Power conversion device

Abstract

Provided is a power conversion device capable of adjusting power supplied from a power source to each load in a configuration in which a power conversion circuit capable of actively converting power for one load is not provided, and a power conversion circuit capable of actively converting power for the other loads and the power source is provided. The power conversion device executes a first operation mode in which, when power is supplied from a primary-side power source to a secondary-side load and a tertiary-side load, a switch element of a primary-side power conversion circuit is on / off-controlled in order to adjust the power supplied to the tertiary-side load, and a switch element of a secondary-side power conversion circuit is on / off-controlled in order to adjust the power supplied to the secondary-side load.

Description

Power conversion device ,

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[0001] The present disclosure relates to a power conversion device.

[0002] In the power conversion device of Patent Document 1, a multi-output power supply configuration is obtained by using a composite winding in a transformer. When charging power from an AC power supply to two DC power supplies using a transformer having a composite winding magnetically coupled to each other, the power conversion device of Patent Document 1 charges one of the DC power supplies with a priority.

[0003] Further, in the power conversion device of Patent Document 2, a multi-output power supply is obtained by using a composite winding in a transformer. When charging a plurality of DC power supplies using a transformer having a composite winding magnetically coupled to each other, the power conversion device of Patent Document 2 provides a switching circuit having a voltage conversion function for all the DC power supplies so that all the DC power supplies can be charged with desired power.

[0004] Patent No. 4263736, Patent No. 5968553

[0005] However, in the power conversion device of Patent Document 1, a bidirectional power conversion circuit for controlling charging is configured using a diode connected in anti-parallel to a switching element. Therefore, even if an attempt is made to control the amount of power received from a DC voltage source by PWM control in a bidirectional switching circuit, it is rectified by the diodes connected in a bridge configuration, so that the amount of charge to the DC power supply cannot be controlled, and as a result, there is a problem that the input power from AC cannot be distributed and controlled.

[0006] Further, in the power conversion device of Patent Document 2, although a method capable of distributively controlling the input power from AC to each DC power supply serving as a load is shown, there is a problem that it is necessary to provide a power conversion circuit capable of actively converting power for all the DC power supplies, leading to an increase in the number of components and cost.

[0007] Therefore, an object of the present disclosure is to provide a power conversion device capable of adjusting the supply power from a power source to each load in a configuration in which a power conversion circuit capable of actively converting power is provided for each of other loads and power sources without providing a power conversion circuit capable of actively converting power for one load.

[0008] The power conversion device according to this disclosure comprises: a transformer having at least a primary winding, a secondary winding, and a tertiary winding magnetically coupled to each other; a primary power conversion circuit that converts the AC power of the primary winding to the DC power of the primary terminal connected to a primary power source; a secondary power conversion circuit that converts the AC power of the secondary winding to the DC power of the secondary terminal connected to a secondary load; a tertiary rectifier circuit that converts the AC power of the tertiary winding to DC power and supplies it to the tertiary terminal connected to a tertiary load; and a control circuit that controls the on / off switching of the switching elements of the primary power conversion circuit and the secondary power conversion circuit. The control circuit, when supplying power from the primary power source to the secondary and tertiary loads, executes a first operating mode in which it controls the on / off switching of the switching element of the primary power conversion circuit to adjust the power supplied to the tertiary load, and controls the on / off switching of the switching element of the secondary power conversion circuit to adjust the power supplied to the secondary load.

[0009] According to the power conversion device of this disclosure, in the first operating mode, power is supplied from the primary power source to the secondary and tertiary loads by distribution. The tertiary rectifier circuit cannot actively adjust the supplied power and also supplies power to the secondary load. However, by controlling the on / off switch element of the primary power conversion circuit to adjust the power supplied to the tertiary load, the primary power conversion circuit can be preferentially controlled to adjust the power supplied to the tertiary load. On the other hand, by controlling the on / off switch element of the secondary power conversion circuit to adjust the power supplied to the secondary load, the power supplied to the secondary load can be adaptively adjusted to match the power supplied from the primary power source, which has been adjusted to adjust the power supplied to the tertiary load. Therefore, even in a configuration where there is no power conversion circuit capable of actively converting power on the tertiary side, the power supplied from the primary power source to the secondary load and the power supplied to the tertiary load can be individually adjusted by controlling the primary and secondary power conversion circuits.

[0010] This is a circuit diagram of the power converter according to Embodiment 1. This is a time chart illustrating the control behavior of the first operating mode according to Embodiment 1. This is a diagram illustrating the times t1 to t2 in Figure 2 of the first operating mode according to Embodiment 1. This is a diagram illustrating the times t2 to t4 in Figure 2 of the first operating mode according to Embodiment 1. This is a time chart illustrating the control behavior of the second operating mode according to Embodiment 1. This is a diagram illustrating the times t0 to t1 in Figure 5 of the second operating mode according to Embodiment 1. This is a diagram illustrating the times t1 to t3 in Figure 5 of the second operating mode according to Embodiment 1. This is a time chart illustrating the control behavior of the second operating mode according to Embodiment 1. This is a diagram illustrating the times t0 to t1 in Figure 8 of the second operating mode according to Embodiment 1. This is a diagram illustrating the times t1 to t3 in Figure 8 of the second operating mode according to Embodiment 1. This is a time chart illustrating the control behavior of the third operating mode according to Embodiment 1. This is a diagram illustrating the times t0 to t1 in Figure 11 of the third operating mode according to Embodiment 1. This is a diagram illustrating the times t2 to t3 in Figure 8 of the third operating mode according to Embodiment 1. This is a time chart illustrating the control behavior of the second operating mode according to Embodiment 1. This is a time chart illustrating the control behavior of the first operating mode according to Embodiment 2. This is a diagram illustrating the times t2 to t3 in Figure 15 of the first operating mode according to Embodiment 2. This is a diagram illustrating the times t3 to t4 in Figure 15 of the first operating mode according to Embodiment 2. This is a time chart illustrating the control behavior of the second operating mode according to Embodiment 2. This is a time chart illustrating the control behavior of the third operating mode according to Embodiment 2. This is a diagram illustrating the times t2 to t3 in Figure 19 of the third operating mode according to Embodiment 2. This is a diagram illustrating the times t3 to t4 in Figure 19 of the third operating mode according to Embodiment 2. This is a diagram illustrating the schematic hardware configuration of the control circuit according to Embodiment 1.

[0011] 1. Embodiment 1 Figure 1 is a circuit diagram of a power conversion device 50 in Embodiment 1 of the present invention. The power conversion device 50 includes a transformer 5, a primary power conversion circuit 10, a secondary power conversion circuit 20, a tertiary rectifier circuit 30, and a control circuit 6.

[0012] The transformer 5 has at least a primary winding 5a, a secondary winding 5b, and a tertiary winding 5c ​​that are magnetically coupled to each other. The primary power conversion circuit 10 converts the AC power of the primary winding 5a to the DC power of the primary power source 1 connected to the primary terminals 15a and 15b. The secondary power conversion circuit 20 converts the AC power of the secondary winding 5b to the DC power of the secondary load 2 connected to the secondary terminal 25. The tertiary rectifier circuit 30 converts the AC power of the tertiary winding 5c ​​to DC power and supplies it to the tertiary load 3 connected to the tertiary terminal 35. The control circuit 6 controls the on / off switching of the switching elements of the primary power conversion circuit 10 and the secondary power conversion circuit 20.

[0013] In this embodiment, the primary power source 1 is a DC power supply that functions as both a power source and a load. The secondary load 2 is a secondary DC power supply 2 that functions as both a power source and a load. In this example, the secondary DC power supply 2 is a rechargeable and dischargeable energy storage device. The secondary DC power supply 2 has a secondary load capacitor 23 connected in parallel to the secondary DC power supply 2. The tertiary load 3 is a tertiary DC power supply 3 that functions as both a power source and a load. In this example, the tertiary DC power supply 3 is a rechargeable and dischargeable energy storage device.

[0014] 1-1. Circuit Configuration <Transformer 5> As described above, the transformer 5 has at least a primary winding 5a, a secondary winding 5b, and a tertiary winding 5c ​​that are magnetically coupled to each other. The transformer 5 has a core 5d, and the primary winding 5a, secondary winding 5b, and tertiary winding 5c ​​are wound around the core 5d. In this embodiment, the tertiary winding 5c ​​is of the center-tapped type. As will be described later, the voltage conversion ratio between the windings is determined by the ratio of the number of turns N1 of the primary winding 5a, the number of turns N2 of the secondary winding 5b, and the number of turns N3 of the tertiary winding 5c.

[0015] <Primary side circuit configuration> Primary side terminals 15a and 15b have a positive terminal 15a and a negative terminal 15b. The positive terminal of the primary side power source 1 is connected to the positive terminal 15a, and the negative terminal of the primary side power source 1 is connected to the negative terminal 15b. The primary side terminals 15a and 15b are connected to the primary side power conversion circuit 10 by primary side buses 16a and 16b. The positive terminal 15a is connected to the positive terminal bus 16a, and the negative terminal 15b is connected to the negative terminal bus 16b.

[0016] In this embodiment, a primary capacitor 11 is connected between the positive terminal primary busbar 16a and the negative terminal primary busbar 16b. DC power supplied from the primary power source 1 via the primary terminals 15a and 15b is smoothed by the primary capacitor 11 and supplied to the primary power conversion circuit 10.

[0017] A primary side detection circuit 41 is provided to detect one or both of the voltage and current of the primary side power conversion circuit 10. In this embodiment, the primary side detection circuit 41 is provided on the primary side buses 16a and 16b and detects the primary side power supply voltage Vdc1 and the primary side power supply current Idc1. The primary side detection circuit 41 is provided in the portion of the primary side buses 16a and 16b between the primary side capacitor 11 and the primary side power conversion circuit 10.

[0018] The primary power conversion circuit 10 is a power conversion circuit that converts the DC power of the primary buses 16a and 16b with the AC power of the primary winding 5a. In this embodiment, the primary power conversion circuit 10 is an H-bridge circuit of four switch elements 10a to 10d. Specifically, the primary power conversion circuit 10 includes a first leg in which a first leg positive-side switch element 10a connected to the positive-side primary bus 16a and a first leg negative-side switch element 10b connected to the negative-side primary bus 16b are connected in series, and a second leg in which a second leg positive-side switch element 10c connected to the positive-side primary bus 16a and a primary second leg negative-side switch element 10d connected to the negative-side primary bus 16b are connected in series. An intermediate connection wire between the first leg positive-side switch element 10a and the first leg negative-side switch element 10b is connected to one terminal of the primary winding 5a, and an intermediate connection wire between the second leg positive-side switch element 10c and the primary-side second leg negative-side switch element 10d is connected to the other terminal of the primary winding 5a. The positive-side switch element is referred to as the upper arm, and the negative-side switch element is referred to as the lower arm.

[0019] <Secondary Circuit Configuration> The secondary terminals 25a and 25b have a positive terminal 25a and a negative terminal 25b. The positive terminal of the secondary DC power supply 2 is connected to the positive terminal 25a, and the negative terminal of the secondary DC power supply 2 is connected to the negative terminal 25b. The secondary terminals 25a and 25b are connected to the secondary power conversion circuit 20 by secondary buses 26a and 26b. The positive terminal 25a is connected to the positive bus 26a, and the negative terminal 25b is connected to the negative bus 26b.

[0020] In this embodiment, a secondary capacitor 22 is connected between the positive-side secondary busbar 26a and the negative-side secondary busbar 26b. The DC power converted by the secondary power conversion circuit 20 is smoothed by the secondary capacitor 22 and supplied to the secondary DC power supply 2 via the secondary terminals 25a and 25b.

[0021] Furthermore, the secondary load capacitor 23, which is connected in parallel to the secondary DC power supply 2, is located outside the power converter 50, and the capacitance of the secondary load capacitor 23 is greater than the capacitance of the secondary capacitor 22.

[0022] A secondary detection circuit 42 is provided to detect one or both of the voltage and current of the secondary power conversion circuit 20. In this embodiment, the secondary detection circuit 42 is provided on the secondary buses 26a and 26b and detects the secondary load voltage Vdc2 and the secondary load current Idc2. The secondary detection circuit 42 is provided in the portion of the secondary buses 26a and 26b between the secondary capacitor 22 and the secondary terminals 25a and 25b. Therefore, the secondary capacitor 22 is positioned between the secondary detection circuit 42 and the secondary power conversion circuit 20. Consequently, the positive-negative capacitance of the portion of the secondary buses 26a and 26b on the secondary power conversion circuit 20 side is smaller than the positive-negative capacitance of the portion of the secondary buses 26a and 26b on the secondary terminals 25a and 25b side is smaller than the positive-negative capacitance of the portion of the secondary buses 26a and 26b on the secondary terminals 25a and 25b side is smaller than the positive-negative capacitance of the portion of the secondary buses 26a and 26b on the secondary terminals 25a and 25b side is smaller than the detection location of the secondary detection circuit 42. Therefore, the detection circuit 42 on the secondary side can detect the current and voltage that have been smoothed by the capacitor 22 on the secondary side.

[0023] The secondary power conversion circuit 20 is a power conversion circuit that converts the AC power of the secondary winding 5b and the DC power of the secondary buses 26a and 26b. In this embodiment, the secondary power conversion circuit 20 is an H-bridge circuit of four switch elements 20a to 20d. Specifically, the secondary power conversion circuit 20 comprises a first leg in which a first leg positive-side switch element 20a connected to the positive-side secondary bus 26a and a first leg negative-side switch element 20b connected to the negative-side secondary bus 26b are connected in series, and a second leg in which a second leg positive-side switch element 20c connected to the positive-side secondary bus 26a and a second leg negative-side switch element 20d connected to the negative-side secondary bus 26b are connected in series. An intermediate connection wire between the first leg positive-side switch element 20a and the first leg negative-side switch element 20b is connected to one terminal of the secondary winding 5b, and an intermediate connection wire between the second leg positive-side switch element 20c and the second leg negative-side switch element 20d is connected to the other terminal of the secondary winding 5b.

[0024] A secondary boost reactor 21 is connected between the secondary winding 5b and the secondary power conversion circuit 20. In this example, the secondary boost reactor 21 is connected between the intermediate connection wire of the first leg and one terminal of the secondary winding 5b.

