Step-down charging circuit, step-down charging system and electric vehicle

Abstract

The utility model relates to a step-down charging circuit, a step-down charging system and an electric vehicle. The step-down charging circuit comprises a multi-phase bridge arm circuit which comprises a first bridge arm circuit and at least two second bridge arm circuits, the first end of the first bridge arm circuit is used for receiving input voltage of charging equipment, and the second end of the first bridge arm circuit is connected with the second ends of the at least two second bridge arm circuits; the first ends of the at least two second bridge arm circuits are used for outputting reduced output voltage to the battery pack of the electric vehicle, and the first ends of the at least two second bridge arm circuits are connected together; one end of the inductance circuit is connected to the middle connection point of the first bridge arm circuit, and the other end is connected to the middle connection point of the second bridge arm circuit; the capacitor circuit is connected with the second bridge arm circuit in parallel; and the control unit is configured to output a set PWM signal to the upper bridge arm control end of the first bridge arm circuit, the upper bridge arm and the lower bridge arm of the first bridge arm circuit are not switched on or switched off at the same time, the upper bridge arm of the second bridge arm circuit is normally switched on, and the lower bridge arm of the second bridge arm circuit is normally switched off. The application can reduce voltage and increase current, and improve the charging speed.

Description

Technical Field

[0001] The present application relates to the technical field of battery charging, and particularly to a step-down charging circuit, a step-down charging system, and an electric vehicle. Background Art

[0002] With the popularization of new energy vehicles in the market, the charging technology of new energy vehicles is also gradually improving. However, in practice, there are many limitations in the charging process of new energy vehicles, such as: limitations of charging piles, limitations of DC charging ports, limitations of vehicle charging circuits, and limitations of power batteries, etc.

[0003] In related technologies, the charging scheme of new energy vehicles is limited by the maximum current (250A) of the national standard vehicle DC charging socket. The charging current is limited, the charging speed is also affected, and the charging experience of users is also affected. Summary of the Utility Model

[0004] To solve or partially solve the problems existing in related technologies, the present application provides a step-down charging circuit, a step-down charging system, and an electric vehicle, which can increase the charging current, improve the charging speed, and enhance the charging experience of users.

[0005] The first aspect of the present application provides a step-down charging circuit, including:

[0006] A multi-phase bridge arm circuit, which includes a first bridge arm circuit and at least two second bridge arm circuits. The first end of the first bridge arm circuit is used to receive the input voltage of the charging device, the second end is connected to the second ends of at least two second bridge arm circuits, and the first ends of at least two second bridge arm circuits are used to output the stepped-down output voltage to the battery pack of the electric vehicle, and the first ends of at least two second bridge arm circuits are commonly connected;

[0007] An inductor circuit, one end of which is connected to the middle connection point of the first bridge arm circuit, and the other end is respectively connected to the middle connection points of the second bridge arm circuits;

[0008] A capacitor circuit, which is connected in parallel with the second bridge arm circuit;

[0009] A control unit, which is configured to output a set pulse width modulation (PWM) signal to the control end of the upper bridge arm of the first bridge arm circuit. Among them, the upper bridge arm and the lower bridge arm of the first bridge arm circuit are not simultaneously turned on or turned off, the upper bridge arm of the second bridge arm circuit is in a normally turned-on state, and the lower bridge arm of the second bridge arm circuit is in a normally turned-off state.

[0010] In one embodiment, the control unit includes a PWM signal source, and the PWM signal source is configured to output a set duty cycle.

[0011] In one embodiment, the multiphase bridge arm circuit is a three-phase six-arm structure. Each arm includes a switching device, and the control end of each arm is provided at the switching device. The control unit is connected to the control ends of the switching devices of each arm.

[0012] In one embodiment, the switching device includes a transistor and a diode reversely connected in parallel with the transistor, and the base of the transistor is connected to the control unit.

[0013] In one embodiment, it further includes an input filter circuit correspondingly connected to the first end and the second end of the first bridge arm circuit, or further includes an output filter circuit correspondingly connected to the first end and the second end of the second bridge arm circuit.

[0014] In one embodiment, the capacitor circuit includes a first capacitor, and the first capacitor is connected in parallel with the second bridge arm circuit.

