Power supply systems and feedback through a transformer

A method comprising:

• operating a power converter circuit to input energy to a primary winding of a transformer and subsequently receive the energy through a secondary winding of the transformer over multiple cycles, the power converter circuit producing an output voltage using the energy received through the secondary winding;
• switching modal operation of the power converter circuit between a first mode and a second mode over a range of different magnitudes of power delivered by the output voltage to a dynamic load;
• wherein operation of the first mode includes controlling a frequency of energizing the primary winding over multiple cycles to be substantially constant;
• wherein operation of the second mode includes varying a frequency of energizing the primary winding, the method further comprising:
• switching the modal operation of the power converter circuit between the first mode and the second mode based on feedback conveyed from the secondary winding to the primary winding over the multiple cycles;
• and
• comparing a time associated with receiving the feedback to a setpoint time value, the setpoint time value corresponding to a minimum desired frequency of inputting energy into the primary winding over multiple cycles.