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BERTAN - Precision High Voltage Power Solutions:

    A Del Global Technologies Company

Series 105/106

The definitions which follow, except where noted, are used with permission of the Power Sources Manufacturing Association, Inc. from their "Handbook of Standardized Terminology for the Power Sources Industry".

 Portions of this text have been reprinted from IEEE Std 100-1988, IEEE Standard Dictionary of Electrical and Electronics Terms, copyright 1988 by the Institute of Electrical and Electronics Engineers, Inc., with permission of the IEEE Standards Department.
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AC: In text, use lower case: ac. Abbreviation for Alternating Current.

 AC BROWNOUT: The condition that exists when the ac line voltage drops below some specified value.

 AC LINE: The set of conductors that route ac voltage from one point to another.

 AC LINE FILTER: A circuit filter placed in the ac line to condition or smooth out variations that are higher in frequency than the line frequency.

 ANSI: Abbreviation for American National Standards Institute.

 AWG: Abbreviation for American Wire Gauge.

 ABSOLUTE ACCURACY: The correctness of the indicated value in terms of its deviation from the true or absolute value.

 ALTERNATING CURRENT: (ac) A periodic current the average value of which over a period is zero. Unless distinctly specified otherwise, the term refers to a current which reverses at regularly recurring intervals of time and which has alternately positive and negative values.

 AMBIENT TEMPERATURE: The average temperature of the environment immediately surrounding the power supply. For forced air-cooled units, the ambient temperature is measured at the air intake. See also Operating Temperature, Storage Temperature, Temperature Coefficient.

 AMPERE: (A) Electron or current flow representing the flow of one coulomb per second past a given point in a circuit.

 AMPLIFIER: A circuit or element that provides gain.

 AMPLIFIER, DC: A direct coupled amplifier that can provide gain for zero-frequency signals.

 AMPLIFIER, DIFFERENTIAL: An amplifier which has available both an inverting and a noninverting input, and which amplifies the difference between the two inputs.

 AMPLIFIER, INVERTING: An amplifier whose output is 180° out of phase with its input. Such an amplifier can be used with degenerative feedback for stabilization purposes.

 AMPLIFIER, NONINVERTING: An amplifier whose output is in phase with its input.

 AMPLIFIER, OPERATIONAL: A dc amplifier whose gain is sufficiently large that its characteristics and behavior are substantially determined by its input and feedback elements. Operational amplifiers are widely used for signal processing and computational work.

 ANODE: 1) (electron tube or valve) An electrode through which a principal stream of electrons leaves the interelectrode space. 2) (semiconductor rectifier diode) The electrode from which the forward current flows within the cell. (IEEE Std 100-1988)

 APPARENT POWER: Power value obtained in an ac circuit as the product of current times voltage.

ARC: A discharge of electricity through a gas, normally characterized by a voltage drop in the immediate vicinity of the cathode approximately equal to the ionization potential of the gas. (IEE Std 100-1988)

 ASYMMETRICAL WAVEFORM: A current or voltage waveform that has unequal excursions above and below the horizontal axis.

 ATTENUATION: Decrease in amplitude or intensity of a signal.

AUTHORIZED PERSON: A qualified person who, by nature of his duties or occupation, is obliged to approach or handle electrical equipment or, a person who, having been warned of the hazards involved, has been instructed or authorized to do so by someone in authority.

AUTO TRANSFORMER: A single winding transformer with one or more taps.

 AUTOMATIC CROSSOVER: The characteristic of a power supply having the capability of switching its operating mode automatically as a function of load or setting from the stabilization of voltage to the stabilization of current. The term automatic crossover power supply is reserved for those units having substantially equal stabilization for both voltage and current. Not used for voltage-limited current stabilizers or current-limited voltage stabilizers. See also CROSSOVER POINT.

 AUTOMATIC GAIN CONTROL (AGC): A process or means by which gain is automatically adjusted in a specified manner as a function of input or other specified parameters. (IEEE Std 100-1988)

AUXILIARY SUPPLY: A power source supplying power other than load power as required for the proper functioning of a device.

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BANDWIDTH: Based on the assumption that a power supply can be modeled as an amplifier, the bandwidth is that frequency at which the voltage gain has fallen off by 3 dB. Bandwidth is an important determinant of transient response and output impedance.

 BASEPLATE: Mounting platform for power supply components.

 BASEPLATE TEMPERATURE: The temperature at the hottest spot on the mounting platform of the supply.

 BEAD: A small ferrite normally used as a high frequency inductor core.

 BEAM SUPPLY: Power supply which provides the accelerating energy for the electrons or ions. (Bertan High Voltage)

 BENCH POWER SUPPLY: A power source fitted with output controls, meters, terminals and displays for experimental bench top use in a laboratory.

 BIAS SUPPLY: Power supply which provides the voltage to the Wehnelt electrode or grid. This voltage controls the amount of current the load demands from the beam supply. The bias output "floats" on the beam output in E-Beam applications. (Bertan High Voltage)

 BIFILAR WINDING: Two conductors wound in parallel.

 BIPOLAR: Having two poles, polarities or directions.

 BIPOLAR PLATE: An electrode construction where positive and negative active materials are on opposite sides of an electronically conductive plate.

 BIPOLAR POWER SUPPLY: A special power supply which responds to the sense as well as the magnitude of a control instruction and is able to linearly pass through zero to produce outputs of either positive or negative polarity.

 BIT: A binary unit of digital information having a value of "0" or "1". See also Byte.

 BLACK BOX: Element in a system specified by its function, or operating characteristics.

 BLEED: A low current drain from a power source.

 BLEEDER RESISTOR: A resistor that allows a small current drain on a power source to discharge filter capacitors or to stabilize an output.

 BOBBIN: 1) A non-conductive material used to support windings. 2) A cylindrical electrode (usually the positive) pressed from a mixture of the active material, a conductive material, such as carbon black, the electrolyte and/or binder with a centrally located conductive rod or other means for a current collector.

 BODE PLOT: A plot of gain versus frequency for a control loop. It usually has a second plot of phase versus frequency.

 BOOST REGULATOR: One of several basic families of switching power supply topologies. Energy is stored in an inductor during the pulse then released after the pulse.

 BREAKDOWN VOLTAGE: 1)The voltage level which causes insulation failure. 2) The reverse voltage at which a semiconductor device changes its conductance characteristics.

BRIDGE CIRCUIT: Circuit with series parallel groups of components.

 BRIDGE CONVERTER: A power conversion circuit with the active elements connected in a bridge configuration.

 BRIDGE RECTIFIER: Full-wave rectifier circuit employing two or more rectifiers in a bridge configuration.

 BROWNOUT: The condition created during peak usage periods when electric utility companies intentionally reduce their line voltage by approximately 10 to 15 percent to counter excessive demand.

 BUCK REGULATOR: One of several switching power supply topologies where a series of pulses are applied by a switching device to an averaging L-C filter and then applied to a load.

 BUFFER: An isolating circuit used to prevent a driven circuit from influencing a driving circuit. (IEEE Std 100-1988)

 BULK CAPACITOR: The energy storage capacitor at the front end of a regulator.

 BULK VOLTAGE: The voltage across a bulk capacitor.

 BURN IN: The operation of a newly fabricated device or system prior to application with the intent to stabilize the device, detect defects, and expose infant mortality.

BUS: The common primary conductor of power from a power source to two or more separate circuits.

 BYTE: A sequence of binary digits, frequently comprised of eight (8) bits, addressed as a unit. Also see BIT.

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CGS UNIT: Abbreviation for the Centimeter-Gram Second Unit of measurement.

