hello, this is my first post here and hope someone can help. im trying to build a brushless motor controller, this is the first time i have messed with this stuff so i used a purpose made controller (mc33033). im working in a small market (maybe 100 units) so the final design cannot use these special purpose components, for now im trying to understand brushless motor operation better.
im having problems reversing the motor, it clearly has less torque when turning CCW. also it uses more current when turning CCW and the p-channel gate seems to be turning off (high) before it should as thou its current limiting but removing the gate from the circuit leaves a nice clean square wave from the chip. frankly, im stumped, there are no big power supply ripples any were, and everything else seems normal. has anyone here ever used brushless drives and experienced this kind of problem before.
this is the drive running CW everything looks fine. the top trace is the phase A p-channel gate (other p-channel gates are similar) the bottum trace is from the current sense resistor for all the phases. both use x10 probe
this is the same signals running in CCW
the current is much higher but if i remove the gate from the circuit i get a clean square wave from the chip.
https://www.onsemi.com/pub_link/Collateral/MC33033-D.PDF
this is the brushless controller that i used, i have build the circuit described on page 19 only i have omitted the mc33039 and other components on pins 10 and 11 that are part of the feedback loop.
and these are the fets i used
p-channel
https://media.digikey.com/pdf/Data%20Sheets/International%20Rectifier%20PDFs/IRF9Z30PBF.pdf
n-channel
https://media.digikey.com/pdf/Data%20Sheets/International%20Rectifier%20PDFs/IRFZ20.pdf
i would guess if i could get rid of the current spikes in CCW, everything would run normal in both directions. i dont really understand exactly whats going on here, backEMF diodes? to much gate drive? not enough gate drive? designer head space?
any insight you may have would be more then i have now, and very much appreciated.
im having problems reversing the motor, it clearly has less torque when turning CCW. also it uses more current when turning CCW and the p-channel gate seems to be turning off (high) before it should as thou its current limiting but removing the gate from the circuit leaves a nice clean square wave from the chip. frankly, im stumped, there are no big power supply ripples any were, and everything else seems normal. has anyone here ever used brushless drives and experienced this kind of problem before.
this is the drive running CW everything looks fine. the top trace is the phase A p-channel gate (other p-channel gates are similar) the bottum trace is from the current sense resistor for all the phases. both use x10 probe
this is the same signals running in CCW
the current is much higher but if i remove the gate from the circuit i get a clean square wave from the chip.
https://www.onsemi.com/pub_link/Collateral/MC33033-D.PDF
this is the brushless controller that i used, i have build the circuit described on page 19 only i have omitted the mc33039 and other components on pins 10 and 11 that are part of the feedback loop.
and these are the fets i used
p-channel
https://media.digikey.com/pdf/Data%20Sheets/International%20Rectifier%20PDFs/IRF9Z30PBF.pdf
n-channel
https://media.digikey.com/pdf/Data%20Sheets/International%20Rectifier%20PDFs/IRFZ20.pdf
i would guess if i could get rid of the current spikes in CCW, everything would run normal in both directions. i dont really understand exactly whats going on here, backEMF diodes? to much gate drive? not enough gate drive? designer head space?
any insight you may have would be more then i have now, and very much appreciated.
