PCB design considerations for higher current power supplies.

In the process of designing a DC output Power Supply of more than say 200W, things like resistance, inductance and EM noise in PCBs can become a problem.

Solutions vary from ordering thicker copper layers, to designing the PCB with tracks that are wider or on both sides. But considerations need to be given to safety when high voltages or currents are involved. So we also want to increase clearance in these areas.

Where this becomes tricky, is where a PCB contains both power electronics, and control/driver logic. It seems like a contradiction, we want to have two different parts of the PCB with different design rules. So how can we deal with this:

1. Manually place parts/tracks in the power electronics further apart (and try not the make mistakes).
2. Make the power and control circuitry separate PCB projects with different design rules, and mush them together. (not ideal from a workflow perspective when design changes are needed.)
3. Design using the wider clearance rules, then ignore the tons of errors you get for the logic section (again try not to mess something up)
4. Make the power and control circuitry entirely separate PCBs, and solder them together. (Not uncommon, and can save on space and the logic PCB can be made from thinner copper/FR4)

None of these is ideal, The last one can still run into problems with resistive voltage dividers which you really do want near the output/capacitors for your power supply.

However there is a better way, that is to add copper to keep out shapes around the power electronics. Add larger round keep out shapes around capacitor pins in the side of the PCB the copper isn't connected to. Add one or more rectangular keep outs around the middle section of a voltage divider to remove the risk of arcing to sense circuits.

By using this method you can use copper pour shapes instead of tracks. We copy the same ideas as used in 4 layers PCBs where the power/ground layers flow around vias/thru-hole pins, but apply to main current paths. So for a large filter capacitor, the positive is a copper pour on the top, and the negative is a copper pour on the bottom. We get selected parts of the PCB with even lower resistance/inductance, but without needing to use 4 layers. If you decide to move a component, you can easily select its keep out shapes and move those too.

Anyway, I wrote an entire tutorial on using DesignSpark PCB to make a 500V capacitor bank. The ideas work for other PCB software, hosted elsewhere I wanted more people to see it.

Increasing PCB clearance in HV circuits (PCBway blog)