| 摘要 |
PROBLEM TO BE SOLVED: To solve the problems that, when a conventional thermionic cathode type discharge lighting device starts at preheating and moves to a lighting stage, a discharge lamp turns on at a capacitance range of frequency (a frequency lower than f0) impedance exceeding a resonant frequency f0 of a series LC resonant circuit frequency-gain curves caused by a variable response of the discharge lamp, and then, resonance deviation wherein a current phase flowing in a half-bridged switching element advances ahead of its voltage is generated, and the discharge lamp is destroyed due to increase of heat generation of the switching element. SOLUTION: The discharge lamp lighting device has a frequency control circuit capable of surely turning on the discharge lamp at a frequency higher than a resonant frequency f0, as a direct-current voltage is arbitrarily set up on a variable-capacitance diode based on respective power source starting periods, preheating periods, starting periods, and lighting periods, and the direct-current voltage at the time of starting is set up to be a setting value wherein its frequency becomes higher than the resonant frequency f0 of the series LC resonant circuit frequency-gain curves. COPYRIGHT: (C)2008,JPO&INPIT |
