9781119594147

An up-to-date, practical guide on upgrading from silicon to GaN, and how to use GaN transistors in power conversion systems design

This updated, third edition of a popular book on GaN transistors for efficient power conversion has been substantially expanded to keep students and practicing power conversion engineers ahead of the learning curve in GaN technology advancements. Acknowledging that GaN transistors are not one-to-one replacements for the current MOSFET technology, this book serves as a practical guide for understanding basic GaN transistor construction, characteristics, and applications. Included are discussions on the fundamental physics of these power semiconductors, layout, and other circuit design considerations, as well as specific application examples demonstrating design techniques when employing GaN devices.

GaN Transistors for Efficient Power Conversion, 3rd Edition brings key updates to the chapters of Driving GaN Transistors; Modeling, Simulation, and Measurement of GaN Transistors; DC-DC Power Conversion; Envelope Tracking; and Highly Resonant Wireless Energy Transfer. It also offers new chapters on Thermal Management, Multilevel Converters, and Lidar, and revises many others throughout.

Written by leaders in the power semiconductor field and industry pioneers in GaN power transistor technology and applications
Updated with 35% new material, including three new chapters on Thermal Management, Multilevel Converters, Wireless Power, and Lidar
Features practical guidance on formulating specific circuit designs when constructing power conversion systems using GaN transistors
A valuable resource for professional engineers, systems designers, and electrical engineering students who need to fully understand the state-of-the-art

GaN Transistors for Efficient Power Conversion, 3rd Edition is an essential learning tool and reference guide that enables power conversion engineers to design energy-efficient, smaller, and more cost-effective products using GaN transistors.

Alex Lidow, Ph.D., is CEO of Efficient Power Conversion Corporation (EPC), USA.

Michael de Rooij, Ph.D., is Vice President of Applications Engineering at EPC Corporation, USA.

Johan Strydom, Ph.D., is Advanced Development Manager, Kilby Labs, Texas Instruments, USA.

David Reusch, Ph.D., is Principal Scientist, VPT, Inc., USA.

John Glaser is Director, Applications Engineering, EPC Corporation, USA.

