/diy/ - Do It Yourself

I may want to have two 3-phase H bridges in parallel, I'm wondering how to place the transistors close to each other. For a given phase that I'll call [A], is it better to have a pair of [A]'s half-bridges where each low-side FET is closest to its corresponding high-side FET? Or is it better to have both of [A]'s low-side FETs right next to each other? I know it would be ideal to have all four of [A]'s transistors as close together as possible, but my geometry means one compromise or another needs to be made. Pic related. I'm thinking it's the one on the left.

My issue is that TO-220 FETs can only handle so much current, hence the need for 2 sets of them. Any SMT package is harder to sink current from, and larger THT packages will be harder to fit. My PCB and its components will be fitting in a 32mm wide enclosure, and TO-220s are 10mm wide. I might maybe be able to squeeze two in sideways, but the pins are going to be bent at a sheer angle since the pads themselves are 15mm long. I guess I can trim the pads. The whole PCB will be pressed with its FETs against a big heat sink.

They'll be driven from the same gate drive output (though on seperate totem-pole current amplifiers), and will be identical parts, maybe even hand-matched if I need to.