Hi! So for the bldc motor I want to use in my robotic arm (at least in the basepart) I need a very strong bldc controller that can handle 40V and 40A. For the whole project I wanted to use the FOC library as a standard. I didn’t find a good controller that can support my needs so I decided to start building my own. I would appreciate any feedback on the design and any INPUT !
It sounds like a cool project, we can get a discussion going here as the design evolves…
A thought I have: while the NVTFS5C673NL looks like a nice FET, if you actually want to handle 40A, I think you should go for a FET rated somewhat higher, maybe something like this.
The schematic also doesn’t have any bulk capacitance on it yet, but I assume you still plan to add it.
What type of connectors / pads will you use for 40A?
For such high currents the board should be 2Oz or 3Oz outer layer copper, and you may need additional solder or bus-bars on the power traces. It should probably be 4 layers to have a chance to route the signals somewhat away from the power carrying traces, and have decent grounding. The layout will probably be interesting to discuss.
Looks like the driver handles a lot of the complexity for you. It has a fixed 10V gate drive and integrated what looks like a pretty sophisticated charge pump circuit for the high side drive…
Welcome, and thank you, this is interesting. Please share your progress.
On the driver choice, the cost of one driver is over $200 at JLC, This will be a very expensive driver board. Also, the availability is very limited these days with the silicon shortage and all.
On the MOSFETs, as @runger pointed out, you want a lot of headroom to handle 40A. My Level2 electric car charger is 30A, so designing a PCB for handling 40A continuous power per phase is not a trivial task. In addition to that, the nvtfs5c453 are out of stock completely. You need a lot physically bigger mosfet to make good copper contact to carry that much current. I would even go for TO-263-6L or HSOF-8 packages/footprints to ensure sufficient contact and thermal headroom.
Finally I finished migrating away from the drv8305 to the DRV8323HRTAR (without SPI). This migration was a necessity due to the ongoing chip shortage. I also implemented the HSBA6074 FETS which @runger suggested. If anyone has additional input please let me know here
DRV8323HRTAR is also not in stock, and you cannot manually solder, it’s a WQFN package. I even tried the global sourcing, its completely out. Only Mouser have it, and they got about 100 left. By the time you read this the inventory may be gone completely.
For 40A continuous current you will need 2oz/4layer solid plates minimum with an impedance control and large heatsinks with forced cooling to dissipate about 80W at maximum current, or liquid cooling. Your PCB will be quite expensive.
As I said, you will be better off with large footprints (HYG050N13NS1B6) and a very common driver (IR2136STRPBF) as your first design. But you don’t have to listen to me of course.
I’m very curious to see the PCB layout.
PS To give you an idea of what you are trying to achieve, this is a 1000W motor, along with one of my BLCD controllers I have built for a much smaller motor, with those same small MOSFETs you want to use as a comparison.
The motor is 1000W, and you want your board to push 1600W (40Vx40A) continuous current so you will essentially try to drive a 50% bigger motor with that same tiny mosfet. Do you really think this is a good idea?
When the cable connectors are bigger than your mosfets, I say you may want to go back and rethink your design.
If you ask me, you need something like that (that driver is built for the big motor above):