Bidirectional cycle resonance isolation type DC-DC converter

Abstract

The invention relates to a bidirectional cyclic resonance isolation type DC-DC converter. The system comprises a conversion main circuit and a control circuit, the conversion main circuit comprises a high-frequency transformer, windings on the two sides of the high-frequency transformer are respectively connected with a cyclic resonant converter used for voltage conversion in a matched mode, during voltage conversion, one cyclic resonant converter is used for carrying out DC-AC conversion firstly, and then one cyclic resonant converter is used for carrying out DC-AC conversion. At least carrying out AC-DC conversion through the cooperation of the high-frequency transformer and another cyclic resonant converter, and generating a target conversion voltage after the AC-DC conversion; the cyclic resonant converter comprises a resonant conversion bridge circuit and a resonant inductor adaptively connected with the resonant conversion bridge circuit. The two sides of the high-frequency transformer are respectively connected with one cyclic resonant converter, so that the number of switching tubes used during cyclic conversion can be reduced, the voltage on a resonant capacitor can be reduced, soft switching in the whole process is realized, the cost is reduced, and the efficiency of voltage conversion is improved.

Description

Technical Field

[0001] The present invention relates to a DC-DC converter, and more particularly to a bidirectional cyclic resonant isolated DC-DC converter. Background Art

[0002] In recent years, with the rapid development of DC power distribution, DC transformers, and DC electric vehicle charging pile technologies, DC-DC converters with bidirectional power flow have also received increasing research. A bidirectional DC-DC converter is a power device capable of bidirectional energy flow. It can serve as a connection bridge between a distributed new energy power generation system and an energy storage system, and can provide a reliable channel for the dynamic conversion between the energy storage system and the power generation system, thereby completing the safe transfer of energy. With the rapid progress of different material switching devices and power electronics-related technologies, the power density and efficiency of bidirectional DC-DC converters have been effectively improved.

[0003] According to the presence or absence of electrical isolation, bidirectional DC-DC converters can be divided into isolated and non-isolated types. Although the structure of non-isolated bidirectional DC-DC converters is relatively simple, they cannot achieve electrical isolation and cannot be applied in high-power requirements. Currently, the topologies applied to high-power isolated bidirectional DC-DC converters generally use dual active bridges, which can be divided into voltage type and current type according to the presence or absence of a storage inductor; in addition, according to whether they are resonant, DC-DC converters can also be divided into non-resonant and resonant types.

[0004] Non-resonant bidirectional DC-DC converters have the characteristics of simple control and easy module parallel connection. However, due to their large turn-off losses, the improvement of efficiency is limited. Although methods such as minimum return power optimization, current stress optimization, and root mean square current optimization can improve efficiency, the improvement space is limited, and the control complexity is increased.

[0005] For resonant bidirectional DC-DC converters, there are types such as LC series and LC parallel resonance, LCC and LLC series-parallel resonance, etc. Among them, LLC resonant types have a relatively high switching frequency, and at the same time, the voltage regulation range is wide. The symmetric bidirectional LLC resonant converter with an auxiliary inductor has one less resonant capacitor than the traditional LLC resonant converter, but the switching frequency range is still wide.

[0006] For a symmetric bidirectional LLC resonant converter, by adding a bidirectional AC switch on the secondary side of the transformer, while maintaining high efficiency, the voltage regulation ability of the converter can be increased through PWM modulation. However, this increases the cost and complexity. To improve the wide-range output of the bidirectional DC-DC converter, a full-bridge structure can be adopted, adding an auxiliary transformer and switching tubes to form a flyback bidirectional DC-DC converter, which can achieve soft switching within the full load range and reduce switching losses. However, the disadvantage is that the circuit is complex and will lead to increased costs.

[0007] For a dual active bridge DC-DC converter, its control methods usually include frequency conversion control, phase shift control, PWM control, synchronous rectification control, etc. Among them, in the frequency conversion control mode, the voltage gain changes with the operating frequency of the converter. Therefore, there are high requirements for the transformer design. If the design is not good, greater losses will be generated, resulting in a decrease in efficiency. At the same time, the switching speed of the energy bidirectional flow is relatively slow, and the converter current is uncontrollable, restricting the application in module parallel connection and high-power occasions;

[0008] When using duty cycle control, the amount of energy transfer of the converter is controlled by the duty cycle, and it is difficult for the switching tubes to achieve soft switching. Therefore, it is only applicable to occasions with small power transmission and occasions that do not require high-efficiency energy transmission;

[0009] When using phase shift control, the converter is controlled by controlling the phase shift angle, which is widely applied. Summary of the Invention

[0010] The object of the present invention is to overcome the deficiencies existing in the prior art and provide a bidirectional cyclic resonant isolated DC-DC converter, which is respectively connected with a cyclic resonant converter on both sides of the high-frequency transformer, so as to reduce the number of switching tubes used in the cyclic conversion, reduce the voltage on the resonant capacitor, achieve soft switching throughout the process, reduce costs, and improve the efficiency of voltage conversion.

[0011] According to the technical solution provided by the present invention, a bidirectional cyclic resonant isolated DC-DC converter, the DC-DC converter includes a main conversion circuit and a control circuit for controlling the working state of the main conversion circuit, wherein,

[0012] The main conversion circuit includes a high-frequency transformer, and the windings on both sides of the high-frequency transformer are respectively adaptively connected with a cyclic resonant converter for voltage conversion. Among them, during voltage conversion, a cyclic resonant converter is first used for DC-AC conversion, and then, through the cooperation of the high-frequency transformer and another cyclic resonant converter, at least AC-DC conversion is performed, and the target conversion voltage is generated after the AC-DC conversion;

[0013] The cyclic resonant converter includes a resonant conversion bridge circuit and a resonant inductor adaptively connected to the resonant conversion bridge circuit, where

[0014] The resonant conversion bridge circuit includes a first bridge arm of resonant conversion and a second bridge arm of resonant conversion. The first bridge arm of resonant conversion includes a first bridge arm switching tube and a first bridge arm resonant capacitor, and the second bridge arm of the resonant converter includes a second bridge arm switching tube and a second bridge arm resonant capacitor, where

[0015] The first end of the first bridge arm switching tube and the first end of the second bridge arm switching tube are connected to the first end of the resonant inductor. The second end of the resonant inductor is connected to the first end of the corresponding side winding of the high-frequency transformer. The second end of the corresponding side winding of the high-frequency transformer is connected to the first end of the first bridge arm resonant capacitor and the first end of the second bridge arm resonant capacitor.

[0016] The second end of the first bridge arm resonant capacitor is adaptively connected to the second end of the first bridge arm switching tube to form the first connection end of the bridge circuit of the resonant conversion bridge circuit; at the same time, the second end of the second bridge arm resonant capacitor is adaptively connected to the second end of the second bridge arm switching tube to form the second connection end of the bridge circuit of the resonant conversion bridge circuit.

[0017] For any cyclic resonant converter, the corresponding control ends of the first bridge arm switching tube and the second bridge arm switching tube in the cyclic resonant converter are both connected to a control circuit. The control circuit is used to configure the switching states of the first bridge arm switching tube and the second bridge arm switching tube in the cyclic resonant converter so that the cyclic resonant converter enters the LC series resonance state, and the corresponding DC-AC conversion or AC-DC conversion is performed based on the cyclic resonant converter in the LC series resonance state.

[0018] Each cyclic resonant converter is also adaptively connected to a filter circuit, where

[0019] The cyclic resonant converter is adaptively connected to the corresponding filter circuit through the first connection end of the bridge circuit and the second connection end of the bridge circuit;

[0020] When the cyclic resonant converter performs DC-AC conversion, the filter circuit connected to the cyclic resonant converter is used for input voltage filtering;

[0021] When the cyclic resonant converter performs AC-DC conversion, the filter circuit connected to the cyclic resonant converter is used for output voltage filtering.

[0022] The filter circuit adopts a π filter circuit, where

[0023] The filtering circuit includes a first filtering capacitor, a filtering inductor, and a second filtering capacitor. The first end of the first filtering capacitor is connected to the first end of the filtering inductor to form a first endpoint of the filtering circuit after connection. The second end of the filtering inductor is connected to the first end of the second filtering capacitor and the first connection end of the bridge circuit;

[0024] The second end of the first filtering capacitor is connected to the second end of the second filtering capacitor and the second connection end of the bridge circuit to form a second endpoint of the filtering circuit after connection. Among them, a filtering port voltage is generated based on the first endpoint and the second endpoint of the filtering circuit;

[0025] When the cycloconverter connected to the filtering circuit performs DC-AC conversion, the current filtering circuit filters the input voltage and loads the filtered input voltage onto the connected cycloconverter;

[0026] When the cycloconverter connected to the filtering circuit performs AC-DC conversion, the current filtering circuit filters the output voltage to generate a target voltage after filtering the target conversion voltage, and stabilizes the target voltage at the reference voltage.

[0027] During voltage conversion, for any resonant conversion bridge circuit, there is:

[0028] Based on the first resonant capacitor voltage on the first resonant capacitor and the second resonant capacitor voltage on the second resonant capacitor, a total resonant capacitor voltage is generated;

[0029] The total resonant capacitor voltage is not greater than the filtering port voltage of the filtering circuit connected to the current resonant conversion bridge circuit.

[0030] During DC-AC conversion, determine the cycloconverter that performs DC-AC conversion, and control the corresponding switching states of the first bridge arm switch tube and the second bridge arm switch tube in the determined cycloconverter circuit through a control circuit, so as to generate a sinusoidal first resonant current based on the LC series resonance formed by the current cycloconverter;

[0031] During AC-DC conversion, determine the cycloconverter that performs AC-DC conversion, and control the corresponding switching states of the first bridge arm switch tube and the second bridge arm switch tube in the determined cycloconverter circuit through a control circuit, so as to generate a second resonant current based on the LC series resonance formed by the current cycloconverter. Among them,

[0032] The current direction of the second resonant current is opposite to the current direction of the first resonant current;

[0033] Based on the second resonant current, a target voltage is generated after passing through the corresponding connected filtering circuit.

[0034] During voltage transformation, the target voltage is sampled to generate a transformed sampled voltage after sampling, and the generated transformed sampled voltage is loaded into the pulse width modulation circuit within the control circuit, where

[0035] Based on the received transformed sampled voltage and the reference voltage, the pulse width modulation circuit generates a group of voltage transformation PWM signals. Based on the generated group of voltage transformation PWM signals, the switching states of the first arm switch tubes and the second arm switch tubes in each resonant transformation bridge circuit are regulated to stabilize the target voltage at the reference voltage.

[0036] The pulse width modulation circuit is adaptively connected to the current direction selection circuit and the switch tube drive circuit, where

[0037] The current direction selection circuit is connected to two voltage sensors. Each voltage sensor is used to collect the filtered port voltage of the corresponding filter circuit. The connection state between the voltage sensor and the pulse width modulation circuit is configured through the current direction selection circuit to load the transformed sampled voltage into the pulse width modulation circuit;

[0038] The switch tube drive circuit is adaptively connected to the first arm switch tubes and the second arm switch tubes in two cyclic resonant converters;

[0039] For the received transformed sampled voltage and the reference voltage, the pulse width modulation circuit performs at least PI regulation, generates a modulated PWM signal after PI regulation, and the generated modulated PWM signal generates a group of voltage transformation PWM signals through the switch tube drive circuit.

[0040] Both the first resonant current and the second resonant current are loaded into the pulse width modulation circuit;

[0041] The pulse width modulation circuit performs overcurrent protection on the first resonant current and the second resonant current, and regulates the state of the generated modulated PWM signal based on the overcurrent protection state.

