Phase current measurement in DRV8301-HC-C2-KIT

Ning Sa

Other Parts Discussed in Thread: DRV8312, DRV8301, CONTROLSUITE

According to the FOC theory, the phase current should be directly measured from the stator. However, the schematic of DRV8301-HC-C2-KIT shows the current shunt resistors are at the low side of each half bridge. The method should be equivalent to direct phase current measurement. How can I understand it? Thanks

over 13 years ago

0 Ryan Kehr over 13 years ago

TI__Guru 55605 points

Ning,

I have attached a document for the FOC algorithm that we include in kits like the DRV8312.

5611.Sensorless FOC of PMSM.pdf

0 Ning Sa over 13 years ago in reply to Ryan Kehr

Prodigy 150 points

Rya,

I think I have read it before. It's basically the same as the doc in DRV8301 kit.

I don't understand why the FOC algorithm requires coil current but it actually measured the lower leg current. In single shunt reconstruction, the current measurement is done at specific PWM times. Thus, I read some code the FOC sensorless sample project in controlsuite, C:\TI\controlSUITE\development_kits\DRV830x-HC-C2-KIT_v100\PM_Sensorless\, it seems that the ADC is triggered by PWM1 SOCA when the counter is down to zero. However, the it also means there is no power to the coils during current measurement. Is it reasonable or totally ridiculous? Or, do you have any other docs?

thank you.

nign

0 LT Thomas over 13 years ago in reply to Ning Sa

TI__Intellectual 880 points

Ning,

This may help. The bottom most waveform (ADCresult4) is how the total phase current responds.

0 Yuncheng Song over 13 years ago in reply to LT Thomas

Intellectual 320 points

Hello LT,

Thanks for the nice drawing.

Latter on, I read the FOC control code coming with drv8301 kit. It actually triggered the ADC conversion at PWM time-base counter to 0. Thus, the upper arm of a half bridge is off, and the lower arm is open,which is not quiet consistent with the drawing you posted above. Probably, its still depend on the PWM configurations and the actual HW configurations.

bestm