Patent ID: 6404261
Filing Date: 2002-06-11
Classification: H02J,H03K

Abstract:
A switch circuit for a battery-powered equipment comprising a 4-terminal bi-directional semiconductor switch and a protection diode, wherein the switch has a main current path between first and second main terminals that serve for coupling the switch in series with a battery between a power line and a reference line of the equipment, the switch has a control-gate terminal that serves for applying a control signal to the switch to form a conduction channel in a body region of the switch, the conduction channel forming part of the main current path for turning the switch on and off, the switch has a back-gate terminal coupled to said reference line to form a bias path that serves for applying a bias potential to the body region, and the protection diode has a diode path coupled to a terminal of the switch to protect the switch and battery in the event of a reverse voltage polarity across the first and second main terminals of the switch, the switch circuit being characterised by the diode path being coupled in the bias path in series with the back-gate terminal so as to provide in the bias path a rectifying barrier that blocks current flow between the body region and the back-gate terminal in the event of a reverse voltage polarity across the first and second main terminals.