PFC bus capacitor discharging device and method and vehicle

Abstract

The invention discloses a PFC bus capacitor discharging device and method and a vehicle, the PFC bus capacitor discharging device is integrated in a three-phase vehicle-mounted charger, and the PFC bus capacitor discharging device comprises a control module, a first bridge arm, a second bridge arm, a first controllable switch K1, a first power inductor L11, a first pre-charging resistor R1, a second controllable switch K2, a second power inductor L21, a second pre-charging resistor R2 and a first mode switching controllable switch K4. When the PFC bus capacitor needs to be discharged, the control module controls a first mode switching controllable switch K4 to be switched on, a first controllable switch K1 to be switched off or switched on, and a second controllable switch K2 to be switched off or switched on, and controls an upper switch tube Q1 of a first bridge arm and a lower switch tube Q4 of a second bridge arm to be switched on or an upper switch tube Q3 of the second bridge arm and a lower switch tube Q2 of the first bridge arm to be switched on. And a PFC bus capacitor discharge loop is further formed. Under the condition that an extra discharge circuit is not introduced, rapid and safe discharge is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric vehicle charging and discharging, and in particular relates to a PFC bus capacitor discharging device, method and vehicle. Background Art

[0002] In the existing on-board charger design technology, the PFC (Power Factor Correction) topology architecture is mostly used. By controlling the on and off of the switch tube, the input AC power is converted into high-voltage DC power with a high power factor. The DC power is then converted into a wide range of high-voltage DC power that can be used for battery charging through the post-stage DCDC isolation conversion module. Based on the PFC+DCDC bidirectional hardware architecture, the control method can also be changed to achieve reverse transmission of electric energy, that is, the DC power of the car power battery is inverted into AC power, and the function of the car power battery to output AC power to the outside is realized.

[0003] During the operation of the three-phase on-board charger, the PFC bus capacitor used for energy storage and filtering will store high-voltage electric energy. To ensure the stability of the input voltage of the subsequent DCDC isolation conversion module, the PFC bus capacitor capacity is mostly designed to be 500uF or above. After the three-phase on-board charger is shut down, if there is no load, the PFC bus capacitor will remain in a high-voltage state for a long time. If it is not discharged in time, there will be certain safety hazards to the product itself and the user. Therefore, measures need to be taken to release the electric energy stored in the PFC bus capacitor in time after the three-phase on-board charger is shut down.

[0004] CN116742937A discloses a method, device, electronic device and storage medium for discharging a vehicle-mounted charger, which turns on two power devices (i.e., switch tubes) of a bridge arm at the same time, and the two power devices of the bridge arm are regarded as two resistors connected in parallel to the positive and negative electrodes of the AC end capacitor, thereby forming a discharge current loop; the electric energy in the AC end capacitor is consumed by the two resistors (i.e., the internal resistance of the two power devices of the bridge arm), thereby reducing the voltage of the AC end capacitor, and the discharge operation can be stopped after reaching a safe voltage. Although it does not introduce an additional discharge circuit, it is only suitable for unidirectional vehicle-mounted chargers, and the discharge object implemented is the AC end capacitor rather than the bus capacitor; in addition, it only uses the internal resistance of the two power devices to consume electric energy to achieve discharge. The internal resistance of the power device after turning on is small, and the resistance value used to consume electric energy after being connected in parallel is even smaller, the discharge speed is slow, and rapid discharge cannot be achieved, and the safety is not high. Summary of the invention

[0005] The object of the present invention is to provide a PFC bus capacitor discharge device, method and vehicle, which are suitable for a three-phase on-board charger to quickly discharge the PFC bus capacitor, thereby improving discharge safety without introducing an additional discharge circuit.