[0015] In one embodiment, the inductor circuit includes a plurality of inductors. One ends of the plurality of inductors are commonly connected, and the other ends are respectively connected to the intermediate connection points of the corresponding-phase bridge arm circuits.

[0016] The second aspect of the present application provides a buck charging system applied to an electric vehicle, including:

[0017] The battery pack of the electric vehicle;

[0018] The buck charging circuit as described above,

[0019] wherein the buck charging circuit is used to be connected between a charging device and the battery pack, step down the input voltage received from the charging device and output it to the battery pack for charging the battery pack, and the input voltage received from the charging device is greater than the voltage of the battery pack.

[0020] In one embodiment, it further includes:

[0021] The multiphase bridge arm circuit of the buck charging circuit is a three-phase bridge arm circuit, and the first bridge arm circuit is used to connect the charging device, and the two second bridge arm circuits are used to connect the battery pack;

[0022] A drive motor, the drive motor includes the inductor circuit, and the inductor circuit includes three inductors. One ends of the three inductors are commonly connected, and the other ends are respectively connected to the intermediate connection points of the corresponding-phase bridge arm circuits;

[0023] A switch branch, one end of which is connected to the first end of the first bridge arm circuit, and the other end of which is connected to the first end of the second bridge arm circuit.

[0024] In one embodiment, the switching branch includes an insulated gate bipolar transistor (IGBT), and the control terminal of the insulated gate bipolar transistor (IGBT) is connected to the control unit.

[0025] The third aspect of this application provides an electric vehicle with the buck charging system as described above.

[0026] The technical solution provided by this application may include the following beneficial effects:

[0027] The technical solution of this application, by means of the conduction / disconnection of the upper and lower arms of each arm circuit in the multi-phase bridge arm circuit, and in cooperation with the connection of the inductor circuit and the capacitor circuit, can form multiple buck circuits, and the multiple buck circuits are connected in parallel, which can increase the output current, and then form a buck charging circuit for charging the battery pack of the electric vehicle. This buck charging circuit steps down the input voltage received from the charging device and outputs it to the battery pack of the electric vehicle for charging the battery pack. Thus, when the output voltage of the charging device is greater than the maximum voltage of the battery pack, buck-boost current can be achieved, the charging current can be increased, the charging speed can be improved, and the user's charging experience can be enhanced.

[0028] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] By describing the exemplary embodiments of this application in more detail in conjunction with the drawings, the above and other objects, features, and advantages of this application will become more obvious. Among them, in the exemplary embodiments of this application, the same reference numerals generally represent the same components.

[0030] Figure 1 is the circuit schematic diagram of the buck charging circuit shown in the embodiment of this application;

[0031] Figure 2 is the circuit schematic diagram of the Buck circuit in the related art;

[0032] Figure 3 is the specific circuit schematic diagram of the buck charging circuit shown in the embodiment of this application;

[0033] Figure 4 is the schematic diagram of the current flow direction of part of the buck charging circuit shown in the embodiment of this application;

[0034] Figure 5 is the circuit schematic diagram of the connection between the buck charging circuit shown in the embodiment of this application and the charging pile and the battery pack;

[0035] Figure 6 is the circuit schematic diagram of the vehicle charging process in the related art;

[0036] Figure 7 It is the circuit schematic diagram of the buck charging system shown in the embodiments of the present application;

[0037] Figure 8 It is the equivalent circuit schematic diagram of the buck charging system shown in the embodiments of the present application. Embodiment

[0038] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0039] The terms used in the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "the" and "said" used in the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0040] It should be understood that although the terms "first", "second", "third", etc. may be used in the present application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0041] In the related art, the charging scheme of new energy vehicles is limited by the maximum current (250A) of the national standard vehicle DC charging socket, resulting in limited charging current and affected charging speed, which also affects the charging experience of users.

[0042] In view of the above problems, the embodiments of the present application provide a buck charging circuit, which can be applied to electric vehicles. By stepping down and boosting the current at the vehicle end, it avoids the limitation of the maximum current (250A) of the national standard vehicle DC charging socket, shortens the charging time, thereby being able to increase the charging current, improve the charging speed of new energy vehicles, and enhance the charging experience of users.

