Patent ID: 8115421
Filing Date: 2012-02-14
Classification: G02F,H05B

Abstract:
1. A discharge lamp lighting device comprising: an inverter circuit which supplies electric power to a discharge lamp provided with a hot cathode; and a preheating circuit which supplies a preheating current to the hot cathode of the discharge lamp by a switching operation of the inverter circuit, wherein a burst dimming signal to determine a ratio between an ON period and an OFF period is inputted, a lamp current for the discharge lamp is stopped from flowing in the OFF period of the burst dimming signal while a voltage is applied to both ends of the discharge lamp, the lamp current is supplied in the ON period of the burst dimming signal by causing a dielectric breakdown of the discharge lamp, the preheating current is supplied constantly to the hot cathode of the discharge lamp in the ON period and the OFF period of the burst dimming signal, the inverter circuit is an inverter circuit of a frequency variable type in which power supply to the discharge lamp is reduced as a drive frequency increases, and the lamp current to the discharge lamp is stopped from flowing while the hot cathode is continuously preheated in the OFF period of the burst dimming signal by increasing the drive frequency of the inverter circuit up to such a level that a voltage-current characteristic of the inverter circuit have no intersecting point with a voltage-current characteristic of the discharge lamp.