| Flyback power converter has the advantages of small size, simple circuit and good reliability, therefore it’s widely used in lower power electronic products. With the proposal of US DoEVI energy efficiency and EU EN55022 specification and other design standards, demands on the efficiency and electromagnetic interference of power converter are getting higher and higher. Meanwhile, Power MOSFET driver circuit is directly related to the power conversion efficiency and EMI,and there is contradiction and compromisebetween efficiency and EMI. This thesis will focus on research and design of power MOSFET driver circuit, in order to optimize the efficiency and EMI of the power converter.This thesis firstly analyzed the development and main design methods of driver circuit of power MOSFET for flyback power converter. Based onthe switching process of power MOSFET and reflected problem of the conventional drive circuit, proposed a dynamic driver circuit which can significantly improve the efficiency and EMI characteristicof flyback switching power converter. Then this paper studied the analog and digital design schemes of dynamic driver circuit, both can dynamically drive power MOSFET, to adaptively fit the demands on efficiency and EMI. At the same time, this thesisdesignedcorresponding concrete realization circuit for the design.The function of the circuit was verified by simulation analysis.In addition, the paper also studied the layout design of dynamic driver circuit and post-simulation. Finally, the efficiency and EMI of a flyback power converterwith dynamic drive circuitwere tested, thenthe results were compared with energy efficiency requirements and the test results of a flyback power converterwith the conventional drive circuit, which verified the effectiveness of the proposed circuit.The simulation results show:when the converter works in heavy load and light load, the rising time of power MOSFET is less than 200ns and 150ns, and the falling time of power MOSFET is always less than 100ns, adaptively adjusting switch time on the premise of ensuring quick switch of power MOSFET.The test results showed that:dynamic drive technologycan guaranteethe average efficiency of flyback switching power converters (5V/2A)to be more than 78.7%, satisfyingthe sixth energy efficiency requirements, and greatly improve the EMI of power system compared with the conventional drive technology, EMI margin always greater than 6dB under different frequency. |
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