A high-frequency isolated bidirectional converter

Abstract

The present invention discloses a high-frequency isolated bidirectional converter, which includes a switching circuit, a resonant circuit, a transformer, and a full-bridge switching circuit. One side of the full-bridge switching circuit and the switching circuit are respectively used as the second external connection side and the first external connection side of the high-frequency isolated bidirectional converter. Among them, the resonant circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, and a selection switch. One end of the second capacitor is connected to one end of the first capacitor and the second inductor. This end of the second inductor is also connected to the other end of the first capacitor / second capacitor through the selection switch. The other end of the second capacitor is also connected to one end of the first inductor. The other ends of the first capacitor and the second inductor are connected to the switching circuit. The other end of the second inductor and the other end of the first inductor are connected to the primary winding of the transformer. The secondary winding of the transformer is connected to the midpoint of the bridge arm of the full-bridge switching circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power conversion, and more particularly to a high-frequency isolated bidirectional converter. Background Art

[0002] A bidirectional DC-DC converter is a DC / DC converter that can adjust the bidirectional transmission of energy as needed, and is mainly used in energy storage systems, vehicle power systems, feedback charging and discharging systems, hybrid energy electric vehicles and other scenarios.

[0003] In a traditional LLC resonant bidirectional converter, zero-voltage switching (ZVS) conduction of the primary-side switching tubes and zero-current switching (ZCS) turn-off of the rectifier-side switching tubes can be achieved regardless of whether it operates in the forward or reverse direction. However, when the energy flows in the reverse direction, its circuit characteristics no longer exhibit LLC resonance characteristics but degenerate into LC resonance characteristics, and the maximum voltage gain of LC resonance becomes 1, greatly reducing the voltage gain during reverse operation and significantly narrowing the operating voltage range. Therefore, it is not very suitable for operating in a state of bidirectional energy flow over a wide voltage range, restricting its application scenarios. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-frequency isolated bidirectional converter with no loss in gain during both forward and reverse operation and capable of expanding the operating voltage range.

[0005] To solve the above technical problem, the present invention provides a high-frequency isolated bidirectional converter, including a switching circuit, a resonant circuit, a transformer, and a full-bridge switching circuit. One side of the full-bridge switching circuit and the switching circuit are respectively used as the second external connection side and the first external connection side of the high-frequency isolated bidirectional converter. Among them, the resonant circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, and a selection switch. One end of the second capacitor is connected to one end of the first capacitor and the second inductor. This end of the second inductor is also connected to the other end of the first capacitor / second capacitor through the selection switch, so as to be connected to the first capacitor through the selection switch when the high-frequency isolated bidirectional converter operates in the first state, and be connected to the second capacitor through the selection switch when in the second state. The other end of the second capacitor is also connected to one end of the first inductor. The other ends of the first capacitor and the second inductor are connected to the switching circuit. The other ends of the second inductor and the first inductor are connected to the primary winding of the transformer. The secondary winding of the transformer is connected to the midpoint of the bridge arm of the full-bridge switching circuit. Among them, in the first state, power is transmitted from the first external connection side to the second external connection side, and in the second state, power is transmitted from the second external connection side to the first external connection side.

[0006] Its further technical solution is as follows: The switching circuit includes two switching tubes, and the two switching tubes are connected in series to form a bridge arm. The two ends of this bridge arm serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the midpoint and the lowermost end of the bridge arm of the switching circuit.

[0007] Its further technical solution is as follows: The switching circuit includes two switching tubes, and the two switching tubes are connected in series to form a bridge arm. The two ends of this bridge arm serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the uppermost end and the midpoint of the bridge arm of the switching circuit.

[0008] Its further technical solution is as follows: The switching circuit includes four switching tubes, and every two switching tubes are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, their two ends serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the midpoints of the two bridge arms of the switching circuit.

[0009] Its further technical solution is as follows: The full-bridge switching circuit includes four switching tubes, and every two switching tubes are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, their two ends serve as the second external connection side of the high-frequency isolation bidirectional converter. The same-name end and the different-name end of the secondary winding of the transformer are respectively connected to the midpoints of the two bridge arms.

