What is CLO in lighting?

what is clo in lighting

Nowadays, you can find more people interested in light sources that offer energy savings due to the increasing energy regulations related to light-emitting diodes or LEDs and their power supplies. This innovative source also brought another important element to the market, CLO or Constant Light Output which provides an interesting solution for the environment and your budget.

In this blog post, you will learn a little bit more about CLO and its relation to lighting.

What is CLO in lighting and Why CLO?

CLO is a system that compensates for the light depreciation in a LED helping it maintain a constant light level and extend its lifetime.

If you’re not familiar with any of these words, we’ll go through each of them right now. First, let’s remember that a LED produces light when an electric current passes through a semiconducting material that we know as the diode which emits photons creating the light we see.

Each LED bulb emits a certain amount of light which is all the visible light that you can see when you turn it on. This measurement is the luminous flux which you might also hear as lumen or LM (its physical unit). However, this brightness doesn’t last forever since the luminous lux decreases after some time when the LED uses its diodes which leads to the light depreciation process.

light process
 Light depreciation process

This is when CLO makes its entrance, lighting designers came up with the idea of creating a programmable drive that will compensate for the light depreciation since this one has an almost linear process in a diode’s service life. It basically helps the LED to last longer and gives you an idea of when it’s going to stop working.

Take into account LED lights don’t depend on heat to produce the photons (light), they are actually cooler making them safer and more energy-efficient than conventional bulbs.

the led street lamp01 1
LED street light application

Creating a predicted light depreciation is a great breakthrough in LED technology which proposes better environmental conditions through an algorithm. Yet, this algorithm can vary depending on the time rate and current values which will directly affect how the CLO will maintain the luminous flux over time. It’s useful to have an accurate lifetime prediction to avoid components failing. Luckily, the diversity of LED drivers allowed the creations of methods that can give you effective results.

energy efficient
CLO curve

What is an LED driver with CLO?

A driver with CLO is basically a power supply that is able to keep a constant light level after you program it to compensate for the light depreciation of your luminaire. You might know a little bit more about CLO, but you should also take into account that is not the only element within a LED driver. It’s part of the parameters that you can add when having a LED with programmable features.

clo curve
CLO Curve
LED driver with CLO function

Programmable LED drivers

They are drivers that provide flexible features in LED’s functions. The increasing energy regulations have pressured lighting designers to create more innovative and practical products. However, there were still many variables they couldn’t control, and that’s when the programmable LED drivers arrived in the market.

These drivers work as a self-contained power supply that LEDs need to regulate the power they require. Take into account that diodes they emit have low energy consumption, therefore, it’s better for them to have a specialized power supply.

by nfc
Program the LED drivers through NFC

Programmable drivers became popular right away offering a product that didn’t need that much inventory and that also had the option of turning the driver’s output over time. Maintaining the constant power output was important as well so designers created the main attributes to the programmability allowing the driver could match with the user’s luminaires.

Some of the parameters that accompany CLO start with the output current which describes the maximum current you should use in your LED. Then, we have the dimming mode which is crucial to lowering the brightness of a light. Users program this mode along with the timer dimming that controls the speed of the LED while switching. Finally, we have the NTC (Negative Temperature Coefficient) and the Thermal protection which help detect over-temperature situations.

clo mode
CLO setting interface

Benefits of LED Driver CLO

You now understand that CLO is part of the main elements that make a LED driver more efficient. It’s the result of an optimization to look for sustainable facilities that focused on reducing over-illumination. This idea led to fewer luminaires, hence less installed output reducing energy consumption Overall, adding CLO to your LED driver has many advantages such as:

  • Luminaires won’t have over-illumination
  • It reduces operating costs
  • It doesn’t have a significant environmental impact
  • It offers a consistent light level which prolongs the products’ lifetime.

Using CLO allows you to estimate the light degradation process using a method where the system uses a report of over LM80 and its data that LED manufacturers usually give. After a few math calculations, the CLO is able to process an exponential regression has the values of 6,000 operating hours which give you the light degradation five or six times its useful life.

How to set LED Driver CLO

The LED gets a constant luminous flux that the programmed driver supplies compensating the diodes’ light depreciation. Yet, these diodes can meet a variation in light level causing lighting designers to create a system that could calculate the estimate of light depreciation. Thankfully, setting CLO is a very simple process. First, you have to know that you can program an LED driver by many methods; By Near Field Communication (NFC) programming, cable, potentiometers, and cellphone.

In this case, we’ll focus on setting CLO by NFC, this is not an isolated action and you should do it along with the other parameters. For example, you should first choose PWM dimming and select the current after you open the software and connect it to your computer. Then, you should select the time dimming bottom which will allow you to set the dimming curve


CLO or Constant Light Output works as a function in some luminaires which compensates for the drop of a LED’s luminous flux. It basically powers the bulbs so it has more hours of service life to almost 50 or 80% of its initial luminous flux. CLO is useful to reduce the environmental impact of the luminaires as well as the operational costs.

You can send us a message if you still have doubts about CLO.

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