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
    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.
  2. KJ6EAD

    Senior Member

    Apr 30, 2011
    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.
  3. Wendy


    Mar 24, 2008
    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
    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


    Nov 30, 2010
    I second that vote. 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.