[0043] The technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0044] Figure 1It is the circuit schematic diagram of the buck charging circuit shown in the embodiments of the present application.

[0045] As Figure 1 shown, the embodiments of the present application provide a buck charging circuit, including:

[0046] A multi-phase bridge arm circuit, which includes a first bridge arm circuit and at least two second bridge arm circuits. The first end of the first bridge arm circuit is used to receive the input voltage of the charging device, the second end is connected to the second ends of the at least two second bridge arm circuits, and the first ends of the at least two second bridge arm circuits are used to output the bucked output voltage to the battery pack of the electric vehicle, and the first ends of the at least two second bridge arm circuits are commonly connected;

[0047] An inductor circuit, one end of which is connected to the middle connection point of the first bridge arm circuit, and the other end is respectively connected to the middle connection points of the second bridge arm circuits;

[0048] A capacitor circuit, which is connected in parallel with the second bridge arm circuit;

[0049] A control unit, which is configured to output a set pulse width modulation (PWM) signal to the control end of the upper bridge arm of the first bridge arm circuit. Among them, the upper bridge arm and the lower bridge arm of the first bridge arm circuit are not simultaneously turned on or off, the upper bridge arm of the second bridge arm circuit is in a normally-on state, and the lower bridge arm of the second bridge arm circuit is in a normally-off state.

[0050] As Figure 1 shown, assuming that the multi-phase bridge arm circuit is a three-phase bridge arm circuit, that is, the three-phase bridge arm circuit includes a first bridge arm circuit M1, a second bridge arm circuit M2, and a second bridge arm circuit M3; the positive input terminal of the first bridge arm circuit M1 is the first end a1, and the negative input terminal of the first bridge arm circuit M1 is the second end b1. That is to say, the first end of the first bridge arm circuit M1 is used as the input terminal; the positive output terminal of the second bridge arm circuit M2 is the first end a2, the negative output terminal of the second bridge arm circuit M2 is the second end b2, the positive output terminal of the second bridge arm circuit M3 is the first end a3, and the negative output terminal of the second bridge arm circuit M3 is the second end b3. Among them, each phase of the bridge arm circuit includes an upper bridge arm and a lower bridge arm. The upper bridge arm is close to the first end of its own bridge arm circuit, and the lower bridge arm is close to the second end of its own bridge arm circuit. The connection point between the upper bridge arm and the lower bridge arm in the same bridge arm circuit is the middle connection point of the bridge arm circuit.

[0051] In the first bridge arm circuit M1, the connection point between the upper bridge arm and the lower bridge arm is the middle connection point O1 of the bridge arm circuit; in the second bridge arm circuit M2, the connection point between the upper bridge arm and the lower bridge arm is the middle connection point O2 of the bridge arm circuit; in the second bridge arm circuit M3, the connection point between the upper bridge arm and the lower bridge arm is the middle connection point O3 of the bridge arm circuit.

[0052] SeeFigure 2 , Figure 2 is the schematic diagram of a Buck circuit in the related art.

[0053] The Buck (step-down) circuit is equivalent to a DC-DC step-down converter. Its basic working principle is to convert the input DC voltage into a lower DC voltage for output by controlling the on and off of the switching device. During a switching cycle, as Figure 2 shown, when the switching transistor VT is on, the input voltage is directly connected to the inductor L, and the current of the inductor L linearly increases. Electrical energy is stored in the inductor L in the form of magnetic energy. At the same time, the capacitor C supplies energy to the load R. When the switching transistor VT is off, due to the fact that the current in the inductor L cannot change suddenly, the inductor L generates an induced electromotive force, whose direction is opposite to the input voltage. At this time, the inductor L releases energy to the load R through the freewheeling diode VD and charges the capacitor C to maintain the stability of the output voltage.

[0054] Referring to Figure 1 , in the step-down charging circuit of the embodiment of the present application, when the upper arm of the first bridge arm circuit M1 is on, the lower arm of the first bridge arm circuit M1 can be equivalent to the diode in the Buck circuit of the related art, and at this time the lower arm is disconnected. When the upper arm of the first bridge arm circuit M1 is off, the current in the inductor circuit cannot change suddenly, and the circuit will supply power to the load through the inductor circuit and the capacitor circuit. At this time, the lower arm of the first bridge arm circuit M1 is in the on state to form a current loop, that is, the upper arm and the lower arm of the first bridge arm circuit are not on at the same time or not off at the same time. The upper arm of the second bridge arm circuit is regarded as a path, and the lower arm is regarded as an open circuit, that is, the upper arm of the second bridge arm circuit is in a normally on state, and the lower arm of the second bridge arm circuit is in a normally off state.

