DC or AC solid state switch with improved line-derived control circuit power supply

Claim 1

A solid state switch having an improved line-derived control circuit power supply and being operable to control either a D.C. or A.C. load supplied from a respective D.C. or A.C. electrical power supply source comprising: a pair of power supply terminals to which either said D.C. or A.C. electrical power supply source is connected; a pair of solid state switching means connected in series with each other and said power supply terminals and said D.C. or A.C. load and being opposed with respect to one another so as to be operable to control current flow from said source to said load in positive and negative directions, respectively, on A.C. and in said positive direction on D.C. and each said solid state switching means comprising unidirectional current conducting means in parallel therewith for passing the current controlled by the other solid state switching means; a common control circuit for said pair of solid state switching means supplied from said source for applying turn-on signals simultaneously to the same to control current flow from said source to said load; external selectively controllable on-off logic signal input means for operating said common control circuit; and a power supply circuit for said common control circuit connected to and supplied from said power supply terminals and including means connecting said power supply terminals and said unidirectional current conducting means of one of said solid state switching means in series to said common control circuit exclusive of said load and the other solid state switching means thereby to avoid leakage current in the load during at least alternate half-cycles of the source voltage; said power supply circuit comprising a diode-isolated, capacitive-reactively coupled voltage dropping line power supply to said common control circuit.