| 摘要 |
PURPOSE:To improve efficiency, by a method wherein the stable fly-back voltage of a bias winding is utilized as a bias voltage while a starting resistor is diverted to the detection of an input voltage after starting. CONSTITUTION:A switching power source device is constituted of a rectifying and smoothing circuit 1, a switching transformer 2, a main switching element 3, starting resistors 4, 5, a biasing capacitor 6, a bias circuit 8, consisting of an input voltage detecting circuit 81, a bias voltage detecting circuit 82 and a switching circuit 53, a controlling and driving circuit 9, the rectifying and smoothing circuit 10 and a detecting circuit 15 for feedback to the controlling and driving circuit 9. Switching circuit 53 is put ON before starting and a bigs voltage is supplied from a trial input voltage: this circuit is started when both of the voltages have exceeded a specified voltage. The switching circuit 83 is put OFF after starting and said voltages are detected by respective detecting circuits 81, 82. According to this method, the title device is stopped when the input voltage is deteriorated to a value lower than the specified voltage.
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