Page 89 - Rashid, Power Electronics Handbook

6

The Power MOSFET

Issa Batarseh 6.1 Introduction........................................................................................ 75
College of Engineering and 6.2 The Need for Switching in Power Electronic Circuits................................. 76
Computer Science
University of Central Florida 6.3 General Switching Characteristics............................................................ 78
Orlando, Florida 32816, USA 6.3.1 The Ideal Switch 6.3.2 The Practical Switch
batarseh@mail.ucf.edu 6.4 The Power MOSFET............................................................................. 80
6.5 MOSFET Structure............................................................................... 81
6.5.1 On-state Resistance 6.5.2 Internal Body Diode 6.5.3 Internal Capacitors
6.6 MOSFET Regions of Operation .............................................................. 83
6.6.1 MOSFET Switching Characteristics 6.6.2 Turn-on Characteristics 6.6.3 Turn-off
Characteristics 6.6.4 Safe-Operation Area
6.7 MOSFET PSpice Model......................................................................... 93
6.7.1 Static Model 6.7.2 Large Signal Model
6.8 Comparison of Switching Devices........................................................... 96
6.9 Future Trends in Power Devices.............................................................. 98
References ........................................................................................... 99

6.1 Introduction drive complexity, fragility, and cost, the power electronic
design engineer must be equipped with a thorough under-
This chapter gives an overview of power MOSFET semicon- standing of the device operation, limitation, drawbacks, and
ductor switching devices. Detailed discussion of the physical related reliability and ef®ciency issues.
structure, fabrication and physical behavior of the device and In the 1980s, the development of power semiconductor
packaging is beyond the scope of this chapter. The emphasis devices took an important turn when new process technology
here will be on the terminal i-v switching characteristics of the was developed that allowed integration of MOS and bipolar
available device, turn-on and turn-off switching characteris- junction transistor (BJT) technologies on the same chip. Thus
tics, PSpice modeling and its current voltage and switching far, two devices using this new technology have been intro-
limits. Even though, most of today's available semiconductor duced: insulated bipolar transition (IGBT) and MOS-
power devices are made of silicon or germanium materials, controlled thyristor (MCT). Many integrated circuit (IC)
other materials such as gallium arsenide, diamond and silicon processing methods as well as equipment have been adapted
carbide are currently being tested. for the development of power devices. However, unlike micro-
One of the main contributions that led to the growth of the electronic ICs, which process information, power device ICs
power electronics ®eld has been the unprecedented advance- process power and so their packaging and processing techni-
ment in semiconductor technology, especially with respect to ques are quite different. Power semiconductor devices repre-
switching speed and power handling capabilities. The area of sent the ‘‘heart'' of modern power electronics, with two major
power electronics started by the introduction of the silicon desirable characteristics of power semiconductor devices guid-
controlled recti®er (SCR) in 1958. Since then, the ®eld has ing their development:
grown in parallel with the growth of the power semiconductor
1. switching speed (turn-on and turn-off times); and
device technology. In fact, the history of power electronics is
2. power handling capabilities (voltage blocking and
very much connected to the development of switching devices
current carrying capabilities).
and it emerged as a separate discipline when high-power and
MOSFET devices were introduced in the 1960s and 1970s.
Improvements in both semiconductor processing technology
Since then, the introduction of new devices has been accom-
and manufacturing and packaging techniques have allowed
panied by dramatic improvement in power rating and switch- power semiconductor development for high-voltage and high
ing performance. Because of their functional importance,
current ratings and fast turn-on and turn-off characteristics.
75
Copyright # 2001 by Academic Press.
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