Power conversion device

Abstract

A power conversion device is provided. A power conversion device is provided with two input terminals, a first converter, and two first output terminals configured so as to output power converted by the first converter. The first converter includes a switching circuit, a flying capacitor, and a reactor. A power conversion device is provided with: a second converter configured so as to perform power conversion using a voltage across a 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 configured so as to output the power converted by the second converter. The second converter includes a primary side circuit and a secondary side circuit. The second converter is an insulated DC / DC converter that electrically insulates the primary-side circuit from the secondary-side circuit.

Description

Technical Field

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

[0002] The power conversion device disclosed in Japanese Patent Application Laid-Open No. 2023-38682 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 power to the high-voltage battery. Thus, the high-voltage battery is charged.

[0003] There are cases where a power conversion device is 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 output terminals corresponding to the respective devices. Summary of the invention

[0004] A power conversion device according to one embodiment of the present disclosure comprises: two input terminals configured to be electrically connected to an external power supply; a first converter configured to convert power input from the external power supply via the two input terminals; and two first output terminals configured to output the power converted by the first converter. The first converter includes: a switching circuit, which is formed by connecting a first switching element, a second switching element, a third switching element, and a fourth switching element in series in sequence; a flying capacitor, which electrically connects a connection point between the first switching element and the second switching element to a connection point between the third switching element and the fourth switching element; a reactor; a first output line, which electrically connects one of the two first output terminals to one end of the switching circuit; a second output line, which electrically connects the other of the two first output terminals to the other end of the switching circuit; a first input line, which electrically connects one of the two input terminals to a connection point between the second switching element and the third switching element; and a second input line, which electrically connects the other of the two input terminals to one of the two first output terminals. The reactor is provided on at least one of the first input line and the second input line. The power conversion device includes: a second converter configured to perform power conversion using the voltage across the flying capacitor as an input voltage; two second converter input terminals electrically connected to the two ends of the flying capacitor; and two second output terminals configured to output the power converted by the second converter. The second converter includes: a primary side circuit configured to convert the power input via the two second converter input terminals into AC power and output it through the switching action of the second converter switching element; and a secondary side circuit configured to convert the AC power into DC power and output it to the two second output terminals. The second converter is an insulating DC / DC converter that electrically insulates the primary side circuit from the secondary side circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 This is a circuit diagram of the power conversion device according to the first embodiment.

[0006] Figure 2 This is a circuit diagram of the power conversion device according to the first embodiment.

[0007] Figure 3 yes Figure 1 A circuit diagram of a second converter included in the power conversion device.

[0008] Figure 4 This is a circuit diagram of a power conversion device according to a second embodiment.

[0009] Figure 5 It is a timing diagram showing the state of the 5th switching element and the 6th switching element, the current flowing in the 5th switching element and the 6th switching element, the current flowing in the 1st coil and the 2nd coil, the voltage across the 1st capacitor and the 2nd capacitor, and the relationship between the voltage across the 1st coil and the 2nd coil.

[0010] Figure 6 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0011] Figure 7 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0012] Figure 8 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0013] Fig. 9 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0014] Fig.10 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0015] Fig.11 It means in Figure 4 FIG. 1 is a diagram of a load current and a no-load current flowing in the second converter.

[0016] Fig.12 A diagram showing a modification example of the second converter.

[0017] Fig.13 A diagram showing a modification example of the second converter.

[0018] Fig.14 A diagram showing a modification example of the second converter.

[0019] Fig.15 A diagram showing a modification example of the second converter.

[0020] Fig.16 A diagram showing a modification example of the second converter. DETAILED DESCRIPTION

[0021] [First embodiment]

[0022] A first embodiment of the power conversion device will be described.

[0023] like Figure 1 As shown, the 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 driving 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.

[0024] <Power conversion device>

[0025] 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 alternately switches polarity between the first terminal T1 and the second terminal T2 over time. The first terminal T1 of the external power source PS is electrically connected to one of the two input terminals 21 and 22, that is, the first input terminal 21. The second terminal T2 of the external power source PS is electrically connected to the other of the two input terminals 21 and 22, that is, the second input terminal 22. The power conversion device 20 charges the high-voltage battery 11 and the low-voltage battery 12 by converting power supplied from the external power source PS electrically connected to the input terminals 21 and 22.

[0026] The first converter 30 converts power input from the external power supply PS via the input terminals 21 and 22. The first converter 30 is a flying capacitor converter and includes a switch circuit 31, a reactor 32, a flying capacitor 33, a first output line L1, and a second output line L2.

[0027] The switch circuit 31 includes a first switch element Q1, a second switch element Q2, a third switch element Q3, and a fourth switch element Q4. The switch circuit 31 is formed by connecting the first switch element Q1, the second switch element Q2, the third switch element Q3, and the fourth switch element Q4 in series. The switch elements Q1 to Q4 are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switch elements Q1 to Q4 may also be IGBTs (Insulated Gate Bipolar Transistors) or GaN-HEMTs.

