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BOOSTXL-DRV8305EVM: how to measure current for control

Dong-Young Lee
Prodigy 40 points
Part Number: BOOSTXL-DRV8305EVM
Other Parts Discussed in Thread: DRV8305

Hi,

I want to do bldc speed control.

Looking at the other control loop, the current control loop is included in the speed contro loopl.

This requires measuring the current, the drv8305 board has three shunt resistors, but this is for vector control.

How can I measure current?

Should I measure all three currents of u, v, and w?

I know that the current of dc-link is used to control the current of the bldc motor.

How can I control the current of the bldc motor using this board? (Do I need additional circuit configuration?)

Thank you 

dongyouong 

  • 0
    TI__Mastermind 18981 points

    Hi DY, 

    Thanks for posting your question to the e2e forum - our team will address your questions within a week's timeframe 

    Best Regards, 
    Andrew 

  • 0 in reply to Andrew Liu
    TI__Mastermind 26046 points

    Hi Dong-young, 

    Closed-loop speed feedback can be implemented using a variety of strategies, such as a Back-EMF comparator to measure the phase voltage BEMF, a virtual center tap to sense the phase voltage, integrating the sensed BEMF voltage from resistor dividers, or using a digital-signal processor to calculate the BEMF from motor phase current. The board should have resistor dividers from the phase voltages A, B, C going back to ADC inputs on the microcontroller to use for sensorless commutation. 

    Torque feedback is implemented by measuring the magnitude of the motor phase currents, and is a little harder to implement. The DRV8305 includes 3 low-side current sense amplifiers to measure the motor phase currents, and you can use them to control the torque gains using a PI loop or can be used for sensorless commutation to calculate the BEMF. The board's low-side CSA outputs should be going back to ADC inputs on the microcontroller to use for sensorless commutation. 

    If you would like more training on sensorless control, we have a training video here: https://www.youtube.com/watch?v=teeMdFaykPE

    Thanks,
    Aaron