Analysis of key issues in solar LED lighting system design

Analysis of key issues in solar LED lighting system design
Introduction: Solar panels are used to generate electricity when there is sunlight. The power generated should be calculated based on the power of lighting electricity and the lighting time. For example, if the power of the lighting fixture is 2 watts, and the continuous lighting time is required to be 10 hours when there is no sunlight, and considering the conversion loss of the conversion circuit, the power generated by the solar panel must be about 3 watts....
In today's increasingly scarce energy, the use of natural energy has become the focus of people's attention. Among various natural energies, the endless solar energy is favored for its ubiquitous advantages.
In fact, all energy on the earth comes from the sun. The generation of coal and oil, the growth of plants, the movement of water and wind. .. .. However, due to the dispersion and instability of solar energy, it is not easy to directly use solar energy. In recent years, with the shortage of energy and the improvement of solar energy utilization technology, direct use of solar energy has become a reality.
There are many ways to use sunlight, and using silicon photovoltaic cells to generate electricity is one of the most convenient ways. At present, the main application area of ​​silicon photovoltaic cell power generation is to solve the lighting problem in areas with difficult power supply.
The sunlight on a sunny day in summer is less than 1,000 watts per square meter. It can be seen that although solar energy is huge, it is very scattered. The light/electricity conversion efficiency of commercial silicon solar panels is about 14%, and the price is also relatively high. Therefore, solar energy is generally used for low-power power generation. Due to the low power generation, the power consumption cannot be too large. In order to achieve the best lighting effect at a small input power, the luminous efficiency of the lighting source is very important. At low power, the light efficiency of traditional light sources is very low and is not suitable for use in solar lighting systems. In recent years, semiconductor light emitting diode technology has been continuously improved and has become a new type of lighting source. It has high light efficiency when used in low-power lighting applications. The advantages of solar LED lighting systems composed of solar panels and batteries are obvious.
A complete solar lighting system mainly consists of the following five parts:
1. Solar panels
Solar panels are used to generate electricity when there is sunlight. The power generation should be calculated based on the power and lighting time of the lighting. For example, if the power of the lighting fixture is 2 watts, and the continuous lighting time is required to be 10 hours when there is no sunlight, and considering the conversion loss of the conversion circuit, the power generation of the solar panel must be about 3 watts.
2. Battery
The function of the battery is to store the electricity generated by the solar cell when there is sunlight for use when there is no sunlight. The capacity of the battery should be determined according to the power of the solar panel and the power of the LED lamp and the lighting time. For example, if a 2-watt LED lamp and a 3-watt solar panel are used, and the continuous lighting time is required to be 10 hours when there is no sun, a 12V/2.2AH battery can be selected.
3. Solar charging control circuit
The function of this part of the circuit is to control the charging level when the sun is sufficient and the lighting time is long. The battery will stop charging when it is full, so as to prevent the battery from being overcharged and damaged, so as to protect the battery and extend its service life.
? 4. LED driver
This is the core control circuit of the system. It has three functions:
①. Complete the constant current drive control of the light-emitting diode so that the current flowing through the light-emitting tube does not change with the voltage of the battery.
②. It has a light control function, automatically turning off the light at dawn and automatically turning on the light at dark.
③. Low voltage protection. When the battery voltage drops to 10.8 volts, the output is turned off to avoid over-discharge and damage to the battery.
5. LED lighting lamp
The light-emitting diode has a high light efficiency at low power. If a good light-emitting diode is used to make a semiconductor lamp, it will have a good brightness of about 2 watts. A 2-watt semiconductor lamp can be made of two 1-watt high-power light-emitting diodes in series, or 40 low-power light-emitting tubes, 2 in series and then 20 in parallel. When using low-power light-emitting diodes in series/parallel to make a semiconductor lamp, a 10Ω resistor should be connected in series in each string to balance the current between the strings. At present, the cost of using low-power light-emitting tubes to make semiconductor lamps is relatively low. When making semiconductor lamps, the LED driver is installed inside the lamp body.
A practical implementation scheme of a 2-watt solar LED lighting system is shown in the figure:
This system uses two 1-watt high-power light-emitting tubes, which can meet the lighting requirements of a small range.
The DP-12M LED driver used in the LED lamp in the system has been encapsulated into a sealed curing module with a volume of 30x24x15mm, which is suitable for installation inside semiconductor lamps. The module has 5 leads, the red wire is connected to the positive pole of the battery, the black wire is connected to the negative pole of the battery, the yellow wire is connected to the positive pole of the LED, the white wire is connected to the negative pole of the LED, and the blue wire is the control wire, which is connected to the solar panel.
The SUN-300 used in the system is a 300 mA solar charge controller, which is also packaged into a curing module. The module has three leads, the orange wire is connected to the positive pole of the solar panel, the red wire is connected to the positive pole of the battery, and the black wire is the common ground wire, which is connected to the negative pole of the solar panel and the battery. The volume is the same as the DP-12M driver.
? The 3-watt solar panel and the 12V/2.2AH lead-acid battery are used for power generation and storage.
When there is sunlight, the solar panel charges the battery through the SUN-300, and the light control function of the LED driver module DP-12M turns off the light. When the battery is full, the charging control circuit stops charging. When there is no sunlight, the light automatically lights up under the control of the DP-12M. If the battery voltage drops to 10.8V due to continuous lighting, the low-voltage protection function inside the DP-12M will automatically shut down the light to protect the battery from over-discharge damage. Therefore, this is an unattended automatic solar lighting system. If the LED light is to be used indoors, the blue line of the driver can be suspended to cancel the light control function, and a control switch can be added to the light.
To make this kind of low-power semiconductor light for indoor use, a small-capacity battery, LED light-emitting diode, and DP-12M light-emitting diode driver are generally placed inside the lamp body to form an integrated lamp. When used outdoors, the solar panel can be placed behind the lamp body to form a fully integrated solar light.
For high-power use, the battery can be placed externally, and each battery can carry multiple LED semiconductor lights with built-in controllers. The solar panel and charging controller should also increase the power accordingly. Therefore, in actual applications, various practical forms and various power application systems can be formed as needed to meet various lighting needs.
When making semiconductor lights, the heat dissipation problem of the light-emitting diode must be solved. Saying that light-emitting diodes are cold light sources only means that the luminous body of the light-emitting diode is not a burning body. However, the resistance heat generated when current flows through the semiconductor material will still cause the light-emitting tube to heat up. Light-emitting diodes made of semiconductor materials are not resistant to high temperatures. Overheating will cause them to age quickly and shorten their service life. When using low-power light-emitting tubes to make semiconductor lamps, the tube spacing can be increased to increase the heat dissipation area. When using high
-power light-emitting tubes to make semiconductor lamps, a heat sink exposed to the air should be added, or the metal shell should be used for heat dissipation. In short, the heat dissipation of the lamp body should be used as much as possible to reduce the temperature of the light-emitting tube when it is working, so that the semiconductor lamp can truly have a long life.