Power conversion device and power conversion method
Patent Information
- Application Number
- JP2023184737
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-10-27
- Publication Date
- 2026-02-12
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a power conversion device and a power conversion method for converting power between input and output. [Background technology]
[0002] In order to reduce global energy consumption, there is a demand for high efficiency power conversion devices that use semiconductor switching elements. To increase the efficiency of power conversion devices, it is necessary to reduce the energy lost in the switching elements.
[0003] The resonant converter circuit is known as a highly efficient DC-DC converter. In this resonant converter, for example, an inductance component (resonant inductor) and a resonant capacitor inserted in series with the transformer winding realize zero voltage switching when the switching element is turned on and a reduction in the cutoff current when the switching element is turned off, thereby reducing switching losses.
[0004] However, with this type of resonant converter, when the output voltage is low or the input voltage is high, it is necessary to shorten the switching period to throttle down the output. This increases the cutoff current and switching frequency, which increases the switching loss at turn-off and tends to reduce efficiency.
[0005] Patent Document 1 discloses a DC / DC converter technology that has a primary circuit with a full-bridge configuration and can handle a wide output voltage range by switching between full-bridge operation and modified half-bridge operation. In addition, a technology is generally known for expanding the output voltage range in a resonant converter equipped with a full-bridge circuit by switching between full-bridge operation and half-bridge operation depending on the output voltage. [Prior art documents] [Patent documents]
[0006] [Patent Document 1] JP 2022-183908 A Summary of the Invention [Problem to be solved by the invention]
[0007] In conventional resonant converters, the full-bridge circuit operates as a full bridge when the output voltage is high, and operates as a half bridge when the output voltage is low, making it possible to operate with high efficiency under both high and low output voltage conditions.
[0008] However, the output voltage ranges at which high efficiency can be achieved differ greatly between full-bridge operation and half-bridge operation, so that sufficiently high efficiency cannot always be achieved when the output voltage is in the intermediate range.
[0009] An object of the present invention is to provide a power conversion device and a power conversion method that can obtain high efficiency over a wide output voltage range. [Means for solving the problem]
[0010] In order to achieve the above object, a power conversion device of the present invention is configured as follows.
[0011] a first resonant converter having a first full-bridge circuit that converts a DC current from a DC power source into an AC current, and a first rectifier circuit connected to the first full-bridge circuit via a first transformer and converting the AC current converted by the first full-bridge circuit into a DC current; a second resonant converter having a second full-bridge circuit that converts a DC current from a DC current into an AC current, and a second rectifier circuit connected to the second full-bridge circuit via a second transformer and converting the AC current converted by the second full-bridge circuit into a DC current; and a control unit that controls the first resonant converter and the second resonant converter, and converts input power into output power, wherein the control unit selects whether the first full-bridge circuit and the second full-bridge circuit operate as a full-bridge or a half-bridge based on at least a voltage value of the output power.
[0012] Also, there is provided a power conversion method for converting input power into output power by converting a DC current from a DC power supply into an AC current using a first full bridge circuit and a second full bridge circuit, and then converting the AC current converted by the first full bridge circuit and the second full bridge circuit into a DC current using a rectifier circuit, in which whether the first full bridge circuit and the second full bridge circuit operate as a full bridge or a half bridge is selected based on at least a voltage value of the output power. Effect of the Invention
[0013] According to the present invention, it is possible to provide a power conversion device and a power conversion method that can obtain high efficiency over a wide output voltage range. [Brief description of the drawings]
