Single-Chip Solid-State Relay

0 Light-duty (25 to 600 W ) solid-state relays 1 have recently been introduced on the marketby Sharp.These smalland com- pact devices switch accurately at the zero-crossing and provide the required electrical separation. The photograph shows clearly that switching occurs exactly at the zero-crossing. This D1 GD 1N 4001 S SINGLE-CHIP SOLID-STATE RELAY preventsswitch-oncurrentsoflamps D becoming large and so extends the life of the lamp. The breakdown voltage of the triac sec- tion is 2 kV and the pins are on a 0.1 in ST1 R1 1W G grid. C1 100n The relay requires an energizing cur- rentof10mA at1.4V,butwithinductive loadsabout25mA isnecessary. Theadditionalcomponentsshownin the diagram make the relay more universally usable. Diode Di prevents theICbeingdamagediftheinputis connected incorrectly. Transistor Ti sets the trigger current to precisely 10mA.TheRCnetworkattheoutput protects the triac from sharp voltage peaks. The IC may be used without heat sink to switch currents up to 1 A....