Patent ID: 7619391

Claim:
A battery powered electrical appliance comprising: a rechargeable battery for supplying electrical power for operating the electrical appliance; a battery circuit selectively connectable to the rechargeable battery and including an adverse condition detecting circuit for detecting an adverse operating condition of the rechargeable battery and generating a disable signal in response to detection of an adverse operating condition of the rechargeable battery; a control circuit connected to an electrically driven load of the electrical appliance for controlling operation of the electrical appliance and sending an enable signal to the battery circuit to operate the electrical appliance; and an interface circuit interposed between and connecting the battery circuit and the control circuit to each other, a single link connecting the interface circuit to the battery circuit, the enable signal being forwarded to the battery circuit through the single link and the disable signal being forwarded to the interface circuit through the single link, the interface circuit generating a logic signal in response to receiving a disable signal and supplying the logic signal to the control circuit to stop operation of the electrical appliance, the interface circuit including first and second comparators, each comparator having a reference terminal and an input terminal, a first resistor connected in the single link, and a voltage divider connected between the single link, on a first side of the resistor, closer to the control circuit than to the battery circuit, and ground, supplying respective reference potentials to the reference terminals of the first and second comparators to establish an operating range for a detected operating condition of the rechargeable battery, wherein the input terminals of the first and second comparators are connected to the single link at a second side of the resistor, closer to the battery circuit than to the control circuit, for supplying the disable signal to the first and second comparators to generate the logic signal.