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F28035 Experimenter's Kit - Want to generate more number of PWM signals

Prasanth Sahu
Prodigy 40 points

Hi,

I am new to using F28035 Experimenter's kit. I am working on Cascaded H - bridge inverters. I have 6 single phase inverters, each requiring 4 pwm signals. With F28035 micro-controller, I am could drive only 3 of the inverters by generating 12 pwm signals. I would like to know if it is possible to generate 24 pwm signals? Or is there a way by which I could use 2 such micro-controllers, to drive all the six single phase inverters?

  • 0
    TI__Mastermind 27200 points

    Prasanth,

    You could approach this by cascading two F28035 devices, generating six PWM pairs from each.  If necessary, PWM time-bases can be synchronized by connecting the EPWMSYNCO pin on the first (master) device to the EPWMSYNCI pin on the second (slave).

    An alternative approach is to move to a device such as the F28377D, which has 12 independent PWM modules.

    Regards,

    Richard

  • 0 in reply to Richard Poley
    Prodigy 40 points

    Richard,

    Thanks a lot for the response. Is cascading the two devices same as synchronization?  Could you please detail me how the synchronization can be done?

    I understand that EPWMSYNCO pin on the master device should be connected to EPWMSYNCI pin on the slave. 

    Both the devices should produce distinct pwm outputs depending on certain criteria (eg. depending on the dc voltage of each inverter).

    Regards,

    Prasanth

  • 0 in reply to Prasanth Sahu
    TI__Mastermind 27200 points

    Prasanth,

    On C2000, the time-bases of different PWM modules can be synchronized to allow the phase shift between different channels to be controlled.  This is done by passing a synchronizing pulse from a master to an adjacent slave module.  The attached slide shows the principle.  More information can be found for the F28035 in section 2.2.3.3 of the ePWM user's guide:

    http://www.ti.com/lit/ug/spruge9e/spruge9e.pdf

    The SYNC pulse can be cascaded from one PWM module to the next inside the device, and can be passed from one device to the next using the pins I mentioned.  I don't know if this is what you want to do in your application, but if so the technique allows you to connect multiple F28035 devices together while maintaining a known phase relationship between their PWMs.

    Regards,

    Richard

    C2000 PWM phase sync.pdf

  • 0 in reply to Richard Poley
    Prodigy 40 points

    Richard,

    Thanks a lot for your input. Synchronization did work for me.

    Regards,

    Prasanth