JP7833686B2 - power supply device - Google Patents

Description

This disclosure relates to a power supply device that supplies control power.

Power converters used in solar power generation systems and energy storage systems often output PWM signals using power semiconductors to perform power conversion. In such systems, if the main power supply is interrupted and the control power is lost without the power converter being able to shut down, there is a possibility of power converter failure.

Furthermore, in the case of charging stations or charge/discharge stations connected to electric vehicles, for example, if the station loses its main power supply, it is necessary to not only shut down the power converter but also to properly complete communication and control sequences with the vehicle.

To prepare for a loss of the main power supply, it is conceivable to install energy storage devices such as capacitors as a backup for the control power supply (see, for example, Patent Document 1). In this case, power can be supplied from the energy storage device for a period of time, allowing the power converter to be safely shut down.

Japanese Patent Publication No. 2020-58232

In conventional circuit configurations using backup energy storage devices, the signal often passes through a converter both during charging and discharging, resulting in reduced efficiency.

This disclosure is made in light of these circumstances, and its purpose is to provide technology that enables high efficiency and miniaturization of power supply devices equipped with backup energy storage devices.

To solve the above problems, a power supply device in one aspect of this disclosure comprises: a backup energy storage device; a charging path for charging the energy storage device; a first conduction control circuit connected to the charging path; a discharge path for discharging from the energy storage device; a second conduction control circuit connected to the discharge path; a first power supply path to which a first converter that converts the voltage of power supplied from a main power source is connected; a second power supply path to which a second converter, whose input side is connected to the discharge path, is connected; and a load supply path connected to a connection point where the output side of the first power supply path and the output side of the second power supply path merge, for supplying power to a load. The connection point is connected to the charging path.

According to this disclosure, it is possible to achieve higher efficiency and miniaturization of power supply devices equipped with backup energy storage devices.

This is a diagram illustrating a charge/discharge device according to an embodiment. This figure shows an example of the configuration of a power supply unit according to an embodiment. This figure shows a truth table summarizing the on/off control of the charging switch. This figure shows a truth table summarizing the on/off control of the discharge switch.

Figure 1 is a diagram illustrating a charging/discharging device 10 according to an embodiment. The charging/discharging device 10 is a V2H (Vehicle to Home) device for connecting the electric vehicle 20 with the power receiving point of the commercial power grid (hereinafter simply referred to as the grid) 2 within the home. The charging/discharging device 10 and the electric vehicle 20 are connected by a DC charging/discharging cable 30. A gun connector 30a is attached to the end of the charging/discharging cable 30, and the charging/discharging device 10 and the electric vehicle 20 are connected when the user inserts the gun connector 30a into the inlet of the electric vehicle 20.

The charging/discharging device 10 comprises a DC/DC converter 11, an inverter 12, a main control unit 13, and a power supply unit 14. The DC/DC converter 11 and the inverter 12 constitute the main power circuit. One end of the DC/DC converter 11 is connected to the electric vehicle 20 via a charging/discharging cable 30, and the other end of the DC/DC converter 11 is connected to the inverter 12. The DC/DC converter 11 is a bidirectional DC/DC converter for charging and discharging the drive battery mounted on the electric vehicle 20.

The inverter 12 is a bidirectional inverter connected between the DC/DC converter 11 and the distribution board 3 connected to the power grid 2. The inverter 12 can convert the DC power input from the DC/DC converter 11 into AC power and output the converted AC power to the distribution board 3. The inverter 12 can also convert the AC power supplied from the power grid 2 via the distribution board 3 into DC power and output the converted DC power to the DC/DC converter 11.

Furthermore, another DC/DC converter connected to a solar cell, another DC/DC converter connected to a stationary battery, etc., may be connected to the DC bus Bdc between the DC/DC converter 11 and the inverter 12.

The main control unit 13 comprehensively controls the entire charge/discharge device 10. The main control unit 13 can be realized through the collaboration of hardware and software resources, or solely through hardware resources. Hardware resources that can be used include analog circuits, logic circuits, microcontrollers, DSPs, ROMs, RAMs, ASICs, FPGAs, and other LSIs. Software resources that can be used include firmware and other programs.

