Glossary
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Term Acronym Definition
A
AC-DC  

Pertaining to electronic equipment capable of operation from either an alternating - current or direct current primary power source.

AC-DC CONVERTER  

A device to convert alternating current to direct current. Often referred to as an off-line converter where the ac voltage is rectified to dc, perhaps including power factor correction or other processing.

 

AC-OK Signal  

The signal used to indicate the loss of AC input voltage from the 115/230V line.

ALTITUDE TESTING  

Generally performed to determine the proper functioning of modules at specified altitudes. MIL-STD-810.

AMBIENT TEMPERATURE  

The temperature of the environment, usually the still air in the immediate proximity of the power supply.

APPARENT POWER  

A value of power for AC circuits that is calculated as the product of rms current times rms voltage, without taking power factor into account.

B
Bus Converter Module BCM

A VTM V•I Chip that has been optimized for IBA applications. The BCM provides an isolated intermediate bus voltage to power niPOLs from a pre-regulated DC source. The BCM is superior in all respects to conventional brick-type IBCs.

BANDWIDTH  

A range of frequencies over which a certain phenomenon is to be considered.

BASEPLATE  

All modular products have an aluminum mounting base at which Vicor specifies operating temperatures and which should be affixed to a thermally conductive surface for cooling.

BELLCORE SPECIFICATION  

A telecommunications industry standard developed by Bellcore.

B-IPOLAR TRANSISTOR  

A transistor that operates by the action of minority carriers across a P/N junction; it is a current controlled device as opposed to a voltage controlled device.

BOBBIN  

A device upon which the windings of a transformer or inductor are wound; it provides a form for the coil and insulates the windings from the core.

BOOSTER CONVERTER  

A “slave” module in a driver/booster combination, connected to the driver module. Several boosters can be connected to a driver module.

BREAKDOWN VOLTAGE  

A voltage at which dielectric insulation fails by excessive leakage current or arcing. In reference to power supplies, the breakdown voltage is the maximum AC or DC voltage that can be applied from input to output and/or chassis.

BRIDGE CONVERTER  

A DC-DC converter topology (configuration) employing two or four active switching components in a bridge configuration across a power transformer.

BRIDGE RECTIFIER  

A full–wave rectifier circuit employing four rectifiers in a bridge configuration.

BROWNOUT  

A reduction of the AC mains distribution voltage, usually caused deliberately by the utility company to reduce power consumption when demand exceeds generation or distribution capacity.

BURN-IN  

Operating a newly manufactured power supply, usually at rated load, for a period of time in order to force component infant mortality failures or other latent defects.

C
CANADIAN STANDARDS ASSOCIATION CSA

Defines the standards and safety requirements for power components.

CAPACITIVE COUPLING  

Coupling of a signal between two circuits due to discrete or parasitic capacitance between the circuits.

CENTER TAP  

An electrical connection made at the center of a transformer or inductor winding, usually so as to result in an equal number of turns on either side of the tap.

C-GRADE  

Industry standard where the operating temperature of a device does not drop below –20 degrees Celsius.

CHASSIS MOUNT CONFIGURATION  

A configuration where the modules or AC front ends are mounted directly to the chassis.

COMMON–MODE NOISE  

Noise present equally on two conductors with respect to some reference point; often used specifically to refer to noise present on both the hot and neutral AC lines with respect to ground.

COMPAC  

A Vicor DC input power supply that provides EMC filtering and transient suppression for industrial, military, and telecommunications markets.

CONSTANT–CURRENT POWER SUPPLY  

A power supply designed to regulate output current for changes in line, load, ambient temperature, and drift resulting over time.

CONSTANT–VOLTAGE POWER SUPPLY  

A power supply designed to regulate output voltage for changes in line, load, ambient temperature, and drift over time.

CONTROL CIRCUIT  

A circuit in a closed-loop system, typically containing an error amplifier, that controls the operation of the system to achieve regulation.

