See below for the special

Ground loop: An unwanted feedback problem caused by two or more circuits sharing a common electrical line, usually a common ground line.

Half-bridge converters: Two-transistor switching power supply configuration used in medium-power applications.

Half-wave rectifier: Single-diode rectifier circuit that rectifies only one-half the input AC wave.

Harmonic distortion: AC current outputs with multiple harmonic frequencies to AC line frequency provoked by the switching devices in a power supply.

Head room: In a linear regulator, the head room is the difference between the secondary voltage supplied by the power transformer at nominal input voltage and the regulated output voltage. Head room is necessary to ensure proper regulation under full load and low input voltage operation.

Heat sink: Device used to conduct away and disperse the heat generated by electronic components.

Hi-pot (high potential voltage): See: Isolation test voltage.

Holdup time: The time under worst case conditions during which a power supply’s output voltage remains within specified limits following the loss or removal of input power; also called “ride-through”.

Hybrid supplies: A power supply that combines two or more different regulation techniques, such as ferroresonant and linears or switching and linear.

IEC (International Electrotechanical Commissions): An international safety agency headquartered in Geneva, Switzerland.

IFB3 - Interleaved Full-Bridge Boost Buck, the patented dc-dc converter topology from Powerstax providing high efficiency, high power density and great versatility in a compact and reliable package.

Inhibit: The ability to electrically turn off the output of a power supply from a remote location.

Input voltage range: The range of source voltages for which the power supply meets its specifications.

Inrush current: A high surge of input current that occurs in switchers and occasionally in linears upon initial turn on, caused by charging of the input capacitors.

Isolating power supply is a PSU that provides isolation between input and output. Isolation is absence of DC current pass between two circuits. Isolation in PSU is provided by transformers. Most of commercially available AC-DC PSU are isolating. Low input voltage DC-DC PSU are often non-isolating, such as a car phone charger. Note that isolation does not mean a complete absence of AC current path- some AC currents can still flow from input to output through physical and/or stray capacitance.

Instantaneous current limiting circuit: See: Cycle-by-cycle current limiting circuit.

Insulation: Material used to insulate a device by preventing or reducing the transmission of electricity.

Inverter: A power converter which changes DC Input power into AC output power.

Isolation: The degree of electrical separation between two points. It can be expressed in terms of voltage (breakdown), current (galvanic), or resistance and/or capacitance (impedance). In power supplies, it is important to maximize the input to output isolation.

Isolation test voltage: Ability of a power supply to withstand a high voltage potential placed either from the input terminals to ground, from any of the output terminals to ground, or between any pair of input and output terminals. This specification is important for safety reasons and is partially dependent on the mechanical design of the power supply.