Bidirectional current blocking MOSFET for battery disconnect switching including protection against reverse connected battery charger

摘要

A bidirectional current blocking switch is disclosed. The switch includes a four-terminal MOSFET in which there is no source-body short. The voltages applied to the source and drain terminals are both higher than the voltage applied to the body terminal (for an N-channel) device so that the source-body and drain-body junction of the MOSFET never become forward-biased. The switch of this invention is particularly useful for switching a cascaded set of batteries in a portable computer. Also included is a disclosure of circuitry to protect the switch against a reverse connected battery charger.