Motor drive system

Abstract

The present invention discloses a motor drive system having a pre-charge circuit with an intelligent charge and discharge mechanism. In terms of charging, the conduction timing of the low-impedance path can be postponed through a delay circuit. The detection circuit can also detect the system state and the battery voltage simultaneously, and perform a discharge procedure in the non-driving mode and when the battery voltage continuously decreases. Moreover, in the discharge procedure, various applications can be realized by utilizing the driving mechanism of the motor drive system.

Description

Technical Field

[0001] The present invention relates to a motor drive system, and more particularly to a motor drive system having a pre-charge circuit with an intelligent charge and discharge mechanism. Background Art

[0002] In an existing motor electric drive system, in order to avoid a large instantaneous current during the power-on driving process, which may cause system damage and reduced lifespan. Therefore, a pre-charge circuit is usually arranged between a power source (such as a battery) and a controller. Its purpose is to charge the internal capacitor with a lower current and then turn on the switch on the main loop to avoid the generation of a large instantaneous current that may damage the system.

[0003] Generally speaking, the pre-charge circuit can work normally during the startup process, but problems often occur during the power-off process. For example, when the system is about to be shut down, its controller does not drive the motor, so the current consumption of the system is very low at this time, and it takes a long time (in the range of 10 seconds to minutes) for the internal capacitor to discharge below the rated safety voltage. During this discharge process, if the power source is restarted in real time, or battery units that have not been powered on are started in segments, since the capacitor voltage has not reached below the threshold voltage for starting pre-charge, an instantaneous large current will be generated, causing system damage or system failure. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a motor drive system having a pre-charge circuit with an intelligent charge and discharge mechanism in view of the deficiencies of the prior art.

[0005] To solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a motor drive system for driving a motor. The motor drive system includes a battery pack, a power control circuit, a capacitor, an inverter circuit, a motor control circuit, a state detection circuit, a pre-charge circuit, a delay circuit, and a discharge control circuit. The battery pack includes a first battery unit and a second battery unit connected in series between a first input terminal and a second input terminal. The power control circuit is configured to control the on and off of the battery pack. The capacitor is connected between the first input terminal and the second input terminal. The inverter circuit is connected between the first input terminal and the second input terminal to be powered by the battery pack, and has a plurality of switching components bridged to form a plurality of output terminals, wherein the plurality of output terminals are respectively connected to a plurality of phase windings of the motor. The motor control circuit is configured to generate a set of motor control signals to control the switching actions of the plurality of switching components, so that each phase winding of the motor is energized to drive the motor. The state detection circuit is configured to detect the operating state of the motor drive system. The pre-charge circuit includes a high-impedance path, a low-impedance path, a pre-charge switch, and a detection circuit. The high-impedance path is connected between the second input terminal and the battery pack. The low-impedance path is connected between the second input terminal and the battery pack, wherein the resistance value of the high-impedance path is greater than the resistance value of the low-impedance path. The pre-charge switch is disposed on the low-impedance path. The detection circuit is configured to: compare a first voltage at the first input terminal with a pre-charge start voltage, and correspondingly generate a detection result signal, wherein, in response to the first voltage being higher than the pre-charge start voltage, the detection result signal is used to control the pre-charge switch to conduct, and in response to the first voltage being less than or equal to the pre-charge start voltage, the detection result signal is used to control the pre-charge switch to turn off. The detection circuit is further configured to detect whether the operating state is a non-driving mode, and whether the first voltage decreases over time, wherein, in response to detecting that the operating state is the non-driving mode and the first voltage decreases over time, an output is provided for a discharge indication signal for performing a discharge procedure on the capacitor, and the output of the discharge indication signal is stopped until it is detected that the first voltage no longer decreases over time. The delay circuit is disposed between the detection circuit and the pre-charge switch and is configured to delay the detection result signal by a predetermined delay time. The discharge control circuit is configured to perform the discharge procedure according to the discharge indication signal, including: obtaining a current operating angle of the motor through the motor control circuit; and according to the current operating angle, correcting the set of motor control signals by a correction angle to drive the motor to stop and enter a discharge mode.

