Patent ID: 7541773

Claim:
A battery-powered tool comprising: a regulated power supply that supplies a fixed voltage; a motor driven by a battery pack, the battery pack generating a voltage that changes depending on a residual amount of charges in the battery pack and a load imposed on the motor; a main switch connected between the battery pack and the motor; a switching element connected in series with the motor, the battery pack and the main switch; a first voltage comparison circuit having a first input terminal applied with a first detection voltage indicative of a voltage of the battery pack, a second input terminal applied with a first reference voltage, and a first output terminal, the first voltage comparison circuit comparing the first detection voltage with the first reference voltage and selectively outputting one of a first signal and a second signal to the first output terminal, the first signal being output when the first detection voltage is above the first reference voltage and the second signal being output when the first detection voltage falls below the first reference voltage, wherein the switching element is rendered ON in response to the first signal whereas the switching element is rendered OFF in response to the second signal; and a motor-operation detecting circuit that detects a driving status of the motor and outputs a third signal when the motor is driven and a fourth signal when the motor is not driven, wherein the first voltage comparison circuit does not output the second signal when the third signal is output from the motor-operation detecting circuit.