DC / DC converter, vehicle-mounted charger and electric vehicle

Abstract

The utility model discloses a DC / DC converter, a vehicle-mounted charger and an electric vehicle. The DC / DC converter comprises a chopping unit, a transformer and a rectifying unit. Wherein the bus capacitor is coupled with the chopping unit, the chopping unit is coupled with the primary side of the transformer, and the secondary side of the transformer is coupled with the rectifying unit; the chopping unit and the rectifying unit are both coupled to a controller. In the specific implementation, when the controller determines to discharge the bus capacitor, the controller can control the rectification unit to short-circuit the secondary side of the transformer and control the chopping unit to close the loop formed between the bus capacitor and the primary side of the transformer. By implementing the application, the cost can be reduced, and the safety is good.

Description

[0001] This application claims the priority of the Chinese patent application filed with the China Patent Office on September 26, 2021, with application number 202111129516.2 and application name “A discharge method for a bus capacitor and related equipment”, the entire contents of which are incorporated by reference in this application. Technical Field

[0002] The present application relates to the field of power supply technology, and in particular to a DC / DC converter, an on-board charger and an electric vehicle. Background Art

[0003] There is a large-capacity capacitor (i.e. bus capacitor) between the positive and negative bus bars of an electric vehicle. When the vehicle is no longer in use or fails, in order to ensure high-voltage safety, the voltage on the bus capacitor needs to be quickly reduced to below the safe voltage.

[0004] The methods used in the prior art can be found in Figure 1 ,like Figure 1 As shown, the prior art is to add a switch and a resistor between the positive and negative busbars. When the busbar capacitor needs to be actively discharged, the switch is closed, and the energy on the busbar capacitor can be consumed through the resistor. However, the prior art method of achieving active discharge of the busbar capacitor by adding a switch and a resistor is relatively costly. Summary of the invention

[0005] The present application provides a bus capacitor discharge method and related equipment, which can reduce costs and have good safety.

[0006] In the first aspect, an embodiment of the present application provides a method for discharging a bus capacitor, which is applicable to a DC / DC converter, and the DC / DC converter includes a chopper unit, a transformer, and a rectifier unit. Among them, the bus capacitor is coupled to the chopper unit, the chopper unit is coupled to the primary side of the transformer, and the secondary side of the transformer is coupled to the rectifier unit; the chopper unit and the rectifier unit are both coupled to the controller. In a specific implementation, when the controller determines to discharge the bus capacitor, it can control the rectifier unit to short-circuit the secondary side of the transformer, and control the chopper unit to close the loop formed between the bus capacitor and the primary side of the transformer. In an embodiment of the present application, the controller controls the rectifier unit to short-circuit the secondary side of the transformer and controls the chopper unit to close the loop formed between the bus capacitor and the primary side of the transformer. At this time, in addition to the on-impedance of the chopper unit and the impedance of the primary side of the transformer, the bus capacitor also passes through the equivalent on-impedance of the secondary side loop of the transformer to form a closed discharge loop. The embodiment of the present application does not need to add switches and resistors to realize active discharge of the capacitor, and the cost is low; and the state of the rectifier unit is controlled by the controller during the discharge of the bus capacitor, which can avoid the problem of excessive output voltage on the secondary side of the transformer due to the unstable state of the rectifier unit. In general, the implementation of the embodiment of the present application is low-cost and high-safety.

[0007] In combination with the first aspect, in a possible implementation manner, the controller may further control the rectifying unit to rectify the voltage on the secondary side of the transformer when determining to stop discharging the bus capacitor.

[0008] In combination with the first aspect, in a second possible implementation manner, the controller may determine to discharge the bus capacitor upon receiving an instruction to actively discharge the bus capacitor.

[0009] In combination with the first aspect, in a third possible implementation, the controller may determine to discharge the bus capacitor when it detects that the voltage across the bus capacitor is greater than a preset voltage threshold.

[0010] In combination with the first possible implementation manner of the first aspect, in a fourth possible implementation manner, the controller may determine to stop discharging the bus capacitor upon receiving an instruction to stop discharging the bus capacitor.

[0011] In combination with the first possible implementation of the first aspect, in a fifth possible implementation, the controller may determine to stop discharging the bus capacitor when it detects that the voltage across the bus capacitor is lower than a preset voltage threshold.

[0012] In combination with the first aspect or any one of the above possible implementations of the first aspect, in a sixth possible implementation, the above rectifier unit includes a first switch tube and a second switch tube. The secondary-side coupled rectifier unit of the above transformer can be specifically implemented as follows: one end of the secondary side of the transformer is coupled to the first end of the first switch tube, the other end of the secondary side of the transformer is coupled to the first end of the second switch tube, the second end of the first switch tube is coupled to the second end of the second switch tube, and the third end of the first switch tube and the third end of the second switch tube are both coupled to the above controller. The controller can control the first switch tube and the second switch tube to be turned on to realize that the rectifier unit short-circuits the secondary side of the transformer.