[0006] Preferably, the power control circuit further generates a power status signal corresponding to the turn-on and turn-off of the battery pack, and the detection circuit is further configured to, in response to detecting that the operating state is the non-driving mode, determine whether the battery pack is turned on or off according to the power status signal; in response to detecting that the battery pack is turned off, output the discharge indication signal.

[0007] Preferably, the detection circuit is further configured to: in response to detecting that the battery pack is turned on, detect whether the first voltage decreases over time.

[0008] Preferably, when the detection circuit is configured to detect whether the first voltage decreases over time, it further determines whether the rate of decrease of the first voltage is greater than a first predetermined rate of decrease. If so, the first voltage is determined to decrease over time.

[0009] Preferably, when the detection circuit is configured to determine that the first voltage does not decrease over time, it further detects whether a motor lock instruction is received from a user input. Wherein, in response to receiving the motor lock instruction, the detection circuit is configured to output the discharge indication signal.

[0010] Preferably, when the detection circuit is configured to detect whether the first voltage decreases over time, it further determines whether the rate of decrease of the first voltage is less than a second predetermined rate of decrease. If so, the first voltage is determined to no longer decrease over time.

[0011] Preferably, the motor control circuit is further configured to detect a plurality of phase currents of the plurality of phase windings of the motor to generate an angle information for indicating the current operating angle of the motor.

[0012] Preferably, in response to detecting that the operating state is not the non-driving mode, the detection circuit is further configured to detect whether an electronic brake instruction is received from a user input. If so, output the discharge indication signal.

[0013] Preferably, when outputting the discharge indication signal in response to receiving the electronic brake instruction from the user input, the detection circuit is further configured to detect whether the first voltage decreases over time. In response to detecting that the first voltage no longer decreases over time, stop outputting the discharge indication signal.

[0014] Preferably, when the pre-charge switch is turned off, the battery pack charges the capacitor through the high-impedance path with a pre-charge current, and the predetermined delay time is at least greater than a charging time related to the pre-charge current and the capacitance value of the capacitor.

[0015] One of the beneficial effects of the present invention is that the motor drive system provided by the present invention has a pre-charge circuit with an intelligent charge and discharge mechanism. In terms of charging, the conduction timing of the low-impedance path can be postponed through a delay circuit, and the internal capacitance after charging can be used to avoid damage to the system caused by an instantaneous large current when the system restarts quickly.

[0016] On the other hand, the detection circuit of the pre-charge circuit can detect the system status and the battery voltage simultaneously, and perform a discharge procedure when in the non-driving mode and when the battery voltage continues to decrease, so that the voltage can be lower than the rated safety voltage and the pre-charge start voltage. Moreover, in the discharge procedure, various applications can also be realized by using the driving mechanism of the motor drive system.

[0017] To enable a further understanding of the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the provided drawings are only for reference and illustration, and are not used to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a functional block diagram of the motor drive system according to an embodiment of the present invention.

[0019] Figure 2 It is a functional block diagram of the motor control circuit according to an embodiment of the present invention.

[0020] Figure 3 It is a detailed functional block diagram of the detection circuit according to an embodiment of the present invention and a block diagram of its peripheral circuit.

[0021] Figure 4 It is a graph of voltage and current versus time when the pre-charge circuit applies an intelligent discharge mechanism according to an embodiment of the present invention.

[0022] Figure 5 It is a graph of voltage and current versus time when the pre-charge circuit applies a delayed conduction mechanism according to an embodiment of the present invention.

[0023] Figure 6 It is a flowchart of the detection circuit for executing a status detection program according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following is to illustrate the implementation mode of the "motor drive system" disclosed in the present invention through specific specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Additionally, the drawings of the present invention are only for simple schematic illustration and are not drawn according to actual dimensions, with prior notice. The following implementation modes will further detail the relevant technical content of the present invention, but the disclosed content is not intended to limit the protection scope of the present invention. In addition, the term "or" used herein should, depending on the actual situation, possibly include any one or a combination of more of the associated listed items.

