Power System

Abstract

To provide a power supply system capable of properly supplying power.SOLUTION: In a power supply system 1, a voltage monitor 41 detects a voltage of output power output from a DC / DC converter 10, a step-down unit 42 steps down the voltage of the output power and supplies the same to a load unit LD, and a distributor control unit 43 controls the step-down unit 42 based on the voltage detected by the voltage monitor 41. In the above-described configuration, when the voltage detected by the voltage monitor 41 is in a power sufficiency condition of equal to or higher than a predetermined threshold voltage, the distributor control unit 43 controls the step-down unit 42 to step down the voltage of the output power and supply the same to the load unit LD. On the other hand, in the case of a power shortage state in which the voltage detected by the voltage monitor 41 is lower than the threshold voltage, the distributor control unit 43 controls the step-down unit 42 to supply the voltage of the output power to the load unit LD without stepping down the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system. [Background technology]

[0002] As a conventional power supply system, for example, Patent Document 1 describes an in-vehicle power system that distributes power supplied from a power supply and supplies it to multiple in-vehicle loads. This in-vehicle power system includes, for example, a DC / DC converter that steps down the voltage of the power, a main power distribution box connected to the DC / DC converter, and an electrical wiring box connected to the main power distribution box. The main power distribution box supplies the power stepped down by the DC / DC converter to the electrical wiring box, and the electrical wiring box supplies the power supplied from the main power distribution box to the in-vehicle loads. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-057564 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the in-vehicle power system described in the above-mentioned Patent Document 1 is thought to boost the voltage of power using a DC / DC converter when power becomes scarce due to power consumption by in-vehicle loads, but in this case, the boosted power may be supplied even to in-vehicle loads that have sufficient power, which may result in an in-vehicle load being oversupplied with power.

[0005] The present invention has been made in view of the above, and has an object to provide a power supply system that can supply power appropriately. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a power supply system according to the present invention comprises a DC / DC converter capable of transforming the voltage of DC power, and a power distributor that distributes output power, which is DC power output from the DC / DC converter, to loads, wherein the power distributor includes a voltage detection unit that detects the voltage of the output power, a step-down unit that can step down the voltage of the output power and supply it to loads, and a distributor control unit that controls the step-down unit based on the voltage detected by the voltage detection unit, wherein the distributor control unit controls the step-down unit to step down the voltage of the output power and supply it to the loads when the voltage detected by the voltage detection unit is equal to or higher than a predetermined threshold voltage, which is a power sufficiency state, and controls the step-down unit to step down the voltage of the output power and supply it to the loads when the voltage detected by the voltage detection unit is less than the threshold voltage, which is a power shortage state. [Effects of the Invention]

[0007] The power supply system of the present invention controls the voltage of the DC power supplied to the load units on the power supply distributor side, so compared to when the voltage of the DC power is controlled on the DC / DC converter side, it is possible to control the voltage individually for multiple load units, and as a result, it is possible to supply power to the load units appropriately. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a power supply system according to an embodiment. [Figure 2] FIG. 2 is a circuit diagram showing an example of the configuration of a step-down unit according to the embodiment. [Figure 3] FIG. 3 is a diagram showing an example of an operation pattern of the power supply system according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing an example of the operation of the power supply system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0010] A power supply system 1 according to an embodiment will be described with reference to the drawings. The power supply system 1 is mounted on a vehicle and supplies power to a load LD of the vehicle. As shown in Fig. 1, the power supply system 1 includes a DC / DC converter 10, a converter control unit 20, a 12V battery 30, and a plurality of power supply distributors 40 (40A to 40D). Note that in Fig. 1, power supply distributors 40C and 40D have the same configuration as power supply distributor 40B, and are shown in a simplified form.

[0011] The DC / DC converter 10 is a converter capable of transforming the voltage of DC power. The DC / DC converter 10 is connected to, for example, an external power supply (not shown), and transforms (steps up or down) the voltage of the DC power supplied from the power supply in accordance with the control of the converter control unit 20, and outputs the output power, which is the transformed DC power, to the power supply distributor 40A.

