An electric vehicle on-board charger, control system and control method

Abstract

This invention belongs to the field of power electronics and electric vehicle charging technology, and discloses an on-board charger, control system, and control method for electric vehicles. The on-board charger effectively suppresses recovery current and achieves zero-current turn-off by introducing a coupling inductor and a series current-limiting inductor. By connecting the primary windings of two identical small transformers in series and the secondary windings in parallel, and through the combination of the current-limiting inductor and the coupling inductor, zero-current turn-off of the power switching diode is achieved, significantly reducing switching losses and electromagnetic interference. This invention can reduce secondary current stress and rectification losses while maintaining isolation, weaken recovery-related losses and ringing, improve EMI, and enhance high-temperature reliability.

Description

Technical Field

[0001] This invention belongs to the field of power electronics and electric vehicle charging technology, specifically relating to an on-board charger, control system, and control method for electric vehicles. Background Technology

[0002] Single-phase on-board chargers (OBCs) commonly come in single-stage and two-stage types. Single-stage solutions have fewer components but struggle to provide isolation; two-stage solutions balance power factor and safety through front-stage power factor correction (PFC) and rear-stage isolation conversion. Bridgeless dual-boost front-stage converters have attracted attention due to their fewer diodes and lower conduction losses, but the body diode suffers from reverse recovery issues.

[0003] Chinese patent publication number CN109510453A, entitled "An EV On-board Charger Based on SiC Power Devices," includes a main circuit and a control circuit. The main circuit comprises a rectifier and filter module and an LLC resonant DC-DC circuit. The rectifier and filter module adopts a totem-pole bridgeless power factor correction circuit structure and is directly connected to a three-phase AC input power supply. The LLC resonant DC-DC circuit consists of a first half-bridge LLC converter and a second half-bridge LLC converter with identical topologies. The first and second half-bridge LLC converters are connected in parallel and then in series between the rectifier and filter module and the output side. The first and second half-bridge LLC converters respectively include a half-bridge inverter module, a high-frequency transformer module, and a passive rectifier and filter module. The rectifier and filter module and the LLC resonant DC-DC circuit are respectively connected to the control circuit. This patent application fails to solve the problem of reducing secondary current stress and rectification losses while maintaining isolation. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention aims to provide an electric vehicle on-board charger, control system and control method. By introducing a coupling inductor and a series current-limiting inductor, recovery current can be effectively suppressed and zero current switching (ZCS) can be achieved. By connecting the primary sides of two identical small transformers in series and the secondary sides in parallel, secondary current stress and rectification loss are reduced while maintaining isolation, recovery-related losses and ringing are weakened, EMI is improved and high-temperature reliability is enhanced.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an on-board charger for an electric vehicle, characterized in that it comprises: a power supply Vin, a first coupling inductor Lm1, a second coupling inductor Lm2, a third coupling inductor Lm3, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a current-limiting inductor Ls, a resonant inductor Lr, a first magnetizing inductor Lt1, a second magnetizing inductor Lt2, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a ninth diode D9, a tenth diode D10, an eleventh diode D11, a twelfth diode D12, a resonant capacitor Cr, a first capacitor C1, a first transformer T1, a second transformer T2, a filter capacitor Co, and a DC battery; The positive terminal of the power supply Vin is connected to the first terminal of the first coupling inductor Lm1. The second terminal of the first coupling inductor Lm1 is connected to the source of the second switch S2, the first terminal of the current-limiting inductor Ls, and the drain of the first switch S1. The negative terminal of the power supply Vin is connected to the anode of the second diode D2 and the cathode of the first diode D1. The cathode of the second diode D2 is connected to the drain of the second switch S2, the cathode of the fourth diode D4, the first terminal of the first capacitor C1, the drain of the fourth switch S4, and the drain of the sixth switch S6. The second terminal of the current-limiting inductor Ls is connected to the first terminal of the second coupling inductor Lm2 and the first terminal of the third coupling inductor Lm3. The second terminal of the second coupling inductor Lm2 is connected to the anode of the fourth diode D4. The second terminal of the third coupling inductor Lm3 is connected to the cathode of the third diode D3. The anode of the first diode D1 is connected to... The source of the first switching transistor S1, the anode of the third diode D3, the second terminal of the first capacitor C1, the source of the third switching transistor S3, and the source of the fifth switching transistor S5 are connected; the source of the fourth switching transistor S4 is connected to the drain of the third switching transistor S3, the drain of the fifth switching transistor S5, the source of the sixth switching transistor S6, and the first terminal of the resonant inductor Lr; the source of the fifth switching transistor S5 is connected to the first terminal of the resonant capacitor Cr; the second terminal of the resonant inductor Lr is connected to the first terminal of the first magnetizing inductor Lt1 and the first terminal of the primary winding of the first transformer T1; the second terminal of the resonant capacitor Cr is connected to the first terminal of the second magnetizing inductor Lt2 and the first terminal of the primary winding of the second transformer T2; the second terminal of the first magnetizing inductor Lt1 is connected to the second terminal of the primary winding of the first transformer T1, the second terminal of the second magnetizing inductor Lt2, and the second terminal of the second magnetizing inductor Lt2. The first end of the secondary coil of the first transformer T1 is connected to the anode of the tenth diode D10, the cathode of the eleventh diode D11, the second end of the secondary coil of the first transformer T1, the cathode of the eleventh diode D11, and the anode of the twelfth diode D12; the anode of the ninth diode D9 is connected to the anode of the eleventh diode D11; the cathode of the tenth diode is connected to the cathode of the twelfth diode D12, the cathode of the sixth diode D6, the cathode of the eighth diode D8, the first end of the filter capacitor Co, and the positive terminal of the DC battery; the first end of the secondary coil of the second transformer T2 is connected to the anode of the sixth diode D6, the cathode of the fifth diode D5, the second end of the secondary coil of the second transformer T2, the cathode of the seventh diode D7, and the anode of the eighth diode D8; the anode of the fifth diode D5 is connected to the anode of the seventh diode D7, the second end of the filter capacitor Co, and the negative terminal of the DC battery.

