JP6428524B2 - Vehicle power supply system - Google Patents

Description

  The technology disclosed in this specification relates to a vehicle power supply system mounted on a vehicle. Note that the “vehicle” in this specification includes both an electric vehicle including only a driving motor without an engine and a hybrid vehicle including both a driving motor and an engine.

  Patent Document 1 discloses a main power source, a main power source wiring connected to the main battery, a power control unit including a smoothing capacitor for smoothing a voltage of the main power source wiring, and a main power source between the main battery and the power control unit. A switch for switching between conductive and non-conductive wiring, a sub-battery having a lower voltage than the main battery, a sub power wiring connected to the sub battery, and a main power wiring and a sub power wiring on the power control unit side of the switch. There is disclosed a vehicle power supply system including a DC-DC converter that is connected and capable of performing a boosting operation for boosting power from a sub power supply wiring to a main power supply wiring.

  In the above vehicle power supply system, power can be supplied from the sub-battery to the power control unit by the DC-DC converter performing step-up operation without switching the switch from non-conduction to conduction. For this reason, for example, immediately after switching the switch from non-conduction to conduction by supplying power from the sub-battery to the power control unit and precharging the smoothing capacitor, the difference between the voltage of the main battery and the voltage of the smoothing capacitor Therefore, it is possible to prevent a large inrush current from flowing through the main power supply wiring. Further, for example, when a so-called open failure occurs in which a failure occurs when the switch is in a non-conducting state, power can be supplied from the sub battery to the power control unit. Thereby, for example, the engine can be cranked using the power of the sub-battery.

JP 2007-318849 A

When power is supplied from the sub battery to the power control unit, large power cannot be supplied. In this specification, it is possible to supply a large amount of power to the power control unit while preventing the performance of the main battery from being deteriorated using the main battery while the main power supply wiring is non-conductive by the switch. Provide technology.

  A vehicle power supply system disclosed in this specification includes a main battery, a main power supply wiring, a power control unit, a switch, a subbattery, a sub power supply wiring, a transformer, a first circuit, and a second circuit. And a third circuit. The main power supply wiring is connected to the main battery. The power control unit includes a smoothing capacitor that smoothes the voltage of the main power supply wiring. The switch switches between conduction and non-conduction of the main power supply wiring between the main battery and the power control unit. The sub battery has a lower voltage than the main battery. The sub power supply wiring is connected to the sub battery. The transformer includes a first coil, a second coil, and a third coil. The first circuit connects the main coil and the first coil on the main battery side of the switch. The second circuit connects the main coil and the second coil on the power control unit side of the switch. The third circuit connects the sub power supply wiring and the third coil. The first circuit has a function of a DC-AC converter. The second circuit has an AC-DC converter function.

  In the above-described vehicle power supply system, the power supplied from the main power supply wiring on the main battery side of the switch is supplied to the first circuit, the first coil of the transformer, and the second coil in a state where the main power supply wiring is non-conductive. It can be supplied to the main power supply wiring on the power control unit side of the switch via the second circuit. According to this configuration, the power of the main battery can be supplied to the power control unit in a state where the main power supply wiring is non-conductive. A large amount of power can be supplied to the power control unit in a state where the main power supply wiring is non-conductive by the switch. Further, according to the above vehicle power supply system, by arranging the third circuit between the third coil of the transformer and the sub power supply wiring, the first circuit or the second circuit and the third circuit are used, Power can be interchanged between the main power supply wiring and the sub power supply wiring.

The control device of the power control unit precharges the smoothing capacitor via the AC-DC converter of the second circuit by operating the DC-AC converter of the first circuit in a state where the main power supply wiring is turned off by the switch. While performing the charge control, the duty ratio of the DC-AC converter of the first circuit is controlled so that the voltage of the main battery does not become lower than a predetermined reference value during the precharge control. According to this configuration, it is possible to prevent the performance of the main battery from being deteriorated due to excessive reduction in the voltage of the main battery. Details and further improvements of the technology disclosed in this specification will be described in detail in the section of Detailed Description.

It is a block diagram of the electric system of the electric vehicle of an Example. It is a figure which shows the schematic structure of the 1st circuit of an Example, a 2nd circuit, and a 3rd circuit. It is a flowchart of the process which a power supply control unit performs at the time of the precharge of the smoothing capacitor of 1st Example. It is a flowchart of the process which a power supply control unit performs at the time of the precharge of the smoothing capacitor of 2nd Example. It is a figure which shows the structure of the outline of the modification of a 3rd circuit. It is a figure which shows the structure of the outline of the modification of a 2nd circuit and a 3rd circuit.

(First embodiment)
In FIG. 1, the block diagram of the electric system of the electric vehicle 2 of an Example is shown. The electric vehicle 2 of the present embodiment is a hybrid vehicle that can travel using the power of an engine (not shown) or can travel using the power of the main battery 4. When traveling using the power of the engine, a part of the power generated by the engine is transmitted to drive wheels (not shown), while the remainder of the power of the engine is used to generate power by the first motor 6. The driving wheel is rotated by driving the second motor 8 with the electric power generated by the first motor 6. When starting the engine, power from the main battery 4 of the power supply system 1 is supplied to the first motor 6 so that the first motor 6 functions as a cell motor. When traveling using the power of the main battery 4, the drive wheels are rotated by driving the second motor 8 with the power from the main battery 4.

  The power supply system 1 includes a main battery 4, a sub battery 22, a power control unit (PCU) 12, a first circuit 28, a second circuit 30, a third circuit 32, a transformer 36, and a main power supply wiring 10. And a sub power supply wiring 24 and an electronic control unit (ECU) 60. The main battery 4 is a secondary battery such as a nickel metal hydride battery or a lithium ion battery. In this embodiment, the voltage of the main battery 4 is about 300V. The voltage of the main battery 4 is measured by the voltage sensor 50. The electric vehicle 2 can generate power with the first motor 6 using the power of the engine, and charge the main battery 4 with the power generated by the first motor 6. Further, when the traveling electric vehicle 2 decelerates, the regenerative power generation can be performed by the second motor 8, and the power generated by the second motor 8 can be charged to the main battery 4.

  The main battery 4 is connected to the PCU 12 via the main power supply wiring 10. The main power supply wiring 10 includes a positive line 10 a connected to the positive terminal of the main battery 4 and a negative line 10 b connected to the negative terminal of the main battery 4.