CONVERTER  

An electrical circuit that accepts a DC input and generates a DC output of a different voltage usually achieved by high–frequency switching action and employing inductive and capacitive filter elements.

CREST FACTOR  

In an AC circuit, the mathematical ratio of the peak to rms values of a waveform. Crest factor is sometimes used for describing the current stress in AC mains supply wires, since for a given amount of power transferred, the RMS value, and hence the losses, become greater with increasing peak values. Crest factor gives essentially the same information as power factor, and is being replaced by power factor in power supply technology.

CROSS REGULATION  

The effect of a load change on one output to the regulation of another output. It usually applies only to non postregulated (quasi) outputs.

CROWBAR  

An overvoltage protection method that shorts the power supply output to ground in order to protect the load when an overvoltage fault is detected.

CURRENT LIMITING  

An overload protection circuit that limits the maximum output current of a power supply in order to protect the load and/or the power supply.

CURRENT MODE  

A control method for switch-mode converters where the converter adjusts its regulating pulsewidth in response to measured output current and output voltage, using a dual loop control circuit.

CURRENT MONITOR  

An analog power supply signal that is linearly proportional to output current flow.

D
DC-DC CONVERTER  

A circuit which converts DC power form one voltage to another.

 

DC-DC POWER SUPPLY  

Provides one or more dc output voltages.

 

DC-OK SIGNAL  

Signal used to monitor the status of the DC output.

DERATING  

A reduction in an operating specification to improve reliability. For power supplies it is usually a specified reduction in output power to facilitate operation at higher temperatures.

DESIGN LIFE  

The expected lifetime of a power supply during which it will operate to its published specifications.

DIFFERENTIAL–MODE NOISE  

Noise that is measured between two lines with respect to a common reference point excluding common-mode noise. The resultant measurement is the difference of the noise components of the two lines. The noise between the DC output and DC return is usually measured in power supplies.

DISTRIBUTED POWER ARCHITECTURE  

Distributed power architectures distribute a single bus voltage multiple DC-DC converter modules through out the system.

DRIFT  

The change in an output voltage, after a warm-up period, as a function of time when all other variables such as line, load, and operating temperature are held constant.

DRIVER MODULE  

The controlling module in a standalone or driver/booster configuration. The driver module contains all the control circuitry.

DROPOUT  

The lower limit of the AC input voltage where the power supply just begins to experience insufficient input to maintain regulation. The dropout voltage for linears is largely line dependent, whereas for most switchers it is largely load dependent, and to a smaller degree line dependent.

DYNAMIC LOAD REGULATION  

The delta in output voltage when the output load is rapidly changed.

E
EFFICIENCY  

The ratio of total output power to input power expressed as a percentage. Normally specified at 75% full load and nominal input voltage.

ELECTRONIC LOAD  

An electronic device designed to provide a load to the outputs of a power supply, usually capable of dynamic loading, and frequently programmable or computer controlled.

ELECTROMAGNETIC COMPATIBILITY EMC

Relating to compliance with electromagnetic emissions and susceptibility standards.

ELECTROMAGNETIC INTERFERENCE EMI

Unwanted noise generated during the operation of a power supply or other electrical or electronic equipment.

EQUIVALENT SERIES RESISTANCE ESR

The value of resistance in series with an ideal capacitor that duplicates the performance characteristics of a real capacitor.

F
FACTORIZED BUS Vf

An output voltage produced by a PRM or DC–DC converter, which can be controlled to stabilize or vary the output of one or more VTMs.

FACTORIZED POWER ARCHITECTURE FPA

FPA is a novel power distribution architecture that separates the classic functions of a DC-DC converter, as typically used in Distributed Power Architecture systems, into independent regulation and isolation/transformation building blocks.

Although, in its "pure" form, FPA would be implemented with a variety of V•I Chip, traditional power products, such as DC-DC converters, niPOLs and box switchers, can be part of an FPA system.

