Figures xiii
Preface xvii
1 Practical Introduction to LEDs 1
What Is an LED? 1
Small LEDs versus Power Devices 2
Phosphors versus RGB 3
Inside an LED 4
Is an LED Right for My Application? 6
Haitz’s Law(s) 8
The Wild West 10
LEDs and OLEDs and ... ? 11
2 Light Bulbs and Lighting Systems 13
Light Sources 13
Incandescent 13
Halogen 14
Fluorescent 14
Induction Lighting 15
High Intensity Discharge (HID) Lamps 15
Characteristics of Light Sources 16
Light Quality 16
Effi cacy 17
Timing 17
Dimming 18
Aging 19
Types of Bulbs 19
Bulb Shapes 19
Bulb Bases 21
Specialty Bulbs 21
History of Lighting 22
Governments 23
Lighting Systems 23
3 Practical Introduction to Light 27
The Power of Light 27
Background: Light as Radiation 27
Radiometric versus Photometric 28
Luminous Intensity, Illuminance, and Luminance (or Candela, Lux,
and Nits) 32
Luminous Intensity 32
Illuminance 34
Luminance 36
Summary of Amount of Light 37
What Color White? 37
MacAdam Ellipses 39
A Note about Color Space Standards 41
Color Rendition: How the Light Looks versus How Objects Look 41
The Human Factor 43
4 Practical Characteristics of LEDs 47
Current, Not Voltage 47
Forward Voltage 48
Reverse Breakdown 49
Not Effi ciency—Effi cacy! 51
LED Optical Spectra 54
Overdriving LEDs 57
Key Datasheet Parameters 58
Binning 58
The Tolerance Game 60
5 Practical Thermal Performance of LEDs 61
Mechanisms Behind Thermal Shifts 61
Electrical Behavior of LEDs With Temperature 62
Optical Behavior of LEDs With Temperature 63
Other Performance Shifts With Temperature 64
LED Lifetime: Lumen Degradation 66
LED Lifetime: Catastrophic Failure 67
Paralleling LEDs 67
6 Practical Thermal Management of LEDs 71
Introduction to Thermal Analysis 71
Calculation of Thermal Resistance 72
The Ambient 74
Practical Estimation of Temperature 75
Heat Sinks 76
Fans 78
Radiation Enhancement 79
Removing Heat from the Drive Circuitry 79
7 Practical DC Drive Circuitry for LEDs 81
Basic Ideas 81
Battery Basics 82
Overview of SMPS 85
Buck 86
Boost 88
Buck-Boost 89
Input Voltage Limit 91
Dimming 92
Ballast Lifetime 94
Arrays 95
8 Practical AC Drive Circuitry for LEDs 99
Safety 99
Which AC? 101
Rectifi cation 103
Topology Selection 106
Nonisolated Circuitry 109
Isolation 110
Component Selection 112
EMI 114
Power Factor Correction 117
Lightning 119
Dimmers 120
Ripple Current Effects on LEDs 122
Lifetime 125
UL, Energy Star, and All That 126
9 Practical System Design With LEDs 131
PCB Design 131
Getting the Light Out 136
LEDs in Harsh Environments 139
Designing With the Next Generation LED in Mind 141
Lighting Control 142
DALI Protocol 142
DMX512 Protocol 143
802.15.4 and ZigBee Open-Standard Technology 143
Powerline Communication 144
10 Practical Examples 145
Example: Designing an LED Flashlight 145
Initial Marketing Input 145
Initial Analysis 146
Specifi cation 148
Power Conversion 150
Thermal Model 153
PCBs 155
Final Design 156
Example: Designing a USB Light 157
Initial Marketing Input 157
Initial Analysis 157
Specifi cation 158
Power Conversion 159
Thermal Model 161
PCB 163
Final Design 163
Example: Designing an Automobile Taillight 165
Initial Marketing Input 165
Initial Analysis 165
Specifi cation 167
Power Conversion 167
Thermal Model 172
PCB 172
Final Design 174
Example: Designing an LED Light Bulb 175
Initial Marketing Input 175
Initial Analysis 175
Specifi cation 178
Power Conversion 181
PCBs 184
11 Practical Measurement of LEDs and Lighting 187
Measuring Light Output 187
Lux Meter 187
Integrating Sphere 189
Goniophotometer 192
Special Considerations in Measuring Light Output of LEDs 192
LED Measurement Standards 192
Luminaire Light Output (LM-79) 192
LED Lifetime (LM-80) 193
ASSIST 193
Measuring LED Temperature 194
Measuring Thermal Resistance 195
Measuring Power, Power Factor, and Effi ciency 197
Accuracy versus Precision 197
Measuring DC Power 197
Measuring AC Power 200
Measuring Power Factor 201
Measuring Ballast Effi ciency 201
EMI and Lightning 202
Accelerated Life Tests 203
12 Practical Modeling of LEDs 207
Preliminaries 208
Practical Overview of Spice Modeling 209
What Not to Do 212
What to Do 213
Modeling Forward Voltage 214
Reverse Breakdown 219
Modeling Optical Output 221
Modeling Temperature Effects 224
Modeling the Thermal Environment 226
A Thermal Transient 228
Some Comments on Modeling 229
References 231
Index 233
IEEE Press Series on Power Engineering