[0013] In combination with the sixth possible implementation of the first aspect, in a seventh possible implementation, the secondary side of the transformer includes a first end, a second end, and a third end. One end of the secondary side of the transformer is coupled to the first end of the first switch tube, and the other end of the secondary side of the transformer is coupled to the first end of the second switch tube. This can be specifically implemented as follows: the first end of the secondary side of the transformer is coupled to the first end of the first switch tube, and the second end of the secondary side of the transformer is coupled to the first end of the second switch tube; the second end of the first switch tube and the second end of the second switch tube are coupled to one end of the load, and the other end of the load is coupled to the third end of the secondary side of the transformer.

[0014] In combination with the seventh possible implementation of the first aspect, in an eighth possible implementation, the load includes a battery, and the DC / DC converter is arranged between the battery and the power battery, wherein the power battery is coupled to the bus capacitor and the chopper unit.

[0015] In combination with the eighth possible implementation of the first aspect, in a ninth possible implementation, the DC / DC converter further includes an isolating switch, which is coupled to the controller. The third end of the secondary side of the transformer is coupled to the battery through the isolating switch. When determining to discharge the bus capacitor, the controller controls the isolating switch to disconnect. By implementing the embodiment of the present application, the voltage backflow of the battery can be prevented, which is safe and reliable.

[0016] In combination with the sixth possible implementation of the first aspect, in the tenth possible implementation, the above-mentioned rectifier unit also includes a third switch tube and a fourth switch tube. The secondary-side coupled rectifier unit of the above-mentioned transformer can also be specifically implemented as follows: one end of the secondary side of the transformer is also coupled to the second end of the third switch tube, the other end of the secondary side of the transformer is also coupled to the second end of the fourth switch tube, the first end of the third switch tube and the first end of the fourth switch tube are coupled to one end of the load, and the other end of the load is coupled to the second end of the first switch tube and the second end of the second switch tube. The controller can realize that the rectifier unit short-circuits the secondary side of the transformer by controlling both the first switch tube and the second switch tube to be turned on, or controlling both the third switch tube and the fourth switch tube to be turned on. The embodiment of the present application provides another circuit diagram applicable to the discharge method of the bus capacitor, which improves the applicability of the embodiment of the present application.

[0017] In combination with the tenth possible implementation manner of the first aspect, in an eleventh possible implementation manner, the load includes a power factor correction circuit. The DC / DC converter is provided between the power factor correction circuit and the power battery, and the power battery is coupled to the bus capacitor and the chopper unit, the power factor correction circuit is coupled to the secondary side of the transformer through the rectifier unit, and the power factor correction circuit is in a non-operating state when the secondary side of the transformer is short-circuited.

[0018] In combination with the first aspect or any one of the above possible implementations of the first aspect, in a twelfth possible implementation, the above control chopping unit to close the loop formed by the bus capacitor and the primary side of the transformer can be specifically implemented as follows: the controller alternately sends a first control signal and a second control signal to the above chopping unit at a first preset frequency. The chopping unit includes a first bridge arm and a second bridge arm in parallel, and each bridge arm includes two switch tubes connected in series. The first control signal can control the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to be turned on, and control the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to be turned off; the second control signal controls the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to be turned off, and can control the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to be turned on.

[0019] In combination with the twelfth possible implementation manner of the first aspect, in the thirteenth possible implementation manner, the above-mentioned controller can also send the above-mentioned first control signal and the above-mentioned second control signal to the above-mentioned chopping unit alternately at a second preset frequency when determining to stop discharging the bus capacitor.

[0020] In combination with the first aspect or in combination with the first possible implementation of the first aspect, in a fourteenth possible implementation, the DC / DC converter further includes a first switch and a first resistor. Wherein, the two ends of the first switch and the first resistor connected in series are coupled between the two ends of the transformer. The controller can further short-circuit the secondary side of the transformer by controlling the first switch to close. By implementing the embodiment of the present application, the discharge speed of the bus capacitor is further improved.

[0021] In a second aspect, an embodiment of the present application provides a discharge device for a bus capacitor, the discharge device comprising: a transceiver, a controller and a memory, wherein the transceiver, the controller and the memory are connected via a bus system. The transceiver can receive and send instructions; the memory can store instructions; the controller can call the instructions stored in the above memory to execute the method steps in the first aspect or in any possible implementation method in combination with the first aspect.

[0022] In a third aspect, an embodiment of the present application provides an electric vehicle, which includes the discharge device provided in the second aspect and a power battery; wherein the discharge device can output a voltage to the power battery, or convert the output voltage of the power battery and provide it to a load in the electric vehicle.

[0023] It should be understood that the implementation and beneficial effects of the above-mentioned aspects of the present application can be referenced to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural block diagram of a part of the prior art for discharging bus capacitor;

[0025] Figure 2 A structural block diagram of bus capacitor discharge provided in an embodiment of the present application;

[0026] Figure 3 A circuit diagram for discharging a bus capacitor provided in an embodiment of the present application;

[0027] Figure 4 An equivalent circuit diagram of bus capacitor discharge provided in an embodiment of the present application;

[0028] Figure 5 Another circuit diagram of bus capacitor discharge provided in an embodiment of the present application;

[0029] Figure 6 Another structural block diagram of bus capacitor discharge provided in an embodiment of the present application;

[0030] Figure 7 A schematic diagram of the structure of a discharge device for a bus capacitor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The implementation of the technical solution of the present application is further described in detail below in conjunction with the accompanying drawings.