 CSA: Abbreviation for Canadian Standards Association.

 CAPACITANCE: Inherent property of an electric circuit or device that opposes change in voltage. Property of circuit whereby energy may be stored in an electrostatic field.

 CAPACITANCE, DISTRIBUTED: The capacitance in a circuit resulting from adjacent turns on coils, parallel leads and connections.

 CAPACITIVE COUPLING: Coupling resulting from the capacitive effect between circuit elements.

 CAPACITIVE EFFECT LEAKAGE CURRENT: The current flow between segregated conductive metal parts; voltage and frequency dependent.

 CAPACITOR: A device that stores a charge. A simple capacitor consists of two conductors separated by a dielectric.

 CAPACITOR INPUT FILTER: Filter employing capacitor as its input.

 CATHODE: 1) (electron tube or valve) An electrode through which a primary stream of electrons enters the interelectrode space. 2) (semiconductor rectifier diode) The electrode to which the forwward current flows within the cell. (IEEE Std 100-1988)

CATHODE RAY TUBE (CRT): A display device in which controlled electron beams are used to present alphanumeric or graphical data on an electroluminescent screen. (IEEE Std 100-1988)

 CATHODE-RAY TUBE: An electron-beam tube in which the beam can be focused to a small cross section on a luminescent screen and varied in position and intensity to produce a visible pattern. (IEEE Std 100-1988)

CENTER TAP: Connection made to center of an electronic device.

 CHARGE: 1) The conversion of electrical energy, provided in the form of a current from an external source, into chemical energy within a cell or battery. 2) The potential energy stored in a capacitive electrical device.

 CHASSIS: The structure supporting or enclosing the power supply.

 CHASSIS GROUND: The voltage potential of the chassis.

 CHOKE COIL: An inductor.

 CHOKE, RF: A choke coil with a high impedance at radio frequencies.

 CIRCUIT INPUT FILTER: A filter employing an inductor (L) or an inductor/capacitor (L/C) as its input.

 CIRCULAR MIL: Cross-sectional area of a conductor one mil in diameter.


 CLAMP DIODE: A diode in either a clipper or clamp circuit.

 CLIPPER CIRCUIT: A circuit that blocks or removes the portion of a voltage waveform above some threshold voltage.

 CLOSED LOOP CONTROL: A type of automatic control in which control actions are based on signals fed back from the controlled equipment or system. (IEEE Std 100-1988)

 CLOSED-LOOP CONTROL SYSTEM: (control system feedback) A control system in which the controlled quantity is measured and compared with a standard representing the desired performance. Note: Any deviation from the standard is fed back into the control system in such a sense that it will reduce the deviation of the controlled quantity from the standard. (IEEE Std 100-1988)

 COLLECTOR: 1) Electronic connection between the electrochemical cell electrode and the external circuit. 2) In a transistor, the semiconductor section which collects the majority carriers.


 COMMON-MODE NOISE: The component of noise voltage that appears equally and in phase on conductors relative to a common reference.

 COMMON-MODE OUTPUT: That electrical output supplied to an impedance connected between the terminals of the ungrounded floating output of a power supply, amplifier, or line-operated device, and the ground point to which the source power is returned.

COMMON POINT: With respect to operationally programmable power supplies one output/sense terminal is designated "common" to which load, reference and external programming signal all return.

 COMMON RETURN: A return conductor common to two or more circuits.

 COMPARISON AMPLIFIER: A dc amplifier which compares one signal to a stable reference, and amplifies the difference to regulate the power supply power-control elements.

 COMPENSATION: The addition of circuit elements to assist in stabilization of a control loop.

 COMPLIMENTARY TRACKING: A system of interconnection of two voltage stabilizers by which one voltage (the slave) tracks the other (the master).

 COMPLIANCE: Agency certification that a product meets its standards. See also SAFETY COMPLIANCE.

COMPLIANCE VOLTAGE: The output dc voltage of a constant current supply.

COMPLIANCE RANGE: Range of voltage needed to sustain a given constant current throughout a range of load resistance.

 CONDUCTANCE (G): The ability to conduct current. It is equal to amperes per volt, or the reciprocal of resistance, and is measured in siemens (metric) or mhos (English). G = 1/R.

 CONSTANT CURRENT LIMITING CIRCUIT: Current-limiting circuit that holds output current at some maximum value whenever an overload of any magnitude is experienced.

 CONSTANT CURRENT LOAD: An electronic load with a control loop to regulate the current drawn from the power supply.

 CONSTANT CURRENT POWER SUPPLY: A power supply that regulates its output current, within specified limits, against changes in line, load,ambient temperature and time.

 CONSTANT VOLTAGE CHARGE: A charge during which the voltage across the battery terminals is maintained at a steady state.

 CONSTANT VOLTAGE POWER SUPPLY: A power supply that regulates its output voltage within specified limits, against changes in line, load, ambient temperature and time.

 CONTINUOUS DUTY: A requirement of service that demands operation at a substantially constant load for an indefinitely long time. See also INTERMITTENT DUTY.

 CONTROL GRID: A grid, ordinarily placed between the cathode and an anode, for use as a control electrode. (IEEE Std 100-1988)

CONTROL LOOP: A feedback circuit used to control an outputsignal. See also LOOP.

 CONTROL RANGE: The parameter over which the controlled signal maybe adjusted and still meet the unit specifications.

 CONTROL REMOTE: Control over the stabilized output signal by means located outside or away from the power supply. May or may not be calibrated.

 CONTROL RESOLUTION: The smallest increment of the stabilized output signal that can be reliably repeated.

 CONVECTION-COOLED POWER SUPPLY: A power supply cooled exclusively from the natural motion of a gas or a liquid over the surfaces of heat dissipating elements.

 CONVERTER: A device that changes the value of a signal or quantity. Examples: DC-DC; a device that delivers dc power when energized from a dc source. Fly-Back; a type of switching power supply circuit. See also FLYBACK CONVERTER. Forward; a type of switching power supply circuit. See also FORWARD CONVERTER.

 CORE: Magnetic material serving as a path for magnetic flux.

 CORONA:1) (air) A luminous discharge due to ionization of the air surrounding a conductor caused by a voltage gradient exceeding a certain critical value. 2) (gas) A discharge with slight luminosity produced in the neighborhood of a conductor, without greatly heating it, and limited to the region surrounding the conductor in which the electric field exceeds a certain value. 3) (partial discharge) (corona measurement) A type of localized discharge resulting from transient gaseous ionization in an insulation system when the voltage stress exceeds a critical value. The ionization is usually localized over a portion of the distance between the electrodes of the system. (IEEE Std 100-1988)

 CORONA EXTINCTION VOLTAGE: (CEV) (corona measurement) The highest voltage at which continuous corona of specified pulse amplitude no longer occurs as the applied voltage is gradually decreased from above the corona inception value. Where the applied voltage is sinusoidal, the CEV is expressed as 0.707 of the peak voltage. (IEEE Std 100-1988)

 CORONA INCEPTION VOLTAGE: (CIV) (corona measurement) The lowest voltage at which continuous corona of specified pulse amplitude occurs as the applied voltage is gradually increased. Where the applied voltage is sinusoidal, the CIV is expressed as 0.707 of the peak voltage. (IEEE Std 100-1988)

 CREEPAGE: The movement of electrolyte onto surfaces of electrodes or other components of a cell with which it is not normally in contact.

CREEPAGE DISTANCE: The shortest distance separating two conductors as measured along a surface touching both conductors.

 CROSS-REGULATION: In a multiple output power supply, the percent voltage change at one output caused by the load change on another output.