[0025] Each switching element in the primary and secondary power conversion circuits 10 and 20 uses an IGBT (Insulated Gate Bipolar Transistor) with a diode connected in antiparallel. The gate terminal of each switching element is connected to the control circuit 6. Each switching element is turned on or off by a control signal output from the control circuit 6. Each switching element may also be a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) with the function of a diode connected in antiparallel, an FET (Field Effect Transistor) with a diode connected in antiparallel, or a bipolar transistor with a diode connected in antiparallel.

[0026] <Tertiary side circuit configuration> The tertiary terminals 35a and 35b have a positive terminal 35a and a negative terminal 35b. The positive terminal of the tertiary DC power supply 3 is connected to the positive terminal 35a, and the negative terminal of the tertiary DC power supply 3 is connected to the negative terminal 35b. The tertiary terminals 35a and 35b are connected to the tertiary rectifier circuit 30 by tertiary busbars 36a and 36b. The positive terminal 35a is connected to the positive busbar 36a, and the negative terminal 35b is connected to the negative busbar 36b.

[0027] In this embodiment, a tertiary capacitor 32 is connected between the positive terminal tertiary busbar 36a and the negative terminal tertiary busbar 36b. The DC power converted by the tertiary rectifier circuit 30 is smoothed by the tertiary capacitor 32 and supplied to the tertiary DC power supply 3 via the tertiary terminals 35a and 35b.

[0028] A tertiary detection circuit 43 is provided to detect one or both of the voltage and current of the tertiary rectifier circuit 30. In this embodiment, the tertiary detection circuit 43 is provided on the tertiary buses 36a and 36b and detects the tertiary load voltage Vdc3 and the tertiary load current Idc3. The tertiary detection circuit 43 is provided in the portion of the tertiary buses 36a and 36b between the tertiary capacitor 32 and the tertiary terminals 35a and 35b. Therefore, the tertiary capacitor 32 is positioned between the tertiary detection circuit 43 and the tertiary rectifier circuit 30. Consequently, the positive-negative capacitance of the portion of the tertiary buses 36a and 36b on the tertiary rectifier circuit 30 side is smaller than the positive-negative capacitance of the portion of the tertiary buses 36a and 36b on the tertiary terminals 35a and 35b detection location of the tertiary detection circuit 43. Therefore, the detection circuit 43 on the tertiary side can detect the current and voltage that have been smoothed by the capacitor 32 on the tertiary side.

[0029] A tertiary smoothing reactor 31 is connected between the tertiary terminals 35a and 35b and the tertiary rectifier circuit 30. In this example, the tertiary smoothing reactor 31 is connected in series with the tertiary busbar 36a on the positive side of the tertiary rectifier circuit 30, rather than with the tertiary capacitor 32.

[0030] The tertiary rectifier circuit 30 converts the AC power from the tertiary winding 5c ​​of the transformer 5 into DC power and supplies it to the tertiary terminals 35a and 35b. In this embodiment, the tertiary rectifier circuit 30 is a center-tapped single-phase full-wave rectifier circuit. Specifically, the tertiary winding 5c ​​is a center-tapped type and has a tertiary winding 5c1 on one side of the center tap and a tertiary winding 5c2 on the other side. One terminal of the tertiary winding 5c ​​(one side of the tertiary winding 5c1) is connected to the anode of the first rectifier diode 30a, the other terminal of the tertiary winding 5c ​​(the other side of the tertiary winding 5c2) is connected to the anode of the second rectifier diode 30b, the cathode of the first rectifier diode 30a and the cathode of the second rectifier diode 30b are connected to the positive side of the tertiary bus 36a, and the center tap of the tertiary winding 5c ​​is connected to the negative side of the tertiary bus 36b. The tertiary rectifier circuit 30 may be a bridge-type single-phase full-wave rectifier circuit.

[0031] 1-2. Control circuit 6 The control circuit 6 controls the on / off switching of the switch elements 10a to 10d of the primary power conversion circuit 10 and the switch elements 20a to 20d of the secondary power conversion circuit 20.

[0032] 1-2-1. The operating mode switching control circuit 6 is configured to switch between and execute the first operating mode, the second operating mode, and the third operating mode.

[0033] The control circuit 6 determines to execute the first operating mode when power is supplied from the primary power source 1 to the secondary DC power supply 2 and the tertiary DC power supply 3. The control circuit 6 determines to execute the second operating mode when power is supplied from either or both of the primary power source 1 and the secondary DC power supply 2 to the tertiary DC power supply 3. The control circuit 6 determines to execute the third mode when power is supplied from the secondary DC power supply 2 to the primary power source 1 and the tertiary DC power supply 3.

[0034] In the first operating mode, the average value of the primary power supply current Idc1 over one AC period is positive, and the primary power source 1 functions as a power source. The average value of the secondary load current Idc2 over one AC period is positive, and the secondary DC power source 2 functions as a load. The average value of the tertiary load current Idc3 over one AC period is positive, and the tertiary DC power source 3 functions as a load. In the second operating mode, the average value of the tertiary load current Idc3 over one AC period is positive, and the tertiary DC power source 3 functions as a load. As will be described later using Figure 5, if "Vdc1 ≥ Vdc2 × N1 / N2", the primary power source 1 functions as a power source, and the average value of the primary power supply current Idc1 over one AC period is positive. As will be described later using Figure 8, if "Vdc1 < Vdc2 × N1 / N2", the secondary DC power source 2 functions as a power source, and the average value of the secondary load current Idc2 over one AC period is negative. In order to secure power to supply the tertiary DC power supply 3, if it is insufficient to have only one of the primary power source 1 and the secondary DC power supply 2 function as a power source, both will function as power sources. In the third operating mode, the average value of the primary power supply current Idc1 over one AC period becomes negative, and the primary power source 1 functions as a load; the average value of the secondary load current Idc2 over one AC period becomes negative, and the secondary DC power supply 2 functions as a power source; and the average value of the tertiary load current Idc3 over one AC period becomes positive, and the tertiary DC power supply 3 functions as a load.

[0035] Here, as shown in Figure 1, the primary power supply current Idc1 has a positive current direction from the primary power source 1 to the primary power conversion circuit 10, the secondary load current Idc2 has a positive current direction from the secondary power conversion circuit 20 to the secondary DC power supply 2, and the tertiary load current Idc3 has a positive current direction from the tertiary rectifier circuit 30 to the tertiary DC power supply 3.

[0036] The control circuit 6 determines which of the first, second, or third operating modes to execute, depending on whether the primary power source 1 functions as a power source or load, or whether the secondary DC power source 2 functions as a power source or load. An example of a method for determining the operating mode will be described later, but the operating mode should be determined using various determination methods depending on the state of each power source and load.

[0037] 1-2-2. When the first operation mode control circuit 6 supplies power from the primary power source 1 to the secondary DC power supply 2 and the tertiary DC power supply 3, it executes a first operation mode in which it controls the on / off switching elements 10a to 10d of the primary power conversion circuit 10 to adjust the power supplied to the tertiary DC power supply 3, and controls the on / off switching elements 20a to 20d of the secondary power conversion circuit 20 to adjust the power supplied to the secondary DC power supply 2.

[0038] In this embodiment, the control circuit 6 controls the on / off switching elements 20a to 20d of the secondary power conversion circuit 20 so as to boost the secondary winding voltage Vtr2, which is the voltage generated in the secondary winding 5b, using the secondary boost reactor 21 in the first operating mode. In the first operating mode, a relatively large amount of power can be transmitted to the secondary DC power supply 2 by boosting the voltage of the secondary power conversion circuit 20.

[0039] In the first operating mode, the control circuit 6 calculates a primary duty cycle Duty 1 for adjusting the power supplied to the tertiary DC power supply 3 based on the voltage or current of the tertiary rectifier circuit 30, and calculates a secondary duty cycle Duty 2 for adjusting the power supplied to the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20. Then, based on the primary duty cycle Duty 1, the control circuit 6 sets the primary on period Ton 1 of the switch element of the primary power conversion circuit 10, and based on the secondary duty cycle Duty 2, sets the secondary on period Ton 2 of the secondary power conversion circuit 20.

[0040] In the first operating mode, power is supplied by distributing it from the primary power source 1 to the secondary DC power supply 2 and the tertiary DC power supply 3. The tertiary rectifier circuit 30 cannot actively adjust the supplied power and also supplies power to the secondary DC power supply 2. However, by calculating the primary duty cycle Duty 1 for adjusting the power supplied to the tertiary DC power supply 3, the primary power conversion circuit 10 can be preferentially controlled to adjust the power supplied to the tertiary DC power supply 3. On the other hand, by calculating the secondary duty cycle Duty 2 for adjusting the power supplied to the secondary DC power supply 2, the power supplied to the secondary DC power supply 2 can be adaptively adjusted to match the power supplied from the primary power source 1, which has been adjusted to adjust the power supplied to the tertiary DC power supply 3. Therefore, even in a configuration where a power conversion circuit capable of actively converting power is not provided on the tertiary side, the power supplied from the primary power source 1 to the secondary DC power supply 2 and the power supplied to the tertiary DC power supply 3 can be individually adjusted by controlling the primary and secondary power conversion circuits.

[0041] In the first operating mode, the control circuit 6 sets the duty cycle Duty2 for the secondary side to be less than or equal to the duty cycle Duty1 for the primary side, and sets the secondary side on period Ton2 during the primary side on period Ton1.

[0042] With this configuration, while power is being supplied from the primary power source 1 to the tertiary DC power supply 3 by the primary duty cycle Duty 1, the amount of voltage boost from the secondary boost reactor 21 can be adjusted by the secondary duty cycle Duty 2, thereby adjusting the power supplied to the secondary DC power supply 2.

[0043] In this embodiment, the control circuit 6 calculates the duty cycle Duty 1 for the primary side based on the tertiary load voltage Vdc 3 or the tertiary load current Idc 3. For example, the control circuit 6 changes the duty cycle Duty 1 for the primary side by feedback control so that the tertiary load voltage Vdc 3 approaches the target value Vdc 3* of the tertiary load voltage. Duty 1 is limited to an upper and lower limit range of 0 or more and 1 or less. For example, the control circuit 6 calculates the duty cycle Duty 1 for the primary side by PI control based on the deviation ΔVdc 3 between Vdc 3 and Vdc 3*, as shown in the following equation. Here, Kp 3 is a positive proportional gain, Ki 3 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the primary duty cycle Duty1 by feedback control so that the tertiary load current Idc3 approaches the target value Idc3* for the tertiary load current. ΔVdc3 = Vdc3* - Vdc3 Duty1 = {Kp3 + Ki3 / s} × ΔVdc3 ... (1) 0 ≤ Duty1 ≤ 1

[0044] The control circuit 6 calculates the duty cycle Duty2 for the secondary side based on the secondary load voltage Vdc2 or the secondary load current Idc2. For example, the control circuit 6 changes the duty cycle Duty2 for the secondary side by feedback control so that the secondary load current Idc2 approaches the target value Idc2* for the secondary load current. Idc2* is set to a positive value and changes according to the state of the secondary DC power supply 2 or the control target. Duty2 is limited to an upper and lower limit range of 0 or more and Duty1 or less. For example, the control circuit 6 calculates the duty cycle Duty2 for the secondary side by PI control based on the deviation ΔIdc2 between Idc2 and Idc2*, as shown in the following equation. Here, Kp2 is a positive proportional gain, Ki2 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the duty cycle Duty2 for the secondary side by feedback control so that the secondary load voltage Vdc2 approaches the target value Vdc2* for the secondary load voltage. Idc2*>0 ΔIdc2=Idc2*-Idc2 Duty2={Kp2+Ki2 / s}×ΔIdc2 ...(2) 0≦Duty2≦Duty1

[0045] Then, as shown in the following equation, the control circuit 6 multiplies the period Tachf obtained by subtracting the dead time Td from half of one AC period Tac by the primary-side duty ratio Duty1 to set the primary-side on period Ton1, and multiplies the period Tachf by the secondary-side duty ratio Duty2 to set the secondary-side on period Ton2. Tachf = Tac / 2 - Td Ton1 = Tachf × Duty1 ··· (3) Ton2 = Tachf × Duty2

[0046] <Control Behavior in the First Operation Mode>The control behavior in the first operation mode will be described using FIGS. 2 to 4. FIG. 2 shows the switching pattern of one AC period Tac and the voltage / current waveforms at various locations in the first operation mode. Specifically, the gate signals (on signals) of the switch elements 10a to 10d of the primary-side power conversion circuit 10, the gate signals (on signals) of the switch elements 20a to 20d of the secondary-side power conversion circuit 20, the primary winding voltage Vtr1 which is the voltage across both ends of the primary winding 5a, the primary-side power supply current Idc1 which is the current supplied from the primary-side terminals 15a and 15b to the primary-side power conversion circuit 10, the primary winding current Itr1 which is the current supplied from the primary-side power conversion circuit 10 to the primary winding 5a, the secondary-side load current IdcX which is the current supplied from the secondary-side power conversion circuit to the secondary-side terminals 25a and 25b, and the third-side load current Idc3 which is the current supplied from the third-side rectification circuit 30 to the third-side terminals 35a and 35b are shown.

[0047] The control circuit 6 switches the switch elements of the primary-side and secondary-side power conversion circuits that are on in the first half FH and the second half SH of one AC period Tac, and provides a dead time Td during which all the switch elements of the primary-side and secondary-side power conversion circuits are turned off between the first half FH and the second half SH. This is common to the first operation mode, the second operation mode, and the third operation mode.

[0048] In the first operation mode, the control circuit 6 sets the primary-side on period Ton1 and the secondary-side on period Ton2 immediately after the start of the first half FH or the second half SH.

[0049] It should be noted that in the original text, "2次側負荷電流Idc2" seems to be a miswriting. I translated it as "2次側負荷電流IdcX" according to the context. If there is an error in the original text, please correct it in time.During the primary side ON period Ton1 of the first half FH, the diagonally opposite primary side first leg positive electrode switch element 10a and primary side second leg negative electrode switch element 10d are turned on, and a positive primary side power supply voltage Vdc1 is applied to the voltage Vtr1 of the primary winding 5a. During the primary side ON period Ton1 of the second half SH, the primary side second leg positive electrode switch element 10c and primary side first leg negative electrode switch element 10b are turned on, and a negative primary side power supply voltage Vdc1 is applied to the voltage Vtr1 of the primary winding 5a.

