CN219124101U - Bidirectional conversion circuit, bidirectional conversion device and LLC bidirectional converter - Google Patents

Abstract

The utility model discloses a bidirectional conversion circuit, a bidirectional conversion device and an LLC bidirectional converter, which relate to the technical field of circuit conversion, and the bidirectional conversion circuit is provided with a resonance unit, wherein the resonance unit comprises a first inductor, a first capacitor and a change-over switch, the first inductor is connected with a control end of the change-over switch, and the first capacitor is connected with the change-over switch in parallel; the resonance unit is used for keeping the voltage constant when the voltage is converted, so as to obtain a constant voltage; the change-over switch is used for carrying out circuit switching under different modes, the first inductor is used as resonance of circuits with different flow directions under different modes, the voltage is constant, the first inductor is arranged in the resonance unit, and the circuit switching is carried out through the change-over switch, so that the first inductor forms different circuit loops and is used as resonance of different flow directions circuits, the excitation inductance in the transformer is avoided, and the loss and the circuit cost during bidirectional conversion are reduced.

Description

Bidirectional conversion circuit, bidirectional conversion device and LLC bidirectional converter

Technical Field

The present utility model relates to the field of circuit conversion technologies, and in particular, to a bidirectional conversion circuit, a bidirectional conversion device, and an LLC bidirectional converter.

Background

The DC-DC converter is a converter for regulating energy transmission and has wide application in occasions such as micro energy storage systems, vehicle-mounted power supply systems, feedback charge-discharge systems, hybrid energy electric vehicles and the like. However, the soft switching range is narrow, the turn-off current is large, and the like, so that the overall efficiency of the converter is affected. At present, the exciting inductance of the transformer is mainly used as inductance to perform circuit transformation, but the complexity of the manufacturing process of the transformer is increased, the cost is higher, and meanwhile, the air gap of the magnetic core of the transformer is increased, so that the efficiency of the transformer is reduced.

Disclosure of Invention

The utility model mainly aims to provide a bidirectional conversion circuit, a bidirectional conversion device and an LLC bidirectional converter, and aims to solve the technical problems of low bidirectional conversion efficiency and high cost in the prior art.

To achieve the above object, the present utility model proposes a bidirectional conversion circuit including a resonance unit including: the switching device comprises a first inductor, a first capacitor and a switching switch, wherein the first inductor is connected with a control end of the switching switch, and the first capacitor is connected with the switching switch in parallel;

the resonance unit is used for keeping the voltage constant when the voltage is converted to obtain a constant voltage;

the change-over switch is used for switching circuits in different modes, and the first inductor is used as resonance of circuits with different flow directions in different modes to keep the voltage constant.

Optionally, the resonance unit further includes: a second inductor;

the first end of the first capacitor is connected with the first switching end of the switching switch, the first end of the second inductor is connected with the second end of the first capacitor, and the second end of the second inductor is connected with the second switching end of the switching switch.

Optionally, the bidirectional conversion circuit further comprises a high-voltage unit, a transformation unit and a low-voltage unit, wherein the high-voltage unit, the resonance unit, the transformation unit and the low-voltage unit are sequentially connected;

the high-voltage unit is used for accessing high-voltage direct-current voltage and converting the high-voltage direct-current voltage into high-voltage alternating-current voltage;

the resonance unit is used for keeping the high-voltage alternating voltage constant to obtain constant alternating voltage;

the transformation unit is used for reducing the constant alternating voltage to obtain reduced alternating voltage;

the low-voltage unit is used for converting the reduced alternating voltage to obtain reduced direct voltage and outputting the reduced direct voltage.

Optionally, the high voltage unit includes: the high-voltage power supply comprises a high-voltage power supply port, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube;

the high-voltage power supply port is used for accessing or outputting high-voltage direct-current voltage;

the high-voltage power supply port is respectively connected with the input end of the first switching tube and the input end of the second switching tube;

the output end of the third switching tube and the output end of the fourth switching tube are grounded;

the output end of the first switching tube, the output end of the second switching tube, the input end of the third switching tube and the input end of the fourth switching tube are respectively connected with the resonance unit.

