Solid-state relay using light-emitting diodes

Claim 1

A fast response AC or DC solid state relay comprising: A. A pair of input terminals; B. A ''''coil'''' section comprising: a diode bridge arrangement having an input and an output, said input of said bridge being connected to said input terminals; at least one field effect transistor connected as a constant current element; and a light emitting diode forming a series circuit with said field effect transistor, said circuit being connected to the output of said bridge arrangement, said light emitting diode for emitting light continuously when a current of the appropriate polarity and magnitude passes through it; C. A pair of output terminals; D. A ''''contact'''' section being connected between said output terminals and comprising: first and second silicon-controlled rectifiers, each having an anode, a cathode, and a gate electrode, the anode of said first silicon-controlled rectifier being connected to the cathode of said second silicon-controlled rectifier and the anode of said second silicon controlled rectifier being connected to the cathode of said first silicon-controlled rectifier; and a photo sensitive field-effect transistor, said transistor having source and drain electrodes and a photo sensitive gate, said source electrode being connected to the gate of said first silicon-controlled rectifier and said drain electrode being connected to the gate of said second silicon-controlled rectifier so as to cause said silicon-controlled rectifiers to be in a conductive state in response to light emitted by said light emitting diode.