1.College of Electrical Engineering Automation, Fuzhou University;2.Center for Advanced Power-conversion Technology and Equipment, Southeast University
The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)
A high-efficiency forward converters often use high-frequency resonance to achieve magnetic reset and soft switching. At high fre-quencies, the non-linear parasitic capacitance of the MOSFET will have a more obvious impact on the resonance, which will not only cause resonance point shift, soft switching failure, but also make the magnetic core unable to resonate normally. In order to calculate the resonance parameters under the influence of nonlinear parasitic capacitance, Simplis is used to build a simulation model, and the basic mathematical expressions are derived; the piecewise linear method is used to calculate the capacitor charging and discharging time during the resonance process, and the resonance parameter value is established according to the conservation of energy Constraint equations. The calculated resonance parameters can not only overcome the influence of MOSFET's nonlinear capacitance without reducing the frequency and duty cycle. When the magnetizing inductance is set to its upper limit, the magnetic loss is the smallest, and the highest efficiency can be obtained at this time.