Charging circuit, on-board charger, and vehicle

Abstract

The present application relates to the technical field of on-board charging, and provides a charging circuit, an on-board charger, and a vehicle. The charging circuit comprises a power factor correction unit and a resonant unit. An input end of the power factor correction unit is electrically connected to an external power supply, and an output end thereof is electrically connected to an input end of the resonant unit. An output end of the resonant unit is electrically connected to a load. The power factor correction unit is not internally provided with a voltage-stabilizing capacitor, and the power factor correction unit is configured to rectify and boost a voltage from the external power supply to generate a fluctuating output voltage to the resonant unit. The resonant unit is configured to regulate the output voltage at a fixed conversion ratio to generate a fluctuating voltage to charge the load.

Description

A charging circuit, an on-board charger, and a vehicle

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202411951204.3, filed on December 26, 2024, entitled “A charging circuit, an on-board charger and a vehicle”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of on-board charging technology, and in particular to a charging circuit, an on-board charger, and a vehicle. Background Technology

[0004] With the rapid development of new energy vehicles, especially electric vehicles, the power density requirements for power devices are becoming increasingly stringent. Generally, for the same output power, the size of the device limits the improvement of power density. For on-board chargers of electric vehicles, since they use external AC power to charge loads (such as power batteries with the function of receiving and storing electrical energy), they inevitably require large power devices such as rectifiers, inverters, boost converters, and voltage regulators.

[0005] In related technologies, on-board chargers are basically divided into two main structures: PFC (Power Factor Correction) and LLC (Resonant Converter). Among them, the electrolytic capacitor used for voltage regulation in PFC occupies a relatively large volume, which greatly affects the improvement of power density and indirectly leads to the increase in cost, which is very detrimental to the miniaturization and cost reduction of on-board chargers. Summary of the Invention

[0006] In view of the above problems, this application provides a charging circuit, an on-board charger, and a vehicle, which better solves the above problems.

[0007] In a first aspect, some embodiments of this application provide a charging circuit, which includes: a power factor correction unit and a resonant unit;

[0008] The input terminal of the power factor correction unit is electrically connected to the external power supply, and the output terminal is electrically connected to the input terminal of the resonant unit.

[0009] The output terminal of the resonant unit is electrically connected to the load;

[0010] The power factor correction unit is configured to rectify and boost the voltage from the external power supply to generate a fluctuating output voltage to the resonant unit.

[0011] The resonant unit is configured to regulate the output voltage with a fixed turns ratio, generating a fluctuating voltage to charge the load.

[0012] In some embodiments, the power factor correction unit includes: a first bridge arm, a second bridge arm, and a third bridge arm;

[0013] The first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, and the first end of the resonant unit, respectively.

[0014] The second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, and the second end of the resonant unit, respectively.

[0015] The third end of the first bridge arm is electrically connected to the first phase line of the external power supply;

[0016] The third end of the second bridge arm is electrically connected to the second phase line of the external power supply;

[0017] The third end of the third bridge arm is connected to the neutral wire of the external power supply.

[0018] The external power supply is a single-phase power supply, and the first phase line and the second phase line are obtained by splitting one phase line of the external power supply into two paths.

[0019] In some embodiments, the power factor correction unit further includes: a first inductor and a second inductor;

[0020] The first end of the first inductor is electrically connected to the first phase line, and the second end is electrically connected to the third end of the first bridge arm.

[0021] The first end of the second inductor is electrically connected to the second phase line, and the second end is electrically connected to the third end of the second bridge arm;

[0022] The first inductor, the second inductor, the first bridge arm, and the second bridge arm form a boost structure, which boosts the voltage from the external power supply by changing the duty cycle of the switching transistors in the first and second bridge arms.

[0023] The switching frequency of the switching transistor in the third bridge arm is the same as the frequency of the external power supply. By changing the on and off state of the switching transistor in the third bridge arm, the voltage from the external power supply is rectified.

[0024] In some embodiments, the power factor correction unit includes: a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm;

[0025] The first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, the first end of the fourth bridge arm, and the first end of the resonant unit, respectively.

[0026] The second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, the second end of the fourth bridge arm, and the second end of the resonant unit, respectively.

[0027] The third end of the first bridge arm is electrically connected to the first phase line of the external power supply;

[0028] The third end of the second bridge arm is electrically connected to the second phase line of the external power supply;

[0029] The third end of the third bridge arm is electrically connected to the third phase line of the external power supply;

[0030] The third end of the fourth bridge arm is connected to the neutral wire of the external power supply.

[0031] The external power supply is a three-phase power supply, providing the first phase line, the second phase line, and the third phase line respectively.

[0032] In some embodiments, the power factor correction unit further includes: a first inductor, a second inductor, and a third inductor;

[0033] The first end of the first inductor is electrically connected to the first phase line, and the second end is electrically connected to the third end of the first bridge arm.

[0034] The first end of the second inductor is electrically connected to the second phase line, and the second end is electrically connected to the third end of the second bridge arm;

[0035] The first end of the third inductor is electrically connected to the third phase line, and the second end is electrically connected to the third end of the third bridge arm.

[0036] The first inductor, the second inductor, the third inductor, the first bridge arm, the second bridge arm, and the third bridge arm form a boost structure, which boosts the voltage from the external power supply by changing the duty cycle of the switching transistors in the first bridge arm, the second bridge arm, and the third bridge arm.

[0037] The switching frequency of the transistor in the fourth bridge arm is the same as the frequency of the external power supply. By changing the on and off state of the transistor in the fourth bridge arm, the voltage from the external power supply is rectified.

[0038] In some embodiments, the resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a fourth inductor, and a transformer;

[0039] The first end of the fifth bridge arm and the first end of the sixth bridge arm are both electrically connected to the first end of the power factor correction unit;

[0040] The second end of the fifth bridge arm and the second end of the sixth bridge arm are both electrically connected to the second end of the power factor correction unit;

[0041] The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer.

[0042] The first terminal of the fourth inductor is electrically connected to the third terminal of the sixth bridge arm, and the second terminal is electrically connected to the primary side of the transformer.

[0043] The secondary side of the transformer is electrically connected to the third end of the seventh bridge arm and the third end of the eighth bridge arm, respectively.

[0044] The first end of the seventh bridge arm is electrically connected to the first end of the eighth bridge arm and the first end of the load, respectively.

[0045] The second end of the seventh bridge arm is electrically connected to the second end of the eighth bridge arm and the second end of the load, respectively.

