Power conversion device

Abstract

To supply power to multiple devices that require different voltages.SOLUTION: A power conversion device 20 includes a first converter 30 that performs power conversion of power input from an external power supply PS. The first converter 30 includes a flying capacitor 33. The power conversion device 20 includes a second converter 50 that performs power conversion using a voltage across the flying capacitor 33 as an input voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] The power conversion device disclosed in Patent Document 1 is mounted on a vehicle. The vehicle includes a high-voltage battery and a low-voltage battery. The power conversion device converts power supplied from an external power source and outputs the converted power to the high-voltage battery. This charges the high-voltage battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-38682 A Summary of the Invention [Problem to be solved by the invention]

[0004] A power conversion device may be required to have a plurality of output terminals with different output voltages. For example, when a power conversion device supplies power to a plurality of devices with different required voltages, it is required to provide an output terminal corresponding to each of the devices. [Means for solving the problem]

[0005] A power conversion device that solves the above problem is a power conversion device comprising: two input terminals to which an external power source is electrically connected; a first converter that performs power conversion of power input from the external power source via the two input terminals; and two first output terminals to which power converted by the first converter is output. The first converter comprises a switching circuit in which each switching element is connected in series to each other in the order of a first switching element, a second switching element, a third switching element, and a fourth switching element; a flying capacitor that electrically connects a connection point between the first switching element and the second switching element and a connection point between the third switching element and the fourth switching element; and a reactor. One of the two first output terminals is electrically connected to one end of the switching circuit via a first output line, and the other of the two first output terminals is electrically connected to the other end of the switching circuit via a second output line. One of the two input terminals is connected to the second switching element via a first output line. a first input line electrically connected to a connection point between the flying capacitor and the third switching element via a first input line, the other of the two input terminals electrically connected to one of the two first output terminals via a second input line, and the reactor is provided in at least one of the first input line and the second input line. The power conversion device comprises: a second converter that performs power conversion using a voltage across the flying capacitor as an input voltage, two second converter input terminals electrically connected to both ends of the flying capacitor, and two second output terminals to which power converted by the second converter is output, the second converter comprises: a primary side circuit that converts power input via the two second converter input terminals into AC power by switching operation of second converter switching elements and outputs the power, and a secondary side circuit that converts the AC power into DC power and outputs the DC power to the two second output terminals, and the second converter is an isolated DC / DC converter in which the primary side circuit and the secondary side circuit are electrically insulated from each other.

[0006] The first converter performs power conversion of the power input from an external power source. The second converter performs power conversion using the voltage across the flying capacitor as the input voltage. This makes it possible to output voltages of different values ​​from the first output terminal and the second output terminal. The power conversion device can supply power to multiple devices that require different voltages.

[0007] In the above power conversion device, the second converter may include a first connecting line and a second connecting line, each having one end connected to the primary side circuit and the other end connected to the secondary side circuit, a first capacitor provided on the first connecting line, and a second capacitor provided on the second connecting line.

[0008] In the above power conversion device, the secondary side circuit may include a first leg having a first coil and a first diode connected in series to each other, and the other end of the first connection line being connected to a connection point between the first coil and the first diode, a second leg having a second coil and a second diode connected in series to each other, and the other end of the second connection line being connected to a connection point between the second coil and the second diode, a first wiring connecting the first coil and the second coil to one of the two second output terminals, and a second wiring connecting the first diode and the second diode to the other of the two second output terminals, and the first diode and the second diode may be connected such that their anode terminals are on the negative side of the second output terminal and their cathode terminals are on the positive side of the second output terminal.

[0009] In the above power conversion device, the external power supply may be an AC power supply having a first terminal electrically connected to a first input terminal that is one of the two input terminals, and a second terminal electrically connected to a second input terminal that is the other of the two input terminals, and the first converter may include a positive pole wire through which the second input line is electrically connected to the first output line and a negative pole wire through which the second input line is electrically connected to the second output line, a first element arranged on the positive pole wire, and a second element arranged on the negative pole wire, and the first element and the second element may be configured to flow a current from the second element to the second input line when the first terminal is positive, and to flow a current from the second input line to the first element when the second terminal is positive.

[0010] In the above power conversion device, the first input terminal and the second input terminal may be connected via a switch, and the first element may be a switching element. Regarding the above-mentioned power conversion device, the power conversion device may be mounted on a vehicle, and a high-voltage battery may be electrically connected to the two first output terminals, and a low-voltage battery may be electrically connected to the two second output terminals. Effect of the Invention

[0011] According to the present invention, it is possible to supply power to a plurality of devices requiring different voltages. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a circuit diagram of a power conversion device according to a first embodiment. [Diagram 2] FIG. 2 is a circuit diagram of the power conversion device of the first embodiment. [Diagram 3] FIG. 3 is a circuit diagram of the second converter. [Figure 4] FIG. 4 is a circuit diagram of a power conversion device according to the second embodiment. [Diagram 5]FIG. 5 is a time chart showing the relationship between the states of the fifth switching element and the sixth switching element, the currents flowing through the fifth switching element and the sixth switching element, the currents flowing through the first coil and the second coil, the voltages across the first capacitor and the second capacitor, and the voltages across the first coil and the second coil. [Figure 6] FIG. 6 is a diagram showing the load current and the non-load current. [Figure 7] FIG. 7 is a diagram showing the load current and the non-load current. [Figure 8] FIG. 8 is a diagram showing the load current and the non-load current. [Figure 9] FIG. 9 is a diagram showing the load current and the non-load current. [Figure 10] FIG. 10 is a diagram showing the load current and the non-load current. [Figure 11] FIG. 11 is a diagram showing the load current and the non-load current. [Figure 12] FIG. 12 is a diagram showing a modification of the second converter. [Figure 13] FIG. 13 is a diagram showing a modification of the second converter. [Figure 14] FIG. 14 is a diagram showing a modification of the second converter. [Figure 15] FIG. 15 is a diagram showing a modification of the second converter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [First embodiment] A first embodiment of a power conversion device will be described. As shown in FIG. 1, a vehicle 10 includes a high-voltage battery 11, a low-voltage battery 12, and a power conversion device 20. The high-voltage battery 11 supplies power to, for example, a main engine of the vehicle 10. The main engine is, for example, a traction motor that drives the vehicle 10. The low-voltage battery 12 supplies power to, for example, an auxiliary engine of the vehicle 10. The auxiliary engine is an electrical component other than the main engine. The rated voltage of the high-voltage battery 11 is higher than the rated voltage of the low-voltage battery 12. Therefore, in order to charge the high-voltage battery 11, a higher voltage needs to be applied than when charging the low-voltage battery 12.