[0006] In the first aspect, the present invention provides a PFC bus capacitor discharge device, which is integrated in a three-phase on-board charger (i.e., is composed of a part of the circuit of the three-phase on-board charger), including: a control module, a first bridge arm connected in parallel with the PFC bus capacitor and with the midpoint connected to the first phase line L1, and a second bridge arm connected in parallel with the second phase line L2, a first controllable switch K1 and a first power inductor L11 connected in series on the first phase line L1, a first pre-charging resistor R1 connected in parallel with the first controllable switch K1, a second controllable switch K2 and a second power inductor L21 connected in series on the second phase line L2, a second pre-charging resistor R2 connected in parallel with the second controllable switch K2, and a first mode switching controllable switch K4. The first mode switching controllable switch K4 is located between the AC input terminal and the first controllable switch K1 and the second controllable switch K2, one end of the first mode switching controllable switch K4 is connected to the first phase line L1, and the other end of the first mode switching controllable switch K4 is connected to the second phase line L2. When the control module determines that the PFC bus capacitor needs to be discharged according to the size of the PFC bus capacitor voltage (i.e., the voltage across the PFC bus capacitor, corresponding to the electric energy stored in the PFC bus capacitor), the control module controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be opened or closed, and the second controllable switch K2 to be closed or opened, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to be turned on, or the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on, thereby forming different PFC bus capacitor discharge loops.

[0007] In the second aspect, the present invention provides six PFC bus capacitor discharge methods, all of which use the above-mentioned PFC bus capacitor discharge device. When the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than the preset voltage threshold, it means that the PFC bus capacitor needs to be discharged. The specific implementation methods of the six PFC bus capacitor discharge methods are as follows:

[0008] The first PFC bus capacitor discharge method includes: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to disconnect, and the second controllable switch K2 to disconnect, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to conduct according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the first pre-charging resistor R1 and the second pre-charging resistor R2. During the discharge process, the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm are kept in the off state.

[0009] The second PFC bus capacitor discharge method includes: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than the preset voltage threshold, the control module controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to close, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to conduct according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, and the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the first pre-charging resistor R1. During this discharge process, the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm are always kept in the off state.

[0010] The third PFC bus capacitor discharge method includes: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than the preset voltage threshold, the control module controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to close, and the second controllable switch K2 to open, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to turn on according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the second pre-charging resistor R2 consumes the electric energy stored in the PFC bus capacitor. During this discharge process, the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm are always kept in the off state.

[0011] The fourth PFC bus capacitor discharge method includes: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to open, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to conduct according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the first pre-charging resistor R1 and the second pre-charging resistor R2. During the discharge process, the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm are kept in the off state.

[0012] The fifth PFC bus capacitor discharge method includes: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to close, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to conduct according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, and the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the first pre-charging resistor R1. During this discharge process, the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm are always kept in the off state.

[0013] The sixth PFC bus capacitor discharge method includes: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be closed, and the second controllable switch K2 to be disconnected, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on according to the preset frequency f and the preset duty cycle D. The electric energy is output from the positive electrode of the PFC bus capacitor, passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the second pre-charging resistor R2. During this discharge process, the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm are always kept in the off state.

[0014] Preferably, if any one of conditions 1a to 1d is met, it means that the three-phase on-board charger is in a stopped state; wherein,

[0015] Condition 1a: When the charging gun is in the plugged-in state, charging stops after the control module sends a stop charging command.

[0016] Condition 1b: Charging stops after the charging gun is unplugged.

[0017] Condition 1c: When the discharge gun is in the plugged-in state, the discharge stops after the control module issues a stop discharge output command.

[0018] Condition 1d: Discharging stops after the discharge gun is pulled out.

[0019] Preferably, the value range of the preset frequency f is: f≤1kHz; the value range of the preset duty cycle D is 50% to 100%.

[0020] In a third aspect, the present invention provides a vehicle, comprising the above-mentioned PFC bus capacitor discharge device.

[0021] The present invention is applicable to a three-phase on-board charger. Without introducing an additional discharge circuit and increasing product cost, the first pre-charging resistor R1 and / or the second pre-charging resistor R2 are reasonably reused to consume the electric energy stored in the PFC bus capacitor, and the discharge current is limited within a safe threshold range, without any impact on the reliability of the device and the product, thereby achieving the purpose of fast and safe discharge, improving the discharge safety and reliability, and having stronger engineering applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the principle architecture block diagram of the three-phase on-board charger.

[0023] Figure 2 This is a partial circuit schematic diagram of a three-phase on-board charger.

[0024] Figure 3 Schematic diagram of power flow in the three-phase working mode of a three-phase on-board charger.

[0025] Figure 4 Schematic diagram of power flow in single-phase working mode of three-phase on-board charger.

[0026] Figure 5 This is a flow chart of the first PFC bus capacitor discharging method in an embodiment of the present invention.

[0027] Figure 6 Schematic diagram of a first PFC bus capacitor discharge circuit in an embodiment of the present invention.

