LED lighting industry is an emerging industry, with its unique advantages by people of all ages. Now in photovoltaic projects, improve light efficiency, energy saving and high reliability has become a common pursuit of the goal. When we discussed and used LED light source, think of the long life of the LED, energy saving, high brightness. It is also because of this LED light source was popular. LED light source despite these advantages, but not as people say so magical. Only to its accompanied by the appropriate and efficient LED power supply, and reasonable circuit design, sound anti-static measures, proper installation and use of technology in order to give full play to the advantages of the LED light source above. Here I LED light source in the engineering application of some common sense to do a brief introduction, for your reference.

Second, LED life of understanding: LED's life, generally considered the ideal state in 100,000 hours. In actual use of the process with the use of its intensity will gradually decay over time, that electrical energy into light energy efficiency decreased. The effective range of light intensity that we can really be used in its initial light intensity decays to 70% or more, whether life can be defined as the luminous efficiency decreased to 70% of the time. There is no clear national standards to measure. And the life of its LED chip packaging technology and quality, process directly related, according to test data for a certain LED chip packaging factory some continuous light conditions at 20mA its brightness after 4000 hours decay reached 50%. But with the improvement of technology, technology, the light fades slowly more and more time, that longer life expectancy.

Three, LED energy-saving and reliability: LED is a current control element, the current flowing through the direct electrical energy into light energy, it is also known as the photoelectric converter. Because of friction and mechanical losses do not exist, so the energy saving is higher than the general efficiency of the light source, but the LED light source and not like an ordinary light source can be used directly as the grid voltage, it must be configured with a voltage conversion device to meet their rated voltage, current, to work properly, the LED dedicated power supply. However, a variety of LED power conversion efficiency and performance vary, so choose a suitable and efficient LED dedicated power supply, in order to truly reflect the LED light source performance features. Because of the low efficiency of the LED power supply itself consumes a lot of power, with the LED in the use of the process did not reflect the characteristics of energy-efficient LED's. And LED power supply must also be highly reliable power supply to the LED light source system long life.

Fourth, the basic characteristics of the LED and precautions when using 1. Optical characteristics: LED current through the LED greater within its current limit parameters, the higher its luminous brightness. That is proportional to the current through the LED brightness of the LED. However, green and blue and white in a high current saturation phenomenon occurs not only significantly reduce the luminous efficiency, and life will be shortened. 2. Optical properties: LED by color red, orange, yellow, green, blue, purple, white and other colors. Brightness divided by general light, bright, ultra-bright, etc., the same kind of chip in different package, its brightness is not the same. According to human vision can be divided into visible and invisible. According to how much light color can be divided into many types of monochrome, color, colorful. Purity of the color vary widely different prices, the current price of pure white LED special expensive. At the same time emitting a different perspective, also different light effects, the use of special needs attention. 3. Common LED electrical performance parameters: (1) LED forward voltage, different colors of LED forward current at rated conditions, with their different forward voltage drop value, red, yellow: between 1.8 ~ 2.5V, green and blue: between 2.7 ~ 4.0V. For the same color LED, the forward voltage drop and the light intensity is not entirely consistent. In the following table: LED Model:.. 5 4HCA light color appearance of the color wavelength λD (nm) Forward Voltage VF luminance Iv (mcd) IF = 20mA Min Max red transparent water 645 ~ 660 ~ 50 1.8 2.5 300 570 - transparent yellow-green water 575 1.8 2.5 50 300 585 transparent yellow water to 590 1.8 2.5 500 to 5,000 transparent blue water 455 ~ 475 2.7 4.0 500 to 7,000 515 to 535 transparent green water 2.7 4.0 2,000 to 10,000 blue-green water, clear 490 to 515 2.7 4.0 2000 10000 white transparent water - 2.7 4.0 3,000 to 15,000 should make full use of the forward voltage drop at rated current values are the same, a small range of LED light intensity in the same circuit. The only way to ensure consistent LED glow. The specific electrical parameters according to product label spectral parameter values of each packaging factory packaging provided. (Some companies are inconsistent with each batch sorting) (2) LED rated current. LED rated current varies, Common LED current is typically 20mA, High Power LED current is typically 40 mA or 350 mA range. Current parameters according to each specific packaging plant to provide value. General LED reverse voltage: VR = 5V under conditions of reverse current: IR≤10μA. (3) LED power LED power sizes also vary, there is 70mW, 100mW, 1W, 2W, 3W, 5W etc., it must be based on the selected LED, design and rational use of circuit and configure the appropriate LED number to make fully meet LED power rating, if the design of the circuit so that each LED balancing voltage or current is too high it will seriously affect the life of LED LED burn even if the share of low voltage or current is strong enough to excite the LED light We can not give full play to the desired effect LED, reach our desired goal. 4. Temperature characteristics: (1) LED soldering temperature should be below 250 ℃, soldering time between 3 ~ 5S. To avoid high temperature so that the LED chip damage. (2) The LED light output is inversely proportional to temperature, the temperature not only affects the brightness of the LED, but also affect its life. Minimize the use of heating circuit, and do some heat treatment. 5. Anti-static properties. LED assembly process must strengthen anti-static measures, because the operation will generate static electricity and the human body itself, for the most vulnerable LED two-electrode electrostatic reverse breakdown, which seriously affect the life of the LED even make it completely scrapped. Such as anti-static environment is not very perfect, can give users increased LED antistatic wrist strap, set a good anti-static grounding systems, ion fans and other equipment.

