OVERCURRENT PROTECTING CIRCUIT OF BATTERY

Japanese Patent JP3886501

B2

PROBLEM TO BE SOLVED: To improve a detecting accuracy by reducing the variation range of a resistor between a drain and a source of an FET used to detect a discharge overcurrent or charging overcurrent to the variation range of a battery voltage.
SOLUTION: A control circuit 3 uses a voltage between the battery 1, a first FET Q1 in series with the battery 1 and a second FET Q2 as an operating voltage. The control circuit 3 controls off the FET Q2 when the battery voltage VB is a predetermined value or more, energizes a discharge current Io to a parasitic diode D1 of forward direction of the FET Q2, and increases the drop voltage VDSS of the FET Q2 larger than that at the energizing time of a body. At this time, the value of a control signal DOUT for turning on the FET Q1 becomes a VB-VDSS of the operating voltage of the control circuit 3. Since this becomes a voltage VGS between the gate and the source of the FET Q1, the variation range of the resistor RDD between the drain and the source of the FET Q1 is reduced. Therefore, the variation range of the voltage of the FET Q1 for detecting the discharge overcurrent is reduced, and the detecting accuracy is improved.

Shinma Eitoshi

JP2004095284A

February 28, 2007

March 29, 2004

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Saitama NEC Corporation

H02H7/18; H02J7/00; H01M2/34; (IPC1-7): H02J7/00; H01M2/34; H02H7/18

JP8214460A
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Seisei Nishimura

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