we know that when the frequency is increased the volume of transformer will be decreased. that is one of high frequensy switching power supply situations.
but why? How the volume of transformer is related to the frequency?
when the frequency increases, the time period decreases. so the small transformer can handle these small time period signals without satuaration. large transormers also can handle, but small transformers are preferred by space consriaint. and also parasitics will be less in small transformer.