DC-DC conversion circuit with high power density

Abstract

The utility model relates to the technical field of electronic power converters, in particular to a DC-DC conversion circuit with high power density, which comprises three LLC half-bridge resonance circuits, each of the three LLC half-bridge resonance circuits comprises a resonance circuit and a half bridge, and each of three groups of transformers comprises a primary winding and two secondary windings. Each resonant circuit comprises a resonant capacitor, a resonant inductor and a transformer primary winding which are sequentially connected in series, upper bridge arms of the half bridges are connected with the positive electrode of the input end, lower bridge arms of the half bridges are connected with the negative electrode of the input end, one end, close to the resonant capacitor, of each resonant circuit is connected with the midpoint of the corresponding half bridge, and the other ends of the resonant circuits are mutually connected. The input ends of the two output rectification circuits are both in star connection with the secondary windings of the three groups of transformers, and the output ends of the two output rectification circuits are both connected with the series-parallel switching circuit. According to the utility model, the voltage and current sharing is realized through the arrangement of the circuit, the dependence on software is reduced, and the power density is improved.

Description

Technical Field

[0001] This utility model relates to the field of electronic power converter technology, specifically to a high power density DC-DC converter circuit. Background Technology

[0002] With the continuous advancement of electric vehicle technology, the demand for charging speed is increasing, which has given rise to megawatt-level fast charging technology; correspondingly, the internal charging module must also meet the requirements of higher power and power density.

[0003] Currently, high-power charging modules generally adopt DC-DC conversion circuits. The primary side is mainly achieved through the series and parallel connection of half-bridge LLC, full-bridge LLC, and three-level LLC circuits, while the secondary side adopts full-bridge rectification technology. In the process of series and parallel connection of circuits, the equalization of voltage and current is mainly achieved by software. However, if the software adjustment scheme is not mature enough, it may cause the module to overheat or even be damaged, which limits the further improvement of power density. Utility Model Content

[0004] The purpose of this invention is to provide a high power density DC-DC converter circuit that achieves voltage and current equalization through circuit design, reduces reliance on software, and increases power density.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] In a first aspect, this utility model provides a high power density DC-DC converter circuit, including a three-phase LLC circuit, three sets of transformers, and two output rectifier circuits; the three-phase LLC circuit includes three LLC half-bridge resonant circuits, each of the three LLC half-bridge resonant circuits including a resonant circuit and a half-bridge; each of the three sets of transformers includes a primary winding and two secondary windings; the resonant circuit includes a resonant capacitor, a resonant inductor, and the primary winding of the transformer connected in series; the upper arm of each half-bridge is connected to the positive terminal of the input, and the lower arm of each half-bridge is connected to the negative terminal of the input; the end of the resonant circuit closest to the resonant capacitor is connected to the midpoint of the corresponding half-bridge, and the other ends of the resonant circuits are interconnected; the input terminals of the two output rectifier circuits are star-connected to the secondary windings of the three sets of transformers, and the output terminals of the two output rectifier circuits are connected to a series-parallel switching circuit.

[0007] In conjunction with the first aspect, optionally, the half-bridge includes two series-connected switching transistors.

[0008] In conjunction with the first aspect, optionally, the switching transistor is a MOSFET.

[0009] In conjunction with the first aspect, optionally, an input capacitor is also connected in series between the positive and negative terminals of the input terminal.

[0010] In conjunction with the first aspect, optionally, the two output rectifier circuits are a first output rectifier circuit and a second output rectifier circuit, the two secondary windings of the transformer are a first secondary winding and a second secondary winding, one end of each of the first secondary windings of the three transformers is connected to the first output rectifier circuit, the other ends of each of the first secondary windings of the three transformers are interconnected, one end of each of the second secondary windings of the three transformers is connected to the second output rectifier circuit, and the other ends of each of the second secondary windings of the three transformers are interconnected.

