JP2006042523A - Power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently charge capacitors in a short period of time and with a simple circuit structure, in a power supply that charges the capacitors with a solar cell. <P>SOLUTION: A power supply which accumulates electrical energy from the solar cell in a plurality of capacitors via an electricity accumulating switch, when accumulating electricity and outputs the electrical energy accumulated in the capacitors by opening the electricity accumulating switch, when discharging, is provided with a capacitor changeover means that changes over a plurality of the capacitors to a series connection or a parallel connection. When a terminal voltage of the capacitors reaches a voltage that shows a fully-charged state, in particular, the capacitors are changed from the charging state to the discharging state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power supply device configured to store (or charge) electrical energy generated by a solar cell during the day and to output the stored electrical energy at night.

Conventionally, as shown in FIG. 8, a power supply device configured to charge a secondary battery 58 with a solar battery 28 in the daytime and drive an electronic device or the like with the charged electric energy at night is known. .
6 and 7 show the output characteristics of a general solar cell panel.
In FIG. 8, during power storage, the open / close switch 481 of the power storage switch 48 is closed and the open / close switch 482 is open. Thereafter, when the voltage detection means 781 detects full charge, the switch drive circuit 782 opens the open / close switch 481 of the power storage switch 48, closes the open / close switch 482, and enters a discharge state.
When the capacity of the secondary battery 58 is 12 V and 1 Ahr and the output of the solar battery is 12 V (1 A), the time t4 required until the end of power storage is (12 V × 1 Ahr) / (12 V × 1 A) = 1 hr. See FIG.

Recently, as shown in FIG. 9, a capacitor 59 such as an electric double layer capacitor (EDLC) having a much longer charge / discharge cycle life than a conventional secondary battery is used as a power storage means.
As shown in FIG. 9, during the daytime power storage, the open / close switch 491 of the power storage switch 49 is closed, the open / close switch 492 is opened, and the solar cell 29 stores power in the capacitor 59.
In FIG. 9, during storage, the open / close switch 491 of the storage switch 49 is closed and the open / close switch 492 is open. Thereafter, when the voltage detection means 791 detects full charge, the switch drive circuit 792 opens the open / close switch 491 of the power storage switch 49, closes the open / close switch 492, and enters a discharge state.
Here, under the same conditions as in FIG. 8, if the maximum stored voltage of the capacitor 59 is 12V,
12whr = 12 × 3600 (J) = 43200 (J)
43200J = 1/2 × C × V2 = 1/2 × C × 12 × 12
C = 600F, 12VMAX is obtained.
Assuming the required time t5 (hr) to the end of charging, from C · V = I · T, t5 = (C · V / I) / 3600 seconds = (600 × 12/1) / 3600 seconds = 2 hr
It becomes.
Thus, the capacitor requires twice as much time as the secondary battery.

In many cases, a capacitor is used as a power storage unit, and a constant voltage power source is configured to drive an electronic device. In general, a variable capacitor discharge voltage is constant via a DC / DC converter. It is configured to obtain an output for driving the electronic device by controlling the voltage to be a voltage.
In this case, since the discharge characteristic of the capacitor is a characteristic in which the voltage gradually decreases from the fully charged state, the output voltage of the DC / DC converter is higher than the full charge voltage of the capacitor so that the DC / DC converter is so-called. As a step-up DC / DC converter, the configuration can be simplified. In that case, the full charge voltage of the capacitor is set to be equal to or lower than the output voltage of the DC / DC converter.
The storage characteristics in the cases of FIG. 8 and FIG. 9 are shown in FIG.

