Patent ID: 6965204
Filing Date: 2005-11-15
Classification: H05B,Y02B

Abstract:
1. A ballast arrangement for a discharge lamp with resonant ignition, comprising a coil which is situated in a diagonal branch of a bridge-shaped commutation circuit, and which is arranged in series with the electrical lamp connections, and comprising a capacitor arranged in parallel with these connections, which commutation circuit supplies a comparatively low-frequency square-wave supply voltage of comparatively small amplitude to the lamp in the normal operating phase of the lamp wherein an arc discharge continuously takes place in the lamp, and which commutation circuit supplies, in an ignition phase preceding said normal operating phase, a comparatively high-frequency supply voltage to the lamp which causes said coil and said capacitor to become electrically resonant, characterized in that, in a take-over/warm-up phase between said ignition phase and said normal operating phase, a supply voltage having a comparatively lower frequency than said comparatively high-frequency supply voltage is supplied to the lamp, the frequency of which, as compared to the frequency of said comparatively high-frequency supply voltage, is reduced by one frequency step in one or a number of time-sequential steps in order to each time optimize the current supplied to the lamp in the take-over/warm-up phase.