Technical Analysis Of Solar LED Lamp Design
With the development and progress of solar photovoltaic technology, solar cells , as a new energy source, are firstly used in lighting fixtures for civilian use.
With the development and progress of solar photovoltaic technology, solar cells , as a new energy source, are firstly used in lighting fixtures for civilian use. Solar lighting products have the dual advantages of environmental protection and energy saving. Solar LED lighting products are a new generation of green and environmentally friendly lighting products. Its main components include solar photovoltaic cells (PV technology) and semiconductor lighting sources (LEDs). Because LED solar lights integrate the advantages of solar photovoltaic power generation and LED solid-state lighting, the solar LED lighting system realizes the perfect combination of a new generation of energy and new light sources. However, in the design of solar lighting fixtures, many factors are involved in the control of light source, solar cell system, and battery charge and discharge. Any problem in any link will cause product defects.
First, first understand the composition of solar lamps and lanterns:
The key to the perfect combination of solar photovoltaic power generation technology and LED lighting is that both are direct current, low voltage and can match each other. Therefore, the combination of the two does not need to convert the direct current generated by the solar cells into alternating current, thus greatly improving the efficiency of the entire lighting system. At the same time, with the help of grid-connected technology or the use of battery charging and discharging energy, its advantages are more obvious.
1. Solar panel
2. Charge and discharge controller
5. Lamp housing
2. Problems to be paid attention to when designing and using: (Take LED lawn lamp as an example)
1. The characteristics of the LED are close to those of Zener diodes, the operating voltage varies by 0, 1V, and the operating current may vary by about 20mA. For the sake of safety, the series current limiting resistor is generally used, and the huge energy loss is obviously not suitable for solar lawn lights, and the brightness of the LED varies with the working voltage. It is a good way to use a boost circuit, and a simple constant current circuit can also be used. In short, the current must be automatically limited, otherwise the LED will be damaged.
2. Generally, the peak current of LED is 50~100mA, and the reverse voltage is about 6V. Be careful not to exceed this limit, especially when the solar battery is reversed or the battery is empty, and the peak voltage of the boost circuit is too high, it is likely to exceed this limit and damage the LED. LED.
3. The temperature characteristics of LED are not good, the temperature rises by 5°C, and the luminous flux drops by 3%, so please pay attention to it in summer.
4. The working voltage is highly discrete. The same model and the same batch of LEDs have certain differences in working voltage, so it is not suitable for parallel use. It must be used in parallel, and current sharing should be considered.
5. The color temperature of super bright white LED is 6400k~30000k. At present, ultra-bright white LEDs with low color temperature have not yet entered the market, so solar lawn lights made of ultra-bright white LEDs have poor penetrating ability, so attention should be paid to optical design.
6. Static electricity has a great impact on ultra-bright white LEDs. Anti-static facilities must be installed during installation, and workers must wear anti-static wrists. Ultra-bright white LEDs damaged by static electricity may not be visible to the naked eye at the time, but their service life will be shortened.
7. Pay attention to the photosensitive sensor in the system combination. Solar lights need light-controlled switches. Some designers often use photoresistors to automatically switch lights. In fact, the solar battery itself is an excellent photosensitive sensor, and it is used as a photosensitive switch. , The characteristics are better than photoresistors. It is not a big problem for the application of solar garden lights, but for solar lawn lights that only use one 1, 2VNi-Cd battery , the solar cell module is composed of four solar cells connected in series, the voltage is low, and the voltage is lower under weak light. Even when it was dark, the voltage was lower than 0.7V, causing the light control switch to fail. In this case, as long as a transistor is directly coupled and amplified, the problem can be solved.
8. Control the load size according to the battery voltage level. Solar lights often have high requirements for the duration of continuous rainy days, which increases the cost of the system. We reduce the number of LEDs or energy-saving lamps connected when the battery voltage drops in continuous rainy days, or reduce the daily light-emitting time of solar lamps, which reduces the cost of the system.
9. Flickering and dimming, brightening and dimming are good ways to save energy. On the one hand, it can increase the irradiation effect of solar lawn lights. On the other hand, it can control the average output current of the battery by changing the blinking duty cycle, prolonging the working time of the system, or Under the same conditions, the cost can be reduced.
10. Switching speed of three-color primary-color high-efficiency energy-saving lamps. This problem is very important, it even determines the service life of the solar lawn lamp, the three-color primary color high-efficiency energy-saving lamp has a starting current as high as 10 to 20 times when it is started, and the system will cause a large drop in voltage when it bears such a large current. , the solar lawn lamp cannot be started or started repeatedly, resulting in final damage.
11. At present, solar cells cannot be used in main road lighting. There is a statutory illuminance requirement for the lighting of main roads, but the current conversion efficiency and price of solar cells cannot meet this requirement. But in the near future, with the improvement of various technical levels, solar cells will definitely be applied to the lighting of main roads.
12. Regarding energy storage capacitors, the service life of solar cells is more than 25 years, and the service life of ordinary batteries is 2 to 3 years, so batteries are the weakest link in solar power systems. Energy storage capacitors can solve this problem to a certain extent. The service life of the energy storage capacitor can reach more than 10 years, and the control circuit is simple, but the high price limits its application. Currently, it is only used in some traffic lights and decorative lights. With the improvement of technical level and the decline of product price, it will be the most promising ideal energy storage component for solar cells.
To sum up, a solar cell is a giant PN junction that converts solar energy into electrical energy. LED is another PN junction that can convert electrical energy into light. Its conversion efficiency is constantly improving. It is believed that it will soon reach the level of energy-saving lamps, and its service life can reach more than 100,000 hours. This is the real meaning. Green lighting on.