Research On Power Factor Correction Technology In LED Driver

With the development of the current global economic, the shortage of resources and environmental pollution problems are becoming more acute, global energy and environmental pressures are increasing. In this context, along with the actively promoting of "green lighting project" and gradually increasing of the awareness of energy saving around the world. LED lighting technology is introduced into lighting applications which has become the main trend of lighting market and industrial developing environment.LED is short for Lighting Emitting Diode. Since LED lighting with long life, high luminous efficiency, environmental protection, small size, good impact resistance, easy and flexible control and so forth, so it is widely used in building exterior and landscape lighting, traffic lights and LCD display, vehicle indicates class lighting and plant lighting and other fields. At present, despite the policy guiding role in the development of LED lighting industry is continuously strengthen in other countries which makes Chinese LED lighting industry developing environment Optimistic and market potential huge, the technology and the cost of are the two biggest issues which hinders the popularity of LED lighting technology. However, in the LED drive power, the low power factor, bad electromagnetic compatibility and low efficiency are three main problems exposed. Therefore, the study of the power LED drive power factor technology will provide important theoretical basis for flourishing LED lighting market.Power Factor Correction(PFC) is designed to improve the power factor in the circuit. The technology can not only reduce the reactive power grid, but also reduce the harmonic pollution and improve the quality of power supply. So how to suppress and eliminate harmonic pollution on the public grid, improve power factor has become a major subject of research of current domestic and foreign power sector. Throughout the development of PFC technology, PFC technology can be divided into two categories: one is passive power factor correction, also known as PPFC or called passive PFC technology, the other is an active power factor correction, also known as APFC or called active PFC technology. Now, the APFC circuit people most concerned is mainly divided into two levels of APFC circuit and single-stage APFC circuit.On the basis of LED drive power factor technical documents at home and abroad, firstly, this paper will make a brief analysis of advantages and disadvantages of passive power factor correction and active power factor correction technology and the development status of Power Factor technology at home and abroad. Secondly, this paper will do a brief introduction to LED lighting technology and switching power supply technology. Then this paper will make a simple comparison for single-stage APFC and two-stage APFC technology. Finally, in-depth study of the active power factor correction technology through a single-stage PFC circuit. This article will introduce the single-stage APFC technology in details by using 50 W single-ended Flyback switching power which is designed by MP4021 which incorporates PSR and single-stage APFC. And this paper will design a control circuit to remove current ripple which caused by single-stage APFC. This paper will also detailed some power parameters and estimate the loss of transformer, switch and output rectifier diode. At last this paper will make a brief analysis of the knowledge of EMC in switching power?...