Patent ID: 8441211

Claim:
An electronic ballast capable of self-protection at a natural or premature end of life of a fluorescent light tube, wherein the electronic ballast is connected in parallel to a first filament and a second filament provided respectively at two ends of the fluorescent light tube and comprises: a controller configured for generating at least a first output signal and a second output signal, wherein the first output signal and the second output signal are voltage signals having a same frequency but different phases; a first power switch and a second power switch, wherein the first power switch has a first end connected in series to a first end of the second power switch, has a second end connected to a positive electrode of a power supply, and receives the first output signal so as to be switched according to the first output signal, and the second power switch has a second end connected to a negative electrode of the power supply and receives the second output signal so as to be switched according to the second output signal; a direct-current (DC) blocking capacitor connected in series to a line connecting the first power switch and the second power switch; a resonant circuit comprising a resonant inductor and a resonant capacitor, wherein the resonant inductor is connected in series between the DC blocking capacitor and the first filament, and the resonant capacitor is connected in parallel between the first filament and the second filament, so as for the resonant circuit to oscillate according to switching of the first power switch and the second power switch and thereby cause the resonant capacitor to generate a voltage; a voltage sensor connected in series to the resonant capacitor and connected in parallel between the first filament and the second filament so as to sense an alternating-current (AC) voltage proportional to a voltage across the fluorescent light tube; and a regulator connected separately to the voltage sensor and the controller so as to receive the AC voltage from the voltage sensor, convert the AC voltage into a DC voltage, and deliver the DC voltage to the controller; wherein the controller, upon determining that the DC voltage exceeds a preset tolerable voltage level, generates an interruption control signal for immediately stopping operation of the controller.