Marc Dyble, product marketing manager of SSL products at Osram Opto Semiconductors discussed the potential of mixing monochromatic LEDs with phosphor-converted LEDs (PC-LEDs) to realize high CRI and high effect at the same time. He presented this approach at the LED Lights Show in Las Vegas last week.
Dyble said that color mixing, marketed as Brilliant Mix by Osram Opto, provides an alternative method of attaining high CRI for applications such as high-end retail. He explained that typical approach today to attaining warm/neutral white light with LEDs and high CRI (>90) comes with a lose of lighting effect in the 75 lm/W range. Instead, if a combination of monochromatic LEDs (amber) are placed alongside phosphor-converted blue LEDs either in a multichip chip-on-board or multichip array, lighting effect in the 90 lm/W range (up to 110 lm/W at the LED level) can be obtained at 2700K.
Dyble explained that there are some precautions to taking this approach. For instance, an optical mixing chamber may be required to obtain the necessary color consistency. In addition, the correlated color temperature (CCT) over temperature may differ. To improve stability, light and temperature sensors can be installed and compensation circuitry can be implemented.
However, Dyble argues that a color mixing approach should definitely prove better than methods that overdrive the LEDs and lead to early lighting failure. In addition, from a user standpoint a balance can be made between lighting effect and color rendering by adjusting the monochromatic to PC-LED driving ratio. “One of the reasons we’ve been able to do this is because we’ve been able to linearize the lighting effect of monochromatic LEDs,” said Dyble.
He added that currently Osram Opto and Cree have cross-licensing agreements in the area of color mixing.