JPH0583868A - Overdischarge preventing circuit - Google Patents

Abstract

PURPOSE:To prevent overdischarge due to forgetting of opening of a power switch in an apparatus in which a battery is used as a power source. CONSTITUTION:One end side of a battery Batt is connected to a terminal 11a of a changeover switch 11, connected to the emitter of a transistor TR1, and the collector of the transistor TR1 is connected to a voltage detector 12. The terminal M of the detector 12 is connected to the base of a transistor TR2 and one end of a capacitor C1. The base of the transistor TR1 is connected to the collector of the transistor TR2, and the base of the transistor TR2 is connected in series with a common side 11c of the capacitor C1 and the switch 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overdischarge prevention circuit for preventing overdischarge of a battery.

[0002]

2. Description of the Related Art At present, batteries are used in places where they cannot be easily seen as a power source for portable electric products and toys. A microcomputer is built in the electric product to perform various complicated operations. In addition to the above, an electric product incorporating this microcomputer is also equipped with a safety circuit for preventing malfunction.

[0003]

By the way, as described above, the battery is arranged so as not to be noticed when the electric product is forgotten to be turned off and left unattended, and the degree of consumption of the battery cannot be visually recognized. May cause over discharge. When the low level of the output voltage becomes the minimum state due to such over-discharge, the probability that the electrolytic solution leaks from the battery becomes considerably high. Such over-discharging of batteries is particularly common in children's toys. There are many complaints in the market that they are stored in a toy box in a discharged state and stain other toys.

However, an electric product incorporating a microcomputer incorporates the above-mentioned safety circuit as a safety measure, but does not include a circuit for preventing malfunction and cutting off the power supply.

In view of the above situation, it is an object of the present invention to provide an over-discharge prevention circuit capable of preventing over-discharge and preventing liquid leakage even when left in a power-on state.

[0006]

An over-discharge prevention circuit according to the present invention is an over-discharge prevention circuit for preventing over-discharge of a battery, wherein one end side of the battery is connected to a switching means,
A first transistor for controlling and outputting the current from the battery;
A voltage detecting means for dividing the output voltage from the first transistor to a desired ratio, and a divided voltage output terminal of the voltage detecting means for controlling the operation of the first transistor.
The problem described above is solved by connecting the control terminal of the transistor and the control terminal in series with the capacitor and the switching means.

[0007]

In the over-discharge prevention circuit according to the present invention, the switching of the second transistor is turned off in accordance with the voltage-divided output from the voltage detecting means, and in this state the first transistor is turned off. Stop the current supply.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an overdischarge prevention circuit according to the present invention will be described with reference to the drawings.

The over-discharge prevention circuit 10 shown in FIG.
In an over-discharge prevention circuit for preventing over-discharge of att, a first transistor that connects one end side of a battery Batt to a terminal 11a of a changeover switch 11 as a changeover means and controls and outputs a current from the battery Batt is used. A transistor TR1, a voltage detection circuit 12 which is a voltage detection means for dividing the output voltage from the transistor TR1 into a desired ratio, and a divided voltage output terminal M of the voltage detection circuit 12 control the operation of the transistor TR1. Is connected to the control terminal B of the transistor TR2 which is a second transistor, and the control terminal B is connected to the capacitor C1 and the common side of the changeover switch 11 in series.

Power is supplied via the output terminal 13 from the collector side of the transistor TR1 to operate each electric circuit arranged thereafter.

The voltage detection circuit 12 is composed of, for example, two resistors R _A and _B. One end of the resistor R _A is
It is connected to the collector side of the transistor TR1. Also, one end of the resistor _B is grounded. The two resistors R _A and _B are connected to each other at their other ends. The voltage of the series connection portion M of the resistor _RA and the resistor _{B represents} a divided resistance voltage obtained by dividing the output voltage of the transistor TR1 into the ratio of the two resistors.

The operation of the overdischarge prevention circuit 10 will be described with reference to FIG. In the changeover switch 11, the terminal 11a is connected to the positive electrode side of the battery Batt, and the terminal 11b side is grounded. First, change the switch 11 to the terminal 11
A current flows through the capacitor C1 when it is turned to the a side. The capacitor C1 is connected to the base side of the transistor TR2. When the changeover switch 11 is activated to the ON state, the capacitor C1 supplies the base current to the base of the transistor TR2 until it is charged up. By supplying this base current, the transistor T
R2 is turned on and absorbs the base current of the transistor TR1. The transistor TR1 is turned on by the absorption of the base current. At this time, the transistor TR1 supplies a voltage Vcc substantially equal to that of the battery Batt from the collector side via the output terminal 13.

On the other hand, the output voltage from the collector side of the transistor TR1 is also supplied to the voltage detection circuit 12. The voltage detection circuit 12 includes two resistors _RA and _B described above.
In the serial connection portion M, the divided resistance voltage is supplied to the base side B which is the control terminal of the transistor TR2.
Therefore, when the transistor TR1 is turned on, the base current for turning on the transistor TR2 is supplied from the voltage detection circuit 12. By operating in this way, this over-discharge prevention circuit completes the loop of the power supply. With this loop, the over-discharge prevention circuit can stably supply power to each circuit via the output terminal 13.