[0055] The working principle of the step-down charging circuit provided in this embodiment is as follows:

[0056] As Figure 1As shown, assume that the upper arm of the first bridge arm circuit M1 is turned on and the lower arm is turned off, the upper arm of the second bridge arm circuit M2 is turned on and the lower arm is turned off, and the upper arm of the second bridge arm circuit M3 is turned on and the lower arm is turned off. The upper arm of the first bridge arm circuit M1 can be equivalent to the switching transistor VT in the Buck circuit, the lower arm of the first bridge arm circuit M1 can be equivalent to the freewheeling diode VD in the Buck circuit, the inductor circuit can be equivalent to the inductor L in the Buck circuit, and the capacitor circuit can be equivalent to the capacitor C in the Buck circuit. Based on this, two step-down lines can be determined in this embodiment. One is from the first end a1 (Vin) of the first bridge arm circuit M1 - the upper arm of the first bridge arm circuit M1 - the inductor circuit - the upper arm of the second bridge arm circuit M2 - the first end a2 (Vout) of the second bridge arm circuit M2, and the other is from the first end a1 (Vin) of the first bridge arm circuit M1 - the upper arm of the first bridge arm circuit M1 - the inductor circuit - the upper arm of the second bridge arm circuit M3 - the first end a3 (Vout) of the second bridge arm circuit M3. The two step-down lines are in parallel, and the current can be shared through the parallel step-down lines, so as to increase the total output current to achieve current boost while stepping down. The value of the output voltage Vout can be calculated by Vout = Vin × D, where D is the duty cycle of the PWM (Pulse Width Modulation) signal output by the control unit to the control terminal of the upper arm of the first bridge arm circuit M1. When the input voltage Vin received from the charging device is stepped down by the step-down charging circuit and then output to the battery pack of the electric vehicle for charging the battery pack, the charging device can be a charging pile.

[0057] The technical solution of this application, by means of the on / off of the upper and lower arms of each bridge arm circuit in the multi-phase bridge arm circuit, and in cooperation with the connection of the inductor circuit and the capacitor circuit, can form a step-down charging circuit, step down the input voltage received from the charging device and then output it to the battery pack of the electric vehicle for charging the battery pack. Thus, when the output voltage of the charging device is greater than the maximum voltage of the battery pack, step-down and current boost can be achieved, the charging current can be increased, the charging speed can be improved, and the user's charging experience can be enhanced.

[0058] Figure 3 is the specific circuit schematic diagram of the step-down charging circuit shown in the embodiment of this application.

[0059] As Figure 3 shown, in one embodiment, the multi-phase bridge arm circuit can be a three-phase bridge arm circuit. Among them, the multi-phase bridge arm circuit can be a three-phase six-arm structure, each arm includes a switching device, the control terminal of each arm is provided on the switching device, the control unit is connected to the control terminals of the switching devices of each arm, and the control unit includes a PWM signal source, and the PWM signal source is configured to output a set duty cycle. As Figure 3As shown in the figure, in the first bridge arm circuit, the switching device of the upper bridge arm is defined as Q1, the switching device of the lower bridge arm is defined as Q2, and the connection point of the switching device Q1 and the switching device Q2 is the middle connection point of the first bridge arm circuit; in a second bridge arm circuit, the switching device of the upper bridge arm is defined as Q3, the switching device of the lower bridge arm is defined as Q4, and the connection point of the switching device Q3 and the switching device Q4 is the middle connection point of this second bridge arm circuit; in another second bridge arm circuit, the switching device of the upper bridge arm is defined as Q5, the switching device of the lower bridge arm is defined as Q6, and the connection point of the switching device Q5 and the switching device Q6 is the middle connection point of this second bridge arm circuit. Among them, the capacitor circuit includes a first capacitor C1, and the first capacitor C1 is connected in parallel with the second bridge arm circuit, that is, the positive electrode of the first capacitor C1 is connected to the first end of the second bridge arm circuit, and the negative electrode is connected to the second end of the second bridge arm circuit. When the switching device Q1 is turned on, the input voltage Vin magnetizes the inductor and also charges the first capacitor C1; when the switching device Q1 is turned off, the inductor discharges through the switching device Q2, and the inductor current decreases, then the output voltage Vout can be maintained by the discharge of the first capacitor C1 and the decreasing inductor current.