[0046] In some embodiments, the switching frequency of the switching transistors in the fifth and sixth bridge arms is fixed at a preset frequency. By changing the on and off states of their switching transistors, the output voltage is inverted in combination with the first capacitor and the fourth inductor to obtain a fluctuating inverter voltage.

[0047] The transformer is configured to transform the inverter voltage to obtain a regulated fluctuating inverter voltage;

[0048] By changing the on and off states of the switching transistors in the seventh and eighth bridge arms, the fluctuating inverter voltage is rectified to obtain the fluctuating voltage.

[0049] In some embodiments, the resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a second capacitor, a fourth inductor, a fifth inductor, and a transformer;

[0050] The first end of the fifth bridge arm and the first end of the sixth bridge arm are both electrically connected to the first end of the power factor correction unit;

[0051] The second end of the fifth bridge arm and the second end of the sixth bridge arm are both electrically connected to the second end of the power factor correction unit;

[0052] The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer.

[0053] The first terminal of the fourth inductor is electrically connected to the third terminal of the sixth bridge arm, and the second terminal is electrically connected to the primary side of the transformer.

[0054] The secondary side of the transformer is electrically connected to the first terminal of the second capacitor and the first terminal of the fifth inductor, respectively.

[0055] The second terminal of the fifth inductor is electrically connected to the third terminal of the seventh bridge arm;

[0056] The second terminal of the second capacitor is electrically connected to the third terminal of the eighth bridge arm;

[0057] The first end of the seventh bridge arm is electrically connected to the first end of the eighth bridge arm and the first end of the load, respectively.

[0058] The second end of the seventh bridge arm is electrically connected to the second end of the eighth bridge arm and the second end of the load, respectively.

[0059] In some embodiments, when the load is charging, the switching frequency of the switching transistors in the fifth and sixth bridge arms is fixed at a preset frequency. By changing the on and off states of the switching transistors, the output voltage is inverted in combination with the first capacitor and the fourth inductor to obtain a fluctuating inverter voltage.

[0060] The transformer is configured to transform the inverter voltage to obtain a regulated fluctuating inverter voltage;

[0061] By changing the on and off states of the switching transistors in the seventh and eighth bridge arms, and combining this with the second capacitor and the fifth inductor to rectify the fluctuating inverter voltage, a fluctuating voltage is obtained.

[0062] In some embodiments, when the load is discharged, the stable voltage continuously generated by the load is inverted into a stable inverter voltage after passing through the seventh bridge arm, the eighth bridge arm, the second capacitor, and the fifth inductor.

[0063] The stable inverter voltage is rectified into a stable rectified voltage after passing through the fifth and sixth bridge arms;

[0064] The stable rectified voltage is inverted by the power factor calibration unit to output the industrial frequency AC voltage.

[0065] In some embodiments, the charging circuit further includes: a step-down unit;

[0066] A step-down unit is used to reduce fluctuating voltage to power low-voltage equipment; or...

[0067] A step-down unit is used to reduce the stable voltage generated by the load to supply power to low-voltage equipment.

[0068] In some embodiments, the step-down unit includes: multiple inverter bridge arms, a step-down transformer, multiple rectifier bridge arms, and a voltage regulator capacitor;

[0069] The first end of multiple inverter bridge arms is electrically connected to the first end of the resonant unit, and the second end is electrically connected to the second end of the resonant unit.

[0070] The third end of each inverter bridge arm is electrically connected to the primary side of the step-down transformer;

[0071] The secondary side of the step-down transformer is electrically connected to the first end of multiple rectifier bridge arms, the first end of the voltage stabilizing capacitor, and the first end of the low-voltage equipment, respectively.

[0072] The second end of each of the rectifier bridge arms is electrically connected to the second end of the voltage regulator capacitor and the second end of the low-voltage equipment.

[0073] Among them, multiple inverter bridge arms are used to invert fluctuating voltage or stable voltage;

[0074] A step-down transformer is used to step down the fluctuating voltage or the stable voltage after inversion to obtain a fluctuating step-down voltage or a stable step-down voltage.

[0075] Multiple rectifier bridge arms, combined with voltage-stabilizing capacitors, rectify fluctuating or stable step-down voltages to obtain a stable rectified voltage for powering low-voltage equipment.

[0076] In some embodiments, the charging circuit further includes a filtering unit;

[0077] The filter unit is located between the input terminal of the power factor correction unit and the output terminal of the external voltage. It is used to filter and regulate the voltage output by the external voltage, or to filter and regulate the voltage transmitted in reverse by the load.

[0078] In some embodiments, the load includes a device having the function of receiving and storing electrical energy.

[0079] Secondly, embodiments of this application provide an on-board charger, which includes a charging circuit as described in any of the first aspects.

[0080] In some embodiments, a power module is included, which is partially submerged in a waterway. The power module integrates a target switch, which is all the switches including the power factor correction unit and the resonant unit.

[0081] In some embodiments, the target switching transistor also includes all the switching transistors in the buck unit.

[0082] In some embodiments, the on-board charger includes: a power board;

[0083] The power module also integrates a driver chip, which is controlled by the power board to control the on and off of each switching transistor;

[0084] The power board is connected to the power module. The power board integrates a control chip to control all the switching transistors in the power factor correction unit and the resonant unit to realize the function of the on-board charger.

[0085] In some embodiments, the power module is directly attached to the water channel and partially submerged in the water channel;

[0086] The power module includes: overcurrent terminals, a plastic-encapsulated housing, a heat sink, and signal terminals;

[0087] The switching transistor is integrated and then encapsulated in a plastic housing.

[0088] The heat sink base plate serves as the bottom of the power module, is mounted on the outside of the plastic-encapsulated housing, and is submerged in the water channel;

[0089] The overcurrent terminal extends out of the plastic-encapsulated housing for connection to low-voltage equipment inside the vehicle;

[0090] The signal terminals extend out of the plastic-encapsulated housing for connection to the power board.

[0091] In some embodiments, the heat dissipation base plate is provided with comb-like teeth, which are embedded in the water channels and become part of the water channels.

[0092] In some embodiments, the on-board charger further includes: a filter board, an auxiliary power drive board, and magnetic components;

[0093] After the filter board is integrated with the magnetic components, it is connected to the power board. The filter board is used to filter and stabilize the voltage output from the external power supply or the load.

[0094] The auxiliary power driver board is connected to the power board and power module respectively, and is used to provide the required low voltage to the power board and driver chip.

[0095] Magnetic components include: the inductor in the power factor correction unit, the transformer in the resonant unit, and the transformer in the step-down unit;

[0096] The power board also integrates other components, including: sampling structure, communication structure, power factor correction unit, resonant unit, and the remaining structures in the step-down unit excluding the switching transistor, inductor, and transformer.

