Development of low power buck convertor for enhanced light load efficiency

Power consumption and device size have been placed at the primary concerns for battery-operated portable applications. Switching converters also known as DC/DC convertors gain popularity in powering portable devices due to their high efficiency, compact sizes and high current delivery capability. Currently, the Synchronous Buck convertor has become much more popular in portable devices due to their very high power efficiency and widely availability. However the portable devices usually operate at light loads (standby mode) most of the time and are required to deliver high current only for very short periods, while the conventional Synchronous Buck converter suffers from low power efficiency at light loads due to the negative value of inductor current at light loads. In this research, a novel technique for designing a buck converter is proposed which automatically senses the zero inductor current and forces the convertor to step from automatically from Continuous Conduction Mode (CCM) to Discontinuous conduction mode (DCM) when the inductor current tries to go negative, thereby preventing the inductor current to go negative and hence improve convertor´s power efficiency at light loads. A synchronous buck convertor which steps down 1.8V input voltage to 1V output is designed in PSIM software with a switching frequency of 1MHz. The simulation results shows that the proposed convertor has better efficiency than the conventional convertor at light loads whereas at heavy loads both convertors have almost same efficiency.