[0010] Its further technical solution is as follows: The high-frequency isolation bidirectional converter further includes a first filter capacitor and a second filter capacitor. The two ends of the first filter capacitor are connected to the first external connection side of the high-frequency isolation bidirectional converter, and the two ends of the second filter capacitor are connected to the second external connection side.

[0011] To solve the above technical problems, the present invention further provides a high-frequency isolation bidirectional converter, which includes a switching circuit, a resonant circuit, a transformer, and a full-bridge switching circuit. One side of the full-bridge switching circuit and the switching circuit serves as the second external connection side and the first external connection side of the high-frequency isolation bidirectional converter respectively. Among them, the resonant circuit includes a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, and a selection switch. Two ends of the second capacitor are respectively connected to one end of the third inductor and the first inductor. The other end of the third inductor is connected to one end of the first capacitor. One end of the second inductor is connected between the third inductor and the second capacitor, and this end of the second inductor is also connected to the other end of the first capacitor / the first inductor through the selection switch, so as to be connected to the first capacitor through the selection switch when the high-frequency isolation bidirectional converter operates in the first state, and connected to the first inductor through the selection switch in the second state. The other end of the first capacitor and the other end of the second inductor are connected to the switching circuit. The other end of the second inductor and the other end of the first inductor are connected to the primary winding of the transformer. The secondary winding of the transformer is connected to the midpoint of the bridge arm of the full-bridge switching circuit. Among them, in the first state, electric power is transmitted from the first external connection side to the second external connection side, and in the second state, electric power is transmitted from the second external connection side to the first external connection side.

[0012] Compared with the prior art, the resonant circuit in the high-frequency isolation bidirectional converter of the present invention has the same equivalent circuit when the energy flows in the forward and reverse directions, and there is no loss in the gain during the forward and reverse operations, solving the problem that the traditional LLC resonant circuit cannot work with the same performance in the reverse direction, that is, the high-frequency isolation bidirectional converter of the present invention can step up the voltage when the energy flows in the reverse direction, can effectively increase the input and output voltage range of the converter, and realize wide voltage range conversion. Description of the Drawings

[0013] Figure 1 is a schematic circuit diagram of the first embodiment of the high-frequency isolation bidirectional converter of the present invention.

[0014] Figure 2 is a schematic circuit diagram of the second embodiment of the high-frequency isolation bidirectional converter of the present invention.

[0015] Figure 3 is a schematic circuit diagram of the third embodiment of the high-frequency isolation bidirectional converter of the present invention. Detailed Embodiments

[0016] To enable those of ordinary skill in the art to more clearly understand the purpose, technical solutions, and advantages of the present invention, the following further elaborates on the present invention in conjunction with the drawings and embodiments.

[0017] Refer to Figure 1 , Figure 1This is a circuit schematic diagram of the first embodiment of the high-frequency isolation bidirectional converter 10 of the present invention. In the embodiment shown in the attached drawings, the high-frequency isolation bidirectional converter 10 includes a switching circuit 11, a resonant circuit 12, a transformer T1, and a full-bridge switching circuit 14. One side of the full-bridge switching circuit 14 and the switching circuit 11 serves as the second external connection side and the first external connection side of the high-frequency isolation bidirectional converter 10 respectively to connect to a load and a power supply. Among them, the resonant circuit 12 includes a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2, and a selection switch S. One end of the second capacitor C2 is connected to one end of the first capacitor C1 and the second inductor L2. This end of the second inductor L2 is also connected to the other end of the first capacitor C1 / second capacitor C2 through the selection switch S to be connected to the other end of the first capacitor C1 through the selection switch S when the high-frequency isolation bidirectional converter 10 operates in the first state, and to be connected to the other end of the second capacitor C2 through the selection switch S in the second state. The other end of the second capacitor C2 is also connected to one end of the first inductor L1. The other ends of the first capacitor C1 and the second inductor L2 are connected to the switching circuit 11. The other end of the second inductor L2 and the other end of the first inductor L1 are connected to the primary winding of the transformer T1. The secondary winding of the transformer T1 is connected to the midpoint of the bridge arm of the full-bridge switching circuit 14. Among them, in the first state, electric power is transmitted from the first external connection side to the second external connection side, and in the second state, electric power is transmitted from the second external connection side to the first external connection side, that is, when the energy flows forward, the working state of the high-frequency isolation bidirectional converter 10 is the first state, and when the energy flows backward, the working state of the high-frequency isolation bidirectional converter 10 is the second state. Preferably, the inductance values of the first inductor L1 and the second inductor L2 are the same.