  The PCU 12 is provided between the main battery 4 and the first motor 6 and the second motor 8. The PCU 12 includes a smoothing capacitor 14, a converter 16, and an inverter 18. The smoothing capacitor 14 smoothes the voltage of the main power supply wiring 10. The voltage of the smoothing capacitor 14 is measured by the voltage sensor 53. The converter 16 boosts the voltage of the power supplied from the main battery 4 to a voltage suitable for driving the first motor 6 and the second motor 8 as necessary. Converter 16 can also step down the voltage of the power generated by first motor 6 or second motor 8 to a voltage suitable for charging main battery 4. In this embodiment, the voltage used to drive the first motor 6 and the second motor 8 is about 600V. The inverter 18 converts the DC power supplied from the main battery 4 into three-phase AC power for driving the first motor 6 and the second motor 8. The inverter 18 can also convert the three-phase AC power generated by the first motor 6 and the second motor 8 into DC power for charging the main battery 4.

  A system main relay (SMR) 20 is provided between the main battery 4 and the PCU 12. The SMR 20 includes a switch 20a that switches between conduction and non-conduction of the positive electrode line 10a of the main power supply wiring 10, and a switch 20b that switches between conduction and non-conduction of the negative electrode line 10b of the main power supply wiring 10. That is, the SMR 20 switches between conduction and non-conduction of the main power supply wiring 10.

  The electric vehicle 2 includes a sub battery 22 having a lower voltage than the main battery 4. The sub battery 22 is a secondary battery such as a lead battery. In the present embodiment, the voltage of the sub-battery 22 is about 13V to 14.5V. The voltage of the sub battery 22 is measured by the voltage sensor 54. The sub battery 22 is connected to an auxiliary device 26 such as a power steering or an air conditioner via a sub power supply wiring 24. The current value of the sub power supply wiring 24 is measured by the current sensor 52.

  A first circuit 28 is connected between the main power supply wiring 10 on the main battery 4 side of the SMR 20 and the first coil 36 c of the transformer 36. As will be described in detail later, the transformer 36 includes a second coil 36a and a third coil 36b in addition to the first coil 36c. The second circuit 30 is connected between the main power supply wiring 10 closer to the PCU 12 than the SMR 20 and the second coil 36a. The third circuit 32 is connected between the sub power supply wiring 24 and the third coil 36b. The main power supply wiring 10 closer to the main battery 4 than the SMR 20 is connected to the sub power supply wiring 24 via the first circuit 28, the transformer 36 and the third circuit 32. The combination of the first circuit 28, the transformer 36, and the third circuit 32 can perform a step-down operation for supplying power by stepping down from the main power supply wiring 10 to the sub power supply wiring 24. It is also possible to perform a boosting operation that boosts the voltage to 10 and supplies power. The combination of the first circuit 28, the transformer 36, and the third circuit 32 is a so-called bidirectional DC-DC converter, and can be called a step-up / step-down DC-DC converter. Note that the combination of the first circuit 28, the transformer 36, and the third circuit 32 may not perform the boosting operation of boosting power from the sub power supply wiring 24 to the main power supply wiring 10 and supplying power.

  The main power supply wiring 10 and the sub power supply wiring 24 closer to the PCU 12 than the SMR 20 are connected via the second circuit 30, the transformer 36, and the third circuit 32. The combination of the second circuit 30, the transformer 36, and the third circuit 32 can perform a step-down operation for supplying power by stepping down from the main power supply wiring 10 on the PCU 12 side to the sub power supply wiring 24 with respect to the SMR 20. It is also possible to perform a boosting operation for boosting power from the wiring 24 to the main power supply wiring 10 on the PCU 12 side of the SMR 20 and supplying power. That is, the combination of the second circuit 30, the transformer 36, and the third circuit 32 is a so-called bidirectional DC-DC converter, and can be called a step-up / step-down DC-DC converter.

  Further, the main power supply wiring 10 on the main battery 4 side of the SMR 20 and the main power supply wiring 10 on the PCU 12 side of the SMR 20 are connected via the first circuit 28, the transformer 36, and the second circuit 30. The combination of the first circuit 28, the transformer 36, and the second circuit 30 may perform a supply operation of supplying power from the main power supply wiring 10 on the main battery 4 side of the SMR 20 to the main power supply wiring 10 on the PCU 12 side of the SMR 20. In addition, a supply operation of supplying power from the main power supply wiring 10 on the PCU 12 side of the SMR 20 to the main power supply wiring 10 on the main battery 4 side of the SMR 20 can be performed. The combination of the first circuit 28, the transformer 36, and the second circuit 30 performs a supply operation for supplying power from the main power supply wiring 10 on the PCU 12 side of the SMR 20 to the main power supply wiring 10 on the main battery 4 side of the SMR 20. It does not have to be.

  In the power supply system 1, by operating the first circuit 28, the second circuit 30, and the third circuit 32, power is supplied between the main power supply wiring 10 and the sub power supply wiring 24 regardless of conduction / non-conduction of the SMR 20. Can be interchangeable. Specifically, the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs a step-down operation, so that the electric power generated by the first motor 6 and the second motor 8 can be charged to the sub-battery 22. . Further, the combination of the second circuit 30, the transformer 36 and the third circuit 32 performs the boosting operation, so that the first motor 6 and the second motor 8 can be driven using the power of the sub-battery 22. Further, the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs a step-down operation, so that the power from the main battery 4 can be charged to the sub-battery 22. Further, the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs the boosting operation, whereby the power from the sub battery 22 can be charged to the main battery 4. Further, even when the SMR 20 is non-conductive, the combination of the first circuit 28, the transformer 36, and the second circuit 30 performs the supply operation, so that the power from the main battery 4 can be supplied without passing through the sub power supply wiring 24. The power generated by the first motor 6 and the second motor 8 can be charged to the main battery 4.

  FIG. 2 shows a schematic configuration of the first to third circuits 28, 30 and 32 and the transformer 36. The first to third circuits 28, 30, 32 and the transformer 36 are accommodated in one housing 58. The first circuit 28 is connected to the main power supply wiring 10 through the connection wiring 78.

  The first circuit 28 includes a filter 44, a switching circuit 46, and a backflow prevention switch 45. The filter 33 includes a capacitor 44a. The filter 44 suppresses the generation of noise on the main power supply wiring 10 side. The backflow prevention switch 45 is capable of supplying power from the first circuit 28 to the main power supply wiring 10 on the main battery 4 side by switching on and off of the switching element (that is, the switching element is on) and impossible. (Ie, the switching element is turned off).

  The switching circuit 46 includes switching elements 46a, 46b, 46c, and 46d and free-wheeling diodes 46e, 46f, 46g, and 46h connected in parallel to the respective switching elements 46a, 46b, 46c, and 46d. The switching element 46a and the switching element 46b are connected in series, and the switching element 46c and the switching element 46d are connected in series.