[0014] <Power conversion device> The power conversion device 20 includes two input terminals 21 and 22, a first converter 30, two first output terminals 23 and 24, and a capacitor 25. The two input terminals 21 and 22 are electrically connected to an external power source PS. The external power source PS is an AC power source. The external power source PS includes a first terminal T1 and a second terminal T2. The external power source PS switches between the first terminal T1 being positive and the second terminal T2 being positive depending on the passage of time. The first terminal T1 of the external power source PS is electrically connected to the first input terminal 21, which is one of the two input terminals 21 and 22. The second terminal T2 of the external power source PS is electrically connected to the second input terminal 22, which is the other of the two input terminals 21 and 22. The power conversion device 20 charges the high-voltage battery 11 and the low-voltage battery 12 by converting the power supplied from the external power source PS electrically connected to the input terminals 21 and 22.

[0015] The first converter 30 performs power conversion of the power input from the external power supply PS via the input terminals 21 and 22. The first converter 30 is a flying capacitor converter. The first converter 30 includes a switching circuit 31, a reactor 32, a flying capacitor 33, a first output line L1, and a second output line L2.

[0016] The switching circuit 31 includes a first switching element Q1, a second switching element Q2, a third switching element Q3, and a fourth switching element Q4. The switching circuit 31 is configured by connecting the switching elements Q1 to Q4 in series in the order of the first switching element Q1, the second switching element Q2, the third switching element Q3, and the fourth switching element Q4. The switching elements Q1 to Q4 are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switching elements Q1 to Q4 may be IGBTs (Insulated Gate Bipolar Transistors) or GaN-HEMTs.

[0017] The flying capacitor 33 electrically connects the connection point between the first switching element Q1 and the second switching element Q2 and the connection point between the third switching element Q3 and the fourth switching element Q4.

[0018] A switching circuit 31 is electrically connected to the two first output terminals 23, 24. In detail, the first output line L1 electrically connects the first output terminal 23, which is one of the two first output terminals 23, 24, to one end of the switching circuit 31. The second output line L2 electrically connects the first output terminal 24, which is the other of the two first output terminals 23, 24, to the other end of the switching circuit 31. A first switching element Q1 is connected to the first output terminal 23 via the first output line L1. A fourth switching element Q4 is connected to the first output terminal 24 via the second output line L2.

[0019] The first converter 30 includes a fifth switching element Q5, a sixth switching element Q6, a first input line L3, a second input line L4, a positive electrode line L5, and a negative electrode line L6. The fifth switching element Q5 and the sixth switching element Q6 are connected in series to each other. The fifth switching element Q5 and the sixth switching element Q6 are, for example, MOSFETs. The fifth switching element Q5 and the sixth switching element Q6 may be IGBTs or GaN-HEMTs.

[0020] The first input line L3 electrically connects the first input terminal 21 to the connection point between the second switching element Q2 and the third switching element Q3. The reactor 32 is provided in the first input line L3.

[0021] The second input line L4 electrically connects the second input terminal 22 to one of the two first output terminals 23, 24. The positive electrode line L5 electrically connects the second input line L4 and the first output line L1. Therefore, the second input line L4 is electrically connected to the first output terminal 23 via the positive electrode line L5 and the first output line L1.

[0022] The negative electrode line L6 electrically connects the second input line L4 and the second output line L2. Therefore, the second input line L4 is electrically connected to the first output terminal 24 via the negative electrode line L6 and the second output line L2.

[0023] Whether the second input line L4 is electrically connected to the first output terminal 23 or the first output terminal 24 is switched depending on whether the first terminal T1 or the second terminal T2 is positive. The fifth switching element Q5 is disposed on the positive electrode line L5. The sixth switching element Q6 is disposed on the negative electrode line L6. When the switching elements Q5 and Q6 are MOSFETs, the switching elements Q5 and Q6 are provided so that the forward direction of the parasitic diode is from the second output line L2 to the first output line L1. That is, the anode terminal of the parasitic diode is electrically connected to the second output line L2, and the cathode terminal of the parasitic diode is electrically connected to the first output line L1.

[0024] The first output terminal 23 is electrically connected to the positive electrode of the high-voltage battery 11. The first output terminal 24 is electrically connected to the negative electrode of the high-voltage battery 11. In the first converter 30, AC power supplied from the external power source PS is converted to DC power by the switching operations of the first switching element Q1 to the fourth switching element Q4, and the DC power is output from the first output terminals 23, 24. The DC power output from the first output terminals 23, 24 is applied to the high-voltage battery 11. This charges the high-voltage battery 11. The first converter 30 boosts the voltage of the AC power and outputs it. The first converter 30 may also be a converter that lowers the voltage of the AC power and outputs it.

[0025] The capacitor 25 is provided between the first converter 30 and the high-voltage battery 11 . The power conversion device 20 includes two second converter input terminals 41, 42, a second converter 50, and two second output terminals 43, 44.

[0026] The two second converter input terminals 41, 42 are electrically connected to both ends of the flying capacitor 33. In detail, the second converter input terminal 41 is electrically connected to one end of the flying capacitor 33, and the second converter input terminal 42 is electrically connected to the other end of the flying capacitor 33.

[0027] As shown in FIG. 3, the second converter 50 includes a primary circuit 51, a first connection line L11, a second connection line L12, a first capacitor C1, a second capacitor C2, a secondary circuit 61, and a capacitor .

