Design of fully integrated Buck converter with precise DCM operation
For solving the problem that the zero-crossing sensing is not accurate at high frequency,which causes the converter in DCM has a large reverse inductor current loss,an adaptive constant on/off time controlled fully integrated Buck converter is proposed.The control method belongs to PFM(Pulse frequency modulation),which can automatically adjust the on-time and off-time according to the input and output voltage and load,and optimizes the output voltage ripple and efficiency under light load.In addition,a DCM calibration loop is designed to achieve precise DCM operation.The circuit is designed by SMIC 65 nm CMOS process.The simulation results show that,in the case of input voltage of 2.5 V and output voltage of 1.2 V,the load range is 0-150 mA,and the maximum output voltage ripple is 69 mV,the peak efficiency enhancement factor is 34.2%,and the peak efficiency is 73%.At 10 mA light load,the peak efficiency is 51.1%.
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