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DRV8301-HC-C2-KIT GVDD_UV and BackEmf

Christian Barran
Prodigy 120 points
Other Parts Discussed in Thread: DRV8301, TMS320F28035, DRV8312

Good Day,

I have been using CCS and TI's DRV8301 kit along with a TMS320F28035 control card for about  3 months now working on an ebike project. I am an undergrad so excuse my limited knowledge and if these points sound unintelligent. 

I am using the Instaspin GUI code making my little modification but I keen on running into a number of problem (might be my doing). 

Firstly even though I have the DRV8301 set to OverCurrent at 21 amps based on the Rds (setting OC_ADJ_SET) of the MOSFET I get a fault when I run the Duty cycle at about iq 0.8 (80%) and the current is only around 6 to 7 amps. I temporarily solved this by taking off the OC trip and putting it in Current limiting.

Secondly I can't seem to see the proper back Emf waveforms when I connect an Oscilloscope to the phase voltages and measure Vag Vbg and Vcg. I wonder if this is  the DRV doing this or something, or it might have something to do with how the PWM is set up. I am presently writing over the Header file for the PWM to see if I can change this. Additionally I am not getting much toque produce.  

Lastly I tried to port across (use) the same PWM macro from the DRV8312 code on the DRV8301 since this board gives nice back emf waveforms when using Zero Crossing. This resulted in me getting a GVDD_UV fault. Now from my understanding I can not reset this fault unless i switch off power and switch it back on. I have no clue why this fault is happening.

If anyone can elaborate on some of these areas it would be much appreciated. I will continue doing research and testing to find out what is fundamentally wrong.

Regards,

Christian

  • TI__Mastermind 21320 points

    Hi Christian,

    1. Is it possible there are higher peaks than the commanded motor current? The best method is to examine the motor current with a current probe when the FAULT occurs.

    2. What do you mean you can't see the back-EMF? The back-EMF is typically only visible when the corresponding half-bridge is Hi-Z. Do you have a waveform?

    3. Can you provide some more info on what you ported from the DRV8312 code? Which code suite? You might be best asking this question on the C2000 or InstaSPIN forums. When does the GVDD_UV fault occur on motor enable, etc.? Again wave forms are helpful to debug.

  • in reply to Nicholas Oborny
    Prodigy 120 points
    Thanks for the Reply Nick,

    1. Am not sure but it might be possible but it overcurrented at only around 80 to 90 % duty which led me to believe it has to do with the PWM. It might not be a OC but it is something. The OC does not latch so I only assumed this since the fault stopped when I switched to current limiting. Now I get constant current from the regulated supply when I go above that.

    2. I took some screenshots from the oscilloscope but my Lecturer says it suppose to be producing trapezoidal like waveforms as in one in purple from the 8312 photo.
    www.dropbox.com/.../AABLb11y4Jev4X2XnRir6mMWa

    3. I am using CCS 6.1 and I was using the BLDC_ Sensorless code from the 8312. I basically copied across "f2803cbldcpwm_BLDC.h" and using the main code they provided, included the library along with its set up and initialisations. I then commented out the "f2803xpwm_cntl_8301.h" and its associated variables and structures. I use the debug window to set the DutyFunc. It works when DutyFunc = 0.0 iq15 but when I increase it, it trips a fault and the DRV8301 status regs latches to a GVDD_UV fault. Yes when it is enabled (aka set the enable flag).


    Or I now see that I am in Motor Drive Forums. Thanks I would ask it again there if I do not solve it soon.

    Regards,
    Christian