Solid-state relay

Abstract

A solid-state relay having a photo-coupler for controlling supply of AC power to a load is improved so as to eliminate the problem of counterelectromotive force which could happen when the load contains an inductive component and the power to the load is turned off. The solid-state relay of the present invention typically comprises a first and a second light emitting diode which are adapted to be lighted up by an input signal; a photo-diode which is optically coupled to the first light emitting diode and is adapted to selectively supply AC electric power from a power source to the load depending on whether the light from the first light emitting diode is being received or not; a photo-triac which is optically coupled to the second light emitting diode and is adapted to supply the AC electric power from the power source to the load depending on whether the light from the second light emitting diode is being received or not; a time delay circuit which maintains the second light emitting diode lighted up for a certain time interval after the input signal is terminated; and a triac for terminating the supply of the AC electric power to the load when voltage of the power source is below a certain level.

Dependencies are inferred from the claim text.