Patent ID: 8314570

Claim:
A high pressure discharge lamp light source device, comprised of a high pressure discharge lamp having a discharge vessel made from quartz glass and a pair of electrodes arranged oppositely to each other with a spacing of at most 2.0 mm, each electrode having a projection formed at a tip end thereof, and mercury of at least 0.20 mg/mm 3 and a halogen being enclosed in said discharge vessel; and a power supply device for supplying alternating current to said high pressure discharge lamp, wherein the power supply device is adapted to switch between a nominal electric power lighting mode and a low electric power lighting mode, said current in the low electric power lighting mode having a defined current value in a range of 40% to 70% of the nominal electric power consumption, wherein said power supply device, in the low electric power lighting mode, is adapted to alternatingly supply to said high pressure discharge lamp a base current having a defined frequency chosen from a range between 100 Hz and 5 kHz and a boost current having a higher current value than a current value of said base current, and wherein said power supply device satisfies the following conditions: a boost rate a of 1.2 to 3.5, an effective supply time b of the boost current of 0.1 to 3 ms, and a supply time c of the base current of 1 to 400 ms; and wherein the parameters a, b and c are chosen such as to satisfy the formula 0.0009≦a×b÷c≦3.5, with the boost rate a being a quotient of Ib/Ia, Ib being the value of the boost current and Ia being the value of the base current, b being the effective supply time in ms in which said the boost current of value Ib is supplied to one electrode, and c being the time in ms in which the base current of value Ia is supplied.