The power supply unit 14 generates a control power supply for use in the charge/discharge device 10. The power supply unit 14 generates the control power supply by stepping down the voltage of the power obtained from the DC bus Bdc. For example, the power supply unit 14 steps down a voltage of approximately 360V DC obtained from the DC bus Bdc to generate a control power supply of approximately 24V DC. Alternatively, the power supply unit 14 may obtain 200V AC power from outside the inverter 12, perform AC/DC conversion and step-down to generate a control power supply of approximately 24V DC.

Furthermore, the power supply unit 14 can also generate a control power supply by converting power from an external power source when the external power cable connected to the external power source is connected to the external input terminal T1. For example, an auxiliary battery (e.g., a 12V output lead-acid battery) installed in the electric vehicle 20 can be used as the external power source. By plugging the external power cable into the cigarette lighter socket of the electric vehicle 20, the user can use the auxiliary battery as an external power source. Note that the external power source is not limited to the auxiliary battery installed in the electric vehicle 20; other portable batteries or portable generators may also be used.

The power supply unit 14 further steps down the generated control power of approximately 24V according to the supply destination. For example, the power supply unit 14 steps down the control power of approximately 24V to approximately 3-5V and supplies it to the main control unit 13. Alternatively, the power supply unit 14 steps down the control power of approximately 24V to approximately 15V and supplies it to the drive circuit for the switching device used in the main circuit.

In the case of a charge/discharge device 10 that complies with the V2H guidelines established by the CHAdeMO Council, it is necessary to install a sequence circuit used for the charge/discharge sequence with the electric vehicle 20. In that case, the power supply unit 14 steps down a control power supply of approximately 24V to a control power supply of 12V and supplies it to the sequence circuit.

Figure 2 shows an example of the configuration of the power supply unit 14 according to an embodiment. The power supply unit 14 comprises a power storage device C1, a first converter 141, a second converter 142, a control circuit 143, a first conduction control circuit 144, and a second conduction control circuit 145.

The energy storage device C1 is an energy storage device for backing up the control power supply. For example, the energy storage device C1 can use a supercapacitor (electric double-layer capacitor, hybrid capacitor, etc.) or a battery (lithium-ion battery, nickel-metal hydride battery, etc.). In this embodiment, the use of an electric double-layer capacitor is assumed.

The first converter 141 converts and outputs the voltage of the power supplied from the main power source (DC bus Bdc in the circuit configuration of Figure 1). The second converter 142 converts and outputs the voltage of the power supplied from the energy storage device C1 or the auxiliary power source (for example, the auxiliary battery of the electric vehicle 20). The first converter 141 is connected on the first power supply path P1, and the second converter 142 is connected on the second power supply path P2. At the connection point N1 where the output side of the first power supply path P1 and the output side of the second power supply path P2 merge, a load supply path P3 for supplying power to the control load and a charging path P4 for charging the energy storage device C1 are connected.

The input side of the first power supply path P1 is connected to the DC bus Bdc. A first diode D1 for reverse current prevention is connected between the first converter 141 and connection point N1 on the first power supply path P1. Note that the first diode D1 may be provided within the first converter 141. In that case, the voltage detection circuit V1 will be inserted into the anode side of the first diode D1. The input side of the second power supply path P2 consists of a discharge path P5 for discharging from the energy storage device C1 and a path connected to the external input terminal T1, both connected in parallel. A second diode D2 for reverse current prevention is connected between the external input terminal T1 and connection point N2. A third diode D3 for reverse current prevention is connected between the second converter 142 and connection point N1 on the second power supply path P2. Note that the third diode D3 may be provided within the second converter 142.

A first conduction control circuit 144, which controls whether to allow or prohibit charging to the energy storage device C1, is connected to the charging path P4. A second conduction control circuit 145, which controls whether to allow or prohibit discharge from the energy storage device C1, is connected to the discharge path P5.

In Figure 2, the first conduction control circuit 144 includes a charging switch Q1 and a fourth diode D4. The charging switch Q1 can be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). In Figure 2, an N-channel MOSFET is used. In an N-channel MOSFET, a parasitic diode is formed from the source to the drain. SiC-MOSFET, GaN-MOSFET, or Ga2O3-MOSFET may also be used as the MOSFET. When an IGBT is used for the charging switch Q1, an external diode is connected between the source and drain.

