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Glossary of Terms

INPUTVoltage Nominal RMS value(s) of Ac sinewave mains

voltage(s) for which the converter is designed.Nominal voltage Typical frequently used input DC voltages for

which the converter is suitable.Voltage range The range(s) of input DC voltage(s) over which

the converter(s) operates within specification.Frequency The range of mains frequency over which the

converter operates within specification.Inrush current Switching power supplies produce high inrush

current fromt its supply mains at turn on, resultingfrom filter capacitor impedance. These large filtercapacitors act like a short circuit, producing animmediate inrush surge current with a fast rise time.

Current at no load The current drawn by the converter from thesupply when the load current is zero and the inputsupply voltage is at the low end of the specified range.

Current at full load The current drawn by the converter from thesupply when the load current is at maximumrating and the input supply voltage is at the lowend of the specified range.

Reflected ripple The AC current generated at the input of a DC/DCconverter by the switching action of the converter.

Protection Indicates if the converter is fused internally. Therecommended fuse rating for the power supplymay be given.

Reverse voltage prot. Protection circuit built into the input of theconverter to prevent damage if a reverse polarity voltage is applied to the input.

Isolation The electrical separation between the input andoutput expressed as a DC test voltage, and aresistance with parallel capacitance.

Safety isolation The electrical separation between the primary andsecondary circuits and the safety standards towhich the converter conforms in this respect.

Filter Indicates built in line input filter to attenuatereflected ripple current.

OUTPUTPower The maximum continuous power measured in

watts that can be taken from the output (s) of theconverter.

Turn on delay The time in seconds after switch on for theoutput(s) to reach their nominal voltage(s) withinregulation limits.

Overshoot A transient change in output voltage in excess ofspecified regulation limits.

Line regulation The percentage change in output voltage causedby the input voltage varying over the specifiedrange. This range is either mentioned, or is theactual input voltage range.

Load regulation The percentage change in output voltage causedby a specified load variation.

Cross regulation The percentage change in output voltage of oneoutput caused by a specified load variation onanother output of a multi-output converter.

Transient response The maximum time for the output voltage toreturn within regulation limits following a specificload step change.

Setting accuracy The percentage difference between the actualvoltage setting and the nominal output voltage atrated load and nominal line input voltage.

Voltage balance The difference, expressed as a percentagebetween the voltage magnitudes of a twin outputconverter, where the outputs have the samenominal voltage but the opposite polarity.

Voltage adjustment The range over which the output voltage can beadjusted (and the means of adjustment).

Current adjustment The range over which the output current can beadjusted (and the means of adjustment).

Resolution The smallest incremental step adjustment possibleby use of built-in controls.

Ripple and noise The sum of all the voltage noise componentsexpressed as a peak to peak amplitude over aspecified band width.

Switching spike The peak to peak amplitude of the voltage spikewhich occurs at switching frequency on theoutput of switched mode converters.

Drift A change of output voltage over a period of time,independent of input, load and temperaturevariations.

Overvoltage protection A circuit which detects output overvoltages abovea specified level and shuts down the converter toprotect load circuits.

Reverse voltage prot. A built-in circuit (or element) that protects theconverter from a reverse polarity applied acrossthe output terminals.

Short circuit protection Automatic output current limiting to preventdamage to the converter when a short circuit isapplied across the output terminals.

Overload protection A protective feature that limits output power orcurrent demands to prevent damage to theconverter.

Current limit adjustment The range over which the protective current limitcan be adjusted (and the means of adjustment).

Thermal protection An internal temperature trip that shuts down theconverter if the internal temperature exceeds apredetermined limit.

Temperature coefficient The percentage change in output voltage per °Cchange in external ambient temperature averagedover the specified full rating operatingtemperature range.

Impedance The apparent impedance presented by theconverter to its output terminals.

Efficiency The ratio of total output power to total true inputpower expressed as a percentage.

Hold up time The minimum time the converter output(s) remainin regulation after loss of input power under fullrated load and nominal input voltage conditions.

