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TMS320F28035: LLC resonant current is abnormal

user4176626
Prodigy 50 points

Part Number: TMS320F28035

Hi,We are carrying out the 6.6KW OBC project, using the TMS320F28035 for LLC control. Now we are conducting open-loop commissioning. When the output power is >1.3KW, the resonant current will be dithered. The waveforms are shown in the annex. The design specifications are as follows:

Input voltage:390V~410V
The output voltage:250V~470V
Output Power:6.6KW
Output current:0~25A
Lr:20uH
Lm:100uH
Cr:150nF
Fs:92KHZ
  • 0
    TI__Genius 10820 points

    Hello,

    I am trying to understand the problem so please bear with me. Do you mean that instead of the expected fixed PWM switching frequency in open loop you see some frequency dithering at the PWM output, which results in an abnormal tank current? If yes, can you please provide more zoomed-in waveforms of the PWM outputs when this happens? With 'open loop' are you directly changing the switching frequency? Is there some frequency clamping implemented in the code? If yes, could that code be causing this frequency change?

    Also, what is the power converter topology being used, a DAB? Is this an interleaved resonant converter? How many PWMs and PWM modules are being used? 

    I will probably need more information on the PWM configuration too, but that might be a follow-up question.

    Thanks.

    Hrishi 

  • 0 in reply to Hrishi Nene
    TI__Genius 10820 points
    Hi,

    Has this issue been resolved?

    Thank you.
    Hrishi
  • 0 in reply to Hrishi Nene
    Prodigy 50 points

    thank you for your reply,Our issue has been solved.The real reason is the design of magnetic components.