[0011] In conjunction with the first aspect, optionally, the output rectifier circuit includes three half-bridge rectifier branches, each half-bridge rectifier branch including two diodes connected in series. One end of each of the three half-bridge rectifier branches is connected to the positive terminal of the output terminal, and the other end of each of the three half-bridge rectifier branches is connected to the negative terminal of the output terminal. An output capacitor is connected in series between the positive and negative terminals of the output terminal. One end of each of the first secondary windings of the three sets of transformers is connected to the midpoint of the three half-bridge rectifier branches in the first output rectifier circuit, and the other ends of the first secondary windings of the three sets of transformers are interconnected. One end of each of the second secondary windings of the three sets of transformers is connected to the midpoint of the three half-bridge rectifier branches in the second output rectifier circuit, and the other ends of the second secondary windings of the three sets of transformers are interconnected.

[0012] The beneficial effects of this utility model are:

[0013] 1) The input terminal of this utility model is connected to a three-phase LLC circuit, which includes three LLC half-bridge resonant circuits. Each of the three LLC half-bridge resonant circuits includes a resonant circuit and a half-bridge. The half-bridge and the resonant circuit are connected in a star configuration, so that the current flowing through any half-bridge will flow back through the other two half-bridges and then back to the input terminal, which can realize automatic current sharing of the primary input current. Similarly, the input terminals of the two output rectifier circuits are connected in a star configuration to the secondary windings of the three sets of transformers, which can realize automatic current sharing of the secondary output current. Each of the three sets of transformers includes one primary winding and two secondary windings. The input terminals of the two output rectifier circuits are connected in a star configuration to the secondary windings of the three sets of transformers, which realizes automatic voltage equalization of the output. This utility model realizes voltage and current equalization through the circuit itself, reduces the dependence on software, and improves power density.

[0014] 2) The output rectifier circuit includes three half-bridge rectifier branches, each of which includes two diodes connected in series. The input terminals of the output rectifier circuit are all connected in a star configuration to the secondary windings of the three transformers. This ensures that the current flowing through each diode in the output rectifier circuit is consistent, enabling automatic current sharing among the rectifier diodes. It also results in lower output current ripple in the output rectifier circuit, further improving the power density of the circuit. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0016] Figure 1 This is the circuit diagram of this utility model;

[0017] Figure 2 This is a waveform diagram of the switching transistor drive in an embodiment of this utility model;

[0018] Figure 3 This is a schematic diagram of the output current ripple of the output rectifier circuit of this utility model. Detailed Implementation

[0019] The technical solution of this utility model will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of this application, rather than limitations thereof.

[0020] In the description of this utility model, the terms "first" and "second" are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features or the order of the technical features.

[0021] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0022] like Figure 1 As shown, this utility model provides a high power density DC-DC converter circuit, including a three-phase LLC circuit, three sets of transformers and two output rectifier circuits; the three-phase LLC circuit includes three LLC half-bridge resonant circuits, each of the three LLC half-bridge resonant circuits includes a resonant circuit and a half-bridge, and the half-bridge includes two series-connected switching transistors. In some embodiments, the switching transistors are MOSFETs.

[0023] Each of the three transformers includes one primary winding and two secondary windings. The resonant circuit includes a resonant capacitor, a resonant inductor, and the primary winding of the transformer connected in series. The upper arm of each half-bridge is connected to the positive terminal of the input, and the lower arm of each half-bridge is connected to the negative terminal of the input. An input capacitor is also connected in series between the positive and negative terminals of the input. The end of the resonant circuit closest to the resonant capacitor is connected to the midpoint of the corresponding half-bridge, and the other ends of the resonant circuit are all interconnected.