Five, LED circuit connected to a common form of 1. Series: This circuit requires a higher voltage power supply. V = total sum of each LED VF = VF1 + VF2 + VF 3 + VF 4 ------ + VF NI = total value of single LED IF 2. Parallel: This circuit requires a power supply to provide a higher current. V = VF total value of single LED I = total each LEDIF = IF1 + IF2 + IF3 + IF4 ------ + IFN3. Series / parallel combination of a, in practice, the load is often used LED array by series-parallel formation; b, the LED of connection in series / parallel combination, can significantly reduce the impact due to a small number of LED's VF due to the inconsistent; c, LED array format or the number of changes, the current limiting resistor should also change accordingly. Form d, series / parallel combination of the output current will occur with the input voltage and ambient temperature changes and other factors more significant; 4. In order to effectively control the current in the circuit, to be equipped with the appropriate current limiting resistor in the circuit. R = (V input voltage -VLED total voltage) / I (the current limiting resistor current) limiting resistor main function is to control the LED current, the voltage smoother, and brightness of each parallel branch more uniform. Current limiting resistor big is better, but the limiting resistor value can not be too large, otherwise it will increase the power loss and component temperature.

Sixth, classification and characteristics of the power supply 1, according to the driving mode can be divided into two categories: (1) constant formula: a, constant current output driver circuit is constant, while the output DC voltage but with the load resistance of different sizes within a certain range, the load resistance is small, the output voltage is low, the greater the load resistance, the higher the output voltage; b, constant load short circuit is not afraid, but non-load completely open. c, constant current drive circuit drives the LED is an ideal, but the relatively high price. d, should pay attention to withstand the maximum current and voltage values, which limits the number of LED's use; (2) Regulators formula: a, When the voltage regulator circuit parameters to determine the output voltage is fixed, and but with the current output load decrease and change; b, the regulator circuit is not afraid of open load, but the load is prohibited completely short-circuited. c, to the regulator drive circuit drives LED, each string need only add an appropriate resistor so that each string of LED display brightness average; d, the brightness will be affected by changes in the voltage from the rectifier. 2, according to the circuit configuration mode classification (1) resistor, capacitor step-down ways: through capacitor step-down, when the use of flashing due to charge and discharge the role of instantaneous current through the LED is great, easy to damage the chip. Vulnerable to fluctuations in grid voltage, power efficiency, low reliability. (See Figure 1) (2) Resistance Buck ways: through resistance voltage, interference from the grid voltage variation is larger, is not likely to cause the power supply, the dropping resistor to consume much of the energy, so this power supply mode power efficiency is very low, and the system reliability is low. (See Figure II) (3) conventional transformers step-down mode: power, small size, weight emphasis on power efficiency is very low, generally only 45% to 60%, it is generally rarely used, reliability is not high. (4) electronic transformer step-down mode: low power efficiency, voltage range is not wide, generally 180 ~ 240V, moire large. (5) RCC buck mode switching power supply: voltage range is wide, the power efficiency is relatively high, generally can achieve 70% to 80% of applications are wide. Since the oscillation frequency of this type of control is not continuous, the switching frequency is not easy to control the load voltage ripple coefficient is relatively large, abnormal loads and poor adaptability. (6) PWM control mode switching power supply: mainly composed of four parts, the input rectifier filter section, output rectifier filter section, PWM voltage control section, switching energy conversion section. The basic principle of PWM switching regulator is in the input voltage, the internal parameters and external load changes, the control circuit is controlled by the difference signal with a reference signal closed-loop feedback to adjust the main circuit switching device turns on the pulse width, so that the switching power supply output voltage or current is stable (ie, the corresponding power supply or constant current power supply). High power efficiency, in general can do 80% to 90%, the output voltage, current stability. This circuit has generally comprehensive protection measures, a high reliability of power supply. As can be seen from the above described PWM control mode designed LED power supply LED power supply is ideal.