Bidirectional current resonance type DC / DC converter and bidirectional power supply device

Abstract

To provide a bidirectional current resonance type DC / DC converter which can seamlessly switch a power transmission direction without power jump during switching, with relatively simple control.SOLUTION: A bidirectional current resonance type DC / DC converter comprises: a power supply part 10; and a control part 20. The power supply part 10 comprises: a transformer Tr; a first bridge circuit 11; a second bridge circuit 12; a primary side resonance circuit 13; and a secondary side resonance circuit 14. The control part 20 performs: forward control for transmitting power from the first bridge circuit 11 to the second bridge circuit 12, using the first bridge circuit 11 as a drive circuit; reverse control for transmitting power from the second bridge circuit 12 to the first bridge circuit 11, using the second bridge circuit 12 as a drive circuit; and switching control for switching a direction of power transmission. The converter performs phase shift control between respective legs of the drive circuits within a range of a phase shift amount from 0 to a maximum value in the switching control.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bidirectional current resonance type DC / DC converter and a bidirectional power supply device including the bidirectional current resonance type DC / DC converter.

Background Art

[0002] In recent years, as an isolated bidirectional DC / DC converter, a CLLC (also called CLLLC) type bidirectional current resonance type DC / DC converter obtained by making a LLC type current resonance type DC / DC converter bidirectional has attracted attention.

[0003] The LLC type current resonance type DC / DC converter has advantages of being small-sized, highly efficient, having a small number of components, and being low-cost. On the other hand, the output power varies depending on the input voltage and the output voltage, making control difficult. In addition, the controllable voltage range is narrow, and there is a drawback that the output power cannot be reduced to zero only by frequency control.

[0004] The CLLC type bidirectional current resonance type DC / DC converter also has the same drawbacks as the LLC type. Since the output power cannot be reduced to zero only by frequency control, a power jump (instantaneous power fluctuation) occurs when switching the power transmission direction. For this reason, the CLLC type bidirectional current resonance type DC / DC converter has a problem that it cannot switch the power transmission direction seamlessly.

[0005] In the case of a conventionally common voltage-current type DC / DC converter, when the voltage applied to the output side becomes higher than the output voltage value being controlled, the direction of the current naturally reverses and the power transmission direction is reversed. Therefore, there is no need to change the control method, and the power transmission direction can be switched seamlessly. However, in the case of the LLC type or the CLLC type, since the control direction and the direction of the current flow (power transmission direction) are the same, when performing seamless switching of the power transmission direction, in addition to the problem of power jump at the time of switching, the control method also needs to be changed, and seamless switching of the power transmission direction is not easy.

[0006] FIG. 10 is a diagram schematically showing changes in the driving frequency and the output power when switching the power transmission direction of the above-described conventional CLLC bidirectional current resonant DC / DC converter. The third quadrant of FIG. 10 represents the power transmission amount from the primary side to the secondary side, where the horizontal axis Fd is the driving frequency and the vertical axis Pd is the forward output power. The first quadrant represents the power transmission amount from the secondary side to the primary side, where the horizontal axis Fc is the driving frequency and the vertical axis Pc is the reverse output power. In the case of the third quadrant, as the driving frequency Fd increases, the forward output power Pd decreases, but as the driving frequency Fd increases, the rate of decrease of the output power Pd decreases. Similarly, in the case of the first quadrant, as the driving frequency Fc increases, the reverse output power Pc decreases, but as the driving frequency Fc increases, the rate of decrease of the output power Pc decreases.

[0007] For example, in the case of switching the direction from the driving point Ac to the driving point Ad, while decreasing the output, the driving frequency of one side's driving circuit is increased to shift to the Bc point of the maximum frequency. After that, the driving of one side's driving circuit is stopped, and at the same time, the other side's driving circuit is started to be driven at the Bd point of the maximum frequency, and the driving frequency is decreased to shift to the Ad point. In this case, due to the switching of the driving circuit, it instantaneously shifts from the Bc point to the Bd point, so a power jump occurs. The same applies to the switching from the driving point Ad to the driving point Ac.

[0008] In Patent Document 1, for this problem, a control method has been proposed that switches between pulse width modulation control or phase modulation control with a fixed frequency at the resonance frequency and frequency modulation control below the resonance frequency. However, in this control method, when performing pulse width modulation control at the resonance frequency, hard switching occurs, so there is a problem that switching noise is generated.

[0009] In Patent Document 2, as a method for seamless switching of the power transmission direction in a CLLC-type bidirectional current resonance type DC / DC converter, the driving frequency on the primary (power supply) side is maximized (Step 3), the driving on the secondary side starts from the maximum phase difference delay with respect to the primary side (Step 4), the phase difference is reduced by phase shift control (Step 5), and when the phase difference becomes minimum, the power transmission direction is switched (Step 6).

[0010] However, the general driving method of the CLLC method is that the primary (power supply) side is driven by a bridge with a duty of 50%, and the secondary side is diode rectified or synchronously rectified, and it is not a method of driving with a phase difference provided between the primary side and the secondary side. For this reason, in the method described in Patent Document 2, generally known LLC method or CLLC method design techniques, existing hardware and software assets, and knowledge cannot be directly applied, developed, or diverted. Furthermore, Patent Document 2 does not disclose the driving method of the specific secondary side bridge circuit necessary to achieve seamless switching of the power transmission direction, the maximum phase difference, and the minimum phase difference between the driving signals of the primary side and the secondary side.

[0011] In Non-Patent Document 1, regarding seamless switching of the power transmission direction in a CLLC-type bidirectional current resonance type DC / DC converter, the driving frequency of the primary (power supply side) side bridge circuit is maximized, and the phase delay of the secondary side with respect to the primary side is reduced from +0.05, passes through 0, and is increased to -0.05 to switch in the reverse direction. A method has been proposed.

[0012] The method described in Non-Patent Document 1, like the method described in Patent Document 2, cannot utilize general LLC method or CLLC method design techniques, etc. In addition, the phase difference of ±0.05 between the primary side and the secondary side is very narrow, about 1 / 2 of the dead time (about 0.5 μs or less if the driving frequency is about 100 kHz), and control is difficult. Specifically, high-precision control instruction means are required, and since the primary side and the secondary side are insulated from each other, it is necessary to detect the phase considering the detection delay, and it is also difficult to detect the phase difference.

[0013] In addition, the methods of Patent Document 2 and Non-Patent Document 1 are methods of providing a phase difference between the primary-side bridge circuit and the secondary-side bridge circuit. However, since the phase on the secondary side also changes depending on the input voltage and the load at the connection destination, it cannot be easily controlled even assuming the phase difference with respect to the drive signal on the primary side. In addition, since the primary side and the secondary side are insulated from each other, insulation detection is required, which leads to an increase in the detection circuit, higher costs, and a delay in detection. Further, although it depends on the input voltage, when the drive frequency on the primary side is maximized, the current value on the secondary side becomes minimum. Therefore, there is a problem that it is difficult to accurately detect the phase difference even when detecting the current on the secondary side.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0015]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0016] The present invention has been made in view of the above circumstances, and an object thereof is to provide a bidirectional current resonant type DC / DC converter and a bidirectional power supply device that can switch the power transmission direction seamlessly without power jumps during switching with relatively simple control.

