JPS5922459B2 - power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device equipped with a solar cell and a secondary battery charged by the solar cell, and in particular to a power supply device that converts electrical energy into solar cells even when light energy is at low illuminance. The present invention relates to a power supply device that is controlled to be suitable for driving a secondary battery, an electronic device, etc.

One type of power supply device used to drive electronic devices such as desktop computers and electronic wristwatches is one that combines a solar cell and a secondary battery.

The solar cells in such power supplies do not cause any problems when they are set in a sufficiently bright place and are receiving sufficient light energy; When the solar cell is placed in an atmosphere of The drawback was that the electrical energy necessary to charge secondary batteries and drive electronic devices could not be secured. Therefore, conventionally, a voltage regulator diode is connected in parallel to a secondary battery that uses the output of a solar cell as a charging power source, and when the output voltage of the solar cell exceeds the operating voltage set by the voltage regulator diode and resistor, A system has been proposed that prevents overcharging current from flowing to the secondary battery by breaking down a constant voltage diode and bypassing the charging current.

However, in the conventional circuit system described above, a resistor connected in series with a voltage regulator diode is required to set the operating voltage of the bypass circuit that prevents overcharging current to the secondary battery. As the number of devices increases, the space required for their implementation also increases, which creates problems with the layout when mounting them on devices with limited space, such as electronic wristwatches, which hinders the miniaturization and thinning of watches, etc. I will do it. In addition, when a voltage regulator diode breaks down, a considerable amount of bypass current flows, so if there are circuit elements that are airtight, densely packed, and easily affected by heat, such as a wristwatch, the voltage regulator diode The generated heat must be taken into consideration, which limits the capacity and size (shape) of the voltage regulator diode to be mounted, and may not be applicable to circuits that bypass large currents due to heat generation. be.

Furthermore, in general, voltage regulator diodes with low Zener voltages exhibit constant voltage characteristics in the large current region with a soft current rise, and for this reason, they are used at relatively low currents. It is not very desirable as a voltage regulator circuit for a solar cell power supply device such as a wrist watch or a calculator, since the voltage is unstable because the voltage regulator diode exhibits a soft rise before reaching the operating point.

Therefore, if a solar cell is placed in a low-light atmosphere,
Naturally, the current value output from the solar cell is also low, and a constant voltage diode that exhibits constant voltage characteristics in a large current region cannot be expected to stabilize the electrical energy necessary for charging the secondary battery and driving the load. This invention was made in view of the above points, and includes a photoconductive circuit whose conductivity changes depending on the intensity of light on the output side of a solar cell, and a resistance value that changes as the current flowing through this photoconductive circuit increases. By providing a circuit that reduces the amount of power output from the solar cells, it is possible to stably secure the power required for charging secondary batteries and driving loads such as electronic devices even in low illuminance, and it also reduces the cost and cost at the time of implementation. It is an object of the present invention to provide a power supply device which solves the pace problem and can be used regardless of whether the current is low or high.

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure shows a block diagram of a power supply device according to the present invention, in which a regulator circuit 2 for controlling the converted power of the solar cell 1 is connected to the output side of the solar cell 1. The regulator circuit 2 includes a photoconductive circuit 3 connected to the output end of the solar cell 1 and whose conductivity changes depending on the intensity of light;
The photoconductive circuit 3 includes a circuit 4 connected in series to the input side of the photoconductive circuit 3, whose resistance value decreases as the current flowing through the photoconductive circuit 3 increases, and the photoconductive circuit 3 further includes the solar cell 1 and a circuit 4 whose resistance value decreases as the current flowing through the photoconductive circuit 3 increases. placed in an atmosphere with the same light intensity. When the converted power of the solar cell 1 changes depending on the intensity of light, the conductivity of the photoconductive circuit 3 is changed depending on the intensity of the irradiated light in accordance with this change, and at the same time, a part of the power from the solar cell 1 is transferred to the regulator 2. By dividing the current into the secondary battery 5 connected to the solar cell through a backflow prevention circuit 6, and a load 7 such as an electronic circuit driven by the secondary battery 5, a constant amount of power can always be supplied. . FIG. 2 shows a specific circuit example of the power supply device of the present invention based on the above-mentioned block diagram. In addition, a photoconductive element such as a CdS photoconductive cell is applied to the photoconductive circuit 3, and a circuit 4 whose resistance value decreases as the current increases is inserted in the forward direction. It is formed from a diode. Both ends of the series circuit of the photoconductive element 3 and the diode 4 are connected to the solar cell 1.
It is connected in parallel to both ends of the solar cell 1 via a current limiting resistor 8 to prevent a large current from flowing when the cell is irradiated with strong light such as direct sunlight, and is further connected to the photoconductive element 3 and the diode. A secondary battery 5 and a load 7 are connected in parallel to both ends of the series circuit with 4 via a diode forming a backflow prevention circuit 6. In the circuit with the above configuration, the solar cell 1 is irradiated with light, and the intensity L thereof is L. ,L,2
FIG. 3 shows the voltage-current characteristics of the solar cell 1 when the voltage increases as L, 3L, . . . . In Figure 3,
LO is the intensity of light so low that the solar cell 1 cannot generate the predetermined voltage required for the secondary battery 5 and the load 7, and L is the intensity of light at which the solar cell 1 generates the predetermined voltage required. It shows the strength of When the solar cell 1 is activated by light irradiation of 1 L or more, the current (L) generated by the solar cell 1 with respect to the illuminance L of the light is proportional to the illuminance L, so I(
L)=KL (k: constant of proportionality).

