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Circuit Protection Terminology

D Channel

Full duplex 16 kbps (basic rate) or 64 kbps (primary rate) ISDN channel.

D-ISDN

broadband integrated services digital network

Data Circuit-terminating Equipment

Equipment that resides at the customer end of a transmission link and provides all necessary termination function for that link. May be owned by the customer or by the service provider.

Data Terminal Equipment (DTE)

The part of a data station that serves as a data source, destination, or both, and that provides for the data communications control function according to protocol. DTE includes computers, protocol translators, and multiplexers.

DBS

direct broadcast satellite

DC Bias

Direct current (DC) applied to the winding of a core in addition to any time-varying current. Inductance with DC bias is a common specification for powder cores. The inductance will Òroll offÓ gradually and predictably with increasing DC bias.

DC Filter

A filter circuit that removes the AC ripple from a mostly DC current. Usually this is done by using an inductor and capacitor together.

DC Stress

Annealing a magnetic material in the presence of a DC magnetic field to enhance magnetic properties.

DC-DC Converter(CoEv)

A circuit or device that converts a DC input voltage (usually unregulated) to a regulated DC output voltage. The output voltage may be lower, higher, or the same as the input voltage. Switching regulator DC-DC circuits most often require an inductor or transformer to achieve the regulated output voltage. Switching regulator circuits can achieve a higher level of power efficiency when compared to non-switching techniques.

DC-DC Converter(Raychem)

A circuit or device that converts a DC input voltage to a regulated output voltage. The output voltage may be lower, higher or the same as the input voltage. Switching regulator DC-DC circuits can achieve a higher level of power efficiency when compared to non-switching techniques (Also see Boost Regulator and Buck Regulator).

DCE

Data Communications Equipment(EIA expansion) or Data Circuit-Terminating Equipment (CCITT expansion)- The devices and connections of a communications cicuit with the end device (data terminal equipment). A modem can be considered a DCE.

DCR (DC Resistance)(CoEv)

The resistance of an inductor to a DC current (not alternating). The DCR is most often minimized in the design of an inductor. The unit of measure is the Ohm, and is usually expressed as a maximum rating.

DCR (DC Resistance)(Raychem)

The resistance of the inductor winding measured with no alternating current. The DCR is most often minimized in the design of an inductor. The unit of measure is ohms and it is usually specified as a maximum rating.

Decoupling

Refers to a magnetic circuit where comparatively more of the flux generated by the MMF fringes around the magnetic material instead of entering it.

Dedicated Line

A transmission circuit installed between two sites of a private network and "open," or available, at all times.

Demagnetization Curve

That portion of the hysteresis loop that lies between the residual induction point (BR) and the coercive force point (HC).

Demagnetized

A material condition where a ringing AC field has reduced the remnant induction to or near zero. A ringing AC field is a continually decreasing sinusoidal field. A pulsed DC field can be used to achieve gross demagnetization, but with much effort and with residual local magnetization.

Demodulation

Opposite of modulation, the process of retrieving data from a modulated carrier wave.

Density

See Power Density.

Derating

For a DC-DC converter, the specified reduction in output power required for operation at elevated temperatures. The most common operating temperature reange specified. Also see Convection Cooled.

Dial up

A type of communication that is established by a switched-circuit connection using the telephone network.

Dielectric

Material used to prevent two points in a electrical circuit from becoming conductively connected. Sometimes called a dielectric barrier.

Dielectric Strength - Electric Strength - Hipot

The two most important, basic, and unique features that signal-isolation transformers provide are balance and physical separation, i.e. a dielectric barrier. The physical separation of the primary and secondary windings (or line-side and chip-side windings) allows sensitive low-voltage circuits to be safely electromagnetically connected to circuit nodes exposed to high voltage potentials without a direct conductive path.%0aThe voltage rating of a transformer is called out by its dielectric strength level in VACRMS or VDC. The transformer is guaranteed to isolate the primary and secondary windings from high-voltage transients below this rated level. The typical dielectric level for most telecom applications is 1500VACRMS for a one minute duration.%0aAt some voltage potential, a leakage current will begin to flow through the protective insulation. When the magnitude of this current exceeds a predefined level (typically 500µA), Insulation Breakdown or Dielectric Breakdown is said to have occurred.%0aAs per UL1950 (5.3.2):%0a"Insulation breakdown is considered to have occured when the current which flows as a result of the application of the test voltage rapidly increses in an uncontrolled manner, i.e. the insulation does not restrict the flow of the current. Corona discharge or a single momentary flashover is not regarded as insulation breakdown."