[0042] The group of voltage transformation PWM signals includes a DC-AC transformation PWM signal group and an AC-DC transformation PWM signal group, where

[0043] The DC-AC transformation PWM signal group includes a DC-AC transformation first PWM signal and a DC-AC transformation second PWM signal. The DC-AC transformation first PWM signal and the DC-AC transformation second PWM signal are respectively loaded into the cyclic resonant converter for DC-AC transformation to control the switching states of the first arm switch tubes and the second arm switch tubes in the cyclic resonant converter. During the DC-AC transformation process, the first arm switch tubes and the second arm switch tubes are not simultaneously in the on state;

[0044] The AC-DC conversion PWM signal group includes a first AC-DC conversion PWM signal and a second AC-DC conversion PWM signal. Among them, the first AC-DC conversion PWM signal and the second AC-DC conversion PWM signal are respectively loaded onto the cyclic resonant converter for AC-DC conversion to control the corresponding switching states of the first bridge arm switch tube and the second bridge arm switch tube in the cyclic resonant converter. And during the AC-DC conversion process, the first bridge arm switch tube and the second bridge arm switch tube are not simultaneously in the on state;

[0045] The first AC-DC conversion PWM signal is consistent with the first DC-AC conversion PWM signal. At the same time, the second AC-DC conversion PWM signal is consistent with the second DC-AC conversion PWM signal to configure two cyclic resonant converters to respectively perform DC-AC conversion and AC-DC conversion.

[0046] When using two cyclic resonant converters for voltage conversion, there is:

[0047] When performing DC-AC conversion, for the LC series resonance formed by the cyclic resonant converter performing DC-AC conversion, the LC series resonance has a first resonance frequency and a first quality factor;

[0048] When performing AC-DC conversion, for the LC series resonance formed by the cyclic resonant converter performing AC-DC conversion, the LC series resonance has a second resonance frequency and a second quality factor, where,

[0049] The first resonance frequency is equal to the second resonance frequency, and the first quality factor is equal to the second quality factor.

[0050] Advantages of the present invention: The main conversion circuit includes a high-frequency transformer. The first side winding and the second side winding of the high-frequency transformer are both adaptively connected to a cyclic resonant converter to enable bidirectional cyclic resonant isolation DC-DC conversion. The cyclic resonant converter includes a resonant converter circuit and a resonant inductor, which can effectively reduce the number of switch tubes and the conduction loss of the switch tubes, reduce the cost of voltage conversion. In addition, a bidirectional cyclic resonant method is adopted to achieve full-process soft switching, reduce the switching loss, and improve the efficiency.

[0051] For any resonant conversion bridge circuit, the total voltage of the resonant capacitor is not greater than the voltage of the filtering port of the filtering circuit connected to the current resonant conversion bridge circuit, thereby limiting the voltage on the resonant capacitor of the cyclic resonant conversion bridge circuit and improving the reliability of the DC-DC converter. Brief Description of the Drawings

[0052] Figure 1 It is a schematic diagram of an embodiment of the converter of the present invention.

[0053] Figure 2 This is a schematic circuit diagram of an embodiment when the port 1 of the present invention delivers electrical energy to port 2.

[0054] Figure 3 For Figure 2 This is a schematic circuit diagram of an embodiment when the first resonant current and the resonant conversion current are in the positive half-wave when the port 1 delivers electrical energy to port 2 in

[0055] Figure 4 This is a schematic circuit diagram of an embodiment when the port 1 of the present invention delivers electrical energy to port 2.

[0056] Figure 5 For Figure 4 This is a schematic circuit diagram of an embodiment when the first resonant current and the resonant conversion current are in the negative half-wave when the port 1 delivers electrical energy to port 2 in

[0057] Figure 6 This is a schematic circuit diagram of an embodiment when the port 2 of the present invention delivers electrical energy to port 1.

[0058] Figure 7 For Figure 6 This is a schematic circuit diagram of an embodiment when the first resonant current and the resonant conversion current are in the positive half-wave when the port 2 delivers electrical energy to port 1 in

[0059] Figure 8 This is a schematic circuit diagram of an embodiment when the port 2 of the present invention delivers electrical energy to port 1.

[0060] Figure 9 For Figure 8 This is a schematic circuit diagram of an embodiment when the first resonant current and the resonant conversion current are in the negative half-wave when the port 2 delivers electrical energy to port 1 in

[0061] Figure 10 This is an equivalent circuit diagram of an embodiment when the first resonant current and the resonant conversion current are in the positive half-wave when the port 1 of the present invention delivers electrical energy to port 2.

[0062] Figure 11 This is a schematic waveform diagram of an embodiment when the bidirectional cyclic resonant isolation type DC-DC converter of the present invention performs voltage conversion.

[0063] Figure 12 This is a schematic circuit diagram of an embodiment of the control circuit of the present invention.

[0064] Description of the drawing reference numerals: 101 - the first filter capacitor of the first filter circuit, 102 - the second filter capacitor of the first filter circuit, 103 - the filter inductor of the first filter circuit, 110 - the first filter circuit, 120 - the first resonant converter, 121 - the first bridge arm switch of the first resonant converter, 122 - the second bridge arm switch of the first resonant converter, 130 - the second resonant converter, 131 - the high-frequency transformer, 135 - the first bridge arm switch of the second resonant converter, 136 - the second bridge arm switch of the second resonant converter, 140 - the second filter circuit, 141 - the first filter capacitor of the second filter circuit, 142 - the second filter capacitor of the second filter circuit, 143 - the filter inductor of the second filter circuit, 210 - the DC voltage sampling circuit for port 1, 220 - the DC voltage sampling circuit for port 2, 230 - the current direction selection circuit, 240 - the pulse width modulation circuit, 250 - the switch driver circuit. Detailed implementation mode

[0065] The present invention will be further described below in conjunction with the specific drawings and embodiments.

[0066] When performing DC-DC conversion, in order to reduce the number of switching tubes used in the resonant conversion, before each switching tube in the circuit is turned on, the voltage across its two ends has dropped to zero, realizing full-process soft switching, greatly reducing the switching loss of the circuit, reducing costs, and improving the efficiency of voltage conversion. The present invention provides a bidirectional resonant isolation type DC-DC converter. Specifically, the DC-DC converter includes a main conversion circuit and a control circuit for controlling the working state of the main conversion circuit. Among them,

[0067] The main conversion circuit includes a high-frequency transformer 131. The windings on both sides of the high-frequency transformer 131 are respectively adaptively connected to a resonant converter for voltage conversion. Among them, when performing voltage conversion, a resonant converter is used to first perform DC-AC conversion. Thereafter, through the cooperation of the high-frequency transformer 131 and another resonant converter, at least AC-DC conversion is performed, and a target conversion voltage is generated after the AC-DC conversion;

[0068] The resonant converter includes a resonant conversion bridge circuit and a resonant inductor adaptively connected to the resonant conversion bridge circuit. Among them,

[0069] The resonant conversion bridge circuit includes a first bridge arm of the resonant conversion and a second bridge arm of the resonant conversion. The first bridge arm of the resonant conversion includes a first bridge arm switching tube and a first bridge arm resonant capacitor. The second bridge arm of the resonant converter includes a second bridge arm switching tube and a second bridge arm resonant capacitor. Among them,

[0070] The first end of the first leg switching device, the first end of the second leg switching device are connected to the first end of the resonant inductor. The second end of the resonant inductor is connected to the first end of the corresponding side winding of the high-frequency transformer 131. The second end of the corresponding side winding of the high-frequency transformer 131 is connected to the first end of the first leg resonant capacitor and the first end of the second leg resonant capacitor.

[0071] The second end of the first leg resonant capacitor is adaptively connected to the second end of the first leg switching device to form the first connection end of the bridge circuit of the resonant conversion bridge circuit. At the same time, the second end of the second leg resonant capacitor is adaptively connected to the second end of the second leg switching device to form the second connection end of the bridge circuit of the resonant conversion bridge circuit.

[0072] For any cyclic resonant converter, the corresponding control ends of the first leg switching device and the second leg switching device in the cyclic resonant converter are both connected to the control circuit. The control circuit is used to configure the switching states of the first leg switching device and the second leg switching device in the cyclic resonant converter, so that the cyclic resonant converter enters the LC series resonance state, and based on the cyclic resonant converter in the LC series resonance state, the corresponding DC-AC conversion or AC-DC conversion is performed.

[0073] In order to achieve DC-DC conversion, the present invention should at least include a main conversion circuit and a control circuit. Among them, the main conversion circuit is the functional circuit for realizing DC-DC conversion. The control circuit is adaptively connected to the main conversion circuit to control the main conversion circuit to perform corresponding voltage conversion. The mechanism of voltage conversion in cooperation between the main conversion circuit and the control circuit is consistent with the prior art. The situations of the main conversion circuit and the control circuit will be specifically described below.

[0074] Figure 1 An embodiment of the main conversion circuit of the present invention is shown. It can be seen from the figure that the main conversion circuit should include a high-frequency transformer 131. Through the high-frequency transformer 131, high-frequency voltage conversion can be realized, so that the main conversion circuit of the present invention can adapt to high-frequency scenarios. The high-frequency transformer 131 can adopt the commonly used form in the prior art, specifically subject to meeting the requirements of high-frequency voltage conversion. It can be understood that electrical isolation can also be achieved through the high-frequency transformer 131.

[0075] The high-frequency transformer 131 generally has two windings. In an embodiment of the present invention, each winding is adaptively connected to a resonant converter, such as Figure 1In this case, the second-side winding of the high-frequency transformer 131 is adaptively connected to the first resonant converter 120, and the first-side winding of the high-frequency transformer 131 is adaptively connected to the second resonant converter 130. Among them, when the voltage is transformed, the power transmission direction can be from the first resonant converter 120 to the second resonant converter 130, or the power transmission direction can also be from the second resonant converter 130 to the first resonant converter 120. Thus, it can be seen that the DC-DC converter of the present invention can achieve bidirectional voltage transformation.

[0076] Since bidirectional voltage transformation can be performed, when the DC-DC converter of the present invention performs voltage transformation, a resonant converter should be used to first perform DC-AC transformation. Thereafter, at least AC-DC transformation is performed in cooperation with the high-frequency transformer 131 and another resonant converter, and a target transformed voltage is generated after the AC-DC transformation. Specifically, when the Figure 1 transforming main circuit is used, the first resonant converter 120 can be used to first perform DC-AC transformation. Thereafter, the second resonant converter 130 is used to perform AC-DC transformation. It can be understood that the second resonant converter 130 can also be used to first perform DC-AC transformation, and then the first resonant converter 120 is used to perform AC-DC transformation. The specific voltage transformation process is related to the power transmission direction in actual applications.

[0077] It should be noted that the voltage transformation direction can be selected according to actual needs. Of course, after the voltage transformation direction is determined, the control circuit is also required to regulate the working state of the transforming main circuit so that the two resonant converters perform DC-AC transformation and AC-DC transformation in sequence and obtain the target transformed voltage. The resonant converters connected to the two sides of the winding of the high-frequency transformer 131 can adopt the same circuit form. Of course, different circuit forms can also be adopted, which can be specifically selected according to needs. In order to reduce the number of switching tubes and lower the cost, the two resonant converters preferably adopt the same circuit form. In addition, Figure 1 An embodiment in which the two resonant converters adopt the same circuit form is shown in

[0078] In an embodiment of the present invention, the cyclic resonant converter may include a cyclic conversion bridge circuit and a resonant inductor. The resonant conversion bridge circuit includes a first bridge arm of resonant conversion and a second bridge arm of resonant conversion. The first bridge arm of resonant conversion and the second bridge arm of resonant conversion may adopt the same form. For example, the first bridge arm of resonant conversion includes a first bridge arm switching tube and a first bridge arm resonant capacitor, and the second bridge arm of resonant conversion includes a second bridge arm switching tube and a second bridge arm resonant capacitor. Specifically, the first bridge arm switching tube and the second bridge arm switching tube generally may adopt the same type of switching tube, such as IGBT (Insulated Gate Bipolar Transistor) devices, MOSFET devices or other devices that can be used as switching tubes. Figure 1 An embodiment is shown in which both the first bridge arm switching tube and the second bridge arm switching tube adopt IGBT devices.

