LED lighting is incredibly robust and reliable. However, the performance ofLEDscan be reduced and even fail if the LED module is used incorrectly: overdriven or the application environment is too hot, and the unit has not been designed to be fit for purpose. Here’s an overview of the main causes of electrical overstress.
LED Hot Connection
What does LED hot connection mean?
“Hot Connecting” means connecting a circuit comprising one or more bare LEDs to a LED Driver or LED Power Supply that is already powered-up or ‘live’.
What damage might an LED hot connection cause?
Hot Connecting can result in a short but potentially harmful impulse of electrical energy being discharged from the live LED Driver or LED Power Supply into theLEDs. This in turn can result in either immediate damage toLEDsin terms of open-circuits or short-circuits, or latent damage that results in similar LED failure after a potentially long period of time (possibly up to many months).
This kind of LED damage is oftencategorisedunder the term Electrical Overstress (EOS).
What might be the tell-tale signs be for LED hot connection if a unit is returned?
High power LEDs that have suffered from failure due to Hot Connect EOS often show no naked-eye/visible signs of damage, but are frequently electrical short-circuits. Consequently they emit no light or only a very small amount of light and if they are connected in a series string the remaining/undamaged LEDs remain lit.
Direct Connection to Mains Supply or Use of an Incorrect LED Driver
What does this mean?
LEDs must be powered from a DC source that limits the current flowing through them. This is in contrast to incandescent lamps that will operate from AC or DC and which generally require no separate current limiting, or fluorescent lamps that operate from AC only but which do require current limiting (i.e. ballast or control gear).
What damage might connecting to a mains supply or using an incorrect LED driver cause?
If LEDs are connected directly to the UK 230V AC mains supply without any current limiting LED Driver or LED Power Supply they will most likely immediately and catastrophically fail open-circuit, possibly breaking apart explosively in the process. IfLEDsare powered via a LED Driver or LED Power Supply that supplies incorrect current and/or incorrect voltage several outcomes are possible. If the current and/or voltage is too low theLEDswill appear too dim, or fail to light at all. If the current and/or voltage is too high theLEDscould either age prematurely (in the case of minor overdrive) or fail catastrophically (in the case of major overdrive) with all scenarios in between being possible.
What might be the tell-tale signs to look out for if a unit is returned?
LEDsthat have failed catastrophically due to direct mains connection will typically exhibit severe physical damage including breakage and burn marks. However, damage resulting from incorrect drive current and/or voltage may be manifest in many ways ranging from dimly lit but normal-lookingLEDsthrough to severe physical damage.
Installation in an environment that gets too hot
What do we mean by LED installation in an environment that gets too hot?
LEDsdo not emit the same amount of light of the samecoloureternally! The amount of light reduces exponentially and thecolourof whiteLEDstends to become bluer – both as a function of time and temperature. The hotter the environment the shorter the LED life.
What damage might a hot environmentcause?
LEDsinstalled in an environment that is too hot will emit less light than intended and degrade more rapidly than intended both in terms of reduced light output andcolourchange. In extreme cases, physical damage can occur.
What might be the tell-tale signs to look out for if a unit is returned?
Minor LED overheat that results in premature light output/colour degradation may have no physical signs other than the reduction in brightness and colour change. Major overheat, however, can result in visible off-state discolouration and physical heat damage to the LED and surrounding components.
Incorrect Polarity Connection
What do we mean by incorrect polarity connection?
LEDs are electrically polarised and will only operate correctly when their positive terminal (also known as the anode) is connected to the supply positive and their negative terminal (also known as the cathode) is connected to the supply negative. LED connection polarity must be strictly observed!
What damage might incorrect polarity cause?
If LEDs are reverse-connected to a sufficiently low voltage supply it is possible that they will simply conduct no current, emit no light and suffer no damage. In such cases correcting the polarity will result in correct LED operation with no adverse effects. However, if the supply voltage is sufficiently high then immediate and catastrophic damage can be caused resulting in no light emission and typically open-circuit failure.
What might be the tell-tale signs to look out for if a unit is returned?
Incorrect polarity connection that has caused LED failure will typically result in no light emission and open-circuit LEDs. This could result in signatures ranging from no naked-eye/visible signs of damage to physical damage including signs of burn/overheat. We always consider effective thermal management, optical and electrical design, and can talk through options on adding protection circuits to protect against incorrect use or “hot-plugging”.
If the current and/or voltage is too low the LEDs will appear too dim, or fail to light at all. If the current and/or voltage is too high the LEDs could either age prematurely (in the case of minor overdrive) or fail catastrophically (in the case of major overdrive) with all scenarios in between being possible.
There are a number of basic reasons for LED lights to fail but the primary issue is heat. Over-heating can be a result of a number of design and assembly issues but is still the cause of the majority of LED lamp failures – both in the fitting themselves and also the drivers.
For this reason, LEDs generally fall into short-circuit mode following electrostatic breakdown. If high voltage is again applied to an LED in this condition, current flows first to areas with high conductivity and the resulting heat causes vaporization in those areas so that the p-n junction very rarely recovers.
Dead LEDs are another common problem where certain sections or individual LEDs on the strip stop working. This could be due to a weak connection, manufacturing defects, or improper handling that may have caused physical damage.
Reverse polarity has the potential to cause damage to the internal components of your fixture. Without a fail-safe, the fixture would become hotter than normal operating temperatures and would eventually burn. Some electrical components also have the potential to explode when connected backwards.
Flickering and dimming issues with LED lighting can be a concern for users. Low quality LED bulbs and drivers are more likely to experience flickering issues. Problems can also occur in high-quality lights if mistakes are made in the installation process. Another cause for this issue is loose electrical connections.
Unlike incandescent light bulbs, LEDs don't produce light using heat. This is part of what makes them so energy efficient. The downside is that their components can be sensitive to overheating, which can cause them to burn out prematurely.
They also emit less heat than these other types of lighting, making them safer for use in spaces where there is risk of fire. More importantly, LED doesn't get hot enough to be able to ignite anything and they have significantly lower temperature than their counterparts.
It is claimed that LEDs has a wide range of suitable temperature from -30 °C to 60 °C and the optimal temperature for LED lighting is 25 °C. High ambient temperature will degrade the efficacy of LED lighting performance, resulting lower power conversion from electricity to light.
Testing LED lights is simple with a digital multimeter, which will give you a clear reading of how strong each light is. The brightness of the LED while you test it will also indicate its quality.
Over time, this filament gets hotter, weaker and eventually burns out. LEDs, however, do not contain a filament and instead illuminate using a semiconductor. So instead of just instantly burning out like traditional bulbs, LED lights age over time and progressively get dimmer until they stop working altogether.
One common reason LED lights may not turn on is due to a faulty power source. Please check if your LED lights are plugged in and that the power source is functioning normally. Additionally, check the power cord for damages or loose connections. Another reason LED lights may not turn on is due to a faulty LED bulb.
But LEDs are only worth the investment if they hold true to their performance promises. A lamp that boasts an energy efficiency increase of up to 90% compared to other lighting options isn't beneficial if it doesn't function. When it comes to LED lamp failure, the industry standard is 3%.
Most LED EOS and ESD failures occur due to thermal damage, metallization damage, contact damage, or junction damage. Metal melting commonly is observed due to an EOS, ESD-HBM (ESD-Human Body Model) event.
The driver may fail due to overheating, short-circuiting, or poor quality components. LED Lights can last decades, but only if they have a good LED driver. See our How LEDs work section for more about general LEDs.
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