[0025] Referring to Figure 1 As shown, an embodiment of the present invention provides a motor drive system 1 for driving a motor M. The motor drive system 1 includes a battery pack 10, a power control circuit 11, a capacitor C1, an inverter circuit 12, a motor control circuit 13, a state detection circuit 14, a pre-charge circuit 15, and a discharge control circuit 16.

[0026] The battery pack 10 may basically include a first battery cell B1 and a second battery cell B2 connected in series between a first input terminal In1 and a second input terminal In2, but the present invention is not limited thereto, and the battery pack 10 may include more than two battery cells. The first battery cell B1 and the second battery cell B2 may be, for example, lithium-ion batteries, lithium-ion polymer batteries, lead-acid batteries (full-charge lead-acid batteries, deep-cycle lead-acid batteries, and valve-regulated lead-acid batteries), nickel-cadmium batteries, nickel-metal hydride batteries, zinc-air batteries, sodium nickel chloride batteries (zebra), etc., and each includes a built-in over-current protection circuit.

[0027] The power control circuit 11 can be used to control the on and off of the battery pack 10. For example, the power control circuit 11 may be, for example, a power management circuit including a power converter, but the present invention is not limited thereto. The capacitor C1 is connected between the first input terminal In1 and the second input terminal In2. The inverter circuit 12 is connected to the first input terminal In1 and the second input terminal In2 to be powered by the battery pack 10, and has a plurality of switching components bridged to form a plurality of output terminals. For example, as Figure 1 shown, the inverter circuit 12 includes switching components SW1 to SW6 and respectively forms output terminals O1, O2, and O3. The output terminals O1, O2, and O3 are respectively connected to a plurality of phase windings of the motor M. Taking a three-phase motor as an example, the output terminals O1, O2, and O3 may be respectively connected to the U-phase winding, V-phase winding, and W-phase winding of the motor M.

[0028] The motor control circuit 13 can be configured to generate a set of motor control signals to control the switching actions of the above-mentioned switching components, so that each phase winding of the motor M is energized to drive the motor M. The set of motor control signals can include motor control signals H1, H2, H3, L1, L2, and L3. Further reference can be made to Figure 2 , which is a functional block diagram of a motor control circuit according to an embodiment of the present invention. As Figure 2 shown, the motor control circuit 13 can include a first processing circuit 130, a drive control circuit 131, a first voltage detection circuit 132, and a phase current detection circuit 133.

[0029] The first processing circuit 130 can be, for example, a microprocessor or a digital signal processor. The first processing circuit 130 can be configured to execute an algorithm for motor control to obtain independent torque current and field current from the instantaneous phase currents Iu, Iv, and Iw. Simple AC motor control can be implemented using a microprocessor-based control system, while high-order AC inverters will apply a digital signal processor (DSP) for this purpose. The phase current detection circuit 133 can be configured to detect the phase currents Iu, Iv, and Iw of the U-phase winding, V-phase winding, and W-phase winding of the motor M to generate an angle information for indicating the current operating angle of the motor M, and the first voltage detection circuit 132 can be used to detect the first voltage V1 on the first input terminal In1.

[0030] The state detection circuit 14 is configured to detect the operating state of the motor drive system 1. The state detection circuit 14 can be, for example, a Controller Area Network (CAN), which is used to exchange information between various electronic control devices in a mobile vehicle such as an automobile or a locomotive to form an electronic control network.

[0031] The pre-charge circuit 15 can include a low-impedance path P1, a high-impedance path P2, a pre-charge switch SWp, a detection circuit 150, and a delay circuit 151. The low-impedance path P1 and the high-impedance path P2 are respectively connected between the second input terminal In2 and the battery pack 10, and the resistance value of the high-impedance path P2 is greater than that of the low-impedance path P1, and the pre-charge switch SWp is disposed on the low-impedance path P1.

[0032] For example, the low-impedance path P1 includes a resistor R1 and the pre-charge switch SWp, and the high-impedance path P2 includes a resistor R2. Among them, the resistance value of the resistor R2 is higher than that of the resistor R1. Therefore, when the motor drive circuit 1 is started, since there is no charge or only a very low residual voltage on the capacitor C1, the high-impedance path P2 can be used to avoid an instantaneous short circuit caused by the direct conduction of the battery pack 10 and the capacitor C1.