FAULT TOLERANT CONFIGURATION  

A method of parallel operation, using output isolating diodes, in which the failure of a single supply (module) will not result in a loss of power. The total current of the parallel system must not exceed the load requirements to a point where the failure of a single unit will not result in a system overload.

FIELD EFECT TRANSISTOR FET

A majority carrier-voltage controlled transistor.

FINMOD  

A flangeless/finned packaging option available on Vicor’s VI / MI Family converters and accessory modules.

FLATPAC  

A Vicor AC-DC switcher available with one, two or three outputs, with total power rating from 50 to 600W.

FLOATING OUTPUT  

An output of a power supply that is not connected or referenced to any other output, usually denoting full galvanic isolation. Floating outputs can generally be used as either positive or negative outputs. Non floating outputs share a common return line and are hence DC referenced to one another.

FOLDBACK CURRENT LIMITING  

A type of protection circuit where the output current decreases as the overload increases. The output current reaches a minimum as the load approaches a short circuit condition.

FORWARD CONVERTER  

A switching power supply in which the energy is transferred from the input to the output during the “on” time of the primary switching device.

G
GATE IN  

The Gate In pin of the module may be used to turn the module on or off. When Gate In is pulled low (<1 Volt @ 4 mA, referenced to –Vin), the module is turned off. When Gate In is floating (open collector) the module is turned on. The open-circuit voltage of the Gate In pin is less than 10 Volts, referenced to –Vin. A Gate In/Gate Out connection is necessary to run driver/booster configurations.

GATE OUT  

The Gate Out pin is the clock pulse of the converter. It is used to synchronize booster modules to a driver module for high power arrays.

GROUND  

An electrical connection to earth or some other conductor that is connected to earth. Sometimes the term “ground” is used in place of “common,” but such usage is not correct unless the connection is also connected to earth.

GROUND LOOP  

An unintentionally induced feedback loop caused by two or more circuits sharing a common electrical ground.

H
HAVERSINE  

A waveform that is sinusoidal in nature, but consists of a portion of a sine wave superimposed on another waveform. The input current waveform to a typical off-line power supply has the form of a haversine.

HEADROOM  

Used in conjunction with series pass regulators, headroom is the difference between the input and output voltages.

HEATSINK  

A medium of high thermal mass that can absorb (sink) heat indefinitely with negligible change in temperature. Heatsinks are not necessarily needed with Vicor modules, and their use is highly dependent on the individual application, power and ambient temperature.

HIGH LINE INPUT  

The maximum steady-state input voltage on the input pin.

HIPOT  

Abbreviation for high potential, and generally refers to the high voltages used to test dielectric withstand capability for regulatory agency electrical safety requirements.

HOLDUP CAPACITOR  

A capacitor whose energy is used to provide output voltage for a period after the removal of input voltage.

HOLDUP TIME  

The length of time a power supply can operate in regulation after failure of the AC input. Linears have very short holdup times due to the CV 2 energy storage product of their low voltage secondary side output capacitors. Switchers have longer times due to higher voltage primary side energy storage capacitors.

HOT SWAP  

Insertion and extraction of a power supply into a system while power is applied.

I
I-GRADE  

Industry standard where the operation temperature of a device does not drop below –40 degrees Celsius.

IMPEDANCE  

The ratio of voltage to current at a specified frequency.

INDUCED NOISE  

Noise generated in a circuit by varying a magnetic field produced by another circuit.

INPUT LINE FILTER  

An internally or externally mounted lowpass or band-reject filter at the power supply input that reduces the noise fed into the power supply.

INRUSH CURRENT  

The peak current flowing into a power supply the instant AC power is applied. This peak may be much higher than the steady state input current due to the charging of the input filter capacitors.

INRUSH CURRENT LIMITING  

A circuit that limits the amount of inrush current when a power supply is turned on.

INTERMEDIATE BUS ARCHITECTURE IBA

Typified by the distribution of a lower voltage generally produced at the board level by an IBC. Characterized by the use of niPOLs.

