The difference between led lighting source and traditional light source is mainly in the three characteristics of heat, electricity and light.
1. Thermal characteristics
Although LEDs generate very little heat, they need to use multiple multi-watt LEDs in LED lighting, so very high heat is generated. Although the LED efficiency is relatively high, but the high efficiency only supports operation in a small current. Under high current and high temperature conditions, the efficiency is low.
In addition, phosphor-type LEDs lose energy when switching wavelengths, thereby generating heat. Continued high temperature will cause the life of LED chips, phosphors, and packaging resins to decrease. Therefore, in order to maintain the LED's "high efficiency" and "long life" advantages, the junction temperature of the LED must be controlled.
2, electrical characteristics
LED power supply is very different from incandescent lamp and fluorescent lamp. Incandescent lamps can be directly connected to 220V AC. Although fluorescent lamps have ballasts and change-over switches, they also use 220V alternating current. The LED power supply requires a constant current of DC, so 220V AC needs to be converted to DC. The low efficiency of the power supply will directly affect the efficiency of the entire lighting fixture. Therefore, improving the efficiency of the power supply is particularly important for improving the efficiency of LED lighting.
There are two main ways to adjust the LED light. One is to change the constant current, the other is to change the pulse modulation. LED emits light when electrons and holes recombine, and the light beam depends on current. When the current is small, the beam and current are basically proportional, but when the LED current increases, the heat increases, resulting in lower luminous efficiency, and the beam and current are not proportional.
In the method of changing the pulse duty cycle, due to the Talbot-Plateau effect (after receiving the instant flash repeatedly, the human eye will feel the average brightness within the repeated time), the brightness can be changed according to the pulse duty cycle.
3, the characteristics of light
Compared with incandescent lamps and fluorescent lamps, one LED emits less light, so you need to use multiple LEDs. At the same time, due to the small light-emitting area and high brightness of the LED, it is easy to be dizzy when looking directly at the human eye. In order to reduce the brightness, a diffuser is required. However, when using a diffuser, the light diverges in all directions, reducing the light efficiency.
The light distribution of LEDs, incandescent lamps, and fluorescent lamps are different. The so-called light distribution refers to the direction of the light source and the luminous intensity in each direction. Even if it is a light source with the same beam, if the light distribution is different, the illuminance distribution will be different. Sometimes the illuminance of the place that was originally intended to be irradiated decreases, but the illuminance of the rest increases instead.
To reduce the waste of light and control the light distribution, it is necessary to use lenses and mirrors. The LED itself has the advantages of small light-emitting area, light emission range in the hemisphere, and rotational symmetry of the light distribution. Together with the lens and the reflector, a good light source can be formed.
Other in the properties of the light source, there is also the spectrum. The light emission spectrum of LED is concentrated in a very narrow range of specific wavelength and does not emit infrared rays. Therefore, it is better to use LEDs when you do not want to heat the irradiated object. However, the LED itself generates heat, so care must be taken to prevent it from conducting heat. It should also be noted that the color temperature of the phosphor type LED changes accordingly.