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Flyback Smps duty cycle equation.

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dr pepper

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I got this from a site that calculates your flyback transformer.

Duty= Vout(Vin*N)

My flyback trans is running from the mains 320v, and the o/p is 30v, the primary is 84 turns and according to my hand calculations the secondary ought to be 8 turns to get 50% duty cycle.

The above calc doesnt match up at all.
 
The above calc doesnt match up at all.
What does that mean?

Doing the math in my head. 320V supply, 50% duty cycle= the flyback voltage should be 320V, so a 10:1 transformer will give you about 30 volts.
This is all if you are running continuous. But dis-continuous could be another story.
 
yes continuous, i realised my error i was calcing for a circuit using a si gle inductor not a transformer, doh.
 
Your right there Ron.
My design looks as though its going to be a little diffrent, I have a load of 600v fets, 320v reflected will overvolt them slightly, and if theres a lot of ringing probably enough to destroy them, so I'm going to fudge the design to have less reflected voltage and lower duty cycle, this will up the primary current, but thats ok these fets are beefy to247 jobs, way overrated, also the rectifryer will work less hard as the discharge cycle will be longer.
 
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