[0028] Figure 7 This is a flow chart of a second PFC bus capacitor discharging method in an embodiment of the present invention.

[0029] Figure 8 Schematic diagram of a second PFC bus capacitor discharge circuit in an embodiment of the present invention.

[0030] Fig. 9 This is a flow chart of a third PFC bus capacitor discharging method in an embodiment of the present invention.

[0031] Fig.10 Schematic diagram of a third PFC bus capacitor discharge circuit in an embodiment of the present invention.

[0032] Fig.11 This is a flow chart of a fourth PFC bus capacitor discharging method in an embodiment of the present invention.

[0033] Fig.12 Schematic diagram of a fourth PFC bus capacitor discharge circuit in an embodiment of the present invention.

[0034] Fig.13 This is a flow chart of a fifth PFC bus capacitor discharging method in an embodiment of the present invention.

[0035] Fig.14 Schematic diagram of a fifth PFC bus capacitor discharge circuit in an embodiment of the present invention.

[0036] Fig.15 This is a flow chart of a sixth PFC bus capacitor discharging method in an embodiment of the present invention.

[0037] Fig.16 Schematic diagram of a sixth PFC bus capacitor discharge circuit in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to enable a more detailed understanding of the features and technical contents of the embodiments of the present invention, the implementation of the embodiments of the present invention is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not intended to limit the embodiments of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0040] In the following description, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0041] like Figure 1 , Figure 2 As shown, the three-phase on-board charger includes an AC input terminal module 10, a pre-charging module 20, a PFC power conversion module 30, a DCDC isolation conversion module 40, a high-voltage DC terminal (i.e., a battery terminal) 50, and a control module 1. Under the control of the control module 1, when the three-phase on-board charger is charging, the AC power is charged from the AC input terminal module 10 through the pre-charging module 20, the PFC power conversion module 30, the DCDC isolation conversion module 40, and the high-voltage DC terminal (i.e., the battery terminal) 50 to the high-voltage power battery; when the three-phase on-board charger is discharging, the power circuit is just reversed.

[0042] The control module 1 is responsible for sampling, driving, and protecting related signals. The control module 1 collects the AC voltage and AC current of the AC input terminal module 10, the PFC bus capacitor voltage (i.e., the PFC DC bus terminal voltage), the high-voltage DC voltage, and the high-voltage DC current through the sampling circuit, and outputs a PWM signal to control the switch tube in the PFC power conversion module and the switch tube in the DCDC isolation conversion module.

[0043] The AC input terminal module 10 includes an AC input terminal 101 and a first mode switching controllable switch K4, a second mode switching controllable switch K5, and a third mode switching controllable switch K3. The pre-charging module 20 includes a first controllable switch K1, a first pre-charging resistor R1 connected in parallel with the first controllable switch K1, a second controllable switch K2, and a second pre-charging resistor R2 connected in parallel with the second controllable switch K2. The PFC power conversion module 30 includes a first power inductor L11, a second power inductor L21, a third power inductor L31, a three-phase bridge arm 301, and a PFC bus capacitor 302 connected in parallel with the three-phase bridge arm 301. The first bridge arm of the three-phase bridge arm 301 is formed by connecting an upper switch tube Q1 and a lower switch tube Q2, the second bridge arm of the three-phase bridge arm 301 is formed by connecting an upper switch tube Q3 and a lower switch tube Q4, and the third bridge arm of the three-phase bridge arm 301 is formed by connecting an upper switch tube Q5 and a lower switch tube Q6.

[0044] One end of the first phase line L1 is connected to the AC input terminal 101, and the other end is connected to the midpoint of the first bridge arm (i.e., the connection point between the upper switch tube Q1 and the lower switch tube Q2). One end of the second phase line L2 is connected to the AC input terminal 101, and the other end is connected to the midpoint of the second bridge arm (i.e., the connection point between the upper switch tube Q3 and the lower switch tube Q4). One end of the third phase line L3 is connected to the AC input terminal 101, and the other end is connected to the midpoint of the third bridge arm (i.e., the connection point between the upper switch tube Q5 and the lower switch tube Q6). The first controllable switch K1 and the first power inductor L11 are connected in series on the first phase line L1, the first controllable switch K1 is close to the AC input terminal 101, and the first power inductor L11 is close to the first bridge arm. The second controllable switch K2 and the second power inductor L21 are connected in series on the second phase line L2, the second controllable switch K2 is close to the AC input terminal 101, and the second power inductor L21 is close to the second bridge arm. The third power inductor L31 is connected in series to the third phase line L3, and the third mode switching controllable switch K3 is connected in parallel to the third power inductor L31. The first mode switching controllable switch K4 is located between the AC input terminal 101 and the first controllable switch K1 and the second controllable switch K2, and one end of the first mode switching controllable switch K4 is connected to the first phase line L1 and the other end is connected to the second phase line L2. The second mode switching controllable switch K5 is connected to the neutral line N, and one end of the neutral line N is connected to the AC input terminal 101 and the other end is connected to the third phase line L3.

