このリファレンス・デザインでは、TPS92682-Q1 と TPS92520-Q1 を使用して、ヘッドライト・アプリケーション向けに 3 チャネル LED ドライバの包括的な機能を自己完結型で実現する方法を紹介します。このデザインは、車載のボディ・コントロール・モジュールと互換性のある、低コストのハロゲン・ヘッドライト・モジュールの代替品で使用することを意図しています。3 つの LED チャネルは、ハイビームとロービーム、方向指示器 (ウィンカー)、昼間点灯ライト (DRL)、ポジション・ランプ (車幅灯) の駆動に使用できます。このデザインは、1 つの TPS92682-Q1 デュアル・チャネル・コントローラを、定電圧昇圧と定電流 SEPIC に使用しています。また、この昇圧回路を電源とする 1 つの TPS92520-Q1 も使用し、2 つの定電流同期整流降圧コンバータを駆動します。この基板は、グランド・ストリップを採用する設計であり、CISPR 25 Class 5 伝導型の試験結果を含め、EMI 関連規格に準拠した電力段を密閉することができます。
TIDA-050040 | デザイン・フォルダ |
TPS92682-Q1、TPS92520-Q1、MSP432E401Y | デザイン・フォルダ |
TPS92682EVM-070、TPS92682EVM-069、TIDA-050029 | プロダクト・フォルダ |
2 段の定電圧昇圧コンバータは、2 つの同期整流降圧コンバータに電力を供給し、ハイビームやロービーム、および方向指示器 (ウィンカー) の駆動に対応
昼間点灯ライト (DRL) と車幅灯向けの SEPIC コンバータ
ボディ・コントロール・モジュールから供給される電力との互換性を確保
ハイビームとロービームや、方向指示器向けに、単一 LED の短絡や、出力の短絡と開路の検出を実施し、故障の報告と該当回路の無効化で対処
逆極性バッテリ保護
最大 30W のハイビーム / ロービーム
ターン・インジケータは、1.5Hz で最大 15W、50% デューティ・サイクルに対応
方向指示器入力から出力までの遅延時間は 10ms 未満
昼間点灯ライト / 車幅灯:最大 15W
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
Highbeam
Lowbeam
Turn Indicator
Daytime Running Light
Position Marker Light
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 |
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 |
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 |
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 |
This reference design is a self-contained LED headlight driver. Three power inputs, Lowbeam, Turn Indicator and Daytime Running Light/Position Marker Light are reverse battery protected. A fourth reverse battery protected signal input, Highbeam, determines whether to shunt or open via a MOSFET the Highbeam portion of the Highbeam/Lowbeam LED string. Daytime Running Light/Position Market light, as setup for testing, is always powered. Daytime Running Light/Position Marker Light function is determined by the other two power inputs Lowbeam and Turn Indicator. The test board is one of many possible configurations. A table shows light function based on inputs as configured for functional testing:
INPUT | INPUT | INPUT | OUTPUT | OUTPUT | OUTPUT | OUTPUT |
---|---|---|---|---|---|---|
Lowbeam | Highbeam | Turn Indicator | Lowbeam | Highbeam | Turn Indicator | DRL/POS |
0 | 0 | 0 | off | off | off | high |
0 | 0 | 1.5 Hz | off | off | 1.5 Hz | 1.5 Hz |
0 | 1 | 0 | off | off | off | high |
0 | 1 | 1.5 Hz | off | off | 1.5 Hz | 1.5 Hz |
1 | 0 | 0 | on | off | off | high |
1 | 0 | 1.5 Hz | on | on | 1.5 Haz | 1.5 Hz |
1 | 1 | 0 | on | off | off | high |
1 | 1 | 1.5 Hz | on | off | 1.5 Hz | 1.5 Hz |