JP3203378B2 - Battery charge control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charge control device for charging a battery of a portable telephone, for example.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a conventional battery charge control device of this type. In FIG. 2, 1 is a battery charge control device,
Reference numeral 2 denotes a battery to be charged. The battery charging control device 1 includes a main charging circuit 5 having one end connected to an external input power supply and the other end connected to a terminal of the battery 2 and having a protection diode 3 and a control switch 4, and an auxiliary charging circuit 6 described later. And the resistor 7,
8, a voltage detection circuit 9 for detecting the cell voltage of the battery 2 and a microcomputer for controlling the control switch 4 and the auxiliary charging circuit 6 according to the output signal of the voltage detection circuit 9 (Called a microcomputer). The battery 2 includes a battery cell 11 and a protection circuit.
12 and a protection resistor 13.

[0003] In the battery charge control device 1 having the above configuration,
For example, when charging a lithium ion battery, constant voltage charging is performed so that the charging control voltage does not exceed 4.10V. The cell voltage extracted from the battery cell 11 through the protection resistor 13 is divided by the resistors 7 and 8 of the voltage detection circuit 9 and the detection signal is input to the microcomputer 10. The microcomputer 10 controls the control switch 4 based on the output signal, and inputs the voltage of an external input power supply, for example, the output voltage DC 5.8 V of the AC adapter to the control switch 4 through the protection diode 3 to make the charge control voltage and the battery terminal Add to

Here, when the battery voltage is reduced to a so-called overdischarge state of 2 V or less, constant voltage charging is performed through an auxiliary charging circuit 6 for slowly charging according to an auxiliary charging command voltage output by the microcomputer 10. I have to.

[0005]

However, in the battery charge control device 1 having the above-mentioned conventional configuration, the microcomputer 10 that controls the auxiliary charging circuit 6 does not guarantee normal operation when the battery voltage is 3 V or less. There was a problem that the charging circuit 6 malfunctioned.

The present invention solves such a problem of the prior art. When the battery is in an overdischarged state, it operates automatically and completely independently of the control of the microcomputer to reduce the battery voltage to a certain level. It is an object of the present invention to provide a battery charging control device that stably charges.

[0007]

In order to achieve the above object, a battery charging control device according to the present invention comprises a main charging circuit having one end connected to an external input power supply and the other end connected to a terminal of a battery, and having a control switch. A sub-charging circuit connected in parallel to the main charging circuit and having an output voltage slightly lower than the charging control voltage of the battery, a voltage detecting circuit for detecting a cell voltage of the battery, and an output signal of the voltage detecting circuit. and a color and a microcomputer for controlling the control switch of the main charging circuit based, the sub charging circuit the microcomputer
Operates independently of the chromatography data and the battery voltage, when said drops under the output electric pressure of the sub-charging circuit can charge through pre SL sub charging circuit, the output voltage of the battery voltage is the secondary charging circuit When the above is reached, the battery is charged through the main charging circuit.

The sub-charging circuit comprises a constant voltage circuit for outputting a predetermined voltage and a series circuit of a diode for turning off the sub-charging circuit when the output voltage exceeds the predetermined voltage.

According to the above configuration, when the battery voltage is in an overdischarge state equal to or lower than the output voltage of the sub-charging circuit, the constant-voltage circuit automatically operates and charging is performed through the sub-charging circuit. When the voltage reaches or exceeds the output voltage of the sub-charging circuit, the diode connected in series with the constant voltage circuit turns off the auxiliary charging circuit and charges the battery through the main charging circuit controlled by the microcomputer.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a battery charge control device according to an embodiment of the present invention, and the same reference numerals are given to the same functional portions as in FIG. That is, 1 is a battery charge control device, 2 is a battery, 3 is a protection diode, 4 is a control switch, 5 is a main charging circuit, 7 and 8 are resistors, 9 is a voltage detection circuit, 10 is a microcomputer, 11 is a battery cell,
12 is a protection circuit, and 13 is a protection resistor. Reference numeral 20 denotes a characteristic part of the present invention, which is a sub-charging circuit connected in parallel to the main charging circuit 5, and is composed of a series circuit of a constant voltage circuit 21, a diode 22, and a resistor 23. The sub charging circuit 20 outputs a constant voltage slightly lower than the charge control voltage of the battery.

Next, the charging operation of the battery charging control device 1 in the above embodiment will be described. First, a cell voltage is extracted from the battery cell 11 through the protection resistor 13, divided by the resistors 7 and 8 of the voltage detection circuit 9, and a signal corresponding to the cell voltage is input to the microcomputer 10. The microcomputer 10 calculates the battery 2 to have a predetermined charge control voltage based on the signal, and sends a charge command signal to the control switch 4.

If the battery voltage has dropped to an overdischarged state of 2 V or less, the microcomputer 10 does not guarantee normal operation. 20 is used for charging. Secondary charging circuit 20
Is automatically turned on when the battery voltage is sufficiently low, and the microcomputer 10 is charged at a constant voltage of, for example, about 3.5 V at which the operation of the microcomputer 10 is guaranteed. And the battery voltage gradually rises to 3.5V
Is exceeded, the sub-charging circuit 20 is turned off due to the polarity of the diode 22, and normal operation of the microcomputer 10 is guaranteed at this voltage. Thereafter, charging is performed through the main charging circuit 5.

[0013]

As described above, according to the present invention,
When the battery to be charged is in the overdischarged state, the battery is charged slowly through the sub-charging circuit that operates automatically, and when the battery voltage reaches the output voltage of the sub-charging circuit, the main charging is performed by the guaranteed control of the microcomputer. Since charging is performed through the circuit 5, stable charging can be performed at all times, and the effects such as a simple circuit configuration can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a battery charge control device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional battery charge control device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 battery charging control device 2 battery 3 protection diode 4 control switch 5 main charging circuit 7
8: resistance, 9: voltage detection circuit, 10: microcomputer, 11
... battery cell, 20 ... sub-charging circuit, 21 ... constant voltage circuit,
22… Diode.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36

Claims (2)

(57) [Claims] 1. A main charging circuit having one end connected to an external input power supply and the other end connected to a terminal of a battery and having a control switch, and an output voltage connected in parallel with the main charging circuit and slightly lower than a charging control voltage of the battery. It includes a sub-charging circuit having a voltage detection circuit for detecting the cell voltage of the battery, and a microcomputer for controlling the control switch of the main charging circuit based on an output signal of said voltage detection circuit, the secondary charging
The circuit operates independently of the microcomputer,
The battery voltage is above when wanted lower <br/> the output current pressure or under sub-charging circuit to charge through pre SL sub charging circuit, the battery voltage reaches the higher output voltage of the auxiliary charging circuit A battery charging control device characterized in that charging is performed through a main charging circuit at times. 2. The sub-charging circuit comprises a constant voltage circuit for outputting a predetermined voltage, and a series circuit of a diode for turning off the sub-charging circuit when the output voltage exceeds the predetermined voltage. Item 2. The battery charge control device according to Item 1.