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Variable Length Linear LED light

Danielle Costantino85354
Prodigy 10 points
Other Parts Discussed in Thread: UCC28810, TLC5960, LM3464, LM3464A, LM3409HV

 

I am working on a design of a Linear LED light that uses 2 strings of 80 30ma 3.2V LEDs per module, and up to 5 modules in series. This will run off universal line input (85 – 265 Vac) The design must be UL Class 2 compatible so I caint have a HV string of LEDs. The 2 LED strings must be individually dimmable via a PWM signal. The preliminary plan was to use the UCC28810 for PFC flyback and then 2 buck converters to control the LED current. The other option would be to use a C2000 to do all of the control. I would like not to have to use a C2000 if possible, but if it is not realistically possible with all analog components I will make the switch. Another constraint is that the overall system efficiency must be higher than 85%. Does anyone know of a solution to this?

  • 0
    TI__Guru 65340 points

    Hello Daniele,

    For individual string dimming, TLC5960 might be a solution. Dimming is done with a PWM signal so not a lot software neaded and the controller has the possibility to react on voltage changes on the LEDs. Please check out the following application note: http://www.ti.com/litv/pdf/slva474. It describes how to use this part in driving LEDs in TV backlighting, but it might be useful in your system as well.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    TI__Intellectual 2540 points

    Hi Daniele,

    One thing was not clear to me in your post:

    "I am working on a design of a Linear LED light that uses 2 strings of 80 30ma 3.2V LEDs per module, and up to 5 modules in series. This will run off universal line input (85 – 265 Vac) The design must be UL Class 2 compatible so I caint have a HV string of LEDs. "

     

    Am I reading this correctly in that you want 80 LEDs per string at 3.2V each, or 256V per string??

    If indeed the LED voltage is actually <60V, then the TLC5960 is a good option for linear control.  Another linear option would be LM3464 or LM3464A.  A buck converter option could include LM3409HV.  These options are suitable for string voltages under 100V.

    Can you clarify the LED string configuration again so we can help with additional recommendations?

     

    John