Means for Solving the Problems

[0017] In order to solve the above problems, the bidirectional current resonance type DC / DC converter according to the present invention is a bidirectional current resonance type DC / DC converter including a power supply unit and a control unit, wherein the power supply unit includes a transformer including a primary side coil and a secondary side coil, a first bridge circuit including a first leg and a second leg connected in parallel, each leg including an upper arm and a lower arm connected in series, each arm including a switching element, and connected to the primary side coil, a second bridge circuit including a third leg and a fourth leg connected in parallel, each leg including an upper arm and a lower arm connected in series, each arm including a switching element, and connected to the secondary side coil, a primary side resonance circuit provided between the first bridge circuit and the primary side coil, including a first resonance coil and a first resonance capacitor, a secondary side resonance circuit provided between the second bridge circuit and the secondary side coil, including a second resonance coil and a second resonance capacitor, and is provided with wherein the control unit uses the first bridge circuit as a drive circuit, performs synchronous rectification control or diode rectification control on the second bridge circuit, and performs forward control to transmit power from the first bridge circuit to the second bridge circuit, uses the second bridge circuit as a drive circuit, performs synchronous rectification control or diode rectification control on the first bridge circuit, and performs reverse control to transmit power from the second bridge circuit to the first bridge circuit, and performs switching control to switch the power transmission direction after increasing the drive frequency of the drive circuit, In the switching control, the phase shift control between each leg of the drive circuit is performed within a range where the phase shift amount is from 0 to the maximum value, or PWM control is performed on each switching element of the drive circuit, and the on ratio of the switching element is changed within a range from 50% to the minimum value.

[0018] According to this configuration, by performing phase shift control between the legs of the drive circuit or PWM control to change the on ratio of each switching element, seamless switching of the power transmission direction at zero power, which cannot be achieved by frequency control alone, becomes possible. That is, in this configuration, by performing phase shift control of the drive signals between the legs within the range from 0 to the maximum value, or by performing PWM control to change the on ratio of the switching elements within the range from 50% to the minimum value, it is not necessary to use the signals between the primary side and the secondary side for the phase shift control, and it is not necessary to control the phase difference between the first bridge circuit and the second bridge circuit. Therefore, according to this configuration, conventional design methods such as the LLC method or the CLLC method can be utilized, and relatively simple control becomes possible (for example, control within a range approximately 10 times wider than the dead time), and cost reduction can be achieved.

[0019] In the bidirectional current resonant type DC / DC converter, The control unit In the forward control, performs the synchronous rectification control of the second bridge circuit, In the switching control during the forward control, A first process of increasing the drive frequency of the first bridge circuit to a predetermined maximum frequency, Performs phase shift control between the legs of the first bridge circuit, and increases the first phase shift amount of the phase shift control from 0, or performs PWM control of each switching element of the first bridge circuit and decreases the first on ratio of each switching element of the first bridge circuit from 50% as a second process, A third process of stopping the synchronous rectification control of the second bridge circuit when the output current value of the second bridge circuit becomes equal to or less than a predetermined threshold value, A fourth process of stopping the drive of the first bridge circuit when the output voltage value of the second bridge circuit reaches a predetermined upper limit value with the first phase shift amount set to the maximum value or the first on ratio set to the minimum value, Set the driving frequency of the second bridge circuit to a predetermined maximum frequency, set the second phase shift amount between each leg of the second bridge circuit to the maximum value, and start the phase shift control between each leg of the second bridge circuit, or set the second on-ratio of each switching element of the second bridge circuit to the minimum value, and start the PWM control of each switching element of the second bridge circuit as a fifth process, When the output current value of the first bridge circuit becomes equal to or greater than a predetermined threshold value, start the synchronous rectification control of the first bridge circuit as a sixth process, A seventh process of reducing the driving frequency of the second bridge circuit from the maximum frequency by setting the second phase shift amount to 0 or setting the second on-ratio to 50% can be configured to be executed.

[0020] According to this configuration, since the power transmission direction is switched based on the output current value and the output voltage value of the second bridge circuit, seamless switching of the power transmission direction is possible without an external control signal.

[0021] In the bidirectional current resonant DC / DC converter, The control unit, Can be configured to execute at least the fifth process while performing constant voltage control on the second bridge circuit.

[0022] According to this configuration, since the power transmission direction is switched while performing constant voltage control on the second bridge circuit, only the current direction can be switched.

[0023] In the bidirectional current resonant DC / DC converter, The control unit, Execute the third process before executing the second process, Can be configured to execute the seventh process before executing the sixth process.

[0024] In the bidirectional current resonant DC / DC converter, The control unit, In the forward control, perform the diode rectification control of the second bridge circuit, In the switching control during the forward direction control, a first process of increasing the driving frequency of the first bridge circuit to a predetermined maximum frequency; a second process of performing phase shift control between each leg of the first bridge circuit and increasing the first phase shift amount of the phase shift control from 0, or performing PWM control on each switching element of the first bridge circuit and decreasing the first on ratio of each switching element of the first bridge circuit from 50%; a fourth process of stopping the driving of the first bridge circuit when the output voltage value of the second bridge circuit reaches a predetermined upper limit value with the first phase shift amount being set to the maximum value or the first on ratio being set to the minimum value; a fifth process of setting the driving frequency of the second bridge circuit to a predetermined maximum frequency, setting the second phase shift amount between each leg of the second bridge circuit to the maximum value, and starting the phase shift control between each leg of the second bridge circuit, or setting the second on ratio of each switching element of the second bridge circuit to the minimum value and starting the PWM control on each switching element of the second bridge circuit; a seventh process of setting the second phase shift amount to 0 or setting the second on ratio to 50% and decreasing the driving frequency of the second bridge circuit from the maximum frequency can be configured to be executed.

[0025] In order to solve the above problems, a bidirectional power supply device according to the present invention is the bidirectional current resonance type DC / DC converter; a bidirectional DC / AC inverter that performs DC / AC conversion operation and AC / DC conversion operation; a bidirectional power supply device comprising: When switching the direction of power transmission, the connection point voltage between the bidirectional current resonance type DC / DC converter and the bidirectional DC / AC inverter becomes a constant voltage or a voltage determined by the input voltage of the bidirectional current resonance type DC / DC converter.

[0026] According to this configuration, since the connection point voltage (link voltage) between the bidirectional current resonant DC / DC converter and the bidirectional DC / AC inverter is set to a constant voltage or a voltage determined by the power supply voltage on the bidirectional current resonant DC / DC converter side, the capacitor (for example, an electrolytic capacitor) provided for stabilizing the link voltage when switching the power transmission direction is no longer charged and discharged, and the power transmission direction can be immediately switched without wasteful energy transmission.

