current feed back of highpower pfc motor kit

Hello,

Please note that there are two versions of this board which utilize the same PCB.  It will be helpful to know which your are using.

(1) is built around the 'F2805x series of C2000 MCUs - in order to utilize the on-chip PGAs
(TMDXHVMTRKIT5X)
\controlSUITE\development_kits\TMDSHVMTRKIT5X_v1.0\~HVMTRKIT5X_v1.0-HW_Dev_Pkg\

(2) another is built for the other C2000 chip families - this version uses external opamps to bring the shunt current signal into a signal with enough magnitude to provide adequate control of the motor.
(TMDSHVMTRINSPIN or TMDSHVMTRPFCKIT)
\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v2.1\~HVMotorCtrl+PFC-HWdevPkg\HVMotorCtrl+PFCKit-R1.1\

If you take a look at your board and see [M4]-U3 and [M4]-U4 on your board, then you know you have (2).  If you have (1), this might explain what your are seeing.


Thank you,
Brett

Hi,

The newest version of controlSUITE will install HVMotorCtrl+PfcKit_v2.1.  Do note that the only difference between v2.0 and v2.1 is software and software documentation.  I believe that the hardware is identical.  As a result, feel free to refer to the schematic/information found in v2.0 if you wish.

So from your response, your board is (2).  If you measure ADC-A1 or ADC-B1 (at the controlCARD), I believe you should see an AC waveform centered around 1.65V where the magnitude of the AC waveform changes with the load.


Thank you,
Brett

Hey

thank you for the reply, however if that's the case i get from the pcb file ans schematic file that the current wave should have a DC offsite of 1.65v and gain is 8.25. However as i mentioned before,From the scope i can see my current is in good shape sine wave. However if i attach a scope to the ADC A1 and ADC B1 i only got a DC signal. Also from the PCB file  contained in the control suite the R1 in M1 should connect to R28 in M5 and R2 in M1 should connected to R26 in M5. However  I tested the board with my mutimeter, on my board they are not connected.  So is that possible that the pins are supposed to connected is damaged some how so i can't get the wave form which i supposed to see

Hi,

Where are you measuring the current (with the scope)?

Where are you measure ADC-A1 and ADC-B1.  Are you measuring them at the board pads of R26 and R28?

jia li said:

However if i attach a scope to the ADC A1 and ADC B1 i only got a DC signal. Also from the PCB file  contained in the control suite the R1 in M1 should connect to R28 in M5 and R2 in M1 should connected to R26 in M5.

Hey brett

The attachment is the scope screenshoot i got, the yellow one is the current wave form i get directly from a current probe, the blue one is the waveform i get from ADC1 (use ac to remove the dc offsite) could you please tell me why the blue curve is kind of bad?

regards

Hi Jia,

Why do you call the blue waveform bad? 

Please keep in mind that ADC-A1 is the shunt current, the current going between the lower leg's FET and ground.  This is important because, only while the lower leg's FET is on, will ADC-A1 show the phase current.  When the lower leg's FET is off, the shunt will have no current flowing through it, and the voltage on ADC-A1 will be 0.

What this means is that the signal ADC-A1 cannot be sampled whenever you wish.  Instead it must be sampled based on the PWM waveform is being generated.  In our chip, the ePWM module can generate ADC start-of-conversion (SOC) events, so we can devise methods to sample the signal only when it is valid.


Thank you,
Brett

thank you Brett,

another question is that form the schematic file it is as you said has a 1.65v dc off site for the current. But i first thought the gain is 8.25 but from the scope it is not right. Could you please tell me the exact gain of the phase current

thank you

Hi Jia,

Based on your oscilloscope screenshot, and some math, I believe the shunt-current sense circuitry is working as designed.  Seeing a ~400mVp-p waveform on the ADC input, when approximately 2.5Ap-p current goes through the motor, seems correct.

I'll leave it to you to see if you can find what you're missing.  I will say that the gain=8.25 number is the gain of the opamp circuitry specifically.   :)


Thank you,
Brett

Hey Brett

So i guess the way to back calculate the actual current based on what i have at the ADC channel is( ADC-1.65)*8.25= the actual current.

And i still don't get what I'm missing

regards

jia li said:

So i guess the way to back calculate the actual current based on what i have at the ADC channel is( ADC-1.65)*8.25= the actual current.