[0006] Optionally, the second switch S2 has an anti-parallel second body diode Ds2; the first switch S1 has an anti-parallel first body diode Ds1; the third switch S3 has an anti-parallel third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

[0007] Optionally, the third switch S3 is also connected in parallel with a third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

[0008] Optionally, the fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the ninth diode D9, the tenth diode D10, the eleventh diode D11, and the twelfth diode D12 are all silicon carbide Schottky rectifier diodes.

[0009] Optionally, the switching frequencies of the first switch S1 and the second switch S2 are both 20 kHz to 40 kHz.

[0010] Optionally, the switching frequencies of the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6 are all 80–150 kHz.

[0011] Optionally, the turns ratio n of the first coupled inductor Lm1 satisfies:

[0012] in, For charging power, For the power grid frequency, This is the RMS voltage of the power grid. This is the DC link voltage. It is a magnetized inductor.

[0013] Secondly, the present invention provides a control system for an electric vehicle on-board charger, characterized in that it comprises: A low-pass filter is used to filter the initial current; The first subtractor is used to calculate the difference between the low-pass filter output value and the DC battery charging current IRef; The first PI controller is used to input the difference result of the first subtractor and generate the modulation amount; The first absolute value unit is used to input the mains voltage V1 and output the absolute value of the mains voltage. The multiplier is used to calculate the product of the modulation amount of the first PI controller and the absolute value of the grid voltage output by the first absolute valuer; the product is used as a reference grid current. The second absolute value unit is used to input the mains current Is and output the absolute value of the mains current. The second subtractor is used to calculate the difference between the result of the second absolute value generator and the result of the multiplier. The second PI controller is used to input the difference result of the second subtractor and output the modulation index used to drive the first switch S1 and the second switch S2.