The fourth diode D4 is connected in a direction that allows current to flow from connection point N1 towards the energy storage device C1. The fourth diode D4 and the charging switch Q1 are connected in series such that the anodes of the parasitic diodes of the fourth diode D4 and the charging switch Q1 face each other.

The second conduction control circuit 145 includes a discharge switch Q2 and a fifth diode D5. Similar to the charge switch Q1, a MOSFET or IGBT can be used for the discharge switch Q2. In Figure 2, an N-channel MOSFET is used. The fifth diode D5 is connected in a direction that allows current to flow from the energy storage device C1 to the second converter 142. The fifth diode D5 and the discharge switch Q2 are connected in series such that the cathodes of the parasitic diodes of the fifth diode D5 and the discharge switch Q2 face each other.

The voltage supplied from the first power supply path P1 to connection point N1 is set higher than the voltage supplied from the second power supply path P2 to connection point N1. That is, the voltage command value of the first converter 141 is set higher than the voltage command value of the second converter 142. For example, the voltage command value of the first converter 141 is set to 25V, and the voltage command value of the second converter 142 is set to 23V. In this case, the first converter 141 steps down the voltage of the power supplied from the DC bus Bdc to generate a 25V control power supply. The second converter 142 steps up the voltage of the power supplied from the energy storage device C1 or external input terminal T1 to generate a 23V control power supply. As a result, while the voltage of the DC bus Bdc is applied, the output of the first converter 141 takes precedence over the output of the second converter 142.

The control circuit 143 controls the on/off state of the charging switch Q1 and the discharging switch Q2 based on the output voltage of the first converter 141 and the operating state of the power conversion system, including the charge/discharge device 10 supplied from the main control unit 13. The control circuit 143 may be composed of, for example, a logic circuit.

The voltage detection circuit V1 detects the output voltage of the first converter 141 and outputs it to the control circuit 143. The detection point is inside the first diode D1. The voltage detection circuit V1 is composed, for example, of a voltage divider resistor and a differential amplifier. The control circuit 143 monitors the voltage inside the second diode D2 to detect whether or not external power is supplied to the external input terminal T1 via an external power cable. A discharge resistor R is also connected in parallel to the voltage detection circuit V1 and is used to determine whether or not to transition to the third voltage operation mode, which will be described later.

Figure 3 shows a truth table summarizing the on/off control of the charging switch Q1. Figure 4 shows a truth table summarizing the on/off control of the discharging switch Q2. First, we will explain the case where system 2 is normal. In the standby state of the power conversion system including the charge/discharge device 10, everything is voltage-free in the initial state. When DC 360V is applied from the DC bus Bdc to the first converter 141, the conditions of "standby" and "output voltage of the first converter 141 is above the threshold" in the table in Figure 3, and "standby" in the table in Figure 4 are met. The first converter 141 steps down the DC 360V voltage to DC 25V and outputs it. The control circuit 143 turns on the charging switch Q1 to allow current in the charging direction by the first conduction control circuit 144, and maintains the off state of the discharging switch Q2 to prohibit current in the discharging direction by the second conduction control circuit 145, transitioning to the first operating mode.

In the first operating mode, power is supplied to the control load, and charging of the energy storage device C1 is also possible. For example, when charging the energy storage device C1 from the first converter 141 when the voltage of the energy storage device C1 is low, such as during startup, the voltage of the load supply path P3 also decreases, pulled down by the voltage of the energy storage device C1. If that voltage falls below the output voltage of the second converter 142, a circulating current flows through the path from the second converter 142 → first conduction control circuit 144 → energy storage device C1 → second conduction control circuit 145 → second converter 142. In contrast, in the first operating mode, since the discharge switch Q2 is in the off state, the above circulating current does not occur.

When the charging of energy storage device C1 is complete, the voltage of energy storage device C1 becomes approximately the same as the voltage of the load supply path P3. That is, the voltage of energy storage device C1 also becomes 25V.

When the power conversion system starts operation (i.e., when the DC/DC converter 11 and inverter 12 begin power conversion), the conditions of "Operation" and "Output voltage threshold of the first converter 141" in the table of Figure 3 and "Operation" in the table of Figure 4 are met. The control circuit 143 maintains the charging switch Q1 in the ON state, allowing current in the charging direction by the first conduction control circuit 144, and switches to a second operating mode by turning on the discharge switch Q2, allowing current in the discharge direction by the second conduction control circuit 145. In this second operating mode, even if the output of the first converter 141 is lost, instantaneous backup from the energy storage device C1 is always possible.

