Design And Research On Interleaved Boost+LLC Converter

With the development of society,miniaturization,high frequency and high efficiency have become the focus of switching power supply research.But the application of more and more complex occasions,non-isolated Boost,Buck,Buck-Boost and other circuits and isolated forward,flyback and bridge and other circuits are not able to meet the needs of users any more,and the cascaded converter research is increasingly important.The development of science and technology also makes the control of switching power supply change from traditional analog control to digital control.In this paper,the design of interleaved Boost+LLC converter based on digital control is proposed to satisfy the actual project requirements.The reason to select the topology is firstly analyzed,and then the working principle of the circuit is introduced in detail.The proposed converter has two main characteristics: 1)the use of interleaved structure for source converter,can effectively reduce the input current ripple,switching stress and improve the switching frequency;2)the load converter structure that the primary winding of the transformer is connected in series and the secondary winding is connected in parallel,can effectively reduce the size of the transformer,and increase the power density of the converter.The interleaved Boost+LLC converter effectively combines the advantages of Boost circuit and LLC resonant converter.Moreover,it can avoid the shortcomings of the low efficiency of the Boost circuit,so the overall efficiency of the converter is able to be achieved.In the the former Boost circuit,the PI closed-loop control mode is used,so that the output voltage rise steadily and stabilize the set value;while the LLC resonant converter adopts an open-loop and fixed frequency control structure,which can play the role of Boost and electrical isolation,and the fixed frequency is more conducive to the realization of the secondary synchronous rectification,switching losses reduction,and efficiency improvement.In this paper,the working principle of two stage DC/DC converter is analyzed in detail,and the detailed design steps are given.The design of the circuit is simulated by Matlab/Simulink,and the feasibility of the design is verified.Finally,a 3KW experimental prototype of 50~137.5V input and 600V/5A output is built in the laboratory to verify the correctness of the theoretical analysis.