[0012] The converter control unit 20 controls the DC / DC converter 10. The converter control unit 20 is configured with an electronic circuit mainly consisting of a well-known microcomputer including a CPU, ROM and RAM constituting a storage unit, and an interface. For example, when the power supply distributor 40 is in a power sufficient state, the converter control unit 20 controls the DC / DC converter 10 to transform the voltage of the output power output from the DC / DC converter 10 to the voltage of the output power output from the DC / DC converter 10 in a power sufficient state (normal voltage: for example, 13 V). On the other hand, when the power supply distributor 40 is in a power shortage state, i.e., when power is tight, the converter control unit 20 controls the DC / DC converter 10 to boost the voltage of the output power output from the DC / DC converter 10 to a voltage (for example, 14 V to 15 V) that is equal to or higher than the voltage of the output power output from the DC / DC converter 10 in a power sufficient state (13 V).

[0013] The 12V battery 30 is a power storage unit that charges and discharges power. The 12V battery 30 is connected to the DC / DC converter 10, and is charged with power supplied from the DC / DC converter 10, and supplies the charged power to a plurality of power supply distributors 40.

[0014] The plurality of power supply distributors 40 distribute power to the loads LD. The plurality of power supply distributors 40 include, for example, power supply distributors 40A to 40D. The power supply distributor 40A is connected to the DC / DC converter 10, and the power supply distributors 40B to 40D are connected to the DC / DC converter 10. D are connected to the power supply distributor 40A. That is, the power supply distributors 40 are arranged in a layer such that the power supply distributor 40A is provided on the upper layer side, and the power supply distributors 40B to 40C are provided on the lower layer side. D is provided below the power distributor 40A, and is configured in two layers.

[0015] The power supply distributor 40A includes a voltage monitor 41a as a voltage detection unit, a step-down unit 42a, and a distributor control unit 43a. The voltage monitor 41a, the step-down unit 42a, and the distributor control unit 43a are connected to each other so that they can communicate with each other.

[0016] The voltage monitor 41a detects the voltage of the DC power. The voltage monitor 41a is connected to, for example, the DC / DC converter 10, and detects the voltage of the output power, which is the DC power output from the DC / DC converter 10. The voltage monitor 41a outputs the detected voltage to the distributor control unit 43a.

[0017] The step-down unit 42a steps down the voltage of DC power and supplies it to the load unit LD. The step-down unit 42a is connected to, for example, the DC / DC converter 10, and steps down the voltage of the output power output from the DC / DC converter 10 and supplies it to the load unit LD. The step-down unit 42a steps down the voltage of the output power (13 V) output from the DC / DC converter 10 to a predetermined voltage (e.g., 11 V) and supplies it to the load unit LD. Here, as shown in FIG. 2, the step-down unit 42a is configured to include a small current output circuit P1, a medium current output circuit P2, and an ECU 421.

[0018] The small current output circuit P1 is a circuit that outputs a current smaller than that of the medium current output circuit P2, and includes a switch circuit SW1, a coil L1, a diode D1, and a capacitor C1. One end of the switch circuit SW1 is connected to the DC / DC converter 10, and the other end is connected to the load LD. The coil L1 is provided on the power line between the switch circuit SW1 and the load LD. The cathode terminal of the diode D1 is connected to the power line between the switch circuit SW1 and the coil L1, and the anode terminal is connected to ground. The capacitor C1 has one end connected to the power line between the coil L1 and the load LD, and the other end is connected to ground. The small current output circuit P1 is used when a small current flows, and the voltage of the output power output from the DC / DC converter 10 is reduced by PWM control of the switch circuit SW1 by the ECU 421.

[0019] The medium-current output circuit P2 is a circuit that outputs a current larger than that of the small-current output circuit P1 and includes switch circuits SW2 and SW3, a diode D2, a coil L2, and a capacitor C2. The switch circuit SW2 has one end connected to the DC / DC converter 10 and the other end connected to the load LD. The switch circuit SW3 has one end connected to a power line between the switch circuit SW2 and the load LD and the other end connected to ground. The coil L2 is provided on the power line between the switch circuit SW2 and the load LD. The diode D2 has a cathode terminal connected to the power line between the switch circuits SW2 and SW3 and the coil L2 and an anode terminal connected to ground. The capacitor C2 has one end connected to the power line between the coil L2 and the load LD and the other end connected to ground. The medium-current output circuit P2 is used when a medium current flows, and the ECU 421 PWM-controls the switch circuits SW2 and SW3 to reduce the voltage of the output power output from the DC / DC converter 10.

