SMPS transformer design issue

BradtheRad said:

Your secondaries have the same number of turns (9T). Theory says they produce the same voltage. However your specs say you want three different voltages. Does the transformer have internal construction which provides this? Or did you intend to add regulation?

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c_mitra said:

Because you will have difficulty to wind a fractional turn, you can keep the number of turns same for 5V and 6V and use twice the number of turns for the 12V coil. You have not mentioned the current requirement (loads) but it may be simpler to use bifilar and /or trifilar windings in case you need higher currents.

Your input is close to 50V?

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raju D said:

you can use PI Expert for the design

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smijesh said:

Please specify the power or output current requirement, For this TNY switch can deliver 20W
Transformer design step in (PI expert or other tool)

Select transformer (E20 or E25)
Calculate required air gap
Calculate no of turns - primary and secondary
Wire thickness primary(25AWG to 32AWG)
Wire thickness for secondary
For 5K isolation use polyester yellow tape in between winding
For 5K isolation use big bobbin or bobbin having more length between primary to secondary(Crepage)

See similar TOP Switch transformer design

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smijesh said:

L primary = Vin*Ton/I pk Ipk = 5.5*I in
Primary turns Np = √(L primary/Al Vlue of the core )
Secondary – 1 turns(Ns-1) = Npri(Vout -1+Vd)*(1-Dmax) /Vin Dmax
(Vd diode voltage drop , D max Duty cycle )
Secondary – 2 turns(Ns-2) = (Vsec -2 + Vd)*Ns-1 /(Vsec -1 + Vd)
Secondary – 3 turns(Ns-2) = (Vsec -3 + Vd)*Ns-1 /(Vsec -1 + Vd)

Primary

18/230= 100mA

(30AWG copper wire)


12V*1 Amps =12W (20AWG copper wire)
6V*.5Amps =3W (24AWG copper wire)
15V*.25Amps=3.75W (26AWG copper wire)

Hope it is helpful

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