| 摘要 |
PURPOSE:To prevent power feedback noises without requiring a power filter by a method wherein an AC power source, a bi-lateral transistor and a load constitutes a closed circuit to control a base current of a transistor. CONSTITUTION:A lamp voltage VL' is applied to a voltage VS' of the AC power source 8 and also a lamp current iL flows to cause an incandescent lamp 10 to be turned ON in regulating a light. In this case, since the base current iB gradually increases from zero to a value as high as the bi-lateral transistor 9 can be saturated, the bi-lateral transistor 9 is kept is an active region during the period of a phase phi1 to a phase phi2 and kept saturated during the period until the polarity of the voltage VS' being inverted after the phase phi2. As a result, the lamp voltage VL slowly rises during the period from the phase phi1 to phi2 and almost agrees with the VS' after the phase phi2, the lamp current iL also becomes less steep in the rising and the power feedback noises can be prevented. |
