Power unit

Abstract

To provide a power unit which charges a secondary battery cell to restore to a normal charge / discharge operation even when the remaining amount of charge of the second battery cell decreases and an operation of a BMS stops.SOLUTION: A power unit (100) comprises: a solar cell (10) which generates power by light to output power; a secondary battery cell (40) which stores power; a battery management unit (30) which interrupts takeout of power stored in the secondary battery cell (40) to execute a protection operation when storage voltage of the secondary battery cell (40) is equal to or less than protection voltage; and an automatic restoration control unit (50) which is connected between the solar cell (10) and the battery management unit (30), converts a part of power output by the solar cell (10) into first voltage and a first current value to be supplied to the secondary battery cell (40) and executes a restoration charging operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device, and more particularly to a power supply device that stores the output from a solar cell in a secondary battery cell. [Background technology]

[0002] In recent years, solar cells that generate electricity from solar energy have become widespread, and it has become common to generate electricity from the roofs of ordinary houses or unused land. In such solar power generation facilities, when the amount of electricity generated by sunlight is insufficient, electricity is also supplied from the power grid from the power plant. In addition, when the amount of electricity generated by sunlight is greater than the amount of electricity consumed, the surplus electricity is sold through the power transmitter.

[0003] However, in remote areas or undeveloped areas where it is difficult to lay power transmission facilities, it is impossible to supply and sell electricity using a power transmission network, making it difficult to install and utilize photovoltaic power generation facilities. Therefore, an independent power supply device has been proposed that combines solar cells and secondary batteries, temporarily stores electricity generated by the solar cells in the secondary batteries, and extracts the electricity stored in the secondary batteries as needed (for example, see Patent Document 1).

[0004] FIG. 5 is a block diagram showing a schematic configuration of a conventional independent power supply device. As shown in FIG. 5, the conventional independent power supply device includes a solar cell 10, a charge / discharge control unit 20, a battery management unit (BMS: Battery Management System) 30, and a secondary battery cell 40. The output of the solar cell 10 is connected to the input of the charge / discharge control unit 20, and the output of the charge / discharge control unit 20 is connected to the battery management unit 30. The battery management unit 30 is connected to the electrode terminals of the secondary battery cell 40 and is driven by power from the secondary battery cell 40 to obtain the state of the secondary battery cell 40 and control overcharge protection and overdischarge protection. The power stored in the secondary battery cell 40 is output to the load and the charge / discharge control unit 20 via the battery management unit 30, and is used to drive the load and the charge / discharge control unit 20.

[0005] In such a conventional independent power supply device, the charge / discharge control unit 20 and the battery management unit 30 are driven by power taken from the secondary battery cell 40, and the charge / discharge control unit 20 controls the charge / discharge operation of the secondary battery cell 40. However, when the remaining charge of the secondary battery cell 40 decreases and the over-discharge protection function of the battery management unit 30 is activated, power is not supplied from the secondary battery cell 40 to the charge / discharge control unit 20, so that the charge / discharge control unit 20 also stops operating and cannot resume the charging operation. Therefore, the present applicant has proposed a technique for restarting the charging / discharging operation by starting the charge / discharge control unit 20 with power supplied from the solar cell 10 even when the remaining charge of the secondary battery cell 40 decreases and the over-discharge protection is activated (Patent Document 2). Also, in Patent Document 2, even if the secondary battery cell 40 is in an over-discharge state, the charge / discharge control unit 20 can acquire the state of the secondary battery cell 40 from the battery management unit 30 and execute a pre-charge operation to resume charging. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-017778 A [Patent Document 2] Patent No. 6031721 Summary of the Invention [Problem to be solved by the invention]

[0007] In the prior art shown in Patent Document 2, a module with excellent replaceability and portability is used as a secondary battery, and the secondary battery module can be replaced as needed. As a result, it is not expected that the secondary battery module protected from over-discharge will further discharge and reach a deep discharge state. Even if the secondary battery module reaches a deep discharge state, it is possible to easily continue the charge / discharge operation by replacing it with another secondary battery module, and to recover the deep discharged secondary battery module.

