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Stacked flyback transformer

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Taskuraha

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My DCM flyback has specs:

Vin,min =21.6V
Pout,total = 11W
Vo1 = 3.3V (regulated) 1.98W
Vo2 = 20V 4W
Vo3 = 24V 4.8W
Vo4 = 7V 0.210W

I have calculated transformer primary and secondary windings as:

Np = 16
Ns1 = 2
Ns2 = 11
Ns3 = 13
Ns4 = 4

I am going to use stacked windings for first three outputs. So the stacked windings would be Ns1 = 2, Ns2 = 9 (2+9 = 11) and Ns3 = 2 (2+9+2 = 13). Now when calculating peak currents for stacked secondary windings, i am not sure is my calculations right? Pout, total = 11W gives me Ton = 2.18us and primary peak current Ip = 2.9196A ( Lm = 16.128uH ) and currents for stacked windings:

Is1 = Ip*\[\frac{ Np}{Ns1 }\]*\[\frac{Po1+Po2+Po3 }{ Po,total}\] = 2.9196A*\[\frac{ 16}{2 }\]*\[\frac{1.98W+4W+4.8W }{11W }\]=22.89A
Is2 = Ip*\[\frac{ Np}{Ns2 }\]*\[\frac{Po2+Po3 }{ Po,total}\] = 2.9196A*\[\frac{ 16}{11 }\]*\[\frac{4W+4.8W }{11W }\]=3.397A
Is3= Ip*\[\frac{ Np}{Ns3 }\]*\[\frac{Po3 }{ Po,total}\] = 2.9196A*\[\frac{ 16}{13 }\]*\[\frac{4.8W }{11W }\]=1.568A
 

grizedale

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also worth remebering that even of you do stacked windings, its still best to give each secondary "section" its own full layer....this improves cross regulation further.
 

Taskuraha

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Goldsmith, Switching frequency is fs = 200kHz
 

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