Design Of DPWM Flyback Controller Based On FPGA

With the development of power electronics technology,digital control of DC-DC converter is an inevitable trend.Although the traditional analog control technology is relatively mature,it has some shortcomings such as its large size,easy aging components,sensitive to noise etc.,which limit its application in high-performance fields.Digital power supply has the advantages of high integration,flexibility and stability,easy expansion,precision and reliability,and has been paid more and more attention in recent years.The DPWM produced by FPGA has the characteristics of high precision and fast response speed.Meanwhile,FPGA can design the whole control system on the same chip,which greatly reduces the space volume.Therefore,the highly integrated FPGA provides a guarantee for the realization of high-speed and high-precision PWM.The research works are as follows:Firstly,unidirectional flyback converter is introduced for the content studied.Starting from its basic structure,the basic working principle of CCM and DCM modes under different working conditions is analyzed in detail.The thesis introduces three control modes of flyback converter,analyzes the influence of coupling inductor on leakage inductance,puts forward a dissipative absorption circuit with leakage inductance treatment and gives the design index.Secondly,it introduces the research and design of the key modules of the hardware circuit,including the high EMI filter circuit,the dissipative absorption circuit,the ADC conversion circuit and the push pull drive circuit.The performance index of chip,the design and selection of transformer,and the selection of peripheral storage inductor and capacitor are determined.Finally,Simulink was used to build the circuit schematic diagram,and the load resistance and battery model charging,the experimental results meet the design indicators.At the same time,the principle of DPID is introduced,and the incremental algorithm of discrete parallel structure and its advantages are analyzed.Thirdly,the DPWM part of the whole circuit design is analyzed,which is written on the Quartus II FPGA development platform using Verilog HDL hardware language.From the overall structure of input and output,clock allocation,the internal modules of pulse width modulation are described and analyzed in detail.Finally,the simulation experiment of each module is carried out with Modelsim,and the expected design index is achieved.Finally,the system design and system evaluation are verified by simulation and experiment,mainly including the continuous(CCM)and intermittent(DCM)current waveforms of unidirectional fly-back converter.At the same time,the battery pack is used as a load,and the constant current charging,constant voltage charging and constant flow and constant voltage charging mode of the battery pack are simulated and tested,respectively.Simulation and experimental results illustrate that the proposed design method can obtain stable output and fast response speed.