An electric vehicle active discharge system and method

Abstract

The application belongs to the technical field of new energy vehicles, and discloses an electric vehicle active discharge system and method, wherein the system comprises a low-voltage MCU unit, an isolation unit, a high-voltage detection unit, an emergency power supply unit, a delay power supply unit, a logic management unit, a driving unit and a load unit, and each unit constitutes a system circuit. The application meets the requirement of executing effective active discharge logic under normal low-voltage power supply and can accurately diagnose abnormal state of the low-voltage side and trigger high-voltage side discharge logic under abnormal low-voltage power failure through the design of the isolation unit, and the structure is simple and reliable in implementation form. The application reserves sufficient time for complete disconnection of the high-voltage contactor through the design of the delay circuit unit, which produces a 200ms discharge logic delay time after low-voltage power failure. The application prevents active discharge of the high-voltage contactor from being performed when the high-voltage contactor is not completely disconnected, which can cause unexpected consequences of the discharge resistor and the discharge MOS tube.

Description

Technical Field

[0001] This invention belongs to the field of new energy vehicle technology, and specifically relates to an active discharge system and method for electric vehicles. Background Technology

[0002] With the rapid development of modern electric vehicle technology, the voltage and safety levels of electric vehicles are becoming increasingly higher, and the safety protection requirements under fault conditions are becoming increasingly stringent. In the event of a collision or extreme fault conditions, the controller must be able to discharge the charge in the bus capacitor within a specified time without affecting the controller's performance. Currently, electric control products employ three strategies for discharging the bus capacitor: passive discharge, general active generation, and emergency active discharge, to ensure system safety under both normal and abnormal discharge conditions. Currently, passive discharge by the controller often uses a discharge resistor connected in series on the high-voltage bus, generating a certain continuous power consumption. General active discharge uses a low-voltage MCU for algorithm control, rapidly discharging through the motor windings. Emergency active discharge often uses a discharge resistor connected in series with a control switch; when active discharge is required, the switch logic is closed to achieve rapid discharge of the charge in the bus capacitor.

[0003] Currently, the controller's emergency active discharge scheme can execute the active discharge logic through the low-voltage MCU when the low-voltage side power supply is normal. This can be achieved through online monitoring of the bus voltage. However, in the event of an abnormal low-voltage power failure, the low-voltage side power supply is managed by the high-voltage side's emergency power supply logic to initiate active discharge. During the switching process of the vehicle's high-voltage contactor, there is a certain delay before the high-voltage contactor fully disconnects. Active discharge before the high-voltage contactor is fully disconnected can cause unexpected consequences for the discharge resistor and discharge MOSFET, resulting in the high voltage at the high-voltage bus terminal failing to discharge, posing a significant safety hazard to personnel. Summary of the Invention

[0004] To address at least one of the problems in the background art, the present invention proposes an active discharge system and method for electric vehicles.

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

[0006] An active discharge system for electric vehicles, comprising:

[0007] The load unit is equipped with a switching transistor and connected to positive and negative busbars;

[0008] The high-voltage power supply line is connected to the positive and negative busbars at both ends, and is equipped with a series emergency power supply unit and a logic management unit.

[0009] The low-voltage discharge circuit has a low-voltage MCU unit connected to one end and a switching transistor connected to the other end. It is equipped with an isolation unit, a logic management unit and a drive unit connected in series.

[0010] The high-voltage detection unit is connected to the positive busbar at one end and to the isolation unit at the other end.

[0011] The delay circuit unit is connected to the emergency power supply unit, the logic management unit, and the isolation unit, respectively.

[0012] Preferably, the load unit includes several parallel branches;

[0013] At least one branch has a capacitor.

[0014] At least one branch is equipped with a resistor and the switching transistor connected in series;

[0015] At least one branch has a resistor and a diode connected in series.

[0016] Preferably, the load unit is provided with three parallel branches;

[0017] The first branch is equipped with a capacitor;

[0018] The second branch is equipped with a resistor and the aforementioned switch in series;

[0019] The third branch is equipped with a series resistor and a Zener diode.

[0020] Preferably, a voltage regulation node is provided between the resistor and the Zener diode, and both the driving unit and the switching transistor are connected to the voltage regulation node.

[0021] Preferably, the drive unit is also connected to the negative terminal of the bus.

[0022] An active discharge method for an electric vehicle, used in the aforementioned active discharge system for an electric vehicle, includes the following steps:

[0023] When the low-voltage power fails, the low-voltage MCU unit executes a discharge abnormality diagnostic signal;

[0024] The voltage information of the positive and negative busbars is detected by a high-voltage detection unit.

[0025] Voltage information is transmitted through the isolation unit;

[0026] If the voltage of the positive and negative busbars drops to the target voltage, the low-voltage discharge line is energized and the high-voltage power supply line is shut off.

