JP2002281692A - Charging circuit of solar battery, and semiconductor device mounting the charging circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the charging circuit of a solar battery for stably charging a capacitor in the charging circuit of the solar battery, and a semiconductor device that is mounted with the charging circuit. SOLUTION: The charging circuit 2 of the solar battery comprises a solar battery 10, a first capacitor 12 where one end and the other end are connected to a power supply potential line 200 and a ground potential line 202, respectively, a first switch 20 that is serially connected onto the power supply potential line 202, and a stabilization power circuit 22 for stably charging the first capacitor 12, thus controlling the switching of the first switch 20, based on the output voltage of the solar battery 10 by a voltage-controlled circuit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging circuit for a solar cell, and more particularly to a charging circuit for a solar cell capable of stably charging the capacity in the circuit and a semiconductor device having the same. .

[0002]

2. Description of the Related Art Conventionally, in a charging circuit for a solar cell, for example, as disclosed in Japanese Patent Application Laid-Open No. H7-163063, a solar cell charges a capacity (secondary battery) via a resistor. Therefore, a technique capable of sufficiently charging the capacity without using a controller has been proposed.

[0003]

However, such a conventional charging circuit cannot stably charge the capacity when the sunlight is weak. In addition, the charging voltage was unstable, so that it was not possible to charge the battery to just before the withstand voltage of the capacity.
For this reason, it was necessary to use an expensive capacitor having a high withstand voltage.

An object of the present invention is to provide a solar cell charging circuit capable of stably charging the capacity in a solar cell charging circuit and a semiconductor device equipped with the same, in order to solve the above-mentioned problems. It is in.

[0005]

(1) In order to achieve the above object, a charging circuit for a solar cell according to the present invention comprises a solar cell, one end of which is connected to a first potential line of the solar cell, and the other end of which is connected to the first potential line. A first capacitor connected to a second potential line of the solar cell;
A stabilizing power supply circuit connected to the first potential line for boosting a supply voltage from the solar cell and stably charging the first capacity; A first switching means connected between the power supply circuit and the power supply circuit, the opening and closing of which is controlled based on the supply voltage of the solar cell. Thus, by providing the stabilized power supply circuit, the first capacitor can be charged stably. At the same time, by limiting the voltage supply to the stabilized power supply circuit by the first switching means until the voltage reaches a predetermined voltage, if the generated voltage is still low in the power-on state of the solar cell, It is possible to eliminate the inconvenience that a current flows through the stabilized power supply circuit and the output voltage of the solar cell cannot be boosted.

(2) According to the present invention, in the solar cell charging circuit according to (1), one end is connected to a first potential line between the solar cell and the first switching means.
The other end has voltage control means connected to the second potential line, and the first switching means is turned on when a voltage exceeding a first predetermined voltage is supplied by the voltage control means. And By providing such voltage control means for performing voltage control on the first switching means, the charging circuit of the solar cell may be operated.

(3) In the solar cell charging circuit according to (2), the first potential is supplied to a load circuit connected in parallel to the first capacity. There is further provided second switching means for controlling the potential from the line, wherein the second switching means is turned on when a voltage exceeding a second predetermined voltage is supplied by the voltage control means. . Thus, by turning on the second switching means by the voltage control means, the load circuit can be driven before the charging of the first capacitance is completed.

(4) In the solar cell charging circuit according to (2) or (3) above,
On the line connecting the potential line of
A diode having an input side connected to the first potential line, an output side connected to the voltage control means, and one end connected to the output side of the diode;
And a second capacitor connected to a line connected to the second potential line at the other end. Thus, by providing the second capacity and the diode, the charging circuit of the solar cell can be used quickly and in a more stable state, and the output voltage of the solar cell has decreased. In this case, the opening and closing of the switch can be reliably performed.

Further, the charging circuit for a solar cell according to the present invention described in any of the above (1) to (4) may be mounted on a semiconductor device.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram illustrating a circuit configuration example of a solar cell charging circuit 2 according to the first embodiment. FIG. 2 is a diagram showing a circuit configuration example of the voltage control circuit 24 shown in FIG. FIG. 3 is a diagram for explaining the operation timing of the first switch shown in FIG. FIG. 4 is a diagram for comparison with the operation of the charging circuit of the solar cell of FIG. FIG. 5 shows a charging circuit 10 for a solar cell according to the second embodiment.
2 is a diagram illustrating a circuit configuration example of FIG.

(First Embodiment) A solar cell charging circuit 2 shown in FIG. 1 includes a solar cell 10, a first capacitor 12, a resistor 14, a load circuit 16, a first switch 20, a stabilized power supply circuit 22, And a voltage control circuit 24.