In the second operating mode, power from the main power supply is prioritized for charging the energy storage device C1, while backup power from the second converter 142 is provided in case of main power supply failure. Furthermore, the generation of the aforementioned circulating current can be prevented.

During operation of the power conversion system, a power outage in system 2 causes a loss of main power, making it impossible to supply power to the output of the first converter 141. This causes the voltage in the load supply path P3 to drop, and the second converter 142 supplies power to the load supply path P3, bringing the voltage in P3 to 23V. At that time, the voltage of the voltage detection circuit V1 also drops to 23V. However, because a discharge resistor R is connected in parallel with the voltage detection circuit V1, even if the voltage in the load supply path P3 is maintained at 23V, the voltage of the voltage detection circuit V1 will drop even further below 23V. This results in the conditions of "Operation" and "Output voltage threshold of the first converter 141" in the table of Figure 3, and "Operation" in the table of Figure 4. The control circuit 143 turns off the charging switch Q1 to prohibit the charging current by the first conduction control circuit 144, and maintains the discharge switch Q2 in the ON state to allow the discharge current by the second conduction control circuit 145, transitioning to a third operating mode.

In the third operating mode, even if power cannot be supplied from the first converter 141 due to loss of main power or other reasons, a constant voltage can be supplied from the second converter 142 to the load supply path P3. Furthermore, since the charging switch Q1 is in the off state, the above-mentioned circulating current does not occur.

The second converter 142 boosts the voltage of the power supplied from the energy storage device C1 and supplies a voltage of 23V to the load supply path P3. The second converter 142 supplies control power until the power conversion system stops. Once the power conversion system stops and enters standby mode, all power to the power conversion system is eventually lost. By stopping the power conversion system via the third operating mode, it becomes possible to safely and appropriately shut down the system.

Next, we will explain the situation during a power outage in system 2. In the standby state of the power conversion system, including the charge/discharge device 10, all voltages are initially zero. When DC 12V is applied to the second converter 142 from an external power source (hereinafter, assumed to be the auxiliary battery of the electric vehicle 20) via an external power cable, the conditions of "standby" and "output voltage below the threshold of the first converter 141" in the table of Figure 3, and "standby" in the table of Figure 4, are met. The second converter 142 boosts the DC 12V voltage to DC 23V and outputs it. The control circuit 143 switches to a first operating mode, turning on the charging switch Q1 to allow current in the charging direction by the first conduction control circuit 144, and maintaining the off state of the discharge switch Q2 to prohibit current in the discharge direction by the second conduction control circuit 145.

When the charging of energy storage device C1 is complete, the voltage of energy storage device C1 becomes approximately the same as the voltage of the load supply path P3. That is, the voltage of energy storage device C1 also becomes 23V.

When the power conversion system starts operating (i.e., when the DC/DC converter 11 and inverter 12 start power conversion), power supply from the DC bus Bdc begins, and the first converter 141 starts outputting DC 25V. This fulfills the conditions for "Operation" and "Output voltage threshold of the first converter 141" in the table in Figure 3, and for "Operation" in the table in Figure 4. The control circuit 143 maintains the charging switch Q1 in the ON state, allowing current in the charging direction by the first conduction control circuit 144, and switches on the discharge switch Q2, allowing current in the discharge direction by the second conduction control circuit 145, transitioning to a second operating mode. In the second operating mode, even if the output of the first converter 141 is lost, instantaneous backup from the energy storage device C1 is always possible. At this stage, the external power cable may be disconnected to release the connection to the auxiliary battery.

During operation of the power conversion system, if the DC/DC converter 11 stops due to an abnormal shutdown on the electric vehicle 20 side, and the output voltage of the first converter 141 disappears, the conditions of "Operation" and "No output voltage from first converter 141" in the table of Figure 3, and "Operation" in the table of Figure 4 are met. The control circuit 143 turns off the charging switch Q1 to prohibit the charging current by the first conduction control circuit 144, and maintains the discharge switch Q2 in the ON state to allow the discharge current by the second conduction control circuit 145, transitioning to a third operating mode. The first converter 141 stops operating.

