Research And Design Of Buck Switching Power Supply With Floating Gate Voltage Drive And Synchronous Rectification Technology

Switching power supply is a kind of power supply system with stable output voltage.It controls the working state of power switch tube through the feedback signal of output terminal.It has the advantages of low power consumption,high efficiency,small size,fast response speed and so on.It is the power system with the highest market share at present.Nowadays,electronic equipment is developing towards complex functions and small size.As the core component of electronic equipment,the development of switching power supply is imperative,which makes the research of switching power supply become a hot spot.This paper mainly designs a buck DC-DC switching power supply system based on floating gate voltage synchronous rectification technology.The system adopts current PWM mode control to keep the output voltage stable.The main work and achievements of this paper are as follows:First,a synchronous rectifier circuit is designed by using NMOS power switch and NMOS synchronous rectifier to realize the stability of the output voltage.The control signal of the power switch is given by the floating gate voltage circuit,which can ensure the normal operation of the synchronous rectifier circuit.The internal dead zone control circuit is designed to process the control signals of the two NMOS to ensure that the two NMOS will not open at the same time,which can effectively improve the safety of the circuit and reduce the energy loss of the circuit.Second,a floating gate voltage circuit is designed based on the principle of no sudden change of capacitor charge and discharge.The square wave control signal generated by comparator in the circuit is processed from 0-5V square wave to 0-V_IN+5V square wave(V_IN is the input voltage).The square wave controls the NMOS power switch so that it can be fully turned on in the on state.Thirdly,the current sampling circuit and voltage sampling circuit are designed to control the current PWM mode of the circuit.The control mode has a fast response speed,which can effectively detect the change of the output voltage and make the output voltage more stable.Fourthly,based on the 0.4um BCD process model of VIS company in Taiwan,cadence platform is used for design.At the same time,we use spectre simulation tool to verify it.The simulation results show that when the input voltage range is 6-30V.the output voltage can be stable at 3V,the maximum output voltage ripple is 0.5m V,the circuit can work at 1MHz switching frequency,the maximum on-load current is 1A.the maximum efficiency can reach 93%in the whole working range,and the efficiency of other States can also be kept above 85%.