Design Of Buck-type Switching Power Supply Controlled By PWM/PFM

With the increasing demand for electronic products in today's society,the rapid development of electronic devices has been promoted.Especially for the performance of the power supply module of electronic products,higher requirements are put forward,such as high control accuracy,high integration,and high efficiency.It can be seen that there is a larger market application space for switching power supplies with better research performance.In this paper,the topology and working principle of Buck DC-DC switching power supply,Boost DC-DC switching power supply and Buck-Boost DC-DC switching power supply circuit are discussed in detail.Buck topology of mainstream topology.And this paper expounds the specific working principle of different modulation methods of switching power supply,and makes a comparison of the advantages and disadvantages of different modulation methods.After analysis and comparison,the PWM pulse width modulation method is suitable for the switching power supply system to work under heavy load,and the PFM pulse frequency modulation method is more suitable for the switching power supply to work under light load mode.Therefore,in view of the respective characteristics of different modulation methods,the step-down switching power supply designed in this paper uses a PWM / PFM hybrid modulation method to replace the early PWM single modulation method.The PWM / PFM hybrid modulation method enables the switching power supply to automatically switch the modulation method according to different load conditions,so that the system has better adaptability and better system coordination,so that the power efficiency of the switching power supply under light and heavy loads Improved.This paper mainly designs the bandgap reference voltage module,error amplifier circuit module,current sampling circuit module,PWM comparator module,PWM / PFM automatic switching circuit module,etc.And the simulation test of the system's output voltage ripple under different load,the system's working stability,the system's different modulation modes,power conversion efficiency,linear adjustment rate and load characteristics analysis,the relevant indicators basically meet the design requirements.