| 摘要 |
PURPOSE: A protection circuit for charger battery is provided to lengthen useful life of the battery by setting a discharge limiting voltage at an appropriate level regardless of the change of load amount. CONSTITUTION: A protection circuit comprises a residual voltage dividing unit(32) for dividing, at a predetermined ratio, the residual voltage of a charger battery(31), wherein the residual voltage dividing unit changes the ratio in accordance with the control of a voltage division control unit; a residual voltage detection unit(33) for detecting whether the current residual voltage has reached the level of the discharge limiting voltage, based on the voltage divided by the residual voltage dividing unit; a discharged current detection unit for detecting the amount of change of discharged current from the charger battery, and outputting a detection voltage according to the result of the detection; and the voltage division control unit for controlling the voltage dividing ratio of the residual voltage dividing unit in accordance with the detection voltage output from the discharged current detection unit.
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