  The switching circuit 46 is connected to the transformer 36. The transformer 36 includes three coils 36a, 36b, and 36c. The first coil 36 c is connected to the switching circuit 46 via the connection wiring 76. That is, the first circuit 28 connects the main power supply wiring 10 closer to the main battery 4 than the SMR 20 and the first coil 36c. The second coil 36 a is connected to the switching circuit 34 of the second circuit 30 through the connection wiring 72. The third coil 36 b is connected to the switching circuit 38 of the third circuit 32 through the connection wiring 74. The transformer 36 can supply power by stepping down from the second coil 36a to the third coil 36b, or can supply power by stepping up from the third coil 36b to the second coil 36a. Further, in the transformer 36, power can be supplied by stepping down from the first coil 36c to the third coil 36b, or power can be supplied by stepping up from the third coil 36b to the first coil 36c. In addition, power can be supplied from the first coil 36c to the second coil 36a without changing the voltage, or power can be supplied from the second coil 36a to the first coil 36c without changing voltage. .

  One end of the first coil 36 c is connected between the switching element 46 a and the switching element 46 b via the connection wiring 76, and the other end of the first coil 36 c is connected to the switching element 46 c and the switching element via the connection wiring 76. 46d is connected.

  In the switching circuit 46, each of the switching elements 46a, 46b, 46c, and 46d is switched on and off at a predetermined timing, thereby converting DC power supplied from the main power supply wiring 10 to the switching circuit 46 into AC power. That is, the switching circuit 46 functions as a DC-AC converter. In the switching circuit 46, the AC power supplied from the transformer 36 is converted into DC power by the diodes 46e, 46f, 46g, and 46h. That is, the switching circuit 46 also functions as an AC-DC converter (that is, a rectifier).

  The first circuit 28 is controlled by the control circuit 43. Specifically, the control circuit 43 controls the operations of the switching elements 46 a, 46 b, 46 c, 46 d and the backflow prevention switch 45 of the switching circuit 46.

  The second circuit 30 connected to the second coil 36 a is connected to the main power supply wiring 10 via the connection wiring 70. That is, the second circuit 30 connects the main power supply wiring 10 closer to the PCU 12 than the SMR 20 and the second coil 36a. The second circuit 30 includes a filter 33, a switching circuit 34, and a backflow prevention switch 31. The filter 33 includes a capacitor 33a. The filter 33 suppresses the generation of noise on the main power supply wiring 10 side. The backflow prevention switch 31 is in a state in which power can be supplied from the second circuit 30 to the main power supply wiring 10 on the PCU 12 side (that is, in a state in which the switching element is on) and in an impossible state by switching the switching element on and off. (That is, the switching element is off).

  The switching circuit 34 includes switching elements 34a, 34b, 34c, 34d and free-wheeling diodes 34e, 34f, 34g, 34h connected in parallel to the respective switching elements 34a, 34b, 34c, 34d. The switching element 34a and the switching element 34b are connected in series, and the switching element 34c and the switching element 34d are connected in series. One end of the second coil 36 a is connected between the switching element 34 a and the switching element 34 b via the connection wiring 72, and the other end of the second coil 36 a is connected to the switching element 34 c and the switching element via the connection wiring 72. 34d.

  In the switching circuit 34, each of the switching elements 34a, 34b, 34c, and 34d is switched on and off at a predetermined timing, thereby converting DC power supplied from the main power supply wiring 10 to the switching circuit 34 into AC power. That is, the switching circuit 34 functions as a DC-AC converter. In the switching circuit 34, the AC power supplied from the transformer 36 is converted into DC power by the diodes 34e, 34f, 34g, and 34h. That is, the switching circuit 34 also functions as an AC-DC converter (that is, a rectifier).

  The third circuit 32 connected to the third coil 36 b is connected to the sub power supply wiring 24. That is, the second circuit 32 connects the sub power supply wiring 24 and the third coil 36b. The third circuit 32 includes a filter 40, a switching circuit 38, and a backflow prevention switch 41. The filter 40 includes an inductor 40a and a capacitor 40b. The filter 40 suppresses the generation of noise on the sub power supply wiring 24 side. The backflow prevention switch 41 switches between turning on and off of the switching element, whereby the power can be supplied from the third circuit 32 to the sub power supply wiring 24 (that is, the switching element is on) and the state that is not possible (that is, switching) Switch the element off).

  The switching circuit 38 includes switching elements 38a, 38b, 38c, 38d, free-wheeling diodes 38e, 38f, 38g, 38h connected in parallel to the respective switching elements 38a, 38b, 38c, 38d, an inductor 38i, and a capacitor 38j. It has. The switching element 38a and the switching element 38b are connected in series, and the switching element 38c and the switching element 38d are connected in series. One end of the third coil 36 b is connected between the switching element 38 a and the switching element 38 b via the connection wiring 74, and the other end of the third coil 36 b is connected to the switching element 38 c and the switching element via the connection wiring 74. 38d.

  In the switching circuit 38, each of the switching elements 38a, 38b, 38c, and 38d is switched on and off at a predetermined timing, thereby converting DC power supplied from the sub power supply wiring 24 to the switching circuit 38 into AC power. That is, the switching circuit 38 functions as a DC-AC converter. In the switching circuit 38, the AC power supplied from the transformer 36 is converted into DC power by the diodes 38e, 38f, 38g, and 38h. That is, the switching circuit 38 also functions as an AC-DC converter (that is, a rectifier).

  The second circuit 30 and the third circuit 32 are controlled by the control circuit 42. Specifically, the control circuit 42 includes the switching elements 34a, 34b, 34c, 34d and the backflow prevention switch 31 of the switching circuit 34 of the second circuit 30, and the switching elements 38a, 38b of the switching circuit 38 of the third circuit 32. The operations of 38c and 38d and the backflow prevention switch 41 are controlled.

  Next, operations of the first to third circuits 28, 30, and 32 will be described. First, the case where the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs the step-down operation by the operation of the second circuit 30 and the third circuit 32 will be described. When the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs a step-down operation, the switching elements 34a, 34b, 34c, 34d operate in the switching circuit 34 of the second circuit 30, and the DC-AC By functioning as a converter, the DC power supplied from the main power supply wiring 10 is converted into AC power. Then, the converted AC voltage is stepped down by the transformer 36, and the switching circuit 38 of the third circuit 32 functions as an AC-DC converter, thereby converting AC power into DC power. In this case, in the switching circuit 38, rectification by the freewheeling diodes 38e, 38f, 38g, and 38h and smoothing by the inductor 38i and the capacitor 38j are performed. As a result, power can be supplied by stepping down from the main power supply wiring 10 to the sub power supply wiring 24. When the switching circuit 38 functions as an AC-DC converter, each of the switching elements 38a, 38b, 38c, 38d is turned on while a current flows through the free-wheeling diodes 38e, 38f, 38g, 38h connected in parallel. Is done. Thereby, the electric current which flows into free-wheeling diode 38e, 38f, 38g, 38h can be reduced.

