Patent ID: 8686668

Claim:
Apparatus for maintaining at least a holding current in a leading-edge phase-cut dimmer during a period of transient voltage variations, the apparatus connectable to the dimmer and connectable to a load connected to draw current from the dimmer, the apparatus comprising: an edge detector connected to receive a voltage from the dimmer and generate a leading-edge signal in response to a leading-edge of a phase-cut waveform; and a current offset circuit connected to receive the leading-edge signal and draw a supplementary offset current in response to the leading-edge signal, wherein the supplementary offset current is sufficient to maintain at least a holding current in the dimmer during the period of transient voltage variations; wherein the current offset circuit comprises a holding current circuit configured to draw a supplementary current at least as great as a difference between a holding current of the dimmer and a load current when the dimmer is in conduction and the load current is less than the holding current.