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Circuit to limit capacitor power draw

  1. Apr 7, 2008 #1
    Hello all!

    Circuit to limit power draw from capacitor?

    I want to limit my 100,000 uF 35 V capacitor that is charged (via schottky full-wave bridge) to between 4V to 16 V from dumping it's charge all at once.

    I would like the capacitor to provide 300 mW to the load (10 ohm resistance). (ie. 1.25v @ .24A ) What do I need to do?

    I could put diodes in between the capacitor and load for voltage drops - but the capacitors charge will vary from 4V to 16V..

    I want to maximize efficiency.

    Should I be looking at a switch mode DC/DC converter? Like this product?

    LT1933 - 600mA, 500kHz Step-Down Switching Regulator in SOT-23

    http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1032,C1064,P7531#featuresSection

    Is this the type of circuit component I should be searching for to accomplish this?
    Advice on implementing this?
    I'm a bit over my head on this..

    Thank you!

    CH
     
    Last edited: Apr 7, 2008
  2. jcsd
  3. Apr 7, 2008 #2

    berkeman

    User Avatar

    Staff: Mentor

    Yes, you should use a "Buck" DC-DC converter to make your regulated output voltage. The DC-DC can also supply the current limit function that you mention.
     
  4. Apr 7, 2008 #3
    Thank you for your reply!

    I'm glad to have validation for the process I was considering. I have decided to go with one of the LT chip models.

    FYI: Anyone that needs a SPICE program - LT offers a free/excellent one @:

    http://www.linear.com/designtools/software/switchercad.jsp

    CH
     
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