[0028] The primary circuit 51 includes an upper arm switching element Q41 and a lower arm switching element Q42. The upper arm switching element Q41 and the lower arm switching element Q42 each include a free wheel diode D. The primary circuit 51 is a half bridge circuit of switching elements Q41, Q42. The upper arm switching element Q41 and the lower arm switching element Q42 are connected in series to each other. The upper arm switching element Q41 is electrically connected to the second converter input terminal 41. The lower arm switching element Q42 is electrically connected to the second converter input terminal 42. The switching elements Q41, Q42 are, for example, MOSFETs. The switching elements Q41, Q42 may be IGBTs or GaN-HEMTs.

[0029] The secondary circuit 61 includes a first leg 62, a second leg 63, a wiring 64, and a wiring 65. The first leg 62 includes a first coil L21 and a first diode D11 connected in series to each other. The second leg 63 includes a second coil L22 and a second diode D12 connected in series to each other. The secondary circuit 61 is electrically connected to the second output terminals 43, 44. The wiring 64 connects the first coil L21 and the second coil L22 to the second output terminal 43, which is one of the two second output terminals 43, 44. The wiring 65 connects the first diode D11 and the second diode D12 to the second output terminal 44, which is the other of the two second output terminals 43, 44. The wiring 64 is an example of a first wiring. The wiring 65 is an example of a second wiring.

[0030] The anode terminals of the first diode D11 and the second diode D12 are connected to the negative side of the second output terminals 43, 44. The cathode terminals of the first diode D11 and the second diode D12 are connected to the positive side of the second output terminals 43, 44. The second converter 50 is a series resonant circuit.

[0031] One end of each of the first connection line L11 and the second connection line L12 is electrically connected to the primary circuit 51. More specifically, one end of the first connection line L11 is connected to the connection point between the upper arm switching element Q41 and the lower arm switching element Q42. One end of the second connection line L12 is connected to the lower arm switching element Q42.

[0032] The other end of each of the first connection line L11 and the second connection line L12 is electrically connected to the secondary circuit 61. More specifically, the other end of the first connection line L11 is connected to a connection point between the first coil L21 and the first diode D11. The other end of the second connection line L12 is connected to a connection point between the second coil L22 and the second diode D12. This electrically connects the primary circuit 51 and the secondary circuit 61 by the first connection line L11 and the second connection line L12.

[0033] The first capacitor C1 is provided on the first connection line L11. The second capacitor C2 is provided on the second connection line L12. In the second converter 50, the primary side circuit 51 and the secondary side circuit 61 are insulated by the first capacitor C1 and the second capacitor C2. The second converter 50 is an insulating type DC / DC converter in which the primary side circuit 51 and the secondary side circuit 61 are electrically insulated. The second converter 50 of this embodiment is a capacitor insulating converter insulated between the primary side circuit 51 and the secondary side circuit 61 by the first capacitor C1 and the second capacitor C2.

[0034] The second output terminals 43, 44 are electrically connected to the low-voltage battery 12. More specifically, the second output terminal 43 is connected to the positive electrode of the low-voltage battery 12. The second output terminal 44 is connected to the negative electrode of the low-voltage battery 12. Therefore, of the second output terminals 43, 44, the second output terminal 43 is the positive side, and the second output terminal 44 is the negative side.

[0035] The capacitor 54 is provided between the secondary circuit 61 and the low-voltage battery 12 . In the second converter 50, the voltage across the flying capacitor 33 is input as an input voltage to a primary circuit 51. The primary circuit 51 converts the power input via the two second converter input terminals 41, 42 into AC power by the switching operation of the switching elements Q41, Q42. As a result, the AC power is transmitted to the secondary circuit 61 via the first connection line L11 and the second connection line L12. The secondary circuit 61 converts the AC power input from the first connection line L11 and the second connection line L12 into DC power and outputs it to the second output terminals 43, 44. The switching elements Q41, Q42 are an example of a second converter switching element.

[0036] The power conversion device 20 includes a control unit 71. The control unit 71 includes a processor and a storage unit. The processor is, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP). The storage unit includes a random access memory (RAM) and a read only memory (ROM). The storage unit stores program codes or instructions configured to cause the processor to execute processes. The storage unit, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The control unit 71 may be configured by a hardware circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control unit 71, which is a processing circuit, may include one or more processors operating according to a computer program, one or more hardware circuits such as an ASIC or an FPGA, or a combination thereof.

[0037] <Control performed by the control unit> The control unit 71 controls the switching elements Q1 to Q6 to control the voltage of the DC power output from the first converter 30 to the first output terminals 23, 24 and also controls the voltage across the flying capacitor 33.

[0038] When supplying power from the external power source PS to the high voltage battery 11 and the low voltage battery 12, the control unit 71 alternately switches the switching pattern of the switching elements Q1 to Q4 between a first pattern and a second pattern. The first pattern is a switching pattern in which the first switching element Q1 is off, the second switching element Q2 is on, the third switching element Q3 is off, and the fourth switching element Q4 is on. The second pattern is a switching pattern in which the first switching element Q1 is on, the second switching element Q2 is off, the third switching element Q3 is on, and the fourth switching element Q4 is off.

[0039] When the first terminal T1 of the external power supply PS is positive, the control unit 71 turns off the fifth switching element Q5 and turns on the sixth switching element Q6. In this case, a current is permitted to flow from the sixth switching element Q6 to the second input line L4, while a current is restricted from flowing from the second input line L4 to the fifth switching element Q5. A current flows from the sixth switching element Q6 to the second input line L4.

[0040] When the second terminal T2 of the external power supply PS is positive, the control unit 71 turns on the fifth switching element Q5 and turns off the sixth switching element Q6. In this case, a current is allowed to flow from the second input line L4 to the fifth switching element Q5, while a current is restricted from flowing from the second input line L4 to the sixth switching element Q6. A current flows from the second input line L4 to the fifth switching element Q5. The fifth switching element Q5 is an example of a first element. In this embodiment, the first element is a switching element. The sixth switching element Q6 is an example of a second element.

