To provide a stabilizer circuit for a gas discharge lamp in which ignition to the lamp before a cathode is sufficiently heated can be prevented.

In a constitution for controlling a power switch, a comparator 18 circuit generates a comparator output signal to compare a signal at a first input contact with a periodic signal at a second input contact, change a condition when the first signal compared becomes larger than the second signal compared with, and further change a condition when the second signal compared with becomes larger than the first signal compared. A first circuit generates a signal to the first input contact when first energizing a converter, in order to prevent a lamp 12 from igniting an arc while a lamp cathode is heated. A second circuit generating a signal which makes the first input contact ignite the lamp 12, detects an AC current in a resonance load circuit 16 and includes a feedback circuit generating a feedback signal proportional to the AC current. After expected period from first energizationof a conversion circuit 14 to heating of a lamp cathode, the feedback signal is connected to the first input contact.