[0014] Thirdly, the present invention provides a control method for an electric vehicle on-board charger, comprising the following steps: When the AC power supply Vin is in the positive half-cycle, the first switching transistor S1 is turned on, and energy is stored through the first coupling inductor Lm1. When the first switch S1 is turned off, the first coupling inductor Lm1 will recharge the DC circuit with energy. When the AC power supply Vin is in the negative half-cycle, the second switch S2 is turned on, and energy is stored through the first coupling inductor Lm1 and the second coupling inductor Lm2. Turn off the second switch S2, and recharge the DC circuit through the first coupling inductor Lm1 and the second coupling inductor Lm2.

[0015] Optionally, the duty cycles of the first switch S1 and the second switch S2 satisfy the following:

[0016] in D Duty cycle, This is the RMS voltage of the power grid. This is the DC link voltage.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The introduction of a coupling inductor and a series current-limiting inductor in the front-end stage of this invention effectively suppresses recovery current and achieves zero-current switching (ZCS). In the back-end stage, the full-bridge LLC offers advantages in soft switching and high efficiency; connecting the primary sides of two identical small transformers in series and the secondary sides in parallel maintains isolation while reducing secondary current stress and rectification losses. For high-frequency rectification, using SiC (silicon carbide) Schottky diodes further reduces recovery-related losses and ringing, improves electromagnetic interference (EMI), and enhances high-temperature reliability.

[0018] Furthermore, this invention achieves zero-current turn-off of the power switch body diode by combining a current-limiting inductor and a coupling inductor, significantly reducing switching losses and electromagnetic interference.

[0019] This invention employs a dual-transformer series-parallel structure to distribute voltage and current stress, reduce rectification losses, and improve system power density.

[0020] This invention uses a secondary rectifier device with nearly zero reverse recovery charge, maintaining higher efficiency and stability under high frequency and high temperature conditions.

[0021] The control system of this invention adopts a dual-loop control strategy, which is simple in structure, fast in response, and easy to work in conjunction with a DC battery management system (BMS). Attached Figure Description

[0022] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings: Figure 1 This is a diagram illustrating the overall topology of an embodiment of the present invention. Figure 2 This is a schematic diagram of the energy storage process when the first switch S1 is turned on during the positive half-cycle of the AC input according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the energy transfer process after the first switch S1 is turned off according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the energy storage process when the second switch S2 is turned on during the negative half-cycle of the AC input according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the energy feedback process after the second switch S2 is turned off according to an embodiment of the present invention; Figure 6 This is a block diagram of a dual-loop cascade control system according to an embodiment of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0026] When an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments. The use of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather that it may be slightly tilted. "Horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0027] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0029] The present invention will now be described in detail with reference to the accompanying drawings.

[0030] An electric vehicle on-board charger of the present invention includes: a power supply Vin, a first coupling inductor Lm1, a second coupling inductor Lm2, a third coupling inductor Lm3, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a current limiting inductor Ls, a resonant inductor Lr, a first magnetizing inductor Lt1, a second magnetizing inductor Lt2, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a ninth diode D9, a tenth diode D10, an eleventh diode D11, a twelfth diode D12, a resonant capacitor Cr, a first capacitor C1, a first transformer T1, a second transformer T2, a filter capacitor Co, and a DC battery.