[0024] The input terminals of both output rectifier circuits are star-connected to the secondary windings of the three transformers, and the output terminals of both output rectifier circuits are connected to the series-parallel switching circuit. Specifically, the two output rectifier circuits are the first output rectifier circuit and the second output rectifier circuit, the two secondary windings of the transformers are the first secondary winding and the second secondary winding, one end of the first secondary winding of each of the three transformers is connected to the first output rectifier circuit, the other ends of the first secondary windings of the three transformers are interconnected, one end of the second secondary winding of each of the three transformers is connected to the second output rectifier circuit, and the other ends of the second secondary windings of the three transformers are interconnected.

[0025] The output rectifier circuit includes three half-bridge rectifier branches, each containing two diodes connected in series. One end of each half-bridge rectifier branch is connected to the positive terminal of the output, and the other end is connected to the negative terminal of the output. An output capacitor is connected in series between the positive and negative terminals of the output. One end of the first secondary winding of each of the three transformers is connected to the midpoint of the three half-bridge rectifier branches in the first output rectifier circuit, and the other ends of the first secondary windings of the three transformers are interconnected. One end of the second secondary winding of each of the three transformers is connected to the midpoint of the three half-bridge rectifier branches in the second output rectifier circuit, and the other ends of the second secondary windings of the three transformers are interconnected.

[0026] In one illustrative embodiment, such as Figure 1 As shown, MOSFETs Q1 and Q4 are connected in series to form the first half-bridge, MOSFETs Q2 and Q5 are connected in series to form the second half-bridge, and MOSFETs Q3 and Q6 are connected in series to form the third half-bridge. The drains of MOSFETs Q1, Q2, and Q3 are connected to the positive terminal of the input, and the sources of MOSFETs Q4, Q5, and Q6 are connected to the negative terminal of the input. An input capacitor C1 is also connected in series between the positive and negative terminals of the input. Wherein, as... Figure 2 As shown, the switching transistors of the three half-bridge arms are sequentially out of phase by 120°, that is, the driving delay of MOSFET Q3 is 120° compared to the driving delay of MOSFET Q1, and the driving delay of MOSFET Q5 is 120° compared to the driving delay of MOSFET Q3.

[0027] The resonant capacitor Cr1, resonant inductor Lr1, and the primary winding of transformer T1 are connected in series to form the first resonant circuit. Similarly, the resonant capacitor Cr2, resonant inductor Lr2, and the primary winding of transformer T2 are connected in series to form the second resonant circuit. The resonant capacitor Cr3, resonant inductor Lr3, and the primary winding of transformer T3 are connected in series to form the third resonant circuit. The end of the first resonant circuit closest to the resonant capacitor Cr1 is connected to the midpoint of the first half-bridge. The end of the second resonant circuit closest to the resonant capacitor Cr2 is connected to the midpoint of the second half-bridge. The end of the third resonant circuit closest to the resonant capacitor Cr3 is connected to the midpoint of the third half-bridge. The other ends of the primary windings of transformer T1, T2, and T3 in the first, second, and third resonant circuits are interconnected.

[0028] In the first output rectifier circuit, diodes D11 and D14 form the first half-bridge rectifier branch, diodes D12 and D15 form the second half-bridge rectifier branch, and diodes D13 and D16 form the third half-bridge rectifier branch. The cathodes of diodes D11, D12, and D13 are connected to the positive terminal of the first output terminal, and the anodes of diodes D14, D15, and D16 are connected to the negative terminal of the first output terminal. An output capacitor C2 is connected in series between the positive and negative terminals of the first output terminal. One end of the first secondary winding of transformer T1 is connected to the midpoint of the first half-bridge rectifier branch, one end of the first secondary winding of transformer T2 is connected to the midpoint of the second half-bridge rectifier branch, and one end of the first secondary winding of transformer T3 is connected to the midpoint of the third half-bridge rectifier branch. The other ends of the first secondary windings of transformers T1, T2, and T3 are interconnected.

