| 摘要 |
PURPOSE:To perform phase control in synchronization with AC power source completely, by a method wherein clock pulse in synchronization with the AC power source is supplied to clock input of a counter circuit, and reset by output pulse of a zero-cross detection circuit. CONSTITUTION:Since a zero-cross detection circuit 3 generates pulse every half cycle of AC power source, output value of a first counter circuit 5 is reset every time. An oscillation circuit 4 is oscillated in synchronization with the AC power source completely, and supplies clock pulse to the first counter circuit 5. Further, a frequency dividing circuit 6 counts output pulse of the zero-cross detection circuit 3, and produces clock pulse of set frequency and supplies it to a second counter circuit 7. Only when output values of the first counter circuit 5 and the second counter circuit 7 are coincident, a value coincidence circuit 8 generates output pulse and drives a control element 10 through a firing circuit 9 thereby performs phase control of a load 11 in digital manner. Control of phase angle is performed by output value of the second counter circuit 7.
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