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TPS922053: Choosing between buck or buck/boost driver

Joel Santos Rico
Prodigy 10 points
Part Number: TPS922053
Other Parts Discussed in Thread: TPS923653,

Tool/software:

I'm designing an LED driver, so I can dim an LED strip. My LED strip is 24V, and I was considering getting an LED power supply (just because they are easier to source, and are normally neater than other AC/DC converters, without any exposed leads or terminals, specially in the AC side of things). 

I was wondering if a buck driver, like the TPS922053 would be valid in this scenario, where Vin is equal-ish to Vout (I don't plan to drive the LEDs to 100% light, so VOUT should be always lower than VIN). Would a buck/boost driver, like the TPS923653 be better suited for this scenario?

I was also thinking that, because I'm using a driver IC, would it be better if I remove the vias resistors from the LED strip? I don't have details about the LEDs themselves, so I don't exactly know what their Vf is, but I would assume that would lower the total voltage, and I don't really need the vias resistor if the driver is going to control the current, right?

Thanks!

  • 0
    TI__Mastermind 35450 points

    Hi Joel,

    We will give you update next week.

  • 0
    TI__Mastermind 23350 points

    Hi Joel,

    Based on my knowledge, some 24V LED strip in the market need a constant-voltage source to drive and there are current-limiting resistors on the strip. TPS922053 / TPS923653 is not a good candidate to drive such LED strips.

    If you remove the current-limiting resistors (I think I am referring the same thing as the "vias resistors" mentioned by you. Please correct me if I am wrong.), then I would think it is possible to use TPS922053 to drive the LED strip. You should make sure the input voltage is higher than the LED strip voltage. (You can check TPS922053's behavior with high Vout/Vin ratio in this E2E thread - TPS922055: Maximum output duty cycle (minimum difference between Vin and Vout) - Power management forum - Power management - TI E2E support forums). However, I am not sure if it is an applicable way to remove these current-limiting resistors. You may consult the manufacturer / vendor of this LED strip for such information.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Prodigy 10 points

    Hi,

    Thanks for your reply.

    The LED Strip is made of 10cm segments with 6 LEDs and a couple of current-limiting resistors (I meant to write BIAS, not vias). I've asked but not have received the datasheets, but given that it's rated 24V, I would assume that each 10cm segment is paralleled to each other and each segment itself is either 6 x ~3.X Vf LEDs in series or again, two series of 3x ~6Vf LEDs in parallel (the fact that it has two resistors per segment seems to suggest the latter). I use a LED strip just becaues it's a convenient way to get a bunch of LEDs, nothing else. I understand that they are normally driven with a constant voltage source, but I was wondering if I could do the same with an LED driver.

    I could easily remove the resistors as they are exposed in the LED strip. It will take some work, but it's a relatively small run of length, so can be done in 10-15 min. I think that, if those resistors are removed, the voltage of the LEDs should be low enough to make V at CSP at least 2V, but there's no way to know until I get the datasheet of the LEDs.

    So, with all these, would you say that the TPS923653, being of type buck/boost, would be better suited for this scenario, where VIN ~ VOUT?

  • 0 in reply to Joel Santos Rico
    TI__Mastermind 35450 points

    Hi Joel,

    We will give you update later

  • 0 in reply to Joel Santos Rico
    TI__Mastermind 23350 points

    Hi Joel,

    Sorry for the late response.

    Unless you need high dimming accuracy, I would recommend TPS922053 for the ease of design in such condition.

    Best Regards,

    Steven