Patent ID: 6331764
Filing Date: 2001-12-18
Classification: H01L,H01M,H02H,H02J,Y02E

Abstract:
A protection device comprising:a switch having an input terminal and an output terminal, the output terminal for connection to a terminal of a rechargeable battery to be charged, the switch preventing current to flow from its input terminal to the output terminal and into the rechargeable battery when it is opened; anda switch protection circuit comprising a zener diode and a thermal resistor connected in series, the switch protection circuit for connection in parallel with output terminals of a battery charger, the zener diode being thermally coupled to the thermal resistor and a cathode of the zener diode being connected to the input terminal of the switch;wherein the zener diode protects the switch from overvoltage conditions by shunting current away from the switch, and the thermal resistor protects the zener diode from overtemperature conditions by entering a high impedance state to effectively disconnect current from the battery charger when the temperature of the zener diode exceeds a predetermined threshold.