Analysis of the drive power LED lighting problem

For energy saving, LED highbay lights has been a great promotion, but we need to have a power LED driver, which will directly affect the quality of life of the LED, so how to make a LED driver LED power supply is the most important designers . This article describes some of the LED drive power problems, hoping to engineer a little help.
1, the driving circuit is directly affected LED life
We are talking about LED driver includes digital and analog drive two drives, digital drive means driven digital circuits, including digital dimming control, RGB full color changing, etc.. Analog circuit simulation driving means drives, including AC constant current switching power supplies, DC constant current control circuit. The driving circuit by the electronic components, including semiconductor elements, resistors, capacitors, inductors, etc. These components are life, failure of any one device will result in failure of the circuit or part of function failure. LED life is 5-10 million hours, calculated at 50,000 hours, continuous light, nearly six years of life. Switching power supply life is difficult to achieve six years, switching power supplies available on the market warranty period is generally 2-3 years, reaching 6-year warranty is powered military level, the price is 4-6 times the normal power supply, the general Lighting Factory is very difficult to accept. So much for the failure of LED lighting driver circuit failure.
2, the heat problem
LED is cold light source, operating junction temperature must not exceed the limit value, the design when they leave a certain margin. The design of the lamp to be considered beautiful appearance, easy installation, light, heat, and many other aspects, to find a balance point of a number of factors, so that the overall lighting is the best. LED highbay lights development time is not long, you can learn little experience, many designs are constantly improved. Some manufacturers use LED lighting power supply for the outsourcing or outsourcing, lighting designers know much about the power to LED heat a larger space, the power dissipation to less space. Generally good lighting design and then find a suitable power to support, thus giving the power to bring some difficulty matching. Often encountered due to a smaller space inside the lamp or the internal temperature is high, and low cost control can not be assigned to an appropriate power source. Some LED lamps power plant has R & D capabilities, at the beginning of the early assessment of the design of lamps, power supply design simultaneously, we can solve the above problem. To be taken into account in the design of LED heat and power dissipation, the temperature rise of the overall control of lighting, so as to design a better light.
3, power supply design problems
a, power design. Although the LED luminous efficiency, but there are 80-85% of heat loss, resulting in a 20-30 degrees inside the lamp temperature rise, if the room temperature of 25 degrees circumstances, there is 45-55 degrees inside the lamp, the power for a long time in a hot environment to work, to ensure that the life we ​​must increase the power margin, generally left to the 1.5-2 times the margin.
b, component selection. Lamps internal temperature 45-55 degrees, the power and the internal temperature of about 20 degrees, the temperature near the element to reach 65-75 degrees. Some components will drift parameters at high temperatures, and some life will be shortened, so the device can be selected for prolonged use at higher temperatures, with particular attention electrolytic capacitors and wires.
C, electrical performance design. Switching Power Supply for LED design parameters, mainly constant parameter determines the size of the current LED brightness, large errors if the current batch, the entire batch of uneven brightness lamp. And changes in temperature can cause the power supply output current offset. Batch error is generally controlled within + / -5% or less, in order to ensure consistent brightness lamp. LED forward voltage drop of a deviation, constant current power supply design voltage range to include the LED voltage range. Multiple LED series using time series multiplied by the number of minimal pressure drop lower voltage, maximum voltage drop multiplied by the maximum number of concatenated voltage, constant current power supply voltage range slightly wider than this range, the general upper and lower limits of each stay 1-2V margin.
d, PCB layout design. LED lamps left to power small size (unless it is an external power supply), so the higher the PCB design, also many factors to consider. Enough to stay a safe distance, requiring the input and output isolated power supply, primary circuit and the secondary side circuit requires voltage 1500-2000VAC, at least on the PCB 3MM enough to stay the distance. If the metal shell of the lamp, the entire power distribution board should also consider the safety of high-pressure part and the shell distance. If no space is necessary to ensure a safe distance from the case to use other measures to ensure the insulation, such as punch holes in the PCB, add insulation paper, potting insulation glue. Another layout must also consider the heat balance, the heating element should be evenly distributed, not centralized place, to avoid local temperature. Electrolytic capacitors away from heat, slow down aging and prolong life.
e, authentication issues. Currently there are no standards for LED highbay lights  the relevant departments are studying the development, the domestic sales of lighting fixtures certification is the reference standard, the export is done CE or UL certification, and some reference to foreign standard LED lamps do. So this situation, switching power supply design to meet more of these criteria is difficult, we can only meet the different requirements for different authentication.
4, power supply problems in the application
5, the use of parameters.
Purchased power supply mainly depends on the choice of the constant current and constant voltage range. Constant value selection criteria for the LED current downwards. Voltage range of options should be moderate, try not to choose a larger range, to avoid waste of power.


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