Efficient LED Circuit

Discussion in 'General Electronics Chat' started by rappa, Dec 10, 2008.

  1. rappa

    Thread Starter Member

    Nov 17, 2008
    I have been using the LM317T to drive a 1W LED but I'm not really happy with the amount heat it generates.

    Has anyone worked with the an LED driver, such as the STCS1 http://www.st.com/stonline/products/literature/ds/13415/stcs1.pdf ?
    They provide an application circuit on page three. The feedback resistor is determined by Rfb = .100V/I So .286 Ohms for .350A.

    The two challenges I see with the STCS1 are:

    1. It's SOIC-8, so not breadboard friendly. Are there any tricks to getting it on a protoboard/breadboard?

    2. The resistor values to output the necessary currents (.35A, .7A etc) are hard to find. In this case I need a .286 Ohm which I could not find anything close enough in a through-hole package. Is there a calculator of sorts that could determine the arrangement of standard resistors values to achieve this resistance?
  2. SgtWookie


    Jul 17, 2007
    1) Chip carrier. Have a look at this PDF for some tips:

    2) Use resistors in parallel.
    Rt = 1 / ( (1/R1) + (1/R2) +.... (1/Rn) )
    Three 2 Ohm resistors in parallel with two 1 Ohm resistors will get you about 285.7mOhms
  3. rappa

    Thread Starter Member

    Nov 17, 2008
    Thanks for the suggestions