An LDO/PFM dual-mode automatic switching method used in buck DC-DC converters

A PFM (pulse frequency modulation)/LDO (low dropout regulator) dual-mode automatic switching method is proposed in this paper which can be used in buck DC-DC converters. This architecture provides better power conversion efficiency under ultra-light load. Also, it can help to achieve smaller voltage ripples. By using this method, a converter is designed and verified using the SMIC 0.13μm process. The supply voltage of this design is 2V and the output voltage range is from 1V to 1.8V. The simulation results show the converter can switch between the two modes automatically under different load cases. The maximum efficiency improvement of this design is 147.63% at 1mA compared to the PFM converters and the switching time is less than 37μs.