Power conversion device

Abstract

To provide a power conversion device that expands an applicable power conversion range on both a charging side and a discharging side.SOLUTION: A DC / DC converter 5 includes a bidirectional insulated LLC resonant circuit 15. The circuit 15 has: a primary-side circuit 21 that includes six primary-side switching elements S1 to S6; a secondary-side circuit 22 that includes four secondary-side switching elements S7 to S10; and an LLC circuit 23 positioned between a transformer 20 and the primary-side circuit 21, and is configured so as to be executable in charging operation and discharging operation. A controller 17 is configured to modify each switching pattern in the primary-side switching elements S1 to S6 and the secondary-side switching elements S7 to S10 in the charging operation and the discharging operation based on switching control information related to a duty ratio and a phase shift that are set according to a magnitude relation of input-output DC voltage.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The disclosed technology relates to a power conversion device (DC / DC converter) that inputs a DC voltage and converts it into DC voltages of different magnitudes for output.

Background Art

[0002] In recent years, the electrification of automobiles such as electric vehicles and hybrid vehicles has been remarkable. Vehicles that run using this power are equipped with a high-output battery as their power source. In order to charge the battery, these vehicles are also equipped with a charging system (On Board Charger: OBC) that converts commercial AC power into DC power.

[0003] Many OBCs use an AC / DC converter that converts an AC voltage into a DC voltage and a DC / DC converter that converts the DC voltage output from the AC / DC converter into different voltages. The conversion of the voltage magnitude is mainly performed by the DC / DC converter.

[0004] For such DC / DC converters, resonant DC / DC converters are often adopted from the viewpoint of efficiency improvement. However, the resonant DC / DC converter has the disadvantage that the voltage operating range becomes narrow due to the constraint of zero voltage switching (ZVS).

[0005] In commercial power supplies, AC voltages of generally 100V to 200V are used. On the other hand, in the batteries mounted on vehicles, DC voltages from, for example, 48V to high voltages exceeding 400V are used. Therefore, it is preferable that the DC / DC converter can handle such a wide range of power conversions, and an expansion of the power conversion range that can be handled is required.

[0006] Regarding the disclosed technology, in a resonant DC / DC converter, a technology for expanding the power output range has been proposed (Patent Document 1).

[0007] There is disclosed an isolated DC / DC converter provided with a predetermined LLC resonant converter circuit. The on / off operation of a switching element arranged on the input side of the LLC resonant converter circuit is switched by different modulation methods. By doing so, the magnitude of the voltage output to the LLC resonant circuit side is changed.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] The technology of Patent Document 1 is premised on a specific LLC resonant converter circuit and is controlled by a basic operation similar to the asymmetric half-bridge method. Therefore, only a voltage that is half of the input voltage can be utilized, so in practice, it is not suitable for large power.

[0010] Furthermore, since the duty ratio is controlled in a state where it is fixed to a predetermined value (25%, 50%, 75%), in practice, the control range of the output voltage inevitably becomes narrow. Moreover, since that technology targets the charging operation, it does not correspond to the discharging operation.

[0011] Therefore, this specification discloses a technology that can effectively expand the applicable power conversion range to both the charging side and the discharging side in a DC / DC converter.

Means for Solving the Problems

[0012] The disclosed technology relates to a power conversion device including a converter mechanism including a bidirectional isolated LLC resonant circuit and a controller for controlling the converter mechanism, which inputs a DC voltage and converts it into DC voltages of different magnitudes for output.

[0013] The bidirectional insulated LLC resonant circuit includes a transformer having a primary coil and a secondary coil, a primary circuit located on the primary side of the transformer and including a primary input / output terminal pair and six primary side switching elements, a secondary circuit located on the secondary side of the transformer and including a secondary input / output terminal pair and four secondary side switching elements, and an LLC circuit located between the transformer and the primary circuit.

[0014] And a charging operation of inputting a DC voltage to the primary input / output terminal pair and outputting it from the secondary input / output terminal pair, and a discharging operation of inputting a DC voltage to the secondary input / output terminal pair and outputting it from the primary input / output terminal pair are configured to be executable.

[0015] The controller has switching control information regarding a duty ratio and a phase shift set according to the magnitude relationship of the input / output DC voltage, and is configured to change the switching pattern of each of the primary side switching elements and the secondary side switching elements in the charging operation and the discharging operation based on the switching control information.

[0016] That is, this power conversion device is a so-called DC / DC converter, includes a predetermined bidirectional insulated LLC resonant circuit, and is configured to be able to execute a charging operation and a discharging operation. And its controller has switching control information regarding a duty ratio and a phase shift set according to the magnitude relationship of the input / output DC voltage, and based on the switching control information, changes the switching pattern of each of the primary side switching elements and the secondary side switching elements in the charging operation and the discharging operation.

[0017] In this power conversion device, since the charging operation and the discharging operation are controlled by combining the duty ratio and the phase shift according to the magnitude relationship of the input / output DC voltage, high-efficiency and high-precision control can be realized in a simple way, and the power conversion range that can be supported can be effectively expanded on both the charging side and the discharging side.

[0018] The primary circuit may further have an intermediate voltage output part that applies a primary half voltage, which is an intermediate voltage of the primary voltage that is a DC voltage input to the primary input / output terminal pair, to the LLC circuit. Then, when the DC voltage output during the charging operation is greater than the primary half voltage, the controller switches and applies the primary voltage and the primary half voltage to the LLC circuit while controlling the duty ratio.

[0019] By doing so, the positive and negative waveforms of the voltage applied to the primary side of the transformer can be made uniform, and the phenomenon of DC bias can be suppressed during the charging operation.

[0020] For example, the bidirectional isolated LLC resonant circuit may be configured as follows. That is, the primary circuit includes a first leg in which two of the primary switching elements are arranged in series, a second leg in which two element pairs each consisting of two of the primary switching elements connected in series are arranged in series, a third leg in which two primary capacitors are arranged in series, a fourth leg in which one intermediate capacitor is arranged, a fifth leg in which two diodes are arranged in series, a pair of primary main lines with the primary input / output terminal pair arranged at one end and the first leg, the second leg, and the third leg being connected in parallel between each other, a pair of bypass lines connected in parallel to a part between the primary switching elements included in each of the element pairs in the second leg and the fourth leg and the fifth leg being connected in parallel between each other, and a connection line connected to a part between the two diodes in the fifth leg and a part between the two primary capacitors in the third leg.

[0021] The secondary circuit includes a sixth leg and a seventh leg in which two of the secondary switching elements are arranged in series respectively, an eighth leg in which one secondary capacitor is arranged, and a pair of secondary main lines with the secondary input / output terminal pair arranged at one end and the sixth leg, the seventh leg, and the eighth leg being connected in parallel between each other.

[0022] A primary upper relay wiring that connects the end of the positive electrode side of the primary coil and the part between the two element pairs in the second leg, a primary lower relay wiring that connects the end of the negative electrode side of the primary coil and the part between the two primary switching elements in the first leg, a secondary upper relay wiring that connects the end of the positive electrode side of the secondary coil and the part between the two secondary switching elements in the sixth leg, and a secondary lower relay wiring that connects the end of the negative electrode side of the secondary coil and the part between the two secondary switching elements in the seventh leg are further provided. The LLC circuit has a primary resonance capacitor and a primary resonance inductance arranged in series on the primary upper relay wiring.