[0008] However, in the case of an independent power supply device installed in a remote location as described above, it is difficult to repeat maintenance of the equipment in a short period of time. If there is a long period of insufficient sunlight during the rainy season or snowfall, the independent power supply device in the remote location cannot continue charging the secondary battery, so that the operation of the battery management unit 30 in the secondary battery cell 40 in the over-discharged state may cause further discharging, leading to a deep discharge state. Since the battery management unit 30 operates with power supplied from the secondary battery cell 40, the battery management unit 30 becomes inoperative in the secondary battery cell 40 in the deep discharged state, and charging cannot be resumed. In the secondary battery cell 40 in the deep discharged state, the battery management unit 30 is inoperative even when the technology of Patent Document 2 is used, so that the state of the secondary battery cell 40 cannot be obtained and the pre-charge operation cannot be performed.

[0009] As described above, in the conventional technology, when the remaining charge of the secondary battery cell 40 progresses to a deeply discharged state, the battery management unit 30 cannot be restarted even when sunlight returns, so the pre-charge operation and charge / discharge operation cannot be performed by the charge / discharge control unit 20, resulting in the problem that it is not possible to continue storing and supplying the electricity generated by the solar cell 10.

[0010] Therefore, the present invention has been made in consideration of the above-mentioned problems in the conventional technology, and has an object to provide a power supply device that can charge a secondary battery cell and return to normal charging and discharging operation even when the remaining charge of the secondary battery cell is low and the operation of the BMS has stopped. [Means for solving the problem]

[0011] In order to solve the above problems, the power supply device of the present invention comprises a solar cell that generates electricity using light and outputs the electricity, a secondary battery cell that stores the electricity, a battery management unit that performs a protective operation by cutting off the extraction of the electricity stored in the secondary battery cell when the storage voltage of the secondary battery cell is equal to or lower than a protection voltage, and an automatic return control unit connected between the solar cell and the battery management unit that converts a portion of the electricity output by the solar cell into an automatic return current having a first voltage and a first current value and supplies the automatic return current to the battery management unit to perform a return charging operation, the return charging operation being characterized in that the battery management unit repeatedly switches between an operating state and a non-operating state, and when the battery management unit is in the temporary operating state, the automatic return current charges the secondary battery cell.

[0012] In the power supply device of the present invention, even if the remaining charge of the secondary battery cell is low and the operation of the battery management unit (BMS) has stopped, the secondary battery cell can be gradually charged using the output of the solar cell until the secondary battery cell reaches or exceeds its protection voltage, and the battery management unit can be restored to normal charging and discharging operation.

[0013] In one aspect of the present invention, even if the battery management unit is performing the protection operation, the automatic return control unit continues the return charging operation.

[0014] In one embodiment of the present invention, a charge / discharge control unit is connected between the solar cell and the battery management unit, converts the power output from the solar cell into a charging voltage and a charging current, and supplies the charging / discharging control unit, and the charge / discharge control unit is operated by the power stored in the secondary battery cell.

[0015] In one aspect of the invention, the automatic return control unit stops the return charging operation when the charging voltage reaches a predetermined maximum voltage.

[0016] In one aspect of the present invention, the charge / discharge control unit uses maximum power point tracking control.

[0017] In one aspect of the present invention, the automatic return control unit includes a temperature measurement unit that acquires the temperature of the secondary battery cell as a cell temperature, and stops the return charging operation when the temperature rise of the cell temperature is equal to or higher than a predetermined protection temperature.

[0018] In one embodiment of the present invention, the automatic return control unit includes a voltage adjustment unit that boosts a portion of the power from the solar cell and outputs it at the first voltage, and a constant current output unit that is driven by the first voltage output from the voltage adjustment unit and outputs the first current value, and supplies the output of the constant current output unit to the battery management unit.

