A Design Of A Synchronous Step-down Switching Power Supply IC

On the one hand,compared with traditional power,the switch power has many advantages,such as high efficiency,compact size and light weight etc.One the other hand,with the rapid development of communication systems, computers, and other consumptive electronics in recent years,the demand of DC/DC switching power IC in those portable equipments with battery power supply has become more and more, as well as the requirement of it has become more and more strict.But those qualities,such as high conversion efficiency,stabilization,credibility,long supply time and high integration are its changeless pursuing target.According to the practicality,we design a step-down DC/DC switching power IC.For high efficiency,we apply PFM controlling mode to resolve the problem of low efficiency caused by PWM controlling mode when the load is low.In addition,low power sampling technology and synchronous rectifying are also applied for high efficiency.For stabilization and credibility,we apply the piecewise slope compensation technology to resolve the problem of unsteadiness,caused by over compensation.In addition,overheat switching off and under voltage switching off modules are integrated to improve the credibility.Idiographic circuits include:current source and BAND-GAP voltage source circuit, error amplifier circuit, comparer circuit,clock signal and slope signal producing circuit,current sampling circuit, power drive circuit and other modules.The simulated results via Hspice indicate that this IC based on double controlling modes has high efficiency,which can go up to 92% when the load resistance is within a continuous definite range.And all the modules go steadily,which have met the requirements of the project.