Published:2011/7/12 1:16:00 Author:TaoXi | Keyword: Width modulation, frequency modulation, hybrid type, switching, power supply | From:SeekIC
The self-excited oscillation of this circuit is realized by the R13C1. When the power is starting, the 220V AC adds to the primary stage of the transformer T1, and it is secondary transformed, bridge type rectified and filted by this circuit, then the capacitance C6 outputs the 15V unstable smooth DC voltage to add to the input ports of the complex switching power transistors VTl2~VT14; at the same time, this voltage supplies the stable operating voltage for the integrated voltage regulator W724 through the resistor R10 and the regulator VD6. Becasue the output voltage Vo has not established, so the two ends of the sampling voltage divider resistors R17, R24, R18 has no voltage, the VT5 of the error amplifier cuts off because there is no base electrode bias voltage.
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