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Educational use: ElectraCore supports learning and preliminary checks. It does not replace a competent electrician or engineer. Verify results, equipment data, and current local regulations before installation or live work.
Courses/LED & Lighting Design/LED Technology

lesson · 7min · Lesson 3 of 24

LED chip formats: COB, SMD, filament

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 · 7min
LUMEN METHOD · ILLUMINANCEluminaire · lmwork plane · area AEav = N·F·UF·MF÷ Alux (lm/m²)
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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

LED chip formats: COB, SMD, filament

Led Lighting · Lesson 3 · Intermediate

IntermediateReview: professional review pending

Purpose

Compare COB, SMD and filament formats by thermal, optical, electrical and service architecture rather than style labels.

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

COB mounts many dies on one substrate, SMD uses discrete surface-mounted packages, and LED filament structures distribute many small dies along elongated supports. Each format can be engineered well or poorly.

LED JUNCTION LIGHT AND HEAT PATHLED JUNCTION LIGHT AND HEAT PATHDRIVERLEDlight · heatinput · regulation · junction · optics · control · environment

Core theory

COB offers compact high-flux emitting area but concentrates heat and often needs dedicated optics. SMD arrays enable flexible distribution, color mixing and redundancy.

Filament lamps mimic omnidirectional incandescent geometry but have constrained heat removal and compact driver/envelope design. Format alone does not determine efficacy or lifetime.

Check module voltage/current topology, thermal resistance, binning, optics, photobiological risk, replaceability, surge/driver compatibility and complete product certification.

Terms, symbols, and units
TermMeaningSymbolUnit
COBChip-on-board arrayNot applicableNot applicable
SMDSurface-mounted LED packageNot applicableNot applicable
BinningGrouping LEDs by measured output, color or voltageNot applicableNot applicable
Worked exampleTwo formats use identical dies and total current, but one has 4 K/W lower junction-to-ambient thermal resistance at 12 W heat.

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

  1. Thermal: Temperature-rise difference=12×4=48 K.
  2. Meaning: The lower-resistance assembly can run its junction about 48 K cooler under the simplified conditions.
  3. Qualify: Optics, driver, interface and real thermal paths still matter.

Illustrative junction-temperature advantage is 48 K.

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

Does COB inherently guarantee longer life than SMD?

No. Complete thermal, electrical and material design governs.

Answer: No. Complete thermal, electrical and material design governs.

Practical exercise

Select a format for spot, linear and omnidirectional applications using supplied evidence.

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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