Dielectric Withstand Voltage (DWV)(CoEv)

The voltage level at which the dielectric breaks down, allowing conduction between isolated conductors or between a conductor and the core. Isolation, or hipot is the ability of a transformer to withstand a specific breakdown voltage between the primary and secondary windings.

Dielectric Withstand Voltage(Raychem)

Maximum voltage an insulating material can withstand before breaking down (suffering punch through or arcing).

Differential Mode

A current conduction mode in which currents, relative to two conductors, are flowing 180¡ out of phase, with equal magnitude within the conductors.

Differential Mode Current

The intended signal currents that are equal and oppositely directed on pairs of signal and return (ground) conductors.

Differential Mode Noise(CoEv)

Also known as normal-mode noise. It is the electrical interference that is not common to both lines, but is present between both lines.

Differential Mode Noise(Raychem)

Noise component measured between two points with respect to a common point (minus common mode noise).

Differential Mode Voltage

The voltage that drives equal and oppositely directed currents to achieve an intended circuit function. The source of differential mode current.

Digital Signal 0 (DS-0)

North American Digital Hierarchy signaling standard for transmission at 64 kbps. (2) Digital Signal Level 0 is the worldwide standard transmission rate (64 kbps) for PCM digitized voice channels. 24 DSOs exist in each DSI (T1) signal.

Digital Signal 1 (DS-1)

North American Digital Hierarchy signaling standard for transmission sat 2.544 Mbps. Supports 24 simultaneous DS-O signals. Term often used interchangeably with T-1, although DS-1 signals may be exchanged over other transmission systems.

Disable

The act of de-asserting the enable signal to turn off the device. In the case of an EN low device, the EN signal must fall below the typical threshold voltage of 1.5V.

Disaccommodation (DF)

The proportional decrease of permeability after a disturbance of a magnetic material, measured at a constant temperature, over a given time interval. The resultant permeability after magnetic conditioning divided by the permeability of the first measurement times log10 of the ratio of time interval.

Discrete Air Gap

Mechanical air gap created by a small number of breaks in the magnetic path. In a standard C-core this number is generally two, a standard E-core is generally three, etc.

Distortion

Any deviation from the mathematical ideal of a real-world periodic waveform, which is specified as a percent of the desired signal. Distortion can be expressed mathematically in terms of the harmonics of the fundamental frequency. This parameter is of considerable importance in instrumentation transformers.

Distributed Air Gap

A major feature of iron powder cores. It is the cumulative effect of many small gaps distributed evenly throughout the core. In a typical MPP core, the number of separate air gaps results from the use of powder to construct the core and numbers in the millions. The result is minimal fringing flux density compared to a core with one or two discrete air gaps in the magnetic path.

Distributed Capacitance(CoEv)

In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be presented as a single capacitance known as the distributed capacitance. The capacitance is in parallel with the inductor. This parallel combination will resonate at some frequency, which is called the self-resonant frequency (SRF). Lower distributed capacitance for a given inductance will result in a higher SRF and vise versa.

Distributed Capacitance(Raychem)

In the construction of an inductor, each turn of wire or conductor acts as a capacitor plate. The combined effects of each turn can be presented as a single capacitance known as the distributed capacitance. The capacitance is in parallel with the inductor. This parallel combination will resonate at some frequency which is called the self-resonant frequency (SRF). Lower distributed capacitances for a given inductance value will result in a higher SRF value for the inductor and vice versa (Also see SRF)

Distributed Power

System level architecture in which converters operating from a central power bus provide localized power (and various voltage levels) to individual subassemblies/components. The type of power distribution system used is highly dependent upon the needs of a particular application.

DLC

digital loop carrier

DLEC

digital local carrier

DMT

Discrete Multitone. In DMT, a large number of low-rate carrier frequencies are QAM-modulated at a low rate to transmit a single high-rate data stream. DMT is used for ADSL and proposed for VDSL.

DOCSIS

Data Over Cable System Interface Specification

Drift

Change in the output voltage of a converter over a specified period of time. All other operating parameters (load, line, etc.) are assumed to be held constant. Often specified as starting after a warm up period.

Drop Cable

A cable that connects a network device such as a computer to a physical medium such as an Ethernet network. Drop cable is also called transceiver cable because it runs from the network node to a transceiver (a transmit/receiver) attached to the trunk cable.

