Control circuit for gradual extinction of lighting - has phase controlled triac. with RC circuit and diode bridge connected in parallel to switch

摘要

The device is for controlled gradual extinction of lighting following switching out of the lighting circuit, normally for safety reasons. The control circuit (15) is connected in parallel across the lighting switch (12) in one power line. The parallel circuit is based on a phase controlled triac (19) or a pair of thyristors connected back to back in series with an anti-parasitic choke (30). Triggering of the triac is from a diode bridge (27) and a phase shifting RC (21, 22) potentiometer via a diac (25) or a gas filled tube controlling the trigger threshold. The delayed switch-off occurs due to the discharge time of a CR pair (26, 28) across the bridge.