Quote
Cefiar
I'd also considered replacing the 12V reg with a 9V reg (7809). This still gives a reasonable voltage for gate drive (much further up the drive elbow than 5V), and is more than adequate for running the Arduino (taking even more voltage drop away from the Arduino regulator under the shield, and thereby reducing heat generation under there - which could eventually be a problem). It also removes the need for the 12/24V jumper, as it'll always be on regardless. It'll require a heatsink if you run it off 24V, but the same was true for the 12V reg. Also, this gives a 3V margin at 12V, so the reg will run reliably (if not, we can always use a 7808 to get an extra volt overhead, at the expense of drive voltage).
One good reason for keeping the 12v (IMO) is to allow 12V fans to be used with a 24V setup. You can get 24V fans of course, but the 12V ones are cheap and common.
I've been looking into buck converters again, there is a common Chinese module based on MP1584, the module only costs a £1 on ebay so clearly has a cheap BOM, and is quite small, should be good for 2.5A.example here Mini 3A DC-DC Converter Adjustable Step down Power Supply Module