Product How-To: LED arrays are establishing themselves

In the past, single-chip LEDs — also called SMD LEDs — dominated the LED lighting market with performances of up to approximately 3 W. The maximum brightness of single-chip LEDs under real-life conditions is limited to approximately 400 lm for purely physical reasons. As a consequence, many conceptual approaches to illuminants and lighting fixtures are based on the use of multiple surface mount (SMD) LEDs. However, there are considerable disadvantages to this approach, as many applications today demand greater levels of brightness. Sharp, on the other hand, from the early stages on pursued the concept to assemble LED-based illuminants as a matrix of LED dies, and introduced the first multichip LED module as early as 2007 under the name Zenigata. Based on this array concept, Sharp today offers a portfolio of two LED module families in all performance classes and color temperatures (CCTs), with levels of brightness of nearly 7,000 lm. This approach is progressively establishing itself.

Multichip LED modules for a simpler, more flexible lighting design
The brightness of individual single-chip LEDs is not sufficient for many applications, which forces lighting designers to house multiple SMD LEDs in one lamp assembly — a design compromise that limits the creative range in the design of lighting fixtures considerably. Multiple SMD LEDs require a considerable amount of room, particularly determined by the control and cooling elements of the individual SMD LEDs. Furthermore, a multipoint light source requires a complicated optical system to appropriately focus and direct the light, which inevitably leads to multiple shadows.

At this point, LED modules present an effective alternative to the use of multiple SMD LEDs in achieving the necessary brightness. Modules — also called arrays — are easily scaled in their brightness via the number of dies, due to their being made up of a multitude of smaller LEDs. Moreover, the arrays have caught up with high-power single-chip LEDs by now in terms of light output.

Sharp combines up to 170 dies in one array in its LED modules. The highest-performing modules nearly reach 7,000 lm — a brightness which can otherwise only be achieved with multiple SMD LEDs. And the dies of the Sharp arrays are so tightly packed together that they result in a homogeneous, very compact light-emitting surface (LES), which may be set up in a circle or a square, depending on the module type. The 50 W Mega Zeni array ( 2700K, CRI type 83), for example, has a LES of only 176 mm², which puts it among the most compact modules of this performance class currently on the market. Within the Mega Zeni product family, all LESs are of the same size, which means the modules have identical emitting angles and are completely compatible with each other mechanically.

Thanks to the array approach, Sharp can offer a comprehensive portfolio of finely graduated performance classes: The family of the Mini Zenigata includes modules with 4W, 7W and 10W, of up to 1,400 lm and an efficiency of up to 106 lm/W. Their big sister models of the Mega Zenigata line achieve up to 4770 lumen, an efficiency of up to 105 lm/W. They are available in performance classes of 15W, 25W and 50W. Furthermore, the Mega Zenigata modules exist in two different CRI classes — one with values of up to 80 and an ultra high color rendering version with values of at least 90. The Mega Zenigata arrays can also be operated with higher currents under certain circumstances, so that the highest-performance modules achieve a luminance of almost 7,000 lm depending on color temperature and CRI value.

The compact design of the Sharp modules results in similar optical characteristics as those of high-performance, single-point light sources, and therefore the same advantages over the use of multiple SMD LEDs: no forming of multiple shadows and a clear, simple design of secondary optics and cooling elements. They are particularly suited for the design of spot and downlights. Because of their mechanical and optical compatibility, the Mega Zeni modules by Sharp can be the basis for a whole series of lights and lamps with different levels of brightness, but identical reflectors, lenses and housing shells.