[0033] In an embodiment of the present invention, the detection circuit 150 needs to play two roles, namely, determining whether the battery voltage reaches the pre-charge start voltage, and determining whether to activate the discharge mechanism based on the system state and the battery voltage.

[0034] In terms of pre-charging, the detection circuit 150 can be configured to compare a first voltage V1 at a first input terminal Inp with a pre-charge start voltage, and correspondingly generate a detection result signal S1. Among them, in response to the first voltage V1 being higher than the pre-charge start voltage, the detection result signal S1 is used to control the pre-charge switch SWp to conduct. In response to the first voltage V1 being less than or equal to the pre-charge start voltage, the detection result signal S1 is used to control the pre-charge switch SWp to turn off.

[0035] On the other hand, the detection circuit 150 is also configured to detect whether the operating state of the motor drive system 1 is in a non-driving mode, and whether the first voltage V1 decreases over time. In response to detecting that the operating state is in a non-driving mode and the first voltage V1 decreases over time, an output discharge indication signal S2 is used to perform a discharge procedure on the capacitor C1 until it is detected that the first voltage no longer decreases over time, at which point the output of the discharge indication signal S2 stops.

[0036] A delay circuit 151 is provided between the detection circuit 150 and the pre-charge switch SWp, and is configured to delay the detection result signal S1 by a predetermined delay time T1. The delay circuit 151 can be, for example, an RC circuit, and since when the first voltage V1 is higher than the pre-charge start voltage, the detection result signal S1 can be used to control the pre-charge switch SWp to conduct, therefore, the delay circuit 151 can delay the conduction timing of the low-impedance path P1 to gain charging time for the capacitor C1, and the charged capacitor C1 can prevent the system from being damaged due to an instantaneous large current when the system restarts quickly.

[0037] It should be noted that when the pre-charge switch SWp is turned off, the battery pack 10 will charge the capacitor C1 with a pre-charge current Ipc through the high-impedance path P2, and the above-mentioned predetermined delay time T1 needs to be at least greater than the charging time T2 related to the pre-charge current Ipc and the capacitance value of the capacitor C1. Among them, the delay time T1 needs to satisfy: T1>T2 = C1*Vbat / Ipc, where Vbat is the voltage provided by the battery pack 10. Therefore, the parameters of each component in the pre-charge circuit 15 can be designed according to this conditional formula.

[0038] Herein, further reference can be made to Figure 3 which is a detailed functional block diagram of the detection circuit and a block diagram of its peripheral circuit according to an embodiment of the present invention. As Figure 3 shown, the detection circuit 150 can further include a second processing circuit 152, a second voltage detection circuit 153, and a storage unit 154.

[0039] Among them, the second processing circuit 152 can be, for example, a microprocessor or a digital signal processor, and the second voltage detection circuit 153 can be used to obtain the first voltage V1 of the first input terminal In1 and the pre-charge start voltage Vpc (for example, receive a reference voltage), and compare the first voltage V1 with the pre-charge start voltage Vpc and correspondingly output a detection result signal S1.

[0040] On the other hand, the power supply control circuit 11 also correspondingly generates a power supply state signal S3 according to the turn-on and turn-off of the battery pack 10. In response to detecting that the operating state is a non-driving mode, the detection circuit 150, for example, the second processing circuit 152 therein is also configured to determine whether the battery pack is turned on or off according to the power supply state signal S3. In response to detecting that the battery pack 10 is turned off, the detection circuit 150 (or the second processing circuit 152 therein) outputs a discharge indication signal S2 to the discharge control circuit 16.

[0041] In Figure 3 the embodiment of, the controller area network 14' described above is used as the state detection circuit 14 to obtain the operating state of the motor drive system 1 and inform the second processing circuit 152. For example, the controller area network 14' can detect whether the operating state is a driving mode or a non-driving mode.

[0042] Furthermore, the storage unit 154 can be, for example, an Electrically-Erasable Programmable Read-Only Memory (EEPROM), which stores program codes or firmware for implementing various functions of the above-mentioned detection circuit 150 and can be executed by the second processing circuit 152.