DSL

Digital Subscriber Line- Another name for an ISDN BRI channel. Operated at the Basic Rate Interface (with two 64 kbps circuit switched channels and one 16 kbps packet switched channel), the DSL can carry both voice and data signal at the same time, in both directions, as well as the signaling data used for call information and customer data.

DSLAM

digital subscriber line access multiplexer

DSP

Digital Signal Processor- The processing of signal transmission using digital techniques.

Duty Cycle

Maximum recommended usage (cycles) per unit of time. Alternatively, the percent of the ÒonÓ time of a square wave in a switching power supply.

DWDM

dense wavelength division multiplexing

Dynamic Load

Output load that changes rapidly. Normally specified as both a load change value and a rate of change.

Dynamic Response

Output overshoot that occurs when the converter output load is turned on/off or abruptly changed. This overshoot gives the high frequency output impedance of the converter. Also see Output Impedance.

The term for a digital facility used for transmitting data over a telephone network at 2.048 Mbps. The European equivalent of T1.

The highest transmission rate generally available in the European digital infrastructure (34 Mbps).

Echo Cancellation

Process by which a transmitter/receiver cancels out the transmitted signal as to "hear" the received signal better.

Eddy Current Losses(CoEv)

Core losses associated with the electrical resistivity of the magnetic material and induced voltages within the material. Eddy currents are inversely proportional to material resistivity and proportional to the rate of change of flux density. Eddy current losses are present in both the magnetic core and windings of an inductor. Eddy currents in the winding, or conductor, contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux lines. Eddy current and hysteresis losses are the two major core loss factors. Eddy current loss becomes dominant in powder cores as the frequency increases.

Eddy Current Losses(Raychem)

Eddy current losses are present in both the magnetic core and winding of an inductor. Eddy currents in the winding (or conductor) contribute to two main types of losses: losses due to proximity effects and skin effects. As for the core losses, an electric field around the flux lines in the magnetic field is generated by alternating magnetic flux. This will result in eddy currents if the magnetic core material has electrical conductivity. Losses result from this phenomenon since the eddy currents flow in a plane that is perpendicular to the magnetic flux.

EDGE

Enhanced Data rates for Global Evolution

Effective Area (AE)

For a magnetic core of a given geometry, the magnetic cross-sectional area that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core.

Effective Length (le)

For a magnetic core of a given geometry, the magnetic length that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core.

Effective Permeability (µe)

For a magnetic circuit constructed with an air gap, or gaps, the permeability of a hypothetical homogeneous material that would provide the same reluctance, or net permeability.

Effective Volume (Ve)

For a magnetic core of a given geometry, the magnetic volume that a hypothetical toroidal core of the same material properties would possess to be the magnetic equivalent to the given core.

Efficiency

Ratio of total output power to input power expressed as a percentage. Efficiency is derived by the equation: Efficiency (%) Efficiency is normally measured at full rated output power and nominal input line conditions.

Electromagnetic Interference (EMI)

An unwanted electrical energy in any form. EMI is often used interchangeably with ÒnoiseÓ and ÒinterferenceÓ.

Electrostatic Discharge (ESD)

Current produced by two objects having a static charge when they are brought close enough to produce an arc or discharge.

Electrostatic Shield

See Faraday Shield.

EMI

EMI is an acronym for Electromagnetic Interference. It is unwanted electrical energy in any form. EMI is often used interchangeably with Noise.

EMI Filter

Filter placed at the input to an off-line converter that minimizes the effect of EMI on the converter and the associated system.

Enable

The act of asserting the enable signal to turn on the device. In the case of an EN low device, the EN signal must exceed the typical threshold voltage of 1.5V.

Synonyms: EN

Enable High/Low

Some USB controller ships have enable logic that requires the power switch to be active low while others require the switch to be active high. This signal will be connected to the enable pin of the device selected.

Enclosure

Case or container used to package a converter. Typically, converters are packaged in small plastic or metal.

Energy Storage (.5LI2)

The amount of magnetic energy which can be stored in a given inductor in microjoules. It is the product of one half the inductance required in microhenries (µH) and the current (I) squared in amperes.

Energy Storage Inductors

Inductors used for energy storage, generally in power conversion rather than filtering or tuning.

Enterprise Network

A large typical corporate network under the auspices of one organization.

Equivalent Series Inductance (ESL)

Inductance in series with an "ideal" capacitor. Sources include leads, terminals, electrodes etc.

Equivalent Series Resistance (ESR)

Resistance in series with an "ideal" capacitor. Sources include lead resistance, terminal losses, etc. An important specification for high frequency applications.

