Discharge control method and device for bus voltage

Abstract

The invention relates to a discharge control method for bus voltage. The method comprises the following steps: determining the bus voltage; and adaptively enabling a discharge path at an output side of a flyback switching power supply to perform constant power discharge according to the bus voltage, an input side of the flyback switching power supply being coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply providing a constant voltage output. The invention further relates to bus voltage discharge control equipment, a computer readable storage medium, a computer program product, a discharge circuit and an air conditioner compressor.

Description

Technical Field

[0001] The present application relates to the field of high-voltage discharge control, and more specifically, to a bus voltage discharge control method and device, a computer-readable storage medium, a computer program product, a discharge circuit, and an air-conditioning compressor. Background Art

[0002] In electric vehicles, high-voltage products (such as main drive controllers, auxiliary drives, electric air conditioners, and high-voltage DC-DC converters) generally have large-capacity capacitors (for example, front-end filter capacitors) integrated inside. The high voltage on the capacitors poses a threat to electrical appliances and personal safety. Therefore, the state has issued corresponding regulations requiring that when certain conditions are met (for example, after the vehicle is parked, when the power battery is abnormally over-voltage), the large-capacity capacitor must be discharged to a safe voltage within a certain period of time.

[0003] Existing discharge schemes generally use active discharge resistors (for example, cement resistors or special high-power resistors) for constant resistance discharge (i.e., the resistance value of parallel or series resistors is fixed). The discharge curve is fixed and cannot be adjusted, making it difficult to fully utilize the maximum power dissipation of the device and achieve the maximum discharge rate. For example, in electric air-conditioning compressor applications, the rate of capacitor discharge using active discharge resistors is too slow, and the nonlinear extension with voltage changes is inefficient. Moreover, under high-voltage and large-capacitor operating conditions, the higher the voltage and the larger the capacitance, the slower the discharge rate, which can easily cause danger. Summary of the invention

[0004] According to one aspect of the present application, a discharge control method for a bus voltage is provided, the method comprising: determining the bus voltage; and adaptively enabling a discharge path located on the output side of a flyback switching power supply to perform constant power discharge according to the bus voltage, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

[0005] As a supplement or replacement of the above solution, in the above method, the discharge path located at the output side of the flyback switching power supply includes a discharge load and a first switch tube.

[0006] As a supplement or alternative to the above-mentioned scheme, in the above-mentioned method, adaptively enabling the discharge path located on the output side of the flyback switching power supply to perform constant power discharge according to the bus voltage includes: when the bus voltage is less than or equal to a preset threshold, sending a control signal to open the first switch tube, thereby enabling the discharge path.

[0007] As a supplement or alternative to the above scheme, the above method also includes: when discharge is required and the bus voltage is greater than the preset threshold, enabling an active discharge path to perform constant resistance discharge, wherein the active discharge path is different from the discharge path located on the output side of the flyback switching power supply.

[0008] As a supplement or alternative to the above solution, in the above method, the active discharge path includes an active discharge resistor and a second switch tube, and is coupled in parallel with the capacitor carrying the bus voltage and the input side of the flyback switching power supply.

[0009] According to another aspect of the present application, a discharge control device for a bus voltage is provided, the device comprising: a determination device for determining the bus voltage; and an enabling device for adaptively enabling a discharge path located on the output side of a flyback switching power supply to perform constant power discharge according to the bus voltage, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

[0010] As a supplement or replacement for the above solution, in the above device, the discharge path located at the output side of the flyback switching power supply includes a discharge load and a first switch tube.

[0011] As a supplement or alternative to the above solution, in the above device, the enabling device is configured to: when the bus voltage is less than or equal to a preset threshold, send a control signal to open the first switch tube, thereby enabling the discharge path.

[0012] According to another aspect of the present application, a computer-readable storage medium is provided, on which computer instructions are stored. When the computer instructions are executed by a processor, the method described above is implemented.

[0013] According to another aspect of the present application, a computer program product is provided, comprising a computer program, and when the computer program is executed by a processor, the method described above is implemented.

