PURPOSE: To have the captioned discharge lamp lighted and maintained with stability by a method wherein a pulse is impressed on an arc restriking region of lamp voltage and said pulse voltage is changed in response to lamp impedance.
CONSTITUTION: A power current flowing in a discharge lamp 3 is limited by a current-limit element 2 and an arc restriking pulse is impressed on the arc restriking region of the discharge lamp 3 from a pulse generation circuit 4 to light and maintain the lamp by making the source voltage to come close to the lamp voltage. The pulse generation circuit 4 controlls the oscillation constant of an oscillation circuit 8 at an oscillation control part 9 by a signal of a lamp impedance detection circuit 5 in response to the impedance of the discharge lamp 3 to control impression power from a pulse impression part 6. That is to say that when the lamp impedance is 50W1,000Ω, pulse power is made to vary according to a change of the lamp impedance. Further, in case lamp impedance is less than 50Ω and not less than 1,000Ω, the pulse power is made equal to or less than the pulse voltage when said voltage is 50Ω and 1,000Ω respectively.
HORII SHIGERU
OZAWA MASATAKA
YOSHIKAWA NOBUHISA
KOYAMA KAZUTAKA