[0027] Conversely, the low-voltage discharge line is turned off, and the high-voltage power supply line is energized.

[0028] Preferably, the target voltage is the rated voltage of the low-voltage discharge circuit.

[0029] Preferably, the method further includes the following steps:

[0030] Before the low-voltage power failure, the low-voltage MCU unit transmits an active discharge execution signal to energize the low-voltage discharge line.

[0031] Power is supplied to the high-voltage power line.

[0032] Preferably, when a low-voltage power failure occurs, before energizing the low-voltage discharge line, the following steps are included:

[0033] Voltage information is transmitted to the delay circuit unit through the isolation unit;

[0034] The voltage drop of the positive and negative busbars is delayed within a set time by using a delay circuit unit.

[0035] Preferably, the set time is 200ms.

[0036] The beneficial effects of this invention are:

[0037] 1. This invention, through the design of an isolation unit, satisfies the requirement of executing effective active discharge logic during normal low-voltage power supply, and can accurately diagnose the abnormal state on the low-voltage side and trigger the discharge logic on the high-voltage side when abnormal low-voltage power failure occurs. The structure is simple and reliable in implementation.

[0038] 2. By designing a high-voltage detection unit on the high-voltage side, this invention can monitor the potential state of the high-voltage bus voltage in real time during the discharge process, thus preventing the risk that the high-voltage discharge will not reach the standard safe voltage.

[0039] 3. This invention, through the design of a delay circuit unit, generates a 200ms discharge logic delay time after a low-voltage power failure, providing sufficient time for the high-voltage contactor of the entire vehicle to fully disconnect. This prevents unintended discharge due to incomplete disconnection of the high-voltage contactor, which could cause unintended consequences for the discharge resistor and discharge MOSFET.

[0040] 4. This invention enables stable power supply to the entire active discharge logic on the high-voltage side after a low-voltage power failure through an emergency power supply unit.

[0041] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A schematic diagram of the structure of an active discharge system for electric vehicles according to the present invention is shown;

[0044] Figure 2 The normal discharge execution flow waveform of the present invention is shown;

[0045] Figure 3 The waveform diagram of the low-voltage power-down execution process of the present invention is shown. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] An active discharge system for electric vehicles includes a low-voltage MCU unit, an isolation unit, a high-voltage detection unit, an emergency power supply unit, a delayed power supply unit, a logic management unit, a drive unit, and a load unit. These units constitute the system circuit, as detailed below:

[0048] exist Figure 1 In this circuit, a switching transistor is installed in the load unit, with its two ends connected to the positive and negative busbars. Then, the emergency power supply unit and the logic management unit are connected in series to form a high-voltage power supply line, with its two ends connected to the positive and negative busbars respectively. Additionally, the isolation unit, logic management unit, and drive unit form a low-voltage discharge line, with one end connected to the low-voltage MCU unit and the other end connected to the switching transistor. The high-voltage detection unit is connected to the positive busbar at one end and the isolation unit at the other. Furthermore, the delay circuit unit is connected to the emergency power supply unit, logic management unit, and isolation unit respectively, and the drive unit is also connected to the negative busbar.

[0049] It should be noted that the low-voltage MCU unit executes the internal active discharge logic of the low-voltage side MCU. Under normal power supply conditions on the low-voltage side (the negative bus side), it can transmit reliable active discharge execution signals and discharge anomaly diagnostic functions. The high-voltage detection unit can monitor the active discharge process, transmitting the data from the isolation unit to the low-voltage MCU, enabling real-time monitoring of the high-voltage side (the positive bus side) bus voltage potential. The isolation unit uses an isolation chip to achieve low-voltage discharge signal to high-voltage isolated transmission. When the low-voltage side power supply is normal, it can effectively transmit the low-voltage side discharge signal control logic. When the low-voltage side power supply is abnormal, it can maintain the default design state and enable the high-voltage side active discharge logic management unit.

[0050] It should be further explained that the delay circuit unit, as the high-voltage side delay logic unit, can receive the discharge command from the low-voltage side after a low-voltage power failure and transmit the discharge command with a set delay time to the logic management unit for coordination and integration. Finally, it outputs the actual active discharge logic signal from the high-voltage side to the drive unit. The logic management unit is mainly responsible for the main logic management of the high-voltage side active discharge, receiving the discharge command output from the low-voltage side, the high-voltage side delay circuit high-voltage control signal, and the low-voltage discharge signal from the isolation unit, coordinating and integrating the various input signals, and finally outputting the actual active discharge logic signal from the high-voltage side to the drive unit. In addition, the emergency power supply unit receives the high-voltage side bus voltage for power conversion, enabling stable power supply to the entire high-voltage side active discharge logic after a low-voltage power failure. The drive unit receives the output signal from the logic management unit and outputs a MOSFET (switching transistor) drive switching signal for active discharge, receiving power from the high-voltage side to maintain the active discharge state after a low-voltage power failure.

