| 摘要 |
A start-up circuit includes a capacitor which is initially charged by the AC line voltage. When the voltage across the capacitor is sufficient to breakdown a zener diode and overcome the gate to cathode voltage drop of an SCR, the SCR snaps on applying the capacitor voltage to a user circuit which generates a pulse train. The pulse train is applied to a switching device which induces a voltage in a transformer which is fed back to the capacitor and filtered to maintain the SCR in an on state.
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