Patent ID: 8773039

Claim:
A method for controlling a discharge lamp, the method comprising: a) receiving a synchronous signal; b) determining whether a lamp current of the discharge lamp changes or not according to the synchronous signal; c) when the lamp current changes, determining a percentage of change of the lamp current according to the synchronous signal and obtaining a second lamp current after the discharge lamp current changes according to the percentage of change of the lamp current and a first lamp current before the discharge lamp current changes; d) calculating a current difference between the second lamp current and the first lamp current; e) obtaining a modulating signal according to the current difference; and f) generating a pulse voltage signal and then outputting a switch control signal according to a lamp current detecting signal, an average lamp current signal and the modulating signal so as to control the lamp current of the discharge lamp; wherein the pulse voltage signal comprises at least a first voltage, a second voltage and a time period, the pulse voltage signal transits from the first voltage to the second voltage during the time period when the lamp current is transited from the first lamp current to the second lamp current during a transition time, and the transition time or current difference between the second lamp current and the first lamp current is controlled by regulating a value of the second voltage and the time period.