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UCC2895 voltage feedback

vahid hemmat
Prodigy 80 points

In a full bridge dc-dc topology:

how can I change the output voltage level?

I changing the "EAP" pin input voltage manualy with a pot, but it dosent work ..

help me please Im new in SMPS.

  • 0
    TI__Mastermind 25570 points
    Hi EAP is the correct pin to adjust - so you are right there. there are several reasons why EAP may lose control of the output
    1/ The power stage may not be working properly or at all
    2/ The power stage may be operating but stuck at its current limit point - check thins like the current sensing network and the signal at CS
    3/ Is the reference voltage at the REF pin still ok ?
    4/ What value pot are you using - it may be pulling down VREF ?
    Does the system operate at all ? - what is the normal output voltage
    Adjusting the EAP pin will work but it's open loop - you are breaking the feedback loop, If you want to change the output voltage 'properly' then try adjusting the potential divider which is sensing the VOUT. Hope this helps - let me know how you get on. Colin
  • 0 in reply to Colin Gillmor
    Prodigy 80 points
    Hi Colin and thanks for your solution.
    I completed the feedback loop and place a pot between REF and EA+. I also connected the EA+ with a res to ground . by cutting the the res and changing the pot I see Vout changing. but the output voltage level is very low. about 3V.. and I want 20 V output. how can I change the outpot voltage level? and what set the output voltage?