A Study Of Single Stage High Frequency AC/AC Converter

With the application of new materials and the continuous progress in packagingtechnology, the light-emitting diode (LED) has prominent advantages over thetraditional lighting sources such as incandescent lamp, fluorescent lamp, etc. in terms oflighting effect, service life, environmental protection, etc. All these merits of LED havebeen widely applied in the high-power lighting, such as backlight, tunnel illumination,street lighting, etc. In view of this, LED is predicated to be widely used in the lightingindustry in the near future and it will be a very promising new green energy-savinglingting.In the high power LED lighting applications, the power transformationdevice—LED driver must be used to supply the constant current for LEDs due to thegrid voltage is AC voltage. LED driver power should have the function of power-factorcorrection (PFC) in order to reduce the power harmonic pollution. Besides, LED driverpower should realize the function of the input and output electric isolation in order tosatisfy the security requirements. Furthermore, in the high-power lighting with thepurpose to content the requests of general lighting output, LED driver power shouldsupply constant current driver to LEDs in order to realize the function ofmultiple-constant current output. In order to realize the above functions, a modularmulti-channel constant current LED driver is proposed in the paper. It consists of asingle-stage high frequency AC/AC converter and a high frequency AC/DC rectifier.One AC/DC rectifier drives a string of LED to be modular. Modularized designs canwidespread use because it can reduce research and development (R&D) cycle, lowerR&D cost, improve maintainability and promote standardization. The high frequencyAC/DC constant current unit has been researched before, so the main research in thispaper is about the single-stage hign frequency AC/AC cinverter. Therefore, this paper,base on the summary of current two-stage high frequency AC/AC converter and quasisingle-stage high frequency AC/AC converter, the analysis methods of single-stagepower factor cottection circuit is used in this paper to propose a single-stage highfrequency AC/AC converter. And it is characterized by high efficiency, reliability andlow-cost. This paper devotes its efforts in the following aspects.Firstly, based on the deduction of the existing two stage high frequency AC/ACconverter, the single-stage high frequency AC/ACconverter is deduced in detail. And its working principle is analyzable in detail. Then the design principles of parameters arediscussed in depth, on which the parameter design is researched in detail. The method ofselecting components is proposed by designing the input filter, the circuit parameter,and the ripple of energy-storage capacitor, the stress of voltage and current and thescope of ZVS. On this basis, the method to selecting inductors and high frequencytransformeris proposed according to the actual performance. The compensator systemand driver of closed-loop single-stage high frequency AC/AC converter is designed inorder to remain stable. The closed-loop single-stage high frequency AC/AC converter issimulated, and the simulatin results verify the theoretical analysis.Secondly, the LCL-T passive high frequency AC/DC rectifier is proposed inaccording to the requirement of unit input power factor and constant current output ofhigh-frequent AC/DC rectifier modular unit. And its working principle is analyzable indetail.Finally, the experimental platform of the proposed single-stage high frequencyAC/AC converter is given, and the experimental results show that it can achieve powerfactor correction, stable output and soft-switching technology. The final experimentalplatform of proposed LED driver is givin, and the experimental results verify that themodular multi output constant current LED driver is characterized by dynamic attributes.The experimental results demonstrate that the practicability of the theoretical analysis.