[0014] According to another aspect of the present application, a discharge circuit for a bus voltage is provided, the discharge circuit comprising: a first discharge path, for performing constant resistance discharge under conditions where discharge is required and when the bus voltage is greater than a preset threshold, the first discharge path being coupled in parallel with a capacitor carrying the bus voltage; a flyback switching power supply, an input side of which is coupled in parallel with the capacitor carrying the bus voltage and the first discharge path, and provides a constant voltage output; a voltage detection circuit, for detecting the bus voltage; a control circuit, coupled to the voltage detection circuit and comprising a discharge control device as described above; and a second discharge path, for performing constant power discharge under the control of the control circuit, the second discharge path being located at the output side of the flyback switching power supply.

[0015] As a supplement or alternative to the above scheme, in the above discharge circuit, the second discharge path includes a discharge load and a first switch tube, and the control circuit is configured to: when the bus voltage is less than or equal to the preset threshold, send a control signal to open the first switch tube, thereby enabling the second discharge path.

[0016] As a supplement or alternative to the above solution, in the above discharge circuit, the first discharge path includes an active discharge resistor and a second switch tube, and under conditions where discharge is required, the second switch tube receives an enable signal and is turned on, thereby enabling the first discharge path.

[0017] As a supplement or alternative to the above scheme, in the above discharge circuit, the preset threshold is set as follows: when the bus voltage is less than or equal to the preset threshold, the discharge rate of the constant resistance discharge is less than the discharge rate of the constant power discharge.

[0018] According to another aspect of the present application, an air-conditioning compressor is provided, comprising: a capacitor for carrying a bus voltage; and a discharge circuit as described above, for discharging the bus voltage under a condition requiring discharge.

[0019] The inventor of the present application realizes that the speed of (constant) resistance consuming the energy of the energy storage device is first fast and then slow. The main reason for this is that after the voltage is reduced, the discharge current decreases. Therefore, the discharge control scheme of the bus voltage of the embodiment of the present application adaptively enables the discharge path located on the output side of the flyback switching power supply to perform constant power discharge according to the received bus (residual) voltage. Since the discharge curve of constant power discharge is different from the discharge curve of constant resistance discharge, the discharge time can be accelerated by adjusting the discharge curve in time.

[0020] In addition, the discharge control scheme of the bus voltage of one or more embodiments of the present application changes with the bus voltage, and uses a high-voltage flyback switching power supply to discharge during the discharge process, that is, after receiving the discharge enable signal, the MOS tube is turned on, and the load on the low-voltage side of the switching power supply is used to achieve constant power discharge. At the same time, the bus voltage is monitored to avoid the adverse effects of the load on the low-voltage side on the switching power supply when the discharge signal is not received, such as affecting the efficiency of the switching power supply. In addition, after the bus power supply drops to a safe voltage, the load on the low-voltage side (discharge load) is turned off, and then the switching power supply is turned off, thereby further reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects and advantages of the present application will become more fully apparent from the following detailed description in conjunction with the accompanying drawings, wherein the same or similar elements are represented by the same reference numerals.

[0022] Figure 1 A schematic flow chart of a method for controlling a discharge of a bus voltage according to an embodiment of the present application is shown;

[0023] Figure 2 A schematic structural diagram of a bus voltage discharge control device according to an embodiment of the present application is shown;

[0024] Figure 3 shows the discharge curves of bus voltage discharged by different discharge modes; and

[0025] Figure 4 A circuit diagram of a discharge circuit for bus voltage according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0026] Hereinafter, a discharge control scheme of a bus voltage according to various exemplary embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0027] Figure 1 FIG. 1 is a flow chart of a bus voltage discharge control method 1000 according to an embodiment of the present application. Figure 1 As shown, the bus voltage discharge control method 1000 includes:

[0028] In step S110, the bus voltage is determined; and

[0029] In step S120, a discharge path located at the output side of the flyback switching power supply is adaptively enabled according to the bus voltage to perform constant power discharge, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

[0030] Electric vehicles generally have a high-voltage power supply and distribution system, which uses power batteries to provide energy for high-voltage components such as motor controllers, drive motors, and electric compressors. The high-voltage power supply and distribution system may include: an on-board charger assembly, a DC charging interface, an AC charging interface, a DC bus, and a three-phase line for the motor. In the context of this application, the term "bus voltage" is also referred to as the DC bus voltage, that is, the voltage transmitted on the DC bus. In one embodiment, the bus voltage is 400V. In another embodiment, the bus voltage is 800V.