[0050] During the first half FH secondary-on period Ton2, the secondary-side first leg negative electrode switch element 20b is turned on, and the positive reactor current IL2 flowing through the secondary winding 5b and the secondary-side boost reactor 21 recirculates through the secondary-side power conversion circuit 20, boosting the secondary-side boost reactor 21 to the positive side and increasing the power transmitted to the secondary-side DC power supply 2. During the second half SH secondary-on period Ton2, the secondary-side first leg positive electrode switch element 20a is turned on, and the negative reactor current IL2 flowing through the secondary winding 5b and the secondary-side boost reactor 21 recirculates through the secondary-side power conversion circuit 20, boosting the secondary-side boost reactor 21 to the negative side and increasing the power transmitted to the secondary-side DC power supply 2. In other words, during the secondary side ON period Ton2, the secondary side power conversion circuit 20 operates as a boost chopper, and as the secondary side ON period Ton2 increases, the power transmitted to the secondary side DC power supply 2 increases.

[0051] In this embodiment, the control circuit 6 provides a primary side recirculation period Tcr1 immediately after the end of the primary side ON period Ton1, which turns on the switch element of the primary side power conversion circuit 10 so that the current of the primary winding 5a recirculates within the primary side power conversion circuit 10. The control circuit 6 sets the primary side recirculation period Tcr1 to be the period from immediately after the end of the primary side ON period Ton1 to the start of the dead time Td. In the first half of the primary side recirculation period Tcr1 FH, the primary side second leg negative electrode side switch element 10d is turned on, and in the second half of the primary side recirculation period Tcr1 SH, the primary side second leg positive electrode side switch element 10c is turned on.

[0052] With this configuration, during the primary side recirculation period Tcr1, the current in the primary winding 5a is recirculated within the primary side power conversion circuit 10, preventing the boosted energy on the secondary winding 5b side from returning to the primary side power source 1 via the primary winding 5a and the primary side power conversion circuit 10, thereby increasing the power transmitted to the secondary winding 5b. Therefore, by providing the primary side recirculation period Tcr1, the range of power supplied to the secondary side DC power source 2 can be expanded.

[0053] Since the first half FH and the second half SH have similar shapes, the time t0 to t4 of the first half FH will be explained in detail below.

[0054] Figure 3 shows the current flow during the period from time t0 to t2 in Figure 2. Time t0 to t2 is the primary side ON period Ton1 of the first half FH, during which the primary side positive electrode switch element 10a of the first leg and the primary side negative electrode switch element 10d of the second leg are simultaneously turned ON, thereby applying the primary side power supply voltage Vdc1 to the primary winding 5a and transmitting power from the primary side power source 1.

[0055] A voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N2 of the primary winding 5a and the tertiary winding 5c ​​is applied to the tertiary winding 5c. Power is then supplied to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 obtained by the tertiary rectifier circuit 30.

[0056] A voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N2 of the primary winding 5a and secondary winding 5b is applied to the secondary winding 5b. From time t0 to t1 is the secondary ON period Ton2 of the first half FH, during which the secondary first leg negative electrode switch element 20b is turned ON, exciting the secondary boost reactor 21 with the secondary winding voltage Vtr2 (dashed line path in Figure 2), and the secondary boost reactor 21 is boosted to the positive side. Subsequently, from time t1 to t2, the secondary first leg negative electrode switch element 20b is turned OFF, causing the secondary power conversion circuit 20 to rectify and operate as a boost chopper, transmitting the stored energy of the secondary boost reactor 21 to the secondary DC power supply 2 (solid line path in Figure 2). Note that while Figure 2 shows an example where the secondary reactor current IL2 and secondary load current Idc2 increase between times t1 and t2, this represents the case where the secondary winding voltage Vtr2 is higher than the secondary load voltage Vdc2. When the secondary winding voltage Vtr2 is lower than the secondary load voltage Vdc2, the secondary reactor current IL2 and secondary load current Idc2 decrease.

[0057] Next, Figure 4 shows the current flow during the period from time t2 to t4. From time t2 to t4 is the primary side recirculation period Tcr1 of the first half FH. At time t2, the first leg positive electrode switch element 10a on the primary side is turned off, but the second leg negative electrode switch element 10d on the primary side remains on until time t4. This causes the current induced in the primary winding 5a by the current conducting to the secondary winding 5b and tertiary winding 5c ​​to recirculate within the primary side power conversion circuit 10. At this time, the primary side power supply voltage Vdc1 applied to the primary winding 5a is approximately 0V.

[0058] A voltage of approximately 0V is applied to the tertiary winding 5c, and the tertiary rectified voltage Vtr3 after rectification by the tertiary rectifier circuit 30 is also approximately 0V, so the stored energy of the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3.

[0059] A voltage of approximately 0V is applied to the secondary winding 5b, and between times t2 and t3, the secondary power conversion circuit 20 performs rectification and transmits the stored energy of the secondary boost reactor 21 to the secondary DC power supply 2 (path shown by the dashed line in Figure 3). At time t3, when the stored energy of the secondary boost reactor 21 is depleted, the secondary reactor current IL2 and secondary load current Idc2 become 0A.

[0060] If the primary-side second-leg negative electrode switch element 10d is turned off between times t2 and t4, and the primary-side recirculation period Tcr1 is not provided, then between times t2 and t3, both the primary-side power conversion circuit 10 and the secondary-side power conversion circuit 20 will be in rectification operation, and the stored energy of the secondary-side boost reactor 21 will be transmitted to the secondary-side DC power supply 2 and simultaneously to the primary-side power source 1. At this time, the power that was output to the primary-side power source 1 is returned, and the power that can be output to the secondary-side DC power supply 2 will decrease. In other words, by providing the primary-side recirculation period Tcr1 between times t2 and t4, the range of power that can be transmitted to the secondary-side DC power supply 2 can be expanded.

[0061] The period from time t4 to t5 is a dead time Td in preparation for power transmission of the second half SH, during which all primary and secondary switching elements are turned off. There is no current conduction in the primary power conversion circuit 10 and the secondary power conversion circuit 20, and the stored energy of the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3 while both the tertiary rectifier diodes 30a and 30b conduct.

[0062] Note that Figures 2 to 4 show the current path when capacitors 11, 22, 23, and 32 are not involved. In reality, the AC component of the current flows into each capacitor based on the impedance characteristics of the circuit and is smoothed.

[0063] 1-2-3. The second operation mode control circuit 6, when supplying power to the tertiary DC power supply 3 from either or both of the primary power source 1 and the secondary DC power supply 2, executes a second operation mode in which it controls the on / off switching of the switch elements 10a to 10d of the primary power conversion circuit 10 and the switch elements 20a to 20d of the secondary power conversion circuit 20 in order to adjust the power supplied to the tertiary DC power supply 3, and controls the on / off switching of the switch elements 20a to 20d of the secondary power conversion circuit 20 in order to adjust the power supplied from the secondary DC power supply 2.

[0064] In this embodiment, the control circuit 6 controls the on / off switching elements 20a to 20d of the secondary power conversion circuit 20 so as not to boost the voltage generated in the secondary winding 5b in the second operating mode. By not boosting the voltage, the power transmission to the secondary DC power supply 2 can be reduced compared to when the voltage is boosted, and the power supplied from the secondary DC power supply 2 can be controlled.

[0065] In the second operating mode, the control circuit 6 sets a total on-period Tonal for adjusting the total power supplied from one or both of the primary power source 1 and the secondary DC power source 2 to the tertiary DC power source 3 in the first half FH and the second half SH of one AC cycle Tac, respectively, and divides the total on-period Tonal into a primary on-period Ton1 of the primary power conversion circuit 10 for adjusting the power supplied from the primary power source 1 and a secondary on-period Ton2 of the secondary power conversion circuit 20 for adjusting the power supplied from the secondary DC power source 2.

[0066] With this configuration, the total power supplied from one or both of the primary power source 1 and the secondary DC power source 2 to the tertiary DC power source 3 can be adjusted by the total ON period Tonal. By dividing the total ON period Tonal into primary ON period Ton1 and secondary ON period Ton2, the power supplied from primary ON period Ton1 and the power supplied from secondary DC power source 2 can be adjusted individually.

[0067] The control circuit 6 adjusts the total on-time Tonall to adjust the total power supplied to the tertiary DC power supply 3, adjusts the secondary on-time Ton2 to adjust the power supplied from the secondary DC power supply 2, and adjusts the primary on-time Ton1 by subtracting the secondary on-time Ton2 from the total on-time Tonall.

[0068] With this configuration, the total power supplied to the tertiary DC power supply 3 can be adjusted by adjusting the total ON period Tonall, the power supplied from the secondary DC power supply 2 can be preferentially adjusted by adjusting the secondary ON period Ton2, and the power supplied from the primary power source 1 can be subordinately adjusted while preferentially adjusting the total power supplied to the tertiary DC power supply 3 and the power supplied from the secondary DC power supply 2.

[0069] In the second operating mode, the control circuit 6 calculates a tertiary adjustment duty cycle Duty3adj for adjusting the power supplied to the tertiary DC power supply 3 based on the voltage or current of the tertiary rectifier circuit 30, and calculates a secondary duty cycle Duty2 for adjusting the power supplied from the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20. The control circuit 6 then calculates a primary duty cycle Duty1 by subtracting the secondary duty cycle Duty2 from the tertiary adjustment duty cycle Duty3adj. Based on the primary duty cycle Duty1, the control circuit 6 sets the primary on-period Ton1 of the switch element of the primary power conversion circuit 10, and sets the secondary on-period Ton2 of the secondary power conversion circuit 20 based on the secondary duty cycle Duty2.

[0070] In the second operating mode, power is supplied to the tertiary DC power supply 3 from either or both of the primary power source 1 and the secondary DC power supply 2. The tertiary rectifier circuit 30 cannot actively adjust the supplied power, but it can adjust the power supplied to the tertiary DC power supply 3 by calculating a tertiary adjustment duty cycle Duty3adj for adjusting the power supplied to the tertiary DC power supply 3. On the other hand, by calculating a secondary duty cycle Duty2 for adjusting the power supplied from the secondary DC power supply 2, the power supplied from the secondary DC power supply 2 can be adjusted preferentially over the power supplied from the primary power source 1. By subtracting the duty cycle Duty2 for the secondary side from the duty cycle Duty3adj for adjusting the tertiary side to calculate the duty cycle Duty1 for the primary side, the power supplied from the primary side power source 1 can be adaptively adjusted to match the power supplied from the secondary side DC power source 2, which is preferentially adjusted, and the amount of power supplied to the tertiary side DC power source 3 that is required. Therefore, even in a configuration where a power conversion circuit is not provided on the tertiary side, the power supplied from the primary side power source 1 and the secondary side DC power source 2 to the tertiary side DC power source 3, and the power supplied from the secondary side DC power source 2 can be individually adjusted by controlling the primary and secondary side power conversion circuits.

[0071] In the second operating mode, the control circuit 6 sets the duty cycle Duty2 for the secondary side to less than or equal to the duty cycle Duty3adj for tertiary side adjustment, and sets the on-period for the other side immediately after the end of the on-period for either the primary side on-period Ton1 or the secondary side on-period Ton2.

[0072] With this configuration, the total power supply period to the tertiary DC power supply 3 by the duty cycle Duty 3adj for tertiary adjustment can be divided into the power supply period from the secondary DC power supply 2 by the duty cycle Duty 2 for the secondary side and the power supply period from the primary power source 1 by the duty cycle Duty 1 for the primary side, allowing the power supplied from the primary ON period Ton1 and the power supplied from the secondary DC power supply 2 to be adjusted individually.

[0073] In this embodiment, the control circuit 6 calculates the duty cycle Duty3adj for tertiary adjustment based on the tertiary load voltage Vdc3 or the tertiary load current Idc3. For example, the control circuit 6 changes the duty cycle Duty3adj for tertiary adjustment by feedback control so that the tertiary load voltage Vdc3 approaches the target value Vdc3* of the tertiary load voltage. Duty3adj is limited to an upper and lower limit range of 0 or more and 1 or less. For example, the control circuit 6 calculates the duty cycle Duty3adj for tertiary adjustment by PI control based on the deviation ΔVdc3 between Vdc3 and Vdc3*, as shown in the following equation. Here, Kp3 is a positive proportional gain, Ki3 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the duty cycle Duty3adj for tertiary adjustment by feedback control so that the tertiary load current Idc3 approaches the target value Idc3* for the tertiary load current. ΔVdc3 = Vdc3* - Vdc3 Duty3adj = {Kp3 + Ki3 / s} × ΔVdc3 ... (4) 0 ≤ Duty3adj ≤ 1

[0074] The control circuit 6 calculates the duty cycle Duty2 for the secondary side based on the secondary load voltage Vdc2 or the secondary load current Idc2. For example, the control circuit 6 changes the duty cycle Duty2 for the secondary side by feedback control so that the secondary load current Idc2 approaches the target value Idc2* for the secondary load current. Idc2* is changed according to the state of the secondary DC power supply 2 or the control target. Duty2 is limited to an upper and lower limit range of 0 or more and Duty3adj or less. For example, the control circuit 6 calculates the duty cycle Duty2 for the secondary side by PI control based on the deviation ΔIdc2 between Idc2 and Idc2*, as shown in the following equation. Here, Kp2 is a positive proportional gain, Ki2 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the duty cycle Duty2 for the secondary side by feedback control so that the secondary load voltage Vdc2 approaches the target value Vdc2* for the secondary load voltage. ΔIdc2 = Idc2* - Idc2 Duty2 = -{Kp2 + Ki2 / s} × ΔIdc2 ... (5) 0 ≤ Duty2 ≤ Duty3adj

[0075] Control circuit 6 calculates the primary duty cycle Duty 1 by subtracting the secondary duty cycle Duty 2 from the tertiary duty cycle Duty 3adj, as shown in the following equation: Duty 1 = Duty 3adj - Duty 2 ... (6)

[0076] Then, as shown in the following equations, the control circuit 6 sets the primary side on period Ton1 by multiplying the period Tachf, which is obtained by subtracting the dead time Td from half a period of one AC period Tac, by the duty cycle Duty1 for the primary side, and sets the secondary side on period Ton2 by multiplying the period Tachf by the duty cycle Duty2 for the secondary side. Tachf = Tac / 2 - Td Ton1 = Tachf × Duty1 ... (7) Ton2 = Tachf × Duty2

[0077] <Control behavior of the second operating mode when "Vdc1 ≥ Vdc2 × N1 / N2"> Figures 5 to 7 will be used to explain the control behavior of the second operating mode when "Vdc1 ≥ Vdc2 × N1 / N2", and Figures 8 to 10 will be used to explain the control behavior of the second operating mode when "Vdc1 < Vdc2 × N1 / N2". Note that the current and voltage waveforms and current paths change depending on the relative magnitudes of Vdc1 and Vdc2, but the switching pattern in the second operating mode does not change depending on the relative magnitudes.