[0051] Furthermore, the load unit includes several parallel branches, wherein at least one branch is provided with a capacitor; at least one branch is provided with a resistor and a switching transistor connected in series; and at least one branch is provided with a resistor and a diode connected in series.

[0052] It should be noted that a DC voltage is applied to the positive and negative busbars connected to the load unit. Figure 1 The upper middle side is the positive terminal side of the busbar, and the lower side is the negative terminal side of the busbar. Figure 1 In this system, DC+ is the positive terminal of the DC voltage and DC- is the negative terminal of the DC voltage. By using the DC voltage, an independent power supply network can be designed on the high-voltage side, so that the high-voltage side discharge logic and drive unit can continue to operate reliably after the low-voltage power failure, thus ensuring the high-voltage safety of the entire vehicle.

[0053] Furthermore, in Figure 1In this configuration, the load unit has three parallel branches. The first branch contains a capacitor; the second branch contains a series resistor and a switching transistor; and the third branch contains a series resistor and a Zener diode. Additionally, a Zener node is located between the resistor and Zener diode in the second branch, and both the drive unit and the switching transistor are connected to this Zener node.

[0054] An active discharge method for an electric vehicle, used in the aforementioned active discharge system for an electric vehicle, includes the following steps:

[0055] Before the low-voltage power failure, the low-voltage MCU unit transmits an active discharge execution signal to energize the low-voltage discharge line.

[0056] Powering the high-voltage power supply line

[0057] When the low-voltage power fails, the low-voltage MCU unit executes a discharge abnormality diagnostic signal;

[0058] The voltage information of the positive and negative busbars is detected by a high-voltage detection unit.

[0059] Voltage information is transmitted through the isolation unit;

[0060] If the voltage of the positive and negative busbars drops to the target voltage (i.e., the rated voltage of the low-voltage discharge line), the low-voltage discharge line is energized and the high-voltage power supply line is shut off.

[0061] Conversely, the low-voltage discharge line is turned off, and the high-voltage power supply line is energized.

[0062] Furthermore, before energizing the low-voltage discharge line during a low-voltage power outage, the following steps are included:

[0063] Voltage information is transmitted to the delay circuit unit through the isolation unit;

[0064] The voltage drop of the positive and negative busbars is delayed within a set time (optional 200ms) by a delay circuit unit.

[0065] It should be noted that before the low-voltage power failure, the current on the low-voltage side flows through the low-voltage MCU unit to the isolation unit, logic management unit, and drive unit. When the low-voltage power failure occurs, the voltage MCU unit detects the discharge anomaly and then obtains the voltage of the positive bus through the high-voltage detection unit. If the voltage is high, the isolation unit will transmit a control signal to the delay circuit unit. The delay circuit unit will then delay for 200ms to wait for the positive bus voltage to drop. After the voltage drops, the emergency power supply unit can supply power to the delay circuit unit, logic management unit, and drive unit.

[0066] It should be further noted that, when performing active discharge, the signal timing on the high-voltage side (positive bus side) can be referenced. Figure 2 As shown in the figure, the specific explanation is as follows.

[0067] 1) t0~t1 stage:

[0068] At time t0, both the high and low voltage sides are in normal power supply state. The level state of the delay circuit unit is normally low and the delay logic is not triggered. The high voltage side receives the discharge enable signal from the low voltage MCU unit, which causes the high voltage side control logic signal to flip. Since the high voltage main contactor is not disconnected, the bus voltage does not change.

[0069] 2) After t1:

[0070] At time t1, the high-voltage side receives an active discharge signal command from the low-voltage side. The high-voltage side receives a discharge anomaly diagnostic signal from the low-voltage MCU unit, causing a level change and activating the drive unit. Since the main contactor is completely disconnected, the bus voltage rapidly drops to a safe level. The low-voltage detection unit is at a high level, and the low-voltage MCU unit identifies it as a continuous discharge state.

[0071] like Figure 3 The diagram shown is the timing diagram for low-voltage power failure, as detailed below:

[0072] t0~t1 stage:

[0073] During stage t0, both the high and low voltage sides are in normal power supply state. The discharge enable signal on the high voltage side is also in the disabled state, and no discharge enable signal is output. The drive unit does not execute the discharge logic, and the resistor is in an unloaded state. At this time, the bus voltage remains unchanged at the given value, and the low voltage MCU recognizes it as an undischarged state. Stages t1 to t2:

[0074] During phase t1, the low-voltage side is in a low-voltage power-off state, and low-voltage power is provided by the emergency power supply unit. After the low-voltage power-off, the delay signal of the delay circuit unit is triggered, and the drive logic is controlled by the delay signal to discharge after a delay of 200ms. At this time, the discharge command of the low-voltage MCU unit is in the enabled state. After receiving the discharge command, the high-voltage side performs a level flip. Since the high-voltage contactor is not disconnected, the bus voltage does not change, and the low-voltage MCU recognizes it as an undischarged state.

