Loading... Please wait...

LED Brands

Our Newsletter

Critical Design Elements

Lite On LED takes into account several key factors which affects the success of a LED lighting design and reliability in the workplace:

LED Selection

Today’s LED lighting sources are extremely variable in terms of light output and life expectancy. At Lite On LED we make a careful selection of our Light Emitting Diodes (LED) to ensure good colour matching and consistency, lumen/light output and lumen maintenance or life span. We select our LEDs from top manufacturers including CREE, Bridgelux, Everlight, Seoul Semiconductors, Samsung and LG and only those LEDs with proven LM-80 or life time data.

Ambient and operating temperature

The life and light output of an LED light bulb is largely determined by two factors

  1. The temperature of the LED chip or case (TC, TS).
  2. The temperature of the LED driver/power supply (TD).

Therefore, both LED chip and driver temperature will be affected by the outside ambient temperature (TA). Lite On LED takes a careful consideration and measurement of the environmental and operating temperatures which will affect the life time and reliability of your LED lighting installation. 

LED Light bulb case and heat sink temperature and design

The LED chip in your LED light bulb is sensitive to high temperatures such that overly high temperatures of > 85°C will significantly shorten the life of your LED bulb as well as the lumen output or brightness. For example, the lumen maintenance for a BRIDGELUX ES BXRA-W0802 with a case temperature of 55°C or 85°C is approximately 94% over 6,000 hours, whereas at a case temperature of 105°C the lumen maintenance is approximately 91% of the original brightness. This equates to a decline to 70% brightness by approximately 20,000 hours at 105°C versus approximately 40,000 hours at 85°C. At case temperatures greater than 105°C the LED will fail within a relatively short time, potentially approximately 2,000 hours.

Therefore, due to the importance of LED case temperature thermal management techniques in the form of passive and active cooling methods have been developed to maintain the temperature of the LED chip temperature within normal operating temperatures, typically between at 55°C and 85°C. On LED manufacturer data sheets this is typically referred to as LED case temperature (TS).

In our laboratory tests we have found that LED heat sink temperature is generally equal to LED case temperature below approximately 60°C in lower power LEDs for 6-8W, although there are some exceptions with older less efficient models with poor heat sink design. In general a poor heat sink design will have difficulty conducting heat away from the LED chip leading to a much higher LED case temperature compared with the LED heat sink temperature with a differential of up to 20°C.

In higher power LED light bulbs (10W+) such as 10W 500lm+ we measure case temperatures of approximately 70°C, whilst heat sink temperatures are approximately 62°C. What this tells us is that as the LED chip gets hotter the ability for the heat sink to transfer heat away from the LED chip is reduced.

Therefore, proper thermal management and heat sink design is paramount and will separate the “winners from the losers” in this emerging industry.

LED light bulb – Driver / Power Supply Temperature

The quantity of light produced by the LED light bulb is proportional to the amount of direct current (DC) flowing through the circuit. This requires the conversion of mains AC currents using some relatively simple (internal or external) electronic circuitry referred to as the constant voltage or constant current power supply or LED driver. 

The main issue with power supply temperatures is the use of electrolytic capacitors in the LED driver or power supply. The electrolytic capacitors are very sensitive to heat such that every 10°C increase in temperature leads to a 50% decrease in the life of the capacitor, such that the life may be reduced from 40,000 hours to 20,000 hours, and so on.

Therefore, Lite On LED takes temperature measurements and makes careful consideration of the operating environment when selecting power supplies for specific applications. This can significantly lengthen the lifetime of the complete lighting system and reduce future maintenance costs.

References and Further Reading

Lifetime of White LEDs. Sept 2009. Building Technologis Program. US Department of Energy. www.eere.energy.gov

LED Lighting: A Case Study in Thermal Management, Qpedia September 2009, Vol III, Issue VIII, 6-15.

Extend the life of LED lighting systems with thermal management, Rick Zarr Texas Instruments, EDN Network, September 2012

US DOE (2010). Demonstration Assessment of Light-Emitting Diode (LED) Retrofit Lamps. Host Site: InterContinental Hotel, San Francisco, California. Final Report prepared in support of the U.S. DOE Solid-State Lighting Technology Demonstration GATEWAY Program.

NIC Components Corp. Extended Lifetime Aluminium Electrolytic Capacitors.

Determination of the shelf life of aluminum electrolytic capacitors. Edward McFaddin, 2002. University of North Texas

Determination of the shelf life of aluminum electrolytic capacitors. Arne Albertsen, Jianghai Europe GmbH

Metallized Polyester Film Capacitors MKT1817 Data Sheet Vishay Roederstein

Lay-Ekuakille AG et al (2009). "Led-based Public Lighting System Reliability for a Reduced Impact on Environment and Energy Consumption." Energy and Environment Research Center, Dipartimento d’Ingegneria dell’Innovazione, Università Degli Studi del Salento (2008): 8. Web. 30 Dec

Sebitosi AB & Pillay P (2003). "White LEDs for Rural Lighting." IEEE- Institute of Electrical and Electronics Engineers: 2619-2623.

Extend the life of LED lighting systems with thermal management, Rick Zarr Texas Instruments, EDN Network, September 2012

next.gif Understanding LED Lighting Technology and Concepts