Optionally, the first switching tube includes: the first MOS pipe, the second switch tube includes: the second MOS pipe, the third switching tube includes: the third MOS transistor, the fourth switching transistor includes: a fourth MOS transistor;

the drain electrode of the first MOS tube and the drain electrode of the second MOS tube are respectively connected with the high-voltage power supply port, and the source electrode of the first MOS tube, the source electrode of the second MOS tube, the drain electrode of the third MOS tube and the drain electrode of the fourth MOS tube are respectively connected with the resonance unit;

and the source electrode of the third MOS tube and the source electrode of the fourth MOS tube are grounded.

Optionally, the low-voltage unit includes: a fifth switching tube, a sixth switching tube, a seventh switching tube and an eighth switching tube;

the low-voltage power supply port is used for accessing or outputting a step-down direct-current voltage;

the input end of the fifth switching tube and the input end of the sixth switching tube are respectively connected with the low-voltage power supply port

The output end of the fifth switching tube, the output end of the sixth switching tube, the output end of the seventh switching tube and the output end of the eighth switching tube are respectively connected with the transformation unit;

the input end of the seventh switching tube and the input end of the eighth switching tube are grounded.

Optionally, the fifth switching tube includes: a fifth MOS transistor, the sixth switching transistor includes: a sixth MOS transistor, the seventh switching transistor includes: seventh MOS pipe, eighth switching tube includes: an eighth MOS transistor;

the drain electrode of the fifth MOS tube and the drain electrode of the sixth MOS tube are respectively connected with the power supply port;

the source electrode of the fifth MOS tube, the source electrode of the sixth MOS tube, the drain electrode of the seventh MOS tube and the drain electrode of the eighth MOS tube are respectively connected with the voltage transformation unit;

and the source electrode of the seventh MOS tube and the source electrode of the eighth MOS tube are grounded.

Optionally, the transformation unit includes: a transformer;

the primary side of the transformer is connected with the resonance unit, and the secondary side of the transformer is connected with the low-voltage unit.

Furthermore, to achieve the above object, the present utility model also proposes a bidirectional conversion device comprising a bidirectional conversion circuit as described above.

Furthermore, to achieve the above object, the present utility model also proposes an LLC bidirectional converter comprising a bidirectional conversion circuit as described above.

In the utility model, a resonance unit is arranged in a bidirectional conversion circuit, the resonance unit comprises a first inductor, a first capacitor and a change-over switch, the first inductor is connected with a control end of the change-over switch, and the first capacitor is connected with the change-over switch in parallel; the resonance unit is used for keeping the voltage constant when the voltage is converted, so as to obtain a constant voltage; the change-over switch is used for carrying out circuit switching under different modes, the first inductor is used as resonance of circuits with different flow directions under different modes, the voltage is constant, the first inductor is arranged in the resonance unit, and the circuit switching is carried out through the change-over switch, so that the first inductor forms different circuit loops and is used as resonance of different flow directions circuits, the excitation inductance in the transformer is avoided, and the loss and the circuit cost during bidirectional conversion are reduced.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of a bi-directional conversion circuit according to a first embodiment of the present utility model;

FIG. 2 is a schematic diagram of a circuit structure of a prior art bi-directional conversion circuit;

fig. 3 is a schematic diagram of a bidirectional conversion circuit according to a second embodiment of the present utility model.

The achievement of the objects, functional features and advantages of the present utility model will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

Reference numerals illustrate:

reference numerals	Name of the name	Reference numerals	Name of the name
				10	Resonant unit	M1～M4	First to fourth MOS transistors
L1	First inductor	30	Transformation unit
				L2	Second inductor	TX	Transformer
C1	First capacitor	40	Low-voltage unit
				20	High-voltage unit	V2	Low-voltage power supply port
V1	High voltage power supply port	401～404	Fifth to eighth switching tubes
				201～204	First to fourth switching tubes	M5～M8	Fifth to eighth MOS transistors

Detailed Description

It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model.