[0020] The distributor control unit 43a shown in FIG. 1 controls the step-down unit 42a based on the voltage detected by the voltage monitor 41a. The distributor control unit 43a includes an electronic circuit mainly composed of a well-known microcomputer including a CPU, a ROM and RAM constituting a storage unit, and an interface. When the voltage detected by the voltage monitor 41a is equal to or higher than a predetermined threshold voltage, indicating a power-sufficient state, the distributor control unit 43a controls the step-down unit 42a to step down the voltage of the output power (e.g., 13 V) from the DC / DC converter 10 to a predetermined voltage (e.g., 11 V) and supply it to the load LD. On the other hand, when the voltage detected by the voltage monitor 41a is lower than the threshold voltage, indicating a power-deficient state, the distributor control unit 43a controls the step-down unit 42a to supply the voltage of the output power (e.g., 14 V to 15 V) from the DC / DC converter 10 to the load LD without stepping it down.

[0021] Next, we will explain power supply distributor 40B, which is provided below power supply distributor 40A. Power supply distributor 40B includes a voltage monitor 41b as a voltage detection unit, multiple step-down units 42b, and a distributor control unit 43b. Voltage monitor 41b, step-down units 42b, and distributor control unit 43b are connected to each other so that they can communicate with each other.

[0022] The voltage monitor 41b detects the voltage of the DC power. The voltage monitor 41b is connected to, for example, the power supply distributor 40A, and detects the voltage of the output power output from the power supply distributor 40A. The voltage monitor 41b outputs the detected voltage to the distributor control unit 43b.

[0023] The step-down unit 42b steps down the voltage of the DC power and supplies it to the load LD. The step-down unit 42b is connected to, for example, a power supply distributor 40A, and steps down the voltage of the output power output from the power supply distributor 40A and supplies it to the load LD. The step-down unit 42b steps down the voltage of the output power output from the power supply distributor 40A (for example, 13 V) to a predetermined voltage (for example, 11 V) and supplies it to the load LD. Note that the step-down unit 42b is configured to include, for example, a small current output circuit P1, a medium current output circuit P2, and an ECU 421, as shown in FIG. 2.

[0024] The distributor control unit 43b controls the step-down unit 42b based on the voltage detected by the voltage monitor 41b. The distributor control unit 43b includes an electronic circuit mainly composed of a known microcomputer including a CPU, a ROM and RAM constituting a memory unit, and an interface. When the voltage detected by the voltage monitor 41b is equal to or higher than a predetermined threshold voltage, indicating a power-sufficient state, the distributor control unit 43b controls the step-down unit 42b to step down the voltage of the output power (e.g., 13V) from the power distributor 40A to a predetermined voltage (e.g., 11V) and supply it to the load LD. On the other hand, when the voltage detected by the voltage monitor 41b is lower than the threshold voltage, indicating a power-deficient state, the distributor control unit 43b controls the step-down unit 42b to supply the voltage of the output power (e.g., 14V to 15V) from the power distributor 40A to the load LD without stepping it down. Note that the power distributors 40C and 40D have the same configuration as the power distributor 40B, and therefore detailed description thereof will be omitted.

[0025] Next, we will explain the operation patterns of the power supply system 1. Fig. 3 is a diagram showing an example of an operation pattern of the power supply system 1 according to the embodiment.

[0026] As shown in FIGS. 1 and 3, when the voltages V1 to V4 detected by the power distributors 40A to 40D are normal voltages (e.g., 13 V) (pattern 1), the power supply system 1 determines that the power distributors 40A to 40D are in a power sufficient state. In this case, the converter control unit 20 controls the DC / DC converter 10 to set the voltage of the output power output from the DC / DC converter 10 to the voltage of the output power output from the DC / DC converter 10 in a power sufficient state (e.g., 13 V). The divider control unit 43a of the power distributor 40A controls the step-down unit 42a to step down the voltage of the output power output from the DC / DC converter 10 and supply it to the load LD. The divider control unit 43b of the power distributor 40B controls all the step-down units 42b to step down the voltage of the output power output from the DC / DC converter 10 and supply it to the load LD. Similarly to the power distributors 40A and 40B, the power distributors 40C and 40D step down the voltage of the output power output from the DC / DC converter 10 and supply it to the load LD.

