Help choosing efficient regulators

Discussion in 'The Projects Forum' started by Lectraplayer, Jun 28, 2015.

  1. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
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    I'm wanting to build a few power regulators and boosters for several projects, and am trying to figure out what is most energy efficient. I intend for all to use standard "parts drawer^ components when possible.

    One is a 48 volt .75 amp DC supply for a WIFI router (a really nice one!). I'm not sure why the cheapest capable supply I'm finding is $75 plus tax. ...but I do have a transformer I can get 60 volts from.

    I also have several battery chargers. These will be run at a static voltage, 14.4 volt 1 Amp for VRLA batteries and 4.2 volt and between .5 amp and 1 amp for lithium cells. Most will pull from a car battery, but I'm also wanting to charge both batteries at a low rate from USB power (5 volt .5 amp to .9 amp max). I have thought about a joule thief for the booster, but I read it's not all that efficient. One boost will be 11 volts to 14.4 volts, which is minor. Also contenplating USB to 14.4 volts @ .1 amp.

    What booster and regulators are the most effccient?
     
  2. #12

    Expert

    Nov 30, 2010
    16,837
    7,489
    Switching regulators. They contain an inductor and switch the current on and off, really fast. Efficiency rates usually show up between 85% and 95%.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,555
    3,362
    Ditto. You can find what you described on e-bay very inexpensively.
     
  4. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
    77
    5
    I have not dealt with these. How well do they regulate with a variable input? As we all know, batteries go through a range.
     
  5. #12

    Expert

    Nov 30, 2010
    16,837
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    They are called, "regulators" because they regulate. If the input voltage didn't vary, you wouldn't need a regulator, so they must have been invented to regulate a variable input...right? In my experience, way tighter than a volt, like a tenth of a volt, or less, including noise and ripple. How well do you need your voltages regulated that you suspect a regulator might not regulate enough?
     
  6. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
    77
    5
    One would think, but I have seen some write ups call all sorts of things "regulators" when they don't regulate. ...so I have to ask.

    As mentioned, these projects will be battery chargers, which requires an open circuit voltage that is "dancing upon the head of a needle," as some write ups call it. However, "sag," which is a drop in voltage caused by load current, is acceptable, and being designed for.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,563
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    When charging lithium cells, you need pretty precise voltage regulation - over charging them by a fraction of a volt can be dangerous!

    With lead acid, the difference between 13.6V and 14.4V is the difference between leaving it float charging for months, or gassing off the distilled water in weeks if not days. But you need to start off at 14.4V to get the main bulk charge in there.

    For reference: the 48V originally mentioned is frequently used in telecoms equipment - surplus PSUs sometimes come up at low prices.

    48V is also used for high spec professional microphones - but expect PSUs with weedy current and eye-watering prices.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    48V is commonly used in telecoms gear - surplus PSUs sometimes come up at almost scrap metal prices.
     
  9. Lectraplayer

    Thread Starter Member

    Jan 2, 2015
    77
    5
    Sadly, I never seem to be near telecom equipment when it's coming out, or I would Bogardt from that. Anything else is either a cheezy CAT-5 feeder with reports of blown equipment associated with it. I trust my analog regulation better. I may also add battery backup to the router while I have my iron out. ;)

    My other batteries seem to only be getting partially charged with the factory solutions I am using. Even NFF, they seem to be losing capacity within 4 or 5 partial cycles. Again, I think I can build better.
     
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