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LAUNCHXL-F28379D: Issue in the evaluation of LAUNCHXL-F28379D + BOOSTXL-3PHGANINV + 2MTR-DYNO

Intellectual 2450 points

Replies: 6

Views: 382

Part Number: LAUNCHXL-F28379D

Hello,

My customer has some issues in his evaluation of a C2000 motor control solution:

The Launchpad with the 3PHGANINV board works fine with the motors, using code from ControlSuite.

Then they tried to use 2 legs only of the 3PHGANINV so to have an H-bridge. They programmed the epwm2 and epwm3 using Simulink and saw on an oscilloscope that the signals were correctly generated. But there is no power transferred, so the GAN FETs are not switching. Vin = 30 V was used. Could you help there?

Also, they would like to add their architecture to DesignDrive so to benefit from the SFRA features. Could you please advise how to proceed so they could use the SFRA and tune the compensator for their application?

Thank you,
François.

  • There should be no issue with H bridge operation. If the three PWM config would work fine, why not two? If anything, I will advise them to review the GaN inverter schematic and see where they miss it. Would start from ENABLE signal going into the buffer.

    If they are evaluating the FCL example, then they also have access to the SFRA library. This example plots the loop Bode plot. If not, here below is the where the example is available in controsuite.

    C:\ti\controlSUITE\libs\app_libs\motor_control\libs\FCL_SFRA

     Compensator design will have to be performed by them and the SFRA will be able to show what the resultant loop plot is.

  • In reply to Ramesh Ramamoorthy:

    Francois,

    Let me know if the issue is all resolved. If so, pls close this thread.

    Thanks.

  • In reply to Ramesh Ramamoorthy:

    Hi,
    In the application report which is given below,
    www.ti.com/.../spracb8a.pdf
    inverter is driven at fsw=10kHz.

    do you have any suggestion up to which switching frequency can i increase using the same configuration? (Vin = 28VDC, Iout_ph = 3Arms)

    best regards
  • In reply to hyuruk:

    Hi Hyuruk,

    The main challenge with increasing PWM frequency while using FCL is that it will result in loss of max modulation index evels. A certain amount of time is spent in doing the calculations needed to update the PWM and that time window is lost in being able to generate valid duty cycles.

    With a 10KHz carrier, and at double sampling, and with a 1us calc time, max duty cycle range is about 96%. If you double the frequency, then it will reduce to 92%.

    Let me know if this answered you.

    Btw, I accidentally clicked the thread as resolved. You can reject it and continue.

    Thanks.
  • In reply to Ramesh Ramamoorthy:

    Hi Ramesh,

    first of all thank you for your quick response.
    in my application modulation index may not be so much high.
    actually i will drive low inductance motor and i want to increase fsw as much as i can. But this time as you now layout parasitic inductance and switching losses play as an important parameters. So may be i increase switching frequency step by step and observe Vds and temperature. and/or by regarding your any suggestion from your experiments/analysis etc. about BOOSTXL-3PHGANINV , may i increase fsw up to the value given from you.

    thank you

    best regards
  • In reply to hyuruk:

    Hi Hyuruk,

    The boostxl-3phganinv is built using GaN switches that can provide very high speed efficient switching. The layout is also done considering the switching speed of the switches. So, I believe it is ok to use this board at higher switching frequencies. You need to keep in mind that with FCL, as the switching frequency goes higher, the max modulation index will drop down.

    Hope it helps.

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