TMS320F280049C: Software Synchronization of multiple HRPWM Modules

Ahmed,

HRPWM synchronization requires a very specific process. So you definitely dont want to send a SYNCO from the parent EPWM to the child EPWM on EVERY CTR=ZERO or CTR=PRD event. What you want to do is do ONE SWSYNC pulse at the time of initialization. In doing so ONLY the first cycle of your two in phase EPWM may have a jitter but for the rest of the cycles there wont be jitter.

IF you need to resync with a new PHASE SHIFT, you will set the new phase shift value, and then ONLY ONCE you SEND a SWSYNC. Again on the first cycle of the new phase shift you may have jitter but on all following cycles, you should be good, without jitter and with the new PHASE.

Nima

Thank you Nima for your detailed answer.

So, I can deduce from your response that if I have to update my phase every switching cycle, I cannot use HR Period control. Because then I will get jittering every cycle as I update the phase using SWSYNC. Is this true?

Thanks,

Ahmed

So in your case it is necessary to change the phase every PWM cycle?

Subrahmanya and Manish Bhardwaj is it possible to change the HR phase shift every PWM cycle without the jitter?

Nima

Ahmed, 

How many channels are you synchronizing?

So far just 2. ePWM1 with ePWM2.

Yes, because we are using frequency modulation and the phase changes with frequency. So I have to update the phase every cycle as the frequency changes.

Ahmed,

You want both freq and phase to be high resolution, this can certainly we done with either freq being high res or phase being high resolution. When both are high resolution there is a SW work around using TRREM register.

If phase and freq are independently controlled? or they are driven from a fixed equation from the control loop output. 

For example in a CLLLC stage we are using high res frequency when it;s in frequency mode, when it is in phase shift mode we switch to regular resolution frequency. 

-Manish 

I don't think we need phase to be high resolution. We are using it for Full bridge LLC, so the phase shift between the two legs is always half the period, which changes every cycle. We are interested in having high resolution period and duty cycle, and be able to update the phase between several ePWM modules but not necessarily in high resolution.