[0045] The control module 1 is connected to the control end of the first controllable switch K1 to control the first controllable switch K1 to be closed / opened. The control module 1 is connected to the control end of the second controllable switch K2 to control the second controllable switch K2 to be closed / opened. The control module 1 is connected to the control end of the first mode switching controllable switch K4 to control the first mode switching controllable switch K4 to be closed / opened. The control module 1 is connected to the control end of the second mode switching controllable switch K5 to control the second mode switching controllable switch K5 to be closed / opened. The control module 1 is connected to the control end of the third mode switching controllable switch K3 to control the third mode switching controllable switch K3 to be closed / opened. The control module is connected to the control end of the upper switch tube Q1, the control end of the lower switch tube Q2, the control end of the upper switch tube Q3, the control end of the lower switch tube Q4, the control end of the upper switch tube Q5, and the control end of the lower switch tube Q6, and respectively controls the upper switch tube Q1 to be turned on / off, the lower switch tube Q2 to be turned on / off, the upper switch tube Q3 to be turned on / off, the lower switch tube Q4 to be turned on / off, the upper switch tube Q5 to be turned on / off, and the lower switch tube Q6 to be turned on / off.

[0046] In some embodiments, the first mode switching controllable switch K4 , the second mode switching controllable switch K5 , the third mode switching controllable switch K3 , the first controllable switch K1 , and the second controllable switch K2 may be relays.

[0047] In some embodiments, the upper switch tube Q1 , the lower switch tube Q2 , the upper switch tube Q3 , the lower switch tube Q4 , the upper switch tube Q5 , and the lower switch tube Q6 may be MOS tubes or IGBTs.

[0048] The three-phase on-board charger supports three-phase AC charging and single-phase AC charging, which is achieved by controlling the first mode switching controllable switch K4, the second mode switching controllable switch K5, and the third mode switching controllable switch K3.

[0049] When the external three-phase AC power is charged normally, the control module 1 controls the first mode switching controllable switch K4 to be disconnected, the second mode switching controllable switch K5 to be disconnected, and the third mode switching controllable switch K3 to be disconnected. After pre-charging, the first controllable switch K1 is controlled to be closed, and the second controllable switch K2 is controlled to be closed. The first phase line L1, the second phase line L2, and the third phase line L3 respectively complete the AC / DC voltage conversion and power factor correction through the first power inductor L11, the second power inductor L21, the third power inductor L31, the three-phase bridge arm, and the PFC bus capacitor. The power flow of the three-phase AC charging is shown in FIG. Figure 3 .

[0050] When the external single-phase AC power is charged normally, according to the national standard requirements, the first phase line L1 and the neutral line N of the AC input are defaulted to work, and the control module 1 controls the first mode switching controllable switch K4 to be closed, the second mode switching controllable switch K5 to be closed, and the third mode switching controllable switch K3 to be closed. After pre-charging, the first controllable switch K1 is controlled to be closed and the second controllable switch K2 is controlled to be closed to form a two-way staggered parallel circuit architecture. The first controllable switch K1, the first power inductor L11, the upper switch tube Q1, and the lower switch tube Q2 constitute the first high-frequency power conversion bridge arm, the second controllable switch K2, the second power inductor L21, the upper switch tube Q3, and the lower switch tube Q4 constitute the second high-frequency power conversion bridge arm, the upper switch tube Q5, the upper switch tube Q6, the third mode switching controllable switch K3, and the second mode switching controllable switch K5 constitute the industrial frequency power conversion bridge arm, completing the AC / DC voltage conversion and power factor correction when single-phase input is used. For the power flow of single-phase AC power charging, refer to Figure 4 .