Foreword xv

Acknowledgments xvii

1 GaN Technology Overview 1

1.1 Silicon Power Metal Oxide Silicon Field Effect Transistors 1976–2010 1

1.2 The Gallium Nitride Journey Begins 2

1.3 GaN and SiC Compared with Silicon 2

1.3.1 Bandgap (E_g) 3

1.3.2 Critical Field (E_crit) 3

1.3.3 On‐Resistance (R_DS(on)) 4

1.3.4 The Two‐Dimensional Electron Gas (2DEG) 4

1.4 The Basic GaN Transistor Structure 6

1.4.1 Recessed Gate Enhancement‐Mode Structure 7

1.4.2 Implanted Gate Enhancement‐Mode Structure 8

1.4.3 pGaN Gate Enhancement‐Mode Structure 8

1.4.4 Hybrid Normally Off Structures 8

1.4.5 Reverse Conduction in HEMT Transistors 10

1.5 Building a GaN Transistor 11

1.5.1 Substrate Material Selection 11

1.5.2 Growing the Heteroepitaxy 12

1.5.3 Processing the Wafer 12

1.5.4 Making Electrical Connection to the Outside World 13

1.6 GaN Integrated Circuits 15

1.7 Summary 21

References 21

2 GaN Transistor Electrical Characteristics 25

2.1 Introduction 25

2.2 Device Ratings 25

2.2.1 Drain‐Source Voltage 25

2.3 On‐Resistance (R_DS(on)) 30

2.4 Threshold Voltage 33

2.5 Capacitance and Charge 34

2.6 Reverse Conduction 37

2.7 Summary 39

References 40

3 Driving GaN Transistors 41

3.1 Introduction 41

3.2 Gate Drive Voltage 44

3.3 Gate Drive Resistance 45

3.4 Capacitive Current‐Mode Gate Drive Circuits for Gate Injection Transistors 46

3.5 dv/dt Considerations 48

3.5.1 Controlling dv/dt at Turn‐On 48

3.5.2 Complementary Device Turn‐On 49

3.6 di/dt Considerations 51

3.6.1 Device Turn‐On and Common‐Source Inductance 51

3.6.2 Off‐State Device di/dt 53

3.7 Bootstrapping and Floating Supplies 54

3.8 Transient Immunity 57

3.9 High‐Frequency Considerations 59

3.10 Gate Drivers for Enhancement‐Mode GaN Transistors 60

3.11 Cascode, Direct‐Drive, and Higher‐Voltage Configurations 60

3.11.1 Cascode Devices 60

3.11.2 Direct‐Drive Devices 63

3.11.3 Higher‐Voltage Configurations 64

3.12 Summary 64

References 65

4 Layout Considerations for GaN Transistor Circuits 69

4.1 Introduction 69

4.2 Minimizing Parasitic Inductance 69

4.3 Conventional Power‐Loop Designs 72

4.3.1 Lateral Power‐Loop Design 72

4.3.2 Vertical Power‐Loop Design 73

4.4 Optimizing the Power Loop 74

4.4.1 Impact of Integration on Parasitics 75

4.5 Paralleling GaN Transistors 76

4.5.1 Paralleling GaN Transistors for a Single Switch 76

4.5.2 Paralleling GaN Transistors for Half‐Bridge Applications 79

4.6 Summary 83

References 83

5 Modeling and Measurement of GaN Transistors 85

5.1 Introduction 85

5.2 Electrical Modeling 85

5.2.1 Basic Modeling 85

5.2.2 Limitations of Basic Modeling 88

5.2.3 Limitations of Circuit Simulation 90

5.3 Measuring GaN Transistor Performance 91

5.3.1 Voltage Measurement Requirements 94

5.3.2 Probing and Measurement Techniques 96

5.3.3 Measuring Non‐Ground‐Referenced Signals 99

5.3.4 Current Measurement Requirement 100

5.4 Summary 101

References 102

6 Thermal Management 105

6.1 Introduction 105

6.2 Thermal Equivalent Circuits 105

6.2.1 Thermal Resistances in a Lead Frame Package 105

6.2.2 Thermal Resistances in a Chip‐Scale Package 107

6.2.3 Junction‐to‐Ambient Thermal Resistance 108

6.2.4 Transient Thermal Impedance 109

6.3 Improving Thermal Performance with a Heatsink 110

6.3.1 Selection of Heatsink and Thermal Interface Material (TIM) 111

6.3.2 Heatsink Attachment for Bottom‐Side Cooling 112

6.3.3 Heatsink Attachment for Multisided Cooling 113

6.4 System‐Level Thermal Analysis 114

6.4.1 Thermal Model of a Power Stage with Discrete GaN Transistors 115

6.4.2 Thermal Model of a Power Stage with a Monolithic GaN Integrated Circuit 117

6.4.3 Thermal Model of a Multiphase System 118

6.4.4 Temperature Measurement 120

6.4.4.1 Optical 120

6.4.4.2 Physical Contact 121

6.4.4.3 Temperature‐Sensitive Electrical Parameter 122

6.4.5 Experimental Characterization 122

6.4.6 Application Examples 124

6.5 Summary 128