[0023] In this way, with a relatively simple circuit configuration, the power conversion range that can be handled can be effectively expanded for both the charging side and the discharging side.

[0024] The bidirectional isolated LLC resonance circuit may further have a secondary LLC circuit located between the transformer and the secondary circuit.

[0025] In this way, the power conversion range that can be handled can be expanded even more effectively for both the charging side and the discharging side.

[0026] The above bidirectional isolated LLC resonance circuit may also be configured as follows. That is, the primary circuit includes a first leg and a second leg in each of which two of the primary switching elements are arranged in series, a third leg in which two primary capacitors are arranged in series, a pair of primary main lines at one end of which the primary input / output terminal pair is arranged and to which the first leg, the second leg, and the third leg are connected in parallel with each other, two of the primary switching elements are arranged in series such that their energization directions are opposite to each other, and a connection line that is connected to the part between the two primary switching elements in the second leg and the part between the two primary capacitors in the third leg.

[0027] The secondary-side circuit includes a sixth leg and a seventh leg in each of which two of the secondary-side switching elements are arranged in series, an eighth leg in which one secondary-side capacitor is arranged, a pair of secondary-side main lines at one end of which the secondary-side input / output terminal pair is arranged and in which the sixth leg, the seventh leg, and the eighth leg are parallel and connected to each other in between.

[0028] Furthermore, the LLC circuit further includes a primary-side upper relay wiring that connects the positive-pole-side end of the primary-side coil and a portion between the two primary-side switching elements in the second leg, a primary-side lower relay wiring that connects the negative-pole-side end of the primary-side coil and a portion between the two primary-side switching elements in the first leg, a secondary-side upper relay wiring that connects the positive-pole-side end of the secondary-side coil and a portion between the two secondary-side switching elements in the sixth leg, and a secondary-side lower relay wiring that connects the negative-pole-side end of the secondary-side coil and a portion between the two secondary-side switching elements in the seventh leg, and the LLC circuit has a primary-side resonance capacitor and a primary-side resonance inductance arranged in series with the primary-side upper relay wiring.

[0029] With this circuit configuration as well, similar to the above-described bidirectional isolated LLC resonance circuit, with a relatively simple circuit configuration, the power conversion range that can be handled can be effectively expanded for both the charging side and the discharging side.

[0030] Also in the case of this bidirectional isolated LLC resonance circuit, it may be that the bidirectional isolated LLC resonance circuit further has a secondary-side LLC circuit located between the transformer and the secondary-side circuit.

[0031] If so, similar to the above-described bidirectional isolated LLC resonance circuit, the power conversion range that can be handled can be expanded even more effectively for both the charging side and the discharging side.

Advantages of the Invention

[0032] According to the disclosed technology, in a DC / DC converter, the applicable power conversion range can be effectively expanded on both the charging side and the discharging side. Therefore, a DC / DC converter suitable for an OBC or the like can be provided.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

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Figure 8A

Figure 8B

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Figure 10

Figure 11

Figure 12A

Figure 12B

Figure 13

Figure 14

Figure 15

Figure 16

Mode for Carrying Out the Invention

[0034] Hereinafter, the disclosed technology will be described. However, the following description is merely illustrative in nature. The components of the circuit are also provided with predetermined symbols together with alphanumeric codes. For convenience, the symbols may be used for explanation or illustration.

[0035] <Overview of the Power Conversion Device> FIG. 1 illustrates an example of applying the power conversion device according to the disclosed technology to an in-vehicle charging system 3 (OBC). The charging system 3 is mounted on a vehicle 1 that runs using electric power such as an electric vehicle and a hybrid vehicle, together with a high-output battery 4 for driving and a low-output lead-acid battery 4a for electrical components.

[0036] The upper part of FIG. 1 shows the vehicle 1 and the commercial power supply 2 during charging. The commercial power supply 2 outputs a high-voltage alternating voltage such as 100V and 200V. By connecting the commercial power supply 2 and the vehicle 1 with a cable, the battery 4 is charged. The charging system 3 converts the alternating voltage into a direct current voltage corresponding to the battery 4 when interposed between the battery 4 and the commercial power supply 2 at that time.

[0037] As shown in the middle part of FIG. 1, the charging system 3 is composed of a DC / DC converter 5, an AC / DC converter 6, etc. The AC / DC converter 6 is a device that converts an alternating input voltage E1 into a direct current output voltage V1 or converts a direct current input voltage V4 into an alternating output voltage E2.

[0038] The DC / DC converter 5 is a device that inputs a DC voltage and converts it into DC voltages of different magnitudes for output. That is, it corresponds to a "power conversion device", and the disclosed technology is applied to this DC / DC converter 5.

[0039] The DC / DC converter 5 converts the DC voltage V1 converted by the AC / DC converter 6 into a predetermined DC voltage V2 and outputs it to the side of the battery 4 or the lead-acid battery 4a (charging operation described later). The DC / DC converter 5 also converts the DC voltage V3 input from the side of the battery 4 or the lead-acid battery 4a into a predetermined DC voltage V4 and outputs it to the AC / DC converter 6 (discharging operation described later).

[0040] In the case of this DC / DC converter 5, since it is incorporated in the charging system 3, as will be described later, in terms of its structure and function, it is configured to be superior in the charging operation to the discharging operation. Therefore, the structure and function will be described mainly based on the charging operation.

[0041] As shown in the lower diagram of FIG. 1, the DC / DC converter 5 includes a converter mechanism 16 including an output current sensor 10, a primary-side first voltage sensor 11, a primary-side second voltage sensor 12, a secondary-side voltage sensor 13, a bidirectional insulated LLC resonant circuit 15, etc., and a controller 17 for controlling the converter mechanism 16.

[0042] The output current sensor 10 is a Hall element type sensor and is installed at predetermined positions on the primary-side main line 36 and the secondary-side main line 54 described later. As shown in FIG. 2, the output current 10 directly measures the current (output current Iout) flowing through the primary-side input / output terminal 30 and the secondary-side input / output terminal 50 and outputs it to the controller 17.

[0043] The primary-side first voltage sensor 11 is installed at a predetermined position on the primary-side main line 36, directly measures the high-voltage (primary-side voltage Vin) acting between the pair of primary-side main lines 36, 36, and outputs it to the controller 17. The primary-side second voltage sensor 12 is installed at a predetermined position between the primary-side main line 36 on the negative electrode side and the connection line 38, directly measures the voltage (primary-side half voltage Vin(LO)), which is a low-voltage intermediate voltage acting between the primary-side main line 36 and the connection line 38, and outputs it to the controller 17.

[0044] The secondary-side voltage Vout sensor 13 is installed at a predetermined position on the secondary-side main line 54, directly measures the high-voltage (secondary-side voltage Vout) acting between the pair of secondary-side main lines 54, 54, and outputs it to the controller 17.

