JPH03155341A - Protective circuit for charging circuit - Google Patents

Abstract

PURPOSE:To prevent abnormal high tension from being generated between charging terminals by controlling switching elements in a charging circuit, when voltage between the charging terminals is increased in the charging circuit for a charging battery comprising solar cells. CONSTITUTION:By a solar battery 1, via a power supply section 8, a charging battery 3 is charged. Through the power supply section 8, by the switching working of a MOS transistor 24, the charging battery 3 is charged via a coil 6 and a diode 7. In a normal state, to the input terminal 31 of a comparator 26, voltage lower than a reference voltage is applied, and an output terminal 27 is set in an open state. When the charging battery 3 is removed from terminals 4, 5, then high tension is generated between the terminals 4, 5. In this case, the output terminal 27 of the comparator 26 goes to L level, and via a comparator 9, transistors 19, 23 are conducted. Accordingly, the MOS transistor 24 is turned OFF, and voltage rise between the charged terminals 4, 5 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a charging circuit for a rechargeable battery such as a lead-acid battery, and particularly to a protection circuit.

(b) Conventional technology Equipment that uses solar cells as a power source has been developed, but such solar cells generate electricity only when light is shining on them, so they cannot be used when there is no light shining on them. . Therefore, such devices are configured to charge a rechargeable battery with the power obtained from the solar battery, and to utilize the power stored in the rechargeable battery when the power from the solar battery becomes insufficient. As a technique for charging a rechargeable battery using the t-current obtained from a solar cell, for example, Japanese Patent Laid-Open No. 64
There is one disclosed in Publication No.-34137.

(c) Problem to be solved by the invention In a circuit that charges a rechargeable battery using the electric power induced in a coil as a result of the switching operation of a switching element, when the charging load disappears, the coil releases energy that can no longer be output. Since there is no light, an abnormally high voltage will be output between the charging terminals, causing a problem such as electric shock or other accidents. The present invention aims to provide a protection circuit for a charging circuit that solves this problem.

(d) Means for Solving the Problems The protection circuit of the present invention connects a coil that is inserted and connected in a power supply path between a solar cell and a rechargeable battery, and a terminal of the coil on the rechargeable battery side and ground. a switching element that is connected to and shorts between the terminal and ground when in a conductive state; and a switching element that is connected to detect the voltage output from the solar cell and controls the switching operation of the switching element; The first hysteresis comparator has a hysteresis characteristic, and the second hysteresis comparator has a hysteresis characteristic and is connected to detect a voltage between charging terminals to which the rechargeable battery is connected. .

(*) Function The present invention provides a first hysteresis filter provided to control the switching operation of a switching element by utilizing the reversal operation of a second hysteresis fan balator when the voltage between charging terminals to which a rechargeable battery is connected increases. This is designed to prevent the reversal operation of the hysteresis balator.

(F) Embodiment The circuit shown in FIG. 1 is an embodiment of the protection circuit of the present invention. (1) is a solar cell, (2) is a power switch, (3
) is a rechargeable battery, and is connected between charging terminals <4) and (5). (6) and (7) are power supply paths (
8) is a fill and a diode inserted and connected within. (9) is the output terminal (10) and the hysteresis terminal (
11), which has a voltage division point ( A) The first input terminal (15) connected to
and the second grounded via the reference voltage element (16).
It has an input terminal (17). (18) A hysteresis resistor that sets the hysteresis characteristics of the first hysteresis comparator (9), and is connected between the hysteresis output terminal 11) and the first input terminal (15). In such a configuration, when the voltage input to the first input terminal (15) is lower than the reference pressure input to the second input terminal (17), the output terminal (10) is in the oven state and the hysteresis The output level of the output terminal (11) is at L (low). And the first input terminal 15
) is higher than the reference voltage input to the second input terminal (17), the output level of the output terminal (10) becomes L, and the hysteresis output terminal (11)
It is configured to be in the oven. Therefore, according to such a configuration, when the output level of the hysteresis output terminal (11) is L, the hysteresis resistor (18) is connected in parallel to the second resistor (14), and the hysteresis output terminal (11) is connected in parallel to the second resistor (14). When in the oven condition, the hysteresis resistor (18) has no effect on the circuit. Therefore, the first hysteresis comparator (9
) The relationship between the input voltage of the power supply path (8) and the output voltage of the output terminal (10) is as shown in FIG. (19
), the collector is connected to the power supply path (8) via the resistor (20).
a first switching transistor whose emitter is grounded and whose base is connected to the output terminal (9) of the first hysteresis comparator (9);
10) and is also connected to a power supply path (8) via a resistor (21). (22) and (
23), the emitters are commonly connected to each other, and the collectors are connected to the power supply line (8) and the ground line (12), respectively.
second and third switching transistors connected to said first switching transistor (19), the bases of which are each connected to the collector of said first switching transistor (19);