The following description of the embodiments of the present utility model will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present utility model are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.

Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present utility model.

Referring to fig. 1, fig. 1 is a schematic diagram of a bidirectional conversion circuit according to a first embodiment of the present utility model. The present utility model proposes a first embodiment of a bi-directional conversion circuit.

In this embodiment, as shown in fig. 1, the bidirectional conversion circuit includes a resonance unit 10, and the resonance unit 10 includes: the switching device comprises a first inductor L1, a first capacitor C1 and a switching switch K, wherein the first inductor L1 is connected with a control end of the switching switch K, and the first capacitor C1 is connected with the switching switch K in parallel; the resonance unit 10 is configured to perform voltage conversion to obtain a constant voltage; the switch K is configured to switch the circuit in different modes, and use the first inductance L1 as resonance of the circuit in different flow directions in different modes to perform constant voltage.

The resonance unit 10 is configured to perform voltage stabilization in the bidirectional conversion circuit, for example, when performing voltage boosting, the resonance unit 10 performs voltage stabilization to obtain a constant high voltage; when the voltage is reduced, the resonance unit 10 keeps the low voltage constant, and a constant low voltage is obtained.

In a specific implementation, by providing the first inductor L1, the first capacitor C1 and the switch K in the resonant unit 10, in different modes, the first inductor L1 is used as resonance of circuits with different flow directions in different modes by controlling the position of the switch K, so that the high voltage or the low voltage can be kept constant. Devices that do not participate in resonance do not have excess inductance and do not additionally generate current to avoid additional losses. The different modes include a boost mode and a buck mode, with the current flow of the boost mode and the buck mode being different.

It should be understood that the switch K may be a single pole double throw switch, or may be another type of switch, and this embodiment is not limited thereto, and in different modes, the switch K may be controlled to switch to different circuit loops, and the switch K may include a first switch end and a second switch end, for example, in a boost mode, the switch K is switched to the first switch end, so that the first inductor L1 and the first capacitor C1 are connected in parallel, in a buck mode, the switch K is switched to the second switch end, so that the first inductor L1 and the first capacitor C1 are connected in series, and so on, so that a soft switch may be implemented in any direction of the bidirectional conversion circuit, and loss when the bidirectional conversion circuit is reduced.

As shown in fig. 2, fig. 2 is a schematic circuit diagram of a bidirectional conversion circuit in the prior art, in which an inductance LM-TX exists in a transformer, and the inductance LM-TX of the transformer is used as resonance to perform bidirectional conversion, but because the transformer needs to be additionally designed with an inductance, the complexity of the manufacturing process of the transformer is increased, the cost is higher, and the magnetic core of the transformer needs to be increased with an air gap, so that the efficiency of the transformer is reduced, and when energy is transmitted from V2 to V1, the LM-TX of the transformer is in operation, so that the working efficiency of the transformer is reduced.

In this embodiment, the resonance unit 10 further includes: a second inductance L2; the first end of the first capacitor C1 is connected with the first switching end of the switching switch K, the first end of the second inductor L2 is connected with the second end of the first capacitor C1, and the second end of the second inductor L2 is connected with the second switching end of the switching switch K.

It should be understood that the first capacitor C1 is connected in series with the second inductor L2, the first end of the first inductor L1 is connected to the loop of the resonant unit 10, the second end of the first inductor L1 is connected to the control end of the switch K, and the switch K can selectively switch the first end of the first capacitor C1 or the second end of the second inductor L2.

In the embodiment, a resonance unit is arranged in the bidirectional conversion circuit and comprises a first inductor, a first capacitor and a change-over switch, wherein the first inductor is connected with a control end of the change-over switch, and the first capacitor is connected with the change-over switch in parallel; the resonance unit is used for keeping the voltage constant when the voltage is converted, so as to obtain a constant voltage; the change-over switch is used for carrying out circuit switching under different modes, the first inductor is used as resonance of circuits with different flow directions under different modes, the voltage is constant, the first inductor is arranged in the resonance unit, and the circuit switching is carried out through the change-over switch, so that the first inductor forms different circuit loops and is used as resonance of different flow directions circuits, the excitation inductance in the transformer is avoided, and the loss and the circuit cost during bidirectional conversion are reduced.