[0043] Under the above architecture, the detection circuit 150 can determine whether the battery pack 10 is offline or a part of the battery cells is offline by detecting whether the operating state of the motor drive system 1 is a non-driving mode and whether the first voltage V1 drops over time. If it is already offline, a discharge procedure is performed on the capacitor C1 to make the first voltage V1 lower than the pre-charge start voltage Vpc, or further adjust its discharge time so that the first voltage V1 is lower than the rated safety voltage within a rated time.

[0044] Please refer back to Figure 1 , the discharge control circuit 16 can be configured to execute a discharge procedure according to the discharge indication signal S2. Specifically, this discharge procedure is applicable to an existing motor drive circuit, which uses the motor M as a load. At the time point when it is determined that the system is in a non-driving mode, it drives each phase winding of the motor M in a driving manner similar to the general driving manner but with different phase angles, so that the rotor of the motor M is stationary without shaking.

[0045] Specifically, the discharge control circuit 16 can obtain the current operating angle of the motor M through the motor control circuit 13 (for example, the phase current detection circuit 133 and the first processing circuit 130 therein), and then, based on the obtained current operating angle, correct the motor control signal group with a correction angle to drive the motor M to stop and enter the discharge mode.

[0046] For example, for a three-phase motor, with reference to a common six-step square wave drive signal table, the current operating angle can be determined based on the detected phase currents Iu, Iv, and Iw. The discharge control circuit 16 can correct the motor control signal group with a correction angle of +90 degrees or -90 degrees according to the current operating angle to generate new motor control signals H1, H2, H3, L1, L2, and L3 to drive the motor M. At this time, since the stator electromagnetic force of the motor M is parallel to the magnetic field direction of the rotor, the rotor of the motor M can be made to stand still without shaking.

[0047] The determination criteria of the detection circuit 150 will be further described below. Specifically, when the detection circuit 150 detects whether the first voltage V1 decreases over time, it can essentially determine whether the decrease rate of the first voltage V1 is greater than a first predetermined decrease rate. If so, the first voltage V1 is determined to decrease over time. For example, the first predetermined decrease rate can be, for example, -7 V / s, but this is only an example and the present invention is not limited thereto. On the other hand, the detection circuit 150 can also determine whether the decrease rate of the first voltage V1 is less than a second predetermined decrease rate. If so, the first voltage V1 is determined to no longer decrease over time. For example, the second predetermined decrease rate can be, for example, -3 V / s, but this is only an example and the present invention is not limited thereto.

[0048] Reference can be further made to Figure 4 , which is a graph of voltage and current versus time for the pre-charge circuit applying an intelligent discharge mechanism according to an embodiment of the present invention, showing the capacitor voltage Vc (i.e., the first voltage V1) and the capacitor discharge current Ic1 respectively. As Figure 4 shown, between time t0 and t1, the capacitor voltage Vc continuously decreases. The detection circuit 150 detects that the operating state of the motor drive system 1 is the non-drive mode and the capacitor voltage Vc decreases over time. Therefore, at time t1, the discharge mechanism is turned on, causing the capacitor discharge current Ic1 to rise and the capacitor voltage Vc to rapidly decrease. In other words, the forced pre-charge circuit 15 is initialized.

[0049] Reference can be further made to Figure 5 , which is a graph of voltage and current versus time for the pre-charge circuit applying a delayed conduction mechanism according to an embodiment of the present invention, showing the capacitor voltage Vc (i.e., the first voltage V1), the pre-charge switch signal Vgs, the detection result signal S1, and the capacitor charging current Ic2 respectively. As Figure 4As shown, at time t0, only the first battery cell B1 of the battery pack 10 is turned on. However, the voltage provided by the first battery cell B1 is still higher than the pre-charge start voltage Vpc. At time t1, the second battery cell B1 is powered on. At this time, since the capacitor voltage Vc is higher than the pre-charge start voltage Vpc, the detection result signal S1 can be used to control the pre-charge switch SWp to conduct. However, due to the existence of the delay circuit 151, the conduction timing of the low-impedance path P1 is delayed by the delay time T1. Therefore, charging time is obtained for the capacitor C1, so that before the pre-charge switch signal Vgs reaches the conduction point P1, the capacitor C1 already has enough power, and the charged capacitor C1 can avoid the system being damaged due to the instantaneous large current generated during a rapid system restart.

