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CCS/BOOSTXL-DRV8301: How to read low side current if high side switches are on with duty cycle of 100% ?

Ata Khiabani
Intellectual 780 points
Part Number: BOOSTXL-DRV8301

Tool/software: Code Composer Studio

Hello,

In order to read the low side currents, the low side switch should be on and this is how the currents are read in Insta-spin FOC. My question is that what if two high side switches are completely "ON" during the sampling time and one of them is completely "OFF" during the sampling time. In this case, I can only read one current correctly, right? Is there a way to read the other currents also, or maybe calculate them based on the switching states?

I am asking this question because I want to implement direct torque control (DTC) algorithm and in this algorithm, switches are on/off completely during the sampling time.

Regards,

Ata

  • 0
    TI__Guru 65430 points

    Ata,

    This depends on which 2 of the 3 phases have the shunt amps and which phases are on during the sampling time. If you know the total current into the bridge then you should be able to calculate the current in all three phases using two shunt amps.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Intellectual 780 points

    Adam,

    suppose all three legs have shunt resistors. High side switches of the legs U and V are completely on and low side switch of W is completely on during the sampling time. In this case, I can measure the current of phase W, but I don't have the total current into the bridge. I mean how should I measure that when I don't have shunt resistor at the input of the bridge and the only shunt resistors are on the low side switches? Please tell me if I am missing something here.

    Regards,

    Ata

  • 0 in reply to Ata Khiabani
    TI__Guru 65430 points

    Ata,

    Any current out of the bridge, through the motor, then back into the bridge to GND must travel through a LS FET in which case you can measure the total current.

    Regards,

    -Adam