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DRV8323R: 6-step commution with 6x PWM Mode

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Replies: 15

Views: 2662

Part Number: DRV8323R

Hi,

I designed motor driver with DRV8323RH.

1x PWM mode is working.

And 6x PWM mode is working, when I use SVPWM.

But it doesn't working with 6-step commutation.

For example, hall signal is as follows. [Mode is 6xPWM mode]

HallA : high

HallB : high

HallC : low

then, I assigned INLx and INHx signals as follows.

INLA : low, INHA:low

INLB : !PWM, INHB:PWM

INLC : high, INHC:low

I check the INLx and IHLx signals with scope, and it is right.

But, GLx and GHx signal is wrong. 

In this case,

GLA : low, GHA : low(--> But GHA shows high )

GLB : PWM, GHB : !PWM

GLC : high, GHC : low 

I don't know why GHA is high. What should I check?

  • Hi,

    The 6 Step commutation works in 1x PWM Mode. Please, verify you are in 1x PWM mode and have correct pin configurations, as stated in the highlighted text and table. 

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

    Hi,

    My developed board works well using 1xPWM mode.

    And also 6xPWM mode works well using sinusoidal commutation.

    So, the pin connection is right.

    I tried to 6-step commutation with 6xPWM mode.

    But the GHx signal is different according to INHx.

  • In reply to Min-su Kim:

    Hi,

    I see you also have written in original post inverted gate signal values on Phase B when compared to PWM input signals

    (INLB : !PWM, INHB:PWM >> GLB : PWM, GHB : !PWM)

    Can you verify if you are measuring the voltages using the correct device pins? Thank you very much.

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

    Additionally, please verify in firmware the value sent for INHA is written correctly. Thank you.

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

    Sorry, thers is a mistake writing in original post.

    I check the input signal, gate signal and voltage in MOSFET output.

    I think gate signal is wrong.

    INLA : low   , INHA:low

    GLA : low, GHA : high(<-- wrong, it shoould be low)

    (So high side of mosfet turns on. It should be turn off)

    INLB : !PWM, INHB:PWM

    GLB : !PWM, GHB : PWM

    INLC : high, INHC:low

    GLC : high, GHC:low

  • In reply to Min-su Kim:

    Thank you very much.

    Now, you are using 6x PWM Mode with 6-step commutation. The datasheet illustrates the truth table of 6-step commutation only in 1x PWM Mode. Do you need to utilize 6x PWM Mode with 6-step commutation or can you use 1x PWM Mode with 6-step commutation?

    Additionally, are you using the hall sensors as position feedback to the MCU and interpreting it in firmware, not to the DRV, is that correct? So you apply the control through the INHx/INLx signals depending on position feedback.

    In 1x PWM Mode with 6-step commutation, you can set the Hall sensors tied directly to the INLA = HALLA, INHB =  HALLB, and INLC = HALLC for position feedback. Then, apply the PWM through INHA. It will simplify your firmware and you have a truth table for 1x PWM Mode 6-step commutation in the synchronous or asynchronous drive.

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

    I can use 1xPWM mode. and it works well.
    I know 1xPWM mode is simple with hall sensor.
    But, I try to use 6xPWM mode with 6-step commutation

    Hall sensor is used and the firmware was implemented.
    I checked IHx/ILx signals related to hall sensor signals. it is right.
    But the gate signal(GHx) is high, when both IHx and ILx are low. I think it is wrong.
    Could you check the gate signals?
  • In reply to Min-su Kim:

    I will discuss with colleagues and/or experiment and get back to you with information and/or results.

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

    Feedback:

    Can you verify if your commutation tables follows the steps outlined in the table shown in the following blogs?

    e2e.ti.com/.../generate-your-own-commutation-table-trapezoidal-control-3-phase-bldc-motors-using-hall-sensors


    e2e.ti.com/.../generate-your-own-commutation-table-part-2

     

    Hector Hernandez
    Motor Applications Team

  • In reply to Hector Hernandez Luque:

     a firmware is implemeted well according to communication table.

    The problem is the gate signal when INLx and INHx signal is low.

    Both gate signal(GHx, GLx) should be low, but GHx is high in 6xPWM mode.

    This is unnatural.

    thank you.

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