First, the basic knowledge of LED

1. LED luminescence principle

LED (Light Emitting Diode) is an abbreviation for light-emitting diode. Diodes made of compounds of gallium (Ga), arsenic (AS) and phosphorus (P) can emit visible light when electrons and holes are combined, so they can be used to make light-emitting diodes, which can be used as indicators in circuits and instruments, or to form text or digital displays. Gallium arsenide diodes glow red, gallium phosphide diodes glow green, and silicon carbide diodes glow yellow.

With the progress of science and technology, there is an LED that can emit a similar incandescent light color, which provides a long-life and high-efficiency lighting source for modern lighting, and the most valuable thing is that the LED device has a life of more than 50,000 to 100,000 hours, suitable for a variety of occasions.

2. Characteristics of LED

The light emitted by LEDs is different from natural light, its spectrum is not continuous, and the infrared part is missing, so unlike incandescent lamps, the heat generated by LEDs is not dissipated by radiation, but must be dissipated by conduction, which is why LEDs are called cold light sources.

LEDs have the following advantages:

High efficiency and energy saving: White LED is the most energy-efficient white light source device known at present. Only a few kilowatt-hours of electricity are consumed in 1,000 hours (ordinary 60W incandescent lamps consume 1 kilowatt-hour in 17 hours, and ordinary 10W energy-saving lamps consume 1 kilowatt-hour of electricity in 100 hours)

Ultra-long life: semiconductor chips are luminous, no filament, no glass bubbles, not afraid of vibration, not easy to break, and the service life can reach more than 50,000 hours (the service life of ordinary incandescent lamps is only hundreds of hours, and the service life of ordinary energy-saving lamps is only 8,000 hours)

Green and environmentally friendly: it does not contain harmful elements such as mercury and xenon, which is conducive to recycling and utilization, and does not produce electromagnetic interference (ordinary lamps contain elements such as mercury and lead, and electronic ballasts in energy-saving lamps will produce electromagnetic interference, and mercury elements are still present in the lamps)

Eyesight protection: DC drive, no flicker (ordinary lamps are AC driven, it will inevitably produce strobe)

High light efficiency: low heat generation: 90% of the electrical energy is converted into visible light (80% of the electrical energy of ordinary incandescent lamps is converted into heat energy, and only 20% of the electrical energy is converted into light energy)

The market potential is large: low-voltage, DC power supply, battery and solar power supply can be used, which can be used in remote mountainous areas and field lighting and other places lacking electricity and less electricity.

According to the prediction of international authoritative institutions, semiconductor light-emitting diode lighting will replace the existing traditional light source in the next 5-10 years, of course, this will depend on the cheaper white LED, and scientific and technological progress will inevitably cause the rapid growth of the overall capacity of the market. Technicians have measured that at the same brightness, the power consumption of LED is only 1/10 of that of incandescent lamps, and the life span is 100 times that of incandescent lamps. Because LED has the advantages of energy saving, environmental protection, long life and small size, experts call it another leap in the history of human lighting after incandescent lamps and fluorescent lamps. According to the U.S. Department of Energy, a complete replacement of traditional lighting devices will begin in 2010. Japan, the United States, Europe, South Korea and other countries have officially launched the LED lighting strategic plan. According to reports, at the World Expo held in Shanghai, China this year, many developed country pavilions have fully used LED as a lighting source. In China, the application of LED is also in a vigorous stage of development, but because China has not mastered the core technology of high-power LED, the country is still in the stage of imported semiconductor chips and domestic packaging, so the price is still at a high level compared to foreign countries, and the application is slightly affected.

3. Electrical characteristics of LED light-emitting diodes

LED is in a positive working state, when it reaches its luminous voltage value, LED begins to emit light, when the voltage continues to increase, the luminous brightness of LED increases sharply, if the voltage is slightly increased, the LED may burn out instantly, it can be seen that LED belongs to a kind of current device, it is this characteristic that determines that the LED must work safely in a constant current state, which is the main aspect of the LED device in the use of other light sources is inconsistent, and it is also the key factor for the safe use of LED, Points that require the designer's full attention.