The circuit configuration during the off period is shown in Fig. 4.19(b). When the chopper is turned off , the decay of current in the inductor L2 causes a voltage L to occur across it. This adds to the source voltage V to forward-bias the diode switch S1 and turn it ON, Current flows into the high voltage side, thereby transferring power to the latter from the low voltage side. During this time, the current decays to a valleymagnitude, which we shall denote by L2, Depending on the circuit parameters and the duty cycle,