Patent ID: 8089220
Filing Date: 2012-01-03
Classification: H05B,Y10S

Abstract:
1. A circuit arrangement for operating a high-pressure discharge lamp comprising: a bridge circuit with at least two switches, a control apparatus, which is designed to drive the at least two switches; wherein the bridge circuit is in the form of a half-bridge circuit with precisely two switches, the control apparatus being designed to alternately switch the first switch and the second switch in the bridge circuit on and off at a first frequency and, during the off phase of the one switch, to drive the other switch with a square-wave signal of a second frequency, which is higher than the first frequency, the circuit arrangement furthermore comprising: a voltage measurement apparatus for measuring an actual value of the voltage across the high-pressure discharge lamp; a reference value apparatus, which provides at least one upper limit value for the voltage across the high-pressure discharge lamp; a comparison apparatus for comparing the actual value of the voltage across the high-pressure discharge lamp with the at least one limit value; the comparison apparatus being designed in such a way that, in the case in which the actual value of the voltage across the high-pressure discharge lamp is above the at least one limit value, it drives the control apparatus in such a way that the control apparatus extends a predeterminable switch-on duration of the signal with which the one switch of the half-bridge circuit is driven during the off phase of the other switch, at least for a predeterminable period of time.