Key issues in solar LED lighting system design

In today's increasingly scarce energy sources, the use of natural energy has become the focus of attention. In all kinds of natural energy, endless solar energy is favored by its ubiquitous advantages.

In fact, all the energy on Earth comes from the sun. Coal and oil production, plant growth, water and wind movement. .. However, due to the dispersion and instability of solar energy, direct use of solar energy is not easy. 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 to use it. At present, the most important application area of ​​silicon photovoltaic power generation is to solve the lighting problem in areas with power supply difficulties.

In the summer, the sun light is less than 1000 watts per square meter. It can be seen that although the solar energy is huge, it is very scattered. Commercial silicon solar cells constitute a significant advantage in solar LED lighting systems.

The complete solar lighting system consists of the following five parts:

1, solar panels

Solar panels are used to generate electricity when there is sunlight. The power generated depends on the power of the lighting and the lighting time. For example, the power of the lighting fixture is 2 watts, and the continuous illumination time is 10 hours when there is no sunlight. Considering the conversion loss of the conversion circuit, the power generation capacity 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 cells in the presence of sunlight for use when there is no sunlight. The capacity of the battery is determined by the power of the solar panel and the power of the LED lamp and the lighting time. For example, with 2 watt LED lights, 3 watt solar panels, continuous lighting time of 10 hours when there is no sun, 12V/2.2AH batteries can be used.

3, solar charging control circuit

The function of this part of the circuit is to control the charging level when the sunlight is sufficient and the illumination time is long. When the battery is full, the charging is stopped, and the battery is not overcharged to protect the battery and prolong its service life.

4, LED driver

This is the core control circuit of the system. It has three functions:

1. Complete the constant current driving control of the LED so that the current flowing through the LED does not change with the voltage of the battery.

2, with light control function, automatically turn off the lights when the daylight, automatically turn on the lights when it is dark.

3. Low voltage protection. When the battery voltage drops to 10.8 volts, the output is turned off to prevent over-discharge from damaging the battery.

5, Led Lighting

Light-emitting diodes have high light efficiency at low power. Good light-emitting diodes are used for semiconductor lamps. There are good brightness around 2 watts. Two-watt semiconductor lamps can be connected in series with two high-power LEDs of 1 watt. 40 low-power LEDs are connected in series and then 20 strings are connected in parallel. When a small-power LED is used in series/parallel to make a semiconductor lamp, a 10Ω resistor is connected in series to balance the current between the strings. At present, the cost of using a small power LED for semiconductor lamps is relatively low. When making a semiconductor lamp, the LED driver is mounted inside the lamp body.

The DP-12M LED driver used in the LED light in the system has been packaged into a hermetic curing module with a volume of 30x24x15mm, which is suitable for installation inside semiconductor lamps. The module has 5 leads, the red line is connected to the battery positive pole, the black line is connected to the battery negative pole, the yellow line is connected to the positive pole of the light-emitting tube, the white line is connected to the negative pole of the light-emitting tube, the blue line is the control line, and the solar panel is connected.

The SUN-300 used in the system is a 300 mA solar charging controller, which is also packaged as a curing module. The module has three leads, the orange wire is connected to the positive electrode of the solar panel, the red wire is connected to the positive electrode of the battery, and the black wire is the common ground wire. The negative pole of the battery board and battery. The volume is the same as the DP-12M drive.

3 watt solar panels and 12V/2.2AH lead-acid batteries 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 drive module DP-12M turns off the light. When the battery is full, the charge control circuit stops charging. When there is no sunlight, the light automatically lights up under the control of the DP-12M. If continuous lighting causes the battery voltage to be as low as 10.8V, the low-voltage protection inside the DP-12M automatically turns the lamp off 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 drive is suspended to cancel the light control function, and a control switch can be added to the light.

The production of such small-power semiconductor lamps for indoor use generally involves placing a small-capacity storage battery, an LED light-emitting diode, and a DP-12M light-emitting diode driver in the interior of the lamp body to form an integrated lamp, and the solar cell panel can be placed in outdoor use. A fully integrated solar lamp is formed behind the lamp body. The high-power use can externally store the battery. Each battery can carry more LED semiconductor lamps with internal controllers. The solar panels and the charging controller should also increase the power accordingly. Therefore, in practical applications, various practical forms and various power application systems can be formed as needed to meet various lighting needs.

When manufacturing a semiconductor lamp, it is necessary to solve the heat dissipation problem of the LED. The fact that a light-emitting diode is a cold light source means that the illuminant portion of the light-emitting diode is not a hot body, but the resistance heat generated when a current flows through the semiconductor material causes the light-emitting tube to heat up, and the light-emitting diode made of a semiconductor material is not resistant to high temperature and overheating. It will make it age quickly and shorten its service life. When using a small power LED to make a semiconductor lamp, the pipe pitch can be increased to increase the heat dissipation area. When using a high-power LED to make a semiconductor lamp, add a heat sink exposed to the air, or use a metal case to dissipate heat. In short, use the heat dissipation of the lamp body as much as possible to reduce the temperature during operation of the LED, so that the semiconductor lamp can truly long life.

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