[0014] [Figure 1] 1 is a circuit configuration diagram of a power conversion device according to a first embodiment. [Diagram 2] FIG. 11 is a gate signal waveform diagram illustrating a full-bridge operation. [Diagram 3]FIG. 4 is a gate signal waveform diagram illustrating an operation of a half bridge. [Figure 4] FIG. 11 is a gate signal waveform diagram illustrating a phase shift operation in a full-bridge operation. [Figure 5A] FIG. 11 is an operational diagram illustrating an operation by a full bridge. [Figure 5B] FIG. 11 is an operational diagram illustrating an operation by a full bridge. [Figure 5C] FIG. 11 is an operational diagram illustrating an operation by a full bridge. [Figure 5D] FIG. 11 is an operational diagram illustrating an operation by a full bridge. [Figure 6A] FIG. 4 is an operational diagram illustrating an operation by a half bridge. [Figure 6B] FIG. 4 is an operational diagram illustrating an operation by a half bridge. [Figure 6C] FIG. 4 is an operational diagram illustrating an operation by a half bridge. [Figure 6D] FIG. 4 is an operational diagram illustrating an operation by a half bridge. [Figure 7A] FIG. 11 is an operational diagram illustrating a phase shift operation in a full-bridge operation. [Figure 7B] FIG. 11 is an operational diagram illustrating a phase shift operation in a full-bridge operation. [Figure 7C] FIG. 11 is an operational diagram illustrating a phase shift operation in a full-bridge operation. [Figure 7D] FIG. 11 is an operational diagram illustrating a phase shift operation in a full-bridge operation. [Figure 7E] FIG. 11 is an operational diagram illustrating a phase shift operation in a full-bridge operation. [Figure 8] FIG. 2 is a diagram for explaining a method of selecting the operation of the first resonant converter and the second resonant converter. [Figure 9] FIG. 4 is a waveform diagram illustrating the relationship between the selection of the operation of the first resonant converter and the second resonant converter and the efficiency. [Figure 10]10 is an operational diagram for explaining the relationship between the presence or absence of a phase shift operation in a resonant converter operating in a full-bridge manner and the input voltage of a resonant converter operating in a half-bridge manner. FIG. [Figure 11] FIG. 11 is a circuit configuration diagram of a power conversion device according to a second embodiment. [Figure 12] FIG. 13 is a diagram for explaining the number Nhb of resonant converters operated in a half-bridge manner relative to an output voltage. [Figure 13] FIG. 2 is a diagram for explaining the number Nhb of resonant converters operated in a half-bridge manner relative to an input voltage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. EXAMPLES
[0016] 1 is a circuit diagram of a power conversion device 1 according to a first embodiment of the present invention. In FIG. 1, the power conversion device 1 is connected between a DC power source 3 and a load 4, and supplies power from the DC power source 3 to the load 4.
[0017] The power conversion device 1 includes first resonant converters 10, 20, input terminals J1, J2, output terminals J3, J4, and a control unit 2 that controls the switching elements of the first resonant converters 10, 20. The input sides of the first resonant converter 10 and the second resonant converter 20 are connected in series between the input terminals J1-J2, and the output sides are connected in parallel between the output terminals J3-J4. The power of a DC power source 3 input between the input terminals J1-J2 is converted and output between the output terminals J3-J4.
[0018] The first resonant converter 10 includes a switching circuit (first full-bridge circuit) 11 and a rectifier circuit 12. The switching circuit 11 has a switching leg in which an upper arm switching element Q11 (first switching element) and a lower arm switching element Q12 (second switching element) are connected in series at a node Nd11 (first node) and a switching leg in which an upper arm switching element Q13 (third switching element) and a lower arm switching element Q14 (fourth switching element) are connected in series at a node Nd12 (second node) connected in parallel.
[0019] In other words, the switching circuit (first full-bridge circuit) 10 comprises a first switching leg having a first upper arm switching element Q11 and a first lower arm switching element Q12 connected in series to each other, and a second switching leg having a second upper arm switching element Q13 and a second lower arm switching element Q14 connected in series to each other and connected in parallel to the first switching leg.
[0020] This switching circuit 11 receives the voltage across the smoothing capacitor C11 (first smoothing capacitor), converts it into an AC voltage (rectangular wave), and outputs it between nodes Nd11 and Nd12. A resonant capacitor Cr1, a resonant inductor Lr1, and a winding N11 of a transformer T1 (first transformer) are connected in series between nodes Nd11 and Nd12, which are the output of the switching circuit 11. Note that the leakage inductance of the transformer T1 may be used as the resonant inductor Lr1.
[0021] A winding N12 of the transformer T1, which is magnetically coupled to the winding N11, is connected to the input of a rectifier circuit 12 in which diodes D15 to D18 are bridge-connected, and a smoothing capacitor C12 is connected to the output of the rectifier circuit 12. This smoothing capacitor C12 is connected in parallel between the output terminals J3 and J4.