[0032] See also Figure 2 , Figure 2 A structural block diagram of the bus capacitor discharge provided in the embodiment of the present application. The bus capacitor discharge method provided in the embodiment of the present application can be applied to Figure 2 The DC / DC converter 21 shown in FIG. The DC / DC converter 21 includes a chopper unit 211, a transformer 212, and a rectifier unit 213. The bus capacitor 20 is coupled to the chopper unit 211, the chopper unit 211 is coupled to the primary side of the transformer 212, and the secondary side of the transformer 212 is coupled to the rectifier unit 213. The chopper unit 211 and the rectifier unit 213 are both coupled to the controller 22.

[0033] It should be pointed out first that the "coupling" described in this application refers to direct or indirect connection. For example, A and B are connected, which can be either A and B directly connected, or A and B indirectly connected through one or more other electrical components, for example, A and C can be directly connected, and C can be directly connected to B, so that A and B are connected through C.

[0034] The chopper unit 211 may be, for example, a full-bridge circuit, a half-bridge circuit, a BUCK converter, a BOOST converter, a BUCK-BOOST converter, or the like.

[0035] The rectifier unit 213 may be, for example, a half-bridge rectifier circuit, a full-bridge rectifier circuit, etc. It is understandable that the rectifier device in the rectifier unit is a controllable switch device such as a switch tube, and the on-off state may be controlled by the controller 22 .

[0036] The controller 22 can be, for example, a central processing unit (CPU), other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0037] The bus capacitor discharge method provided in the embodiment of the present application can be executed by the controller 22. In a specific implementation, when the controller 22 determines to discharge the bus capacitor 20, it controls the rectifier unit 213 to short-circuit the secondary side of the transformer 212, and controls the chopper unit 211 to close the loop formed between the bus capacitor 20 and the primary side of the transformer 212. It can be understood that the transformer 212 is not an ideal transformer and has a leakage inductance. When the secondary side of the transformer 212 is short-circuited, the secondary side of the transformer 212 and the on-impedance of the rectifier unit 213 can be sensed to the primary side of the transformer 212 through the secondary side of the transformer 212, that is, the equivalent on-impedance of the secondary side loop of the transformer 212 is present in the primary side loop of the transformer 212. Therefore, the bus capacitor 20 can form a closed discharge loop through the on-impedance of the chopper unit 211, the on-impedance of the primary side of the transformer 212, and the equivalent on-impedance of the secondary side loop of the transformer 212.

[0038] In some feasible implementations, the controller 22 may receive external instructions. For example, if the DC / DC converter 21 is provided in an electric vehicle, the controller 22 may receive instructions issued by a vehicle controller in the electric vehicle, such as an instruction to actively discharge the bus capacitor 20. When the controller 22 receives the instruction to actively discharge the bus capacitor 20, it determines to discharge the bus capacitor 20, which can be understood as the controller 22 entering the active discharge mode of the bus capacitor.

[0039] Further, in some feasible implementations, when the controller 22 determines to stop discharging the bus capacitor 20, it can be understood that the controller 22 exits the bus capacitor active discharge mode, and the controller 22 controls the rectifier unit 213 to rectify the voltage on the secondary side of the transformer 212. In other words, the rectifier unit 213 does not short-circuit the secondary side of the transformer 212 at this time. Exemplarily, when the voltage across the bus capacitor 20 is lower than the preset voltage threshold, the controller 22 determines to stop charging the bus capacitor 20. Optionally, the controller 22 may monitor the voltage across the bus capacitor 20, and determine to stop discharging the bus capacitor 20 when it is detected that the voltage across the bus capacitor 20 is lower than the preset voltage threshold. Alternatively, the vehicle controller in the electric vehicle may monitor the voltage across the bus capacitor 20, and send an instruction to stop discharging the bus capacitor to the controller 22 when it is detected that the voltage across the bus capacitor 20 is lower than the preset voltage threshold, and the controller 22 determines to stop charging the bus capacitor 20 when receiving the instruction to stop discharging.

[0040] In an embodiment of the present application, the controller controls the rectifier unit to short-circuit the secondary side of the transformer and controls the chopper unit to close the loop formed between the bus capacitor and the primary side of the transformer. At this time, in addition to the on-impedance of the chopper unit and the impedance of the primary side of the transformer, the bus capacitor also passes through the equivalent on-impedance of the secondary side loop of the transformer to form a closed discharge loop. The embodiment of the present application does not need to add switches and resistors to achieve active discharge of the capacitor, and the cost is low; and the state of the rectifier unit is controlled by the controller during the discharge of the bus capacitor, which can avoid the problem of excessive output voltage on the secondary side of the transformer due to the unstable state of the rectifier unit. In general, the implementation of the embodiment of the present application is low-cost and high-safety.

[0041] The active discharge of the bus capacitor is described below in conjunction with the circuit diagram provided in the embodiment of the present application.