(24) is a rechargeable battery whose drain is the coil (6) (
3) is connected to the terminal (B) on the side, and its source is connected to the ground line (12), and its gate is connected to the second switch via the resistor (25). It is connected to the emitter of the switching transistor (22) and the emitter of the third switching transistor (23). (26) is an output terminal (27) connected to the first input terminal (15) of the first hysteresis comparator (9) and a hysteresis output terminal (2).
8) a second hysteresis comparator having
A third terminal connected in series between the charging terminals (4) and (5)
A first input terminal (31) is connected to a voltage dividing point (C) formed by a resistor (29) and a fourth resistor (30), and a second input terminal (32) is grounded via a reference voltage element (16). )
have. (33) is a hysteresis resistor that sets the hysteresis characteristic of the second hysteresis comparator (26), and is connected between the hysteresis output terminal (28) and the first input terminal (31). In such a configuration, when the voltage input to the first input terminal (31) is lower than the reference voltage fully input to the second input terminal (32), the output terminal (27) is in an oven state;
The output level of the hysteresis output terminal (28) is at L (low), and when the voltage that can be input to the first input terminal (31) is higher than the reference voltage input to the second input terminal (32), , the output level of the output terminal (27) is L
Therefore, the hysteresis output terminal (28) is configured to be in the oven state. Therefore, according to this configuration, when the output level of the hysteresis output terminal <28> is at L, the hysteresis resistor (33) is connected to the fourth resistor (30).
is connected in parallel to the hysteresis output terminal (
When 28) is in the oven state, the hysteresis resistor (33) has no effect on the circuit.

Therefore, the voltage input between the charging terminals (4) and (5) of the second hysteresis comparator (26) and the output terminal (2
The relationship between 7) and the output voltage is as shown in FIG. In such a circuit configuration, the voltage at which the solar cell (1) outputs maximum power is Vs, and the first hysteresis comparator (
9) is set so that VL<Vs<Vu, where v8 and VL are the operating voltage points at which the inverting operation occurs. Also, the voltage division point (C) between the third resistor (29) and the fourth resistor (30)
The inverting operation of the second hysteresis comparator (26), which is provided to perform an inverting operation depending on the input voltage, is possible when the rechargeable battery (3), which is a charging load, is not connected between the charging terminals (4) and (5). By connecting the charging terminal (4
) and (5) is set to be carried out when the voltage between them becomes abnormally high. Therefore, in the normal state, the output terminal (27) of the second hysteresis comparator (26)
is in an oven state and has no effect on the first hysteresis comparator (9).

The present invention is constructed as described above, and the operation of the circuit will be explained next.

When the power switch (2) is closed, the power generated by the solar cell (1) can be output to the power supply path (8).
Since the open circuit voltage of the solar cell (1) is high, the output signal of the output terminal (10) of the first hysteresis comparator (9) becomes L level.Therefore, the base is connected to the output terminal (10). First switching transistor (1
9) is in a non-conductive state without being biased. Therefore, the collector of the first switching transistor (19) becomes a high potential, and the second switching transistor (22) whose base is connected to the collector becomes biased and becomes conductive. When the second switching transistor (22) is in a conductive state, a MOS transistor (24) is connected between the collector and emitter of the second switching transistor (22).
Since a bias voltage is applied to the gate of the MOS transistor (24), the MOS transistor (24) becomes conductive. When the MOS transistor (24) becomes conductive, the terminal (B) of the coil (6>) is grounded, so a current flows through the coil (6), and the current value increases with time.

As the current output from the solar cell (1) increases, the output voltage decreases as is clear from the characteristic diagram of the solar cell shown in FIG. The rotor (9) operates in reverse,
The output of the output terminal (10) becomes the oven. As a result, a bias current is supplied to the base of the first switching transistor (19) through the resistor (21), and the transistor (19) is inverted to a conductive state.
A third switching transistor (19) whose base is connected to the collector of the switching transistor (19)
23) is reversed to a conductive state when the bias is removed. Said third
When the switching transistor (23) is inverted to a conductive state, the gate of the MOS transistor (24) is grounded, so that the MO8I-run sister (24) is inverted to a non-conductive state. The MOS transistor (2
4) is reversed from the conductive state to the non-conductive state, the fill (6
), an induced voltage VC is generated in the diode (7)
Through this, the charging voltage Va can be fully supplied to the rechargeable battery (3), and the value of Va becomes Va=VL+VC-VF. However, ■ is the forward pressure of the diode (7). In this way, the charging voltage supplied to the rechargeable battery (3) is a boosted voltage of the voltage generated by the solar battery (1).As the current output from the solar battery (1) decreases, the output voltage increases. When the voltage increases and the voltage becomes higher than a predetermined value, that is, vH, the first hysteresis fan balator (9) performs an inverting operation, and the output signal at its output terminal (10) becomes L level.As a result, the first switching Transistor (19
) becomes non-conductive, the second switching transistor (22) and the MOS transistor (24)
) is reversed to conductive state. When the MO3I-run sister (24) is reversed to a conductive state, the terminal of the coil (6) (
B) will be grounded and energy will be stored in the coil (6). Then, by the above-mentioned operation, MO
When the S transistor (24) is reversed to a non-conducting state, the voltage vc induced in the coil (6) and the solar cell (1)
The resulting voltage is added and supplied to the rechargeable battery (3), thereby performing a charging operation.

