Is A High-Power LED The Best Choice For Your Application?

Feb. 16, 2012
A few considerations can eliminate the gray area in your design choices.

Fig 1. Single 1-W LEDs can serve as high-power, high-brightness devices.

Fig 2. Certain LED applications fall into a gray area where low-power and high-power components both can fit the bill. However, choosing which one to use requires more consideration.

Developments in high-power LEDs represent one of the most significant innovations to hit the lighting industry in recent years. Loosely defined as LEDs with at least a 1-W capacity, high-power or high-brightness LEDs have invigorated the industry by offering unparalleled benefits in lighting performance, energy efficiency, durability, and cost savings.

But while these benefits have been rightfully celebrated in industry publications and reflected in the rapidly expanding high-power catalogues of top LED manufacturers and leading suppliers, high power isn’t necessarily the best choice for every light technology application. In fact, standard LED technology can provide comparable brightness performance in many situations while generating significant cost, design, and performance benefits.

Standard Versus High-Power LEDs

To illustrate how a standard LED array can provide significant design process, cost, and real-estate savings compared to a high-power LED, consider a theoretical application that requires 90 lumens of light output or brightness. This brightness can be achieved by using a single 1-W high-power LED or an array of six standard LEDs (Fig. 1).

The design process required for a standard LED array can be far simpler than that required for a high-power technology because of greatly simplified thermal-management considerations. In our example, the 1-W LED will be driven at 350 mA of current compared to just 120 mA of current for the array of six standard LEDs.

The high-power technology will require a heatsink and metal-core printed-circuit board (MCPCB) to ensure the junction temperature isn’t high enough to cause a loss in efficacy, a decrease in life hours, or color degradation. Standard LEDs don’t require heatsinks, an MCPCB, capacitors, or resistors, so they’re easier to design, test, and manufacture. This simplified process not only saves time and money during the manufacturing process, it speeds up time-to-market as well.

Cost Savings

The thermal management needs of a high-power LED can add significant cost to the LED. The most costly design addition is the heatsink, which can be made from a variety of metal materials from relatively inexpensive aluminum to more conductive but also more expensive materials such as copper and silver. These expensive materials can add between $1 and $10 to the cost of the high-power product, a cost that isn’t applicable to standard LED devices.

Similarly, high-power LEDs also require the use of an MCPCB to serve as another passive cooling technique for controlling junction temperature. These boards dissipate heat more efficiently than the more affordable FR4 PCBs used with standard LEDs because materials in MCPCBs have better thermal conductivity. However, they can be up to five times more expensive than the FR4 PCBs. The ability to use a more affordable FR4 PCB, eliminate the need for an expensive heatsink, and simplify design considerations can lead to cost savings up to 60%.

Real Estate Savings

Finally, when there are significant internal space limitations in a device, a standard LED will again often be the best choice. As mentioned, high-power LEDs require the addition of heatsinks, a bulky cooling technology overall. Their primary task is to create more surface area to be cooled by convection and radiation. A larger surface area can help reduce heat more effectively, but it also adds bulk to the high-power LED, which can create design obstacles in smaller spaces and smaller products.

Standard LED arrays also often do not require the space-consuming drivers, capacitors, and resistors needed by their high-power LED counterparts, allowing for real estate savings to reach as high as 50%. For applications with limited space, an array of standard LEDs can provide the same brightness as a high-power LED with significant real estate savings.

Application demands

So how is it possible to figure out if a high-power LED or some combination of one or more standard LEDs is more suitable for a particular application? For some designs, the choice is clear.

Smaller, battery-operated, or portable devices such as consumer electronics, accent lighting, and standard indicator lights have long used standard LEDs and will likely continue to do so. Along the same line, some areas will continue to use high-power LED technology including general outdoor lighting, large area indoor lighting (track lighting, bulb replacement), and automotive forward lighting.

Other applications, though, fall into a gray area and may take careful consideration, such as small-space lighting like glove compartments and cabinets, interior and exterior signage, dental and medical devices, and industrial control status indicators (Fig. 2).

Out Of The Gray

LED makers can help their clients find a fruitful way out of the gray area and select the technology that’s right for them. For example, a leading appliance manufacturer was working on lighting for the inside cabin of a refrigerator. The original design required three high-power 1-W LEDs to meet a specific brightness level.

Lumex provided an alternative solution by offering an array of 18 standard high-brightness 5-mm LEDs with special lensing. By making this change from three high-power LEDs to the 18 standard LEDs, the appliance manufacturer realized a 50% cost savings with no excess heat generation within the refrigerator.

Sometimes high-power technologies are the best fit for these gray areas. Another client, a supplier of calibration monitoring systems, approached Lumex to analyze the efficiency of its existing 3- by 3-in. board, which uses 36 1/4-W, standard surface-mount LEDs. A custom designed solution replaced the 36 1/4-W LEDs with nine 1-W high-power components without changing the power requirements. Despite the need to add a MCPCB, the new technology still generated 25% cost savings and 15% real estate savings.

Making The Right Choice

The best way to make the right LED choice for your product is to speak with your supplier, who should have a wide catalogue of both standard and high-power LEDs. Rather than pushing you toward a particular cookie-cutter technology, the supplier should take the time to truly understand your unique technology needs and specific application requirements.

A quality supplier then will create a customized solution by asking questions to ascertain what minimum/maximum intensity output is needed, how much power will be available, the ideal cost range for the overall system, the internal space restrictions, the size of the area to illuminate, where the product will be used, and the general operating temperature. Thoroughly exploring these criteria will help you decide if a standard or a high-powered LED solution is more suitable for your application and if it can have a significant impact on the success of your product design and the bottom line.

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