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Courses/LED & Lighting Design/Driver Circuits

lesson · 9min · Lesson 8 of 24

Dimming methods: PWM, 0-10V, DALI

Course syllabusCourse overview
01LED Technology
  1. ReadHow LEDs produce light: p-n junction
  2. ReadEfficacy: lumens per watt explained
  3. ReadLED chip formats: COB, SMD, filament
  4. ReadThermal management: heatsinks and junction temperature
  5. quizLED technology quiz
02Driver Circuits
  1. ReadConstant current vs constant voltage drivers
  2. ReadDriver efficiency and power factor
  3. ReadDimming methods: PWM, 0-10V, DALI
  4. ReadDriver selection and compatibility
  5. quizDriver circuit quiz
03Emergency Lighting
  1. ReadBS 5266 categories: escape, standby, high-risk
  2. ReadSelf-contained vs central battery systems
  3. ReadMaintained vs non-maintained operation
  4. ReadTesting requirements and log books
  5. quizEmergency lighting quiz
04Lux Calculations
  1. ReadIlluminance, luminous flux, and efficacy
  2. ReadLumen method: average illuminance
  3. ReadRoom index, UF, and MF
  4. exerciseLux calculation worked example
05Lighting Control & Quality
  1. ReadColour temperature: warm, neutral, cool white
  2. ReadColour rendering index (Ra/CRI)
  3. ReadGlare: UGR and how to reduce it
  4. ReadSmart lighting systems: DALI 2 and IoT
  5. quizFinal assessment
Lesson · 9min
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In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources

In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources
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ElectraCore lesson handout

Dimming methods: PWM, 0-10V, DALI

Led Lighting · Lesson 8 · Intermediate

IntermediateReview: professional review pending

Purpose

Distinguish PWM, analogue 0/1–10 V and DALI control paths and predict failure/standby behavior.

Before you beginVoltage, current and power · Basic semiconductor and circuit concepts

Learning objectives

  • Trace electrical-to-light conversion
  • Use declared operating boundaries
  • Separate component and luminaire metrics
  • Check control and load compatibility

PWM controls average LED energy by pulse timing; analogue interfaces command a level using voltage/current conventions; DALI uses addressed digital messages over a bus. These are not interchangeable terminals.

DRIVER OUTPUT AND CONTROL WINDOWDRIVER OUTPUT AND CONTROL WINDOWDRIVERLEDlight · heatinput · regulation · junction · optics · control · environment

Core theory

PWM frequency/duty, minimum pulse and camera/flicker needs must match the driver/load. Some ‘PWM dimming’ products expect a logic input; others PWM-switch their power output.

0–10 V and 1–10 V can differ in source/sink behavior, off state, polarity and isolation. Confirm wiring and control supply rather than joining labels.

DALI uses IEC 62386-based devices and commissioned addresses/groups/scenes. Verify DALI-2 products in the public database and design bus power, voltage drop, topology, failure level and emergency/control interactions.

Terms, symbols, and units
TermMeaningSymbolUnit
PWMPulse-width modulationNot applicableNot applicable
DALIDigital Addressable Lighting InterfaceNot applicableNot applicable
FadeControlled transition between light levelsNot applicableNot applicable
Average ideal output fraction ≈ duty cycle

Only for a linear ideal PWM response; real driver/light response and minimum pulses differ.

dimensionless or %
Worked exampleAn ideal PWM channel is on 2 ms in each 10 ms period.

Assumptions: Supplied photometric/electrical values share the stated measurement boundary; Manufacturer limits remain governing.

  1. Duty: D=2/10=0.20.
  2. Ideal average: Average fraction≈20%.
  3. Qualify: Perceived brightness, camera banding and driver limits are not established.

Ideal average output fraction is 20%.

Reasonableness check: The result identifies whether it describes LED package, module, driver or complete luminaire and avoids claiming field performance from one laboratory number.

Common mistakes
  • Dividing lumens by LED-chip watts while calling it luminaire efficacy
  • Connecting constant-current LEDs to a constant-voltage source without current control
  • Assuming every dimmable driver works with every dimmer

Where this appears in practice

A reliable LED installation coordinates light source, optics, thermal path, driver, supply/protection, controls, environment and maintainability.

SafetyLED outputs can create glare/photobiological hazards and drivers can contain mains voltage and stored charge after switch-off. Isolate, prove dead, observe discharge instructions and never defeat thermal interfaces or enclosure barriers.
Local code checkConfirm current luminaire/module/controlgear safety and performance standards, BS 7671, exact driver/module/luminaire data, photobiological risk, thermal/fire enclosure requirements, EMC/flicker/harmonic obligations and control-protocol certification. A CE/UKCA or DALI-2 mark does not prove two arbitrary components are electrically, thermally or functionally compatible.

Knowledge check

Are 0–10 V and DALI terminals interchangeable if both dim?

No. One is analogue and one is a powered digital bus with different electrical/protocol rules.

Answer: No. One is analogue and one is a powered digital bus with different electrical/protocol rules.

Practical exercise

Draw power/control paths and failure states for PWM, 1–10 V and DALI examples.

Summary

  • Metric boundary changes the answer
  • LED current and junction temperature govern life/output
  • Driver and dimmer must match electrically and functionally

Sources and review

  • IEC 62031:2026: LED modules safety requirements: IEC; 2026; International
  • IEC 61347-2-13:2024: LED controlgear safety: IEC; 2024; International
  • DALI-2 certification overview: DALI Alliance; Current certification database/status must be checked; International

Editorial review date: 2026-08-22. Professional electrical review is pending.

Educational material for learning and preliminary checks. Verify current local requirements and exact equipment instructions. This lesson does not replace competent professional work.

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