Patent ID: 7053564
Filing Date: 2006-05-30
Classification: H05B,Y02B

Abstract:
1. A ballast device for a discharge lamp comprising: a DC voltage supply stage; semiconductor switches being switched at a radiofrequency clock frequency so as to change the current direction through the discharge lamp; a starting transformer; a series capacitor through which a DC voltage of said DC voltage supply stage is supplied to the starting transformer, and a ballast inductance connected to an electrode of the discharge lamp which is not connected to the starting transformer, wherein there is a first connecting point between the series capacitor and the starting transformer, there is a second connecting point between the discharge lamp and the ballast inductance, a capacitor is connected in series with a switch between the first and second connecting points, said capacitor forms a series resonant circuit with the ballast inductance, and said series resonant circuit is tuned to a higher harmonic of the clock frequency.