Systems and methods are provided to implement power supply units (PSUs) that are capable of operating on input power having different types of input voltage waveforms, including, but not limited to, pure sinusoidal waveforms, non-pure sinusoidal waveforms, and non-sinusoidal waveforms. Such a PSU may operate to continue supplying DC output power to a system load as long as the PSU is powered by any one of a variety of such different input power types, while at the same time also effectively monitoring for presence of input power provided to the PSU and shutting down the PSU in event of absence or termination of the input power to the PSU. Such a PSU may also automatically identify and adapt to changes between different types of input power while at the same time continuing to supply DC output power to a system load in an uninterrupted manner for as long as some type of input power is being provided to the PSU.