[0097] Thirdly, some embodiments of this application also provide a vehicle, which includes the on-board charger described in the second aspect above.

[0098] The charging circuit provided in this application eliminates the need for electrolytic capacitors, utilizes the characteristics of the load itself, and breaks through the biases of related technologies by directly using fluctuating voltage to charge the load. This significantly reduces size and overhead, resulting in substantial cost savings and greatly contributing to the miniaturization and cost reduction of on-board chargers. Furthermore, because the frequency of the switching transistors in the resonant unit is fixed, there is no need to adjust the voltage range by adjusting the frequency, thus simplifying the drive control (i.e., control logic). Integrating all the switching transistors into a single power module further facilitates convection cooling of the coolant. While ensuring adequate heat dissipation, the assembly process is relatively simple, production line operation is convenient, and it possesses high practicality. Attached Figure Description

[0099] Various other advantages and benefits will become apparent to those skilled in the art from the following detailed description of some embodiments of this application. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0100] Figure 1 shows a partial structure of an on-board charger based on a related technology;

[0101] Figure 2 shows a heat dissipation structure for an on-board charger in a related technology.

[0102] Figure 3 is a modular schematic diagram of the charging circuit in some embodiments of this application;

[0103] Figure 4 is a modular schematic diagram of a charging circuit in some embodiments of this application;

[0104] Figure 5 is a modular schematic diagram of a charging circuit including a step-down unit in some embodiments of this application;

[0105] Figure 6 is a schematic diagram of a first structure of a power factor correction unit combined with a first structure of a resonant unit and including a step-down unit in some embodiments of this application.

[0106] Figure 7 is a schematic diagram of a power factor correction unit in some embodiments of this application, combining a first structure with a resonant unit and a second structure, and including a step-down unit.

[0107] Figure 8 is a schematic diagram of a second structure of a power factor correction unit combined with a second structure of a resonant unit and including a step-down unit in some embodiments of this application.

[0108] Figure 9 is a structural schematic diagram of an on-board charger in some embodiments of this application;

[0109] Figure 10 is a schematic diagram of the power module 2 in some embodiments of this application. Detailed Implementation

[0110] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this application, and are merely some embodiments of this application, not all embodiments, and are not intended to limit this application.

[0111] The applicant found that current on-board chargers for electric vehicles are basically divided into two main structures: PFC (Power Factor Correction) and LLC (Resonant Converter). Among them, the electrolytic capacitors used for voltage regulation in PFC occupy a relatively large volume. For example, as shown in Figure 1, an on-board charger structure of a related technology, where 16 represents electrolytic capacitors, can be seen to be numerous and occupy a large volume. This not only greatly affects the improvement of power density, but also indirectly leads to an increase in cost, which is very detrimental to the miniaturization and cost reduction of on-board chargers.

[0112] Furthermore, the applicant's research revealed that current on-board chargers, whether PFC or LLC structures, all use MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) as their switching transistors, and these MOSFETs are all discrete. For example, as shown in Figure 2, a related on-board charger heat dissipation structure uses bolts 6 to press spring contacts 5, and then fixes the MOSFET to the heat sink 3 for heat dissipation. This assembly process is relatively complex, inconvenient for production line operation, and results in relatively poor heat dissipation, affecting the stability of the switching transistor during production and use.

[0113] To address the aforementioned problems, the applicant, through in-depth research, has creatively proposed a charging circuit, an on-board charger, and a vehicle, which effectively solves the problems. The technical solution of this application is explained and described in detail below.

[0114] This application provides a charging circuit applicable to scenarios where an AC power source provides AC power to charge a load. The charging circuit includes a power factor correction unit and a resonant unit. Referring to the modular schematic diagram of the charging circuit shown in Figure 3, the input terminal of the power factor correction unit is electrically connected to an external power source, and its output terminal is electrically connected to the input terminal of the resonant unit; the output terminal of the resonant unit is electrically connected to the load. The load can include any device capable of receiving and storing electrical energy, such as a power battery commonly used in electric vehicles.

[0115] The charging circuit of this application innovatively eliminates the need for a voltage regulator capacitor in the power factor correction unit. Traditional PFC structures, however, typically include multiple voltage regulator capacitors (i.e., the electrolytic capacitors in Figure 1). The reason for this is the conventional misconception that a stable DC power supply is necessary. Generally, a traditional PFC rectifies and boosts the external power supply voltage into a stable DC power supply. Then, an LLC (Limited Circuit) uses different switching frequencies to regulate this stable DC power supply, obtaining a stable and suitable voltage range for charging the load. For example, assuming an external power supply provides 220V AC power, this 220V AC power is rectified and boosted by the PFC to become a stable 400V DC voltage. This stable 400V DC voltage is then regulated by the LLC using different switching frequencies to obtain a stable and suitable voltage range of 400V–600V for charging the load.

[0116] In the charging circuit of this application, the power factor correction unit does not include a voltage regulator capacitor. Instead, the power factor correction unit is configured to rectify and boost the voltage from an external power source, generating a fluctuating output voltage to the resonant unit. That is, the voltage output by the power factor correction unit to the resonant unit is a fluctuating, rippled DC voltage. Continuing with the previous example: an external power source provides 220V AC power, which, after rectification and boosting by the power factor correction unit, is converted into a fluctuating, rippled 300V–400V DC voltage. The resonant unit is configured to regulate the output voltage with a fixed turns ratio, generating a fluctuating voltage to charge the load. In other words, the switching frequency of the resonant unit is fixed, not variable. Therefore, it regulates the voltage output by the power factor correction unit with a fixed turns ratio. For example, the power factor correction unit outputs a fluctuating, rippled DC voltage of 300V to 400V to the resonant unit. The resonant unit uses a fixed switching frequency and transformer turns ratio to regulate the voltage, for example, by boosting the voltage by 1.5 times, thus obtaining a fluctuating, rippled voltage range of 450V to 600V to charge the load.

[0117] The resonant unit of this application outputs a ripple voltage. Since the output of the resonant unit is connected to the load, and the load can be regarded as a large capacitor with a high capacitance, and the characteristics of the capacitor itself determine that it can effectively clamp the ripple voltage. Therefore, it can ensure that the ripple voltage output by the resonant unit forms a stable DC voltage without affecting the service life of the load itself.