[0045] Based on these measured values, the controller 17 outputs a drive voltage to the ten switching elements S1 to S10 (the first to tenth switching elements S1 to S10) of the bidirectional isolated LLC resonant circuit 15 for on / off control. That is, the energized state (on) and non-energized state (off) of these switching elements S1 to S10 are switched at a predetermined timing.

[0046] (Bidirectional isolated LLC resonant circuit) Fig. 2 shows the bidirectional isolated LLC resonant circuit 15 (hereinafter also referred to as the converter circuit 15). The converter circuit 15 is generally composed of a transformer 20, a primary-side circuit 21 located on the primary side thereof, a secondary-side circuit 22 located on the secondary side thereof, and an LLC circuit 23 located between the transformer 20 and the primary-side circuit 21.

[0047] The primary circuit 21 has a pair of primary input / output terminals 30 (primary input / output terminal pair) and six primary switching elements S1 to S6. The secondary circuit 22 has a pair of secondary input / output terminals 50 (secondary input / output terminal pair) and four secondary switching elements S7 to S10. With the converter circuit 15 configured in this way, the DC / DC converter 5 is configured to be capable of performing a charging operation of inputting a DC voltage to the primary input / output terminals 30 and outputting it from the secondary input / output terminals 50, and a discharging operation of inputting a DC voltage to the secondary input / output terminals 50 and outputting it from the primary input / output terminals 30.

[0048] The primary switching elements S1 to S6 and the secondary switching elements S7 to S10 are composed of known MOSFETs or the like having terminals such as gates, sources, and drains. They turn on by applying a predetermined driving voltage to the gate terminals. The primary switching elements S1 to S6 and the secondary switching elements S7 to S10 are all arranged such that the current conduction direction in the on state is from the positive electrode side to the negative electrode side. The primary switching elements S1 to S6 and the secondary switching elements S7 to S10 include freewheel diodes 24 connected in antiparallel.

[0049] The transformer 20 has a primary coil 20a and a secondary coil 20b. N1 is the number of turns of the primary coil 20a, and N2 is the number of turns of the secondary coil 20b. N1:N2 represents the turns ratio. In the case of the converter circuit 15 in this embodiment, N1:N2 is 1:1. However, the turns ratio can be changed according to the specifications of the operating range of the input / output voltage.

[0050] The primary circuit 21 has a first leg 31, a second leg 32, a third leg 33, a fourth leg 34, a fifth leg 35, a pair of primary main lines 36, 36, a pair of bypass lines 37, 37, and a connection line 38.

[0051] In the first leg 31, two primary side switching elements S3 and S4 are arranged in series. In the second leg 32, four primary side switching elements S5, S1, S2, and S6 are connected in series. For the sake of convenience of explanation, these are also assumed to be two element pairs 25 each consisting of two primary side switching elements (S5, S1 and S2, S6) connected in series and arranged in series.

[0052] In the third leg 33, two primary side capacitors C1 and C2 are arranged in series. The capacitances of these primary side capacitors C1 and C2 are the same. In the fourth leg 34, one intermediate capacitor C3 is arranged. In the fifth leg 35, two diodes D1 and D2 are arranged in series. These diodes D1 and D2 are arranged such that the current conduction direction is from the negative electrode side to the positive electrode side.

[0053] The first leg 31, the second leg 32, and the third leg 33 are connected in parallel between a pair of primary side main lines 36, 36. At one end of these primary side main lines 36, 36, a primary side input / output terminal 30 is arranged. In order from the side of the primary side input / output terminal 30, the third leg 33, the second leg 32, and the first leg 31 are arranged.

[0054] A pair of bypass lines 37, 37 are connected in parallel to the portions between the primary side switching elements (S5, S1 and S2, S6) included in each of the element pairs 25, 25 in the second leg 32. And between these bypass lines 37, 37, the fourth leg 34 and the fifth leg 35 are connected in parallel. The connection line 38 is connected to the portion between the two diodes D1, D2 in the fifth leg 35 and the portion between the two primary side capacitors C1, C2 in the third leg 33 (intermediate voltage output portion 43).

[0055] The positive electrode side end of the primary side coil 20a and the portion between the two element pairs 25, 25 in the second leg 32 are connected by a primary side upper relay wiring 45. And the negative electrode side end of the primary side coil 20a and the portion between the two primary side switching elements S3, S4 in the first leg 31 are connected by a primary side lower relay wiring 46.

[0056] In the primary-side upper relay wiring 45, a primary-side resonance capacitor Cr and a primary-side resonance inductance Lr (leakage inductance) are arranged in series in order from the side of the second leg 32. An exciting inductance Lm is connected in parallel with the primary-side coil 20a.

[0057] The exciting inductance Lm may be an inductance generated by the main magnetic flux of the transformer 20. The LLC circuit 23 is constituted by the primary-side resonance inductance Lr, the exciting inductance Lm, and the primary-side resonance capacitor Cr. Note that the primary-side resonance inductance Lr may also be a parasitic element of the transformer 20.

[0058] The secondary-side circuit 22 has a sixth leg 51, a seventh leg 52, an eighth leg 53, and a pair of secondary-side main lines 54, 54.

[0059] In the sixth leg 51, two secondary-side switching elements S7, S8 are arranged in series. In the seventh leg 52, two secondary-side switching elements S9, S10 are arranged in series. In the eighth leg 53, one secondary-side capacitor C4 is arranged. The sixth leg 51, the seventh leg 52, and the eighth leg 53 are connected in parallel between the pair of secondary-side main lines 54, 54. At one end of these secondary-side main lines 54, 54, a secondary-side input / output terminal 50 is arranged. In order from the side of the secondary-side input / output terminal 50, the eighth leg 53, the seventh leg 52, and the sixth leg 51 are arranged.

[0060] A part between the positive-pole side end of the secondary-side coil 20b and the two secondary-side switching elements S7, S8 in the sixth leg 51 is connected by a secondary-side upper relay wiring 57. And a part between the negative-pole side end of the secondary-side coil 20b and the two secondary-side switching elements S9, S10 in the seventh leg 52 is connected by a secondary-side lower relay wiring 58.

[0061] During the charging operation, a primary-side voltage Vin is applied to a pair of primary-side main lines 36, 36. Therefore, the primary-side voltage Vin is similarly applied to each of the first leg 31, the second leg 32, and the third leg 33.

[0062] And during the charging operation, further, a voltage (transformer voltage VTR) acts between the primary-side upper relay wiring 45 and the primary-side lower relay wiring 46, and a current (transformer current ITR) flows through the primary-side upper relay wiring 45. Thereby, a secondary-side voltage Vout is applied to a pair of secondary-side main lines 54, 54, and a current (output current Iout) flows through the secondary-side input / output terminals 50.

[0063] (Control during the charging operation by the controller) Next, the control during the charging operation by the controller 17 will be described (the control of the discharging operation will be described later).

[0064] FIG. 3 shows a control block diagram of the controller 17 during the charging operation. FIG. 4 shows a table summarizing the switching control information that the controller 17 has. FIG. 5 shows the resonance curve of the LLC circuit 23. FIG. 6 shows an example of various waveforms and switching patterns (switching time chart) during the charging operation.