[0051] The AC input end of the three-phase on-board charger is the input interface of the charger in the charging state, and is the output interface of the charger in the discharging state (inversion). When the three-phase on-board charger changes from the working state (whether the charging state or the discharging state) to the stopping state, the DCDC isolation conversion module 40, the PFC power conversion module 30, and the pre-charging module 20 will stop working in sequence according to the shutdown sequence, and the electric energy stored in the PFC bus capacitor 302 has not been released in time, so it has a certain high voltage.

[0052] The control module 1, the first controllable switch K1, the first pre-charging resistor R1, the first power inductor L11, the first bridge arm, the second controllable switch K2, the second pre-charging resistor R2, the second power inductor L21, the second bridge arm and the PFC bus capacitor 302 in the above-mentioned three-phase on-board charger are used to form a PFC bus capacitor discharge device. The PFC bus capacitor discharge method in the embodiment of the present invention adopts the PFC bus capacitor discharge device. When the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than the preset voltage threshold, it means that the PFC bus capacitor needs to be discharged. In some embodiments, if any of the conditions 1a to 1d is met, it means that the three-phase on-board charger is in a stopped state; wherein, condition 1a: when the charging gun is in the plug-in state, the control module 1 stops charging after issuing a stop charging instruction; condition 1b: charging stops after the charging gun is unplugged; condition 1c: when the discharge gun is in the plug-in state, the control module 1 stops discharging after issuing a stop discharge output instruction; condition 1d: discharge stops after the discharge gun is unplugged. In some embodiments, the preset voltage threshold is 60V.

[0053] like Figure 5 As shown, the first PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0054] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0055] The second step is to control the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be opened, and the second controllable switch K2 to be opened, and control the upper switch tube Q1 and the lower switch tube Q4 to be turned on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0056] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0057] Step 4: Control the first mode switching controllable switch K4 to be turned off, the upper switch tube Q1 to be turned off, the lower switch tube Q4 to be turned off, and then end.

[0058] like Figure 6 As shown, electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q1, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q4, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the electric energy stored in the PFC bus capacitor is consumed by the first pre-charging resistor R1 and the second pre-charging resistor R2.

[0059] The upper switch tube Q1 and the lower switch tube Q4 are turned on at the same time for D*Ts, and then turned off; after (1-D)*Ts time, the upper switch tube Q1 and the lower switch tube Q4 are turned on at the same time for D*Ts time, and then turned off, and this cycle is repeated. Wherein, Ts represents the PWM signal period. After the control module 1 collects that the voltage of the PFC bus capacitor drops to a safe voltage (for example, less than or equal to 60V), the control module 1 stops sending the PWM signal and completes the discharge of the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q3, the lower switch tube Q2, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state. Since the first pre-charging resistor R1 and the second pre-charging resistor R2 are used as charging surge current limits for the PFC bus capacitor during normal startup, winding resistors or power resistors such as PTC and NTC are generally selected, and the instantaneous power resistance capacity is very strong; therefore, it can fully withstand the discharge power of the PFC bus capacitor and meet the discharge speed, safety and reliability requirements of the PFC bus capacitor.

[0060] In some embodiments, the value range of the preset frequency f is: f≤1kHz; the value range of the preset duty cycle D is 50% to 100%.

[0061] The voltage calculation formula on the capacitor at any time when the PFC bus capacitor is discharged is: Among them, the capacitor discharge time constant τ=R*C, R is the discharge resistor, C is the capacity of the discharged capacitor, and Vc is the initial voltage of the PFC bus capacitor. Generally, after 3 to 5 time constants, the electricity on the capacitor will be basically discharged. When t=3τ, Uc(t)≈0.05Vc. The maximum voltage of the PFC bus capacitor generally does not exceed 800V. Calculated based on the maximum voltage of 800V, the residual voltage of the PFC bus capacitor after 3τ is 0.05*800V=40V. That is: after 3τ discharge time, the residual voltage on the PFC bus capacitor can be maintained within the 60V safe voltage range. Taking the equivalent capacitance value C=500uF of the PFC bus capacitor 302, the resistance value of the first pre-charging resistor R1 is equal to 100Ω, and the resistance value of the second pre-charging resistor R2 is equal to 100Ω as an example, the discharge time under different preset frequencies f and different preset duty cycles D is explained.

