LED Lighting Depends On Drivers

Figures indicate that widespread use of LED lighting by 2027 could save the equivalent electricity of that produced annually by 44 large electrical power plants, worth $30 billion based on today’s electricity prices. One fifth of global electricity is used in lighting, producing 1.9 billion tons of carbon dioxide (CO₂) annually. To put that into context, that’s 70% of the world’s passenger vehicle CO₂ output and 6% of global greenhouse gas emissions, so the potential for energy savings is immense.¹

LED lights and drivers continue to be among our most rapidly developing technologies with new innovations emerging on an ever-rolling production line (see “LEDs: In The Beginning”). White LED efficiency has already increased by a factor of 10 since 2000. By 2020, the U.S. Department of Energy (DoE) estimates that commercial LED lighting efficiency will be as high as 258 lumens per watt, or two and a half times as efficient as today’s fluorescent lamps, resulting in 90% energy savings. By then, the cost of LEDs will fall by 80% and global penetration will be 60%. In fact, the DoE believes that no other lighting technology offers the United States so much potential to save energy and enhance the quality of its built environments.

Shops, offices, factories, warehouses, art galleries, schools, and museums are just some on a long list of private and public spaces offering a massive potential market for the new technology. A significant proportion of that market will be retrofit rather than newly built, as 80% of the buildings that will be in use in 2050 have already been constructed.

LED lights are nothing without an LED driver, yet not many people are aware of drivers and how vital they are in providing the variable and highly adaptable range of lighting designs now offered. LED drivers are the interface between the fittings and the main power supply. Every lighting solution requires a unique driver design, and rapidly evolving driver technology is providing ever more comprehensive options to provide energy savings, definition, ambience, or old-fashioned wow factor.

What’s Not To Like?

The initial cost of installing LED lighting is higher than traditional technologies, but energy and maintenance cost savings cancel that out very quickly. They cost less over the life of the system and provide a better, brighter quality of light. Also, exchanging incandescent bulbs for new LEDs can reduce a building’s carbon footprint from lighting by 85%.

LEDs have an average lifespan of over 100,000 hours, the equivalent of 11 years of continuous operation or 22 years at half power. That’s and more than 10 times longer than any other light source currently on the market. LED lifetimes are rated differently from those of conventional lights, which go out when the filament breaks. An LED’s typical lifetime is defined as the average number of hours until light falls to 70% of initial brightness. By dimming over time in contrast to the abrupt failure of traditional bulbs, operators can replace the fitting before the lights go out, which is an advantage in safety-critical environments.

LEDs emit more light per watt than traditional light bulbs, which is where the energy savings come in. In addition, their efficiency is not affected by shape and size, unlike fluorescent light bulbs or tubes. Conventional light bulbs waste most of their energy as heat. For example, an incandescent bulb gives off 90% of its energy as heat, and a compact fluorescent bulb wastes 80% as heat. LEDs remain cool.

This obviously leads to additional savings in air conditioning. Cool LEDs lend themselves particularly well to the theater where hot stage lights can cause problems for actors, as well as to operating theaters where, again, being in the spotlight doesn’t necessarily require higher temperatures. Furthermore, LEDs give off light in a specific direction and are up to eight times more efficient than incandescent and fluorescent bulbs, which waste energy by emitting light in all directions.

LEDs light up very quickly and can easily be dimmed either by pulse-width modulation or by lowering the forward current. In addition, they don’t use lead or mercury, so they’re kinder to the environment. And since they don’t have any glass components, they aren’t vulnerable to vibration or breakage like conventional bulbs. LEDs are therefore well suited for use in areas like sports facilities and high-crime locations.

The Heart Of The LED

LEDs offer huge benefits. But to ensure optimum energy efficiency, reliability, and durability, they need the support of dedicated control gear. LED drivers play an important role in the overall design of lighting by regulating the power output. The main task of an LED driver is a constant light output, meaning a steady power supply to the LEDs, despite possible power variations (Fig. 1).

