I have 5 Half-bridges that I am paralleling in my motor drive. THe problem I am running into is that the MOSFETs themselves are big and on the PCB they are going to be lined up in 10cm rows daisy chained together by a wide, but long straight traces. I have rail clamp diodes and RC snubbers to try and shield the "MOSFET bunch" from the inductive flyback of the motor and it's wires. BUt I foresee problems from the parasitic inductances that connect the MOSFETs to each other within the bunch. It's not practical for me to add rail clamp diodes and/or RC snubbers for every single MOSFET.
Is there a way to go about this? RIght now, my best...but somewhat precarious bet is to rely on my one big discrete snubber to absorb the motor's flyback, and rely on each FET's parasitic diode to deal with the remaining inductive kick that will occur from the traces paralleing the FETs together. I hate relying on that instrinisc diode though, and adding individual snubbers to each FET just lengthens these paralleling traces as well as destroying how tight and clean they already are.
I'm unsure if the inductance from the traces alone (assuming the snubber has completely dealt with the motor inductance) is enough to cause the problems I am afraid of. The totally length of the trace daisy chaining the FETs together would be about 10~12cm divided into ~2cm of trace connecting each FET together.
To give you an idea, it's going to look something like this:
**broken link removed**
Is there a way to go about this? RIght now, my best...but somewhat precarious bet is to rely on my one big discrete snubber to absorb the motor's flyback, and rely on each FET's parasitic diode to deal with the remaining inductive kick that will occur from the traces paralleing the FETs together. I hate relying on that instrinisc diode though, and adding individual snubbers to each FET just lengthens these paralleling traces as well as destroying how tight and clean they already are.
I'm unsure if the inductance from the traces alone (assuming the snubber has completely dealt with the motor inductance) is enough to cause the problems I am afraid of. The totally length of the trace daisy chaining the FETs together would be about 10~12cm divided into ~2cm of trace connecting each FET together.
To give you an idea, it's going to look something like this:
**broken link removed**
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