[0031] In step S110, the bus voltage is determined, that is, the residual voltage value of the bus voltage is detected during the discharge process using the first discharge path. Then in step S120, the discharge path located on the output side (low voltage side) of the flyback switching power supply is adaptively enabled according to the determined value or detected value of the bus voltage to perform constant power discharge. In other words, when the determined value or detected value of the bus voltage meets certain conditions, the discharge path is switched in time, for example, the discharge path on the output side of the flyback switching power supply (that is, the second discharge path different from the first discharge path) is enabled to perform discharge.

[0032] It should be noted that, in the context of the present application, a "flyback switching power supply" is used to convert high-voltage electrical energy in a power grid into low-voltage electrical energy. Moreover, the flyback switching power supply can adjust the output voltage (provide a constant voltage output), thereby facilitating the constant power discharge of the discharge path (i.e., the second discharge path) on the output side of the flyback switching power supply. In one or more embodiments, the discharge path on the output side of the flyback switching power supply includes a discharge load (e.g., a dummy load) and a first switch tube (e.g., an insulated gate bipolar transistor IGBT, a metal oxide semiconductor MOS tube or a triode, etc.).

[0033] In one embodiment, step S120 includes: when the bus voltage is less than or equal to a preset threshold, sending a control signal to turn on the first switch tube, thereby enabling the discharge path. That is, during the discharge process, if it is detected that the bus residual voltage is less than or equal to the preset threshold, the discharge path on the output side of the flyback switching power supply is enabled by sending a control signal to turn on the first switch tube.

[0034] refer to Figure 3 , which shows the discharge curve of bus voltage discharged by different discharge methods. Figure 3 As shown, curve 310 shows the discharge curve of constant power discharge, curve 320 shows the discharge curve of constant current discharge, and curve 330 is the discharge curve of constant resistance discharge. Dashed line 340 is the tangent of curve 330, and the slope of the tangent can represent the discharge rate of curve 330 at a certain time point. Figure 3 As can be seen from the curve 330, with the passage of time, the absolute value of the slope of the tangent 340 gradually decreases, that is, the discharge rate of the constant resistance discharge method gradually slows down. Therefore, in one or more embodiments, the preset threshold value can be set so that before the bus voltage drops to the threshold value, the discharge rate of the constant resistance discharge is greater than the discharge rate of the constant power discharge, and after the bus voltage is less than or equal to the threshold value, the discharge rate of the constant resistance discharge is less than or equal to the discharge rate of the constant power discharge. By making full use of the discharge curve characteristics of the constant power discharge and the constant resistance discharge, and switching the discharge path in time to adjust the discharge curve, the discharge can be accelerated (shortening the time it takes for the bus voltage to drop to a safe voltage).

[0035] although Figure 1 Not shown, in one or more embodiments, the above method 1000 also includes: when a discharge condition is required (i.e., the capacitor carrying the bus voltage needs to be discharged) and the bus voltage is greater than a preset threshold (i.e., the bus residual voltage has not yet dropped to the preset threshold), enabling an active discharge path to perform constant resistance discharge, wherein the active discharge path is located on the input side of the flyback switching power supply, is different from the discharge path on the output side and is isolated from each other.

[0036] In one or more embodiments, the active discharge path includes an active discharge resistor (e.g., a cement resistor or a high-power resistor) and a second switching tube (e.g., an insulated gate bipolar transistor IGBT, a metal oxide semiconductor MOS tube or a triode, etc.), and is coupled in parallel with a capacitor carrying the bus voltage and the input side of the flyback switching power supply.

[0037] In addition, it is easy for a person skilled in the art to understand that the bus voltage discharge control method 1000 provided in the above one or more embodiments of the present application can be implemented by a computer program. For example, the computer program is included in a computer program product, and when the computer program is executed by a processor, the bus voltage discharge control method 1000 of one or more embodiments of the present application is implemented. For another example, when a computer-readable storage medium (such as a USB flash drive) storing the computer program / instructions is executed by a processor, the bus voltage discharge control method 1000 of one or more embodiments of the present application can be executed.