[0041] 1, when the first terminal T1 of the external power supply PS is positive and in the first pattern, a current flows in the order of the first terminal T1 of the external power supply PS → the reactor 32 → the second switching element Q2 → the flying capacitor 33 → the fourth switching element Q4 → the sixth switching element Q6 → the second terminal T2 of the external power supply PS. This charges the flying capacitor 33.

[0042] 1, when the first terminal T1 of the external power supply PS is positive and in the second pattern, a current flows in the order of the first terminal T1 of the external power supply PS → the reactor 32 → the third switching element Q3 → the flying capacitor 33 → the first switching element Q1 → the high-voltage battery 11 → the sixth switching element Q6 → the second terminal T2 of the external power supply PS. As a result, the flying capacitor 33 is discharged.

[0043] 2, when the second terminal T2 of the external power supply PS is positive and in the second pattern, a current flows in the order of the second terminal T2 of the external power supply PS → the fifth switching element Q5 → the first switching element Q1 → the flying capacitor 33 → the third switching element Q3 → the reactor 32 → the first terminal T1 of the external power supply PS. This charges the flying capacitor 33.

[0044] 2, when the second terminal T2 of the external power supply PS is positive and in the first pattern, a current flows in the order of the second terminal T2 of the external power supply PS → the fifth switching element Q5 → the high-voltage battery 11 → the fourth switching element Q4 → the flying capacitor 33 → the second switching element Q2 → the reactor 32 → the first terminal T1 of the external power supply PS. As a result, the flying capacitor 33 is discharged.

[0045] The control unit 71 controls the switching elements Q1 to Q6 so that the output voltage output from the first output terminals 23, 24 follows the target value and the voltage across the flying capacitor 33 follows the target value. In this way, the control unit 71 can charge the high-voltage battery 11 by controlling the output voltage output from the first output terminals 23, 24. The control unit 71 can control the voltage across the flying capacitor 33.

[0046] Controller 71 controls switching elements Q41, Q42 to control the voltage of DC power output from second converter 50 to second output terminals 43, 44. For example, controller 71 alternates between a third pattern and a fourth pattern for switching elements Q41, Q42. The third pattern is a switching pattern in which upper arm switching element Q41 is on and lower arm switching element Q42 is off. The fourth pattern is a switching pattern in which upper arm switching element Q41 is off and lower arm switching element Q42 is on.

[0047] The control unit 71 controls the switching elements Q41, Q42 so that the output voltages output from the second output terminals 43, 44 follow the target value. In this way, the control unit 71 can charge the low-voltage battery 12 by controlling the output voltages output from the second output terminals 43, 44.

[0048] When power is supplied from the external power source PS to the high-voltage battery 11 and power is not supplied to the low-voltage battery 12, the control unit 71 alternately switches the switching patterns of the switching elements Q1 to Q4 between a fifth pattern and a sixth pattern. The fifth pattern is a switching pattern in which the first switching element Q1 is off, the second switching element Q2 is off, the third switching element Q3 is on, and the fourth switching element Q4 is on. The sixth pattern is a switching pattern in which the first switching element Q1 is on, the second switching element Q2 is on, the third switching element Q3 is off, and the fourth switching element Q4 is off.

[0049] When the first terminal T1 of the external power supply PS is positive, the control unit 71 turns off the fifth switching element Q5 and turns on the sixth switching element Q6. In this case, a current is permitted to flow from the second output line L2 to the sixth switching element Q6, while a current is restricted from flowing from the first output line L1 to the fifth switching element Q5. A current flows from the sixth switching element Q6 to the second input line L4.

[0050] When the second terminal T2 of the external power supply PS is positive, the control unit 71 turns on the fifth switching element Q5 and turns off the sixth switching element Q6. In this case, a current is permitted to flow from the second input line L4 to the fifth switching element Q5, while a current is restricted from flowing from the second input line L4 to the sixth switching element Q6. A current flows from the second input line L4 to the fifth switching element Q5.

[0051] When the first terminal T1 of the external power supply PS is positive and in the fifth pattern, current flows in the following order: first terminal T1 of the external power supply PS → reactor 32 → third switching element Q3 → fourth switching element Q4 → sixth switching element Q6 → second terminal T2 of the external power supply PS.

[0052] When the first terminal T1 of the external power supply PS is positive and in the sixth pattern, current flows in the following order: first terminal T1 of the external power supply PS → reactor 32 → second switching element Q2 → first switching element Q1 → high-voltage battery 11 → sixth switching element Q6 → second terminal T2 of the external power supply PS.

[0053] When the second terminal T2 of the external power supply PS is positive and in the sixth pattern, current flows in the following order: second terminal T2 of the external power supply PS → fifth switching element Q5 → first switching element Q1 → second switching element Q2 → reactor 32 → first terminal T1 of the external power supply PS.

[0054] When the second terminal T2 of the external power supply PS is positive and in the fifth pattern, current flows in the following order: second terminal T2 of the external power supply PS → fifth switching element Q5 → high-voltage battery 11 → fourth switching element Q4 → third switching element Q3 → reactor 32 → first terminal T1 of the external power supply PS.

[0055] The control unit 71 controls the switching elements Q1 to Q6 so that the output voltages output from the first output terminals 23, 24 follow a target value. In this way, the control unit 71 can charge the high-voltage battery 11 by controlling the output voltages output from the first output terminals 23, 24.

[0056] [Operation of the first embodiment] The power conversion device 20 includes a first converter 30 and a second converter 50. The first converter 30 can transform and output a voltage input from an external power supply PS. The second converter 50 can use a voltage across the flying capacitor 33 as an input voltage and transform and output the input voltage. This allows the power conversion device 20 to output different output voltages. As in the embodiment, if the power conversion device 20 is mounted on the vehicle 10, the high-voltage battery 11 can be charged by the first converter 30 and the low-voltage battery 12 can be charged by the second converter 50.

[0057] The control unit 71 controls the switching elements Q1 to Q6 to charge the high-voltage battery 11 and control the voltage across the flying capacitor 33. Since the voltage across the flying capacitor 33 is the input voltage input to the second converter 50, controlling the voltage across the flying capacitor 33 makes it possible to control the input voltage of the second converter 50.

