LEDvolution Learning Time - Lifespan of LEDs in practice LED luminaires have a long but not infinite lifespan (useful life). Learn more about the LEDvolution approach towards this interesting topic!

1. Lifespan of LEDs in practice - The LEDvolution approach
LED luminaires have a long but not infinite lifespan (useful life)!
April 2015

2. All lighting products fail at some point …
For conventional, lamp-based lighting systems (e.g. incandescent, fluorescent and high-intensity discharge systems),
failure most commonly results when a lamp “burns out.” In almost all cases, other system components (e.g. the ballast or
luminaire housing) last longer than the lamp and have lifespans that are not dependent on the lamp.
Lamp-based system = failure when lamp “burns out”
Unlike conventional lighting systems, LED systems are mostly not lamp based but a collection of several integrated
components like LED modules, heat sink, power supply units, housing structures and optical elements. Regardless of the
product type, LED system performance and lifespan (useful life) are typically affected by interactions between these
system components.
LED systems = failure when one component fails
Conclusion: Establishing a rated lifespan (useful life) for a complete LED system is further complicated by the cost and
impracticality of traditional lifespan testing, especially because the continued development and advancement of LED
technology can render results obsolete before testing is finished. Consequently, the typical approach to characterising
lifespan is no longer viable for LED systems.

3. Lifespan (useful life) of LEDs in practice - The LEDvolution approach
LEDvolution defines the lifespan (useful life) of LED luminaires as follows:
The rated lifespan (useful life) assigned by LEDvolution is a statistical estimate of how long a product is
expected to perform its intended functions under a specific set of environmental, electrical and mechanical
conditions.
light
ON
struc-
ture
L70
beam
angle
CCT
1All intended functions are subject to the luminaire being operated within the
electrical values, operating range and environmental conditions specified in
the product data sheet or installation guide.
LEDvolution luminaires’ intended functions during the
entire lifespan:1
1. The LED luminaire produces light.
2. The LED luminaire provides at minimum 70% of the
initial light flux (L70).
3. The LED luminaire’s CCT must not deviate (colour shift)
more than +/- 10% from the initial value.
4. The beam angle and light distribution must not deviate
more than +/- 10% from the initial values.
5. The product’s structure does not undergo major
alterations.
Terminology:
The terms “lifespan” and “useful life” are commonly used in relation to longevity of
lighting products. The proper technical term, however, is “service life” which is
also stated on LEDvolution’s product data sheets.

4. The rated lifespan (useful life) of a LED system may, among other factors, be affected by its design,
materials, selection of components (LED chips, PSU, etc.), the manufacturing process and the
environment it’s used in (ambient temperature, humidity, etc.). Importantly, the rated lifespan for a
complete LED system (luminaire) cannot be longer than the lifetime of any of its components.
Power
Supply
PCB
Lens
(if used)
Reflectors
(if used)
Diffuser
(If used)
Thermal Management
Heat sink
Power
Input
Light
Output
LED Luminaire Reliability Management to determine the rated lifespan
LED Chip
1 22 3 54 6 73
5 000 to 70 000 hours2
20 000 to 75 000 hours2
> 50 000 hours2
> 100 000 hours2
Power Management: This functional unit includes the power supply unit (PSU) / driver which
ensures that proper power is delivered to the LED light engine. The reliability of the power supply
unit and the driver is key to the lifespan (useful life) estimate of the LED luminaire.
Thermal Management: This functional unit ensures that the heat generated by the LED light
engine and power system is appropriately dissipated to maximise the lifespan of the LED package
and power system components.
Optical Management: This functional unit ensures that the light generated by the LED light
engine is properly bundled and directed towards the desired surface. This includes lenses, reflectors
and diffusers.
> 100 000 hours2
infinite if used under the right conditions
> 100 000 hours2
2Estimated lifespan dependent on selected
components, supplier selection, product design
and on the environment used in.
Conclusion: Failure of any of these functional units could lead to failure of the LED luminaire. In reality, the overall lifespan of a LED
luminaire can be statistically determined by knowing the lifespan and failure rate of each of these functional units.
Assembly Integrity: This functional unit ensures that the overall housing design and the entire assembly process provide for sufficient long-term
protection from dust, moisture, vibration and other adverse environmental effects.
Power Management Optical Management
LED Luminaire Assembly Integrity
Optical Management
LED system / LED luminaire
1
2
3
3
5
4
6
7

