The circuit uses 4047 IC and IRF540 MOSFET instead of 2N3055 transistor. You’ll need a 2-3A center tapped transformer to handle/supply 100W load. The FET is better than transistor in both stability and responsibility.
IRF540 has specifically been designed to minimize input capacitance and gate charge. It is therefore suitable as primary switch in advanced highefficiency, high-frequency isolated DC-DC converters for Telecom and Computer applications. It is also intended for any applications with low gate drive requirements.