[0065] As shown by the arrow line in FIG. 5, the LLC circuit 23 generally adjusts the output voltage within an operating range of a frequency between the lower limit value fm and the upper limit value fr of the resonance frequency. Therefore, also in the LLC circuit 23 of this DC / DC converter 5, the operating frequency can be set within this range. However, the operating frequency of the LLC circuit 23 is preferably fixed to the upper limit value fr of the resonance frequency or a value in the vicinity thereof, as shown by the circled mark in FIG. 5. By doing so, the exciting inductance Lm can be reduced, and the transformer 20 can be miniaturized.

[0066] Therefore, in this controller 17, with the operating frequency of the LLC circuit 23 fixed at the upper limit value fr of the resonance frequency or a value near it, the output current Iout is controlled according to the required output voltage. Note that the lower limit value fm and the upper limit value fr of the resonance frequency are determined by the performance of the primary resonance capacitor Cr, the primary resonance inductance Lr, and the exciting inductance Lm that constitute the LLC circuit 23.

[0067] Although not shown in the figure, the controller 17 includes hardware such as a processor and a memory, and software such as a control program and data implemented in the memory. Through the cooperation of these, as shown in FIG. 3, the controller 17 has a configuration including a voltage balance adjuster 17a, a current adjuster 17b, a control unit 17c, a drive circuit 17d, and the like.

[0068] Based on the primary voltage Vin input from the primary side first voltage sensor 11 and the primary side half voltage Vin(LO) input from the primary side second voltage sensor 12, the voltage balance adjuster 17a outputs a first parameter da * and a second parameter db * to the control unit 17c for use in setting the duty ratio in PWM control.

[0069] Based on the primary voltage Vin, the secondary voltage Vout input from the secondary side voltage sensor 13, the output current Iout input from the output current sensor 10, and the command value of the output current Iout (output current command value), the current adjuster 17b outputs a reference parameter dctl * (corresponding to the command value of the duty ratio) to the control unit 17c.

[0070] The control unit 17c receives the first parameter da * , the second parameter db * , and the reference parameter dctl *At the same time, the primary voltage Vin, the secondary voltage Vout, and the phase angle Δφ used for the phase shift are input. The control unit 17c has predetermined switching control information regarding the switching of the converter circuit 15.

[0071] Fig. 4 shows a table summarizing the switching control information. Fig. 4(a) is a table summarizing the switching control information during the charging operation, and Fig. 4(b) is a table summarizing the switching control information during the discharging operation. These switching control information are set according to the magnitude relationship of the DC voltages input to and output from the converter circuit 15, and include information regarding PWM control and phase shift.

[0072] During the charging operation, it is divided into four charging voltage ranges of the first to the fourth according to the magnitude relationship between the primary voltage Vin (input voltage) and the secondary voltage Vout (output voltage) of the converter circuit 15, and switching control information is set for each of them (the first to the fourth charging-time switching control information). According to these first to fourth charging-time switching control information, in all charging voltage ranges, the ninth and tenth switching elements S9 and S10 of the secondary circuit 22 are always turned off.

[0073] During the discharging operation, it is divided into two discharging voltage ranges of the first and the second according to the magnitude relationship between the secondary voltage Vout (input voltage) and the primary voltage Vin (output voltage) of the converter circuit 15, and switching control information is set for each of them (the first and the second discharging-time switching control information). According to these first and second discharging-time switching control information, in all discharging voltage ranges, the first, second, fifth, and sixth switching elements S1, S2, S5, and S6 of the primary circuit 21 are always turned off.

[0074] The first charging voltage range is the case where the secondary voltage Vout exceeds the primary voltage Vin. According to the first charging-time switching control information, in the first charging voltage range, the full-bridge method is used as the control method, and PWM control is performed in the switching of each switching element S1 to S8.

[0075] Among them, phase shift is performed on the seventh and eighth switching elements S7 and S8 of the secondary circuit 22. Specifically, a process of shifting the switching patterns of the seventh and eighth switching elements S7 and S8 by the phase angle Δφ is performed (see FIG. 7). Thereby, ZVS (Zero Voltage Switching) becomes possible even at a high voltage.

[0076] The second charging voltage range is the case where the secondary voltage Vout is less than or equal to the primary voltage Vin and exceeds 1 / 2 of the primary voltage Vin. According to the second charging-time switching control information, in the second charging voltage range, the full-bridge method is used for the control method in the same manner as the first charging-time switching control information, and PWM control is performed in the switching of each switching element S1 to S8. Since the output voltage is not high, ZVS is possible. Therefore, unlike the first charging-time switching control information, no phase shift is performed in the secondary circuit 22.

[0077] The third charging voltage range is the case where the secondary voltage Vout is less than or equal to 1 / 2 of the primary voltage Vin and exceeds 1 / 4 of the primary voltage Vin. According to the third charging-time switching control information, in the third charging voltage range, the third switching element S3 of the primary circuit 21 is always turned off and the fourth switching element S4 is always turned on, so that the half-bridge method is used for the control method, and PWM control is performed on the other switching elements S1, S2, S5 to S8.

[0078] The fourth charging voltage range is the case where the secondary voltage Vout is less than or equal to 1 / 4 of the primary voltage Vin. According to the fourth charging-time switching control information, in the fourth charging voltage range, the primary side phase shift method is used for the control method. That is, the fifth and sixth switching elements S5 and S6 of the primary circuit 21 are always turned off, and PWM control is performed in the switching of the first to fourth switching elements S1 to S4 while performing a phase shift in the third and fourth switching elements S3 and S4.

[0079] Based on such first to fourth charging-time switching control information, the control unit 17c changes the switching patterns of the primary-side switching elements S1 to S6 and the secondary-side switching elements S7 and S8 in the charging operation and outputs a predetermined control signal to the drive circuit 17d (the discharging operation will be described later).

[0080] As shown in FIG. 3, the PWM frequency TPWM and the dead time Td are input to the drive circuit 17d together with the control signal. Based on these input information, the drive circuit 17d outputs a drive voltage to the first to tenth switching elements S1 to S10. Thereby, the converter mechanism 16 operates, and the charging operation required in the DC / DC converter 5 is performed.

[0081] (Specific example of switching control during charging operation) FIG. 6 illustrates various waveforms in the second charging voltage range and the switching patterns of the switching elements S1 to S6 in the primary-side circuit 21.

[0082] The waveform shown at the top of FIG. 6 is a triangular wave used for PWM control. The time chart shown in the middle of FIG. 6 is the switching pattern of each switching element S1 to S6 corresponding to the PWM control. And the waveform shown at the bottom of FIG. 6 is an image diagram of the waveform of the transformer voltage VTR obtained by these switching patterns.

[0083] The period of the triangular wave is the switching frequency TSW. The first parameter da * sets a PWM signal with a pulse width corresponding to the period TA during which the first and fourth switching elements S1 and S4 are turned on based on the triangular wave. The second parameter db * sets a PWM signal with a pulse width corresponding to the period TB during which the second and third switching elements S2 and S3 are turned on based on the triangular wave. The period of the transformer voltage VTR is the PWM frequency TPWM.

