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TIDM-02002: LLC Transformer Ringing Problem At Light Load Condition in Open Loop

Mayank Kumar
Prodigy 20 points
Part Number: TIDM-02002
Other Parts Discussed in Thread: TMS320F28379D

Tool/software:

 

Hii ,

I am working on a 6.6 kW LLC resonant converter is being tested in open-loop operation with an initial PWM duty cycle of 45% and a switching frequency of 350 kHz using TMS320F28379D. During the first lab trial, the converter is supplied with an input voltage ranging from 10V to its rated 400V. However, a significant ringing phenomenon is observed across the transformer voltage, with an oscillation frequency of 3.8 MHz.

Converter Features

  • Operating frequency range is from 150khz to 300khz
  • Resonant frequency is 200khz
  • Suggest solution to mitigate this ringing issue.
  • Describe a systematic open-loop test procedure for verifying LLC converter performance and ensuring stable operation.

Above attached image are transformer primary voltage and primary current

Operating Condition : 20 V Input, 0.25 A load current, 350 khz PWM , 45 % duty

  • 0
    TI__Genius 11945 points

    20V input is not an operating point for this converter. Pls use the User Guide to check what min voltage this converter runs at. I believe this is 250V to 400V. Pls use the UG and follow the step by step testing procedure for this design

  • 0 in reply to Shamim Choudhury
    Prodigy 20 points

    Dear Shamim

    We cannot give directly rating voltage which is 400 V to the converter. Initially we have to check by slowly building the voltage and go to the rated zone.

    second when i am going for higher voltage which i have check too upto 100 V ringing is subsequently increasing.