[0019] In one aspect of the present invention, a backflow prevention diode is connected between the constant current output unit and the battery management unit. Effect of the Invention

[0020] The present invention provides a power supply device that can charge a secondary battery cell and return to normal charging and discharging operation even when the remaining charge of the secondary battery cell is low and the operation of the BMS has stopped. [Brief description of the drawings]

[0021] [Figure 1] 1 is a block diagram illustrating a schematic configuration of a power supply device 100 according to a first embodiment. [Diagram 2] 2 is a circuit diagram showing an example of an automatic return control unit 50. FIG. [Diagram 3] 3 is a timing chart showing the operation of the power supply device 100, where FIG. 3(a) shows the output of the automatic return control unit 50, FIG. 3(b) shows the stored voltage of the secondary battery cell 40, FIG. 3(c) shows the operating state of the battery management unit 30, and FIG. 3(d) shows the charging voltage of the charge / discharge control unit 20. [Figure 4] 3 is a flowchart showing the operation of the automatic return control unit 50 shown in FIG. 2. [Diagram 5] FIG. 1 is a block diagram showing a schematic configuration of an independent power supply device that has been proposed in the past. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. FIG. 1 is a block diagram showing a schematic configuration of a power supply device 100 according to this embodiment. As shown in FIG. 1, the power supply device 100 of this embodiment includes a solar cell 10, a charge / discharge control unit 20, a battery management unit (BMS: Battery Management System) 30, a secondary battery cell 40, and an automatic return control unit 50.

[0023] The solar cell 10 is a photoelectric conversion device that generates electricity using light and outputs the electric power. The configuration of the solar cell 10 is not limited, and a compound semiconductor solar cell such as a monocrystalline silicon, polycrystalline silicon, amorphous silicon, dye-sensitized silicon, or CIGS-based solar cell can be used. The solar cell 10 may be shaped to be placed on a stand, or may be shaped to be laid on a road surface or a wall. The output of the solar cell 10 is electrically connected to the input of a charge / discharge control unit 20, and the electric power generated by the solar cell 10 is input to the charge / discharge control unit 20.

[0024] The charge / discharge control unit 20 is electrically connected between the solar cell 10 and the battery management unit 30, and converts the power output from the solar cell 10 into a charging voltage and a charging current, and supplies the same to the battery management unit 30. The charge / discharge control unit 20 is composed of an electronic circuit including an integrated circuit (IC) and is operated by the power stored in the secondary battery cell 40. The specific operation of the charge / discharge control unit 20 is not limited, and a pulse width modulation (PWM) method or a maximum power point tracking (MPPT) method can be used. In order to efficiently store the power generated by the solar cell 10 in the secondary battery cell 40, it is preferable to use the maximum power point tracking method.

[0025] The battery management unit 30 is electrically connected to the electrode terminals of the secondary battery cells 40, and is a part that acquires the state of the secondary battery cells 40 and manages over-discharge protection, over-charge protection, etc. The battery management unit 30 is composed of electronic circuits including ICs and the like, and is operated by the power stored in the secondary battery cells 40. When the stored voltage of the secondary battery cells 40 is equal to or lower than the protection voltage, the battery management unit 30 cuts off the extraction of the power stored in the secondary battery cells 40 to perform an over-discharge protection operation. When the stored voltage of the secondary battery cells 40 is equal to or higher than a predetermined value, the battery management unit 30 cuts off the charging operation to the secondary battery cells 40 to perform an over-charge protection operation. The specific operation of the battery management unit 30 is not limited, and a known battery management system (BMS) can be used.

[0026] The secondary battery cell 40 is a part that stores the power supplied from the charge / discharge control unit 20 and the automatic return control unit 50 via the battery management unit 30, and also extracts the stored power via the battery management unit 30 and supplies the power to the load and the charge / discharge control unit 20. The specific configuration of the secondary battery cell 40 is not limited, and a lithium ion battery, a nickel metal hydride battery, a nickel cadmium battery, an all-solid-state battery, or the like can be used. In order to reuse resources, it is preferable to reuse lithium ion batteries used in electric vehicles or hybrid cars as the secondary battery cell 40.

