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C2000 Digital Power Supply Workshop Lab2

Francesco Musolino
Prodigy 160 points

Hi, I'd like to use my F28035 Development Kit to perform some of the Labs in the DPS Workshop v.1.2.

To this purpose I downloaded the ZIP file that include all the workshop projects (from here

http://processors.wiki.ti.com/index.php/C2000_DPSWorkshop). I'm using CCS v5.5.0.

In the Lab2 a project is proposed concerning open loop control for two buck converters with over current limitation. To simulate the same hardware setup as it is described in the lab2, I fed the ADC input ports (A0-A1-A5-A6 and B1) with voltages that simulate a specific set of voltages and currents of the bucks (I checked the .xls calculation file for this part). As a first try, I decided to set the voltages that simulate the inductor currents (ADC A1 and A5 inputs) to be 0, in order to be sure that the implemented over current protection is inactive,

In the debugging view I setted the Real Time mode with continuous refresh.  At the beginning the FaultFlg1 and 2 are both 1 indicating overcurrent issues, then when I try to clear them (by setting ClearFault1=0,  ClearFault2=0)  I noted that FaultFlg1 remains 1, while  FaultFlg2=0. So when I change the duty cycle 2 from 0.0 to 0.05 I have the right PWM from ePWM2A but nothing from ePWM1A.

So I modified the "DevitInit" and the "PWM_1ch_Cnf" files to route the PWM signal to ePWM1B instead of ePWM1A and now I can see the correct PWM signals exiting from GPIO00 and GPIO01 pins. 

My question is: why ePWM1A doesn't work properly? This is for sure not an hardware problem since I built and debugged different files that exercise ePWM1A on GPIO00 and all of them generate a corrent PWM waveform. Are there anyone that experience the same problem (even for different project files) ? Is there something that I missed to insert or that I have to modify?

Thank you very much-

  • 0
    TI__Mastermind 27200 points
    Francesco,

    I confirm the workshop code for lab 2 does work correctly on the DPS workshop board. I was looking at your ADC input choice for the inductor currents. Referring to figure 4.2 in the datasheet for F28035, I noticed your choice of channel A1 for inductor current feedback is not routed through the internal comparator. I wonder if you have anything connected to the COMP1 input (channel A2)? If not, perhaps when the workshop code configures COMP1 to trip PWM1A the trip is permanently active and that is why you cannot clear it with the ClearFault1 flag.

    PWM trips can be configured separately for each PWM output, so perhaps when you modified PWM_1ch_Cnf you have a configuration where the comparator trip is not acting on either output. I don't know, but I suggest checking the ADC channel allocation again.

    Best regards,

    Richard
  • 0 in reply to Richard Poley
    Prodigy 160 points

    Thanks Richard for your quickly reply,

    your analysis is correct !

    I first considered ADC-A2 and ADC-A4 as inputs for the inductor currents IL1 and IL2 and, in addition, I modified the original workshop file "Lab2-Main.c" at rows 347,348 as follow:

    ChSel[3]=2;

    ChSel[4]=4;

    and everything works as intended.

    Thank you very much

    Sincerely

    Francesco