[0038] refer to Figure 2 , Figure 2 A bus voltage discharge control device 2000 according to an embodiment of the present application is shown, and the device 2000 includes: a determination device 210 and a start device 220. The determination device 210 is used to determine the bus voltage; and the start device 220 is used to adaptively start the discharge path located at the output side of the flyback switching power supply according to the bus voltage to perform constant power discharge, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

[0039] In the context of this application, the term "bus voltage" is also referred to as the DC bus voltage, that is, the voltage transmitted on the DC bus. In one embodiment, the bus voltage is 400V. In another embodiment, the bus voltage is 800V.

[0040] The determining device 210 is used to determine the bus voltage, that is, to detect the residual voltage value of the bus voltage during the discharge process using the first discharge path. Subsequently, the enabling device 220 is configured to adaptively enable the discharge path located on the output side (low-voltage side) of the flyback switching power supply to perform constant power discharge according to the determined value or detected value of the bus voltage. In other words, when the determined value or detected value of the bus voltage meets certain conditions, the discharge path is switched in a timely manner, for example, the enabling device 220 enables the discharge path on the output side of the flyback switching power supply (that is, the second discharge path different from the first discharge path) to perform discharge.

[0041] It should be noted that, in the context of the present application, a "flyback switching power supply" is used to convert high-voltage electrical energy in a power grid into low-voltage electrical energy. Moreover, the flyback switching power supply can adjust the output voltage (provide a constant voltage output), thereby facilitating the constant power discharge of the discharge path (i.e., the second discharge path) on the output side of the flyback switching power supply. In one or more embodiments, the discharge path on the output side of the flyback switching power supply includes a discharge load (e.g., a dummy load) and a first switch tube (e.g., an insulated gate bipolar transistor IGBT, a metal oxide semiconductor MOS tube or a triode, etc.).

[0042] In one embodiment, the enabling device 220 is configured to send a control signal to turn on the first switch tube when the bus voltage is less than or equal to a preset threshold, thereby enabling the discharge path. That is, during the discharge process, if the bus residual voltage determined by the determining device 210 is less than or equal to the preset threshold, the enabling device 220 enables the discharge path on the output side of the flyback switching power supply by sending a control signal to turn on the first switch tube.

[0043] Figure 4 FIG. 4 shows a circuit diagram of a discharge circuit 4000 for bus voltage according to an embodiment of the present application. Figure 4As shown, the discharge circuit 4000 includes: a first discharge path 440, a flyback switching power supply 460, a voltage detection circuit 450, a control circuit 420 and a second discharge path 470. The first discharge path 440 is used to perform constant resistance discharge under the condition where discharge is required (the capacitor DC_Link needs to be discharged) and when the bus residual voltage (HV+) is greater than the preset threshold, and the first discharge path 440 is coupled in parallel with the capacitor DC_Link carrying the bus voltage; the flyback switching power supply 460, whose input side is coupled in parallel with the capacitor DC_Link carrying the bus voltage and the first discharge path 440, and provides a constant voltage output; the voltage detection circuit 450 is used to detect the bus voltage; the control circuit 420 is coupled with the voltage detection circuit 450 (the control circuit 420 may include the discharge control device 2000 as described above in one or more embodiments); and the second discharge path 470 is used to perform constant power discharge under the control of the control circuit 420, and the second discharge path 470 is located at the output side of the flyback switching power supply 460.

[0044] like Figure 4 As shown, in the above-mentioned discharge circuit 4000, the second discharge path 470 includes a discharge load (also called a dummy load) 475 and a first switch tube SW3. In one embodiment, the control circuit 420 is configured to: when the bus voltage is less than or equal to a preset threshold, send a control signal to turn on the first switch tube (such as Figure 4 As shown, the control circuit 420 turns on the first switch SW3 by sending a control signal to the enabling device DCha_EN2, thereby enabling the second discharge path 470.

[0045] Continue to refer Figure 4 , the first discharge path 440 includes an active discharge resistor ( Figure 4 The resistors R3 and R6 in the embodiment and the second switch tube SW2 are connected, and under the condition that discharge is required, the second switch tube SW2 receives an enable signal (for example, from the enable device DCha_EN1) and is turned on, thereby enabling the first discharge path 440.