[0079] It should be understood that when the cyclic resonant converter is connected to the winding on one side of the high-frequency transformer 131, it specifically means that the cyclic conversion bridge circuit and the resonant inductor in the cyclic resonant converter are adaptively connected to the corresponding winding of the high-frequency transformer 131. Specifically,

[0080] The first ends of the first bridge arm switching tube and the second bridge arm switching tube are connected to the first end of the resonant inductor. The second end of the resonant inductor is connected to the first end of the corresponding side winding of the high-frequency transformer 131. The second end of the corresponding side winding of the high-frequency transformer 131 is connected to the first end of the first bridge arm resonant capacitor and the first end of the second bridge arm resonant capacitor.

[0081] The second end of the first bridge arm resonant capacitor is adaptively connected to the second end of the first bridge arm switching tube to form the first connection end of the bridge circuit of the resonant conversion bridge circuit; at the same time, the second end of the second bridge arm resonant capacitor is adaptively connected to the second end of the second bridge arm switching tube to form the second connection end of the bridge circuit of the resonant conversion bridge circuit.

[0082] In specific implementation, when the first bridge arm switching tube and the second bridge arm switching tube adopt IGBT devices, the first ends of the first bridge arm switching tube and the second bridge arm switching tube are the collector ends of the adopted IGBT devices, and the corresponding second ends of the first bridge arm switching tube and the second bridge arm switching tube are the emitter ends of the adopted IGBT devices. When the first bridge arm switching tube and the second bridge arm switching tube are other types of switching tubes, the corresponding situations of the first ends and the second ends of the first bridge arm switching tube and the second bridge arm switching tube can be determined accordingly, and no further examples will be given here.

[0083] Figure 1 In the two cyclic resonant converters shown, the first cyclic resonant first bridge arm switching tube 121 serves as the first bridge arm switching tube in the first cyclic resonant converter 120, and the first cyclic resonant second bridge arm switching tube 122 serves as the second bridge arm switching tube in the first cyclic resonant converter 120. At the same time, the capacitor C11 As the first bridge arm resonant capacitor in the first cycle resonant converter 120, capacitor C 12 As the second bridge arm resonant capacitor in the first cycle resonant converter 120, inductor L 1σ As the resonant inductor in the first cycle resonant converter 120. Figure 1 Among them, D1+ is the first connection end of the bridge circuit of the first cycle resonant converter 120, and D1- is the second connection end of the bridge circuit of the first cycle resonant converter 120.

[0084] Figure 1 Among them, the second cycle resonant first bridge arm switch 135 serves as the first bridge arm switch in the second cycle resonant converter 130, and the second cycle resonant second bridge arm switch 136 serves as the second bridge arm switch in the second cycle resonant converter 130. At the same time, capacitor C 21 As the first bridge arm resonant capacitor in the second cycle resonant converter 130, capacitor C 22 As the second bridge arm resonant capacitor in the second cycle resonant converter 130, inductor L 2σ As the resonant inductor in the second cycle resonant converter 130. Figure 1 Among them, D2+ serves as the first connection end of the bridge circuit of the second cycle resonant converter 130, and D2- serves as the second connection end of the bridge circuit of the second cycle resonant converter 130.

[0085] When the main conversion circuit adopts the above structural form, the main conversion circuit is adaptively connected to the control circuit. Specifically, it means that at least the corresponding control terminals of the first bridge arm switch and the second bridge arm switch in each cycle resonant converter are adaptively connected to the control circuit to configure the switching states of the first bridge arm switch and the second bridge arm switch in each cycle resonant converter by using the control circuit. After that, based on the corresponding conduction states of the first bridge arm switch and the second bridge arm switch, the cycle resonant converter can perform the corresponding DC-AC conversion or AC-DC conversion. Among them, when the cycle resonant converter performs DC-AC conversion or AC-DC conversion, a corresponding LC series resonance will be formed. For example, for the first cycle resonant converter 120, inductor L 1σ can form a corresponding LC series resonance with capacitor C 12 and capacitor C 12 The other cases of forming series resonance can refer to the description here.

[0086] It should be noted that when the first bridge arm switch and the second bridge arm switch adopt IGBT devices, the corresponding control terminals of the first bridge arm switch and the second bridge arm switch are the gate terminals of the IGBT devices used.

[0087] As can be seen from the above description, for any cyclic resonant converter, the DC-AC conversion or AC-DC conversion performed should be related to the direction of power transmission in the main conversion circuit. Specifically, as described above, when the power transmission direction is from the first cyclic resonant converter 120 to the second cyclic resonant converter 130, the first cyclic resonant converter 120 is used for DC-AC conversion. Specifically, the LC series resonance formed based on the first cyclic resonant converter 120 can perform DC-AC conversion. Thereafter, the AC-DC conversion is performed based on the LC series resonance formed by the second cyclic resonant converter 130. Similarly, when the first cyclic resonant converter 120 is used for AC-DC conversion, the LC series resonance formed based on the first cyclic resonant converter 120 can perform AC-DC conversion, and the DC-AC conversion is performed based on the LC series resonance formed by the second cyclic resonant converter 130. For the case where the second cyclic resonant converter 130 performs DC-AC conversion or AC-DC conversion, reference can be made to the description of the first cyclic resonant converter 120 here.

[0088] As can be seen from the above description, when the above cyclic resonant converter is used for voltage conversion, the number of switching tubes in the main conversion circuit can be effectively reduced, thereby reducing the cost of DC-DC conversion and improving the efficiency of voltage conversion.

[0089] In an embodiment of the present invention, each cyclic resonant converter is also adaptively connected to a filter circuit, where

[0090] The cyclic resonant converter is adaptively connected to the corresponding filter circuit through the first bridge connection end and the second bridge connection end;

[0091] When the cyclic resonant converter performs DC-AC conversion, the filter circuit connected to the cyclic resonant converter is used for filtering the input voltage;

[0092] When the cyclic resonant converter performs AC-DC conversion, the filter circuit connected to the cyclic resonant converter is used for filtering the output voltage.

[0093] It should be understood that in order to improve the quality of voltage conversion, each cyclic resonant converter should also be adaptively connected to a filter circuit. At this time, the main conversion circuit should include two cyclic resonant converters and two filter circuits, where one filter circuit is correspondingly connected to one cyclic resonant converter. Specifically, the corresponding connection means that the cyclic resonant converter is connected to the corresponding filter circuit through the first bridge connection end and the second bridge connection end.

[0094] Specifically, when the cycloconverter connected to the filter circuit performs DC-AC conversion, the current filter circuit is first used to filter the input voltage, and then the cycloconverter performs DC-AC conversion; when the cycloconverter connected to the filter circuit performs AC-DC conversion, the cycloconverter is first used to perform AC-DC conversion, and then the filter circuit is used to filter the output voltage, and the target voltage is generated after the output voltage is filtered.

[0095] In specific implementation, the filter circuits in the main conversion circuit are preferably of the same circuit form. In an embodiment of the present invention, the filter circuit adopts a π filter circuit, where

[0096] the filter circuit includes a first filter capacitor, a filter inductor, and a second filter capacitor. The first end of the first filter capacitor is connected to the first end of the filter inductor to form a first endpoint of the filter circuit after connection. The second end of the filter inductor is connected to the first end of the second filter capacitor and the first connection end of the bridge circuit;

[0097] The second end of the first filter capacitor is connected to the second end of the second filter capacitor and the second connection end of the bridge circuit to form a second endpoint of the filter circuit after connection. Among them, the filter port voltage is generated based on the first endpoint and the second endpoint of the filter circuit;

[0098] When the cycloconverter connected to the filter circuit performs DC-AC conversion, the current filter circuit filters the input voltage and loads the filtered input voltage to the connected cycloconverter;

[0099] When the cycloconverter connected to the filter circuit performs AC-DC conversion, the current filter circuit filters the output voltage to generate the target voltage after filtering the target conversion voltage, and stabilizes the target voltage at the reference voltage.

[0100] Figure 1 An embodiment in which both filter circuits adopt π filter circuits is shown, where the two filter circuits include a first filter circuit 110 and a second filter circuit 140. The first filter circuit 110 is adaptively connected to the first cycloconverter 120, and the second filter circuit 140 is adaptively connected to the second cycloconverter 140.

[0101] Figure 1Among them, the first filtering capacitor 101 of the first filtering circuit is the first filtering capacitor within the first filtering circuit 110, the second filtering capacitor 102 of the first filtering circuit is the second filtering capacitor within the first filtering circuit 110, the filtering inductor 103 of the first filtering circuit is the filtering inductor within the first filtering circuit 110. The corresponding connection relationships of the first filtering capacitor 101, the second filtering capacitor 102, and the filtering inductor 103 of the first filtering circuit, as well as the connection and cooperation with the first resonant converter 120, can all be referred to Figure 1 the embodiments shown. Figure 1 Among them, for the first filtering circuit 110, Ud1+ is the first end point of the filtering circuit of the first filtering circuit 110, Ud1- is the second end point of the filtering circuit of the first filtering circuit 110. Based on the first end point and the second end point of the filtering circuit within the first filtering circuit 110, port 1 is formed. U o1 is the filtering port voltage of the first filtering circuit 110, that is, U o1 is the voltage of port 1.

[0102] In addition, Figure 1 Among them, the first filtering capacitor 141 of the second filtering circuit is the first filtering capacitor within the second filtering circuit 140, the second filtering capacitor 142 of the second filtering circuit is the second filtering capacitor within the second filtering circuit 140, the filtering inductor 143 of the second filtering circuit is the filtering inductor within the second filtering circuit 140. The corresponding connection relationships of the first filtering capacitor 141, the second filtering capacitor 142, and the filtering inductor 143 of the second filtering circuit, as well as the connection and cooperation with the second resonant converter 130, can all be referred to Figure 1 the embodiments shown. Figure 1 Among them, for the second filtering circuit 140, Ud2+ is the first end point of the filtering circuit of the second filtering circuit 140, Ud2- is the second end point of the filtering circuit of the second filtering circuit 140. Based on the first end point and the second end point of the filtering circuit within the second filtering circuit 140, port 2 is formed. U o2 is the filtering port voltage of the second filtering circuit 140, that is, U o2 is the voltage of port 2.

[0103] It should be noted that for a DC-DC converter, the input voltage and the reference voltage should be provided according to the actual application scenario. That is, the conditions of the input voltage and the reference voltage are related to the actual application scenario. Among them, the input voltage should be applied to the filter circuit for input voltage filtering, and the target voltage can be obtained through the filter circuit for output voltage filtering. After determining the reference voltage, the control circuit and the main conversion circuit cooperate to generate the target voltage and make the target voltage stable at the reference voltage. Among them, the target voltage being stable at the reference voltage specifically means that the target voltage is consistent with the reference voltage, or the difference between the target voltage and the reference voltage is within the allowable range, and the allowable range is generally related to the actual application scenario and is subject to meeting the actual application requirements.

[0104] In an embodiment of the present invention, during voltage conversion, for any resonant conversion bridge circuit, there is:

[0105] Based on the first resonant capacitor voltage on the first resonant capacitor and the second resonant capacitor voltage on the second resonant capacitor, a total resonant capacitor voltage is generated;

[0106] The total resonant capacitor voltage is not greater than the filter port voltage of the filter circuit connected to the current resonant conversion bridge circuit.

