Hi,
I am controlling a 30 amp motor through PWM from a microntroller to a driver to four parallelized mosfets (to split up the current and power dissipation). The core of my schematic is shown in the attachment. The input is coming from a micro controller.
This part of my circuit works, however I have been having some trouble dealing with the noise and voltage spikes on the supply line from what I believe is the switching motor collapsing field effect. That is the reason for diode D1. Without those Cap's and Chokes (inductors) the 14 V line is all screwed up, however those filters help significantly. However, I am still having a voltage spike up to about 20 volts every 20 kHz (my PWM switching frequency) that these filters don't seem to be getting rid of. That spike is not allowable for the rest of my circuit (rectangle box) and I was wondering if anybody has any idea's to help get rid of the voltage spike.
I have tried a 15V zener diode to ground with no success. I've also tried putting power diode in series on the 14V supply rail in order to try to block the spike from going back onto the line, however this causes my mosfet driver IC to break. I'm guessing that the current had to flow somewhere and since it can't go back out on the supply rail from my diode blocking it, the current flows into the driver, thus breaking it.
Any help would be greatly appreciated.
Thanks.
I am controlling a 30 amp motor through PWM from a microntroller to a driver to four parallelized mosfets (to split up the current and power dissipation). The core of my schematic is shown in the attachment. The input is coming from a micro controller.
This part of my circuit works, however I have been having some trouble dealing with the noise and voltage spikes on the supply line from what I believe is the switching motor collapsing field effect. That is the reason for diode D1. Without those Cap's and Chokes (inductors) the 14 V line is all screwed up, however those filters help significantly. However, I am still having a voltage spike up to about 20 volts every 20 kHz (my PWM switching frequency) that these filters don't seem to be getting rid of. That spike is not allowable for the rest of my circuit (rectangle box) and I was wondering if anybody has any idea's to help get rid of the voltage spike.
I have tried a 15V zener diode to ground with no success. I've also tried putting power diode in series on the 14V supply rail in order to try to block the spike from going back onto the line, however this causes my mosfet driver IC to break. I'm guessing that the current had to flow somewhere and since it can't go back out on the supply rail from my diode blocking it, the current flows into the driver, thus breaking it.
Any help would be greatly appreciated.
Thanks.