Research And Design Of A PWM/PSM Dual Modulation Buck DC-DC Converter

At present,in various electronic products,a DC power supply is required to provide a stable working voltage.The research purpose of a power management chip is mainly to provide a stable working voltage while obtaining higher power utilization efficiency.The rapid development of DC-DC converters is an inevitable trend of electric energy utilization in today's society.In order to obtain ideal conversion efficiency in a wide load range,this thesis designs a PWM/PSM hybrid modulation DC-DC converter.It has good efficiency in a wide load range.The innovatively designed"synchronization generating circuit"solves the problem that the control loop of the traditional hybrid modulation DC-DC converter is too complicated.In addition,according to loss analysis,a floating gate width control circuit is designed from the perspective of POWER MOS parasitic capacitance to change the size of POWER MOS.The power management system applied to portable devices can greatly improve the battery life of limited batteries.The circuit integrates a buck(Buck)core module,amplifier,comparator,ramp signal and minimum duty cycle signal synchronous generation module,zero current detection(Zero Current Detection,ZCD)module,discontinuous conduction mode(Discontinuous Conduction Mode,DCM)control module,PWM/PSM logic switching module and tunable gate width control module.This article uses the slope and falling edge of the ramp generation circuit to innovatively design a minimum duty cycle signal OSC,V_RAMPsignal and clock signal V_CLKsynchronous generation circuit,which simplifies the circuit scale and reduces static loss.When the load is light,the method of simultaneous detects the duty cycle and output voltage is adopted to automatically switch the modulation mode into the PSM modulation mode,reducing the operating frequency of the switching circuit,and at the same time static loss is reduced.In addition,according to the load change,the gate width control module is used to change the size of the step-down core module according to the load size at light load,and the small-size step-down core module is selected for work at light load,which further improves the conversion efficiency of the circuit.This thesis adopts TSMC 65nm standard CMOS craft to carry on the design,adopts Cadence software to carry on the circuit design and simulation.The simulation results show that:according to the design,the circuit can automatically switch between PWM and PSM modulation when the load changes,and the conversion efficiency of the circuit is as high as 86.3%when the load is 1m A ultralight.Finally,the drawing and post-simulation of the circuit layout are completed.