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DRV10970: Question about the BLDC

Eric Li
Prodigy 10 points
Part Number: DRV10970

Tool/software:

Hi all,

I am looking for answers to the following questions: 

  • Absence of sensored FOC and sensored sinusoidal product:

The featured integrated BLDC drivers shown in TI.com only provide sensored trapezoidal products. Even the sensored sinusoidal product DRV10970  is available now but it seems that the sensored FOC and sensored sinusoidal is less competitive compared with sensored trapezoidal products. I wonder which reason leads to it.

  • FOC: Improving acoustic performance with automatic dead time compensation:

Table 3-1 in the attachment indicates that FOC control improves acoustic performance with automatic dead time compensation. I wonder if it benefits from the additional control of automatic dead time compensation, or just the nature benefit of FOC.

  • How sinusoidal control determine the angle of three phase references:

Compared with other methods: Trapezoidal control use the truth table to know switch states of FETs after gaining the information form Hall sensor. FOC control determine the angle of references through complex calculation based on the angle of rotor, the current loop and speed loop. However, I have no idea about how sinusoidal control determine the angle. Whether it simply follows the angle of the rotor or have additional calculations to meet the control requirements?

  • 0
    TI__Expert 5550 points

    Hi Eric,

    • Absence of sensored FOC and sensored sinusoidal product:

    Sensored Trapezoidal needs 3 HALL sensors to find rotor position and commutate. 

    Sensored Sinusoidal commutation is based on U Phase and hence only one HALL element is sufficient. The commutation is done every 180 degree by detecting HALL state.

    FOC need three phase BEMF information as precisely as possible. From three phase BEMF data position and speed is extracted and with this information stator windings are excited to maintain 90 degrees torque all the time.  Hence three Hall sensor which can provide BEMF sinusoidal way is preferred, the common HALL sensors in the market are digital which changes state. Nowadays we get analog Hall sensor as well.  

    • FOC: Improving acoustic performance with automatic dead time compensation:

    Because FOC modulates current continuously unlike in other every 180 degree, the harmonic content is managed to compensate for the dead time effect.

    • How sinusoidal control determine the angle of three phase references:

    I explained this for 1st question, commutation is based on the BEMF zero cross detection method, the better the accuracy the better is torque which ensure BEMF is well aligned with Phase current. In sensorless DRV10x has good current sense accuracy and also there is provision for lead angle adjustment for the user to tune to get good performance.

    Thanks and Best Regards,

    Venkatadri S

  • 0 in reply to Venkatadri Shantaram84961
    TI__Prodigy 10 points

    Thank you for your detailed response, but I still need your help to resolve my remaining confusion.

    • Absence of sensored FOC and sensored sinusoidal product:

    It seems that Sensored Sinusoidal commutation need less HALL sensors. So why sensored Sinusoidal products are less in number than sensorless. In contrast, the sensored trapezoidal products are no less than sensorless.

    • How sinusoidal control determine the angle of three phase references:

    Could you share more information about “there is provision for lead angle adjustment for the user to tune to get good performance.”

    Best Regards

    Eric Li