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TPS92692-Q1: ILED value in the excel calculation tool

Ryuji
Guru 20090 points
Part Number: TPS92692-Q1

Hello,

In the calculation tool of TPS92692-Q1, ILED is calculated based on Vout(min) and Po(max).
Could you please let me know this reason?
Our customer would like to regulate the ILED as 1A.
In this case, can we input the "ILED" directly?

Best Regards,
Ryuji 

  • 0
    TI__Mastermind 25500 points

    Hello Ryuji-san,

    That tool is set up a little differently than a lot of others. I don't think it's set up to enter LED current directly. But when I have used it I have just set the VLED min/nom/max all the same and then entered the max power as 1A*VLED so that it sets the current at 1A. I hope that helps.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Guru 20090 points

    Hello Clint san,

    I appreciate your support.

    If you know , could you please let me know the reason why the deice is not calculate led current by output power?
    Is it general to calculate from the power that achieves the necessary Lumen, rather than keeping the LED current constant?
    In that case, if Vf,LED is Max values, the maximum power becomes larger than Po (max). Is not this a problem?

    Best Regards,
    Ryuji

  • 0 in reply to Ryuji
    TI__Mastermind 25500 points

    Hello Ryuji-san,

    As I mentioned, that is just how the systems engineer that developed the calculator likes to do it. It works the same, you just manipulate the numbers a bit differently. But to your point, for the Po(max) value you enter you need to take into account the maximum Vf expected for the LED string at the maximum regulated current. So if the max Vf is 16.5V and you want a string current of 1A you set Po(max) at 16.5W.

    The 692 is a current regulator, so if you need to regulate the exact output power you would need to monitor the Vf and adjust the current with IADJ accordingly. Otherwise most LED drivers are simply set for a constant current. Lumen output should be calculated for the steady state Vf of the LEDs when they are warm if need be.

    Regards,

    Clint