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How to generate a three-phase symmetric PWM using N2HET?

Jan Nárovec
Intellectual 410 points
Other Parts Discussed in Thread: TMS570LS3137

Hi,

I know how to generate a single phase symmetric/asymmetric PWM signal, but I don't have an idea on how to make the N2HET (@TMS570LS3137) to generate a three-phase symmetric PWM. Any help would be appreciated.

Regards

  Jan

  • 0
    TI__Mastermind 22375 points

    Jan,

    Thanks for using our forum.

    I've contacted our NHET experts and we will be back to you shortly.

  • 0 in reply to Jean-Marc Mifsud
    TI__Expert 4225 points

    Hi Jan,

    We have some complex examples and some very simple example can post it for you sometimes later on.

    We will tar up.

  • 0 in reply to Henry Nguyen
    TI__Genius 13810 points

    http://www.ti.com/tool/drv8301-ls31-kit

    Once installed, check the folder C:\ti\motorwarexxxx\sw\drivers\het\src\32b\hercules\tms570ls3137

    Here is the HET file.

    Note:

    C:\ti\motorwarexxxx\sw\solutions\foc_encoder_speed\boards\drv8301kit_revD\hercules\tms570ls3137\projects\ccs5\project01

    find sys_main.c

    look for

    // Initialize the PWM base period

    hetRAM1->Instruction[26U].Control = T*vCNT_SCALE;

     To achieve the high resolution less than 1 LRP pulse, please make sure this number is an odd number, so that +1 is an even number (which is the period of PWM). 

    Regards,

    Haixiao

     

  • 0 in reply to Haixiao Weng
    Intellectual 410 points

    4010.NHETTest3.txt

    I created my own three-phase symmetric PWM generator with automatic dead-band calculation (see attachement). The code hasn't been tested on a real hardware yet (just in HET IDE simulator).

    Thanks,

      Jan

  • 0 in reply to Jan Nárovec
    TI__Guru 68920 points

    Thanks Jan!   Love to see people sharing HET ideas.

    Here's something similar that we've been working on;  it was simulated and we did some testing on HW.
    I remember there was a boundary condition when the counter rolled over from FFFFFFFh -> 00000000h that was tricky to find.

    You might find this one useful too even if it helps w. hints in debugging yours.  It's been on our backlog for a while to make a 'Video' / appnote explaining this, but there are some comments in the code at least...

    http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/312/1856.pwm_5F00_3Phase.het

    The major difference between the above post and the post from Haixiao is that the above supports both hi-res period and duty cycle;  so to a good extent (except for the minimum period) the dependence on the loop resolution period of the N2HET is removed.    Minimum period has to be multiple LRPs though or there won't be enough time to process, but that is usually not a problem for PWMs in the 20us+ period range.

    Best Regards,

    Anthony