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Measuring Feedback Loop from flyback

Question asked by Edwin Marte on Oct 11, 2016

Hello All,

 

a few days ago I received a Isolated universal mains flyback converter demo board (TEA1721ADB1061). My main intention was to measure the Feedback Loop. I am using the analog discovery analyzer with isolation transformer. I inserted a 22 ohm in series with R3 (from schematic) to be able to inject a signal. 

 

I placed a 1000 ohm load across the 12V output, I measured 13.48V constant in that output. My problem is that when I touch the 22 ohm resistor, the feedback loop, with the scopes probe the output voltage drops suddenly to 0.3-0.8 Volts. I haven't been able to make any measurements.

 

I wanted to be able to measure the feedback loop  to check if this controller will satisfy an application e are working on. In the data sheet there is no much information compensation , how it works or how it colud be done. Anybody has any more information besides the one provided by data sheet of  TEA1721?

 

Any help appreciated,

Edwin

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