| 摘要 |
A lighting circuit for an HID lamp causing no erroneous operation of a lighting circuit even when counter-electromotive force is generated due to the inductance in the wirings when the lighting circuit and the HID lamp are located at a long distance and not causing flicker even when the inter-electrode resistance of the HID lamp differs depending on the direction of the application voltage, comprising a control section (C) adapted, upon application of an AC rectangular wave voltage to an HID lamp (1) by a full-bridge type inverter (9), for detecting a resistance value in a positive direction and a resistance value in a negative direction of the HID lamp (1) corresponding to the direction of the polarity of the AC rectangular wave voltage, setting the duty ratio between the positive direction and the negative direction of the AC rectangular waveform voltage so as to be in an inverse proportion with the magnitude for each of the resistance values, and switching each of the switching elements (12A-12D) of the inverter (9) so as to form a voltage waveform to be kept at a ground potential for a predetermined period of time when the direction of the AC rectangular waveform voltage is inverted.
|
