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C

Case Temperature

Temperature of the case when the converter and surrounding system are operating normally. Often used as a specification for converters with extended temperature ranges. Case temperature is at times referred to as Base Plate Temperature. Also see Operating Temperature Range.

CCC - China Compulsory Certification

Chinese government’s safety/EMC licensing system. This system requires manufacturers in 132 product categories to obtain the CCC Mark before exporting or selling into the Chinese marketplace.

CE

“CE“ is the abbreviation of French phrase “Conformité Européene” – European Conformity. Originally as EC mark, and it was officially replaced by the current CE marking. A CE Marking on a product is a manufacturer's declaration that the product complies with the essential requirements of the relevant European health, safety and environmental protection legislations.

Common Mode Noise

Noise component that is common to both the converter output and return lines with respect to the input ground.

Constant Current Power Supply

A regulated power supply which acts to keep its output current constant in spite of changes in load, line or temperature. Thus, for a change in load resistance, the output current remains constant to a first approximation, while the output voltage changes by whatever amount necessary to accomplish this.

Constant Voltage Power Supply

A regulated power supply which acts to keep its output voltage constant in spite of changes in load, line or temperature. Thus, for a change in load resistance, the output voltage of this type of supply remains constant to a first approximation, while the output current changes by whatever amount necessary to accomplish this.

Converter

A power supply or an adaptor. More often than not, it refers to an adaptor that converts AC to DC, or DC to DC output. Also see Adaptor, Inverter and Power Supply.

Cross Regulation

For a multiple output converter or adaptor, the change in voltage on one output (expressed as a percent) caused by a load change on another output.

Crowbar

Circuit that crowbars or rapidly shuts down a converter’s output if a preset voltage level is exceeded. The circuit places a low resistant shunt across the output when an overvoltage condition exists.

CSA – Canadian Standards Association

Independent organization that establishes and tests safety standards for electric and electronic components, devices and systems for the Canadian marketplace.

Current Limiting

Feature that protects an adaptor, a converter or a load from damage under overload conditions. The maximum converter output current is automatically limited to a predetermined, safe value. If the adaptor or converter is specified for auto restart, normal operation is automatically restored when overload condition is removed.

Current Limit Knee

On a plot of output voltage vs current, the point at which current begins to limit (or foldback).

CV/CC - Constant Voltage/Constant Current with Automatic Crossover

A power supply which acts as a constant values of load resistance and as a constant current source for comparatively small values of load resistance. The automatic crossover or transition between these two modes of operation occurs at a “critical” or “crossover” value of load resistance.

CV/CL - Constant Voltage/Current Liming with Automatic Crossover

The same as CV/CC operation except for a slightly poorer regulation characteristic for low values of load resistance, i.e., in the “constant current” region of operation.

D

Differential Mode Noise

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

Change in the output voltage of an adaptor or 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.

Dynamic Load

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

E

Efficiency

Ratio of total output to input power expressed as a percentage. Efficiency is normally measured at full rated output power and nominal input line conditions.

EMI - Electromagnetic Interference

Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of spurious emissions and responses, intermodulation products, and the like. Also See Radiated EMI and RFI.

ESD

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

F

FCC – Federal Communications Commission

US government agency that sets standards for, and governs the testing of conducted and radiated emissions. These are system level standards, but they are typically used in specifying adaptors and power supplies.

Floating Output

Converter output that is 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 a common return and as such, are referenced to one another.

Foldback Current Limiting

Use of a fan (or other air moving equipment) with a (sub) system to move air across heat producing components in order to reduce ambient temperature. Also called Forced Convection.

Free Convection

Operating environment where the natural movement of air (not assisted by fans or blowers) maintains the power module within its operating limits. Also called Natural Convection.

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

G

Ground

Electrical connection that is made to earth (or to some conductor that is connected to earth).

Ground Loop

Condition caused when two or more ground system components share a common electrical ground line. A feedback loop is unintentionally induced, causing unwanted voltage levels.

H

Heat Sink

Metal plate, extrusion, case, etc., used to transfer heat away from sensitive components and or circuits.

High Line

Maximum value of input line voltage specified for normal converter operation. Also see Low Line.

Hi-Pot Test - High Potential Test

A test to determine if the breakdown voltage of a transformer or power supply exceeds the minimum requirement. It is performed by applying a high voltage between the two isolated test points.

Hold-Up Time

The time during which a power supply output voltage remains within specification following the loss of input power.

Hot Plug-In

A common requirement in distributed power systems wherein the power board must be capable of being connected/disconnected from the power bus without damage. Power board components must be protected against the resultant high inrush currents.

I

IEC – International Electrotechnical Commission

Organization based in Switzerland that sets standards for electronic products and components. IEC does not conduct and testing; however, their standards have been adopted by many of the national safety and/or testing agencies.

Input Current

Current drawn from the input power bus by a converter when operating under nominal conditions.

Input Voltage Range

Minimum and maximum input voltage limits within which a power supply, an adaptor or a converter operates to specifications.

Inrush Current

Maximum, instantaneous input current drawn by a converter, during turn on. Also called Input Surge Current.

Inrush Current Limiting

Protection circuit that limits the current an adaptor or a converter draws at turn on.

