question about design of a SMPS-Transformer

[El_Paco]

smps transformer design

for a little climatic "room" to calibrate sensors i maked a smps to power the peltier-element.

for this i take the schematic from a ATX-supply.... and make my circuit.

after some time's a friend ask me for the circuit.... but this must changed from 12V --> 24V ..... the troubles begun!

at first -- i try to use 2 transformer which are on the primary side are parallel connected.
Tis works... but if i need much power... above 280W... the primary transistors are destructed... because the back inducted voltage is to high.
One way are 2 high voltage surpressor diodes to prevent this.... but it will take some time to get this from the distributor.....

today i try to make a modified transfomer.... but as i analyse the original transformer... i was surprised because on the secondary part ar more copper wires than on the primary....

ex.:
primary 24
secondary 28

please can somebody explain ??

know somone good theoretical papers for transformerdesign?

any help is recommed, thx

 

[shanren]

smps transformer parallel

hi,you can visit:
h**p://www.smpstech.com
h**p://www.powerdesigner.com
maybe you can find someting useful for you.
i know the transformer design have many rules,flayback have it;s own rule,and forward is quite diffrent from that of flyback.in some case,secondary are more wires than on the primary.for example, the voltage of primary side is 12v,and the duty is 50%,and the ouput is 9v,so the ratio of primary and secondary is about12*50%)/9=1:1.5
so,if you need a 10 turn primary ,so the second will be 15 turns.
https://www.ti.com
https://www.onsemi.com
also have someting useful about smps ,you can serach in the site.