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319Off-line Converter Design and Magnetics

Coming to the secondary side of the worked example, we remember we had lumped

all the current as a 5

V equivalent load of 15 A. But in reality it is only 10 A, two-thirds

of that. So the center of its current ramp, which we had calculated was about 34 A, is

actually (2/3)  34  22.7 A. The balance of this, that is, 34  22.7  11.3 A, refl ects as

(5.6/13)  11.3  4.87A into the 12 V winding. So the center of the 12 V output ’ s current

ramp is 4.87A. We can choose the 12 V winding arrangement using the same arguments

we present below for the 5V winding.

For the 5 V winding, ...