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Determining Peak Secondary Current

 

 

Mathematical Method of determining Peak Secondary Current in Flyback Converters

 

This text describes how to determine the peak secondary current in a flyback converter working on the boundary between continuous and discontinuous mode. For a more intuitive method, please see Flyback Converter Design

 

Energy in the inductor can be represented by:

 and

 

Also

 

 

(where Ls is the secondary winding inductance)

 

Therefore

 

 

Therefore

 

 

Where T is the period of the switching waveform

 

So

 

 

is equal to (1 – Duty Cycle) (i.e. the discharge time of the secondary winding)

 

So

 

 

and

 

 

 

So

 

 

Now, from

 

 

 

i.e. the change in secondary current

 

So

 

 

So to find the peak secondary inductor current, we take the average output current, multiply by 2 and divide by (1-DC)

 

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