We will first introduce the subject of circuit synthesis for the power supply of electronic systems. These will accept either an AC (e.g., from the mains) or DC voltage coming from renewable energy sources. After giving the rationale, we will list several notes that are common knowledge in the subject. That will include the behavior of the passive components (capacitors, inductors, and transformers) and switching electronic components as well as of some circuits which are used within the systems under consideration being frequently implemented no matter the type of the conversion. Attention will be paid to the synthesis of signals used within the controlling circuits of the power supplies. We will especially emphasize here the property of the electronic system, when seen from the power supply source terminals, to behave as highly nonlinear impedance whose value is controlled by the signal being processed (by the amplitude, frequency, and time waveform). We will also introduce our view to some specifics of the simulation of this kind of circuits.