Patent ID: 7378807
Filing Date: 2008-05-27
Classification: H05B

Abstract:
1. A drive circuit for at least one fluorescent lamp comprising: a half-bridge circuit configured to produce a supply voltage; a resonant circuit coupled to the half-bridge circuit configured to be connected to the at least one fluorescent lamp; a diagnosis circuit comprising a resistance element coupled to the resonant circuit, at least one current/voltage converter connected to the resistance element and configured to produce at least one measurement voltage based on a current flowing through the resistance element; and an evaluation circuit operably coupled to the current/voltage converter to receive the at least one measurement voltage; wherein the current/voltage converter is configured to produce a first measurement voltage representative of a voltage across the at least one fluorescent lamp during a first half-cycle and to produce a second measurement voltage representative of a voltage across the fluorescent lamp during a second half-cycle; and wherein the evaluation circuit comprises: a first peak value detection unit coupled to receive the first measurement voltage and configured to produce a first peak value signal; a second peak value detection unit coupled to receive the second measurement voltage and configured to produce a second peak value signal; and an assessment unit configured to produce a diagnosis signal as a function of a comparison of the first and second peak value signals.