References 128

7 Hard‐Switching Topologies 131

7.1 Introduction 131

7.2 Hard‐Switching Loss Analysis 131

7.2.1 Hard‐Switching Transitions with GaN Transistors 132

7.2.2 Output Capacitance (C_OSS) Losses 135

7.2.3 Turn‐On Overlap Loss 138

7.2.3.1 Current Rise Time 139

7.2.3.2 Voltage Fall Time 142

7.2.4 Turn‐Off Overlap Losses 145

7.2.4.1 Current Fall Time 146

7.2.4.2 Voltage Rise Time 147

7.2.5 Gate‐Charge (Q_G) Losses 147

7.2.6 Reverse Conduction Losses (P_SD) 147

7.2.6.1 Impact of Dead Time Selection on Reverse Conduction Loss 147

7.2.6.2 Adding an Anti‐Parallel Schottky Diode 150

7.2.6.3 Dynamic C_OSS‐Related Reverse Conduction Losses 153

7.2.7 Reverse Recovery (Q_RR) Losses 153

7.2.8 Hard‐Switching Figure of Merit 154

7.3 Impact of Parasitic Inductance on Hard‐Switching Losses 154

7.3.1 Impact of Common‐Source Inductance (L_CS) 154

7.3.2 Impact of Power‐Loop Inductance on Device Losses 157

7.4 Frequency Impact on Magnetics 160

7.4.1 Transformers 160

7.4.2 Inductors 161

7.5 Buck Converter Example 162

7.5.1 Comparison with Experimental Measurements 169

7.5.2 Consideration of Parasitic Inductance 170

7.6 Summary 174

References 174

8 Resonant and Soft‐Switching Converters 177

8.1 Introduction 177

8.2 Resonant and Soft‐Switching Techniques 177

8.2.1 Zero‐Voltage and Zero‐Current Switching 177

8.2.2 Resonant DC–DC Converters 179

8.2.3 Resonant Network Combinations 179

8.2.4 Resonant Network Operating Principles 180

8.2.5 Resonant Switching Cells 181

8.2.6 Soft‐Switching DC–DC Converters 182

8.3 Key Device Parameters for Resonant and Soft‐Switching Applications 182

8.3.1 Output Charge (Q_OSS) 182

8.3.2 Determining Output Charge from Manufacturers’ Datasheets 183

8.3.3 Comparing Output Charge of GaN Transistors and Si MOSFETs 184

8.3.4 Gate Charge (Q_G) 185

8.3.5 Determining Gate Charge for Resonant and Soft‐Switching Applications 186

8.3.6 Comparing Gate Charge of GaN Transistors and Si MOSFETs 187

8.3.7 Comparing Performance Metrics of GaN Transistors and Si MOSFETs 187

8.4 High‐Frequency Resonant Bus Converter Example 188

8.4.1 Resonant GaN and Si Bus Converter Designs 191

8.4.2 GaN and Si Device Comparison 191

8.4.3 Zero‐Voltage Switching Transition 193

8.4.4 Efficiency and Power Loss Comparison 195

8.4.5 Impact of Further Device Improvements on Performance 197

8.5 Summary 199

References 199

9 RF Performance 201

9.1 Introduction 201

9.2 Differences Between RF and Switching Transistors 202

9.3 RF Basics 204

9.4 RF Transistor Metrics 205

9.4.1 Determining the High‐Frequency Characteristics of RF Transistors 206

9.4.2 Pulse Testing for Thermal Considerations 207

9.4.3 Analyzing the s‐Parameters 209

9.4.3.1 Test for Stability 209

9.4.3.2 Transistor Input and Output Reflection 210

9.4.3.3 Transducer Gain 211

9.4.3.4 Unilateral/Bilateral Transistor Test 211

9.5 Amplifier Design Using Small‐Signal s‐Parameters 212

9.5.1 Conditionally Stable Bilateral Transistor Amplifier Design 213

9.5.1.1 Available Gain 213

9.5.1.2 Constant Available Gain Circles 213

9.6 Amplifier Design Example 214

9.6.1 Matching and Bias Tee Network Design 216

9.6.2 Experimental Verification 219

9.7 Summary 221

References 221

10 DC–DC Power Conversion 223

10.1 Introduction 223

10.2 Non‐Isolated DC–DC Converters 223

10.2.1 The 12 V_IN–1.2 V_OUT Buck Converter with Discrete Devices 224

10.2.2 The 12 V_IN–1 V_OUTMonolithic Half‐Bridge IC‐Based Point‐of‐Load Module 228

10.2.3 Very‐High‐Frequency 12 V_IN Monolithic Half‐Bridge IC‐Based Point‐of‐Load Module 230

10.2.4 The 28 V_IN–3.3 V_OUT Point‐of‐Load Module 233

10.2.5 The 48 V_IN–12 V_OUT Buck Converter with Parallel GaN Transistors for High‐Current Applications 233

10.3 Transformer‐Based DC–DC Converters 239

10.3.1 Eighth‐Brick Converter Example 239

10.3.2 High‐Performance 48 V Step‐Down LLC DC Transformer 243

10.3.2.1 Circuit Overview 243