[0027] The automatic return control unit 50 is connected in parallel with the charge / discharge control unit 20 between the solar cell 10 and the battery management unit 30, and converts a part of the power output by the solar cell 10 and supplies it to the battery management unit 30. As will be described in detail later, the automatic return control unit 50 supplies a current at a first voltage and a first current value to the battery management unit 30 and the secondary battery cell 40 even when the battery management unit 30 is in a stopped state (non-operating state), and performs a return charging operation on the secondary battery cell 40 until the operation of the battery management unit 30 resumes. In addition, the automatic return control unit 50 continues the return charging operation even during a protection operation in which the battery management unit 30 cuts off the extraction of power from the secondary battery cell 40 in an over-discharged state. In addition, the automatic return control unit 50 stops the return charging operation when the charging voltage of the charge / discharge control unit 20 reaches a predetermined maximum voltage.

[0028] Fig. 2 is a circuit diagram showing an example of the automatic return control unit 50. As shown in Fig. 2, the automatic return control unit 50 includes a first step-up / step-down unit 51, a step-up confirmation unit 52, a second step-up unit 53, and a constant current output unit 54. The combination of the first step-up / step-down unit 51, the step-up confirmation unit 52, and the second step-up unit 53 in this embodiment corresponds to the voltage adjustment unit in the present invention, since it adjusts and outputs the power from the solar cell 10.

[0029] The first step-up / step-down unit 51 is a circuit that steps up or steps down the power input from the input terminals LP1 and LP2, adjusts it to a predetermined expected voltage, and outputs it. Since the output voltage of the solar cell 10 varies from about 5V to about 40V, the operation of the constant current output unit 54 described later is stabilized by adjusting the output to a expected voltage (for example, 12V). In the example shown in FIG. 2, the first step-up / step-down unit 51 includes a resistor R1, a Zener diode ZD1, a DC-DC converter U1, and capacitors C1 and C2. The first step-up / step-down unit 51 steps up an output of about several volts from the solar cell 10 to, for example, 12V, and outputs it to the second step-up unit 53.

[0030] In the event that a large voltage or current fluctuation occurs on the solar cell 10 side connected to the input terminals LP1, LP2, it is preferable to use an insulated type DC-DC converter U1 in order to reduce the impact on the inside of the automatic return control unit 50. By using an insulated type DC-DC converter U1 and connecting the input terminals LP1, LP2 with a Zener diode ZD1, if an excessive voltage difference occurs on the solar cell 10 side, the current is short-circuited via the Zener diode ZD1, thereby suppressing adverse effects on circuits arranged downstream of the DC-DC converter U1.

[0031] The boost confirmation unit 52 is a circuit that monitors the output voltage of the first step-up / step-down unit 51 and operates the second step-up unit 53 when the output voltage reaches a predetermined voltage (12V in the above example). In the example shown in FIG. 2, the boost confirmation unit 52 includes capacitors C3, C4, and C5, a control chip IC1, resistors R2 and R3, and a transistor Q1. In this embodiment, since the boost confirmation unit 52 confirms the output voltage of the first step-up / step-down unit 51, the second step-up unit 53 does not perform a step-up operation at a stage where the step-up in the first step-up / step-down unit 51 is insufficient and does not reach the target output, and the output from the constant current output unit 54 is also stopped as described later. This allows the second step-up unit 53 and the constant current output unit 54 to be driven in a stable state and a stable output current to be continued.

[0032] The second boost unit 53 is a circuit that further boosts the output from the first boost / buck unit 51 and outputs the boosted voltage to the constant current output unit 54. In the example shown in Fig. 2, the second boost unit 53 includes capacitors C6 and C7 and a DC-DC converter U2. The DC-DC converter U2 is controlled to be driven on or off by a control signal from the boost confirmation unit 52, and boosts the input voltage by a predetermined factor and outputs the boosted voltage. As an example, when the output of the DC-DC converter U1 is 12V and the factor is 2, the DC-DC converter U2 outputs 24V.