[0027] In the bidirectional power supply device, The bidirectional current resonant DC / DC converter is configured to be connectable to an electric vehicle, and can be configured to perform a charging operation and a discharging operation on the electric vehicle.

Advantages of the Invention

[0028] According to the present invention, it is possible to provide a bidirectional current resonant DC / DC converter and a bidirectional power supply device that can switch the power transmission direction seamlessly without a power jump during switching with relatively simple control.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0030] Hereinafter, embodiments of the bidirectional current resonance type DC / DC converter and the bidirectional power supply device according to the present invention will be described with reference to the accompanying drawings.

[0031] [Bidirectional Current Resonance Type DC / DC Converter] FIG. 1 shows a bidirectional current resonance type DC / DC converter 1 according to an embodiment of the present invention. The bidirectional current resonance type DC / DC converter 1 includes a DC / DC power supply unit 10 (corresponding to the "power supply unit" of the present invention), a control unit 20, and terminals T1 to T4.

[0032] The DC / DC power supply unit 10 includes a transformer Tr, a first bridge circuit 11, a second bridge circuit 12, a primary side resonance circuit 13, a secondary side resonance circuit 14, and various detection circuits (not shown). Since the circuit configuration of the DC / DC power supply unit 10 is symmetric about the left and right, bidirectional LLC resonance power transmission is possible. Therefore, the circuit configuration of the DC / DC power supply unit 10 is called the CLLC (or CLLLC including the excitation inductance Lm) method.

[0033] Transformer Tr is a high-frequency isolation transformer and includes a primary coil and a secondary coil. The primary coil is connected to the first bridge circuit 11 via the primary resonance circuit 13. The secondary coil is connected to the second bridge circuit 12 via the secondary resonance circuit 14. Transformer Tr may be composed of one or more according to the capacitance. Also, the exciting inductance Lm of transformer Tr is not shown as being included in transformer Tr.

[0034] The first bridge circuit 11 includes a first leg and a second leg connected in parallel, and each leg includes an upper arm and a lower arm connected in series. The upper arm of the first leg includes the switching element Q1, the diode D1, and the capacitor C1. The lower arm of the first leg includes the switching element Q2, the diode D2, and the capacitor C2. The upper arm of the second leg includes the switching element Q3, the diode D3, and the capacitor C3. The lower arm of the second leg includes the switching element Q4, the diode D4, and the capacitor C4.

[0035] The second bridge circuit 12 includes a third leg and a fourth leg connected in parallel, and each leg includes an upper arm and a lower arm connected in series. The upper arm of the third leg includes the switching element Q5, the diode D5, and the capacitor C5. The lower arm of the third leg includes the switching element Q6, the diode D6, and the capacitor C6. The upper arm of the fourth leg includes the switching element Q7, the diode D7, and the capacitor C7. The lower arm of the fourth leg includes the switching element Q8, the diode D8, and the capacitor C8.

[0036] The switching elements Q1 to Q8 are described by the circuit symbols of transistors, but power semiconductor switching elements capable of high-frequency switching such as IGBT (Insulated Gate Bipolar Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), SiC (Silicon Carbide)-MOSFET, and GaN (Gallium Nitride)-MOSFET can be used.

[0037] Diodes D1 to D8 are connected in parallel in the reverse direction to the current paths of switching elements Q1 to Q8. Although diodes D1 to D8 are described as external diodes independent of switching elements Q1 to Q8, they may be parasitic diodes of switching elements Q1 to Q8, or both.

[0038] Capacitors C1 to C8 are capacitors for partial resonance and are connected in parallel to the current paths of switching elements Q1 to Q8 and diodes D1 to D8. Capacitors C1 to C8 may be parasitic capacitors of switching elements Q1 to Q8, external capacitors independent of switching elements Q1 to Q8, or both.

[0039] The primary-side resonance circuit 13 includes a resonance coil Lr1 corresponding to the "first resonance coil" of the present invention and a resonance capacitor Cr1 corresponding to the "first resonance capacitor" of the present invention, which are connected in series to the primary-side coil of the transformer Tr.

[0040] The secondary-side resonance circuit 14 includes a resonance coil Lr2 corresponding to the "second resonance coil" of the present invention and a resonance capacitor Cr2 corresponding to the "second resonance capacitor" of the present invention, which are connected in series to the secondary-side coil of the transformer Tr.

[0041] The resonance coil Lr1 and the resonance capacitor Cr1 are arranged at both ends of the primary-side coil, but they may also be arranged on one side of the primary-side coil. Alternatively, the constants of the resonance capacitor Cr1 and the resonance coil Lr1 may be divided and both may be arranged at both ends of the primary-side coil. The same applies to the resonance coil Lr2 and the resonance capacitor Cr2. Also, part or all of the resonance coils Lr1 and Lr2 may be constituted by the leakage magnetic flux of the transformer Tr, may be constituted by individual coils, or may be both.

[0042] The control unit 20 includes drive circuits for turning on / off the switching elements Q1 to Q8, and a control circuit for sending control signals to the respective drive circuits. The control unit 20 may be composed of an analog circuit, or may be composed of a digital circuit such as a microcontroller or a DSP, or may be composed of a circuit combining an analog circuit and a digital circuit.

[0043] Based on the detection values of various detection circuits (not shown), the control unit 20 monitors the primary voltage V1, the secondary voltage V2, and the primary and secondary currents (not shown), and turns on / off the switching elements Q1 to Q8.

[0044] The control unit 20 executes forward control for causing power transmission from the first bridge circuit 11 on the primary side to the second bridge circuit 12 on the secondary side, reverse control for causing power transmission from the second bridge circuit 12 on the secondary side to the first bridge circuit 11 on the primary side, and switching control for switching the direction of power transmission.

[0045] Specifically, during forward control, the control unit 20 performs frequency control to drive the switching elements Q1 to Q4 in the first bridge circuit 11 serving as a drive circuit within a specified frequency range, while performing synchronous rectification control on the second bridge circuit 12. During forward control and switching control, the control unit 20 performs phase shift control between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4) of the first bridge circuit 11.

[0046] During reverse control, the control unit 20 performs frequency control to drive the switching elements Q5 to Q8 in the second bridge circuit 12 serving as a drive circuit within a specified frequency range, while performing synchronous rectification control on the first bridge circuit 11. During reverse control and switching control, the control unit 20 performs phase shift control between the third leg (switching elements Q5, Q6) and the fourth leg (switching elements Q7, Q8) of the second bridge circuit 12.

