and a switch 307b the slow switch is connected in series with a parallel connection of a capacitor 305 and a resistor 306 equivalent to capacitor 105 and resistor 106 of fig1 the main idea of embodiments of the present invention is to improve the conventional rcd clamp in two aspects to recover part of the power loss in the clamp and to minimize the stray oscillation after the clamp diode is turned off the manifestation of the improvement takes place in effect in two phases in order to recover part of the energy dissipated in the clamp resistor reverse current conduction is necessary in the clamp diode hence a bidirectional switch 304 replaces the clamp diode 104 in fig1 it is assumed that in the first phase the other bidirectional switch 307 is shorted for this discussion the corresponding clamp current during the forward and reverse conduction periods of the bidirectional switch is shown in period 2 and 3 of fig4 theoretically if the reverse conduction time is as long as the forward conduction time and the clamp voltage remains constant during these two conduction periods then all energy losses stated by the formula of the conventional rcd clamp can be completely recovered this is similar to an active clamp but the whole clamp action is completed over a much shorter period rather than over the whole turn off period as in the case of an active clamp as a result the peak clamp voltage of the improved rcd clamp is higher than of an active clamp this should not be viewed as a.