[0078] Figure 5 shows the switching pattern and voltage / current waveforms at each point in the second operating mode when "Vdc1 ≥ Vdc2 × N1 / N2".

[0079] In the second operating mode, the control circuit 6 sets a secondary ON period Ton2 immediately after the start of the first half FH or the second half SH, and sets a primary ON period Ton1 immediately after the end of the primary ON period Ton1.

[0080] During the secondary-on period Ton2 of the first half FH, the diagonally opposite secondary first leg positive electrode switch element 20a and secondary second leg negative electrode switch element 20d are turned on, and a positive secondary load voltage Vdc2 is applied to the voltage Vtr2 of the secondary winding 5b. During the secondary-on period Ton2 of the second half SH, the diagonally opposite secondary first leg negative electrode switch element 20b and secondary second leg positive electrode switch element 20c are turned on, and a negative secondary load voltage Vdc2 is applied to the voltage Vtr2 of the secondary winding 5b.

[0081] During the primary side ON period Ton1 of the first half FH, the diagonally opposite primary side first leg positive electrode switch element 10a and primary side second leg negative electrode switch element 10d are turned on, and a positive primary side power supply voltage Vdc1 is applied to the voltage Vtr1 of the primary winding 5a. During the primary side ON period Ton1 of the second half SH, the primary side second leg positive electrode switch element 10c and primary side first leg negative electrode switch element 10b are turned on, and a negative primary side power supply voltage Vdc1 is applied to the voltage Vtr1 of the primary winding 5a.

[0082] In this embodiment, in the second operating mode, the control circuit 6 performs either or both (in this example, both) of the following: primary side recirculation, which sets a primary side recirculation period Tcr1 to turn on the switch element of the primary side power conversion circuit 10 so that the current of the primary winding 5a recirculates through the primary side power conversion circuit 10 immediately after the end of the primary side ON period Ton1; and secondary side recirculation, which sets a secondary side recirculation period Tcr2 to turn on the switch element of the secondary side power conversion circuit 20 so that the current of the secondary winding 5b recirculates through the secondary side power conversion circuit 20 immediately after the end of the secondary side ON period Ton2.

[0083] The control circuit 6 sets the period from immediately after the end of the secondary side ON period Ton2 to the start of the dead time Td as the secondary side recirculation period Tcr2. During the first half of the secondary side recirculation period Tcr2 FH, the positive electrode switch element 20a of the first leg of the secondary side is turned on, and during the second half of the secondary side recirculation period Tcr2 SH, the negative electrode switch element 20b of the first leg of the secondary side is turned on.

[0084] With this configuration, during the secondary side recirculation period Tcr2, the current in the secondary winding 5b is recirculated within the secondary side power conversion circuit 20, preventing the stored energy of the secondary side boost reactor 21 from returning to the secondary side DC power supply 2, thereby increasing the power transmitted to the tertiary winding 5c. On the other hand, if the secondary side recirculation period Tcr2 is not provided, the secondary side power conversion circuit 20 operates in rectification mode, the stored energy of the secondary side boost reactor 21 is transmitted to the secondary side DC power supply 2, and the power output from the secondary side DC power supply 2 is returned, resulting in wasted power exchange. Therefore, by providing the secondary side recirculation period Tcr2, the range of power that can be supplied from the secondary side DC power supply 2 can be expanded.

[0085] The control circuit 6 sets the period from immediately after the end of the primary side ON period Ton1 to the start of the dead time Td as the primary side recirculation period Tcr1. During the primary side recirculation period Tcr1 of the first half FH, the primary side second leg negative electrode side switch element 10d is turned on, and during the primary side recirculation period Tcr1 of the second half SH, the primary side second leg positive electrode side switch element 10c is turned on.

[0086] During the primary side recirculation period Tcr1, the current in the primary winding 5a is recirculated within the primary side power conversion circuit 10. This prevents the stored energy of the secondary side boost reactor 21 from returning to the primary side power source 1 via the primary winding 5a and the primary side power conversion circuit 10, thereby increasing the power transmitted to the tertiary side DC power supply 3. On the other hand, if the primary side recirculation period Tcr1 is not provided, the primary side power conversion circuit 10 operates in rectification mode, the stored energy of the secondary side boost reactor 21 is transmitted to the primary side power source 1, and the power output from the primary side power source 1 is returned, resulting in wasted power exchange. Therefore, by providing the primary side recirculation period Tcr1, the range of power that can be supplied from the primary side power source 1 can be expanded.

[0087] Since the first half FH and the second half SH have similar shapes, the time intervals t0 to t5 of the first half FH will be explained in detail below.

[0088] Figure 6 shows the current flow during the period from time t0 to t1 in Figure 5. Time t0 to t1 is the secondary side ON period Ton2 of the first half FH, during which the first leg positive electrode switch element 20a and the second leg negative electrode switch element 20d of the secondary side are simultaneously turned ON. As a result, the secondary load voltage Vdc2 and the negative secondary winding voltage Vtr2 generated by the secondary boost reactor 21 are applied to the secondary winding 5b, and power is transmitted from the secondary DC power supply 2.

[0089] A voltage determined by the secondary winding voltage Vtr2 and the turns ratio N2 / N3 of the secondary winding 5b and the tertiary winding 5c ​​is applied to the tertiary winding 5c. Power is then supplied to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the rectified tertiary voltage Vtr3 obtained by the rectifier circuit 30 on the tertiary side.

[0090] At this time, a voltage determined by the secondary load voltage Vdc2, the tertiary load voltage Vdc3, the turns ratio N2 / N3 of the secondary winding 5b and the tertiary winding 5c, and the voltage division ratio between the secondary boost reactor 21 and the tertiary smoothing reactor 31 is applied to the tertiary winding 5c. A voltage determined by the secondary winding voltage Vtr2 of the secondary winding 5b and the turns ratio N1 / N2 of the secondary winding 5b and the primary winding 5a is applied to the primary winding 5a, but because the voltage relationship is "Vdc1 ≥ Vdc2 × N1 / N2", no current is conducted to the primary power conversion circuit 10.

[0091] Next, Figure 7 shows the current flow during the period from time t1 to t3. Time t1 to t3 is the primary side ON period Ton1 of the first half FH, during which the first leg positive electrode switch element 10a and the second leg negative electrode switch element 10d of the primary side are simultaneously turned ON, thereby applying the primary side power supply voltage Vdc1 to the primary winding 5a and transmitting power from the primary side power source 1.

[0092] Time t1 to t5 is the secondary side recirculation period Tcr2 of the first half FH. At time t1, the secondary side second leg negative electrode side switch element 20d is turned off, but the secondary side first leg positive electrode side switch element 20a remains on until time t5.

[0093] A voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N3 of the primary winding 5a and the tertiary winding 5c ​​is applied to the tertiary winding 5c. Power is then supplied to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 obtained by the tertiary rectifier circuit 30.

[0094] A voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N2 of the primary winding 5a and secondary winding 5b is applied to the secondary winding 5b. At time t1, the secondary reactor current IL2 flowing through the secondary boost reactor 21 is conducting in the negative direction. Therefore, from time t1 to t2, the negative secondary reactor current IL2 causes the diode of the secondary second leg positive electrode switch element 20c and the ON-state secondary first leg positive electrode switch element 20a to conduct, resulting in a recirculation operation (path shown by the dashed line in Figure 7). Power is then transmitted to the tertiary DC power supply 3 by the secondary winding voltage Vtr2, and the stored energy of the secondary boost reactor 21 is reduced until IL2 = 0A. Furthermore, between times t2 and t3, due to the voltage relationship "Vdc1 ≥ Vdc2 × N1 / N2", the secondary power conversion circuit 20 operates in rectification mode, and power is transmitted from the primary power source 1 to the secondary DC power supply 2 (the solid line path in Figure 7). The next period between times t3 and t6 is the same as the operation between times t2 and t5 of the first operating mode described above using Figure 2.

[0095] <Control behavior of the second operating mode when "Vdc1 < Vdc2 × N1 / N2"> Next, Figure 8 shows the switching pattern and voltage / current waveforms at each point in the second operating mode when "Vdc1 < Vdc2 × N1 / N2". The switching patterns of the primary and secondary power conversion circuits are the same as in Figure 5 when "Vdc1 ≥ Vdc2 × N1 / N2", so the explanation is omitted.

[0096] Figure 9 shows the current flow during the period from time t0 to t1 in Figure 8. Time t0 to t1 is the secondary side ON period Ton2 of the first half FH, during which the first leg positive electrode switch element 20a and the second leg negative electrode switch element 20d of the secondary side are simultaneously turned ON. This applies the secondary load voltage Vdc2 and the negative secondary winding voltage Vtr2 generated by the secondary boost reactor 21 to the secondary winding 5b, thereby transmitting power from the secondary DC power supply 2.

[0097] At this time, since the voltage relationship is "Vdc1 < Vdc2 × N1 / N2", the primary power conversion circuit 10 operates in rectification mode, and the primary winding voltage Vtr1 becomes equal to the primary power supply voltage Vdc1.

[0098] A voltage determined by the primary winding voltage Vtr1 and the turns ratio N1 / N3 of the primary winding 5a and the tertiary winding 5c ​​is applied to the tertiary winding 5c. Power is then supplied from the secondary DC power supply 2 to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 obtained by the tertiary rectifier circuit 30.

[0099] Since the voltage relationship is "Vdc1 < Vdc2 × N1 / N2", as described above, the primary power conversion circuit 10 operates in rectification mode, and power is transmitted from the secondary DC power supply 2 to the primary power source 1.

[0100] Next, Figure 10 shows the current flow during the period from time t1 to t3. Time t1 to t3 is the primary side ON period Ton1 of the first half FH, during which the first leg positive electrode switch element 10a and the second leg negative electrode switch element 10d on the primary side are simultaneously turned ON, thereby applying the primary side power supply voltage Vdc1 to the primary winding 5a and transmitting power from the primary side power source 1.

[0101] Time t1 to t4 is the secondary side recirculation period Tcr2 of the first half FH. At time t1, the secondary side second leg negative electrode side switch element 20d is turned off, but the secondary side first leg positive electrode side switch element 20a remains on until time t4.

[0102] A voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N3 of the primary winding 5a and the tertiary winding 5c ​​is applied to the tertiary winding 5c. Power is then supplied to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 obtained by the tertiary rectifier circuit 30.

[0103] The secondary winding 5b is subjected to a secondary winding voltage Vtr2 determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N2 of the primary winding 5a and secondary winding 5b. At time t1, the secondary reactor current IL2 flowing through the secondary boost reactor 21 is conducting in the negative direction. Between times t1 and t2, the negative secondary reactor current IL2 causes the diode of the secondary second leg positive electrode switch element 20c and the ON-state secondary first leg positive electrode switch element 20a to conduct, resulting in a recirculation operation (path shown by the dashed line in Figure 10). Power is then transmitted to the tertiary DC power supply 3 by the secondary winding voltage Vtr2, and the stored energy of the secondary boost reactor 21 is reduced until IL2 = 0A. Furthermore, between times t2 and t3, the voltage relationship is "Vdc1 < Vdc2 × N1 / N2", so the secondary power conversion circuit 20 does not conduct current, and no power is transmitted to the secondary DC power supply 2. Here, the relationship of current at time t1 is as follows: Itr1 = IL2 × N2 / N1 + IL3 × N3 / N1 (8)

[0104] The primary winding current Itr1 is the current that compensates for the difference between the tertiary reactor current IL3, which corresponds to the charging current of the tertiary DC power supply 3, and the secondary reactor current IL2, which is a negative value. In other words, at time t1, the secondary reactor current IL2 is conducting to charge the primary power source 1 and the tertiary DC power supply 3. However, the secondary reactor current IL2 recirculates within the secondary power conversion circuit 20 from time t1 to t2, transmitting the stored energy of the secondary boost reactor 21 to the primary winding 5a and tertiary winding 5c. Meanwhile, the tertiary reactor current IL3 continues to conduct due to the tertiary smoothing reactor 31, and the primary winding current Itr1 of the primary winding 5a conducts in a manner that satisfies the relationship in equation (8). From time t1 to t2, the primary winding current Itr1 changes from a negative to a positive current, changing from the dashed line path to the solid line path in Figure 10. The next period from time t3 to t5 is the same as the operation from time t3 to t5 of the first operating mode described above using Figure 2.

[0105] <Alternating Positive and Negative Power Transmission> As explained with reference to Figures 5 and 8, in the second operating mode, the control circuit 6 controls the on / off switching of the switch elements of the primary power conversion circuit 10 and the secondary power conversion circuit 20 so that the primary power supply current Idc1 at the primary terminals 15a and 15b or the secondary load current Idc2 at the secondary terminals 25a and 25b alternately flow in positive and negative directions within half a cycle of one AC period Tac. This adjusts one or both of the power supplied from the primary power source 1 and the power supplied from the secondary DC power source 2.