Ultimately, efficiency and durability are tied not only to the LEDs themselves but also to the drivers that operate them. At their simplest, drivers take the input current and input voltage and then reconfigure them for use by an LED. In that sense, they are a lot like the ballasts used for decades in fluorescent lights.

Drivers are key in enabling market growth for LEDs in several ways. Innovations in design are allowing products to do more with less by improving the overall efficiency. Yet there is a misconception that driver technology is static and standardised. The reality is that there is no such thing as a “universal” LED driver. Every application requires a unique driver design, and the quality of the driver has a significant effect on the performance of the LED.

A range of factors determines the type of LED driver required, including the type and quality of LEDs being installed, whether they will be placed individually or in series strings, whether there are size limitations, and, ultimately, the main design goal of the installation.

Today’s drivers come in two versions, constant current and constant voltage, with a number of variations. In simple terms, constant current drivers tend to be used when one driver is required per light fitting. The current will remain the same, whatever the number of LEDs in the fixture. Constant voltage drivers are best for applications where the user requires flexibility with the number of luminaires connected to one power supply. As lamps are added, the current will increase to the maximum limit.

Dimming

With the overall design goal in mind, another important lighting concept is the availability of dimming functions. With dimmable drivers, LEDs can be used to create a certain ambience or to highlight certain features. In addition, dimmable drivers allow for further energy savings to be achieved as they work on the premise that the human eye struggles to distinguish between LED lights that are on at 100% and those that are on at 90%. 

It is a common mistake to think that dimming lights will result in a loss of energy. The opposite is actually true. Although the driver efficiency will reduce a little as the LEDs are dimmed, overall significant energy will be saved. Also, dimming lights to half power can greatly extend the lifespan of LEDs, decreasing maintenance costs.

LEDs usually can be dimmed between 100% and 5%, or even lower, and are controlled by a phase dimmer switch, Digital Addressable Lighting Interface (DALI) controller, or 0-10V controller. DALI is widely recognised as the leading intelligent dimming protocol for LEDs. DALI drivers let users program their LED installations using digital signals to send control information to each light. Users then can set different lighting and ambient levels for displays, maximizing their investment.

Analog 0-10V drivers offer a less costly and more basic dimming solution to the DALI digital protocol. They can be easily programmed with a simple passive controller or a fixed or variable resistor. These controls use voltage input to manage the intensity of the light. For example, lights would be on at 100% at 10 V. At 5 V, lights would be powered at 50%. And at 0 V, lights would be off.

Two main dimming protocols typically use a phase control dimmer switch: triac (leading edge) and trailing edge. Triac is the cheapest and most common method of dimming, but it generates an undesirable amount of electromagnetic interference (EMI). Trailing edge dimming is more expensive than TRIAC but produces much less EMI.

The Results Are Clear

LED lighting gives off a better, brighter quality of light. Used with the right kind of driver, it also can provide a highly adaptable and flexible lit environment using an array of color temperatures and profiles. An expert lighting consultant is as important as a good builder.

In the workplace, good lighting can have a positive influence on health and wellbeing. On the factory floor, better lighting improves performance. Studies show that increasing light levels from 300 lux to 2000 lux improves productivity by 8%, increases task performance by 16%, and reduces rejects by 29%. It also makes a positive contribution to safety, reducing accident rates by 52%. Absenteeism and general health are also improved. The quality of lighting in a workplace can have a significant effect on productivity. With

In the workplace, good lighting can have a positive influence on health and wellbeing. Enhanced lighting allows workers to concentrate better on their work, which in turn increases productivity and improves performance. Studies show that good lighting can lead to a 10-50% increase in productivity and decrease errors by 30-60%. It also decreases eye-strain, headaches, nausea, and neck pain.²

In retail, clever lighting choices can subtly influence our buying decisions, and LED lighting provides the flexibility to highlight products and save energy where it is needed less. Leading U.K. retailer Next plc recently announced the rollout of 110,000 LED luminaires across its stores. Luxury car manufacturer BMW is also in the fast lane, having already installed LED solutions in a number of showrooms including its prestigious premises in Rome, Italy (Fig. 2).