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TPS92512: PWM dimming Inductance ring

li darren
Intellectual 520 points
Part Number: TPS92512

Hi，

There is new project， 24V vin，6 string LED，1.5A，used TPS92512.

Inductance  ring when duty cycle < 100%, 100% duty cycle is OK. PWM frequency is 1Khz. when PWM frequency is 30Khz , the inductance does not ring.  What advice do you have? By the way,  is TPS92512 PWM dimming frequency range 100hz to 1Khz?

  • 0
    TI__Mastermind 25500 points

    Hello,

    Do you have scope shots showing what you are talking about? I am not sure I understand what you mean by "inductance ring". Do you have a schematic and BOM I could check as well?

    The 100Hz to 1kHz dimming range is specified only because that is the range where you can get a good dimming ratio. You can dim at higher PWM frequencies, you will just be much more limited in your minimum duty cycle and linear dimming range.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Intellectual 520 points

    Hi Clint,

    It can be heard the inductance sound when PWM dimming input duty < 100%,  it is 1Khz frequency sound(PWM dimming is 1Khz).

    PL-Belmon 22 Table-2A-REV2.pdf

  • 0 in reply to li darren
    TI__Mastermind 25500 points

    I see. Audible noise from the inductor is a pretty common issue when PWM dimming in the audible frequency range. This generally requires some experimentation with trying different inductors and/or core technologies until you find one that doesn't exhibit magnetostriction (which causes the audible noise) at the frequency you are using. So it may take a few tries but you can eventually find one that doesn't make noise.

    Regards,

    Clint