05 May
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What is the principle of LED? What can the ETL logo say?

Posted By: John Times Read: 55

LED (Light Emitting Diode, LED) is an abbreviation for LED, also known as LED, is a solid-state semiconductor device that directly converts electricity into light. This kind of semiconductor component has been generally used as an indicator light and a display panel. However, with the increase of technology, it has been used as a light source. It can directly convert electric energy into light energy with high efficiency, and has a maximum of tens of thousands of hours. ~100,000 hours of service life, not only the traditional light bulb is fragile, and can save electricity. At the same time, it has environmental protection, no mercury, small size, can be applied in low temperature environment, light source has directionality, causing less light damage and rich color gamut. Etc.

With the advent of white LEDs and the introduction of more technologies, lighting devices such as indicator lights, automobile anti-fog lamps, and indoor lighting in household appliances and notebook computers are becoming more and more popular, and the application of LEDs is becoming more and more popular.

LED invention

In 1955, Rubin Braunstein of the Radio Corporation of America discovered the infrared radiation of gallium arsenide (GaAs) and other semiconductor alloys. In 1962, Nick Holonyak Jr of General Electric Company (GE) of the United States Developed LED LEDs for visible light. However, the real take-off of LEDs began to become more and more important after the appearance of white LEDs in the 1990s, and the application surface became wider and wider.

LED lighting principle

So what is the working principle of LED? LED is an electronic component that can convert electrical energy into light energy. At the same time, it has the characteristics of a diode, that is, it has a positive pole and a negative pole. The most special thing about LED is that it only emits light when it is energized from the positive pole, so it is generally given When DC is applied, the LED will illuminate steadily, but if AC is connected, the LED will flash and the flashing frequency will depend on the frequency of the input AC. The principle of LED illumination is the applied voltage, which allows electrons to be released in the form of light after they are combined in the semiconductor. At present, different types of LEDs developed by the global industry can emit light of different wavelengths from infrared to blue, and the industry also has purple-ultraviolet LEDs. In recent years, the most attractive development of LEDs is to apply fluorescent powder on blue LEDs. , white light LED products that convert blue light into white light. The reason why LED is called the new source of the century is that the LED has the characteristics of point light source and solid state light source, which can save energy, high shock resistance, long life, small volume response, and high color saturation.

LED color classification:

Since the generated photons have different energies depending on the manufacturing materials of the LEDs, the industry controls the wavelength of the LEDs by manufacturing materials, thereby producing various LEDs having different spectra and colors.

The world's first LED is made of arsenic (As) gallium (Ga), which operates at 1.424V and emits light in the infrared spectrum. After that, the industry developed phosphorous (P) gallium (Ga) as the material of the LED, the operating voltage is 2.261V, and the emitted light is green. In the early days of the industry, LEDs of all wavelengths ranging from infrared to green light were formulated through the materials required for these two types of LEDs, and common red LEDs, yellow LEDs, orange LEDs, etc. were developed. The three types of LEDs are called three-element LEDs because they use three elements of gallium, arsenic, and phosphorus, while the blue, green, and infrared LEDs are called 2-element LEDs. The industry later developed a 4-element LED that uses four elements of mixed aluminum (Al), calcium (Ca), indium (In), and nitrogen (N) to emit light in all visible and partial ultraviolet spectra.

LED brightness:

There are three types of illuminance that LED products will look at, such as illuminance unit Lux, Lumen; lumen, luminescence intensity (Candle power; CD), and each of the three units is suitable. The fields used, but are numerically interoperable.

1 CD denotes the luminous intensity of a completely radiated object at an area of ​​one-sixtieth of a square centimeter at the freezing point of platinum. Suitable for use in the field of active lighting, such as white heat bulbs.

1 lm means that 1 CD light is irradiated at a distance of 1 cm and the area is 1 square centimeter. Suitable for use in reflective and penetrating luminaires, such as projectors.

1 Lux means the illuminance of 1 Lm light evenly distributed over an area of ​​1 square meter. Suitable for use in the field of photography.

In general, the luminous intensity of a single LED is in units of CD and is equipped with a viewing angle parameter, and the luminous intensity of the LED varies from the number of bits mCD to 5,000 mCD. When the manufacturer marks a single LED product, the luminous intensity specification is the luminous intensity at the maximum viewing angle and the maximum luminous intensity at the center position when the LED is illuminated at a current of 20 mA.

LED energy efficiency

Based on the environmental standpoint and energy conservation demands, governments around the world pay attention to the economic and energy-saving benefits brought by LED and energy-saving lamps, and manufacturers are optimistic about the business opportunities of this lighting revolution. In addition to the phased ban on the use of white light bulbs by the European Union and the US Congress, Canada has announced that it will completely ban white light bulbs in 2010, and some states, including California, will also ban white light bulbs in 2012. Australia has announced that it will ban the sale of white light bulbs in 2010. China and Japan also have LED incentive schemes in the planning.

Although there is another energy-saving lighting product (CFL) on the market, the lighting quality is still not enough. The startup time is longer than that of the general white light bulb, and the brightness of the light source cannot be adjusted. The popularity is still insufficient. high. LEDs have more energy-saving benefits, and with the improvement of technology, the brightness has reached a satisfactory level, but the high price is a big problem. In the future, as the global LED manufacturers' production pace is accelerated, the price can be accelerated after the price is lowered. The popularity of LED lamps.

