Chapter 5: Power Electronics: Devices and Circuits potx

Chapter 5

Power Electronics: Devices and

Circuits

5.1 Introduction

Power electronics is an enabling technology for all electrical and electronic apparatus

requiring electric power to drive. Over the past twenty years, the power electronics

industry has grown tremendously. Its growth is a result from increasing demand of re￾liable, efficient, compact and cost effective power supplies for telecommunication, com￾puter, and motor drive industries as well as for medical equipments and military use.

This growth is facilitated by the significant improvement in semiconductor technology

in which smaller packaging and higher power handling devices have been marketed. In

response to the advancement in semiconductor and magnetics technology, power elec￾tronics researchers and engineers have strived to thoroughly employ these technologies

through new circuit design and topologies, optimized control and packaging techniques,

in order to meet the industry demands.

Power electronics is all about using electronic devices and circuits with storage el￾ement to control the level of voltage and current, either in the form of AC or DC. Power

electronics circuits are switching converters with periodic switching actions to process

the electrical energy to meet the design specification. Apart from semiconductors, in￾ductor and transformer are the critical magnetic components in the power switching

converter. Their functions such as storage element, power splitting, and safety isolation

83

5. Power Electronics: Devices and Circuits 84

will be explained in detail in Chapter 6. In order to control power, some form of control

techniques are needed and will be discussed in Chapter 7.

This chapter we will begin with the semiconductor devices used for power con￾verters. We then analyze the basic DC/DC converters at the steady state. That is,

the output voltage and current are at stable condition. Finally, the operation of gate

driver, which drives the transistor, is presented.

5.2 Electrical Energy Conversion by Switching

The characteristics of power conversion by power electronics converters are summarized

as follows:

1. Electrical energy can be generated, transmitted and converted to a form that is

suitable for the load we are interested in.

2. Power Electronics concerns conversion and processing of electrical energy by

power semiconductor devices and storage elements.

3. Power Electronics technologies enable great efficiency enhancement, tremendous

size and weight reduction of electrical equipment.

4. Power Electronics technologies are based on switching on and off the power source

by power semiconductors. The electrical energy conversion process can be pre￾cisely controlled in a manner far much better than electromechanical devices.

5. Power Electronics applications include power supplies for computers, communi￾cation equipment, machine drives, lighting, automobile and many applications.

6. Electrical energy conversion can be classified into the following four categories :

AC to AC, AC to DC, DC to DC, and DC to AC.