[0028] The flying capacitor 33 electrically connects a connection point between the first switching element Q1 and the second switching element Q2 to a connection point between the third switching element Q3 and the fourth switching element Q4 .

[0029] The two first output terminals 23 and 24 are electrically connected to a switch circuit 31. The first output line L1 electrically connects the first output terminal 23, which is one of the two first output terminals 23 and 24, to one end 31A of the switch 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 and 24, to the other end 31B of the switch circuit 31. The first output terminal 23 is connected to a first switch element Q1 via the first output line L1. The first output terminal 24 is connected to a fourth switch element Q4 via the second output line L2.

[0030] 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 line L5, and a negative line L6. The fifth switching element Q5 and the sixth switching element Q6 are connected in series with 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 also be IGBTs or GaN-HEMTs.

[0031] The first input line L3 electrically connects the first input end 21 to a connection point between the second switching element Q2 and the third switching element Q3. The reactor 32 is provided on the first input line L3.

[0032] The second input line L4 electrically connects the second input terminal 22 to one of the two first output terminals 23 and 24. 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.

[0033] The positive line L5 electrically connects the second input line L4 to the first output line L1. Therefore, the second input line L4 is electrically connected to the first output end 23 via the positive line L5 and the first output line L1.

[0034] The negative electrode line L6 electrically connects the second input line L4 to the second output line L2. Therefore, the second input line L4 is electrically connected to the first output end 24 via the negative electrode line L6 and the second output line L2.

[0035] The fifth switch element Q5 is arranged on the positive line L5. The sixth switch element Q6 is arranged on the negative line L6. When the switch elements Q5 and Q6 are MOSFETs, the switch elements Q5 and Q6 are arranged so that the forward direction of the parasitic diode is from the second output line L2 toward the first output line L1. That is, the anode terminal of the parasitic diode of the switch element Q6 is electrically connected to the second output line L2, and the cathode terminal of the parasitic diode of the switch element Q5 is electrically connected to the first output line L1.

[0036] 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, the AC power supplied from the external power supply PS is converted into DC power by the switching action of the first switching element Q1 to the fourth switching element Q4, and output from the first output terminals 23 and 24. The DC power output from the first output terminals 23 and 24 is applied to the high-voltage battery 11. Thus, the high-voltage battery 11 is charged. The first converter 30 boosts the voltage of the AC power and outputs it. Alternatively, the first converter 30 steps down the voltage of the AC power and outputs it.

[0037] The capacitor 25 is provided between the first converter 30 and the high-voltage battery 11 .

[0038] The power conversion device 20 includes two second converter input terminals 41 and 42 , a second converter 50 , and two second output terminals 43 and 44 .

[0039] The two second converter input terminals 41 and 42 are electrically connected to both ends of the flying capacitor 33. 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.

[0040] like Figure 3 As shown, the second converter 50 includes a primary-side circuit 51 , a first connection line L11 and a second connection line L12 , a first capacitor C1 , a second capacitor C2 , a secondary-side circuit 61 , and a capacitor 54 .

[0041] The primary side 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 freewheeling diode D. The primary side circuit 51 is a half-bridge circuit of the switching elements Q41 and Q42. The upper arm switching element Q41 and the lower arm switching element Q42 are connected in series with 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 and Q42 are, for example, MOSFETs. The switching elements Q41 and Q42 may also be IGBTs or GaN-HEMTs.

[0042] The secondary side circuit 61 includes a first branch 62, a second branch 63, a wiring 64, and a wiring 65. The first branch 62 includes a first coil L21 and a first diode D11 connected in series with each other. The second branch 63 includes a second coil L22 and a second diode D12 connected in series with each other. The secondary side circuit 61 is electrically connected to the second output terminals 43 and 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 and 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 and 44. The wiring 64 is an example of the first wiring. The wiring 65 is an example of the second wiring.

[0043] The anode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal on the negative side of the second output terminals 43 and 44. The cathode terminal of the first diode D11 is electrically connected to the first coil L21. The cathode terminal of the second diode D12 is electrically connected to the second coil L22. Thus, the cathode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal on the positive side of the second output terminals 43 and 44 via the coils L21 and L22. In one example, the anode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal 44. The cathode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal 43. The second converter 50 is a series resonant circuit.

[0044] The first connection line L11 and the second connection line L12 each include a first end and a second end. The first end of each of the first connection line L11 and the second connection line L12 is electrically connected to the primary side circuit 51. The first end of the first connection line L11 is connected to a connection point between the upper arm switching element Q41 and the lower arm switching element Q42. The first end of the second connection line L12 is connected to the lower arm switching element Q42.