[0084] The third parameter dc * and the fourth parameter dd *is the reference parameter dctl * , the first parameter da * , and the second parameter db * are obtained by the following formula. The third parameter dc * = reference parameter dctl * + the first parameter da * The fourth parameter dd * = reference parameter dctl * + the second parameter db * Here, the first parameter da * , the second parameter db * , and the reference parameter dctl * are all between 0 and 0.5. That is, the duty ratio setting range is between 0% and 50%.

[0085] The third parameter dc * sets a PWM signal with a pulse width corresponding to the period TC during which the fifth switching element S5 is turned on based on a triangular wave. The fourth parameter dd * sets a PWM signal with a pulse width corresponding to the period TD during which the sixth switching element S6 is turned on based on a triangular wave.

[0086] By performing such PWM control, the positive and negative waveforms of the transformer voltage VTR can be made equal, so the phenomenon of DC bias can be suppressed.

[0087] In the example of FIG. 6, the duty ratio is maximized (the first parameter da * = the second parameter db * = 0.5, dc * = dd * ). As a result, period TA = period TB, period TC = period TD, and the transformer voltage VTR fluctuates at 1 / 2 of the primary voltage Vin, and the voltage waveform input to the LLC circuit 23 can be maintained in a sinusoidal shape. ZVS is possible even when the secondary voltage Vout exceeds 1 / 2 of the primary voltage Vin, that is, the primary-side half voltage Vin(LO).

[0088] In the two primary capacitors C1 and C2, the balance of their charging voltages can also be stabilized. And with the change of the reference parameter dctl * it becomes possible to control the transformer current ITR.

[0089] FIG. 7 illustrates the switching patterns of the switching elements S1 to S8 in the primary circuit 21 and the secondary circuit 22 in the first charging voltage range. The switching patterns of the switching elements S1 to S6 in the primary circuit 21 are the same as those in the second charging voltage range shown in FIG. 6.

[0090] In the first charging voltage range, different from the second charging voltage range, a phase shift is performed in the seventh and eighth switching elements S7 and S8 of the secondary circuit 22. As a result, in these seventh and eighth switching elements S7 and S8, different from the second charging voltage range, the phase is shifted from the switching patterns of the other switching elements S1 to S6 by the phase angle Δφ.

[0091] FIGS. 8A and 8B show image diagrams of the current paths of the converter circuit 15 in the first to sixth states st1 to st6 shown at the top of FIG. 7. In the first charging voltage range, the current paths change in the order of the first state st1, the second state st2, the third state st3, the second state st2, the fourth state st4, the fifth state st5, the sixth state st6, and the fifth state st5. And the change is repeated.

[0092] In the first state st1, the first, fourth, and eighth switching elements S1, S4, and S8 are on, and the second, third, and fifth to seventh switching elements S2, S3, S5 to S7 are off. As a result, as indicated by the arrow dashed line in the upper diagram of FIG. 8A, in the primary circuit 21, current flows out from the intermediate voltage output part 43, and the transformer current ITR flows through the primary coil 20a (from the positive electrode side to the negative electrode side) of the transformer 20. At this time, the primary half voltage Vin(LO) acts on the LLC circuit 23.

[0093] Accordingly, in the secondary circuit 22, as indicated by the arrow dashed line in the upper diagram of FIG. 8A, current flows through the secondary coil 20b (from the negative electrode side to the positive electrode side) of the transformer 20 and passes through the internal path of the secondary circuit 22 in the order of the eighth switching element S8 and the tenth switching element S10 (freewheeling diode 24). That is, at this time, no current flows from the converter circuit 15 to the outside.

[0094] In the second state st2, the first, fourth, and seventh switching elements S1, S4, and S7 are on, and the second, third, fifth, sixth, and eighth switching elements S2, S3, S5, S6, and S8 are off. As a result, as indicated by the arrow dashed line in the middle diagram of FIG. 8A, the current path in the primary circuit 21 is the same as that in the first state st1.

[0095] On the other hand, in the secondary circuit 22, as indicated by the arrow dashed line in the middle diagram of FIG. 8A, current flows in from the secondary input / output terminal 50 (negative electrode side), passes through the tenth switching element S10 (freewheeling diode 24), the secondary coil 20b (from the negative electrode side to the positive electrode side) of the transformer 20, and the seventh switching element S7 (freewheeling diode 24) in this order, and is output from the secondary input / output terminal 50 (positive electrode side). Therefore, at this time, current flows from the converter circuit 15 to the outside.

[0096] In the third state st3, the first, fourth, fifth, and seventh switching elements S1, S4, S5, and S7 are on, and the second, third, sixth, and eighth switching elements S2, S3, S6, and S8 are off. As a result, as indicated by the arrow dashed line in the lower diagram of FIG. 8A, in the primary circuit 21, when current flows in from the primary input / output terminal 30 (positive electrode side), the transformer current ITR flows through the primary coil 20a (from the positive electrode side to the negative electrode side) of the transformer 20 and flows out from the primary input / output terminal 30 (negative electrode side). At this time, the primary voltage Vin acts on the LLC circuit 23.

[0097] In the secondary circuit 22, the current path is the same as that in the second state st2, as indicated by the arrow dashed line in the lower diagram of FIG. 8A. Therefore, at this time, current flows from the converter circuit 15 to the outside.

[0098] Subsequent to the third state st3, the second state st2 is reached again. After that, the fourth state st4 is reached.

[0099] In the fourth state st4, the second, third, and seventh switching elements S2, S3, S7 are on, and the first, fourth to sixth, and eighth switching elements S1, S4 to S6, S8 are off. As a result, as indicated by the arrow dashed line in the upper diagram of FIG. 8B, in the primary circuit 21, a current flows from the primary input / output terminal 30 (positive electrode side) at the primary voltage Vin, and the transformer current ITR flows through the primary coil 20a (from the negative electrode side to the positive electrode side) of the transformer 20 and into the intermediate voltage output portion 43. Thereby, the primary capacitor C2 (negative electrode side) is charged.

[0100] Accordingly, in the secondary circuit 22, as indicated by the arrow dashed line in the upper diagram of FIG. 8B, a current flows through the secondary coil 20b (from the positive electrode side to the negative electrode side) of the transformer 20 and through the internal path of the secondary circuit 22 in the order of the ninth switching element S9 (freewheeling diode 24) and the seventh switching element S7. That is, no current flows from the converter circuit 15 to the outside at this time.

[0101] In the fifth state st5, the second, third, and eighth switching elements S2, S3, S8 are on, and the first, fourth to seventh switching elements S1, S4 to S7 are off. As a result, as indicated by the arrow dashed line in the middle diagram of FIG. 8B, the current path in the primary circuit 21 is the same as that in the fourth state st4.