[0107] Figure 1 In, for the circulating conversion bridge circuit in the first circulating resonant converter 120, during voltage conversion, the voltage on capacitor C 11 is the first resonant capacitor voltage, and the voltage on capacitor C 12 is the second resonant capacitor voltage. By adding the first resonant voltage and the second resonant voltage, the total resonant capacitor voltage can be generated. That is, when generating the total resonant capacitor voltage, it is necessary to add the first resonant capacitor voltage and the second resonant capacitor voltage. From Figure 1 the circuit form showing the connection and cooperation between the first filter circuit 110 and the first circulating resonant converter 120, it can be seen that the total resonant capacitor voltage should not be greater than the filter port voltage U o1 of the first filter circuit 110.

[0108] Figure 1 In, for the circulating conversion bridge circuit in the second circulating resonant converter 130, during voltage conversion, the voltage on capacitor C 21 is the first resonant capacitor voltage, and the voltage on capacitor C 22 is the second resonant capacitor voltage. By adding the first resonant voltage and the second resonant voltage, the total resonant capacitor voltage can be generated. From Figure 1 the circuit form showing the connection and cooperation between the second filter circuit 140 and the second circulating resonant converter 130, it can be seen that the total resonant capacitor voltage should not be greater than the filter port voltage U o2 of the second filter circuit 140.

[0109] It can be understood that when the total voltage of the resonant capacitor is not greater than the voltage of the filtering port of the filtering circuit connected to the current resonant conversion bridge circuit, the limitation of the total voltage of the resonant capacitor in the resonant conversion bridge circuit can be realized, thereby improving the reliability of the main conversion circuit during voltage conversion.

[0110] In an embodiment of the present invention, when performing DC-AC conversion, a cyclic resonant converter for performing DC-AC conversion is determined, and the control circuit controls the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in the determined cyclic resonant converter circuit, so as to generate a sinusoidal first resonant current based on the LC series resonance formed by the current cyclic resonant converter;

[0111] When performing AC-DC conversion, a cyclic resonant converter for performing AC-DC conversion is determined, and the control circuit controls the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in the determined cyclic resonant converter circuit, so as to generate a second resonant current based on the LC series resonance formed by the current cyclic resonant converter, where

[0112] the current direction of the second resonant current is opposite to the current direction of the first resonant current;

[0113] Based on the second resonant current, a target voltage is generated after passing through the corresponding filtering circuit

[0114] As can be seen from the above description, the control circuit is mainly used to control the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in each cyclic resonant converter, so as to configure the cyclic resonant converter to form a corresponding LC series resonance and perform DC-AC conversion or AC-DC conversion. Controlling the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube specifically means controlling the first bridge arm switch and the second bridge arm switching tube to be in the on state or in the off state.

[0115] It can be understood that during a primary voltage conversion, a cyclic resonant converter only performs DC-AC conversion or AC-DC conversion. That is, during a primary voltage conversion, the types of voltage conversions performed by the two cyclic resonant converters in the conversion main circuit are different. Specifically, when the cyclic resonant converter performs DC-AC conversion, a first resonant current can be generated based on the LC series resonance formed by the corresponding cyclic resonant converter; after generating the first resonant current, a second resonant current can be generated based on the high-frequency transformer 131 and another cyclic resonant converter. At this time, when the cyclic resonant converter performs AC-DC conversion, a resonant conversion current can be generated based on the corresponding second resonant current. Among them, the resonant conversion current is the current before passing through the corresponding filter circuit, and a stable DC output current is formed after the resonant conversion current passes through the filter circuit. The waveform of the first resonant current is sinusoidal. The resonant conversion current generally includes two half-wave currents. Specifically, the resonant conversion current includes a first half-wave resonant conversion current and a second half-wave resonant conversion current. Among them, the first half-wave resonant conversion current and the second half-wave resonant conversion current are alternately distributed in sequence.

[0116] During specific implementation, the cyclic resonant converters performing DC-AC conversion and AC-DC conversion can be determined according to the direction of power transmission. The specific method for determining the cyclic resonant converters performing DC-AC conversion and AC-DC conversion can refer to the corresponding descriptions above and will not be elaborated here.

[0117] When the first resonant current is a sinusoidal current, the first resonant current can include a positive half-wave resonant current and a negative half-wave resonant current. Among them, the amplitude direction of the first half-wave resonant conversion current is corresponding and consistent with the positive half-wave resonant current in the first resonant current, that is, the phase and direction of the first half-wave resonant conversion current are the same as those of the positive half-wave resonant current. The amplitude direction of the second half-wave resonant conversion current is opposite to the amplitude direction of the negative half-wave resonant current in the first resonant current, so that the resonant conversion current forms a DC state. Figure 11 Among them, the DC current Id1 and the DC current Id2 are the corresponding resonant conversion currents respectively. When the resonant conversion current is formed based on the DC current Id1, the first cyclic resonant converter 120 should perform AC-DC conversion. When the resonant conversion current is formed based on the DC current Id2, the second cyclic resonant converter 130 should perform AC-DC conversion. It should be understood that the resonant conversion current corresponds to the target voltage.

[0118] It should be noted that for the current directions of the first resonant current and the second resonant current, it generally refers to the direction relationship between the current flow direction and the high-frequency transformer 131, such as flowing towards the high-frequency transformer 131 or flowing out from the high-frequency transformer 131. Specific examples of the current direction will be given below in combination with the specific conversion process.

[0119] Taking the direction of energy flowing from port 1 to port 2 in the following as the forward operating state of the converter. At this time, the direction of energy flowing from port 2 to port 1 in the following is taken as the reverse operating state of the transformer. The specific situations of the current directions in the forward operating state and the reverse operating state will be explained below. Figure 1 Taking the direction of energy flowing from port 1 to port 2 in the following as the forward operating state of the converter. At this time, the direction of energy flowing from port 2 to port 1 in the following is taken as the reverse operating state of the transformer. The specific situations of the current directions in the forward operating state and the reverse operating state will be explained below. Figure 1 Taking the direction of energy flowing from port 2 to port 1 in the following as the reverse operating state of the transformer. The specific situations of the current directions in the forward operating state and the reverse operating state will be explained below.

[0120] Figure 11 An embodiment of the first resonant current and the resonant conversion current is shown in the following. Figure 11 In the following, Ug is the reference voltage, and i 1 ~ is the resonant sampling current obtained by sampling the resonant current generated in the first cycle resonant converter 120. Id1 is the DC current of port 1 generated by the first filter circuit 110. i 2 ~ is the resonant sampling current obtained by sampling the resonant current generated in the second cycle resonant converter 130. Id2 is the DC current flowing to port 2 after passing through the second cycle resonant converter 130.

[0121] As can be seen from the above description, during forward operation, U o1 is the input voltage, U o2 is the output voltage. When the voltage is transformed, the first cycle resonant converter 120 can perform DC-AC conversion, and the second resonator 130 performs AC-DC conversion. At this time, a first resonant current is generated in the first cycle resonant converter 120, a second resonant current is generated in the second cycle resonant converter 130, and a corresponding resonant conversion current is formed based on the generated second resonant current, and the first resonant current is not generated simultaneously in the second cycle resonant converter 130.

[0122] Similarly, during reverse operation, U o2 is the input voltage, U o1 is the output voltage. When the voltage is transformed, the second cycle resonant converter 130 can perform DC-AC conversion, and the first cycle resonator 120 performs AC-DC conversion. At this time, when a first resonant current is generated in the second cycle resonant converter 130, a second resonant current is generated in the first cycle resonant converter 120, and a corresponding resonant conversion current can be formed using the second resonant current, and the first resonant conversion current is not generated simultaneously in the first cycle resonant converter 120.

[0123] In an embodiment of the present invention, when the voltage is transformed, the target voltage is sampled to generate a transformed sampling voltage after sampling, and the transformed sampling voltage generated by sampling is loaded into the pulse width modulation circuit 240 in the control circuit, where

[0124] Based on the received transformed sampled voltage and the reference voltage, the pulse width modulation circuit 240 generates a group of voltage transformation PWM signals. Among them, based on the generated group of voltage transformation PWM signals, the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in each resonant transformation bridge circuit are regulated to stabilize the target voltage at the reference voltage.

[0125] In order to stabilize the target voltage at the reference voltage, when the control circuit controls the operation of each cyclic resonant converter, the target voltage should be sampled at least. After sampling the target voltage, a transformed sampled voltage can be generated. Specifically, the transformed sampled voltage is in a proportional state with the target voltage. For example, the transformed sampled voltage can be consistent with the magnitude of the target voltage. The target voltage can be sampled by using existing common methods. For example, the target voltage can be sampled through a voltage sensor. The voltage sensor can adopt existing common forms, such as a Hall voltage sensor. Of course, other types of voltage sensors can also be used. The type of the voltage sensor can be selected according to needs and will not be elaborated one by one here.

[0126] It should be noted that when the main transformation circuit adopts Figure 1 the circuit form of, when sampling the target voltage, that is, sampling the filtered port voltage of the filter circuit for output voltage filtering, and thus the transformed sampled voltage can be obtained.

[0127] In specific implementation, the control circuit at least includes the pulse width modulation circuit 240. When the control circuit regulates the operating state of the main transformation circuit, the pulse width modulation circuit 240 can generate a group of voltage transformation PWM signals. By using the generated group of voltage transformation PWM signals, the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in each resonant transformation bridge circuit can be regulated simultaneously, so that the two cyclic resonant converters perform DC-AC transformation and AC-DC transformation respectively. Among them, when the pulse width modulation circuit 240 generates a group of voltage transformation PWM signals, it should be at least based on the transformed sampled voltage and the reference voltage. The situation of generating a group of voltage transformation PWM signals based on the transformed sampled voltage and the reference voltage can refer to the corresponding description below.

[0128] In an embodiment of the present invention, the group of voltage transformation PWM signals includes a DC-AC transformation PWM signal group and an AC-DC transformation PWM signal group, where

[0129] The DC-AC conversion PWM signal group includes a first DC-AC conversion PWM signal and a second DC-AC conversion PWM signal. Among them, the first DC-AC conversion PWM signal and the second DC-AC conversion PWM signal are respectively loaded onto the cyclic resonant converter for DC-AC conversion to control the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in the cyclic resonant converter. And during the DC-AC conversion process, the first bridge arm switching tube and the second bridge arm switching tube are not simultaneously in the conducting state;

[0130] The AC-DC conversion PWM signal group includes a first AC-DC conversion PWM signal and a second AC-DC conversion PWM signal. Among them, the first AC-DC conversion PWM signal and the second AC-DC conversion PWM signal are respectively loaded onto the cyclic resonant converter for AC-DC conversion to control the corresponding switching states of the first bridge arm switching tube and the second bridge arm switching tube in the cyclic resonant converter. And during the AC-DC conversion process, the first bridge arm switching tube and the second bridge arm switching tube are not simultaneously in the conducting state;

[0131] The first AC-DC conversion PWM signal is consistent with the first DC-AC conversion PWM signal. At the same time, the second AC-DC conversion PWM signal is consistent with the second DC-AC conversion PWM signal to configure two cyclic resonant converters to respectively perform DC-AC conversion and AC-DC conversion.

[0132] It can be seen from the above description that the main conversion circuit includes two cyclic resonant converters, and the two cyclic resonant converters respectively perform different voltage conversions. Therefore, in order to meet the control of voltage conversion, the voltage conversion PWM signal group should include the DC-AC conversion PWM signal group and the AC-DC conversion PWM signal group. Among them, the DC-AC conversion PWM signal group should be loaded onto the cyclic resonant converter that needs to perform DC-AC conversion, and the AC-DC conversion PWM signal group should be loaded onto the cyclic resonant converter that needs to perform AC-DC conversion.

[0133] Since each cyclic resonant converter includes a first bridge arm switching tube and a second bridge arm switching tube, therefore, the DC-AC conversion PWM signal group includes a first DC-AC conversion PWM signal and a second DC-AC conversion PWM signal. At the same time, the AC-DC conversion PWM signal group includes a first AC-DC conversion PWM signal and a second AC-DC conversion PWM signal.