[0031] The positive terminal of the power supply Vin is connected to the first terminal of the first coupling inductor Lm1. The second terminal of the first coupling inductor Lm1 is connected to the source of the second switch S2, the first terminal of the current-limiting inductor Ls, and the drain of the first switch S1. The negative terminal of the power supply Vin is connected to the anode of the second diode D2 and the cathode of the first diode D1. The cathode of the second diode D2 is connected to the drain of the second switch S2, the cathode of the fourth diode D4, the first terminal of the first capacitor C1, the drain of the fourth switch S4, and the drain of the sixth switch S6. The second terminal of the current-limiting inductor Ls is connected to the first terminal of the second coupling inductor Lm2 and the first terminal of the third coupling inductor Lm3. The second terminal of the second coupling inductor Lm2 is connected to the anode of the fourth diode D4. The second terminal of the third coupling inductor Lm3 is connected to the cathode of the third diode D3. The anode of the first diode D1 is connected to... The source of the first switching transistor S1, the anode of the third diode D3, the second terminal of the first capacitor C1, the source of the third switching transistor S3, and the source of the fifth switching transistor S5 are connected; the source of the fourth switching transistor S4 is connected to the drain of the third switching transistor S3, the drain of the fifth switching transistor S5, the source of the sixth switching transistor S6, and the first terminal of the resonant inductor Lr; the source of the fifth switching transistor S5 is connected to the first terminal of the resonant capacitor Cr; the second terminal of the resonant inductor Lr is connected to the first terminal of the first magnetizing inductor Lt1 and the first terminal of the primary winding of the first transformer T1; the second terminal of the resonant capacitor Cr is connected to the first terminal of the second magnetizing inductor Lt2 and the first terminal of the primary winding of the second transformer T2; the second terminal of the first magnetizing inductor Lt1 is connected to the second terminal of the primary winding of the first transformer T1, the second terminal of the second magnetizing inductor Lt2, and the second terminal of the second magnetizing inductor Lt2.

[0032] The first end of the secondary coil of the first transformer T1 is connected to the anode of the tenth diode D10, the cathode of the eleventh diode D11, the second end of the secondary coil of the first transformer T1, the cathode of the eleventh diode D11, and the anode of the twelfth diode D12; the anode of the ninth diode D9 is connected to the anode of the eleventh diode D11; the cathode of the tenth diode is connected to the cathode of the twelfth diode D12, the cathode of the sixth diode D6, the cathode of the eighth diode D8, the first end of the filter capacitor Co, and the positive terminal of the DC battery; the first end of the secondary coil of the second transformer T2 is connected to the anode of the sixth diode D6, the cathode of the fifth diode D5, the second end of the secondary coil of the second transformer T2, the cathode of the seventh diode D7, and the anode of the eighth diode D8; the anode of the fifth diode D5 is connected to the anode of the seventh diode D7, the second end of the filter capacitor Co, and the negative terminal of the DC battery.

[0033] When the AC power supply Vin is in the positive half-cycle, the first switching transistor S1 is turned on, and energy is stored through the first coupling inductor Lm1. When the first switch S1 is turned off, the first coupling inductor Lm1 will recharge the DC circuit with energy. When the AC power supply Vin is in the negative half-cycle, the second switch S2 is turned on, and energy is stored through the first coupling inductor Lm1 and the second coupling inductor Lm2. Turn off the second switch S2, and recharge the DC circuit through the first coupling inductor Lm1 and the second coupling inductor Lm2.

[0034] Among them, the first switch S1, the second switch S2, the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the first coupling inductor Lm1, the second coupling inductor Lm2, the third coupling inductor Lm3, the current limiting inductor Ls, and the first capacitor C1 are the front-end circuit.

[0035] The third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the resonant inductor Lr, the resonant capacitor Cr, the first transformer T1, the second transformer T2, the fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the ninth diode D9, the tenth diode D10, the eleventh diode D11, the twelfth diode D12, and the filter capacitor Co constitute the subsequent stage circuit.

[0036] The introduction of a coupling inductor and a series current-limiting inductor in the front-end stage of this invention effectively suppresses recovery current and achieves zero-current turn-off. In the back-end stage, the full-bridge LLC offers advantages in soft switching and high efficiency; connecting the primary windings of two identical small transformers in series and the secondary windings in parallel maintains isolation while reducing secondary current stress and rectification losses. For high-frequency rectification, using SiC Schottky diodes further reduces recovery-related losses and ringing, improves electromagnetic interference, and enhances high-temperature reliability.

[0037] Example 1 like Figure 1 As shown, the present invention provides an on-board charger for electric vehicles, comprising a front-end circuit and a rear-end circuit.

[0038] like Figure 1 As shown, the front-end circuit includes a first switching transistor S1, a second switching transistor S2, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first coupling inductor Lm1, a second coupling inductor Lm2, a third coupling inductor Lm3, a current-limiting inductor Ls, and a first capacitor C1.