[0022] The second resonant converter 20 includes a switching circuit (second full-bridge circuit) 21 and a rectifier circuit 22. The switching circuit 21 has a switching leg in which an upper arm switching element Q21 and a lower arm switching element Q22 are connected in series at a node Nd21, and a switching leg in which an upper arm switching element Q23 and a lower arm switching element Q24 are connected in series at a node Nd22, which are connected in parallel. The switching circuit 21 receives the voltage across the smoothing capacitor C21, converts it into an AC voltage (rectangular wave), and outputs it between the nodes Nd21 and Nd22. In addition, a resonant capacitor Cr2, a resonant inductor Lr2, and a winding N21 of a transformer T2 (second transformer) are connected in series between the nodes Nd21 and Nd22, which are the output of the switching circuit 21. Note that the leakage inductance of the transformer T2 may be used as the resonant inductor Lr2.
[0023] A winding N22 of the transformer T2, which is magnetically coupled to the winding N21, is connected to the input of a rectifier circuit 22 in which diodes D25 to D28 are bridge-connected, and a smoothing capacitor C22 is connected to the output of the rectifier circuit 22. This smoothing capacitor C22 is connected in parallel between the output terminals J3 and J4.
[0024] The control unit 2 detects the input voltages and output voltages of the first and second resonant converters 10, 20, and controls the switching elements Q11-Q14, Q21-Q24. Diodes D11-D14, D21-D24 are connected in anti-parallel to the switching elements Q11-Q14, Q21-Q24, respectively. When MOSFETs are used as the switching elements Q11-Q14, Q21-Q24, the parasitic diodes of the MOSFETs can be utilized, and therefore the diodes D11-D14, D21-D24 can be omitted.
[0025] The control operation of the control unit 2 of the power conversion device 1 will be described below with reference to the drawings.
[0026] 2 to 4 show the gate signal waveforms of the switching elements Q11 to Q14, and Vg11 to Vg14 respectively show the gate signals of the switching elements Q11 to Q14, where High indicates the on state and Low indicates the off state. Furthermore, Tsw indicates the switching period and Tp indicates the phase shift amount. FIGS. 5A to 5D, 6A to 6D, and 7A to 7E show the circuit operation of the first resonant converter 10. However, an exciting inductance Lm1 of the transformer T1 is defined in parallel with the winding N11.
[0027] The operation of the first resonant converter 10 in the full bridge mode will be described with reference to FIG. 2 and FIG. 5A to FIG. 5D. FIG. 2 shows the gate signal waveform when the first resonant converter 10 is operated in the full bridge mode. The switching element Q11 and the switching element Q12 are operated so that one is in the on state and the other is in the off state with a period in which both are in the off state sandwiched between them. Similarly, the switching element Q13 and the switching element Q14 are operated so that one is in the on state and the other is in the off state with a period in which both are in the off state sandwiched between them. The switching element Q11 and the switching element Q14 are operated at the same timing, and the switching element Q12 and the switching element Q13 are also operated at the same timing. The circuit operation will be described below with reference to FIG. 5A to FIG. 5D. However, FIG. 5A (A1), FIG. 5B (A2), FIG. 5C (A3), and FIG. 5D (A4) show the circuit operation in modes A1 to A4, respectively.
[0028] (Mode A1) In mode A1, switching elements Q11 and Q14 are on, switching elements Q12 and Q13 are off, and the voltage of smoothing capacitor C11 is output from switching circuit 11 and applied to resonant capacitor Cr1, resonant inductor Lr1, and winding N11. Current flows through resonant capacitor Cr1, resonant inductor Lr1, and winding N11, and a current induced in winding N12 passes through diodes D15 and D18 and flows to both ends of smoothing capacitor C12.
[0029] (Mode A2) When charge accumulates in the resonant capacitor Cr1 and the resonant current due to the resonant capacitor Cr1 and resonant inductor Lr1 stops flowing, the state changes to mode A2. The excitation current of the transformer T1 flows through the resonant capacitor Cr1, resonant inductor Lr1, and winding N11 (excitation inductance Lm1). This current becomes the resonant current due to the resonant capacitor Cr1, resonant inductor Lr1, and excitation inductance Lm1. The voltage of the winding N12 is lower than the voltage of the output smoothing capacitor C12, so no current flows through the winding N12.