[0033] The constant current output unit 54 is a circuit that operates on the voltage output from the DC-DC converter U2 and outputs a constant current from output terminals LP3 and LP4 to the battery management unit 30. In the example shown in FIG. 2, the constant current output unit 54 includes a control chip IC2, resistors R4 and R5, and a variable resistor BLK1. In the example shown in FIG. 2, a backflow prevention diode SD1 is connected between the constant current output unit 54 and the output terminal LP3. As an example, when the output from the DC-DC converter U2 is 24 V (first voltage), a constant current of 70 mA (first current value) is output from the constant current output unit 54.

[0034] Next, the operation of the power supply device 100 according to the present embodiment will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a timing chart showing the operation of the power supply device 100, in which Fig. 3(a) shows the output of the automatic return control unit 50, Fig. 3(b) shows the stored voltage of the secondary battery cell 40, Fig. 3(c) shows the operating state of the battery management unit 30, and Fig. 3(d) shows the charging voltage of the charge / discharge control unit 20. Fig. 4 is a flowchart showing the operation of the automatic return control unit 50 shown in Fig. 2. Figs. 3 and 4 assume a situation in which insufficient sunlight continues for a long period of time, the charging state of the secondary battery cell 40 progresses to a deep discharge state, the battery management unit 30 is in an inoperative state, and sunlight is obtained for the solar cell 10.

[0035] The horizontal axis of Fig. 3(a) to Fig. 3(d) indicates a common time axis with the time when the solar cell 10 receives sunlight being set as 0. The vertical axis of Fig. 3(a) indicates the current value supplied from the automatic return control unit 50 to the battery management unit 30. The vertical axis of Fig. 3(b) indicates the stored voltage of the secondary battery cell 40, where Vmin indicates the protection voltage at which the battery management unit 30 activates the over-discharge protection, and Vmax indicates the voltage at which the battery management unit 30 activates the over-charge protection. The vertical axis of Fig. 3(c) indicates the operating state of the battery management unit 30, where OFF indicates a non-operating state and ON indicates an operating state. The vertical axis of Fig. 3(d) indicates the charging voltage output by the charge / discharge control unit 20 to the battery management unit 30, and max indicates the maximum charging voltage set in the charge / discharge control unit 20.

[0036] In Fig. 3, the period from time t=0 to t=t1 is the voltage adjustment preparation period. As shown in Figs. 3(a) to 3(d), during the voltage adjustment preparation period, the output current of the automatic return control unit 50 is 0. Also, the stored voltage of the secondary battery cell 40 is in a deep discharge state. Also, the battery management unit 30 is in a non-operating state. Also, the charge / discharge control unit 20 is in a non-operating state and its output is 0.

[0037] The period from time t=t1 to t=t2 is the automatic return period. As shown in Fig. 3(a) to Fig. 3(d), during the automatic return period, the output current of the automatic return control unit 50 is I1. Also, the storage voltage of the secondary battery cell 40 gradually rises from a deep discharge state to the over-discharge protection voltage Vmin. Also, the battery management unit 30 alternates between a non-operating state and an operating state. Also, the charge / discharge control unit 20 is not operating and its output is 0.

[0038] The normal charging period is from time t=t2 to t=t3. As shown in Fig. 3(a) to Fig. 3(d), during the normal charging period, the output current of the automatic return control unit 50 is I1. The stored voltage of the secondary battery cell 40 exceeds the over-discharge protection voltage Vmin. The battery management unit 30 is in an operating state. The charge / discharge control unit 20 is operating and supplies the output of the solar cell 10 to the secondary battery cell 40 as a charging voltage. Here, Fig. 3(b) and Fig. 3(d) show a constant rate of increase as an example of the change in the graph during the normal charging period, but since the power generated by the solar cell 10 is supplied as a charging voltage by the charge / discharge control unit 20, the rate of increase and the increase / decrease are not necessarily constant.