Error Amplifier

Operational or different amplifier used in the control feedback loop of a converter. The amplifier produces an error voltage when the output (tapped off a voltage divider network) differs from a reference voltage. This error voltage is used to adjust the oepratioin of the PWM so as to correct the sensed output voltage. Sometimes called a Reference Amplifier.

Ethernet

A baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks operate at 10 Mbps using CSMA/CD to run over coaxial cable. Ethernet has become a series of standards produced by IEEE referred to as IEEE 802.3.

Excitation Current

The current required to overcome the losses in a core, which begins to produce magnetic energy (or flux) in an inductor.

Failure Mode

Reason for which a converter either does not meet or stops meeting its specified parameters.

Fan Cooled

See Forced Air Cooling.

Faraday Shield

Electrostatic shield that reduces coupling capacitance in transformers. The shield, which effectively reduces output common mode noise, is placed between the primary and secondary windings of a transformer.

Fault Mode Current

Input current drawn by a converter when the output is shorted.

FDM

frequency division multiplexing

FDMA

frequency division multiple access

Federal Communications Commission (FCC)

US government agency that sets standards for, and governs the testing oc conducted and radiated emissions. These are system level standards, but they are typically used in specifying converters. Also see Electromagnetic Interference.

Feed Forward

Method of improving line regulation by directly sensing the input voltage of the converter. Also see Line Regulation.

Ferrite Core

Ferrite is a magnetic material which consists of a mixed oxide of iron and other elements that are made to have a crystalline molecular structure. The crystalline structure is created by firing the ferrite material at a very high temperture for a specified amount of time and temperature profile. The general composition of ferrites is xxFe204 where xx represents one or several metals. The most popular metal combinations are manganese and zinc(MnZn) and nickel and zinc (NiZn). These metals can be easily magnetized.

Ferrite/Ferrite Cores

Ferrite is a magnetic material that consists of a mixed oxide of iron and other elements that are made to have a crystalline molecular structure. Firing the ferrite material at a very high temperature for a specified amount of time and temperature profile creates the crystalline structure. The general composition of ferrite is xxFe2O4 where xx represents one or several metals. The most popular metal combinations are manganese and zinc (MnZn) and nickel and zinc (NiZn). These materials can be easily magnetized with little coercive force. Available in a variety of shapes and sizes, these ceramic magnetic cores are composed of ferric oxide and a combination of manganese, zinc, or nickel. The shapes EE, PQ, UU, ETD, and dual-slab are used for high frequency power applications. Telecommunications and low power applications use pot cores, touch tone cores, EP, and RM. Slugs, rods, and beads are used for radio frequency applications.

Ferromagnetism

Ferromagnetic materials have atomic fields that align themselves parallel with externally applied fields creating a total magnetic field much greater than the applied field. Ferromagnetic materials have permeabilities much greater than air (1). Above the curie temperature, the ferromagnetic materials become paramagnetic.

Ferroresonat Transformer

Transformer in which part of the core is driven in saturation by a resonant tank circuit. The output of the transformer, taken from the saturated protion, is relative immune to variations in input voltage.

Fiber Optic Cable

A transmission medium that uses glass or plastic fibers, rather than copper wire, to transport data or voice signals. The signals is imposed on the fiber via pulses (modulation) of light from a laser or a light-emitting diode (LED). Because of its high bandwidth and lack of susceptibility to interference, fiber-optic cable is used in long-haul or noisy applications.

Fiber Optics

A method for the transmission of information (sound, pictures, data). Light is modulated and transmitted over high purity, hair-thin fibers of glass. The bandwidth capacity of fiber optic cable is much greater than that of conventional cable or copper wire.

Field Strength (H)

The parameter characterizing the amplitude of AC or DC field strength. The magnitude of current, number of turns, and winding geometry determine field strength.

Filter(CoEv)

A circuit or device whose purpose is to control electrical energy at a given frequency or over a range of frequencies. Groups of passive components are commonly used to construct many types of filters, including resistors, capacitors, and inductors.

Filter(Raychem)

A circuit or device whose purpose is to control electrical energy at a given frequency or over a range of frequencies. Groups of passive components are commonly used to construct many types of fileters. These passive components include resistors, capacitors and inductors.

Flag

Power switch output that provides the USB controller the power switch device status. When FLG = High, the output MOSFET allows power to flow from the supply rail.

