Switch-mode power supplies (SMPS) like dc-dc converters provide their best efficiency with heavier loads. When a device using a dc-dc converter goes into standby mode, efficiency drops considerable. Virtually the only current flowing at this time is the quiescent current (IQ).
One way to achieve greater efficiency is to use a very low IQ dc-dc IC that automatically adjusts its configuration and operation to boost efficiency during light-load conditions. Another approach for boosting efficiency at light loads is to add an low-dropout regulator (LDO) to power the load. Here’s a summary of both methods.