Power switch with normally on transistor

Abstract

A power switch comprising: a cascode having a normally ON transistor connected in series with a normally OFF transistor at a cascode node; a safety switch between a gate of the normally ON transistor and a first ground common to the cascode and the switch; and a controller comprising: a controller power supply having a power supply output connected to the cascode node at which output the controller power supply provides a voltage relative to a second ground that is floating relative to the first ground; a first controller output connected to the gate of the normally ON transistor at which the controller generates a first voltage relative to the second ground; wherein the controller power supply is connected to the safety switch and voltage provided by the controller power supply is coupled to and operates to maintain the safety switch OFF and nonconducting and in the absence of the voltage the safety switch is turned ON and conducting.

Dependencies are inferred from the claim text.