LED-based retrofit lamps remain the most popular topic in the solid-state lighting (SSL) industry, despite the fact that a form factor such as the A-lamp does little to support the inherent advantages of led bulb sources. Still, the huge number of retrofit-lamp sockets installed around the globe make the retrofit lamp important to both lamp manufacturers and users looking to proliferate SSL technology and save energy. And while the basic size and type of socket may be fixed, manufacturers are taking vastly different approaches to try and win in what could be a short-lived market.
Many of the lamp-design topics we will discuss here could be examined relative to many different types of retrofit lamps. The potential list includes LED-based led tube designed for linear fluorescent sockets and directional and reflector products such as PAR, MR, and BR lamps. In this article, however, we will focus on omnidirectional A-lamps that are the most prevalent lamp in use.
You need look no further than at a list of the most popular articles on the LEDs Magazine website for 2012 for proof of the appeal of the topic at hand. More than 25% of the top 20 list had a retrofit lamp focus.
But ironically, the opportunity for companies to sell retrofit lamps is inherently limited. Socket saturation will occur fairly quickly. As we’ve reported previously, outspoken Tempo Industries CEO Terry Walsh predicted saturation within five years at The LED Show led display last summer.
Saturation will happen for two reasons. First, demand will drop as long-lasting LED lamps become predominant and don’t need to be replaced often. Second, purpose-built SSL luminaires will make much better use of LED sources and will become increasingly popular even in residential applications. For all of those retrofit-lamp startups out there burning through venture money, the message had better be get to market quickly. And for companies such as Philips Lighting, that may have invested more than anyone in retrofit lamp development, good job but get your money back in a hurry.
In actuality, there is still a huge opportunity. In a report issued in April 2012, Strategies Unlimited reported that there were $2.2 billion in LED-based retrofit lamps sold in 2011. The report projects 30% annual growth through 2016. But saturation could happen shortly after the 2016 timeframe.
Lamp design
Having covered the market a bit, let’s transition to a discussion of the products and design approaches. We will start with Philips because of the noted success the company has had including with the US Department of Energy (DOE) L Prize winning lamp and the latest change to their design approach.
Philips has built retrofit lamps using a number of approaches, but is probably best known for the remote-phosphor-based designs that have a yellow or orange tint when powered off. As we covered in a recent contributed article, remote-phosphor designs that combine very efficient blue LEDs with phosphor on a secondary optic, provide an efficacy advantage over designs that use phosphor-converted white LEDs. Moreover, remote phosphor can provide more consistent color maintenance because the phosphor is not subject to the heat generated by the LED, and therefore doesn’t shift in color over time.
The Philips remote-phosphor design was first revealed several years back when the company announced their entry into the L Prize competition for a 60W-equivalent retrofit lamp. The company first commercialized the technology in the lamps sold under the EnduraLED and Ambient LED brands in different parts of the globe. Later, the company commercialized the L Prize winner that had to meet higher standards than the Energy Star-compliant EnduraLED products.