[0058] The first capacitor C1 and the second capacitor C2 block DC power while passing AC power, so that in the second converter 50, the primary side circuit 51 and the secondary side circuit 61 are insulated from each other by the first capacitor C1 and the second capacitor C2.

[0059] When the primary side circuit 51 and the secondary side circuit 61 are insulated by the first capacitor C1 and the second capacitor C2, the transformation ratio may not be increased as compared to the case of insulation using a transformer. As a result, the difference between the voltage input from the external power supply PS and the output voltage of the second converter 50 may not be increased. For example, if the target value of the output voltage of the second converter 50 is 14 [V] and the voltage of the power supplied from the external power supply PS is several hundred [V], it is necessary to step down the several hundred [V] to 14 [V]. It is difficult to step down the several hundred [V] to 14 [V] by the second converter 50 without a transformer.

[0060] In contrast, in the power conversion device 20 of the present embodiment, the voltage across the flying capacitor 33 is used as the input voltage of the second converter 50. The input voltage of the second converter 50 can be controlled by controlling the voltage across the flying capacitor 33 with the first converter 30. By making the voltage across the flying capacitor 33 lower than the voltage of the power supplied from the external power supply PS, the second converter 50 can easily output the target value of the output voltage. For example, if the voltage across the flying capacitor 33 is set by the first converter 30 to the same value as the target value of the output voltage of the second converter 50, there is no need to step down the voltage with the second converter 50. Therefore, even if a transformer is not used, the output voltage of the second converter 50 can be controlled.

[0061] [Effects of the first embodiment] (1-1) The first converter 30 performs power conversion of the power input from the external power supply PS. The second converter 50 performs power conversion using the voltage across the flying capacitor 33 as the input voltage. This makes it possible to output voltages of different values ​​from the first output terminals 23, 24 and the second output terminals 43, 44. The power conversion device 20 can supply power to a plurality of devices requiring different voltages. In this embodiment, by supplying power to both the high voltage battery 11 and the low voltage battery 12, it is possible to charge both the high voltage battery 11 and the low voltage battery 12.

[0062] (1-2) In the second converter 50, the primary circuit 51 and the secondary circuit 61 are insulated from each other by the first capacitor C1 and the second capacitor C2. The capacitor is smaller than a transformer. Therefore, compared to the case where the primary circuit 51 and the secondary circuit 61 are insulated from each other by using a transformer, it is possible to suppress an increase in size of the second converter 50, and therefore an increase in size of the power conversion device 20.

[0063] Moreover, by controlling the voltage across the flying capacitor 33 in the first converter 30, the input voltage of the second converter 50 can be controlled. As a result, the output voltage of the second converter 50 can be controlled.

[0064] (1-3) The external power supply PS is an AC power supply. The power conversion device 20 includes a fifth switching element Q5 and a sixth switching element Q6. The fifth switching element Q5 and the sixth switching element Q6 are configured to pass a current from the sixth switching element Q6 to the second input line L4 when the first terminal T1 of the external power supply PS is positive, and to pass a current from the second input line L4 to the fifth switching element Q5 when the second terminal T2 of the external power supply PS is positive. This allows power conversion to be performed even when the external power supply PS is an AC power supply.

[0065] (1-4) The power conversion device 20 is mounted on a vehicle 10. The vehicle 10 is equipped with a high-voltage battery 11 required to drive a main engine, and a low-voltage battery 12 required to drive an auxiliary engine. For this reason, the power conversion device 20 needs to output a voltage for charging the high-voltage battery 11 and a voltage for charging the low-voltage battery 12. The power conversion device 20 outputs a voltage for charging the high-voltage battery 11 from first output terminals 23, 24, and outputs a voltage for charging the low-voltage battery 12 from second output terminals 43, 44. This allows the high-voltage battery 11 and the low-voltage battery 12 to be charged by a single power conversion device 20.

[0066] [Second embodiment] A second embodiment of the power conversion device will be described. 4, the power conversion device 20 of the second embodiment includes a switch 34 in addition to the configuration of the power conversion device 20 of the first embodiment. The switch 34 connects the first input terminal 21 and the second input terminal 22 when in a closed state.

[0067] In the power conversion device 20 of the second embodiment, in addition to the operation of the first embodiment, the low-voltage battery 12 can be charged by supplying power from the high-voltage battery 11 to the low-voltage battery 12. When the low-voltage battery 12 is charged by the high-voltage battery 11, the switch 34 is closed. When the high-voltage battery 11 and the low-voltage battery 12 are charged by the external power supply PS, the switch 34 is opened.

[0068] The control performed by the control unit 71 when the low-voltage battery 12 is charged by the high-voltage battery 11 will be described. The control unit 71 maintains the first switching element Q1 and the third switching element Q3 OFF. The control unit 71 maintains the second switching element Q2 and the fourth switching element Q4 ON. In this state, the fifth switching element Q5 and the sixth switching element Q6 are operated as a chopper to step down the voltage input from the high voltage battery 11. In detail, the fifth switching element Q5 and the sixth switching element Q6 are alternately turned ON to step down and output the voltage input from the high voltage battery 11, thereby controlling the voltage across the flying capacitor 33.

[0069] Controller 71 alternately turns on upper arm switching element Q41 and lower arm switching element Q42. This causes series resonance operation to control the output voltage of second converter 50. This makes it possible to charge low voltage battery 12. The operation of second converter 50 of this embodiment will now be described in detail.

[0070] Figure 5 shows the on and off states of the upper arm switching element Q41 and the lower arm switching element Q42, the current Ip flowing through the upper arm switching element Q41, the current In flowing through the lower arm switching element Q42, the current IL1 flowing through the first coil L21, the current IL2 flowing through the second coil L22, the voltage VCp across the first capacitor C1, the voltage VCn across the second capacitor C2, the voltage VLp across the first coil L21, and the voltage VLn across the second coil L22.

[0071] 6 to 11 show a load current I1 and a non-load current I2. The load current I1 is a current that flows through the low-voltage battery 12, which is a load. The non-load current I2 is a current that does not flow through the low-voltage battery 12, which is a load.