[0118] This application creatively breaks away from the biases of traditional technology, cleverly utilizing the characteristic that the load itself can be equivalent to a large capacitor (especially since the capacity and voltage level of power batteries, which are currently typical loads, are getting larger and larger, exhibiting the characteristic of larger capacitance), directly eliminating the need for electrolytic capacitors, significantly reducing size and saving costs, which is very beneficial for the miniaturization and cost reduction of on-board chargers. At the same time, since the frequency of the switching transistor in the resonant unit is fixed, there is no need to adjust the voltage range by adjusting the frequency, thus simplifying the drive control (i.e., control logic).

[0119] In some embodiments of this application, considering that the resonant unit outputs a rippled voltage, which may affect the electromagnetic compatibility of the entire charging circuit, the charging circuit further includes a filtering unit. Referring to Figure 4, a modular schematic diagram of a charging circuit is shown. The filtering unit is disposed between the input terminal of the power factor correction unit and the output terminal of the external voltage. The filtering unit is used to filter and regulate the voltage output by the external voltage, or to filter and regulate the voltage transmitted in reverse by the load, thereby meeting the electromagnetic compatibility design requirements.

[0120] The charging circuit provided in this application has various structures for the power factor correction unit and the resonant unit. Only a few different structural forms are exemplified below. Those skilled in the art can obtain the remaining structures by simple transformations or reasoning based on the listed structural forms. They will not be described in detail here.

[0121] The first structural form of the power factor correction unit in this application:

[0122] The power factor correction unit includes: a first bridge arm, a second bridge arm, and a third bridge arm; the first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, and the first end of the resonant unit, respectively; the second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, and the second end of the resonant unit, respectively.

[0123] The third end of the first bridge arm is electrically connected to the first phase line of the external power supply; the third end of the second bridge arm is electrically connected to the second phase line of the external power supply; and the third end of the third bridge arm is electrically connected to the neutral line of the external power supply. The external power supply is a single-phase power supply, and the first and second phase lines are obtained by splitting a single phase line from the external power supply into two paths. Generally, each bridge arm is formed by two MOSFETs connected in series, and the third end of the bridge arm refers to the connection point of the two series-connected MOSFETs. This first structure can be considered as the structure of a power factor correction unit for a single-phase external power supply. Typically, a single-phase power supply has only one live wire L and one neutral wire N. The live wire L is divided into two paths: one path L1 is electrically connected to the third end of the first bridge arm, and the other path L2 is electrically connected to the third end of the second bridge arm. The remaining neutral wire N is electrically connected to the third end of the third bridge arm.

[0124] In addition, if there is a boost requirement, the power factor correction unit also needs to include: a first inductor and a second inductor; the first end of the first inductor is electrically connected to the first phase line and the second end is electrically connected to the third end of the first bridge arm; the first end of the second inductor is electrically connected to the second phase line and the second end is electrically connected to the third end of the second bridge arm, that is, the first inductor is located between the first phase line L1 and the first bridge arm, and the second inductor is located between the second phase line L2 and the second bridge arm.

[0125] The first inductor, the second inductor, the first bridge arm, and the second bridge arm form a boost converter structure. The voltage from the external power supply is boosted by changing the duty cycle of the switches in the first and second bridge arms. The switching frequency of the switch in the third bridge arm is the same as the frequency of the external power supply, meaning its duty cycle is 0.5. The voltage from the external power supply is rectified by changing the on / off state of the switch in the third bridge arm.

[0126] The second structural form of the power factor correction unit in this application:

[0127] The power factor correction unit includes: a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm; the first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, the first end of the fourth bridge arm, and the first end of the resonant unit, respectively; the second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, the second end of the fourth bridge arm, and the second end of the resonant unit, respectively.

[0128] The third end of the first bridge arm is electrically connected to the first phase line of the external power supply; the third end of the second bridge arm is electrically connected to the second phase line of the external power supply; the third end of the third bridge arm is electrically connected to the third phase line of the external power supply; and the third end of the fourth bridge arm is electrically connected to the neutral line of the external power supply. The external power supply is a three-phase power supply, providing the first, second, and third phase lines respectively. This second structure can be considered as the structure of a power factor correction unit for a three-phase external power supply. Generally, a three-phase power supply has three live wires L1, L2, and L3 and one neutral wire N. Each live wire is electrically connected to the third end of its corresponding bridge arm, and the remaining neutral wire N is electrically connected to the third end of the fourth bridge arm.

[0129] Similarly, if a boost converter is required, the power factor correction unit also needs to include: a first inductor, a second inductor, and a third inductor; the first end of the first inductor is electrically connected to the first phase line, and the second end is electrically connected to the third end of the first bridge arm; the first end of the second inductor is electrically connected to the second phase line, and the second end is electrically connected to the third end of the second bridge arm; the first end of the third inductor is electrically connected to the third phase line, and the second end is electrically connected to the third end of the third bridge arm. That is, the first inductor is located between the first phase line L1 and the first bridge arm, the second inductor is located between the second phase line L2 and the second bridge arm, and the third inductor is located between the third phase line L3 and the third bridge arm.

[0130] The first, second, and third inductors, along with the first, second, and third bridge arms, form a boost converter structure. The voltage from the external power supply is boosted by changing the duty cycle of the switches in the first, second, and third bridge arms. The switching frequency of the switch in the fourth bridge arm is the same as the frequency of the external power supply, meaning its duty cycle is 0.5. By changing the on / off state of the switch in the fourth bridge arm, the voltage from the external power supply is rectified.

[0131] The first structural form of the resonant unit in this application:

[0132] The resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a fourth inductor, and a transformer. The first end of the fifth bridge arm and the first end of the sixth bridge arm are both electrically connected to the first end of the power factor correction unit; the second end of the fifth bridge arm and the second end of the sixth bridge arm are both electrically connected to the second end of the power factor correction unit.

[0133] The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer. The first terminal of the fourth inductor is electrically connected to the third terminal of the sixth bridge arm, and the second terminal is electrically connected to the primary side of the transformer. The secondary side of the transformer is electrically connected to the third terminals of the seventh and eighth bridge arms, respectively. The first terminal of the seventh bridge arm is electrically connected to the first terminal of the eighth bridge arm and the first terminal of the load, respectively. The second terminal of the seventh bridge arm is electrically connected to the second terminal of the eighth bridge arm and the second terminal of the load, respectively.

[0134] The switching frequency of the switching transistors in the fifth and sixth bridge arms is fixed at a preset frequency (this preset frequency is an empirical value obtained through a large number of tests, and the optimal value can be 180kHz). By changing the on and off states of their switching transistors, the fluctuating output voltage is inverted in combination with the first capacitor and the fourth inductor to obtain the fluctuating inverter voltage.

