Haversine A waveform that is sinusoidal in nature, but consists of a portion of a sine wave superimposed on another waveform. The input current waveform to a typical off-line power supply has the form of a haversine.
Headroom Used in conjunction with series pass regulators, and is the difference between the input and output voltages.
Hi-Pot (Dielectric Withstand) Abbreviation for High Potential, and generally refers to the high voltages used to test dielectric withstand capability for regulatory agency electrical safety requirements.
Hold-up Time The time during which a power supply's output voltage remains within specification following the loss of input power. (Typically 16-20ms). Determined by the storage factor within the power supply. In linear supplies, the time output fails when AC input fails, is almost immediate. In switching power supplies, energy is stored in the bulk (input electrolytic) capacitor providing a useable hold up time to protect against transient power outages. Since this is highly proportional to AC voltage and DC load, it is given under specified conditions. High AC voltage and low DC loads provide the best conditions.