When a load, that is, a photoconductive element 2 whose resistance value changes depending on the illuminance L (having a characteristic that the resistance value decreases as the illuminance L increases) is connected to the solar cell 1 in parallel, both ends of the photoconductive element 2 The potential difference V(L) appearing in is V(L)=i(L)
・R(L) (R(L): resistance value of photoconductive element 2 depending on illuminance, i(L): resistance value of photoconductive element 2 depending on illuminance)
(current flowing through).

Now, the illuminance L of the light irradiated to the solar cell 1 is L in Fig. 3,
2L, 3L, ..., the potential E at the connection point A in FIG. 2 (the potential E is the potential E when the potential at the connection point B in FIG. In order to keep the voltage (potential) at the voltage V(L) = E (constant) on the broken line 10 in FIG. 3, the photoconductive element (regulator) 2 should be The resistance R(L) is 1R(L)=E/
! (L door R(2L)=E/21(L)tsuR(3L)=E
/31(L), . . . as long as it is satisfied.

In other words, if the resistance value R(L) of the photoconductive element 2 is decreased so that (L) remains constant as the illuminance L increases, the potential difference between both ends of the photoconductive element 2 will be maintained even if the illuminance of light changes. can be kept constant. That is, by utilizing the fact that the electrical conductivity of the photoconductive element 2 changes depending on the intensity of light, the electrical energy and secondary energy required to drive the electronic device (load) 5 out of the power generated by the solar cell 1 are This is because the photoconductive element 2 consumes excess electrical energy other than the electrical energy required to properly charge the battery.

A curve 11 in FIG. 4 shows the resistance value R ( Although the charging current to the secondary battery 5 based on this characteristic curve 11 is zero, the light intensity-resistance characteristic of the regulator circuit 2 is shown as a curve 12 in FIG. If the characteristic has a resistance value slightly higher than 11, the potential at the connection point A in FIG. The power from the solar cell 1 will be supplied to the solar cell 1.

In addition, in FIG. 4, low illuminance L. In the region of , the solar cell 1 cannot generate a predetermined voltage, but if the resistance value of the regulator circuit 2 is suddenly increased as shown in the part 11a of the characteristic curve 11, the potential difference between both ends of the regulator circuit 2 becomes a constant value E. is maintained. Furthermore, in the high illuminance area, the resistance value R(L) shown in curve 11 of FIG.
The reason why is almost stabilized as in the portion 11b is because the current limiting resistor 8 is provided. Furthermore, in the circuit of FIG. 2, when the intensity of light is sufficiently large, the current flowing through the regulator circuit 2 is relatively large.

Therefore, the diode 4 in the regulator circuit 2 is sufficiently biased, and the voltage drop caused by the diode 4 is negligible compared to the voltage drop caused by the photoconductive element 3. Therefore, the potential difference across the regulator circuit 2 is approximately equal to the potential difference across the photoconductive element 3. When a CdS photoconductive cell is used in the photoconductive circuit 3, its light intensity-resistance characteristic is approximately inversely proportional to the light intensity L, as shown by the straight line 13 in FIG. Since the current flowing through the regulator circuit 2 is small, there is a voltage drop due to the diode 4, and the resistance value component caused by this voltage drop is added to the resistance value of the CdS photoconductive cell 3, making the resistance value of the regulator circuit 2 the first. It will be increased as shown in part 13a in Figure 5a. The characteristic curve 13 including the portion 13a is the light intensity-resistance characteristic required of the regulator circuit 2 necessary to keep the potential of the connection point A1, that is, the connection point B constant in FIG. It shows the characteristics when the conductive cell 3 is present in the same light intensity atmosphere as the solar cell 1. Also,
The intensity of the light irradiated to the CdS photoconductive cell 3 is determined by the solar cell 1
If the intensity of the light is made relatively weak compared to the intensity of the light irradiated on the
It becomes possible to bring the characteristic curve 13 close to or to overlap the characteristic curve 11. As a means for weakening the intensity of light to the CdS photoconductive cell 3, a filter, an aperture, or the like is used to adjust the amount of light incident on the CdS photoconductive cell.

