Research And Design Of High Efficiency, High Precision And Wide Load Range Psr Flyback Converter

With the development of consumer electronics,the performance requirement of switching power supply is becoming higher and higher.For switching power supply which transforms high-voltage power supply into low-voltage power supply rail,Reliability,efficiency and cost are the most important performance indexes.And the PSR Flyback converter is widely used in all kinds of AC-DC switching power supply products because of its simple principle,low cost and high reliability due to eliminating the use of optocoupler.In this paper,the PSR Flyback converter is taken as the research object.This paper starts with the transformer model,then introduces the basic working principle of Flyback converter and analyzes its loss at the power stage.Afterwards,it introduces the control scheme of the Flyback converter under the constant voltage condition and analyzes the small signal model,especially the peak current mode PWM scheme and the PFM scheme.And finally this paper discusses the basic conditions to ensure the stability of the loop and the way of frequency compensation.On this basis,this paper introduces the architecture of controller IC which designed in this paper and the operating principle of constant current and constant voltage control loop.For the performance optimization of controller IC,This paper focuses on two aspects.The first one is about efficiency.In this paper,the peak current mode PWM/PFM hybrid control scheme is adopted which could widen the load range of the system under constant voltage mode,thus greatly reducing the power loss on dummy load.Simultaneously,this paper introducing wait mode to reduce power consumption of controller IC under light load and valley detection mechanism to reduce switching loss.And the second one is about accuracy.In this paper,the influence of valley detection time on the output accuracy of constant current is eliminated by optimizing the constant current control scheme.Then,the strategy of auxiliary winding bus detection is introduced to eliminate the influence of logic and driving delay on the peak current of primary side.Subsequently,this paper introduces the sub modules such as low power start-up module,high PSR BGR,driver,LDO,peak current limit and switching frequency control module.In this paper,the above modules are analyzed qualitatively and quantitatively,and finally verified by cadence based on the 0.18 μm BCD process.And finally,this paper designs the parameters of the peripheral components of the converter system,and carries out simulation verification and layout drawing for the chip.The simulation results show that the system has an output accuracy of 2% and an efficiency of 80%.