[0039] The subsequent circuit includes: third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, resonant inductor Lr, resonant capacitor Cr, first transformer T1, second transformer T2, fifth diode D5, sixth diode D6, seventh diode D7, eighth diode D8, ninth diode D9, tenth diode D10, eleventh diode D11, twelfth diode D12, and filter capacitor Co.

[0040] In the front-end circuit, a coupled inductor (turns ratio 1:n:n) is constructed, consisting of a first coupled inductor Lm1, a second coupled inductor Lm2, and a third coupled inductor Lm3. A current-limiting inductor Ls is connected in series in the energy recovery path; the first switch S1 is driven during the positive half-cycle of the AC input, and the second switch S2 is driven during the negative half-cycle to form two boost processes, thereby achieving power factor correction in continuous current mode.

[0041] The front-end circuit adopts a bridgeless dual boost topology, combining a coupled inductor (1:n:n) and a series current-limiting inductor Ls to achieve zero-current turn-off (ZCS) of the power switch and obtain input characteristics with near unity power factor.

[0042] The primary windings of the first transformer T1 and the second transformer T2 are connected in series, and their secondary windings are connected in parallel. The first capacitor C1 connects the two stages, and the battery side is filtered by the filter capacitor Co.

[0043] The second switch S2 has an anti-parallel second body diode Ds2; the first switch S1 has an anti-parallel first body diode Ds1; the third switch S3 has an anti-parallel third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

[0044] The third switch S3 is also connected in parallel with a third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

[0045] The primary windings of the first transformer T1 and the second transformer T2 are connected in series to share the primary voltage stress and number of turns, thereby reducing the number of turns and stress of a single transformer; the secondary windings are connected in parallel to share the output current and diode conduction losses, and the total leakage inductance of the two transformers is used as the resonant inductance Lr.

[0046] The operating frequency of the subsequent circuit is higher than the resonant frequency to maintain the ZVS of the main bridge; within this range, the near-zero reverse recovery charge of the fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the ninth diode D9, the tenth diode D10, the eleventh diode D11 and the twelfth diode D12 widens the soft-switching margin.

[0047] The operating frequencies of the first transformer T1 and the second transformer T2 are set higher than the resonant frequency to ensure that the main bridge switch achieves zero voltage switching (ZVS). The fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the ninth diode D9, the tenth diode D10, the eleventh diode D11, and the twelfth diode D12 are all silicon carbide Schottky rectifier diodes, which achieve zero current switching (ZCS), thereby reducing reverse recovery losses and electromagnetic interference.

[0048] In the turn-off path, a current-limiting inductor Ls is used to limit the recovery current slope of the body diode, causing the body diode to conduct and naturally cross zero before the main switch, thus achieving the turn-off of the preceding switch ZCS. At the output, a filter capacitor Co smooths the current and directly charges the DC battery.

[0049] Pre-amplifier optimization: By combining Ls with the coupling inductor, zero-current turn-off of the power switch body diode is achieved, significantly reducing switching losses and electromagnetic interference.

[0050] High efficiency in the subsequent stage: The use of a dual-transformer series-parallel structure distributes voltage and current stress, reduces rectification losses, and improves system power density.

[0051] Device upgrade: SiC secondary rectifier devices are used, which have almost zero reverse recovery charge, maintaining higher efficiency and stability under high frequency and high temperature conditions.

[0052] Simple and reliable control: The dual-loop control strategy has a simple structure, fast response, and is easy to work with DC battery management system (BMS).

[0053] Example 2 like Figure 6 As shown, the control system of the present invention adopts a dual-loop cascade structure, and the control system includes: A low-pass filter is used to filter the initial current; The first subtractor is used to calculate the difference between the low-pass filter output value and the DC battery charging current IRef; The first PI controller is used to input the difference result of the first subtractor and generate the modulation amount; The first absolute value unit is used to input the mains voltage V1 and output the absolute value of the mains voltage. The multiplier is used to calculate the product of the modulation amount of the first PI controller and the absolute value of the grid voltage output by the first absolute valuer. The second absolute value unit is used to input the mains current Is and output the absolute value of the mains current. The second subtractor is used to calculate the difference between the result of the second absolute value generator and the result of the multiplier. The second PI controller is used to input the difference result of the second subtractor and output the modulation index used to drive the first switch S1 and the second switch S2.

