flyback converter

Thread Starter

pini200

Joined Feb 15, 2016
14
Hi
i have a problem
i build ac dc converter based on flyback and i get in outpout sawtooth with rippel 1v
i should get stable voltage in outpout
input: 110-230Vac,outpot 12v 1A
i used chip viper37LD and isolated feedback
pic.PNGpic.PNG
 

ian field

Joined Oct 27, 2012
6,539
Hi
i have a problem
i build ac dc converter based on flyback and i get in outpout sawtooth with rippel 1v
i should get stable voltage in outpout
input: 110-230Vac,outpot 12v 1A
i used chip viper37LD and isolated feedback
View attachment 101499View attachment 101499
You could have Trr trouble in the rectifier - a Schottky barrier type is faster, as long as you keep within its low reverse voltage rating.

You may also need a LC Pi network as the output filter, use wire about 2 - 3mm dia - about half dozen or so turns on a ferrite slug.

The output filter electrolytic(s) need to have very low ESR - you could also add film capacitors in parallel, at least 0.22uF.
 

Roderick Young

Joined Feb 22, 2015
408
Are you sure you have the phasing right on that transformer? Could it be that you are rectifying the forward part of the pulse, and not the flyback?
 

ian field

Joined Oct 27, 2012
6,539
Are you sure you have the phasing right on that transformer? Could it be that you are rectifying the forward part of the pulse, and not the flyback?
Forward conduction in a flyback converter would be obvious by the low output.

If you increased the secondary turns to correct it - you'd soon find out if the rectifier didn't have high enough PIV rating.
 
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