AB20-3 Datasheet, PDF (1/37 Pages) Lumileds Lighting Company – Electrical Design Considerations for SuperFlux LEDs

application brief AB20 3
replaces AN1149 3
Electrical Design
Considerations for
SuperFlux LEDs
Table of Contents
Overview
Summary
2
Electrical Design Process Overview
3
Circuit Design Overview
4
Worst Case Circuit Analysis and Validation
5
Comparison of Different Methods of Worst Case Circuit Analysis
5
Characterization of Prototype LED Signal Lamp
7
Validation of LED Signal Lamp
7
Key Concepts for Electrical Design of LED Signal Lamps
8
Resistor Limited Drive Circuits
8
Effect of LED String Length on Forward Current Regulation
9
Forward Current Variations between LED Emitters in an Array
10
EMC Transient Protection Circuits
12
Stop/Tail Drive Circuits
12
Theory
Electrical, Optical, and Thermal Characteristics of LED Emitters
13
LED Emitter Modeling
16
Linear Forward Voltage Model
17
Luminous Flux Models Versus Forward Current and Temperature
18
Thermal Resistance Models
19
Applications
Resistive Current Limiting
21
CHMSL Design Example
24
EMC Transient Protection
27
Special Considerations for Dual Luminous Intensity Operation
29
Luminous Flux Variations at Low Currents
29
PWM Drive Circuit for Tail Functions
30
Current and Voltage Regulator Circuits
31
Operation of Shunt, Series Pass, and Switching Regulators
32