[0039] The automatic return end period begins at time t=t3. When the charging voltage output by the charge / discharge control unit 20 reaches max, the output current of the automatic return control unit 50 becomes zero.

[0040] As shown in Fig. 4, when the automatic return operation starts, the automatic return control unit 50 adjusts the output from the solar cell 10 to a predetermined scheduled voltage as a pre-adjustment operation in step S1. In the example circuit shown in Fig. 2, the pre-adjustment operation is executed in the DC-DC converter U1 of the first step-up / step-down unit 51, and continues as long as power is being supplied from the solar cell 10 even after step S2.

[0041] Step S2 is a boost confirmation operation, which confirms whether the result of the preliminary adjustment operation has been adjusted to the scheduled voltage. In the example of the circuit shown in FIG. 2, the boost confirmation operation is executed by the control chip IC1, and a control signal is sent to the DC-DC converter U2. As a specific example, the boost confirmation unit 52 monitors the output from the first boost / buck unit 51 and confirms whether the output of the DC-DC converter U1 has been adjusted to a predetermined voltage value (scheduled voltage, for example, 12V). If the output of the DC-DC converter U1 has not reached the scheduled voltage, the boost confirmation unit 52 sends an OFF signal and repeats the preliminary adjustment operation of step S1, and if it has reached the scheduled voltage, it sends an ON signal and proceeds to step S3.

[0042] Step S3 is a boost output operation, which further boosts the voltage adjusted to the expected voltage in the preliminary adjustment operation, and outputs a constant current at a first current value. In the circuit example shown in FIG. 2, the boost output operation is performed by the DC-DC converter U2 of the second boost unit 53 and the control chip IC2. As a specific example, when an ON signal is sent from the boost confirmation unit 52 to the DC-DC converter U2 as a control signal, the DC-DC converter U2 performs a boost operation, and boosts the expected voltage (12V) to the first voltage (24V). The constant current output unit 54 is driven by the first voltage boosted by the second boost unit 53, and outputs the first current value.

[0043] In the example circuit shown in Fig. 2, in steps S2 and S3, if the output of DC-DC converter U1 is not the scheduled voltage (12V), boost confirmation unit 52 sends an OFF signal to DC-DC converter U2. Therefore, no boost operation is performed in DC-DC converter U2, and the output is 0V and 0mA. When the output of DC-DC converter U2 reaches the scheduled voltage, boost confirmation unit 52 sends an ON signal to DC-DC converter U2, and DC-DC converter U2 performs boost operation to output a first current value (70mA) at a first voltage (24V).

[0044] During the voltage adjustment preparation period from t=0 to t=t1 in FIG. 3(a), the first step-up / step-down unit 51 is not able to adjust to the scheduled voltage, so the step-up in the second step-up unit 53 and the current output in the constant current output unit 54 are not executed, and the output current is 0. When t=t1 occurs and the step-up confirmation unit 52 confirms that the voltage has been adjusted to the scheduled voltage, the step-up in the second step-up unit 53 and the current output in the constant current output unit 54 are executed, and a constant current at the first current value (I1) is output from the output terminals LP3 and LP4 to the battery management unit 30. This allows the constant current output from the automatic return control unit 50 to be quickly changed from 0 to the first current value at time t=t1, and a stable constant current output can be performed. In addition, the output of the solar cell 10 is not directly supplied to the battery management unit 30.

[0045] During the automatic return period from t=t1 to t=t2 in FIG. 3, the automatic return current of the first voltage and the first current is supplied from the automatic return control unit 50 to the battery management unit 30, and the return charging operation continues. When the secondary battery cell 30 is in a deep discharge state, the battery management unit 30 is in a non-operating state, but when the automatic return current is supplied, it temporarily enters an operating state. At this time, the battery management unit 30 executes management of the secondary battery cell 30, but since the storage voltage is less than the over-discharge protection voltage Vmin and is in a deep discharge state, it transitions to a non-operating state again. However, even during this temporary return of the battery management unit 30 to the operating state, the automatic return current is supplied to the secondary battery cell 40 in the charging direction, although for a short time, and the storage voltage rises slightly due to the return charging operation.

