Philips has once again created an LED-based retrofit lamp with a novel shape that still delivers an omnidirectional beam that the company expects to win Energy Star certification. The design looks somewhat akin to a doughnut on top of an Edison base although there is only a flat area rather than a whole in the center of the doughnut. The solid-state lighting (SSL) design enabled a new approach to thermal management that does not rely on a visible metal heat sink.
The dimmable 10.5W SlimStyle LED lamp delvers 800 lm, making it equivalent to a 60W incandescent lamp. The lamp features a 2700K warm-white CCT with a CRI of 80. That level of color rendering is typical of LED lamps as we recently reported based on a US Department of Energy (DOE) Caliper report on A-lamps.
While the 80 CRI is acceptable in the Energy Star program it will not qualify the lamps for the more stringent Voluntary California Quality LED Lamp Specification that requires a CRI of 90. Moreover, some lighting professionals believe that consumers will find that 80-CRI LED lamps fall short of delivering an incandescent-like experience just as compact fluorescent lamps (CFLs) have failed to meet consumer expectations.
Philips has yet to reveal pricing for the new lamps, in part because the launch partner Home Depot will have a say on the retail price. The company has said earlier this year, however, that it would deliver a sub-$10 60W equivalent lamp by the end of the year. The lamp is due on Home Depot shelves January 2, 2014.
The likely key to a low price and minimal thermal management is the use of mid-power LEDs in the lamps. Those LEDs are operated at lower drive currents and therefore the junction temperature in the LED remains lower than in designs that use high-power LEDs. A lower junction temperature means that less heat has to be conducted away from the LEDs.
Still, there is clearly some innovative thermal design in the lamps, and indeed that implementation may not be the cost saver that some sources are reporting in news accounts. Thermoplastics aren't necessarily cheaper than metal heat sinks, and the new Philips design uses some type of thermally conductive material to draw heat toward the flat center of the lamps where it can be dissipated into the air.
Philips has rated the new lamp for 25,000 hours of life. That projection is lower than some other lamps on the market. The use of mid-power LEDs may play a role in that rating because the lower-power devices are often packaged in plastic packages that can cause degradation more quickly than in higher-power LEDs packaged on a ceramic substrate.