Power Electronics

LEDs Proliferate As Design-Ins in Lighting Systems Increase

According to the NPD DisplaySearch Quarterly LED Supply/Demand Market Forecast Report, the penetration of LEDs in lighting will reach 16.8% in 2015. The report also found that spotlights and LED street lights will gain higher penetration in lighting due to government incentive programs. Manufacturers of LEDs, as well as related parts such as LED drivers and power supplies, are responding wth a pletheora of new products.

Following are recent LED lighting system product introductions that indicate trends in the LED lighting industry.

One of the most active U.S. LED manufacturers, Cree, Inc. now delivers a new dome lens and universal driver with dimming options (Fig. 1). The new lens enables up to a 5% increase in system efficacy compared to the standard lens and delivers a hemispheric light pattern. Cree LMH2 modules enable true 50 W and 70 W ceramic metal halide LED replacements and support an expansive range of lighting applications, including downlights, wall sconces, pendants, flush-mounted, spot, track and ceiling fan lights.

The LMH2 module is also now available with a 120-277V universal driver with 0/1-10 volt dimming capability. The extremely versatile and modular LMH2 LED offers a range of lumen, color temperature, driver and beam shape options in one common form factor - enabling lighting manufacturers to quickly customize their applications and speed time-to-market.

Optimized with the new hemispheric beam shape of the dome lens, the drop-in ready LMH2 delivers up to 80 lumens-per-watt system efficacy combined with 90+ CRI. Featuring Cree TrueWhite® Technology, the new LMH2 module is available in 2000 and 3000 lumens and delivers more than 95 lumens per watt at the light source. The module is available in color temperatures of 2700 K, 3000 K, 3500 K and 4000 K. Designed for 50,000 hours of operation and dimmable to five percent, the LMH2 comes with Cree’s warranty. The LMH2 light source is also UL-recognized and complies with multiple international regulatory and safety standards. Luminaire makers seeking ENERGY STAR® qualification will have access to specification and performance data, including LM-80 reports, which can speed regulatory approvals.

58 Watt LED Panel Light

Taiwan-based GlacialLight launched the GL-PL0312 LED Panel Light. This high efficiency 58W LED panel shown in Fig. 2 is a replacement for older, less-efficient light sources. Its key advantages are surprisingly low energy and maintenance costs, thanks to LED technology that brings greatly reduced power costs, long life, and low heat. The GL-PL0312 panel is the simple choice for any location that requires area illumination and could benefit from lower energy costs and more satisfied employees, visitors, customers, and guests.

The GL-PL0312 panels bring area illumination on demand with their broad 120° beam angle. Their natural illumination is intended for interior lighting applications. Typical applications for the 1195mm long by 295mm wide panels include hospitals, airports, offices, supermarkets, stores, and most other commercial, and retail locations. Each compact panel is only 13mm deep, minimizing architectural and interior design impact, and uses sturdy but lightweight materials to achieve a weight of just 4.1kg.

Long Service Life

The GL-PL0312’s long lifetime LED technology slashes maintenance and replacement costs, with a rated service life of 30,000 hours. Saving money for customers has been a key goal in the design of this product. LEDs are much more energy efficient than traditional light sources, so the GL-PL0312 panels offer a luminous efficacy of up to 66, even as they reduce power usage. This efficient energy conversion also cuts waste heat, keeping indoor temperatures under control to deliver noticeable reductions in cooling and air conditioning costs.

Three color variants are available. The warm white GL-PL0312-WW panel fills internal spaces with warm bright illumination with a color temperature of 3000K and a Color Rendering Index (CRI) of 80. The natural white GL-PL0312-NW provides balanced natural illumination at 4000K with a Color Rendering Index (CRI) of 80. The cool white GL-PL0312-CW achieves maximum luminous efficiency of 66 lumens per watt with its cool 5700K illumination and a CRI of 70 or higher. (For an explanation of CRI and other LED terms, see LED Lighting Glossary).

The GL-PL0312 panels accept a wide range of AC voltages from 100 volts to 240 volts, making them suitable for a variety of operating environments worldwide.

This product does not contain mercury or other hazardous chemicals. GlacialLight protects the environment by making the GL-PL0312 completely RoHS compliant. The GL-PL0312 does not emit harmful UV or IR radiation, making it far more eco-friendly than traditional lighting fixtures and technologies.

High Power LED Lighting Series

Everlight Electronics Co., Ltd., headquartered in Taiwan, introduced a new and smaller C52 COB LED series that is suitable for directional and decorative applications such as MR lamps and P35 bulbs (Fig. 3). For these types of applications, an LED light source must exhibit compact size, high efficiency, sufficient lumen output, high CRI, high color uniformity, and proper light distribution to maintain a comfortable and uniform lighting environment - all at consumer acceptable prices.