[0054] Outer loop (battery-side current loop): The DC battery charging current IRef is the controlled variable; it is adjusted by the first PI controller and compared with the reference value; the output adjustment signal is multiplied by the absolute value of the grid voltage to generate a unity power factor grid current reference.

[0055] Inner loop (grid current loop): The grid input current is the controlled variable; the second PI controller is used to generate the front-stage PWM modulation quantity, and the first switch S1 and the second switch S2 are driven according to the half-cycle polarity; only the first switch S1 is driven in the positive half-cycle and only the second switch S2 is driven in the negative half-cycle.

[0056] Post-stage control: The operating frequency is fixed above the resonant frequency; the main switch ZVS and secondary switch ZCS are realized by using fixed frequency and fixed phase shift control; the phase shift angle is used to adjust the output power.

[0057] In single-phase AC input (e.g., 220 V, 50 Hz) and kW-level power scenarios, the preferred switching frequency for the front-end stage is 20–40 kHz, and the preferred switching frequency for the rear-end stage is 80–150 kHz. The reverse withstand voltage of the SiC diode should not be lower than the secondary peak reverse voltage and should have an engineering margin. The control parameters (PI coefficient, phase shift, and dead zone) should be tuned according to EMI and temperature rise targets.

[0058] Example 3 In this embodiment, the electric vehicle on-board charger adopts a bridgeless dual boost topology structure, dividing the AC input terminal into two independent boost channels with positive and negative half cycles; the positive half cycle drives the first switch S1, and the negative half cycle drives the second switch S2.

[0059] like Figures 2 to 5 The diagram shown illustrates the current path of the front-end circuit of this invention under different operating modes.

[0060] The control method for an electric vehicle on-board charger of the present invention includes the following steps: like Figure 2 As shown, during the positive half-cycle of the AC input, the first switch S1 is turned on, and energy is stored through the first coupling inductor Lm1.

[0061] like Figure 3 As shown, after the first switch S1 is turned off, the first coupling inductor Lm1 will recharge the DC circuit with energy.

[0062] like Figure 4 As shown, during the negative half-cycle of the AC input, the second switch S2 is turned on, and energy is stored through the first coupling inductor Lm1 and the second coupling inductor Lm2.

[0063] like Figure 5 As shown, after the second switch S2 is turned off, the DC circuit is recharged through the first coupling inductor Lm1 and the second coupling inductor Lm2.

[0064] By switching between the four operating modes described above, continuous current mode operation of the front-end and zero-current turn-off of the power switch are achieved. Coupled inductors Lm1, Lm2, and Lm3 (turns ratio 1:n:n) are introduced into the boost branch to magnetically couple energy between the two channels, achieving current balance and energy sharing.

[0065] A current-limiting inductor Ls is inserted in series in the rectification path to control the rising slope of the reverse recovery current of the body diode, so that the diode current naturally crosses zero before the main switch is turned on, thereby achieving zero-current turn-off of the switch.

[0066] A DC bus capacitor C1 is connected in parallel on the output side to stabilize the bus voltage and provide energy input to the subsequent stage. The boost relationship between the output voltage and the input voltage is maintained by adjusting the duty cycle D.

[0067] In each half-cycle, only the first switch S1 or the second switch S2 is working. When the first switch S1 is turned on, energy is stored through the first coupling inductor Lm1; when the second switch S2 is turned on, energy is stored through the second coupling inductor Lm2 and the first coupling inductor Lm1.

[0068] When either the first switch S1 or the second switch S2 is turned off, energy is fed back to the DC link via the first diode D1 and the fourth diode D4. Ls limits the recovery current slope of the body diode to facilitate ZCS. In continuous current mode (Continuous Conduction Mode, CCM), the output and duty cycle relationship of the preamplifier circuit is as follows:

[0069] in D Duty cycle, This is the RMS voltage of the power grid. This is the DC link voltage.