[0045] The second end of each of the first connection line L11 and the second connection line L12 is electrically connected to the secondary side circuit 61. The second end of the first connection line L11 is connected to the connection point between the first coil L21 and the first diode D11. The second end of the second connection line L12 is connected to the connection point between the second coil L22 and the second diode D12. Thus, the primary side circuit 51 and the secondary side circuit 61 are electrically connected through the first connection line L11 and the second connection line L12.

[0046] 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 that electrically insulates the primary side circuit 51 and the secondary side circuit 61. The second converter 50 of the present embodiment is a capacitor insulation converter that insulates the primary side circuit 51 and the secondary side circuit 61 by the first capacitor C1 and the second capacitor C2.

[0047] The second output terminals 43 and 44 are electrically connected to the low-voltage battery 12. 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 and 44, the second output terminal 43 is the positive side, and the second output terminal 44 is the negative side.

[0048] The capacitor 54 is provided between the secondary side circuit 61 and the low voltage battery 12 .

[0049] In the second converter 50, the voltage across the flying capacitor 33 is input as an input voltage to the primary side circuit 51. The primary side circuit 51 converts the power input through the two second converter input terminals 41 and 42 into AC power by the switching operation of the switching elements Q41 and Q42. Thus, the AC power is transmitted to the secondary side circuit 61 via the first connection line L11 and the second connection line L12. The secondary side 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 and 44. The switching elements Q41 and Q42 are examples of the second converter switching elements.

[0050] 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 CPU (Central Processing Unit), a GPU (Graphics Processing Unit) or a DSP (Digital Signal Processor). The storage unit includes a RAM (Random Access Memory) and a ROM (Read Only Memory). The storage unit stores program codes or instructions configured so that the processor performs processing. The storage unit, that is, the computer-readable medium, includes all available media that can be accessed by a computer, whether general or special. The control unit 71 can also be composed of a hardware circuit structure such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), etc. The control unit 71 as a processing circuit may include one or more processors that act according to a computer program, one or more hardware circuits such as an ASIC, an FPGA, or a combination thereof.

[0051] <Control by the control unit>

[0052] The control unit 71 controls the voltage of the DC power output from the first converter 30 to the first output terminals 23 and 24 by controlling the switching elements Q1 to Q6 , and controls the voltage across the flying capacitor 33 .

[0053] When the control unit 71 supplies power from the external power supply PS to the high voltage battery 11 and the low voltage battery 12, the switching mode of the switching elements Q1 to Q4 is alternately switched between the first mode and the second mode. The first mode is a switching mode in which the first switching element Q1 is turned off, the second switching element Q2 is turned on, the third switching element Q3 is turned off, and the fourth switching element Q4 is turned on. The second mode is a switching mode in which the first switching element Q1 is turned on, the second switching element Q2 is turned off, the third switching element Q3 is turned on, and the fourth switching element Q4 is turned off.

[0054] When the first terminal T1 of the external power supply PS is positive, the control unit 71 turns off the fifth switch element Q5 and turns on the sixth switch element Q6. In this case, on the one hand, the current is allowed to flow from the sixth switch element Q6 to the second input line L4, and on the other hand, the current is restricted from flowing from the second input line L4 to the fifth switch element Q5. The current flows from the sixth switch element Q6 to the second input line L4.

[0055] When the second terminal T2 of the external power supply PS is positive, the control unit 71 turns on the fifth switch element Q5 and turns off the sixth switch element Q6. In this case, on the one hand, the current is allowed to flow from the second input line L4 to the fifth switch element Q5, and on the other hand, the current is restricted from flowing from the second input line L4 to the sixth switch element Q6. The current flows from the second input line L4 to the fifth switch element Q5. The fifth switch element Q5 is an example of the first element. In the present embodiment, the first element is a switch element. The sixth switch element Q6 is an example of the second element.

[0056] like Figure 1 As shown by the dotted line LC1, when the first terminal T1 of the external power supply PS is positive and the switching mode is the first mode, the 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. Thus, the flying capacitor 33 is charged.

[0057] like Figure 1 As shown by the double-dotted chain line LC2, when the first terminal T1 of the external power supply PS is positive and the switching mode is the second mode, the 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.

[0058] like Figure 2 As shown by the dotted line LC3, when the second terminal T2 of the external power supply PS is positive and the switching mode is the second mode, the 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. Thus, the flying capacitor 33 is charged.

[0059] like Figure 2 As shown by the double-dotted chain line LC4, when the second terminal T2 of the external power supply PS is positive and the switching mode is the first mode, the 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.

[0060] The control unit 71 controls the switching elements Q1 to Q6 so that the output voltage output from the first output terminals 23 and 24 follows the target value and the voltage across the flying capacitor 33 follows the target value. Thus, the control unit 71 can charge the high-voltage battery 11 by controlling the output voltage output from the first output terminals 23 and 24. The control unit 71 can control the voltage across the flying capacitor 33.