INTERMEDIATE BUS CONVERTER IBC

Available from several manufacturers, an IBC is generally a brick converter providing an unregulated and isolated intermediate voltage from a pre-regulated DC bus. Typical intermediate voltages provided are 12, 8, 5 or 3 Vdc and typical loads are niPOLs.

ISOLATION  

Two circuits that are completely electrically separated with respect to DC potentials, and almost always AC potentials. In power supplies, it is defined as the electrical separation of the input and output via the transformer.

ISOLATION VOLTAGE  

The maximum AC or DC voltage that may be continuously applied from input to output and/or chassis of a power supply.

L
LEAKAGE CURRENT  

A term relating to current flowing between the AC supply wires and earth ground. The term does not necessarily denote a fault condition. In power supplies, leakage current usually refers to the 60 Hz current that flows through the EMC filter capacitors connected between the AC lines and ground (Y caps).

LINEAR REGULATOR  

A regulating technique where a dissipative active device such as a transistor is placed in series with a power supply output to regulate the output voltage.

LINE REGULATION  

The change in output voltage when the AC input voltage is changed from minimum to maximum specified.

LINE VOLTAGE (Mains)  

The sine wave voltage provided to the power supply, usually expressed in volts rms.

LOAD REGULATION  

The change in output voltage when the load on the output is changed.

LOCAL SENSING  

Using the voltage output terminals of the power supply as sense points for voltage regulation.

LONG TERM STABILITY  

Power supply output voltage change due to time with all other factors held constant. This is expressed in percent and is a function of component aging.

LOW LINE  

The minimum steady state voltage that can be applied between the + and - input pins of a converter and still maintain output regulation.

M
MAINS  

The utility AC power distribution wires.

MARGINING  

Adjusting a power supply output voltage up or down from its nominal setting in order to verify system performance margin with respect to supply voltage. This is usually done electrically by a system-generated control signal.

MEGA MODULES  

A chassis mount packaging option that incorporates one, two, or three VI/MI-200 Family converters for single, dual or triple outputs having a combined power of up to 600W.

M-GRADE  

An industry standard where the operating temperature of a device does not drop below –55 degrees Celsius.

MILSPECS  

Military standards that a device must meet to be used in military environments.

MINIMOD  

A junior size (VI-J00) version of the VI/MI-200 Family of DC-DC converters offering up to half the power in a 2.28" x 2.4" x 0.5" package.

MINIMUM LOAD  

The minimum load current/power that must be drawn from the power supply in order for the supply to meet its performance specifications. Less frequently, a minimum load is required to prevent the power supply from failing.

MODULE EVALUATION BOARD  

A test fixture used to evaluate Vicor modules. AC and DC input versions are available.

MEAN TIME BETWEEN FAILURE MTBF

MTBF is the point at which 63% of a given population no longer meet specification. It can either be calculated or demonstrated. The usual calculation is per MIL-STD-217 Rev. E. Demonstrated reliability is usually determined by temperature accelerated life testing and is usually greater than calculated MTBF.

N
NOMINAL INPUT  

The center value for the input voltage range.

NOMINAL VALUE  

A usual, average, normal, or expected operating condition. This stated value will probably not be equal to the value actually measured.

NON-ISOLATED POINT-OF-LOAD CONVERTER niPOL

Available from many manufacturers in many configurations, typical niPOLs are simple buck converters providing low Vouts from an intermediate bus.

O
OFF LINE  

A power supply that receives its input power from the AC line, without using a 50/60 Hz power transformer prior to rectification and filtering; hence the term “off–line” power supply.

OPEN FRAME  

A power supply where there is no external metal chassis; the power supply is provided to the end user essentially as a printed circuit board that provides mechanical support as well as supporting the components and making electrical connections.

OPERATING TEMPERATURE  

The range of temperatures in which a unit can operate within specifications.

