| 摘要 |
PURPOSE:To control a load accurately with low noise by supplying an AC current to the load when the computed value of a power detector becomes higher than the prescribed level and stopping the supply of the AC current to the load when the pulse number of a zero cross detector becomes the prescribed number. CONSTITUTION:A thyristor 3 is connected in series between a load 1 and a power source 2. A voltage detector 4 outputs detected voltage waveforms (a), (b), and a current detector 5 outputs a detected current waveform (c). A zero cross detector 6 inputs the waveform (a) and applies a zero cross pulse to a counter 7 whenever crossing the zero point. When the counter 7 becomes the prescribed pulse number, it outputs a pulse. A power detector 8 inputs the waveforms (b), (c) and the instantaneous value is computed by a power value integrator 11. The output of the integrator 11 is inputted to a comparator 12, and when the integrated value becomes higher than the prescribed level, it conducts a thyristor 3 through a gate controller 13. A transistor (TR) 14 is provided at the output of the integrator 11, and the TR 14 is controlled by the output of the counter 7. |
