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Problem with regulation in flyback smps

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saurav_sdpl

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, I have designed a flyback smps for 4.2V/2A.using TNY268.

Underno-load condition its working fine between 100V ac to 250V ac.

but when i am giving .5A load the voltage dips to 2.9V, ie i am not able to achieve regulation.

I have used 3.3V /.5W zener. biasing resistance for zener is 270r, and opto used is SFH6186.

Wat could be the possible causes for this.

its urgent
 

Re: flyback smps

are you sure that the transformer bobin,core,wire guage,turns are fine?
have you used PI design software for calculating that ? only if you confirm on that,proceed to other parts of the circuit.

regards,
 

Re: flyback smps

try this

use TL431 feedback circuit
use UFR series output diodes like UF5402

check the transformer design

good luck:D

regards
satya
 

Re: flyback smps

0
the turns i have used on primary is 104, with 36SWG, and secondary 6T, 21swg

core:EF20,
 

flyback smps

do one thing..go thru the link below..
down load the PI expert design software and enter your design parameters..It will give you the components to be used in the ckt(core,bobin,turns,swg etc)

**broken link removed**

Added after 1 minutes:

cross check it first,whether you have used the same stuffs.
 

Re: flyback smps

try this winding data

core EF20
primary turns=86
secondary turns=3

primary inductance=1000uHenries

regards
satya
 

Re: flyback smps

actually when i am changing the value of bias resistance for zener, the regulated voltage o/p changes.

ehen R=320r, o/p=4.4v
when r=270r,o/p=4.25v

what does this imply.
 

Re: flyback smps

plz check wats wrong with the circuit for 4.2V/2A
 

Re: flyback smps

i can not see the circuit in above (Doc1.doc)file

please send the circuit one more time

regards

satya
 

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