[0134] It should be noted that when loading the DC-AC conversion PWM signal group into the corresponding cyclic resonant converter, specifically, the first DC-AC conversion PWM signal and the second DC-AC conversion PWM signal are respectively loaded into the corresponding first leg switching transistor and the second leg switching transistor; similarly, when loading the AC-DC conversion PWM signal group into the corresponding cyclic resonant converter, specifically, the first AC-DC conversion PWM signal and the second AC-DC conversion PWM signal are respectively loaded into the corresponding first leg switching transistor and the second leg switching transistor, as Figure 1 shown in the example. When performing DC-AC conversion using the first cyclic resonant converter 120, the second cyclic resonant converter 130 is used for AC-DC conversion. At this time, the first DC-AC conversion PWM signal should be loaded onto the first leg switching transistor 121 of the first cyclic resonant converter, and the second DC-AC conversion PWM signal should be loaded onto the second leg switching transistor 122 of the first cyclic resonant converter. At the same time, the first AC-DC conversion PWM signal is loaded onto the first leg switching transistor 135 of the second cyclic resonant converter, and the second AC-DC conversion PWM signal is loaded onto the second leg switching transistor 136 of the second cyclic resonant converter. When performing AC-DC conversion using the first cyclic resonant converter 120 and DC-AC conversion using the second cyclic resonant converter 130, the specific corresponding relationship can be referred to the description here, and no further examples will be given.

[0135] When performing DC-AC conversion using the first cyclic resonant converter 120 and AC-DC conversion using the second cyclic resonant converter 130, then Figure 11 in, 121 / 135 represents the first DC-AC conversion PWM signal / the first AC-DC conversion PWM signal, and 122 / 136 represents the second DC-AC conversion WPM signal / the second AC-DC conversion PWM signal. It can be seen from the figure that the first leg switching transistor 121 of the first cyclic resonant converter and the second leg switching transistor 122 of the first cyclic resonant converter are not simultaneously in the on state. At the same time, the first leg switching transistor 135 of the second cyclic resonant converter and the second leg switching transistor 136 of the second cyclic resonant converter are not simultaneously in the on state.

[0136] During specific implementation, the first AC-DC conversion PWM signal is consistent with the first DC-AC conversion PWM signal. At the same time, the second AC-DC conversion PWM signal is consistent with the second DC-AC conversion PWM signal, as Figure 11 shown. At this time, the current directions of the first resonant current and the resonant conversion current can be configured, and the situation of the current direction can be referred to the corresponding description above.

[0137] In an embodiment of the present invention, the pulse width modulation circuit 240 is adaptively connected to the current direction selection circuit 230 and the switching transistor driving circuit 250, where

[0138] The current direction selection circuit 230 is connected to two voltage sensors. Each voltage sensor is used to collect the filtered port voltage of the corresponding filter circuit. The connection state between the voltage sensor and the pulse width modulation circuit 240 is configured through the current direction selection circuit 230 to load the transformed sampling voltage to the pulse width modulation circuit 240.

[0139] The switch tube driving circuit 250 is adaptively connected to the first leg switch tubes and the second leg switch tubes in two resonant converters.

[0140] For the received transformed sampling voltage and the reference voltage, the pulse width modulation circuit 240 performs at least PI regulation, generates a modulated PWM signal after PI regulation, and the generated modulated PWM signal generates a voltage transformation PWM signal group through the switch tube driving circuit 250.

[0141] Figure 1 An embodiment of the control circuit is shown. It can be seen from the figure that the control circuit further includes a current direction selection circuit 230 and a switch tube driving circuit 250. The current direction selection circuit 230 and the switch tube driving circuit 250 are both connected to the pulse width modulation circuit 240. At this time, the pulse width modulation circuit 240 and the switch tube driving circuit 250 cooperate to generate a corresponding voltage transformation PWM signal group.

[0142] It can be seen from the above description that the main transformation circuit can achieve bidirectional transformation. Therefore, it can be seen from the above description that the target voltage can be obtained through the filtered port voltage of the corresponding port of the first filter circuit 110 or the second filter circuit 140. In order to adapt to bidirectional transformation, the transformed sampling voltage obtained by sampling the target voltage can be loaded into the pulse width modulation circuit 240 through the current direction selection circuit 230. The current direction selection circuit 230 should be adaptively connected to two voltage sensors and can control the connection between the voltage sensor and the pulse width modulation circuit 240. In order to load the voltage transformation PWM signal group into the corresponding resonant converter, the switch tube driving circuit 250 should be correspondingly connected to all the first leg switch tubes and the second leg switch tubes. The specific corresponding connection is based on being able to load the voltage transformation PWM signal group into the corresponding first leg switch tubes and second leg switch tubes and being able to control the corresponding switch states of the first leg switch tubes and the second leg switch tubes.

[0143] When the pulse width modulation circuit 240 and the switch tube driving circuit 250 cooperate and the switch tube driving circuit 250 generates a voltage transformation PWM signal group, Figure 1An embodiment of the pulse width modulation circuit 240 is also shown. As can be seen from the figure, the pulse width modulation circuit 240 may include a PI regulator and a PWM control unit. Among them, the PI regulator is connected to the current direction selection circuit 230, and the transformed sampling voltage can be loaded into the PI regulator through the current direction selection circuit 230. At this time, the PI regulator should also receive a reference voltage. Figure 1 In this case, the port output voltage setting is the reference voltage.

[0144] After receiving the transformed sampling voltage and the reference voltage, the PI regulator can perform PI regulation. It can be understood that when performing PI regulation, the main purpose is to stabilize the target voltage at the reference voltage. The PI regulation method and process can be consistent with the prior art and will not be elaborated here. Further, according to the result of the PI regulation, the PI regulator can generate a modulated PWM signal through the PWM control unit and load the generated modulated PWM signal into the switch tube drive circuit 250, so that the switch tube drive circuit 250 can generate a voltage conversion PWM signal group.

[0145] In an embodiment of the present invention, when voltage conversion is performed, both the first resonant current and the second resonant current are loaded into the pulse width modulation circuit 240.

[0146] The pulse width modulation circuit 240 performs overcurrent protection on the first resonant current and the second resonant current, and regulates the generated modulated PWM signal based on the overcurrent protection state.

[0147] In order to achieve overcurrent protection, the first resonant current and the second resonant current should be loaded into the pulse width modulation circuit 240. As Figure 1 can be seen, the first resonant current and the second resonant current are loaded into the PWM control unit of the pulse width modulation circuit 240.

[0148] From the above description, the first resonant current is the resonant current when the cyclic resonant converter performing DC-AC conversion operates, and the second resonant current is the resonant current when the cyclic resonant converter performing AC-DC conversion operates. For example, when the first cyclic resonant converter 120 performs DC-AC conversion, the resonant current flowing through the first cyclic resonant converter 120 is obtained through a current sensor, and at this time, the first resonant current can be obtained. Similarly, the second resonant current flowing through the second cyclic resonant converter 130 can be obtained through a current sensor. When using the first cyclic resonant converter 120 for AC-DC conversion and using the second cyclic resonant converter 130 for DC-AC conversion, the cases of obtaining the first resonant current and the second resonant current can refer to the description here and will not be exemplified one by one.

[0149] From Figure 1It can be known that when obtaining the first resonant current and the second resonant current, the current sensor should be adaptively connected to the second end of the corresponding winding of the high-frequency transformer 131, such as Figure 1 in, i 1 ~ can be the resonant sampling current of the first resonant current. At this time, i 2 ~ can be the resonant sampling current of the second resonant current. The resonant sampling current of the first resonant current can be obtained by the current sensor collecting the resonant current of the first-side winding of the high-frequency transformer 131, and the resonant sampling current of the second resonant current is obtained by the current sensor collecting the resonant current of the second-side winding of the high-frequency transformer 131.

[0150] After loading the resonant sampling current of the first resonant current and the resonant sampling current of the second resonant current into the pulse width modulation circuit 240, the resonant sampling current of the first resonant current and the resonant sampling current of the second resonant current can be compared with the overcurrent protection threshold set in the PWM control unit. For example, the corresponding peaks of the first resonant current and the second resonant current can be compared with the overcurrent protection threshold. When the peak exceeds the set overcurrent protection threshold, it is considered that an overcurrent phenomenon has occurred. At this time, the PWM control unit can be turned off to generate a modulated PWM signal; if the corresponding peaks of the first resonant current and the second resonant current are both lower than the overcurrent protection threshold, it can be considered that no overcurrent phenomenon has occurred, and the PWM control unit is kept generating the modulated PWM signal normally. It can be understood that the overcurrent protection threshold is related to the application scenario of the DC-DC converter of the present invention, etc., and the overcurrent protection threshold can be specifically set according to actual requirements.

[0151] Figure 12An embodiment of the control circuit of the present invention is shown. The DC voltage of port 1 is sampled and obtained through the DC voltage sampling circuit 210 of port 1, and the DC voltage of port 2 is sampled and obtained through the DC voltage sampling circuit 220 of port 2. Among them, the DC voltage sampling circuit 210 of port 1 includes a first Hall voltage sensor 211, a resistor R211, and a resistor R212. The first Hall voltage sensor 211 can adopt a commonly used form in the prior art. The HV+ terminal of the first Hall voltage sensor 211 is connected to the first end of the resistor R211, and the second end of the resistor R211 is connected to the first filter circuit endpoint Ud1+ of the first filter circuit 110, so that the DC voltage Uo1 of port 1 is input to the first Hall voltage sensor 211 through the resistor R211. The HV- terminal of the first Hall voltage sensor 211 is connected to the second filter circuit endpoint Ud1- of the first filter circuit 110. The positive power supply terminal of the first Hall voltage sensor 211 is connected to the +12V voltage, and the negative power supply terminal of the first Hall voltage sensor 211 is connected to the -12V voltage. The output terminal of the first Hall voltage sensor 211 is connected to the first end of the resistor R212 and the current direction selection circuit 230. The second end of the resistor R212 is grounded, and the output current of the first Hall voltage sensor 211 is converted into a voltage U1+ through the resistor R212.

[0152] Figure 12 Among them, the DC voltage sampling circuit 220 of port 2 includes a second Hall voltage sensor 221, a resistor R221, and a resistor R222. The HV+ terminal of the second Hall voltage sensor 221 is connected to the first end of the resistor R221, and the second end of the resistor R221 is connected to the first filter circuit endpoint Ud2+ of the second filter circuit 140, so that the DC voltage Uo2 of port 2 is input to the second Hall voltage sensor 221 through the resistor R221. The HV- terminal of the second Hall voltage sensor 221 is connected to the second filter circuit endpoint Ud2- of the second filter circuit 140. The positive power supply terminal of the second Hall voltage sensor 221 is connected to the +12V voltage, and the negative power supply terminal of the second Hall voltage sensor 221 is connected to the -12V voltage. The output terminal of the second Hall voltage sensor 221 is connected to the first end of the resistor R222 and the current direction selection circuit 230. The second end of the resistor R222 is grounded, and the output current of the second Hall voltage sensor 221 is converted into a voltage U2+ through the resistor R222.

[0153] Figure 12An embodiment of the current direction selection circuit 230 is also shown in the figure. In the figure, the current direction selection circuit 230 may include a connector J231. The connector J231 has three terminals. Among them, the first terminal of the connector J231 is connected to the first terminal of the resistor R222. The second terminal of the connector J231 is connected to the pulse width modulation circuit 240. The third terminal of the connector J231 is connected to the first terminal of the resistor R212. Through the selector of the connector J231, the second terminal of the connector J231 can be connected to the first terminal of the connector J231, or the second terminal of the connector J231 can be connected to the third terminal of the connector J231. Specifically, the selector can be manually operated or automatically operated, and can be specifically selected according to needs. The current direction selection circuit 230 can also adopt other forms, which can be specifically selected according to needs, so as to meet the corresponding current selection criteria.