[0061] The control unit 71 controls the voltage of the DC power output from the second converter 50 to the second output terminals 43 and 44 by controlling the switching elements Q41 and Q42. For example, the control unit 71 alternately switches the switching mode of the switching elements Q41 and Q42 between the third mode and the fourth mode. The third mode is a switching mode in which the upper arm switching element Q41 is turned on and the lower arm switching element Q42 is turned off. The fourth mode is a switching mode in which the upper arm switching element Q41 is turned off and the lower arm switching element Q42 is turned on.

[0062] The control unit 71 controls the switching elements Q41 and Q42 so that the output voltage output from the second output terminals 43 and 44 follows the target value. Thus, the control unit 71 can charge the low voltage battery 12 by controlling the output voltage output from the second output terminals 43 and 44.

[0063] When power is supplied from the external power supply 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 mode of the switching elements Q1 to Q4 between the fifth mode and the sixth mode. The fifth mode is a switching mode in which the first switching element Q1 is turned off, the second switching element Q2 is turned off, the third switching element Q3 is turned on, and the fourth switching element Q4 is turned on. The sixth mode is a switching mode in which the first switching element Q1 is turned on, the second switching element Q2 is turned on, the third switching element Q3 is turned off, and the fourth switching element Q4 is turned off.

[0064] When the first terminal T1 of the external power supply PS is positive, the control unit 71 turns off the fifth switch element Q5 and turns on the sixth switch element Q6. In this case, on the one hand, the current is allowed to flow from the second output line L2 to the sixth switch element Q6, and on the other hand, the current is restricted from flowing from the first output line L1 to the fifth switch element Q5. The current flows from the sixth switch element Q6 to the second input line L4.

[0065] When the second terminal T2 of the external power supply PS is positive, the control unit 71 turns on the fifth switch element Q5 and turns off the sixth switch element Q6. In this case, on the one hand, the current is allowed to flow from the second input line L4 to the fifth switch element Q5, and on the other hand, the current is restricted from flowing from the second input line L4 to the sixth switch element Q6. The current flows from the second input line L4 to the fifth switch element Q5.

[0066] When the first terminal T1 of the external power supply PS is positive and the switching mode is the fifth mode, the current flows in the order of the first terminal T1 of the external power supply PS → the inductor 32 → the third switching element Q3 → the fourth switching element Q4 → the sixth switching element Q6 → the second terminal T2 of the external power supply PS.

[0067] When the first terminal T1 of the external power supply PS is positive and the switching mode is the sixth mode, the current flows in the order of the first terminal T1 of the external power supply PS → the inductor 32 → the second switching element Q2 → 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.

[0068] When the second terminal T2 of the external power supply PS is positive and the switching mode is the sixth mode, the 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 second switching element Q2 → the inductor 32 → the first terminal T1 of the external power supply PS.

[0069] When the second end T2 of the external power supply PS is positive and the switching mode is the fifth mode, the current flows in the order of the second end T2 of the external power supply PS → the fifth switching element Q5 → the high-voltage battery 11 → the fourth switching element Q4 → the third switching element Q3 → the reactor 32 → the first end T1 of the external power supply PS.

[0070] The control unit 71 controls the switching elements Q1 to Q6 so that the output voltage output from the first output terminals 23 and 24 follows the target value. Thus, the control unit 71 can charge the high-voltage battery 11 by controlling the output voltage output from the first output terminals 23 and 24 .

[0071] [Function of the first embodiment]

[0072] The power conversion device 20 includes a first converter 30 and a second converter 50. The first converter 30 can transform the voltage input from the external power supply PS and output it. The second converter 50 can use the voltage across the flying capacitor 33 as an input voltage, transform the input voltage and output it. Thus, the power conversion device 20 can output different output voltages. If the power conversion device 20 is mounted on the vehicle 10 as in the embodiment, 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.

[0073] 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. The voltage across the flying capacitor 33 becomes the input voltage to the second converter 50, so the input voltage of the second converter 50 can be controlled by controlling the voltage across the flying capacitor 33.

[0074] The first capacitor C1 and the second capacitor C2 block DC power and allow AC power to pass through. Thus, 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.

[0075] 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 compared to the case of using a transformer for insulation. As a result, there is a case where the difference between the voltage input from the external power supply PS and the output voltage of the second converter 50 cannot be increased. For example, when 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 voltage from several hundred [V] to 14 [V]. It is difficult to step down the voltage from several hundred [V] to 14 [V] by the second converter 50 without a transformer.

[0076] In contrast, the power conversion device 20 of the present embodiment uses the voltage across the flying capacitor 33 as the input voltage of the second converter 50. By controlling the voltage across the flying capacitor 33 by the first converter 30, the input voltage of the second converter 50 can be controlled. 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 made the same as the target value of the output voltage of the second converter 50 by the first converter 30, it is not necessary to step down the voltage by the second converter 50. Therefore, even without using a transformer, the output voltage of the second converter 50 can be controlled.

