Light-source switching and driving unit

摘要

The present invention is a light-source switching and driving unit where an accurate stop operation and a strong holding force are obtained and which is capable of reducing a noise and preventing an impact to light-source lamps. In this unit, a plurality of light-source lamps for being switched and used are disposed. When a burnout sensor detects the burnout of a lamp being currently used, a spare light-source lamp is moved to a predetermined position by a stepping motor. In switching one lamp to another lamp, a pulse generating circuit generates a drive pulse which gradually increases when the stepping motor is started and a drive pulse which gradually decreases when the stepping motor is stopped. The stepping motor is driven by these drive pulses. With this, in switching one lamp to another lamp, a slow operation can be realized when the motor is started and when the motor is stopped.