OVERCHARGE PROTECTION DEVICE AND METHODS FOR LITHIUM-BASED RECHARGEABLE BATTERIES

摘要

This invention includes a battery overprotection device comprising a thermal resistor, a zener diode, a pass element and a control circuit. The thermal resistor is used as an over-temperature limiting device, rather than an overcurrent device. By thermally coupling the thermal resistor to the zener diode, the thermal resistor protects the zener diode from "burning up" as a result of continuous power dissipation. When the zener is subjected to continuous power dissipation, its temperature rises. As the temperature rises, the thermal resistor's impedance increases, thereby reducing the power dissipation in the zener. The zener/thermal resistor combination serves as an auxiliary safety circuit for the transistor and control circuit.