Synchronising ePWM1 and ePWM11 in F28075

Prakash Kumar Thulasi Kumar

Expert 2015 points

Hi Guys,

CCS v 6.2(compiler version = TI v15.12.3.LTS)

TMX320F28075 Control Card

control Suite v 3.4.1

I need to synchronise ePWM1 and ePWM11. Normally they are synchronized. But I have configured as:

ePWM1 Counter Mode = UP_Down -> Used for Symmetrical PWM

ePWM11 Counter Mode = UP -> Used in Sigma Delta Filter Synchronisation (I need only one CMPC/CMPD event)

This configuration makes the two ePWMs out of sync. Please let me know how to synchronise the ePWMS with the above configuration?

over 9 years ago

0 Subrahmanya over 9 years ago

TI__Mastermind 24095 points

Hi,

What are the period values being used in EPWM1 and EPWM11?
What is the source of sync out pulse from EPWM1?
Also, When you say out of sync - what is the phase error observed?

-Bharathi.

0 Prakash Kumar Thulasi Kumar over 9 years ago in reply to Subrahmanya

Expert 2015 points

Epwm1 - UpDown
TMPRD = 600
CMPA = 300
ZRO = SET
CAD = CLEAR

Epwm11 - Up
TMPRD = 1200
CMPA = 300
ZRO = SET
CAU = CLEAR

Note : When I set for Epwm11 - Up TMPRD = 2, CMPA = 1 it is in sync.

I have not configured any Synco or Synci pulse.

There is no constant phase shift error. It is randomly changing when the program is running.

0 Subrahmanya over 9 years ago in reply to Prakash Kumar Thulasi Kumar

TI__Mastermind 24095 points

Below is the period calucation for different modes,
For further details refer to Figure 13-6. Time-Base Frequency and Period of TRM.

For Up Count and Down Count
TPWM = (TBPRD + 1) x TBCLK
FPWM = 1/ (TPWM)

For Up and Down Count
TPWM = 2 x TBPRD x TBCLK
FPWM = 1 / (TPWM)

0 Prakash Kumar Thulasi Kumar over 9 years ago in reply to Subrahmanya

Expert 2015 points

Yes. In my case the time period for both PWM is 20 us. The only mistake I see is, I have set 600 instead of 599 for epwm1 TMPRD, which I don't think will cause such error.
Or am I missing something here?

0 Subrahmanya over 9 years ago in reply to Prakash Kumar Thulasi Kumar

TI__Mastermind 24095 points

Hi Prakash,

I believe this could certainly be a possible source to the problem.
The error adds up over a number of cycles.
Fix this and try out... Let's debug other sources if it doesn't fix the problem.
Also, please let me know how you are you identifying phase error.

-Bharathi.

0 Prakash Kumar Thulasi Kumar over 9 years ago in reply to Subrahmanya

Expert 2015 points

I will try it and let you know.
I simply see in oscilloscope, if epwm1 is triggered then I expect epwm11 to be triggered at the same point as both of them are set at ZRO.

0 Prakash Kumar Thulasi Kumar over 9 years ago in reply to Subrahmanya

Expert 2015 points

You are right. I changed ePwm11 TBPRD to 1199 and it is now in sync.
Thanks Bharathi.

0 Subrahmanya over 9 years ago in reply to Prakash Kumar Thulasi Kumar

TI__Mastermind 24095 points

That's great! Let us know if you run into any issues.

0 Yanfeng Shen over 9 years ago in reply to Subrahmanya

Prodigy 10 points

I am using F280725 to generate two phase-shifted PWM waveforms. However, there is a constant phase-shift error, in my case = 30ns. When the phase-shift reg. is set to 0, the outputs of PWM1A and PWM2A are phase-shifted instead of being fully synchronized. I wonder what the reason is?

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Synchronising ePWM1 and ePWM11 in F28075