Patent ID: 6747423
Filing Date: 2004-06-08
Classification: H05B

Abstract:
A circuit for operating a gas discharge lamp from a DC voltage supply, said circuit comprising:first, second, third and fourth controllable switches, said first and second switches being arranged in series with each other between DC voltage supply terminals, and said second and fourth switches being arranged in series with each other between said DC voltage supply terminals; a first nodal point between said first and second switches and a second nodal point between said nodal point between said third and fourth switches being connectable to opposite terminals of a gas discharge lamp; a control circuit connected to open and close said switches according to a first state, a second state and a start state, wherein said first state and said second state occur alternately to each other at first frequency, and wherein in said first state, said second and third switches remain open and said first switch remains closed while said fourth switch opens and closes at a second frequency which is higher than said first frequency, in said second state, said first and fourth switches remain open and said third switch remains closed while said second switch opens and closes at said second frequency, and in said start state, said fourth switch remains closed, said third switch remains open and said first and second switches open and close alternately at a third frequency.