Flyback transformer output current
Flyback transformer output current
(OP)
Hello,
My question is:
What is the maximum current drawn from a SMPS flyback converter at 7V if the transformer is rated for 10VA, 12V at the single output?
Is this the same as with the regular transformers - 0.83A?
The converter is going to be used for supplying 7V from 85-275V AC at the input. The switching device is TNY268. The transformer is SPW717014 from HARTU.
Regards
Zdravko
My question is:
What is the maximum current drawn from a SMPS flyback converter at 7V if the transformer is rated for 10VA, 12V at the single output?
Is this the same as with the regular transformers - 0.83A?
The converter is going to be used for supplying 7V from 85-275V AC at the input. The switching device is TNY268. The transformer is SPW717014 from HARTU.
Regards
Zdravko





RE: Flyback transformer output current
Now to your question:
"What is the maximum current drawn from a SMPS flyback converter at 7V if the transformer is rated for 10VA, 12V at the single output?"
I assume the correct wording should have been:
"What is the maximum current that can be drawn from a SMPS flyback converter … ?"
Well certainly you would not want to be drawing more than 830mA RMS from the winding, but that may not be the limiting factor. The way you are driving the transformer must affect how much power can be delivered. Things like flux in the core, flux waveshape, frequency of operation, will be significant contributors to evaluating how much power can be pushed through the transformer.
RE: Flyback transformer output current
Thank you for responding.
RE: Flyback transformer output current
Consider a mains transformer rated for 230V. It has a VA rating which tells you how much current can be drawn from it. If you now run the transformer at 180V, which can be done, the VA rating will be lower. It is true that the iron losses (core losses) will be lower at 180V but the copper losses at the same current will be the same. I suppose you might increase the current rating a little because the core is not getting quite so hot, but that is not a good way to go.
At the end of the day the VA ratings of a transformer is based on temperature. If it gets too hot, the self-fluxing wire on the transformer will break down, and the transformer will fail. If the transformer does not overheat then that power level is acceptable. The only warning is that the temperature has to be measured inside the winding, as the hottest point will be somewhere in the middle of the winding. This hot spot will govern the limiting power level. Only the manufacturer will really be able to measure this.
Why not just ask the manufacturer’s applications engineers? Failing that I would avoid overrunning the transformer in this way.
RE: Flyback transformer output current
I am concerning to change the transformer.
Regards
Zdravko
RE: Flyback transformer output current