OPTOISOLATOR  

An electro-optical device that transmits a signal across a DC isolation boundary.

OR’ING DIODES  

Diodes used to isolate supplies from one another under a fault condition.

OUTPUT FILTERING  

Filter used to reduce switching power supply noise and ripple.

OUTPUT GOOD  

A power supply status signal that indicates the output voltage is within a certain tolerance. An output that is either too high or too low will deactivate the Output Good signal.

OUTPUT IMPEDANCE  

The ratio of change in output voltage to change in load current.

OUTPUT NOISE  

The AC component that may be present on the DC output of a power supply. Switch-mode power supply output noise usually has two components: a lower frequency component at the switching frequency of the converter and a high frequency component due to fast edges of the converter switching transitions. Noise should always be measured directly at the output terminals with a scope probe having an extremely short grounding lead.

OUTPUT POWER RATING  

The maximum power in watts that the power supply can provide and still maintain safety agency approvals.

OUTPUT VOLTAGE ACCURACY  

See Setpoint Accuracy

OVERLOAD PROTECTION  

A power supply protection circuit that limits the output current under overload conditions.

OVERTEMP WARNING  

A TTL– compatible signal that indicates an overtemperature condition exists in the power supply.

OVERVOLTAGE PROTECTION OVP

A circuit that either shuts down the power supply or crowbars the output in the event of an output overvoltage condition.

P
PARALLEL BOOST  

VI/MI-200 Family booster modules may be added to a driver to create multi-kilowatt arrays. Boosters do not contain any feedback or control circuitry.

PARALLEL OPERATION  

Connecting the outputs of two or more power supplies together for the purpose of obtaining a higher output current. This requires power supplies specially designed for load sharing.

PERIODIC AND RANDOM DEVIATION PARD

Periodic And Random Deviation, referring to the sum of all ripple and noise components on the DC output of a power supply, regardless of nature or source.

PEAK POWER  

The absolute maximum output power that a power supply can produce without immediate damage. Peak power capability is typically well beyond the continuous output power capability and the resulting average power should not exceed rated specifications.

POST REGULATOR  

A secondary regulating circuit on an auxiliary output of a power supply that provides regulation on that output.

POWER CONVERSION  

Is the process of converting power from one form into another.

POWER FAIL  

A power supply interface signal that gives a warning that the input voltage will no longer sustain full power regulated output.

POWER FACTOR  

The ratio of true power to apparent power in an AC circuit. In power conversion technology, power factor is used in conjunction with describing AC input current to the power supply.

POWER SUPPLY  

A source of electrical energy employed to furnish the tubes and semiconductor devices of an electronic circuit with the proper electric voltages and currents for their operation.

Also: power supplies

PRELOAD  

A small amount of current drawn from a power supply to stabilize its operation.

PRE-REGULATOR MODULE PRM

A V•I Chip that takes an unregulated, wide range (up to 5:1) DC bus (e.g. a 36–75V bus used in 48V telecom systems) and produces a Factorized Bus output to drive VTMs or other FPA products. The PRM is a very high efficiency (up to 99%) non–isolated buck/boost converter that can control the Factorized Bus.

PRIMARY  

The input section of an isolated power supply. It is connected to the AC mains and, hence, has dangerous voltage levels present.

PRODUCT GRADE  

The environmental and acceptance tests performed on Vicor products.

PULSE–WIDTH MODULATION PWM

A switching power conversion technique where the on-time (or width) of a duty cycle is modulated to control power transfer for regulating power supply outputs.

PUSH-PULL CONVERTER  

A switch–mode power supply topology that utilizes a center-tapped transformer and two power switches. The two switches are alternately driven on and off.

Q
QUASI-REGULATED OUTPUT  

The regulation of an auxiliary output that is accomplished by regulation of the main output. A transformer turns ratio, commensurate with the desired auxiliary output voltage, is used in conjunction with the output around which the main control loop is closed. Quasi-regulated outputs are significantly affected by second–order effects in the converter.

