Patent ID: 8203282

Claim:
An electronic ballast comprising: an inverter circuit with at least one switching element for converting a DC voltage into a high-frequency voltage; a resonant circuit for lighting a discharge lamp at a high frequency by a resonant action, the resonant circuit being connected between both ends of the inverter circuit; a control circuit for controlling an operation of the inverter circuit; dimming circuit adapted to change an output voltage to the discharge lamp by changing an operating frequency of the inverter circuit; DC component detecting circuit adapted to detect a DC voltage component of the discharge lamp; protecting circuit adapted to detect an output signal of the DC component detecting circuit for every predetermined period and controlling the switching element so as to reduce or stop an output to the discharge lamp when the output signal exceeds a predetermined reference value; and operation prohibiting circuit adapted to prohibit an operation of the protecting circuit when a periodic change amount in the output signal of the DC component detecting circuit reaches a predetermined value or higher.