[0077] [Effects of the First Embodiment]

[0078] (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. As a result, voltages of different values ​​can be output from the first output terminals 23, 24 and the second output terminals 43, 44. Power can be supplied to a plurality of devices with different required voltages through the power conversion device 20. In the embodiment, the high-voltage battery 11 and the low-voltage battery 12 can be charged by supplying power to both the high-voltage battery 11 and the low-voltage battery 12.

[0079] (1-2) 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 capacitor is smaller than the transformer. Therefore, compared with the case where the primary side circuit 51 and the secondary side circuit 61 are insulated using a transformer, the size of the second converter 50 and the size of the power conversion device 20 can be suppressed.

[0080] Furthermore, by controlling the voltage across the flying capacitor 33 by the first converter 30 , the input voltage of the second converter 50 can be controlled. Thus, the output voltage of the second converter 50 can be controlled.

[0081] (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 so that when the first end T1 of the external power supply PS is positive, a current flows from the sixth switching element Q6 to the second input line L4, and when the second end T2 of the external power supply PS is positive, a current flows from the second input line L4 to the fifth switching element Q5. Thus, even when the external power supply PS is an AC power supply, power conversion can be performed.

[0082] (1-4) The power conversion device 20 is mounted on the vehicle 10. The vehicle 10 includes: a high-voltage battery 11 required to drive the main engine and a low-voltage battery 12 required to drive the auxiliary engine. Therefore, 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 the first output terminals 23 and 24 and outputs a voltage for charging the low-voltage battery 12 from the second output terminals 43 and 44. Thus, the high-voltage battery 11 and the low-voltage battery 12 can be charged by one power conversion device 20.

[0083] [Second embodiment]

[0084] A second embodiment of the power conversion device will be described.

[0085] like Figure 4 As shown in FIG. 1 , 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 end 21 and the second input end 22 by being in a closed state.

[0086] In the power conversion device 20 of the second embodiment, in addition to the operation in the first embodiment, power is supplied from the high voltage battery 11 to the low voltage battery 12, so that the low voltage battery 12 can be charged. 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.

[0087] 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.

[0088] The control unit 71 maintains the first switch element Q1 and the third switch element Q3 to be turned off. The control unit 71 maintains the second switch element Q2 and the fourth switch element Q4 to be turned on. In this state, the fifth switch element Q5 and the sixth switch element Q6 are operated as choppers, thereby reducing the voltage input from the high-voltage battery 11. By alternately turning on the fifth switch element Q5 and the sixth switch element Q6, the voltage input from the high-voltage battery 11 is reduced and output, thereby controlling the voltage across the flying capacitor 33.

[0089] The control unit 71 turns on the upper arm switching element Q41 and the lower arm switching element Q42 alternately. The output voltage of the second converter 50 is controlled by the series resonance operation based on this. The low voltage battery 12 can be charged thereby. The operation of the second converter 50 of this embodiment will be described in detail.

[0090] Figure 5 Shown are the connection (ON) and disconnection (OFF) of the upper arm switching element Q41 and the lower arm switching element Q42, the current Ip flowing in the upper arm switching element Q41, the current In flowing in the lower arm switching element Q42, the current IL1 flowing in the first coil L21, the current IL2 flowing in 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.

[0091] Figure 6 to Figure 11 A load current I1 and a no-load current I2 are shown. The load current I1 is a current flowing at the low-voltage battery 12 as a load. The no-load current I2 is a current not flowing at the low-voltage battery 12 as a load.

[0092] like Figure 5 As shown, at time T11, the upper arm switching element Q41 is turned on, and the lower arm switching element Q42 is turned off. Figure 6As shown, at time T11, the upper arm switching element Q41 is turned on, so that the voltage across the flying capacitor 33 as a DC power supply is input to the second converter 50. The load current I1 flows through the path passing 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. The no-load current I2 flows through the path passing 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.

[0093] At time T12, the upper arm switching element Q41 is switched off. As a result, no power is supplied from the flying capacitor 33 to the second converter 50. The load current I1 flows due to the energy stored in the first coil L21. Figure 7 As shown, the load current I1 flows through the path passing through the first coil L21, the low voltage battery 12 and the first diode D11. The no-load current I2 flows due to the energy stored in the second coil L22. The no-load current I2 flows through the path passing through the second coil L22, the second capacitor C2, the freewheeling diode D of the lower arm switch element Q42, the first capacitor C1, and the first coil L21. The no-load current I2 causes the lower arm switch element Q42 to conduct in reverse.

[0094] At time T13, the lower arm switching element Q42 is turned on in the state of reverse conduction. The lower arm switching element Q42 is reversely conducted, so that the voltage across the lower arm switching element Q42 is 0. Therefore, ZVS (Zero Voltage Switching) can be achieved. Figure 8 As shown, the path through which the load current I1 flows is the same as that at time T12. The no-load current I2 flows through the path through the second coil L22, the second capacitor C2, the lower arm switching element Q42, the first capacitor C1, and the first coil L21.

