LED bulb technology development trend

The continuous rise in energy prices and the ban on the sale of traditional incandescent lamps have led to the climax of investment development. Especially due to the earthquake in Japan, the Asian LED market broke out.

Due to the long life characteristics of LEDs, although everyone agrees that integrated integrated LED lamps will be the market development trend. However, since conventional incandescent lamps account for more than half of the total number of luminaire applications, it is foreseeable that in the next three to five years, LED replacement lamps developed using interfaces such as E14, E26, E27, and B22 of traditional incandescent lamps. Will still occupy a place in the market.

From the market trend, the bulb will develop towards cheaper prices, higher light efficiency, higher reliability and safety.

The US Energy Star requires LED bulbs to have a minimum efficacy of less than 50 lm/W (<10 W) and a long-term requirement of 70 lm/W. At present, the majority of products of regular manufacturers on the market are generally around 70 lm/W.

Safety and reliability are the life of LEDs. However, due to the lack of effective regulation and supervision in the LED market, the safety and reliability of LED lamps in each enterprise are uneven. The market factory is full of inferior bulbs.

Blindly spelling prices but neglecting product quality is the root cause of such high product defect rates. How to design a bulb lamp with superior performance and reliability at the lowest cost is a challenge for every LED designer.

Prior art routes and trends:

1, thermal plastic radiator + non-isolated drive has become the trend of market development:

There are three main types of existing bulb radiators: aluminum, ceramics and thermal plastics. Aluminum has two heat sinks, die-cast aluminum and extruded aluminum. Aluminum radiators are the main form of radiators currently used in the market.

Use an aluminum heat sink with an isolated drive power supply and carefully design insulation protection and safety clearance to meet safety requirements. Compared with the non-isolated drive power supply, the isolated drive power supply is 5% to 10% lower, and the price is about 5 yuan, and the production process is relatively complicated. This leads to high cost and reduced light efficiency. As a result, more and more lighting fixtures use bulb and lamp solutions for ceramic and thermally conductive plastic radiators.

Compared with plastic heat sinks, ceramic heat sinks have the disadvantages of large weight, large difference in thermal conductivity of batches, and fragility. Therefore, the thermal plastic radiator will be the main trend in the development of the bulb market.

Each of these three materials has advantages and disadvantages. Summarized as follows:

Small power LEDs will dominate the bulb market application:

Low-power LEDs have an advantage over high- power LEDs in price. Multiple LEDs form a surface illumination source that avoids glare. Therefore, the use of multiple low-power LEDs as the light source will still be the mainstream direction of the LED bulb market design.

For low power LEDs, such as the Dus E5 of Osram,

Taiwan's Everlight's 5630, 7030 are ideal for bulb applications.

3, COB (Chip on Board) package applied to bulbs, simplifying design and production

COB technology simplifies design and improves product consistency and reliability. Increase productivity with dedicated COB LED connectors. Since no additional metal substrate is required, the overall lamp cost is reduced.

The figure below shows the installation diagram and basic performance parameters of the CREE CXA1507 with a dedicated COB connector.

ENERGY STAR is expected to abolish the requirements for full-angle glow bulbs:

ENERGY STAR has a full-angle illumination requirement for LED bulbs. The luminous flux in the 135° to 180° illumination range accounts for at least 5% of the total luminous flux. As shown below:

To achieve full-angle illumination, it is now generally achieved using Remote phosphor, mechanical design and optical design techniques:

a. Remote phosphor (remote phosphor with blue LED)

The commonly used white LEDs themselves have phosphors. And Remote

The phosphor technique refers to a configuration in which a fluorescent material of a converted wavelength is separated from a blue LED as a light source. Light from a plurality of blue LEDs is mixed and irradiated onto the fluorescent material to produce white light. (As shown below)

The light emitted by the blue LED is converted into white light by the phosphor, and is uniformly radiated in all directions, so that a uniform full-angle luminous bulb can be obtained.

The efficacy of a bulb with Remote phospor technology is 20% better than that of a white LED bulb with the same power, while the junction temperature of the LED is 15 °C lower. Currently, both NVC lighting and Philips lighting use Remote.

The phosphor technology of the bulb lamp is available.

Intematix is ​​a well-known company in the field of Remote phosphors and has received six patents for Remote phosphors from the US Patent and Trademark Office. Its Remote phosphor diffusion cover of the ChromaLit(TM) brand (pictured below).

b. Institutional design

Through reasonable mechanism design, the LEDs are evenly distributed in different directions of the bulb. Multiple LEDs emit light simultaneously in all directions to meet the requirements of ENERGY STAR full-angle illumination.

Bulbs that are designed to achieve full-angle illumination through a mechanical design can be designed to be clever and creative. However, this method also has the disadvantages of complicated design and production, and high cost.

c. Optical design

With a COB or ordinary white LED, with a specially designed full-angle lens, a full-angle luminous bulb can also be designed. The following is an 800lm full-angle illuminating bulb with 8 CREE XBDs and a dedicated lens.

Since the illumination angle of LEDs is generally less than 120 degrees, lamps designed with full-angle illumination need to increase the complexity of the design and increase the cost of the lamps. A typical lighting application does not require a full-angle illumination of the bulb. As a result, ENERGY STAR is revisiting the requirements for full-angle lighting and is likely to abolish this requirement for LED bulbs by the end of the year.

5, intelligent dimming control for high-end bulb applications

The current dimming method of LED bulbs generally follows the past thyristor dimming method. The thyristor dimming method has problems of dimming the light, poor compatibility of the dimmer, and low overall efficiency. In future high-end bulb applications, smart wireless dimmers will be seen for LED bulbs. For example, Zigbee technology uses a smart phone to dim the bulb, and an intelligent dimming bulb that automatically adjusts the spatial illumination according to whether there is activity or the intensity of natural light.

TI/SVA, NXP, ATMEL have similar smart dimming control IC solutions to choose from.

LED bulb overall solution