Patent ID: 7545107

Claim:
An electrodeless discharge lamp lighting device comprising: an induction coil wound in the vicinity of an electrodeless discharge lamp; a power supply circuit for outputting a DC voltage; an inverter circuit which has at least one switching element and which converts the DC voltage output from the power supply circuit into a high-frequency voltage and outputs the high-frequency voltage to the induction coil; and a frequency varier that disperses the frequency of a noise by varying the frequency of the high-frequency voltage output from the inverter circuit to the induction coil at the time of lighting the electrodeless discharge lamp, wherein a frequency variation range Δf of the high frequency voltage output from the inverter circuit satisfies the expression: Δf<fav/Q 1 wherein, fav represents an average frequency of the high frequency voltage output from the inverter circuit to the induction coil at the time of lighting the electrodeless discharge lamp, and Q 1 represents the value (X 1 /R 1 ) obtained by dividing an imaginary component X 1 by a real component R 1 , wherein X 1 is the imaginary component of an impedance Z 1 across both ends of the induction coil at a time of lighting the electrodeless discharge lamp at the average frequency fav, and R 1 is the real component thereof.