[0095] As time passes from time T13, the output current output from the first coil L21 and the second coil L22 decreases. At time T14, the current is switched to discharge from the first capacitor C1 and the second capacitor C2. As a result, the current polarity of the no-load current I2 changes. Fig. 9 As shown, the load current I1 flows through the 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 voltage of the first capacitor C1 and the second capacitor C2 decreases due to discharge. Energy is stored in the first coil L21 and the second coil L22.

[0096] At time T15, the lower arm switching element Q42 is switched off. Fig.10 As shown, the load current I1 flows through the path passing through the first capacitor C1, the flyback diode D of the upper arm switch element Q41, the second capacitor C2, the second coil L22, the low voltage battery 12, and the first diode D11. The no-load current I2 flows through the path passing through the second capacitor C2, the second coil L22, the first coil L21, the first capacitor C1, and the flyback diode D of the upper arm switch element Q41. The load current I1 and the no-load current I2 cause the upper arm switch element Q41 to conduct in reverse.

[0097] At time T16, the upper arm switch element Q41 is switched on. The upper arm switch element Q41 is reversely conducted, so that the voltage across the upper arm switch element Q41 is 0. Therefore, ZVS can be achieved. Fig.11 As shown, the load current I1 and the no-load current I2 change from the freewheeling diode D of the upper arm switching element Q41 to a path passing through the upper arm switching element Q41.

[0098] [Function of the Second Embodiment]

[0099] The power conversion device 20 includes a switch 34. By closing the switch 34 and controlling the first to sixth switching elements Q1 to 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, thereby charging the low voltage battery 12.

[0100] Here, the second converter 50 of the present embodiment is a capacitor insulation converter that insulates the primary side circuit 51 from the secondary side circuit 61 by the first capacitor C1 and the second capacitor C2. The capacitor insulation converter does not have a transformer, so it is not easy to step down the input voltage. In particular, it is not easy to step down the input voltage when the load is light. In the case of using a half-bridge circuit as the primary side circuit 51 as in the present embodiment, there is a case where the voltage can only be stepped down to 1 / 2 of the input voltage. Therefore, there is sometimes a need to reduce the voltage across the flying capacitor 33 according to the output voltage of the second converter 50. For example, when 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 of the input voltage, it is necessary to make the voltage across the flying capacitor 33, which becomes the input voltage of the second converter 50, 30 [V]. The lower the voltage across the flying capacitor 33, the greater the current. The 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 greater the current flowing through these switching elements Q2, Q4, Q5, and Q6. As a result, the rated current required for the switching elements Q2, Q4, Q5, and Q6 may increase.

[0101] In the present embodiment, the secondary side circuit 61 includes: a branch 62 in which the first coil L21 and the first diode D11 are connected in series; and a branch 63 in which the second coil L22 and the second diode D12 are connected in series. In the secondary side circuit 61, output currents are generated in the coils L21 and L22 of each branch 62 and 63. The sum of the output currents of the two coils L21 and L22 becomes the overall output current, so the current input to the secondary side circuit 61 can be increased. As a result, a voltage reduction using the secondary side circuit 61 can be achieved, and the voltage of the flying capacitor 33 can be increased accordingly.

[0102] [Effects of the Second Embodiment]

[0103] (2-1) The power conversion device 20 includes the switch 34 . Thus, the low-voltage battery 12 can be charged using the high-voltage battery 11 .

[0104] (2-2) The secondary side circuit 61 includes branches 62 and 63. Thus, the output current of the secondary side circuit 61 can be increased. By increasing the output current of the secondary side circuit 61, the output voltage of the secondary side circuit 61 is reduced. 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 required output voltage can be output to the second converter 50. Therefore, by reducing the voltage across the flying capacitor 33, the current flowing in the switching elements Q2, Q4, Q5, and Q6 can be suppressed from increasing.

[0105] [Change example]

[0106] Each embodiment can be implemented by modification as follows. Each embodiment and the following modification examples can be implemented in combination with each other within the range that there is no technical contradiction.

[0107] ○ In the first embodiment, the second converter 50 may be Fig.12 The structure shown. Fig.12 The second converter 50 shown is an LLC converter and includes a primary-side circuit 51 , a first connection line L11 and a second connection line L12 , a first capacitor C1 , a second capacitor C2 , a secondary-side circuit 61 , inductors 52 and 53 , and a capacitor 54 .

[0108] 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 with each other. The second upper arm switching element Q13 and the second lower arm switching element Q14 are connected in series with 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 also be IGBTs or GaN-HEMTs. The switching elements Q11 to Q14 are an example of switching elements for the second converter.

