Patent ID: 8508145

Claim:
A fluorescent lamp device comprising: a fluorescent lamp; a frequency generator for generating a pulse signal; a driver circuit coupled to said frequency generator for generating at least one driving signal according to said pulse signal; a half bridge power switch unit coupled to said driver circuit for generating an AC signal according to said at least one driving signal; a resonant tank electrically connected between said half bridge power switch unit and said fluorescent lamp for filtering said AC signal to supply power to said fluorescent lamp; a protection circuit electrically connected to said fluorescent lamp for stably adjusting voltage of said fluorescent lamp, said protection circuit comprising a comparator for comparing a signal indicating a terminal voltage of said fluorescent lamp with a reference voltage to generate a comparison signal to decrease said supply power when said signal exceeds said reference voltage; and a pulse width modulator electrically connected to said driver circuit for providing a pulse width modulation signal to said driver circuit according to said comparison signal, so as to generate said at least one driving signal, wherein said pulse width modulator comprises: an error amplifier; a resistor electrically connected to an inverting input of said error amplifier; a capacitor having one terminal electrically connected to said resistor and said inverting input of said error amplifier to form an integrator; a comparator having a non-inverting input electrically connected to an output of said error amplifier and the other terminal of said capacitor; a switch controlled at least by said comparison signal; and a controlled current source electrically connected to said inverting input of said error amplifier through said switch.