One end is a power supply potential line 20 of the solar cell 10.
0, the first capacitor 12 having the other end connected to the ground potential line 202. A first switch 20, a stabilized power supply circuit 22, and a resistor 1 are provided on a power supply potential line 200 between the solar cell 10 and the first capacitor 12.
4 are connected in series. Also, one end of the solar cell 10
The other end is connected to the ground potential line 202 between the first switch 20 and the first switch 20, and a voltage control circuit 24 for controlling opening and closing of the first switch is provided. First capacitor 1
2, a load circuit 16 is connected in parallel.

In this embodiment, the stabilized power supply circuit 22
This is a DC-DC converter, which is a circuit for boosting the supply voltage from the solar cell 10 and stably supplying the voltage to the first capacitor 12. The first switch 20 is a switch for controlling voltage supply from the power supply potential of the solar cell 10 to the first capacitor 12. In the present embodiment, the first switch 20 is formed of, for example, a P-channel MOS transistor, the drain of which is on the side of the solar cell 10, the source of which is on the side of the stabilized power supply circuit 22, and the like.
The gate is connected to the voltage control circuit 24. The voltage control circuit 24 includes a power supply potential VC supplied from the solar cell 10.
C is a circuit for controlling the opening and closing of the first switch 20 based on C. In the present embodiment, the voltage control circuit 24 has, for example, a configuration as shown in FIG. 2, the voltage control circuit 24 includes a resistor 30 and a diode 32. The voltage control circuit 24 has a function of adjusting the power supply potential VCC by the resistor 30 and applying a forward voltage by the diode 32. The load circuit 16 is a general circuit or device driven based on a power supply generated by the solar cell 10, such as an oscillation circuit used for time measurement, for example.

The operation of the solar cell charging circuit 2 according to the present invention will be described below with reference to FIGS.

Before explaining the operation of the solar cell charging circuit in the present embodiment in FIG. 3, first, referring to FIG.
The operation of the circuit when the switch 20 and the voltage control circuit 24 are not provided and only the stabilized power supply circuit 22 is provided in particular will be described.

FIG. 4 shows a solar cell 10 and a stabilized power supply circuit 2.
2 and changes with time of the voltage or the capacitance value of the first capacitor 12. The solar cell 10 gradually increases its output voltage VCC with time t. But,
Between the time points t0 and t3, the first capacitor 12 is not rapidly charged due to the operating current in the stabilized power supply circuit 22. Then, at time t3, the supply voltage from the solar cell 10 starts to be boosted by the stabilized power supply circuit 22, and after this time t3, the first capacitor 12
Can be charged quickly. In order to solve such a problem, the present invention further provides a first switch 20 and a voltage control circuit 2 for controlling the switch.
4 was provided. As a result, the first capacitor 12 can be rapidly charged as described below.

Next, the solar cell charging circuit 2 according to the present invention.
Will be described with reference to FIG. In FIG. 3, the power supply voltage VCC of the solar cell 10 increases with time as the solar radiation increases. In the period from time t0 to time t1, the first switch 20 (P-channel MOS transistor) is in the off state because no voltage is applied to the gate until the threshold voltage level is reached. In this state, the voltage from the solar cell 10 is not supplied to the stabilized power supply circuit 22.

Node A in voltage control circuit 24 at time t1
When the voltage reaches the voltage V1, the voltage is clamped to the voltage V1 by the forward voltage of the diode 32.

Thereafter, the power supply potential VCC further rises,
At time t2, when the voltage at the node A reaches the voltage V2, the potential difference between the nodes A and B reaches the threshold voltage Vtp of the first switch 20 (P-channel MOS transistor). Then, the first switch 20 (P-channel MOS transistor) is turned on, the voltage boosted by the stabilized power supply circuit 22 is supplied to the first capacitor 12, and thereafter, the boosted power supply potential V of the solar cell 10
CC is continuously supplied to the first capacitor 12.

By providing the stabilized power supply circuit 22, the first capacitor 12 can be charged stably. At the same time, the first switch 2
By limiting the voltage supply to the stabilized power supply circuit 22 by 0 until the voltage reaches a predetermined voltage, if the generated voltage is still low in the power-up state of the solar cell 10, the power supply to the stabilized power supply circuit 22 The inconvenience that the output voltage of the solar cell 10 cannot be boosted due to the current flowing can be solved.

(Second Embodiment) A solar cell charging circuit 102 shown in FIG. 5 includes a second switch 40, a second capacitor 42, and a diode in addition to the above-described solar cell charging circuit 2 shown in FIG. 44.

