Topologia of the fountain ATX seventeam, design of the trafo

Was it looking at this scheme of the fountain seveteam http: // SOURCES=DOWNLOAD
and I kept a doubt:
1º) Is a GAP necessary (slit) in the trafo in this topologia of fountain, I eat in the fountains chaveada flyback?
2º) Is It how the fountain chaveada flyback what when the Mosfet chaveia the wrist, the energy is stored in the trafo in magnetic, and alone form when the mosfet is in Off is that the energy is transferred to load?
I found this very interesting topologia, being able to economize us capacitores when if the topologia half bridge was compared
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For flyback, gap is necessary, yes.

As for the second one, the 2-transistor forward, i have built one myself and can comment on it - it is very efficient, doesn't require very high voltage transistors, AND most importantly it can be driven with a single ended controller (such as the UC3842 for example). I use a custom pulse skipping controller made with a 555 and a couple comparators. My power supply is 230v AC in, +/-70v DC out, 400W. Transistors are IRF740 and they run cool (idle at room temp, 60-70C at full load with 30C ambient). I only have an ATX power supply heatsink for the transistors, there is no fan. It may need a bigger heatsink when it'll be mounted in a box though.

Most computer power supplies nowadays use the one-transistor forward or two-transistor forward topologies. Some go as far as saying half-bridge is outdated. But half-bridge can get almost double the power output from a given core size, so it's all about the controller complexity. I like the 2-transistor forward because it is simpler.