Patent ID: 7218059

Claim:
A discharge-lamp control device for controlling a discharge-lamp having two electrodes, comprising: a first driving unit configured to be connected to one of the two electrodes to supply electric power at an operating frequency to the discharge-lamp, the first driving unit comprising a first transformer having a first primary coil and a first secondary coil, and a first capacitor connected in parallel to the first secondary coil, the first driving unit having first impedance characteristics with a minimum impedance at a first frequency and a maximum impedance at a second frequency, the second frequency being lower than the first frequency; and a second driving unit configured to be connected to the other of the two electrodes to supply electric power at the operating frequency to the discharge-lamp, the second driving unit comprising a second transformer having a second primary coil and a second secondary coil, and a second capacitor connected in parallel to the second secondary coil, the second driving unit having second impedance characteristics with a minimum impedance at a third frequency and a maximum impedance at a fourth frequency, the fourth frequency being lower than the third frequency, wherein the first frequency is set to be higher than the third frequency, the second frequency is set to be lower than the fourth frequency, and the operating frequency is selected to fall within a frequency bandwidth from the fourth frequency through the third frequency.