[0106] As shown in Figure 5, when "Vdc1 ≥ Vdc2 × N1 / N2", the secondary load current Idc2 flows alternately positive and negative within half a cycle of one AC period Tac (within the first half FH and the second half SH). As shown in Figure 8, when "Vdc1 < Vdc2 × N1 / N2", the primary power supply current Idc1 flows alternately positive and negative within half a cycle of one AC period Tac (within the first half FH and the second half SH).

[0107] In this way, by alternately transmitting power in positive and negative directions from the primary power source 1 or the secondary DC power source 2 within half a cycle of one AC cycle Tac, the power supplied from the primary power source 1 or the secondary DC power source 2 can be adjusted within half a cycle of one AC cycle Tac, enabling power distribution adjustment with minimal fluctuations.

[0108] 1-2-4. When the third operation mode control circuit 6 supplies power from the secondary DC power supply 2 to the primary power source 1 and the tertiary DC power supply 3, it executes a third operation mode in which it controls the on / off switching of the switch elements 20a to 20d of the secondary power conversion circuit 20 to adjust the power supplied to the tertiary DC power supply 3, and controls the on / off switching of the switch elements 10a to 10d of the primary power conversion circuit 10 to adjust the power supplied from the secondary DC power supply 2.

[0109] In this embodiment, the control circuit 6 controls the on / off switching of the switch elements 10a to 10d of the primary-side power conversion circuit 10 to boost the voltage generated in the secondary winding 5b in the third operating mode. By boosting the voltage, the power supplied from the secondary-side DC power supply 2 can be increased compared to when the voltage is not boosted.

[0110] In the third operating mode, the control circuit 6 calculates a secondary duty cycle Duty 2 for adjusting the power supplied to the tertiary DC power supply 3 based on the voltage or current of the tertiary rectifier circuit 30, and calculates a primary duty cycle Duty 1 for adjusting the power supplied from the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20. Then, based on the primary duty cycle Duty 1, the control circuit 6 sets the primary on period Ton 1 of the switch element of the primary power conversion circuit 10, and based on the secondary duty cycle Duty 2, sets the secondary on period Ton 2 of the secondary power conversion circuit 20.

[0111] In the third operating mode, power is supplied from the secondary DC power supply 2 to the primary power source 1 and the tertiary DC power supply 3. The tertiary rectifier circuit 30 cannot actively adjust the supplied power and also supplies power to the primary power source 1. However, by calculating the duty cycle Duty 2 for the secondary side to adjust the power supplied to the tertiary DC power supply 3, the secondary power conversion circuit 20 can be controlled preferentially to adjust the power supplied to the tertiary DC power supply 3. On the other hand, by calculating the duty cycle Duty 1 for the primary side to adjust the power supplied from the secondary DC power supply 2, the power supplied from the secondary DC power supply 2 can be adjusted while simultaneously adjusting the power supplied to the tertiary DC power supply 3. Therefore, even in a configuration where a power conversion circuit is not provided on the tertiary side, the power supplied to the tertiary DC power supply 3 and the power supplied from the secondary DC power supply 2 can be adjusted individually by controlling the primary and secondary power conversion circuits.

[0112] In the third operating mode, the control circuit 6 sets the duty cycle Duty1 for the primary side to be less than or equal to the duty cycle Duty2 for the secondary side, and sets the primary side on period Ton1 during the secondary side on period Ton2.

[0113] With this configuration, while power is being supplied from the secondary DC power supply 2 to the tertiary DC power supply 3 by the secondary duty cycle Duty 2, the amount of voltage boost from the secondary boost reactor 21 can be adjusted by the primary duty cycle Duty 1, thereby adjusting the power supplied from the secondary DC power supply 2.

[0114] In this embodiment, the control circuit 6 calculates the duty cycle Duty 2 for the secondary side based on the tertiary load voltage Vdc 3 or the tertiary load current Idc 3. For example, the control circuit 6 changes the duty cycle Duty 2 for the secondary side by feedback control so that the tertiary load voltage Vdc 3 approaches the target value Vdc 3* of the tertiary load voltage. Duty 2 is limited to an upper and lower limit within the range of 0 or more and 1 or less. For example, the control circuit 6 calculates the duty cycle Duty 2 for the secondary side by PI control based on the deviation ΔVdc 3 between Vdc 3 and Vdc 3*, as shown in the following equation. Here, Kp 3 is a positive proportional gain, Ki 3 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the duty cycle Duty2 for the secondary side by feedback control so that the tertiary load current Idc3 approaches the target value Idc3* for the tertiary load current. ΔVdc3 = Vdc3* - Vdc3 Duty2 = {Kp3 + Ki3 / s} × ΔVdc3 ... (9) 0 ≤ Duty2 ≤ 1

[0115] The control circuit 6 calculates the primary duty cycle Duty 1 based on the secondary load voltage Vdc2 or the secondary load current Idc2. For example, the control circuit 6 changes the primary duty cycle Duty 1 by feedback control so that the secondary load current Idc2 approaches the target value Idc2* for the secondary load current. Idc2* is set to a negative value and changes according to the state of the secondary DC power supply 2 or the control target. Duty 1 is limited to an upper and lower limit range of 0 or more and Duty 2 or less. For example, the control circuit 6 calculates the primary duty cycle Duty 1 by PI control based on the deviation ΔIdc2 between Idc2 and Idc2*, as shown in the following equation. Here, Kp2 is a positive proportional gain, Ki2 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the primary duty cycle Duty1 by feedback control so that the secondary load voltage Vdc2 approaches the target value Vdc2* for the secondary load voltage. Idc2* ≤ 0 ΔIdc2 = Idc2* - Idc2 Duty1 = -{Kp2 + Ki2 / s} × ΔIdc2 ... (10) 0 ≤ Duty1 ≤ Duty2

[0116] Then, as shown in the following equations, the control circuit 6 sets the primary side on period Ton1 by multiplying the period Tachf, which is obtained by subtracting the dead time Td from half a period of one AC period Tac, by the duty cycle Duty1 for the primary side, and sets the secondary side on period Ton2 by multiplying the period Tachf by the duty cycle Duty2 for the secondary side. Tachf = Tac / 2 - Td Ton1 = Tachf × Duty1 ... (11) Ton2 = Tachf × Duty2

[0117] <Control Behavior in the Third Operating Mode> The control behavior in the third operating mode will be explained using Figures 11 to 13. The case where "Vdc1 ≥ Vdc2 × N1 / N2" will be explained.

[0118] In the third operating mode, the control circuit 6 sets a secondary side ON period Ton2 and a primary side ON period Ton1 immediately after the start of the first half FH or the second half SH.

[0119] During the secondary-on period Ton2 of the first half FH, the diagonally opposite secondary-side positive-side switch element 20a of the first leg and secondary-side negative-side switch element 20d of the second leg are turned on, and a negative secondary winding voltage Vtr2 is applied to the secondary winding 5b. During the secondary-on period Ton2 of the second half SH, the secondary-side positive-side switch element 20c of the second leg and secondary-side negative-side switch element 20b of the first leg are turned on, and a positive secondary winding voltage Vtr2 is applied to the secondary winding 5b.

[0120] During the first half FH's primary-side ON period Ton1, the primary-side first leg negative electrode switch element 10b is turned on, and the negative primary winding current Itr1 flowing through the primary winding 5a recirculates through the primary-side power conversion circuit 10, boosting the secondary-side boost reactor 21 to the negative side and increasing the power supplied from the secondary-side DC power supply 2. During the second half SH's primary-side ON period Ton1, the primary-side first leg positive electrode switch element 10a is turned on, and the positive primary winding current Itr1 flowing through the primary winding 5a recirculates through the primary-side power conversion circuit 10, boosting the secondary-side boost reactor 21 to the positive side and increasing the power supplied from the secondary-side DC power supply 2. In other words, during the primary side ON period Ton1, the secondary side power conversion circuit 20 operates as a boost chopper, and as the primary side ON period Ton1 increases, the power supplied from the secondary side DC power supply 2 increases.

[0121] In this embodiment, the control circuit 6 provides a secondary side recirculation period Tcr2 immediately after the end of the secondary side ON period Ton2, in which it turns on the switch element of the secondary side power conversion circuit 20 so that the current of the secondary winding 5b recirculates within the secondary side power conversion circuit 20. The control circuit 6 sets the secondary side recirculation period Tcr2 to be the period from immediately after the end of the secondary side ON period Ton2 to the start of the dead time Td. In the first half of the secondary side recirculation period Tcr2 FH, the secondary side second leg negative electrode side switch element 10d is turned on, and in the second half of the secondary side recirculation period Tcr2 SH, the secondary side second leg positive electrode side switch element 20c is turned on.

[0122] With this configuration, during the secondary side recirculation period Tcr2, the current in the secondary winding 5b is recirculated within the secondary side power conversion circuit 20. This prevents the boosted energy on the secondary winding 5b from returning to the secondary side DC power supply 2 via the secondary winding 5b and the secondary side power conversion circuit 20, thereby increasing the power transmitted from the secondary side DC power supply 2. Therefore, by providing the secondary side recirculation period Tcr2, the range of power supplied from the secondary side DC power supply 2 can be expanded.

[0123] Figure 12 shows the current flow during the period from time t0 to t2 in Figure 11. From time t0 to t1 is the primary side ON period Ton1 of the first half FH, when the primary side first leg negative electrode switch element 10b turns ON, the terminals of the primary winding 5a are short-circuited, and the primary winding voltage Vtr1 and secondary winding voltage Vtr2 become approximately 0V (path of the dashed line in Figure 12). The secondary side boost reactor 21 is excited by the secondary side load voltage Vdc2, and from time t1 to t2, the primary side first leg negative electrode switch element 10b turns OFF, causing the primary side power conversion circuit 10 to rectify and operate as a boost chopper that transmits the stored energy of the secondary side boost reactor 21 to the primary side power source 1 (path of the solid line in Figure 12).

[0124] Between times t0 and t1, the tertiary rectified voltage Vtr3 of the tertiary winding 5c ​​is also approximately 0V, so the energy stored in the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3 while both the tertiary rectifier diodes 30a and 30b conduct (paths shown by the dashed and solid lines in Figure 12). Between times t1 and t2, a voltage determined by the primary power supply voltage Vdc1 and the turns ratio N1 / N3 of the primary winding 5a and tertiary winding 5c ​​is applied to the tertiary winding 5c, and power is supplied from the secondary DC power supply 2 to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 after rectification by the tertiary rectifier circuit 30 (paths shown by the solid line in Figure 12).

[0125] Next, from time t2 to t4 is the secondary side freewheeling period Tcr2 of the first half FH. At time t2, the positive electrode switch element 20a of the first leg of the secondary side is turned off, but the negative electrode switch element 20d of the second leg of the secondary side remains on until time t4. As a result, the negative secondary side reactor current IL2 causes the diodes of the second leg negative electrode switch element 20d and the first leg negative electrode switch element 20b of the secondary side to conduct, resulting in freewheeling.

[0126] Figure 13 shows the current flow during the period from time t2 to t3. During the period from time t2 to t3, the voltage relationship is Vdc1 < Vtr2 × N1 / N2, so the primary power conversion circuit 10 operates in rectification mode, and the voltage Vtr1 across the primary winding 5a becomes equal to the primary power supply voltage Vdc1. A voltage determined by the primary winding voltage Vtr1 and the turns ratio N1 / N3 between the primary winding 5a and the tertiary winding 5c ​​is applied to the tertiary winding 5c, and power is supplied from the secondary DC power supply 2 to the tertiary DC power supply 3 via the tertiary smoothing reactor 31 by the tertiary rectified voltage Vtr3 after rectification by the tertiary rectifier circuit 30. Therefore, by providing a secondary return period Tcr2, the range of power supplied to the tertiary DC power supply 3 can be expanded.

[0127] During the period from time t3 to t4, the voltage relationship becomes Vdc1 ≤ Vtr2 × N1 / N2, the primary power conversion circuit 10 completes its rectification operation, the voltage Vtr1 across the primary winding 5a becomes approximately 0V, a voltage of approximately 0V is applied to the tertiary winding 5c, the tertiary rectified voltage Vtr3 after rectification by the tertiary rectifier circuit 30 also becomes approximately 0V, and the stored energy of the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3.

[0128] Between times t3 and t4, the stored energy in the secondary boost reactor 21 gradually decreases due to current loss from recirculation, and the secondary reactor current IL2 gradually decreases. Between times t4 and t6 corresponds to a dead time, but between times t4 and t5, the secondary power conversion circuit 20 rectifies, the secondary load current Idc2 increases from 0, and the stored energy in the secondary boost reactor 21 returns to the secondary DC power supply 2.

[0129] 1-2-5. Switching between the first to third operating modes using common control values ​​The first to third operating modes were described individually above. Below, the switching and execution of the first to third operating modes using common control values ​​will be explained.