[0042] In some possible implementations, see Figure 3 , Figure 3 A circuit diagram of bus capacitor discharge provided in an embodiment of the present application. Figure 3 As shown, the DC / DC converter 21a includes a chopper unit 211a, a transformer 212a and a rectifying unit 213a.

[0043] The rectifying unit 213a includes a first switch tube Q 31 And the second switch tube Q 32 The present application uses each switch tube as a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) for exemplary description. It should be understood that each switch tube may also be other semiconductor devices such as an Insulated Gate Bipolar Transistor (IGBT).

[0044] The transformer 212a includes a leakage inductance L r31 and the ideal transformer T 31 It should be noted that the leakage inductance L r31 and the ideal transformer T 31 Specifically presented as a real transformer. For example, the ideal transformer T 31 The secondary side of the transformer 212a has three taps, forming a first end, a second end and a third end.

[0045] The first end of the secondary side of the transformer 212a (ie, the ideal transformer T 31 The first end of the secondary side ①) is coupled to the first switch tube Q 31 The first end (ie, drain) of the transformer 212a and the second end (ie, the ideal transformer T31 The second end of the secondary side ②) is coupled to the second switch tube Q 32 The first end (ie, drain) of the first switch tube Q 31 The second end (ie, source) of the second switch tube Q 32 The second end (ie, source) of the transformer 212a is coupled to one end of the load, and the other end of the load is coupled to the third end of the secondary side of the transformer 212a (ie, the ideal transformer T 31 The first switch tube Q 31 The third terminal (i.e., the gate) and the second switch tube Q 32 The third ends (i.e., gates) of the transistors are all coupled to different output ports in the controller.

[0046] In a specific implementation, the controller can control the first switch tube Q 31 And the second switch tube Q 32 Both are turned on, thereby achieving short circuit of the secondary side of the transformer 212a.

[0047] For example, taking the chopper unit 211a as a full-bridge circuit, the chopper unit 211a includes a first bridge arm and a second bridge arm connected in parallel, and each bridge arm includes two switch tubes connected in series. In other words, the first switch tube in the first bridge arm (i.e. Figure 3 The switch tube Q shown in 33 ) and the second switch tube in the first bridge arm (i.e. Figure 3 The switch tube Q shown in 35 ) in series; the first switch tube in the second bridge arm (i.e. Figure 3 The switch tube Q shown in 34 ) and the second switch tube in the second bridge arm (i.e. Figure 3 The switch tube Q shown in 36 ) in series. In the specific implementation, the switch tube Q 33 The second end (source) of the switch tube Q 35 The first end (ie, drain) of is coupled to one end of the transformer 212a, and the switch tube Q 34 The second end (source) of the switch tube Q 36 The first end (ie, drain) of is coupled to the other end of the transformer 212a. 33 The first end (ie, drain) of the switch tube Q 34 The first end (ie, drain) is coupled to the bus capacitance C 31 One end of the switch tube Q 35 The second end (source) of the switch tube Q 36 The second end (i.e. source) is coupled to the bus capacitance C 31 The other end of each switch tube (such as switch tube Q 33 , switch tube Q 34 , switch tube Q 35, switch tube Q 36 The gates of the controllers are coupled to different output ports.

[0048] The controller can determine the bus capacitance C 31 When discharging, the first control signal and the second control signal are sent alternately to the chopping unit 211 a at a first preset frequency.

[0049] In a specific implementation, the first control signal can control the switch tube Q 33 And the switch tube Q 36 conduction, and control switch tube Q 35 And the switch tube Q 34 At this time, the bus capacitor C 31 , switch tube Q 33 , leakage inductance L r31 、Ideal transformer T 31 And the switch tube Q 36 form Figure 4 The equivalent circuit is shown in FIG. Where, I dis is the bus capacitance C 31 The discharge current in this closed loop, R P is the switch tube Q 33 The on-resistance and Q 36 The on-resistance of the ideal transformer T 31 The sum of the on-resistance of the primary side, R S is an ideal transformer T 31 The equivalent on-resistance of the secondary circuit.

[0050] The second control signal can control the switch tube Q 35 And the switch tube Q 34 conduction, and control switch tube Q 33 And the switch tube Q 36 At this time, the bus capacitor C 31 , switch tube Q 34 、Ideal transformer T 31 , leakage inductance L r31 And the switch tube Q 35 It can also form Figure 4 The equivalent circuit is shown in FIG. Where, I dis Or bus capacitance C 31 The discharge current in this closed loop, R P is the switch tube Q 35 The on-resistance and Q of the switch tube 34 The on-resistance of the ideal transformer T 31 The sum of the on-resistance of the primary side, R S is an ideal transformer T 31 The equivalent on-resistance of the secondary circuit.

[0051] Optionally, the controller determines the bus capacitance C 31 When the discharge is stopped, the controller sends the first control signal and the second control signal to the chopper unit 211a alternately at the second preset frequency. It can be understood that the controller determines the bus capacitor C 31 Stop discharging and determine the bus capacitance C 31 To discharge, the controller sends the first control signal and the second control signal to the chopper unit 211a alternately. In other words, the switch tubes on the same bridge arm in the chopper unit 211a are complementary. The difference is that the controller sends the control signal to the chopper unit 211a at different frequencies. For example, the controller determines that the bus capacitor C 31 The frequency of sending the control signal during discharge is a first preset frequency, which is related to the bus capacitor C 31 For another example, the controller determines the discharge time of the bus capacitor C 31 The frequency of sending the control signal when discharging is stopped is a second preset frequency, and the second preset frequency is related to the magnitude of the DC voltage of the load.