LED life:

Generally, the LED has a long luminescence lifetime, and most of the products are marked as more than 100,000 hours, but in fact the brightness of the LED is attenuated, and after a period of use, the brightness will decay to half or even less. Fortunately, with the advancement of technology in the industry, there are many solutions to reduce the problem of LED brightness degradation. In the production process, the selection of materials such as 4-element LEC materials can have a longer period of brightness decay, and the LED technology used by manufacturers has a great relationship with how long the finished product can last. Color matching is also the key to the production of

LED factories.

The service life of LEDs is 1,000 hours longer than that of general daylight bulbs and 10,000 hours of daylight lamps. The service life of LEDs can reach 50,000 hours, which greatly reduces the cost of lamp replacement. This feature helps LED luminaires have a good reason to replace ordinary light bulbs with LEDs in terms of price competition. This advantage allows many environments that were originally not economically open and cannot be turned on all day, with LED lighting. Make public or private places safer. For example, public parking lots, refrigerators, etc., the largest retailer in the United States, Wal-Mart, has recently switched its refrigeration equipment to power-saving LED products.

The obvious disadvantage of LEDs is the heat dissipation problem. Improper heat dissipation will cause the luminosity and service life of LED lamps to be attenuated. Fortunately, this part has been significantly improved by the blessing of new technologies.

LED application:

In addition to the LED indicators on the various electronic products we are familiar with, LED screens, LED lighting, LED backlights for LCD screens, LED backlights for mobile phones, new generation OLED screens, PLED screens, etc. As the application of LED is gradually developing steadily, LED applications in some fields have become more mature due to the development of the market, and the speed of popularization has begun to accelerate, which has invisibly created amazing business opportunities.

At present, high-brightness white LED light source is the focus of the current US-European LED giants' competitive research and development. It is estimated that after 2011, LED will be widely popularized in the general lighting market. Although Asia's high-brightness production scale accounted for 76% of the global market share in 2006, the white LED light source patents are owned by Nichia and TG in Japan, Cree in the US, and Philips Lumileds and Osram in Europe. Although there are no standard specifications for midstream modules, they are still dominated by international companies including National, Laminar, Osram, Lumiled, and Vishay. The United States and Japan have also begun to actively develop safety regulations and energy standards for lighting applications.

The biggest application of LED at this stage is the backlight of mobile phone buttons, the indicator lights of various electronic exhibits, and the large LED screens recently applied to advertising billboards, as well as the backlights applied to LCD screens, are attracting more and more attention. The application is becoming more widespread. It is estimated that more LED products will be available in the second half of 2007. In 2008, LED lighting products can be further reduced to the extent that some consumers can accept. In the future development, governments will actively apply LEDs to public utilities. Speed ​​is expected to accelerate the decline in LED prices. As consumers adopt more, the economic benefits and energy-saving benefits will be considerable.

LED global market development:

In 2005, the global high-brightness LED market reached US$5.8 billion, reaching US$6.6 billion in 2006. It is estimated to increase to US$10.6 billion in 2011, with an average annual growth rate (AAGR) of 10.2%. Shipments of high-brightness LEDs reached 4.8 billion in 2005, an increase of 6.5 billion in 2006, and an estimated 8.8 billion in 2011, with an average annual growth rate of 10.3%. In 2005, the sales of LED substrate materials exceeded US$1 billion, reaching US$1.1 billion in 2006, and estimated US$1.8 billion in 2011, with an average annual growth rate of 9.7%.

In 2006, the LED lighting output value of Taiwan was NT$21 billion. In 2010, it will increase to 93 billion yuan, and in 2015 it will reach 540 billion yuan. In the upstream light source segment, Taiwan's output is the highest in the world. In 2006, the output value of high-brightness LEDs did not include mobile phone applications up to NT$15 billion. The upstream LED light source industry in Taiwan is an important global position because it is in a leading position in red and green LED technology. Downstream applications Taiwan's lighting production quality is good, and the price and global access are advantages. Taiwan manufacturers have a global market share of 48% for backlights of liquid crystal panels (LCDs). Therefore, it is also an advantage for Taiwanese companies to develop LED backlight modules, and automotive LED products are also regarded as one of the key projects.

It is estimated that LEDs will gradually replace existing incandescent lamps in 2007, and gradually replace fluorescent lamps in 2011. The EU has gradually phased out incandescent bulbs since 2007. Australia has announced that it will completely ban incandescent bulbs from 2010, so the LED market prospects are worth looking forward to. In the next five years, the market application should be based on LED billboards or display backlights, automotive and general lighting for the market development.


Epistar LED Bulb/ETL LED Bulb

The ETL mark on the product indicates that the product has passed the ETL test and complies with the relevant standards.

For distributors, retailers and consumers, they have purchased third-party tested and certified products. Will the retailer accept products with the ETL logo?

The ETL mark is proof that the product complies with the mark, and ETL is also a Nationally Recognized Test Laboratory (NRTL), so there is no reason for the retailer not to accept products bearing the ETL mark.

ETL certification test project

1) Leakage current test: The sample used for the leakage current test has not been tested before the test.

2), normal temperature rise: test test method: thermocouple: standard requirements use 24-30AWG thermocouple, (currently used in laboratory 30AWG)

3), leakage current test after the tide: general test conditions: T = 32 +/- 2 ° C, RH = 88 ± 2%.

Duration: 48 hours after completion, take out leakage current test test conditions T=20~30 °C, RH=93+/-3%), withstand voltage test: generally no double insulation and grounding products required products: 1000 V / 1 Minute (the device target voltage climb time is set to 5 seconds, the cutoff current is set to 8.3 mA, and then held for 1 minute at the target voltage)

ETL needs to carry out factory inspections and inspections before issuing certificates. After that, it will carry out irregular inspections of factory inspections every quarter. In addition to the factory inspection fees, the fees must be paid quarterly.

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