[0027] When voltages V1, V3, and V4 detected by power distributors 40A, 40C, and 40D are equal to or higher than a threshold voltage (normal voltage) and voltage V2 detected by power distributor 40B is lower than the threshold voltage (low voltage) (pattern 2), power supply system 1 determines that power distributor 40B is in a power shortage state. In this case, converter control unit 20 controls DC / DC converter 10 to boost the voltage of the output power output from DC / DC converter 10 to a first voltage (e.g., 14 V) that is equal to or higher than the voltage of the output power output from DC / DC converter 10 in a power sufficient state (e.g., 13 V). Distributor control unit 43a of power distributor 40A controls voltage step-down unit 42a to step down the voltage of the output power boosted to the first voltage by DC / DC converter 10 and supply it to load LD. The distributor control unit 43b of the power distributor 40B controls all of the step-down units 42b to supply the voltage of the output power boosted to the first voltage by the DC / DC converter 10 to the load unit LD without stepping it down (conversion OFF). Note that, like the power distributor 40A, the power distributors 40C and 40D step down the voltage of the output power boosted to the first voltage by the DC / DC converter 10 and supply it to the load unit LD.

[0028] When the voltages V1 to V4 detected by the power distributors 40A to 40D are lower than the threshold voltage (low voltage) (pattern 3), the power supply system 1 determines that all of the power distributors 40A to 40D are in a power shortage state. In this case, the converter control unit 20 controls the DC / DC converter 10 to boost the output power voltage to a second voltage (e.g., 15V) that is equal to or higher than the first voltage (e.g., 14V). The distributor control unit 43a of the power distributor 40A controls the step-down unit 42a to supply the output power voltage boosted to the second voltage by the DC / DC converter 10 to the load LD without stepping it down (conversion OFF). The distributor control unit 43b of the power distributor 40B controls all the step-down units 42b to supply the output power voltage boosted to the second voltage by the DC / DC converter 10 to the load LD without stepping it down (conversion OFF). Like the power distributor 40B, the power distributors 40C and 40D supply the output power voltage boosted to the second voltage by the DC / DC converter 10 to the load LD without lowering the voltage (conversion OFF).

[0029] Next, an example of the operation of the power supply system 1 will be described. The power supply distributor 40 detects the voltage of the output power output from the DC / DC converter 10 (step S1). If the detected voltage of the output power is equal to or higher than the threshold voltage, indicating a power sufficiency state (step S2; Yes), the power supply distributor 40 steps down the voltage of the output power and supplies it to the load LD (step S3), and then ends the process. On the other hand, if the detected voltage of the output power is lower than the threshold voltage, indicating a power deficiency state (step S2; No), the power supply distributor 40 steps up the voltage of the output power output from the DC / DC converter 10 (step S4). Then, the power supply distributor 40 supplies the stepped-up voltage of the output power to the load LD without stepping it down (step S5), and then ends the process.

[0030] As described above, the power supply system 1 according to the embodiment includes the DC / DC converter 10 and the power distributor 40. The DC / DC converter 10 is a converter capable of transforming the voltage of DC power. The power distributor 40 distributes the output power, which is DC power output from the DC / DC converter 10, to the load LD. The power distributor 40 includes a voltage monitor 41, a step-down unit 42, and a distributor control unit 43. The voltage monitor 41 detects the voltage of the output power output from the DC / DC converter 10. The step-down unit 42 steps down the voltage of the output power and supplies it to the load LD. The distributor control unit 43 controls the step-down unit 42 based on the voltage detected by the voltage monitor 41. In the above configuration, when the voltage detected by the voltage monitor 41 is equal to or higher than a predetermined threshold voltage, indicating a power sufficient state, the distributor control unit 43 controls the step-down unit 42 to step down the voltage of the output power and supply it to the load LD. On the other hand, when the voltage detected by the voltage monitor 41 is below the threshold voltage, indicating a power shortage, the distributor control unit 43 controls the step-down unit 42 to supply the output power to the load unit LD without stepping down the voltage.