[0052] In some possible implementations, Figure 3 The load connected to the DC / DC converter 21a shown in FIG. 2 is a storage battery. The DC / DC converter 21a is arranged between the storage battery and the power battery. The bus capacitor C 31 It is provided between the power battery and the DC / DC converter 21a. For example, the transformer 21a is used in the power supply system of an electric vehicle to convert the output voltage of the power battery into the charging voltage of the battery. 31 When discharging, the bus capacitor discharging method provided in the embodiment of the present application can be executed.

[0053] Optionally, the power battery can be switched on by switching S 31 The controller determines the bus capacitance C 31 When discharging, switch S 31 Disconnect to prevent the power battery from continuing to supply power to the bus capacitor C 31 Provide energy. Optionally, the switch S 31 It can be a semiconductor switch such as MOSFET or IGBT, and the switch S is controlled by the controller 31 Alternatively, the switch S 31 It can be a mechanical switch, which is disconnected when the user presses the ignition off button when the electric car stops.

[0054] Furthermore, in some feasible implementations, the DC / DC converter 21a further includes an isolating switch 215, and the third terminal of the secondary side of the transformer 212a (i.e., the ideal transformer T31 The third end ③ of the secondary side is coupled to the load (eg, a battery) through the isolation switch 215. The isolation switch 215 is a switch tube Q 37 For example, the ideal transformer T 31 The third end of the secondary side ③ coupling switch tube Q 37 The drain of the switch tube Q 37 The source is coupled to the positive electrode of the battery, and the switch tube Q 37 The negative electrode of the battery is coupled to the gate of the first switch tube Q 31 The second end (ie, source) of the second switch tube Q 32 In a specific implementation, the controller can determine the bus capacitance C 31 When discharging, the control switch tube Q 37 Disconnect, thus preventing the battery voltage from flowing back, which is safe and reliable.

[0055] Optional, ideal transformer T 31 The third terminal ③ of the secondary side can be coupled to the switch tube Q through the inductor L1 37 The drain of the inductor L1 and the switch tube Q 37 A capacitor C is connected in parallel between the coupling node of the drain and the negative electrode of the battery. 32 , inductor L1 and capacitor C 32 An LC filter is formed to filter out the ripple interference of the output voltage of the rectifier unit 213a. 37 A filter capacitor C is connected in parallel between the coupling node of the source coupling battery and the negative electrode of the battery 33 , the filter capacitor C 33 Can be installed close to the battery.

[0056] In the embodiment of the present application, by increasing the control of the switch tube included in the rectifier unit, the secondary side of the transformer is short-circuited, so that the equivalent on-impedance of the secondary side of the transformer is increased in the discharge circuit of the bus capacitor. Compared with the state where the secondary side of the transformer is not short-circuited, the embodiment of the present application has an additional equivalent on-impedance of the secondary side of the transformer to consume the energy on the bus capacitor, which can speed up the discharge speed of the bus capacitor. And by controlling the switch tube in the rectifier unit, it is possible to avoid the situation where the output voltage of the secondary side of the transformer is too high due to the uncontrolled switch tube in the rectifier unit. Compared with the discharge method of adding resistors and switches in the prior art, the cost of the embodiment of the present application is also low. In general, the implementation of the embodiment of the present application has a fast discharge speed, low cost and high safety.

[0057] Optionally, in some possible implementations, see Figure 5 , Figure 5 Another circuit diagram of bus capacitor discharge provided in the embodiment of the present application. Figure 5 As shown, the DC / DC converter 21b includes a chopper unit 211b, a transformer 212b and a rectifier unit 213b.

[0058] The rectifying unit 213b includes a first switch tube (eg, a switch tube Q 51 ), the second switch tube (for example, the switch tube Q 52 ), the rectifying unit 213b further includes a third switch tube Q 53 And the fourth switch tube Q 54 .

[0059] The transformer 212b includes a leakage inductance (eg, a secondary leakage inductance L r51 、Primary leakage inductance L r51 ′), distributed capacitance, (for example, secondary side distributed capacitance C r51 , primary side distributed capacitance C r51 ′) and the ideal transformer T 51 It should be noted that the secondary leakage inductance L r51 、Primary leakage inductance L r51 ′、Secondary side distributed capacitance C r51 , primary side distributed capacitance C r51 ′ and the ideal transformer T 51 Specifically presented as an actual transformer.

