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current

Marco Dini
Prodigy 30 points

I'm using the "ac led lighting & communications kit"(TMDSIACLEDCOMKIT). The increase of current on each string of LEDs, increases the duty cycle. The problem is that for I=0.3A, the duty cycle=95%. How can I further increase the current? How is it possible to feed the led with current of about I=0.7A?

Thanks

  • 0
    TI__Guru 57255 points

    Marco,

    The I-V curve of an LED is similar to that of a diode.  Over a certain voltage threshold, any additional voltage allows the current through the LED to increase at an exponential rate.  For the TMDSIACLEDCOMKIT, the LED panel consists of 10 LEDs.  This makes the voltage threshold around 2.8V*10=28V.  Any voltage greater than 28V will allow more current to go through the LED string.

    The topology of the TMDSIACLEDCOMKIT contains several power converter stages.  The LLC stage creates the maximum voltage (and therefore the maximum current) that can be delivered through each LED string.  Each LED string control stage is powered by the LLC stage output and controls a FET in series with the LED strings and chops this voltage.  This allows a constant current (LED lumen output) to be output.

    In short, you'll likely need to increase the voltage reference that the LLC Resonant stage is using.  Reference voltages between 28V and 36VDC should be safe for the LED panel.


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Prodigy 30 points

    Ok thank you, but

    How do I increase  the voltage reference that the LLC resonant stage is using? When I use the software TMDSIACLEDCOMKIT_GUI, I can't move the slider labelled "Resonant Output". The error is shown in this figure.

    Thank you,

    Marco

  • 0 in reply to Marco Dini
    TI__Guru 57255 points

    Marco,

    I know it is an inconvenience, but can you try to change your computer's "language and regional settings" to be English (specifically to have the computer use decimal points rather than decimal commas).  I believe everything should work then.


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Prodigy 30 points

    Thank you so much.

    Marco