[0018] In this embodiment, when the energy flows forward, that is, when the electric power is transmitted from the first external connection side to the second external connection side, the first external connection side of the high-frequency isolation bidirectional converter 10 serves as a DC input terminal and can be externally connected to a power supply, and its second external connection side serves as a DC output terminal and can be externally connected to a load; and when the energy flows backward, that is, when the electric power is transmitted from the second external connection side to the first external connection side, the second external connection side of the high-frequency isolation bidirectional converter 10 serves as a DC input terminal, and its first external connection side serves as a DC output terminal. In the resonant circuit 12 of the high-frequency isolation bidirectional converter 10 of the present invention, when the energy flows forward, the first capacitor C1 is short-circuited, and when the energy flows backward, the second capacitor C2 is short-circuited, so that the equivalent circuit of the resonant circuit 12 is the same when the energy flows forward and backward, and there is no loss in the gain during forward and reverse operation, solving the problem that the traditional LLC resonant circuit cannot work with the same performance in reverse, that is, it can step up the voltage when the energy flows backward, effectively improving the input and output voltage range of the converter, realizing wide voltage range conversion, and being applicable to high-power circuits.

[0019] In some embodiments, the switching circuit 11 is a full-bridge structure, including four switching transistors, namely the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4. Every two switching transistors are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, both ends thereof serve as the first external connection side of the high-frequency isolation bidirectional converter 10. Among them, the midpoint of the bridge arm formed by the series connection of the first switching transistor Q1 and the second switching transistor Q2 is connected to the first capacitor C1, and the midpoint of the bridge arm formed by the series connection of the third switching transistor Q3 and the fourth switching transistor Q4 is connected to the second inductor L2.

[0020] In the embodiment shown in the attached drawings, the full-bridge switching circuit 14 includes four switching transistors, namely the fifth switching transistor Q5, the sixth switching transistor Q6, the seventh switching transistor Q7, and the eighth switching transistor Q8. Every two switching transistors are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, both ends thereof serve as the second external connection side of the high-frequency isolation bidirectional converter 10. Among them, the midpoint of the bridge arm formed by the series connection of the fifth switching transistor Q5 and the sixth switching transistor Q6 and the midpoint of the bridge arm formed by the series connection of the seventh switching transistor Q7 and the eighth switching transistor Q8 are respectively connected to the same-name end and the different-name end of the secondary winding of the transformer T1. Based on this design, when the energy flows forward, the full-bridge switching circuit 14 can rectify the voltage waveform periodically output by the transformer T1 to generate the working voltage required by the load. Preferably, the switching transistors are MOS, IGBT or other controllable power switching transistors to achieve better circuit performance. In some embodiments, a diode can also be connected in parallel to each switching transistor. If the switching transistor is a MOS transistor, a diode is connected in parallel between its drain and source electrodes. If the switching transistor is an IGBT transistor, a diode is connected in parallel between its emitter and collector electrodes.

[0021] Furthermore, the high-frequency isolation bidirectional converter 10 further includes a first filter capacitor C3 and a second filter capacitor C4. Both ends of the first filter capacitor C3 are connected to the first external connection side of the high-frequency isolation bidirectional converter 10, and both ends of the second filter capacitor C4 are connected to the second external connection side of the high-frequency isolation bidirectional converter 10.

