Patent ID: 7425804

Claim:
A lamp drive device of a projector, comprising: a lamp which projects light towards an image formation unit; a lamp power supply unit which supplies a lamp drive current to said lamp; a switching element connected in series with said lamp; a lamp drive current detection circuit which detects the magnitude of said lamp drive current; a lamp drive circuit which, based upon the output of said lamp drive current detection circuit, ON/OFF drives said switching element with a PWM control signal, so that said lamp is driven at constant power; a lamp shorted out decision circuit which, based upon said PWM control signal, decides whether or not said lamp is in a shorted out state; and a display section which displays said shorted out state; wherein said lamp shorted out decision circuit comprises: a pulse width detection means which detects the pulse width of said PWM control signal after the driving of said lamp has been started; a lamp drive ON/OFF means which, if said pulse width detected by said pulse width detection means is less than or equal to a predetermined width, stops the driving of said lamp, and thereafter starts driving of said lamp for a second time; and a decision means which, after the driving of said lamp by said lamp drive ON/OFF means has been started for a second time, decides that said lamp is in said lamp shorted out state, if said pulse width detected by said pulse width detection means is less than or equal to a predetermined width.