R
RATED OUTPUT CURRENT  

The maximum load current that a power supply can provide at a specified ambient temperature.

REFLECTED RIPPLE CURRENT  

The rms or peak-to-peak AC current present at the input of the power supply that is a result of the switching frequency of the converter.

REGULATION  

The ability of a power supply to maintain an output voltage within a specified tolerance as referenced to changing conditions of input voltage and/or load.

REGULATION BAND  

The total error band allowable for an output voltage. This includes the effects of all of the types of regulation: line, load, temperature, and time.

REGULATORY AGENCIES  

CSA: Canadian Standards Association; FCC: Federal Communications Commission; FTZ: Fernmelde Technisches Zentralamt; TÜV: Technischer Überwachungs Verein; U.L.: Underwriters Laboratory; VDE: Verband Deutscher Electrotechniker.

REMOTE INHIBIT  

A power supply interface signal, usually TTL compatible, that commands the power supply to shut down one or all outputs.

REMOTE ON/OFF  

Enables power supply to be remotely turned on or off. Turn-on is typically performed by open circuit or TTL logic “1”, and turn-off by switch closure or TTL logic “0”.

REMOTE SENSE  

Wires connected in parallel with power supply output cables such that the power supply can sense the actual voltage at the load to compensate for voltage drops in the output cables and/or isolation devices.

RETURN  

The designation of the common terminal for the power supply outputs. It carries the return current for the outputs.

REVERSE VOLTAGE PROTECTION  

A protection circuit that prevents the power supply from being damaged in the event that a reverse voltage is applied at the input or output terminals.

RADIO FREQUENCY INTERFERENCE RFI

An abbreviation for Radio Frequency Interference, undesirable noise produced by a power supply or other electrical or electronic device during its operation. In power supply technology, RFI is usually taken to mean the same thing as EMC.

RIPPLE AND NOISE  

The amplitude of the AC component on the DC output of a power supply usually expressed in millivolts peak-to-peak or rms. For a linear power supply it is usually at the frequency of the AC mains. For a switching power supply, it is usually at the switching frequency of the converter stage.

S
SAFETY GROUND  

A conductive path to earth that is designed to protect persons from electrical shock by shunting away any dangerous currents that might occur due to malfunction or accident.

SECONDARY  

The output section of an isolated power supply, it is isolated from the AC mains and specially designed for safety of personnel who might be working with power on the system.

SAFETY EXTRA LOW VOLTAGE SELV

A term generally defined by the regulatory agencies as the highest voltage that can be contacted by a person and not cause injury. It is often specifically defined as 30Vac or 42.4Vdc.

SETPOINT ACCURACY  

Ratio of actual to specified output voltage.

SEQUENCING  

The technique of establishing a desired order of activating the outputs of a multiple output power supply.

SOFT START  

A technique for gradually activating a power supply circuit when the power supply is first turned on. This technique is generally used to provide a gradual rise in output voltages and inrush current limiting.

SOFT LINE  

A condition where there is substantial impedance present in the AC mains feeding input power to a power supply. The input voltage to the power supply drops significantly with increasing load.

SPLIT BOBBIN WINDING  

A transformer winding technique where the primary and secondary are wound side-by-side on a bobbin with an insulation barrier between them.

STANDBY CURRENT  

The input current drawn by a power supply when shut down by a control input (remote inhibit) or under no load.

STIFF LINE  

A condition where there is no significant impedance present in the AC mains feeding input power to a power supply. The input voltage to the power supply does not change appreciably with load.

SWITCHING FREQUENCY  

The rate at which the DC voltage is switched on and off in a switching power supply.

T
TEMPERATURE COEFFICIENT  

The average output voltage change expressed as a percent per degree Celsius of ambient temperature change. This is usually specified for a predetermined temperature range.

TEMPERATURE DERATING  

Reducing the output power of a power supply with increasing temperature to maintain reliable operation.

