Alternative to adjustable linear regs ?

Discussion in 'General Electronics Chat' started by Dyslexicbloke, Jun 23, 2011.

  1. Dyslexicbloke

    Thread Starter Well-Known Member

    Sep 4, 2010
    528
    34
    Hi folks,
    I generally keep LM317’s or LM350T’s in my bench stock k to avoid having a load of different 78 series regs.
    Granted they need a couple of additional components but they also work well as current sources so on balance I think they are well worth having on hand.

    Having said that just recently I have been looking at circuits that need a big input voltage range and even for relatively small currents a single linear regulator dropping from 30V to 5V is going to dissipate enough power to need a sizeable heat sink.
    Add to that the fact that a 317 will only accept about 36V and I am left wondering if there is a better solution.

    Do any of you know of an adjustable switching or PWM based monolithic regulator that would accept a wide input voltage, preferably well above 36v and down to 5V whilst still being easy to deploy with a minimum of external components?

    If the answer is yes and magnetics are going to be required where would I go looking for them or should I be thinking about winding them?

    Almost all my projects now, large and small, are aimed at alternative energy so I guess I should be going for the efficient switching supply option anyway but I am not finding it an easy field to tackle.

    Looking forward to your comments.
    Al
     
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,426
    364
    I get surplus DC-DC converters based on the MC36043A control chip and modify them. You can get them in the form of car USB power supplies or old car cell phone chargers. $1.25 and up at the local thrift store or on eBay. The MC34063A can handle inputs as high as 40V.

    http://www.onsemi.com/pub_link/Collateral/MC34063A-D.PDF
    http://www.onsemi.com/pub_link/Collateral/AN920-D.PDF
    http://focus.ti.com/lit/ds/symlink/mc34063a.pdf
    http://focus.ti.com/lit/an/slva252b/slva252b.pdf
    http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001232.pdf
    http://www.fairchildsemi.com/ds/MC%2FMC34063A.pdf
     
  3. Wendy

    Moderator

    Mar 24, 2008
    21,012
    2,744
    Only partly joking, the 555. I've been working on a circuit that might make a good switching regulator. I'll post it when I have something more concrete.
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,907
    1,789
    Give the National Semiconductor website a try. They have a boatload of sample designs you can search by first inputing your circuit specs.

    They are generally very good at using standard off the shelf magnetics.
     
  5. #12

    Expert

    Nov 30, 2010
    17,887
    9,293
    I second that vote. www.national.com has a "simple switcher" calculator that is like going to heaven compared to doing it by hand.
    Texas Instruments must have something similar. I can tell because it's in my notes.
     
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