[0030] (Mode A3) When the switching elements Q11 and Q14 are turned off, the state becomes mode A3. The current flowing through the switching elements Q11 and Q14 is commutated to the diodes D12 and D13, and flows to the smoothing capacitor C11. At this time, the switching elements Q12 and Q13 are turned on. The voltage of the smoothing capacitor C11 is applied to the resonant capacitor Cr1, the resonant inductor Lr1, and the winding N11 (excitation inductance Lm1) in the opposite direction to mode A2, and the current in the winding N11 decreases. A voltage is applied to the winding N11, and a current induced in the winding N12 passes through the diodes D16 and D17 and flows to both ends of the smoothing capacitor C12.
[0031] (Mode A4) When the current in winding N11 is reversed, the state changes to mode A4. This mode A4 is the symmetric operation of mode A1. After that, the symmetric operation of mode A2 and mode A3 is performed, and then the mode returns to mode A1. However, if the switching frequency is higher than the resonant frequency of resonant capacitor Cr1 and resonant inductor Lr1, mode A2 and its symmetric operation are omitted.
[0032] Next, the operation of the first resonant converter 10 by the half bridge will be described with reference to FIG. 3 and FIG. 6A to FIG. 6D. FIG. 3 shows the gate signal waveform when the first resonant converter 10 is operated by the half bridge. The switching element Q11 and the switching element Q12 are operated so that one is in the on state and the other is in the off state, with a period in which both are in the off state in between, as in the full bridge operation shown in FIG. 2. Meanwhile, the switching element Q13 is maintained in the off state, and the switching element Q14 is maintained in the on state. The switching element Q14 may be operated at the same timing as the switching element Q11. The circuit operation will be described below with reference to FIG. 6. However, (B1) of FIG. 6A, (B2) of FIG. 6B, (B3) of FIG. 6C, and (B4) of FIG. 6 show the circuit operation in modes B1 to B4, respectively.
[0033] (Mode B1) In mode B1, switching elements Q11 and Q14 are on, switching elements Q12 and Q13 are off, and the voltage of smoothing capacitor C11 is output from switching circuit 11 and applied to resonant capacitor Cr1, resonant inductor Lr1, and winding N11. Current flows through resonant capacitor Cr1, resonant inductor Lr1, and winding N11, and a current induced in winding N12 passes through diodes D15 and D18 and flows to both ends of smoothing capacitor C12.
[0034] (Mode B2) When charge accumulates in the resonant capacitor Cr1 and the resonant current due to the resonant capacitor Cr1 and resonant inductor Lr1 stops flowing, the state changes to mode B2. The excitation current of the transformer T1 flows through the resonant capacitor Cr1, resonant inductor Lr1, and winding N11 (excitation inductance Lm1). This current becomes the resonant current due to the resonant capacitor Cr1, resonant inductor Lr1, and excitation inductance Lm1. The voltage of the winding N12 is lower than the voltage of the output smoothing capacitor C12, so no current flows through the winding N12.
[0035] (Mode B3) When switching element Q11 is turned off, the state changes to mode B3. The current flowing through switching element Q11 is commutated to diode D12. At this time, switching element Q12 is turned on. The voltage of resonant capacitor Cr1 is applied to resonant inductor Lr1 and winding N11 (excitation inductance Lm1), and the current in winding N11 decreases. The current induced in winding N12 passes through diodes D16 and D17 and flows to both ends of smoothing capacitor C12.
[0036] (Mode B4) When the current in winding N11 is reversed, the state changes to mode B4. This mode B4 is the symmetric operation of mode B1. After that, the symmetric operation of mode B2 and mode B3 is performed, and then the mode returns to mode B1. However, if the switching frequency is higher than the resonant frequency of resonant capacitor Cr1 and resonant inductor Lr1, mode B2 and its symmetric operation are omitted.
