nff*41 Solid lllfll State APPLICATIONS H > ■O Power Transistors Power Transistor Applications This Manual is intended as a guide to the designers of power transistor circuits. It includes a brief introduction to solid-state physics and general information on electrical ratings, packaging and mounting techniques, and thermal factors for power transistor devices. Detailed discussions are provided on the theory of operation, basic design concepts, operating parameters, structures, geometries, and capabilities of power transistors. Specific design criteria and procedures are supplied for circuits that use power transistors in the amplification, rectification, conversion, control, and switching of electrical power. Design examples are given, and practical circuits are shown and analyzed. This Manual is a comprehensive, authoritative, up-to-date text on the design of power transistor circuits. It will be found extremely useful by circuit and systems designers, educators, students, hobbyists, and others. Solid State Somerville, NJ • Brussels • Paris • London Hamburg • Sao Paulo • Hong Kong Information furnished by RCA is believed to be accurate and reliable. However, no responsibility is assumed by RCA for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or other- wise under any patent or patent rights of RCA. Copyright 1983 by RCA Corporation (All rights reserved under Pan-American Copyright Convention) Printed in USA/ 10-83 Trademark(s)® Registered Marca(s) Registrada(s) Hi Contents Page Basic Design Considerations 3 Semiconductor Materials 3 Junctions , 5 Transistor Structures 6 Geometries 14 Special Processing Techniques 15 RCA SwitchMax Power Transistors 19 Packaging, Handling and Mounting 21 Hermetic Packages 21 Molded Plastic Packages 26 Special Handling Considerations 30 Ratings and Characteristics 31 Basis for Device Ratings 31 Voltage Ratings 32 Current, Temperature and Dissipation Ratings 33 Effect of External Heat Sinks 35 Second Breakdown 39 High-Voltage Surface Effects 40 Thermal-Cycling Ratings .41 Safe-Operating-Area Ratings 42 Basic Transistor Characteristics 43 Power Transistors in Switching Service 48 Linear Regulators for DC Power Supplies 53 Basic Power-Supply Elements 53 Series Regulators 59 Foldback-Limited Regulated Power Supply 67 Foldback-Limited Regulated Supply Using a Hybrid-Circuit Regulator 71 High-Output-Current Voltage Regulator with Foldback Current Limiting 73 Shunt Regulators 76 Switching-Regulator Power Supplies 77 Basic Regulator Operation 77 Design of a Practical Switching-Regulator Supply 78 Step-Down Switching Regulator 87 20-kHz Switching Regulator 87 Pulse- Width-Modulated Switching-Regulator Supply 93 Power Conversion 95 Basic Circuit Elements 95 Types of Inverters and Converters 95 Design of Practical Inverter Circuits 100 Design of Off-the-Line Inverter and Converter Circuits 105 230- Watt, 40-kHz Off-Line Forward Converter 107 340- Watt, 20-kHz, 15- Ampere Off-Line Flyback Converter 1 14 450- Watt, 40-kHz, 240 VAC-to-5 VDC Forward Converter 120 900- Watt, Off-Line Half-Bridge Converter 122 I* Contents (Cont'd) Page 1-Kilowatt, 20-kHz Off-Line Driven Converter 133 2-Kilowatt Stepped Sine-Wave Inverter 138 20-Ampere Sine- Wave Inverter 146 Overload Protection 150 Fuse Basics 1 50 External Protection 152 Internal Protection 152 Audio Power Amplifiers 156 Classes of Operation 1 56 Drive Requirements 157 Effect of Operating Conditions on Circuit Design 159 Basic Circuit Configurations 161 Power Output in Class B Audio Amplifiers • 171 Thermal-Stability Requirements I 74 Effect of Large Phase Shifts * I 75 Effect of Excessive Drive 176 Vbe Multiplier Bias Circuit I 78 Audio Amplifiers using All Discrete Devices 179 Audio Amplifiers with IC Preamplifiers and Discrete Output Stages 187 TV Deflection Systems 209 Scanning Fundamentals 209 Horizontal Deflection Circuits 217 Vertical Deflection Circuits 224 Ultrasonic Power Sources 234 Characteristics of Ultrasonic Transducers 234 Ultrasonic Generators 237 Ultrasonic Power Amplifiers 242 Automotive Applications 243 General Device Requirements • 243 Automotive Ignition Systems 246 High-Reliability Transistors 257 Specifications and Standards 257 JAN and J ANTX Power Transistors 257 Non-JAN Type Transistors • 258 Radiation-Hardened Power Transistors 262 Types of Radiation 262 Radiation-Hardening Techniques 262 Appendices A - Power Transistor Product Matrices 264 B - Terms and Symbols 270 Index 272 Power Transistor Applications Basic Design Considerations Solid-state devices are small but versatile units that can perform a great variety of control functions in electronic equipment. Like