Synonyms: FLG

Flag delay time

Design feature that delays the FLG notification signal in response to an abnormal condition (hot plug event, overcurrent surge, overtemperature condition). This feature minimizes unnecessary nuisance ÒtripsÓ caused by the inrush current of high capacitive loads.

Floating Output

Converter output that ungrounded and not referenced to another output. Typically, floating outputs are fully isolated and may be referenced positive or negative by the user. Outputs that are not floating share common return and as such, are referenced to one another.

FLP

field labor provider

Flux Density (B)

The corresponding parameter for the induced magnetic field in an area perpendicular to the flux path. Flux density is determined by the field strength and permeability of the medium in which it is measured.

Flux Transfer Ratio

The numeric amount of flux intercepted by the secondary winding and the total flux created by the applied ampere-turns.

Flux(CoEv)

In magnetics, the magnetic field. Flux implies flow, which is not the case in magnetics. That is, no one has measured a magnetic ÒflowÓ. Flux is represented conceptually as Òmagnetic lines of forceÓ. Flux density is measured in Gauss or Teslas.

Flux(Raychem)

Product of the average component of magnetic induction perpendicular to any given surface in a magnetic field by the area of that surface, expressed in webers.

Flyback

Actually an isolated storage inductor, a flyback transformer is a combination of an isolating transformer, output inductor, and flywheel diode. These use a gapped core and have a power handling capability of 100VA. Storing energy in the gap when the switch is on and delivering energy to the load when the switch is off, they do not perform like standard transformers.

Flyback Converter

Also called a "buck-boost" converter, this topology typically uses a single transistor switch and eliminates the need for an output inductor. Energy is stored in the transformer primary during the first half of the switching period when the transistor switch is on. During the second half or "flyback" period when the transistor is off, this energy is tranferred the transformer secondary and load. Also see Boost Regulator, Buck Regulator, Bridge Converter, Forward Converter, Push-Pull Converter and Resonant Converter.

Flyback Transformer

Transformer used in a flyback power supply. Also called horizontal output transformer.

Foldback Current Limiting

Converter protection technique in which the circuit is protected under overload conditions by reducing the output current as the load approaches short circuit. This minimized internal power dissipation under short circuit conditions.

Forced Air Cooling

Use of a fan (or other air moving equipment) within a (sub) system to move air across heat producing components in order to reduce the ambient temperature. Also called forced convection.

Forward Converter

Also called a "Buck-Derived" converter, this topology, like the flyback converter, typically uses a single transistor switch. Unlike the flyback converter, energy is tranferred to the transformer secondary while the transistor switch is "on", and stoed in a output inductor. See Boost Regulator, Buck Regulator, Bridge Converter, Flyback Converter, Push Pull Converter and Resonant Converter.

Forward Converter Transformer

A transformer which operates by transferring power to the load during the on time and resetting in the off time. Since this transformer only transfers power during half of an input cycle it is required to be larger than a push-pull transformer for example.

FPGA

field-programmable gate array

Fractional T1

A WAN communications service that provides the user with some portion of a T1 circuit which has been divided into 24 separate 64 kbps channels.

Frame Relay

A streamlined packet switching protocol designed to provide high-speed frame or packet switching with minimal delay and efficient bandwidth usage.

Free Convection

Operating environment where the natural movement of air (unassisted by fans or blowers) maintains the power module within its operating limits. Also called natural convection.

Frequency of Operation

See Switching Frequency

Fringing Fields or Fringing Flux

The field(s) associated with the divergence of the flux from the shortest path between poles in a magnetic circuit. Where flux passes through a high permeability into a lower permeability material, the flux redistributes and tends to have a Òbarreling effectÓ between the two poles. See also leakage flux.

Full Bridge

Four power switches are used in a full bridge and usually utilize a single primary winding. Full supply voltage is obtained in both directions and utilizes the core and windings more effectively. Voltage on the switches does not exceed the supply voltage.

Full Bridge Converter

Converter topology that typically operates as forward converter but uses a bridge circuit, consisting of four switching transistors, to drive the transformer primary. Also see Bridge Converter.

Full Load

Maximum value of output load specified for a converter under continuous operating conditions.

Full Load Voltage

Variations in winding resistance, turns ratio, and leakage can cause minor discrepancies in output voltage, which is the full load voltage.

Full Winding

A winding for toroidal cores that will result in 45% of the coreÕs inside diameter remaining.

Full-Wave Rectifier

See Rectification

Functions

Class of devices designed to perform a specific task. Examples include USB internet cameras, joysticks, mice, and digital cameras.