[0102] On the other hand, in the secondary circuit 22, as indicated by the arrow dashed line in the middle diagram of FIG. 8B, a current flows in from the secondary input / output terminal 50 (negative electrode side) and passes through the eighth switching element S8 (freewheeling diode 24), the secondary coil 20b (from the positive electrode side to the negative electrode side) of the transformer 20, and the ninth switching element S9 (freewheeling diode 24) in that order, and is output from the secondary input / output terminal 50 (positive electrode side). Therefore, a current flows from the converter circuit 15 to the outside at this time.

[0103] In the sixth state st6, the second, third, sixth, and eighth switching elements S2, S3, S6, and S8 are on, and the first, fourth, fifth, and seventh switching elements S1, S4, S5, and S7 are off. As a result, as indicated by the arrow dashed line in the lower diagram of Fig. 8B, in the primary circuit 21, a current flows from the primary input / output terminal 30 (positive electrode side) with the primary voltage Vin, so that the transformer current ITR flows through the primary coil 20a (from the negative electrode side to the positive electrode side) of the transformer 20 and flows out from the primary input / output terminal 30 (negative electrode side).

[0104] In the secondary circuit 22, as indicated by the arrow dashed line in the lower diagram of Fig. 8B, the current path is the same as that in the fifth state st5. Therefore, at this time, a current flows from the converter circuit 15 to the outside.

[0105] Subsequent to the sixth state st6, the fifth state st5 is reached again. After that, the first state st1 is reached again, and thereafter, the above-described states such as the second state st2 are repeated.

[0106] Thus, when the DC voltage output during the charging operation is greater than the primary half voltage Vin(LO), the controller 17 causes the LLC circuit 23 to operate by switching between the primary voltage Vin and the primary half voltage Vin(LO) while controlling the duty ratio.

[0107] Therefore, as described above, the positive and negative waveforms of the transformer voltage VTR can be made uniform, so that the phenomenon of DC bias can be suppressed. If the duty ratio is maximized, the voltage waveform input to the LLC circuit 23 can be maintained in a sine wave shape.

[0108] Fig. 9 illustrates the switching patterns of the switching elements S1, S2, S5, and S6 in the converter circuit 15 and its primary circuit 21 and secondary circuit 22 in the third charging voltage range.

[0109] In the third charging voltage range, the third switching element S3 is always turned off, and the fourth switching element S4 is always turned on. Therefore, the converter circuit 15 is equivalent to the circuit shown in Fig. 9(a).

[0110] In this case, according to the above example, the switching pattern and the waveform of the transformer voltage VTR are as shown in Fig. 9(b). Note that as shown in the equivalent circuit of Fig. 9(a), it becomes a half-bridge LLC circuit. Generally, the half-bridge LLC circuit is a circuit for small capacity, but in the present invention, in the output voltage range during this operation, as shown in Fig. 4(a), control is performed with an output voltage operation range from Vin / 4 to Vin / 2.

[0111] Fig. 10 shows an equivalent circuit of the converter circuit 15 and an image diagram of its current path in the fourth charging voltage range. In the fourth charging voltage range, while performing a phase shift in the switching S3, S4 of the third and fourth switching elements, substantially, the second and fifth states st2, st5 in the first charging voltage range described above are repeated.

[0112] (Control during discharge operation by the controller) Next, the control during the discharge operation by the controller 17 will be described.

[0113] In this converter circuit 15, there is no resonance capacitor in the secondary circuit 22. However, all of the primary side switching elements S1 to S6 are turned off, and these freewheel diodes 24 are utilized. In that state, by switching the secondary side switching elements S7 to S10, the converter circuit 15 can execute a discharge operation in which power is input from the secondary side and output from the primary side.

[0114] However, in that case, since only a square wave is applied to the excitation inductance Lm, it is not possible to resonate with the primary-side resonance capacitor Cr. Therefore, as the resonance elements during discharge, it becomes a normal series resonance type operation having only the primary-side resonance capacitor Cr and the primary-side resonance inductance Lr. As a result, the operating range of the input / output power during discharge is basically limited by the turns ratio of the transformer 20. That is, the secondary-side voltage Vout becomes the same as the primary-side voltage Vin.

[0115] However, during discharge, there may be a case where the primary-side voltage Vin is higher than the secondary-side voltage Vout. On the other hand, a step-up operation can be realized by performing a phase shift in the third and fourth switching elements S3 and S4 of the primary-side circuit 21. Therefore, in this DC / DC converter 5, the primary-side voltage Vin can be made higher than the secondary-side voltage Vout. Note that since constant control of the AC output voltage can be performed in the AC / DC converter 6 during discharge, PWM control for changing the duty ratio is unnecessary.

[0116] Thereby, during the discharge operation, it is divided into the first and second discharge voltage ranges according to the magnitude relationship between the primary-side voltage Vin (output voltage) and the secondary-side voltage Vout (input voltage). As shown in FIG. 4(b), switching control information is set for each of them (first and second discharge-time switching control information).

[0117] According to these first and second discharge-time switching control information, in all discharge voltage ranges, PWM control with a duty ratio fixed at 50% is performed by all the switching elements S7 to S10 of the secondary-side circuit 22.

[0118] The first discharge voltage range is the case where the secondary-side voltage Vout and the primary-side voltage Vin are the same. According to the first discharge-time switching control information, in the first discharge voltage range, the full-bridge method is used as the control method, and all the switching elements S1 to S6 of the primary-side circuit 21 are always turned off.

[0119] The second discharge voltage range is the case where the primary-side voltage Vin is higher than the secondary-side voltage Vout. According to the second discharge-time switching control information, in the second discharge voltage range, the first, second, fifth, and sixth switching elements S1, S2, S5, S6 of the primary-side circuit 21 are always turned off, and a phase shift is performed in the third and fourth switching elements S3, S4.

[0120] Fig. 11 illustrates the switching patterns of the switching elements S3, S4, S7 to S10 in the primary-side circuit 21 and the secondary-side circuit 22 in the second discharge voltage range. Figs. 12A and 12B show image diagrams of the current paths of the converter circuit 15 in the first to fourth states st1 to st4 shown at the top of Fig. 11. In the second discharge voltage range, the current path changes in the order of the first state st1, the second state st2, the third state st3, and the fourth state st4. And this change is repeated.

[0121] Note that in the first discharge voltage range, there are no second state st2 and fourth state st4 associated with the phase shift. Therefore, since only the first state st1 and the third state st3 are repeated, a detailed description thereof is omitted.

[0122] In the first state st1, the seventh, tenth, and fourth switching elements S7, S10, S4 are on, and the eighth, ninth, and third switching elements S8, S9, S3 are off. Thereby, as indicated by the arrow dashed line in the upper diagram of Fig. 12A, in the secondary-side circuit 22, current flows in from the secondary-side input / output terminal 50 (positive electrode side), flows through the secondary-side coil 20b of the transformer 20 (from the positive electrode side to the negative electrode side), and flows out from the secondary-side input / output terminal 50 (negative electrode side).

[0123] Accordingly, in the primary circuit 21, as shown by the arrow dashed line in the upper figure of 12A, current flows in from the primary input / output terminal 30 (negative electrode side), passes through the fourth switching element S4 (free wheel diode 24), the primary coil 20a of the transformer 20 (from the negative electrode side to the positive electrode side), and the first and fifth switching elements S1, S5 (free wheel diode 24) in this order, and is output from the primary input / output terminal 30 (positive electrode side). Therefore, at this time, current flows from the converter circuit 15 to the outside.