[0031] With this configuration, the power supply system 1 controls the voltage of the DC power supplied to the load section LD on the power supply distributor 40 side, so that compared to the case where the voltage of the DC power is controlled on the DC / DC converter 10 side, it is possible to individually control the voltage for the multiple load sections LD, and as a result, it is possible to appropriately supply power to the load sections LD.

[0032] The power supply system 1 further includes a converter control unit 20 that controls the DC / DC converter 10. In a power shortage state, the converter control unit 20 controls the DC / DC converter 10 to boost the voltage of the output power output from the DC / DC converter 10 to a voltage equal to or higher than the voltage of the output power output from the DC / DC converter 10 in a power sufficient state. The distributor control unit 43 controls the step-down unit 42 to supply the output power voltage boosted by the DC / DC converter 10 to the load LD without stepping it down. With this configuration, the power supply system 1 can appropriately supply power to the load LD by cooperatively controlling the step-down unit 42 of the power distributor 40 and the DC / DC converter 10.

[0033] In the power supply system 1, the power supply distributor 40 includes a power supply distributor 40A connected to the DC / DC converter 10, and a power supply distributor 40B connected to the power supply distributor 40A. The power supply distributor 40A includes a voltage monitor 41a that detects the voltage of the output power output from the DC / DC converter 10 and input to the power supply distributor 40A, a step-down unit 42a that can step down the voltage of the output power output from the DC / DC converter 10 and input to the power supply distributor 40A and supply it to a load LD, and a distributor control unit 43a that controls the step-down unit 42a based on the voltage detected by the voltage monitor 41a. The power supply divider 40B includes a voltage monitor 41b that detects the voltage of the output power output from the power supply divider 40A and input to the power supply divider 40B, a step-down unit 42b that can step down the voltage of the output power output from the power supply divider 40A and input to the power supply divider 40B and supply it to the load LD, and a divider control unit 43b that controls the step-down unit 42b based on the voltage detected by the voltage monitor 41b. When the power supply divider 40A is in a power sufficient state and the power supply divider 40B is in a power shortage state, the converter control unit 20 controls the DC / DC converter 10 to step up the voltage of the output power to a first voltage that is equal to or higher than the voltage of the output power output from the DC / DC converter 10 in the power sufficient state. The divider control unit 43a controls the step-down unit 42a to step down the voltage of the output power that has been stepped up to the first voltage by the DC / DC converter 10 and supply it to the load LD. The distributor control unit 43b controls the step-down unit 42b to supply the voltage of the output power boosted to the first voltage by the DC / DC converter 10 to the load LD without stepping it down. Furthermore, when the power supply distributor 40A and the power supply distributor 40B are in a power shortage state, the converter control unit 20 controls the DC / DC converter 10 to step up the voltage of the output power to a second voltage that is equal to or higher than the first voltage. The distributor control unit 43a controls the step-down unit 42a to supply the voltage of the output power boosted to the second voltage by the DC / DC converter 10 to the load LD without stepping it down. The distributor control unit 43b controls the step-down unit 42b to supply the voltage of the output power boosted to the second voltage by the DC / DC converter 10 to the load LD without stepping it down.With this configuration, the power supply system 1 can individually adjust and supply power to the load LD according to the power supply state of each of the power supply distributors 40A and 40B by cooperatively controlling the step-down section 42 of the power supply distributor 40 and the DC / DC converter 10.

[0034] In the power supply system 1, the voltage of the output power output from the DC / DC converter 10 is set to approximately 13V to 15V, and the power supply distributor 40 does not have a boost section but has a step-down section 42, thereby lowering the voltage of the entire system and achieving power saving effects.

[0035] In the above explanation, an example has been described in which the power supply system 1 controls the power supply distributor 40 and the DC / DC converter 10 in a coordinated manner, but the present invention is not limited to this. For example, the power supply system 1 may control the power supplied to the load LD by controlling the power supply distributor 40 alone, without transforming the voltage of the output power output from the DC / DC converter 10 in accordance with the power supply situation such as a shortage.

