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TMS320F28379D: Synchronous Rectification in a Wireless Charging System via External ePWM Trigger

Part Number: TMS320F28379D
Other Parts Discussed in Thread: C2000WARE

Tool/software:

Greetings, 

I have a high-frequency (up to 500 kHz) zero-crossing detector that measures the input current (I_r) of a full-bridge synchronous rectifier as seen below: 

The 3.3-V digital output of the ZCD circuit is connected to GPIOs 120 or 161 on the F28379D control card. How can I use either GPIO to synchronize ePWM signals to the ZCD signal to allow me to drive my FB synchronous rectifier correctly based on measured current?


I am open to any suggestions. 

Thank you,
Ma

  • Hi Ma,

    You can use the INPUT XBAR to connect the GPIO signal to be used as the EPWM External Sync-In signal. Let me know if you have any specific questions on how to accomplish this.

    Best Regards,

    Allison

  • Hi Allison,


    Thank you for getting back to me. I want to use ePWM 1 and 2 for the full-bridge synchronous rectifier, and they should use the external Sync-In signal coming from the ZCD. 

    On the other hand, I want to use ePWM 3 and 4 to operate a second-stage DC/DC converter, and ideally, ePWM 3 and 4 should have their own internal synchronization because the ZCD signal is not always present. In other words, ePWM 3 and 4 should not be synchronized to ePWM 1.


    Is there an example code or documentation that can help me get started with this?

    Respectfully,
    MA 

  • Hi MA,

    Please note that the synchronization scheme for each EPWM module is mapped out in the device documentation (see TRM figure below):

    If you are wanting to internally sync two PWM modules independent of EPWM1 and EPWM2, I would perhaps suggest using EPWM4/5/etc. You can see in the figure above that EPWM3 is linked to EPWM1/2 and EPWM4 cannot be directly synced to EPWM3; however, you can use EPWM4 sync-out signals as the sync-in source for EPWM5 (and so on) as well as use EXTSYNCIN2.

    We have software examples that can be used as a starting point or reference. Our EPWM examples are located in C2000Ware at C:\ti\c2000\C2000Ware_5_02_00_00\driverlib\f2837xd\examples\cpu1\epwm. There is specifically an EPWM synchronization example there (note that it does not use external sync, but rather internally syncs EPWM modules. You can always use this as a reference as I mentioned).

    The best documentation resources to read through would be our device technical reference manual (see Chapter 15 and the Time-Base submodule section for descriptions on synchronizing EPWMs as well as the register descriptions listed at the end of that chapter).

    Additionally, some other helpful EPWM resources that may be beneficial:

    Hope this helps!

    Best Regards,

    Allison