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What is a good Boost-LED-Driver with multi channel high precision dimming options (shunt FET dimming)

Stefan Krueger
Intellectual 670 points
Other Parts Discussed in Thread: TPS92661-Q1, TPS92641, LM3409, TPS92515, LM5122Hello TI-Community,
i am searching for a solution to build a small battery (4s1p: 13,2V; 8-14,4V LiFePo4) powered multi-colored - multi-'pixel' (RGB or RGBA or more colors per pixel) high power led fixture for a theater prop.

i have found the article in the blog post about shunt FET dimming - and that is also what i found should be the best bet for my approach in general.

for this i found that the TPS92661-Q1 could be one option to have a bunch of things integrated.

other option would be to just use some small FETs and drive theme with an PCA9685 (16-channel, 12-bit PWM I2C-bus LED controller) or similar.

in the blog post it mentions
  • TPS92641
    Synchronous Buck Controllers for Precision Dimming LED Drive
    20,000:1 Shunt FET PWM Dimming
  • LM3409
    PFET Buck Controller for High Power LED Drives
    10,000:1 PWM Dimming Range
  • TPS92515
    2A LED Driver with Integrated NFET, High-Side Current Sense, and Shunt PWM Dimming Capable
    10,000:1 Shunt PWM Dimming Range
currently iam planing on using 12 leds and to drive the leds at about 0,5 - 1A
so if i want to drive theme all with the same constant current driver i would need about up to 40V output.
so i need a boost regulator to boost my battery voltage up.
Is there an boost constant current led driver you can recommend for this kind of setup?

this is my first design with dc/dc converters and its only an single build up -
so i am fine with easy (but pricy) modules ore similar recommendations :-)
looking forward to your suggestions, tips and ideas.
sunny greetings
stefan
  • 0
    TI__Mastermind 25500 points

    Hello Stefan,

    Actually probably the easiest is to refer to the TPS92662 EVM which has a boost stage using the LM5122 that is likely plug and play for what you need. Currently access to the EVM information is restricted, but as I understand that will change very soon. You can likely click "request" on the EVM page and just ask for access to the EVM document for the schematic (and not have to buy the EVM), but if not let me know. I will see if there is some other way to get you the schematic soon, at least the boost section.

    We will figure it out, but please have some patience as it is the holidays and we are all on vacation for some amount of time. Thanks.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Intellectual 670 points
    Hi Clint,

    thanks for your time in this holiday season :-)
    i know most people are on vacation in this time and the project for me is with no target dates - so all relaxed :-)


    the TPS92662-Q1 and also the Six Channel Matrix Evaluation Module seems really to complicated for me at the moment ;-)
    i have a light feeling that it was not a good idea to look at the complex automotive things ;-)


    LM5122 has webbench support - so i just tried and opened a design...
    if I am reading through this design and the datasheets i think i have to start at a lower/ easier level and
    read / study some more basics regarding all these different dc/dc converter topology ...

    and if i understand it correctly its much easier to to a buck topology than a boost - specially with shunt dimming.

    as i mentioned in the first post - i will only build a handful of these devices - all myself hand-assembled..
    some things for me to consider is part-size (smallest i can handle reliable is 0603, and i prefer NON-QFN housings ;-) ) and that i have only the option to create two-layer board-designs currently...

    i think i will first try to understand and recreate a Step-Down design -
    based for example on TPS92515 - there is already a example design + webbench support ;-)
    and the basic design (without fancy EMI filtering) seems much easier for me to understand..

    if the EVM design becomes 'non restricted' i will have a look at this too...

    i will let you know when i have got some more basic knowledge and feel ready to go deeper with this ;-)


    sunny greetings
    stefan
  • 0 in reply to Stefan Krueger
    TI__Mastermind 25500 points

    Hello Stefan,

    Sounds good. You are correct, the automotive designs are more complex than necessary for many other designs as there are more strict requirements (EMI, protection, etc...) so it is likely your design could be much less complex. I will mark this as "TI thinks resolved" but feel free to post any further questions you have in this thread when you are ready and I will be notified.

    Regards,

    Clint