JP2559633Y2 - 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 charging control device.

[0002]

2. Description of the Related Art Recent electronic equipment such as a portable personal computer or a word processor is configured to be driven by a built-in rechargeable secondary battery, as shown in FIG. (2
0), the battery (21) is charged. When the battery is fully charged, the charge control circuit (22) turns off the switching transistor (20) to prevent overcharging (see, for example, No. 61-1227).

[0003]

When the switching transistor is destroyed and short-circuited despite the fact that the control circuit outputs a signal to make the switching transistor non-conductive, the battery is fully charged. However, there is a problem that a large charging current continues to flow and the battery is deteriorated or destroyed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and includes a switching transistor and a current detection resistor provided in a charging path of a secondary battery, and a full charge of the secondary battery. Control means for controlling the switching transistor to be non-conductive at the time, and controlling to shift to trickle charging when a voltage is detected between the current detection resistors during the non-conductive control.

[0005]

The present invention is constructed as described above, so that when the secondary battery is fully charged and the control means turns off the switching transistor to stop charging, if a voltage is generated across the current detection resistor, trickle charging is performed. By controlling to shift, deterioration or destruction due to overcharge of the secondary battery is prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

[0007] (1) is a known switching power supply circuit,
The control is performed by the oscillation control circuit (2) to generate a predetermined output voltage on the secondary side of the transformer (3). The output voltage on the secondary side is rectified by a diode (4) so as to act as a charging voltage, and then supplied to a secondary battery (8) via a current detection resistor (5), a switching transistor (6) and a diode (7). Supplied.
(9) is a charge control circuit composed of a microprocessor, which controls the conduction of the switching transistor (6), detects the charge amount of the secondary battery (8), and detects the voltage between the current detection resistors (5). ing. Reference numeral (10) denotes a photocoupler connected between the oscillation control circuit (2) and the charge control circuit (9). The charge control circuit (9) controls the light emission luminance of the light emitting diode (11), so that the oscillation control circuit ( 2) to control the output current on the secondary side of the transformer (3).

Next, the operation of the present invention having the above configuration will be described with reference to the flowchart of FIG.

First, when the secondary battery (8) is charged, the output of a signal for turning on the switching transistor (6) from the charge control circuit (9) causes the switching transistor (6) to turn on and the secondary battery to turn on. Charging is performed until the battery (8) is fully charged (steps (S1) and (S1)).
2)). At this time, the charge control circuit (9) controls the light emission luminance of the light emitting diode (11) of the photocoupler (10) according to the terminal voltage between the current detection resistors (5), so that the oscillation control circuit (2) controls the phototransistor ( Oscillation control is performed based on the signal of 12). This allows the transformer (3)
Is made constant current, and the secondary battery (8) is charged with constant current.

Next, when charging proceeds and the secondary battery (8) is fully charged, the voltage of the secondary battery (8) is detected and step (S2) is performed.
The charge control circuit (9) that has detected the full charge at step (S)
In 3), the switching transistor (6) is turned off to stop charging the secondary battery (8). This prevents overcharge of the secondary battery (8).

The charging control circuit (9), which has stopped charging in this way, subsequently checks in step (S4) whether or not a voltage is generated between the current detection resistors (5), and the switching transistor (6) is short-circuited. Detect if not. If the switching transistor (6) is normal, the transistor (6) is non-conductive, the charging current does not flow, and no voltage is generated between the current detection resistors (5). However, when the switching transistor (6) is broken and short-circuited, a charging current flows regardless of the non-conduction signal from the charging control circuit (9), and a voltage is generated between the current detection resistors (5).
Therefore, the charge control circuit (9), which has detected the voltage generation in step (S4), proceeds to step (S5) to control the light emission of the light emitting diode (11) of the photocoupler (10), thereby oscillating through the phototransistor (12). The control circuit (2) is controlled to perform trickle charging. That is, the oscillation control circuit (2) controls the oscillation of the switching power supply circuit (1), the charging current flowing to the secondary battery (8) decreases, and the adverse effect on the secondary battery (8) can be reduced.

Thus, the switching transistor (6)
Even if the battery is short-circuited, it is possible to prevent a large charging current from continuing to flow and to prevent the secondary battery from deteriorating.

[0013]

As described above, the charge control device of the present invention is provided with a means for detecting whether or not the switching transistor for controlling charging of the secondary battery has been destroyed. By controlling to shift to the charging mode, a large charging current is prevented from continuing to flow in the secondary battery to protect the secondary battery, and the practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a charge control device of the present invention.

FIG. 2 is a flowchart showing the operation of FIG.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switching power supply circuit 2 Oscillation control circuit 5 Current detection resistor 6 Switching transistor 8 Secondary battery 9 Charge control circuit

Claims (1)

(57) [Scope of request for utility model registration] A switching transistor and a current detection resistor provided in a charging path of the secondary battery;
Turn off the switching transistor when fully charged
At the time of the non-conduction control.
Control means for controlling a transition to trickle charging when a voltage is detected between the output resistances .