Patent ID: 7315133
Filing Date: 2008-01-01
Classification: H05B

Abstract:
1. A discharge lamp lighting apparatus comprising: a high-voltage transformer defining a primary side and a secondary side; a switching circuit to drive the primary side of the high-voltage transformer; a discharge lamp connected to the secondary side of the high-voltage transformer; a frequency changing means to change an operating frequency of the switching circuit according to lighting conditions of the discharge lamp before and after the discharge lamp is turned on; a first resonant circuit formed at the primary side of the high-voltage transformer and having a specific resonant frequency; and a second resonant circuit formed at the secondary side of the high-voltage transformer and having a specific resonant frequency different from the resonant frequency of the first resonant circuit, wherein the switching circuit, before the discharge lamp is turned on to be lighted, is operated at a frequency ranging in proximity of a series resonant frequency of the second resonant circuit, and, after the discharge lamp is turned on and lighted, is operated at a frequency ranging in proximity of a frequency at which a voltage-current phase difference at the primary side of the high-voltage transformer is minimized.