[0037] In the above description, the switching element Q13 is maintained in the OFF state, but to achieve half-bridge operation, it is sufficient to maintain any one of the switching elements Q11 to Q14 in the OFF state. Therefore, the switching element to be maintained in the OFF state may be sequentially switched among the switching elements Q11 to Q14 for each switching period, in which case the energy loss generated in the switching elements can be dispersed. In this half-bridge operation, the AC component of the voltage output by the full-bridge circuit is half that of the full-bridge operation, so that it can operate efficiently when the output voltage is low or the input voltage is high.
[0038] Next, the phase shift operation in the full-bridge operation of the first resonant converter 10 will be described with reference to FIG. 4 and FIG. 7A to FIG. 7E.
[0039] 4 shows gate signal waveforms when the first resonant converter 10 is operated in a phase shift mode in a full-bridge mode. The switching elements Q11 and Q12 are operated so that one is in an on state and the other is in an off state with a period in which both are in an off state between them, and the switching elements Q13 and Q14 are operated so that one is in an on state and the other is in an off state with a period in which both are in an off state between them, which is the same as the full-bridge mode shown in FIG. 2. On the other hand, the timing of the switching elements Q11 and Q14 is such that the switching element Q14 is operated at a timing earlier than the switching element Q11 by a certain phase shift amount Tp. Similarly, the switching element Q13 is operated at a timing earlier than the switching element Q12 by a phase shift amount Tp.
[0040] In other words, the control unit 2 shifts the period during which the first upper arm switching element Q11 is in the ON state and the period during which the second lower arm switching element Q14 is in the ON state by a constant phase shift amount TP, and shifts the period during which the first lower arm switching element Q12 is in the ON state and the period during which the second upper arm switching element Q13 is in the ON state by a constant phase shift amount TP, thereby causing the first full-bridge circuit 11 to perform full-bridge operation.
[0041] The circuit operation will be described below with reference to Figures 7A to 7E, where Figures 7A (C1) to 7E (C5) show the circuit operation in modes C1 to C5, respectively.
[0042] (Mode C1) In mode C1, switching elements Q11 and Q14 are on, switching elements Q12 and Q13 are off, and the voltage of smoothing capacitor C11 is output from switching circuit 11 and applied to resonant capacitor Cr1, resonant inductor Lr1, and winding N11. Current flows through resonant capacitor Cr1, resonant inductor Lr1, and winding N11, and current induced in winding N12 passes through diodes D15 and D18 and flows to both ends of smoothing capacitor C12.
[0043] (Mode C2) When the switching element Q14 is turned off, the state becomes mode C2. The current flowing through the switching element Q14 is commutated to the diode D13. At this time, the switching element Q13 is turned on. The voltage of the resonant capacitor Cr1 is applied to the resonant inductor Lr1 and the winding N11 (excitation inductance Lm1), and the current in the winding N11 decreases.
[0044] (Mode C3) When the switching element Q11 is turned off, the state becomes mode C3. The current flowing through the switching element Q11 is commutated to the diode D12 and flows to the smoothing capacitor C11. At this time, the switching element Q12 is turned on. The voltage of the smoothing capacitor C11 is applied to the resonant capacitor Cr1, the resonant inductor Lr1, and the winding N11 (excitation inductance Lm1) in the opposite direction to mode C1, and the current in the windings N11 and N12 decreases rapidly.
[0045] (Mode C4) When the current in winding N12 decreases and reaches zero, mode C4 is entered: the current in winding N12 increases in the opposite direction and flows through diodes D16 and D17 to both ends of smoothing capacitor C12.
[0046] (Mode C5) When the current in the winding N11 is reversed, the state changes to mode C5. This mode C5 is a symmetric operation of mode C1. After that, the symmetric operations of modes C2 to C4 are performed, and then the mode returns to C1.
[0047] In the above explanation, switching element Q13 and switching element Q14 are operated at a timing earlier than switching element Q11 and switching element Q12 by the phase shift amount Tp, but conversely, switching element Q11 and switching element Q12 may be operated at a timing earlier than switching element Q13 and switching element Q14 by the phase shift amount Tp. In this phase shift operation in full-bridge operation, the output voltage of the full-bridge circuit becomes zero during the period of mode C2 due to the phase shift by the phase shift amount Tp, so that it is possible to lower the output voltage for the same input voltage, or to raise the input voltage for the same output voltage, compared to the normal full-bridge operation shown in Figure 2.
