• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 32 subscribers
  • Views 1347 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8313: DRV8313 Trapezoidal commutation, single shunt current measurement, accuracy

Martin Rupp49
Prodigy 30 points
Part Number: DRV8313
Other Parts Discussed in Thread: BOOSTXL-DRV8301

We are running a brushless motor application using the DRV8313 with trapezoidal commutation and PWM. For current measurement, we are using a single shunt (one shunt for all three phases). We found that measurement results are not reliable because of the current that runs through the body diode while PWM is OFF. Is there a way to achieve more or less accurate results for trapezoidal commutation (total current matches the voltage drop accross the shunt resistor und thus creating a voltage proportional to the total current flowing through the motor windings?).

Thanks

Martin

  • 0
    TI__Guru** 114905 points
    Hi Martin,

    Are you using a bidirectional current sense amplifier? This allows the current to be measured when the device is driving through the FETs and coasting (through the body diodes). The ADC reads Offset/2 for zero current and can be calibrated.

    An example of this can be seen in figure 8 of the BOOSTXL-DRV8301 hardware user guide ( www.ti.com/.../slvu974.pdf ).
  • 0
    TI__Mastermind 21320 points

    Martin,

    Some additional input. This configuration is used all the time for BLDC current monitoring.

    One comment. You cannot measure current in this configuration when the power stage is in brake mode (all three low-side or all three high-side MOSFETs ON). In this case current will just recirculate inside of the half-bridges through the motor windings.

    Also, as Rick mentioned, if you wish to measure regenerative (negative) currents you will need a bidirectional shunt amplifier.

  • 0 in reply to Rick Duncan
    Prodigy 30 points

    Hi Rick,

    I am using the shunt in conjunction with a comparator. So it's not really a current measurement, it's more of an overcurrent protection (when the comparator triggers, the driver is shut down). Could you explain a little further how the you could measured the current when pwm off and the current is flowing through the body diode?

    Thanks

    Martin