[0022] In this embodiment, when the energy is transmitted forward, by controlling the switching frequencies of the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4, a wide-range voltage output of the high-frequency isolation bidirectional converter 10 can be achieved, and the two switching transistors on each bridge arm are complementarily turned on, enabling soft switching of the circuit. When the energy is transmitted backward, the equivalent circuit of the resonant circuit 12 is the same as that when the energy is transmitted forward. Therefore, by controlling the switching frequencies of the fifth switching transistor Q5, the sixth switching transistor Q6, the seventh switching transistor Q7, and the eighth switching transistor Q8, the same wide-range voltage conversion as that during forward transmission can be achieved, and the two switching transistors on each bridge arm are complementarily turned on, enabling soft switching of the circuit.

[0023] Refer toFigure 2 , Figure 2 It is a schematic circuit diagram of the second embodiment of the high-frequency isolation bidirectional converter 10 of the present invention. The difference between this embodiment and the first embodiment lies in the specific structure of the switching circuit 11, and the other circuit structures are the same or similar. In this embodiment, the switching circuit 11 includes two switching tubes, namely the first switching tube Q1 and the second switching tube Q2. The first switching tube Q1 and the second switching tube Q2 are connected in series to form a bridge arm. The two ends of this bridge arm serve as the first external connection side of the high-frequency isolation bidirectional converter 10. The first capacitor C1 is connected to the midpoint of the bridge arm, and the second inductor L2 is connected to the lowermost end of the bridge arm. It can be understood that in some other embodiments, the first capacitor C1 can be connected to the uppermost end of the bridge arm, and the second inductor L2 can be connected to the midpoint of the bridge arm. Its circuit working process and working principle are similar to those of this embodiment, and it can also achieve wide voltage range conversion.

[0024] Refer to Figure 3 , Figure 3 It is a schematic circuit diagram of the third embodiment of the high-frequency isolation bidirectional converter 10 of the present invention. The difference between this embodiment and the first embodiment lies in the specific structure of the resonant circuit 12, and the other circuit structures are the same or similar. In this embodiment, the resonant circuit 12 includes the first inductor L1, the second inductor L2, the third inductor L3, the first capacitor C1, the second capacitor C2, and the selection switch S. The two ends of the second capacitor C2 are respectively connected to one end of the third inductor L3 and the first inductor L1. The other end of the third inductor L3 is connected to one end of the first capacitor C1. One end of the second inductor L2 is connected between the third inductor L3 and the second capacitor C2, and this end of the second inductor L2 is also connected to the other end of the first capacitor C1 / the first inductor L1 through the selection switch S, so as to be connected to the other end of the first capacitor C1 through the selection switch S when the high-frequency isolation bidirectional converter 10 operates in the first state, and be connected to the other end of the first inductor L1 through the selection switch S in the second state. The other end of this first capacitor C1 and the other end of the second inductor L2 are connected to the switching circuit 11. The other end of this second inductor L2 and the other end of the first inductor L1 are connected to the primary winding of the transformer T1. It can be seen that the resonant circuit 12 in this embodiment is a five-element resonant circuit, and the equivalent circuits during the forward and reverse energy flows are the same, and there is no loss in the gain during the forward and reverse operations. It can also effectively increase the input and output voltage ranges of the high-frequency isolation bidirectional converter 10 and achieve wide voltage range conversion.

[0025] In summary, the resonant circuit in the high-frequency isolation bidirectional converter of the present invention has the same equivalent circuit during the forward and reverse energy flows, and there is no loss in the gain during the forward and reverse operations, solving the problem that the traditional LLC resonant circuit cannot work with the same performance in the reverse direction, that is, the high-frequency isolation bidirectional converter of the present invention can step up the voltage during the reverse energy flow, can effectively increase the input and output voltage ranges of the converter, and achieve wide voltage range conversion.

