ZHCU578 October   2018

 

  1.    说明
  2.    资源
  3.    特性
  4.    应用
  5.    设计图像
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TPS92692-Q1
    3. 2.3 LM74700
    4. 2.4 System Design Theory
      1. 2.4.1 Design Procedure
        1. 2.4.1.1  Operating Parameters, Duty Cycle
        2. 2.4.1.2  Setting the Switching Frequency
        3. 2.4.1.3  Inductor Value Calculation
        4. 2.4.1.4  Peak Inductor Current
        5. 2.4.1.5  Calculating RIS (R9)
        6. 2.4.1.6  Minimum Output Capacitance
        7. 2.4.1.7  Setting the LED Current
        8. 2.4.1.8  Soft-Start Capacitor
        9. 2.4.1.9  Overvoltage Protection (OVP)
        10. 2.4.1.10 Main N-Channel MOSFET Selection
        11. 2.4.1.11 Rectifier Diode Selection
        12. 2.4.1.12 Thermal Protection
      2. 2.4.2 Designing for Low EMI
        1. 2.4.2.1 EMI Performance
        2. 2.4.2.2 EMI Filter Design
          1. 2.4.2.2.1 Additional EMI Considerations
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Nominal Operation Waveforms
          1. 3.2.2.1.1 Loop Stability Measurements Block Diagram
        2. 3.2.2.2 Efficiency and Line Regulation: Done for different power level for Boost (Hi Beam and Lo Beam) or Boost to Battery for Lo Beam only
        3. 3.2.2.3 Thermal Scan
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Related Documentation
    1. 5.1 商标

2.4 System Design Theory

This reference design consists of a high-performance LED controller configured in a boost or buck-boost topology. It uses EMI filtering and a load disconnect FET for high slew rate PWM dimming (see Figure 4). The input voltage range from 8 V to 16 V nominal operation with the capability to run as low as 6 V for warm crank operation. It can operate ss high as 42 V for load dump operation with reduced number of LEDs at output or input voltage transient suppressor since it can exceed the 65 V rating of the TPS92692. This design supports up to 1.25 A of output current and an output power rating of 55 W. The design is optimized to drive seven high beam LEDs and seven low beam LEDs for a total of 14 LED strings at 1.25 A from a typical voltage supply of 13 V. However, multiple combinations of input supplies and LED loads along with external synchronization or PWM can easily be created using this reference design as a starting point. Standard recommended component values (such as the VCC capacitor) are not covered in this section.

TIDA-050002 schematic_tiduec3.gif
R18 is populated to allow for PWM dimming
Figure 4. TIDA050002 Schematic