 CROSSOVER POINT: That point on the operating locus of a voltage/current automatic crossover power supply formed by the intersection of the voltage-stabilized and current-stabilized output lines. The resistance value (E/I) defined by this intersection is the matching impedance of the power supply, which will draw the maximum output power. See also AUTOMATIC CROSSOVER.

 CROSSOVER, VOLTAGE/CURRENT: Voltage/Current crossover is that characteristic of a power supply that automatically converts the mode of operation from voltage regulation to current regulation (or vice versa) as required by preset limits.

 CROWBAR: An overvoltage protection circuit which rapidly places a low resistance shunt across the power supply output terminals if a predetermined voltage is exceeded.



 CURRENT LIMIT KNEE: The point on the plot of current vs voltage of a supply at which current starts to foldback, or limit.

 CURRENT LIMITING: An electronic overload protection circuit which limits the maximum output current to a preset value.

 CURRENT MODE: The functioning of a power supply so as to produce a stabilized output current.

 CURRENT SENSING RESISTOR: A resistor placed in series with the load to develop a voltage proportional to load current.

 CURRENT SOURCE: A power source that tends to deliver constant current.

 CURRENT STABILIZATION: The process of controlling an output current.

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DC: In text, use lower case: dc. Abbreviation for Direct Current.

 DC COMPONENT: The dc value of an ac wave that has an axis other than zero.

 DC-DC CONVERTER: A circuit or device that changes a dc input signal value to a different dc output signal value.


 DERATING: (reliability) The intentional reduction of stress/strength ratio in the application of an item, usually for the purpose of reducing the occurrence of stress-related failures. (IEEE Std 100-1988)

DIELECTRIC: An insulating material between conductors.

 DIELECTRIC CONSTANT (K): For a given dielectric material, the ratio of the value of a capacitor using that material to the value of an equivalent capacitor using a standard dielectric such as dry air or a vacuum.

 DIELECTRIC WITHSTAND VOLTAGE: Voltage an insulating material will withstand before flashover or puncture. See also HI-POT TEST, ISOLATION.

 DIFFERENTIAL VOLTAGE: The difference in voltages at two points as measured with respect to a common reference.

 DRIFT: A change in output over a period of time independent of input, environment or load.

 DRIVER: A current amplifier used for control of another device or circuit.

 DUTY CYCLE: 1) The ratio of time on to time off in a recurring event. 2) The operating regime of a cell or battery including factors such as charge and discharge rates, depth of discharge, cycle length and length of time in the standby mode.

 DYNAMIC FOCUS: A means of modulating the focus voltage as a function of the beam position. (Bertan High Voltage)

 DYNAMIC LOAD: A load that rapidly changes from one level to another. To be properly specified, both the total change and the rate of change must be stated.

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EMF: Abbreviation for Electromotive Force.

 EMI: Abbreviation for Electromagnetic Interference.

 EMI FILTER: A circuit composed of reactive and resistive components for the attenuation of radio frequency components being emitted from a power supply. See also EMI.

 EMI FILTERING: Process or network of circuit elements to reduce electromagnetic interference emitted from or received by an electronic device. See also EMI.

 ESD: Abbreviation for Electrostatic Discharge.

 ESL: Abbreviation for Equivalent Series Inductance.

 ESR: Abbreviation for Equivalent Series Resistance.

 EARTH: An electrical connection to the earth frequently using a grid or rod(s). See also GROUND.

 E-BEAM: Electron Beam. (Bertan High Voltage)

 EDDY CURRENTS: A circulating current induced in a conducting material by a varying magnetic field.

 EFFECTIVE VALUE: The value of a waveform that has the equivalent heating effect of a direct current. For sine waves, the value is .707 X Peak Value; for non-sinusoidal waveforms, the Effective Value = RMS (Root Mean Square) Value.

 EFFICIENCY: 1) The ratio of total output power to total input power, expressed as a percentage, under specified conditions. 2) The ratio of the output of a secondary cell or battery on discharge to the input required to restore it to the initial state of charge under specified conditions.

 ELECTRIC: Containing, producing, arising from, actuated by, or carrying electricity, or designed to carry electricity and capable of so doing. Examples: Electric eel, energy, motor, vehicle, wave. Note: Some dictionaries indicate electric and electrical as synonymous, but usage in the electrical engineering field has in general been restricted to the meaning given in the definitions above. It is recognized that there are borderline cases wherein the usage determines the selection. See ELECTRICAL. (IEEE Std 100-1988)

 ELECTRICAL: (general) Related to, pertaining to, or associated with electricity but not having its properties or characteristics. Examples: Electrical engineer, handbook, insulator, rating, school, unit.
Note: Some dictionaries indicate electric and electrical as synonymous, but usage in the electrical engineering field has in general been restricted to the meaning given in the definitions above. It is recognized that there are borderline cases wherein the usage determines the selection. See ELECTRIC. (IEEE Std 100-1988)

 ELECTRON (e-): Negatively charged particle.

 ELECTRON BEAM: A collection of electrons which may be parallel, convergent, or divergent. (Bertan High Voltage)

 ELECTRON GUN: (electron tube) An electrode structure that produces and may control, focus, deflect, and converge one or more electron beams. (IEEE Std 100-1988)

 ELECTRON VOLT: A measure of energy. The energy acquired by an electron passing through a potential of one volt.

 ELECTRONIC: Of, or pertaining to, devices, circuits, or systems utilizing electron devices. Examples: Electronic control, electronic equipment, electronic instrument, and electronic circuit. (IEEE Std 100-1988)

 ELECTRONIC LOAD: A test instrument designed to draw various and specified amounts of current or power from a power source.

 ELECTROPHORESIS: A movement of colloidal ions as a result of the application of an electric potential. (IEEE Std 100-1988)

 EMISSION: 1) (laser-maser) The transfer energy from matter to a radiation field. 2) (radio-noise emission) An act of throwing out or giving off, generally used here in reference to electromagnetic energy. (IEEE Std 100-1988)

 EMISSION CURRENT: The current resulting from electron emission. (IEEE Std 100-1988)

 EQUIVALENT CIRCUIT: An electrical circuit that models the fundamental properties of a device or circuit.

 EQUIVALENT LOAD: An electrical circuit that models the fundamental properties of a load.

 EQUIVALENT SERIES INDUCTANCE (ESI): The amount of inductance in series with an ideal capacitor which exactly duplicates the performance of a real capacitor.

 EQUIVALENT SERIES RESISTANCE (ESR): The amount of resistance in series with an ideal capacitor which exactly duplicates the performance of a real capacitor.

 ERROR AMPLIFIER: An operational amplifier, or differential amplifier, in a control loop that produces an error signal whenever a sensed output differs from a reference voltage.

 ERROR SIGNAL: The output voltage of an error amplifier produced by the difference between the reference and the input signal times the gain of the amplifier.

 ERROR VOLTAGE:The output voltage of the error amplifier in a control loop.

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FET: Abbreviation for Field Effect Transistor.

 FAILURE MODE: The way in which a device has ceased to meet specified minimum requirements.

 FALL TIME: The time required for a pulse to decrease from 90 percent to 10 percent of its maximum positive (negative) amplitude.

 FAN COOLED: A method of forced-air cooling used to maintain design.

FARAD: Unit of measurement of capacitance. A capacitor has a capacitance of one farad when a charge of one coulomb raises its potential one volt: C = Q/E.

 FEEDBACK: The process of returning part of the output signal of a system to its input.

 FEED FORWARD: A control technique whereby the line regulation of a power supply is improved by directly sensing the input voltage.

