The quality of LED driver power supply will directly affect the life of the LED, so how to do an LED driver power supply, LED power supply designer's top priority. This article describes some of the LED driver power supply problems in the hope that useful to the design engineer. 

 

1, LED drive circuit directly affect life 

 

We are talking about LED driver includes two types of digital drives and analog drive, digital drive means driven digital circuits, including digital dimming control, RGB full color changes and so on. Analog circuit simulation driving means drives, including AC constant current switching power supply, DC constant current control circuit. Driver circuit electronic components, including semiconductor elements, resistors, capacitors, inductors, etc. These components have a life, any device failure will cause the failure of the entire or part of the circuit ineffective. LED life is 5-10 million hours by 50,000 hours count, continuous light, nearly six years of life. Switching power supply life is difficult to achieve six years, switching power supply warranty on the market is generally 2-3 years, up to 6 year warranty is military power level, the price is 4-6 times the normal power supply, the general lighting plant is difficult to accept. So much for LED lamp drive circuit failure fault. 

 

2, the heat problem 

 

LED cold light source, operating junction temperature must not exceed limits, but also to leave some margin design. Entire lighting design to consider appearance, easy installation, many aspects of light, heat, etc., to seek balance many factors, so the overall development time is the best lighting fixtures. LED not long, can learn little experience, a lot of design is constantly improved. Some manufacturers of LED lamps used for outsourcing or outsourcing power, lighting designers know much power to the LED heat dissipation larger space, the smaller the power of heat to space. Lighting design is generally good and then find a suitable power source to complete, thus giving the power to bring a certain degree of difficulty matching. Often encountered inside the lamp due to a smaller space, or a higher internal temperature, and low cost control, can not be assigned to an appropriate power source. Some LED lighting plant has a power research and development capabilities, at the beginning of the initial lighting design to assess the power of design simultaneously, will be able to solve the above problems. To be taken into account in the design of the cooling LED heat and power, the overall lamp temperature control, in order to design a better lighting. 

 

3, power supply design problems 

 

a, power design. Although the LED luminous efficiency, but there are 80-85% of the heat loss, resulting in 20-30 degree temperature rise inside the lamp, if the room temperature of 25 degrees, the lamps inside there is 45-55 degrees, the power for a long time in a hot environment under the 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. The internal temperature of 45-55 degrees lower lighting conditions, as well as the internal power supply temperature of about 20 degrees, the temperature near the device to reach 65-75 degrees. Some components in high temperature parameter drift, and some life will be shortened, so the device to choose, special attention can prolonged use at higher temperatures electrolytic capacitors and wires. 

 

c, the electrical properties of the design. Switching power supply for LED design parameters, mainly constant parameter determines the size of the current LED brightness, if the bulk of the current error is large, then the brightness of the entire batch of lamps uneven. And changes in temperature can cause the power supply output current offset. Batch error is generally controlled within + 5%, in order to ensure consistent brightness light. LED forward voltage drop of a deviation, constant current power supply design voltage range to include LED voltage range. Use multiple LED series, when multiplied by the series number for minimum pressure drop lower voltage, maximum voltage drop multiplied by the number of upper voltage series, 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 fixtures left to power small size (unless it is an external power supply), so the higher PCB design, also many factors to consider. Enough to stay a safe distance, requiring the input and output isolated power supply, the primary circuit and the secondary side circuit requires pressure 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 a safe distance from the high-pressure section and housing. 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, adding insulation paper, potting insulation glue. Another cloth board should also consider the heat balance, the heating element evenly distributed, not centralized place, to avoid local temperature. Electrolytic capacitors away from heat, slow down aging and prolong life. 

 

e, authentication issues. Currently no standard for LED lamps, study and formulate relevant state departments are domestic sales lighting fixtures certified reference standard, export is done CE or UL certification, and some reference LED lighting standards abroad to do. So for this situation, switching power supply design to meet more of these criteria is difficult, we can only meet different authentication for different requirements. 

 

4, the parameter 

 

Purchased power in the choice mainly depends on the constant current and constant voltage range. LED constant current value is selected as the next standard current bias. Voltage range of options should be moderate, try not to choose a wide range, to avoid power wastage. 

 

LED drive circuit affect the life, so when necessary rigorous circuit design, LED cold light source, workers junction temperature should not exceed limits, while maintaining the appearance of the beautiful but also take into account the heat, every step must be rigorous.