[0060] The working principle of the buck charging circuit provided in this embodiment is as follows:

[0061] As Figures 3 to 5 shown, assume that the switching device Q1 is turned on, the switching device Q2 is turned off, the switching device Q3 is turned on, the switching device Q4 is turned off, the switching device Q5 is turned on, and the switching device Q6 is turned off. Also refer to Figure 2 , the switching device Q1 can be equivalent to the switch tube VT in the Buck circuit, the switching device Q2 can be equivalent to the freewheeling diode VD in the Buck circuit, the inductor circuit can be equivalent to the inductor L in the Buck circuit, and the first capacitor C1 can be equivalent to the capacitor C in the Buck circuit. Based on this, this embodiment can include two buck lines, one is Vin - Q1 - inductor circuit - Q3 - Vout, and the other is Vin - Q1 - inductor circuit - Q5 - Vout, and the value of the output voltage Vout can be calculated by Vout = Vin × D, where D is the set duty cycle output by the PWM signal source in the control unit to the control terminal of the switching device Q1.

[0062] It can be seen that the buck principle of this embodiment refers to the buck method of the Buck circuit. Based on this, it can be determined that when the switching device Q1 is turned off, the switching device Q2 is turned on, the switching device Q3 is turned on, the switching device Q4 is turned off, the switching device Q5 is turned on, and the switching device Q6 is turned off. Therefore, the control unit can control according to the on - and - off characteristics of each switching device. Among them, the switching on and off of the control switching device are well - known to those skilled in the art, so it will not be elaborated in detail here.

[0063] For example, if the input voltage is 12V and the desired output voltage is 5V, by using the solution of the embodiment of the present application, through reasonable selection of the conduction time of the switching device (the duty cycle is 5 / 12), and appropriate inductor and capacitor parameters, a stable 5V output can be achieved.

[0064] Furthermore, the inductor circuit of the embodiment of the present application may include multiple inductors. One end of the multiple inductors is commonly connected, and the other ends are respectively connected to the intermediate connection points of the corresponding phase bridge arm circuits. Among them, the number of inductors in the inductor circuit can be determined according to the number of phases of the bridge arm circuit, that is, the number of phases of the multi-phase bridge arm circuit is the same as the number of inductors in the inductor circuit. When the multi-phase bridge arm circuit is a three-phase bridge arm circuit, the inductor circuit can be three inductors connected in a star shape.

[0065] When the inductor circuit includes inductors L1, L2, and L3 connected in a star shape, the other end of inductor L1 is connected to the intermediate connection point between switching devices Q1 and Q2, the other end of inductor L2 is connected to the intermediate connection point between switching devices Q3 and Q4, and the other end of inductor L3 is connected to the intermediate connection point between switching devices Q5 and Q6. Inductors L1, L2, and L3 are the same, and the relevant parameters can be determined by those skilled in the art according to actual needs. Then, two buck circuits can be determined in this embodiment. One is Vin - Q1 - L1 - L3 - Q3 - Vout, and the other is Vin - Q1 - L1 - L3 - Q5 - Vout.

[0066] As Figure 3 shown, the switching device includes a transistor and a diode connected in anti-parallel with the transistor, and the base of the transistor is connected to the control unit. Generally, the switching devices in the multi-phase bridge arm circuit are the same. Assuming that switching devices Q1, Q3, and Q5 need to be turned on simultaneously, taking the switching device including only one transistor as an example, assuming that the transistor is an NPN-type triode. Generally speaking, the base B of the NPN-type triode receives a control signal to turn on or off the NPN-type triode. When the NPN-type triode is turned on, the current flows from the collector C of the NPN-type triode to the emitter E. According to Figure 3 the layout of switching device Q1 in, it can be inferred that the current flow direction in switching device Q1 is opposite to the current flow directions in switching devices Q3 and Q5. Refer to Figure 4 . If the current flow direction of switching device Q1 is correct, the current flow directions of switching devices Q3 and Q5 with the same structure as switching device Q1 are different from the common expected current flow directions of switching devices Q3 and Q5. Therefore, a diode is connected in anti-parallel to the NPN-type triode. At this time, the current of switching devices Q3 and Q5 can flow to the output terminal through the anti-parallel diode. It should be noted that the transistor in this embodiment is not limited to a triode or a field effect transistor, and the selection of relevant devices can be made according to actual needs.