[0060] One end of the secondary side of the transformer 212b (ie, the ideal transformer T 51 The secondary side of the secondary side) passes through the secondary side leakage inductance L r51 And the secondary side distributed capacitance C r51 Coupling switch Q 51 The first end (ie, drain) and the third switch tube Q 53 The second end (ie, source) of the transformer 212b and the other end (ie, ideal transformer T 51 The other end of the secondary side) is coupled to the switch tube Q 52 The first end (ie, drain) and the fourth switch tube Q 54 The second end (ie, source) of each switch tube (eg, switch tube Q 51 , Q 52 , Q 53 , Q 54 The third ends (i.e., gates) of the transistors (e.g., etc.) are all coupled to different output ports in the controller.

[0061] In the specific implementation, the controller can control the switch tube Q 51 And the switch tube Q 52 The third switch tube Q is turned on to short-circuit the secondary side of the transformer 212b. 53 And the fourth switch tube Q 54Both are turned on, and the secondary side of the transformer 212b can also be short-circuited.

[0062] For example, taking the chopper unit 211b also being a full-bridge circuit as an example, Figure 5 The chopper unit 211b shown in FIG. Figure 3 The structure of the chopping unit 211a described above is the same, and the details can be referred to in conjunction with the above Figure 3 The described embodiment of the chopping unit 211 a is not described in detail here.

[0063] The controller can determine the bus capacitance C 51 When discharging, the first control signal and the second control signal are sent to the chopping unit 211b according to the first preset frequency. At this time, the equivalent circuit obtained is still as follows: Figure 4 As shown, the discharge closed loop formed still includes an ideal transformer T 51 The equivalent on-resistance of the secondary circuit.

[0064] Depend on Figure 3 and Figure 5 It can be seen that the structure of the rectifier unit 213b coupled to the secondary side of the transformer 212b in the embodiment of the present application is similar to Figure 3 The structure of the rectifier unit 213a coupled to the secondary side of the transformer 212a shown in FIG. 1 is different.

[0065] In some feasible implementations, the load connected to the DC / DC converter 21b in the embodiment of the present application is a power factor correction (PFC) circuit, and the DC / DC converter 21b is arranged between the PFC circuit and the power battery. 51 It is arranged between the power battery and the DC / DC converter 21b, that is, the power battery is coupled to the bus capacitor C 51 And a chopper unit 211b. Wherein, the PFC circuit is in a non-operating state when the secondary side of the transformer 212b is short-circuited, that is, all the switch tubes in the PFC circuit are in a disconnected state.

[0066] Exemplarily, the input end of the PFC circuit is an AC power grid, and the three-phase voltage and three-phase current of the AC power grid are respectively output to the DC / DC converter 21b through the PFC circuit. The PFC circuit can adjust the phase difference between the three-phase voltage and the three-phase current. The specific implementation can refer to the existing technology and will not be described here.

[0067] It can be understood that the bus capacitance C 51When the discharge stops, the three-phase voltage and three-phase current output by the AC power grid are transmitted to the DC / DC converter 21b through the PFC circuit, that is, sequentially transmitted to the rectifier unit 213b, the transformer 212b and the chopper unit 211b, and then reach the bus capacitor C 51 and power battery. However, when the bus capacitor C 51 During active discharge, the bus capacitor C 51 Switch S between the power battery 51 Shut down to avoid voltage backflow of the power battery. At this time, the bus capacitor C 51 The voltage at both ends passes through the on-resistance of the chopper unit 211 b, the on-resistance of the primary side of the transformer 212 b, and the equivalent on-resistance of the secondary side loop of the transformer 212 b in sequence.

[0068] For example, Figure 5 The DC / DC converter 21b shown in FIG. 2 can be applied to an on-board charger OBC (On-board Charger) on an electric vehicle.

[0069] In the embodiment of the present application, the switch tube included in the rectifier unit is controlled to short-circuit the secondary side of the transformer, so that the equivalent conduction impedance of the secondary side of the transformer is increased in the discharge circuit of the bus capacitor. Figure 3 The DC / DC converter shown in the embodiment of the present application can be applied to different DC / DC converter structures, for example, the power supply circuit of the power battery can be shared. When the bus capacitor is actively discharged, the PFC circuit does not work, and the bus capacitor is discharged by using the power supply circuit of the power battery, which has strong applicability.

[0070] Optionally, in some feasible implementations, the bus capacitor discharge method provided in the embodiments of the present application may be applicable to Figure 6 The DC / DC converter shown in FIG. The DC / DC converter includes a chopper unit, a transformer, a rectifier unit, a first switch S 61 And the first resistor R L Among them, the first switch S 61 With the first resistor R L The two ends of the series connection are connected in parallel between the two ends of the transformer. Figure 6 The first switch S 61 With the first resistor R L Taking the two ends of the series connection as an example, the two ends of the secondary side of the transformer are connected in parallel. It can be understood that the first switch S 61 With the first resistor R L The two ends after the series connection can also be connected in parallel between the two ends of the primary side of the transformer.

[0071] When the controller determines to discharge the bus capacitor, it controls the rectifier unit to short-circuit the secondary side of the transformer, controls the chopper unit to close the loop formed between the bus capacitor and the primary side of the transformer, and controls the first switch S 61 At this time, the bus capacitor can form a closed discharge loop through the on-resistance of the chopper unit, the on-resistance of the primary side of the transformer, and the equivalent on-resistance of the secondary side loop of the transformer. The equivalent impedance of the secondary side loop of the transformer is due to the first switch S 61 Closed and increased the first resistor R L In other words, the impedance of the closed discharge loop formed in the embodiment of the present application becomes larger, which can speed up the discharge speed of the bus capacitor.

