LED調光：知っておくべきこと

DOE SSLプログラム

2012年12月10日

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Report Overview

「LED Dimming: What You Need to Know」は、2012年12月10日にDOE SSLプログラムが発表した総合ガイドです。この報告書は、LED光源の調光に関する課題・技術・ベストプラクティスについて詳細な情報を提供し、特に位相制御式調光器との互換性問題に焦点を当てています。

Key Insight: LED dimming in the real world can be challenging, especially with phase-cut dimmers. Wide variation in LED source and dimmer characteristics means little can be assumed, not all claims are equal, and performance is difficult to predict without testing.

主なデータポイント

>150M
Phase-cut dimmers installed in U.S.
2 Methods
Primary LED dimming approaches
7.5-16.3%
テストにおけるちらつき率の範囲
20％
負荷のTHD-Iリミット

Key Insights Summary

LEDs Are Inherently Dimmable

LEDs can be dimmed using either Constant Current Reduction (CCR/Analog) or Pulse Width Modulation (PWM) methods. Each approach has different trade-offs in terms of performance, efficiency, and potential issues like color shift or flicker.

LEDにはドライバーが必要です

Unlike incandescent sources that behave like simple resistive loads, LEDs require drivers to convert AC voltage to regulated constant current. The driver's design and compatibility with dimming equipment largely determine dimming performance.

Phase-Cut Dimming Challenges

フェーズカット調光器は白熱灯用に設計されたため、LED負荷との互換性に重大な問題が生じることがあります。具体的には、デッドトラベル、ポップオン、ドロップアウト、フラッシング、ゴースト現象、可聴ノイズなどが発生します。

Dimming Affects Power Quality

Dimming an LED source can change driver behavior, potentially degrading efficiency, increasing flicker, and reducing power quality as measured by Power Factor and Total Harmonic Distortion metrics.

Transfer Function Mismatches

Different manufacturers use different control and light source transfer functions (linear, square, S-curve). Mismatches between dimmer and LED source transfer functions can lead to unexpected dimming behavior.

読み込みルールが変更されました

Traditional dimmer loading rules based on incandescent wattage don't apply to LEDs. Minimum and maximum load requirements vary significantly between different dimmer and LED source combinations.

コンテンツ概要

Document Contents

Why Dim LED Sources?

Dimming LED sources offers multiple benefits beyond simple ambiance control:

  • Additional energy savings beyond what's achieved by switching to LED technology
  • Increased visual task performance by adjusting light levels to specific needs
  • エンハンスト・アンビエンス and space flexibility
  • Fewer light sources to specify, maintain, and stock
  • デマンドレスポンスによる負荷遮断 capabilities
  • Potentially improved efficacy and lifetime of the light source

Dimming Challenges

しかしながら、LED光源の調光には、いくつかの重大な課題が存在します：

  • 大幅なばらつき in LED source and dimmer characteristics
  • 想定できることはほとんどない based on historical practices with incandescent lighting
  • Not all claims are equal due to lack of standard testing procedures
  • Difficult to predict 実際のテストを伴わないパフォーマンス
  • Circuit-level interactions between LED drivers and dimmers create compatibility issues

LED Dimming Basics

Understanding these fundamental concepts is crucial for successful LED dimming implementations:

キーコンセプト： LEDs are fundamentally different from incandescent sources. Incandescent sources behave like simple resistive loads, while LEDs are complex electronic devices that require drivers to function properly.

LEDs vs. Incandescent Sources

アスペクト Incandescent Sources LED Sources
Electrical Behavior Simple resistive load Complex electronic load
Current Control Vrms adjustment sufficient Requires constant current regulation
Dimming Method Reduce voltage/current CCRまたはPWM
Response Time Slow (thermal persistence) Instantaneous
Directionality Bidirectional Unidirectional

LEDドライバ

LEDは以下のためにドライバを必要とします：

  • Convert AC voltage to regulated DC current
  • Compensate for manufacturing variations in LED forward voltage (Vf)
  • Implement dimming functionality (CCR or PWM)
  • Protect LEDs from overcurrent and overtemperature conditions

Dimming Technologies

レポートでは、調光技術を主に2つのアプローチに分類しています：

1. Coincident AC Power and Control Signal

  • Phase-cut AC sine wave (forward or reverse phase)
    • 2-Wire (hot, dimmed hot)
    • 3線式（ホット線、調光ホット線、ニュートラル線）
  • Reduced amplitude AC sine-wave

2. Separate AC Power and Control Signal

  • Fluorescent 3-Wire
  • 0-10V
  • DALI （デジタルアドレス可能照明インターフェース）
  • DMX512
  • PWM (Pulse Width Modulation)

Recommendation: Consider control technologies which separate AC power and the control signal, if possible. This approach typically provides better dimming performance and fewer compatibility issues.

Dimming Methods

LEDの調光には主に2つの方式があり、それぞれ特徴が異なります：

Constant Current Reduction (CCR/Analog)

  • Method: Varying LED current while keeping LED always on
  • Advantages:
    • Longer LED lifetime (lower current and temperature)
    • ノイズ発生なし
    • Potentially higher efficacy at lower dimming levels
    • フリッカーを発生させません
  • デメリット:
    • Possible objectionable color shift
    • More difficult regulation at deep dimming levels

パルス幅変調（PWM）

  • Method: Maintaining same LED current but varying on/off times
  • Advantages:
    • Longer LED lifetime (less on time, lower temperature)
    • Good dimming regulation at deep dimming levels
    • No color shift
  • デメリット:
    • Potential noise generation
    • PWM周波数は、望ましくないちらつきを回避するために重要です。
    • Minimum dimming level limitations

ちらつきの問題

Flicker refers to the variation in time (modulation) of light output (luminous flux). While present in all traditional commercial electric light sources running on AC power, it can be more problematic with LED sources.

