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ePWM submodule bug?

Simon Kissling
Prodigy 60 points

Other Parts Discussed in Thread: TMS320F28335

Hello,

I do a current control on a DC brushless motor. Depending on the motor position, I turn off the two MOSFETs on a phase-leg, I turn off the high-side and turn on the low-side on an another phase-leg and the last phase-leg is controled with PWM on the two MOSFETs. To turn off/on a MOSFET, I use the continuous software force on output A (AQCSFRC.CSFA), and I can disable it to return on a PWM command.

I do this control with the TMS320F28335, and it seems that the DSP does little phase-leg short-circuit when I disable the forcing and return to a PWM control.

I have change how to do the forcing by using the GPIOmux and by toggling between a PWM output and a simple GPIO and it works perfectly.

Can you confirm me the problem with the AQCSFRC.CSFA register's or explain me if I haven't understood something in the use of this register?

Thank you. Simon

  • 0
    Mastermind 7585 points

    How is the external circuitry on your PWM's?  The PWM'S 1-6 have internal pull-up's, which are disabled by default. So it depends on your external pull-up/pull-downs at ePMW1A/1B etc. how the power switches will respond to AQCSFRC.

     

  • 0 in reply to Frank Bormann
    Prodigy 60 points

    Thanks for your response Franck,

    I don't know the external circuitry because I use a module where I have just access at the DSP for the programmation. However I have disabled the pull-up of the ePWM1A/1B etc. But normally the external pull-up/pull-down haven't any impact on the level output except if the output is in high-impedance state. Is it possible to have a high-impedance state on the output when I use the AQCSFRC?

    Thanks for your help!