[0062] For example: D = 100%, f = 0 (i.e., the PWM control signal is continuously at a high level), the upper switch Q1 and the lower switch Q4 remain turned on during the entire discharge process of the PFC bus capacitor 302 until the discharge reaches a safe voltage. At this time, the discharge time is calculated according to the capacitor discharge formula:

[0063] t=3τ=3*(100Ω+100Ω)*500uF=0.3s

[0064] For example: D = 50%, f = 1kHz (i.e. the PWM control signal is a periodic signal), then the voltage of the PFC bus capacitor at any time is: After n cycles, the residual voltage of the PFC bus capacitor is:

[0065]

[0066] Taking n=600 can discharge the capacitor voltage to below 40V, that is, after 600 PWM discharge cycles (i.e. after 0.6s), the residual voltage of the PFC bus capacitor is:

[0067] The discharge time in the above two cases is less than 1s, and the discharge time is fast. And because the power resistor (i.e., the first pre-charging resistor R1 and the second pre-charging resistor R2) is connected in series in the discharge circuit, the discharge current is effectively controlled, and has no impact on the reliability of the device and product.

[0068] like Figure 7 As shown, the second PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0069] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0070] The second step is to control the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to close, and control the upper switch tube Q1 and the lower switch tube Q4 to turn on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0071] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0072] Step 4: Control the first mode switching controllable switch K4 to be turned off, the second controllable switch K2 to be turned off, the upper switch tube Q1 to be turned off, the lower switch tube Q4 to be turned off, and then end.

[0073] like Figure 8 As shown, the electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q1, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, the lower switch tube Q4, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the first pre-charging resistor R1 consumes the electric energy stored in the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q3, the lower switch tube Q2, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state.

[0074] like Fig. 9 As shown, the third PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0075] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0076] The second step is to control the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be closed, and the second controllable switch K2 to be opened, and control the upper switch tube Q1 and the lower switch tube Q4 to be turned on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0077] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0078] Step 4: Control the first mode switching controllable switch K4 to be turned off, the first controllable switch K1 to be turned off, the upper switch tube Q1 to be turned off, the lower switch tube Q4 to be turned off, and then end.

[0079] like Fig.10As shown, the electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q1, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q4, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the second pre-charging resistor R2 consumes the electric energy stored in the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q3, the lower switch tube Q2, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state.

[0080] like Fig.11 As shown, the fourth PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0081] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0082] The second step is to control the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be opened, and the second controllable switch K2 to be opened, and control the upper switch tube Q3 and the lower switch tube Q2 to be turned on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0083] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0084] Step 4: Control the first mode switching controllable switch K4 to be turned off, the upper switch tube Q3 to be turned off, the lower switch tube Q2 to be turned off, and then end.

[0085] like Fig.12 As shown, the electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q3, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q2, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the first pre-charging resistor R1 and the second pre-charging resistor R2 consume the electric energy stored in the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q1, the lower switch tube Q4, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state.

[0086] like Fig.13 As shown, the fifth PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0087] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0088] The second step is to control the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be disconnected, and the second controllable switch K2 to be closed, and the upper switch tube Q3 and the lower switch tube Q2 to be turned on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0089] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0090] Step 4: Control the first mode switching controllable switch K4 to be turned off, the second controllable switch K2 to be turned off, the upper switch tube Q3 to be turned off, the lower switch tube Q2 to be turned off, and then end.

[0091] like Fig.14 As shown, the electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q3, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, and the lower switch tube Q2, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the first pre-charging resistor R1 consumes the electric energy stored in the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q1, the lower switch tube Q4, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state.

[0092] like Fig.15 As shown, the sixth PFC bus capacitor discharge method is executed by the control module 1 and includes:

[0093] The first step is to determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold when the three-phase on-board charger stops working. If so, execute the second step, otherwise end.

[0094] The second step is to control the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be closed, and the second controllable switch K2 to be opened, and control the upper switch tube Q3 and the lower switch tube Q2 to be turned on according to the preset frequency f and the preset duty cycle D, and then execute the third step.

[0095] Step 3: determine whether the PFC bus capacitor voltage is greater than a preset voltage threshold, if so, return to step 2, otherwise, execute step 4.

[0096] Step 4: Control the first mode switching controllable switch K4 to be turned off, the first controllable switch K1 to be turned off, the upper switch tube Q3 to be turned off, the lower switch tube Q2 to be turned off, and then end.