[0046] During the automatic return period, the automatic return current continues to be supplied from the automatic return control unit 50 to the battery management unit 30, so that such non-operation and temporary return of the battery management unit 30 are repeated. During this repetition, short-term charging and a slight increase in the stored voltage are repeated due to the return charging operation, and when the stored voltage of the secondary battery cell 40 reaches the over-discharge protection voltage Vmin at time t=t2, the battery management unit 30 permits the extraction of power from the secondary battery cell 40, and the operating state can be continued.

[0047] After time t=t2, the stored voltage of the secondary battery cell 40 is higher than the over-discharge protection voltage Vmin, and the battery management unit 30 permits the extraction of power from the secondary battery cell 40. Therefore, the battery management unit 30 and the charge / discharge control unit 20 are operated by the output of the secondary battery cell 40, and it is possible to continue charging the secondary battery cell 40 with power from the solar cell 10 and supplying power from the secondary battery cell 40 to the load.

[0048] Step S4 is a maximum output check operation, and if the charging voltage output by the charge / discharge control unit 20 has not reached the maximum voltage max, the process proceeds to step S3, and if it has reached the maximum voltage max, the process proceeds to step S5. As shown in Fig. 1, the output of the charge / discharge control unit 20 and the output of the automatic return control unit 50 are both connected to the battery management unit 30, so that the automatic return control unit 50 can obtain the charging voltage output by the charge / discharge control unit 20 by monitoring the voltage applied to the output terminals LP3 and LP4 of the automatic return control unit 50.

[0049] Step S5 is an output stop operation, and the automatic return control unit 50 stops supplying current to the battery management unit 30 at the first voltage and the first current value. In the example circuit shown in Fig. 2, when a voltage higher than the voltage set by the backflow prevention diode SD1 is applied to the output terminal unit LP3, the constant current output unit 54 stops outputting at a constant current. As a specific example, when the charging voltage of the charge / discharge control unit 20 is higher than the first voltage (24V), the automatic return control unit 50 performs an output stop operation.

[0050] After time t=t3, the charge / discharge control unit 20 can supply the charging voltage to the battery management unit 30 at the set maximum voltage, and the current value output from the automatic return control unit 50 becomes 0. The stored voltage of the secondary battery cell 40 is managed by the battery management unit 30 and controlled between the over-discharge protection voltage Vmin and the over-charge protection voltage Vmax. The charge / discharge control unit 20 is operated by the power supplied from the secondary battery cell 40, and charges the secondary battery cell 30 with the power generated by the solar cell 10 via the battery management unit 30.

[0051] As described above, in the power supply device 100 of this embodiment, the automatic return control unit 50 is connected between the solar cell 10 and the battery management unit 30, and even if the battery management unit 30 is in a stopped state, a part of the power output by the solar cell 10 is converted to a first voltage and a first current value and supplied to the battery management unit to perform a return charging operation. As a result, even if the secondary battery cell 30 is in a deep discharge state and the battery management unit 30 is unable to extract power or obtain information from the secondary battery cell 30, the secondary battery cell 40 can be gradually charged by the return charging operation. In addition, the power consumed by the operation of the battery management unit 30 can be suppressed, and the return charging operation can be continued efficiently.

[0052] In addition, the automatic return control unit 50 is connected in parallel with the charge / discharge control unit 20, and no power is consumed by the automatic return control unit 50 when it is operating. Therefore, even if the output of the solar cell 10 is relatively small, the automatic return charging operation can be continued efficiently to gradually charge the secondary battery cell 40.

[0053] Second embodiment Next, a second embodiment of the present invention will be described. Descriptions of contents that overlap with the first embodiment will be omitted. In the first embodiment, the automatic return control unit 50 continues the return charging operation until the charging voltage output from the charge / discharge control unit 20 reaches the maximum voltage max. In this embodiment, if the secondary battery cell 40 is short-circuited, the automatic return control unit 50 stops the return charging operation at the first voltage and first current value.

