Research On Full-bridge Resonant Converter Based On The Loosely Coupled Transformer

The contactless electrical energy transmission system realizes contactless power transfer with high security, reliability, high efficiency and flexibility by the combination of electromagnetic inductive coupling technology, high frequency converter technology, power electronic technology and other advanced technology. Its prospect in many application such as public transport systems, aviation and space systems, robots, medical plants, lighting, mining and underwater application is widely used..In this paper, full-bridge resonant converter based on the loosely coupled transformer which is widely used in the high power situation and realizes inductive power transfer is researched. First the operation principle, the research actuality and the trend of development are introduced and the model of the loosely coupled inductive power transfer full-bridge resonant converter is analyzed. Then the primary and secondary compensation of the loosely coupled inductive power transfer full-bridge resonant converter is focused on. The function of the primary capacitance and secondary capacitance are analyzed from reducing system apparent power and promoting the system transfer capability.Then the research focuses on the series-series and the series-parallel compensated loosely coupled full-bridge resonant converter which are widespreadly used in many fields. The normalized expressions of the output voltage, the phase angle and the condition when the phenomenon of frequency bifurcation occur is inferred. The expressions are analyzed by the use of the software Matlab. The deference of voltage transfer characteristic is gained between the phenomenon of frequency bifurcation occurring and not occurring. The factor which makes frequency bifurcation occur is construed also. The reasonable choice of operating frequency and compensated capacitance is still given under a certain condition.At last, the elementary exploration on the mode of the loosely coupled inductive power transfer full-bridge resonant converter is carried on. Analysis and research focuses on how to realize the PFM control and frequency tracking control of the loosely coupled full-bridge resonant converter. The PFM control and frequency tracking control of the loosely coupled full-bridge resonant converter are realized, and experimental results from a prototype of full-bridge converter are given, which verify the correctness of analysis and conclusion in the paper.