Trading volts for amps?

Discussion in 'General Electronics Chat' started by JoshK, Feb 27, 2016.

  1. JoshK

    Thread Starter Member

    Dec 24, 2009
    23
    1
    I have 60 VDC @ 0.25A. (That is 15 watts)
    But I want to run a 4V LED.
    When I connect the 60V @ 0.25A direct to the LED, it just runs at 2.50V @ 0.25A because I am short on amps.

    I want 4 VDC @ 3.75A. That would still be about 15 watt, and it can handle this great. Ok, I know I will lose some watts during the conversion. But anyway...

    How do I trade volts for amps to keep my watts about the same? What components do I need to do this properly?
     
    Last edited: Feb 27, 2016
  2. wayneh

    Expert

    Sep 9, 2010
    12,135
    3,052
    Assuming your 60v supply is DC, I'd shop for a DC-DC converter with specs that meet your needs. They're very inexpensive on e-bay these days. I'd look for one rated to 20w or more, since I suspect the specs might be exaggerated instead of conservative.

    Are you sure your LED needs 4v? It has an internal current control? If not you may need an LED driver. This is a constant current supply instead of a constant voltage.
     
  3. JoshK

    Thread Starter Member

    Dec 24, 2009
    23
    1
    Thanks. I was hoping to learn though, versus finding something already made. For example, is the answer a buck-regulator with an inductor and other required components? Or would that not solve my problem? What would be the amp-mode equivilent regulator - since you mentioned amp-mode?

    Yes I am very sure of the LED and power supply specs. Constant current would be best. But it's not necessary since I just don't have the watts to blow it out.
     
    Last edited: Feb 27, 2016
  4. #12

    Expert

    Nov 30, 2010
    16,304
    6,814
    http://www.ti.com/ww/en/simple_switcher/index.html

    I think I'm kind of burned out right now. JoshK shows up saying he lives in a universe where the only power source is 60 VDC with inadequate current. He can't plug into a wall outlet, buy a different battery, or purchase a finished product, so please design one for me. These constraints seem artificial and arbitrary. The link I posted is a calculator to do this job and the first run shows 17 ways to do it. Please plug in to that website and start your design.
     
  5. JoshK

    Thread Starter Member

    Dec 24, 2009
    23
    1

    <SNIP>. But thanks to your link I found the TPS54560 chip. That's all I needed to know.

    Moderators note: removed personal attack.
     
    Last edited by a moderator: Feb 28, 2016
  6. wayneh

    Expert

    Sep 9, 2010
    12,135
    3,052
    OK well you didn't start off saying you wanted a DIY solution, the longer and more expensive path to your goal. But yes, you need an efficient buck converter with a controlled current output.
     
  7. JoshK

    Thread Starter Member

    Dec 24, 2009
    23
    1
    Thanks Wayneh. Yea I forgot to mention I wanted to learn.
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    Rule of thumb for DC-DC converters is that you can shoot for 80% conversion efficiency. You might make it or you might not, but getting closer to 100% is going to be incredibly hard. Good Luck.
     
  9. #12

    Expert

    Nov 30, 2010
    16,304
    6,814
    The Simple Switcher site advertises several designs at 80% and at least on at a higher rate.
     
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