the gate of MOSFET N1, and a drive signal SOdriverL to the gate of MOSFET N2. The sources of both MOS transistor N1 and MOS transistor N2 are grounded.

4. The discharge method for a brushless DC motor according to claim 3, characterized in that: Both MOS transistors P1 and P2 are PMOS transistors, and both MOS transistors N1 and N2 are NMOS transistors.

5. The discharge method for a brushless DC motor according to claim 1, characterized in that: The voltage divider detection module includes resistors R1 and R2. One end of resistor R1 is electrically connected to the power supply VDD, and the other end of resistor R1 is electrically connected to one end of resistor R2. The module outputs the detection voltage Vdiv to the non-inverting input of comparator U1. The other end of the resistor R2 is grounded.

6. The discharge method for a brushless DC motor according to claim 1, characterized in that: The discharge module includes a MOS transistor N3. The drain of the MOS transistor N3 is electrically connected to the power supply VDD, and the output terminal of the comparator U1 is electrically connected to the gate of the MOS transistor N3; The source of the MOS transistor N3 is grounded.

7. The discharge method for a brushless DC motor according to claim 1, characterized in that: Step S01 further includes setting an exit threshold a, an exit threshold b, and an exit threshold c; It further includes the following steps S021. When the detected voltage Vdiv < a and lasts for 10 μs, it operates normally.

8. The discharge method for the brushless DC motor according to claim 7, characterized in that: It further includes the following steps S031. When the detected voltage Vdiv < b and lasts for 50 μs, return to step S02.

9. The discharge method for a brushless DC motor according to claim 8, characterized in that: It further includes the following steps S041. When the detected voltage Vdiv < c and lasts for 100 μs, return to step S03, otherwise proceed to step S042; S042. When the detected voltage Vdiv > C and lasts for 10 ms, shut down.

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