Abstract: Ultra-bright white LEDs, due to their unique advantages such as small size, low temperature resistance, long life and no pollution, with the improvement of luminous efficiency, their application surface is expanding, the paper from the principle of solar LED lamps, The main technology and performance indicators introduced the application of super bright white LEDs in solar lamps.
Solar radiant energy is inexhaustible and is an energy source that humans can freely use. Today, with the world's energy shortage and environmental pollution becoming increasingly serious, the full development and utilization of solar energy is an energy strategy decision for the sustainable development of governments around the world. Compared with traditional lighting tools, the ultra-bright white LED lighting source is small in size, light in weight, good in directionality and resistant to various harsh conditions, and has incomparable advantages in terms of power consumption, life and environmental protection. In addition, the energy saving and easy installation of solar lamps make it possible for the LED lamps to reach wherever there are power frequency AC lamps.
1 super bright white LED
1. 1 principle of illumination
Ultra-high-brightness LED (UHB) refers to an LED. LED with a luminous efficacy of 100 lm/W or more generates a stimulated electronic transition light radiation inside it. The wavelengths of light produced are different according to the physical properties of different semiconductor basic materials. The substantial structure of the light-emitting diode is a P-N junction. When the semiconductor P-N is connected with a forward current, a minority carrier is injected, and the light-emitting recombination of the minority carrier is the working mechanism of the light-emitting diode. Semiconductor P-N junction luminescence is essentially solid luminescence, and various solid luminescence is the result of electronic transitions in different energy states within the solid. The luminescence mechanism of semiconductor materials determines that a single LED chip cannot emit a continuous spectrum of white light, and white light must be synthesized in other ways. White LEDs are typically coated with a fluorescent material on a blue-emitting InGaN substrate that emits yellow light when excited by blue light, and a mixture of blue and yellow light forms white light.
1. 2 working characteristics
Since LEDs are DC-powered devices, it is easy to make DC lamps, which are widely used in DC systems, such as solar lighting products. Ultra-bright white LEDs are used in solar luminaires. The single beam-type ultra-high-brightness LED tube produces too much light direction and has a poor overall visual effect. Therefore, flat-type ultra-bright LEDs or flat-type and beam-light should be preferred. The combination of super bright LEDs combines multiple LEDs together and arranges them into a regular LED light source.
Ultra-bright white LED light source must ensure a certain intensity of illumination, but also to have a higher light efficiency, but the increase of current, although the luminous flux increases, but on the other hand, the increase of current will cause the heat of the light source The increase in the loss, usually results in an increase in the temperature of the tube, the overall effect is that the light effect is reduced, so the intersection of the luminous flux and the light effect is the best working point, generally 17. 5 mA.
Super bright white LED light source has the following advantages:
(1) Long life. The life of LEDs is as long as 100,000 h, while the life of incandescent lamps is generally less than 2 000 h, and the life of fluorescent lamps is only about 5,000 h.
(2) High efficiency. Compared with the traditional first-generation lighting source incandescent lamp, the power consumption of LED is only 10%~20% of the former.
(3) Green and environmental protection. Compared with the widely used second-generation fluorescent lamps, LEDs are mercury-free and stroboscopic, making them an environmentally friendly light source.
(4) Low temperature resistance. The ambient temperature is between -40 Â°C and 80 Â°C, and the environment is very adaptable.
2 Super bright white LED application in solar lamps
2. 1 Principle of solar LED lamps
Figure 1 Block diagram of solar lamps
Solar LED lamps collect solar energy from solar modules during the day and convert them into electrical energy for storage. In the evening, LEDs are used for lighting, which is a modern green energy-saving product.
With intelligent control system, no electricity is required for all-weather power supply. In the design of the system, consider the rainy weather, store the extra excess energy in the battery, and ensure that there is enough power for rainy days.
As shown in Figure 1, the detailed principle is: the solar energy converted by the solar cell photovoltaic panel is transferred into the battery pack through the intelligent solar controller. When the natural illuminance falls to the illumination source, the intelligent controller compares the circuit. The electric energy in the battery is output to the LED light source to emit visible light. When the natural illuminance is raised to no longer need the illumination source, the intelligent controller compares the circuit to turn off the power output to the LED light source, so that the LED light source no longer emits energy.
