Charging circuit
AssigneeSanyo Electric Co., Ltd.
InventorMikitaka Tamai
Life of this patent
Estimating the term…
Abstract
An over-charge protection FET and an over-discharge protection FET are connected in series with the rechargeable battery and turned ON or OFF by a control circuit. An ON-OFF switching device is connected between G and S of the over-charge protection FET and controlled by an output signal from the control circuit. An over-charge protection FET drain voltage input circuit is connected to the input side of the ON-OFF switching device. When the drain voltage of the over-charge protection FET is high, the input circuit sets the ON-OFF switching device to the ON state to forcibly set the over-charge protection FET to the OFF state.
Claims21
A charging circuit for charging a rechargeable battery comprising:
- (1) an over-charge protection FET having a gate and a source, connected in series with the rechargeable battery, to protect the rechargeable battery from excessive charge;
- (2) an over-discharge protection FET connected in series with the rechargeable battery and the over-charge protection FET, to protect the rechargeable battery from excessive discharge;
- (3) a control circuit to prevent excessive charge and discharge of the rechargeable battery by detecting rechargeable battery voltage and controlling the ON-OFF state of the over-charge protection FET and the over-discharge protection FET;
- (4) an ON-OFF switching device having an input side, connected between the gate and the source of the over-charge protection FET and controlled by an output signal from the control circuit;
- and
- (5) a drain voltage input circuit connected to the input side of the ON-OFF switching device, which switches the ON-OFF switching device to the ON state when the drain voltage of the over-charge protection FET is high to forcibly maintain the over-charge protection FET in the OFF state.
A charging circuit for charging a rechargeable battery comprising:
- (1) an over-charge protection FET having a gate and a source, connected in series with the rechargeable battery, to protect the rechargeable battery from excessive charge;
- (2) an over-discharge protection FET connected in series with the rechargeable battery and the over-charge protection FET, to protect the rechargeable battery from excessive discharge;
- (3) a control circuit to prevent excessive charge and discharge of the rechargeable battery by detecting rechargeable battery voltage and controlling the ON-OFF state of the over-charge protection FET and the over-discharge protection PET;
- (4) an ON-OFF switching device having an input side, connected, between the gate and the source of the over-charge protection FET and controlled by an output signal from the control circuit;
- and
- (5) a drain voltage input circuit connected to the input side of the ON-OFF switching device, which switches the ON-OFF switching device to the ON state when the drain voltage of the over-charge protection FET is high to forcibly maintain the over-charge protection PET in the OFF state,
- (6) a resistor connecting the gate of the over-charge protection FET to the rechargeable battery;
- (7) a capacitor connected to said resistor and the gate of the over-charge protection FET to delay gate voltage rise in the over-charge protection FET;
- and wherein
- (8) the charging circuit is designed such that when rechargeable battery voltage is abnormally low, the capacitor delays the rise in gate voltage of the over-charge protection FET, the ON-OFF switching device is prevented from turning ON before the gate voltage rises, and the over-charge protection FET is kept in the ON state to allow charging of a rechargeable battery with low battery voltage but no internal short-circuit.
Dependencies are inferred from the claim text.