With the development and advancement of solar photovoltaic technology, solar cells as a new energy source are first applied to lighting fixtures in civilian applications, and solar lighting products have the dual advantages of environmental protection and energy conservation. Solar LED lighting products are a new generation of green lighting products, its main components include solar photovoltaic cells (PV technology) and semiconductor lighting sources (LED). Because the LED solar light integrates the solar LED lighting system with the advantages of solar photovoltaic power generation and LED solid-state lighting, it realizes the perfect combination of new generation energy and new light source. However, in the design of solar lighting fixtures, there are many factors involved in the control of the light source, the solar cell system, and the battery charge and discharge. Any problem in any one of the links will cause product defects.
First, first understand the composition of solar lamps:
The key to the perfect combination of solar photovoltaic technology with LED lighting is that both are DC, 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 cell into alternating current, thereby greatly improving the efficiency of the entire lighting system. At the same time, with the help of grid-connected technology or the use of batteries to charge and discharge energy, its advantages are more obvious.
1, solar panels
2, charge and discharge controller
3, battery
4, the load
5, the lamp housing
Second, the design should pay attention to the problem: (taking LED lawn light as an example)
1. The characteristics of the LED are close to the Zener diode, the working voltage changes by 0, 1V, and the operating current may vary by about 20mA. For safety reasons, the use of series current limiting resistors under normal conditions, the great energy loss is clearly not suitable for solar lawn lights, and the brightness of the LED varies with the operating voltage. It is a good idea to use the booster circuit. You can also use a simple constant current circuit. In short, you must automatically limit the current, otherwise the LED will be damaged.
2. The peak current of general LED is 50~100mA, and the reverse voltage is about 6V. Be careful not to exceed this limit, especially when the solar cell is reversed or the battery is unloaded. When the peak voltage of the booster circuit is too high, it is likely to exceed this limit. LED.
3, LED temperature characteristics are not good, the temperature rises 5 ° C, the luminous flux drops 3%, pay attention to summer use.
4, the working voltage is discrete, the same model, the same batch of LED operating voltage has a certain difference, should not be used in parallel. Must be used in parallel, and should consider current sharing.
5, super bright white LED color temperature is 6400k ~ 30000k. At present, ultra-bright white LEDs with low color temperature have not yet entered the market, so the solar lawn light produced by ultra-bright white LEDs has relatively poor penetrating power, so attention should be paid to optical design.
6. Static electricity has a great influence on super bright white LEDs. Anti-static facilities should be installed during installation. Workers should wear anti-static wrists. Ultra-bright white LEDs that are damaged by static electricity may not be visible to the eye at the time, but their service life will be shorter.
7, the system should pay attention to the photosensitive sensor, the solar light needs a light control switch, some designers often use a photoresistor to automatically switch the light, in fact, the solar cell itself is an excellent photosensitive sensor, use it to do the photosensitive switch The characteristics are better than the photoresistor. The application of solar garden lights is not a big problem, but for a solar lawn lamp using only 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 under low light is lower. As a result, no black voltage has fallen below 0, 7V, causing the light control switch to malfunction. In this case, the problem can be solved by adding a transistor directly coupled to the amplification.
8. According to the high and low battery voltage control, the solar light often has a high requirement for 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 is reduced in continuous rainy days, or reduce the daily lighting time of solar lamps, which reduces the cost of the system.
9, flickering light, gradually brightening and darkening is a good way to save energy, on the one hand can increase the solar lawn light illumination effect, on the other hand can change the flashing duty cycle to control the average output current of the battery, extend the system working time, or in Under the same conditions, the cost can be reduced.
10. The switching speed of the three-color base color high-efficiency energy-saving lamp. This problem is very important. It even determines the service life of the solar lawn lamp. The three-color base color high-efficiency energy-saving lamp has up to 10~20 times the starting current when starting. The system will cause a large voltage drop when subjected to such a large current. The solar lawn light cannot be started or repeatedly started, resulting in the final damage.
11. At present, solar cells cannot be used in main road lighting. The lighting of the main roads of the highway has legal illumination requirements. In terms of the current conversion efficiency and price of solar cells, this requirement cannot be met. However, in the near future, with the improvement of various technical levels, solar cells will definitely be applied to the illumination of highway main roads.
12. With regard to 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 the battery is the weakest link in the solar power system. The storage capacitor can solve this problem to some extent. The life of the storage capacitor can be more than 10 years, and the control circuit is simple, but the expensive price limits its application. Currently it is only applied to some traffic lights and decorative lights. With the improvement of technical standards and the decline of product prices, it will be the most promising energy storage component for solar cell equipment.
In summary, a solar cell is a huge 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 the level of energy-saving lamps can be reached soon, and the service life can reach more than 100,000 hours. This is the real meaning. Green lighting on.
Reverse Conducting Thyristor(RCT) is also called Reverse- appreciation Thyristor.The characteristic is that a diode is connected in reverse parallel between the anode and cathode of thyristor, so that the transmitting junction of anode and cathode is short-circuited.As a result of this special circuit structure, it has high voltage resistance, high temperature resistance, short turn-off time, low switching voltage and other good performance.For example, the turn-off time of the reverse thyristor is only a few microseconds, and the working frequency is dozens of KHZ, which is better than the fast thyristor (FSCR).This device is suitable for switching power supply and UPS uninterrupted power supply. One RCT can replace one thyristor and one continuous current diode respectively.
Reverse Conducting Thyristor(RCT)
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