That is, the heavy pressure output from the solar cell (1) is vH and VL.
As the MOS transistor (24) conducts and deconducts repeatedly and charges the rechargeable battery (3), the maximum power that is output from the solar cell (1) is utilized. Then, the charging operation will be performed.

The charging operation of the charging circuit of this embodiment is performed as described above, and next, the operation of the protection circuit will be explained. Charging terminal (
4) In a normal state where the rechargeable battery (3) is connected between (5), the voltage between the charging terminals (4) and (5) will not become abnormally high and the second hysteresis comparator (26) A voltage lower than the reference voltage is applied to the first input terminal (31), and the output terminal (27) of the second hysteresis comparator (26) is in an oven state. When the rechargeable battery (3) is in this state, the charging terminal (4)
(5), the voltage between the charging terminals (4) and (5) will become abnormally high. When the voltage between the charging terminals (4) and (5) increases, the second hysteresis comparator (26
)'s first input terminal (31) t:=The voltage that can be input also becomes high, and when that voltage reaches the set value Vh, the second hysteresis damper (26) performs an inverting operation. When the second hysteresis comparator (26) performs an inverting operation, an L level signal is output to the output terminal (27) and the hysteresis output terminal (28) becomes in an oven state.

When the L level signal is output to the output terminal (27), the signal input to the first input terminal (15) of the first hysteresis comparator (9) can be maintained at the L level, so the output terminal (10) The oven state is entered and the first switching transistor (19) is made conductive. When the first switching transistor (19) becomes conductive, the third switching transistor (23) is biased and becomes conductive as described above, and the MO
In order to ground the gate of the S transistor (24),
The OS transistor (24) is made non-conductive. Therefore, the voltage induced by the coil (6) disappears, and an abnormal rise in the voltage that could not be output between the charging terminals (4) and (5) is suppressed. In such a state, when the pressure between the charging terminals (4) and (5) decreases and the voltage value reaches the set value Vt, the second hysteresis damper
(26) operates in reverse and its output terminal (27) becomes in the oven state. As a result, the detection inversion operation of the first hysteresis balator (9) in the normal state is performed as described above, and the MOS) run sister (2)
The operation of generating the induced heavy pressure in the fill (6) by the switching operation of 4) is started again. At this time, if the rechargeable battery (3) is fully connected between the charging terminals (4) and (5), charging operation will start, and if the rechargeable battery (3) is not connected, the voltage will rise abnormally. A protection operation is performed by the accompanying inversion operation of the second hysteresis comparator (26). Therefore, the operating point at which the second hysteresis comparator (26) is inverted for protective operation is set in consideration of electric shock and the withstand voltage of circuit components such as capacitors connected between the charging terminals (4 and 5). To be done is to be done.

In the Naoki example, a MOS)-Run Sister (24) was used as a switching element to short-circuit between the rechargeable battery side terminal of the fill (6) and the ground, but it is of course possible to use other switching elements. .

(G) Effects of the Invention The protection circuit of the present invention is capable of stopping the switching operation of a switching element that performs a switching operation to generate an induced voltage from a filler when the voltage between charging terminals to which a rechargeable battery is connected increases. Therefore, the voltage at the charging terminal can be suppressed to a safe voltage. In addition, since a hysteresis comparator is used as a means of detecting the voltage rise between the charging terminals, when the voltage drops due to switching stop operation, it does not immediately return to the original state, but due to the hysteresis characteristic, switching is performed only by the operating width. The switching operation of the element can be stopped, and the present invention has the advantage that a stable protection operation can be performed with a simple circuit.

[Brief explanation of the drawing]

The circuit shown in FIG. 1 is an embodiment of the protection circuit of the present invention.
FIG. 2 is a characteristic diagram of the solar cell, and FIGS. 3 and 4I50 are characteristic diagrams of a hysteresis comparator. Explanation of main drawing numbers (1)...Solar cell, (3)...Rechargeable battery, (
4) (5)...Charging terminal, (6)...Coil,
(8)...Power supply path, (9)...First hysteresis damper (12)...Grounding line, (19)
...First switching transistor (22)
...Second switching transistor (23)...
・Third switching transistor (24)...
MOS)-run sister (26)...Second hysteresis comparator

Claims (1)

[Claims] (1) A coil that is inserted into the power supply path between the solar cell and the rechargeable battery, and when the coil is connected between the rechargeable battery side terminal of the coil and ground and is in a conductive state, the terminal a first hysteresis comparator connected to detect the voltage output from the solar cell, controlling the switching operation of the switching element, and having a hysteresis characteristic; a second hysteresis comparator connected to detect a voltage between charging terminals to which a rechargeable battery is connected and having a hysteresis characteristic; when the voltage between the charging terminals increases, the second hysteresis comparator A protection circuit for a charging circuit, characterized in that the inversion operation of the first hysteresis comparator is prevented by the inversion operation of the first hysteresis comparator, thereby stopping the switching operation of the switching element.