[0072] It can be understood that although the embodiment of the present application adds switches and resistors, compared with the prior art, since the rectifier unit is controlled to short-circuit the secondary side of the transformer, the increased resistance can be sensed to the primary side of the transformer, increasing the impedance of the discharge circuit of the bus capacitor, which can further improve the discharge speed of the bus capacitor.

[0073] See also Figure 7 , Figure 7 A schematic diagram of a structure of a discharge device for a bus capacitor provided in an embodiment of the present application. Figure 7 As shown, the DC / DC converter includes a transceiver 71, a controller 72 and a memory 73. The transceiver 71, the controller 72 and the memory 73 are connected via a bus system. The transceiver 71 can receive and send instructions; the memory 73 can store instructions; the controller 72 can call the instructions stored in the memory 73 to execute the above-mentioned instructions. Figures 1 to 6 For any possible embodiment described, its specific implementation principle and technical effect can be found in the explanation of the above embodiment and will not be repeated here.

[0074] It should be understood that the memory mentioned in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache.

[0075] It should be noted that when the controller 72 is a general-purpose processor, DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, the memory 73 (storage module) is integrated into the controller 72.

[0076] It should be noted that the above terms “first” and “second” are only used for descriptive purposes and should not be understood as indicating or implying relative importance.

[0077] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A DC / DC converter, characterized in that: The DC / DC converter is used to receive power from a power battery and supply power to a storage battery. The DC / DC converter includes a bus capacitor, a full-bridge circuit, a transformer, and a rectifier unit. The bus capacitor is coupled to the full-bridge circuit, and the full-bridge circuit is coupled to the primary side of the transformer. The secondary side of the transformer includes three taps, and the three taps form a first end, a second end, and a third end, wherein: The first end of the secondary side of the transformer is coupled to the drain of the first switch tube of the rectifier unit, the second end of the secondary side of the transformer is coupled to the drain of the second switch tube of the rectifier unit, the third end of the secondary side of the transformer is used to couple to one end of the battery, and the source of the first switch tube and the source of the second switch tube are used to couple to the other end of the battery; In the process where the DC / DC converter is used to discharge the bus capacitor: The full-bridge circuit closes the loop formed between the bus capacitor and the primary side of the transformer and the first switch tube and the second switch tube are turned on, so that the bus capacitor forms a closed discharge loop through the on-impedance of the full-bridge circuit, the on-impedance of the primary side of the transformer and the on-impedance of the secondary side loop of the transformer.

2. The DC / DC converter according to claim 1, characterized in that: The DC / DC converter also includes an isolating switch and a filter capacitor, wherein the drain of the isolating switch is used to couple the third end of the secondary side of the transformer through an inductor, the source of the isolating switch is used to couple the positive electrode of the battery, and the source of the isolating switch is also used to couple the negative electrode of the battery through the filter capacitor, and the isolating switch is disconnected when the DC / DC converter is used to discharge the bus capacitor.

3. The DC / DC converter according to claim 1 or 2, characterized in that: When the DC / DC converter is used to discharge the bus capacitor, in response to the voltage across the bus capacitor being lower than a preset voltage threshold, the rectifying unit rectifies the voltage on the secondary side of the transformer.

4. The DC / DC converter according to claim 1, characterized in that: The full-bridge circuit comprises a first bridge arm and a second bridge arm connected in parallel, and each of the first bridge arm and the second bridge arm comprises two first switching tubes and a second switching tube connected in series; The source of the first switch tube of the first bridge arm and the drain of the second switch tube of the first bridge arm are used to couple one end of the primary side of the transformer, and the source of the first switch tube of the second bridge arm and the drain of the second switch tube of the second bridge arm are used to couple the other end of the primary side of the transformer; The drain of the first switch tube of the first bridge arm and the source of the second switch tube of the first bridge arm are used to couple one end of the bus capacitor, and the drain of the first switch tube of the second bridge arm and the second end of the second switch tube of the second bridge arm are used to couple the other end of the bus capacitor.

5. The DC / DC converter according to claim 4, characterized in that: In the process where the DC / DC converter is used to discharge the bus capacitor: The first switch tube in the first bridge arm and the second switch tube in the second bridge arm are turned on, and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm are turned off; or, The first switch tube in the first bridge arm and the second switch tube in the second bridge arm are turned off, and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm are turned on.

6. The DC / DC converter according to claim 4, characterized in that: The DC / DC converter is used to couple the power battery through a semiconductor switch or a mechanical switch. The DC / DC converter also includes a controller. When the DC / DC converter is used as the bus capacitor, the controller is used to: Controlling the semiconductor switch or mechanical switch to disconnect; Controlling the first switch tube and the second switch tube of the rectifier unit to be turned on; Control the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to turn on and control the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to turn off, or control the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to turn off and control the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to turn on.