[0047] Figures 2 to 4 show the flow of control (switching control) when switching the power transmission direction of the bidirectional current resonance type DC / DC converter 1. Specifically, the flow of control when the output power decreases and the output voltage increases during forward power transmission in the bidirectional current resonance type DC / DC converter 1 under constant voltage control, and the converter performs a switching of the power transmission direction to the reverse direction, and the flow of control when the reverse output power decreases after the switching of the power transmission direction to the reverse direction and the converter performs a switching of the power transmission direction to the forward direction are shown.

[0048] In Fig. 2, the flow of processing when the output decreases during forward power transmission will be described. It is assumed that the bidirectional current resonance type DC / DC converter 1 is performing power transmission from the first bridge circuit 11 to the second bridge circuit 12. In this case, the control unit 20 executes forward control, sets the input to the voltage V1 for the first bridge circuit 11, performs frequency control with a phase difference of 0° (no phase difference) between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4), and performs synchronous rectification control and constant voltage control of the voltage V2 for the second bridge circuit 12 (S101).

[0049] When the control unit 20 detects a decrease in the output power due to an increase in the voltage V2, it increases the driving frequency F1 of the first bridge circuit 11 to a predetermined maximum frequency F1max (Yes in S102). Until the driving frequency F1 reaches the maximum frequency F1max (No in S102), step S101 is executed. When the output power further decreases, the control unit 20 starts phase shift control and increases the phase difference between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4) of the first bridge circuit 11, that is, the first phase shift amount θ1, from 0° (S103). If the output power decreases due to an increase in the voltage V2 in step S103, the first phase shift amount θ1 is increased, and if the output power increases due to a decrease in the voltage V2, the first phase shift amount θ1 is decreased. That is, when the output power is greater than the target power, the control unit 20 increases the first phase shift amount θ1, and when the output power is less than the target power, the control unit 20 decreases the first phase shift amount θ1. By performing phase shift control in this way, it is possible to perform control without being affected by resonance due to the parasitic capacitance of the elements constituting the circuit.

[0050] When the output current (secondary side current) of the second bridge circuit 12 is greater than a predetermined threshold value (No in S104), the control unit 20 continues the synchronous rectification control of the second bridge circuit 12 (S105). If the first phase shift amount θ1 is not 0° (No in S106), the steps after S103 are executed. If the first phase shift amount θ1 is 0° (Yes in S106), the steps after S101 are executed. On the other hand, when the output current of the second bridge circuit 12 is less than or equal to the threshold value (Yes in S104), the control unit 20 stops the synchronous rectification control of the second bridge circuit 12 (S107).

[0051] Furthermore, until the output power further decreases and the first phase shift amount θ1 reaches the maximum value (a preset maximum value or 180°) (No in S108), steps S103 and subsequent steps are executed. On the other hand, when the first phase shift amount θ1 reaches the maximum value (Yes in S108), and despite the output from the first bridge circuit 11 to the second bridge circuit 12 being controlled to the minimum value (0 or a preset minimum value), if the output voltage V2 rises and reaches a predetermined upper limit value (Yes in S109), the control unit 20 stops driving the first bridge circuit 11 (S110). Thereby, the control unit 20 determines to start reversing the power transmission direction (reverse power transmission from the second bridge circuit 12 to the first bridge circuit 11) and continues to FIG. 3 "A" (S201 and subsequent steps). Note that if the output voltage V2 does not rise after the first phase shift amount θ1 reaches the maximum value (No in S109), steps S103 and subsequent steps are executed.

[0052] Next, in FIG. 3, the flow of the startup process during reverse power transmission after FIG. 2 "A" will be described. While stopping the driving of the first bridge circuit 11, the control unit 20 performs constant voltage control of the voltage V2 as the input to the second bridge circuit 12, and sets the phase difference between the third leg (switching elements Q5, Q6) and the fourth leg (switching elements Q7, Q8) to the maximum value (a preset maximum value or 180°), and starts phase shift control with the driving frequency F2 set to the maximum frequency F2max (S201).

[0053] The control unit 20 controls the phase difference between the third leg (switching elements Q5, Q6) and the fourth leg (switching elements Q7, Q8), that is, the second phase shift amount θ2, according to the situation of the voltage V2. When the voltage V2 rises, the second phase shift amount θ2 is decreased from the maximum value (S202). When the output current (primary side current) of the first bridge circuit 11 becomes equal to or greater than a preset threshold value by the phase shift control (Yes in S203), the control unit 20 starts synchronous rectification control of the first bridge circuit 11 (S204). Note that in step S202, when the voltage V2 rises, the second phase shift amount θ2 is decreased, and when the voltage V2 drops, the second phase shift amount θ2 is increased.

[0054] Furthermore, when the output power increases further and the second phase shift amount θ2 reaches 0° (Yes in S205), the control unit 20 performs frequency control to decrease the driving frequency F2 of the second bridge circuit 12 from the maximum frequency F2max (S206), and approaches the output power to the target value. When the output power reaches the target value, if the control unit 20 continues the control (Yes in S207), it executes the steps after S202. If it does not continue the control (No in S207), it ends the process.

[0055] On the other hand, when the output current (primary side current) of the first bridge circuit 11 is less than a preset threshold value (No in S203), the synchronous rectification control of the first bridge circuit 11 is stopped (S208). When the second phase shift amount θ2 is less than the maximum value (No in S209), the steps after S202 are executed. When the second phase shift amount θ2 reaches the maximum value (Yes in S209) and the voltage V2 becomes equal to or lower than a predetermined lower limit value (Yes in S210), the control unit 20 stops the driving of the second bridge circuit 12 on the assumption that the reverse power has decreased and the reverse operation is no longer necessary (S211). Thereby, the control unit 20 determines to start the inversion of the power transmission direction (forward power transmission from the first bridge circuit 11 to the second bridge circuit 12), and continues to FIG. 4 "B" (after S301).

[0056] Next, in FIG. 4, the flow of the startup process during the forward power transmission after FIG. 3 "B" will be described. While stopping the driving of the second bridge circuit 12, the control unit 20 performs constant voltage control of the voltage V2 with the input to the first bridge circuit 11 being the voltage V1, and sets the phase difference between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4) to the maximum value (a preset maximum value or 180°), and starts phase shift control with the driving frequency F1 being the maximum frequency F1max (S301).

[0057] The control unit 20 controls as follows, in the same manner as steps S202 to S207. That is, the control unit 20 controls the phase difference between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4), that is, the first phase shift amount θ1, according to the situation of the voltage V2. When the voltage V2 decreases, the first phase shift amount θ1 is decreased from the maximum value (S302). When the output current of the second bridge circuit 12 becomes equal to or greater than a preset threshold value (Yes in S303), the synchronous rectification control of the second bridge circuit 12 is started (S304). Until the first phase shift amount θ1 reaches 0° (No in S305), the steps after S302 are executed. In step S302, when the voltage V2 decreases, the first phase shift amount θ1 is decreased, and when the voltage V2 increases, the first phase shift amount θ1 is increased.

