Fundamental wave

The lowest-frequency sine wave that composes the AC waveform. AC waveforms, excluding sine waves, consist of a fundamental sine wave and harmonics. When a distorted AC waveform is expanded using Fourier series, it can be separated into the fundamental wave and harmonics. In switching power supplies, operations such as on-off switching are based on the period of this fundamental wave, making it an important waveform that determines the operation.