This book adopts a top-down approach so that readers can start with a glimpse of system-level applications and then proceed to the integrated circuit (IC) chips level and finally down to the semiconductor devices (elements) level. This chapter is a brief introduction of power electronics and power management systems for power device engineers. Power electronics engineers who are specifically focused on power device physics can safely skip this chapter.
1.1 Introduction to Power Electronics
Since the discovery of electricity, electronic appliances are found almost everywhere (now even on Mars). Power delivery is one of the most important and often neglected requirements within electronic equipment. Direct utilization of the alternating current (AC) line voltage or available battery power without any power conversion is rare. Most of the time electric energy required for electronic systems is provided by either internal or external power supplies.
Enviromental protection advocates are now promoting green awareness; thus, power efficient technologies are under consideration as an important design criteria for future applications. Various forms of clean energy such as solar and wind energy need to be converted and stored for use. Efficient energy conversion is the key to cost reduction and better utilization of these natural resources.
Power electronics that use solid-state devices to control and convert electric power are considered as the enabling technology for a greener future. The United States Department of Energy has estimated that approximately 40% of all the energy consumed is first converted into electricity. In the transporation sector the growing use of electric and plug-in hybrid cars and high-speed rail transportation may increase this to even 60% [1].
Figure 1.1 shows how power electronics systems are applied to an electric vehicle. In terms of voltage conversion, power electronic converters can be divided into four types: alternating current/direct current (AC/DC) rectifier; AC/AC converter; DC/DC converter; and DC/AC inverter. Figure 1.2 illustrates these four types of converters. A comprehensive treatment of power electronics is out of the scope of this book, so we focus on DC/DC converters.
A complete power electronics system contains three parts (Figure 1.3). The power converter topology governs how the power elements should be connected and controlled. The topology can be regarded as the “backbone” of the power electronic system. Controllers, which automatically monitor and control the power switches according to input and output conditions, are the “brains” of the system. Power elements such as power devices, transformers, inductors, and capacitors are the basic building blocks for a power supply. They can be viewed as the “muscles” of the power electronic system.
Unfortunately, the best power devices will not necessarily dominate the global marketplace. Successful implementation and adoption of power devices and their controllers within power electronic designs can be subjected to many factors such as economics, market conditions, intellectual property rights, and industry supply relationships. Additional technical factors such as PCB layout, magnetic design, and optimal filtering components all play a vital role.
Figure 1.4 is a black-box illustration of the power electronics systems. Power input is converted to power output by the power converter main circuitry. The controller senses signals from both the input/primary side and output/secondary side and compares it with the reference signal. A control signal is fed into the main power transistors. This structure is for the analog (A) control method. A digital (D) control method needs A/D and D/A converters with a microprocessor or DSP.
Figure 1.1 Electrical power system found in a plug-in hybrid electric vehicle. (Photo courtesy of Argonne National Laboratory [2].).
Figure 1.2 The four different types of power conversions.
Figure 1.3 Power electroni...
