JAJU792 July   2020

 

  1.   概要
  2.   リソース
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 PCB Assembly
      2. 2.2.2 Top Side of PCB Assembly
    3. 2.3 Highlighted Products
      1. 2.3.1 TPS92682-Q1
      2. 2.3.2 TPS92682-Q1
      3. 2.3.3 TPS92520-Q1
      4. 2.3.4 MSP432
      5. 2.3.5 System Design Theory
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 CISPR 25 Class 5 Test Setup
      2. 3.1.2 LED Load Board Top
      3. 3.1.3 LED Load Board Bottom
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1  Boost Turn on Delay
      2. 3.3.2  Highbeam/Lowbeam Turn on Delay
      3. 3.3.3  Highbeam/Lowbeam Switch Node and Ripple Current
      4. 3.3.4  Turn Indicator Turn on Delay
      5. 3.3.5  Turn Indictor Turn Off Delay
      6. 3.3.6  Turn Indicator 1.5 Hz Operation
      7. 3.3.7  Turn Indicator Output Voltage and Current
      8. 3.3.8  Daytime Running Light Turn-on Delay
      9. 3.3.9  Daytime Running Light Switch Node and Output Current
      10. 3.3.10 Highbeam/Lowbeam LED Short
      11. 3.3.11 Highbeam/Lowbeam Fault Indicator
      12. 3.3.12 Turn Indicator Fault Output
      13. 3.3.13 TPS92682-Q1 Boost and SEPIC Interleaving
      14. 3.3.14 TIDA-050040 Full Load Efficiency
      15. 3.3.15 Efficiency Highbeam/Lowbeam
      16. 3.3.16 Efficiency Turn Indicator and Daytime Running Light
      17. 3.3.17 Efficiency Highbeam/Lowbeam and Turn Indicator
      18. 3.3.18 CISPR 25 Class 5 EMI Scan
      19. 3.3.19 Top Side Thermal Image DRL at 15W
      20. 3.3.20 Bottom side thermal image DRL at 15W
      21. 3.3.21 Top Side Thermal Image Highbeam/Lowbeam at 30W, Turn Indicator at 7.5W average
      22. 3.3.22 Bottom Side Thermal Image Highbeam/Lowbeam at 30W, Turn Indicator at 7.5W average
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Documentation Support
    3. 4.3 サポート・リソース
    4. 4.4 Trademarks

1 System Description

This reference design demonstrates a three channel LED driver for front headlight applications. The design uses a single channel of the TPS92682-Q1 for a constant voltage boost converter driving a two channel constant current synchronous buck converter, the TPS92520-Q1. Channel one of the TPS92520-Q1 provides up to 30 watts for Highbeam/Lowbeam applications. The Highbeam input is used to open or shunt the Highbeam section of the LED string, this determines Highbeam or Lowbeam operation. The second channel of the TPS92520-Q1 provides up to 15 watts for Turn Indicator applications. A switched input power of 1.5 Hz drives the Turn Indicator LED string with less than a 10 ms delay from the rising Turn Indicator input. The second channel of the TPS92682-Q1 is set up as a constant current SEPIC to provide up to 15 watts for Day Time Running Light/Position Marker Light. The mode of operation is determined by the Highbeam/Lowbeam and Turn Indicator inputs. The design contains a MSP432 processor to program the TPS92682-Q1 and TPS92520-Q1 via SPI bus, control the headlight functions, read LED string voltages and report faults to the Body Control Module. Each function has its own reverse battery protected input.

This design has single LED short-fault reporting for Highbeam/Lowbeam and Turn Indicator. A Highbeam/Lowbeam fault reduces Lowbeam input current to zero to notify the automotive Body Control Module there is a fault. There is also an open collector fault line available. The Turn Indictor fault is an open collector fault line. Turn Indicator fault goes low when there is an open string, shorted string or shorted LED and the Turn Indicator is disabled. The Printed Circuit Board is setup to use an edge card connector, EC1. The board also has a ground strip to allow enclosing the power stages to meet CISPR 25 Class 5 conducted EMI levels.

Terminology

    HB

    Highbeam

    LB

    Lowbeam

    TI

    Turn Indicator

    DRL

    Daytime Running Light

    POS

    Position Marker Light

The Key System Specifications include the following:

Table 1-1 TPS92682-Q1 Channel One Constant Voltage boost

BOOST

MINIMUM

TYPICAL

MAXIMUM

UNIT

Output Voltage

24

55

55

volts

Output power

45

watts

Maximum Power Input Voltage Range

9

13

16

volts

Input Voltage Range Reduced Power

6

24

volts

Switching Frequency

300

KHz
Table 1-2 TPS92682-Q1 Channel Two Constant Current SEPIC

SEPIC

MINIMUM

TYPICAL

MAXIMUM

UNIT
Output Voltage

3

43

48

volts

Output Current

0.1

0.33

1

amps

Output Power

2

15

watts

Switching Frequency

300

KHz
Table 1-3 TPS92520-Q1 Channel One Constant Current Buck Converter

BUCKS1

MINIMUM

TYPICAL

MAXIMUM

UNIT
Output Voltage

3

34

48

volts

Output Current

0.1

0.88

1.2

amps

Output Power

30

watts

Switching Frequency

400

KHz
Table 1-4 TPS92520-Q1 Channel Two Constant Current Buck Converter

BUCKS2

MINIMUM

TYPICAL

MAXIMUM

UNIT
Output Voltage

3

33

48

volts

Output Current

0.1

0.43

1.2

amps

Output Power

15

watts

Switching Frequency

400

KHz