[0036] Although the power supply system 1 has been described as an example in which the power supply distributors 40A to 40D are configured in two layers, this is not limited to this, and for example, it may be configured in one layer with only the power supply distributor 40A, or may be configured in three or more layers.

[0037] The power supply system 1 may be an integrated control unit that integrates the converter control unit 20 and each distributor control unit 43, or the function of the converter control unit 20 may be performed by the distributor control unit 43a of the power distributor 40A, or the function of the converter control unit 20 may be built into the DC / DC converter 10 so that the function of the converter control unit 20 is performed by the DC / DC converter 10. [Explanation of symbols]

[0038] 1 Power System 10 DC / DC converter 20 Converter control section LD load section 40 Power distributor 40A power divider (1st power divider) 40B power supply divider (second power supply divider) 41 Voltage monitor (voltage detection section) 41a Voltage monitor (first voltage detection unit) 41b Voltage monitor (second voltage detection unit) 42 Step-down section 42a Step-down section (first step-down section) 42b Step-down section (second step-down section) 43 Distribution control unit 43a distributor control unit (first distributor control unit) 43b Distributor control section (second distributor control section)

Claims

[Claim 1] a DC / DC converter capable of transforming the voltage of DC power; a first power distributor connected to the DC / DC converter; a second power supply divider connected to the first power supply divider; a converter control unit (20) that controls the DC / DC converter (10), the first power supply divider includes a first voltage detection unit that detects a voltage of the output power output from the DC / DC converter and input to the first power supply divider; a first step-down unit that steps down a voltage of the output power output from the DC / DC converter and input to the first power supply distributor, and supplies the voltage to a first load unit; a first divider control unit that controls the first step-down unit based on the voltage detected by the first voltage detection unit, the second power supply distributor includes a second voltage detection unit that detects a voltage of the output power output from the first power supply distributor and input to the second power supply distributor; a second step-down unit that steps down the voltage of the output power output from the first power supply distributor and input to the second power supply distributor, and supplies the step-down voltage to a second load unit; a second divider control unit that controls the second step-down unit based on the voltage detected by the second voltage detection unit, the converter control unit controls the DC / DC converter when the first power supply distributor is in a power sufficient state in which the voltage detected by the first voltage detection unit is equal to or greater than a predetermined threshold voltage and the second power supply distributor is in the power sufficient state in which the voltage detected by the second voltage detection unit is equal to or greater than the threshold voltage, and sets a voltage of the output power to a voltage output from the DC / DC converter when the first power supply distributor and the second power supply distributor are in the power sufficient state, the first divider control unit controls the first step-down unit to step down the voltage of the output power from the DC / DC converter and supply the stepped down voltage to the first load unit; the second divider control unit controls the second step-down unit to step down the voltage of the output power from the DC / DC converter and supply the stepped-down voltage to the second load unit; the converter control unit, when the first power supply divider is in the power sufficient state and the second power supply divider is in a power shortage state in which the voltage detected by the second voltage detection unit is less than the threshold voltage, controls the DC / DC converter to boost a voltage of the output power to a first voltage that is equal to or higher than the voltage of the output power output from the DC / DC converter when the first power supply divider and the second power supply divider are in the power sufficient state; the first distributor control unit controls the first step-down unit to step down the voltage of the output power that has been stepped up to the first voltage by the DC / DC converter and supply the voltage to the first load unit; the second distributor control unit controls the second step-down unit to supply the voltage of the output power, which has been stepped up to the first voltage by the DC / DC converter, to the second load unit without stepping down the voltage; Furthermore, the converter control unit controls the DC / DC converter to boost a voltage of the output power to a second voltage that is equal to or higher than the first voltage when the first power supply distributor is in the power shortage state in which the voltage detected by the first voltage detection unit is lower than the threshold voltage and the second power supply distributor is in the power shortage state; the first distributor control unit controls the first step-down unit to supply the voltage of the output power, which has been stepped up to the second voltage by the DC / DC converter, to the first load unit without stepping down the voltage; The second distributor control unit controls the second step-down unit and supplies the voltage of the output power boosted to the second voltage by the DC / DC converter to the second load unit without stepping it down.

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