Patent ID: 8022637

Claim:
A method for detection of a non-zero-voltage switching operation of a first and a second type 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) providing a comparison signal representative of a comparison of the voltage measurement signal with a reference value, wherein the reference value is selected such that it is located asymmetrically between a minimum possible value and a maximum possible value of the voltage measurement signal; c) evaluating the comparison signal in each case before the first semiconductor element is switched on and in each case before the second semiconductor element is switched on, and detecting one of the first and second type non-zero-voltage-switching operations based on these evaluations.