For ease of use, Powerbox use a standard format forpower conversion product specifications. The followingterms and related definitions are listed in the sameorder as they appear in a typical product specification.

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Glossary of Terms

Power fail A logic compatible signal warning that the outputswill fall outside regulation limits due to the loss ofinput power.

Minimum load The load current that can be taken from aconverter output, below which regulation is notguaranteed.

Parallel operation The ability of two or more converter outputs set tothe same voltage to be connected in parallel toprovide increased output current.

Series operation The ability of two or more converter outputs to bewired in series to provide a higher output voltage.

Remote sense A method of compensating the deterioration ofregulation caused by the resistance of loadconnection lead. Accomplished by sensing theoutput voltage at the load and using thedifference between this voltage and the internalreference to regulate the output voltage.

Programming The control of converter output voltage and/orcurrent by varying an external parameter (voltage,current or resistance).

Remote adjustment The ability to vary output voltage and/or currentover a specified range by an external control.

Remote inhibit Converter shutdown into a standby or idle modeby application of an external signal to the inhibitterminal.

Input common Normally referenced to the negative side of theconverter input.

Logic compatibility Type of logic signal that can be used without levelchange or impedance transforms.

On control input voltage Logic “hi” threshold.Off control input voltage Logic “lo” threshold.Shutdown idle current Current drawn by the converter from the supply in

standby.

ENVIRONMENTALOperating temperature The range of ambient or baseplate temperature in

°C over which a converter can be operated safelyat either rated or derated output power.

Derating The output power reduction required for safeoperation above a specified temperature, usuallyexpressed as a % reduction per °C up to themaximum operating temperature.

Storage temperature The range of ambient temperatures over which aconverter may be stored long term withoutdamage. Expressed in °C.

Cooling The process of removing heat dissipated internallywithin the power converter during normaloperation. This may be by natural convection, orconduction to a baseplate, or by forced air.

Humidity The maximum moisture content in the surroundingair for operation of the converter over thespecified operating temperature range. Expressedas a percentage, it is the ratio of the actual massof water vapour present to the mass of watervapour in the same volume of saturated air at thesame temperature and pressure.

Altitude The maximum altitude at which the converter canbe used without derating.

Shock standards Definition of the mechanical “bump” tests thatcan be applied to the converter without damage.

Vibration standards Definition of the amplitude and frequency ofmechanical vibration that can be applied to theconverter without damage.

GENERALMTBF The predicted average length of time (Mean time

between failure)between failures exclusive ofinfant mortality and end of rated life.

MTTR The predicted average length of time to (Meantime to repair) repair a faulty unit with thespecified spares kit.

Safety leakage current When the input voltage is at nominal, the currentflowing from the input lines to the protective earthconductor.

RFI standards Limits laid down by various national andinternational regulatory agencies for radiofrequency interference generated by electrical andelectronic equipment.

Design topology The conversion principle employed (eg. linear,switched mode flyback, half bridge etc).

Switching frequency The typical frequency of the converter switch atfull rated load.

External synchronisation The ability to synchronise the converter switchingfrequency to an external oscillator.

PCB mounting Designed for direct mounting onto printed circuitboards.

Chassis mounting Designed for mounting to a metal or other rigidsurface in the host equipment. The unit has screwterminals for input/output connection.

Encapsulated Totally encapsulated and hermetically sealed in cast epoxy resin or similar plastic.

Ventilated case Enclosed in a metal case with ventilation slots forcooling by convected or forced air.

Case grounding Metal enclosures around converters will normallybe connected to ground internally. Some DC/DCconverters have insulated cases.

Open card PCB format Construction of a converter is on a printed circuitboard without chassis or cover.

L bracket Open chassis construction, chassis normally havingL shaped cross section.

Cased Fully enclosed.

STANDARDSSafety standards Standards laid down by various national and

international regulatory agencies.Approved Approval, listing or certification of the converter

has been obtained for the standards specified.Designed to meet Provided the converter is correctly installed it will

not prevent the host equipment from obtainingofficial recognition to the standards specified.