[0154] When the current direction is from port 1 to port 2, port 1 is used as the power supply side and port 2 is used as the load side. The second terminal of the connector J231 should be connected to the third terminal of the connector J231 to use the filtered port voltage of port 2 as the target voltage. At this time, the transformed sampling voltage generated based on the target voltage can be loaded into the pulse width modulation circuit 240. Similarly, when the current direction is from port 2 to port 1, port 2 is used as the power supply side and port 1 is used as the load side. The second terminal of the connector J231 should be connected to the first terminal of the connector J231 to use the filtered port voltage of port 1 as the target voltage. At this time, the transformed sampling voltage generated based on the target voltage can be loaded into the pulse width modulation circuit 240.

[0155] Figure 12 In the figure, the pulse width modulation circuit 240 includes a PWM pulse width modulation integrated chip 241. Among them, the PWM pulse width modulation integrated chip 241 can adopt a chip with the model UC3825. When the PWM pulse width modulation integrated chip 241 adopts a chip with the model UC3825, the VCC terminal of the PWM pulse width modulation integrated chip 241 is connected to a +12V voltage. The VC terminal of the PWM pulse width modulation integrated chip 241 is connected to the VREF terminal of the PWM pulse width modulation integrated chip 241 and the first terminal of the variable resistor R244. The second terminal of the variable resistor R244 is grounded. The variable control terminal of the variable resistor R244 is connected to the NI+ terminal of the PWM pulse width modulation integrated chip 241 through the resistor R243.

[0156] The NI- terminal of the PWM pulse width modulation integrated chip 241 is connected to one end of the resistor R241 and one end of the capacitor C241. The other end of the resistor R241 is connected to the second terminal of the connector J231. The other end of the capacitor C241 is connected to the E / AOUT terminal of the PWM pulse width modulation integrated chip 241 through the resistor R242.

[0157] The Ilim terminal of the PWM pulse width modulation integrated chip 241 is connected to the cathode terminals of diode D241 and diode D242. The anode terminal of diode D241 receives the first resonant current and is connected to one end of resistor R248, and the other end of resistor R248 is grounded; the anode terminal of diode D242 receives the second resonant current and is connected to one end of resistor R249, and the other end of resistor R249 is grounded.

[0158] The RT terminal of the PWM pulse width modulation integrated chip 241 is grounded through resistor R250, the GND terminal of the PWM pulse width modulation integrated chip 241 is directly grounded, and the SS terminal of the PWM pulse width modulation integrated chip 241 is grounded through capacitor C245.

[0159] The CT terminal of the PWM pulse width modulation integrated chip 241 is connected to one end of resistor R246, one end of capacitor C242, and one end of capacitor C243. The other end of capacitor C243 is grounded. The other end of resistor R246 and the other end of capacitor C242 are connected to one end of capacitor C244. The other end of capacitor C244 is connected to the Ramp terminal of the PWM pulse width modulation integrated chip 241 and one end of resistor R247. The other end of resistor R247 is grounded and is connected to the PWRGND terminal of the PWM pulse width modulation integrated chip 241. The OUTA terminal and OUTB terminal of the PWM pulse width modulation integrated chip 241 are connected to the switch tube drive circuit 250.

[0160] For Figure 12 In the shown pulse width modulation circuit 240, the setting of the reference voltage can be realized through variable resistor R244. Resistors R241 to R243, capacitor C241, and the error amplifier inside the PWM pulse width modulation integrated chip 241 form a PI regulator; resistors R245 to R247 and capacitors C242 to C244 determine the frequency of the modulated PWM signal generated by the PWM pulse width modulation integrated chip 241; resistors R248, R249, diodes D241, D242, and the comparator inside the PWM pulse width modulation integrated chip 241 form a protection circuit to limit the maximum value of the resonant current, that is, the above-mentioned overcurrent protection can be realized.

[0161] When the pulse width modulation circuit 240 adopts the above circuit form, the switching tube driving circuit 250 includes a first transformed PWM signal group generating unit and a second transformed PWM signal group generating unit. Among them, the first transformed PWM signal group generating unit can generate a DC-AC transformed PWM signal group or an AC-DC transformed PWM signal group, and the second transformed PWM signal group generating unit can generate an AC-DC transformed PWM signal group or a DC-AC transformed PWM signal group. Specifically, the first transformed PWM signal group generating unit can be correspondingly connected to one of the cyclic resonant converters, and the second transformed PWM signal group generating unit can be correspondingly connected to the other cyclic resonant converter. For example, the first transformed PWM signal group generating unit can be correspondingly connected to the first cyclic resonant converter 120, and the second transformed PWM signal group generating unit can be correspondingly connected to the second cyclic resonant converter 130.

[0162] Figure 12 An embodiment of the switching tube driving circuit 250 is also shown in the figure. It can be seen from the figure that the first transformed PWM signal group generating unit can be correspondingly connected to the first cyclic resonant converter 120, and the second transformed PWM signal group generating unit is correspondingly connected to the second cyclic resonant converter 130. Therefore, the first transformed PWM signal group generating unit can generate a DC-AC transformed PWM signal group or an AC-DC transformed PWM signal group. At the same time, the second transformed PWM signal group generating unit can generate an AC-DC transformed PWM signal group and a DC-AC transformed PWM signal group, which specifically correspond to the transformations performed by the first cyclic resonant converter 120 and the second cyclic resonant converter 130. For specific reference, please refer to the corresponding description above.

[0163] Figure 12 In this case, the first transformed PWM signal group generating unit includes a first power amplifier 251 and a second power amplifier 252. Among them, both the first power amplifier 251 and the second power amplifier 252 can adopt chips of model MIC4422. When both the first power amplifier 251 and the second power amplifier 252 adopt chips of model MIC4422, there are:

[0164] The VS terminals of the first power amplifier 251 and the second power amplifier 252 are both connected to the +12V voltage, the GND terminals of the first power amplifier 251 and the second power amplifier 252 are both grounded, the IN terminal of the first power amplifier 251 is connected to the OUTA terminal of the PWM pulse width modulation integrated chip 241, and the IN terminal of the second power amplifier 252 is connected to the OUTB terminal of the PWM pulse width modulation integrated chip 241.

[0165] The OUT terminal of the first power amplifier 251 is connected to one end of the capacitor C251 and one end of the resistor R251. The other end of the capacitor C251 and the other end of the resistor R251 are connected to the first end of the primary winding of the pulse transformer T251. The second end of the primary winding of the pulse transformer T251 is connected to the OUT terminal of the second power amplifier 252.

[0166] The first end of the first winding of the secondary side of the pulse transformer T251 is connected to one end of the resistor R253, and the other end of the resistor R253 is connected to the gate terminal of the first bridge arm switch tube 121 of the first resonant cycle. The second end of the first winding of the secondary side of the pulse transformer T251 is connected to the second end of the first bridge arm switch tube 121 of the first resonant cycle. At the same time, the first end of the second winding of the secondary side of the pulse transformer T251 is connected to one end of the resistor R254, and the other end of the resistor R254 is connected to the gate terminal of the second bridge arm switch tube 122 of the first resonant cycle. The second end of the second winding of the secondary side of the pulse transformer T251 is connected to the second end of the second bridge arm switch tube 122 of the first resonant cycle.

[0167] As can be seen from the above description, the switching state of the first bridge arm switch tube 121 of the first resonant cycle can be controlled through the first winding of the secondary side of the pulse transformer T251, that is, a corresponding PWM signal can be generated through the first winding of the secondary side of the pulse transformer T251, and the switching state of the first bridge arm switch tube 121 of the first resonant cycle can be controlled according to the generated PWM signal; the switching state of the second bridge arm switch tube 122 of the first resonant cycle can be controlled through the second winding of the secondary side of the pulse transformer T251, and a corresponding PWM signal can be generated through the second winding of the secondary side of the pulse transformer T251.

[0168] Figure 12 Among them, the second transformed PWM signal group generating unit includes a third power amplifier 253 and a fourth power amplifier 254. Among them, both the third power amplifier 253 and the fourth power amplifier 254 can use a chip with the model number MIC4422. Among them, when both the third power amplifier 253 and the fourth power amplifier 254 use a chip with the model number MIC4422, then there is:

[0169] The VSS terminals of the third power amplifier 253 and the fourth power amplifier 254 are both connected to the +12V voltage. The GND terminals of the third power amplifier 253 and the fourth power amplifier 254 are both grounded. The IN terminal of the third power amplifier 253 is connected to the OUTA terminal of the PWM pulse width modulation integrated chip 241. The IN terminal of the fourth power amplifier 254 is connected to the OUTB terminal of the PWM pulse width modulation integrated chip 241.

[0170] The OUT terminal of the third power amplifier 253 is connected to one end of the capacitor C252 and one end of the resistor R252. The other end of the capacitor C252 and the other end of the resistor R252 are connected to the first end of the primary winding of the pulse transformer T252. The second end of the primary winding of the pulse transformer T252 is connected to the OUT terminal of the fourth power amplifier 254.

[0171] The first end of the first secondary winding of the pulse transformer T252 is connected to one end of the resistor R255. The other end of the resistor R255 is connected to the gate terminal of the first switch tube 135 of the second resonant first bridge arm. The second end of the second secondary winding of the pulse transformer T251 is connected to the second end of the first switch tube 136 of the second resonant first bridge arm. Meanwhile, the first end of the second secondary winding of the pulse transformer T252 is connected to one end of the resistor R256. The other end of the resistor R256 is connected to the gate terminal of the second switch tube 136 of the second resonant second bridge arm. The second end of the second secondary winding of the pulse transformer T252 is connected to the second end of the second switch tube 136 of the second resonant second bridge arm.

[0172] Since the second transformed PWM signal group generating unit has the same form as the first transformed PWM signal group generating unit, the working principle of the second transformed PWM signal group generating unit can refer to the corresponding description of the first transformed PWM signal group generating unit above.

[0173] As can be seen from the above description, the DC-DC converter of the present invention has bidirectional conversion ability. Therefore, the DC-DC converter includes two working modes. Among them, the first working mode can be to transfer electrical energy from port 1 to port 2, and the second working mode can be to transfer electrical energy from port 2 to port 1. Therefore, the first working mode is the forward operating state mentioned above, and the second working mode is the reverse operating state mentioned above. In addition, from Figure 1 the illustrated embodiment, there is also:

[0174] Figure 1 In, the first end of the first switch tube 121 of the first resonant first bridge arm and the first end of the first switch tube 122 of the first resonant second bridge arm are mutually connected to form a node a with the first end of the inductor L 1σ The second end of the corresponding side winding of the high-frequency transformer 131 is connected to the first end of the capacitor C 11 and the first end of the capacitor C 12 to form a node b. The voltage between the node a and the node b is u ab . The first end of the first switch tube 135 of the second resonant first bridge arm and the first end of the first switch tube 136 of the second resonant second bridge arm are mutually connected to form a node c with the first end of the inductor L 2σ The second end of the corresponding side winding of the high-frequency transformer 131 is connected to the first end of the capacitor C 21 and the first end of the capacitor C22 The first end of [] is connected to form node d, and the voltage between node c and node d is u cd .

[0175] Figure 1 In [], U d1 is the voltage difference between the first connection end and the second connection end of the bridge circuit in the first cyclic resonant converter 120, U d2 is the voltage difference between the first connection end and the second connection end of the bridge circuit in the second cyclic resonant converter 130, Io1 is the current when port 1 is the load side, and Io2 is the current when port 2 is the load side.

[0176] The voltage U d1 , the voltage U d2 , the current Id1, the voltage Id2, the voltage Uo2, the voltage Uo, the current Io1, and the current Io2, the corresponding waveforms can be referred to Figure 11 as shown in Figure 11 In [], the quantity in "parentheses" is the corresponding quantity when the power transmission direction is from port 2 to port 1. For example, (voltage U d1 ) represents obtaining the voltage difference between the first connection end and the second connection end of the bridge circuit in the first cyclic resonant converter 120 when the power transmission direction is from port 2 to port 1, Figure 11 For other cases in [], reference can be made to the description here, and no further examples will be given one by one.