[0029] In the second output rectifier circuit, diodes D21 and D24 form the fourth half-bridge rectifier branch, diodes D22 and D25 form the fifth half-bridge rectifier branch, and diodes D23 and D26 form the sixth half-bridge rectifier branch. The cathodes of diodes D21, D22, and D23 are connected to the positive terminal of the second output terminal, and the anodes of diodes D24, D25, and D26 are connected to the negative terminal of the second output terminal. An output capacitor C3 is connected in series between the positive and negative terminals of the second output terminal. One end of the second secondary winding of transformer T1 is connected to the midpoint of the fourth half-bridge rectifier branch, one end of the second secondary winding of transformer T2 is connected to the midpoint of the fifth half-bridge rectifier branch, and one end of the second secondary winding of transformer T3 is connected to the midpoint of the sixth half-bridge rectifier branch. The other ends of the second secondary windings of transformers T1, T2, and T3 are interconnected.

[0030] The output terminals of the first and second output rectifier circuits are connected to the series-parallel switching circuit. The series-parallel switching circuit uses existing technology and will not be described in detail here.

[0031] like Figure 3 As shown, the ripple current coefficient of the three-phase rectifier of this invention is about 0.0447Io, while the ripple coefficient of a conventional bridge rectifier circuit is about 0.48Io. This invention effectively reduces the output current ripple.

[0032] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high power density DC-DC converter circuit, characterized in that, The system includes a three-phase LLC circuit, three sets of transformers, and two output rectifier circuits. The three-phase LLC circuit includes three LLC half-bridge resonant circuits, each of which includes a resonant circuit and a half-bridge. Each of the three sets of transformers includes one primary winding and two secondary windings. The resonant circuit includes a resonant capacitor, a resonant inductor, and the primary winding of the transformer connected in series. The upper arm of each half-bridge is connected to the positive terminal of the input, and the lower arm of each half-bridge is connected to the negative terminal of the input. The end of each resonant circuit closest to the resonant capacitor is connected to the midpoint of the corresponding half-bridge, and the other ends of each resonant circuit are interconnected. The input terminals of the two output rectifier circuits are star-connected to the secondary windings of the three sets of transformers, and the output terminals of the two output rectifier circuits are connected to a series-parallel switching circuit.

2. The high power density DC-DC converter circuit according to claim 1, characterized in that, The half-bridge includes two switching transistors connected in series.

3. The high power density DC-DC converter circuit according to claim 2, characterized in that, The switching transistor is a MOSFET.

4. The high power density DC-DC converter circuit according to claim 1, characterized in that, An input capacitor is also connected in series between the positive and negative terminals of the input terminal.

5. The high power density DC-DC converter circuit according to claim 1, characterized in that, The two output rectifier circuits are the first output rectifier circuit and the second output rectifier circuit. The two secondary windings of the transformer are the first secondary winding and the second secondary winding. One end of the first secondary winding of the three transformers is connected to the first output rectifier circuit, and the other ends of the first secondary windings of the three transformers are interconnected. One end of the second secondary winding of the three transformers is connected to the second output rectifier circuit, and the other ends of the second secondary windings of the three transformers are interconnected.

6. The high power density DC-DC converter circuit according to claim 5, characterized in that, The output rectifier circuit includes three half-bridge rectifier branches, each half-bridge rectifier branch including two diodes connected in series. One end of each of the three half-bridge rectifier branches is connected to the positive terminal of the output terminal, and the other end of each of the three half-bridge rectifier branches is connected to the negative terminal of the output terminal. An output capacitor is connected in series between the positive and negative terminals of the output terminal. One end of the first secondary winding of each of the three sets of transformers is connected to the midpoint of the three half-bridge rectifier branches in the first output rectifier circuit, and the other ends of the first secondary windings of the three sets of transformers are interconnected. One end of the second secondary winding of each of the three sets of transformers is connected to the midpoint of the three half-bridge rectifier branches in the second output rectifier circuit, and the other ends of the second secondary windings of the three sets of transformers are interconnected.

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