Everlight’s COB series is a 3.7W multi chip, ceramic substrate based LED that boasts a low thermal resistance (Rth <1.8°C/W) and superior efficacy of 100lm/W at 3000K CCT and high CRI (>80Ra). It will be available not only in ANSI 3000K CCT but in all Energy Star / ANSI color temperature ranges. Mechanically, the C52 COB series can be mounted directly on a heat sink, eliminating the SMT process. This provides more direct thermal dissipation, ease of assembly, and lowering of the system cost in lighting applications.

The C52 Series uses standard DC chips configured in series and parallel to provide the most convenient driving conditions for existing driver designs. Also, with a ceramic substrate, users can have higher reliability and better thermal dissipation. The C52 Series also can achieve the low cost of industry target, >400lm/$ for a COB LED light source. This is a single emission area COB LED that needs to be used.

Constant Power Regulation

Texas Instruments introduced a new LED controller with constant power regulation. The LM3447 AC/DC LED driver (Fig. 4) includes a dimmer detect, phase decoder and adjustable hold current circuits to provide smooth and flicker-free dimming operation in off-line, isolated LED lighting applications, including A19, E26/27 and PAR30/38 bulbs, as well as can light retrofits.

Traditional drivers use constant current control to accurately regulate LED forward current. This approach produces consistent light output or intensity from LEDs in the same bin. However, once current is applied to the LED, its solder point temperature rises, leading to a decrease in forward voltage and a drop in efficacy. Conversely, by using the new LM3447 with constant power regulation, the LED forward voltage droop over temperature is offset by an increase in LED current to maintain constant LED power. The result is up to 10% improvement in efficacy across the expected operating temperature range of the fixture.

Features of the LM3447 include:

  • Integrated phase dimmer decoding and dimmer detection circuitry allows for easy design and highest efficiency.
  • Operates with leading edge (Triac) and trailing edge dimmers.
  • Primary side control supports isolated lighting designs without opto-couplers.
  • Constant power LED load regulation improves efficacy of LED array by compensating for LED junction temperature changes.
  • Fixed frequency discontinuous conduction mode flyback topology with valley switching simplifies EMI filter design.
  • Greater than 0.9 power factor correction meets all regulatory requirements.

Thermal fold-back protects LED array from over-temperature while still providing reduced light output. LED open- and short-circuit protection and driver IC thermal shutdown protect lamp electronics from damage during fault conditions.

Cirrus Logic introduced its second family of digital LED controllers with digital TruDimT dimmer compatibility technology designed to accelerate worldwide adoption of LED retrofit bulbs. In addition to providing near 100 percent compatibility with the world’s installed base of dimmers, the new CS163X family provides two-channel LED color mixing capabilities. This allows LED bulb manufacturers to more efficiently create warm, natural light quality, while also lowering the cost barrier for two-channel LED retrofit bulbs.

The CS163X family enables improved color quality at up to 30 percent greater efficacy than with single-channel white LEDs. An innovative digital architecture provides the CS163X family with the ability to control two LED strings using components typically used to control a single LED string, resulting in lower system costs compared to today’s two-channel solutions. In addition, the CS163X incorporates powerline calibration technology, allowing manufacturers to calibrate bulb characteristics such as light output and color temperature, by sending commands via the AC mains terminals during the final manufacturing stage. This patent-pending technology allows manufacturers to utilize LEDs with a wider variation in performance characteristics, resulting in lower LED costs, while maintaining consistency in light output and color temperature from bulb to bulb.

LCoS Pico Projector System

Intersil Corporation introduced the Pico-qHD, said to be the world’s lowest cost pico projector system, and the industry’s smallest production-ready LED-based LCoS Pico Projector solution. Developed for low power and cost-sensitive embedded or accessory pico projector applications, the Pico-qHD provides a fully integrated reference design that includes a high volume production optical engine, hardware, firmware and customizable design files. The low cost system solution utilizes Micron’s E330 compact 5.5 cubic centimeter qHD optical engine, allowing for easy integration into a wide range of applications, including Micron’s recently announced portable PoP Video™ pico projector mobile device accessory.

Built on an inexpensive 1.7 inch by 2 inch PCB, the Pico-qHD is designed to meet the low manufacturing cost requirements of consumer applications such as digital cameras, smartphones, tablets, video players and other handheld products. Driven by such applications, Pacific Media Associates forecasts pico projector sales of 58 million units per year by 2015.

The platform is based on Intersil’s new ISL97901, a fully-integrated buck/boost RGB LED driver customized for pico projector display applications. The ISL97901 provides industry-leading overall power efficiency, the smallest solution footprint and the ability to drive RGB or RGB LEDs. The ISL97901 maintains the highest image quality with precise LED current control. A 2.0mA resolution provides consistent white balance setting, yielding uniformity over production units and throughout the life of projectors. Its electronics system can drive up to 1.5A LED current, making it compatible with a variety of high power LEDs, and enabling pico projector engines with brightness levels exceeding 20 lumens.

