Patent ID: 7560873
Filing Date: 2009-07-14
Classification: H05B

Abstract:
1. A method for detection of a non-zero-voltage switching operation of a lamp ballast, the lamp ballast including a half-bridge circuit with a first and a second semiconductor switching element, a resonant circuit connected to the half-bridge circuit, and a snubber capacitance connected in parallel with one of the semiconductor switching elements, the method comprising: a)obtaining a voltage measurement signal representative of a voltage at an output of the half-bridge circuit; b) evaluating the voltage measurement signal at a time before each switching-on time of at least one of the first and second semiconductor switching elements by comparing the voltage measurement signal with a reference value, by b1) comparing the voltage measurement signal with the reference value at a first comparison time, which corresponds to a predetermined flank of a first drive signal, in order to obtain a first comparison result, and b2) comparing the voltage measurement signal with the reference value at a second comparison time, which corresponds to a predetermined flank drive signal, in order to obtain a second comparison result.