| 摘要 |
PURPOSE:To simplify a specific phase detection of the power source in the microwave even with heater and so on, by combining a two-stage integral network and the comparing circuit which compares integrated outputs. CONSTITUTION:When output (a) of the full-wave rectifier is inputted to input terminals 20 and 21, output (d) of comparator 22 is switched to the high level or the low level at the time when output (b) of the first integral network consiting of resistance R2 and capacitor C2 coincides with output (c) of the second integral network consisting of resistance R3 and capacitor C3. Consequently, output (d) of a comparator 22 rises near phase 90 deg. (or 270 deg.) of the AC power source and falls near phase 0 deg. (or 180 deg.). Therefore, if the rise and the fall of output (d) of comparator 22 are set as the power supply time of the heater or the high-voltage transformer in the microwave oven with heater, the rush current at the swtich closing time is minimized. |