 FEED THROUGH: A plated-through hole in a printed circuit board which electrically connects a trace on top of the board with a trace on the bottom side.

 FERRITE: A ceramic material that exhibits low loss at high frequencies, and which contains iron oxide mixed with oxides or carbonates of one or more metals such as manganese, zinc, nickel or magnesium.

FIELD EFFECT TRANSISTOR (FET): Transistor in which the resistance of the current path from source to drain is modulated by applying a transverse electric field between two electrodes. See also JUNCTIONFIELD EFFECT TRANSISTOR, METAL OXIDE, SEMICONDUCTOR FIELD EFFECT TRANSISTOR.

 FIELD EMISSION: Electron emission from a surface due directly to high voltage gradients at the emitting surface. (IEEE Std 100-1988)

FIELD EMISSION GUN: An electron gun with an extractor electrode which pulls or extracts electrons off the filament.

Extraction is accomplished using a high electric field. An extractor power supply is the opposite polarity of the beam supply and it floats on the beam output. (Bertan High Voltage)

 FILAMENT: (electron tube) A hot cathode, usually in the form of a wire or ribbon, to which heat may be supplied by passing current through it. Note: This is also known as a filamentary cathode. (IEEE Std 100-1988)

 FILAMENT CURRENT: The current supplied to a filament to heat it. (IEEE Std 100-1984 )

 FILAMENT OUTPUT: Power supply which heats the filament of an electron column, CRT or x-ray tube. In some applications, the filament output "floats" on the accelerating voltage. (Bertan High Voltage)

FILAMENT VOLTAGE: The voltage between the terminals of a filament. (IEEE Std 100-1988)

 FILTER: One or more discrete components positioned in a circuit to attenuate signal energy in a specified band of frequencies.

 FLASHOVER: 1) (general) A disruptive discharge through air around or over the surface of solid or liquid insulation, between parts of different potential or polarity, produced by the application of voltage wherein the breakdown path becomes sufficiently ionized to maintain an electric arc. 2) (high voltage ac cable termination) A disruptive discharge around or over the surface of an insulating member, between parts of different potential or polarity, produced by the application of voltage wherein the breakdown path becomes sufficiently ionized to maintain an electric arc. 3) (high voltage testing) Term used when a disruptive discharge occurs over the surface of a solid dielectric in a gaseous or liquid medium. (IEEE Std 100-1988)

 FLOATING NETWORK OR COMPONENTS: A network or component having no terminal at ground potential. (IEEE Std 100-1988)

 FLOATING OUTPUT: Ungrounded output of a power supply where either output terminal may be referenced to another specified voltage.

 FLYBACK CONVERTER: A power supply switching circuit which normally uses a single transistor. During the first half of the switching cycle the transistor is on and energy is stored in a transformer primary; during the second half of the switching cycle this energy is transferred to the transformer secondary and the load.

 FOCUS: (oscillograph) Maximum convergence of the electron beam manifested by minimum spot size on the phosphor screen. (IEEE Std 100-1988)

 FOCUSING: The process of controlling the convergence of the electron beam. (IEEE Std 100-1988)

 FOCUSING ELECTRODE: (beam tube) An electrode the potential of which is adjusted to focus an electron beam. (IEEE Std 100-1988)

 FOLDBACK CURRENT LIMITING: A power supply output protection circuit whereby the output current decreases with increasing overload, reaching a minimum at short circuit. This minimizes the internal power dissipation under overload conditions. Foldback current limiting is normally used with linear regulators.

 FORWARD CONVERTER: A power supply switching circuit that transfers energy to the transformer secondary when the switching transistor is on.

FREE WHEEL DIODE: A diode in a pulse-width modulated switching power supply that provides a conduction path for the counter electromotive force of an output choke.

 FREQUENCY: Number of cycles per second (measured in Hertz).

 FULL BRIDGE CONVERTER: A power switching circuit in which four power switching devices are connected in a bridge configuration to drive a transformer primary.

 FULL BRIDGE RECTIFIER: A rectifier circuit that employs four diodes per phase.

 FULL WAVE RECTIFIER: Rectifier circuit that produces a dc output for each half cycle of applied alternating current.

 FUSE: Safety protective device that permanently opens an electric circuit when overloaded. See also OVERCURRENT DEVICE, OVERCURRENT PROTECTIVE DEVICE.

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GPIB: General purpose interface bus, also known as IEEE-488. (Bertan High Voltage)

 GAIN: Ratio of an output signal to an input signal. See also CLOSED LOOP GAIN, GAIN MARGIN, OPEN LOOP GAIN.

 GAUSS: Measure of flux density in Maxwells per square centimeter of cross-sectional area. One Gauss is 10-4 Tesla.

GLITCH: 1) An undesired transient voltage spike occurring on asignal. 2) A minor technical problem arising in electrical equipment.

 GRID: 1) In batteries, a framework for a plate or electrode which supports or retains the active materials and acts as a current collector. 2) In vacuum tubes, an element used to control the flow of electrons. 3) A network of equally spaced parallel lines, one set spaced perpendicular to the other.

 GROUND: A conducting connection, whether intentional or accidental, by which an electric circuit or equipment is connected to earth, or to some conducting body that serves in place of earth. (National Electric Code)

 GROUND BUS: A bus to which individual grounds in a system are attached and that in turn is grounded at one or more points.

GROUND LOOP: A condition that causes undesirable voltage levels when two or more circuits share a common electrical return or ground lines.

 GROUNDED: Connected to or in contact with earth or connected to some extended conductive body which serves instead of the earth.

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HALF-BRIDGE CONVERTER: A switching power supply design in which two power switching devices are used to drive the transformer primary. See also BRIDGE RECTIFIER.

 HALF-WAVE RECTIFIER: A circuit element, such as a diode, that rectifies only one-half the input ac wave to produce a pulsating dc output.

HEADROOM: The difference between the bulk voltage and the output voltage in a linear series pass regulator. See also DIFFERENTIAL VOLTAGE.

 HEAT SINK: The medium through which thermal energy is dissipated.

 HENRY (H): Unit of measurement of inductance. A coil has one henry of inductance if an EMF of one volt is induced when current through an inductor is changing at rate of one ampere per second.

 HERTZ (Hz): The SI unit of measurement for frequency, named in honor of Heinrich Hertz who discovered radio waves. One hertz equals one cycle per second.

 HI-POT TEST (HIGH POTENTIAL TEST): A test performed by applying a high voltage for a specified time to two isolated points in a device to determine adequacy of insulating materials.

 HICCUP: A transient condition that momentarily confuses a control loop.

 HIGH LINE: Highest specified input operating voltage.

 HIGH VOLTAGE ASSEMBLY: The portion of a high voltage power supply which contains the high voltage circuits which are critical to the performance and reliability of a high voltage power supply. (Bertan High 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. Sometimes called Holding Time or Ride-Through.

 HYBRID SUPPLIES: A power supply that combines two or more different regulation techniques, such as ferroresonant and linear or switching and linear, or one that takes advantage of hybrid technology.

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I-BEAM: Ion Beam. (Bertan High Voltage)

 IC: Abbreviation for Integrated Circuit.

 IEC: Abbreviation for International Electrotechnical Commission.

 IEEE: Abbreviation for Institute of Electrical and Electronics Engineers.

 IMPEDANCE (Z): Total resistance to flow of an alternating current as a result of resistance and reactance.

 INDUCED CURRENT: Current that flows as a result of an Induced EMF (Electromotive Force).

 INDUCED EMF: Voltage induced in a conductor in a varying magnetic field.

 INPUT IMPEDANCE: The impedance of the input terminals of a circuit or device, with the input disconnected.