In this way, by limiting the amount of light to the CdS photoconductive cell 3 using the light amount adjustment means, the light intensity-resistance characteristic 13 of the regulator circuit 2 can be adjusted to the level required for charging the secondary battery and driving the load, as in the case of FIG. If the characteristic 14 is matched to the ability to extract electric power, the electric power of the solar cell 1 can be supplied to the secondary battery 5 and the load 7. FIG. 5b shows a characteristic diagram of the charging current flowing to the secondary battery 5 side at this time, and the curve 15 is Cd
The charging current when using only the S photoconductive cell 3 is also
A curve 16 shows the light intensity characteristic of the charging current when using the regulator circuit 2 of the present invention in which the CdS photoconductive cell 3 and the diode 4 are connected in series. As is clear from this characteristic curve 16, by providing the regulator circuit 2 with a diode whose resistance value decreases as the current increases, the electrical energy of the solar cell 1 can be effectively supplied to the load and the secondary battery even in low illuminance. You get it. Furthermore, in a high illuminance area such as direct sunlight, the characteristic 14 in FIG. , almost no charging current flows to the secondary battery 5 side.

Furthermore, if the potential of the secondary battery 5 increases due to overcharging, and the potential of the connection point B increases, this will be equivalent to a decrease in the resistance value of the regulator circuit 2, and the voltage from the solar battery 1 to the secondary battery 5 will increase. The supply of electrical energy to the side is suppressed. Note that by changing the relative relationship between characteristics 12 and 14 in FIG. 5a, the value of the charging current to the secondary battery side can be arbitrarily set.

As described above, according to the power supply device of the present invention, a photoconductive circuit whose conductivity changes depending on the intensity of light is provided on the output side of the solar cell, and a resistance value decreases as the current flowing through this photoconductive circuit increases. Even if the intensity of light to the solar cells is low, the electrical energy from the solar cells can be maintained at the necessary and sufficient output level, making it possible to effectively charge the secondary battery or drive the load. Furthermore, even if the power supply unit containing electronic equipment is placed in a low-light environment such as indoor light, the energy from the solar cell can be used, reducing the energy consumption of the secondary battery. This makes it extremely viable as a semi-permanent power source for electronic watches and the like.

In addition, since a photoconductive element is used in the circuit that controls the output of the solar cell at a constant level, a constant voltage can be achieved simply by adjusting the relationship between the amount of light incident on the photoconductive element and the amount of light incident on the solar cell. In addition, it can be used regardless of whether the current output from the solar cell is low or high.

Furthermore, since the photoconductive element can be manufactured from the same material as the solar cell, it is advantageous in terms of cost and also in terms of characteristics when controlling the output voltage of the power supply device. moreover,
Since the output voltage of the power supply device can be adjusted by adjusting the light incident on the solar cell and the photoconductive element, there is an advantage that problems of cost and space during mounting can be solved. Furthermore, voltage is applied in the forward direction to the forward direction diode and photoconductive element that make up the regulator, and dark current does not flow due to the application of voltage in the reverse direction as in conventional constant voltage diodes, so the regulator element is heated. is suppressed, and the conventional problem can be solved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a power supply device according to the present invention;
The figure is a circuit diagram showing a specific example of the device of this invention, Figure 3 is a voltage-current characteristic diagram of a solar cell, Figure 4 is a light intensity-resistance characteristic diagram of a regulator circuit, and Figure 5a is a CdS photoconductive cell. FIG. 5b is a light intensity-resistance characteristic diagram of the regulator circuit included, and FIG. 5b is a current characteristic diagram flowing to the secondary battery side. 1...Solar cell, 2...Regulator circuit, 3...Photoconductive circuit (CdS photoconductive photon)
, 4...Circuit where resistance value decreases (diode τ)
, 5... Secondary battery, 6... Backflow prevention circuit, 7... Load.

Claims (1)

[Claims] 1 A solar cell that supplies electrical energy to at least a secondary battery, and a solar cell that is connected in parallel to this solar cell and that changes the conductivity according to the intensity of light to use the output of the solar cell to charge the secondary battery, etc. A photoconductive element controlled to a level suitable for the photoconductive element, and a diode connected in series in the forward direction to the photoconductive element and having a property that its resistance value decreases as the current flowing through the photoconductive element increases. power supply.