5. LEDvolution Design Goals and Reliability Impacts on a LED luminaire’s lifespan (useful life)
Power Management
 Design Goals: For proper operation, the power supply and related electronics must provide a well-controlled and (from electrical transients)
protected drive current and possibly other control and monitoring features. All components must be designed to properly function for the
anticipated life of the product.
 Reliability Impact: Component failures due to improperly designed and executed power management may often result in a catastrophic failure of
the LED luminaire, but they can also cause less obvious effects, such as a reduced light output or flicker. Proper power management includes
protection against failure caused by electrical transients. This protection might be built into the driver or might be a separate subsystem of the
LED luminaire.
Thermal Management
 Design Goals: A reliable heat-conducting design, be it passive or active, is required to remove heat from the LED package and luminaire. The
design should ensure that the LED package operates below a manufacturer-reported LM-80 measurement temperature to achieve the desired
lumen maintenance of the fixture. Also, the design must ensure that temperatures for other devices (power supply, control circuitry, optical
components, etc.) do not exceed the manufacturers specified limits.
 Reliability Impact: Improperly designed and executed thermal management will usually result in accelerated lumen depreciation and potentially
degraded colour quality or colour shift of the LED package(s).
Optical Management
 Design Goals: Component choices and manufacturing methods should be chosen in a way that the optical materials retain their integrity
throughout the life of the product; it is desirable that such components not be life-determining.
 Reliability Impact: Optical component failures may degrade lumen output of the luminaire’s LED package(s) or, because of discolouring, may
also result in a colour shift, but rarely result in a catastrophic failure.
Assembly Integrity
 Design Goals: Luminaire housing design and materials must be designed to offer sufficient protection for the LEDs depending on the anticipated
environment. Repairable designs should allow for simple field replacement of any failed component without degrading the integrity of the
housing or other components.
 Reliability Impact: For outdoor or harsh environment applications, housing failure can lead to catastrophic failure of critical light-producing
components. In other cases, mechanical failure may result from insufficient protection for internal components. Any assembly process bears the
risk of occasional random manufacturing defects which might cause failure anytime during the life of the product but should not seriously affect
wear out till end of lifespan.

6. LEDvolution ECO Grid Light T3
31W / 3000lm / 4000k
Lifespan (useful life): 50 000h
Lumen Maintenance Factor: L80
Working Temperature (Ta): +10 to +40°C
Example of a lifespan estimation by LEDvolution
Power Management
PSU / driver from ELT (Spain): ref. LC 142/600C
Maximum ambient temperature (Ta) = +50°C
Lifespan at max. Ta = 50 000 h
Reliability:
•Failure rate 0,2% per 1 000 hours
•Overload protection
•Protection against no load operation
•Overheat protection
•Input voltage: 198 to 264 V (in Europe input is 230 V)
•Power factor: 0,99 (extremely efficiency)
 The max. Ta allowed for our luminaire is +40°C. This allows us to estimate a lifespan for the PSU
of over 50 000 hours.
LED Package
LED chip from Nichia (Japan): ref. NF2L757DRT
Maximum ambient temperature during operation (Ta) = +100°C
Lifespan at Ta 25°C = 100 000 h (L70) (tested by Nichia during 1 000 hours = 0% failure rate) and
lifespan at Ta 100°C = 50 000 h (L70) (tested by Nichia during 1 000 hours = 0% failure rate).
Reliability:
•Failure rate < 0,1% per 1 000 hours at Ta > 40°C
•Moisture resistance: 90%
 The strict observance of the max. Ta and a power supply as specified by the manufacturer allows us to
estimate a lifespan for the LED package of over 50 000 hours (L80).
Thermal Management
Passive cooling system of aluminium (AU4SG) with 3M thermal conductive interface pad:
Aluminium thermal conductivity around 237 W per m2 (for 1 mm thickness) 237 W/m-K.
The entire luminaire body is out of steel and also participates in the thermal dissipation.
Thermal simulation operated during minimum 24 hours of continuous use at max. Ta (+40°C).
The positioning of the PSU inside the luminaire is designed to avoid any overheating caused
by the LED package heat dissipation.
The passive cooling is oversized and able to dissipate 2 times more heat (Watts) than generated
by the LED package, the thermal simulation confirmed the sustainability of the thermal management.
Conclusion: The weakest link of the LEDvolution ECO Grid Light T3 is the PSU with a lifespan of 50 000 hours at 40°C.
-> This component determines the overall lifespan of the entire luminaire.