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DRV8301-HC-C2-KIT: PWM wave setting method and the sampling instant

Cherry Zhou
Mastermind 22235 points

Part Number: DRV8301-HC-C2-KIT

Hi team,

Here're some problems from the customer may need your help:

The PM_Sensorless routine in the DRV830x-HC-C2-Kit_v105 development package for TI\controlSUITE\development_kits.

In this routine, the driver board samples the phase current using the lower leg configuration with 3 sampling resistors.

In the PM_Sensorless project, the 2-way built-in amplifiers of the DRV8301 are used to handle the voltage drop across the two-phase sampling resistors of U and V with a software-configured amplifier gain of 40.

However, the external detector amplifier is configured with a gain of 20, as shown in the following figure:

The three signals EXT_IA-FB, EXT_IB-FB, EXT_IC-FB are not used for the algorithm processing.

1) The gain of the DRV8301 internal amplifier configured in the PM_Sensorless routine is 40 and the gain of the external amplifier configuration is 20. If an external amplifier is used for algorithmic processing, the software gain needs to be configured to a factor of 20x?

2) Regarding the setting of PWM wave:

On the left is f2803xpwm.h（\TI\controlSUITE\libs\app_libs\motor_control\drivers\f2803x_v2.1）

On the right is f2803xpwm_PM.h（\TI\controlSUITE\development_kits\DRV830x-HC-C2-KIT_v105\PM_Sensorless）

As you can see on line 36, why is the setting of AQCTLA different with the same configuration?

3) The following figure shows the sampling instant, why is the configuration different?

On the left is f2803xileg_vdc.h（\TI\controlSUITE\libs\app_libs\motor_control\drivers\f2803x_v2.1）

On the right is f2803xileg_vdc_PM.h（\TI\controlSUITE\development_kits\DRV830x-HC-C2-KIT_v105\PM_Sensorless)

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Prodigy 290 points

    Hi,

    The subject matter expert is out of office today. Please expect response by tomorrow.

     

    Thanks,

    Saravanan

  • 0
    TI__Guru** 109810 points
    Cherry Zhou said:
    1) The gain of the DRV8301 internal amplifier configured in the PM_Sensorless routine is 40 and the gain of the external amplifier configuration is 20. If an external amplifier is used for algorithmic processing, the software gain needs to be configured to a factor of 20x?

    Yes.

    Cherry Zhou said:
    3) The following figure shows the sampling instant, why is the configuration different?
    Cherry Zhou said:
    Could you help check this case? Thanks.

    That depends on the inverter hardware. Please refer to the configuration used in the project, or change it according to the hardware you used.

  • 0 in reply to Yanming Luo
    TI__Mastermind 22235 points

    Hi,

    Thanks for your help.

    Cherry Zhou said:
    3) The following figure shows the sampling instant, why is the configuration different?

    Regarding the Q3:

    Below is CAD_set + CAU_clear. Since sampling is done through the sampling resistor of the lower leg, sampling is done at the middle of the lower leg switch opening, that is, at the middle of the lower leg PWM waveform. Therefore, the triangle wave period is the vertex instant that triggers sampling:

    The figure below shows CAU_set+ CAD_clear, again due to the current captured through the lower leg sampling resistor, the sample is selected at the middle point when the lower leg switching tube is on, that is, when the triangle wave counter is 0:

    Is the above understanding correct?

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Guru** 109810 points

    You may take a loot at the application note of the project you want to use. The ADC trigger and sampling time point depend on the control algorithm and the current sensing circuit on the hardware.

    It's difficult tell you that it's correct or incorrect that should be related to the project as mentioned above. You may refer to the example project directly if you are working a TI EVM kit.

    If you haven't had a chance to look at the workshop material, I think this will help demystify some of the terminology and architecture, and learn about motor control with C2000 MCU to get started developing as well.

    https://training.ti.com/c2000-motorcontrol-training-series