Phase Shifting ePWM on F280049

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

I need to sync two PWM units 180 deg out of phase. How is this done? The system has a total of 12 PWM units. The current design needs to sync unit 1 and unit 4 180 deg out of phase. Is this done in the ePWM pull-down window? I am using an F280049 with the BETA 2019.1 software. I have the PWM units working with all synced at the same start. One other design requirement is to hold one PWM signal high and one low for 8.333ms. Then return to a high frequency PWM. This design is for a 60 Hz inverter. 

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Answers

  • KarenDarnell
    KarenDarnell
    Altair Employee
    edited September 2019

    PWMs on TI boards are daisy chained. This daisy chaining cannot be adjusted using Embed.

     

    Daisy chained PWMs on the F280049 board (which has eight PWMs):

    PWM unit 1 is a lead unit with PWMs 2 and 3 daisy chained.

    PWM unit 4 is a lead unit with PWMs 5 and 6 daisy chained.

    PWM unit 7 is a lead unit with PWM 8 daisy chained.

     

    For a lead, it should not be relative to anything (this unit can take an external input through a GPIO to trigger it).

     

    Daisy chained units can have a phase shift relative to the previous unit (TBPHS). For example, unit 2 is phase shifted with respect to unit 1; unit 3 is phase shifted with respect to unit 2.

     

    You want unit 1 and unit 4 to be 180 deg out of phase, but because of the way daisy chaining works, this is not possible unless unit 4 is reassigned to unit 2. Then it can be phase shifted 180 deg.

     

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