[0075] 3) After stage t2:

[0076] Both low-voltage sides of t2 are in a low-voltage power-off state, with low-voltage power supplied by the emergency power supply unit. The delayed turn-on logic rises to a high level after a 200ms delay. Due to the main contactor opening, the bus voltage drops, and the discharge signal level flips. The high-voltage detection unit is at a low level, and the low-voltage MCU identifies it as a continuous discharge state.

[0077] It should be noted that in this invention, by building an active discharge logic unit circuit on the high-voltage side, the traditional low-voltage active discharge is functionally upgraded. This upgrade ensures that after a low-voltage power failure, a complete hardware discharge logic on the high-voltage side can achieve self-protection against abnormal discharge and rapid and effective maintenance of normal discharge. It boasts advantages such as high logic adaptability and low design cost, and generates a 200ms discharge logic delay time during an abnormal low-voltage power failure, providing sufficient time for the vehicle's high-voltage contactor to fully disconnect. This prevents unintended consequences to the discharge resistor and discharge MOSFET (switching transistor) caused by active discharge before the high-voltage contactor is fully disconnected. Furthermore, it effectively meets the stringent high-voltage safety requirements for active discharge.

[0078] In the event of an abnormal power failure on the low-voltage side, the controller can be backed up by emergency power supply from the high-voltage side and managed for drive logic. A 200ms discharge logic delay is introduced after the low-voltage power failure, providing sufficient time for the high-voltage contactor of the entire vehicle to fully disconnect. This prevents unintended consequences to the discharge resistor and discharge MOSFET caused by active discharge before the high-voltage contactor is fully disconnected. When the main contactor fully disconnects after the 200ms delay, a continuous discharge state can be switched to achieve rapid charge dissipation, ensuring reliable and safe vehicle operation.

[0079] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electric vehicle active discharge system, comprising: The utility model relates to a kind of active discharge system of electric vehicle, including: Load unit, provided with switch tube, connected with positive and negative bus bar; High-voltage power supply circuit, two ends are connected with positive and negative bus bar respectively, provided with series-connected emergency power supply unit and logic management unit; Low-voltage discharge circuit, one end is connected with low-voltage MCU unit, the other end is connected switch tube, provided with isolation unit, the logic management unit and drive unit in series; High-voltage detection unit, one end is connected with positive bus bar, the other end is connected with the isolation unit; Delay circuit unit is connected with the emergency power supply unit, the logic management unit and the isolation unit respectively.

2. An active discharging system for an electric vehicle as claimed in claim 1, wherein, The load unit includes several parallel branches; Among them, at least one branch is provided with capacitor; At least one branch is provided with series-connected resistance and switch tube; At least one branch is provided with series-connected resistance and diode.

3. An active discharging system for an electric vehicle as claimed in claim 2, wherein, The load unit is provided with three parallel branches; Among them, the first branch is provided with capacitor; The second branch is provided with series-connected resistance and switch tube; The third branch is provided with series-connected resistance and voltage stabilizing diode.

4. The active discharging system of claim 3, wherein, The resistance and voltage stabilizing diode are provided with voltage stabilizing node, and the drive unit and switch tube are connected with the voltage stabilizing node.

5. An active discharging system for an electric vehicle as claimed in any one of claims 1 to 4, wherein, The drive unit is also connected with bus bar negative pole.

6. An electric vehicle active discharge method, characterized by, A kind of active discharge system of electric vehicle for any one of claims 1-5, including the following steps: When low-voltage power failure, low-voltage MCU unit executes discharge abnormal diagnosis signal; Voltage information of positive and negative bus bar is detected by high-voltage detection unit; Voltage information is transmitted by isolation unit; If the voltage of positive and negative bus bar drops to target voltage, low-voltage discharge circuit is powered on, and high-voltage power supply circuit is turned off; Conversely, low-voltage discharge circuit is turned off, and high-voltage power supply circuit is powered on.

7. The method of claim 6, wherein the method further comprises: The target voltage is the rated voltage of low-voltage discharge circuit.

8. The method of claim 6, wherein the method further comprises: Including the following steps: Before low-voltage power failure, active discharge execution signal is transmitted by low-voltage MCU unit, so that low-voltage discharge circuit is powered on; High-voltage power supply circuit is powered on.

9. The method of claim 6, wherein the method further comprises: Before low-voltage power failure, when low-voltage discharge circuit is powered on, including the following steps: Voltage information is transmitted to delay circuit unit by isolation unit; Voltage drop of positive and negative bus bar is delayed by delay circuit unit within set time.

10. The method of claim 9, wherein the method further comprises: The set time is 200ms.

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