I don't recall if i posted this before, but this seems like a good thread to post it in.

This is a photo of a crudely thrown together synchronous buck. the mosfets are irfz44.

The board is the heatsink, and at 50 khz each half bridge is good for 5 amps average current flowing through the inductor.

5 amps at 50 volts input, 24 out, 50% duty cycle, about 5 watts loss.

it would be good for more current but the fets took 100ns to turn on because i was driving the transformer though a cheap signal generator.

no load loss is ~ 1/2 watt, depending on the time of day and frequency.

The 200 volt 470uF capacitors on the input (top left) have an internal resistance high enough such that 10 amps of inductor current at 50% duty cycle they lose about one half watt each. They aren't new however, so ymmv. The input capacitor losses for single phase buck are not negligible. its a tradeoff between cost, lifetime and losses.

the switches are turned on through ~20 ohms, off through 10 ohms.

the two toroidal inductors are not necessary. the ferrite core in the center is 20 turns of 14 awg with a 1.2 mm gap. it starts to saturate at 12 amps. but even if it does the mosfets don't care, so it does not need soft starting. its losses are very low, it could probably handle 500 watts of power without overheating at a much higher frequency.

(note that the inductor requirements change with duty cycle, 500 watts would be best case of 50% duty cycle)

Don't use binding posts for the capacitors, the 6 inches of wire between the capacitor and the circuit means your turn off losses will still be excessive. it needs to be a direct connection. just use double sided board and cut the traces out with a dremel for prototyping.

As you probably know the output capacitor only carries the ripple current, which is typically on the order of 10-15% designed full load current.

also, since at full load 80-90% of the inductor current is continuous, there's no reason not to use 10 awg solid wire

Also, if you insist on using cmos for switching, use something like a 74act14 schmitt trigger and wire up all 6 inverters in parallel, then drive the fet though the proper resistor.