[0109] The secondary side circuit 61 includes four diodes D1 to D4. The secondary side circuit 61 is a full bridge circuit of diodes D1 to D4. The diode D1 and the diode D2 are connected in series in a forward direction to each other. The diode D3 and the diode D4 are connected in series in a forward direction to each other.

[0110] The inductor 52 is provided on the first connection line L11. The inductor 52 is provided between the first capacitor C1 and the primary side circuit 51. The inductor 53 connects the first connection line L11 and the second connection line L12. The inductor 53 is provided between the group of the first and second capacitors C1 and C2 and the secondary side circuit 61.

[0111] The secondary side 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.

[0112] 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 diodes D1 and 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 diodes D3 and D4.

[0113] In the LLC converter, the switching elements Q11 to Q14 can be soft-switched using resonance formed by the first capacitor C1, the second capacitor C2, and the inductors 52 and 53. This can reduce power loss caused by switching of the switching elements Q11 to Q14.

[0114] ○ In the first embodiment, the primary side circuit 51 of the second converter 50 may be Fig.13The circuit structure shown. The primary side circuit 51 has two second converter switching elements Q21 and Q22 connected in series. The secondary side circuit 61 is, for example, a full bridge circuit of diodes. The first connecting line L11 is connected to the connection point between the two second converter switching elements Q21 and Q22. The second connecting line L12 is connected to the second converter switching element Q22. The primary side circuit 51 converts the input power into AC power through the switching action of the two second converter switching elements Q21 and Q22. The secondary side circuit 61 converts the AC power into DC power. Even when using Fig.13 Even in the case of the second converter 50 shown, the same effects as those of the embodiment can be obtained.

[0115] ○ In the first embodiment, the second converter 50 may be Fig.14 The circuit structure shown. Fig.14 The circuit structure shown is a Cuk circuit. The primary side 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 and 42 to each other via the first inductor 81. The secondary side 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 and 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 side. The cathode terminal of the diode 83 is electrically connected to the second output terminal 44 side. The primary side circuit 51 and the secondary side circuit 61 are insulated by the first capacitor C1 and the second capacitor C. Even when using Fig.14 Even in the case of the second converter 50 shown, the same effects as those of the embodiment can be obtained.

[0116] ○ In the first embodiment, the second converter 50 may be Fig.15 The circuit structure shown. Fig.15 The circuit structure shown is a SEPIC circuit. The primary side circuit 51 and Fig.14 The circuit structure shown is the same. The secondary side 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 and 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 side circuit 51 and the secondary side circuit 61 are insulated by the first capacitor C1 and the second capacitor C2. Even when using Figure 5 Even in the case of the second converter 50 shown, the same effects as those of the embodiment can be obtained.

[0117] ○ In the first embodiment, the fifth switching element Q5 as the first element and the sixth switching element Q6 as the second element may also be diodes. In this case, the diode is provided so that the direction from the second output line L2 toward the first output line L1 becomes the forward direction. The anode terminal of the diode as the first element is electrically connected to the cathode terminal of the diode as the second element. The cathode terminal of the diode as the first element is electrically connected to the first output line L1. The anode terminal of the diode as the second element is electrically connected to the second output line L2.

[0118] ○ In each embodiment, the external power supply PS may be a DC power supply. Alternatively, in this case, the power conversion device 20 does not include the fifth switching element Q5 and the sixth switching element Q6. When the positive side of the DC power supply is connected to the input terminal 21, the negative side is connected to the second output line L2. When the negative side of the DC power supply is connected to the input terminal 21, the positive side is connected to the first output line L1. In addition, when the external power supply PS of the second embodiment is used as a DC power supply, the second element may be a diode.

[0119] 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 the first end T1 side and the second end T2. That is, the reactor 32 may be provided on at least one of the first input line L3 and the second input line L4.

[0120] In the first embodiment, the second converter 50 may step up the input voltage and output the result, or may step down the input voltage and output the result.

[0121] ○ 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 and 22. For example, the control unit 71 alternately switches the switching mode of the first switching element Q1 to the sixth switching element Q6 between the seventh mode and the eighth mode. The seventh mode is a switching mode in which the first switching element Q1 is turned on, the second switching element Q2 is turned on, the third switching element Q3 is turned off, the fourth switching element Q4 is turned off, the fifth switching element Q5 is turned off, and the sixth switching element Q6 is turned on. The eighth mode is a switching mode in which the first switching element Q1 is turned off, the second switching element Q2 is turned off, the third switching element Q3 is turned on, the fourth switching element Q4 is turned on, the fifth switching element Q5 is turned on, and the sixth switching element Q6 is turned off.

[0122] In the first embodiment, the second converter 50 may be an insulating DC / DC converter in which the primary-side circuit and the secondary-side circuit are electrically insulated by a transformer.

