JPH0715889A - Control circuit for solar battery - Google Patents

Abstract

PURPOSE:To eliminate the need for an adjusting mechanism and a hysteresis circuit, and to enable large current control by connecting a solar battery to a coil terminal for a relay, discriminating day and night and supplying day load and night load with outputs respectively through the contact terminals of two kinds of the normal open and normal close of the relay. CONSTITUTION:Night operating load 9 such as an illumination, an LED pilot lamp, etc., is connected to a secondary battery 2 through the normal-close contact terminal 7 of a relay 4 and operated at night. On the other hand, the operating voltage of a solar battery 1 rises and power sufficiently smaller than the generated power of the solar battery 1 is applied to a coil 5 by day, and day operating load 8 such as a ventilating fan, a pump, etc., is connected to the secondary battery 2 through a normal-open contact terminal 6 and operated. Day and night are discriminated at low speed by the coil resistance of the coil 5 at that time, but no thermal damage is generated by the control of large currents owing to low contact resistance and no-intermediate state. Accordingly, heat is not also dissipated and large currents can be controlled by simple circuit constitution, thus obtaining a control circuit capable of discriminating day and night.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell control circuit for charge / discharge control and output control used in a solar cell power supply system for charging a secondary battery with a solar cell.

[0002]

2. Description of the Related Art A solar battery power supply system for charging a secondary battery with a solar battery requires a control circuit for protecting the secondary battery such as a lead storage battery from overcharge prevention and overdischarge prevention. A control circuit for day / night discriminating output applying an optical sensor function is often used.

In the conventional day / night discrimination output circuit, a circuit system in which an output voltage of a solar cell is detected by an IC circuit and a semiconductor switch element of an output portion is opened / closed at high speed by a logic circuit together with an overdischarge prevention circuit is often used. In addition, the conventional overcharge prevention circuit connects the solar cell and the secondary battery via the backflow prevention diode, detects the voltage rise of the secondary battery with the IC circuit, and operates the semiconductor switch element at high speed to short-circuit the solar cell. Alternatively, an open circuit system is used.

Further, Japanese Patent Laid-Open No. 1-234737 discloses a switch circuit in which a ventilation fan and a bidirectional control element are connected in series to a commercial power source, and between a pole and a gate pole of the bidirectional control circuit element. A resistor and a reed switch are connected to each other, and a gate circuit in which another resistor is connected between the other pole of the bidirectional control element and the gate pole, and an electromagnetic coil provided in parallel with the reed switch, A ventilator comprising a solar cell connected to an electromagnetic coil is disclosed.

[0005]

However, one of the problems of the conventional example is that the semiconductor switch element has a small allowable current and is easily damaged by heat. In the case of an overcharge prevention circuit, for example, when a solar cell with a rated output of 8V and a maximum output of 48W for charging a 6V secondary battery is used, the short-circuit current is 6A to 7A. At this time, when it is sufficiently turned on, the voltage drop of the semiconductor switch element such as the power transistor or the power MOS-FET is generally 0.1 V or less and the heat generation is 0.7 W or less, but the operation of the solar cell is performed during the switching time. 48W when the switch speed is slow because it passes a point
When the chattering of a short period occurs due to the addition of the electric power of, heat destruction occurs. The radiating fins for reducing the temperature rise are large and the cost is high. The permissible current of the switch element that can be obtained at a lower price is generally 3 A to 5 A or less.

Further, another one of the problems of the conventional example is that a hysteresis circuit and a logic circuit for preventing chattering due to high-speed opening / closing of the semiconductor switch element are necessary for day / night discrimination output control and charge / discharge control. The control requires a hysteresis circuit for brightness instability, and the charge / discharge control circuit requires a voltage detection IC or a hysteresis circuit for voltage detection instability.

Further, in the conventional example, an adjusting mechanism is required for temperature correction of the charging voltage. When a thermistor is used for the temperature correction circuit, there is a large variation in resistance, and individual adjustment by variable resistance is necessary.

The present invention solves the above problems.
A first object of the present invention is to provide a solar cell control circuit which has a simple circuit configuration without an adjusting mechanism and a special hysteresis circuit, can control a large current without radiating heat, and can perform day / night discrimination output. .