[0054] In this embodiment, the automatic return control unit 50 includes a temperature measurement unit that measures the temperature of the secondary battery cell 40 to obtain cell temperature information. The automatic return control unit 50 also records in advance the allowable temperature rise of the secondary battery cell 40 as a protection temperature.

[0055] At time t=t1 when the automatic return control unit 50 starts to output the first current value to the battery management unit 30, the temperature measurement unit measures the temperature of the secondary battery cell 40 and acquires cell temperature information at the start of the return charging operation. In addition, the automatic return control unit 50 continues to acquire cell temperature information of the secondary battery cell 40 by the temperature measurement unit while continuing the return charging operation and outputting the first current value to the battery management unit 30.

[0056] The automatic return control unit 50 calculates the temperature rise from the start of the return charging operation from the acquired cell temperature information, and stops the return charging operation if the temperature rise exceeds the protection temperature. This is because if a fault such as a short circuit occurs inside the secondary battery cell 40, the power supplied in the return charging operation is not stored in the secondary battery cell 40, and the power is consumed inside the secondary battery cell 40, causing the cell temperature to rise.

[0057] As described above, in the power supply device 100 of this embodiment, the automatic recovery control unit 50 can protect the secondary battery cell 40 in which a failure has occurred by stopping the recovery charging operation when the temperature rise of the cell reaches or exceeds the protection temperature.

[0058] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0059] 100...Power supply device 10...Solar cell 20...Charge / discharge control unit 30…Battery management section 40...Secondary battery cell 50...Automatic return control unit 51…First step-up / step-down section 52…Boost check section 53…Second booster section 54...Constant current output section

Claims

1. A solar cell that generates electricity using light and outputs power; A secondary battery cell that stores the power; a battery management unit that performs a protection operation by cutting off extraction of the power stored in the secondary battery cell when the stored voltage of the secondary battery cell is equal to or lower than a protection voltage; an automatic return control unit connected between the solar cell and the battery management unit, converting a part of the power output by the solar cell into an automatic return current having a first voltage and a first current value, and supplying the automatic return current to the battery management unit to perform a return charging operation; The power supply device is characterized in that the recovery charging operation is characterized in that the battery management unit repeatedly switches between operating and non-operating states, and in the temporary operating state of the battery management unit, the automatic recovery current charges the secondary battery cell.

2. 2. The power supply device according to claim 1, Even if the battery management unit is performing the protection operation, The power supply device, wherein the automatic return control unit continues the return charging operation.

3. 3. The power supply device according to claim 1, a charge / discharge control unit connected between the solar cell and the battery management unit, converting the power output from the solar cell into a charging voltage and a charging current, and supplying the charging voltage and the charging current to the battery management unit; The power supply device, wherein the charge / discharge control unit is operated by the power stored in the secondary battery cell.

4. 4. The power supply device according to claim 3, The power supply device, wherein the automatic return control unit stops the return charging operation when the charging voltage reaches a predetermined maximum voltage.

5. 5. The power supply device according to claim 3, The power supply device, wherein the charge / discharge control unit uses maximum power point tracking control.

6. 6. A power supply device according to claim 1, the automatic return control unit includes a temperature measurement unit that acquires a temperature of the secondary battery cell as a cell temperature, A power supply device comprising: a power supply unit that stops the return charging operation when the temperature rise of the cell reaches or exceeds a predetermined protection temperature.

7. 7. A power supply device according to claim 1, The automatic return control unit is a voltage adjusting unit that boosts a portion of the power from the solar cell and outputs the boosted power as the first voltage; a constant current output unit that is driven by the first voltage output from the voltage adjustment unit and outputs a first current value; a constant current output section for supplying an output from the constant current output section to the battery management section;

8. 8. The power supply device according to claim 7, A power supply device comprising: a reverse current prevention diode connected between the constant current output unit and the battery management unit.

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