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Configuration for very high PWM-Frequency

Andreas Rom
Prodigy 20 points

Other Parts Discussed in Thread: CONTROLSUITE, MOTORWARE

Hello together -


I want to use the InstaSPIN-solution with a custom designed board.

The power-FETs and drivers are very fast and tests showed me so far, that operating at a 
PWM-frequency of 350kHz is no problem for the power-bridge.

I have spent much time until now studying the behavior and the characteristics of Instaspin and found that there seems to be a upper limit
around 90kHz for the USER_PWM_FREQ in the labs.
So my question:
What can i do to operate Motor-Identification and Motor drive with InstaSPIN at a freqeuncy of 350kHz ?
What do i have to change in software and what are the correct parameters ?

I hope you can help me by providing some tips or reference.

Andreas

  • 0
    TI__Guru** 117080 points
    It's not very reasonable to use so high PWM frequency for motor control. If you have to do this, please refer to below steps.
    1. Use a timer (CPU timer, or othe ePWM) for motor control whcih interrupt freq is less than 30KHz, run the InstaSPIN-FOC in this ISR.
    2. It's better to sample motor line current using sensor, not using shunt resistor.
  • 0 in reply to Yanming Luo
    Prodigy 20 points
    Hi Yanming,
    Thank you very much for your response,
    I already expected something like this as a solution..

    I now try to use CPUTimer2 as Source for an Interrupt, as a I found CPUTimer0 and CPUTimer1 are already in use
    for cpu_usage and FOE - purposes.
    I started with the Example from the controlSuite; this works well but when I now try to port this to motorware
    using the functions given in timer.c and timer.h, until now I couldn't manage the Interrupts to occur.
    I tried to get further information from the datasheet and now found the line
    [...]Timer 2 is reserved for DSP/BIOS. If the application is not using DSP/BIOS, then Timer 2 can be used in the application [...]
    at page 105 .

    Can you please tell me, what this means ? Is motorware using DSP or BIOS?

    Thank you so far -
    Andreas
  • 0 in reply to Andreas Rom
    TI__Guru** 117080 points
    Motorware didn't use DSP/BIOS now, you can use cpu timer or other epwm timer for InstaSPIN-FOC control interrupt.