By the way, in the configuration as described above, when a capacitor is used as a medium for storing electrical energy generated by a solar battery, the storage efficiency is higher than when a secondary battery having a storage capacity equivalent to that of the capacitor is used. There is a problem that is bad.
The condition becomes worse when the stored energy is the same and the maximum stored voltage of the capacitor is low.
As a result, there is a problem that it takes a long time to reach a fully charged state.
In order to solve such a problem, it is necessary to increase the surface area of the solar cell panel, and as a result, there arises a problem that the power supply device becomes larger and expensive.
Alternatively, a large-scale circuit configuration called a “maximum output point tracking system (MPPT system)” in which the charging medium is charged with the maximum power while constantly monitoring the maximum output point of the solar cell is required.
Therefore, the present invention has been made for the purpose of providing a power supply device capable of charging a capacitor with a simple and efficient circuit configuration in a short time.

The power supply device according to claim 1 of the present invention stores electrical energy from a solar cell in a plurality of capacitors via a storage switch during storage, and opens the storage switch during discharge to store the electrical energy stored in the capacitor. In a power supply configured to output,
Capacitor switching means for switching the plurality of capacitors to series connection or parallel connection is provided.
According to a second aspect of the present invention, there is provided control means for operating the capacitor switching means when a predetermined condition is satisfied.
The predetermined condition is, for example, a condition in which the terminal voltage of the capacitor becomes a voltage indicating a storage expiration state, and the storage state is switched to the discharge state. Or it is a case where a switching command is inputted separately.

The power supply device according to claim 3 stores the electric energy from the plurality of solar cells in the capacitor via the storage switch when storing electricity, and outputs the electrical energy stored in the capacitor by opening the storage switch when discharging. The configured power supply device is characterized by comprising solar cell switching means for switching the plurality of solar cells to parallel connection or series connection.
According to a fourth aspect of the present invention, there is provided control means for operating the solar cell switching means when a predetermined condition is satisfied.
The predetermined condition is, for example, a condition in which the terminal voltage of the capacitor reaches a generated electromotive voltage of one solar cell or a voltage close to the generated electromotive voltage. Or it is a case where a switching command is inputted separately.

With the above configuration, the capacitors are connected in series during power storage and switched to parallel connection during discharging, so that the input voltage range of the step-up DC / DC converter can be narrowed.
Further, during power storage using a plurality of solar cells, the solar cells are connected in parallel from the start of power storage until a predetermined condition is satisfied, and then connected in series after satisfying the predetermined condition from the start of power storage. The time required for expiration can be shortened.

Below, the power supply device concerning this invention is demonstrated in detail with reference to FIG. 1 which showed the embodiment.
In FIG.
Reference numeral 1 denotes a power supply device, a plurality of solar cells 2, 2, 2 and 2, a solar cell switching means 3 for switching the plurality of solar cells to a serial connection or a parallel connection, and the power supply device 1 in a storage state or a discharge state. The storage switch 4 for switching to the state, the plurality of capacitors 5, 5, 5, 5, the capacitor switching means 6 for switching the plurality of capacitors to series connection or parallel connection, the solar cell switching means 3, the storage switch 4, A control means 7 for controlling the capacitor switching means 6 and an output terminal 8 for outputting power are provided. In conjunction with the storage switch 4, an output switch 9 may be provided that opens during storage and closes during discharge.

When the terminal voltage of the capacitor reaches the generated electromotive voltage of one solar cell during power storage, the control means 7 switches the solar cells to the serial connection by the solar battery switching means, and further the terminal voltage of the capacitor becomes a voltage indicating the storage expiration state. When it reaches, the storage switch 4 is opened and switched to a discharge state, and the capacitor switching means 6 switches the capacitor to parallel connection.
At the time of discharging, when the terminal voltage of the capacitor becomes a voltage indicating a discharge completion state, the control means 7 closes the storage switch 4 and switches to the storage state.

Thus, the input voltage range of the step-up DC / DC converter can be narrowed by connecting the capacitors in series during power storage and connecting them in parallel during discharge.
Moreover, the time required for power storage expiration can be further shortened by switching the solar cell from parallel connection to serial connection during power storage.

