CHARGING TYPE POWER SUPPLY DEVICE

Japanese Patent JP3157121

B2

PROBLEM TO BE SOLVED: To make it impossible to charge a battery which is overdischarged and is in an abnormal condition and thereby prevent the destruction or other problems of the battery by not allowing charging current to flow by turning a switching circuit off when a secondary battery becomes a threshold voltage of a MOS transistor or below and a charger is connected at that time.
SOLUTION: When the voltage of a secondary battery 101 in an overdischarged condition becomes a threshold voltage of a P-channel MOS transistor 504 or below due to self discharge or other causes, a charge and discharge controlling circuit 102 outputs an overdischarge signal, in other words, sends a Low signal to an output terminal 112A and a High signal to a low voltage detecting circuit 107. Then, the low voltage detecting circuit 107 outputs a Low signal to an output terminal 112B regardless of the output of the charge and discharge controlling circuit 102 to turn the voltage between the gate and the source of a FET-B111 in a switching circuit 103 to zero volt and thereby turn the FET-B111 off. Even if a charger 108 is connected under this condition, the FET-B111 is in an off state and a parasitic diode is reversely connected and therefore charging current is not allowed to flow into the secondary battery 101.

Takayuki Takashina
Shinichi Yoshida
Hiroshi Mukainakano

JP2167697A

April 16, 2001

February 04, 1997

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Seiko Instruments Inc.

H02J7/10; G01R19/165; H01M10/44; H02H7/18; H02J7/00; H02J; (IPC1-7): H02J7/00

JP9163612A
JP984256A

Keinosuke Hayashi

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