[0058] Furthermore, when the output power increases and the first phase shift amount θ1 of the first bridge circuit 11 reaches 0° (Yes in S305), frequency control is performed to decrease the drive frequency F1 of the first bridge circuit 11 from the maximum frequency F1max according to the output power (S306). When the control is to be continued (Yes in S307), the state shifts from "C" in FIG. 2 to the state of step S101. When the control is not to be continued (No in S307), the process ends.

[0059] On the other hand, when the output current of the second bridge circuit 12 is less than a preset threshold value (No in S303), the synchronous rectification control of the second bridge circuit 12 is stopped (S308). When the first phase shift amount θ1 is less than the maximum value (No in S309), the steps after S302 are executed. When the first phase shift amount θ1 reaches the maximum value (Yes in S309), until an external voltage is applied to the second bridge circuit 12 and the voltage V2 reaches a predetermined upper limit value (No in S310), the steps after S302 are executed. When it becomes equal to or greater than the upper limit value (Yes in S310), the state shifts from "D" in FIG. 2 to the state of step S110.

[0060] In the above description, the process of becoming Yes in step S102 and maximizing the driving frequency F1 of the first bridge circuit 11 corresponds to the "first process" of the present invention. The process of increasing the first phase shift amount θ1 of the first bridge circuit 11 in step S103 corresponds to the "second process" of the present invention. The processes in steps S104 and S107 where the output current of the second bridge circuit 12 becomes equal to or less than the threshold value and the synchronous rectification control of the second bridge circuit 12 is stopped correspond to the "third process" of the present invention. The processes in steps S108 to S110 where the first phase shift amount θ1 of the first bridge circuit 11 becomes maximum, the voltage V2 becomes equal to or higher than the upper limit value, and the driving of the first bridge circuit 11 is stopped correspond to the "fourth process" of the present invention.

[0061] The process of starting phase shift control with the maximum phase difference and the maximum frequency F2max for the second bridge circuit 12 while keeping the driving of the first bridge circuit 11 stopped in step S201 corresponds to the "fifth process" of the present invention. The processes of decreasing the second phase shift amount θ2 of the second bridge circuit 12 in steps S202 to S204 and starting the synchronous rectification control of the first bridge circuit 11 when the output current of the first bridge circuit 11 becomes equal to or higher than the threshold value correspond to the "sixth process" of the present invention. The processes in steps S205 and S206 where the second phase shift amount θ2 of the second bridge circuit 12 becomes 0° and frequency control is performed to lower the driving frequency F2 from the maximum frequency F2max correspond to the "seventh process" of the present invention.

[0062] In the above description, the "third process" is performed after the "second process" and the "seventh process" is performed after the "sixth process". However, since stopping or starting the synchronous rectification control depends on the threshold value of the output current and is independent of the operation of the phase shift control of the drive circuit, the synchronous rectification control may be stopped when performing the phase shift control. That is, the "second process" may be performed after the "third process" and the processes in steps S203 and S204 of the "sixth process" may be performed after the "seventh process".

[0063] FIG. 5 is a timing diagram showing the change in the phase difference θ (first phase shift amount θ1) between the first leg and the second leg of the first bridge circuit 11.

[0064] FIG. 5(A) shows a state where the phase difference θ between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4) is 0° (no phase difference), corresponding to the state of step S101 in FIG. 2.

[0065] In FIG. 5(B), a slight phase difference θ occurs between the first leg and the second leg, and in FIG. 5(C), the phase difference θ has increased. These correspond to the state of step S103 in FIG. 2. In FIG. 5(D), the phase difference θ = 180° (maximum value) between the first leg and the second leg, which corresponds to the state of Yes in step S108 in FIG. 2.

[0066] [Bidirectional power supply device] FIG. 6 shows a configuration diagram of a power supply system using the bidirectional power supply device 2 according to an embodiment of the present invention. In FIG. 6, the bidirectional power supply device 2 is applied to V2H (Vehicle to Home).

[0067] The bidirectional power supply device 2 includes a DC / DC power supply unit 10, a DC / AC power supply unit 30, a control unit 21 for controlling these, and terminals T1 to T6. The DC / DC power supply unit 10 and the part of the control unit 21 related to the control of the DC / DC power supply unit 10 (that is, the part having the function of the control unit 20) correspond to the bidirectional current resonance type DC / DC converter 1, and the DC / AC power supply unit 30 and the part of the control unit 21 related to the control of the DC / AC power supply unit 30 correspond to the bidirectional DC / AC inverter of the present invention.

[0068] The DC / DC power supply unit 10 has the same configuration as the DC / DC power supply unit 10 of the bidirectional current resonance type DC / DC converter 1. An electrolytic capacitor (not shown) for voltage stabilization is connected to the connection point (between terminals T3 and T4) of the DC / DC power supply unit 10 and the DC / AC power supply unit 30.

[0069] The DC / AC power supply unit 30 includes a plurality of switching elements and inductors, and is configured to perform a DC / AC conversion operation of converting DC power into AC power and an AC / DC conversion operation of converting AC power into DC power under the control of the control unit 21 (for example, under PWM control).

[0070] The control unit 21 has the functions of the above control unit 20, and is further configured to perform switching control (for example, PWM control) for turning on and off a plurality of switching elements of the DC / AC power supply unit 30. Similar to the control unit 20, the control unit 21 may be composed of an analog circuit, a digital circuit such as a microcontroller or a DSP, or a circuit combining an analog circuit and a digital circuit.

[0071] In the bidirectional power supply device 2, the DC / DC power supply unit 10 and the DC / AC power supply unit 30 are connected to each other via terminals T3 and T4. The DC-side terminals T1 and T2 of the bidirectional power supply device 2 are connected to an electric vehicle (EV) 40 via a charge / discharge connector (not shown). The AC-side terminals T5 and T6 of the bidirectional power supply device 2 are connected to a load 50 such as household electrical appliances and electrical equipment, and are also connected to a power conditioner device (PCS) 61 of a solar panel (PV) 60, and are further connected to a power grid 71 (grid power supply V4) via a grid disconnector (SW) 70.

[0072] The bidirectional power supply device 2 is provided with an operation unit (for example, an operation panel) (not shown). When a charge instruction is received by the operation unit, a charging operation is performed on the electric vehicle 40, while when a discharge instruction is received by the operation unit, a discharging operation is performed on the electric vehicle 40.

[0073] Specifically, during the charging operation, the bidirectional power supply device 2 operates as a charging power supply, converts the grid power supplied to the terminals T5 and T6 and / or the generated power of the solar panel 60 converted into AC by the power conditioner device 61 into DC power, and supplies the DC power to the electric vehicle 40 under constant current control.

[0074] During the discharging operation, when the power system 71 is energized, the bidirectional power supply device 2 operates as a regenerative power source, converts the DC power stored in the battery of the electric vehicle 40 into commercial frequency AC power, and outputs the AC power to the terminals T5 and T6 through system connection.