[0070] To ensure the stability of the front-end body diode ZCS, the turns ratio n of the first coupling inductor Lm1 must satisfy:

[0071] in, For charging power, For the power grid frequency, This is the RMS voltage of the power grid. This is the DC link voltage. It is a magnetized inductor.

[0072] The subsequent stage uses a full-bridge drive and an LLC resonant cavity (Lr, Cr). The operating frequency is set higher than the resonant frequency, allowing the parasitic capacitance of the bridge arms to charge and discharge naturally, thus achieving ZVS of the main bridge. The total leakage inductance of the first transformer T1 and the second transformer T2 constitutes the resonant inductance Lr. The primary side is connected in series to reduce turns and the secondary side is connected in parallel to reduce losses. The SiC Schottky diode significantly reduces recovery-related losses and overshoot under the secondary ZCS condition, which can correspondingly reduce the RCD (Resistor-Capacitor-Diode, resistor, capacitor and diode) or RC (Resistor-Capacitor, resistor-capacitor) absorption parameters.

[0073] Unless otherwise specified, the equipment components involved in the above embodiments are all conventional equipment components, and the structural settings, working methods or control methods involved are all conventional settings, working methods or control methods in the art unless otherwise specified.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. An on-board charger for electric vehicles, characterized in that, include: Power supply Vin, first coupling inductor Lm1, second coupling inductor Lm2, third coupling inductor Lm3, first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, current limiting inductor Ls, resonant inductor Lr, first magnetizing inductor Lt1, second magnetizing inductor Lt2, first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5, sixth diode D6, seventh diode D7, eighth diode D8, ninth diode D9, tenth diode D10, eleventh diode D11, twelfth diode D12, resonant capacitor Cr, first capacitor C1, first transformer T1, second transformer T2, filter capacitor Co, and DC battery; The positive terminal of the power supply Vin is connected to the first terminal of the first coupling inductor Lm1. The second terminal of the first coupling inductor Lm1 is connected to the source of the second switch S2, the first terminal of the current limiting inductor Ls, and the drain of the first switch S1. The negative terminal of the power supply Vin is connected to the anode of the second diode D2 and the cathode of the first diode D1. The cathode of the second diode D2 is connected to the drain of the second switch S2, the cathode of the fourth diode D4, the first terminal of the first capacitor C1, the drain of the fourth switch S4, and the drain of the sixth switch S6. The second terminal of the current limiting inductor Ls is connected to the first terminal of the second coupling inductor Lm2 and the first terminal of the third coupling inductor Lm3. The second terminal of the second coupling inductor Lm2 is connected to the anode of the fourth diode D4. The second terminal of the third coupling inductor Lm3 is connected to the cathode of the third diode D3. The anode of the first diode D1 is connected to the source of the first switch S1, the anode of the third diode D3, the second terminal of the first capacitor C1, the source of the third switch S3, and the source of the fifth switch S5. The source of the fourth switch S4 is connected to the drain of the third switch S3, the drain of the fifth switch S5, the source of the sixth switch S6, and the first terminal of the resonant inductor Lr; the source of the fifth switch S5 is connected to the first terminal of the resonant capacitor Cr; the second terminal of the resonant inductor Lr is connected to the first terminal of the first magnetizing inductor Lt1 and the first terminal of the primary winding of the first transformer T1; the second terminal of the resonant capacitor Cr is connected to the first terminal of the second magnetizing inductor Lt2 and the first terminal of the primary winding of the second transformer T2; the second terminal of the first magnetizing inductor Lt1 is connected to the second terminal of the primary winding of the first transformer T1, the second terminal of the second magnetizing inductor Lt2, and the second terminal of the second magnetizing inductor Lt2. The first end of the secondary coil of the first transformer T1 is connected to the anode of the tenth diode D10, the cathode of the eleventh diode D11, the second end of the secondary coil of the first transformer T1, the cathode of the eleventh diode D11, and the anode of the twelfth diode D12; the anode of the ninth diode D9 is connected to the anode of the eleventh diode D11; the cathode of the tenth diode is connected to the cathode of the twelfth diode D12, the cathode of the sixth diode D6, the cathode of the eighth diode D8, the first end of the filter capacitor Co, and the positive terminal of the DC battery; the first end of the secondary coil of the second transformer T2 is connected to the anode of the sixth diode D6, the cathode of the fifth diode D5, the second end of the secondary coil of the second transformer T2, the cathode of the seventh diode D7, and the anode of the eighth diode D8; the anode of the fifth diode D5 is connected to the anode of the seventh diode D7, the second end of the filter capacitor Co, and the negative terminal of the DC battery.