The second converter 142 boosts the voltage of the power supplied from the energy storage device C1 and supplies a voltage of 23V to the load supply path P3. The second converter 142 supplies control power until the power conversion system stops. Once the power conversion system stops and enters standby mode, all power to the power conversion system is eventually lost. By stopping the power conversion system via the third operating mode, it becomes possible to safely and appropriately shut down the system.

As described above, according to this embodiment, since a power converter is not provided on the charging side of the energy storage device C1, no conversion loss occurs during charging. The second converter 142, provided on the discharge side of the energy storage device C1, is a unidirectional converter, allowing for miniaturization. Furthermore, the second converter 142 is shared as a power converter for the auxiliary power supply. Therefore, an increase in circuit size is suppressed. Also, since the charging path P4 and the discharge path P5 are separate, charging and discharging of the energy storage device C1 can be switched without interruption. Additionally, the second converter 142 allows the energy storage device C1 to be used down to a low voltage region (low SOC region). Furthermore, by setting the output voltage of the first converter 141 higher than the output voltage of the second converter 142, it becomes possible to preferentially consume power supplied from the main power supply.

The present disclosure has been described above based on embodiments. The embodiments are illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of their components and processing steps, and that such modifications also fall within the scope of this disclosure.

In the circuit configuration shown in Figure 2, the fourth diode D4 and the fifth diode D5 may be replaced with switching elements (e.g., MOSFETs). In that case, the first conduction control circuit 144 and the second conduction control circuit 145 are each composed of bidirectional switches. For example, in the operating mode when the second converter 142 fails, the control circuit 143 controls the second conduction control circuit 145 to the ON state, enabling direct charging of the energy storage device C1 from the auxiliary power supply. Furthermore, by controlling the first conduction control circuit 144 to the ON state, power can be supplied directly from the energy storage device C1 to the load supply path P3.

In the circuit configuration shown in Figure 2, if the losses due to the circulating current can be tolerated, a configuration in which at least one of the charging switch Q1 and the discharging switch Q2 is omitted is also possible.

Furthermore, while the enable/disable state of the charging switch Q1 in Figure 3 is determined by whether the output voltage of the first converter 141 is above or below a threshold, hysteresis may be introduced into the threshold. This would prevent chattering of the charging switch Q1. Alternatively, the input voltage of the first converter 141 may be used instead of the output voltage of the first converter 141 to determine the enable/disable state of the charging switch Q1 in Figure 3. In that case, a separate circuit for detecting the input voltage of the first converter 141 would be required.

The charging and discharging device 10 according to this embodiment may not be a standalone device, but may be incorporated into a power conditioner of a solar power generation system, a power conditioner of a stationary energy storage system, or a power station that hybridizes both.

Furthermore, the electric vehicle 20 may be an electric motorcycle (electric scooter) or an electric bicycle. It may also be a low-speed electric vehicle such as a golf cart or a land car used in shopping malls or entertainment facilities.

Furthermore, the embodiment may be specified by the following items.

[Item 1]
A backup energy storage device (C1),
A charging path (P4) for charging the aforementioned energy storage device (C1),
A first conductive control circuit (144) connected to the charging path (P4),
A discharge path (P5) for discharging from the energy storage device (C1),
A second conduction control circuit (145) connected to the discharge path (P5),
A first power supply path (P1) to which a first converter (141) that converts the voltage of power supplied from the main power source is connected,
The input side of the second power supply path (P2) is connected to the second converter (142) which is connected to the discharge path (P5),
The system includes a load supply path (P3) connected to a connection point (N1) where the output side of the first power supply path (P1) and the output side of the second power supply path (P2) merge, and for supplying power to a load.
A power supply device (14) to which the connection point (N1) is connected to the charging path (P4).
According to this, it is possible to achieve higher efficiency and miniaturization of the power supply device (14).
[Item 2]
The power supply device (14) according to item 1, wherein the first converter (141) supplies power to the connection point with priority over the second converter (142).
According to this, power supplied from the main power source can be used preferentially.
[Item 3]
The power supply device (14) according to item 2, comprising at least a mode in which the first conduction control circuit (144) permits current in the charging direction and the second conduction control circuit (145) permits current in the discharge direction.
According to this, power from the main power supply is prioritized for charging the energy storage device (C1), while backup power from the second converter 142 is provided in case of a loss of the main power supply.
[Item 4]
The power supply device (14) according to item 2, comprising at least a mode in which the first conduction control circuit (144) permits current in the charging direction and the second conduction control circuit (145) prohibits current in the discharge direction.
According to this, it is possible to prevent the generation of circulating current via the second converter (142) when charging the energy storage device (C1).
[Item 5]
The second converter (142) is further comprising:
The power supply device (14) according to claim 2, wherein an external input terminal (T1) for inputting a secondary power supply is provided on the input side of the second converter (142).
According to this, power can be supplied from the auxiliary power source to the energy storage device (C1) and the load without the need to install an additional converter.
[Item 6]
The power supply device (14) according to item 2, comprising at least a mode in which the first conduction control circuit (144) prohibits current in the charging direction and the second conduction control circuit (145) permits current in the discharge direction.
According to this, even if the main power supply is lost, a constant voltage can be supplied from the second converter (142) to the load supply path (P3).

