• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 83 subscribers
  • Views 668 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.

TMS320F28027: Slope compensation of HVPSFB_v1.1 PCMC in controlSUITE

Kuerbis
Expert 4145 points
Part Number: TMS320F28027

Hi Team,

 

Would you please explain how to do slope compensation in this HVPSFB PCMC?

 

Thanks and Best regards,

Kuerbis

  • 0
    TI__Genius 11855 points

    In a PCM control buck converter (and all buck derived converters such as PSFB dc/dc), the PWM switch is turned off when the sensed inductor feedback (iL) becomes equal to the slope compensated voltage loop output.

    So if the average inductor current for the switching cycle is IL, the PWM duty is d, the PWM period is T, and the voltage loop output is Vc, then the slope mc can be calculated from:

    IL+m1*d*T/2 = Vc - mc*d*T

    where m1 is the slope of the inductor current feedback which is given by m1 = (Vg-Vo)/L. The quantity (Vg-Vo) is the voltage across the inductor L.

    This is the theory that has been published and discussed widely in literature. Using this theory one can calculate the slope value (mc) for the compensating ramp.

    For this PSFB design we don't have any detail documentation showing this calculation. However, it can be inferred from the equation that with regulated Vo and at constant power (when Vc remains constant), the duty d has to be lower for higher input voltage Vg and vice versa (to maintain Vo regulation). This will require the slope mc to be higher with higher Vg. For lower Vg, the slope mc will be lower. This is the general rule followed in this design.

    Shamim