Zero Cross Detection in BLDC motor

[Iraianbu]

I need to do zero crossing detection in BLDC motor. I try with the circuit mentioned above but i can't get exact output. what change will be made so that i can get that output.

output wave which i got .

Channel-1 (yellow) : OP AMP output
channel-2 (blue) : Hall sensor output

Back EMF wave.

 

[KlausST]

Hi,

You want a digtal output --> thus us a a comparator
(an opamp is for analog output ... unless specified otherwise in the datasheet)

Nowadays comparators (as well as OPAMPs) usually don´t need R5. In worst case it may cause more problems than benefit.

Show the complete circuit, including comparator´s power supply.
Also show the exact part name of the comparator.

C1 and the source resistane generate a tau of about 12ms. For my taste a bit high.

(There is no need for R11, just choose correct values for R7 and R3 ... to lower part count.)

Klaus

 

[Iraianbu]

At Low Speed output

At High speed output

Above circuit output channel 1 (yellow) is Hall signal and channel 2 (Green) is ZCD output .There is a Phase delay between channel 1 and 2 of 15 deg at low speed and the phase shift is increased 24 deg when speed is increased. change the speed low to high 10 deg phase Delay is occurred. Can anyone find me a right way to solve this issues .

 

[d123]

Hi,

Make the 15nF capacitors much smaller, such as 150pF. Or put a speed-up capacitor of a few pF from OA OUT to IN- or IN+. Feed-forward capacitors can be useful, and damp by removing ringing from high slew rate OA signals that exceed OA bandwidth/slew rate. I read that Cfeedforward should be 0.5 * OA CM input capacitance (the larger of the two input capacitance values in the op amp datasheet).

 

[danadakk]

Maybe for future reference you can consider sensor less control for better
performance :

https://www.infineon.com/dgdl/Infineon-AN93637_PSoC_4_Sensorless_Field_Oriented_Control_(FOC)-ApplicationNotes-v05_00-EN.pdf?fileId=8ac78c8c7cdc391c017d0740371063ac

Regards, Dana.

 

[KlausST]

Hi,

again: Why an OPAMP?
The filter R5/C1 will introduce about 200us.

debugging:
If you are not satisfied with the output (of OPAMP, comparator, filter...) then check it´s input(s).

Klaus