Efficiency Optimization Design And Implementation Of CCM/DCM Primary Side Regulation Flyback Converter

In all kinds of electronic products,power management chip plays an indispensable role.Flyback converter is the most widely used circuit topology in the isolation power supply,in which the flyback transformer stores energy and transmits it,so the flyback converter is often used in low-power scenarios.But the flyback transformer needs to store energy,in order to prevent the transformer saturation,the flyback transformer’s air gap and leakage sense is larger,resulting in the flyback converter system efficiency is low.This thesis focuses on how to improve the efficiency of the primary side regulated Flyback system from three aspects:(1)The designed primary side regulated Flyback control chip can adjust the output voltage stability by sampling the auxiliary winding voltage information.Compared with the secondary side flyback regulation,the system in this thesis reduces the components such as optical coupler,so that the system has higher efficiency and lower cost.(2)The system loss model of the primary side regulated Flyback is established,and based on this,the appropriate off-chip parameters are designed to reduce the loss of off-chip components such as transformers and power tubes,thus improving the efficiency of the primary side regulated Flyback.(3)In this thesis,a PWM-PFM-PWM control method is proposed to optimize the system efficiency at the chip level.When the load is under the preset heavy load,the system works in the PWM mode of 100k Hz,when the load is reduced to the light load threshold,the system works in the PFM mode,and when the load is further reduced to the extremely light load,the system works in 25k Hz PWM mode.Through testing,the maximum efficiency of the system is close to 90%,which is about 4%higher than the traditional PWM control method.At the same time,in terms of chip design,based on the analysis of the flyback converter working sequence and common feedback technology,modulation method,on the basis of,from the perspective of the switching cycle average method,the completion of the original edge feedback loop of the flyback converter modeling analysis and compensation network design,the simulation available in this thesis,the design of the primary side regulated Flyback phase margin of the closed-loop system is 80°,the stability is good.In this thesis,the BCD process of 0.18μm was applied,emphatically introduces the feedback voltage sampling module,the output current detection module,the adaptive lock circuit,pulse width PFM/PWM mode switching circuit,dynamic adjust the adaptive preface blanking module circuit,core subsidiary circuit simulation analysis for different process Angle,finally completed the primary side regulated Flyback chip layout design and verification,the overall layout of the chip,with an area of 2.6mm~2,was completed and has passed DRC and ERC check,as well as LVS verification.,the primary side regulator flyback designed in this paper can realize the mode switch of8m A-0.8A,and the output voltage deviation is within±4%and the output ripple is less than 1%in the full load range,which meets the design requirements.