Another two improved topologies are shown in Fig. 4(c) and
(d), in which a simply active clamp circuit is introduced to solve
the starting problem and full-load range problem [35], [36]. The
difference between the two topologies is the connection of the
clamp capacitor and the voltage across the clamp capacitor. The
voltage across the clamp capacitor in Fig. 4(c) is higher than
in Fig. 4(d). The zero-voltage switching of all active switches
can be achieved, and the voltage surges across the turn-OFF
switch are low. Furthermore, all magnetic components can be
integrated into one magnetic assembly using the method proposed in [38]. Therefore, this topology has reduced number of
components. According to the design criterions described earlier, the topology shown in Fig. 4(d) is a better choice than the
others.