2 circuits, 3 distribution boards, 10 charge/discharge device, 11 DC/DC converter, 12 inverter, 13 main control unit, 14 power supply unit, 20 electric vehicle, 141 first converter, 142 second converter, 143 control circuit, 144 first conduction control circuit, 145 second conduction control circuit, Bdc DC bus, C1 energy storage device, D1-D5 diodes, Q1 charging switch, Q2 discharging switch, P1 first power supply path, P2 second power supply path, P3 load supply path, P4 charging path, P5 discharging path, T1 external input terminal, V1 voltage detection circuit, R discharge resistor.

Claims (6)

A backup power storage device,
A charging path for charging the aforementioned energy storage device,
A first conductive circuit connected to the charging path,
A discharge path for discharging from the aforementioned energy storage device,
A second conduction control circuit connected to the discharge path,
The first power supply path is connected to the first converter, which converts the voltage of the power supplied from the main power source,
The input side is connected to the discharge path, and the second power supply path is connected to the second converter,
A load supply path is provided, which is connected to the connection point where the output side of the first power supply path and the output side of the second power supply path merge, and is used to supply power to a load.
The aforementioned connection point is connected to the charging path ,
The first conduction control circuit includes a first diode connected in a direction such that current flows from the connection point toward the energy storage device, and a charging switch connected in series with the first diode, wherein the charging switch is kept turned on so that current flows in the charging direction through the charging path.
The second conduction control circuit includes a second diode connected in a direction that causes current to flow from the energy storage device to the second converter, and a discharge switch connected in series with the second diode, wherein the discharge switch is kept turned on so that current flows in the discharge direction through the discharge path.
Power supply device. The power supply device according to claim 1, wherein the first converter supplies power to the connection point with priority over the second converter. A backup power storage device,
A charging path for charging the aforementioned energy storage device,
A first conductive circuit connected to the charging path,
A discharge path for discharging from the aforementioned energy storage device,
A second conduction control circuit connected to the discharge path,
The first power supply path is connected to the first converter, which converts the voltage of the power supplied from the main power source,
The input side is connected to the discharge path, and the second power supply path is connected to the second converter,
A load supply path is provided, which is connected to the connection point where the output side of the first power supply path and the output side of the second power supply path merge, and is used to supply power to a load.
The aforementioned connection point is connected to the charging path,
The first converter supplies power to the connection point with priority over the second converter.
A power supply device comprising at least a mode in which the first conduction control circuit permits current in the charging direction and the second conduction control circuit permits current in the discharge direction. The power supply device according to claim 2, comprising at least a mode in which the first conduction control circuit permits current in the charging direction and the second conduction control circuit prohibits current in the discharge direction. A backup power storage device,
A charging path for charging the aforementioned energy storage device,
A first conductive circuit connected to the charging path,
A discharge path for discharging from the aforementioned energy storage device,
A second conduction control circuit connected to the discharge path,
The first power supply path is connected to the first converter, which converts the voltage of the power supplied from the main power source,
The input side of the second converter is connected to the discharge path,
The second power supply path to which the second converter is connected,
A load supply path is provided, which is connected to the connection point where the output side of the first power supply path and the output side of the second power supply path merge, and is used to supply power to a load.
A power supply device having an external input terminal for inputting a secondary power supply on the input side of the second converter. The power supply device according to claim 2, comprising at least a mode in which the first conduction control circuit prohibits current in the charging direction and the second conduction control circuit permits current in the discharge direction.