  Next, a case where the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs the boosting operation by the operation of the second circuit 30 and the third circuit 32 will be described. When the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs the boosting operation, the switching elements 38a, 38b, 38c, 38d operate in the switching circuit 38 of the third circuit 32, and the DC-AC By functioning as a converter, the DC power supplied from the sub power supply wiring 24 is converted into AC power. The converted AC voltage is boosted by the transformer 36, and the switching circuit 34 of the second circuit 30 functions as an AC-DC converter, thereby converting AC power into DC power. In this case, in the switching circuit 34, rectification is performed by the free-wheeling diodes 34e, 34f, 34g, and 34h, and smoothing is performed in the filter 33. As a result, power can be supplied from the sub power supply wiring 24 to the main power supply wiring 10 while being boosted. When the switching circuit 34 functions as an AC-DC converter, each of the switching elements 34a, 34b, 34c, 34d is turned on while a current flows through the free-wheeling diodes 34e, 34f, 34g, 34h connected in parallel. Is done. Thereby, the electric current which flows into free-wheeling diode 34e, 34f, 34g, 34h can be reduced.

  During the step-up / step-down operation of the combination of the second circuit 30, the transformer 36 and the third circuit 32, the backflow prevention switch 45 of the first circuit 28 cannot be supplied from the first circuit 28 to the main power supply wiring 10 on the main battery 4 side. By maintaining this state, power can be prevented from being unintentionally supplied to the main power supply wiring 10 on the main battery 4 side.

  Next, the case where the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs the step-down operation by the operation of the first circuit 28 and the third circuit 32 will be described. When the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs the step-down operation, the switching elements 46a, 46b, 46c, 46d operate in the switching circuit 46 of the first circuit 28, and the DC-AC By functioning as a converter, the DC power supplied from the main power supply wiring 10 is converted into AC power. Then, the converted AC voltage is stepped down by the transformer 36, and the switching circuit 38 of the third circuit 32 functions as an AC-DC converter, thereby converting AC power into DC power. In this case, the switching circuit 38 operates in the same manner as when the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs the step-down operation. As a result, power can be supplied by stepping down from the main power supply wiring 10 to the sub power supply wiring 24.

  Next, the case where the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs the boosting operation by the operation of the first circuit 28 and the third circuit 32 will be described. When the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs the boosting operation, the switching circuit 38 of the third circuit 32 is a combination of the second circuit 30, the transformer 36, and the third circuit 32. As in the case of the step-up operation, the DC power supplied from the sub power supply wiring 24 is converted into AC power by functioning as a DC-AC converter. The converted AC voltage is boosted by the transformer 36, and the switching circuit 46 of the first circuit 28 functions as an AC-DC converter, thereby converting AC power into DC power. In this case, in the switching circuit 46, rectification is performed by the freewheeling diodes 46e, 46f, 46g, and 46h, and smoothing is performed in the filter 44. As a result, power can be supplied from the sub power supply wiring 24 to the main power supply wiring 10 while being boosted. When the switching circuit 46 functions as an AC-DC converter, each of the switching elements 46a, 46b, 46c, 46d is turned on while a current flows through the free-wheeling diodes 46e, 46f, 46g, 46h connected in parallel. Is done. Thereby, the electric current which flows into the free-wheeling diodes 46e, 46f, 46g, and 46h can be reduced.

  During the step-up / step-down operation of the combination of the first circuit 28, the transformer 36, and the third circuit 32, the backflow prevention switch 31 of the second circuit 30 cannot be supplied from the second circuit 30 to the main power supply wiring 10 on the PCU 12 side. By keeping the power on, power can be prevented from being unintentionally supplied to the main power supply wiring 10 on the PCU 12 side.

  Next, the case where the combination of the first circuit 28, the transformer 36, and the second circuit 30 performs the supply operation by the operation of the first circuit 28 and the second circuit 30 will be described. When the combination of the first circuit 28, the transformer 36, and the second circuit 30 performs the supply operation, the switching circuit 46 of the first circuit 28 is a combination of the first circuit 28, the transformer 36, and the third circuit 32. As in the case of performing the step-down operation, the DC power supply functions as a DC-AC converter, thereby converting the DC power supplied from the main power supply wiring 10 into AC power. Then, the converted AC voltage is converted from AC power to DC power in the switching circuit 34 of the second circuit 30 without changing the voltage in the transformer 36. In this case, the switching circuit 34 functions as an AC-DC converter so that the combination of the second circuit 30, the transformer 36, and the third circuit 32 performs a boosting operation. Convert to. As a result, power is supplied from the main power supply wiring 10 on the main battery 4 side of the SMR 20 to the main power supply wiring 10 on the PCU 12 side of the SMR 20 without changing the voltage while the SMR 20 maintains the main power supply wiring 10 in the non-conductive state. can do.

  Further, when the combination of the first circuit 28, the transformer 36, and the second circuit 30 performs the supply operation, the switching circuit 34 of the second circuit 30 is connected to the second circuit 30, the transformer 36, and the third circuit 32. As in the case where the combination performs a step-down operation, the DC power supplied from the main power supply wiring 10 is converted into AC power by functioning as a DC-AC converter. The converted AC voltage is converted from AC power to DC power in the switching circuit 46 of the first circuit 28 without changing the voltage in the transformer 36. In this case, the switching circuit 46 functions as an AC-DC converter so that the combination of the first circuit 28, the transformer 36, and the third circuit 32 performs a step-up operation. Convert to. As a result, the SMR 20 supplies power without changing the voltage from the main power supply wiring 10 on the PCU 12 side of the SMR 20 to the main power supply wiring 10 on the main battery 4 side of the SMR 20 with the main power supply wiring 10 kept non-conductive. can do.

  During this supply operation, power is unintentionally supplied to the sub power supply wiring 24 by maintaining the backflow prevention switch 41 of the third circuit 32 in a state in which it cannot be supplied from the third circuit 32 to the sub power supply wiring 24. Can be prevented.

  Through the operations of the first to third circuits 28, 30, and 32 described above, power can be interchanged between the main power supply wiring 10 on the main battery 4 side, the main power supply wiring 10 on the PCU 12 side, and the sub power supply wiring 24. it can. As a result, the electric power stored in the vehicle can be used effectively.

