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Original question:

TPS92512: LED flickering problem

TPS92512: Audible noise from Inductor

Jay Kim
Intellectual 475 points
Part Number: TPS92512

Hello,

Upon attached schematic, audible noise generated from Inductor(L1 and L3) when dimming.

- Using PWM frequency 16.kHz : Barely hearable(Very high frequency noise)

- Using PWM frequency under 16kHz : Hearable. getting louder when decrease PWM frequency.

TPS92512 reference kit is bit better than our board but I also can hear noise from it.

Any recommends to get rids of this noise would be very appreaciated.

Thanks.

  • 0
    TI__Mastermind 28655 points
    Hello Jay,

    Audible noise when PWM dimming is common. Trying different inductors may yield better results, possibly through hole parts can be better. Also note that ceramic capacitors can also be audible. It is really just trying different parts to find the best solution.

    BR,
  • 0 in reply to Irwin Nederbragt
    Intellectual 475 points

    Hello,

    I had tried several different inductors but didn't solve problem yet.

    (1) Any recommends vendor of inductor?

    (2) Now it's 33uH, trying other capacity could help?

    (3) Now it's ferrite type, other types are not recommended?

        

  • 0 in reply to Jay Kim
    TI__Mastermind 28655 points

    Hello Jay,

    1)  You can try the distributed airgap inductors.  Also you can RTV the coil or varnish.  It is a difficult problem due to the high di/dt in the audible noise band.  You can also increase the PWM frequency but you will lose dimming accuracy.  Another thing to try is partially analog dimming first to get the current amplitude lower then using PWM dimming for deeper dimming.

    2)  You could try a higher value but I think you will find it will still cause noise.  This is a common issue so you may want to search the internet for solutions.  You may even find better parts this way.  I know this to be true for ceramic capacitors which can also emit noise.

    3)  You can use other materials, you just want to make sure it is intended for the application you are using.

    BR,

  • 0 in reply to Irwin Nederbragt
    Intellectual 475 points

    Hello,

    Noted well, Thanks a lot for information!

    BR,