Patent ID: 7002305
Filing Date: 2006-02-21
Classification: H05B

Abstract:
1. An electronic ballast for a discharge lamp comprising: a power converter that provides a regulated output power for operating said discharge lamp, a lamp voltage monitor that monitors a lamp voltage being applied to said lamp from said power converter; a lamp current monitor that monitors a lamp current being supplied to said lamp from said power converter; a controller that regulates said power converter to vary said output power in accordance with said lamp voltage and lamp current being monitored, wherein said controller comprises: a lamp voltage table specifying a reference lamp voltage to be applied to said lamp, said reference voltage being defined to vary with respect to time elapsed from the start of said lamp; a voltage deviation detector that obtains a voltage-related deviation between said lamp voltage being monitored and said reference voltage corresponding to a time at which said lamp voltage is monitored, in order to give a voltage correction index indicative of said voltage-related deviation, an offset power provider that processes said voltage correction index to give an offset power varying with time, a lamp power table specifying a reference lamp power to be supplied to said lamp, said reference lamp power being defined to vary with respect to time elapsed from the start of said lamp; a target power generator that corrects said reference lamp power into a target lamp power in view of said offset power in accordance with an on-time basis, and a commander that provides a control command for regulating said output power in match with said target lamp power, said voltage deviation detector updating said voltage correction index over a plurality of times until a luminous flux of said lamp converges to a certain level, said target power generator updating said target lamp power in correspondence with said updated voltage correction index.