Jump to content
Electronics-Lab.com Community

Alf_Melmok

Members
 View Profile  See their activity

  • Posts

    4

  • Joined

  • Last visited

    Never

 Content Type 

Posts posted by Alf_Melmok

  2. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    You are right, i forgot about  the voltage losses.
    In my country mains voltage change from 200 to 240 very often (In rare cases, even is worse (phase is not uniformly loaded)). That's why i want to limit the input voltage.
    It's a vicious circle. In my country i can't buy op amp that you recommend. So that i can't use 28VAC transformer. And i can't find 28-30VAC transformer. I can't find another scheme similar PSU. I just want this power supply with 20V transformer.  :'(
    Thanks for your help

  3. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted


    Since your voltages are very low, many resistor values will need to be re-calculated.


    Can you help me?


    You do not need to use U4 and D13 since without them the unregulated positive supply is only +26V which is fine for a TL071 or TL081 opamp.


    I want to limit the input voltage. If the line voltage change. So that the output has always been a 20V.


    With U4 and D13 the maximum output voltage will be only about +14.4V. Without U4 and D13 the maximum output voltage will be about +20V.


    Just in this scheme, the output voltage 30VDC (U4+D13=30,2V). I decided if I'm have 20V, then i  need replace the U4 and D13 (18+2,4=20,4V). I was wrong? The output voltage of 20V was enough for me.


    If U5 is a -5V regulator then it will not work (it is not needed anyway) since its input voltage is too low.


    It also surprised me. I think D7 not needed. Am I right?
    Or, maybe, you advise me another way in my situation. I read this and some similar forum almost 2 weeks and dont know what to do. Thank you anyway.
×
×
  • Create New...