A first embodiment of the power supply apparatus will be described in detail with reference to FIG.
FIG. 2 shows an embodiment in the case where it is desired to output a power supply with a capacitor voltage of 6 V or less. (A) shows the state of the switch during storage, and (b) shows the state of the switch during discharge. .
In the figure,
11 is a power supply device, which includes a solar cell 21, a diode 22 for preventing backflow to the solar cell 21, a storage switch 41 for switching between a storage state and a discharge state, two capacitors 51 and 52, Capacitor switching means 61 for switching capacitors 51 and 52 between series connection and parallel connection, and a control signal for switching from the charged state to the discharged state when the terminal voltage of the capacitor reaches a predetermined voltage (full charge voltage) And a switch drive circuit 72 for switching and controlling the storage switch 41 and the capacitor switching means 61 by a control signal output from the voltage detection means 71.

The storage switch 41 includes two opening / closing switches 41a and 41b, and the switch driving circuit 72 closes the opening / closing switch 41a during storage (see FIG. 2A) and opens the opening / closing switch 41b (FIG. 2). (See (a) of FIG. 2), during discharge, the open / close switch 41a is opened (see (b) of FIG. 2), and the open / close switch 41b is closed (see (b) of FIG. 2). These open / close switches 41a and 41b perform a latch operation.
When the voltage detecting means 71 detects that the terminal voltage of the capacitor has increased to a predetermined storage completion voltage during storage, the open / close switch 41a is opened and the open / close switch 41b is closed during storage, resulting in a discharge state.
When the voltage detecting means 71 detects that the terminal voltage of the capacitor has dropped to a predetermined discharge completion voltage at the time of discharging, the open / close switch 41a is closed and the open / close switch 41b is opened at the time of power storage to enter a storage state.

The capacitor switching means 61 includes two changeover switches 61a and 61b, and the switch drive circuit 72 switches the changeover switches 61a and 61b to the series connection side during storage (see (a) of FIG. 2). At that time, the selector switches 61a and 61b are switched to the parallel connection side (see FIG. 2B). These change-over switches 61a and 61b perform a latch operation.

When the capacity of the solar cell 21 is 12V (1A) and the capacitance of each of the capacitors 51 and 52 is 1200F (6V), the required time t1 until the charge expires in FIG. 2 is calculated as follows. The
12whr = 12 × 3600 (J) = 43200 (J)
43200J = 1/2 × C × V ² = 1/2 × C × 12 × 12
C = 1200F, 6VMAX (equivalent to 600F, 12VMAX) is obtained.
Assuming the required time t1 (hr) to the end of charging, from C · V = I · T, t1 = (C · V / I) / 3600 seconds = (1200 × 6/1) / 3600 seconds = 2 hr
It becomes.

On the other hand, the time t2 required to store 1200F, 6VMAX capacitors in parallel is
t2 = (C · V / I) / 3600 seconds = ((1200 + 1200) × 6/1) / 3600 seconds = 4 hr
It becomes.
Therefore, by switching the capacitor according to the configuration of FIG. 2, as shown in the graph of FIG. 3, the time required to complete the charging can be reduced by half.

In this way, when the required time t1 has elapsed during power storage and the voltage detection means 71 detects that the terminal voltage of the capacitor has increased to a predetermined power storage completion voltage, the open / close switch 41a is opened during power storage, and the open / close The switch 41b is closed and a discharge state is entered.
At the time of discharging, the open / close switch 41a is opened (see FIG. 2B) and the open / close switch 41b is closed (see FIG. 2B). Since the change-over switches 61a and 61b are switched to the parallel connection side (see FIG. 2B), the power is output as a capacitor having a capacity of 1200F (6V) + 1200F (6V).