[0075] On the other hand, when the power system 71 is de-energized during a power outage, the bidirectional power supply device 2 during the discharging operation operates the system disconnector 70 to disconnect from the power system 71, performs independent operation, and supplies AC power to the load 50. The power conditioner device 61 can supply AC power to the load 50 in connection (pseudo-connection) with the AC power supplied by the bidirectional power supply device 2.

[0076] When there is surplus power in the generated power of the solar panel 60, the bidirectional power supply device 2 can use the surplus power to charge the electric vehicle 40, and can store power in the battery of the electric vehicle 40 even during a power outage of the power system 71. Thereby, the bidirectional power supply device 2 can perform independent operation for a long time.

[0077] Therefore, during the discharging operation from the terminals T1 and T2 to the terminals T5 and T6 by constant voltage control, when surplus power is generated and the direction of current flow is reversed, the bidirectional power supply device 2 needs to smoothly and seamlessly switch the power transmission direction without a power jump during switching. Also, when the surplus power decreases and the direction of current flow returns to its original state after switching the power transmission direction, it is necessary to smoothly and seamlessly return the power transmission direction from the charging operation to the discharging operation.

[0078] The DC / DC power supply unit 10 during the discharging operation takes the voltage V1, which is the battery voltage of the electric vehicle 40, as an input, and performs constant voltage control of the link voltage V2 (corresponding to the "connection point voltage" of the present invention), which is the voltage at the connection point (between the terminals T3 and T4) with the DC / AC power supply unit 30. The DC / AC power supply unit 30 converts the DC link voltage V2 into a commercial AC voltage (voltage V3) by a DC / AC conversion operation, and performs constant voltage control of the voltage V3.

[0079] When the generated power of the solar panel 60 becomes greater than the power consumption of the load 50 and surplus power is generated, the voltage V3 rises, and the DC / AC power supply unit 30 starts a power conversion operation in the reverse direction (charging direction) (AC / DC conversion operation). As a result, in the bidirectional power supply device 2, the direction of the current is reversed and the link voltage V2 rises. The DC / DC power supply unit 10, under the control (switching control) of the control unit 21, can reverse the current direction smoothly and seamlessly without a power jump during switching even when the link voltage V2 rises, and reverse the power transmission direction. Also, when the difference between the power consumption of the load 50 and the generated power of the solar panel 60 decreases after the switching of the power transmission direction and there is no surplus power, the voltage V3 drops, and the DC / AC power supply unit 30 starts the power conversion operation in the original discharging direction (DC / AC conversion operation). As a result, in the bidirectional power supply device 2, the direction of the current is reversed and the link voltage V2 decreases. The DC / DC power supply unit 10, under the control (switching control) of the control unit 21, can reverse the current direction smoothly and seamlessly without a power jump during switching even when the link voltage V2 decreases, and return the power transmission direction to the original direction.

[0080] Fig. 7 schematically shows the changes in the driving frequency and output power when the power transmission direction of the DC / DC power supply unit 10 in the bidirectional power supply device 2 is switched.

[0081] The third quadrant of Fig. 7 shows the power transmission amount on the discharging side (from the V1 side to the V3 side). The horizontal axis Fd represents the driving frequency of the DC / DC power supply unit 10, and the vertical axis Pd represents the discharging power. The first quadrant of Fig. 7 shows the power transmission amount on the charging side (from the V3 side to the V1 side). The horizontal axis Fc represents the driving frequency of the DC / DC power supply unit 10, and the vertical axis Pc represents the charging power.

[0082] During the discharging operation of the bidirectional power supply device 2, the control unit 21 controls the DC / DC power supply unit 10 and the DC / AC power supply unit 30 so that the discharging power (the output power of the bidirectional power supply device 2) becomes the Ad point. After that, when the power difference between the power consumption of the load 50 and the generated power of the solar panel 60 decreases, the driving frequency of the first bridge circuit 11 of the DC / DC power supply unit 10 increases, the discharging power drops to the Bd point, and the driving frequency reaches the maximum frequency on the discharging side.

[0083] When the driving frequency reaches the maximum frequency on the discharge side, the control unit 21 starts the phase shift control of the first bridge circuit 11 and increases the first phase shift amount θ1 between the first leg (switching elements Q1, Q2) and the second leg (switching elements Q3, Q4) from 0°. When the discharge power decreases to point Cd by the phase shift control, the control unit 21 stops the synchronous rectification control of the second bridge circuit 12 of the DC / DC power supply unit 10. Furthermore, when the output power decreases and the first phase shift amount θ1 reaches the maximum value, the discharge power reaches point Dd and becomes zero. When the discharge power becomes zero, the control unit 21 stops driving the first bridge circuit 11.

[0084] When surplus power (the power difference between the generated power of the solar panel 60 and the power consumption of the load 50) occurs in the generated power of the solar panel 60, the DC / AC power supply unit 30 starts a reverse power conversion operation (AC / DC conversion operation) under the control of the control unit 21, and the link voltage V2 rises. The control unit 21 starts phase shift control with the driving frequency set to the maximum frequency and the second phase shift amount θ2 between the third leg (switching elements Q5, Q6) and the fourth leg (switching elements Q7, Q8) of the second bridge circuit 12 set to the maximum value so that the charging power (the output power of the bidirectional power supply device 2) becomes point Dc.

[0085] When the surplus power increases, the control unit 21 decreases the second phase shift amount θ2. When the charging power rises to point Cc by the phase shift control, the control unit 21 starts the synchronous rectification control of the first bridge circuit 11. When the second phase shift amount θ2 becomes 0°, the charging power rises to point Bc. When the charging power rises to point Bc, the control unit 20 performs frequency control to decrease the driving frequency of the second bridge circuit 12 from the maximum frequency, bringing the charging power closer to the target value at point Ac.

[0086] Note that the relationship lines of the charging power and the discharging power with respect to the driving frequency in FIG. 7 differ depending on the input voltage, and the higher the input voltage, the higher the output value even at the same driving frequency. The maximum frequency during discharging and the maximum frequency during charging may be the same value or different values. Also, although no hysteresis was provided for the power values at the start / stop of the synchronous rectification control on the discharging side and the charging side, it is preferable to provide hysteresis to prevent hunting. For each of these operating conditions, different maximum frequencies are stored in the storage unit (not shown) in the control unit 20 or the control unit 21 with respect to the input voltage range during charging / discharging, and the optimum maximum frequency may be read out and controlled according to the operating conditions.

[0087] According to the bidirectional current resonance type DC / DC converter 1 and the bidirectional power supply device 2, by performing phase shift control of the drive circuit of the DC / DC power supply unit 10, seamless switching of the power transmission direction with zero power (without power jump during switching) that cannot be achieved by frequency control alone becomes possible. That is, in the bidirectional current resonance type DC / DC converter 1 and the bidirectional power supply device 2, by performing phase shift control of the drive signals between the legs of the drive circuit of the DC / DC power supply unit 10 in the range from 0 to the maximum value, it is not necessary to use the signals between the primary side and the secondary side for the phase shift control, and it is also not necessary to control the phase difference between the first bridge circuit 11 and the second bridge circuit 12. Therefore, conventional design methods such as the LLC method or the CLLC method can be used, and relatively simple control becomes possible (for example, control in a range about 10 times wider than the dead time), and cost reduction can be achieved.

