The quality of the LED driver power supply will directly affect the LED life, so how to do a LED driver power supply, LED power supply designers a top priority.
In the current life in order to save energy, LED 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 do an LED drive power is LED power supply designers The top priority. This article describes some of the LED driver power supply problems, hoping to engineer a little help.
1, LED drive circuit directly affects life
We are talking about LED driver includes a digital drive and analog drive types, digital drive driving digital circuit means, including digital dimming control, RGB full color changing and so on. Analog circuit simulation driving means driving, including AC constant current switching power supply, DC constant current control circuit. Driver circuit by the electronic components, including semiconductor elements, resistors, capacitors, inductors, etc. These components have life, any device failure will cause the failure of the entire or part of the circuit function failure. LED life is 5-10 million hours by 50,000 hours count, continuous light, nearly six years of life. Switching power of life is difficult to achieve six years, the market ** switching power supply warranty period is usually 2-3 years, up to 6-year warranty is a military grade power supply, the price is 4-6 times the normal power supply, the general lighting plant is very difficult to accept. So much for the fault LED lighting driver circuit.
2, the heat problem
LED cold light source, operating junction temperature not exceeding the limit, but also to leave a margin design. The lighting is designed to consider the appearance, ease of installation, many aspects of light, heat, etc., to find a balance point in a number of factors, such as a whole is the development of lighting fixtures .LED best time is not long, you can learn little experience, a lot of design is constantly improved. Some manufacturers use the power LED lamps for outsourcing or outsourcing, lighting designer for power know much larger space to LED heat dissipation, small to supply the cooling space. Generally good lighting design and then find the appropriate power to support, so give the power to bring some difficulty matching. Frequently encountered due to the smaller space inside the lamp or high internal temperatures, and low cost control, can not be assigned to the appropriate power source. Some LED lighting plant has a power research and development capabilities, at the beginning of the initial design lamps evaluate power supply design simultaneously, will be able to solve the above problems. To be considered in the design of the cooling heat and power LED, the overall control of the temperature rise of the lamp, so as to design a better lighting.
3, power supply design problems
a, power design. Although the LED luminous efficiency, but there are 80-85% of heat loss, resulting in an internal temperature 20-30 lamps ($ 10.6626) degrees, 25 degrees if the temperature conditions, there are 45-55 degrees inside the lamp, power long time work in high temperature environment, to ensure the life we must increase the power margin, generally left to the 1.5-2-fold margin.
b, component selection. The internal temperature of 45-55 degrees lower lighting conditions, as well as the internal power supply temperature around 20 degrees, the temperature near the device to reach 65-75 degrees. Some elements in high temperature parameter drift, some life will be shortened, so the device to choose, pay special attention to long-term use can be at a higher temperature electrolytic capacitors and conductors.
c, the electrical properties of the design. Switching Power Supply for LED design parameters, the main parameters are constant, the size of the current depends LED brightness, if the bulk of the current error is large, the brightness of the entire batch of uneven light. And the change in temperature can cause the power supply output current offset. Batch error is usually controlled within +/- 5%, in order to ensure consistent brightness light .LED forward voltage drop of a deviation, constant voltage power supply design range to include LED voltage range. Use multiple LED series, when multiplied by the series number of minimum pressure drop lower voltage, maximum voltage drop multiplied by the number of tandem upper limit voltage constant current power supply voltage range slightly wider than this range, upper and lower limits of each general stay 1-2V margin.
d, PCB layout design. LED lighting
power left smaller sizes (except external power supply), so higher in PCB design, factors to be considered, too. Enough to stay a safe distance, requiring the input and output isolated power supply, the primary circuit and the secondary side voltage circuit requirements 1500-2000VAC, at least on the PCB 3MM enough to stay away. If the metal shell of the lamp, the entire power distribution board should also consider the safety distance and high-pressure part of the housing. If no space is necessary to ensure a safe distance from the case to use other measures to ensure that the insulation, such as punch holes in the PCB, add insulation paper, insulation potting 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 lighting, the relevant state departments are to study and formulate domestic sales of lighting fixtures certified reference standard, the export is done CE or UL certification, and some reference standard LED lamps do abroad. So for this case, switching power supply design must meet these criteria are more difficult, we can meet different requirements for different certification.
4, using the parameters
Purchased power mainly depends on the choice of constant current and constant voltage range. LED current value is selected as the standard current downwards. Voltage range of options should be moderate, try not to choose a wide range, to avoid wasting power.