[0067] As a preferred embodiment of the present application, the buck charging circuit of the present application further includes an input filtering circuit connected corresponding to the first end and the second end of the first bridge arm circuit. Among them, the input filtering circuit is an input filtering capacitor circuit, mainly including a second capacitor C2. The positive electrode of the second capacitor C2 is connected to the first end of the first bridge arm circuit, and the negative electrode is connected to the second end of the first bridge arm circuit. Obviously, the second capacitor C2 is connected in parallel at the input end of the buck charging circuit. On the one hand, the second capacitor C2 can smooth the input voltage Vin, so that the buck charging circuit of this embodiment can obtain more stable input conditions, thereby ensuring the quality of its output voltage. On the other hand, it can also store energy.

[0068] Furthermore, the buck charging circuit of the present application further includes an output filtering circuit connected corresponding to the first end and the second end of the second bridge arm circuit. Among them, the output filtering circuit includes an RC parallel circuit (not shown in the figure). The RC parallel circuit includes a resistor branch and a capacitor branch. The capacitor branch can include multiple capacitors connected in series, and the resistor branch can include a resistor. The RC parallel circuit can be arranged at the output end of the buck charging circuit, and the present application does not limit it. The RC parallel circuit can absorb spike voltages and noise, and can also suppress transient overvoltages and high-frequency noise in the buck charging circuit to improve the stability of the buck charging circuit.

[0069] Corresponding to the foregoing embodiment of the buck charging circuit of the present application, the present application also provides a buck charging system and a corresponding embodiment.

[0070] Figure 6 is the circuit schematic diagram of the vehicle charging process in the related art.

[0071] See Figure 6 , when the electric vehicle is charging normally, the switching devices Km1, Km3, and Km4 are closed, and the switching device km2 is open; the current of the charging pile flows out from the positive electrode through the DC charging socket and enters the battery through km4 and km1, and then returns to the charging pile through Km3. The current flow direction can be seen in Figure 6 as shown by the arrow; due to the limitation of the vehicle DC charging socket, the maximum current for the electric vehicle to charge in the traditional way is 250A, which limits the upper limit of the vehicle charging current.

[0072] Figure 7 is the circuit schematic diagram of the buck charging system shown in the embodiment of the present application, Figure 8 is the equivalent circuit schematic diagram of the buck charging system shown in the embodiment of the present application.

[0073] As Figure 7 and Figure 8 shown, the embodiment of the present application provides a buck charging system applied to an electric vehicle, including:

[0074] Step-down charging circuit and battery pack of electric vehicle. The step-down charging circuit is used to be connected between a charging device and the battery pack of the electric vehicle, step down the input voltage received from the charging device and output it to the battery pack for charging the battery pack, where the input voltage received from the charging device is greater than the voltage of the battery pack. The circuit and principle of the step-down charging circuit can be referred to Figure 1 、 Figure 3 、 Figure 4 and Figure 5 as described. The charging device can be a charging pile or other devices.

[0075] As Figure 7 shown, further, the step-down charging system of the embodiment of the present application further includes:

[0076] The multiphase bridge arm circuit of the step-down charging circuit is a three-phase bridge arm circuit, and the first bridge arm circuit is used to connect the charging device, and the two second bridge arm circuits are used to connect the battery pack;

[0077] Drive motor, the drive motor includes an inductance circuit, and the inductance circuit includes three inductors. One ends of the three inductors are commonly connected, and the other ends are respectively connected to the intermediate connection points of the corresponding phase bridge arm circuits;

[0078] Switch branch, one end of which is connected to the first end of the first bridge arm circuit, and the other end is connected to the first end of the second bridge arm circuit.

