removed diode d9 and capacitor c13 in the circuit !

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i switched on the supply, i gven i/p ac 47 volts,then i got drain to source 103 volts,the result i got here.. At output: +12V output i got 39volt +5v output i got 0.00volt -5V output i got -18volt apart from these ,the clamping section resistor 100K 2W getting more heat and transformer noise is comming ,instead SB180 i am using UF4007 is their any problem?or please suggest other diode
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Heatcon Schematic_9 25W_tny277PN_0.pdf31.28 KB

Hello Arunsoman,

Assuming there are no problems with bad PCB electrical connections, the problem you described could indicate an error on transformer polarity. If there is any phase error on the transformer construction, the power supply is not any more in flyback mode, but in forward mode. On this case the transformer is heavily saturated, hence the heat and noise. The output voltage is now the reverse voltage and this could explain the 39V you see there. If this is the case you can easily fix the error, just check the transformer construction and pay extra attention to pin numbers and polarity of windings (beginning and end of winding direction for each pin).
The SB180 is a schottky diode, UF4007 is a standard diode. Theoretically any diode rated for at least 1A and 80V could do the job, but you can get big penalties in efficiency and EMI levels. After you manage to fix the problems I suspect you have with your transformer polarity you can try to replace the rectifying diodes and see if the performance you get is still acceptable for your design target with an UF4007. For better performance you can find a big list of schottky diodes at like these ones: 11DQ09, SB1100, MBR1100, SR1010, SR108, SB190, etc. or you can go for 2A diodes with even more options.


the path opened in the 5V track ,after correction i got all the supply outputs In +12V output i got 11.47 Volt without load with load 10.5V In +5V = 4.9 with and without load in -5V= -5.55 volt with and without load Sir current also less in the 12V output