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Stable auxiliary converter

source:Industry News Popular:adapter release time:2021-06-11 10:07:03 Article author:sznbone

  Some changes can be made to the basic self-excited oscillation converter. A stable auxiliary voltage output can be provided by adding a high-voltage Zener to the input, while maintaining a stable operating frequency.

Stable auxiliary converter(图1)

  The figure is an improved circuit based on the basic circuit. This circuit is more suitable for dual-voltage operation, and the energy of the flyback is returned to the same input power adapter as the primary load.

  ZD1 guarantees the stability of the input voltage and the constant working frequency. This auxiliary converter can be used as a clock signal for the control circuit to directly drive the switching power transistor. This method can also be used to design a simple and effective switching power supply adapter.

  An energy recovery winding P2 and a diode D have been added to the transformer, so that the excess flyback energy can be returned to the same power adapter capacitor C2 connected to the primary winding P. This makes the average load current on the ZD very small, allowing the Zener diode to do a simple and effective pre-adjustment. Because both the forward and flyback voltages are adjusted by ZD1, it provides an adjusted flyback voltage and an adjusted output voltage. For the entire circuit, it is very important that the windings P and P3 adopt the double-wire winding method and an energy recovery diode D is connected to the upper end of the flyback winding P3. During the conduction period of Q1, the D here can make the switch tube set The electrode is isolated from the turn-to-turn capacitance of the transformer T1.

  The DC power adapter of the auxiliary converter is supplied by the 300V main power adapter through R1 and R2. These two resistors have been selected so that the change of the dual-voltage operation input terminal will not affect the working conditions of the ZD1. In addition, another transistor Q2 is added to the base of the conversion transistor Q to allow the input of an external synchronization signal of the conversion frequency. It should be noted that Q2 can terminate the on-time of the switch in advance without extending the on-time. The operating frequency of the converter is only possible. Synchronize to a higher frequency. For each synchronization pulse, the conduction of Q will cause a rapid flyback working process and enter a higher frequency operation state at the same time.


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