Referring to fig. 3, fig. 3 is a schematic diagram of a bidirectional conversion circuit according to a second embodiment of the present utility model.

Based on the first embodiment, the bidirectional conversion circuit in this embodiment further includes a high voltage unit 20, a voltage transformation unit 30, and a low voltage unit 40, where the high voltage unit 20, the resonance unit 10, the voltage transformation unit 30, and the low voltage unit 40 are sequentially connected.

The high voltage unit 20, the resonance unit 10, the transformation unit 30, and the low voltage unit are sequentially connected, the high voltage unit 20 may be connected to a high voltage dc voltage in the step-up mode, and the high voltage unit 20 may output a low voltage dc voltage in the step-down mode. The resonance unit 10 may be constant for different voltages including a high voltage or a low voltage in different modes, and a constant voltage is obtained by constant for the high voltage or the low voltage. The voltage transformation unit 30 is used to step down a constant voltage transmitted from the resonance unit 10, step up a low voltage transmitted from the low voltage unit 30, and the like. The low voltage unit 40 may convert the ac voltage into the dc voltage, and output the converted dc voltage. The low voltage unit 40 may also receive a low voltage dc voltage, and convert the low voltage dc voltage into a low voltage ac voltage to the voltage transformation unit 30.

In this embodiment, the high voltage unit 20 is configured to switch in a high voltage dc voltage and convert the high voltage dc voltage into a high voltage ac voltage; the resonance unit 10 is configured to perform constant high-voltage ac voltage to obtain constant ac voltage; the voltage transformation unit 30 is configured to step down the constant ac voltage to obtain a step-down ac voltage; the low voltage unit 40 is configured to convert the reduced ac voltage to obtain a reduced dc voltage, and output the reduced dc voltage.

In a specific implementation, when energy is converted from the high voltage unit 20 to the low voltage unit 40, the current flows from left to right, and the switch K switches the first inductor L1 to the second inductor L2 close to the end of the transforming unit 30, so that the first inductor L1 is put into resonance, and the exciting inductance inside the transformer TX is not used, so that the loss caused by the current can be reduced. When energy is converted from the low-voltage unit 40 to the high-voltage unit 20, the current flow direction is from right to left, the change-over switch K switches the first inductor L1 to the end of the first capacitor C1, which is close to the high-voltage unit 20, so that the first inductor L1 is subjected to resonance, no extra inductor exists in the transformation unit 30, the loss caused by the current can be reduced, the self-inductance is not needed to be considered, the conversion efficiency is improved, and the effect caused by the switching of the first inductor L1 at different positions according to the flow direction of the energy is also different.

In this embodiment, the high voltage unit 20 includes: a high-voltage power supply port V1, a first switching tube 201, a second switching tube 202, a third switching tube 203, and a fourth switching tube 204; the high-voltage power supply port V1 is used for accessing or outputting high-voltage direct-current voltage; the high-voltage power supply port V1 is connected to the input end of the first switching tube 201 and the input end of the second switching tube 202 respectively; the output end of the third switching tube 203 and the output end of the fourth switching tube 204 are grounded; the output end of the first switching tube 201, the output end of the second switching tube 202, the input end of the third switching tube 203 and the input end of the fourth switching tube 204 are respectively connected with the resonance unit 10.