[0177] Next, in combination with Figures 2 to 9 an example will be given of the voltage conversion method and process of the DC-DC converter of the present invention. Specifically,

[0178] When the configuration is in the first working mode, power is transmitted from port 1 to port 2. At this time, it is in the forward operating state. The first cyclic resonant converter 120 is used for DC-AC conversion, and the second cyclic resonant converter 130 is used for AC-DC conversion. Then, a resonant current i 1 is generated in the first cyclic resonant converter 120. Based on the resonant current i 1 , a first resonant current can be formed. A resonant current i 2 is generated in the second cyclic resonant converter 130. Based on the resonant current i 2 , a second resonant current can be formed. As can be seen from the above description, the waveform of the resonant current i 1 is sinusoidal.

[0179] When the resonant current i 1 , the resonant current i 2 is in the positive half-wave, the DC current Id1 at port 1 flows to the first cyclic resonant converter 120, and the resonant current i 1 flows to the first-side winding of the high-frequency transformer 131, and the resonant current i2 Flows from the second-side winding of the high-frequency transformer 131 to the second resonant converter 130, and the second resonant converter 130 outputs a DC current Id2 to port 2, as Figure 2 shown.

[0180] Furthermore, as Figure 3 shown, when the port 1 delivers electrical energy to the port 2, when the resonant current i 1 and the resonant current i 2 are in the positive half-wave, the first bridge-arm switch tube 121 of the first resonant converter 120 is turned on, and the second bridge-arm switch tube 122 of the first resonant converter 120 is in the off state. The resonant current i 1 has two branches, which are respectively: the resonant current i 11 and the resonant current i 12 . The loop of the resonant current i 12 is: U1+ terminal → the first bridge-arm switch tube 121 of the first resonant converter 120 → inductor L 1σ → the first-side winding of the high-frequency transformer 131 → capacitor C 12 → U1- terminal; the loop of the resonant current i 11 is: the first bridge-arm switch tube 121 of the first resonant converter 120 → inductor L 1σ → the first-side winding of the high-frequency transformer 131 → capacitor C 11 → the first bridge-arm switch tube 121 of the first resonant converter 120. The U1+ terminal is the first connection terminal of the bridge circuit of the first resonant converter 120, and U1- is the second connection terminal of the bridge circuit of the first resonant converter 120. The subsequent descriptions can all refer to this description.

[0181] When using the second resonant converter 130 for AC-DC conversion, then: the first bridge-arm switch tube 135 of the second resonant converter 130 is in the on state, and the second bridge-arm switch tube 136 of the second resonant converter 130 is in the off state. The resonant current i 2 also has two branches, which are respectively the resonant current i 21 and the resonant current i 22 . The loop of the resonant current i 22 is: U2- terminal → capacitor C 22 → the second-side winding of the high-frequency transformer 131 → inductor L 2σ → the first bridge-arm switch tube 135 of the second resonant converter 130 → U2+ terminal; the loop of the resonant current i 21 is: the first bridge-arm switch tube 135 of the second resonant converter 130 → capacitor C 21 → the second-side winding of the high-frequency transformer 131 → inductor L 2σ → the first bridge-arm switch tube 135 of the second resonant converter 130, as Figure 3As shown. The U2+ terminal is the first connection terminal of the bridge circuit of the second resonant converter 130, and the U2- is the second connection terminal of the bridge circuit of the second resonant converter 130. The following description can refer to this description. From Figure 3 In, the resonant current i 1 flows to the first side winding of the high-frequency transformer 131, and the resonant current i 2 flows out from the same-name terminal of the second side winding of the high-frequency transformer 131.

[0182] Figure 4 The resonant current i 1 and the resonant current i 2 are shown in. When in the negative half-wave, the DC current Id1 at port 1 flows to the first resonant converter 120, and the resonant current i 1 and the resonant current i 2 are reversed. The DC current Id2 output by the second resonant converter 130 flows to port 2.

[0183] Figure 5 is shown in Figure 4 The resonant current i 1 and the resonant current i 2 in. When in the negative half-wave, at this time, the first bridge-arm switch tube 121 of the first resonant converter is in the off state, and the second bridge-arm switch tube 122 of the first resonant converter is in the on state. The resonant current i 1 still has two branches, which are respectively: the resonant current i 11 and the resonant current i 12 . Specifically, the loop of the resonant current i 11 is: U1+ → capacitor C 11 → the first side winding of the high-frequency transformer 131 → inductor L 1σ → the second bridge-arm switch tube 122 of the first resonant converter → U1-; the loop of the resonant current i 12 is: the second bridge-arm switch tube 122 of the first resonant converter → capacitor C 12 → the first side winding of the high-frequency transformer 131 → inductor L 1σ → the second bridge-arm switch tube 122 of the first resonant converter.

[0184] During specific implementation, the inductor L 1σ resonates with the capacitor C 11 and the capacitor C 12 simultaneously, generating the resonant current i 11 and the resonant current i 12 . Since the capacitance values of the capacitor C 11 and the capacitor C 12 are the same, therefore, the resonant current i 11 and the resonant current i 12 are also currents with the same value.

[0185] In the second resonant converter 130, the second-bridge-arm switching transistor 136 of the second resonant loop conducts, and the first-bridge-arm switching transistor 135 of the second resonant loop is in the off state. The resonant current i 2 also has two branches, namely the resonant current i 21 and the resonant current i 22 . The loop of the resonant current i 21 is: U2 → the second-bridge-arm switching transistor 136 of the second resonant loop → inductor L 2σ → the second-side winding of the high-frequency transformer 131 → capacitor C 21 → U2+; the loop of the resonant current i 21 is: the second-bridge-arm switching transistor 136 of the second resonant loop → inductor L 2σ → the second-side winding of the high-frequency transformer 131 → capacitor C 22 → the second-bridge-arm switching transistor 136 of the second resonant loop, as Figure 5 shown.

[0186] Figure 6 An embodiment in which the DC-DC converter is in the second operating mode is shown in . At this time, electric energy is transmitted from port 2 to port 1. At this time, the second resonant converter 130 is used to perform DC-AC conversion, and the first resonant converter 120 is used to perform AC-DC conversion. At this time, based on the resonant current i 1 generated in the first resonant converter 120, a second resonant current can be formed, and based on the resonant current i 2 generated in the second resonant converter 130, a first resonant current can be formed. It can be seen from the above description that the waveform of the resonant current i 2 is sinusoidal.

[0187] When the resonant current i 1 , the resonant current i 2 are in the positive half-wave, the DC current Id2 at port 2 flows to the second resonant converter 130, the resonant current i 2 flows to the second-side winding of the high-frequency transformer 131, and the resonant current i 1 flows from the first-side winding of the high-frequency transformer 131 to the first resonant converter 120, and the DC current Id1 output by the first resonant converter 120 flows to port 1 and is output.

[0188] Figure 7 An embodiment in which the resonant current i 1 , the resonant current i 2 are in the positive half-wave is shown in . At this time, the first-bridge-arm switching transistor 135 of the second resonant loop is in the on state, and the second-bridge-arm switching transistor 136 of the second resonant loop is in the off state. The resonant current i 2 also has two branches, namely the resonant current i21 and the resonant current i 22 . The resonant current i 22 has a loop as follows: U2+ terminal → the first bridge arm switch tube 135 of the second cycle resonance → inductor L 2σ → the second side winding of the high-frequency transformer 131 → capacitor C 22 → U2- terminal; the resonant current i 21 has a loop as follows: the first bridge arm switch tube 135 of the second cycle resonance → inductor L 2σ → the second side winding of the high-frequency transformer 131 → capacitor C 21 → the first bridge arm switch tube 135 of the second cycle resonance.

[0189] Figure 7 In [the relevant context], the first bridge arm switch tube 121 of the first cycle resonance in the first cycle resonance converter 120 is in the conducting state, and the second bridge arm switch tube 122 of the first cycle resonance is in the off state. The resonant current i 1 has two branches, which are respectively: the resonant current i 11 and the resonant current i 12 .

[0190] The loop of the resonant current i 12 is as follows: U1- terminal → capacitor C 12 → the first side winding of the high-frequency transformer 131 → inductor L 1σ → the first bridge arm switch tube 121 of the first cycle resonance → U1+ terminal; the loop of the resonant current i 11 is as follows: the first bridge arm switch tube 121 of the first cycle resonance → capacitor C 11 → the first side winding of the high-frequency transformer 131 → inductor L 1σ → the first bridge arm switch tube 121 of the first cycle resonance.

[0191] Figure 8 An embodiment is shown in [the relevant context] in which the resonant current i 1 , the resonant current i 2 is in the negative half-wave. The DC current Id2 at port 2 flows to the second cycle resonance converter 130, and the resonant current i 1 and the resonant current i 2 are reversed. The DC current Id1 output by the first cycle resonance converter 120 flows to port 1 and is output.

[0192] Figure 9 An embodiment is shown in [the relevant context] in which the resonant current i 1 , the resonant current i 2 is in the negative half-wave, and the resonant current i 1 , the resonant current i 2For the corresponding situation, specifically, the second bridge arm switch tube 136 of the second cycle resonance is in the conducting state, and the first bridge arm switch tube 135 of the second cycle resonance is in the off state. The resonance current i 2 has two branches, namely the resonance current i 21 and the resonance current i 22 . Among them, the loop of the resonance current i 21 is: U2+ terminal → capacitor C 21 → the second side winding of the high-frequency transformer 131 → inductor L 2σ → the second bridge arm switch tube 136 of the second cycle resonance → U2- terminal; the loop of the resonance current i 22 is: the second bridge arm switch tube 136 of the second cycle resonance → capacitor C 22 → the second side winding of the high-frequency transformer 131 → inductor L 2σ → the second bridge arm switch tube 136 of the second cycle resonance.

[0193] Inside the first cycle resonance converter 120, the second bridge arm switch tube 122 of the first cycle resonance is in the conducting state, and the first bridge arm switch tube 121 of the first cycle resonance is in the off state. The resonance current i 1 has two branches, namely: the resonance current i 11 and the resonance current i 12 . Among them, the loop of the resonance current i 11 is: U1- terminal → the second bridge arm switch tube 122 of the first cycle resonance → inductor L 1σ → the first side winding of the high-frequency transformer 131 → capacitor C 11 → U1+ terminal; the loop of the resonance current i 12 is: the second bridge arm switch tube 122 of the first cycle resonance → inductor L 1σ → the first side winding of the high-frequency transformer 131 → capacitor C 12 → the second bridge arm switch tube 122 of the first cycle resonance.

[0194] As can be seen from the above description, for the first bridge arm switch tube and the second bridge arm switch tube in each cycle resonance converter, before the first bridge arm switch tube and the second bridge arm switch tube are turned on, the voltage across the first bridge arm switch tube and the second bridge arm switch tube has dropped to zero, thereby realizing the full-process soft switching of the first bridge arm switch tube and the second bridge arm switch tube, greatly reducing the switching loss of the converter of the present invention.

[0195] In an embodiment of the present invention, when two cycle resonance converters are used for voltage conversion, there is:

[0196] When performing DC-AC conversion, for the LC series resonance formed by the cycle resonance converter performing DC-AC conversion, the LC series resonance has a first resonance frequency and a first quality factor;

[0197] When performing AC-DC conversion, for the LC series resonance formed by a cyclic resonant converter that performs AC-DC conversion, the LC series resonance has a second resonance frequency and a second quality factor, where,

[0198] The first resonance frequency is equal to the second resonance frequency, and the first quality factor is equal to the second quality factor.