[0124] In the second state st2, the seventh, tenth, and third switching elements S7, S10, S3 are on, and the eighth, ninth, and fourth switching elements S8, S9, S4 are off. As a result, as shown by the arrow dashed line in the lower figure of Fig. 12A, the current path in the secondary circuit 22 is the same as that in the first state st1.

[0125] On the other hand, in the primary circuit 21, as shown by the arrow dashed line in the lower figure of Fig. 12A, current flows through the primary coil 20a of the transformer 20 (from the negative electrode side to the positive electrode side), and flows through the internal path of the primary circuit 21 passing through the first and fifth switching elements S1, S5 (free wheel diode 24) and the third switching element S3 in this order. That is, at this time, no current flows from the converter circuit 15 to the outside.

[0126] In the third state st3, the eighth, ninth, and third switching elements S8, S9, S3 are on, and the seventh, tenth, and fourth switching elements S7, S10, S4 are off. As a result, as shown by the arrow dashed line in the upper figure of Fig. 12B, in the secondary circuit 22, current flows in from the secondary input / output terminal 50 (positive electrode side), flows through the secondary coil 20b of the transformer 20 (from the negative electrode side to the positive electrode side), and flows out from the secondary input / output terminal 50 (negative electrode side).

[0127] Accordingly, in the primary circuit 21, as shown by the arrow dashed line in the upper diagram of FIG. 12B, current flows in from the primary input / output terminal 30 (negative electrode side), and passes through the sixth and second switching elements S6, S2 (free wheel diode 24), the primary coil 20a of the transformer 20 (from the positive electrode side to the negative electrode side), and the third switching element S3 (free wheel diode 24) in this order, and is output from the primary input / output terminal 30 (positive electrode side). Therefore, at this time, current flows from the converter circuit 15 to the outside.

[0128] In the fourth state st4, the eighth, ninth, and fourth switching elements S8, S9, S4 are on, and the seventh, tenth, and third switching elements S7, S10, S3 are off. As a result, as shown by the arrow dashed line in the lower diagram of FIG. 12B, the current path in the secondary circuit 22 is the same as that in the third state st3.

[0129] Accordingly, in the primary circuit 21, as shown by the arrow dashed line in the lower diagram of FIG. 12B, current flows through the primary coil 20a of the transformer 20 (from the positive electrode side to the negative electrode side), and flows through the internal path of the primary circuit 21 that passes through the fourth switching element, the sixth and second switching elements S4, S6, S2 (free wheel diode 24) in this order. That is, at this time, no current flows from the converter circuit 15 to the outside.

[0130] Subsequent to the fourth state st4, the first state st1 is reached again, and thereafter, each of the above-described states such as the second state st2 is repeated.

[0131] <Verification of Effects> The effects of the DC / DC converter 5 were verified by simulation. First, the stability of the primary side half voltage Vin(LO) during the charging operation was verified.

[0132] Fig. 13 shows the verification results. The upper graph in Fig. 13 is the change over time of the voltages of the two primary capacitors C1 and C2 at startup. The middle graph in Fig. 13 is the change over time of the corresponding input voltage (primary-side voltage Vin), and the lower graph in Fig. 13 is the change over time of the corresponding output current Iout.

[0133] The voltage difference between the two primary capacitors C1 and C2 at the start of startup was 200V, but it was immediately confirmed that the difference became 0, that is, it converged to the primary-side half voltage Vin(LO). Note that the pulsation of the input voltage is due to the output from the PFC circuit.

[0134] Next, the results of simulations for two cases during the charging operation with different input and output voltages are shown. Case 1 is when the input voltage (primary-side voltage Vin) is 400V and the output voltage (secondary-side voltage Vout) is 300V (the second charging voltage range). Case 2 is when the input voltage (primary-side voltage Vin) is 400V and the output voltage (secondary-side voltage Vout) is 450V (the first charging voltage range). In both cases, the output power is 4kW.

[0135] Fig. 14 shows the main specifications such as the transformer voltage VTR over time in the simulations for Case 1 and Case 2 arranged so that they can be compared.

[0136] As shown in Fig. 14, it was confirmed that buck-boost operation can be realized with a constant input voltage and charging can be performed with a constant power. Therefore, according to the disclosed technology, the power conversion range that can be handled can be effectively expanded on both the charging side and the discharging side, and a small and highly efficient power conversion device can be realized.

[0137] <Modification example of the bidirectional isolated LLC resonant circuit> Fig. 15 shows a modification example (the second converter circuit 15B) of the above-described converter circuit 15. The second converter circuit 15B is different from the above-described converter circuit 15 in that an LLC circuit is also provided on the secondary-side circuit 22 side. In other respects, it is the same, so the same components are denoted by the same reference numerals and the description thereof is omitted.

[0138] That is, the second converter circuit 15B further has an LLC circuit (secondary LLC circuit 60) located between the transformer 20 and the secondary circuit 22 (so-called CLLC converter). Specifically, in the secondary LLC circuit 60, a secondary resonant capacitor 61 and a secondary resonant inductance 62 (leakage inductance) are arranged in series in order from the side of the sixth leg 51 on the secondary upper relay wiring 57. A secondary exciting inductance may be connected in parallel with the secondary coil 20b.

[0139] The secondary resonant capacitor 61 and the secondary resonant inductance 62 constitute the secondary LLC circuit 60. Therefore, according to the second converter circuit 15B, the power response range during the discharge operation can be further expanded.

[0140] <Another form of the bidirectional isolated LLC resonant circuit> FIG. 16 shows another form of the converter circuit 15 (third converter circuit 15C). The configuration of the primary side circuit 21 of the third converter circuit 15C is different from that of the converter circuit 15 described above. Since the secondary side circuit of the third converter circuit 15C is the same as the secondary side circuit 22 of the converter circuit 15 described above, the same reference numerals are used for the same configurations and the description thereof is omitted.

[0141] The primary side circuit 21 of the third converter circuit 15C is also the same as the converter circuit 15 described above in that it has a primary side input / output terminal 30 and six primary side switching elements S1 to S6, and a third leg 33 in which two primary side capacitors C1 and C2 are arranged in series, and a first leg 31 in which two primary side switching elements S3 and S4 are arranged in series.

[0142] In addition to these, the primary side circuit 21 of the third converter circuit 15C has a second leg 32 in which two primary side switching elements S5 and S6 are arranged in series. Then, between a pair of primary side main lines 36, 36 where the primary side input / output terminal 30 is arranged at one end, the first leg 31, the second leg 32, and the third leg 33 are connected in parallel.

[0143] And a single connection line 38 is connected to a portion between two primary-side switching elements S5 and S6 in the second leg 32 and a portion between two primary-side capacitors C1 and C2 in the third leg 33. Two primary-side switching elements S1 and S2 are arranged in series on this connection line 38 such that the energization directions of both face inward and face each other.

