Research On Half-Brigde Llc Resonant Converter With High Power Factor

With the rapidly development of science and technology, power electronic devices are widely used for the industrial production and daily life, because of its high frequency, modularization and high reliability. However, a large of power electronic devices are widely used for the power network, the harmonic pollution is more and more serious, and the normal work of the power network is affected. Therefore, developing green and high efficient of the power electronic devices are the requirement of social development. Based on this background, a two-stage circuit structure of the LLC resonant converter with high power factor was proposed in this this article, which could be widely used for distributed power system. The front-end converter was power factor correction device, and the second stage converter was LLC resonant converter, power factor and circuit efficiency of the device can be improved significantly.First of all, the operating principle of Bridgeless PFC converter was analysted in this paper, and based on the average current mode control method, the double closed-loop control circuit scheme of Bridgeless PFC converter was proposed. And then, small signal model for the Bridgeless PFC converter were presented by the small signal analysis method, and the transfer function of the open-loop control system was derived. After that, passive lossless snubber was proposed to improve the trajectory of the switch, and the rise rate of the switch voltage was obviously alleviated.Secondly, the operating principle of Half-Brigde LLC resonant converter was analysted in this article, and the equivalent circuit model of half-brigde LLC resonant converter was established by the First Harmonic Analysis method. In one resonant cycle, half-brigde LLC resonant converter was divided into six different operating modal, the work process of the circuit were analyzed in detail. And then, base on the perspective of wider input voltage range and high circuit efficiency, the resonant tank parameters were optimized. After that, in order to optimize the circuit structure and reduce the volume of the converter, magnetic integration technique of the half-brigde LLC resonant converter was introduced, resonant inductor and magnetizing inductance can be constructed in one magnetic core with the magnetic integration technique.Finally, a480W experimental prototype was developed, and the experimental prototype was test, the key waveforms of the experimental prototype were measured. The results of the key waveforms reveal that the unity power factor was implemented, and the efficiency of the circuit was improved.