is used the diode exhibits a recovered charge area accordingly current i dl annuls at a time t 11 intermediary between times t 10 and t 12 time t 11 corresponds to the time when the current in switch k reaches value i 0 between times t 10 and t 12 diodes d 1 and d 2 remain blocked voltage v l across inductance l becomes approximately equal to voltage v s at time t 12 the current through diode dl reaches value i rm corresponding to the maximum recovered charges from time t 12 the charges recovered by diode dl decrease diode dl then behaves as a capacitor the equivalent diagram of this operating phase c is shown in fig7 c where diode dl has been symbolized in the form of a capacitor the rest of the elements are the same as in fig7 b since the number of spirals of inductance l 1 is small as compared to the number of spirals of inductance l 0 voltage v l1 thereacross is small as a result the capacitance formed by diode dl charges negatively this phenomenon is illustrated in fig6 b by a pursuit of the decrease of current i dl until a time t 13 in the form of a capacitor charge the current decreases to a current i r conditioned by inductance l 2 indeed voltage v l which decreases during this phase c becomes negative until diode d 2 is turned on when voltage v l becomes sufficiently negative time t 13 as for diode dl voltage v dl reaches at time t 13 value u2212 v s v l1 v l2 v d2 voltage v l reaches at time t 13 value u2212.