Mos-gated photo-coupled relay having a reduced turn-on time

摘要

A photo-coupled solid-state relay (38; 62; 84) and a method of activating the relay utilize a power-conserving technique to reduce the amount of current applied to a light-emitting diode (46; 70; 92) of an optical control circuit (40; 64; 86) of the relay, after the relay has been activated. The power-conserving technique can be used to reduce the turn-on time of the relay and/or reduce the amount of current consumed by the control circuit when the relay is activated. The solid-state relay may be used in a number of high power switching applications, such as a power switch in a modem of a personal computer. The control circuit includes first and second current paths (50 and 52; 74 and 76; 96 and 98) that connect the light-emitting diode to a current source. In operation, input current is conducted through the first and second current paths to the light-emitting diode to activate the output transistors (30 and 32) of the relay. After the output transistors have been activated, an active device (42 and 44; 66; 88) on one of the current paths is turned "off" to reduce the amount of input current applied to the light-emitting diode, while maintaining the output transistors in the activated state. <IMAGE>