  The specific circuit configuration of the first to third circuits 28, 30, and 32 shown in FIG. 2 is merely an example, and in the second circuit 30 and the third circuit 32, the voltage is stepped down from the main power supply wiring 10 to the sub power supply wiring 24. As long as the step-down operation for supplying power and the step-up operation for boosting power from the sub power supply wiring 24 to the main power supply wiring 10 are possible, any configuration may be used. Similarly, the first circuit 28 is configured to step down from the main power supply wiring 10 to the sub power supply wiring 24 and supply power, and from the main power supply wiring 10 on the main battery 4 side of the SMR 20 to the PCU 12 side of the SMR 20 side. Any configuration may be used as long as the supply operation to the main power supply wiring 10 is possible.

  The control circuits 42 and 43 are controlled by the ECU 60. The ECU 60 includes a CPU and a memory. The ECU 60 is connected to each part 12, 20, 42, 43 of the power supply system 1 and controls each part 12, 20, 42, 43 according to a program stored in the memory.

  In the electric vehicle 2 shown in FIG. 1, when switching the SMR 20 from non-conduction to conduction, if the voltage of the main battery 4 and the voltage of the smoothing capacitor 14 of the PCU 12 are different, immediately after the SMR 20 switches to conduction. A large inrush current flows through the main power supply wiring 10. Therefore, in the electric vehicle 2, before the SMR 20 is switched from non-conduction to conduction, the smoothing capacitor 14 is precharged in order to make the voltage of the main battery 4 coincide with the voltage of the smoothing capacitor 14.

  With reference to FIG. 3, the process which ECU60 performs in the case of a precharge is demonstrated. In S12, the ECU 60 causes the combination of the first circuit 28, the transformer 36, and the second circuit 30 to perform the supply operation, and causes the combination of the second circuit 30, the transformer 36, and the third circuit 32 to perform the boost operation. Instructions for operating the first to third circuits 28, 30 and 32 are transmitted to the control circuits 42 and 43. As a result, the combination of the first circuit 28, the transformer 36, and the second circuit 30 starts the supply operation, so that the power supply from the main battery 4 to the PCU 12 is performed while the SMR 20 maintains the main power supply wiring 10 in the non-conductive state. Is started. In this supply operation, the switching circuit 46 of the first circuit 28 functions as a DC-AC converter, and the switching circuit 34 of the second circuit 30 functions as an AC-DC converter.

  Furthermore, when the combination of the second circuit 30, the transformer 36, and the third circuit 32 starts the boosting operation, the power supply from the sub battery 22 to the PCU 12 is performed while the SMR 20 maintains the main power supply wiring 10 in the non-conductive state. Be started. In this step-up operation, the switching circuit 38 of the third circuit 32 functions as a DC-AC converter, and the switching circuit 34 of the second circuit 30 functions as an AC-DC converter. During the precharge, the backflow prevention switches 41 and 45 are turned off, and the backflow prevention switch 31 is turned on.

  At the timing when the supply operation is started in S12, the duty ratio of the first circuit 28 and the third circuit 32 is set to a default value (initial value) such as 10%, for example. The duty ratios of the first circuit 28 and the third circuit 32 are kept low at the initial stage of precharge. This is because the voltage of the smoothing capacitor 14 is approximately 0 V in the early stage of precharge, and the smoothing capacitor 14 may be damaged if a high voltage is suddenly applied to the smoothing capacitor 14. In the second circuit 30, the switching elements 34 a, 34 b, 34 c, 34 d of the switching circuit 34 operate according to the duty ratios of the first circuit 28 and the third circuit 32. Note that a program for controlling the operation of the switching elements 34a, 34b, 34c, 34d according to the duty ratios of the first circuit 28 and the third circuit 32 is stored in the ECU 60 in advance. The ECU 60 supplies the operation timing of the switching elements 34 a, 34 b, 34 c, 34 d corresponding to the duty ratios of the first circuit 28 and the third circuit 32 to the control circuit 42.

  Next, in S14, the ECU 60 determines whether or not the duty ratio of the first circuit 28 is a predetermined upper limit value (for example, 50%). When the duty ratio of the first circuit 28 is a predetermined upper limit value (YES in S14), the process proceeds to S20. On the other hand, when the duty ratio of the first circuit 28 is smaller than the upper limit value (NO in S14), in S16, the ECU 60 uses the measurement result of the voltage sensor 50 to lower the voltage VB of the main battery 4 set in advance. It is determined whether or not the voltage is lower than Vx (lower than lower limit voltage Vx). For example, the preset lower limit voltage Vx is set to SOC 20%. The SOC of 20% is, for example, a standard for the charging rate that can cause the performance deterioration of the main battery 4 to be accelerated. This is an example of the minimum output voltage under a predetermined load condition set in order to suppress the performance degradation that can be caused by the voltage VB of the main battery 4 being excessively lowered.

  The lower limit voltage Vx is set by selecting an optimum value by experiment or computer simulation based on, for example, the electrical specifications of the main battery 4 and the usage environment (temperature, humidity, and load conditions). Note that SOC (State Of Charge) is sometimes referred to as a charging rate, and is a charging rate (unit%) of the main battery 4 when the full charge is 100%.

  If the voltage VB of the main battery 4 is less than the preset lower limit voltage Vx (YES in S16), the process proceeds to S20 without changing the duty ratio of the first circuit 28. On the other hand, when voltage VB of main battery 4 is equal to or higher than preset lower limit voltage Vx (NO in S16), in S18, ECU 60 instructs control circuit 43 to increase the duty ratio of first circuit 28. Send. For example, the ECU 60 increases the current duty ratio by 5%. In accordance with this, the ECU 60 transmits an instruction to adjust the duty ratio of the second circuit 30 to the control circuit 42. As a result, the power supplied from the main power supply wiring 10 on the main battery 4 side to the main power supply wiring 10 on the PCU 12 side increases. When the process of S18 ends, the process returns to S14. According to this configuration, when the voltage VB of the main battery 4 is less than the preset lower limit voltage Vx, the power supplied from the main battery 4 is increased by not changing the duty ratio of the first circuit 28. I won't let you. Thereby, it can prevent that the performance of the main battery 4 falls by the voltage of the main battery 4 dropping too much.