[0026] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Those skilled in the art can make various equivalent changes and improvements based on the above embodiments. Any equivalent changes or modifications made within the scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A high-frequency isolated bidirectional converter, characterized in that: The high-frequency isolation bidirectional converter includes a switching circuit, a resonant circuit, a transformer, and a full-bridge switching circuit. One side of the full-bridge switching circuit and the switching circuit serves as the second external connection side and the first external connection side of the high-frequency isolation bidirectional converter respectively. Among them, the resonant circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, and a selection switch. One end of the second capacitor is connected to one end of the first capacitor and the second inductor. This end of the second inductor is also connected to the other end of the first capacitor / second capacitor through the selection switch, so as to be connected to the first capacitor through the selection switch when the high-frequency isolation bidirectional converter operates in the first state, and be connected to the second capacitor through the selection switch when in the second state. The other end of the second capacitor is also connected to one end of the first inductor. The other ends of the first capacitor and the second inductor are connected to the switching circuit. The other ends of the second inductor and the first inductor are connected to the primary winding of the transformer. The secondary winding of the transformer is connected to the midpoint of the bridge arm of the full-bridge switching circuit. Among them, in the first state, electric power is transmitted from the first external connection side to the second external connection side, and in the second state, electric power is transmitted from the second external connection side to the first external connection side.

2. The high-frequency isolated bidirectional converter according to claim 1, characterized in that: The switching circuit includes two switching tubes. The two switching tubes are connected in series to form a bridge arm. The two ends of this bridge arm serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the midpoint and the lowermost end of the bridge arm of the switching circuit.

3. The high-frequency isolated bidirectional converter according to claim 1, characterized in that: The switching circuit includes two switching tubes. The two switching tubes are connected in series to form a bridge arm. The two ends of this bridge arm serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the uppermost end and the midpoint of the bridge arm of the switching circuit.

4. The high-frequency isolated bidirectional converter according to claim 1, characterized in that: The switching circuit includes four switching tubes. Every two switching tubes are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, their two ends serve as the first external connection side of the high-frequency isolation bidirectional converter. The first capacitor and the second inductor are respectively connected to the midpoints of the two bridge arms of the switching circuit.

5. The high-frequency isolated bidirectional converter according to claim 1, characterized in that: The full-bridge switching circuit includes four switching tubes. Every two switching tubes are connected in series to form a bridge arm. After the two bridge arms are connected in parallel, their two ends serve as the second external connection side of the high-frequency isolation bidirectional converter. The same-named end and the different-named end of the secondary winding of the transformer are respectively connected to the midpoints of the two bridge arms.

6. The high-frequency isolated bidirectional converter according to claim 1, characterized in that: The high-frequency isolation bidirectional converter further includes a first filter capacitor and a second filter capacitor. The two ends of the first filter capacitor are connected to the first external connection side of the high-frequency isolation bidirectional converter. The two ends of the second filter capacitor are connected to the second external connection side.

7. A high-frequency isolated bidirectional converter, characterized in that: The high-frequency isolation bidirectional converter includes a switching circuit, a resonant circuit, a transformer, and a full-bridge switching circuit. One side of the full-bridge switching circuit and the switching circuit serves as the second external connection side and the first external connection side of the high-frequency isolation bidirectional converter respectively. Among them, the resonant circuit includes a first inductor, a second inductor, a third inductor, a first capacitor, a second capacitor, and a selection switch. Two ends of the second capacitor are respectively connected to one end of the third inductor and the first inductor. The other end of the third inductor is connected to one end of the first capacitor. One end of the second inductor is connected between the third inductor and the second capacitor, and this end of the second inductor is also connected to the other end of the first capacitor / the first inductor through the selection switch, so as to be connected to the first capacitor through the selection switch when the high-frequency isolation bidirectional converter operates in the first state, and be connected to the first inductor through the selection switch when in the second state. The other end of the first capacitor and the other end of the second inductor are connected to the switching circuit. The other end of the second inductor and the other end of the first inductor are connected to the primary winding of the transformer. The secondary winding of the transformer is connected to the midpoint of the bridge arm of the full-bridge switching circuit. Among them, in the first state, power is transmitted from the first external connection side to the second external connection side, and in the second state, power is transmitted from the second external connection side to the first external connection side.

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