[0046] like Figure 4 As shown, the flyback switching power supply 460 may include a switch tube SW1, a pulse width modulation PWM control circuit 430, a transformer T1, a voltage regulator tube D1 and a capacitor C1. The gate of the switch tube SW1 is coupled to the pulse width modulation PWM control circuit 430. The PWM control circuit 430 may automatically adjust the duty cycle according to the output feedback of the flyback switching power supply 460, thereby achieving a constant voltage output (regardless of whether the bus voltage drops or the output load increases).

[0047] The voltage detection circuit 450 may include a voltage divider resistor (composed of resistors R4 ... R4n and R5) and a voltage divider detection circuit 410. In one embodiment, the total resistance of the resistors R4 ... R4n and R5 (compared to the active discharge resistors R3 and R6) is a larger resistor in the MΩ level, while the active discharge resistor is a smaller resistor in the kΩ level.

[0048] The voltage detection circuit 450 can calculate the bus residual voltage according to the resistance values ​​of the resistors R4 ... R4n and R5 through the voltage detected by the voltage divider detection circuit 410 (i.e., the voltage of the resistor R5), and provide it to the control circuit 420. In one embodiment, the control circuit 420 is configured to send a control signal to turn on the first switch tube SW3 when the bus voltage is less than or equal to a preset threshold, thereby enabling the second discharge path 470. In one or more embodiments, the preset threshold can be selected so that when the bus (residual) voltage is less than or equal to the preset threshold, the discharge rate of the constant resistance discharge using the first discharge path 440 is less than the discharge rate of the constant power discharge using the second discharge path 470.

[0049] In one embodiment, the discharge circuit 4000 operates as follows: first, the second switch tube SW2 is turned on to discharge through the active discharge resistor (R3, R6), and after the bus voltage drops to a certain value, the first switch tube SW3 is turned on through the control of the control circuit 420, and the dummy load 475 on the low-voltage side of the flyback switching power supply 460 is used to accelerate the discharge. At this time, the constant resistance discharge through the first discharge path 440 can be stopped by disconnecting the second switch tube SW2 to reduce the heat loss on the resistor. Of course, those skilled in the art can understand that if necessary, the second switch tube SW2 can be temporarily disconnected to continue the constant resistance discharge. The voltage detection circuit 450 keeps monitoring the bus voltage. After the bus voltage drops to a safe voltage, the control circuit 420 stops discharging through the second discharge path by sending a control signal. Then, the flyback switching power supply 460 can also be turned off to further reduce energy consumption.

[0050] In the above-mentioned discharge circuit 4000, the influence of the discharge load (dummy load) on the switching power supply when no discharge signal is received can be avoided through the control of the control circuit 420, thereby avoiding affecting the efficiency of the switching power supply. At the same time, after the bus power supply drops to a safe voltage, the discharge load is turned off, and then the switching power supply is turned off, thereby further reducing energy consumption.

[0051] The above-mentioned discharge circuit 4000 can be applied to various high-voltage products, including but not limited to air-conditioning compressors. In one embodiment, the air-conditioning compressor may include: a capacitor DC_Link for carrying a bus voltage; and a discharge circuit 4000 for discharging the bus voltage under a condition requiring discharge.

[0052] In summary, the discharge control scheme of the bus voltage of the embodiment of the present application adaptively enables the discharge path located on the output side of the flyback switching power supply to perform constant power discharge according to the received bus (residual) voltage. Since the discharge curve of the constant power discharge is different from the discharge curve of the constant resistance discharge, the discharge time can be accelerated by adjusting the discharge curve in a timely manner. In addition, the discharge control scheme of the bus voltage of one or more embodiments of the present application uses a high-voltage flyback switching power supply to discharge during the discharge process as the bus voltage changes, that is, after receiving the discharge enable signal, the MOS tube is turned on, and the load on the low-voltage side of the switching power supply is used to achieve constant power discharge. At the same time, the bus voltage is monitored to avoid the adverse effect of the load on the low-voltage side on the switching power supply when the discharge signal is not received, such as affecting the efficiency of the switching power supply. In addition, after the bus power supply drops to a safe voltage, the load on the low-voltage side (discharge load) is turned off, and then the switching power supply is turned off, thereby further reducing energy consumption.

