| 摘要 |
PURPOSE:To phase control a load with substantially constant power without influence of variation in the voltage of an AC power source by setting the front edge of each half-wave of the power source to the ON period of a load. CONSTITUTION:The output of a half-wave rectified AC power source 1 is applied through an impedance element 5 to a transistor (TR) 4, the output of which controls ON of a load 3. Then, the current of the load 3 generates a voltage at a resistor 7. When the current reaches the maximum set vaue, a thyristor 6 is conducted, thereby bypassing the input current of the TR4. Thus, the TR4 is interrupted, and the load 3 is OFF controlled. Then, the load 3 is ON controlled at the front edge of each half wave of the power source 1. Even if the variation in the voltage of the power source 1 occurs at this time, the effective power applied to the load 3 is substantially constant. Accordingly, the load 3 is controlled with substantially constant power. In this manner, the load can be phase controlled with substantially constant power without influence of the variation in the voltage of the AC power source. |