[0079] Compare Figure 6 and Figure 7 , in this embodiment, the step-down charging circuit can, on the basis of the three-phase bridge arm circuit and the three-phase drive motor at the vehicle end, design a switch branch at the first end of the first bridge arm circuit and the first end of the second bridge arm circuit in the three-phase bridge arm circuit. By disconnecting the switch branch, two step-down circuits can be formed on the three-phase bridge arm circuit and the three-phase drive motor, giving full play to the maximum voltage limit capacity of the charging device such as a charging pile. When the switch branch is in the closed state, that is, the connection form of the three-phase bridge arm circuit and the three-phase drive motor is similar to that of the inverter and the motor at the vehicle end, and when the switch branch is in the open state, a step-down charging circuit can be formed.

[0080] Refer to Figure 7 and Figure 8, in one embodiment, when the electric vehicle is charging, that is, when the charging pile charges the battery pack of the electric vehicle through the DC charging socket, the BMS (Battery Management System) of the electric vehicle first determines the maximum voltage of the DC charging socket. If the maximum output voltage of the DC charging socket is greater than the maximum voltage of the battery pack, the step-down and current-boosting link can be entered. In the step-down and current-boosting link, the switching devices km1, km3, and km4 are closed, and the switching branch is disconnected. The current flows from the charging pile through the DC charging socket and the switching device km4 into the first end of the switching device Q1, then passes through the inductor L1 (motor coil) and then enters the inductor L2 (motor coil) and the inductor L3 (motor coil) respectively. After that, it passes through the switching devices Q3 and Q5 respectively and then charges the battery pack centrally, and then returns to the charging pile through the switching device km3. Among them, the switching device Q1, the inductor L1, the inductor L2, and the switching device Q3, and the switching device Q1, the inductor L1, the inductor L3, and the switching device Q5 form two step-down circuits. When continuously controlling the on-off of the switching device Q1, a stable output can be formed. Among them, the step-down calculation formula of the step-down charging circuit can be Vout = Vin * D, where Vout is the output voltage of the battery pack after step-down, Vin is the output voltage of the charging pile, and D is the PWM duty cycle.

[0081] It can be found that the embodiment of the present application can improve the existing electrical circuit at the vehicle end (design a switching branch between the first end of the first bridge arm circuit and the first end of the second bridge arm circuit), and then can exert the maximum voltage upper limit capacity of the charging pile. After passing through the DC charging socket with high voltage and low current, step-down and current-boosting are performed at the vehicle end, avoiding the limitation of the maximum current (250A) of the DC charging socket of national standard vehicles, and also shortening the charging time, thereby improving the charging speed of new energy vehicles. The technical solution of the present application efficiently utilizes the high-voltage charging pile, inputs a higher-level voltage than the battery pack to the vehicle end, and then performs step-down and current-boosting after entering the vehicle end to achieve a larger current than normal charging, so as to reduce the charging time and improve the charging experience.

[0082] Preferably, the switching branch may include a switch K1. The switch K1 is an insulated gate bipolar transistor IGBT, and the control end of the IGBT is connected to the control unit. In this embodiment, the on-off of the IGBT can be controlled by the control unit. The switch K1 can be an insulated gate bipolar transistor IGBT (Insulate-Gate Bipolar Transistor) made of silicon carbide. This is because the resistance of the switching branch in the closed state should be as small as possible, and an IGBT switch made of silicon carbide is preferably used, and this switch has no obvious influence on other functions in non-step-down modes.

[0083] In the embodiment of the present application, the charging pile charges the battery pack through a step-down charging circuit. Therefore, when charging, the BMS of the vehicle can determine the maximum voltage of the DC charging socket of the charging pile. If the maximum output voltage of the DC charging socket is greater than the maximum voltage of the battery pack, then a step-down and current-boosting operation can be performed.

[0084] When the vehicle is charging, the current of the charging pile flows out from the positive electrode to the first end of the first bridge arm circuit, flows from the first end of the second bridge arm circuit to the battery pack, and finally returns to the negative electrode of the charging pile through the negative electrode of the battery pack, forming a charging loop.