  In S20, the ECU 60 determines whether or not the duty ratio of the third circuit 32 is a predetermined upper limit value (for example, 50%). When the duty ratio of the third circuit 32 is a predetermined upper limit value (YES in S20), the process proceeds to S28. On the other hand, when the duty ratio of the third circuit 32 is smaller than the upper limit value (NO in S20), in S22, the ECU 60 determines whether the voltage VS of the sub-battery 22 is less than the preset lower limit voltage Vy (the lower limit voltage Vy is set to be lower). Judge whether or not. The lower limit voltage Vy set in advance is, for example, the lowest output voltage set in advance for each vehicle. The sub-battery 22 supplies electric power to a vehicle auxiliary machine (for example, power steering, air conditioner). The minimum value of the output voltage for supplying power to the auxiliary equipment of the vehicle is determined for each vehicle. For this reason, the lower limit voltage Vy is preset according to the structure of the vehicle.

  If the voltage VS of the sub-battery 22 is less than the preset lower limit voltage Vy (YES in S22), the process proceeds to S28 without changing the duty ratio of the third circuit 32. On the other hand, when voltage VS of sub battery 22 is equal to or higher than preset lower limit voltage Vy (NO in S22), in S24, ECU 60 causes current IS discharged from sub power supply wiring 24 to be less than preset upper limit current Iz. Or not (lower than the upper limit current Iz). In the sub-battery 22, a maximum value of the discharge current corresponding to the performance of the sub-battery 22 is set. The upper limit current Iz may be equal to the maximum value of the discharge current according to the performance of the sub-battery 22, or may be slightly smaller than the maximum value of the discharge current. If the current IS of the sub power supply wiring 24 is greater than or equal to the preset upper limit current Iz (NO in S24), the process proceeds to S28 without changing the duty ratio of the third circuit 32.

  On the other hand, when the current IS of the sub power supply wiring 24 is less than the preset upper limit current Iz (YES in S24), the ECU 60 controls an instruction to increase the duty ratio of the third circuit 32 in S26. Transmit to circuit 42. For example, the ECU 60 increases the current duty ratio by 5%. In accordance with this, the ECU 60 transmits an instruction to adjust the duty ratio of the second circuit 30 to the control circuit 42. As a result, the power supplied from the sub power supply wiring 24 (sub battery 22) to the main power supply wiring 10 on the PCU 12 side increases. When the process of S26 ends, the process returns to S20. According to this configuration, when the voltage VS of the sub battery 22 is less than the preset lower limit voltage Vy, the power supplied from the sub battery 22 is increased by not changing the duty ratio of the third circuit 32. I won't let you. Thereby, it is possible to prevent the voltage of the sub battery 22 from being lowered.

  In S28, the ECU 60 determines that the difference (VB−VL) between the voltage VB of the main battery 4 measured by the voltage sensor 50 and the voltage VL of the smoothing capacitor 14 measured by the voltage sensor 56 is equal to or less than a predetermined potential difference Vz. Judge whether there is. The predetermined potential difference Vz is caused by welding of the contacts of the switches 20a and 20b of the SMR 20 due to an inrush current flowing from the main battery 4 to the smoothing capacitor 14 immediately after the SMR 20 is switched from non-conduction to conduction, The voltage difference is such that the function is not disabled.

  If the difference (VB−VL) between the voltage VB of the main battery 4 and the voltage VL of the smoothing capacitor 14 is not equal to or less than the predetermined potential difference Vz (NO in S28), the difference between the voltage VB and the voltage VL of the smoothing capacitor 14 The process of S28 is repeatedly executed until (VB−VL) becomes equal to or smaller than the predetermined potential difference Vz. This prevents a problem from occurring in the switches 20a and 20b of the SMR 20 due to an inrush current flowing from the main battery 4 to the smoothing capacitor 14 immediately after the SMR 20 is switched from non-conduction to conduction. On the other hand, if it is equal to or smaller than the predetermined potential difference Vz (YES in S28), in S30, the ECU 60 sends a signal for stopping the operation of the first to third circuits 28, 30, 32 to the control circuits 42, 43. To finish the precharge.

  When the precharge ends, the ECU 60 switches the SMR 20 from non-conduction to conduction. Since the smoothing capacitor 14 has already been precharged, a large inrush current does not flow from the main battery 4 to the smoothing capacitor 14 when the SMR 20 is switched from non-conduction to conduction.

  In the above configuration, the smoothing capacitor 14 can be precharged using the power of the main battery 4. According to this configuration, the precharge time can be shortened compared to a configuration in which only the sub-battery 22 is used to precharge the smoothing capacitor 14. Further, in the above configuration, the power of the sub battery 22 is also used for precharging the smoothing capacitor 14. According to this configuration, the precharge time can be further shortened.

  Further, as a configuration for precharging the smoothing capacitor 14 using the power of the main battery 4, the main power supply wiring 10 on the main battery 4 side and the sub power supply wiring 24 are connected via a DCDC converter, and the main power supply on the PCU 12 side is also connected. A configuration in which the power supply wiring 10 and the sub power supply wiring 24 are connected via another DCDC converter is conceivable. In this configuration, the power of the main battery 4 is stepped down and supplied to the sub power supply line 24, and the power of the sub power supply line 24 is stepped up and supplied to the smoothing capacitor 14. In the configuration of the present embodiment, the number of switch circuits and the number of transformers on the sub power supply wiring 24 side can be reduced as compared with the configuration in which two DCDC converters are arranged. As a result, it is not necessary to operate the switch circuit on the sub power supply wiring 24 side. Further, since the power of the main battery 4 is temporarily supplied to the sub power supply wiring 24, it is not necessary to step down the voltage. For this reason, the loss of the electric power by transformation can be reduced.

  Further, when the SMR 20 has an open failure, power can be supplied from the main battery 4 to the PCU 12 via the first circuit 28 and the second circuit 30. As a result, even if the SMR 20 has an open failure while the engine is stopped, the engine can be cranked and the engine can be started by supplying power from the main battery 4 to the PCU 12.

(Second embodiment)
With reference to FIG. 4, the power system 1 according to the second embodiment will be described while referring to differences from the power system 1 according to the first embodiment. The power supply system 1 of the second embodiment is different from the power supply system 1 of the first embodiment in processing at the time of precharging. Specifically, in the power supply system 1 of the first embodiment, the power of the sub-battery 22 is supplied to the main power supply wiring 10 on the PCU 12 side at the time of precharging, whereas in the power supply system of the second embodiment, at the time of precharging. By supplying the power of the main battery 4 to the sub power supply wiring 24, the sub battery 22 is charged. Since other configurations are the same as those of the power supply system 1 of the first embodiment, description thereof is omitted.

