An object of the invention is to provide a light source driving method for supplying electric power to a light source of a projector, and to provide a projector using this light source driving method. A coarse phase recovery is performed to determine a first phase angle which provides a first best estimate of the information symbol corresponding to the digital signal. An amplifying circuit amplifies the drive signal detected by the detecting polarized portion and inputs the amplified signal to the driving polarized portion to oscillate the piezoelectric vibrating member.