Electronic ballast for a discharge lamp

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.