  FIG. 4 shows a flowchart of processing executed by the ECU 60 during precharging. In S112, the ECU 60 causes the combination of the first circuit 28, the transformer 36, and the second circuit 30 to perform the supply operation, and causes the combination of the first circuit 28, the transformer 36, and the third circuit 32 to perform the step-down operation. Instructions for operating the first to third circuits 28, 30, 32 are transmitted to the control circuits 42, 43. As a result, the combination of the first circuit 28, the transformer 36, and the second circuit 30 starts the supply operation, so that the power supply from the main battery 4 to the PCU 12 is performed while the SMR 20 maintains the main power supply wiring 10 in the non-conductive state. Is started. In this supply operation, the switching circuit 46 of the first circuit 28 functions as a DC-AC converter, and the switching circuit 34 of the second circuit 30 functions as an AC-DC converter.

  Further, the combination of the first circuit 28, the transformer 36, and the third circuit 32 starts the step-down operation, so that the power from the main battery 4 to the sub-battery 22 is maintained while the SMR 20 keeps the main power supply wiring 10 non-conductive. Supply is started. In this step-down operation, the switching circuit 46 of the first circuit 28 functions as a DC-AC converter, and the switching circuit 38 of the third circuit 32 functions as an AC-DC converter. The duty ratio of the first circuit 28 at the timing when the supply operation is started in S112 is set to a default value (initial value) similar to S12 in FIG. In the second circuit 30, the switching elements 34 a, 34 b, 34 c, 34 d of the switching circuit 34 operate according to the duty ratio of the first circuit 28. Note that the backflow prevention switches 31, 41, 45 are switched from the non-supply state to the supply state.

  In the third circuit 32, the power supplied to the sub power supply wiring 24 is controlled by the operation of the switching elements 38a, 38b, 38c, and 38d. At the timing when the supply operation is started in S112, the power supplied to the sub power supply wiring 24 is kept low. This is to avoid a situation where the voltage applied to the sub-battery 22 exceeds the maximum voltage Vm determined by the performance of the sub-battery 22.

  Next, the ECU 60 executes the processes of S114 to S118 similar to the processes of S14 to S18 in FIG. Next, in S120, the ECU 60 determines whether or not the voltage VS of the sub-battery 22 is less than a preset maximum voltage Vm (is less than the maximum voltage Vm). If the voltage VS of the sub-battery 22 is not less than the maximum voltage Vm (NO in S120), the process proceeds to S124. If the voltage VS of the sub-battery 22 is less than the maximum voltage Vm (YES in S120), the process proceeds to S128.

  In S124, the switching of the third circuit 32 is stopped, and the backflow prevention switch 41 is switched from the supply state to the non-supply state. Thereby, it is possible to prevent unintended power from being supplied to the sub-battery 22. According to this configuration, it is possible to avoid deterioration of the sub-battery 22 due to excessive power being supplied to the sub-battery 22. When the process of S124 is completed, the process proceeds to S128. In S124, the duty ratio of the first circuit 28 may be decreased in a state where the backflow prevention switch 41 is maintained in the supply state without stopping the switching of the third circuit 32. Thereby, the power supplied to the sub power supply wiring 24 may be reduced.

  The process of S128 is the same as the process of S28 of FIG. If NO in S128, the process returns to S120. On the other hand, if YES in S128, the process of S130 similar to S30 of FIG. 2 is executed, and the process at the time of precharging is terminated.

  According to the configuration of the present embodiment, precharge to the smoothing capacitor 14 and charge to the sub-battery 22 can be executed in parallel.

  The configurations of the first to third circuits 28, 30, and 32 are not limited to the configurations of the above-described embodiments. For example, the combination of the second circuit 30, the transformer 36, and the first circuit 28 allows the power of the main power supply wiring 10 on the PCU 12 side to be supplied to the main power supply wiring 10 on the main battery 4 side. One circuit 28 may be controlled.

  When power is not supplied from the sub power supply wiring 24, the third circuit 32 may include a diode 238e instead of the switching element 38a and the diode 38e as shown in FIG. Similarly, the third circuit 32 may replace the switching element 38b and the diode 38f with the diode 238f, the switching element 38c and the diode 38g with the diode 238g, and the switching element 38d and the diode 38h with the diode 238h, respectively. That is, the third circuit 32 functions as an AC-DC converter, but may not function as a DC-AC converter.

  Further, when power is not supplied from the main power supply wiring 10 on the PCU 12 side, as shown in FIG. 6, the second circuit 30 may have a diode 334e instead of the switching element 34a and the diode 34e. Similarly, the second circuit 30 may replace the switching element 34b and the diode 34f with the diode 434f, the switching element 34c and the diode 34g with the diode 334g, and the switching element 34d and the diode 34h with the diode 334h, respectively. That is, the second circuit 30 may function as an AC-DC converter, but may not function as a DC-AC converter.

  When power is not supplied to the main power supply wiring 10 on the main battery 4 side, the first circuit 28 functions as a DC-AC converter, but does not have to function as an AC-DC converter.

  In the first embodiment, the power of the sub-battery 22 is supplied to the PCU 12 during precharging. In the second embodiment, the power of the main battery 4 is supplied to the sub-battery 22 during precharging. However, during the precharge, the third circuit 32 is not operated, and it is not necessary to supply power between the sub battery 22 and the main power supply wiring 10. In this case, for example, in the flowchart of FIG. 3, the ECU 60 does not have to execute the processes of S20 to S26.

  In each of the above embodiments, power is supplied to the PCU 12 from the main battery 4 via the first circuit 28, the transformer 36, and the second circuit 30 in both precharge and engine cranking. However, in either one of precharge and engine cranking, power is not supplied from the main battery 4 to the PCU 12 via the first circuit 28, the transformer 36, and the second circuit 30, and the third circuit from the sub battery 22 is supplied. 30, power may be supplied to the PCU 12 via the transformer 36 and the second circuit 30.

  Whether the ECU 60 should supply power from the sub-battery 22 to the PCU 12 during pre-charging using the charge amount of the sub-battery 22 before starting the processing of FIG. 3 or FIG. It may be determined whether the process of FIG. 3 is to be executed) or whether power is to be supplied from the main battery 4 to the sub-battery 22 (that is, whether the process of FIG. 4 is to be executed). For example, the ECU 60 estimates the charge amount of the sub battery 22 based on the discharge performance of the sub battery 22 (that is, the relationship between the current IS and the voltage VS at the time of discharge), and the estimated charge amount is a predetermined charge amount. In the case where the number is larger than that, it is determined that power should be supplied from the sub-battery 22 to the PCU 12 during the precharge (that is, the processing of FIG. 3 should be executed), and the estimated charge amount is determined in advance. When the charging amount is smaller than the charging amount, it may be determined that power should be supplied from the main battery 4 to the sub battery 22 during precharging (that is, the processing of FIG. 4 should be executed).

