Technical Terms

A

ABSOLUTE ACCURACY

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

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.

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 and forced air-cooled units, the ambient temperature 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)

ANSI

Abbreviation for American National Standards Institute

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.

AWG

Abbreviation for American Wire Gauge.

B

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 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.

BENCH POWER SUPPLY

Power source fitted with output controls, meters, terminals and displays for experimental bench top use in a laboratory.

BIAS SUPPLY

Power source fitted with output controls, meters, terminals and displays for experimental bench top use in a laboratory.

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.

BLEED 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

A switching topology in which the resultant output voltage is lower than its input voltage. The operation of the buck regulator typically uses an inductor, a transistor and a diode to control the inductor energy. Control of the transistor allows for alternating between connecting the inductor to the source voltage to store energy in the inductor and discharging the inductor into the 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.

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.

C

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.

CAPACITANCE, DISTRIBUTED

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.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.

CGS UNIT

Abbreviation for the Centimeter-Gram Second Unit of measurement.

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.

CIRCULATING CURRENT

See GROUND LOOP.

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 CHOKE

See INTEGRATED MAGNETICS.

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 VOLTAGE CHARGE

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

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.

CSA

Abbreviation for Canadian Standards Association.

CURRENT CONTROL

See CURRENT STABILIZATION

CURRENT FOLDBACK

See FOLDBACK CURRENT LIMITING.

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.

D

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.

DECAY TIME

See FALL TIME

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.

E

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.

ELECTRON BEAM

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

ELECTRON (e-)

Negatively charged particle.

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)

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.

ELECTRON VOLT

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

ELECTROPHORESIS

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

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.

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.

ESD

Abbreviation for Electrostatic Discharge.

ESL

Abbreviation for Equivalent Series Inductance.

ESR

Abbreviation for Equivalent Series Resistance.

F

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.

FET

Abbreviation for Field Effect Transistor.

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.

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 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.

G

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 a signal. 2) A minor technical problem arising in electrical equipment.

GPIB

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

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.

GROUNDED

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

GROUND LOOP

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

H

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.

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)

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.

HOLDING TIME

See HOLDUP TIME

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.

I

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

The ability to turn off the ourput of a power supply from a remote location

INDUCED IMPEDANCE

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

INDUCED 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.

INDUCED SURGE

See INRUSH CURRENT

INPUT VOLTAGE RANGE

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

INRUSH CURRENT

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

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 TRANSFORMER

A transformer with a one-to-one turns ratio. See also STEP-DOWN TRANSFORMER STEP-UP TRANSFORMER, TRANSFORMER

ISOLATION VOLTAGE

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

J

JOULE (J)

Unit of energy equal to one watt-second.

K

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.

L

LATCH-UP

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

L-C FILTER

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

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.

LED

Symbol for Light-Emitting Diode.

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.

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.

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.

LINEAR PASS

See SERIES PASS

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.

LINE CONDITIONER

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

LINE EFFECT

See LINE REGULATION.

LINE 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.

LINE REGULATIOR

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

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 EFFECTS

See LOAD REGULATION

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 voltage terminals as the error-sensing points to provide feedback to the voltage regulator.

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.

M

MAINS

The utility AC power source.

MASTER-SLAVE OPERATION

A method of interconnecting two or more supplies such that one of them (the master) serves to control the others (the slaves). The outputs of the slave supplies always remain equal to or proportional to the output of the master

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.

MOSFET

Abbreviation for Metal Oxide Semiconductor Field Effect Transistor.

MTBF

Abbreviation for Mean Time Between Failure.

N

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.

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.

NO LOAD VOLTAGE

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

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.

O

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

OP-AMP

Abbreviation for Operational Amplifier

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.

OPTO-ISOLATOR

See OPTO-COUPLER.

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 RIPPLE AND NOISE

See PERIODIC and RANDOM DEVIATION.

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.

OVERCURRENT PROTECTION

See OUTPUT CURRENT LIMITING.

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.

OVP

Abbreviation for Overvoltage Protection.

P

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

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.

PARD (periodic and random deviation)

Replaces the former term ripple of noise. PARD is the periodic and random deviation referring to the sum of all the ripple and noise components on the dc output of a power supply regardless of nature or source

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.

PIV

Abbreviation for Peak Inverse Voltage.

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.

PPM

Abbreviation for parts per million.

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.

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.

PROGRAMMABLE POWER SUPPLY

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

PROGRAMMING

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

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.

PWM

Variously, the abbreviation for Pulse-Width Modulation, Pulse-Width Modulator

R

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 PROGRAMMING

See PROGRAMMING.

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.

RFI

Abbreviation for Radio Frequency Interference.

RIDE-THROUGH

See HOLDUP TIME

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 AND NOISE

See PERIODIC and RANDOM DEVIATION (PARD).See PERIODIC and RANDOM DEVIATION (PARD).

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.

RMS VALUE

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

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.

S

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.

SCR

Abbreviation for Silicon-Controlled Rectifier.

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 REGULATION

See LINEAR REGULATION

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.

SETTING 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

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.

SI

Abbreviation for System International d'Unites.

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

SOA

Abbreviation for Safe Operating Area.

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.

SYSTEME INTERNATIONAL d'UNITES (SI)

The International System of Units comprised of Base Units, Supplementary Units and Derived Units.

T

TRANSIENT RESPONSE TIME

The room temperature or temperature of the still air surrounding the power supply, with the supply operating.

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.

TEMPERATURE EFFECT

See TEMPERATURE COEFFICIENT.

TEMPERATURE RANGE, OPERATING

See OPERATING TEMPERATURE RANGE

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.

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.

TTL

Abbreviation for transistor-transistor logic

U

UL

Abbreviation for Underwriters Laboratories Incorporated.

UNDERSHOOT

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

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.

UPS

Abbreviation for Uninterruptible Power Supply.

V

VARISTOR

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

VDE

Abbreviation for Verband Deutscher Elektrotechniker.

VOLTAGE DIVIDER

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

VOLTAGE DOUBLER

See VOLTAGE MULTIPLIER.

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

VOLT (V)

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

W

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 specified operating voltage, or range of voltages, of a component, device or cell.

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.

X

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)

Z

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.