Here, if the changeover switch 11 is left in the ON state, the output current I _O continues to flow through the collector of the transistor TR1, and eventually the voltage level of the voltage Vcc of the battery Batt and the voltage dividing resistance voltage V becomes low. It is decreasing. Due to the voltage drop of the divided resistance voltage V, the base current cannot be supplied to the base of the transistor TR2. By stopping the supply of the base current, the transistor TR2 stops operating, and thus the transistor TR1 also stops operating.

By thus configuring the divided resistance voltage by combining the resistance values of the power supply detection circuit 12, it is possible to easily set a desired voltage level for stopping the supply of power. By shutting off this power supply at a desired voltage, over-discharge of the battery can be avoided. By preventing this over-discharge, leakage of the electrolytic solution can be avoided. In particular, this method is effective for toys handled by children.

The overdischarge prevention circuit 10 will be described with reference to a more specific circuit diagram shown in FIG. Here, common parts are given the same reference numerals, and description thereof is omitted. The changeover switch 11 for turning on / off the power supply has one terminal 11a connected to the positive electrode side of the battery Batt and the other terminal side terminal 11b grounded. The changeover switch 13
The terminal 11c corresponding to the common of is connected to one end of the capacitor C1. The other end of the capacitor C1 is connected to the voltage detection circuit 12 and also connected to the NP via the resistor R2.
It is connected to the base of an N-type transistor TR2.

The transistor TR2 has its emitter side grounded and its collector side connected to the base of a PNP type transistor TR1 via a resistor R1. The emitter side of the transistor TR1 is connected to the positive side of the power source,
The collector side is connected to one end of the resistor R3 of the voltage detection circuit 12, and power is supplied to various circuits for power source drive control.

In the voltage detection circuit 12, the resistors R3 and R4 are connected in series, and the other end of the resistor R4 is grounded. The voltage detecting unit 12 calculates the divided resistance voltage V ₁ of the resistors R3 and R4 as the resistor R2 and the capacitor C.
1 to each one end side. It should be noted that the light-emitting diode D1 used as a power lamp may be caused to emit light on the basis of the divided resistance voltage V ₁ to indicate power-on. The light emitting diode D1 has an anode side connected to the voltage detection circuit 12 and a cathode side grounded.

The operation of the overdischarge prevention circuit 10 will be described. In FIG. 2, the changeover switch 11 is in a state where the power is currently off. In this state, the capacitor C1
It is grounded via the terminal 11b of the changeover switch 11 and the resistor R4 of the voltage detection unit 12. Therefore, the capacitor C1 is discharged.

Here, the terminal 11 of the changeover switch 11
Tilt to side a to turn on the power. When the power is turned on, the power supply voltage Vcc is applied to the emitter of the transistor TR1 and the capacitor C1 via the terminals 11a and 11c of the changeover switch 11. The capacitor C1 has a resistance R
Current through the base of the transistor TR2 via 2,
The transistor TR2 is turned on. When the transistor TR2 is turned on, the base current of the transistor TR1 is absorbed and the transistor TR1 is turned on. When the transistor TR1 is turned on, the transistor TR1 supplies power to the operated circuit and the voltage detection circuit 12. This power supply detection circuit 1
At 2, the voltage supplied from the transistor TR1 is divided by the resistors R3 and R4, and the divided resistance voltage V is applied to one end of the resistor R2 to supply a base current. In this way, a power supply loop is formed.

If left in this power-on state, the output current I _O will continue to flow through the collector of the transistor TR1 and eventually the voltage levels of the power supply voltage Vcc and the voltage dividing resistance voltage V will drop. Due to the voltage drop of the voltage dividing resistance voltage V, the base current cannot be supplied to the base of the transistor TR2. By stopping the supply of the base current, the transistor TR2 stops operating, and thus the transistor TR1 also stops operating.

With this configuration, not only is it possible to easily set the voltage level for stopping the supply of a desired power source by setting the voltage dividing resistance voltage of the power source detecting section 12, but it is also a problem in the market. It is possible to avoid leakage of electrolyte from the battery due to discharge. In particular, it is effective when used with toys handled by children.

[0023]

As is apparent from the above description, according to the overdischarge prevention circuit of the present invention, it is possible to prevent liquid leakage from the battery due to forgetting to turn off the power supply. In particular, it is effective when used with toys handled by children.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of an embodiment of an overdischarge prevention circuit according to the present invention.

FIG. 2 is a more specific circuit diagram of the overdischarge prevention circuit shown in FIG.

[Explanation of symbols]

 10 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Over discharge prevention circuit 11 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Changeover switch 12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Voltage detection circuit 13 ・ ・Output terminal Batt Battery TR1, TR2 ... Transistor C1 ... Capacitor

Claims (1)

[Claims] 1. An over-discharge prevention circuit for preventing over-discharge of a battery, comprising: a first transistor connecting one end side of the battery to a switching means and controlling and outputting a current from the battery; Voltage detection means for dividing the output voltage from the transistor to a desired ratio, and a divided voltage output terminal of the voltage detection means are connected to a control terminal of a second transistor for controlling the operation of the first transistor, and An over-discharge prevention circuit characterized in that the control terminal is connected in series with a capacitor and the switching means.