Battery Power Management for Portable Devices Yevgen Barsukov Jinrong Qian ARTECH HOUSE BOSTON LONDON artechhouse.com
Contents Preface xi Acknowledgments xiii Foreword xv 1 Battery Chemistry Fundamentals and Characteristics 1 1.1 Introduction 1 1.2 Battery Fundamentals and Electrical Behavior Under DC and Transient Conditions 2 1.3 General Battery Characteristics 8 1.3.1 Chemical Capacity and Energy 8 1.3.2 Battery Impedance 9 1.3.3 Usable Capacity 12 1.3.4 Power Capability and the Ragone Plot 14 1.3.5 Durability, Cycle Life, and Shelf-Life 15 1.3.6 Self-Discharge Properties 17 1.4 Monitoring and Safety 19 1.5 Overview of Different Battery Technologies 22 1.5.1 Lead Acid 22 1.5.2 Nickel Cadmium 27 1.5.3 Nickel Metal-Hydride 31 1.5.4 Lithium Ion Battery 34 v
vi Battery Power Management for Portable Devices 1.5.5 Battery Chemistries Overview 43 References 43 2 Battery Charger Techniques 45 2.1 Lead-Acid Battery Charger 45 2.2 NiCd and NiMH Battery Charger 47 2.2.1 Nickel-Based Battery Charge Characteristics and Charge Profile 47 2.2.2 NiMH Battery Charger Design Example 49 2.3 Li-Ion and Li-Polymer Battery Charger 50 2.3.1 Li-Ion and Li-Polymer Charge Characteristics and Principle 50 2.3.2 Charge Temperature Qualification and JEITA Guideline 53 2.3.3 Linear Battery Charger 55 2.3.4 Switch-Mode Battery Charger 58 2.3.5 Switch-Mode Battery Charger Design Example 61 2.3.6 USB Battery Charging 63 2.3.7 Port Detecting and Self-Enumerating Charger 65 2.4 Battery Charger and System Interactions 65 2.5 Dynamic Power Management Battery Charger 67 2.5.1 System Bus Voltage-Based Dynamic Power Path Management (DPPM) Charger 67 2.5.2 Input Current-Based Dynamic Power Management (DPM) Linear Charger 70 2.5.3 Switch-Mode DPM Battery Charger with Power Source Selector 73 2.5.4 Narrow Voltage Direct Current (NVDC) DPM Battery Charger 76 2.5.5 Battery Charging System Topology Comparisons 78 2.6 Battery Charger Design Examples in End Equipment 78 2.6.1 Tablet Charger Design Example 78 2.6.2 Notebook and Ultrabook Battery Charger Design Example 80 2.7 LiFeP04 Battery Charger 85 2.8 Wireless Charging Technology 87
Contents vii 2.9 Solar Charging System 88 References 91 3 Battery Safety and Protections 93 3.1 Introduction 93 3.2 Safety Events Triggered External to the Battery Pack 97 3.2.1 Overvoltage Applied to a Battery Pack 97 3.2.2 Overdischarge 98 3.2.3 Overcurrent During Discharge 99 3.2.4 Overcurrent During Charge 101 3.3 Safety Events Triggered Inside the Battery Pack 102 3.3.1 Pack Internal Short Circuit 103 3.3.2 Cell Overvoltage 104 3.3.3 Cell Internal Short Circuit 106 3.4 Final Thoughts 109 References 110 4 Cell-Balancing Techniques: Theory and Implementation 111 4.1 Introduction 111 4.2 Types of Battery Cell Imbalance That Affect the Charge/Discharge Voltage 112 4.2.1 State-of-Charge (SOC) Imbalance 112 4.2.2 Total Capacity Differences 115 4.2.3 Impedance Differences 118 4.3 Effect of Imbalancing on Performance 122 4.3.1 Premature Cell Degradation Through Exposure to Overvoltage 122 4.3.2 Safety Hazards Resulting from Overcharged Cells 123 4.3.3 Early Charge Termination Resulting in Reduced Capacity 123 4.3.4 Early Discharge Termination 124 4.4 Hardware Implementation of Balancing 125 4.4.1 Current Bypass 125 4.4.2 Charge Redistribution 127
