I try to implement the Center-Aligned PWM on an STM32F410 and the current measurement triggers from the PWM generation timer. I have some trouble in finding the right measurement point for my currents, because somehow I'm never able to get all three phase currents in full resolution. The Center-Aligned PWM works fine as this image shows:
(UV-Phases Center Aligned PWM)
I first tried to synchronize the measurement when all low side MOSFETs are open, since this makes the most sense to me, because I measure at the low sides. This is the result:
(Low Side Currents UVW in RGB) (Osci Triggering Measurement in Blue)
From the V Phase, I always get only half the wave correct. It has nothing to do with saturation, the driver is able to measure up to 7A per phase, where here is only around 700mA applied. Also the ADC goes not in any saturation at all.
Then I tried to measure when all the high side MOSFETs are on, but this is even worse, but expected:
(HIGH Side MOSFETS ON) (Osci High Side Triggering Measurement in Blue)
Here can be seen, that the V-phase is measured correct, but this time U and W have only half the resolution.
Has any one an idea what is wrong here, that I cannot measure the currents of all three phases? The Center-Aligned PWM works fine as the first image shows, so all phases are centered correctly. Also the measurement triggering is perfectly synchronized. Do I need to measure at a different point?
**Edit: ** A solution I just found is to assume Iv = -(Iu + Iw), this seems to work pretty good. Is it possible, that not all three phase currents can be measured simultaneous?