Patent ID: 8242702
Filing Date: 2012-08-14
Classification: H05B

Abstract:
1. A method for driving a fluorescent lamp connected to a series resonant circuit having a resonant circuit inductance and a resonant circuit capacitance, comprising: applying an excitation AC voltage having an excitation frequency to the series resonant circuit using a half-bridge circuit, having an output, to which the series resonant circuit is coupled, and having a first and a second switch, driven in the on state and in the off state with a fundamental frequency predetermined by a frequency signal or with an increased frequency with respect to the fundamental frequency; detecting a resonant circuit current flowing through the resonant circuit; driving the switches with the fundamental frequency or with the increased frequency with respect to the fundamental frequency in a manner dependent on a temporal change in the resonant circuit current between two temporally spaced-apart evaluation instants lying within a switched-on duration of one of the switches; during a switched-on duration of one of the switches, switching off the switch at the latest after a predetermined maximum time duration has elapsed after the presence of a predetermined phase angle of the resonant circuit current, wherein the time duration is dependent on a temporal change in the resonant circuit current between two temporally spaced-apart evaluation instants lying within the switched-on duration; determining a first difference value, dependent on a difference between values of the resonant circuit current at the evaluation instants; determining a second difference value, dependent on a difference between the first difference value and a reference value; and setting the maximum time duration such that it is dependent on at least one second difference value that was determined for one switched-on duration.