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tps54020 as Current Source

David Ayers
Prodigy 150 points
Other Parts Discussed in Thread: TPS54020

Is it possible to configure the TPS54020 as a constant current source? I would like to use it as an LED driver in an imaging application. The internal MOSFET configuration is preferred over the configurations I've seen for drivers that are specifically used for LED's.

  • 0
    TI__Guru**** 191445 points
    You might possibly do that. Typically insted of voltage feedback, you would sense the current with a resistor between the bottom LED and GND. If you are looking at TPS54020 wich has 0.6 V reference and 10A output you could be looking at 6W of power dissipation in that resistor. Can you post your actual requirement? Maybe there is a better solution, we have a rather large offering of dedicated LED drivers.
  • 0 in reply to JohnTucker
    Prodigy 150 points
    We are trying to drive 31 LED's, each with a forward voltage of 3.5 - 3.7V, and a load current of 6 to 9 amps. I can break them up into serial strings of either 3 or 6 LED's each. This is a retrofit, so the 12V power supply already in use would be ideal. However, we can obtain power supplies with higher voltages. The boost current LED drivers would seem like the best solution, but they are quite complicated, there are no examples that indicate that my design will work, and so far, I've been unable to successfully simulate them (even using the exact circuit in the example). The spice model crunches forever and never finishes.
  • 0 in reply to David Ayers
    TI__Guru**** 191445 points
    Whid devices did you look at specifically? Pspice does take a while...I ran some simulations last week that took a couple hours for each, just a few msec of analysis.
    Just to recap, you have Vin = 12 V, Vout = 108 -115V, Iout 6 to 9 A. It would probably be better if broke them up to get a lower voltage.
  • 0 in reply to JohnTucker
    Prodigy 150 points
    Yes - the plan was to break it up into either a string of three (max. of 11.1 V), or a string of 6 (max. of 22.2 V). Only the string of 6 would need the boost converter. Either that, or switch to a higher voltage supply. I actually can't find a boost converter that will support my 6 - 9 amp requirement. On the buck converter end, I've been looking at the LM3434.
    I wasn't aware that the spice simulation would take that long, no wonder I was having trouble.