2. The on-board charger for an electric vehicle according to claim 1, characterized in that, The second switch S2 has an anti-parallel second body diode Ds2; the first switch S1 has an anti-parallel first body diode Ds1; the third switch S3 has an anti-parallel third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

3. An electric vehicle on-board charger according to claim 2, characterized in that, The third switch S3 is also connected in parallel with a third body diode Ds3; the fourth switch S4 has an anti-parallel fourth body diode Ds4; the fifth switch S5 has an anti-parallel fifth body diode Ds5; and the sixth switch S6 has an anti-parallel sixth body diode Ds6.

4. An electric vehicle on-board charger according to claim 1, characterized in that, The fifth diode D5, the sixth diode D6, the seventh diode D7, the eighth diode D8, the ninth diode D9, the tenth diode D10, the eleventh diode D11, and the twelfth diode D12 are all silicon carbide Schottky rectifier diodes.

5. An electric vehicle on-board charger according to claim 1, characterized in that, The switching frequencies of the first switch S1 and the second switch S2 are both 20kHz to 40kHz.

6. An electric vehicle on-board charger according to claim 1, characterized in that, The switching frequencies of the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6 are all 80–150 kHz.

7. An electric vehicle on-board charger according to claim 1, characterized in that, The turns ratio n of the first coupled inductor Lm1 satisfies: in, For charging power, For the power grid frequency, The RMS voltage of the power grid. This is the DC link voltage. It is a magnetized inductor.

8. A control system for an on-board charger for an electric vehicle as described in any one of claims 1 to 7, characterized in that, include: A low-pass filter is used to filter the initial current; The first subtractor is used to calculate the difference between the low-pass filter output value and the DC battery charging current IRef; The first PI controller is used to input the difference result of the first subtractor and generate the modulation amount; The first absolute value unit is used to input the mains voltage V1 and output the absolute value of the mains voltage. The multiplier is used to calculate the product of the modulation amount of the first PI controller and the absolute value of the grid voltage output by the first absolute valuer. The product result is used as a reference grid current; The second absolute value unit is used to input the mains current Is and output the absolute value of the mains current. The second subtractor is used to calculate the difference between the result of the second absolute value generator and the result of the multiplier. The second PI controller is used to input the difference result of the second subtractor and output the modulation index used to drive the first switch S1 and the second switch S2.

9. A control method for an electric vehicle on-board charger as described in any one of claims 1 to 7, characterized in that, Includes the following steps: When the AC power supply Vin is in the positive half-cycle, the first switching transistor S1 is turned on, and energy is stored through the first coupling inductor Lm1. When the first switch S1 is turned off, the first coupling inductor Lm1 will recharge the DC circuit with energy. When the AC power supply Vin is in the negative half-cycle, the second switch S2 is turned on, and energy is stored through the first coupling inductor Lm1 and the second coupling inductor Lm2. Turn off the second switch S2, and recharge the DC circuit through the first coupling inductor Lm1 and the second coupling inductor Lm2.

10. The control method for an electric vehicle on-board charger according to claim 9, characterized in that, The duty cycles of the first switch S1 and the second switch S2 satisfy: in D Duty cycle, The RMS voltage of the power grid. This is the DC link voltage.

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