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Standard lights are undergoing a revolution. In order to protect energy and cope with global warming, some states in the United States and other countries have begun to ban the use of low-efficiency incandescent bulbs. Various new technologies are being used to replace incandescent bulbs, with compact vacuum fluorescent lamps (CFLs) being the main alternative. Although this CFL lamp consumes only 20% of the incandescent lamp, it contains toxic mercury. In contrast, LED lights provide a more efficient and environmentally friendly solution.

Led's original commercial application appeared in the 1970s, but because of its extremely low light output, the range of applications is limited to areas such as indicator lights and calculator displays. Today, high-power LEDs that produce white light continue to increase in efficiency and prices are declining year by year, making it one of the options to consider for mainstream lighting applications. It is expected that with the development of LED technology, its luminous efficiency will reach 150 lm/W in 2012, and the cost of 1000 lumens will be less than US$5 (source: OIDA). At that time, LED is expected to become the main source of indoor lighting.

It is precisely because the goal of using LEDs to achieve standard bulb replacement is completely feasible, and it is a very important step in reducing the consumption of lighting energy in residential, office, factory and municipal buildings. A $10 million grand prize to reward the first company or individual to develop a 60-watt incandescent replacement lamp that uses LEDs in standard A19 bulbs. The award is a sub-item for the Bright Tomorrow Lighting Prizes, and the "Lighting the Tomorrow Lighting Award" is part of the Energy Independence and Security Act, which has recently become the official law of the United States. Once the award is finalized, the US Government Procurement Office must purchase such LED bulbs and use them in all government offices.

However, in order to win the award, the design must meet the following conditions: the bulb must be capable of producing 900 lumens of light; the power consumption is less than 10 watts (luminous efficiency greater than 90 lumens per watt); the relative color temperature (CCT) must be between 2750K to Between 3000K; expected working life of more than 25,000 hours, and lumen maintenance rate of 70%; bulbs must be able to mass production and mass sales.

Therefore, the main problem faced by design engineers who are interested in this award is that the designed power supply must be able to drive the LEDs efficiently to achieve the required brightness, and the size of the board must be met by colleagues who meet EMC regulations. Small enough to fit into a normal fixture. Because of the major breakthroughs in LED technology, design and implementation, no matter who becomes the ultimate winner of the 10 million award, it will be well deserved. LEDs currently achieve a maximum luminous efficiency of about 75 lm/W, but LED manufacturers are making great progress. Once the LED's luminous efficiency reaches 100 lm/W, the LED will achieve a 90 lm/W target. However, this still requires a very compact power supply with 90% efficiency.

Power Integrations can now design a power solution that fits into the bulb housing, which is more than 90% efficient, low cost and suitable for mass production. The 10W power supply based on Power Integrations' LNK306PN discussed in this paper is simple in design and low in cost. It not only has a working efficiency of more than 91%, but also provides constant LED current and can meet EMI requirements.

Efficient power supplies are a necessary factor in the successful development of incandescent lamp replacement solutions, but first they will face heat dissipation problems. For example, a 70% efficient power supply converts 30% of the electrical energy into thermal energy. Unless the heat is dissipated, the rising temperature of the lamp will significantly reduce the life of the LED and the power supply. More importantly, the use of high-efficiency power supplies is a fundamental requirement to minimize the so-called "total cost of lighting." The total cost of lighting consists of the initial cost of the bulb (and replacement of the bulb) and the cost of the electrical energy consumed. If LED lamp manufacturers want to take a certain share of the LED lamp market, they must prove that their LED lamps have a lower overall cost than similar products. As shown in Figure 1, even if the power efficiency of the LED is increased by 1%, the energy saving effect is very obvious.