Circuit arrangement for operating at least one high pressure discharge lamp

Abstract

The present invention relates to a circuit arrangement for operating at least one high-pressure discharge lamp (16) having four switches (Q1 to Q4) in a full bridge arrangement, a first and a second switch (Q1, Q2) forming the first half-bridge arm, and a third and a fourth switch (Q3, Q4) forming the second half-bridge arm, at least two terminals for coupling the high pressure discharge lamp between the midpoint (M1, M2) of the first and of the second half-bridge arms, at least one terminal for supplying the circuit arrangement with a DC voltage signal (Uv), and a drive circuit for driving the four switches, the drive circuit being designed to provide a first drive signal ({overscore (A)}) for the switches (Q1, Q2) of the first half-bridge arm and a second drive signal (B) for the switches (Q3, Q4) of the second half-bridge arm in such a way that the first and the second drive signals ({overscore (A)}, B) are derived from a base signal (A) whose clock pulse is swept between a first and a second frequency, and in such a way that the first and the second drive signals ({overscore (A)}, B) have a phase difference which is modulated with a prescribeable third frequency (fAM), wherein, in order to modulate the phase difference the drive circuit comprises at least one switch (24) which is designed in such a way as to switch to and fro between derivatives of the base signal with a different phase shift in time with the third frequency (fAM).

Dependencies are inferred from the claim text.