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TMS320F28377S: Using TBPHSHR for phase offset of interleaved synchronous buck converter [F28377S]

Lance Hummel
Intellectual 960 points
Part Number: TMS320F28377S
Other Parts Discussed in Thread: C2000WARE

Hi all,

I'm starting to work on coding for an interleaved converter with four phases switching at 400kHz per leg.  Because of the 100MHz EPWMCLK limitation I need to setup a fractional phase offset, but I also need to be able to use the CMPAHR and CMPBHR functionality to get acceptable resolution to control of the output voltage.  Is there any way to be able to use a fixed setting for the TBPHSHR register to get a fixed fractional phase shift while using the HRPWM module CMPAHR and CMPBHR  registers to control the actual pulse widths?

I end up with a phase offset of 62.5 counts for one of the phases, and 187.5 for another, while the other only needs an integer offset of 125 counts.

  • 0
    TI__Genius 10820 points

    Hi Lance,

    This is possible. We have a software example in C2000Ware that could help. This example provides correct PWM waveform generation for HRPRD, HRDUTY, HRPHS and HRDB. This is mainly for the multi-phase variable frequency type of applications that use HR frequency and HR phase. It is applicable to your use-case too.

    This code is in C2000Ware under <path_to_C2000Ware>\device_support\f2837xd\examples\cpu1\hrpwm_deadband_sfo_v8 and also in f2807x, f2837xs device_support. 

    Please note that this code will add some software overhead. As the frequency and phase shift is fixed in your case, you will just need to run the additional code once.

    I hope this helps.

    Hrishi

  • 0 in reply to Hrishi Nene
    Intellectual 960 points
    Hrishi,

    Thanks for the response. That was helpful. Ultimately the requirements changed on the hardware side and things got changed to a 250kHz switching frequency which gives a nice integer count offset at 100MHz.

    Lance