#1.The Importance Of Optical Design
LED is a point light source, which is different from energy-saving lamps or incandescent lamps currently on the market. As the name suggests, a point light source is the light emitted by a point, and the light emitted by this point also has another important feature, that is, there is light in only one direction (all traditional back reflectors are meaningless to the LED itself).
If we want to use this special light for lighting, we must do some processing on this light to meet our requirements and goals, so we need to add optical design to turn this relatively concentrated point light source into Astigmatism with a certain angle, which is the familiar straw hat LED. Straw hat LED is a packaging form professionally used in lighting design. On the one hand, it can make the 100 150 200W Wide Angle UFO LED High Bay Lights change from a concentrated point light source to a diffuse A light source, on the other hand, has less of a light decay effect and lets more light through for us to use.
Although the straw hat LED has made a qualitative leap in the optical angle, it is still a point light source compared to the surface light source we are familiar with. Because the brightness is too concentrated, if the human eye looks directly at the light source, it will still hurt us. Eyes cause some damage.
Therefore, when LED lighting is used in home lighting, we need to further process the light and add a certain optical design to achieve the purpose of direct observation by the human eye, while softening the light. The angle of illumination, although the straw hat LED itself has achieved a range of 120 degrees, if it is directly applied to home lighting, it gives us the feeling that the roof is completely dark, and we need to use the outermost transparent cover of the lamp to disperse the light again. , thus adapting to normal household lighting.
#2.The Difference Between High-Power And Low-Power LED
With the continuous development of LED technology, people have developed single LED chips with increasing power to adapt to High Power LED Bulb Light With High Lumen LEDs. Great, but not great value for money. Let’s take some common LEDs as an example to do an analysis.
At present, a large number of single 0.06W power is used in the industry, and its maximum brightness can reach 7LM. We temporarily calculate it according to the ordinary 6LM. If we want to make the power reach 1W, we need to use 17 same LEDs. The total brightness It is 17*6=102LM, that is to say, it can achieve 100LM/W. If we use a single chip with a power of 1W, its output brightness can reach up to 80LM, and the commonly used ones are generally around 60LM. The main difference, it can be seen that for home use, we still have to choose low-power LEDs.
From the perspective of product cost, the cost of high-power LEDs is higher than that of low-power LEDs. This comes from two aspects. One is the cost of the LED itself, and the other is that high-power LEDs need to add aluminum heat sinks. The circuit board, coupled with natural heat dissipation, can meet the requirements.
From the perspective of product maintenance costs in the future, if our lamps fail during use, we can find any electrical repair shop to replace the damaged LED. The cost of a 0.06W LED is at most 1 yuan, plus the maintenance fee is no more than 5 yuan, if it is to replace a 1W LED, the LED cost will be 8 yuan, and the maintenance cost will be about 15 yuan. Relatively speaking, low-power LEDs can be purchased in any electronic market, but high-power LEDs may not be available everywhere.
It is a market trend and the mainstream of future development for LEDs to move towards high power. However, due to the technical failure to achieve the desired results, from a technical point of view, it is not yet suitable for home lighting.
#3.The Importance Of Thermal Design
LED itself is a semiconductor device, and all semiconductor devices have certain temperature requirements for normal operation, including ambient temperature and operating temperature. Generally, the ambient temperature for the normal operation of semiconductor devices is lower than 80 degrees. When the temperature of the PN junction inside the LED reaches 140 degrees, it will fail. During normal operation, its own temperature will be radiated through the pins or special base, and then radiated into the surrounding air through the circuit board or aluminum substrate connected to the pins to ensure the normal operation of the LED.
Generally speaking, if the power of a single chip is greater than 0.2W, an aluminum substrate must be used for heat dissipation. If the power is higher, an aluminum shell and aluminum heat sink should be added. Of course, this is related to the number and density of LEDs in the entire lamp, and the heat dissipation design should also be considered for low-power LEDs that are too concentrated. This is like every electronic product around you, such as: TVs, monitors, computer hosts, etc. Improper heat dissipation design will directly lead to shortened LED life and accelerated light decay.
Now most of the upper limit of junction temperature can reach about 120 degrees, and the current CREE should be considered relatively high, which is 150 degrees.
The thermal resistance of the lamp bead varies according to the structure of the packaging material. Some multi-chips are as high as dozens, and single-chips are generally single digits, at most a dozen. Of course, this is directly related to the junction temperature, which is related to the life of the LED and the Integral Precision Dia Casting LED Canopy Light efficiency. Waiting for important parameters.
At present, the design life of most LED lamps is 20000~50000H, which is determined by many factors. First of all, the life of IC and so on limits the life of the whole lamp.
From the perspective of heat dissipation in terms of structural layout, it is actually a problem of contact thermal resistance and heat conduction bottleneck, which involves many things and is not easy to list. Generally speaking, the structure is integrated, and the large area is in good contact. The lamp beads on the PCB should be evenly distributed as much as possible to avoid the concentration of heat sources.
Of course, the higher the driving efficiency, the better. The layout should be based on the largest heat source, that is, LED lamp beads. Glue filling and other methods can be used to achieve the effect of heat dissipation, fixed insulation.
Comprehensive consideration: the temperature rise of a good heat dissipation design is best controlled below 35. The junction temperature is below 80. The theoretical lifespan is more than 50,000.
#4.Current Heat Dissipation Design Problems
- Natural heat dissipation is too limited by space (radiation heat dissipation itself is less affected and limited by space size).
- The natural heat dissipation area has limited room for improvement (limited convection heat dissipation).
- At present, metal parts are used as radiators, and the heat conduction in a small space is sufficient. (The temperature difference of the radiator is small, and the influence of thermal conductivity is small).
- Most of the heat dissipation design can only focus on the selection of lamp beads, heat dissipation area, interface contact thermal resistance, and radiation heat dissipation. Almost dead end.
- At present, the breakthrough point of heat dissipation design is the heat dissipation design of the lighting system, which is the result of the combination of actual production, material accessories, structural modeling and heat dissipation design.