[0053] The above examples mainly illustrate the discharge control scheme of the bus voltage of the embodiment of the present application. Although only some of the embodiments of the present application are described, it should be understood by those skilled in the art that the present application can be implemented in many other forms without departing from its subject matter and scope. Therefore, the examples and embodiments shown are regarded as illustrative rather than restrictive, and the present application may cover various modifications and substitutions without departing from the spirit and scope of the present application as defined in the claims.

Claims

1. A method for controlling a bus voltage discharge, characterized in that: The method comprises: determining the bus voltage; and A discharge path at the output side of a flyback switching power supply is adaptively enabled according to the bus voltage to perform constant power discharge, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

2. The method of claim 1, wherein: The discharge path at the output side of the flyback switching power supply includes a discharge load and a first switch tube.

3. The method of claim 2, wherein: Adaptively enabling a discharge path at the output side of the flyback switching power supply to perform constant power discharge according to the bus voltage includes: When the bus voltage is less than or equal to a preset threshold, a control signal is sent to turn on the first switch tube, thereby enabling the discharge path.

4. The method of claim 3, further comprising: When discharge is required and the bus voltage is greater than the preset threshold, an active discharge path is enabled to perform constant resistance discharge, wherein the active discharge path is different from a discharge path located at the output side of the flyback switching power supply.

5. The method of claim 4, wherein: The active discharge path includes an active discharge resistor and a second switch tube, and is coupled in parallel with a capacitor carrying the bus voltage and an input side of the flyback switching power supply.

6. A bus voltage discharge control device, characterized in that: The device comprises: a determining device for determining the bus voltage; and An enabling device is used to adaptively enable a discharge path located at the output side of a flyback switching power supply to perform constant power discharge according to the bus voltage, wherein the input side of the flyback switching power supply is coupled in parallel with a capacitor carrying the bus voltage, and the flyback switching power supply provides a constant voltage output.

7. The device of claim 6, wherein: The discharge path at the output side of the flyback switching power supply includes a discharge load and a first switch tube.

8. The device of claim 7, wherein: The enabling device is configured to: When the bus voltage is less than or equal to a preset threshold, a control signal is sent to turn on the first switch tube, thereby enabling the discharge path.

9. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the computer instructions are executed by a processor, the method according to any one of claims 1 to 5 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

11. A discharge circuit for bus voltage, characterized in that: The discharge circuit comprises: A first discharge path, used for performing constant resistance discharge under a condition where discharge is required and when the bus voltage is greater than a preset threshold, the first discharge path being coupled in parallel with a capacitor carrying the bus voltage; A flyback switching power supply, the input side of which is coupled in parallel with the capacitor carrying the bus voltage and the first discharge path, and provides a constant voltage output; A voltage detection circuit, used for detecting the bus voltage; a control circuit coupled to the voltage detection circuit and comprising a discharge control device as claimed in any one of claims 6 to 8; and The second discharge path is used for performing constant power discharge under the control of the control circuit, and the second discharge path is located at the output side of the flyback switching power supply.

12. The discharge circuit according to claim 11, wherein: The second discharge path includes a discharge load and a first switch tube, and the control circuit is configured to send a control signal to turn on the first switch tube when the bus voltage is less than or equal to the preset threshold, thereby enabling the second discharge path.

13. The discharge circuit according to claim 11, wherein: The first discharge path includes an active discharge resistor and a second switch tube, and under a condition where discharge is required, the second switch tube receives an enable signal and is turned on, thereby enabling the first discharge path.

14. The discharge circuit according to claim 11, wherein: The preset threshold is set such that when the bus voltage is less than or equal to the preset threshold, the discharge rate of the constant resistance discharge is less than the discharge rate of the constant power discharge.

15. An air-conditioning compressor, characterized in that: The air conditioning compressor comprises: capacitors to carry the bus voltage; and The discharge circuit according to any one of claims 11 to 14 is used to discharge the bus voltage under a condition where discharge is required.

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