| 摘要 |
<p>A solid-state relay having a photo-coupler for controlling supply of AC power to a load (12) is improved so as to eliminate the problem of counterelectromotive force which could happen when the load (12) contains an inductive component and the power to the load (12) is turned off. The solid-state relay of the present invention typically comprises a first and a second light emitting diode (4, 15) which are adapted to be lit up by an input signal; photo-diodes (5) which are optically coupled to the first light emitting diode (4) and are adapted to selectively supply AC electric power from a power source (13) to the load (12) depending on whether the light from the first light emitting diode (4) is being received or not; a photo-triac (18) which is optically coupled to the second light emitting diode (15) and is adapted to supply the AC electric power from the power source (13) to the load (12) depending on whether the light from the second light emitting diode (15) is being received or not; a time delay circuit (24) which maintains the second light emitting diode (15) lit up for a certain time interval after the input signal is terminated; and a triac (19) for terminating the supply of the AC electric power to the load (12) when voltage of the power source (13) is below a certain level.</p> |
