Low Power LED General Lighting Application Isolated High Power Factor LED Driver Solution

[Source: "High-tech LED - Technology and Applications" July issue / Anson Semiconductor]

In recent years, many countries around the world have been working to replace energy-efficient incandescent lamps with more energy-efficient lighting solutions. With the continuous improvement of light-emitting diodes (LEDs) in almost every aspect of illuminating performance and cost, LEDs have become a very attractive solution in the field of general lighting. From the perspective of power supply, LED lighting also includes different types of high-voltage AC-DC, medium-voltage AC-DC or DC-DC, and battery power. This article will focus on driver solutions for low-power (typically less than 30W) AC-DC LED general-purpose lighting applications and their examples in applications such as PAR30 and A-type lamps.

AC-DC power conversion topology comparison

For low-power AC-DC LED power conversion, different topologies such as isolated flyback or non-isolated buck can be selected. The so-called "isolation" refers to the electrical isolation between the input and output using a transformer or the like. Both of these topologies have their own characteristics. In comparison, the non-isolated topology design and circuit board configuration are simple, the board size is small, the number of components is small, and the energy efficiency is higher. The isolation topology is easy to meet the safety requirements, but the magnetic design is complicated and requires a large circuit. Board size. This article will focus on the AC-DC LED driver solution in an isolated topology.

LED driver application requirements

For LED general lighting applications, the current cost is relatively high, so high-performance LED drivers will undoubtedly be more popular. In addition, LED drivers should also have high energy efficiency (low loss), high reliability, compliance with electromagnetic interference (EMI) and harmonic content or power factor (PF) standards, flexibility, adapt to wide environmental conditions, and can be retrofitted to existing Application, support for traditional control mode work (compatible with traditional dimming).

Among them, in terms of power factor requirements, the US ENERGY STAR project solid-state lighting standard has mandatory requirements for PFC (regardless of the power level), applicable to specific products, such as recessed lights, cabinet lights and table lamps. Wait. The standard requires a power factor greater than 0.7 for residential applications and a power factor greater than 0.9 for commercial applications, while integral LED bulbs require a lamp power factor greater than 0.7 for input power greater than 5 W. Of course, not all countries absolutely mandate improved power factor in lighting applications, but some applications may have this requirement. For example, utilities may strongly promote the commercial use of products with high power factor in utilities.

For more information, please refer to the July issue of "High-tech LED - Technology and Applications" magazine.

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