• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 82 subscribers
  • Views 549 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

tms320f28035: Phase shift full bridge primary current reconstruction.

evs
Genius 5910 points
Part Number: TMS320F28035
Other Parts Discussed in Thread: UCC28950

Hi,

I'm designing a phase shift full bridge converter. I'm struggling with the primary transformer current reconstruction. My initial plan was to get the RMS current. But didn't take into account  the Circulating current of the Ls.

 So peak current is also ok. only I can't find a point to ADC sample correctly  for that either.

 Currently I use 1 low side current sense resistor. I'm thinking to change to a current sense transformer to reduce switching noise.

 When I look into the schematics of the UCC28950 and TMDSHVPSFBKIT . They use a current transformer at the Vin+ supply.  Without any additional core reset circuit. How do you  prevent it from saturated  at full load? I think that is a really odd please. Can you please explain?

And any suggestions how to detect if the core is saturating?

Thanks!

  • 0
    TI__Genius 10820 points

    Hi,

    The TMDSHVPSFBKIT implementation does not use ADC results to implement peak current mode control. Instead on-chip analog comparator on the C2000 controller is used to implement cycle by cycle peak current mode control operation. Sensing primary current in the +Vin line provides the benefit of protecting the power stage in case of a shoot through fault. The 4.87k resistor is used to reset the current sense transformer. This resistor is selected to be 100x of the sense resistor (48.7 ohms).

    I hope this helps.

    Hrishi