[0048] Although the circuit operation has been described above using the first resonant converter 10, the circuit operation of the second resonant converter 20 is similar to that of the first resonant converter 10.
[0049] Next, a method for selecting the operation of the first resonant converter 10 and the second resonant converter 20 by the control unit 2 will be described with reference to FIG.
[0050] When the output voltage value is high (higher than the first output voltage threshold) or when the input voltage value is low (lower than the second input voltage threshold), both the first resonant converter 10 and the second resonant converter 20 are operated in full-bridge configuration. Conversely, when the output voltage value is low (lower than the second output voltage threshold) or when the input voltage value is high (higher than the first input voltage threshold), both the first resonant converter 10 and the second resonant converter 20 are operated in half-bridge configuration.
[0051] Furthermore, when the output voltage value or the input voltage value is an intermediate voltage (when the output voltage value is higher than the second output voltage threshold and lower than the first output voltage threshold, or when the input voltage value is lower than the first input voltage threshold and higher than the second input voltage threshold), one of the first resonant converter 10 and the second resonant converter 20 is operated in a half-bridge configuration, and the other is operated in a full-bridge configuration. For example, the first resonant converter 10 is operated in a half-bridge configuration, and the second resonant converter 20 is operated in a full-bridge configuration.
[0052] FIG. 9 is a waveform diagram showing the relationship between the selection of the operation of the first resonant converter 10 and the second resonant converter 20 and the efficiency. Here, a indicates the efficiency when both the first resonant converter 10 and the second resonant converter 20 are operated by full bridge, b indicates the efficiency when one of the first resonant converter 10 and the second resonant converter 20 is operated by half bridge and the other is operated by full bridge, and c indicates the efficiency when both the first resonant converter 10 and the second resonant converter 20 are operated by half bridge. When the output voltage is high, a (both the first resonant converter 10 and the second resonant converter 20 are operated by full bridge) is selected, and when the output voltage drops, b (one of the first resonant converter 10 and the second resonant converter 20 is operated by half bridge and the other is operated by full bridge) is selected, and when the output voltage drops further, c (both the first resonant converter 10 and the second resonant converter 20 are operated by half bridge) is selected, thereby making it possible to obtain high efficiency over a wide output voltage range.
[0053] FIG. 10 shows the relationship between the presence or absence of phase shift operation in the resonant converter operating in full bridge mode and the input voltage of the resonant converter operating in half bridge mode when one of the first resonant converter 10 and the second resonant converter 20 is operated in half bridge mode and the other is operated in full bridge mode. Here, b1 is the case where the resonant converter operating in full bridge mode does not perform phase shift operation, and b2 is the case where the resonant converter operating in full bridge mode performs phase shift operation. By performing phase shift operation in the resonant converter operating in full bridge mode as in b2, it is possible to suppress the rise in the input voltage of the resonant converter operating in half bridge mode. In this case, if the amount of phase shift is increased, the input voltage of the resonant converter operating in full bridge mode becomes higher and the input voltage of the resonant converter operating in half bridge mode becomes lower. Therefore, by changing the amount of phase shift, it is also possible to control the input voltage of the resonant converter operating in half bridge mode to a constant value.
[0054] According to the first embodiment of the present invention, the control unit 2 is configured to select whether the first resonant converter 11 and the second resonant converter 21 should operate in a full-bridge configuration or a half-bridge configuration based on the voltage value of the output voltage, thereby making it possible to provide a power conversion device 1 and a power conversion method that can achieve high efficiency over a wide output voltage range.
[0055] Example 2 11 is a circuit configuration diagram of a power conversion device 1a according to a first embodiment of the present invention. This power conversion device 1a is connected between a DC power source 3a and a load 4a, and supplies power from the DC power source 3a to the load 4a.
[0056] The power conversion device 1a includes a first resonant converter 10, a second resonant converter 20, input terminals J1a, J2a, output terminals J3a, J4a, and a control unit 2a that controls the switching elements of the first resonant converter 10 and the second resonant converter 20, 20.