FIG. 4 shows an embodiment in which the generated electromotive force per solar cell panel is lower than the rated voltage (maximum charging voltage) of the capacitor, and the solar cell switching means is used. a) shows a state in which solar cells are connected in parallel, and (b) shows a state in which the solar cells are connected in series.
In the figure,
12 is a power supply device, solar cells 22a and 22b, solar cell switching means 32 for switching two solar cells between series connection and parallel connection, a diode 23 for preventing backflow to the solar cells, and a storage state Storage switch 42 for switching between a charge state and a discharge state, a capacitor 53, and a voltage detection means for outputting a control signal for switching from the charge state to the discharge state when the terminal voltage of the capacitor reaches a predetermined voltage (full charge voltage) 73, a switch driving circuit 74 that switches and controls the storage switch 42 by a control signal output from the voltage detection means 73, and the terminal voltage of the capacitor is set to a predetermined switching voltage (in this case, set to 6V). The voltage detection means 75 for outputting a control signal for switching the solar cell to the serial connection when the And a switch driving circuit 76 for switching control to the series connection from the parallel connection of two solar cells by controlling the solar cell switching means 32 by a control signal that.

  The operations of the power storage switch 42, the voltage detection means 73, and the switch drive circuit 74 are the same as in the case of FIG.

In FIG.
The required time t3 until the charging is completed when the capacity of the solar cell 22 is 6 V (1 A) and the capacitance of the capacitor 53 is 600 F (12 V) (equivalent to 1200 F (6 V) × 2) is shown in FIG. It is calculated as follows when the terminal voltage of the capacitor shown in 4 (a) is divided into the storage time ta up to 6V and the storage time tb from 6V to 12V shown in FIG. 4 (b).
ta = (C · V / I) / 3600 seconds = (600 × 6/2) / 3600 seconds = 0.5 hr
tb = (C · V / I) / 3600 seconds = (600 × (12−6) / 1) / 3600 seconds = 1.0 hr
Therefore,
t3 = ta + tb = 1.5 hr
It becomes.
Therefore, by switching the solar cell from parallel connection to series connection with the configuration of FIG. 4, as shown in the graph of FIG. 5, the time required for charging expiration is further shortened than the embodiment shown in FIG. Can do it.

When the generated electromotive force per one solar cell panel is higher than the rated voltage (maximum charging voltage) of the capacitor, as shown in FIG. 1, the configuration of FIG. 2 and the configuration of FIG. 4 are used together. It goes without saying that it is possible.

It is the block diagram which showed the structure of embodiment of the power supply device concerning this invention. 1 is a configuration diagram of Example 1. FIG. It is a figure which shows the electrical storage characteristic in the case of Example 1. FIG. FIG. 6 is a configuration diagram of Example 2. It is a figure which shows the electrical storage characteristic in the case of Example 2. FIG. It is an output characteristic (IV characteristic under specific illumination intensity) figure of a general solar cell panel. It is an illumination intensity dependence characteristic (IV characteristic under each illumination intensity) of a general solar cell panel. It is an example of the power supply device by the combination of the conventional secondary battery and a solar cell. It is an example of the power supply device by the combination of the conventional capacitor and a solar cell. It is a figure which shows the charge characteristic of the power supply device by the combination of the conventional secondary battery and a solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Power supply device 21 Solar cell 22 Diode 41 Storage switch 41a, 41b, Open / close switch 51, 52 Capacitor 61 Capacitor switching means 61a, 61b Changeover switch 71 Voltage detection means 72 Switch drive circuit

Claims (4)

In a power supply device configured to store electrical energy from a solar cell in a plurality of capacitors via a storage switch during power storage, and to output the electrical energy stored in the capacitor by opening the power storage switch during discharge,
A power supply device comprising a capacitor switching means for switching the plurality of capacitors to a serial connection or a parallel connection. The power supply apparatus according to claim 1, further comprising a control unit that operates the capacitor switching unit when a predetermined condition is satisfied. In a power supply device configured to store electrical energy from a plurality of solar cells in a capacitor via a storage switch during power storage, and to output the electrical energy stored in the capacitor by opening the power storage switch during discharge,
A power supply device comprising solar cell switching means for switching the plurality of solar cells to parallel connection or series connection. The power supply apparatus according to claim 3, further comprising a control unit that operates the solar cell switching unit when a predetermined condition is satisfied.

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