Battery Power Management for Portable Devices 4.4.3 Charge Shuttles 128 4.4.4 Inductive Converter-Based Cell Balancing 129 4.5 Balancing Algorithms 133 4.5.1 Cell Voltage Based 134 4.5.2 SOC Based 135 4.5.3 SOC and Total Capacity Based 137 4.6 Summary 137 5 Battery Fuel Gauging: State of Charge, Remaining Capacity, and State of Health Indication 139 5.1 Introduction 139 5.2 State ofcharge and Accuracy Definitions 143 5.3 Basic Battery Remaining Capacity Monitoring Methods 147 5.3.1 Voltage Correlation 147 5.3.2 Voltage Correlation with IR Correction 148 5.3.3 Hardware Implementation of Voltage Correlation 150 5.3.4 Coulomb Counting: Current Integration Method 151 5.3.5 Coulomb Counting with Voltage-Based Early Learning 155 5.3.6 Hardware Implementation of Coulomb Counting Gauging 157 5.4 Advanced Gauging Methods: Impedance Track 158 5.4.1 Basic Concept 158 5.4.2 Voltage Correlation in IT 159 5.4.3 Full Chemical Capacity (C^J Update in IT 160 5.4.4 Battery Impedance Update in IT 162 5.4.5 Thermal Modeling to Account for Temperature Effects on Usable Capacity 164 5.4.6 Load Modeling 166 5.4.7 Bringing It All Together: Predicting Usable Capacity and Energy for Present Conditions 167 5.4.8 State of Health 169 5.4.9 Hardware Implementation of IT Algorithm 171 5.5 Host-Side and Pack-Side Gauging 171 5.6 Summary 173
Contents ix 6 System Considerations 175 6.1 Introduction 175 6.2 Battery Pack Electronics: General Considerations 175 6.3 Battery Pack ESD Design Considerations 177 6.3.1 ESD Fundamentals 177 6.3.2 Where Does the Current Flow During ESD Hits? 178 6.3.3 ESD Design Hardening 181 6.3-4 Pack Insertion Issues 184 6.4 Electromagnetic Interference (EMI) Solutions 185 6.4.1 EMI Solutions in the Battery Management Unit 185 6.4.2 EMI Design Considerations in Battery Charging System Applications 187 6.4.3 Measuring the EMI 188 6.4.4 Conducted EMI 190 6.4.5 Approach for Minimizing Conducted Differential Noise 192 6.4.6 Approach for Minimizing Common Mode EMI Noise 193 6.4.7 Minimizing the Radiated EMI 197 6.5 Power Components and PCB Thermal Design Considerations 199 6.6 Assuring That an Intended Battery Is Used with the Device: Authentication 201 References 206 7 Design Examples: Complete Battery Solutions for Specific Portable Systems 207 7.1 Introduction 207 7.2 Cell Phones and Smartphones 208 7.2.1 Battery Selection 208 7.2.2 Battery Pack Electronics 211 7.2.3 Battery Charging 215 7.3 Tablet Computers 215 7.3.1 Battery Pack Electronics 217 7.3.2 Battery Charging 218
X Battery Power Management for Portable Devices 7.4 Notebook PCs 218 7.4.1 Battery Selection 218 7.4.2 Battery Pack Electronics 220 7.4.3 Battery Charging 222 7.5 Ultrabooks 222 7.5.1 Battery Selection 222 7.5.2 Battery Pack Electronics 224 7.5.3 Charging and Power Architecture 224 7.5.4 Ultrabook Battery Charger Design Example 227 7.6 Digital Cameras 229 7.6.1 Battery Pack Electronics 231 7.6.2 Battery Charging 232 7.7 Industrial and Medical Handheld Devices 232 7.7.1 Battery Selection 232 7.7.2 Battery Pack Electronics 233 7.7.3 Battery Charging 235 7.8 Conclusion 235 About the Authors 237 Index 23?