A high-voltage discharge lamp operating device capable of reducing the
size and the weight of a DC-DC converter circuit, and accordingly of the
operating device without generating any magnetic saturation of a
transformer core part even when igniting a lamp in the operating device
for operating a HID head lamp for a vehicle. A PWM control unit (6)
comprises a power control unit (31) which receives a voltage detection
signal and controls the duty of the signal waveform of a PWM control
signal, an error amplifier (32) which compares the output from the power
control unit (31) with the reference voltage and outputs an error level
signal, an oscillation frequency control means (36) for outputting a
rectangular wave signal so as to realize a high frequency for a
predetermined period from the ignition of a HID lamp (5) and a low
frequency after the elapse of a predetermined period, a triangular wave
oscillator (34) which converts the rectangular wave signal into the
triangular signal, and a comparator (35) which compares the error level
signal with the triangular wave signal and outputs to a switching element
(12) the PWM control signal on H-level during the period in which the
triangular wave signal is high.