It should be understood that the high voltage power supply port V1 may be connected to the high voltage direct current voltage or output the high voltage direct current voltage, and the high voltage power supply port V1 is connected to the input terminal of the first switching tube 201 and the input terminal of the second switching tube 202, and the first switching tube 201 includes: first MOS pipe M1, second switch tube 202 includes: the second MOS transistor M2, the third switching transistor 203 includes: third MOS pipe M3, fourth switching tube 204 includes: fourth MOS transistor M4. The drain electrode of the first MOS transistor M1 and the drain electrode of the second MOS transistor M2 are respectively connected with the high-voltage power supply port V1, and the source electrode of the first MOS transistor M1, the source electrode of the second MOS transistor M2, the drain electrode of the third MOS transistor M3 and the drain electrode of the fourth MOS transistor M4 are respectively connected with the resonance unit 10; the source electrode of the third MOS transistor M3 and the source electrode of the fourth MOS transistor M4 are grounded.

It should be noted that, the gates of the first MOS transistor M1, the second MOS transistor M2, the third MOS transistor M3, and the fourth MOS transistor M4 may be connected to the control module, and the control module outputs a control signal to the first MOS transistor M1 to the fourth MOS transistor M4 to control the on or off of the first MOS transistor M1 to the fourth MOS transistor M4, so as to convert the high-voltage dc voltage into the high-voltage ac voltage. The grid electrode of the first MOS tube M1 and the drain electrode of the third MOS tube M3 are respectively connected with the first end of the first capacitor C1 and the first switching end of the switching switch K, and after the switching switch K is switched to the first switching end, the source electrode of the first MOS tube M1 and the drain electrode of the third MOS tube M3 are connected with the second end of the first inductor L1. The source electrode of the second MOS tube M2 and the drain electrode of the fourth MOS tube M4 are respectively connected with the first end of the first inductor L1, and the first end of the first inductor L1 is also connected with the voltage transformation unit 30.

The drain electrode of the first MOS tube M1 and the drain electrode of the second MOS tube M2 are respectively connected with the positive electrode of the high-voltage power supply port V1, and the source electrode of the third MOS tube M3 and the source electrode of the fourth MOS tube M4 are grounded.

In this embodiment, the low-voltage unit 40 includes: a low-voltage power supply port V2, a fifth switching tube 401, a sixth switching tube 402, a seventh switching tube 403, and an eighth switching tube 404; the low-voltage power supply port V2 is used for accessing or outputting a step-down direct-current voltage; the input end of the fifth switching tube 401 and the input end of the sixth switching tube 402 are respectively connected with the low-voltage power supply port V2; the output end of the fifth switching tube 401, the output end of the sixth switching tube 402, the output end of the seventh switching tube 403 and the output end of the eighth switching tube 404 are respectively connected with the transformation unit 30; the input terminal of the seventh switching tube 403 and the input terminal of the eighth switching tube 404 are grounded.

It should be understood that the low voltage power supply port V2 may be connected to the low voltage dc voltage or output the low voltage dc voltage, and the low voltage power supply port V2 is connected to the input terminal of the fifth switching tube 401, the input terminal of the sixth switching tube 402, the output terminal of the seventh switching tube 403, and the output terminal of the eighth switching tube 404.

In this embodiment, the fifth switching tube 401 includes: a fifth MOS transistor M5, the sixth switching transistor 402 includes: sixth MOS transistor M6, said seventh switching transistor 403 includes: seventh MOS transistor M7, the eighth switching transistor 404 includes: eighth MOS transistor M8; the drain electrode of the fifth MOS tube M5 and the drain electrode of the sixth MOS tube M6 are respectively connected with the low-voltage power supply port V2; the source electrode of the fifth MOS transistor M5, the source electrode of the sixth MOS transistor M6, the drain electrode of the seventh MOS transistor M7, and the drain electrode of the eighth MOS transistor M8 are respectively connected to the voltage transformation unit 30; the source electrode of the seventh MOS tube M7 and the source electrode of the eighth MOS tube are grounded.

The transforming unit 30 includes: a transformer TX; the primary side of the transformer TX is connected to the resonance unit 10, and the secondary side of the transformer TX is connected to the low voltage unit 40.