[0135] The transformer is configured to transform the fluctuating inverter voltage to obtain a regulated fluctuating inverter voltage; by changing the on and off states of the switching transistors in the seventh and eighth bridge arms, the fluctuating inverter voltage is rectified to obtain the fluctuating voltage.

[0136] The first structural form of the resonant unit described above can charge the load, but considering practical needs, the load may also need to output electrical energy under certain conditions. Therefore, the second structural form of the resonant unit in this application is proposed:

[0137] The resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a second capacitor, a fourth inductor, a fifth inductor, and a transformer. The first end of the fifth bridge arm and the first end of the sixth bridge arm are electrically connected to the first end of the power factor correction unit; the second end of the fifth bridge arm and the second end of the sixth bridge arm are electrically connected to the second end of the power factor correction unit.

[0138] The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer; the first terminal of the fourth inductor is electrically connected to the third terminal of the sixth bridge arm, and the second terminal is electrically connected to the primary side of the transformer; the secondary side of the transformer is electrically connected to the first terminal of the second capacitor and the first terminal of the fifth inductor, respectively.

[0139] The second terminal of the fifth inductor is electrically connected to the third terminal of the seventh bridge arm; the second terminal of the second capacitor is electrically connected to the third terminal of the eighth bridge arm; the first terminal of the seventh bridge arm is electrically connected to the first terminal of the eighth bridge arm and the first terminal of the load, respectively; the second terminal of the seventh bridge arm is electrically connected to the second terminal of the eighth bridge arm and the second terminal of the load, respectively.

[0140] When the load is charging, the switching frequencies of the switching transistors in the fifth and sixth bridge arms are fixed at a preset frequency. By changing the on and off states of the switching transistors, the output voltage is inverted using the first capacitor and the fourth inductor to obtain a fluctuating inverter voltage. The transformer transforms the inverter voltage to obtain a regulated fluctuating inverter voltage. By changing the on and off states of the switching transistors in the seventh and eighth bridge arms, the fluctuating inverter voltage is rectified using the second capacitor and the fifth inductor to obtain a fluctuating voltage.

[0141] When the load is discharging, that is, when the load outputs power frequency AC voltage through the charging circuit, the stable voltage continuously generated by the load is inverted into a stable inverter voltage after passing through the seventh bridge arm, the eighth bridge arm, the second capacitor, and the fifth inductor; the stable inverter voltage is rectified into a stable rectified voltage after passing through the fifth bridge arm and the sixth bridge arm; the stable rectified voltage is then inverted into a power frequency AC voltage after passing through the power factor calibration unit for output.

[0142] The power factor correction unit and resonant unit structures described above can be combined in any way to form a charging circuit. For example: combining the first power factor correction unit structure with the first resonant unit structure can produce a charging circuit that charges the load when the external power supply is single-phase; combining the first power factor correction unit structure with the second resonant unit structure can produce a charging circuit that charges the load when the external power supply is single-phase, and the load can output AC voltage at power frequency to the outside; combining the second power factor correction unit structure with the second resonant unit structure can produce a charging circuit that charges the load when the external power supply is three-phase, and the load can output AC voltage at power frequency to the outside, and so on.

[0143] In addition, electric vehicles typically include a step-down unit (DC-DC converter), so the charging circuit also includes a step-down unit; see Figure 5 for a modular schematic diagram of a charging circuit containing a step-down unit. The step-down unit is used to reduce fluctuating voltage to power low-voltage devices; alternatively, it can reduce the stable voltage generated by the load to power low-voltage devices. Low-voltage devices generally refer to equipment that uses low voltage, such as the vehicle battery, air conditioner, and vehicle infotainment system.

[0144] In some embodiments of this application, the step-down unit includes: multiple inverter bridge arms, a step-down transformer, multiple rectifier bridge arms, and a voltage regulator capacitor; the first end of the multiple inverter bridge arms is electrically connected to the first end of the resonant unit, and the second end is electrically connected to the second end of the resonant unit; the third end of each inverter bridge arm is electrically connected to the primary side of the step-down transformer.

[0145] The secondary side of the step-down transformer is electrically connected to the first end of multiple rectifier bridge arms, the first end of the voltage stabilizing capacitor, and the first end of the low-voltage equipment, respectively; the second end of multiple rectifier bridge arms is electrically connected to the second end of the voltage stabilizing capacitor and the second end of the low-voltage equipment.

[0146] In this system, multiple inverter bridge arms are used to invert fluctuating voltage (when the external power supply provides voltage) or stable voltage (when the load provides voltage); step-down transformers are used to step down the fluctuating voltage or stable voltage after inversion to obtain fluctuating step-down voltage or stable step-down voltage; multiple rectifier bridge arms, combined with voltage stabilizing capacitors, rectify the fluctuating step-down voltage or stable step-down voltage to obtain stable rectified voltage to power low-voltage equipment.

[0147] To better understand the above structural form, refer to the structural diagram of the first structure of the power factor correction unit combined with the first structure of the resonant unit and including the step-down unit shown in Figure 6. The external power supply is a single-phase power supply. The live wire L is divided into two paths, which are respectively connected to the first inductor L1 and the second inductor L2. The first inductor L1 is connected to the switching transistors Q1 and Q2 (Q1 and Q2 form the first bridge arm), and the second inductor L2 is connected to the switching transistors Q3 and Q4 (Q3 and Q4 form the second bridge arm). The neutral wire N of the single-phase power supply is connected to the switching transistors Q5 and Q6 (Q5 and Q6 form the third bridge arm). Among them, Q1, Q2, Q3, and Q4 are high-frequency transistors, commonly known as fast transistors, and Q5 and Q6 are power frequency transistors, commonly known as slow transistors. The above parts constitute the power factor correction circuit.

[0148] The first inductor L1, the second inductor L2, and the switching transistors Q1, Q2, Q3, and Q4 constitute the BOOST boost circuit. By changing the duty cycle of the switching transistors Q1, Q2, Q3, and Q4, the output voltage of the power factor correction unit can be adjusted. The switching frequency of the switching transistors Q5 and Q6 is the same as the frequency of the external power supply, with a duty cycle of 0.5. Switch Q5 conducts during the negative half-cycle of the external power supply voltage, and switch Q6 conducts during the positive half-cycle of the external power supply voltage, used to rectify the AC power output from the external power supply into DC power.

