Patent ID: 8193727
Filing Date: 2012-06-05
Classification: H05B

Abstract:
1. An electronic ballast comprising: an inverter circuit having at least one switching element and functional to convert a DC voltage into a high-frequency voltage; a resonant circuit connected between outputs of the inverter circuit so as to light a discharge lamp at high frequency by a resonant action; a preheating circuit connected to a filament of the discharge lamp and functional to preheat the filament; a control circuit for controlling the inverter circuit to operate; dimming circuit adapted to continuously change an output voltage to the discharge lamp by changing an operation frequency in the inverter circuit; end of life detection circuit adapted to detect whether or not the discharge lamp is at the end stage of the life at every predetermined time and output a life end detection signal upon detection of a life end state; protection circuit adapted to reduce or stop an output to the discharge lamp by controlling the switching element in response to a life end detecting signal inputted from the end of life detection circuit; and wherein the end of life detection circuit outputs the life end detection signal upon detection of a life end state at least twice in succession.