Wall Adapter LED Driver

Phihong USA introduced a new line of constant-current LED drivers designed as fixed wall plug adapters. The low cost adapter-style drivers (Fig. 5) are available for North American input voltages, and provide ample power for consumer lighting applications.

Three individual series, with outputs ranging from 6W to 24W total power, are now available to meet the needs of standard residential, office, and retail lighting applications. The PDA006A series consists of 6W LED adapters available in 350mA, 700mA, and 1000mA outputs, which makes them ideal for small porch lights and desk lamps. The PDA012A series consists of 12W LED adapters available in 350mA, 700mA, 1000mA, and 1500mA outputs, which makes them ideal for floor lamps, cabinet lighting, and retail display lighting. The final series, designated the PDA024A, consists of 24W LED adapters and is available in 700mA, 1000mA and 1500mA outputs, which makes them ideal for bright displays and higher power under-counter lighting.

All the drivers in the energy efficient series’ feature Level V efficiency markings and have power factors greater than 0.90. Additional standard features on the UL1310 Class 2 output drivers include over-voltage, over-current, short-circuit, and open-circuit protections.

Radial-Fin Heat Sink Extrusions

Ohmite Manufacturing announces the Wakefield Solutions’ 19000 Series radial-fin heat sink extrusions for LED light engines (Fig. 6). The 19000 Series is designed to help LED engineers meet both space constraints and operating parameters.

The 19000 heat sinks are designed to make maximum use of available resources. Besides being black anodized for maximum thermal performance, they are also constructed with a radial-fin geometry that has been optimized for natural convection.

These design benefits are ideal for many types of LED lighting fixtures. Though 19000 Series heat sinks are most commonly used in both recessed and externally mounted downlighting applications, they are equipped with extrusion profiles that suit a variety of LED configurations. Mounting features are incorporated as part of the extrusion, so that the 19000 series can be easily mounted with standard hardware. Each extrusion profile has screw bosses located precisely to enable easy LED substrate attachment, and provisions for slip-nut attachment make it easy to assemble the 19000 series heat sinks into diverse lighting fixtures.

Wakefield offers five different models of the 19000 series, each designed for a different maximum power rating and expected temperature rise above ambient temperature. Options range from a maximum 14.7° C rise for a 4.5 watt power rating to a maximum 29.2° C rise for a 42.8 watt power rating. All models do not exceed a maximum LED substrate temperature of 75° C, and are available in multiple sizes, weights, and thermal resistances.

DC-DC LED Driver

CUI Inc announced the addition of a surface mount series to its high efficiency, constant current dc-dc LED driver family. Designed to drive high power LEDs, the VLD25-SMT series provides efficiency levels of up to 96%, current accuracy of ±2%, and an ultra-wide input range of 5.5 to 48 Vdc. The series offers two means of LED dimming: PWM digital dimming and analog dimming control via a trim pot, making it ideal for applications where precise accuracy and brightness control is needed, including signage, transport, consumer electronics, and signaling.

The series is compact, measuring 0.94 x 0.54 x 0.30 inches in a 16-pin SMT package. Available output currents include 300, 350, 500, 600, and 700 mA with an output voltage range of 3.3 to 36 Vdc. The VLD25-SMT series has an ambient operating temperature range of -40°C to +85°C at full load in the 300 mA and 350 mA versions and -40°C to +71°C in the 500 mA, 600 mA, and 700 mA versions. Short-circuit protection and on/off control are standard features.


LED Lighting Glossary

CCT, Correlated Color Temperature is the absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source. Usually specified in Kelvin (K). The lower the Kelvin temperature, the warmer the light feels, or appears.

COB, chip on board is a bare chip mounted directly onto the printed circuit board. After its wires are attached, a glob of epoxy or plastic is used cover the chip and its connections.

CRI, color rendering index (also called color rendition index), is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully compared with an ideal or natural light source.

Downlight is a light fixture installed into a hollow opening in a ceiling. When installed it appears to have light shining from a hole in the ceiling, concentrating the light in a downward direction as a broad floodlight or narrow spotlight.

LEED stands for Leadership in Energy and Environmental Design and was developed by the U.S. Green Building Council (USGBC) to set a benchmark for design, construction, and operation of high-performance green buildings.

Level V is the highest rating in both use efficiency and no load power consumption specified by an international marking protocol that identifies the efficiency level met by an external power supply.

Related Articles:

Managing Currents in Dual- Synchronous Controllers

Is the Thermal Resistance of LEDs Constant?

Optimizing LED Lighting Systems For Efficiency, Size and Cost

Next-Generation Solid-State Lighting Fixtures Need Optimized LED Drivers
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