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TMS320C28345: LOW SIDE CURRENT SENSE BLDC FOC

Raj
Intellectual 361 points

Part Number: TMS320C28345
Other Parts Discussed in Thread: CONTROLSUITE

Dear Team,

I hope this message finds you well.

We are currently in the process of implementing the FOC algorithm using the C2000 MCU. In our design, we have opted for a low side current sensing technique, where the shunt outputs are fed to the op-amp, and the op-amp reference voltage has been set to zero. However, we've realized that ideally, it should be set to half of the operating voltage, which was an oversight on our part. Our corrected board will soon be in our hands.

We've encountered a bit of confusion regarding the current sensing method. Upon reviewing your example code, we noticed that you utilize an inline current sensing method, resulting in both positive and negative values at the ADC pin. Consequently, your alpha and beta values fluctuate between positive and negative.

However, due to our op-amp configuration, we only receive positive values, capturing solely the positive half cycle of current data. Consequently, our alpha and beta values consistently remain positive.

We're concerned that this discrepancy might pose challenges for our software algorithm. Could you please advise if there's a method to obtain both positive and negative current values, or if there's an alternative approach we should consider?

Any assistance you could provide would be greatly appreciated.

Warm regards,

Raj

  • 0
    TI__Guru** 117230 points

    A 1.5V (half of ADC range) offset voltage must be added to the amplifier input to converter the bidirectional current +/-0.N * gain to 0~3.0V for ADC input.

    You may take a look at the example projects and the hardware schematic of the High voltage kit in controlSUITE.

    CONTROLSUITE
    http://www.ti.com/tool/CONTROLSUITE

    C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\~HVMotorCtrl+PFC-HWdevPkg

    C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVACI_Sensorless_2833x

    Or

    C:\ti\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\HVPM_Sensorless_2833x

  • 0
    Intellectual 361 points

    Hi yanming Leo,

    Thanks for the quick reply!!

    We studied the code as you provided, But by mistakenly we have set offset voltage to zero so we will get positive values only ( in a week we will get our board in hand - it is in fabrication process)

    There is no any alternatives way to solve this problem?

    Best 

  • 0 in reply to Raj
    TI__Guru** 117230 points

    No. You have to add a positive offset voltage like 1.65V.