[0057] The configurations of the first resonant converter 10 and the second resonant converter 20 are similar to those of the power conversion device 1 of the first embodiment. On the other hand, in the power conversion device 1a of the second embodiment, the input sides of the first resonant converter 10 and the second resonant converter 20 are connected in parallel between the input terminals J1a and J2a, and the output sides are connected in series between the output terminals J3a and J4a. The power of the DC power supply 3a input between the input terminals J1a and J2a is converted and output between the output terminals J3a and J4a.
[0058] In this way, the power conversion device 1a has the input sides of the first resonant converter 10 and the second resonant converter 20 connected in parallel and the output sides connected in series, making it more suitable for cases where the input voltage is low and the output voltage is high compared to the power conversion device 1 shown in Figure 1.
[0059] The second embodiment of the present invention also makes it possible to provide a power conversion device 1 and a power conversion method that can achieve high efficiency over a wide output voltage range.
[0060] In the above-mentioned first and second embodiments, the number of resonant converters is two, but the power conversion device of the present invention may include three or more resonant converters. In this case, the number Nhb of resonant converters operating in half-bridge mode should be increased as the output voltage decreases as shown in Fig. 12, and the number Nhb of resonant converters operating in half-bridge mode should be increased as the input voltage increases as shown in Fig. 13.
[0061] In addition, whether the first resonant converter 10 and the second resonant converter 20 are operated in half-bridge or full-bridge configuration may be determined solely by determining whether the output voltage is high, medium or low, or whether the first resonant converter 10 and the second resonant converter 20 are operated in half-bridge or full-bridge configuration may be determined solely by determining whether the input voltage is high, medium or low.
[0062] As described above, in the present invention, a power conversion device is configured using a plurality of resonant converters, and by mixing resonant converters that operate in half-bridge mode and resonant converters that operate in full-bridge mode depending on the output voltage and input voltage conditions, it is possible to realize a power conversion device and a power conversion method that can obtain high efficiency over a wide output voltage range. [Explanation of symbols]
[0063] REFERENCE SIGNS LIST 1, 1a...power conversion device, 2, 2a...control unit, 3, 3a...DC power supply, 4, 4a...load, 10...first resonant converter, 11, 21...switching circuit, 12, 22...rectifier circuit, 20...second resonant converter, C11, C12, C21, C22...smoothing capacitor, Cr1, Cr2...resonant capacitor, J1, J2, J1a, J2a... Input terminals, J3, J4, J3a, J4a·Output terminals, Lr1, Lr2·Resonant inductor, Lm1·Magnetizing inductance, T1, T2·Transformers, N11, N12, N21, N22·Windings, Q11 to Q14, Q21 to Q24·Switching elements, D11 to D18, D21 to D28·Diodes, Nd11, Nd12, Nd21, Nd22·Nodes
Claims
1. a first resonant converter including a first full-bridge circuit that converts a DC current from a DC power supply into an AC current, and a first rectifier circuit that is connected to the first full-bridge circuit via a first transformer and converts the AC current converted by the first full-bridge circuit into a DC current; a second resonant converter including: a second full-bridge circuit that converts a direct current from a direct current into an alternating current; and a second rectifier circuit that is connected to the second full-bridge circuit via a second transformer and converts the alternating current converted by the second full-bridge circuit into a direct current; a control unit that controls the first resonant converter and the second resonant converter; A power conversion device that converts input power into output power, comprising: the control unit selects, based on at least a voltage value of the output power, whether to cause the first full-bridge circuit and the second full-bridge circuit to operate as a full-bridge or as a half-bridge in which some switching elements included in the first full-bridge circuit and the second full-bridge circuit are maintained in an off state.
2. The power conversion device according to claim 1, a first smoothing capacitor connected to the first full-bridge circuit; a second smoothing capacitor connected to the second full bridge circuit; a first resonant capacitor connected to the output of the first full bridge circuit; a second resonant capacitor connected to the output of the second full bridge circuit; Equipped with a first full-bridge circuit and a second full-bridge circuit connected in series to each other, and a first rectifier circuit and a second rectifier circuit connected in parallel to each other.
3. The power conversion device according to claim 1, a first smoothing capacitor connected to the first full-bridge circuit; a second smoothing capacitor connected to the second full bridge circuit; a first resonant capacitor connected to the output of the first full bridge circuit; a second resonant capacitor connected to the output of the second full bridge circuit; Equipped with a first full-bridge circuit and a second full-bridge circuit connected in parallel to each other, and a first rectifier circuit and a second rectifier circuit connected in series to each other.