The first end of the secondary side of the transformer TX is connected with the source electrode of the fifth MOS tube M5 and the drain electrode of the seventh MOS tube M7 respectively, the second end of the secondary side of the transformer TX is connected with the source electrode of the sixth MOS tube M6 and the drain electrode of the eighth MOS tube M8 respectively, the source electrodes of the seventh MOS tube M7 and the eighth MOS tube M8 are grounded, and the drain electrode of the fifth MOS tube M5 and the drain electrode of the sixth MOS tube M6 are connected with the positive electrode of the low-voltage power port V2 respectively. The gates of the fifth MOS tube M5, the sixth MOS tube M6, the seventh MOS tube M7 and the eighth MOS tube M8 are connected with the control module, and the control module can output control signals to control the fifth MOS tube M5 to the eighth MOS tube M8 and control the fifth MOS tube M5 to the eighth MOS tube M8 to be turned on or turned off, so that low-voltage alternating-current voltage is converted, and low-voltage direct-current voltage is obtained. In the buck mode, the low voltage unit 40 converts the buck ac voltage to obtain a buck dc voltage and outputs the buck dc voltage, and in the boost mode, the low voltage unit 40 converts the buck dc voltage to obtain a buck ac voltage and transmits the buck ac voltage to the transformer TX, so that the transformer TX boosts the buck ac voltage to obtain a boost ac voltage and transmits the boost ac voltage to the resonance unit 10, so that the resonance unit 10 constantly boosts the ac voltage to obtain a constant ac voltage and transmits the constant ac voltage to the high voltage unit 20, and the high voltage unit 20 converts the constant ac voltage to a high voltage dc voltage and outputs the high voltage dc voltage.

In the embodiment, a high-voltage unit, a transformation unit and a low-voltage unit are further arranged in the bidirectional conversion circuit, and the high-voltage unit, the resonance unit, the transformation unit and the low-voltage unit are sequentially connected; the high-voltage unit is used for accessing high-voltage direct-current voltage and converting the high-voltage direct-current voltage into high-voltage alternating-current voltage; the resonance unit is used for keeping the high-voltage alternating voltage constant to obtain constant alternating voltage; the transformation unit is used for reducing the constant alternating voltage to obtain reduced alternating voltage; the low-voltage unit is used for converting the reduced alternating voltage to obtain reduced direct voltage and outputting the reduced direct voltage. The high-voltage unit, the resonance unit, the transformation unit and the low-voltage unit are used for bidirectional transformation, the resonance is carried out through the inductance in the resonance unit, no extra inductance exists in the transformation unit, the loss during bidirectional transformation is reduced, and the transformation efficiency is improved.

In order to achieve the above purpose, the present utility model further provides a bidirectional conversion device. The bi-directional conversion means comprises a bi-directional conversion circuit as described above. The bidirectional conversion device can adopt the technical schemes of all the embodiments, so that the bidirectional conversion device has at least the beneficial effects brought by the technical schemes of the embodiments, and is not described in detail herein.

To achieve the above object, the present utility model also proposes an LLC bidirectional converter comprising a bidirectional conversion circuit as described above. The LLC bidirectional converter can adopt the technical schemes of all the embodiments, so that the LLC bidirectional converter has at least the beneficial effects brought by the technical schemes of the embodiments, and will not be described in detail herein.

The foregoing description is only of the preferred embodiments of the present utility model, and is not intended to limit the scope of the utility model, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.

Claims (10)

1. A bidirectional conversion circuit, characterized in that the bidirectional conversion circuit comprises a resonance unit comprising: the switching device comprises a first inductor, a first capacitor and a switching switch, wherein the first inductor is connected with a control end of the switching switch, and the first capacitor is connected with the switching switch in parallel;

the resonance unit is used for keeping the voltage constant when the voltage is converted to obtain a constant voltage;

the change-over switch is used for switching circuits in different modes, and the first inductor is used as resonance of circuits with different flow directions in different modes to keep the voltage constant.