[0088] In the bidirectional current resonance type DC / DC converter 1 and the bidirectional power supply device 2, since the power transmission direction is switched based on the output current value and the output voltage value of the DC / DC power supply unit 10, seamless switching of the power transmission direction is possible without an external control signal. Also, in the bidirectional current resonance type DC / DC converter 1 and the bidirectional power supply device 2, by switching the power transmission direction while controlling the second bridge circuit 12 of the DC / DC power supply unit 10 at a constant voltage, switching of only the current direction becomes possible.

[0089] Note that, although a method of changing the phase shift amount between the legs on the driving side from 0° to the maximum value or 180° is used to reduce the output from the maximum driving frequencies (maximum frequencies F1max and F2max), the method is not limited thereto, and the load current may be limited and the output may be reduced by shortening the on ratio of the switching element from 50% to the minimum value (predetermined minimum value or 0%) using PWM control.

[0090] Figures 8(A) to (D) are timing diagrams showing changes in the duty D of the PWM control of the first bridge circuit 11. (A) to (D) of FIG. 8 correspond to (A) to (D) of FIG. 5. FIG. 8(A) shows a state where the duty D = 50%. In FIG. 8(B), the duty D becomes smaller than 50%. In FIG. 8(C), the duty D becomes even smaller. Then, in FIG. 8(D), the duty D = 0%. Note that, in FIG. 8, the duty D is changed by performing turn-off timing control, but the duty D may be changed by performing turn-on timing control, or the duty D may be changed by performing other control.

[0091] As described above, embodiments of the bidirectional current resonance type DC / DC converter and the bidirectional power supply device according to the present invention have been described, but the present invention is not limited to the above embodiments.

[0092] [Diode Rectification Control] In the above embodiment, synchronous rectification control is performed on the second bridge circuit 12 during forward control, and synchronous rectification control is performed on the first bridge circuit 11 during reverse control. However, diode rectification control may be performed instead of synchronous rectification control.

[0093] In the case of diode rectification control, during forward control, the switching elements Q5 to Q8 of the second bridge circuit 12 are continuously turned off to perform diode rectification on the second bridge circuit 12, and during reverse control, the switching elements Q1 to Q4 of the first bridge circuit 11 are continuously turned off to perform diode rectification on the first bridge circuit 11.

[0094] Also, in the case of diode rectification control, for example, in the switching control during power transmission from the first bridge circuit 11 to the second bridge circuit 12 (during forward control), the third process and the sixth process may be omitted, and the first process, the second process, the fourth process, the fifth process, and the seventh process may be executed.

[0095] That is, in the case of diode rectification control, (1) The "first process" of maximizing the driving frequency F1 of the first bridge circuit 11, and (2) The "second process" of increasing the first phase shift amount θ1 between the legs of the first bridge circuit 11 from 0 by phase shift control (or decreasing the on ratio (first on ratio) of the switching elements Q1 to Q4 from 50% by PWM control), and (3) The "fourth process" of stopping the driving of the first bridge circuit 11 when the first phase shift amount θ1 reaches the maximum value (or the first on ratio reaches the minimum value), the voltage V2 becomes equal to or higher than the upper limit value, and (4) While the driving of the first bridge circuit 11 is stopped, start phase shift control with the maximum phase difference and the maximum frequency for the second bridge circuit 12 (or start PWM control with the minimum on ratio (second on ratio) and the maximum frequency for the switching elements Q5 to Q8 of the second bridge circuit 12), the "fifth process", and (5) The "seventh process" of performing frequency control to lower the driving frequency F2 from the maximum frequency F2max when the second phase shift amount θ2 between the legs of the second bridge circuit 12 becomes 0° (or the second on ratio becomes 50%). may be executed.

[0096] [Control of Link Voltage] Fig. 9 schematically shows the change in the link voltage V2 when switching between the discharge operation and the charging operation of the bidirectional power supply device 2 according to the above embodiment.

[0097] In the case of Fig. 9(A), the link voltage V2 of the DC / DC power supply unit 10 during the discharge operation is the a voltage, but the link voltage V2 of the DC / AC power supply unit 30 during the charging operation is the b voltage (where the b voltage < the a voltage). Therefore, when switching between the charging operation and the discharge operation, charging and discharging occur in the electrolytic capacitor for voltage stabilization connected to the connection point (between terminals T3 and T4) where the link voltage V2 is generated, and wasted power is consumed.

[0098] On the other hand, in the case of Fig. 9(B), both the link voltage V2 of the DC / DC power supply unit 10 during the discharge operation and the link voltage V2 of the DC / AC power supply unit 30 during the charging operation are the c voltage. Therefore, even when switching between the charging operation and the discharge operation, charging and discharging do not occur in the electrolytic capacitor for voltage stabilization connected to the connection point (between terminals T3 and T4), so wasted power is not consumed. For this reason, in the case of Fig. 9(B), when switching the power transmission direction, the power transmission direction can be switched immediately without waiting for a change in the link voltage V2. Note that the link voltage V2 may be variable or fixed, for example, by the voltage V1.

[0099] That is, the bidirectional power supply device 2 can immediately switch the power transmission direction without waiting for a change in the link voltage V2 by making the link voltage V2 of the DC / DC power supply unit 10 and the DC / AC power supply unit 30 a constant voltage or a voltage determined by the input voltage (voltage V1) of the DC / DC power supply unit 10 when switching the power transmission direction.

[0100] [Other Modification Examples] The bidirectional current resonance type DC / DC converter according to the present invention includes a transformer, a first bridge circuit, a second bridge circuit, a primary side resonance circuit, a secondary side resonance circuit, and a control unit. The control unit uses the first bridge circuit as a drive circuit, performs synchronous rectification control or diode rectification control on the second bridge circuit, and performs forward control to cause power transmission from the first bridge circuit to the second bridge circuit. The second bridge circuit is used as a drive circuit, synchronous rectification control or diode rectification control is performed on the first bridge circuit, and reverse control to cause power transmission from the second bridge circuit to the first bridge circuit. And switching control is executed to switch the power transmission direction after increasing the drive frequency of the drive circuit. In the switching control, the phase shift control between the legs of the drive circuit is performed in a range where the phase shift amount is from 0 to the maximum value (a preset maximum value or 180°), or in PWM control, the on ratio of the switching element is changed in a range from 50% to the minimum value (a preset minimum value or 0%). If so, the configuration can be changed as appropriate.

