Solar-powered high-brightness white
This article describes the flash device is a camera to capture speeding on the highway when the auxiliary lighting. Based on field work requirements, lighting adequate source of energy and the life of the circuit using a solar battery-powered, thus requiring the device has a static low-power features. White LED with high brightness, low power consumption, long life advantages compared with other lighting devices. This article will specifically introduce a solar-powered high-brightness white LED flash circuit design program, described the static low power consumption of the power supply design and circuit implementation, and discuss the problem should be noted that in the design process.
Two system components
Figure l-based system block diagram. The following charging protection circuit section in Figure 1, the flash control circuit part of the white LED protection circuit parts of the analysis.
2.1 Solar charging protection circuit
2.1.1 solar panels
Solar panels, not only during the day can provide electricity, and to provide electricity at night. Solar panels with the transistor composed of semiconductor material is silicon, there are also some other alloy.
Different parts of the surface of the solar panels made up of two properties. By light irradiation, the light energy into electrical energy, so that current flows from one side to the other.
Solar panels to the sun or the light irradiation, generally can be issued the equivalent 1/10 to receive light energy. In order to make solar cell panels to minimize light reflection, the light energy into electrical energy, generally cast in the above layer to prevent light reflection film on the surface of the solar panels purple.
The solar-powered part by solar panels (PV modules), the charging circuit and battery. PV modules absorb light in the daytime, the solar energy into electrical energy stored in solar cells. Generally sunny, ideal light intensity, full of power as long as four hours. The system uses a 15V solar panels, the actual measured solar panels at both ends of the supply voltage is 17V ~ 20V, the charging current of 200mA ~ 800mA.
2.1.2 battery design capacity
Energy storage for solar cell power supply system is the battery. Phalanx supporting batteries and solar cells usually work in a floating state, the voltage with the square power generation and load changes in electricity consumption. Its capacity is much greater than the required load power. The battery energy is also affected by the influence of ambient temperature. In order to match with the solar cells, requiring the battery long life and simple maintenance.
(1) the selection of the battery
Types of batteries and solar cells, supporting the use of a lot of the widely used lead-acid maintenance-free batteries, three kinds of ordinary lead-acid batteries and alkaline nickel-cadmium battery. Domestic use of lead-acid maintenance-free batteries, because of its inherent "free" maintenance features and characteristics of the environment cleaner, it is suitable for reliable solar power systems, especially unattended workstations. Ordinary lead-acid batteries require regular maintenance and its larger environmental pollution, mainly suitable for the ability to maintain or low-grade occasions. Alkaline nickel-cadmium batteries have better low-temperature, over charge, over discharge performance, but its price is higher, applies only to special occasions.
(2) battery capacity calculation
The capacity of the battery is very important to ensure continuous power supply. Within a year, square generating capacity in each month are very different. Square generating capacity can not meet the electricity needs to rely on battery power to give complement; more than the electricity needs of the month, rely on the battery the excess energy stored. So square generating capacity deficiencies and excess value, is one of the basis for determining the battery capacity. Similarly, the continuous rainy days during the load electricity must also be obtained from the battery. Therefore, during the power consumption is one of the factors determine the battery capacity.
Therefore, the battery capacity Bc is calculated as follows:
Where: A is a safety factor of 1.1 to 1.4;
QL is the load average power consumption, operating current multiplied by the number of hours worked;
NL for the longest consecutive number of rainy days;
To a temperature correction factor, and generally take more than 0 ° C l, -10% 1.1 -10 ℃ to take 1.2 below;
Cc battery depth of discharge, general lead-acid battery 0.75 0.85 alkaline nickel-cadmium batteries.
The system requirements, by calculating the the selection 12V8Ah ordinary lead-acid batteries.
2.1.3 The charge protection circuit
Solar charging protection circuit, overcharge and over discharge protection of two parts.
Overcharge protection: when the solar panels to charge the battery, the battery output voltage to exceed 14.5V overcharge road control relay to make solar panels to stop charging. Battery output voltage down to 14V, the solar panels to re-charge the battery.
Over-discharge protection: When the battery output voltage is below 10.5V, the battery stops the supply of outside circuit. When the battery voltage exceeds 10.5V, re-out circuitry.
Charging protection circuit consists of two operational amplifiers, the circuit shown in Figure 2. In Figure 2 Vi1, Vi2 were battery output voltage Vref is the reference voltage for the op amp, and its specific value depending on the requirements set by the user. In the actual design process, pay attention to the feedback resistor selection in Figure 2, the feedback resistor, the greater the control output corresponding to the input Vi back to the difference between the smaller.
(This article switched from electronic engineering world: http://www.eeworld.com.cn/dygl/2012/0111/article_9916.html)