A second object of the present invention is to provide a solar cell control circuit in which the temperature of the charge / discharge voltage can be easily corrected.

[0010]

In order to achieve the above object, a relay is used as a switch element and is connected to an output terminal of a secondary battery and a solar cell through a normally open and normally closed contact terminal of the relay, An optical sensor is connected to the coil terminal to connect a solar cell as a drive power source to distinguish day and night, and there are two types of contact terminals: a relay daytime closed, a night open normally open and a day open, and a night closed normally closed. Is applied to supply the output to the daytime and nighttime operation loads, respectively.

Further, since there is almost no heat generation and there is no need for a high-speed switch, LEDs having a small temperature variation and a negative temperature characteristic are connected in series to approximate the temperature characteristic of a secondary battery, and as an analog voltage detecting means. A plurality of light-emitting diodes (hereinafter referred to as LEDs) connected in series in the forward direction,
Alternatively, the charging / discharging output is controlled by connecting to the coil terminal of the relay through a switching element that operates according to the current signals of a plurality of LEDs connected in series in the forward direction.

Due to the hysteresis of the coil current of the relay, there is little chattering and a simple circuit configuration.
It realizes charge / discharge control.

[0013]

With the above structure, when the output generated in the solar cell due to sunshine is applied to the coil of the relay, the contact terminal opens and closes. 0.02kW / m ^{2 to} 0.1kW in the daytime even in rainy weather
Since there is a light amount of / m ² , even a solar cell with a maximum output of 10 W can supply electric power of 200 mW to 1000 mW to the coil, and most commercially available relays operate even when driven directly.
During the daytime, the normally closed contact terminal is kept in the off state, and the normally open contact terminal is kept in the on state. In a configuration in which the exciting current of the coil is controlled by a semiconductor switching element that amplifies the output of the solar cell using a secondary battery as a power source, the same function is achieved at an illuminance of several tens of lux or less.

Further, in the case of the overcharge prevention circuit, when the voltage of the secondary battery rises, a plurality of LEDs connected in series are forward biased, and an exciting current flows through the coil of the relay directly or through the switch element. When the coil reaches the moving voltage, the secondary battery and the solar battery connected via the normally closed contact terminal are opened and charging is stopped. Due to the gradient of the current-voltage characteristic due to the resistance of the coil and the nature of the open circuit voltage of the relay being lower than the sensing voltage, the opening and closing of the contacts automatically has a hysteresis, and the chattering due to the drop of the battery voltage after the charging is stopped is mitigated. If a series adjustment resistor is connected to the coil, the chattering period becomes longer.

If a bypass resistor is connected in parallel with the contact,
During the daytime, the secondary battery is pushed and charged by a constant current that does not depend on the opening and closing of the contact terminals, the battery voltage drops slowly due to charging stoppage, and there is almost no chattering, and both the contact life of the relay and the life of the secondary battery are extended.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A solar cell control circuit according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) A typical embodiment of a solar cell control circuit having a day / night discrimination output function according to the present invention is shown in FIGS. 1 and 2. In FIG. 1, a solar cell 1 is connected via a backflow prevention diode 3 so as to charge a secondary battery 2.
The solar cell 1 is connected to the coil 5 of the relay 4, and the secondary battery 2 is connected.
A daytime operation load 8 and a nighttime operation load 9 are connected to one of the normally open contact terminals 6 for daytime closing and nighttime opening connected to the other terminal of the normally closed contact terminal 7 for daytime opening and nighttime closing. To do. At night, through the other terminal of the normally closed contact terminal 7, lighting or L
When the night operation load 9 such as an ED indicator lamp is connected to the secondary battery 2 to operate, and the operating voltage of the solar cell 1 rises during the daytime, the power generation power of the solar cell 1 is sufficiently less than 200 mW.
A power of 1000 mW is applied to the coil 5, and a daytime operation load 8 such as a ventilation fan or a pump is connected to the secondary battery 2 via one terminal of the normally open contact terminal 6 to operate. The resistance value of the coil 5 is generally proportional to the square of the rated voltage of the relay, so the current is automatically limited, but a relay with a lower rated voltage than the rating of the power supply unit may be used, or the excitement voltage and open circuit voltage of the relay may be used. The adjustment resistor 10 is connected in series to the coil 5 for the purpose of increasing the hysteresis generated by the difference between the two and eliminating chattering of the contacts. Day / night discrimination by coil resistance is slow, but contact resistance is low and there is no intermediate state, so thermal damage does not occur due to large current control.

