First, the design principles of LED lamps and lanterns
Constant current and step-down are the current and voltage used when LED works. Attention should be paid to the working environment, the choice of lamp materials and heat dissipation methods, the packaging of LED chips and the design of radiator, all of which should be considered comprehensively.
Second, the design concept of LED lamps
There are two design concepts of LED lamps: one is that in 2008, Philips proposed to design lamps according to the needs of the environment, which is called scene lighting, and the other is that in 2009, Casio proposed to design lamps according to people's needs, which is called mood lighting.
Third, the key factors of LED lamps design
1. Heat dissipation is the key to LED lamp design.
Generally, led is often called cold light source, because the light emitting principle of led is that electrons recombine to emit photons directly without heating. However, due to Joule heat, the light emitted by LED carries heat. Different from the traditional light source, the traditional light source such as tungsten lamp concentrates heat on the filament, while the heat of LED light source concentrates on the PN junction surface of LED. Comparatively speaking, the heat dissipation area of tungsten lamp is still much larger than the PN junction interface, and even the PN junction surface can be regarded as 1 point, and the heat energy generated by LED lighting is all concentrated in one point. In engineering design, the heat generated in the form of "surface" can be treated by heat sink or increasing the thermal convection space by itself, while the heat dissipation treatment of "point" heat source is more complicated and difficult. Improper handling will easily lead to breakdown and damage of PN junction surface due to high heat and high current, and the service life of the product will also be affected if the device is in a high heat state for a long time.
On the other hand, in order to improve the brightness performance of LED chips, it is necessary to apply more power to the unit LED, and at the same time, the design of lamps will use more LEDs to run at the same time, which will generate a lot of heat in lamps. When the brightness of a single LED die increases, the power consumption also increases from 0. 1W to 1, 3 or even 5W. According to the measurement results of LED light source model, due to the improvement of luminous efficiency, the thermal resistance of packaging module will also increase.
LED is different from incandescent lamp, fluorescent lamp and other traditional lighting sources. Excessive temperature will shorten or even terminate its service life. The original life of a single LED module is 20,000-40,000 hours, which may be reduced to only 2,000 hours due to poor power and heat dissipation. Moreover, LED is a temperature-sensitive device, and the luminous efficiency drops sharply with the increase of temperature. Therefore, the structural design of the system and the development of heat dissipation technology are urgent problems to be solved in the design of LED lamps.
2.2 secondary light distribution design. LED lights are very important.
The light intensity distribution of light source in all directions of space is light distribution. In order to make the light emitted by LED chip output better, get the maximum utilization, and meet the design requirements in the lighting field, it is necessary to design the optical system of LED. Among them, the design in the packaging process is called primary optical design. When using LED light-emitting devices, the design of the luminous effect and the distribution of light intensity and color temperature of the whole system is called secondary optical design, also called secondary light distribution.
The secondary light distribution design of LED lamps plays an important role in the final lighting equipment and engineering performance. First, part of the light can not reach the effective illumination range, resulting in energy loss, which requires secondary light distribution to improve the utilization rate of light energy; Secondly, the uniformity of illumination distribution on the packaged image surface can not meet the design requirements, and the illumination value of each point is difficult to be greater than the required minimum illumination value, which requires the secondary light distribution design of LED lamps.
3.3 Reliability. LED lighting system is the foundation.
LED light source, some people call it long life lamp. As a solid-state light-emitting device, its theoretical life should be more than 654.38+ 10,000 hours, and its service life is much longer than that of traditional light sources. Therefore, it can be used in some occasions that are difficult to replace and maintain, and the maintenance cost can be greatly reduced. But at present, this advantage is not seen in many practical applications. On the contrary, what users see is serious light attenuation and short service life, and some of them are broken in less than 10000 hours.
4. Color development and glare of indoor LED lights.
According to experts in the industry, when about 30% people use LED tubes and cups at home, it is the real heyday of LED. In other words, the wide application of LED in indoor lighting is the real spring of LED industry. It goes without saying that the quality of indoor lighting design directly affects people's daily life and work. In addition to the problem that the cost of LED lamps is difficult to be accepted by the public, the health and comfort of human beings working and living under LED light source is the core issue of indoor LED lamps. This mainly includes the color rendering and glare of LED lamps.
The sensitivity of human eyes to chromatic aberration is much higher than that to light intensity. Therefore, for lighting, the color rendering of light source is often more important than luminous efficiency. At present, white LED generally uses blue LED and yellow yttrium aluminum garnet (YAG) phosphor excited by blue light to synthesize white light. Because its luminescent spectrum only contains blue and yellow spectra, it has the problems of high color temperature and low color rendering index, which does not meet the requirements of ordinary lighting. Therefore, it is an important subject for LED white lighting to add a proper amount of red phosphor and maintain a high luminous efficiency. In addition, the glare of LED lighting is too strong, and only a part of it shines into the eyes from a distance, which is too dazzling. This is also a technical problem that needs to be solved urgently.
In addition, for LED lamps, power supply, light source and driving circuit are all very important components and also very key technologies. But I prefer to separate them, and don't think this is the key technology of LED lights.