[0149] The resonant unit consists of switching transistors Q7, Q8 (Q7 and Q8 form the fifth bridge arm), Q9, Q10 (Q9 and Q10 form the sixth bridge arm), Q11, Q12 (Q11 and Q12 form the seventh bridge arm), Q13, Q14 (Q13 and Q14 form the eighth bridge arm), a first capacitor C1, a transformer T1, and a fourth inductor L4. The switching frequencies of the switching transistors Q7, Q8, Q9, and Q10 are fixed. At this switching frequency, the fluctuating DC power output from the power factor correction unit is converted into sinusoidal AC power by the first capacitor C1, the transformer T1, and the fourth inductor L4. After being rectified by the switching transistors Q11, Q12, Q13, and Q14, it is converted into fluctuating DC power and output to the load. In Figure 6, the load is represented by the power battery BAT.

[0150] In the buck converter, the fluctuating voltage is inverted into AC by switching transistors Q15, Q16, Q17, and Q18, then transformed by transformer T2, and finally rectified by switching transistors Q19, Q20, Q21, Q22, Q23, Q24, Q25, and Q26 to output a low-voltage DC voltage. This voltage charges the vehicle battery and the vehicle's low-voltage equipment (represented by R in the diagram). Alternatively, the buck converter can also reverse the voltage output. The low-voltage DC voltage from the battery is inverted by switching transistors Q19, Q20, Q21, Q22, Q23, Q24, Q25, and Q26, transformed by transformer T2, and then rectified by switching transistors Q15, Q16, Q17, and Q18 to output a high-voltage DC voltage.

[0151] Referring to Figure 7, the diagram illustrates the structure of the power factor correction unit (first structure) combined with the resonant unit (second structure) and includes a step-down unit. The difference between Figure 7 and Figure 6 is that a second capacitor C2 and a fifth inductor L5 are added to the secondary side of transformer T1 in the resonant unit to achieve the reverse function of the charging circuit. The load, represented by the power battery BAT in Figure 7, generates a DC voltage that is inverted into a high-frequency sinusoidal AC voltage by switches Q11, Q12, Q13, Q14, the second capacitor C2, the fifth inductor L5, and transformer T1. This AC voltage is then rectified into DC voltage by switches Q7, Q8, Q9, and Q10, and finally inverted into a mains frequency AC voltage by switches Q1, Q2, Q3, Q4, Q5, and Q6 before being output. The remaining structure is the same as in Figure 6 and will not be described further.

[0152] Referring to Figure 8, which shows a schematic diagram of the second structure of the power factor correction unit combined with the second structure of the resonant unit and includes a step-down unit, the difference between Figure 8 and Figure 7 is that the external power supply is a three-phase power supply, and the input of the power factor correction unit is three-phase AC. Switches Q1, Q2, Q3, Q4, Q5, Q6, the first inductor L1, the second inductor L2, and the third inductor L3 are used to boost the three-phase AC voltage. Switches Q7 and Q8 (in Figure 8, Q7 and Q8 form the fourth bridge arm; Q9 and Q10 form the fifth bridge arm; Q11 and Q12 form the sixth bridge arm; Q12 and Q14 form the seventh bridge arm; and Q15 and Q16 form the eighth bridge arm) are used for rectification, outputting a boosted DC voltage. The remaining structure is the same as in Figure 7 and will not be described again.

[0153] The above explains and describes the charging circuit that omits the electrolytic capacitor. In order to solve the problem of heat dissipation caused by the discrete switching transistors, this application also proposes an on-board charger based on the above charging circuit. The on-board charger includes the charging circuit of any of the above.

[0154] In some embodiments of this application, the on-board charger includes: a power module, partially submerged in a water channel, and a target switching transistor integrated in the power module. This target switching transistor includes all the switching transistors in the power factor correction unit and the resonant unit, as well as all the switching transistors in the buck unit. That is, switching transistors Q1 to Q26 in Figures 6 and 7, or switching transistors Q1 to Q28 in Figure 8, are all integrated in the power module.

[0155] In some embodiments of this application, the on-board charger further includes a power board.

[0156] The power module also integrates a driver chip, which is controlled by the power board to control the on and off states of each switching transistor.

[0157] The power board is connected to the power module. The power board integrates a control chip to control all the switching transistors in the power factor correction unit, resonant unit, and buck unit to realize the function of the on-board charger.

[0158] For on-board chargers, to achieve the corresponding functions, they also include: a filter board, an auxiliary power drive board, and magnetic components. Referring to a schematic diagram of an on-board charger structure shown in Figure 9, Figure 9 includes: a power board 1, a power module 2, a filter board 4, an auxiliary power drive board 5, magnetic components 6, and a water channel 3. The filter board 4, integrated with the magnetic components 6, is connected to the control board 1. The filter board 4 is used to filter and stabilize the voltage output from the external power supply or the load. That is, the filter board is the aforementioned filtering unit.

[0159] The auxiliary power driver board 5 is connected to the power board 1 and the power module 2 respectively, and is used to provide the required low voltage to the power board 1 and the driver chip. It is generally 12V; the magnetic components include: the inductors in the power factor correction unit (the first inductor L1 and the second inductor L2 in Figures 6 and 7), the transformer in the resonant unit (T1 in Figures 6, 7 and 8), and the transformer in the step-down unit (T2 in Figures 6, 7 and 8);

[0160] Power board 1 is connected to power module 2. Besides integrating the control chip, power board 1 also integrates other components to control all the switching transistors in the power factor correction unit and resonant unit, thereby realizing the function of the on-board charger. In other words, the main function of the charging circuit is implemented by power board 1. These other components of power board 1 include: the sampling structure, communication structure, power factor correction unit, resonant unit, and the remaining structures in the step-down unit excluding the switching transistors, inductors, and transformers (e.g., the first capacitor C1 and the fourth inductor L4 in Figure 6; the first capacitor C1, the second capacitor C2, the fourth inductor L4, and the fifth inductor L5 in Figure 7, etc.).

[0161] The power module 2 is directly attached to the water channel 3, and part of it is submerged in the water channel. Referring to the structural schematic diagram of the power module 2 shown in Figure 10, it includes: an overcurrent terminal 21, a plastic-encapsulated housing 22, a heat dissipation base plate 23, and a signal terminal 24.

[0162] The switching transistor is integrated and encapsulated in a plastic housing 22; the heat dissipation base plate 23 serves as the bottom of the power module 2, is installed outside the plastic housing 22, and is submerged in the water channel 3; the overcurrent terminal 21 extends out of the plastic housing 22 and is used to connect with the low-voltage equipment in the vehicle (i.e., the external low-voltage high-current load) to ensure the normal operation of the external low-voltage load; the signal terminal 24 extends out of the plastic housing 22 and is used to connect with the power board 1.

