LED driver Circuit

Discussion in 'The Projects Forum' started by kaushizcute, Feb 28, 2012.

  1. kaushizcute

    Thread Starter New Member

    Feb 16, 2012
    24
    0
    I am making an LED driver circuit which will drive 2 strings of LEDs connected in parallel.

    Each string has 4 LEDs in series.

    Specification of each LED is 2.2V, 20mA.

    This means the supply that i need to give to the driver should be 8.8V or say 9V and 40mA.

    My original supply is directly from car battery which gives a spike of 9V-16V. If i introduce an led driver directly to this supply it will burn.

    So i need to stabilize this spike to say 9V and this 9V now will be the supply for my LED driver. With this 9V i will attach a current limiter.

    Now i want to know how will this voltage regulation take place meaning the circuit that i need to make or is there any IC available.
     
  2. bedfordwheelnuts

    New Member

    Apr 19, 2011
    7
    1
    use an On-Semi device like the 20mA constant current driver NSI45020W. Small Cheap, and does exactly what you want to do. Because it's a constant current device, any variation in voltage, as you say from a car pwer supply, will have no effect on the brightness of your LED. (Easily used with a PWM dimming circuit too.)
    Rgds Jeff
     
    kaushizcute likes this.
  3. kaushizcute

    Thread Starter New Member

    Feb 16, 2012
    24
    0
    but the current is 20mA and the circuit needs 40mA
     
  4. biiiboooy

    New Member

    Feb 28, 2012
    2
    1
    you can use a 7809 voltage regulator IC. It will maintain 9V across your circuit even if your supply increases.
     
    kaushizcute likes this.
  5. kaushizcute

    Thread Starter New Member

    Feb 16, 2012
    24
    0
    ok.
    so i will need to drop 0.2V.
    how will i limit the current? a resistor would be sufficient or any ic is required.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Actually this is incorrect. Any regulator circuit, be it voltage or current, will work to prevent this. My favorite is a LM317T current regulator

    [​IMG]

    There are many schemes that will work.

    Have you read this article? It covers the basics in chapters 1 and 2.

    LEDs, 555s, Flashers, and Light Chasers
     
Loading...