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

2.4.2.1 EMI Performance

Figure 5 shows the passing conducted EMI scan for this design at a nominal 13 V input voltage and driving a 14 LEDs load in both high-beam and low-beam mode (seven LEDs in series for low beam and seven LEDs in series for high beam) at 1.25 A of LED current. The blue trace is the peak scan, and the line labeled C25Px denotes the peak limits for CISPR-25 Class 3. The black trace is the average scan with the line labeled "C25Ax" denoting average limits for CISPR-25 Class 3. The scan covers the entire conducted frequency range from 150 kHz to 108 MHz.

This performance by board layout only and without shielding. This pre-compliance test scan is used for engineering development and evaluation and not a certified EMI test result. If an official EMI test result is required, it is the responsibility of the end-user to submit any design based on this reference design to a certified EMI lab.

TIDA-050002 EMI_No_Shield.gifFigure 5. CISPR-25 Class 3 Conducted EMI Scan (C25Px: Peak Limits, C25Ax: Average Limits)
No Shielding: VIN = 13 V, VF = 44 V, ILED = 1.25 A (Pre-Compliance Data)
TIDA-050002 PCB_Picture_Shield.gifFigure 6. Shielding is required on Switching Components to pass CISPR-25 Class 5 Conducted EMI
TIDA-050002 EMI_Shield.gifFigure 7. CISPR-25 Class 5 Conducted EMI Scan (C25Px: Peak Limits, C25Ax: Average Limits)
VIN = 13 V, VF = 44 V, ILED = 1.25 A (Pre-Compliance Data)