I am trying to use this ups design(below image)(max 500mA) but I want to use switching regulator instead of linear regulator to keep regulated Vout as constant possible even when battery drop below Vout.
Ex: 6V battery and 9v power supply -> Vout needs to be 4.7v -> I would like to get Vout of 4.7v even when the battery voltage is 4.7v. (Note: D3 is reducing battery voltage by 0.7v)
what kind of switching regulator I can use and how can I design it so it can step down when the voltage is above 4.7 v and step down when below. (This ups circuit need to pass intrinsic safety requirement)