LED and Dimmers

LED-based lighting offers many potential benefits such as energy saving, longer product life spans and new fixture options that enable them to be used in almost any application. An Ecobelle 10W LED light bulb can replace the light output of a 60W incandescent lamp, deliver a useful lifetime averaging 17 years (based on 4 hours a day, i.e. 25,000 hours), reducing users overall carbon footprint.

Despite the growing popularity of LED lighting sources the technology comes with challenges associated with using LEDs to meet customer expectations. Issues with compatibility tend to be the greatest source of frustration among specifies and their customers. Therefore it is imperative that LED lamps, drivers and controls are properly specified to maintain a high level of expected performance.

Why worry about dimming your LEDs?

The dimming of lighting is typically considered to maximize energy savings, extend system life, enhance flexibility, increase productivity, and provide a safe, comfortable environment for building occupants. To achieve this, a wide range of controls are available – from a single switch dimmer to a centralized lighting control system – that provide maximum flexibility.

Regardless of the control system, it is critical to work with a brand who can guarantee compatibility and performance eliminating many of the common concerns and issues that are seen with LED installations.

There is a broad spectrum of LED lamp and fixtures manufacturers, and not all of them are familiar with the various control types available, with not all controls being equally reliable. Dimmers and dimming systems that are specifically designed for use with LED sources will typically perform better than those designed to control incandescent sources.

If all factors are not considered when choosing LED bulbs for certain fixtures, the resulting outcome can be dimmable products not working as claimed and produce the following issues:

  • Never turning off completely
  • Flickering effect as a result of voltage fluctuations (applicable when multiple appliance are being used on the same system
  • Drop-out – when lights turn off before the dimming slider on the switch reaches the lowest setting
  • Pop-on – when lights do not turn on after being dimmed to the lowest setting and only turn on when the dimming slider is moved up to a higher setting

Considerations when using LED Dimmed Lighting

Carefully consider the following six issues to effectively align customer expectations with LED dimming system performance.

  1. Application type – retrofit or new construction?

    New construction enables you to use a variety of control options best suited to your objectives, while retrofit applications are often limited to certain applications. Defining the application will determine how to think about the other factors in an LED-based lighting and control system. To ensure your system compatibility with Ecobelle products, please visit the Info Hub on the Ecobelle website, where you can access continuously updated information regarding dimmable LED bulbs and their compatibility with the dimmer manufacturers.

  2. LED product type – lamp or fixture?

    LED lamps are designed to replace traditional light bulbs. The bases of these bulbs have integral drivers that determine whether they are dimmable (Fig. 1). LED fixtures can vary from cove lights to down lights and usual have an external driver. Some fixture manufacturers offer different driver options (Fig. 2) on the same fixture to support different control technologies or applications, i.e. dimmable or non-dimmable.

    Fig 1. Overview of an LED lamp


    Source: Illumination in Focus Spring 2013 Edition

    Fig 2. Overview of LED fixtures


    Source: Illumination in Focus Spring 2013 Edition

  3. Dimming range

    Not all LED products are created equally. It is important that you select products that match specific purposes. For example, using a product that has a dimming capability of 20% would not make sense for a media room, but may be more appropriate for an office space.The dimming functionality of an LED bulb is purely reliant on the driver type used for that particular lamp. Choosing the right dimming control will allow you to reduce undesirable effects (outlined earlier).

  4. Dimming performance

    Generally, the experience with dimming traditional light sources is smooth and continuous, with no abrupt change in light quality as the light source is dimmed. To replicate this smoothness, ensure your LED products incorporate high quality drivers from reputable brands.

  5. Amount of fixtures/bulbs

    Applying LED loads to incandescent dimmers may impact lighting performance and damage product life span. It is important to remember that all dimmers are rated for a maximum load (in volts, amps, and/or watts) that must not be exceeded.

    It is not as simple as dividing a 500W dimmer by the 10W LED bulb you have chosen to determine that 50 lamps can be used on the circuit. For example, each 10W LED bulb may only draw a continuous wattage of 8W, but may have a startup inrush current or repetitive current during every half life cycle that makes it appear much worse (Fig. 3)

    Fig 3. An example of relationship between inrush voltage and current


    Source: Illumination in Focus Spring 2013 Edition

    Similarly, some LED drivers may not perform well if they are required to control a very minimal load. It is usually fairly easy to meet the 25-40W minimum load requirement with incandescent bulbs, but not so easy with LEDs. Users may need four or more bulbs to meet predefined fixture requirements.

  6. LED control type compatibility

    A variety of controls are available, i.e. high and low voltage control systems, wireless, etc., but it is important to consider specific systems that are best suited for LED. With the increased usage and preference for more efficient lighting substitutions, it is becoming more common for applications to move away from control choices used for tradition incandescent loads. Therefore, becoming educated on the types of controls available, such as 0-10V, forward (TRAIC based dimmer) or reverse phase (Trailing Edge Dimmers), EcoSystem, or others, will be necessary to ensure appropriate pairing of products and fixtures.

Dimmers that are not suited for LED

One of the biggest challenges LED lighting designers face is the dimming performance of their LEDs with TRIAC (Triode for Alternating Current) based dimmers, sometimes called leading edge dimmers. In many cases, this causes flickering and reduced dimming range when compared to incandescent lamps.

The problem with TRIAC based dimmers is they are designed for incandescent, which operate at higher power levels. When the dimmer interacts with the low current and non-reversible nature of LEDs the TRIACs tend to intermittently turn on and off, creating a flicker. In addition, the low current designed LEDs typically fall below the minimum load requirement of TRIAC based dimmers, which can cause a flickering effect and/or a limited dimming range.

Solutions

Although there are multiple methods that attempt to resolve this issue, many LED driver manufacturers incorporate bleeder and damping circuitry into the LED drivers and controllers to ensure currents equalize, overcoming the previously stated TRAIC based dimming challenges. But, for an overall increased chance of compatibility, trailing-edge dimmers (reverse phase dimmers) typically are better suited for compatibility with the captive load of an LED driver.