[0101] That is, in the embodiment, one drive frequency is set to the maximum value, the phase shift amount is increased from 0 to the maximum value for switching, the other drive frequency is set to the maximum value, and after the phase shift amount is decreased from the maximum value to 0, the drive frequency is decreased from the maximum value. However, with one drive frequency sufficiently high (for example, about 1.5 to 2 times the resonance frequency determined by the resonance coil and the resonance capacitor), the drive frequency is increased while the phase shift amount is increased from 0, and the other drive frequency is set to a sufficiently large value and the phase shift amount is set to the maximum value. Then, the phase shift amount is decreased from the maximum value while the drive frequency is decreased from a sufficiently large value. After the phase shift amount becomes 0, the drive frequency may continue to be decreased.

[0102] Note that when the drive frequency is higher than the resonance frequency, the rate of decrease in gain due to the increase in the drive frequency decreases. On the other hand, when the drive frequency increases, the heat generation of the transformer and the resonance coil increases. Therefore, it is preferable to determine the maximum values (maximum frequencies F1max, F2max) of the drive frequencies in consideration of both.

Explanation of Reference Numerals

[0103] 1 Bidirectional current resonance type DC / DC converter 2 Bidirectional power supply device 10 DC / DC power supply section 11 First bridge circuit 12 Second bridge circuit 13 Primary side resonance circuit 14 Secondary side resonance circuit 2 Bidirectional power supply device 20, 21 Control section 30 DC / AC power supply section 40 Electric vehicle 50 Load 60 Solar panel 61 Power conditioner device 70 System disconnector 71 Power system

Claims

1. A bidirectional current resonance type DC / DC converter including a power supply unit and a control unit, wherein the power supply unit includes a transformer including a primary coil and a secondary coil, a first bridge circuit including a first leg and a second leg connected in parallel, each leg including an upper arm and a lower arm connected in series, each arm including a switching element, and connected to the primary coil, a second bridge circuit including a third leg and a fourth leg connected in parallel, each leg including an upper arm and a lower arm connected in series, each arm including a switching element, and connected to the secondary coil, a primary resonance circuit provided between the first bridge circuit and the primary coil, including a first resonance coil and a first resonance capacitor, a secondary resonance circuit provided between the second bridge circuit and the secondary coil, including a second resonance coil and a second resonance capacitor, and is provided with, wherein the control unit uses the first bridge circuit as a drive circuit, performs synchronous rectification control or diode rectification control on the second bridge circuit, and performs forward control to cause power transmission from the first bridge circuit to the second bridge circuit, uses the second bridge circuit as a drive circuit, performs synchronous rectification control or diode rectification control on the first bridge circuit, and performs reverse control to cause power transmission from the second bridge circuit to the first bridge circuit, and executes switching control to switch the power transmission direction after increasing the drive frequency of the drive circuit, in the switching control, the phase shift control between each leg of the drive circuit is performed in a range where the phase shift amount is from 0 to the maximum value, or PWM control is performed on each switching element of the drive circuit, and the on ratio of the switching element is changed in a range from 50% to the minimum value characterized by a bidirectional current resonance type DC / DC converter.

2. The control unit in the forward control, performs the synchronous rectification control of the second bridge circuit, in the switching control during the forward control, a first process of increasing the drive frequency of the first bridge circuit to a predetermined maximum frequency, a second process of performing phase shift control between each leg of the first bridge circuit and increasing the first phase shift amount of the phase shift control from 0, or performing PWM control on each switching element of the first bridge circuit and decreasing the first on ratio of each switching element of the first bridge circuit from 50% A third process of stopping the synchronous rectification control of the second bridge circuit when the output current value of the second bridge circuit becomes equal to or less than a predetermined threshold value; A fourth process of stopping the driving of the first bridge circuit when the output voltage value of the second bridge circuit reaches a predetermined upper limit value by setting the first phase shift amount to a maximum value or setting the first on-ratio to a minimum value; A fifth process of starting the phase shift control between the legs of the second bridge circuit by setting the driving frequency of the second bridge circuit to a predetermined maximum frequency and setting the second phase shift amount between the legs of the second bridge circuit to a maximum value, or starting the PWM control of each switching element of the second bridge circuit by setting the second on-ratio of each switching element of the second bridge circuit to a minimum value; A sixth process of starting the synchronous rectification control of the first bridge circuit when the output current value of the first bridge circuit becomes equal to or greater than a predetermined threshold value; A seventh process of reducing the driving frequency of the second bridge circuit from the maximum frequency by setting the second phase shift amount to 0 or setting the second on-ratio to 50%; The bidirectional current resonant type DC / DC converter according to claim 1, characterized in that the above is executed.

3. The control unit While performing constant voltage control on the second bridge circuit, at least the fifth process is executed. The bidirectional current resonant type DC / DC converter according to claim 2, characterized in that the above is executed.

4. The control unit Executes the third process before executing the second process, Executes the seventh process before executing the sixth process. The bidirectional current resonant type DC / DC converter according to claim 2, characterized in that the above is executed.

5. The control unit In the forward control, diode rectification control of the second bridge circuit is performed. In the switching control during the forward control, A first process of increasing the driving frequency of the first bridge circuit to a predetermined maximum frequency; Performing phase shift control between the legs of the first bridge circuit, and increasing the first phase shift amount of the phase shift control from 0, or performing PWM control of each switching element of the first bridge circuit and decreasing the first on-ratio of each switching element of the first bridge circuit from 50%; A fourth process of stopping the driving of the first bridge circuit when the output voltage value of the second bridge circuit reaches a predetermined upper limit value by setting the first phase shift amount to a maximum value or setting the first on-ratio to a minimum value; A fifth process of starting the phase shift control between the legs of the second bridge circuit by setting the driving frequency of the second bridge circuit to a predetermined maximum frequency and setting the second phase shift amount between the legs of the second bridge circuit to a maximum value, or starting the PWM control of each switching element of the second bridge circuit by setting the second on-ratio of each switching element of the second bridge circuit to a minimum value; A seventh process of reducing the driving frequency of the second bridge circuit from the maximum frequency by setting the second phase shift amount to 0 or setting the second on-ratio to 50%; is executed The bidirectional current resonant type DC / DC converter according to claim 1, characterized in that.

6. A bidirectional current resonant type DC / DC converter according to any one of claims 1 to 5, A bidirectional DC / AC inverter that performs a DC / AC conversion operation and an AC / DC conversion operation, A bidirectional power supply device comprising: When switching the power transmission direction, the connection point voltage of the bidirectional current resonant type DC / DC converter and the bidirectional DC / AC inverter becomes a constant voltage or a voltage determined by the input voltage of the bidirectional current resonant type DC / DC converter The bidirectional power supply device is characterized by this.

7. The bidirectional current resonant type DC / DC converter is configured to be connectable to an electric vehicle, Performing a charging operation and a discharging operation on the electric vehicle The bidirectional power supply device according to claim 6, characterized in that.

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