Publitek European Editors writes:
Many security and motion detector systems rely on small, semi-autonomous nodes that are easy and simple to install. This implies the use of a battery-based power source and low-power operation in order to minimize the number of battery changes during the lifetime of the product.
Over its lifetime, the output voltage of a battery falls, with the biggest decline when the charge is nearing full depletion. A converter type that can accommodate this change in voltage but can still provide relatively high voltages for sensors and RF transmitters is the buck-boost converter – it operates the buck part of the circuit when the battery is fresh, moving to boost operation when the voltage falls below the threshold of the electronic circuitry it powers. A number of vendors have developed integrated buck-boost converters optimized for battery systems
Buck-Boost Converters Help Extend Battery Life for Motion Detection - [Link]