You can use this observation to build a "buck-boost" topology that can make the output voltage larger or smaller than the input voltage. This is common for 1sNp Li-ion batteries that need a high-current 3.3V rail - buck from 4.2V to 3.3V at full charge, boost from 3V to 3.3V at low charge.
There's actually a bunch of ways to make buck-boost style converters that can do both functions, like the cuk and sepic topologies. There's also bidirectional bridge converters that can change input and output direction - you see this a lot on hybrid vehicles (12V to 48V or vice versa) and electric vehicles (48V to 400V and vice versa).
There's actually a bunch of ways to make buck-boost style converters that can do both functions, like the cuk and sepic topologies. There's also bidirectional bridge converters that can change input and output direction - you see this a lot on hybrid vehicles (12V to 48V or vice versa) and electric vehicles (48V to 400V and vice versa).