 INPUT LINE FILTER: A low-pass or band-reject filter at the input of a power supply which reduces line noise fed to the supply. This filter may be external to the power supply.


 INPUT VOLTAGE RANGE: The range of input voltage values for which a power supply or device operates within specified limits.

 INRUSH CURRENT: The peak instantaneous input current drawn by a power supply at turn on.

 INRUSH CURRENT LIMITING: The circuit characteristic that limits inrush current when a power supply is turned on.

 INSTANTANEOUS VALUE: The measured value of a signal at a given moment in time.

 INSULATION: Non-conductive materials used to separate electric circuits.

 INSULATION RESISTANCE:The resistance offered, usually measured in megohms, by an insulating material to the flow of current resulting from an impressed dc voltage.

 INVERTER: 1) A device that changes dc power to ac power. 2) A circuit, circuit element or device that inverts the input signal.

 ION BEAM: A collection of ions which may be parallel, convergent, or divergent. (Bertan High Voltage)

 ION GUN: A device similar to an electron gun but in which the charged particles are ions. Example: proton gun. (IEEE Std 100-1988)

 ISOLATION: The electrical separation between two circuits, or circuit elements.


 ISOLATION VOLTAGE: The maximum ac or dc specified voltage that may be continuously applied between isolated circuits.

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JOULE (J): Unit of energy equal to one watt-second.

KELVIN (K): 1) Unit of temperature in the International System of Units (Sl) equal to the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The kelvin temperature scale uses Celsius degrees with the scale shifted by 273.16. Therefore, 0 K is at absolute zero. Add 273.16 to any Celsius value to obtain the corresponding value in kelvins. 2) A technique using 4 terminals to isolate current carrying leads from voltage measuring leads.

 KIRCHOFF'S CURRENT LAW: At any junction of conductors in a circuit, the algebraic sum of the current is zero.

 KIRCHOFF'S VOLTAGE LAW: In a circuit, the algebraic sum of voltages around the circuit is equal to zero.

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L-C FILTER: A low pass filter that consists of an inductance (L) and a capacitance (C). Also known as an averaging filter.

 LED: Symbol for Light-Emitting Diode.

 LATCH-UP: A part of the control circuit for a power supply that goes into a latched condition.

 LEAKAGE CURRENT: 1) The ac or dc current flowing from input to output and/or chassis of an isolated device at a specified voltage. 2) The reverse current in semiconductor junctions.

 LINE: 1) Medium for transmission of electricity between circuits or devices. 2) The voltage across a power transmission line. See also HIGH LINE, LOW LINE.

 LINE CONDITIONER: A circuit or device designed to improve the quality of an ac line.


 LINE REGULATION: The percentage change in output due to the input voltage varying over its specified limits, at specified loadvalues, with all other factors constant.

 LINE REGULATOR: Power conversion equipment that regulates and/or changes the voltage of incoming power.

 LINEAR: 1) In a straight line. 2) A mathematical relationship in which quantities vary in direct proportion to one another, the result of which, when plotted, forms a straight line.


 LINEAR REGULATION: A regulation technique wherein the control device, such as transistor, is placed in series or parallel with the load. Output is regulated by varying the effective resistance of the control device to dissipate unused power. See also LINEAR SUPPLY, REGULATION.

 LINEAR REGULATOR: A power transformer or a device connected in series with the load of a constant voltage power supply in such a way that the feedback to the series regulator changes its voltage drop as required to maintain a constant dc output.

 LINEAR SUPPLY REGULATION: An electronic power supplyemploying linear regulation techniques. See also LINEAR REGULATION.

 LINEARITY: 1) The ideal property wherein the change in the value of one quantity is directly proportional to the change in the value of another quantity, the result of which, when plotted on graph, forms a straight line. 2) Commonly used in reference to Linearity Error.

 LINEARITY ERROR: The deviation of the output quantity from a specified reference line.

 LINE TRANSIENT: A perturbation outside the specified operating range of an input or supply voltage.

 LOAD: Capacitance, resistance, inductance or any combination thereof, which, when connected across a circuit determines current flow and power used.

 LOAD DECOUPLING: The practice of placing filter components at the load to attenuate noise.


 LOAD IMPEDANCE: The complex resistance to the flow of current posed by a load that exhibits both the reactive and resistive characteristics.

 LOAD REGULATION: 1) Static: The change in output voltage as the load is changed from specified minimum to maximum and maximum to minimum, with all other factors held constant. 2) Dynamic: The change in output voltage expressed as a percent for a given step change in load current. Initial and final current values and the rates of change must be specified. The rate of change shall be expressed as current/unit of time, e.g., 20 amperes A/µ second. The dynamic regulation is expressed as a ± percent for a worst case peak-to-peak deviation for dc supplies, and worst case rms deviation for ac supplies.

 LOCAL CONTROL: Control over the stabilized output signal by means located within or on the power supply. May or may not be calibrated.

 LOCAL SENSING: Using the power supply output voltageterminals as the error-sensing points to provide feedback to the voltage regulator.

 LOGIC GROUND: Common return or reference point for logic signals.

 LOGIC HIGH: A voltage representing a logic value of one (1) in positive logic.

 LOGIC INHIBIT/ENABLE: A referenced or isolated logic signal that turns a power supply output off or on.

 LOGIC LOW: A voltage representing a logic value of zero (0) in positive logic.

 LONG-TERM STABILITY: The output voltage change of a power supply, in percent, due to time only, with all other factors held constant. Long-term stability is a function of component aging.

 LOOP: The path used to circulate a signal. See also CLOSED LOOP, CONTROL LOOP, OPEN LOOP.

 LOOP GAIN: The ratio of the values of a given signal from one point to another in a loop. See also GAIN.

 LOOP RESPONSE: The speed with which a loop corrects for specified changes in line or load.

 LOOP STABILITY: A term referencing the stability of a loop as measured against some criteria, e.g., phase margin and gain margin.

 LOW LINE: Lowest specified input operating voltage.

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MOSFET: Abbreviation for Metal Oxide Semiconductor Field Effect Transistor.

 MTBF: Abbreviation for Mean Time Between Failure.

 MAXIMUM LOAD: 1) The highest allowable output rating specified for any or all outputs of a power supply under specified conditions including duty cycle, period and amplitude. 2) The highest specified output power rating of a supply specified under worst case conditions.

 MINIMUM LOAD: 1) The lowest specified current to be drawn on a constant voltage power supply for the voltage to be in a specified range. 2) For a constant current supply, the maximum value of load resistance.

 MODULAR: 1) A physically descriptive term used to describe a power supply made up of a number of separate subsections, such as an input module, power module, or filter module. 2) An individual power unit patterned on standard dimensions and capable of being integrated with other parts or units into a more complex and higher power system.

 MODULATOR: The control element of a switching power supply.

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NEGATIVE FEEDBACK:1) (circuits and systems) The process by which part of the signal in the output circuit of an amplifying device reacts upon the input circuit in such a manner as to counteract the initial power, thereby decreasing the amplification. 2) (control) (industrial control) A feedback signal in a direction to reduce the variable that the feedback represents. 3) (degeneration) (stabilized feedback) (data transmission) The process by which a part of the power in the output circuit of an amplifying device reacts upon the input circuit in such a manner as to reduce the initial power, thereby reducing the amplification. (IEEE Std 100-1988)

 NEGATIVE RAIL: The more negative of the two conductors at the output of a power supply.

 NEGATIVE REGULATOR: A voltage regulator whose output voltage is negative compared to the voltage at the return.

