ARRANGEMENT FOR DIMMING AT LEAST TWO PARALLEL-ARRANGED DISCHARGE LAMPS

摘要

An AC supply system for two or more parallel discharge lamps with means for dimming the lamps in steps. There are n ballast impedances for each lamp (n = 2 or more) and n-1 diode bridges therefor. Each diode bridge is connected in series with at least one ballast impedance and in parallel with another ballast impedance. Two diagonal terminals of each diode bridge an connected to the corresponding diagonal terminals of the corresponding diode bridge for another one of the lamps. There are n-1 switching elements arranged to selectively interconnect the aforesaid diagonal terminals of the respective diode bridges in a manner such that the number of dimming steps is greater than the number of ballast impedances per lamp and wherein a failure of one or more lamps does not affect the light output of the remaining lamps.