To avoid the phenomenon of unsightly flickering in images projected by the projector, in high pressure discharge lamps—especially in high intensity discharge lamps, such as high pressure mercury lamps, metal halide lamps, and xenon lamps—that are used in projectors, even in the presence of the phenomenon of cyclical modulation of the lamp voltage by the returning the light spectrum when the light reflected by the dynamic color filter returns back through the optical system to the lamp, at least during steady operation of the discharge lamp (Ld), a target lamp current signal generation circuit (Up) acquires multiple lamp voltage detection signal (Sv) over a period that is at least as long as the color order cycle of the dynamic color filter (Of) and generates a target lamp current signal (St) based on the multiple lamp voltage detection signals (Sv) that were acquired.