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Which injection transformer for feedback loop measurements?
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jmw:
I'm trying to follow the procedure in AN-1889 for measuring the feedback loop gain in a power converter. A transformer is used to couple a function generator signal across a small resistor without passing DC, but I'm not sure what kind of transformer to use. The note says "There are special transformers for such measurements available, which offer a very flat voltage transmission over a wide frequency band." What kinds of commercially available transformers specifically fit this bill? I was browsing Digikey and thought maybe things under current-sense transformers or pulse transformers seem like they could work. Has anyone done this and have recommendations?
uer166:
Got this guy at work not long ago, can't comment on how good it is, but it's designed for your application: https://www.picotest.com/products_J2101A.html
jmw:
Did some searching, looks like this topic has come up before. Seems the options are that Pico-test unit or similarly priced, or homebrew it. Guess that's another project to put on the board :-DD
Mechatrommer:
--- Quote from: uer166 on April 23, 2020, 06:09:45 am ---Got this guy at work not long ago, can't comment on how good it is, but it's designed for your application: https://www.picotest.com/products_J2101A.html
--- End quote ---
$525 can buy a lot of stuff... did the OP created this thread due to this thread? https://www.eevblog.com/forum/testgear/injection-transformers-bode-plots-application/?topicseen Jay_Diddy_B uses much cheaper Wurth 744 229 Common Mode choke. ($2.46 USD Qty 1 Digikey) maybe testing and try and error with much cheaper transformer first can give us much lesson before we can spend anything near $500 bucks. if i want to do real life testing on this, i will start first with my function generator and/or if necessary wind my own HF transformer with available ferrite core in my stock. ymmv.
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