The circuit shown in the schematic diagram below is an isolated dc-to-dc step up converter. Being isolated means that there is no electrical connection between the input and the output. We can say that there will be no current or electron transfer from input to output, since the output current loop ant the input current loop is isolated by a transformer. Only magnetic induction is the medium of power transfer, and an optocoupler as the feedback transfer.
The output voltage will be kept constant by the feedback mechanism, so we don’t have to worry about dynamic characteristic of the load powered by this circuit. [Circuit’s schematic diagram source: seekic.com]