Solid state relay circuit employing MOSFET power switching devices

Claim 1

A solid state relay employing a MOSFET device as its power switching element; said solid state relay comprising an input circuit for receiving low voltage, low power input switching signals which vary between an on value and an off value; an oscillator circuit connected to said input circuit for producing a relatively high frequency output in response to said on value switching signal; a control circuit for applying and removing gate voltage to said MOSFET device and coupling means for coupling said control circuit to said high frequency output; said control circuit including control transistor means connected to the gate of said MOSFET device and operable to discharge the gate capacitance of said MOSFET device when said control transistor means is conductive; capacitance means coupled between the gate of said control transistor means and said coupling means for rendering said control transistor means nonconductive in the presence of an output from said coupling means; and circuit means including a diode directly connecting the output of said coupling means to the gate of said MOSFET device and to said control transistor means, whereby said circuit means including said diode can cause charging of the gate capacitance of said MOSFET device only when said control transistor is nonconductive.