フリッカーを気にする人はいるのか？

  • Anyone who is sensitive to light modulation
  • Those responsible for human health, well-being and/or performance in spaces with electric lighting
  • リスクのある集団：
    • Photosensitive epileptics (1 in 4000)
    • Migraine sufferers
    • Young people
    • Autistic individuals

フリッカーメトリクス

  • パーセントフリッカー: (Max-Min)/(Max+Min) × 100%
  • フリッカー指数： Area above average / Total area

レポートの試験結果によると、調光レベルや機器の組み合わせによって、フリッカー率は7.5%～16.3%、フリッカー指数は0.02～0.06の範囲で変動することが示されている。

Power Quality

Dimming an LED source can change the behavior of the driver, potentially affecting power quality:

パワー・クオリティとは何ですか？

Power quality refers to displacements and distortions to voltage and current waveforms, measured by:

  • 力率（PF）: 有効電力（P）と皮相電力（S）の関係は力率（PF）により、PF = P/S で表される。
  • Total Harmonic Distortion (THD):
    • THD-V（電圧）
    • THD-I（電流）

Who Cares About Power Quality?

  • Electricity producers and consumers:
    • Increased current requirements
    • Electricity transport (I²R) losses
    • ワイヤー、回路ブレーカー、変圧器のサイジング
    • Potential equipment damage or degraded performance
  • Lighting equipment manufacturers:
    • ANSI C82.77-2002における自主的要件
    • システム設計におけるトレードオフ
    • コストとサイズの制約

Phase-Cut Dimming

Phase-cut dimming is the most commonly deployed dimming technology, with a large installed base in the U.S. (NEMA estimates >150 million units).

フェーズカット vs サイン波調光

  • フェーズカット： ACサイン波の一部をカット
    • フォワードフェーズ（リーディングエッジ）
    • 逆位相（トレーリングエッジ）
  • サイン波： Reduces amplitude of entire sine wave

Designed for Incandescent Sources

Phase-cut dimmers were originally designed for incandescent sources, which:

  • Behave like simple resistive loads
  • 実質的にはVrmsのみを考慮する。
  • Are bidirectional (work with both positive and negative voltage)
  • Have thermal persistence (light continues after current stops)

Compatibility Issues

The report identifies numerous compatibility issues that can occur with phase-cut dimming of LED sources:

  • デッドトラベル: Adjusting dimmer setting without corresponding change in light level
  • ポップオン： Dimmer setting needs to be raised above existing setting to get light output at turn-on
  • Drop-out: No light output at the bottom of the dimming range
  • ポップコーン： Different turn-on times for different light sources on a dimmed circuit
  • Flashing: Light source intermittently on when it should be off
  • ゴーストイング: 光源がオフであるべき時に低レベルでオン状態
  • Audible noise 調光器またはLEDドライバーから
  • Inoperability or premature failure

Sources of Compatibility Issues

  • LED負荷では、調光器によって生成されるVrmsおよび/または導通角を測定できません
  • LED load doesn't draw enough current to keep dimmer switching elements closed
  • LED load creates series impedance that disrupts dimmer timing elements
  • LED load in off state doesn't pass dimmer current in a manner that keeps advanced features functioning
  • LED load draws currents that create stresses beyond what dimmer's rated wattage indicates

Recommendations

レポートでは、LED調光を成功させるための複数の提言を行っています：

Know Your Options

  • Determine if the LED product is a lamp or luminaire
    • ランプ： Typically retrofit with standard base, constrained to phase control
    • Luminaires: 多くの場合、ドライバーオプションにより様々な制御オプションが提供されます
  • Consider control technologies which separate AC power and control signal
  • Use a phase-cut dimmer with a neutral if possible
  • Consider using dimming controls designed specifically for LED sources

Take Advantage of Available Information

  • Research the designed, claimed dimming performance of LED sources
  • Look for recommended dimming control selection guidance
  • Pay attention to specific makes/models recommendations
  • Note dimmer loading requirements (max/min number of LED sources per control)

Ask the Right Questions

  • What are the dimming transfer functions?
  • LEDドライバーはCCRとPWMのどちらを実装していますか？
  • What is the PWM dimming frequency?
  • Does dimming performance vary at different input voltages?
  • Was the LED source evaluated for flicker and power quality over the dimming range?
  • Does the dimmer require a neutral or trim-adjustment?

トレードオフを検討する

  • Application needs vs. wants
    • フリッカーはどの程度重要ですか？
    • How much does power quality matter?
  • Option 1: Only use LED sources and phase-cut dimmers with defined compatibility
  • オプション2：全コンポーネントを組み込んだ設置モックアップ

Analyze Risk

  • Common "fixes" for compatibility issues:
    • Change LED source, driver, or dimming control
    • Add incandescent or dummy loads
    • ニュートラルワイヤーを追加
  • Often there are no good solutions once products are installed
  • Have a plan BEFORE products are ordered and installed

Note: このHTML版はLED調光レポートの包括的な概要を提供します。完全なPDFドキュメントには、追加の技術詳細、図表、およびテスト結果が含まれています。完全な技術リファレンスとして、フルPDFのダウンロードを推奨します。