[0050] For further reference Figure 6 , which is a flowchart of a state detection program executed by the detection circuit according to an embodiment of the present invention. Specifically, the detection circuit 150 can start a discharge program according to various states of the system. The following provides an example, but the present invention is not limited thereto. As Figure 6 shown, the state detection program includes:

[0051] Step S100: Detect whether the motor drive system is in a non-driving mode or a driving mode.

[0052] In response to detecting that the motor drive system is in the non-driving mode, go to step S101: Detect whether the battery pack is turned off. In response to detecting that the motor drive system is in the driving mode, go to step S102: Detect whether an electronic brake instruction from a user input is received. For example, the detection circuit can receive the electronic brake instruction input by the user from the above-mentioned controller area network 14'.

[0053] In response to detecting that the battery pack is turned off in step S101, go to step S103: Execute the discharge program, and then end the process.

[0054] In response to detecting that the battery pack is turned on in step S101, go to step S104: Detect whether the drop rate of the first voltage is greater than 7V / s.

[0055] In response to detecting that the drop rate of the first voltage is greater than 7V / s in step S104, go to step S105: Execute the discharge program. Then go to step S106: Detect whether the drop rate of the first voltage is less than 3V / s. If so, go to step S107 to terminate the discharge program. Otherwise, repeat step S105. After step S107, return to step S100.

[0056] In response to detecting that the falling rate of the first voltage in step S104 is not greater than 7V / s, step S108 is entered: Detect whether a motor locking instruction from a user input is received. For example, the detection circuit can receive the motor locking instruction input by the user from the above-mentioned Controller Area Network 14'.

[0057] Among them, in response to receiving the motor locking instruction in step S108, step S109 is entered: Execute the discharge program, otherwise return to step S100.

[0058] After that, from step S109, step S110 is entered: Detect whether the falling rate of the first voltage is less than 3V / s. If so, step S111 is entered to terminate the discharge program. Otherwise, step S109 is repeated. After step S111, return to step S100.

[0059] On the other hand, in response to receiving the electronic brake instruction in step S102, step S112 is entered to execute the discharge program, otherwise return to step S100.

[0060] After step S112, step S113 is entered: Detect whether the falling rate of the first voltage is less than 3V / s. If so, step S114 is entered to terminate the discharge program. Otherwise, step S112 is repeated. After step S114, return to step S100.

[0061] In the above process, whether it is the electronic brake instruction or the motor locking instruction, it can be received through the Controller Area Network 14', thereby executing the discharge program, protecting the system from large current impacts, and at the same time, various applications can be realized by using the driving mechanism of the motor drive system.

[0062] Beneficial effects of the embodiment

[0063] One of the beneficial effects of the present invention is that the motor drive system provided by the present invention has a pre-charge circuit with an intelligent charge and discharge mechanism. In terms of charging, the conduction time of the low-impedance path can be postponed through a delay circuit, and the internal capacitor after charging can be used to avoid damage to the system caused by instantaneous large current when the system restarts quickly.

[0064] On the other hand, the detection circuit of the pre-charge circuit can detect the system state and the battery voltage at the same time, perform the discharge program in the non-driving mode and when the battery voltage continues to decrease, so that the voltage can be lower than the rated safety voltage and the pre-charge start voltage, and in the discharge program, various applications can also be realized by using the driving mechanism of the motor drive system.

[0065] The above-disclosed content is only a preferred and feasible embodiment of the present invention, and does not limit the protection scope of the claims of the present invention. Therefore, all equivalent technical changes made by using the content of the specification and drawings of the present invention are included in the protection scope of the claims of the present invention.

