White LED enters indoor lighting

The successful development of white LEDs has really ignited the brilliance of “green lighting”. With the continuous advancement of LED technology, LED is gradually developing from the signal and display stage to the lighting application stage. Its long life, high efficiency and energy saving features have been recognized. White LED is getting more and more widely used in the field of indoor lighting.

White LED has many advantages

White LEDs have many advantages for indoor lighting. First, the brightness and color of the LED can be adjusted to meet the color requirements of interior decoration lighting. In the development of the scene lighting market, it has the advantage that the traditional light source is incomparable. Second, the LED is easy to dynamically control, and the cluster control can be designed according to the user's needs. In some occasions requiring programming capability, it can provide a reasonable solution and provide convenience for intelligent management of indoor lighting. Third, the LED is small in size and more decorative. It can be integrated with the building through the design of the luminaire to achieve the effect of “seeing the light without seeing the light”. Fourth, LEDs have long life and no mercury, which is in line with the national “energy saving and emission reduction” policy requirements. Fifth, the LED directional radiation within a certain beam angle, used for spotlights, downlights and other lamps, is conducive to improve the downlight ratio.

With the improvement of LED technology, the emergence of energy-saving effects, and the decline of cost, LED has begun to enter commercial lighting and even some domestic lighting markets, both in the international market and in the domestic market, showing a good momentum of development. LED lighting is still very expensive in the current stage of indoor lighting applications, but because LED lamps have higher luminous efficiency, they can save power consumption costs, and have a longer life, which can reduce replacement and maintenance costs. Therefore, consider white light. In the development direction of LED indoor lighting, the return on investment of white LED lamps is the most important factor compared to traditional lighting methods (incandescent lamps, halogen lamps, compact fluorescent lamps, straight tube fluorescent lamps and metal halide lamps). According to the analysis, the investment recovery period of LED lamps is 1.7 years to 3.4 years compared with incandescent lamps; compared with halogen lamps, the investment recovery period of LED lamps is 1.7 years to 3.5 years. Therefore, in place of incandescent and halogen lamps, the application of white LEDs has a very attractive rate of investment recovery. Compared to compact fluorescent lamps, LED lamps have a payback period of 4.5 to 6.2 years in some applications; LED lamps do not have a good payback period compared to straight tube fluorescent lamps and metal halide lamps.

The author believes that the application direction of white LED in indoor lighting is mainly concentrated in several aspects: firstly, it should replace the traditional light source with low light efficiency, such as incandescent lamp and halogen lamp. It should vigorously develop LED lamps that can achieve the same lighting effect, and gradually replace compact. Fluorescent lamp. In such applications, LED lamps need to pursue an appropriate service life and optimized cost performance while meeting the lighting conditions. Secondly, it can be applied to the field of directional illumination, including spotlights, glare lamps and local illumination. This field can maximize the small size and directional illumination of LED light sources. For directional lighting applications, ensuring that a large amount of light reaches the mission area and the quality of the light is a key factor. LED lights can meet the light intensity, light distribution and color rendering requirements of the target task. Finally, the field of scenarios and controlled lighting. The color of the LED light source is rich, the color light source is full, and the LED light source has fast response, short starting time and convenient dimming. By utilizing the above advantages of the LED light source, the LED lamp can be applied to a lighting environment that requires color conversion, and to a scene that requires dimming and frequent lighting.

Key technologies need to break through

Although white LEDs continue to expand their application share in the field of indoor lighting, white LED lighting faces many challenges. LED lights not only need to pay attention to the related performance of chips or packaged devices, but also need to focus on the electronic technology, thermal management and optical technology of LED lighting.

The first is the driver problem. LEDs can only be driven by direct current, and no alternating current or voltage can be applied across the LEDs. At the same time, in order to obtain high-quality lighting effects, the LED output is stable, long-life luminous flux, and the input current of the LED needs to be constant. However, existing power supply systems typically use 120V or 220V AC. On the other hand, since the LED light source itself consumes a small amount of power, the matching LED control device (including the drive) consumes less power at a rated state. Under the conditions of meeting various safety regulations, the LED control device also needs to evaluate the power factor when operating with the rated voltage and frequency after combining with the LED light source. In view of the inherent characteristics of the switching power supply, some of the high power factor driving power consumption is close to the adapted LED product. Therefore, when designing the LED light source driving, attention should be paid to the energy efficiency level of the LED control device, and the line power factor should be properly considered. At the same time, the dimming or control of the LED driver is also a hot spot of the current driving technology. The switch of the LED lamp should be controlled according to the requirements of different application scenarios, or the luminous flux output of the LED lamp should be adjusted. At present, the main research contents of LED driver technology are to improve control precision, improve power factor, and reduce power consumption of the driver itself.

Followed by thermal management technology. Accumulation of heat not only affects the electrical performance of the LED, but may eventually lead to LED failure. Therefore, in order to ensure the life of the LED lamp, heat dissipation becomes a key technology for white LED application, and reducing or rapidly dissipating the heat generated by the LED becomes the primary problem in the application design of the white LED. Excellent thermal management technology can further improve system performance, increase the quantity and quality of light output, and ensure long-term reliability of the system. Depending on the thermal power of the LED, the size of the lamp, and the application location, active or passive cooling can be selected.

Finally, the optical design problem. LED is a directional point source. How to creatively apply these two characteristics of LED to create a comfortable light environment is the core of LED light optical design technology. The LED light source itself generally has a lens or a transmissive material for improving the light emission efficiency, and at the same time satisfies the light distribution of about 120 degrees of light emission, which is generally called a primary optical design. However, in order to meet the various needs of indoor lighting, it is necessary to redistribute the light as needed, which is called a secondary optical design. At present, depending on the application, the secondary optical design can achieve high efficiency and precise light distribution requirements by different means, such as total reflection lens, high reflectivity reflector, and mixing cavity.