7. The DC / DC converter according to claim 6, characterized in that: During the process of the DC / DC converter discharging the bus capacitor, the controller is used to: sending a first control signal and a second control signal alternately to the chopping unit at a first preset frequency; In response to the voltage across the bus capacitor dropping below a preset voltage threshold, alternately sending a first control signal and a second control signal to the chopping unit at a second preset frequency; The first control signal is used to control the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to be turned on and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to be turned off, and the second control signal is used to control the first switch tube in the first bridge arm and the second switch tube in the second bridge arm to be turned off and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm to be turned on; The second preset frequency is not equal to the first preset frequency and the second preset frequency is determined according to the DC voltage of the battery.

8. The DC / DC converter according to claim 6, characterized in that: The DC / DC converter is applied to an electric vehicle, and the electric vehicle further comprises a vehicle controller, wherein the vehicle controller is used to monitor the voltage across the bus capacitor, and when the DC / DC converter discharges the bus capacitor, the controller is used to: Receiving an active discharge instruction from the vehicle controller and controlling the DC / DC converter to discharge the bus capacitor according to the active discharge instruction; Receive a stop discharge instruction from the vehicle controller and control the DC / DC converter to stop discharging the bus capacitor according to the instruction of the stop discharge instruction.

9. A vehicle-mounted charger, characterized in that: The on-board charger includes a power factor correction circuit, a rectifier unit, a transformer, a full-bridge circuit and a bus capacitor, wherein the power factor correction circuit is used to receive AC power from an AC power grid and sequentially supply power to the power battery through the rectifier unit, the transformer, the full-bridge circuit and the bus capacitor; The on-board charger is also used to receive power from the power battery and supply power to the storage battery. The secondary side of the transformer includes three taps, and the three taps form a first end, a second end, and a third end. The first end of the secondary side of the transformer is coupled to the drain of a switch tube, the second end of the secondary side of the transformer is coupled to the drain of another switch tube, the third end of the secondary side of the transformer is used to couple to one end of the storage battery, and the source of the one switch tube and the source of the other switch tube are used to couple to the other end of the storage battery. When the on-board charger is used to discharge the bus capacitor: The power factor correction circuit does not work, and the one switch tube and the other switch tube are turned on, so that the bus capacitor forms a closed discharge loop through the on-impedance of the full-bridge circuit and the on-impedance of the transformer.

10. The vehicle-mounted charger according to claim 9, characterized in that: The full-bridge circuit comprises a first bridge arm and a second bridge arm connected in parallel, and each of the first bridge arm and the second bridge arm comprises two first switching tubes and a second switching tube connected in series; The source of the first switch tube of the first bridge arm and the drain of the second switch tube of the first bridge arm are used to couple one end of the primary side of the transformer, and the source of the first switch tube of the second bridge arm and the drain of the second switch tube of the second bridge arm are used to couple the other end of the primary side of the transformer; The drain of the first switch tube of the first bridge arm and the source of the second switch tube of the first bridge arm are used to couple one end of the bus capacitor, and the drain of the first switch tube of the second bridge arm and the second end of the second switch tube of the second bridge arm are used to couple the other end of the bus capacitor; When the on-board charger is used to discharge the bus capacitor: The first switch tube in the first bridge arm and the second switch tube in the second bridge arm are turned on, and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm are turned off; or, the first switch tube in the first bridge arm and the second switch tube in the second bridge arm are turned off, and the second switch tube in the first bridge arm and the first switch tube in the second bridge arm are turned on.

11. The vehicle-mounted charger according to claim 10, characterized in that: The drain of the first switch tube of the first bridge arm and the source of the second switch tube of the first bridge arm are used to couple one end of the power battery through a switch, and the switch is disconnected during the discharge process of the bus capacitor.

12. The vehicle-mounted charger according to claim 9, characterized in that: The on-board charger also includes an isolating switch and a filter capacitor, the drain of the isolating switch is used to couple the third end of the secondary side of the transformer through an inductor, the source of the isolating switch is used to couple the positive electrode of the battery, and the source of the isolating switch is also used to couple the negative electrode of the battery through the filter capacitor, and the isolating switch is disconnected during the discharge process of the bus capacitor.

13. The vehicle-mounted charger according to claim 9, characterized in that: The on-board charger further comprises a controller. When the on-board charger is used to discharge the bus capacitor, the controller is used to: In response to the voltage across the bus capacitor being lower than a preset voltage threshold, the one switch tube and the other switch tube are controlled to stop discharging the bus capacitor.

14. The vehicle-mounted charger according to claim 9, characterized in that: The controller is used to: receiving an active discharge instruction from a vehicle controller and controlling the one switch tube and the other switch tube to discharge the bus capacitor; Receive a stop discharge instruction from a vehicle controller and control the one switch tube and the other switch tube to stop discharging the bus capacitor.

15. An electric vehicle, characterized in that: The electric vehicle comprises a storage battery, a power battery and a DC / DC converter as described in any one of claims 1 to 9 or an on-board charger as described in any one of claims 9 to 14, wherein: The DC / DC converter is used to receive power from the power battery and supply power to the storage battery; The on-board charger is used to receive AC power from an AC power grid and supply power to the power battery.

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