Power

1
Introduction

1.1

INTRODUCTION TO POWER PROCESSING

The field of power electronics is concerned with the processing of electrical power using electronic devices [1–7]. The key element is the switching converter, illustrated in Fig. 1.1. In general, a switching converter contains power input and control input ports, and a power output port. The raw input power is processed as specified by the control input, yielding the conditioned output power. One of several basic functions can be performed [2]. In a dc–dc converter, the dc input voltage is converted to a dc output voltage having a larger or smaller magnitude, possibly with opposite polarity or with isolation of the input and output ground references. In an ac–dc rectifier, an ac input voltage is rectified, producing a dc output voltage. The dc output voltage and/or ac input current waveform may be controlled. The inverse process, dc–ac inversion, involves transforming a dc input voltage into an ac output voltage of controllable magnitude and frequency. Ac–ac cycloconversion involves converting an ac input voltage to a given ac output voltage of controllable magnitude and frequency. Control is invariably required. It is nearly always desired to produce a well-regulated output

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Introduction

voltage, in the presence of variations in the input voltage and load current. As illustrated in Fig. 1.2, a controller block is an integral part of any power processing system. High efficiency is essential in any power processing application. The primary reason for this is usually not the desire to save money on one’s electric bills, nor to conserve energy, in spite of the nobility of such pursuits. Rather, high efficiency converters are necessary because construction of low-efficiency converters, producing substantial output power, is impractical. The efficiency of a converter having output power and input power is

The power lost in the converter is

Equation (1.2) is plotted in Fig. 1.3. In a...