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UCC27423: Driving RGB LED array with power FET's

Jerry Bucci
Expert 1540 points
Part Number: UCC27423
Other Parts Discussed in Thread: LM5163, LM317

Hi,

I am designing a RGB array control and I have a few questions.

The array is made up of a bunch of series and parallel LED strips. The power supply is a DC 40V power pack. The max size of the array requires about 4A at 40V for each color.  I need to drive the 3 color arrays with PWM from a TI micro. My original idea was to use 3 MOSFETs that can handle the 4A. I was going to put  gate drivers, such as the UCC27423 between the micro and the FET's. However, the max voltage on the UCC27423 is 16V.

While looking around at LED drivers , I see many are high side controllers? I would rather use low side switching of the LED's unless there is some reason why I shouldn't do that. I also, don't want to add a bunch of IC's to develop different DC voltages. Thus far I just have the 40V DC power supply and a buck converter(LM5163) off that for the micro 3.3V. Can you recommend what to use between the power MOSFTEs and the micro? Also, if there are parts that have the driver and power FET in the same package that would be fine, as long as the cost is similar to separate devices.

Thanks,

Jerry

  • +1
    TI__Genius 11770 points

    Hi Jerry,

    As far as I am aware, low-side drive for the power FETs seems reasonable. With how our gate drivers work, the VDD voltage is the voltage the gates of the FET is driven at, so most are around 12V - 26V with some exceptions. Usually the absmax Vgs voltage for power NMOS is +-20V, so 40V would probably break the FET. I think there will need to be a 10-20V rail generated somewhere in the system.

    Here are some ideas. Firstly, you could get a cheap adjustable LDO like LM317 for a 12V rail and use pretty much any low-side gate driver. There are also some of our gate drivers that include the LDO. The TPS2819 seems like a decent option.  I am on the gate drivers team, and those are my specialty, but here are some other options with the FET included like you ask:

    First, these seem like they could work https://www.ti.com/power-management/power-switches/low-side-switches/products.html

    We also have motor drivers which include the FET, but they are more focused on half-bridges. 

    Lastly, LED drivers like you mentioned seem like a good choice. I'm not entirely sure why high-side is prevalent for those, but I think it has to do with fault conditions. Some seemed to be low-side when I looked though. 

    Please let me know if you have any more questions. 

    Thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Expert 1540 points

    Alex,

    Thanks very much!

    The  TPS2819 looks pretty good. I'll look closer at it and the other info you supplied

    Jerry