 NEGATIVE TEMPERATURE COEFFICIENT: A decreasing function with increasing temperature. The function may be resistance, capacitance, voltage, etc.

 NO LOAD VOLTAGE: Terminal voltage of battery or supply when no current is flowing in external circuit. See OPEN CIRCUIT VOLTAGE.

 NODE: The junction of two or more branches in a circuit.

 NOISE: The aperiodic random component on the power source output which is unrelated to source and switching frequency. Unless specified otherwise, noise is expressed in peak-to-peak units over a specified bandwidth.

 NOMINAL VALUE: The stated or objective value of a quantity or component, which may not be the actual value measured.

 NOMINAL VOLTAGE: The stated or objective value of a given voltage, which may not be the actual value measured.

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OP-AMP: Abbreviation for Operational Amplifier.

 OVP: Abbreviation for Overvoltage Protection.

 OFF LINE POWER SUPPLY: 1) A power supply in which the ac line is rectified and filtered without using a line frequency isolation transformer. 2) A power supply switched into service upon line loss to provide power to the load without significant interruption. See also UNINTERRUPTIBLE POWER SUPPLY.

 OFFSET CURRENT: The direct current that appears as an error at either terminal of a dc amplifier when the input current source is disconnected.

 OFFSET VOLTAGE: The dc voltage that remains between the input terminals of a dc amplifier when the output current voltage is zero

 OHM: Unit of measure of resistance.

 OPEN-CIRCUIT VOLTAGE (OCV): The difference in potential between the terminals of a cell or voltage when the circuit is open (no-load condition). See NO LOAD VOLTAGE.

 OPEN-FRAME CONSTRUCTION: A construction technique where the supply is not provided with an enclosure.

 OPEN LOOP: A signal path without feedback.

 OPEN LOOP GAIN: Ratio of output signal to input signal without feedback.

 OPERATING TEMPERATURE RANGE: The range of ambient, baseplate or case temperatures through which a power supply is specified to operate safely and to perform within specified limits. See also AMBIENT TEMPERATURE, STORAGE TEMPERATURE.

 OPERATIONAL AMPLIFIER (OP-AMP): A high gain differential input device that increases the magnitude of the applied signal to produce an error voltage.

 OPERATIONAL POWER SUPPLY: A power supply with a high open loop gain regulator which acts like an operational amplifier and can be programmed with passive components.

 OPTO-COUPLER: A package that contains a light emitter and a photoreceptor used to transmit signals between electrically isolated circuits.


 OSCILLATOR: A nonrotating device for producing alternating current, the output frequency of which is determined by the characteristics of the device. (IEEE Std 100-1988)

 OUTPUT: The energy or information delivered from or through a circuit or device.

 OUTPUT CURRENT LIMITING: A protective feature that keeps the output current of a power supply within predetermined limits during overload to prevent damage to the supply or the load.

OUTPUT FILTER: One or more discrete components used to attenuate output ripple and noise.

 OUTPUT IMPEDANCE:The impedance that a power supply appears to present to its output terminals.

 OUTPUT RANGE: The specified range over which the value of a stabilized output quantity (voltage or current) can be adjusted.


 OUTPUT VOLTAGE: The voltage measured at the output terminals of a power supply.

 OUTPUT VOLTAGE ACCURACY: The tolerance in percent of the output voltage

 OVERCURRENT DEVICE: A device capable of automatically opening an electric circuit, both under predetermined overload and short-circuit conditions, either by fusing of metal or by electromechanical means.


 OVERLOAD PROTECTION:A feature that senses and responds to current of power overload conditions. See also OUTPUT CURRENT LIMITING.

 OVERSHOOT: A transient change in output voltage in excess of specified output regulation limits, which can occur when a power supply is turned on or off, or when there is a step change in line or load.

 OVERVOLTAGE: 1) The potential difference between the equilibrium of an electrode and that of the electrode under an imposed polarization current. 2) A voltage that exceeds specified limits.

 OVERVOLTAGE PROTECTION (OVP): A feature that senses and responds to a high voltage condition. See also OVERVOLTAGE, CROWBAR.

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PIV: Abbreviation for Peak Inverse Voltage.

 PPM: Abbreviation for parts per million.

 PWM: Variously, the abbreviation for Pulse-Width Modulation, Pulse-Width Modulator.

 PAD: A conductive area on a printed circuit board used for connection to a component lead or terminal area, or as a test point.

 PARALLEL: 1) Term used to describe the interconnection of power sources in which like terminals are connected such that the combined currents are delivered to a single load. 2) The connection of components or circuits in a shunt configuration.

 PARALLEL OPERATION: The connection of two or more power sources of the same output voltage to obtain a higher output current. Special design considerations may be required for parallel operation of power sources.

 PASS ELEMENT: A controlled variable resistance device, either a vacuum tube or semiconductor, in series with the dc power source used to provide regulation.

 PEAK: Maximum value of a waveform reached during a particular cycle or operating time.

 PEAK INVERSE VOLTAGE (PIV): Maximum value of voltage applied in a reverse direction.

 PEAK OUTPUT CURRENT: The maximum current value delivered to a load under specified pulsed conditions.

 PEAK-TO-PEAK: The measured value of a waveform from peak in a positive direction to peak in a negative direction.

 PERIODIC AND RANDOM DEVIATION (PARD): The sum of all ripple and noise components measured over a specified band width and stated, unless otherwise specified, in peak-to-peak values.

 PHASE ANGLE: The angle that a voltage waveform leads or lags the current waveform.

 POLARITY: Property of device or circuit to have poles such as north and south or positive and negative.

 POSITIVE RAIL: The most positive of the two output conductors of a power supply.

 POST REGULATION: Refers to the use of a secondary regulator on a power supply output to improve line/load regulation and to attenuate ripple and noise.

 POT: Abbreviation for potentiometer.

 POTTING: An insulating material for encapsulating one or more circuit elements.

 POWER FACTOR: The ratio of true to apparent power expressed as a decimal, frequently specified as lead or lag of the current relative to voltage.

 POWER FACTOR CORRECTION: 1) Technique of forcing current draw to approach being in-phase with the voltage in an ac circuit. 2) Addition of capacitors to an inductive circuit to offset reactance.

 POWER RATING: Power available at the output terminals of a power source based on the manufacturers specifications.

 POWER SOURCE: Any device that furnishes electrical power, including a generator, cell, battery, power pack, power supply, solar cell, etc.

 POWER SUPPLY: A device for the conversion of available power of one set of characteristics to another set of characteristics to meet specified requirements.Typical application of power supplies include to convert raw input power to a controlled or stabilized voltage and/or current for the operation of electronic equipment.

 POWER SUPPLY CORD: An assembly of a suitable length of flexible cord provided with an attachment plug at one end.

 PREREGULATION: The initial regulation circuit in a system containing at least two cascade regulation loops.

 PRIMARY CIRCUIT: A circuit electrically connected to the input or source of power to the device.

 PRIMARY SIDE CONTROL: A name for an off-line switching power supply with the pulse-width modulator in the primary.

 PROGRAMMING: The control of a power supply parameter, such as output voltage, by means of a control element of signal.

 PROGRAMMABLE POWER SUPPLY: A power supply with an output controlled by an applied voltage, current, resistance or digital code.

 PROGRAMMABLE COEFFICIENT: The required range in control resistance to produce a one volt change in output voltage. Expressed in ohms per volt. The ratio of change in a control parameter to induce a unit change in an output, e.g., 100 ohms/volt, or 100 ohms/ampere.

 PULSE-WIDTH MODULATION (PWM): A method of regulating the output voltage of a switching power supply by varying the duration, but not the frequency, of a train of pulses that drives a power switch.