2. 2 The main technology of solar LED lamps
1) Intelligent solar controller: It adopts the control circuit composed of low-power CMOS components. This circuit is completely composed of hardware control system. The key of this circuit is to design a better voltage for the charge and discharge characteristics of the battery. The comparison point, at the same time, the reliable selection of the device, coupled with the charging and discharging state indicating circuit formed by the LED, becomes an intelligent controller with practical functions, and has the functions of preventing overdischarge and overcharging of the battery. The system adopts a direct-coupled charge-discharge controller circuit. According to the matching characteristics of the LED and the battery, the power can be adaptive. In the few months when the solar radiation is insufficient, the battery is discharged due to the low state of charge of the battery. The terminal voltage is also low, so that the load operating current is small, the power is small, and the system can work for a longer period of time. On the other hand, when the solar radiation is sufficient, the load operating current is large, the power is large, and the light is brighter.
2) Solar LED light source: In solar LED lamps, the number of LEDs used by the light source varies from one to thousands. When a certain number of LEDs form a light source, the arrangement and combination are a very important key. point. That is, different arrangements and combinations have an effect on the overall brightness. Based on the optical principle and mathematical derivation, the mathematical model is established on the LED array combination to most effectively exert the luminous efficiency of the super bright white LED, and the number of LEDs per unit area is reduced to reduce the cost.
2. 3 Performance indicators of solar LED lamps
Table 1 Main performance indicators of solar LED lamps
2. 4 Application examples
Solar LED luminaires can be installed in squares, campuses, parks without the need for special personnel management and control, one-time investment and installation without the need for future electricity bills, no need to set up transmission lines or trenching cables, and its unique high brightness and low cost. , streets, etc.
Many domestic solar lamp manufacturers mainly promote solar energy low-voltage energy-saving lamps on the light source, while low-voltage energy-saving lamps need to be pulsed and generated by high-frequency high-voltage oscillation in principle, so in the process of DC inverter, it is inevitable Excessive inefficient power consumption is generated, which increases the power consumption of the overall solar luminaire. In addition, the luminous efficiency of the energy-saving lamp is far less than that of the LED, so the cost of the solar energy-saving lamp series is higher than that under the same brightness and the same rainy day. The cost of solar LED series lamps is more than 50% higher, and the service life of luminous sources is 70% lower than that of solar LED series lamps. Therefore, solar LED series lamps are obviously competitive in the market.
At present, the solar LED lamps mentioned above have been established in Baoding, Beijing, Zhengzhou, Henan and other places, and are widely used in Inner Mongolia and Shaanxi. Its high brightness and low cost have been adopted by society and consumers. Recognition. For example, the column light source of one of the solar LED lamps consumes only about 3.5 W, but the brightness of the emitted light has reached the brightness of 20 W energy-saving lamps or 40 W incandescent lamps, at such low energy consumption and high brightness. With the support of solar energy, the solar cell capacity can only be 12 W, and the 12V/ 24 Ah battery pack can guarantee that the LED light source will continue to work effectively on 5 rainy days, while the 20 W energy-saving lamp will have to Want to work under the same conditions, the solar cell capacity must be at least 70 W, the battery pack should reach more than 70 Ah, and the ultra-bright LED has an average service life of 100,000 hours, and the service period is at least 10 years, and the energy-saving lamp The service life is only 8 000 ~ 10 000 h.
The 21st century will be based on solid luminescent materials, namely the new light source represented by LED and the century of green lighting. In the future, with the great attention and investment of governments, LED will surely become a new and competitive green light source in this century and set off a new revolution in the field of lighting. Solar LED lamps are favored by customers because of their superior energy-saving effect and humanistic light source lighting control. Their cost performance has been basically the same as that of industrial frequency AC lamps, which is easy for customers to accept, so there is a market for solar energy development and application as long as there is sufficient solar energy.
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