CCS/TMS320F28035: The output ringing issue of PSFB peak current mode control

Ku Chester

Prodigy 210 points

Part Number: TMS320F28035
Other Parts Discussed in Thread: SFRA

Tool/software: Code Composer Studio

Hi Champs,

I have some problems when doing psfb topology by peak current mode control.

The PWM switching frequence is about 47KHz, and using type III compensator.

When closed-loop gain and BW is very small, output(Vo_blue line) at full & half loads is stable, and there are some small ringing at light loads(10%).

After adjust the compensator to increase the bandwidth to 500Hz, the amplitude and range of output ringring at light loads become larger(1%~20%).

I want to know the reason for the output ringing, because of the compensator or somthing else.

Would you kindly help to suggest how to solve or improve this problem?

Thanks.

Regard,

over 5 years ago

0 Manish Bhardwaj over 5 years ago

TI__Mastermind 43730 points

Ku,

I am not familiar with PSFB,

It may be possible that you have a plant change during light load.

Are you using PCMC ? or average CMC?

Are you able to replicate issue in any modelling environment?

-Manish

0 Ku Chester over 5 years ago in reply to Manish Bhardwaj

Prodigy 210 points

Hi Manish,

Yes, I'm using PCMC, and what does it mean about a plant change during light load?

0 Shamim Choudhury over 5 years ago in reply to Ku Chester

TI__Genius 10995 points

In PCMC you may need to adjust the slope (of the internal ramp) with load. If the slope is not enough it can cause oscillation. If the slope is too much it will make the response very slow.

Also, what is the oscillation frequency? IF it is half the PWM frequency then it is from inadequate slope compensation. If it is some other frequency then it might be caused by voltage loop compensation. When you increase the BW you may not have enough phase margin. So you will have to adjusts the zeros and high freq pole of the voltage loop controller.

I also suggest that you use our SFRA to get a plot of the loop gain to check the BW and PM/GM.

Shamim

0 Manish Bhardwaj over 5 years ago in reply to Shamim Choudhury

TI__Mastermind 43730 points

Ku,

Shamim provided some ideas for you to try, please let us know where you are at.

-Manish

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CCS/TMS320F28035: The output ringing issue of PSFB peak current mode control