 PULSE-WIDTH MODULATOR (PWM): An integrated discrete circuit used in switching-type power supplies, to control the conduction time of pulses produced by the clock.

 PUSH-PULL CIRCUIT: A circuit containing two like elements that operate in 180-degree phase relationship to produce additive output components of the desired wave, with cancellation of certain unwanted products. Note: Push-pull amplifiers and push-pull oscillators are examples. (IEEE Std 100-1988)

 PUSH-PULL CONVERTER: A power switching circuit that uses two or more power switches driven alternately on and off.

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QUIESCENT: At rest; inactive.

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RFI: Abbreviation for Radio Frequency Interference.

 RMS VALUE: In text, use lower case: rms. Abbreviation for Root Mean Square Value.

 RATED OUTPUT CURRENT: The maximum continuous load current a power supply is designed to provide under specified operating conditions.

 RECOVERY TIME: The time required for the measured characteristic to return to within specified limits following an abnormal event.

 RECTIFICATION: The process of changing an alternating current to a unidirectional current. See FULL-WAVE RECTIFIER, HALF-WAVE RECTIFIER.

 RECTIFIER: A component that passes current only in one direction, e.g., a diode.

 REFERENCE GROUND: Defined point in a circuit or system from which potential measurements shall be made.

 REFERENCE VOLTAGE: The defined or specified voltage to which other voltages are compared.

 REGULATED POWER SUPPLY: A device that maintains within specified limits a constant output voltage or current for specified changes in line, load temperature or time.

 REGULATION: The process of holding constant selected parameters, the extent of which is expressed as a percent.

 REGULATOR: The power supply circuit that controls or stabilizes the output parameter at a specified value.

 REMOTE CONTROL: 1) (general) Control of an operation from a distance: this involves a link, usually electrical, between the control device and the apparatus to be operated. Note: Remote control may be over (A) direct wire, (B) other types of interconnecting channels such as carrier-current or microwave, (C) supervisory control, or (D) mechanical means. 2) (programmable instrumentation) A method whereby a device is programmable via its electrical interface connection in order to enable the device to perform different tasks. (IEEE Std 100-1988)


 REMOTE SENSING: A technique for regulating the output voltage of a power supply at the load by connecting the regulator error-sensing leads directly to the load. Remote sensing compensates for specified maximum voltage drops in the load leads. Care should be exercised to avoid opening load handling leads to avoid damaging the power supply. Polarity must be observed when connecting sense leads to avoid damaging the system.

 REPEATABILITY: The ability to duplicate results under identical operating conditions.

 RESET SIGNAL: A signal used to return a circuit to a desired state.

 RESISTANCE (R): Property of a material that opposes the flow of current.

 RESOLUTION: The smallest increment of change in output that can be obtained by an adjustment.

 RESONANCE: 1) The state in which the natural response frequency of a circuit coincides with the frequency of an applied signal, or vice versa, yielding intensified response. 2) The state in which the natural vibration frequency of a body coincides with an applied vibration force, or vice versa, yielding reinforced vibration of the body.

 RESONANT CIRCUIT: A circuit in which inductive and capacitive elements are in resonance at an operating frequency.

 RESONANT CONVERTER: A class of converters that uses a resonant circuit as part of the regulation loop.

 RESONANT FREQUENCY: The natural frequency at which a circuit oscillates or a device vibrates. In an L-C circuit, inductive and capacitive reactances are equal at the resonant frequency.

RESPONSE TIME: The time required for the output of a power supply or circuit to reach a specified fraction of its new value after step change or disturbance.

 RETURN: The name for the common terminal of the output of a power supply; it carries the return current for the outputs.

REVERSE VOLTAGE PROTECTION: A circuit or circuit element that protects a power supply from damage caused by a voltage of reverse polarity applied at the input or output terminals.


RIPPLE: The periodic ac component at the power source output harmonically related to source or switching frequencies. Unless specified otherwise, it is expressed in peak-to-peak units over a specified band width.


 RIPPLE VOLTAGE: The periodic ac component of the dc output of a power supply.

 RISE TIME: The time required for a pulse to rise from 10 percent to 90 percent of its maximum amplitude.

 ROOT MEAN SQUARE (RMS) VALUE: 1) (periodic function) The square root of the average of the square of the value of the function taken throughout one period (IEEE Std 100-1988). 2) For a sine wave, 0.707 x Peak Value.

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SCR: Abbreviation for Silicon-Controlled Rectifier.

 SI: Abbreviation for System International d'Unites.

 SOA: Abbreviation for Safe Operating Area.

 SAFE OPERATING AREA (SOA): A manufacturer specified power/time relationship that must be observed to prevent damage to power bipolar semiconductors.

 SAFETY COMPLIANCE: Certification, recognition or approval by safety agencies such as Underwriters Laboratories Inc. (UL/U.S.A.), Canadian Standards Association (CSA), etc. See also COMPLIANCE.

SAFETY GROUND: A conductive path from a chassis, panel or case to earth to help prevent injury or damage to personnel and equipment.

 SECONDARY CIRCUIT: A circuit electrically isolated from the input or source of power to the device.

 SECONDARY OUTPUT: An output of a switching power supply that is not sensed by the control loop.

 SENSE AMPLIFIER: An amplifier which is connected to the output voltage divider to determine, or sense, the output voltage. (Bertan High Voltage)

 SENSE LINE: The conductor which routes output voltage to the control loop. See also REMOTE SENSING.

 SENSE LINE RETURN: The conductor which routes the voltage on the output return to the control loop. See also REMOTE SENSING.

 SEQUENCING: The process that forces the order of turn on and turn off of individual outputs of a multiple output power supply.

 SERIES: 1) The interconnection of two or more power sources such that alternate polarity terminals are connected so their voltages sum at a load. 2) The connection of circuit components end to end to form a single current path.

 SERIES PASS: A controlled active element in series with a load that is used to regulate voltage.


 SERIES REGULATOR: A regulator in which the active control element is in series with the dc source and the load.

 SETTING RANGE: The range over which the value of the stabilized output quantity may be adjusted.

 SETTLING TIME: The time for a power supply to stabilize within specifications after an excursion outside the input/output design parameters.

 SHIELD: Partition or enclosure around components in a circuit to minimize the effects of stray magnetic and radio frequency fields. See also ENCLOSURE, ELECTROSTATIC SHIELD, FARADAY SHIELD.

 SHOCK HAZARD: A potentially dangerous electrical condition that may be further defined by various industry or agency specifications.

 SHORT CIRCUIT: A direct connection that provides a virtually zero resistance path for current.

 SHORT CIRCUIT CURRENT (SCC): The initial value of the current obtained from a power source in a circuit of negligible resistance.

 SHORT CIRCUIT PROTECTION: A protective feature that limits the output current of a power supply to prevent damage.

 SHORT CIRCUIT TEST: A test in which the output is shorted to ensure that the short circuit current is within its specified limits.

 SHUNT: 1) A parallel conducting path in a circuit. 2) A low value precision resistor used to monitor current.

 SHUNT REGULATOR: A linear regulator in which the control element is in parallel with the load, and in series with an impedance, to achieve constant voltage across the load.

 SIGNAL GROUND:The common return or reference point for analog signals.

 SINE WAVE: A wave form of a single frequency alternating current whose displacement is the sine of an angle proportional to time or distance.

 SLAVE: A power supply which uses the reference in another power supply, the master, as its reference.

 SLEW RATE: The maximum rate of change a power supply output can produce when subjected to a large step response or specified step change. The power supply is turned on.

