Regulator IC help

Discussion in 'General Electronics Chat' started by gobi615, Mar 7, 2013.

  1. gobi615

    Thread Starter Member

    Jul 26, 2011
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    Hi , is there any regulator IC gives output voltage 13V to 16Vdc for input voltage of 12Vdc .
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    A step-up or boost regulator
     
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    LM2577 converter
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,163
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    An MC34063A will do the trick. These are switching regulators, so your design problem does not stop with finding the IC. You need to carefully select an inductor and find a source of low ESR capacitors. You need to follow the calculations in the datasheet to avoid nasty surprises in the final product. Last point is:

    "Only a fool would build a switch mode power supply on a bradboard."

    At least nobody here would ever do such a thing.
     
  5. gobi615

    Thread Starter Member

    Jul 26, 2011
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    Is linear regulator like 7815 can boost voltage from 12V to 15V ?
     
  6. Evil Lurker

    Member

    Aug 25, 2011
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    No they are step down only. Linear regulators work by more or less by "dropping" excess voltage... which for practical intents and purposes means converting excess voltage into heat.

    Not too big a fan of the LM2577's either, although that particular switching regulator would work OK, if you were to design your own dc-dc converter the lowish switching frequency may mean being forced to use "exotic" inductors... powdered iron cores such as type 26 or type 52 will work, but depending on how much inductance you need they may end up being huge to accomodate the necessary number of turns of wire needed to create the amount of inductance needed (as in the case of a single layer wound toroid) and then core losses start to come into play. Ferrites can work too, but you have to be careful not to saturate them thanks to their high permeability and lack of "built in" distributed air gap like the powdered iron cores have. That leaves the exotic materials like Koolmu and what not which have more permeability than the typical powdered iron core but less than ferrites. Although these are readily available, the catch is these inductors can actually cost more than the IC, PCB, and all the other components combined.

    In addition going from 12v to 13v is not a very large step and your typical boost converter might not be able to handle the small gap. Plus if you ever wanted to run your 13v widget off a 12v lead acid battery you would be out of luck since they typically have a maximum resting charge voltage of around 13.8v IIRC. My suggestion would be to look at some of the SEPIC (called automatic step up step down or something like that) power supply modules on Ebay (ironically also based on the LM2577) and perhaps "upgrade" them from the crappy chinese components they typically use (like replacing the input and output filter capacitors with some good low ESR high ripple rated Japanese manufactured ones from say Nichicon). By going with the SEPIC topology you can spit out a constant 13v (or whatever) all the way from a full charge on a battery till its run down to the point where it doesn't need to be discharged anymore (you can run one completely flat if you need to, but it isn't good for their longevity).

    Again though there is a catch with SEPICs, and that is depending on how they are set up and what components are used and how fast their switching frequency is efficiency can suffer. Not only that but depending on how they are set up it is theoretically possible to exceed the ripple current tolerances for the capacitors, especially the crucial coupling capacitor. Thats why I am a bit leery of the ones on Ebay, you take an IC like an LM2577 which is on the low end frequency wise and a cheap Sus'con or Cheng capacitor and you have a recipe for a short lived product.
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    I have some chips here for 5V -> 3,3V, at 2MHz.
    They use 1uH inductors.
    These cost not even 1 cent each.

    Maybe it could be hacked into a booster...but ehm, not for that voltage.
    This is new technology.

    OP does not write how much current is required.

    For some 100mA inductor costs are neglible.

    It could be done with 78l05, 10f200, and a digital MOSFET. Many ways to boost voltage. There are 100s of specialized chips as well.
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
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    How much current do you need ?
     
  9. takao21203

    Distinguished Member

    Apr 28, 2012
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    I made a jouletheif type circuit with 2.2uH kind of inductors, really tuned it to the margin.

    The blue LED would turn dim, if I inserted another inductor pointing into the air, and touch the other end with a screwdriver. Without the loading coil, it would not do anything. Must have been shortwave band. On a breadboard...

    Yet of course avoiding adjacent rows like the plague. Only good for 1 or 2Mhz.
     
  10. gobi615

    Thread Starter Member

    Jul 26, 2011
    30
    0
    Hi , these power supply is for mosfet driver supply so they require very low current something around microamps(uA).
     
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