Back in mid-December, Toshiba announced that it was entering mass production of LEDs using a 200-mm (8-in) silicon substrate or so called gallium-nitride-on-silicon (GaN-on-Si) technology. The company has now published data sheets for the initially available products revealing a 3000K LED, a 4000K LED, and two 5000K LEDs.
|Toshiba TL1F1 GaN-on-Si LED|
At the time of the announcement, Toshiba didn't specify efficacy, forward voltage, CRI, or other characteristics of the LEDs, although we speculated on the particulars and were fairly accurate. The cool-white TL1F1-NW0,L 5000K LED with a CRI of 70 offers the best efficacy of the new products.
Toshiba characterized the LEDs at 350-mA drive current. Based on the typical forward voltage of 2.9V, the TL1F1-NW0,L delivers 110 lm/W. The 5000K TL1F1-NW1,L drops to 94 lm/W with a rise in CRI to 80. Both the 4000K TL1F1-WH1,L and 3000K TL1F1-LW1,L deliver 84 lm/W. And both offer a CRI of 80.
Those efficacy values will certainly vary. SSL designers will likely consider the worst-case forward voltage of 3.6V when developing products. That consideration would make the top efficacy of the cool-white LED drop to the 90 lm/W range. The minimum forward voltage is 2.8V.
The data sheets also reveal maximum ratings for the new LEDs. The devices can take as much as 800-mA of continuous drive current or 1A when pulsed. Power dissipation maxes out at 2.9W. Operating the devices at maximum power almost doubles the luminous flux output.