Need help with high current voltage limiting

Discussion in 'The Projects Forum' started by capitanfracassa, Oct 12, 2009.

  1. capitanfracassa

    Thread Starter New Member

    Oct 12, 2009
    I am running an AC HID lamp on a battery through an inverter, with the following constraints:

    1. The voltage of the battery range from 16.5V when full to 12.5V when depleted.

    2. The inverter has a 15V high voltage shut-off and a 10.5V low voltage shutoff.

    3. The LAMP + control gear consumes about 25W. Assuming the inverter also consumes something, I think the current draw from the battery is 2A-2.5A.

    without modifications, the lamp won't run if the battery is charged over 75-80% capacity.

    As a temporary kludge, I placed six MUR810 8A diodes in series. That works, but it means I have a 5W hip warmer that I really don't need.

    looking for a magic bullet, but I'll settle for a silver one ;-) Any ideas?

    Thanks for reading.
  2. bertus


    Apr 5, 2008

    You could use a buck-boost converter.
    This will regulate down in the input is to high and up if the input is to low.
    With the LM5118 you could make a converter to give 12 Volts constant at the output.

    The datasheet has some example schematics.
    On page 23 there is an example for 4 - 70 volts input and 12 volts output.

  3. capitanfracassa

    Thread Starter New Member

    Oct 12, 2009
    Thanks! .