4. The power conversion device according to claim 1, The control unit when a voltage value of the input power is higher than a first input voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated as half-bridges; When a voltage value of the input power is lower than a second input voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated in a full-bridge configuration.
5. The power conversion device according to claim 1, The control unit When a voltage value of the output power is higher than a first output voltage threshold, the first full bridge circuit and the second full bridge circuit are operated in a full bridge mode; When a voltage value of the output power is lower than a second output voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated as half-bridges.
6. The power conversion device according to claim 1, The control unit a first full-bridge circuit configured to operate in a half-bridge configuration and a second full-bridge circuit configured to operate in a full-bridge configuration when a voltage value of the output power is lower than a first output voltage threshold and higher than a second output voltage threshold.
7. The power conversion device according to claim 1, the first full-bridge circuit includes a first switching leg having a first upper arm switching element and a first lower arm switching element connected in series to each other, and a second switching leg having a second upper arm switching element and a second lower arm switching element connected in series to each other and connected in parallel to the first switching leg; The control unit a second full-bridge circuit configured to change a phase difference between the switching legs of the first full-bridge circuit, the second full-bridge circuit controlling an input voltage value of the second resonant converter, the second full-bridge circuit operating as a half-bridge.
8. 7. The power conversion device according to claim 6, the control unit, when the voltage value of the output power is lower than the first output voltage threshold and higher than the second output voltage threshold, operates the second full-bridge circuit as a half-bridge when the voltage value of the output power drops to a voltage lower than the second output voltage threshold while operating the first full-bridge circuit as a half-bridge.
9. 7. The power conversion device according to claim 6, the control unit, when the voltage value of the input power is higher than a second input voltage threshold and lower than the second input voltage threshold, operates the first full-bridge circuit as a half-bridge, and when the voltage value of the input power becomes higher than the second input voltage threshold, the control unit operates the second full-bridge circuit as a half-bridge.
10. 10. The power conversion device according to claim 1, each of the first full-bridge circuit and the second full-bridge circuit includes a plurality of switching elements; the control unit sequentially switches the switching elements to be maintained in an off state among the plurality of switching elements of the first full-bridge circuit and the second full-bridge circuit, which are operated as half-bridges.
11. The power conversion device according to claim 1, The first full bridge circuit includes: a first switching element and a second switching element connected in series at a first node between both ends of a first smoothing capacitor, a third switching element and a fourth switching element connected in series at a second node between both ends of the first smoothing capacitor, and anti-parallel diodes connected in anti-parallel to each of the first to fourth switching elements, a first smoothing capacitor connected between both ends thereof as an input of the first full-bridge circuit, and a first node connected between the first node and the second node as an output of the first full-bridge circuit.
12. converting a direct current from a direct current power supply into an alternating current by the first full bridge circuit and the second full bridge circuit; converting the AC current converted by the first full-bridge circuit and the second full-bridge circuit into a DC current by a rectifier circuit; A power conversion method for converting input power into output power, comprising: a power conversion method comprising: selecting whether the first full-bridge circuit and the second full-bridge circuit operate as a full-bridge or a half-bridge based on at least a voltage value of the output power;
13. 13. The power conversion method according to claim 12, when a voltage value of the input power is higher than a first input voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated as half-bridges; a power conversion method, characterized in that, when a voltage value of the input power is lower than a second input voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated in a full-bridge configuration;
14. 13. The power conversion method according to claim 12, When a voltage value of the output power is higher than a first output voltage threshold, the first full bridge circuit and the second full bridge circuit are operated in a full bridge mode; a power conversion method, characterized in that, when a voltage value of the output power is lower than a second output voltage threshold, the first full-bridge circuit and the second full-bridge circuit are operated as half-bridges.
15. 13. The power conversion method according to claim 12, a power conversion method, characterized in that, when a voltage value of the output power is lower than a first output voltage threshold and higher than a second output voltage threshold, the first full-bridge circuit is operated as a half-bridge and the second full-bridge circuit is operated as a full-bridge.