other electron devices, they have the ability to control almost instantly the move- ment of charges of electricity. They are used as rectifiers, detectors, amplifiers, oscillators, electronic switches, mixers, and modulators. In addition, solid-state devices have many important advantages over other types of electron devices. They are very small and light in weight. They have no filaments or heaters, and therefore require no heating power or warm-up time. They consume very little power. They are solid in construction, extremely rugged, free from microphonics, and can be made impervious to many severe environ- mental conditions. SEMICONDUCTOR MATERIALS Unlike some electron devices, which depend on the flow of electric charges through a vacuum or a gas, solid-state devices make use of the flow of current in a solid. In general, all materials may be classified into three major categories — conductors, semiconductors, and insulators — depending upon their ability to conduct an electric current. As the name indicates, a semiconductor material has poorer conductivity than a conductor, but better conductivity than an insulator. The material most often used in semicon- ductor devices is silicon. Germanium has higher electrical conductivity (less resistance to current flow) than silicon, and has been used in the past in many low- and medium- power diodes and transistors. Silicon is more suitable for higher power devices than ger- manium. One reason is that it can be used at much higher temperatures. In general, silicon is preferred over germanium because silicon processing techniques yield more economical devices. As a result, silicon has superseded germanium in almost every type of application, including the small-signal area. Resistivity The ability of a material to conduct current (conductivity) is directly proportional to the number of free (loosely held) electrons in the material. Good conductors, such as silver, copper, and aluminum, have large numbers of free electrons; their resistivities are of the order of a few millionths of an ohm-centimeter. Insulators such as glass, rubber, and mica, which have very few loosely held electrons, have resistivities as high as several million ohm-centimeters. Semiconductor materials lie in the range between these two extremes, as shown in Fig. 1 . Pure germanium has a resistivity of 60 ohm- INCREASING RESISTIVITY »• IO" 6 I0~ 3 I I0 3 I0 6 OHM-CM | — I — I | I — I — (-H — I— | — I — I — | COPPER GERMANIUM SILICON GLASS •« INCREASING CONDUCTIVITY 92CS-2I208 Fig. 1 - Resistivity of typical conductor, semiconductor, and insulator. centimeters. Pure silicon has a considerably higher resistivity, in the order of 60,000 ohm- centimeters. As used in solid-state devices, however, these materials contain carefully con- trolled amounts of certain impurities which reduce their resistivity from a low of less than one to greater than 50 ohm-centimeters at room temperature (this resistivity decreases rapidly as the temperature rises). 4 Power Transistor Applications Manual Impurities Carefully prepared semiconductor materials have a crystal structure. In this type of structure, which is called a lattice, the outer or valence electrons of individual atoms are tightly bound to the electrons of adjacent atoms in electron-pair bonds, as shown in Fig. 2. Because such a structure has no loosely held ELECTRON -PAIR BONDS SEMICONDUCTOR ATOMS ELECTRON -PAIR BONDS ATOMS -fy 9 fy <3p- 92CS-2I209 Fig. 2 - Crystal lattice structure. electrons, semiconductor materials are nor- mally poor conductors. One way to separate the electron-pair bonds and provide free electrons for electrical conduction would be to apply high temperature or strong electric fields to the material. Another way to alter the lattice structure and thereby obtain free electrons, however, is to add small amounts of other elements having a different atomic structure. By the addition of almost infinitesimal amounts of such other elements, called impurities, the basic electrical properties of pure semicon- ductor materials can be modified and con- trolled. The ratio of impurity to the semi- conductor material is usually extremely small, in the order of one part in ten million. When the impurity elements are added to the semiconductor material, impurity atoms take the place of semiconductor atoms in the lattice structure. When the impurity atom has one more valence electron than the semiconductor atom, this extra electron cannot form an electron- pair bond because no adjacent valence electron is available. The excess electron is t...
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