I see in buck converter examples that they have fixed/regulated input voltage and a fixed output.
I'm planning to build or buy a for example 9V to 5V buck converter but the 9V side will be composed of parallel batteries. This means the input voltage will not be regulated. And since the battery voltage will drop by time output voltage will be affected proportionally if I use a buck converter.
Is there a DC DC converter or a type of buck converter which both steps down the input voltage and also regulates it to a reference value? Like in my case the input voltage is not regulated(batteries) but the output voltage must regulated to a fixed voltage.