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TMDSCNCD28335: EPWM, Deadband, Software force input

Part Number: TMDSCNCD28335

I am using F28335 experimenters kit for motor control and programming it through Simulink. I am using module A of EPWM to switch all the upper devices of an inverter and module B for all the lower in a complementary fashion. I need to insert dead band for rising as well as the falling edge of the PWM signals, in addition, I require complete control on module A as well as module B using continuous software force input. To insert deadband I am using Active high complementary setting in Deadband submodule of EPWM module. As soon as I use this setting I cannot individually control the A&B modules using software force, If A is kept at low the B will remain at high even if its forced to low. How can I obtain this control?     

  • Deepak,

    Here I assume that you are referring to an Action Qualifier (AQ) force low.

    DEEPAK VERMA68 said:
    If A is kept at low the B will remain at high even if its forced to low.

     If you look at a high-level block diagram(above) for the ePWM module you will see that the Dead-Band(DB) submodule takes effect after the Action Qualifier. Thus the DB can overwrite the effects of the AQ.

    Now, since you have chosen "Active-high complementary" the 'B' channel will always be the complement of A and cannot be independently controlled by any of the normal mechanisms in the AQ. 

    If you wish to independently force the "B" channel you will need to choose something down stream of the DB. The Trip-Zone submodule should work perfectly for this purpose.

    Regards,
    Cody  

  • Hi,

    The software force doesn't work with active high complementary setting in deadband plane for sure. To be able to have such control what can be done is; do not use the dead band plane at all. Add the dead band in the compare signal (modulation wave) for the B submodule. The value of deadband can be calculated as Td*Fclk, where Td is the deadtime to be given and Fclk is the clock frequency of F238335 DSP. Dead band = CMPB - CMPA. Use complemetary settings in action qualifier for A and B submodule.                                                                          

  • Deepak,
    Please let me konw if you are still having issues. The thread will be closing soon due to inactivity.

    Regards,
    Cody