36w design using PI expert 9

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we made a Universal input  36w (80v, 450mA) non dimmable design using PIxls design software9 using LNK419eg. It is working fine but the EI35 transformer is becoming very HOT. It is exceeding 103deg C(27degC ambient). Transformer made sandwich construction and got 82.4% efficiency. Primary copper gauge used 24awg and for secondary also 24awg. For ckt diagram we followed DER 286. Can you explain why transformer is heats up? What should be the values for  VOR and Kp for this design? Kindly help us to make a design to get low temp and good efficiency .

Spread sheet for trf design is attached.


Since the output is 80v , out put filter capacitor should be higher voltage rated. Shall I connect 2no's of 1000uF/63v capacitors in series instead of a single  500uF/160v.   




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36w universal Design1.xls26 KB


Optimize your winding construction.  For 80V output, the interwinding capacitance would be significant.  Put tape between layers.

You can not increase the wire size significantly because in the end you will end up with a longer wire. Try a split single layer design for the primary and secondary winding; (primary, secondary,bias,primary then secondary).

Use a high frequency core like 3F3 or PC95 material in order to reduce core losses.

100V and 120V capacitor are standard.   Use this instead of 160V or 63V in series.  Series E-cap is not recommended due to tolerance.  The voletage stress will not be equal.