[0130] The control circuit 6 calculates a duty cycle Duty3adj for adjusting the power supplied to the tertiary DC power supply 3 based on the voltage or current of the tertiary rectifier circuit 30. For example, the control circuit 6 calculates the duty cycle Duty3adj for adjusting the tertiary based on the tertiary load voltage Vdc3 or the tertiary load current Idc3. For example, the control circuit 6 changes the duty cycle Duty3adj for adjusting the tertiary by feedback control so that the tertiary load voltage Vdc3 approaches the target value Vdc3* of the tertiary load voltage. Duty3adj is limited to an upper and lower limit range of 0 or more and 1 or less. For example, the control circuit 6 calculates the duty cycle Duty3adj for adjusting the tertiary by PI control based on the deviation ΔVdc3 between Vdc3 and Vdc3*, as shown in the following equation. Here, Kp3 is a positive proportional gain, Ki3 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the duty cycle Duty3adj for tertiary adjustment by feedback control so that the tertiary load current Idc3 approaches the target value Idc3* for the tertiary load current. ΔVdc3 = Vdc3* - Vdc3 Duty3adj = {Kp3 + Ki3 / s} × ΔVdc3 ... (12) 0 ≤ Duty3adj ≤ 1

[0131] The control circuit 6 calculates the balance duty cycle Dutybln based on the voltage or current of the secondary power conversion circuit 20. For example, the control circuit 6 calculates the balance duty cycle Dutybln based on the secondary load voltage Vdc2 or the secondary load current Idc2. For example, the control circuit 6 changes the balance duty cycle Dutybln by feedback control so that the secondary load current Idc2 approaches the target value Idc2* for the secondary load current. Idc2* is set to a positive or negative value and changes according to the state of the secondary DC power supply 2 or the control target. Dutybln is limited to an upper and lower limit within the range of -2 × Duty3adj or more and Duty3adj or less. For example, the control circuit 6 calculates the balance duty cycle Dutybln by PI control based on the deviation ΔIdc2 between Idc2 and Idc2*, as shown in the following equation. Here, Kp2 is a positive proportional gain, Ki2 is a positive integral gain, and s is the Laplace operator. Alternatively, the control circuit 6 may change the balance duty cycle Dutybln by feedback control so that the secondary load voltage Vdc2 approaches the target value Vdc2* of the secondary load voltage. ΔIdc2 = Idc2* - Idc2 Dutybln = {Kp2 + Ki2 / s} × ΔIdc2 ... (13) -2 × Duty3adj ≤ Dutybln ≤ Duty3adj

[0132] The control circuit 6 determines to execute the first operating mode if the balancing duty cycle Dutybln is positive, determines to execute the second operating mode if the balancing duty cycle Dutybln is negative and greater than or equal to the inverted sign value of the tertiary side adjustment duty cycle Duty3adj, and determines to execute the third operating mode if the balancing duty cycle Dutybln is negative and less than the inverted sign value of the tertiary side adjustment duty cycle Duty3adj. 1) Dutybln ≥ 0 Determine to execute the first operating mode 2) Dutybln < 0 and Dutybln ≥ -Duty3adj Determine to execute the second operating mode ... (14) 2) Dutybln < 0 and Dutybln < -Duty3adj Determine to execute the third operating mode

[0133] If the control circuit 6 determines to execute the first operating mode, it sets the duty cycle Duty3adj for tertiary adjustment as the duty cycle Duty1 for the primary side, and sets the duty cycle Dutybln for balancing as the duty cycle Duty2 for the secondary side. In the first operating mode, the control circuit 6 sets the duty cycle Duty2 for the secondary side to be less than or equal to the duty cycle Duty1 for the primary side. If the control circuit 6 determines to execute the second operating mode, it sets the absolute value of the balancing duty cycle |Dutybln| as the duty cycle Duty2 for the secondary side, and sets the duty cycle Duty1 for the primary side by subtracting the duty cycle Duty2 for the secondary side from the duty cycle Duty3adj for tertiary adjustment. Furthermore, in the second operating mode, the control circuit 6 sets the duty cycle Duty2 for the secondary side to be less than or equal to the duty cycle Duty3adj for tertiary side adjustment. If the control circuit 6 determines to execute the third operating mode, it sets the duty cycle Duty3adj for tertiary side adjustment as the duty cycle Duty2 for the secondary side, and calculates the duty cycle Duty1 for the primary side by subtracting the duty cycle Duty2 for the secondary side from the absolute value of the balance duty cycle |Dutybln|. In the third operating mode, the control circuit 6 sets the duty cycle Duty1 for the primary side to be less than or equal to the duty cycle Duty2 for the secondary side. 1) When executing the first operating mode Duty1 = Duty3adj Duty2 = Dutybln Duty2 ≤ Duty1 2) When executing the second operating mode... (15) Duty2 = |Dutybln| Duty1 = Duty3adj - Duty2 Duty2 ≤ Duty3adj 2) When executing the third operating mode Duty2 = Duty3adj Duty1 = |Dutybln| - Duty2 Duty1 ≤ Duty2

[0134] Then, as shown in the following equations, the control circuit 6 sets the primary side on period Ton1 by multiplying the period Tachf, which is obtained by subtracting the dead time Td from half a period of one AC period Tac, by the duty cycle Duty1 for the primary side, and sets the secondary side on period Ton2 by multiplying the period Tachf by the duty cycle Duty2 for the secondary side. Tachf = Tac / 2 - Td Ton1 = Tachf × Duty1 ... (16) Ton2 = Tachf × Duty2

[0135] If the system is configured not to execute the third operating mode, the execution of the third operating mode is not checked, and the duty cycle Duty1 for the primary side and Duty2 for the secondary side of the third operating mode are not calculated. If the system is configured not to execute the second operating mode, the execution of the second operating mode is not checked, and the duty cycle Duty1 for the primary side and Duty2 for the secondary side of the second operating mode are not calculated.

[0136] <Modification of Operation Mode Determination> The determination of whether to execute the first operation mode or the second operation mode may be made based on factors other than the positive or negative sign of the balance duty cycle Dutybln. For example, the control circuit 6 may determine whether to execute the first operation mode or the second operation mode based on either or both of the voltage or current of the secondary power conversion circuit 20 and the voltage or current of the primary power conversion circuit 10.

[0137] For example, in Figure 8, which shows the switching pattern when "Vdc1 < Vdc2 × N1 / N2" in the second operating mode, the secondary load current Idc2 is negative. However, if the balancing duty cycle Dutybln is 0, Idc2 becomes 0A. If the balancing duty cycle Dutybln is positive, it becomes the first operating mode, and as shown in Figure 1, Idc2 becomes positive. In other words, the switch from the first operating mode to the second operating mode can be determined by Idc2 becoming positive → 0A, and the switch from the second operating mode to the first operating mode can be determined by Idc2 becoming negative → 0A.

[0138] Furthermore, in Figure 5, which shows the switching pattern when "Vdc1 ≥ Vdc2 × N1 / N2" in the second operating mode, even when the balance duty cycle Dutybln becomes 0, Idc2 does not become 0A, and the operating mode cannot be determined in the same way. However, IL2, which conducts the secondary boost reactor 21 when the balance duty cycle Dutybln is 0, can be estimated from the relationship between the primary duty cycle Duty1, Vdc1, Vdc2, and N1 / N2. This estimated IL2 is used as a threshold, and if Idc2 is greater than the threshold, it is determined to execute the first operating mode, and if Idc2 is less than the threshold, it is determined to execute the second operating mode.

[0139] Alternatively, the control circuit 6 determines, based on the average value of the voltage or current of the secondary power conversion circuit 20 over one AC period Tac, that power is being supplied to the secondary DC power supply 2, and determines to execute the first operating mode. If it determines that power is being supplied from the secondary DC power supply 2, it determines to execute the second operating mode. Alternatively, the control circuit 6 may determine to execute the first operating mode if Idc2* is set to positive, and to execute the second operating mode if Idc2* is set to 0 or negative.

[0140] Furthermore, the control circuit 6 determines whether to execute the second operating mode or the third operating mode if power is supplied from either or both of the primary power source 1 and the secondary DC power supply 2, and if power is supplied from the secondary DC power supply 2 and power is supplied to the primary power source 1, it determines whether to execute the third operating mode. In this case, the control circuit 6 may also determine whether to execute the second operating mode or the third operating mode based on the voltage or current of the secondary power conversion circuit 20 and the voltage or current of the primary power conversion circuit 10.

[0141] <Modified Switching Pattern for Second Operation Mode> As shown in Figures 2, 5, and 8, when the control circuit 6 switches between the first operation mode and the second operation mode, in the second operation mode, immediately after the end of the secondary side on period Ton2, it sets the primary side on period Ton1, and in both the first and second operation modes, immediately after the end of the primary side on period Ton1, it sets the primary side recirculation period Tcr1 to turn on the switch element of the primary side power conversion circuit 10 so that the current of the primary winding 5a recirculates through the primary side power conversion circuit 10.

[0142] With this configuration, as shown in Figures 2, 5, and 8, the behavior of the primary winding current Itr1 during the primary side return flow period Tcr1 in the first operating mode and the behavior of the primary winding current Itr1 during the primary side return flow period Tcr1 in the second operating mode become similar, thereby suppressing power fluctuations when switching between the first and second operating modes.

[0143] Unlike Figures 5 and 8, when the control circuit 6 switches between the second and third operating modes, in the second operating mode, it may set a secondary side on period Ton2 immediately after the end of the primary side on period Ton1, and in both the second and third operating modes, it may set a secondary side recirculation period Tcr2 immediately after the end of the secondary side on period Ton2 to turn on the switch element of the secondary side power conversion circuit 20 so that the current of the secondary winding 5b recirculates through the secondary side power conversion circuit 20.

[0144] In this case, the control behavior of the second operating mode is as shown in Figure 14. The control behavior of the third operating mode is the same as the control behavior shown in Figure 11 of the first embodiment described above. In the second operating mode, the control circuit 6 sets a primary side on period Ton1 immediately after the start of the first half FH or the second half SH, and sets a secondary side on period Ton2 immediately after the end of the primary side on period Ton1.

[0145] During the primary side ON period Ton1 of the first half FH, the diagonally opposite primary side first leg positive electrode switch element 10a and primary side second leg negative electrode switch element 10d are turned on. During the primary side ON period Ton1 of the second half SH, the primary side second leg positive electrode switch element 10c and primary side first leg negative electrode switch element 10b are turned on. Also, during the secondary side ON period Ton2 of the first half FH, the diagonally opposite secondary side first leg positive electrode switch element 20a and secondary side second leg negative electrode switch element 20d are turned on. During the secondary side ON period Ton2 of the second half SH, the diagonally opposite secondary side first leg negative electrode switch element 20b and secondary side second leg positive electrode switch element 20c are turned on.

[0146] The control circuit 6 sets the period from immediately after the end of the secondary side ON period Ton2 to the start of the dead time Td as the secondary side recirculation period Tcr2. During the first half of the secondary side recirculation period Tcr2 (FH), the secondary side second leg negative electrode switch element 20d is turned on, and during the second half of the secondary side recirculation period Tcr2 (SH), the secondary side second leg positive electrode switch element 20c is turned on.

[0147] In the example shown in Figure 14, the control circuit 6 sets the primary side recirculation period Tcr1 immediately after the end of the primary side on period Ton1. The control circuit 6 sets the primary side recirculation period Tcr1 to be the period from immediately after the end of the primary side on period Ton1 to the start of the dead time Td. During the primary side recirculation period Tcr1 of the first half FH, the primary side first leg positive electrode side switch element 10a is turned on, and during the primary side recirculation period Tcr1 of the second half SH, the primary side first leg negative electrode side switch element 10b is turned on.

[0148] As shown in the example in Figure 14, in the second operating mode, if the secondary side on period Ton2 is set immediately after the end of the primary side on period Ton1, and the secondary side recirculation period Tcr2 is set immediately after the end of the secondary side on period Ton2, the behavior of the secondary side reactor current IL2 due to the secondary side recirculation period Tcr2 in the second operating mode becomes similar to the behavior of the secondary side reactor current IL2 due to the secondary side recirculation period Tcr2 in the third operating mode shown in Figure 11. Therefore, power fluctuations when switching between the second operating mode and the third operating mode can be suppressed.

[0149] <Variations of the Recirculation Period> In each operating mode, the control circuit 6 may set the period from immediately after the end of the primary side ON period Ton1 to before the start of the dead time Td as the primary side recirculation period Tcr1. Also, in each operating mode, the control circuit 6 may set the period from immediately after the end of the secondary side ON period Ton2 to before the start of the dead time Td as the secondary side recirculation period Tcr2. If the conduction loss due to recirculation is greater than the turn-off loss of the switch element, stopping the recirculation earlier can reduce the loss.

[0150] <Control of secondary transmission power based on primary voltage or current> In the above embodiment 1, the control circuit 6 was configured to calculate a secondary duty cycle Duty 2 for adjusting the power supplied to the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20 in the first operating mode. The control circuit 6 was configured to calculate a secondary duty cycle Duty 2 for adjusting the power supplied from the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20 in the second operating mode. The control circuit 6 was configured to calculate a primary duty cycle Duty 1 for adjusting the power supplied from the secondary DC power supply 2 based on the voltage or current of the secondary power conversion circuit 20 in the third operating mode. Alternatively, as a common control value for each operating mode, the control circuit 6 was configured to calculate a balancing duty cycle Dutybln based on the voltage or current of the secondary power conversion circuit 20.

[0151] However, the control circuit 6 may use the voltage or current of the primary power conversion circuit 10 instead of the voltage or current of the secondary power conversion circuit 20. For example, the primary power supply voltage Vdc1 or the primary power supply current Idc1 may be used as the voltage or current of the primary power conversion circuit 10. In other words, the voltage or current of the primary power conversion circuit 10 may indirectly adjust the power supplied to the secondary DC power supply 2 or the power supplied from the secondary DC power supply 2. The sum of the transmitted power of the primary power source 1, the transmitted power of the tertiary DC power supply 3, and the transmitted power of the secondary DC power supply 2 is zero if losses are ignored. Therefore, the control circuit 6 may set a target value for the voltage or current of the primary power conversion circuit 10 so that the transmitted power of the secondary DC power supply 2 becomes a target value in each operating mode, and calculate the duty cycle Duty2 for the secondary side, Duty1 for the primary side, or Dutybln for balancing based on the voltage or current of the primary power conversion circuit 10 in each operating mode. For example, similar to the voltage or current of the secondary power conversion circuit 20, the control circuit 6 may change the duty cycle Duty2 for the secondary side, Duty1 for the primary side, or Dutybln for balancing by feedback control so that the primary power supply current Idc1 or primary power supply voltage Vdc1 approaches a target value set so that the transmitted power of the secondary DC power supply 2 becomes a target value.

[0152] <Repeated switching between the first and third operating modes> In the above embodiment 1, the system was configured to execute an intermediate second operating mode between the first and third operating modes. However, the control circuit 6 may be configured to adjust the average power supplied from the primary power source 1 and the average power supplied from the secondary DC power source 2 while adjusting the power supplied to the tertiary DC power source 3 by repeatedly switching between the first and third operating modes, without executing the second operating mode. For example, the control circuit 6 calculates the average execution time ratio between the first and third operating modes so that the average power supplied from the secondary DC power source 2 or the primary power source 1 approaches a target value, and repeatedly switches between the first and third operating modes based on the execution time ratio. For example, the control circuit 6 sets the execution time of the first operating mode and the execution time of the third operating mode within one switching cycle based on the execution time ratio, and in one switching cycle, executes the first operating mode for the execution time of the first operating mode and executes the third operating mode for the execution time of the third operating mode. The first operating mode and the third operating mode may be switched for each AC cycle Tac, or the first operating mode and the third operating mode may be switched for each of multiple AC cycles Tac.