[0144] The control content of the third converter circuit 15C is the same as that of the converter circuit 15 described above. That is, the control method of the third converter circuit 15C, the switching patterns of the respective switching elements S1 to S10, etc. are the same as those of the converter circuit 15 described above.

[0145] Although illustration is omitted, the third converter circuit 15C may also further include an LLC circuit (secondary-side LLC circuit 60) located between the transformer 20 and the secondary-side circuit 22, similar to the second converter circuit 15B.

Description of Reference Numerals

[0146] 1 Vehicle 2 Commercial power supply 3 Charging system 4 Battery 5 DC / DC converter 6 AC / DC converter 15 Bidirectional isolated LLC resonant circuit 16 Converter mechanism 17 Controller 17a Voltage balance adjuster 17b Current adjuster 17c Control unit 17d Drive circuit 20 Transformer 21 Primary-side circuit 22 Secondary-side circuit 23 LLC circuit 25 Element pair 30 Primary-side input / output terminal 31 First leg 32 Second leg 33 Third leg 34 Fourth leg 35 Fifth leg 36 Primary main line 37 Bypass line 38 Connecting line 43 Intermediate voltage output part 45 Primary upper relay wiring 46 Primary lower relay wiring 50 Secondary input / output terminal 51 Sixth leg 52 Seventh leg 53 Eighth leg 54 Secondary main line 55 Secondary capacitor 57 Secondary upper relay wiring 58 Secondary lower relay wiring 60 Secondary LLC circuit 61 Secondary resonance capacitor 62 Secondary resonance inductance S1~S10 Switching element D1,D2 Diode C1, C2 Primary capacitor C3 Intermediate capacitor C4 Secondary capacitor Cr Primary resonance capacitor Lr Primary resonance inductance Lm Excitation inductance

Claims

1. A power conversion device comprising a converter mechanism including a bidirectional isolated LLC resonant circuit and a controller for controlling the converter mechanism, which receives a DC voltage, converts the DC voltage into a different DC voltage, and outputs the converted DC voltage, The bidirectional isolated LLC resonant circuit comprises: a transformer having a primary coil and a secondary coil; a primary side circuit located on a primary side of the transformer and including a primary side input / output terminal pair and six primary side switching elements; a secondary side circuit located on a secondary side of the transformer and including a secondary side input / output terminal pair and four secondary side switching elements; an LLC circuit located between the transformer and the primary side circuit; having a charging operation in which a DC voltage is input to the primary side input / output terminal pair and output from the secondary side input / output terminal pair; a discharging operation of inputting a DC voltage to the secondary side input / output terminal pair and outputting the DC voltage from the primary side input / output terminal pair; is configured to run, The controller: having switching control information relating to a duty ratio and a phase shift that are set according to the magnitude relationship of the input and output DC voltages; The power conversion device is configured to change a switching pattern of each of the primary side switching element and the secondary side switching element in the charging operation and the discharging operation based on the switching control information.

2. 2. The power conversion device according to claim 1, the primary side circuit further includes an intermediate voltage output section for applying a primary side half voltage, which is an intermediate voltage of a primary side voltage, which is a DC voltage input to the primary side input / output terminal pair, to the LLC circuit; When the DC voltage output during the charging operation is greater than the primary side half voltage, the controller switches between the primary side voltage and the primary side half voltage while controlling the duty ratio.

3. In the power conversion device according to claim 1 or 2, the primary side circuit includes a first leg in which two of the primary side switching elements are arranged in series; a second leg in which two pairs of elements each consisting of two of the primary side switching elements connected in series are arranged in series; a third leg in which two primary side capacitors are arranged in series; a fourth leg in which one intermediate capacitor is arranged; a fifth leg in which two diodes are arranged in series; a pair of primary side main lines having the primary side input / output terminal pair arranged at one end, and the first leg, the second leg, and the third leg being parallel and connected to each other in between; a pair of bypass lines connected in parallel to a portion between the primary side switching elements included in each of the element pairs in the second leg, and the fourth leg and the fifth leg being parallel and connected to each other in between; a connection line connected to a portion between the two diodes in the fifth leg and a portion between the two primary side capacitors in the third leg; and the secondary side circuit includes a sixth leg and a seventh leg in which two of the secondary side switching elements are arranged in series in each; an eighth leg in which one secondary side capacitor is arranged; a pair of secondary side main lines having the secondary side input / output terminal pair arranged at one end, and the sixth leg, the seventh leg, and the eighth leg being parallel and connected to each other in between; and a primary side upper relay wiring connecting the positive electrode side end of the primary side coil and a portion between the two element pairs in the second leg; a primary side lower relay wiring connecting the negative electrode side end of the primary side coil and a portion between the two primary side switching elements in the first leg; A secondary-side upper relay wiring that connects the end on the positive electrode side of the secondary-side coil and the portion between the two secondary-side switching elements in the sixth leg. A secondary-side lower relay wiring that connects the end on the negative electrode side of the secondary-side coil and the portion between the two secondary-side switching elements in the seventh leg. It further has A power conversion device in which the LLC circuit has a primary-side resonance capacitor and a primary-side resonance inductance arranged in series with the primary-side upper relay wiring.

4. In the power conversion device according to claim 3, A power conversion device in which the bidirectional insulated LLC resonance circuit further has a secondary-side LLC circuit located between the transformer and the secondary-side circuit.

5. In the power conversion device according to claim 1 or 2, The primary-side circuit A first leg and a second leg in each of which two of the primary-side switching elements are arranged in series, A third leg in which two primary-side capacitors are arranged in series, A pair of primary-side main lines in which the primary-side input / output terminal pair is arranged at one end, and the first leg, the second leg, and the third leg are parallel and connected to each other, Two of the primary-side switching elements are arranged in series so that the energization directions of both are opposite, and are connected to the portion between the two primary-side switching elements in the second leg and the portion between the two primary-side capacitors in the third leg. A connecting wire, It has The secondary-side circuit A sixth leg and a seventh leg in each of which two of the secondary-side switching elements are arranged in series, An eighth leg in which one secondary-side capacitor is arranged, A pair of secondary-side main lines in which the secondary-side input / output terminal pair is arranged at one end, and the sixth leg, the seventh leg, and the eighth leg are parallel and connected to each other, having, a primary upper relay wiring connecting an end portion on the positive electrode side of the primary coil and a portion between the two primary switching elements in the second leg; a primary lower relay wiring connecting an end portion on the negative electrode side of the primary coil and a portion between the two primary switching elements in the first leg; a secondary upper relay wiring connecting an end portion on the positive electrode side of the secondary coil and a portion between the two secondary switching elements in the sixth leg; a secondary lower relay wiring connecting an end portion on the negative electrode side of the secondary coil and a portion between the two secondary switching elements in the seventh leg; further having, a power conversion device in which the LLC circuit has a primary resonance capacitor and a primary resonance inductance arranged in series with the primary upper relay wiring.

6. In the power conversion device according to claim 5, a power conversion device in which the bidirectional insulated LLC resonance circuit further has a secondary LLC circuit located between the transformer and the secondary circuit.

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