[0163] In some embodiments of this application, the heat dissipation base plate 23 is provided with comb-shaped teeth, which are embedded in the water channel 3 and become part of the water channel 3; the coolant flows through the heat dissipation base plate 23 and the comb-shaped teeth of the base plate for convective heat dissipation, which is beneficial to the full heat dissipation of the power module 2, while its assembly process is relatively simple and the production line operation is convenient. The plastic encapsulation shell 22 is preferably made of epoxy resin material to integrally encapsulate the power module 2, which has the characteristics of high temperature resistance and high reliability.

[0164] Based on the above charging circuit, some embodiments of this application also propose a vehicle, which includes the on-board charger mentioned above. Through the above embodiments, the charging circuit, on-board charger, and vehicle provided by this application directly eliminate the need for electrolytic capacitors, utilize the characteristics of the load itself, break through the biases of related technologies, and directly use fluctuating voltage to charge the load, significantly reducing volume overhead and saving costs, which is highly beneficial for the miniaturization and cost reduction of on-board chargers. Simultaneously, since the frequency of the switching transistors in the resonant unit is fixed, there is no need to adjust the voltage range by adjusting the frequency, thus simplifying the drive control (i.e., control logic). Furthermore, integrating all the switching transistors into a single power module is more conducive to coolant convection heat dissipation. While ensuring sufficient heat dissipation, its assembly process is relatively simple, production line operation is convenient, and it has high practicality.

[0165] Although some embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including some embodiments as well as all changes and modifications falling within the scope of the embodiments of this application.

[0166] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0167] The embodiments of this application have been described above in conjunction with the accompanying drawings, and have been detailed. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A charging circuit, wherein, The charging circuit includes: a power factor correction unit and a resonant unit; The input terminal of the power factor correction unit is electrically connected to an external power supply, and the output terminal is electrically connected to the input terminal of the resonant unit. The output terminal of the resonant unit is electrically connected to the load. The power factor correction unit is configured to rectify and boost the voltage from the external power supply to generate a fluctuating output voltage to the resonant unit. The resonant unit is configured to regulate the output voltage with a fixed turns ratio, generating a fluctuating voltage to charge the load.

2. The charging circuit according to claim 1, wherein, The power factor correction unit includes: a first bridge arm, a second bridge arm, and a third bridge arm; The first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, and the first end of the resonant unit, respectively. The second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, and the second end of the resonant unit, respectively. The third end of the first bridge arm is electrically connected to the first phase line of the external power supply; The third end of the second bridge arm is electrically connected to the second phase line of the external power supply; The third end of the third bridge arm is electrically connected to the neutral wire of the external power supply. The external power source is a single-phase power source, and the first phase line and the second phase line are obtained by splitting one phase line of the external power source into two paths.

3. The charging circuit according to claim 2, wherein, The power factor correction unit further includes: a first inductor and a second inductor; The first end of the first inductor is electrically connected to the first phase line, and the second end is electrically connected to the third end of the first bridge arm; The first end of the second inductor is electrically connected to the second phase line, and the second end is electrically connected to the third end of the second bridge arm; The first inductor, the second inductor, the first bridge arm, and the second bridge arm form a boost structure, which boosts the voltage from the external power supply by changing the duty cycle of the switching transistors in the first bridge arm and the second bridge arm. The switching frequency of the switching transistor in the third bridge arm is the same as the frequency of the external power supply. By changing the on and off state of the switching transistor in the third bridge arm, the voltage from the external power supply is rectified.

4. The charging circuit according to any one of claims 1-3, wherein, The power factor correction unit includes: a first bridge arm, a second bridge arm, a third bridge arm, and a fourth bridge arm; The first end of the first bridge arm is electrically connected to the first end of the second bridge arm, the first end of the third bridge arm, the first end of the fourth bridge arm, and the first end of the resonant unit, respectively. The second end of the first bridge arm is electrically connected to the second end of the second bridge arm, the second end of the third bridge arm, the second end of the fourth bridge arm, and the second end of the resonant unit, respectively. The third end of the first bridge arm is electrically connected to the first phase line of the external power supply; The third end of the second bridge arm is electrically connected to the second phase line of the external power supply; The third end of the third bridge arm is electrically connected to the third phase line of the external power supply; The third end of the fourth bridge arm is connected to the neutral wire of the external power supply. The external power source is a three-phase power source, providing the first phase line, the second phase line, and the third phase line respectively.

5. The charging circuit according to claim 4, wherein, The power factor correction unit further includes: a first inductor, a second inductor, and a third inductor; The first end of the first inductor is electrically connected to the first phase line, and the second end is electrically connected to the third end of the first bridge arm; The first end of the second inductor is electrically connected to the second phase line, and the second end is electrically connected to the third end of the second bridge arm; The first end of the third inductor is electrically connected to the third phase line, and the second end is electrically connected to the third end of the third bridge arm; The first inductor, the second inductor, the third inductor, the first bridge arm, the second bridge arm, and the third bridge arm form a boost structure, which boosts the voltage from the external power supply by changing the duty cycle of the switching transistors in the first bridge arm, the second bridge arm, and the third bridge arm. The switching frequency of the switching transistor in the fourth bridge arm is the same as the frequency of the external power supply. By changing the on and off state of the switching transistor in the fourth bridge arm, the voltage from the external power supply is rectified.

6. The charging circuit according to any one of claims 1-5, wherein, The resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a fourth inductor, and a transformer; The first end of the fifth bridge arm and the first end of the sixth bridge arm are both electrically connected to the first end of the power factor correction unit; The second end of the fifth bridge arm and the second end of the sixth bridge arm are both electrically connected to the second end of the power factor correction unit; The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer. The first end of the fourth inductor is electrically connected to the third end of the sixth bridge arm, and the second end is electrically connected to the primary side of the transformer. The secondary side of the transformer is electrically connected to the third end of the seventh bridge arm and the third end of the eighth bridge arm, respectively. The first end of the seventh bridge arm is electrically connected to the first end of the eighth bridge arm and the first end of the load, respectively. The second end of the seventh bridge arm is electrically connected to the second end of the eighth bridge arm and the second end of the load, respectively.

7. The charging circuit according to claim 6, wherein, The switching frequency of each switch in the fifth and sixth bridge arms is fixed at a preset frequency. By changing the on and off states of the switch, combined with the first capacitor and the fourth inductor, the output voltage is inverted to obtain a fluctuating inverter voltage. The transformer is configured to transform the inverter voltage to obtain a regulated fluctuating inverter voltage; The fluctuating inverter voltage is rectified by changing the on and off states of the switching transistors in the seventh and eighth bridge arms to obtain the fluctuating voltage.

