Design And Implementation Of LLC Resonant Soft Switch Digital Control System Based On FPGA

Switching power supplies are moving toward high efficiency,and high power density.It plays an indispensable role in various fields such as military activities,aerospace systems,industrial industrial control,and residents’ lives.Due to the high efficiency of the full-bridge LLC resonant converter,the small voltage stress of the MOSFET,and the generation of small electromagnetic interference,more and more people are paying attention to it,but the pure-bridge LLC resonant converter can not be realized by the traditional FM control.High efficiency,wide range of output.Due to this shortcoming,the application scenario of the full-bridge LLC resonant converter is limited.The hybrid control method based on dynamic topology conversion designed in this paper realizes the high efficiency,wide range and low ripple output of the full-bridge LLC resonant converter.By establishing the fundamental analysis model of the full-bridge LLC resonant converter,the gain characteristics of the full-bridge LLC resonant converter are compared with the normalized inductance ratio K value,the circuit quality factor Q and the operating frequency to divide the the work scope of half-bridge and the full-bridge,and then through testing to further precisely adjust the working range of the half-bridge and the full-bridge.For the control system of full-bridge LLC resonant converter,this paper designs and implements a complete hardware and control algorithm of FPGA-based digital control system.Algorithm design is the key part of this paper.The control algorithms include its soft-start control algorithm,closed-loop control algorithm,half-bridge to full-bridge and full-bridge to half-bridge switching algorithm,and half-bridge and full-bridge soft-shutdown control algorithms.The fuzzy PI is used to realize the accurate,stable and low-ripple output of the half-bridge and full-bridge modes,and a piecewise linear soft-start process is proposed to adapt to different environments and requirements.In addition,this article adds a series of protection measures to the full-bridge LLC resonant converter.In order to verify,the digital control system,a 1KW prototype was designed with an output voltage range of 30-130V.Firstly,Simulink closed-loop simulation is carried out on the hardware parameters of the full-bridge LLC resonant converter,and then tested together with the FGPA-based digital control system.The test results show that the FPGA control system based on dynamic topology conversion can realize the high efficiency and wide range of output of the full-bridge LLC resonant converter.