[0085] It should be noted that the step-down charging system in this embodiment can be an improvement based on the relevant existing circuits in electric vehicles. Therefore, corresponding switching devices can be set in the peripheral circuit of the step-down charging circuit according to actual situations to meet different functional requirements.

[0086] Regarding the step-down charging system in the above embodiment, the operation modes of each device have been described in detail in the embodiment related to the step-down charging circuit, and will not be elaborated here in detail.

[0087] The embodiment of the present application also provides an electric vehicle, including the step-down charging system as described above.

[0088] The embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technologies in the market, or to enable other ordinary skilled persons in the technical field to understand the embodiments disclosed herein.

Claims

1. A step-down charging circuit, characterized in that: include: A multi-phase bridge arm circuit, comprising a first bridge arm circuit and at least two second bridge arm circuits, wherein a first end of the first bridge arm circuit is used to receive an input voltage of a charging device, and a second end is connected to second ends of at least two second bridge arm circuits, and the first ends of at least two second bridge arm circuits are used to output a stepped-down output voltage to a battery pack of an electric vehicle, and the first ends of at least two second bridge arm circuits are connected in common; an inductor circuit, one end of which is connected to the middle connection point of the first bridge arm circuit, and the other end of which is respectively connected to the middle connection point of the second bridge arm circuit; a capacitor circuit connected in parallel with the second bridge arm circuit; A control unit is configured to output a set pulse width modulation (PWM) signal to a control end of an upper bridge arm of the first bridge arm circuit, wherein the upper bridge arm and the lower bridge arm of the first bridge arm circuit are not turned on or turned off at the same time, the upper bridge arm of the second bridge arm circuit is in a normally turned-on state, and the lower bridge arm of the second bridge arm circuit is in a normally turned-off state.

2. The step-down charging circuit according to claim 1, characterized in that: The control unit includes a PWM signal source configured to output a set duty cycle.

3. The step-down charging circuit according to claim 1, characterized in that: The multi-phase bridge arm circuit is a three-phase six-arm structure, each arm includes a switch device, the control end of each arm is arranged on the switch device, and the control unit is connected to the control end of the switch device of each arm.

4. The step-down charging circuit according to claim 3, characterized in that: The switch device comprises a transistor and a diode connected in reverse parallel to the transistor, and the base of the transistor is connected to the control unit.

5. The step-down charging circuit according to claim 1, characterized in that: It also includes an input filter circuit correspondingly connected to the first end and the second end of the first bridge arm circuit, or it also includes an output filter circuit correspondingly connected to the first end and the second end of the second bridge arm circuit.

6. The step-down charging circuit according to claim 1, characterized in that: The capacitive circuit includes a first capacitor, and the first capacitor is connected in parallel with the second bridge arm circuit.

7. The step-down charging circuit according to claim 1, characterized in that: The inductance circuit includes a plurality of inductors, one end of the plurality of inductors is connected in common, and the other end is respectively connected to the middle connection point of the bridge arm circuit of the corresponding phase.

8. A step-down charging system, applied to electric vehicles, characterized in that: include: A battery pack of the electric vehicle; The step-down charging circuit according to any one of claims 1 to 7, The step-down charging circuit is used to connect between a charging device and the battery pack, and to step down the input voltage received from the charging device and output it to the battery pack for charging the battery pack, wherein the input voltage received from the charging device is greater than the voltage of the battery pack.

9. The step-down charging system according to claim 8, characterized in that: Also includes: The multi-phase bridge arm circuit of the step-down charging circuit is a three-phase bridge arm circuit, and the first bridge arm circuit is used to connect the charging device, and the two second bridge arm circuits are used to connect the battery pack; A driving motor, wherein the driving motor comprises the inductance circuit, and the inductance circuit comprises three inductors, one end of the three inductors is connected in common, and the other end is respectively connected to the middle connection point of the bridge arm circuit of the corresponding phase; A switch branch, one end of which is connected to the first end of the first bridge arm circuit, and the other end of which is connected to the first end of the second bridge arm circuit.

10. The step-down charging system according to claim 9, characterized in that: The switch branch includes an insulated gate bipolar transistor IGBT, and a control end of the insulated gate bipolar transistor IGBT is connected to the control unit.

11. An electric vehicle, characterized in that: Comprising the step-down charging system as described in any one of claims 8 to 10.

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