[0199] Specifically, Figure 10 shows that the DC-DC converter of the present invention is in the first operating mode, and the resonant current i 1 and the resonant current i 2 are in the positive half-wave. Figure 1 shows the equivalent circuit diagram of the DC-DC converter. Based on Figure 10 equivalent circuit diagram, the resonant parameters of the first cyclic resonant converter 120 and the second cyclic resonant converter 130 can be calculated. Specifically,

[0200] where,

[0201] u 1 = u C110 + u C120

[0202] u 2 = u C210 + u C220

[0203] i 11 + i 12 = i 1

[0204] i 21 + i 22 = i 2

[0205] C 21 = C 22 = C 2

[0206] C 11 = C 12 = C 1

[0207] Specifically, u C110 is the initial voltage of the capacitor C 11 and u C120 is the initial voltage of the capacitor C 12 and u C210 is the initial voltage of the capacitor C 21 and u C220 is the initial voltage of the capacitor C 22The initial voltage. ω is the angular frequency, where the angular frequency ω refers to the angular frequency of the converter of the present invention during transient operation, and the angular frequency ω is the switching frequency * 2π, where the switching frequency specifically refers to the corresponding switching frequency of the first bridge arm switching tube or the second bridge arm switching tube.

[0208] Subtracting equation (2) from equation (1) gives:

[0209]

[0210] Subtracting equation (4) from equation (3) gives:

[0211]

[0212] When power is transmitted from port 1 to port 2, then:

[0213]

[0214] When power is transmitted from port 2 to port 1, then:

[0215]

[0216] When the cyclic resonant converter is in the resonant state, then:

[0217]

[0218] When power is transmitted from port 1 to port 2, then:

[0219] u 2 = DC voltage of port 2

[0220] jωL m (i 1 -ni 2 )n = DC voltage of port 2

[0221]

[0222] When power is transmitted from port 2 to port 1, then:

[0223] u 1 = DC voltage of port 1

[0224] jωL m (i 1 -ni 2 ) = DC voltage of port 1

[0225] u 2 = jωL m (i 1 -ni 2 )n = n DC voltage of port 1

[0226]

[0227] As can be seen from the above description, for the resonance parameters, there are:

[0228]

[0229] Specifically, is the first resonance frequency, is the second resonance frequency, is the first quality factor, is the second quality factor.

[0230] It should be noted that according to the above calculation of the resonance parameters, the corresponding parameters of the first cyclic resonance converter 120 and the second cyclic resonance converter 130 can be determined, that is, the resonance inductor L 1σ , resonance inductor L 1σ , capacitor C 11 , capacitor C 12 , capacitor C 21 and capacitor C 21 corresponding parameters.

Claims

1. A bidirectional resonant isolated DC-DC converter, characterized in that: The DC-DC converter includes a conversion main circuit and a control circuit for controlling the working state of the conversion main circuit, wherein: The conversion main circuit includes a high-frequency transformer, and the windings on both sides of the high-frequency transformer are respectively adapted to be connected to a cyclic resonant converter for voltage conversion, wherein, during voltage conversion, a cyclic resonant converter is used to first perform DC-AC conversion, and then, at least AC-DC conversion is performed by the high-frequency transformer and another cyclic resonant converter, and a target conversion voltage is generated after the AC-DC conversion; The cyclic resonant converter comprises a resonant conversion bridge circuit and a resonant inductor adaptively connected to the resonant conversion bridge circuit, wherein: The resonant conversion bridge circuit includes a resonant conversion first bridge arm and a resonant conversion second bridge arm, the resonant conversion first bridge arm includes a first bridge arm switch tube and a first bridge arm resonant capacitor, and the resonant converter second bridge arm includes a second bridge arm switch tube and a second bridge arm resonant capacitor, wherein: The first end of the first bridge arm switch tube and the first end of the second bridge arm switch tube are connected to the first end of the resonant inductor, the second end of the resonant inductor is connected to the first end of the corresponding side winding of the high-frequency transformer, and the second end of the corresponding side winding of the high-frequency transformer is connected to the first end of the first bridge arm resonant capacitor and the first end of the second bridge arm resonant capacitor. The second end of the first bridge arm resonant capacitor is adaptively connected to the second end of the first bridge arm switch tube to form a first bridge connection end of the resonant conversion bridge circuit; at the same time, the second end of the second bridge arm resonant capacitor is adaptively connected to the second end of the second bridge arm switch tube to form a second bridge connection end of the resonant conversion bridge circuit; For any cyclic resonant converter, the corresponding control ends of the first bridge arm switch tube and the second bridge arm switch tube in the cyclic resonant converter are connected to the control circuit, and the control circuit is used to configure the switching states of the first bridge arm switch tube and the second bridge arm switch tube in the cyclic resonant converter so that the cyclic resonant converter enters the LC series resonance state, and the corresponding DC-AC conversion or AC-DC conversion is performed based on the cyclic resonant converter entering the LC series resonance state.

2. The bidirectional resonant isolated DC-DC converter according to claim 1 is characterized in that: Each cyclic resonant converter is also adapted to be connected to a filter circuit, wherein: The cyclic resonant converter is adaptively connected to the corresponding filter circuit via the first connecting end of the bridge circuit and the second connecting end of the bridge circuit; When the cyclic resonant converter performs DC-AC conversion, a filter circuit connected to the cyclic resonant converter is used to filter the input voltage; When the cyclic resonant converter performs AC-DC conversion, the filter circuit connected to the cyclic resonant converter is used to filter the output voltage.

3. The bidirectional resonant isolated DC-DC converter according to claim 2 is characterized in that: The filter circuit adopts a π filter circuit, wherein: The filter circuit comprises a first filter capacitor, a filter inductor and a second filter capacitor, wherein a first end of the first filter capacitor and a first end of the filter inductor are connected to each other to form a first terminal of the filter circuit after being connected to each other, and a second end of the filter inductor is connected to a first end of the second filter capacitor and a first connection end of the bridge circuit; The second end of the first filter capacitor is connected to the second end of the second filter capacitor and the second connection end of the bridge circuit to form a second end point of the filter circuit after being connected to each other, wherein a filter port voltage is generated based on the first end point of the filter circuit and the second end point of the filter circuit; When the cyclic resonant converter connected to the filter circuit performs DC-AC conversion, the current filter circuit performs input voltage filtering and loads the filtered input voltage to the connected cyclic resonant converter; When the cyclic resonant converter connected to the filter circuit performs AC-DC conversion, the current filter circuit performs output voltage filtering to generate a target voltage after filtering the target conversion voltage, and stabilizes the target voltage at a reference voltage.

4. The bidirectional cycle resonant isolated DC-DC converter according to claim 3 is characterized in that: When the voltage is converted, for any resonant conversion bridge circuit, we have: generating a resonant capacitor total voltage based on a first resonant capacitor voltage on the first resonant capacitor and a second resonant capacitor voltage on the second resonant capacitor; The total voltage of the resonant capacitor is not greater than the voltage of the filter port of the filter circuit to which the current resonant conversion bridge circuit is connected.

5. The bidirectional cycle resonant isolated DC-DC converter according to claim 3 is characterized in that: When performing DC-AC conversion, a cyclic resonant converter that performs DC-AC conversion is determined, and corresponding switch states of a first bridge arm switch tube and a second bridge arm switch tube in the determined cyclic resonant converter circuit are controlled by a control circuit to generate a sinusoidal first resonant current based on the LC series resonance formed by the current cyclic resonant converter; When performing AC-DC conversion, a cyclic resonant converter that performs AC-DC conversion is determined, and the corresponding switching states of the first bridge arm switch tube and the second bridge arm switch tube in the determined cyclic resonant converter circuit are controlled by a control circuit to generate a second resonant current based on the LC series resonance formed by the current cyclic resonant converter, wherein: The current direction of the second resonant current is opposite to the current direction of the first resonant current; Based on the second resonant current, a target voltage is generated after passing through a correspondingly connected filter circuit.

6. The bidirectional resonant isolated DC-DC converter according to claim 5 is characterized in that: When the voltage is converted, the target voltage is sampled to generate a conversion sampling voltage after sampling, and the conversion sampling voltage generated by sampling is loaded into the pulse width modulation circuit in the control circuit, wherein, Based on the received conversion sampling voltage and the reference voltage, the pulse width modulation circuit generates a voltage conversion PWM signal group, wherein the corresponding switching states of the first bridge arm switch tube and the second bridge arm switch tube in each resonant conversion bridge circuit are regulated based on the generated voltage conversion PWM signal group to stabilize the target voltage at the reference voltage.

7. The bidirectional resonant isolated DC-DC converter according to claim 6 is characterized in that: The pulse width modulation circuit is adaptively connected to the current direction selection circuit and the switch tube drive circuit, wherein: The current direction selection circuit is connected to two voltage sensors, wherein each voltage sensor is used to collect the filter port voltage of the corresponding filter circuit, and the connection state between the voltage sensor and the pulse width modulation circuit is configured by the current direction selection circuit to load the transformed sampling voltage to the pulse width modulation circuit; The switch tube driving circuit is adaptively connected to the first bridge arm switch tube and the second bridge arm switch tube in the two cyclic resonant converters; The pulse width modulation circuit at least performs PI regulation on the received conversion sampling voltage and reference voltage, and generates a modulated PWM signal after the PI regulation, and the generated modulated PWM signal generates a voltage conversion PWM signal group through the switch tube driving circuit.

8. The bidirectional cycle resonant isolated DC-DC converter according to claim 7 is characterized in that: Loading the first resonant current and the second resonant current into the pulse width modulation circuit; The pulse width modulation circuit performs over-current protection on the first resonant current and the second resonant current, and adjusts the state of the generated modulated PWM signal based on the over-current protection state.

9. The bidirectional cycle resonant isolated DC-DC converter according to claim 7, characterized in that: The voltage conversion PWM signal group includes a DC-AC conversion PWM signal group and an AC-DC conversion PWM signal group, wherein: The DC-AC conversion PWM signal group includes a DC-AC conversion first PWM signal and a DC-AC conversion second PWM signal, wherein the DC-AC conversion first PWM signal and the DC-AC conversion second PWM signal are respectively loaded into a cyclic resonant converter performing DC-AC conversion to control the corresponding switching states of a first bridge arm switch tube and a second bridge arm switch tube in the cyclic resonant converter, and during the DC-AC conversion process, the first bridge arm switch tube and the second bridge arm switch tube are not in a conducting state at the same time; The AC-DC conversion PWM signal group includes an AC-DC conversion first PWM signal and an AC-DC conversion second PWM signal, wherein the AC-DC conversion first PWM signal and the AC-DC conversion second PWM signal are respectively loaded into a cyclic resonant converter performing AC-DC conversion to control the corresponding switching states of a first bridge arm switch tube and a second bridge arm switch tube in the cyclic resonant converter, and during the AC-DC conversion process, the first bridge arm switch tube and the second bridge arm switch tube are not in a conducting state at the same time; The first PWM signal for AC-DC conversion is consistent with the first PWM signal for DC-AC conversion. Meanwhile, the second PWM signal for AC-DC conversion is consistent with the second PWM signal for DC-AC conversion, so as to configure two cyclic resonant converters to respectively perform DC-AC conversion and AC-DC conversion.

10. The bidirectional cycle resonant isolated DC-DC converter according to any one of claims 1 to 9, characterized in that: When two cyclic resonant converters are used for voltage conversion, we have: When performing DC-AC conversion, an LC series resonance is formed based on a cyclic resonant converter that performs DC-AC conversion, wherein the LC series resonance has a first resonance frequency and a first quality factor; When performing AC-DC conversion, the LC series resonance formed by the cyclic resonant converter performing AC-DC conversion has a second resonance frequency and a second quality factor, wherein: The first resonant frequency is equal to the second resonant frequency, and the first quality factor is equal to the second quality factor.

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