Solar powered led pathway lights mainly use the energy of solar cells for work. When sunlight shines on the solar cells during the day, the light energy is converted into electrical energy and stored in the battery, which then turns into solar powered led pathway lights at night by the battery. (Light Emitting Diode) provides power. Its advantages are mainly safety, energy saving, convenience, and environmental protection.
Solar powered led lights light source and power system design methods have developed rapidly in recent years due to the unique advantages of solar led pathway lights. Solar powered led pathway lights are small in power, mainly for decoration, and require high mobility. In addition, circuit laying is difficult and waterproof requirements are high. These make solar powered led pathway lights powered by solar batteries show many unprecedented advantages. Especially foreign markets have huge demand for solar powered led pathway lights. In 2002, only Shenzhen used to manufacture and export solar powered led pathway lights to consume 2MW of solar cells, which is equivalent to 1/3 of the domestic solar cell output that year. It still maintains a strong momentum of development, which people did not expect. At the same time, due to the rapid development, some products are not technically mature enough, and there are many defects in the selection of light sources and circuit design, which reduces the economy and reliability of the products and wastes a lot of resources.
According to the above analysis, we think that the Solar powered led pathway lights below 1w has the function of adjusting light and dark and switching frequently, so LED should be used as the light source. However, when using ultra-bright white light LED, special attention should be paid to the maintenance rate of light pass, otherwise it is easy to cause quality accidents. For the solar powered led path lights with high power, it is more reasonable to use trichromatic primary color high efficiency energy saving lamp at present. What should be emphasized here is that the above conclusion is only the current analysis, when the level of LED technology increases, the price drops, the above conclusion needs to be adjusted.
Improvement of efficiency of boost Circuit
Solar powered led path lights generally has boost circuit, at present, manufacturers use concussion circuit, inductor boost voltage. The inductor adopts the standard color code inductor, and the open magnetic circuit is used in the standard color code inductor. The flux loss is large, so the circuit efficiency is low. If the closed magnetic circuit is used to make inductor boost, such as magnetic ring, the efficiency of boost circuit will be greatly improved. We used to make inductors with medium 10 magnetic rings and carried out comparative experiments under the same conditions. The comparative samples are solar powered led path lights produced by a factory in Ningbo, Zhejiang Province and a factory in Zhenjiang, Jiangsu Province. the efficiency of inductors made by closed magnetic circuit is 20% higher than that by using standard color code inductors.
The main results are as follows:
(1) the characteristics of LED are close to those of stabilized diode, the working voltage changes 0.1 V, and the working current may change about 20ma. In order to be safe, using series current limiting resistance in general, the great energy loss is obviously not suitable for solar powered led path lights, and the brightness of LED varies with the working voltage. Boost circuit is a good way, but also can use a simple constant current circuit, in short, must automatically limit the current, otherwise it will damage the LED.
(2) the peak current of the general LED is 50-100mA, the reverse connection of the anti-high energy battery or the no-load of the battery, when the peak voltage of the booster circuit is too high, it is likely to exceed this limit and damage the LED.
(3) the temperature characteristics of LED are not good, the temperature increases by 5 C, and the luminous flux decreases by 3%. Attention should be paid to the use in summer.
(4) the working voltage is discrete, and the working voltage of the same model and the same batch of LED is different, so it is not suitable to be used in parallel. -to be used in parallel, current sharing should be considered.
(5) the color temperature of ultra-bright white light LED is 6400L ≤ 3000K. at present, the ultra-bright white light LED with low color temperature has not yet entered the market, so the ultra-bright white light LED. The light penetration ability of solar lawn is poor, so we should pay attention to it in optical design.
(6) Electroelectricity has a great influence on ultra-bright white LED. It should be installed with antistatic facilities. Workers should wear antistatic wrist straps. Ultra-bright white LED damaged by static electricity can not be seen by their eyes at that time, but its service life will become shorter.
Charge and discharge Control and temperature compensation of Battery
Because the input energy of solar photovoltaic power generation system is very unstable, the charge and discharge control of solar photovoltaic power generation system is more complex than that of ordinary battery. The success of solar powered led path lights charge and discharge control circuit design will determine the success of the product.
A correct control circuit should have the following functions: prevent backcharging function, prevent overcharging function, prevent battery overdischarge function, lead-acid battery temperature compensation function. For solar powered led path lights, if you use Ni-Cd battery, you do not need to prevent battery overdischarge function, if solar cell power is not large relative to battery, you can also do not consider to prevent overcharging function.
This is why many solar powered led path lights currently use Ni-Cd batteries. But if you use other batteries, consider the above functionality.
The solar powered led pathway lights main contents are as follows:
(1) Prevent backcharging function. -generally speaking, series a diode in the solar cell loop, the diode prevents backcharging, this diode should. This is a Schottky diode, and the voltage drop of the Schottky diode is lower than that of the ordinary diode.
(2) Prevent overcharging function. A drain transistor can be connected in series or in parallel in the input loop, and the voltage identification circuit controls the switch of the transistor. The excess solar cell energy is discharged through the transistor to ensure that there is no excessive voltage to charge the battery. The key is to prevent the selection of overcharge voltage, the single lead-acid battery is 2.2V.
(3) In addition to Ni-Cd batteries, other batteries generally need to prevent battery overdischarge function, because battery overdischarge will cause permanent damage. It should be noted that the solar cell system is generally relatively small rate discharge, so the discharge cutoff voltage should not be too low.
(4) Temperature compensation, which describes that the battery voltage control point varies with the ambient temperature, so the solar powered led path lights system should have a reference voltage controlled by temperature.
For a single lead-acid battery is-3 ≤ 7mVcC, we usually choose-4mV=C
1) photosensitive sensor. solar powered led path lights needs light-controlled switch, designers often use photoresistor to automatically turn on and off lamp, in fact, solar cell itself is an excellent photosensitive sensor, using it as photosensitive switch, the characteristics are better than photoresistance. For the solar powered led path lights which uses only one 1.2VNi-Cd cell, the solar cell module is composed of four solar cells in series, the voltage is low, the voltage in weak light is even lower, so that the black voltage is less than 0.7 V, resulting in the failure of optical switch. In this case, as long as a transistor is directly coupled and amplified, the problem can be solved.
(2) the load is controlled according to the voltage of the battery. solar powered led path lights often require high maintenance time for continuous rain, which increases the cost of the system. When the voltage of continuous rain battery is reduced, we can reduce the number of LED access, or reduce the daily luminous time of solar powered led path lights, which can reduce the cost of the system.
(3) the packaging form of solar cells. At present, there are two main packaging forms of solar cells, laminating and dropping glue. The lamination process can ensure the working life of solar cells for more than 25 years. Although the glue dripping is beautiful at that time, the working life of solar cells is only 1-2 years. Therefore, the low power solar powered led path lights below 1W, in the absence of excessive life requirements, can use glue drop packaging form, for the solar powered led path lights with a specified service life, it is recommended to use lamination packaging form.
(4) flicker and change light. Brightening and darkening is a good way to save energy. On the one hand, it can increase the irradiation effect of solar lawn, on the other hand, it can control the average output current of the battery by changing the flicker duty cycle, prolong the working time of the system, or under the same conditions, it can reduce the power of solar cells, and the cost will be greatly reduced.
(5) the switching speed of trichromatic primary color high efficiency energy saving lamp. This problem is very important, it even determines the service life of solar powered led path lights, trichromatic primary color efficient energy-saving lamp has up to 10-20 times start-up current, the system may have a large voltage drop under the condition of such a large current, solar powered led path lights can not start or start again and again until it is damaged.
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