Fundamental wave

The sine wave with the lowest frequency that composes an AC waveform. An AC waveform consists of the fundamental sine wave and harmonics, excluding the sine wave itself. When a distorted AC waveform is expanded using a Fourier series, it can be separated into the fundamental wave and harmonics. In switching power supplies, on/off operations are performed based on the period of this fundamental wave, making it an important waveform that determines operation.