[0123] ○ In each embodiment, it may also be, for example Fig.16 As shown, the first coil L21 and the first diode D11 are switched, and the second coil L22 and the second diode D12 are switched. In this case, the wiring 64 is the second wiring, and the wiring 65 is the first wiring.

[0124] The cathode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal on the positive side of the two second output terminals 43 and 44. The anode terminal of the first diode D11 is electrically connected to the first coil L21. The anode terminal of the second diode D12 is electrically connected to the second coil L22. Thus, the anode terminals of the first diode D11 and the second diode D12 are electrically connected to the second output terminal on the negative side of the second output terminals 43 and 44 via the coils L21 and L22.

[0125] In the second embodiment, the secondary circuit 61 may further include a branch. The branch connects the coil and the diode in series. In this case, the coil of the additional branch and the coils L21 and L22 of the branches 62 and 63 are connected via the first wiring, and the diode of the additional branch and the diodes D11 and D12 of the branches 62 and 63 are connected via the second wiring.

[0126] In each embodiment, the second converter 50 may be a series resonant circuit having a circuit configuration different from that of the embodiment.

Claims

1. A power conversion device comprising: two input terminals configured for electrical connection to an external power source; a first converter configured to convert electric power input from the external power supply via the two input terminals; and two first output terminals configured to output the power converted by the first converter, The power conversion device is characterized in that: The first converter comprises: a switching circuit that sequentially connects a first switching element, a second switching element, a third switching element, and a fourth switching element in series with each other; a flying capacitor that electrically connects a connection point between the first switching element and the second switching element to a connection point between the third switching element and the fourth switching element; Reactor; a first output line electrically connecting one of the two first output terminals to one terminal of the switch circuit; a second output line electrically connecting the other of the two first output terminals to the other terminal of the switch circuit; a first input line electrically connecting one of the two input terminals to a connection point between the second switching element and the third switching element; and a second input line electrically connecting the other of the two input terminals to one of the two first output terminals, The reactor is provided on at least one of the first input line and the second input line. The power conversion device comprises: a second converter configured to perform power conversion using a voltage across both ends of 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 configured to output the electric power converted by the second converter, The second converter comprises: a primary side circuit configured to convert power inputted via the two second converter input terminals into AC power by a switching operation of a second converter switching element and output the AC power; as well as The secondary side circuit is configured to convert the AC power into DC power and output the DC power to the two second output terminals. The second converter is an insulating DC / DC converter that electrically insulates the primary-side circuit from the secondary-side circuit.

2. The power conversion device according to claim 1, characterized in that: The second converter comprises: The first connecting line and the second connecting line; a first capacitor disposed on the first connecting line; and a second capacitor provided on the second connecting line, The first connection line and the second connection line each have a first end connected to the primary-side circuit and a second end connected to the secondary-side circuit.

3. The power conversion device according to claim 2, characterized in that: The secondary side circuit comprises: a first branch having a first coil and a first diode connected in series with each other, wherein the second end of the first connecting line is connected to a connection point between the first coil and the first diode; a second branch having a second coil and a second diode connected in series with each other, wherein the second end of the second connecting line is 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; as well as a second wiring connecting the first diode and the second diode to the other of the two second output terminals, Anode terminals of the first diode and the second diode are electrically connected to the negative second output terminal of the two second output terminals. The cathode terminal of the first diode is electrically connected to the first coil. A cathode terminal of the second diode is electrically connected to the second coil.

4. The power conversion device according to claim 2, characterized in that: The secondary side circuit comprises: a first branch having a first coil and a first diode connected in series with each other, wherein the second end of the first connecting line is connected to a connection point between the first coil and the first diode; a second branch having a second coil and a second diode connected in series with each other, wherein the second end of the second connecting line is 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; as well as a second wiring connecting the first diode and the second diode to the other of the two second output terminals, The cathode terminals of the first diode and the second diode are electrically connected to the second output terminal on the positive side of the two second output terminals. The anode terminal of the first diode is electrically connected to the first coil, An anode terminal of the second diode is electrically connected to the second coil.

5. The power conversion device according to claim 1, characterized in that: The external power source is an AC power source having a first end electrically connected to a first input end as one of the two input ends and a second end electrically connected to a second input end as the other of the two input ends. The first converter comprises: a positive line electrically connecting the second input line to the first output line; a negative line electrically connecting the second input line to the second output line; a first element disposed on the positive line; as well as a second element disposed on the negative electrode line, The first element and the second element are configured such that when the first end is positive, current flows from the second element to the second input line, and when the second end is positive, current flows from the second input line to the first element.

6. The power conversion device according to claim 5, characterized in that: A switch is provided for connecting the first input terminal to the second input terminal, and the first element is a switch element.

7. The power conversion device according to claim 1 or 2, characterized in that: The power conversion device is mounted on a vehicle, The two first output terminals are electrically connected to a high voltage battery, The two second output terminals are electrically connected to a low-voltage battery.

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