THERMAL PAD  

A graphite laminate used as a thermal interface between the converter and a heatsink or chassis.

THERMAL PROTECTION  

A power supply protection circuit that shuts the power supply down in the event of unacceptably high internal temperatures.

TOPOLOGY  

The design type of a converter, indicative of the configuration of switching transistors, utilization of the transformer, and type of filtering. Examples of topologies are the Flyback, Forward, Half Bridge, Full Bridge, Resonant and Zero-Current-Switching.

TRACKING  

A characteristic in a multiple output power supply where any changes in the output voltage of one output caused by line, load, and/or temperature are proportional to similar changes in accompanying outputs.

TRANSIENT RECOVERY TIME  

The time required for an output voltage to be within specified accuracy limits after a step change in line or load conditions.

TRUE POWER  

In an AC circuit, true power is the actual power consumed. It is distinguished from apparent power by eliminating the reactive power component that may be present.

U
UNDERSHOOT  

A transient output voltage change which does not meet the low limit of the voltage accuracy specification and is caused by turning the power supply on or off, or abruptly changing line or load conditions.

UNIVERSAL INPUT  

An AC input capable of operating from major AC lines worldwide, without straps or switches.

V
V•I CHIP  

The physical embodiment of FPA technology in power component form. V•I Chips are available in different sizes (“Double”, “Full” and “Half”), in SMT (J-lead) or through-hole options and with various heatsinking options.

BCMs, PRMs and VTMs are all V•I Chips.

VI-HAM HARMONIC ATTENUATOR MODULE HAM

The VI-HAM is a component level front end that accommodates universal input voltage (85-264), provides line rectification, filtering, transient protection, unity power factor, inrush limiting, and a DC output compatible with the 300V input families of DC-DC converters.

VI-IAM INPUT ATTENUATOR MODULE IAM

A Vicor filter module used to provide EMC conducted noise filtering and transient protection.

VOLTAGE BALANCE  

The difference in magnitudes, in percent, of two output voltages that have equal nominal voltage magnitudes but opposite polarities.

VOLTAGE MODE  

A method of closed loop control of a switching converter to correct for changes in the output voltage.

VOLTAGE TRANSFORMATION MODULE VTM

A V•I Chip that takes a Factorized Bus voltage and provides galvanic isolation and either a step-up or step-down function(depending on application) . The output voltage is determined by the VTM's k factor: Vout = Vin * k. The VTM performs its power conversion function at high efficiency (up to 96%) and has exceptional dynamic response and noise characteristics.

W
WARM-UP DRIFT  

The initial change in the output voltage of a power supply in the time period between turn-on and when the power supply reaches thermal equilibrium at 25 degrees Celsius, full load and nominal line.

WARM-UP TIME  

The time required after initial turn-on for a power supply to achieve compliance to its performance specifications.

X
X-CAPACITOR  

A capacitor connected across the supply lines to suppress normal mode interference.

Y
Y-CAPACITOR  

Power conversion modules generally require bypass capacitors from line to chassis (earth ground) to shunt common mode noise currents and keep them local to the converter. In cases where the converters are operating from rectified AC line voltage, the failure of a bypass capacitor could result in excessive leakage current to the equipment chassis thus creating a ground fault and shock hazard. For this reason, a special classification of capacitor, referred to as a Y-capacitor, is recommended. These capacitors contain a dielectric with unique “self-healing” properties to help prevent against excessive leakage.

To meet general EMC requirements (see chapter 10 of the Vicor Applications Manual), Vicor recommends the use of Y-capacitors with all power conversion modules. Y-capacitors meet IEC384-14, EN132400, an UL 1283 standards.

Z
ZERO-CURRENT-SWITCHING  

The turn-on and turn-off of a switch at zero current, resulting in essentially lossless switching. The zero-current-switching topology allows Vicor converters to operate at frequencies in excess of 1 MHz, with efficiencies greater than 80% and power densities ten or more times greater than conventional topologies.