10.3.2.2 GaN Transistor Advantage in the LLC Converter 244

10.3.2.3 A 1 MHz, 900 W, 48 V–12 V LLC Example Using GaN Transistors 245

10.3.2.4 A 1 MHz, 900 W, 48 V–6 V LLC Example Using GaN Transistors 248

10.4 Summary 249

References 250

11 Multilevel Converters 251

11.1 Introduction 251

11.2 Benefits of Multilevel Converters 251

11.2.1 Applying Multilevel Converters to 48 V Applications 252

11.2.2 Multilevel Converters for High‐Voltage (400 V) Applications 254

11.3 Gate Driver Implementation 255

11.4 Bootstrap Power Supply Solutions for GaN Transistors 256

11.5 Multilevel Converters for PFC Applications 261

11.6 Experimental Examples 263

11.6.1 Low Voltage 263

11.6.2 High Voltage 264

11.7 Summary 264

References 265

12 Class D Audio Amplifiers 269

12.1 Introduction 269

12.1.1 Total Harmonic Distortion 271

12.1.2 Intermodulation Distortion 272

12.2 GaN Transistor Class D Audio Amplifier Example 273

12.2.1 Closed‐Loop Amplifier 274

12.2.2 Open‐Loop Amplifier 276

12.3 Summary 278

References 278

13 Lidar 281

13.1 Introduction to Light Detection and Ranging (Lidar) 281

13.2 Pulsed Laser Driver Overview 281

13.2.1 Pulse Requirements 282

13.2.2 Semiconductor Optical Sources 284

13.2.3 Basic Driver Circuits 285

13.2.4 Driver Switch Properties 286

13.3 Basic Design Process 288

13.3.1 Resonant Capacitive Discharge Laser Driver Design 288

13.3.2 Quantitative Effect of Stray Inductance 289

13.4 Hardware Driver Design 290

13.5 Experimental Results 291

13.5.1 High‐Speed Laser Driver Design Example 291

13.5.2 Fastest 292

13.5.3 Highest Current 293

13.5.4 Low Voltage 293

13.6 Other Considerations 294

13.6.1 Resonant Capacitors 294

13.6.2 Charging 295

13.6.3 Voltage Probing 295

13.6.4 Current Sensing 296

13.6.5 Dual‐Edge Control 297

13.7 Summary 299

References 299

14 Envelope Tracking 301

14.1 Introduction 301

14.2 High‐Frequency GaN Transistors 302

14.3 Topologies for Envelope Tracking Supplies 304

14.3.1 Multiphase Converter 305

14.3.2 Multilevel Converter 306

14.4 Gate Driver Design 307

14.5 Design Example: Tracking a 20 MHz LTE Envelope Signal 308

14.6 Summary 311

References 311

15 Highly Resonant Wireless Power 315

15.1 Introduction 315

15.2 Overview of a Wireless Power System 316

15.3 Amplifiers for Wireless Power Systems 320

15.3.1 The Class E Amplifier 320

15.3.2 ZVS Class D Amplifier 321

15.4 Transistors Suitable for Wireless Power Amplifiers 322

15.4.1 Figure of Merit for Wireless Power Amplifier Topologies 322

15.4.2 GaN Transistors Evaluation in Wireless Power Applications 323

15.5 Experimental Validation of GaN Transistor‐Based Wireless Power Amplifiers 325

15.5.1 Differential‐Mode Class E Amplifier Example 325

15.5.2 Differential‐Mode ZVS Class D Amplifier Example 330

15.6 Summary 334

References 334

16 GaN Transistors for Space Applications 337

16.1 Introduction 337

16.2 Failure Mechanisms 337

16.3 Standards for Radiation Exposure and Tolerance 338

16.4 Gamma Radiation Tolerance 338

16.5 SEE Testing 340

16.6 Neutron Radiation (Displacement Damage) 341

16.7 Performance Comparison Between GaN Transistors and Rad‐Hard Si MOSFETs 343

16.8 Summary 344

References 345

17 Replacing Silicon Power MOSFETs 347

17.1 Introduction: What Controls the Rate of Adoption? 347

17.2 New Capabilities Enabled by GaN Transistors 347

17.3 GaN Transistors are Easy to Use 349

17.4 Cost Versus Time 350

17.4.1 Starting Material 351

17.4.2 Epitaxial Growth 351

17.4.3 Wafer Fabrication 351

17.4.4 Test and Assembly 352

17.5 GaN Transistors are Reliable 352

17.6 Future Direction of GaN Transistors 352

17.7 Summary 353

References 354

Appendix 355

Index 361

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Gan Transistors for Efficient Power Conversion

Gan Transistors for Efficient Power Conversion

1119594146

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