JPH05174874A - Protective device for storage battery pack - Google Patents

Abstract

PURPOSE:To protect a storage battery pack surely as well as to prevent a danger by operating instantly before a spark is generated, by stopping a load current instantly by detecting the load voltage. CONSTITUTION:When a load 2 is normal, the current at a point A is within the scope of a rating voltage. And when a short circuit is generated at the load 2, and an excessive load current flows, the output voltage is reduced according to the value of the load current exponential-functionally. When the output voltage at the point A is made less than a specific value, the voltage at a point B is made less than the minimum voltage to communicate a transistor 42 by the preset ratio of partial pressure resistances 43 and 44. As a result, the voltage at a point C is increased making a transistor 41 off so as to stop the flow of the load current. Therefore, the potential at the point C can be regarded as an overload signal to indicate an overload condition. Consequently, the battery pack 1 can be protected surely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for a storage battery pack used in electronic equipment such as radio equipment.

[0002]

2. Description of the Related Art FIG. 2 shows a structure of a conventional storage battery pack protection device. In FIG. 2, reference numeral 1 denotes nickel-cadmium (Ni-Cd) as a rechargeable secondary battery.
A battery pack (hereinafter simply referred to as a battery pack),
2 is a receiving circuit that operates using the battery pack 1 as a power source,
It is a load as an electronic device including a transmission circuit and other circuits. Usually, the battery pack 1 is configured by combining a plurality of battery cells 11 in series / parallel so as to obtain a desired voltage and supply current. Further, reference numeral 12 is a temperature detection type switch incorporated in the battery pack 1 and turned off when the temperature exceeds a certain temperature.

If the load 2 is short-circuited for some reason, an excessive current flows from the battery pack 1 to the load 2. Then, since the temperature of the battery cell 11 rises due to this excessive current, the switch 12 that has detected the temperature is turned off, and the current flowing through the load can be stopped to protect the battery pack.

[0004]

However, in the above-mentioned conventional example, since the switch 12 is of the temperature detection type, it takes a long time until the switch 12 is turned off due to an excessive current. Therefore, there is a problem that a spark is generated when the load 2 is short-circuited, and the use of this electronic device near a highly flammable substance is dangerous.

The present invention solves the above problems,
An object of the present invention is to provide an excellent protection device for a storage battery pack, which can protect a battery pack reliably by preventing the danger by operating instantaneously before a spark occurs even when the load is short-circuited. And

[0006]

In order to achieve the above object, the present invention provides a voltage detecting means for generating an overload signal when a load voltage applied to a load becomes a predetermined value or less, and a voltage detecting means for receiving the overload signal. And a current control means for stopping the current flowing through the load.

[0007]

Therefore, according to the present invention, when the load is short-circuited, the load voltage is detected and the load current is momentarily stopped when the load is short-circuited. Therefore, the generation of sparks is suppressed and the battery pack can be reliably protected. To do.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to FIG.
Will be described. In FIG. 1, 1 and 2 are a battery pack and a load as in FIG. Reference numeral 3 denotes a protection circuit which is a feature of the present invention, and includes a transistor 31 as a current control means, a transistor 32, a voltage detection means including resistors 33 and 34 for dividing a load voltage, and a resistor 3.
5 and 36.

Next, the operation of the above embodiment will be described. When the load 2 is normal, the load voltage at point A is within the rated voltage range. In this case, resistors 33 and 3
The voltage at the point B divided by 4 is sufficient to turn on the transistor 32. Therefore, the potential at the point C becomes a low value, the base current flows between the emitter and the base of the transistor 31, the resistor 35, the transistor 32, and the resistor 36, and the transistor 31 maintains the conductive state.

When the load 2 is short-circuited and an excessive load current flows, the output voltage, that is, the voltage at the point A, depends on the magnitude of the load current due to the characteristics of the battery pack 1 which is a secondary battery. It decreases exponentially. When the voltage at the point A becomes equal to or lower than a predetermined value, the voltage at the point B becomes lower than the minimum voltage for conducting the transistor 32 due to the preset ratio of the voltage dividing resistors 33 and 34. Therefore, the potential at the point C becomes high, the transistor 31 is turned off, and the load current does not flow. That is, the potential at the point C can be regarded as an overload signal indicating an overload state.

As described above, since the short-circuited state of the load 2 is electrically detected without detecting the temperature rise, it is possible to instantaneously respond to an excessive current, and thus it is possible to prevent the generation of sparks due to the short-circuit. As a result, reliable protection can be achieved without providing a switch inside the battery pack.

In the protection circuit 3 of the above embodiment,
A differential amplifier may be used instead of the transistor 32 to detect the load voltage (output voltage) with high accuracy. Further, as in the conventional example, a temperature detection type switch may be provided in the battery pack 1 to form a double protection device.

[0013]

As is apparent from the above-described embodiment, the present invention provides a spark protection circuit that operates instantly when the load of the battery pack is short-circuited, so that the sparks caused by the short-circuiting of the load can be prevented. This has the effect of preventing the battery pack and ensuring the protection of the battery pack.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a protection device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional protection device.

[Explanation of symbols] 1 nickel-cadmium battery pack 2 load 3 protection circuit 11 battery cell 12 temperature detection type switch 31, 32 transistor 33-36 resistance

Claims (1)

[Claims] 1. A voltage detecting means for generating an overload signal when the load voltage applied to the load is equal to or lower than a predetermined value, and a current control means for limiting a current flowing through the load when the overload signal is received. A storage battery pack protector equipped.