[0097] like Fig.16As shown, the electric energy is output from the positive electrode of the PFC bus capacitor 302, passes through the upper switch tube Q3, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q2, and then returns to the negative electrode of the PFC bus capacitor 302, forming a PFC bus capacitor discharge loop, and the second pre-charging resistor R2 consumes the electric energy stored in the PFC bus capacitor. During this discharge process, the control module 1 will control the upper switch tube Q1, the lower switch tube Q4, the upper switch tube Q5, and the lower switch tube Q6 to remain in the off state.

[0098] An embodiment of the present invention further provides a vehicle, which includes the above-mentioned PFC bus capacitor discharge device.

[0099] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A PFC busbar capacitor discharge device, integrated in a three-phase on-board charger, comprising a control module (1), characterized in that: Also includes: A first bridge arm connected in parallel with the PFC bus capacitor (302) and having its midpoint connected to the first phase line L1, and a second bridge arm connected in series with its midpoint to the second phase line L2, a first controllable switch K1 and a first power inductor L11 connected in series on the first phase line L1, a first pre-charging resistor R1 connected in parallel with the first controllable switch K1, a second controllable switch K2 and a second power inductor L21 connected in series on the second phase line L2, a second pre-charging resistor R2 connected in parallel with the second controllable switch K2, and a first mode switching controllable switch K4; the first mode switching controllable switch K4 is located between the AC input terminal (101) and the first controllable switch K1 and the second controllable switch K2, and has one end connected to the first phase line L1 and the other end connected to the second phase line L2; When the PFC bus capacitor needs to be discharged, the control module (1) controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be opened or closed, the second controllable switch K2 to be closed or opened, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to be turned on, or the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on, so as to form a PFC bus capacitor discharge loop.

2. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to open, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to turn on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

3. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to close, the first controllable switch K1 to open, and the second controllable switch K2 to close, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to be turned on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, and the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

4. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger stops working, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be closed, and the second controllable switch K2 to be opened, and controls the upper switch tube Q1 of the first bridge arm and the lower switch tube Q4 of the second bridge arm to be turned on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q1 of the first bridge arm, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q4 of the second bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

5. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be disconnected, and the second controllable switch K2 to be disconnected, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

6. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be disconnected, and the second controllable switch K2 to be closed, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first pre-charging resistor R1, the first mode switching controllable switch K4, the second controllable switch K2, the second power inductor L21, the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

7. A PFC bus capacitor discharge method, characterized in that: The PFC bus capacitor discharge device as claimed in claim 1 is used, and the method comprises: when the three-phase on-board charger is in a stopped state, if the PFC bus capacitor voltage is greater than a preset voltage threshold, the control module (1) controls the first mode switching controllable switch K4 to be closed, the first controllable switch K1 to be closed, and the second controllable switch K2 to be opened, and controls the upper switch tube Q3 of the second bridge arm and the lower switch tube Q2 of the first bridge arm to be turned on according to the preset frequency f and the preset duty cycle D; the electric energy is output from the positive electrode of the PFC bus capacitor (302), passes through the upper switch tube Q3 of the second bridge arm, the first power inductor L11, the first controllable switch K1, the first mode switching controllable switch K4, the second pre-charging resistor R2, the second power inductor L21, and the lower switch tube Q2 of the first bridge arm, and then returns to the negative electrode of the PFC bus capacitor (302), thereby forming a PFC bus capacitor discharge loop.

8. The PFC bus capacitor discharge method according to any one of claims 2 to 7, characterized in that: If any of the conditions 1a to 1d is met, it means that the three-phase on-board charger is in a stopped state; Condition 1a: When the charging gun is in the plugged-in state, charging stops after the control module (1) issues a stop charging instruction; Condition 1b: Charging stops after the charging gun is pulled out; Condition 1c: When the discharge gun is in the plugged-in state, the discharge stops after the control module (1) issues a stop discharge output command; Condition 1d: Discharging stops after the discharge gun is pulled out.

9. The PFC bus capacitor discharge method according to any one of claims 2 to 7, characterized in that: The value range of the preset frequency f is: f≤1kHz; the value range of the preset duty cycle D is 50% to 100%.

10. A vehicle, characterized in that: It comprises the PFC bus capacitor discharge device as claimed in claim 1.

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