 SLOW START: A feature that ensures the smooth, controlled rise of the output voltage, and protects the switching transistors from transients when the power supply is turned on.

 SNUBBER: An RC network used to reduce the rate of rise of voltage in switching applications.

 SOFT STARTS: Controlled turn on to reduce inrush currents.

 SOURCE: Origin of the input power, e.g., generator, utility lines, mains, batteries, etc.

 SOURCE VOLTAGE EFFECT: The change in stabilized output produced by a specified primary source voltage change.

 STABILITY: 1) The percent change in output parameter as a function of time, with all other factors constant, following a specified warm-up period. 2) The ability to stay on a given frequency or in a given state without undesired variation.

 STANDOFF: A mechanical support, which may be an insulator, used to connect and support a wire or device away from the mounting surface.

 STEP-DOWN TRANSFORMER: (power and distribution transformer) A transformer in which the power transfer is from a higher voltage source circuit to a lower voltage circuit. (IEEE Std 100-1988)

 STEP-UP TRANSFORMER: (power and distribution transformer) A transformer in which the power transfer is from a lower voltage source circuit to a higher voltage circuit. (IEEE Std 100-1988)

STORAGE TEMPERATURE: The range of ambient temperatures through which an inoperative power supply can remain in storage without degrading its subsequent operation. See also AMBIENT TEMPERATURE, OPERATING TEMPERATURE.

 SUMMING POINT: The point at which two or more inputs of an operational amplifier are algebraically added.

 SWITCHING FREQUENCY: The rate at which the dc voltage is switched in a converter or power supply.

 SWITCHING REGULATOR: A switching circuit that operates in a closed loop system to regulate the power supply output.

 SYNCHRONOUS RECTIFICATION: A rectification scheme in a switching power supply in which a FET or bipolar transistor is substituted for the rectifier diode to improve efficiency.

 SYNCHRONOUS RECTIFICATION: A rectification scheme in a switching power supply in which a FET or bipolar transistor is substituted for the rectifier diode to improve efficiency.

 SYSTEME INTERNATIONAL d'UNITES (SI): The International System of Units comprised of Base Units, Supplementary Units and Derived Units.

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TTL: Abbreviation for transistor-transistor logic.

 TEMPERATURE COEFFICIENT: The average percent change in output voltage per degree centigrade change in ambient temperature over a specified temperature range. See also AMBIENT TEMPERATURE.

 TEMPERATURE DERATING: The amount by which power source or component ratings are decreased to permit operation at elevated temperatures.




 THERMAL PROTECTION: A protective feature that shuts down a power supply if its internal temperature exceeds a predetermined limit.

 THREE TERMINAL REGULATOR: A power integrated circuit in a 3-terminal standard transistor package. It can be either a series or shunt regulator IC.

 TIME CONSTANT: Time period required for the voltage of a capacitor in an RC circuit to increase to 63.2 percent of maximum value or decrease to 36.7 percent of maximum value.

 TOLERANCE: Measured or specified percentage variation from nominal.

 TOTAL EFFECT: The change in a stabilized output produced by concurrent worst case changes in all influence quantities within their rated range.

 TRACE: A conducting path on a printed circuit board.

 TRACKING: A characteristic of a multiple-output power supply that describes the changes in the voltage of one output with respect to changes in the voltage or load of another.

 TRACKING REGULATOR: A plus or minus two-output supply in which one output tracks the other.

 TRANSIENT: An excursion in a given parameter, typically associated with input voltage or output loading.

 TRANSIENT EFFECT: The result of a step change in an influence quantity on the steady state values of a circuit.

 TRANSIENT RECOVERY TIME: The time required for the output voltage of a power supply to settle within specified output accuracy limits following a transient.

 UNDERSHOOT: A transient change in output voltage in excess of specified output regulation limits. See OVERSHOOT.

 TRANSIENT RESPONSE: Response of a circuit to a sudden change in an input or output quantity.

 TRANSIENT RESPONSE TIME: The interval between the time a transient is introduced and the time it returns and remains within a specified amplitude range.

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UL: Abbreviation for Underwriters Laboratories Incorporated.

 UPS: Abbreviation for Uninterruptible Power Supply.

 UNDERVOLTAGE PROTECTION: A circuit that inhibits the power supply when output voltage falls below a specified minimum.

 UNDERWRITERS LABORATORIES INCORPORATED (UL): American association chartered to test and evaluate products, including power sources. The group has four locations so an applicant can interact with the office closest in the country to his/her own location.

 UNINTERRUPTIBLE POWER SUPPLY (UPS): A type of power supply designed to support the load for specified periods when the line varies outside specified limits. See also OFF LINE POWER SUPPLY, ON LINE POWER SUPPLY.

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VDE: Abbreviation for Verband Deutscher Elektrotechniker.

 VARISTOR: A two electrode semiconductor device having a voltage-dependent nonlinear resistance.

 VOLT (V): Unit of measurement of electromotive force or potential difference. Symbol E, in electricity; symbol V in semiconductor circuits.

 VOLTAGE DIVIDER: Tapped or series resistance or impedance across a source voltage to produce multiple voltages.


 VOLTAGE DROP: Difference in potential between two points in a passive component or circuit.

 VOLTAGE LIMIT: Maximum or minimum value in a voltage range.

 VOLTAGE LIMITING: Bounding circuit used to set specified maximum or minimum voltage levels.

 VOLTAGE MODE: The functioning of a power supply so as to produce a stabilized output voltage.

 VOLTAGE MONITOR: A circuit or device that determines whether or not an output voltage is within some specified limits.

 VOLTAGE MULTIPLIER: Rectifier circuits that produce an output voltage at a given multiple greater than input voltage, usually doubling, tripling, or quadrupling.

 VOLTAGE REGULATION: The process of holding voltage constant between selected parameters, the extent of which is expressed as a percent. See also REGULATION.

 VOLTAGE SOURCE: A power source that tends to deliver constant voltage.

 VOLTAGE STABILIZATION: The use of a circuit or device to hold constant an output voltage within given limits.

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WARMUP: Process of approaching thermal equilibrium after turn on.

 WARMUP DRIFT: The change in output voltage of a power source from turn on until it reaches thermal equilibrium at specified operating conditions.

WARMUP EFFECT: Magnitude of change of stabilized output quantities during warmup time.

 WARMUP TIME: The time required after a power supply is initially turned on before it operates according to specified performance limits.

 WATT (W): Unit of measure of power equal to 1 joule/sec. (W=EI)

 WEBER (Wb): The SI unit of magnetic flux equal to 108 maxwells. The amount of flux that will induce 1 volt/turn of wire as the flux is reduced at a constant rate to zero over a period of one second.

 WITHSTAND VOLTAGE: The maximum voltage that can be applied between separate circuits without causing failure.

 WORKING VOLTAGE: The specified operating voltage, or range of voltages, of a component, device or cell.

 WORST CASE CONDITION: A set of conditions where the combined influences on a system or device are most detrimental.

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X-RAY TUBE: A vacuum tube designed for producing X-rays by accelerating electrons to a high velocity by means of an electrostatic field and then suddenly stopping them by collision with a target. (IEEE Std 100-1988)

ZENER DIODE: 1) A diode that makes use of the breakdown properties of a PN junction. If a reverse voltage across the diode is progressively increased, a point will be reached when the current will greatly increase beyond its normal cut-off value to maintain a relatively constant voltage. Either voltage point is called the Zener voltage. 2) The breakdown may be either the lower voltage Zener effect or the higher voltage avalanche effect.

 ZENER VOLTAGE: The reverse voltage at which breakdown occurs in a zener diode.

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