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TPS54201: output ripple current

Don Foong
Expert 4100 points
Part Number: TPS54201

Hi Team,

My customer is using TPS54201 for LED driver. It is design to drive in analog mode, current is between 240mA to 320mA. They have measure the current ripple vs PWM control frequency study (attached), they found that the best results is when running at 50kHz, with current ripple of around 20mApp.

Due to design requirement change, they need to further minimize this ripple to smaller value. If this is possible, can you help to provide your suggestion ?

 

Below is the schematic of the TPS54201 circuit.

 

Would any of below help ? Look forward to your feedback and comments, thanks in advance.

 

  1. Increase PWM frequency to 80kHz ~ 100kHz range.

  2. Increase capacitance on LC filter of DCDC output.

  3. Adjust feedback network, what would be the value to use. 

Blue Red LED PWM Freq study 26-Oct.xlsx

  • 0
    TI__Mastermind 22745 points
    Hi Don,
    Thanks for useing TPS54201, I have understand your question, I think another way to decrease the output current ripple is to increase the output capacitor. But I will chekc with our designers , I will reply to you when I get some results.
    Best Regards
    Sean
  • 0
    TI__Mastermind 22745 points
    Hi Don,
    I have get the results from our designer as below:
    Generally, suggest customer to parallel more output caps with LEDs. The effect of more caps in parallel is better than only one/two large caps alone.
    For future more, please check the frequency of current ripple,
    1. If it is equal to converter switching frequency, please parallel more output caps with LEDs.
    2. If it is equal to PWM frequency, please increase the PWM frequency.
    Best Regards
    Sean
  • 0
    TI__Mastermind 22745 points
    Hi Don,
    As we have talked on the phone, the best way is to parallel more output caps with LEDs. The effect of more caps in parallel is better than only one/two large caps alone.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    TI__Expert 4100 points
    Hi Sean,

    Our customer like to know are there upper limit on increasing inductance and capacitance ? When increase L, C will affect to stability loop of the circuit. If you have some guideline to study will be best. Looking forward your advices. Thanks again.
  • 0 in reply to Don Foong
    TI__Mastermind 22745 points
    Hi Don,
    When the output cap is parallel with LEDs, the caps will not affect the stability. No limit for the caps.
    Regards
    Sean