| 摘要 |
PURPOSE:To achieve dimming for a small size and light-weighted spotlight at a low cost by controlling the phase of a commercial power source, and by performing dimming and lighting so as to obtain rated voltage of the lamp when the lamp application voltage is maximized. CONSTITUTION:In a lighting device 2, a condenser C3 for trigger is charged by resistance R3 as well as variable resistance VR, and through the actuation of a trigger device SBS, a triode AC switch (TRIAC) TR is triggered so as to electrify a lamp 1. The value of the resistance R3 is so determined as to obtain maximum output voltage when the value of the variable resistance VR is 0. Zener diodes ZD1, ZD2 are used for suppressing the variation of the output voltage when power source voltage is varied. For the wave shape of the voltage applied to the lamp 1, light adjustment can be executed in a range from thetato 0 through the variation in the variable resistance VR. Light adjustment can thus be done, and small size, light weight as well as inexpensiveness can thereby be achieved. |
