I am using ST's eDesign Suite for designing power supply. The suite helps with circuit, BOM and transformer design specs.

I contacted the transformer design firm to get my transformer designed. I gave them all the information regarding the number of turns and length of wire etc..

They are asking me the polarity of transformer and also start, end pin connection of windings.

Being an amateur in transformer designing, I am unable to find any relevant information for above query.

Need Help with that.

Here is my power supply specs

Input: 100 Vac - 265 Vac - 50 Hz - Operating Vdc [98.7 V - 374.8 V] Output Power: 14.96 W Out 1: 17 Vdc (35 mVpp ripple) - 880 mA max - 14.96 W - Regulated Switching Frequency (fsw): 60 kHz

Transformer Information :-

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Circuit :-

enter image description here

  • \$\begingroup\$ You can see the dots in the schematic. That's the start of the winding. As for pinout, that depends on your layout, creepage requirements and so on. \$\endgroup\$ – winny Jan 13 '17 at 21:07

You define for them where you want the start and end pins. They will wind the transformer and connect the wires to the appropriate pins accordingly.

It's one of those tedious things where you'd perhaps prefer to say 'whatever' and have them draw what they've decided and done, but as the commissioning designer, it's really down to you to choose the transformer pinout, and draw what you want.

You wouldn't go into a restaurant and say 'feed me'. You'd say 'I want the steak, bloody, with new potatoes'. Similarly they are waiting for you to draw a little insulating plate with 6 pins spaced 'yay' apart, labelled primary start, primary end, secondary ...

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