Claims

1. A motor drive system, characterized in that, the motor drive system is used to drive a motor, and the motor drive system includes: a battery pack including a first battery unit and a second battery unit connected in series between a first input terminal and a second input terminal; a power control circuit configured to control the battery pack to be turned on and off; a capacitor connected between the first input terminal and the second input terminal; an inverter circuit connected between the first input terminal and the second input terminal to be powered by the battery pack, and having a plurality of switching components bridged to form a plurality of output terminals, wherein the plurality of output terminals are respectively connected to a plurality of phase windings of the motor; a motor control circuit configured to generate a set of motor control signals to control the switching actions of the plurality of switching components, so that each of the phase windings of the motor is energized to drive the motor; a state detection circuit configured to detect an operating state of the motor drive system; a pre-charge circuit, including: a high-impedance path connected between the second input terminal and the battery pack; a low-impedance path connected between the second input terminal and the battery pack, wherein the resistance value of the high-impedance path is greater than the resistance value of the low-impedance path; a pre-charge switch provided on the low-impedance path; a detection circuit configured to: compare a first voltage at the first input terminal with a pre-charge start voltage and correspondingly generate a detection result signal, wherein, in response to the first voltage being higher than the pre-charge start voltage, the detection result signal is used to control the pre-charge switch to conduct, and in response to the first voltage being less than or equal to the pre-charge start voltage, the detection result signal is used to control the pre-charge switch to turn off; and detect whether the operating state is a non-driving mode and whether the first voltage drops over time, wherein, in response to detecting that the operating state is the non-driving mode and the first voltage drops over time, output a discharge indication signal for performing a discharge procedure on the capacitor until it is detected that the first voltage no longer drops over time, and then stop outputting the discharge indication signal; and a delay circuit provided between the detection circuit and the pre-charge switch, configured to delay the detection result signal by a predetermined delay time; and a discharge control circuit configured to perform the discharge procedure according to the discharge indication signal, including: obtaining a current operating angle of the motor through the motor control circuit; and correcting the set of motor control signals by a correction angle according to the current operating angle to drive the motor to stop and enter a discharge mode.

2. The motor drive system according to claim 1, characterized in that, the power control circuit further correspondingly generates a power state signal according to the turn-on and turn-off of the battery pack, and the detection circuit is further configured to: in response to detecting that the operating state is the non-driving mode, judge whether the battery pack is turned on or off according to the power state signal; in response to detecting that the battery pack is turned off, output the discharge indication signal.

3. The motor drive system according to claim 2, wherein, the detection circuit is further configured to: when detecting that the battery pack is turned on, detect whether the first voltage drops over time.

4. The motor drive system according to claim 3, wherein, when the detection circuit is configured to detect whether the first voltage drops over time, it further determines whether the drop rate of the first voltage is greater than a first predetermined drop rate. If so, the first voltage is determined to drop over time.

5. The motor drive system according to claim 3, wherein, when the detection circuit is configured to determine that the first voltage does not drop over time, it further detects whether a motor lock instruction is received from a user input, wherein, in response to receiving the motor lock instruction, the detection circuit is configured to output the discharge indication signal.

6. The motor drive system according to claim 3, wherein, when the detection circuit is configured to detect whether the first voltage drops over time, it further determines whether the drop rate of the first voltage is less than a second predetermined drop rate. If so, the first voltage is determined to no longer drop over time.

7. The motor drive system according to claim 1, wherein, the motor control circuit is further configured to detect a plurality of phase currents of the plurality of phase windings of the motor to generate an angle information for indicating the current operating angle of the motor.

8. The motor drive system according to claim 1, wherein, in response to detecting that the operating state is not the non-driving mode, the detection circuit is further configured to detect whether an electronic brake instruction is received from a user input. If so, it outputs the discharge indication signal.

9. The motor drive system according to claim 8, wherein, when outputting the discharge indication signal in response to receiving the electronic brake instruction from the user input, the detection circuit is further configured to detect whether the first voltage drops over time. In response to detecting that the first voltage no longer drops over time, it stops outputting the discharge indication signal.

10. The motor drive system according to claim 1, wherein, when the pre-charge switch is turned off, the battery pack charges the capacitor through the high impedance path with a pre-charge current, and the predetermined delay time is at least greater than a charging time related to the pre-charge current and the capacitance value of the capacitor.

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