2. The bi-directional conversion circuit of claim 1, wherein the resonant unit further comprises: a second inductor;

the first end of the first capacitor is connected with the first switching end of the switching switch, the first end of the second inductor is connected with the second end of the first capacitor, and the second end of the second inductor is connected with the second switching end of the switching switch.

3. The bidirectional conversion circuit as recited in claim 2 further comprising a high voltage unit, a voltage transformation unit, and a low voltage unit, the high voltage unit, the resonant unit, the voltage transformation unit, and the low voltage unit being connected in sequence;

the high-voltage unit is used for accessing high-voltage direct-current voltage and converting the high-voltage direct-current voltage into high-voltage alternating-current voltage;

the resonance unit is used for keeping the high-voltage alternating voltage constant to obtain constant alternating voltage;

the transformation unit is used for reducing the constant alternating voltage to obtain reduced alternating voltage;

the low-voltage unit is used for converting the reduced alternating voltage to obtain reduced direct voltage and outputting the reduced direct voltage.

4. The bi-directional conversion circuit of claim 3, wherein the high voltage unit comprises: the high-voltage power supply comprises a high-voltage power supply port, a first switching tube, a second switching tube, a third switching tube and a fourth switching tube;

the high-voltage power supply port is used for accessing or outputting high-voltage direct-current voltage;

the high-voltage power supply port is respectively connected with the input end of the first switching tube and the input end of the second switching tube;

the output end of the third switching tube and the output end of the fourth switching tube are grounded;

the output end of the first switching tube, the output end of the second switching tube, the input end of the third switching tube and the input end of the fourth switching tube are respectively connected with the resonance unit.

5. The bi-directional conversion circuit of claim 4, wherein the first switching tube comprises: the first MOS pipe, the second switch tube includes: the second MOS pipe, the third switching tube includes: the third MOS transistor, the fourth switching transistor includes: a fourth MOS transistor;

the drain electrode of the first MOS tube and the drain electrode of the second MOS tube are respectively connected with the high-voltage power supply port, and the source electrode of the first MOS tube, the source electrode of the second MOS tube, the drain electrode of the third MOS tube and the drain electrode of the fourth MOS tube are respectively connected with the resonance unit;

and the source electrode of the third MOS tube and the source electrode of the fourth MOS tube are grounded.

6. The bi-directional conversion circuit of claim 3, wherein the low voltage unit comprises: a fifth switching tube, a sixth switching tube, a seventh switching tube and an eighth switching tube;

the low-voltage power supply port is used for accessing or outputting a step-down direct-current voltage;

the input end of the fifth switching tube and the input end of the sixth switching tube are respectively connected with the low-voltage power supply port;

the output end of the fifth switching tube, the output end of the sixth switching tube, the output end of the seventh switching tube and the output end of the eighth switching tube are respectively connected with the transformation unit;

the input end of the seventh switching tube and the input end of the eighth switching tube are grounded.

7. The bi-directional conversion circuit according to claim 6, wherein the fifth switching tube comprises: a fifth MOS transistor, the sixth switching transistor includes: a sixth MOS transistor, the seventh switching transistor includes: seventh MOS pipe, eighth switching tube includes: an eighth MOS transistor;

the drain electrode of the fifth MOS tube and the drain electrode of the sixth MOS tube are respectively connected with the power supply port;

the source electrode of the fifth MOS tube, the source electrode of the sixth MOS tube, the drain electrode of the seventh MOS tube and the drain electrode of the eighth MOS tube are respectively connected with the voltage transformation unit;

and the source electrode of the seventh MOS tube and the source electrode of the eighth MOS tube are grounded.

8. The bidirectional conversion circuit as recited in any one of claims 3 to 7 wherein the transformation unit comprises: a transformer;

the primary side of the transformer is connected with the resonance unit, and the secondary side of the transformer is connected with the low-voltage unit.

9. A bi-directional conversion device, characterized in that it comprises a bi-directional conversion circuit according to any of the preceding claims 1 to 8.

10. An LLC bi-directional converter, characterized in that it comprises a bi-directional conversion circuit according to any of the preceding claims 1 to 8.

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