It would help if you gave an example of what you are thinking of. (schematic) There are too many ways of using a transformer.How do you
There is no unique, buck or boost transformer, just combined buck-boost and the result all depends on the phase of the buck/boost winding WRT to the voltage of the supply transformer it is acting on.do you not just add or subtract depending on whether the secondary voltage is lower or higher than the primary voltage? If the secondary voltage is higher, would you add both voltages together and when secondary voltage is less than primary, would you then subtract both voltages?