As the solar cell 1, a single crystal silicon solar cell, a polycrystalline silicon solar cell, a CdS / CdTe compound thin film solar cell or an amorphous silicon thin film solar cell is used, and when the secondary battery 2 has a rating of 12 V, it is generally 34 cells. A module having an operating voltage of about 16 V in which -40 cells are connected in series is used. When the capacity of the secondary battery 2 is 4 Ah or less, a packed battery in which a plurality of sealed nickel-cadmium storage batteries or nickel-hydrogen storage batteries, which are relatively strong against overdischarge, are used at low cost, 1/4 to 1
In the case of a solar cell with a generated current of / 10C, it can be used without an overcharge prevention circuit depending on the usage conditions. When the capacity of the secondary battery 2 is large and the cost is reduced by using the lead storage battery, the control circuit for overcharge prevention and overdischarge prevention omitted in the embodiment of FIG. 1 is necessary. In addition, many output load controls can be performed at the same time by using a relay with multiple normally open contacts and multiple normally closed contacts, and a latching type can be used to save power.

FIG. 2 shows another embodiment according to the present invention in which the output of the solar cell 23 is amplified by the transistor 24 to increase the sensitivity and control the exciting current of the coil 25. In FIG. 2, the resistors 26 and 27 adjust the sensitivity for day / night discrimination, and the adjusting resistor 28 adjusts the voltage hysteresis.
Further, the relay 29 has a plurality of contacts, and controls the daytime operation loads 31, 31a such as a ventilation fan and a pump by the two normally open contact terminals 30, 30a, and the normally closed contact terminal 32 by the illumination or the LED indicator lamp at night. The operating load 33 is controlled. The relay can be easily driven even if the output of the solar cell is small.

(Embodiment 2) FIG. 3 shows a typical embodiment having an overcharge prevention function of a solar cell control circuit having a charge / discharge control function for a secondary battery according to Embodiment 2 of the present invention. In FIG. 3, the solar cell 44 and the secondary battery 45 are connected via the backflow prevention diode 41 and the normally closed contact terminal 43 of the relay 42. Further, in order to charge the secondary battery 45 from the solar battery 44 by charging after the overcharge control, the bypass resistor 46 having a relatively high resistance value is connected to the normally closed contact terminal 43.
Connected in parallel. The positive electrode of the solar cell 44 was connected to one terminal of the coil 47 via the coil 47 of the relay 42, and the adjustment resistor 48 and the collector of the transistor 49 were connected in series to the other terminal.

During the daytime, when the secondary battery 45 is overcharged due to charging from the solar battery 44 and the battery voltage rises above the set value, a plurality of light emitting diodes (hereinafter referred to as LEDs) 50 connected in series for voltage detection are rapidly used. Current flows through the resistance 5
When the base current is supplied from 1 and the transistor 49 is switched on, and the exciting current flows through the coil 47 and reaches the touching voltage, the normally closed contact terminal 43 of the relay 42 is opened and the normal charging from the solar cell 44 is stopped. .

It is also possible to use only a plurality of LEDs 50 connected in series in the forward direction without using the transistor 49.