The second switch 40 is a switch for controlling the power supply potential of the solar cell 10 supplied to the load circuit 16. In the second embodiment, the second switch 40 is formed of, for example, a P-channel MOS transistor, and its drain is connected to the solar cell 10 side.
The source is on the load circuit 16 side, and the gate is on the voltage control circuit 24.
It is connected to the. The voltage control circuit 24
Is a circuit for controlling the opening and closing of the first switch 20 based on the power supply potential VCC supplied from the power supply, and controls the voltage applied to the gate of the second switch 40. The second capacitor 42 is provided to stabilize the voltage applied to the voltage control circuit 24. The diode 44 has a function of applying a forward voltage to the voltage control circuit 24.

The solar cell charging circuit 10 shown in FIG.
2, the voltage control circuit 24 turns on the second switch 40 at the timing t2 in FIG. 3 to drive the load circuit 16 before the charging of the first capacitor 12 is completed. Will be able to do it. Also, the second capacitor 42 and the diode 4
4, the charging circuit 102 of the solar cell can be used quickly and in a more stable state, and the switch of the switch can be reliably connected even when the output voltage of the solar cell 10 decreases. Opening and closing control can be performed.

The present invention is not limited to the examples described with reference to FIGS. 1 to 5, and various changes can be made without departing from the gist of the present invention. For example, in the above-described second embodiment, the first switch 20 and the second switch
The timing of opening / closing control with the switch 40 of FIG.
At the time t2, the timing is not necessarily the same, and the timing of turning on the second switch 40 may be intentionally delayed. Thus, even when the opening / closing timing of each switch is shifted, naturally,
The effects of the present invention can be sufficiently achieved.

Further, by mounting the above-described solar cell charging circuit on the same chip or the same base as other various circuits, it can be used for various semiconductor devices. By using this semiconductor device or an electronic device equipped with this semiconductor device, more stable driving can be performed.

[0026]

According to the present invention, by providing the stabilized power supply circuit 22, the first capacitor 12 can be charged stably, and at the same time, the first switch 20 is charged.
By restricting the supply of voltage to the stabilized power supply circuit 22 until the voltage reaches a predetermined voltage, the current supply to the stabilized power supply circuit 22 is limited when the generated voltage is still low while the power supply of the solar cell 10 is in a rising state. And the inconvenience that the output voltage of the solar cell 10 cannot be boosted can be solved. Accordingly, it has become possible to charge the battery up to the limit of the withstand voltage without using an expensive capacitor having a high withstand voltage.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a circuit configuration example of a solar cell charging circuit 2 according to a first embodiment.

FIG. 2 is a diagram showing a circuit configuration example of a voltage control circuit 24 shown in FIG.

FIG. 3 is a diagram for explaining operation timing of a first switch shown in FIG. 1;

FIG. 4 is a diagram for comparison with the operation timing shown in FIG. 3, particularly in a circuit in which the first switch 20 is not provided.

FIG. 5 is a diagram illustrating a circuit configuration example of a solar cell charging circuit 102 according to a second embodiment.

[Explanation of symbols]

 2, 102: solar cell charging circuit 10: solar cell 12: first capacitor 14, 30: resistor 16: load circuit 20: first switch 22: stabilized power supply circuit 24: voltage control circuit 32, 44: diode 40: Second switch 42: Second capacitor 200: Power supply potential line 202: Ground potential line A, B: Node

Claims (5)

[Claims] 1. A solar cell, a first capacitor having one end connected to a first potential line of the solar cell, and the other end connected to a second potential line of the solar cell, and the first potential line A stabilizing power supply circuit connected to the power supply for boosting a supply voltage from the solar cell and stably charging the first capacity; and the solar cell and the stabilizing circuit on the first potential line. A first switching unit connected between the power supply circuit and the power supply circuit, the opening and closing of which is controlled based on the supply voltage of the solar cell. 2. The charging circuit for a solar cell according to claim 1, wherein one end is connected to the first potential line between the solar cell and the first switching means, and the other end is connected to the second potential. A voltage control unit connected to a line, wherein the first switching unit is turned on when a voltage exceeding a first predetermined voltage is supplied by the voltage control unit. Charging circuit. 3. The solar cell charging circuit according to claim 2, wherein a potential from the first potential line, which is supplied to a load circuit connected in parallel to the first capacitor, is controlled. A charging circuit for a solar cell, further comprising second switching means, wherein the second switching means is turned on when a voltage exceeding a second predetermined voltage is supplied by the voltage control means. . 4. The charging circuit for a solar cell according to claim 2, wherein an input side is connected to the first potential line on a line connecting the first potential line and the voltage control means. A diode having an output connected to the voltage control means; and a second capacitor having one end connected to the output of the diode and the other end connected to a line connected to the second potential line. A charging circuit for a solar cell. 5. A semiconductor device comprising the solar cell charging circuit according to claim 1.