[0072] As shown in Fig. 5, at time T11, the upper arm switching element Q41 is on and the lower arm switching element Q42 is off. As shown in Fig. 6, at time T11, the upper arm switching element Q41 is on, so that the voltage across the flying capacitor 33, which is a DC power supply, is input to the second converter 50. A load current I1 flows through a path that passes through the upper arm switching element Q41, the first capacitor C1, the first coil L21, the low voltage battery 12, the second diode D12, and the second capacitor C2. A non-load current I2 flows through a path that passes through the upper arm switching element Q41, the first capacitor C1, the first coil L21, the second coil L22, and the second capacitor C2. The first capacitor C1 and the second capacitor C2 are charged.

[0073] At time T12, the upper arm switching element Q41 is switched off. This stops power being supplied from the flying capacitor 33 to the second converter 50. A load current I1 flows due to the energy stored in the first coil L21. As shown in FIG. 7, the load current I1 flows through a path passing through the first coil L21, the low-voltage battery 12, and the first diode D11. A non-load current I2 flows due to the energy stored in the second coil L22. The non-load current I2 flows through a path passing through the second coil L22, the second capacitor C2, the freewheeling diode D of the lower arm switching element Q42, the first capacitor C1, and the first coil L21. The non-load current I2 causes the lower arm switching element Q42 to be reverse conductive.

[0074] At time T13, the lower arm switching element Q42 is in reverse conduction and is turned on. Since the lower arm switching element Q42 is in reverse conduction, the voltage across the lower arm switching element Q42 is zero. This enables ZVS (Zero Voltage Switching). As shown in Fig. 8, the path through which the load current I1 flows is the same as at time T12. The non-load current I2 flows through the path that passes through the second coil L22, the second capacitor C2, the lower arm switching element Q42, the first capacitor C1, and the first coil L21.

[0075] As time passes from time T13, the output current from the first coil L21 and the second coil L22 decreases. At time T14, the first capacitor C1 and the second capacitor C2 are switched to discharging. This changes the current polarity of the non-load current I2. As shown in FIG. 9, the load current I1 flows through a path passing through the first capacitor C1, the lower arm switching element Q42, the second capacitor C2, the second coil L22, the low-voltage battery 12, and the first diode D11. The voltages of the first capacitor C1 and the second capacitor C2 decrease due to discharging. Energy is stored in the first coil L21 and the second coil L22.

[0076] At time T15, the lower arm switching element Q42 is switched off. As shown in Fig. 10, a load current I1 flows through a path passing through the first capacitor C1, the freewheeling diode D of the upper arm switching element Q41, the second capacitor C2, the second coil L22, the low-voltage battery 12, and the first diode D11. A non-load current I2 flows through a path passing through the second capacitor C2, the second coil L22, the first coil L21, the first capacitor C1, and the freewheeling diode D of the upper arm switching element Q41. The load current I1 and the non-load current I2 cause the upper arm switching element Q41 to be reverse conductive.

[0077] At time T16, the upper-arm switching element Q41 is switched on. Since the upper-arm switching element Q41 is in reverse conduction, the voltage across the upper-arm switching element Q41 is zero. This enables ZVS. As shown in Fig. 11, the load current I1 and the non-load current I2 change paths from the freewheeling diode D of the upper-arm switching element Q41 to pass through the upper-arm switching element Q41.

[0078] [Operation of the second embodiment] The power conversion device 20 includes a switch 34. By closing this switch 34 and controlling the first switching element Q1 to the sixth switching element Q6, the voltage of the high-voltage battery 11 can be stepped down and input to the second converter 50. The second converter 50 steps down the input voltage and outputs it. This charges the low-voltage battery 12.

[0079] Here, the second converter 50 of this embodiment is a capacitor-insulated converter in which the primary circuit 51 and the secondary circuit 61 are insulated by the first capacitor C1 and the second capacitor C2. The capacitor-insulated converter does not include a transformer, so it is difficult to step down the input voltage. In particular, it is difficult to step down the input voltage when the load is light, and when a half-bridge circuit is used as the primary circuit 51 as in this embodiment, the input voltage may only be stepped down to 1 / 2. For this reason, it may be necessary to lower the voltage across the flying capacitor 33 according to the output voltage of the second converter 50. For example, if the target value of the output voltage of the second converter 50 is 15 [V] and the second converter 50 can only step down to 1 / 2 the input voltage, it is necessary to set the voltage across the flying capacitor 33, which is the input voltage of the second converter 50, to 30 [V]. The lower the voltage across the flying capacitor 33, the larger the current. A current from the high voltage battery 11 is supplied through the second switching element Q2, the fourth switching element Q4, the fifth switching element Q5, and the sixth switching element Q6. The lower the voltage across the flying capacitor 33, the larger the current that flows through these switching elements Q2, Q4, Q5, and Q6. As a result, the current rating required for the switching elements Q2, Q4, Q5, and Q6 may become large.

[0080] In this embodiment, the secondary circuit 61 includes a leg 62 in which a first coil L21 and a first diode D11 are connected in series, and a leg 63 in which a second coil L22 and a second diode D12 are connected in series. In the secondary circuit 61, an output current is generated in each of the coils L21 and L22 of the legs 62 and 63. Since the sum of the output currents of the two coils L21 and L22 is the total output current, the current input to the secondary circuit 61 can be increased. As a result, it becomes possible to step down the voltage using the secondary circuit 61, and the voltage of the flying capacitor 33 can be increased accordingly.

[0081] [Effects of the second embodiment] (2-1) The power conversion device 20 includes a switch 34. This allows the low-voltage battery 12 to be charged using the high-voltage battery 11.

[0082] (2-2) The secondary circuit 61 includes legs 62 and 63. This allows the output current of the secondary circuit 61 to be increased. By increasing the output current of the secondary circuit 61, the output voltage of the secondary circuit 61 decreases. As a result, the step-down ratio of the second converter 50 can be increased. Even if the voltage across the flying capacitor 33 is increased, the output voltage required of the second converter 50 can be output. Therefore, by lowering the voltage across the flying capacitor 33, it is possible to suppress an increase in the current flowing through the switching elements Q2, Q4, Q5, and Q6.

