| 摘要 |
<p>PURPOSE:To enable a light emitting element drive power supply circuit to be lessened in number of parts by removing a light emission capacitor and enhanced in space factor by a method wherein a boosted voltage switch circuit which impresses a boosted voltage higher than usual, each time a distance measuring light emitting element connected to a voltage boosting capacitor emits light rays, is provided. CONSTITUTION:A booster circuit 1, a boosted voltage level switching circuit 5, a constant voltage circuit 11, a CPU 13, an AF unit 12, and a distance measuring light emitting element (AF light emitting diode) 17 which emits light by the action of a light emitting diode drive transistor 16 are provided. The boosted voltage level switching circuit 5 switches the boosted voltage level of a booster capacitor C1 to a second boosted voltage level 2VS higher than a first boosted voltage level. The AF light emitting diode 17 is connected to a second boosted voltage terminal which is switched by the boosted voltage level switching circuit 5 and connected to one end of the booster capacitor C1. By this setup, a power supply circuit of this design can be lessened in number of parts by removing a light emission capacitor and enhanced in space factor.</p> |