When the secondary battery is a lead storage battery having a rating of 12V,
For the relay 42, a rated voltage of 12 V or less can be used, the higher the voltage is, the smaller the exciting current is, and the adjustment resistance 48 is adjusted so as not to exceed the allowable value. When the resistance values of the resistors 51 and 52 are increased, the voltage detection sensitivity is decreased, the voltage hysteresis of the relay 42 is increased, and the chattering cycle due to the drop of the battery voltage is also increased. The charge control voltage is 1 at room temperature.
It is set to 3.8V to 14.7V, and the plurality of LEDs 50 have a low forward rising voltage and little variation in red LE.
8 to 10 Ds were connected in series. It is also possible to use a constant voltage LED molded with a light shielding resin. LED is -2
Since it has a negative temperature coefficient of mV / ° C to -3 mV / ° C, in the case of a lead storage battery (6 cells) with a rated voltage of 12V, 8 LEDs are used.
The temperature coefficient can be almost compensated by connecting 10 cells in series.

FIG. 4 shows the results of temperature characteristic measurement in which nine red LEDs were connected in series in the embodiment of FIG. In FIG. 4, the excitation current of the coil 47 with respect to the storage battery voltage has a gradient, and the voltage at which the relay 42 turns on when the temperature is 25 ° C. is 14.5.
The voltage turned off with respect to V was 14.0 V, and there was a voltage hysteresis of 0.5 V. The temperature characteristic of 55 ° C to -15 ° C is -25 mV / ° C when the transistor 49 is added.
The temperature characteristic of the 2V storage battery was almost equal to −30 mV / ° C., and the temperature was almost compensated.

In the embodiment shown in FIG. 3, the rated voltage is 12V, 30A.
FIG. 5 shows the measurement result of the time change of the storage battery voltage due to chattering when the lead storage battery of h was charged by the polycrystalline solar cell having the maximum output of 30 W. In FIG. 5, the bypass resistor 46
Is 100 ohms, the chattering period is about 2.5 times longer than the case without the bypass resistor 46, and when the bypass resistor 50 ohm is used, there is no chattering.
It converged to a constant voltage of 4.7V and the charging was continued by pushing. The normally closed contact terminal 43 is opened due to overcharge protection, and the 36-cell polycrystalline solar cell has an open voltage of about 20.
When operating at 5V, a voltage difference of 6V from the lead acid battery is added,
When the bypass resistor 46 is 50 ohms, a push-in charging current of 120 mA flows. The power loss is 0.72 W, and it is easy to directly mount a synthetic resistance or a small power resistance on the circuit board.

Next, FIG. 6 shows a typical embodiment having an overdischarge function of a solar cell control circuit having a secondary battery charge / discharge control function according to the present invention. In FIG. 6, the solar cell 62 and the secondary battery 63 are connected via the backflow prevention diode 61. In addition, the coil 65 of the relay 64
The positive electrode of the secondary battery 63 is connected to one terminal, and the adjusting resistor 66 and the collector of the transistor 67 are connected in series to the other terminal. The emitter of the transistor 67 is grounded, and the base is connected to a negative electrode of a plurality of LEDs 69 connected in series for voltage detection and a resistor 70 for releasing the base current through a resistor 68 for limiting the base current. The positive electrode of a plurality of LEDs 69 connected in series is connected to the positive electrode of the secondary battery 63 to monitor the voltage of the secondary battery 63. Further, the positive electrode of the secondary battery 63 and the load 72 are connected via the normally open contact terminal 71 of the relay 64. Normally, the base current is supplied from the secondary battery 63 through the LED 69 and the resistor 68, the transistor 67 is in the ON state, the rated current flows through the coil 65, and the normally open contact terminal 71 is also in the ON state. Therefore, the load 72 is constantly supplied with power from the secondary battery 63.

When the voltage of the secondary battery 63 drops due to the power consumption of the load 72, for example, the rated voltage 12V drops to 10.5V, the base current is suddenly reduced by the voltage detection function of the LED 69 to turn off the transistor 67 and the coil 65. The normally open contact terminal 71 is also turned off, and the secondary battery 63 is prevented from being over-discharged.

It is also possible to use only the LEDs 69 connected in series in the forward direction without using the transistor 67.

The load 72 is an LED indicator light, a lighting, a ventilation fan,
It is a load such as a pump that requires an independent power source using a solar cell, and depending on the type of load, it is easy to combine the day / night discrimination output circuit of FIG. 1 to FIG. 3 or an overcharge prevention circuit and an overdischarge prevention circuit. In the case of over-discharging prevention that does not require temperature correction in the combination, the circuit can be simplified by using a voltage detection IC or the like instead of the LED 69 having the voltage detection function.

