• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1035 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM3410: High power LED driver selection

Rakesh Menon
Prodigy 20 points
Part Number: LM3410
Other Parts Discussed in Thread: TPS92692, TPS92691

Hello,

I'm currently working in a project where I need to control the intensity of 24 high power LEDs in 5 levels. I'm planning to use LumiLeds L1CU-BLU1000000000 (https://www.lumileds.com/uploads/705/PB198-pdf) where the cut-off voltage is 2.83 volts and current is 350mA. As per the requirements, the power supply should be from an SMPS ( maximum output - 12v,6A).

I need to select a constant current driver with PWM facility ( 0-5v max ) to control the LED intensity from a micro-controller. What type of driver IC will be best suit for this application?

What I know so far is:

  1. I can use a constant current boost converter IC with PWM ( input-12v,3A max and output 23v,1.3A) and connect 8 leds in series and 3 such strips in parallel so that each parallel branch would get around 350mA and each LED in the strip would get around 2.8V. In this case I need only one PWM channel from micro-controller to dim all LEDs at a time. If someone could suggest a driver IC for this specification it would be great.Are there any hidden flaws in this Idea or is it less efficient in terms of power consumption?

  2. I can use a constant current buck converter IC with PWM ( input 12V, 3A max and output 9.5V,2.8A) and connect 3 LEDs in series and 8 such parallel strips. Each series strip gets around 350mA and each LED gets around 2.8v (with some resistors added to each series branch)

If I'm using 3 driver ICs and dividing up the LED load among those, is it still okay to use 3 pwm channels from the micro-controller for dimming all the LEDs simultaneously?

I searched and found LM3410 but I'm not quite sure whether it actually suites my application or not.

Please do suggest me a good design method and suitable driver IC.

  • 0
    TI__Mastermind 28655 points
    Hello Rakesh,

    So, is this three strings of 8? The numbers don't add up so I don't know what you are trying to do, 23V and 1.3A don't match 2.83V and 350 mA. The LED link above just shows a general table of multiple color LEDs, no Vf or maximum operating current or any operational curves.

    The LM3410 is good for up to 24V. If your output is 23V is that the absolute maximum? Or, if the LEDs are used at cold temperatures or there is a high tolerance that can cause the LED stack to be above 24V I would not use this part. You can look at the TPS92691 and TPS92692 which would be able to do 23V easily, however if this is 24 LEDs in series that is a different design.

    Regards,
  • 0 in reply to Irwin Nederbragt
    Prodigy 20 points
    Hello Irwin,
    I assumed a driver IC which could at least provide 23v at 1.3A (approximate) from an input SMPS (12v,3A max). If I'm connecting 3 strings of 8 series LED in parallel, to this assumed driver IC, then for each parallel branch the current will be around 1.3A/3 = 0.43A; may be I could add one more parallel branch with a resistor which would consume some current so that all branches will get around 350mA. Each LED in the series circuit if consumes 2.83V each, then it would become 2.83*8 = 22. 64v, I roughly approximated this value to be 23v.

    The 24V output is not absolute maximum. It is just an approximated value for the combination I mentioned above(3 parallel strings each having 8 series LED ). Sorry that I pulled out a general link as reference for LED, the actual datasheet is here: www.mouser.in/.../DS198-1350748.pdf .

    I am thinking about different configurations of arranging these 24 LED so that I could use minimum no of Driver ICs and minimum number of PMW channels from the micro-controller.

    The constrains for me are:
    1) Input power supply - should be an SMPS ( either 9v or 12v, not more than 6Amps)
    2) LED - >30 lumens, blue - 420-500nm
  • 0 in reply to Rakesh Menon
    TI__Mastermind 28655 points
    Hello,

    So this is in the LED datasheet for blue LED: "Blue L1CU-BLU1000000000 2.50 2.83 3.50" This is the min, typ and max Vf of this LED at 350 mA. If maximum is 3.5V times eight LEDs you are at 28V, the LM3410 cannot do this. Also note that the LED Vf is specified at 85 Celsius which means it will be higher at ambient. The 24V is the maximum the LM3410 should be used at, not your maximum. I would look at the TPS92691 or TPS92692 if this is the case. Other wise you could have four strings of six but then you may run into dimming issues if you plan to dim fairly low.

    Regards,
  • 0 in reply to Irwin Nederbragt
    TI__Mastermind 28655 points
    I have not heard back from you so I believe you may have solved the issue.
    The thread will close now but will reopen if you reply.