  Further, at least one of the backflow prevention switches 31, 41, 45 may be a cut-off switch that cuts off power so that power is not supplied between the corresponding coil and the corresponding power supply wiring. For example, when the backflow prevention switch 31 is replaced with a cutoff switch, when the cutoff switch is on, power can be supplied between the second coil 36a and the main power supply wiring 10 on the PCU 12 side, while the cutoff switch is off. In this case, it may be impossible to supply power between the second coil 36a and the main power supply wiring 10 on the PCU 12 side.

  When the switching circuits 34, 38, 46 function as an AC-DC converter, the switching elements 34a, 34b, 34c, 34d, 38a, 38b, 38c, 38d, 46a, 46b included in the switching circuits 34, 38, 46 are used. , 46c, 46d may be kept off (i.e., non-conducting) without operating.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

  In some embodiments, each of the first circuit, the second circuit, and the third circuit may include a DC-AC converter and an AC-DC converter. According to this configuration, electric power can be interchanged between the main battery, the sub-battery, and the power control unit where necessary.

  In some embodiments, each of the first circuit, the second circuit, and the third circuit may include a cut-off switch that cuts off power so that power is not supplied from the corresponding coil to the corresponding power supply wiring. According to this configuration, it is possible to avoid unintentionally supplying power to the main power supply wiring and the sub power supply wiring. For example, when power is supplied from the first circuit to the second circuit via a transformer, the cutoff switch of the third circuit maintains a state in which power cannot be supplied from the third coil to the sub power supply wiring. Thus, it is possible to avoid supplying power to the sub power supply wiring.

  In some embodiments, the vehicle power supply system may include a control device that controls the switch, the first circuit, and the second circuit. The control device performs precharge control in which the DC-AC converter of the first circuit is operated and the smoothing capacitor is charged via the AC-DC converter of the second circuit while the main power supply wiring is turned off by the switch. May be. According to this configuration, the time required for precharging can be shortened as compared with the case where the smoothing capacitor is precharged by supplying power only from the sub-battery.

  In some embodiments, the control device may control the duty ratio of the DC-AC converter of the first circuit so that the voltage of the main battery does not become less than a predetermined reference value during the precharge control. Good. According to this configuration, it is possible to prevent the performance of the main battery from being deteriorated due to excessive reduction in the voltage of the main battery.

  Alternatively, in some embodiments, the third circuit may have the function of an AC-DC converter. The control device may execute charging control for operating the DC-AC converter of the first circuit and supplying power to the sub power supply wiring via the AC-DC converter of the third circuit during the precharge control. According to this configuration, the smoothing capacitor can be precharged and the sub-battery can be charged.

  In some embodiments, the control device may control the third circuit so that the voltage of the sub-battery does not exceed a predetermined upper limit value during the charging control. According to this configuration, it is possible to prevent a voltage exceeding the performance of the sub battery from being applied to the sub battery.

  In some embodiments, the controller may further control the third circuit. The third circuit may have a function of a DC-AC converter. Utilizing a sub power source that operates the DC-AC converter of the first circuit and the DC-AC converter of the third circuit and charges the smoothing capacitor via the AC-DC converter of the second circuit during the precharge control. Control may be performed. According to this configuration, the smoothing capacitor can be precharged by supplying power from both the main battery and the sub-battery. Thereby, the time required for precharging can be shortened.

  In some embodiments, the control device controls the duty ratio of the DC-AC converter of the third circuit so that the voltage of the sub battery does not become less than a predetermined lower limit value during the sub power supply utilization control. Also good. According to this configuration, it is possible to prevent the voltage of the sub-battery from being lowered due to precharging, and the voltage supplied to the auxiliary equipment of the vehicle, such as a power steering or an air conditioner, from being lowered.

  In some embodiments, the control device controls the duty ratio of the AC-DC converter of the third circuit so that the current of the sub power supply wiring does not exceed a predetermined upper limit value during the sub power supply utilization control. May be. According to this configuration, it is possible to perform control so that the current from the sub battery does not exceed the performance of the sub battery during the sub power supply utilization control.

1: Power supply system 2: Electric vehicle 4: Main battery 10: Main power supply wiring 12: PCU
14: Smoothing capacitor 20: SMR
22: Sub battery 24: Sub power supply wiring 26: Auxiliary machine 28: First circuit 30: Second circuit 31, 41, 45: Backflow prevention switch 32: Third circuit 36: Transformer 36a: Second coil 36b: Third coil 36c: 1st coil

Claims (4)

A main battery,
Main power supply wiring connected to the main battery;
A power control unit including a smoothing capacitor for smoothing the voltage of the main power supply wiring;
A switch that switches between conduction and non-conduction of the main power supply wiring between the main battery and the power control unit;
A sub-battery having a lower voltage than the main battery;
Sub power supply wiring connected to the sub battery;
A transformer including a first coil, a second coil, and a third coil;
A first circuit that connects the main coil and the first coil on the main battery side of the switch;
A second circuit that connects the main coil and the second coil closer to the power control unit than the switch;
A third circuit connecting the sub power supply wiring and the third coil ;
A control device for controlling the switch, the first circuit, and the second circuit ;
With
The first circuit has a function of a DC-AC converter ;
The second circuit has to have a function of the AC-DC converter,
The control device includes:
A precharge for operating the DC-AC converter of the first circuit and charging the smoothing capacitor via the AC-DC converter of the second circuit in a state where the main power supply wiring is made non-conductive by the switch. Perform control,
Controlling the duty ratio of the DC-AC converter of the first circuit so that the voltage of the main battery does not become less than a predetermined reference value during the precharge control,
Power supply system for vehicles. The third circuit has an AC-DC converter function;
The control device includes:
During the precharge control, the charge control is performed to operate the DC-AC converter of the first circuit and supply power to the sub power supply wiring through the AC-DC converter of the third circuit,
2. The vehicle power source according to claim 1 , wherein a duty ratio of the AC-DC converter of the third circuit is controlled so that a voltage of the sub-battery does not exceed a predetermined upper limit value during the charging control. system. The third circuit has a function of a DC-AC converter;
The control device includes:
During the precharge control, the DC-AC converter of the first circuit and the DC-AC converter of the third circuit are operated to charge the smoothing capacitor via the AC-DC converter of the second circuit. Sub power supply utilization control to be performed,
2. The vehicle according to claim 1, wherein the duty ratio of the DC-AC converter of the third circuit is controlled so that the voltage of the sub battery does not become less than a predetermined lower limit value during the sub power supply utilization control. Power system. 4. The device according to claim 1, wherein each of the first circuit, the second circuit, and the third circuit includes a cutoff switch that cuts off power so that power is not supplied from the corresponding coil to the corresponding power supply wiring . 5. The vehicle power supply system according to item 1 .

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