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  • Driving Daytime Running Lights LEDs With Thermal Foldback Reference Design

    • TIDUCL3 February   2017

       

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  • Driving Daytime Running Lights LEDs With Thermal Foldback Reference Design
  1. 1 Overview
  2. 2 Resources
  3. 3 Features
  4. 4 Applications
  5. 5 Design Images
  6. 6 System Overview
    1. 6.1 System Description
    2. 6.2 Key System Specifications
    3. 6.3 Block Diagram
    4. 6.4 Highlighted Products
      1. 6.4.1 LMT87-Q1
      2. 6.4.2 TLC555-Q1
      3. 6.4.3 OPA2377-Q1
      4. 6.4.4 TL431-Q1
      5. 6.4.5 TPS92691-Q1
  7. 7 System Design Theory
    1. 7.1  PCB and Form Factor
    2. 7.2  Optimizing Board Performance Based on LED String Voltage and Current
    3. 7.3  Switching Frequency
    4. 7.4  Output Overvoltage Protection (OVP)
    5. 7.5  Current Monitoring (IMON)
    6. 7.6  Thermal Foldback
      1. 7.6.1 Changing Thermal Foldback Response
        1. 7.6.1.1 Changing Starting Point for Thermal Foldback
        2. 7.6.1.2 Changing Slope of Thermal Foldback
        3. 7.6.1.3 Constant Current at High Temperatures
      2. 7.6.2 Thermal Foldback Without PWM Dimming
    7. 7.7  Clock Generation (PWM)
    8. 7.8  Onboard Supply and Setting Duty Cycle
    9. 7.9  Buffering, Averaging, and Filtering
    10. 7.10 Boost Converter
  8. 8 Getting Started Hardware
    1. 8.1 Hardware
    2. 8.2 LED Selection
    3. 8.3 J3, LED+, LED– (Boost)
    4. 8.4 J1, POS(+), NEG(–)
    5. 8.5 J4, Temperature Sensor Connection
    6. 8.6 Duty Cycle Adjust
  9. 9 Testing and Results
    1. 9.1 Duty Cycle Accuracy
    2. 9.2 Thermal Foldback Testing
    3. 9.3 EMI Testing
    4. 9.4 Accuracy Calculation
  10. 10Design Files
    1. 10.1 Schematics
    2. 10.2 Bill of Materials
    3. 10.3 PCB Layout Recommendations
      1. 10.3.1 Layout Prints
    4. 10.4 Altium Project
    5. 10.5 Gerber Files
    6. 10.6 Assembly Drawings
  11. 11Related Documentation
    1. 11.1 Trademarks
  12. 12About the Author
  13. IMPORTANT NOTICE
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DESIGN GUIDE

Driving Daytime Running Lights LEDs With Thermal Foldback Reference Design

1 Overview

The TIDA-01382 implements thermal foldback for derating current through the LEDs without using a microcontroller. This TI Design uses the following devices: the TPS92691-Q1 multi-topology LED driver in boost configuration to control the LEDs, the TLC555-Q1 LinCMOS™ timer together with the OPA2377-Q1 operational amplifier to measure and generate the accurate PWM signal by applying a feedback loop and a precision shunt regulator for setting the accurate duty cycle, and the LMT87-Q1 to implement thermal foldback. The input and output stage of the design is EMI- and EMC-filtered and can be directly supplied by a car battery.

2 Resources

TIDA-01382 Design Folder
TPS92691-Q1 Product Folder
LMT87-Q1 Product Folder
TLC555-Q1 Product Folder
OPA2377-Q1 Product Folder
TL431A-Q1 Product Folder
TIDA-01382 TI_E2E.gif ASK Our E2E Experts

3 Features

  • Thermal Foldback
  • Precision PWM Dimming
  • Efficiency-Optimized Design
  • Operation Through Cold Crank
  • Load Dump Tolerant

4 Applications

  • Automotive Front Lighting
  • Automotive Daytime Running Lights
  • Automotive Tail and Brake Lights

TIDA-01382 tida-01382_board_picture_real.png

5 Design Images

TIDA-01382 blockdiagram.gif
TIDA-01382 ImpNoteAware.gif An IMPORTANT NOTICE at the end of this TI reference design addresses authorized use, intellectual property matters and other important disclaimers and information.

 
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