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Detailed Information about Testing Practical Bode Plot in Regulators

sina kamkar
Intellectual 435 points

Hey guys,

I have read the documentation of AN-1889 "How to Measure the Loop Transfer Function of
Power Supplies" in Completely.

To do the actual and Practical test, I need more detailed information (such as: Part Number T1 (Injection Transformer) and Detailed Information for Oscilloscope and etc).

 I appreciate any helps ;)

  • 0
    TI__Guru**** 191445 points
    You can use pretty much any oscilloscope. As far as the transformer, we have dedicated network analyzers in our lab. It has been many, many years since I have done a manual measurement. Let me see if I can find out some details about the transformer. It looks generic to me based on the photo.
  • 0 in reply to JohnTucker
    Intellectual 435 points

    Thanks John Tucker,

    I need a more precise Specification and Characteristic of this transformer.

    In other words, I want a Part Number to buy it from Distributors.

  • 0 in reply to sina kamkar
    TI__Guru**** 191445 points
    That app note is 9 years old. Probably only the original author would know the part number that was used. I will check to see if he is still around. The ones that we use in our lab are sold along with the network analyzers that we use.
  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    Actually, the app note is much older than nine years.  There is no technical owner listed for it, so it will not be possible to get any additional information on it.  I can tell you that suitable injection transformers are commercially available from vendors such as Ridley Labs or Venable Systems.

  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points
    Some more info you may find useful...

    Here’s a thread using a 10mH common-mode choke …
    www.eevblog.com/.../

    … from this parent thread …
    www.eevblog.com/.../

    Also, check out last EDN Design Idea here …
    m.eet.com/.../15432-91604di.pdf
  • 0
    TI__Expert 4365 points

    I certainly have never used the manual method of creating a Bode plot using a scope. Have always been fortunate to have access to a frequency response analyzer from Venable(Austin TX), A/P Instruments (Ridley - Camarillo CA), or Omicron (PicoTest- Phoenix AZ). Each of these companies should have YouTube videos illustrating the usage of the product. Also, each of these companies has injection transformers available separate from the analyzer they sell.

    Also I know the Venable website has an excellent technical library with classic instructions on loop analysis. PicoTest has some papers and videos. Have not looked at Ridley's site lately.