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

2.4.1.2 Setting the Switching Frequency

For this design, a switching frequency of 275 kHz is selected to keep the fundamental switching noise out of the AM band and reduce the switching power loss for thermal reason. The RT resistor (R20) can be calculated for 275 kHz using Equation 4:

Equation 4. TIDA-050002 eq_Rt_TID50002.gif

A value of 28.7 kΩ is selected for R12.