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TPS40211: Looking to create a true high efficiency constant current driver with ability of adjust the output current from MCU

MazAnglerfish
Prodigy 20 points
Part Number: TPS40211
Other Parts Discussed in Thread: TPS92690, TPS92691

Hi there,

I am new to this forum and I had a question about TPS40211

I would like to use this driver to drive a COB LED FV=40.5 to 54 V (FV changes with LED temperature), FI=2.45A. I would like this controller to be %95+ efficient. And I also would like the controller to be a true constancy current booster. I would like to have analog dimming rather that PWM.

the input is from Li-po battery 7s configuration(17.5-29.4V). I also would like to have the ability to drive another LED (51V 1.5A using the same circuit).

I was looking thought the TPS40211 datasheet and I noticed that the datasheet is very comprehensive in the constant voltage configuration. However, there is not much info on the constant current application. There is one diagram 29 on page  23 which shows the circuit but there is not text describing the design process.

There is also another figure 29 on page 33. 

I was wondering if there is another IC i can use one which is specifically designed for high power COBs? maybe TPS92690? I could not find anything on webench

with the tps40211 I wanted to use analog dimming circuit similar to this one:

Any help could be greatly appreciated. I am willing to pay any freelance capable of designing and prototyping this circuit. PM me if your interested

   

  • 0
    TI__Mastermind 25500 points

    Hello,

    132W is a lot of power but it could be done. I do not think the TPS40211 is likely to get you there however. I would look at the TPS92690 or TPS92691. They have about 2 and 3 times as much gate drive current (respectively) as the 40211. Even so it might require an external low-side gate driver for 130+ watts. Either should be easy enough to design with using the datasheet. The only real issue is driving a big enough FET (it will need to have low Qg, you will need to use a low Fsw, and/or add an external gate driver) and keeping the FET cool. Both are very easy to analog dim.

    As for designing with the 40211 it is the same as with the voltage mode except you are setting a current with the FB voltage rather than an output voltage.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 20 points
    thank Clint for your input. I'll be honest I am not a electrical engineer. I am actually a mechanical engineer with limited electronic background.

    I was looking at TI WEBENCH based on my parameters the TPS40211 seems to work with good efficiency.

    I used 17.5-30 volt input
    Output 40.5volt at 2.45A

    I also ran another design senerio
    54v at 2.45A

    The LED FI is 2.45 with a FV that varies from 40.5-54V so if I am able to cool the LED down then I can get a lower FV and only be using 100W power.

    But it's nice to have some extra power capacity on the board.

    The tsp 92690 seems to have lower efficiencies. Since my unit is battery operated the higher efficiency is desired.
  • 0 in reply to MazAnglerfish
    TI__Mastermind 25500 points

    Hello,

    No problem. The 40211 can likely do it as well but will require careful FET selection and/or added gate drive circuitry. The gate drive of a FET goes up as current goes up, so every bit helps. In any case it isn't a bad choice, but don't take too much stock in webench efficiency numbers or datasheet/EVM efficiency data without looking at all of the factors. It all depends on the components used when the data was taken (or what components webench selects and what losses are entered for them).

    Increased gate drive generally improves efficiency since the FETs are a significant loss element. You would need to compare apples to apples. But I don't need to go on this long, the point is there is a lot involved in efficiency and you can maybe get a little better with a lower Iq chip like the 40211 in many cases, but at high power levels you will be better off with a chip that might require more Iq but will result in less losses in the FET. If you like the 40211 that is no problem, but it is likely (as it might be with the others) to require extra gate drive.

    Regards,

    Clint