Circuit for operating voltage range extension for a relay

摘要

A relay is designed to be used in a circuit where the voltage levels are high in comparison to the spacing between the contacts when open. Contact closure arcing is suppressed by actuating a MOSFET that shorts the contacts together while they open. The same MOSFET can momentarily short the contacts together just before they first begin to close, allowing a test current to be passed through the MOSFET and through the terminals connecting to both relay contacts, to insure that arc suppression will be successful; and if this test fails, then the relay can be disabled by a switch in series with the relay coil to prevent arcing and a possible fire hazard. Relay deactuation can be sensed to trigger arc suppression, and relay actuation can be sensed to initiate fail-safe testing by a circuit that responds no matter which way the relay coil is connected into the external circuit that drives it.