Research On 1.5kW Half-bridge LLc Resonant DC/DC Converter

High frequency, miniaturization, lightweight has become the main trend of the future development of switching power supply, but the problem of low efficiency, loud noise, high switching stress and EMI problem caused by improving frequency has become the main obstacle to the development of switching power supply technology, as a result, the soft switch converter becomes the hotspot of the research. LLC resonant converter has excellent performance, because of its’ high efficiency, magnetic integration, wide soft switch range, smaller voltage stress in rectifier parts, better ability to adjust voltage, LLC resonant converter has been widely spread and application.In this paper, the working principle of the LLC resonant converter is detailed analyzed first. According to the principle, the operating frequency range of the converter is divided into three sections, the working condition of the converter is studied, and a detailed description of the different working stages in each section is carried out. The equivalent circuit of half bridge LLC resonant converter structure was obtained though works principle and topology features of LLC converter. Then converter formula of gain and input impedance was obtained through the modeling analysis by First Harmonic Approximation(FHA), and the effect of the performance caused by element parameters of converters can be studied by Converter gain characteristics curve which was obtained by converter gain formula. By the input impedance formula, the work area of the converter can be divided into the capacity region and the perceptual region, and the condition of the converter works in the perceptual region is obtained. The loss of the switch and the diode is analyzed in detail, and expression of switching loss about converter was obtained, thus find out the key factors of improving converter efficiency. Through the detailed analysis of the switching process of the converter, get the constraint conditions of the zero voltage switching(ZVS) can be realized. According to all the analysis results, considering loss, soft switching reliable implementation condition and converters work performance, a set of simple and effective method of parameter design of LLC resonant converter was produced.Based on the method above, combining with the design requirements, one LLC resonant converter was designed. Verify design parameter with simulation software. Finally produced a prototype, carry on the research of the converter, analysis results, the rationality and feasibility of the methods given in this paper was proved.