[0083] [Example of change] Each embodiment can be modified as follows: Each embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0084] In the first embodiment, the second converter 50 may have a configuration as shown in Fig. 12. The second converter 50 shown in Fig. 12 is an LLC converter. The second converter 50 includes a primary side circuit 51, a first connecting line L11 and a second connecting line L12, a first capacitor C1, a second capacitor C2, a secondary side circuit 61, inductors 52 and 53, and a capacitor 54.

[0085] The primary side circuit 51 includes a first upper arm switching element Q11, a first lower arm switching element Q12, a second upper arm switching element Q13, and a second lower arm switching element Q14. The primary side circuit 51 is a full bridge circuit of the switching elements Q11 to Q14. The first upper arm switching element Q11 and the first lower arm switching element Q12 are connected in series to each other. The second upper arm switching element Q13 and the second lower arm switching element Q14 are connected in series to each other. The upper arm switching elements Q11 and Q13 are electrically connected to the second converter input terminal 41. The lower arm switching elements Q12 and Q14 are electrically connected to the second converter input terminal 42. The switching elements Q11 to Q14 are, for example, MOSFETs. The switching elements Q11 to Q14 may be IGBTs or GaN-HEMTs. The switching elements Q11 to Q14 are an example of second converter switching elements.

[0086] The secondary circuit 61 includes four diodes D1 to D4. The secondary circuit 61 is a full bridge circuit of the diodes D1 to D4. The diodes D1 and D2 are connected in series to each other in the forward direction. The diodes D3 and D4 are connected in series to each other in the forward direction.

[0087] The inductor 52 is provided on the first connection line L11 closer to the primary circuit 51 than the first capacitor C1. The inductor 53 connects the first connection line L11 and the second connection line L12 closer to the secondary circuit 61 than the first capacitor C1 and the second capacitor C2.

[0088] The secondary circuit 61 is electrically connected to the second output terminals 43 and 44. The diodes D1 and D3 are connected to the second output terminal 43. The diodes D2 and D4 are connected to the second output terminal 44.

[0089] The first connection line L11 connects the connection point between the first upper arm switching element Q11 and the first lower arm switching element Q12 to the connection point between the diode D1 and the diode D2. The second connection line L12 connects the connection point between the second upper arm switching element Q13 and the second lower arm switching element Q14 to the connection point between the diode D3 and the diode D4.

[0090] In the LLC converter, soft switching of the switching elements Q11 to Q14 can be performed by utilizing resonance using the first capacitor C1, the second capacitor C2, and the inductors 52 and 53. This makes it possible to reduce power loss due to the switching operation of the switching elements Q11 to Q14.

[0091] In the first embodiment, the primary circuit 51 of the second converter 50 may have a circuit configuration shown in FIG. 13. The primary circuit 51 includes two second converter switching elements Q21, Q22 connected in series to each other. The secondary circuit 61 is, for example, a full bridge circuit of diodes. The first connection line L11 is connected to a connection point between the two second converter switching elements Q21, Q22. The second connection line L12 is connected to the second converter switching element Q22. The primary circuit 51 converts the input power into AC power by the switching operation of the two second converter switching elements Q21, Q22. The secondary circuit 61 converts the AC power into DC power. Even when the second converter 50 shown in FIG. 13 is used, the same effects as those of the embodiment can be obtained.

[0092] In the first embodiment, the second converter 50 may have a circuit configuration shown in FIG. 14. The circuit configuration shown in FIG. 14 is a Cuk circuit. The primary circuit 51 includes a first inductor 81 electrically connected to the second converter input terminal 41, and a second converter switching element Q31 electrically connecting the two second converter input terminals 41, 42 to each other via the first inductor 81. The secondary circuit 61 includes a second inductor 82 electrically connected to the second output terminal 43, and a diode 83 electrically connecting the two second output terminals 43, 44 to each other via the second inductor 82. The anode terminal of the diode 83 is electrically connected to the second output terminal 43. The cathode terminal of the diode 83 is electrically connected to the second output terminal 44. The primary circuit 51 and the secondary circuit 61 are insulated by the first capacitor C1 and the second capacitor C2. Even when the second converter 50 shown in FIG. 14 is used, the same effects as those of the embodiment can be obtained.

[0093] In the first embodiment, the second converter 50 may have a circuit configuration shown in FIG. 15. The circuit configuration shown in FIG. 15 is a SEPIC circuit. The primary circuit 51 is the same as the circuit configuration shown in FIG. 14. The secondary circuit 61 includes a diode 91 electrically connected to the second output terminal 43 and a second inductor 92 electrically connecting the two second output terminals 43, 44 to each other via the diode 91. The anode terminal of the diode 91 is electrically connected to the first capacitor C1. The cathode terminal of the diode 91 is electrically connected to the second output terminal 43. The primary circuit 51 and the secondary circuit 61 are insulated by the first capacitor C1 and the second capacitor C2. Even when the second converter 50 shown in FIG. 5 is used, the same effects as those of the embodiment can be obtained.

[0094] In the first embodiment, the fifth switching element Q5, which is the first element, and the sixth switching element Q6, which is the second element, may be diodes. In this case, the diodes are provided so that the forward direction is from the second output line L2 to the first output line L1. In detail, the anode terminal of the diode, which is the first element, is electrically connected to the cathode terminal of the diode, which is the second element. The cathode terminal of the diode, which is the first element, is electrically connected to the first output line L1. The anode terminal of the diode, which is the second element, is electrically connected to the second output line L2.

[0095] In each embodiment, the external power supply PS may be a DC power supply. In this case, the power conversion device 20 may not include the fifth switching element Q5 and the sixth switching element Q6. When the positive electrode side of the DC power supply is connected to the input terminal 21, the negative electrode side may be connected to the second output line L2. When the negative electrode side of the DC power supply is connected to the input terminal 21, the positive electrode side may be connected to the first output line L1. When the external power supply PS of the second embodiment is a DC power supply, the second element may be a diode.

