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Fine common circuits are presented here for both continuous and discontinuous conduction. The dc to dc step down is a rather simple application of the technique. The rest of the circuits present a challenge because an impedance, an inductor, is inserted between the voltage source and the semiconductor switches. In this case the voltage equations for the loops are derived by considering the various modes of the circuit in order to derive the switching functions and the derived expressions.

9.1 Introduction

Figure 9.1 shows a simple circuit of the step down converter. The chopped voltage of a dc source is applied to a series inductor L and a parallel combination of a smoothing capacitor C and a resistor R. The resistor represents the power-consuming element of the load. The inductor has inductance L and ohmic resistance r. The switch is a MOSFET or an IGBT transistor. A control circuit, not shown in the diagram, generates the gate pulses to switch on and off the transistor. The switch opens and closes at a fixed frequency. The duty-cycle of the switch determines the level of the output voltage.

Figure 9.1: The step down converter

It is possible for this circuit to enter...