[0030]

As is apparent from the above description, according to the solar cell control circuit of the present invention, no special detection circuit is used due to the simple configuration of the relay used as the switch element, the secondary battery and the solar cell. It is possible to discriminate between day and night, and control multiple outputs. There is no voltage loss due to the switch element, there is no damage due to heat generation even without a heat radiation fin, and it is easy to prevent chattering due to hysteresis. Therefore, a small-sized, low-cost and highly reliable solar cell control circuit can be easily obtained. Further, the simple configuration of the relay used as the switch element, the secondary battery, the solar cell, the plurality of LEDs, and the like makes it possible to easily compensate the temperature of the secondary battery such as a lead storage battery, and to prevent the switching element from chattering or thermal damage. A solar cell control circuit capable of discharge control can be easily obtained. Further, it is possible to display the state of charge control or push-in charging for extending the life of the secondary battery by an LED for voltage detection.

Further, since the contact resistance of the relays can be ignored, it is easy to connect a plurality of relays in series and combine the two or more functions of the present invention for preventing overdischarge and for day / night discrimination output.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a solar cell control circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of another solar cell control circuit according to the first embodiment.

FIG. 3 is a circuit diagram of a solar cell control circuit according to the second embodiment.

FIG. 4 is a graph showing measured data of temperature characteristics of the coil current of the relay with respect to the battery voltage.

FIG. 5 is a graph showing actual measurement data in which the time variation of the battery voltage due to the switch operation for preventing overcharge changes with the bypass resistance

FIG. 6 is a circuit diagram of a solar cell control circuit according to another embodiment.

[Explanation of symbols]

 1,23,44,62 Solar cell 2,21,45,63 Secondary battery 3,22,41,61 Backflow prevention diode 4,29,42,64 Relay 5,25,47,65 Coil 6,30,30a , 71 Normally open contact terminal 7, 32, 43 Normally closed contact terminal 8, 31, 31a Daytime operation load 9,33 Nighttime operation load 10, 28, 48, 66 Adjustment resistor 24, 49, 67 Transistor 26, 27, 51, 52, 68, 70 resistance 46 bypass resistance 50, 69 LED 72 load

Claims (3)

[Claims] 1. A solar cell power supply system for charging a secondary battery from a solar cell via a backflow prevention diode,
A normally open contact terminal to which a daytime load is connected and which is closed in the daytime and opened at night, a normally closed contact terminal which is connected to a nighttime load and is to be opened in the daytime and closed at night, and a coil for opening and closing both contact terminals are provided. Equipped with a relay,
By the semiconductor element in which the coil operates by the output of the solar cell due to sunshine, or the output of the solar cell due to sunshine,
A solar cell control circuit having a day / night discrimination output function for opening and closing both contact terminals. 2. A solar cell power supply system for charging a secondary battery from a solar cell via a backflow prevention diode,
A relay having a normally closed contact terminal and a coil for opening and closing the contact terminal, a forward-connected light emitting diode connected to the solar cell and a secondary battery via the relay, or a forward-connected light emitting diode. When the charging voltage of the secondary battery rises to a set value or higher, the light emitting diodes connected in series in the forward direction, or the currents of the light emitting diodes and the switching elements connected in the forward direction suddenly increase. , A normally closed contact terminal is opened, an overcharge prevention function for stopping normal charging from the solar cell, a relay having a normally open contact terminal and a coil for opening and closing the contact terminal, and the relay via the relay Forward connected light emitting diode or forward connected light emitting die connected to solar cell and secondary battery And a switching element operated thereby, when the discharge voltage of the secondary battery drops below a set value, the forward-connected light-emitting diode or the forward-connected light-emitting diode and the current of the switching element sharply decreases, A control circuit for a solar cell having an over-discharge prevention function of stopping the discharge of the secondary battery to a load by opening the normally open contact terminal. 3. The control circuit for a solar cell according to claim 2, wherein a bypass resistor for charging is connected in parallel to the normally closed contact terminal of the relay.