8. The charging circuit according to any one of claims 1-7, wherein, The resonant unit includes: a fifth bridge arm, a sixth bridge arm, a seventh bridge arm, an eighth bridge arm, a first capacitor, a second capacitor, a fourth inductor, a fifth inductor, and a transformer; The first end of the fifth bridge arm and the first end of the sixth bridge arm are both electrically connected to the first end of the power factor correction unit; The second end of the fifth bridge arm and the second end of the sixth bridge arm are both electrically connected to the second end of the power factor correction unit; The first terminal of the first capacitor is electrically connected to the third terminal of the fifth bridge arm, and the second terminal is electrically connected to the primary side of the transformer. The first end of the fourth inductor is electrically connected to the third end of the sixth bridge arm, and the second end is electrically connected to the primary side of the transformer. The secondary side of the transformer is electrically connected to the first terminal of the second capacitor and the first terminal of the fifth inductor, respectively. The second end of the fifth inductor is electrically connected to the third end of the seventh bridge arm; The second terminal of the second capacitor is electrically connected to the third terminal of the eighth bridge arm; The first end of the seventh bridge arm is electrically connected to the first end of the eighth bridge arm and the first end of the load, respectively. The second end of the seventh bridge arm is electrically connected to the second end of the eighth bridge arm and the second end of the load, respectively.

9. The charging circuit according to claim 8, wherein, When the load is charging, the switching frequency of the switching transistors in the fifth and sixth bridge arms is fixed at a preset frequency. By changing the on and off states of the switching transistors, the output voltage is inverted in combination with the first capacitor and the fourth inductor to obtain a fluctuating inverter voltage. The transformer is configured to transform the inverter voltage to obtain a regulated fluctuating inverter voltage; The fluctuating voltage is obtained by changing the on and off states of the switching transistors in the seventh and eighth bridge arms, and by rectifying the fluctuating inverter voltage in conjunction with the second capacitor and the fifth inductor.

10. The charging circuit according to any one of claims 8-9, wherein, When the load is discharged, the stable voltage continuously generated by the load is inverted into a stable inverter voltage after passing through the seventh bridge arm, the eighth bridge arm, the second capacitor, and the fifth inductor. The stable inverter voltage is rectified into a stable rectified voltage after passing through the fifth bridge arm and the sixth bridge arm; The stable rectified voltage is inverted by the power factor calibration unit to output the industrial frequency AC voltage.

11. The charging circuit according to any one of claims 1-10, wherein, The charging circuit further includes: a step-down unit; The step-down unit is used to reduce the fluctuating voltage to supply power to low-voltage equipment; or... The step-down unit is used to step down the stable voltage generated by the load to supply power to the low-voltage equipment.

12. The charging circuit according to claim 11, wherein, The step-down unit includes: multiple inverter bridge arms, a step-down transformer, multiple rectifier bridge arms, and a voltage stabilizing capacitor; The first end of each of the plurality of inverter bridge arms is electrically connected to the first end of the resonant unit, and the second end is electrically connected to the second end of the resonant unit; The third end of each inverter bridge arm is electrically connected to the primary side of the step-down transformer; The secondary side of the step-down transformer is electrically connected to the first end of the plurality of rectifier bridge arms, the first end of the voltage stabilizing capacitor, and the first end of the low-voltage equipment, respectively. The second end of each of the plurality of rectifier bridge arms is electrically connected to the second end of the voltage stabilizing capacitor and the second end of the low-voltage device; The plurality of inverter bridge arms are used to invert the fluctuating voltage or the stable voltage; The step-down transformer is used to step down the fluctuating voltage or the stable voltage after inversion to obtain a fluctuating step-down voltage or a stable step-down voltage. The multiple rectifier bridge arms, in conjunction with the voltage stabilizing capacitor, rectify the fluctuating step-down voltage or the stable step-down voltage to obtain a stable rectified voltage for powering the low-voltage equipment.

13. The charging circuit according to any one of claims 1-12, wherein, The charging circuit further includes: a filtering unit; The filtering unit is disposed between the input terminal of the power factor correction unit and the output terminal of the external voltage, and is used to filter and regulate the voltage output by the external voltage, or to filter and regulate the voltage transmitted in reverse by the load.

14. The charging circuit according to any one of claims 1-13, wherein, The load includes: a device that has the function of receiving and storing electrical energy.

15. An on-board charger, wherein, The on-board charger includes a charging circuit as described in any one of claims 1-14.

16. The on-board charger according to claim 15, wherein, include: A power module, partially submerged in a waterway, integrates a target switching transistor, which includes all the switching transistors in the power factor correction unit and the resonant unit.

17. The on-board charger according to claim 16, wherein, The target switching transistor also includes all the switching transistors in the buck unit.

18. The on-board charger according to any one of claims 15-16, wherein, The on-board charger includes: a power board; The power module also integrates a driver chip, which is controlled by the power board to control the on and off states of each switching transistor. The power board is connected to the power module. The power board integrates a control chip for controlling all the switching transistors in the power factor correction unit, the resonant unit, and the buck unit to realize the function of the on-board charger.

19. The on-board charger according to any one of claims 16-18, wherein, The power module is directly attached to the waterway and is partially submerged in the waterway; The power module includes: overcurrent terminals, a plastic-encapsulated housing, a heat sink, and signal terminals; The integrated switching transistor is encapsulated within the plastic-encapsulated housing. The heat dissipation base plate serves as the bottom of the power module, is installed on the outside of the plastic-encapsulated housing, and is submerged in the water channel; The overcurrent terminal extends out of the encapsulated housing for connection to low-voltage equipment inside the vehicle. The signal terminal extends out of the plastic-encapsulated housing for connection to the power board.

20. The on-board charger according to claim 19, wherein, The heat dissipation base plate is provided with comb-shaped teeth, which are embedded in the water channel and become part of the water channel.

21. The on-board charger according to any one of claims 18-20, wherein, The on-board charger also includes: a filter board, an auxiliary power drive board, and magnetic components; The filter board is integrated with the magnetic device and then connected to the power board. The filter board is used to filter and stabilize the voltage output by the external power supply or the voltage output by the load. The auxiliary power driver board is connected to the power board and the power module respectively, and is used to provide the required low voltage to the power board and the driver chip; The magnetic device includes: an inductor in the power factor correction unit, a transformer in the resonant unit, and a transformer in the step-down unit; The power board also integrates other components, including: a sampling structure, a communication structure, the power factor correction unit, the resonant unit, and the remaining structures in the step-down unit excluding the switching transistor, inductor, and transformer.

22. A vehicle, wherein, The vehicle includes: the on-board charger according to any one of claims 15-21.

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