Supercaps Improve LDO Efficiency- Part 1: Low Noise Linear Supplies

摘要

DC power supplies for portable devices are expected to be extremely efficient for the reason of energy consumption, longer run time from the battery pack and greener environments. Using supercapacitors in combination with LDOs provides a higher efficiency than the LDO alone.State of the art electronic systems employ three fundamental techniques for DC-DC converters: (a) switch-mode power supplies (b) linear power supplies (c) switched capacitor converters. In practical systems, these three techniques are mixed to provide a complex, but elegant, overall solution with energy efficiency, effective silicon or PCB area, and noise and transient performance to suit different electronic circuit blocks[l]. Switching-type DC-DC converters, once the clear choice for 5 V systems, suffer lower efficiency at lower voltages. This is illustrated in Fig. 1, based on the performance of an integrated switching regulator [1]. The graph indicates that the efficiency drops from approximately 79% for a 3.3 V output model to 56% for a 1.2 V output device.