[0153] <Secondary side capacitor 22 and secondary side detection circuit 42> As shown in Figures 2, 5, 8, and 11, in each operating mode, the secondary side load current Idc2 operates in a current discontinuous mode where it becomes 0A every half cycle of one AC period Tac, resulting in a large current ripple. To smooth this current ripple and charge the secondary side DC power supply 2, a large-capacity capacitor is required. In this embodiment, as described above, the secondary load capacitor 23 connected in parallel to the secondary side DC power supply 2 is provided outside the power converter 50, and the capacitance of the secondary load capacitor 23 is larger than the capacitance of the secondary side capacitor 22. Therefore, by reducing the capacitance of the internal secondary side capacitor 22, the size of the power converter 50 itself can be reduced.

[0154] As described above, the secondary detection circuit 42 is provided in the portion of the secondary busbars 26a and 26b between the secondary capacitor 22 and the secondary terminals 25a and 25b. Therefore, the secondary detection circuit 42 can detect the current and voltage smoothed by the secondary capacitor 22. A low-pass filter may be applied to the output signal of the secondary detection circuit 42. In addition, the power converter 50 may be equipped with a large-capacity secondary capacitor 22, or it may not be equipped with a secondary capacitor 22.

[0155] <Modification of the tertiary rectifier circuit 30> In the above embodiment 1, the tertiary rectifier circuit 30 is a center-tapped single-phase full-wave rectifier circuit composed of two rectifier diodes 30a and 30b. The tertiary rectifier circuit 30 may be an H-bridge single-phase full-wave rectifier circuit composed of four rectifier diodes, or a single-phase half-wave rectifier circuit composed of one rectifier diode. Alternatively, the tertiary rectifier circuit 30 may be composed of a switch element having diodes connected in antiparallel, and the control circuit 6 may perform synchronous rectification by controlling the on / off state of the switch element of the tertiary rectifier circuit 30. For example, the tertiary rectifier circuit 30 may be an H-bridge PWM rectifier circuit composed of four switch elements. The control circuit 6 turns on the switch element of the diode that is energized when the diodes connected in antiparallel are energized.

[0156] <Modified Configuration of the Secondary Boost Reactor 21> In the above embodiment 1, the secondary boost reactor 21 was connected between the secondary winding 5b and the secondary power conversion circuit 20. However, the reactor may be connected between the secondary winding 5b and the secondary power conversion circuit 20, or between the primary winding 5a and the primary power conversion circuit 10, or both. Even if the reactor is connected between the primary winding 5a and the primary power conversion circuit 10, the boost operation will be performed in the same way as with the secondary boost reactor 21, and the power supplied from the primary power source 1 and the power supplied to the primary power source 1 can be increased.

[0157] When both a secondary boost reactor 21 and a primary boost reactor are provided, and a primary side recirculation period Tcr1 and a secondary side recirculation period Tcr2 are provided in the first to third operating modes, current flows through either the primary or secondary reactor during the recirculation period. Therefore, the behavior of transmitting the stored energy of the reactor after the recirculation period is common to all operating modes, and power fluctuations when switching operating modes are suppressed.

[0158] One or both of the secondary boost reactor 21 and the primary boost reactor may be composed of the leakage inductance of the transformer 5.

[0159] <When multiple sets of secondary sides are provided> Multiple sets of secondary windings 5b, secondary power conversion circuits 20, and secondary loads 2 may be provided.

[0160] In the first operating mode, the control circuit 6 controls the on / off state of the switching elements of multiple sets of secondary power conversion circuits 20 in order to adjust the power supplied to multiple sets of secondary loads 2. In the first operating mode, the control circuit 6 calculates a common secondary duty cycle Duty 2 for all sets to adjust the total power supplied to all sets of secondary DC power supplies 2 based on the voltage or current of each set of secondary power conversion circuits 20. For example, the average value of the voltage or current of all sets of secondary power conversion circuits 20 may be used. The common secondary duty cycle Duty 2 for all sets is limited to an upper and lower limit within the range of 0 or more and Duty 1 or less. Based on the common secondary duty cycle Duty 2 for all sets, the control circuit 6 sets the secondary on period Ton 2 for each set, and sets the secondary on period Ton 2 for each set during the primary on period Ton 1. The control behavior of the secondary power conversion circuit 20 in each set is the same as in the case of one set, so the explanation will be omitted.

[0161] Furthermore, in the second operating mode, the control circuit 6 calculates a common secondary duty cycle Duty 2 for all sets, based on the voltage or current of the secondary power conversion circuit 20 of each set, in order to adjust the total power supplied from the secondary DC power supply 2 of all sets. The common secondary duty cycle Duty 2 for all sets is limited to an upper and lower limit within the range of 0 or more and Duty 3 adj or less. The control circuit 6 calculates the primary duty cycle Duty 1 by subtracting the common secondary duty cycle Duty 2 for all sets from the tertiary adjustment duty cycle Duty 3 adj.

[0162] In the third operating mode, the control circuit 6 calculates a duty cycle Duty 2 for the secondary side common to all sets based on the voltage or current of the tertiary side rectifier circuit 30. In the third operating mode, the control circuit 6 calculates a duty cycle Duty 1 for the primary side to adjust the total power supplied from the secondary side DC power supply 2 for all sets based on the voltage or current of the secondary side power conversion circuit 20 for each set. The primary side duty cycle Duty 1 is limited to an upper and lower limit within the range of 0 or more and Duty 2 or less.

[0163] Alternatively, as a common control value for each operating mode, the control circuit 6 calculates a common balance duty cycle Dutybln for all sets based on the voltage or current of the secondary power conversion circuit 20 for each set. Similar to the case of one set, the operating mode is determined based on the common balance duty cycle Dutybln for all sets, and a common secondary duty cycle Duty2 for all sets is calculated.

[0164] <When used in electric vehicles, etc.> Furthermore, it is suitable for use in electric vehicles or hybrid vehicles in which the secondary DC power source 2 is a high-voltage battery and the tertiary DC power source 3 is an auxiliary battery. In an electric vehicle, the battery management unit monitors the high-voltage battery, and based on the monitored information, a charging current command is sent from the control unit to the power converter 50 (control circuit 6). A charging voltage command for the auxiliary battery is also sent from the control unit to the power converter 50 (control circuit 6). As in Embodiment 1 above, by controlling based on the target value Idc2* of the secondary load current and the target value Vdc3* of the tertiary load voltage, power distribution control suitable for electric vehicles, etc., is possible.

[0165] <Hardware Configuration of Control Circuit 6> An example of control circuit 6 is described below. The functions of control circuit 6 are realized by the processing circuits and memory devices provided in control circuit 6. As shown in Figure 22, control circuit 6 includes an arithmetic processing unit 90 (computer), a memory device 91, and an input / output device 92. The arithmetic processing unit 90 is equipped with various processing circuits such as a CPU (Central Processing Unit), ASIC (Application Specific Integrated Circuit), and IC (Integrated Circuit). The memory device 91 is equipped with various memory devices such as RAM (Random Access Memory), ROM (Read Only Memory), and EEPROM (Electrically Erasable Programmable Read Only Memory). The input / output device 92 is equipped with an A / D converter, etc., to which sensors such as detection circuits 41, 42, and 43 are connected, and which inputs the output signals of these sensors to the arithmetic processing unit 90. The output device 92 is connected to electrical loads such as gate drive circuits that drive the switching elements of the primary power conversion circuit 10 and the secondary power conversion circuit 20 on and off, and is equipped with drive circuits that output control signals from the arithmetic processing unit 90 to these electrical loads. The storage device 91, such as ROM, stores programs for each process and setting data. Each function of the control circuit 6 is realized by the arithmetic processing unit 90 executing the software (program) stored in the storage device 91 and cooperating with the storage device 91 and other hardware such as the input / output device 92.

[0166] 2. Embodiment 2 The power converter 50 according to Embodiment 2 will now be described. The same components as in Embodiment 1 will not be described. The basic configuration of the power converter 50 according to this embodiment is the same as in Embodiment 1, but it differs from Embodiment 1 in that a primary side recirculation period Tcr1 and a secondary side recirculation period Tcr2 are not provided in each operating mode.

[0167] In Figure 11 of the third operating mode of Embodiment 1, a secondary side recirculation period Tcr2 is provided from time t2 to t4. Therefore, between time t3 and t4, the stored energy of the secondary side boost reactor 21 gradually decreases due to current loss caused by recirculation, and the secondary side reactor current IL2 gradually decreases, but it is not zero at the start of the dead time t4. Consequently, during the dead time from time t4 to t6, from time t4 to t5, the secondary side power conversion circuit 20 performs a rectification operation, the secondary side load current Idc2 increases from zero, and the stored energy of the secondary side boost reactor 21 returns to the secondary side DC power supply 2.

[0168] On the other hand, in the first and second operating modes, as shown in Figure 2 at times t4-t5, Figure 5 at times t5-t6, and Figure 8 at times t4-t5, the secondary reactor current IL2 decreases to 0A during the recirculation period, so there is no stored energy returning to the power source during the dead time after the recirculation period.

[0169] Thus, when a primary side recirculation period Tcr1 and a secondary side recirculation period Tcr2 are provided, there are operating modes in which the stored energy of the secondary side boost reactor 21 returns to the power supply side after the recirculation period, and operating modes in which it does not. There is a concern that the control may become unstable or oscillate due to the sudden change in the transmitted power of each input and output during the switching between operating modes.

[0170] Therefore, in this embodiment, the primary side recirculation period Tcr1 and the secondary side recirculation period Tcr2 are not provided in the first operation mode, the second operation mode, and the third operation mode.

[0171] With this configuration, by unifying the provision of primary side freewheeling periods Tcr1 and secondary side freewheeling periods Tcr2 in all operating modes, it is possible to suppress the oscillation or instability of the control due to abrupt changes in the transmitted power of each input and output when switching operating modes.

[0172] The following section provides a detailed explanation of the control behavior for each operating mode when the primary side recirculation period Tcr1 and the secondary side recirculation period Tcr2 are not provided.

[0173] <First operating mode without freewheeling period> First, the first operating mode without freewheeling period will be explained using Figures 15 to 17. Figure 15 shows the switching pattern and voltage / current waveforms at each point in the first operating mode without freewheeling period.

[0174] The current flow during the period from time t0 to t2 is the same as in Figure 3 shown in Embodiment 1. The current flow during the period from time t2 to t3 is shown in Figure 16. The primary power conversion circuit 10 and the secondary power conversion circuit 20 are turned off and rectification occurs, and the stored energy of the secondary boost reactor 21 is transmitted to the primary power source 1, the secondary DC power supply 2, and the tertiary DC power supply 3.

[0175] Figure 17 shows the current flow during the period from time t3 to t4. At time t3, the primary winding current Itr1 becomes 0A, the stored energy of the secondary boost reactor 21 is transmitted to the secondary DC power supply 2, and the stored energy of the tertiary smoothing reactor 31 causes both the tertiary winding 5c ​​and the tertiary rectifier diodes 30a and 30b to conduct, thereby charging the tertiary DC power supply 3.

[0176] During the period from time t4 to t5, all switching elements are turned off. There is no current conduction in the primary power conversion circuit 10 and the secondary power conversion circuit 20, and the stored energy of the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3 while both the tertiary rectifier diodes 30a and 30b conduct.

[0177] <Second operating mode without freewheeling period> Next, the second operating mode without freewheeling period will be explained using Figure 18. Figure 18 shows the switching pattern and voltage / current waveforms at each point in the second operating mode without freewheeling period when "Vdc1 ≥ Vdc2 × N1 / N2". The current flow during the period from time t0 to t3 is the same as in Figures 6 and 7 shown in Embodiment 1.

[0178] Furthermore, the current flow during the period from time t3 to t6 is the same as that during the first operating mode without a return flow period in Figure 15, from time t2 to t5.

[0179] <Third operating mode without freewheeling period> Next, the third operating mode without freewheeling period will be explained using Figures 19 to 21. Figure 19 shows the switching pattern and voltage / current waveforms at each point in the third operating mode without freewheeling period when "Vdc1 ≥ Vdc2 × N1 / N2".

[0180] The current flow during the period from time t0 to t2 is the same as in Figure 12 shown in Embodiment 1. The current flow during the period from time t2 to t3 is shown in Figure 20. The primary power conversion circuit 10 and the secondary power conversion circuit 20 are turned off and rectification occurs, and the stored energy of the secondary boost reactor 21 is transmitted to the primary power source 1, the secondary DC power supply 2, and the tertiary DC power supply 3.

[0181] Figure 21 shows the current flow during the period from time t3 to t4. At time t3, the primary winding current Itr1 becomes 0A, the stored energy of the secondary boost reactor 21 is transmitted to the secondary DC power supply 2, and the stored energy of the tertiary smoothing reactor 31 causes both the tertiary winding 5c ​​and the tertiary rectifier diodes 30a and 30b to conduct, thereby charging the tertiary DC power supply 3.

[0182] During the period from time t4 to t5, all switching elements are turned off. There is no current conduction in the primary power conversion circuit 10 and the secondary power conversion circuit 20, and the stored energy of the tertiary smoothing reactor 31 is supplied to the tertiary DC power supply 3 while both the tertiary rectifier diodes 30a and 30b conduct.

[0183] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this disclosure. For example, these include modifying, adding or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment.