[0096] In each embodiment, the reactor 32 is provided on the first end T1 side of the external power supply PS, but it may be provided on the second end T2 side or on both ends. That is, it is sufficient that the reactor 32 is provided on at least one of the first input line L3 and the second input line L4.

[0097] In the first embodiment, the second converter 50 may step up the input voltage and output it, or may step down the input voltage and output it. In each embodiment, the power conversion device 20 may be capable of outputting the power input from the high-voltage battery 11 as AC power from the input terminals 21, 22. For example, the control unit 71 alternately switches the switching patterns of the first switching element Q1 to the sixth switching element Q6 between a seventh pattern and an eighth pattern. The seventh pattern is a switching pattern in which the first switching element Q1 is on, the second switching element Q2 is on, the third switching element Q3 is off, the fourth switching element Q4 is off, the fifth switching element Q5 is off, and the sixth switching element Q6 is on. The eighth pattern is a switching pattern in which the first switching element Q1 is off, the second switching element Q2 is off, the third switching element Q3 is on, the fourth switching element Q4 is on, the fifth switching element Q5 is on, and the sixth switching element Q6 is off.

[0098] In the first embodiment, the second converter 50 may be an isolated DC / DC converter in which a primary circuit and a secondary circuit are electrically insulated from each other by a transformer. In the second embodiment, the first coil L21 and the first diode D11 may be interchanged, and the second coil L22 and the second diode D12 may be interchanged. In this case, the wiring 64 is the second wiring. The wiring 65 is the first wiring.

[0099] In the second embodiment, the secondary circuit 61 may further include a leg. The leg is a series connection of a coil and a diode. In this case, the coil of the leg to be added and the coils L21 and L22 of the legs 62 and 63 are connected by a first wiring, and the diode of the leg to be added and the diodes D11 and D12 of the legs 62 and 63 are connected by a second wiring.

[0100] In each embodiment, the second converter 50 may be a series resonant circuit having a circuit configuration different from that in the embodiment. [Explanation of symbols]

[0101] C1...first capacitor, C2...second capacitor, D11...first diode, D12...second diode, L1...first output line, L2...second output line, L21...first coil, L22...second coil, L3...first input line, L4...second input line, L5...positive line, L6...negative line, PS...external power supply, Q1...first switching element, Q2...second switching element, Q3...third switching element, Q4...fourth switching element, Q5...fifth switching element, Q6...sixth switching element, Q41, Q42...second converter switching elements. A switching element, T1...first terminal, T2...second terminal, 10...vehicle, 11...high-voltage battery, 12...low-voltage battery, 20...power conversion device, 21, 22...input terminal, 23, 24...first output terminal, 30...first converter, 31...switching circuit, 32...reactor, 33...flying capacitor, 34...switch, 41, 42...input terminal for second converter, 43, 44...second output terminal, 50...second converter, 51...primary side circuit, 52, 53...inductor, 61...secondary side circuit, 62...first leg, 63...second leg, 64, 65...wiring.

Claims

1. Two input terminals to which an external power source is electrically connected; a first converter that performs power conversion of power input from the external power supply via the two input terminals; A power conversion device including: two first output terminals to which power converted by the first converter is output; The first converter is a switching circuit in which a first switching element, a second switching element, a third switching element, and a fourth switching element are connected in series in this order; a flying capacitor electrically connecting a connection point between the first switching element and the second switching element and a connection point between the third switching element and the fourth switching element; A reactor, one of the two first output terminals is electrically connected to one end of the switching circuit via a first output line; the other of the two first output terminals is electrically connected to the other terminal of the switching circuit via a second output line; one of the two input terminals is electrically connected to a connection point between the second switching element and the third switching element via a first input line; the other of the two input terminals is electrically connected to one of the two first output terminals via a second input line; the reactor is provided in at least one of the first input line and the second input line, The power conversion device is a second converter that performs power conversion using the voltage across the flying capacitor as an input voltage; two second converter input terminals electrically connected to both ends of the flying capacitor; and two second output terminals to which electric power converted by the second converter is output. The second converter is a primary side circuit that converts the power input via the two second converter input terminals into AC power by a switching operation of a second converter switching element and outputs the AC power; a secondary side circuit that converts AC power into DC power and outputs the DC power to the two second output terminals, The second converter is an isolated DC / DC converter in which the primary side circuit and the secondary side circuit are electrically insulated from each other.

2. The second converter is a first connection line and a second connection line, each of which has one end connected to the primary circuit and the other end connected to the secondary circuit; a first capacitor provided on the first connection line; The power conversion device according to claim 1 , further comprising: a second capacitor provided in the second connection line.

3. The secondary side circuit includes: a first leg including a first coil and a first diode connected in series to each other, the other end of the first connection line being connected to a connection point between the first coil and the first diode; a second leg including a second coil and a second diode connected in series to each other, the other end of the second connection line being connected to a connection point between the second coil and the second diode; a first wiring that connects the first coil and the second coil to one of the two second output terminals; a second wiring connecting the first diode and the second diode to the other of the two second output terminals, 3. The power conversion device according to claim 2, wherein the first diode and the second diode are connected such that their anode terminals are connected to the negative side of the second output terminal and their cathode terminals are connected to the positive side of the second output terminal.

4. the external power supply is an AC power supply including a first end electrically connected to a first input end which is one of the two input ends, and a second end electrically connected to a second input end which is the other of the two input ends; The first converter is a positive line electrically connecting the second input line to the first output line and a negative line electrically connecting the second input line to the second output line; A first element disposed on the positive electrode line; A second element disposed on the negative electrode line, 2. The power conversion device according to claim 1, wherein the first element and the second element are configured to pass a current from the second element to the second input line when the first terminal is positive, and to pass a current from the second input line to the first element when the second terminal is positive.

5. the first input terminal and the second input terminal are connected via a switch, The power conversion device according to claim 4 , wherein the first element is a switching element.

6. The power conversion device is mounted on a vehicle, A high-voltage battery is electrically connected to the two first output terminals, The power conversion device according to any one of claims 1 to 5, wherein a low-voltage battery is electrically connected to the two second output terminals.

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