Patent ID: 7486028
Filing Date: 2009-02-03
Classification: H05B,Y02B

Abstract:
1. A ballast arrangement for a discharge lamp with resonant ignition, comprising a coil, wherein said coil is situated in a diagonal branch of a bridge-shaped commutation circuit, and wherein said coil is arranged in series with electrical lamp connections, and a capacitor arranged in parallel with said electrical lamp connections, which commutation circuit supplies a comparatively low-frequency square-wave supply voltage of comparatively small amplitude to the lamp in a normal operating phase of the lamp wherein an arc discharge takes place continuously in the lamp, and, in an ignition phase preceding the normal operating phase, the commutation circuit is commutated at a comparatively high-frequency by a switching voltage at a switching frequency that varies with respect to time, wherein, in the ignition phase, an odd harmonic frequency of the switching frequency is substantially equal to a resonant frequency of said coil and said capacitor, and wherein the switching frequency is decreased to an intermediate value between substantially one third of the resonance frequency and an operating frequency of the discharge lamp during a warm-up phase between the ignition phase and the normal operating phase.