[0184] 1: Primary power source, 2: Secondary load (secondary DC power supply), 3: Tertiary load (tertiary DC power supply), 5: Transformer, 5a: Primary winding, 5b: Secondary winding, 5c: Tertiary winding, 6: Control circuit, 10: Primary power conversion circuit, 15: Primary terminal, 20: Secondary power conversion circuit, 21: Secondary boost reactor, 25: Secondary terminal, 30: Tertiary rectifier circuit, 35: Tertiary terminal, 41, 42, 43: Detection circuit, 5 0: Power converter, Duty1: Primary duty cycle, Duty2: Secondary duty cycle, Duty3adj: Duty cycle for tertiary adjustment, Dutybln: Duty cycle for balancing, FH: First half, SH: Second half, Tac: AC cycle, Tcr1: Primary return period, Tcr2: Secondary return period, Td: Dead time, Ton1: Primary on period, Ton2: Secondary on period, Tonall: Total on period

Claims

1. A transformer having at least a primary winding, a secondary winding, and a tertiary winding that are magnetically coupled to each other; a primary power conversion circuit that converts the AC power of the primary winding to the DC power of the primary terminal connected to a primary power source; a secondary power conversion circuit that converts the AC power of the secondary winding to the DC power of the secondary terminal connected to a secondary load; a tertiary rectifier circuit that converts the AC power of the tertiary winding to DC power and supplies it to the tertiary terminal connected to a tertiary load; and a control circuit that controls the on / off switching of the switching elements of the primary power conversion circuit and the switching elements of the secondary power conversion circuit. The control circuit is a power conversion device that, when supplying power from the primary power source to the secondary and tertiary loads, performs a first operating mode in which it controls the on / off switching of the switching element of the primary power conversion circuit to adjust the power supplied to the tertiary load, and controls the on / off switching of the switching element of the secondary power conversion circuit to adjust the power supplied to the secondary load.

2. The power conversion device according to claim 1, wherein the control circuit controls the switching element of the secondary power conversion circuit to increase the voltage generated in the secondary winding in the first operating mode.

3. A power conversion device according to claim 1 or 2, comprising a detection circuit for detecting the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, and the voltage or current of the tertiary rectifier circuit, wherein the control circuit, in the first operating mode, calculates a primary duty cycle for adjusting the power supplied to the tertiary load based on the voltage or current of the tertiary rectifier circuit, calculates a secondary duty cycle for adjusting the power supplied to the secondary load based on the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, sets a primary on period for turning on the switch element of the primary power conversion circuit based on the primary duty cycle, and sets a secondary on period for turning on the switch element of the secondary power conversion circuit based on the secondary duty cycle.

4. The power conversion device according to claim 3, wherein the control circuit sets the duty cycle for the secondary side to be less than or equal to the duty cycle for the primary side in the first operating mode, and sets the secondary side on period during the primary side on period.

5. The power conversion device according to claim 3 or 4, wherein the control circuit sets a primary side recirculation period in the first operating mode, immediately after the end of the primary side on period, in which the switch element of the primary side power conversion circuit is turned on so that the current of the primary winding is recirculated within the primary side power conversion circuit.

6. The power conversion device according to claim 5, wherein the control circuit switches the switching elements of the primary power conversion circuit that are turned on in the first half and the second half of one AC cycle, provides a dead time between the first half and the second half in which all the switching elements of the primary power conversion circuit are turned off, sets the primary side on period immediately after the start of the first half or the second half in the first operating mode, and sets the period from immediately after the end of the primary side on period to the start of the dead time or a time before the start of the dead time as the primary side return period.

7. The power conversion device according to any one of claims 1 to 6, wherein the secondary load has both the function of a power source and a load, at least the secondary power conversion circuit is capable of bidirectional power transmission, and the control circuit performs a second operating mode in which, when supplying power to the tertiary load from either or both of the primary power source and the secondary load, the control circuit controls the on / off switching of the switch elements of the primary power conversion circuit and the secondary power conversion circuit in order to adjust the power supplied to the tertiary load, and controls the on / off switching of the switch elements of the secondary power conversion circuit in order to adjust the power supplied from the secondary load.

8. The power conversion device according to claim 7, wherein the control circuit controls the switching element of the secondary power conversion circuit to be on or off so as not to increase the voltage generated in the secondary winding in the second operating mode.

9. The power conversion device according to claim 7 or 8, wherein the control circuit adjusts the power supplied from the primary power source and the power supplied from one or both of the secondary loads by controlling the on / off switching elements of the primary power conversion circuit and the secondary power conversion circuit so that, in the second operating mode, the current at the primary terminal or the current at the secondary terminal alternately flows in a positive and negative direction within half a cycle of one AC cycle.

10. The power conversion device according to claim 9, wherein the control circuit sets a total on period in the second operating mode for adjusting the total power supplied from one or both of the primary power source and the secondary load to the tertiary load in the first half and second half of one AC cycle, and divides the total on period into a primary on period of the primary power conversion circuit for adjusting the power supplied from the primary power source and a secondary on period of the secondary power conversion circuit for adjusting the power supplied from the secondary load.

11. The power conversion device according to claim 10, wherein the control circuit adjusts the total on period in the second operating mode to adjust the total power supplied to the tertiary load, adjusts the secondary on period to adjust the power supplied from the secondary load, and adjusts the primary on period by subtracting the secondary on period from the total on period.

12. A power conversion device according to claim 7, comprising a detection circuit for detecting the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, and the voltage or current of the tertiary rectifier circuit, wherein the control circuit, in the second operating mode, calculates a duty cycle for tertiary adjustment to adjust the power supplied to the tertiary load based on the voltage or current of the tertiary rectifier circuit, calculates a duty cycle for secondary adjustment to adjust the power supplied from the secondary load based on the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, calculates a duty cycle for primary adjustment by subtracting the duty cycle for secondary adjustment from the duty cycle for tertiary adjustment, sets a primary on period for turning on the switch element of the primary power conversion circuit based on the primary duty cycle, and sets a secondary on period for turning on the switch element of the secondary power conversion circuit based on the secondary duty cycle.

13. The power conversion device according to claim 12, wherein the control circuit sets the duty cycle for the secondary side to be less than or equal to the duty cycle for adjusting the tertiary side in the second operating mode, and sets an on-period by the other immediately after the end of the on-period by the primary side or the secondary side.

14. The power conversion device according to claim 13, wherein the control circuit performs, in the second operating mode, either or both of the following: primary side recirculation, which sets a primary side recirculation period immediately after the end of the primary side ON period, in which the switch element of the primary side power conversion circuit is turned on so that the current of the primary winding recirculates within the primary side power conversion circuit; and secondary side recirculation, which sets a secondary side recirculation period immediately after the end of the secondary side ON period, in which the switch element of the secondary side power conversion circuit is turned on so that the current of the secondary winding recirculates within the secondary side power conversion circuit.

15. The power conversion device according to claim 14, wherein the control circuit switches the switch elements of the primary power conversion circuit that are turned on in the first half and second half of one AC cycle, and provides a dead time between the first half and the second half in which all the switch elements of the primary power conversion circuit are turned off, and in the second operating mode, immediately after the start of the first half or the second half, an on period is set by one of the duty cycles for the primary side and the duty cycle for the secondary side, and immediately after the end of the on period by one, an on period is set by the other, and when primary side recirculation is performed, the period from immediately after the end of the primary side on period to the start of the dead time or a time before the start of the dead time or a time before the start of the dead time or a time before the start of the dead time or a time before the start of the dead time or a time before the start of the dead time or a time before the start of the dead time is set as the primary side recirculation period, and when secondary side recirculation is performed, the period from immediately after the end of the secondary side on period to the start of the dead time or a time before the start of the dead time is set as the secondary side recirculation period.

16. The power conversion device according to claim 7, comprising a detection circuit for detecting either the voltage or current of the secondary power conversion circuit or the voltage or current of the primary power conversion circuit, wherein the control circuit determines whether to execute the first operating mode or the second operating mode based on either the voltage or current of the secondary power conversion circuit or the voltage or current of the primary power conversion circuit.

17. The power conversion device according to claim 7, wherein the primary power source and the secondary load have both the functions of a power source and a load, the primary power conversion circuit and the secondary power conversion circuit are capable of bidirectional power transmission, and the control circuit performs a third operating mode in which, when supplying power from the secondary load to the primary power source and the tertiary load, it controls the on / off switching element of the secondary power conversion circuit to adjust the power supplied to the tertiary load, and controls the on / off switching element of the primary power conversion circuit to adjust the power supplied from the secondary load.

18. The power conversion device according to claim 17, wherein the control circuit controls the switching element of the primary power conversion circuit to increase the voltage generated in the secondary winding in the third operating mode.

19. A power conversion device according to claim 17, comprising a detection circuit for detecting the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, and the voltage or current of the tertiary rectifier circuit, wherein the control circuit, in the third operating mode, calculates a duty cycle for the secondary side to adjust the power supplied to the tertiary load based on the voltage or current of the tertiary rectifier circuit, calculates a duty cycle for the primary side to adjust the power supplied from the secondary load based on the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, sets a primary on period for turning on the switch element of the primary power conversion circuit based on the primary duty cycle, and sets a secondary on period for the switch element of the secondary power conversion circuit based on the secondary duty cycle.

20. The power conversion device according to claim 19, wherein the control circuit sets the duty cycle of the primary side to be less than or equal to the duty cycle of the secondary side in the third operating mode, and sets the primary side on period during the secondary side on period.

21. The power conversion device according to claim 20, wherein the control circuit sets a secondary recirculation period in the third operating mode, immediately after the end of the secondary on period, in which the switch element of the secondary power conversion circuit is turned on so that the current of the secondary winding is recirculated within the secondary power conversion circuit.

22. The power conversion device according to claim 21, wherein the control circuit switches the switching elements of the primary power conversion circuit that are turned on in the first half and the second half of one AC cycle, and provides a dead time between the first half and the second half in which all the switching elements of the secondary power conversion circuit are turned off, and in the third operating mode, the secondary side on period is set immediately after the start of the first half or the second half, and the period from immediately after the end of the secondary side on period to the start of the dead time or a time before the start of the dead time is set to the secondary side return period.

23. The power conversion device according to claim 17, wherein, when the control circuit is executed by switching between the first operating mode and the second operating mode, in the second operating mode, the primary side on period of the primary side power conversion circuit is set immediately after the end of the secondary side on period of the secondary side power conversion circuit, and in the first and second operating modes, the primary side recirculation period is set immediately after the end of the primary side on period to turn on the switch element of the primary side power conversion circuit so that the current of the primary winding recirculates within the primary side power conversion circuit, and when the control circuit is executed by switching between the second operating mode and the third operating mode, the secondary side on period is set immediately after the end of the primary side on period, and in the second and third operating modes, the secondary side recirculation period is set immediately after the end of the secondary side on period to turn on the switch element of the secondary side power conversion circuit so that the current of the secondary winding recirculates within the secondary side power conversion circuit.

24. The control circuit includes a detection circuit that detects the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, and the voltage or current of the tertiary rectifier circuit, and the control circuit calculates a duty cycle for tertiary adjustment to adjust the power supplied to the tertiary load based on the voltage or current of the tertiary rectifier circuit, calculates a duty cycle for balancing based on the voltage or current of the secondary power conversion circuit and the voltage or current of the primary power conversion circuit, determines to execute the first operating mode if the balancing duty cycle is positive, determines to execute the second operating mode if the balancing duty cycle is negative and is greater than or equal to the inverted sign value of the tertiary adjustment duty cycle, determines to execute the third operating mode if the balancing duty cycle is negative and is less than the inverted sign value of the tertiary adjustment duty cycle, and determines to execute the first operating mode. The power conversion device according to claim 17, wherein the duty cycle for adjusting the tertiary side is set as the duty cycle for the primary side, the duty cycle for balancing is set as the duty cycle for the secondary side, and if it is determined to execute the second operating mode, the absolute value of the duty cycle for balancing is set as the duty cycle for the secondary side, and the duty cycle for the primary side is set by subtracting the duty cycle for the secondary side from the duty cycle for adjusting the tertiary side, and if it is determined to execute the third operating mode, the duty cycle for adjusting the tertiary side is set as the duty cycle for the secondary side, and the duty cycle for the primary side is calculated by subtracting the duty cycle for the secondary side from the absolute value of the duty cycle for balancing, and a primary side on period for turning on the switch element of the primary side power conversion circuit is set based on the primary side duty cycle, and a secondary side on period for turning on the switch element of the secondary side power conversion circuit is set based on the secondary side duty cycle.

25. The power conversion device according to claim 1, wherein the primary power source and the secondary load have both the functions of a power source and a load, the primary power conversion circuit and the secondary power conversion circuit are capable of bidirectional power transmission, and the control circuit, when supplying power from the secondary load to the primary power source and the tertiary load, executes a third operating mode in which it controls the on / off switch element of the secondary power conversion circuit to adjust the power supplied to the tertiary load, and controls the on / off switch element of the primary power conversion circuit to adjust the power supplied from the secondary load, and repeatedly switches between the first operating mode and the third operating mode to adjust the power supplied from the primary power source and the power supplied from the secondary load.

26. The power conversion device according to any one of claims 1 to 25, wherein a plurality of sets of the secondary winding, the secondary power conversion circuit, and the secondary load are provided, and the control circuit controls the switching elements of the plurality of sets of secondary power conversion circuits to adjust the power supplied to the plurality of sets of secondary loads in the first operating mode.

27. The power conversion device according to any one of claims 1 to 26, wherein a reactor is connected between the secondary power conversion circuit and the secondary winding, and between the primary power conversion circuit and the primary winding, or to either or both.

28. The power conversion device according to claim 27, wherein the reactor is composed of the leakage inductance of the transformer.

29. The power conversion device according to any one of claims 1 to 28, wherein the rectifier circuit is composed of diodes.

30. The power conversion device according to any one of claims 1 to 28, wherein the rectifier circuit is composed of a switch element having diodes connected in antiparallel, and the control circuit controls the switching element of the rectifier circuit to turn on and off to perform synchronous rectification.

31. The power conversion device according to any one of claims 1 to 30, wherein the primary power conversion circuit and the secondary power conversion circuit are bridge circuits of the switch element.

32. The power conversion device according to any one of claims 1 to 31, wherein one or both of the primary power source and the secondary load, and the tertiary load are DC voltage sources.

33. The power conversion device according to any one of claims 3, 12, 15, 16, 19, and 24, wherein the detection circuit detects the current flowing through a detection point on the bus connecting the secondary power conversion circuit and the secondary terminal as the current of the secondary power conversion circuit, and the capacitance between positive and negative terminals of the portion of the bus on the secondary power conversion circuit side is smaller than the capacitance between positive and negative terminals of the portion of the bus on the secondary terminal side is smaller than the capacitance between positive and negative terminals of the portion of the bus on the secondary terminal side is smaller than the detection point.

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