In order to improve the power density, all
magnetic components in this topology can be integrated into
one magnetic assembly, which features in wide power regulation range, reduction in the number of magnetic assemblies, and
reduction in the number of windings on the primary side [37].
Fig. 4(b) shows the improved current-fed half-bridge converter
by adding an auxiliary transformer [34]. The new converter has
no starting problem and the full-load range can be achieved.
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.