Power supply apparatus for lamp

Abstract

A power supply apparatus useful for starting and driving a discharge lamp 22 includes a DC-to-DC converter 16 for converting a DC signal from a DC power supply to a second DC signal having a predetermined magnitude which is supplied to the lamp. A current detector 24 develops a DC current representative signal representing DC current supplied to the lamp from the DC-to-DC converter. A combination of the current detector 24, a DC voltage detector 26 and a multiplier 30 develops a DC power representative signal representing DC power supplied from the DC-to-DC converter to the lamp. An error amplifier 32 develops a DC current error signal representing the difference between the DC current representative signal and a predetermined DC current reference signal. An error amplifier 36 develops a DC power error signal representing the difference between the DC power representative signal and a predetermined power reference signal. For a predetermined time period following the start of operation of the power supply apparatus, a combination of a delay circuit 42, a comparator 48 and a clamping diode 52 clamps the DC power error signal so that only the DC current error signal can be outputted. A driver unit 18 controls the DC-to-DC converter 16 in such a manner as to make the DC current error signal zero.

Dependencies are inferred from the claim text.