About LEDs


Points of this article

・"LED" is an acronym for "light-emitting diode"; an LED is a semiconductor that has the property of emitting light when a current passes through it.

・Because LEDs directly convert electrical energy into light energy, they have such features as excellent energy efficiency, low power consumption, and fast response.

LEDs, being “semiconductors that shine”, are employed in a vast range of areas in our daily lives, as indicators, in backlights, and in many other devices.

LEDs are manufactured using compounds formed by combining such elements as gallium (Ga), nitrogen (N), indium (In), aluminum (Al), phosphorus (P), and arsenic (As). The wavelength (emission color) of the light emitted is determined by the materials used.

Due to the commercialization in 1993 of high-brightness blue-light LEDs based on gallium nitride, full-color display using LEDs became possible. Moreover, by combining blue LEDs with yellow phosphors, LEDs emitting white light were achieved, attracting attention for their applications in lighting.

At present, there is a rapidly expanding demand for highly energy-efficient LED lighting, which has applications in a broad range of areas such as in illumination of facilities and outdoor lighting, and above all as the bulb-shaped LED lamps used in households in general.

■Features of LEDs

①Long Lifetimes

Compared with incandescent bulbs, fluorescent lighting, and other lighting types, LED lifetimes are long, reducing the costs incurred in replacement and maintenance. Because when its lifetime is reached an LED gradually becomes less bright rather than suddenly going dark, the lifetime of LED lighting fixtures is defined as the time after which brightness has dropped by approximately 30%.

【Comparison of Lighting Device Lifetimes】

Incandescent bulbs fluorescent lighting LED lighting fixtures
1,000 to 2,000 hours 6,000 to 12,000 hours Approx. 40,000 hours

②Reduced Power Consumption, Energy Savings

Because LEDs have good light emission efficiency and remain bright and vibrant even when using only low amounts of electric power, they are effective energy-saving measures and can help mitigate environmental problems.

③Compactness, Light Weight

LEDs are point light sources with small light-emitting parts, and so they can be utilized in diverse areas, with increased freedom of design for a given application.

④Fast Response

In LEDs, the movement of electrons is directly connected to light emission, so that response is fast, and the LED is lit the instant that current passes. This characteristic can be exploited in indicators and infrared remote control applications where LEDs are turned on and off at super-high speeds, in visible-light communications in which light modulated by data is transmitted and received, and in other technical areas.

⑤Bright at Low Temperatures

Unlike fluorescent lights, which are dimmer at low temperatures, LEDs can maintain high brightness. Light-emission efficiency does not decline even at -20°C, making them well-suited for use in cold regions, as illumination in refrigerators, and in other applications.

⑥Minimal Heat Rays, UV Rays

The light emitted from visible-light LEDs includes hardly any heat rays or UV rays, so that when products or works of art are illuminated by such devices, there is no damage imparted to the illuminated objects in the form of discoloration, degradation, or the like. And there is the further advantage that visible-light LEDs do not attract insects when used outdoors.

■LED Applications

In addition to the features described above, by virtue of such other advantages as ease of waterproofing treatment, excellent resistance to shocks, and high brightness for high visibility both indoors and outdoors, LEDs have come to be used widely in diverse areas.

<General Application Examples>
Light bulbs; illumination in homes, facilities, and sports venues; displays; liquid crystal backlights (in TVs, PC monitors, smartphones, etc.)

Wearable devices; medical equipment; beauty equipment; grow lights for plants; sterilization devices; street lamps; traffic lights; various lamps for automobiles; various illumination and indicators for trains, buses, and other public transportation equipment; etc.

Information on Downloading Technical Documents

Downloadable materials, including lecture materials from ROHM-sponsored seminars and a selection guide for DC-DC converters, are now available.

Download Technical Documents

Downloadable materials, including lecture materials from ROHM-sponsored seminars and a selection guide for DC-DC converters, are now available.