The following figure shown
an example of a three-output flyback regulator built using LM2577 that
has electrical isolation between the input and output voltages. The
values shown in the circuit diagram will be 5V for the voltage.
An electrical isolation is required between the input and output terminals of the power supply for such medical instruments which require it to assure the safety of patients. In the Flyback Regulator circuit, the output may be greater than, less than, or equal to the input voltage (source: national.com)