Insulation

Non-conductive material used to protect and separate electronic components or circuits.

Insulation Resistance

Resistance offered by an insulating material to current flow.

Inverter

Normally it refers to an adaptor or power supply that converts DC to AC current output. Also see Adaptor and Converter.

Isolation

Electrical separation between the input and output of a converter. Normally determined by transformer characteristics and component spacing.

Isolation Voltage

Maximum voltage (AC or DC) that can be continuously applied between isolated circuits without a breakdown occurring. On converters, this is normally specified as input-output or input-case isolation. Minimum isolation voltage levels must be maintained to meet most safety regulations.

L

Leakage Current

Current flowing from input to output or input to case of an isolated converter at a specified voltage level.

Life Test

Reliability test in which a converter is operated (typically under accelerated conditions) over some period of time in order to approximate its life expectancy.

Linear Regulation

Power supply regulation technique in which the regulating device (typically a transistor) is placed in series or parallel with the load. Voltage variations across the load are controlled by changing the effective resistance of changing the effective resistance of the regulating device to dissipate unused power.

Load

Electronic components or circuits connected to the output pins of a converter. The characteristics (resistance, reactance, etc.) of the load determine the amount of power drawn from the converter.

Logic Inhibit/Enable

Signal (typically TTL/CMOS compatible) used to turn a power supply output on/off. Also called Remote On/Off.

Long Term Stability

Change in output voltage of a converter over time with all other factors (line, load, temperature etc.) remaining constant. Expressed as a percent, the output change is primarily due to component aging.

Low Line

Minimum value of input line voltage specified for normal converter operation. Also see High Line.

M

Master/Slave Operation

Connection of two or more converters so on (master) controls the operation of the others (slaves). Mater/slave configurations are used to provide higher output power, wider input voltage ranges, synchronized operation. Also see Auto-Parallel and Auto-Series Operations.

Maximum Load

Highest amount of output load allowable under the continuous operating specifications of a power supply or a converter.

MTBF - Mean Time Between Failure

Unit of measure, expressed in hours, that gives the relative reliability of a converter.

Minimum Load

Minimum amount of output load required on a power supply or a converter in order to maintain normal continuous operating specifications.

Minimum Operating Temperature

Minimum ambient temperature at which a power supply or a converter will start and operate within specifications.

N

No Load Voltage

Voltage level present at the output pins of a power supply or a converter when 0% load is applied.

Noise

Unwanted variations in a power supply or a converter output, normally called “Ripple and Noise” and given as a peak-to-peak value with a specified band width.

Nominal Value

Ideal Value that is used as a reference point. Typically, it is not the same as the value actually measured.

O

Open-Circuit Voltage

See No Load Voltage.

Open Frame

A type of power supply which is not encased in a metal or plastic shell or frame and subsequently is not covered with a potting compound. Open frame converters are easily identified as their component parts are visible.

Operating Temperature Range

Range of temperatures over which a converter can be operated safely within specified limits. Normally specified as ambient, however, at times case or base plate temperature are also used.

OTP – Over Temperature Protection

A protection system for converters where the converter shuts down if the ambient temperature exceeds the converter’s ratings. OTP is intended to save the converter and any downstream equipment in the event of a catastrophic failure of a fan and such. OTP usually measures the hottest item on board the converter rather than ambient temperature. Sometimes it is also referred to as Overheating Protection.

Output Current Limiting

An output protection feature which limits the output current to a predetermined value in order to prevent damage to the power supply or the load under overload conditions. The supply is automatically restored to normal operation following removal of the overload.

Output Voltage

Value of DC voltage measured at the output terminal of a converter.

Output Voltage Accuracy

Maximum allowable deviation of the DC output of a converter from its ideal or nominal value. Expressed as a percentage of output value. Often called output voltage tolerance.

Output Voltage Range

Minimum and maximum output voltage limits within which a converter meets it operating specifications.

Overload Protection

An output protection feature which limits the output current of a power supply under overload conditions so that it will not be damaged.

Overshoot

Transient change in output voltage that exceeds specified accuracy limits. Typically occurs on converter turn on/off or with a step change in output load or input line.

OVP – Overvoltage Protection

Output monitoring circuit activated if a preset voltage level is exceeded. Depending on the type of circuit used, the OVP shuts down the converter, “crowbars” the faulty output or switches the converter to a different operating mode.

P

Parallel Operation

Operating mode in which two or more power supplies are connected in parallel. The output currents are summed together in a single load, providing a higher level of output power than that available from a single unit. Parallel operation requires models specifically designed to share loads. Also see Master/Slave Operation.

PARD – Periodic and Random Deviation

Noise and ripple voltage superimposed on a converter’s DC output. Typically specified at full load, it is expressed in peak-to-peak or RMS volts over a given bandwidth.

Polarity

Ability of a converter to produce an output that is positive or negative referenced to ground. Also see Floating Output.

Post Regulation

Output circuit that uses an additional linear regulator to improve line/load regulation and reduce ripple and noise.

Power Density

Ratio of converter output power to converter volume.

Power Factor Correction

Design technique usually applied to the input of converters that improves the converter’s power factor and minimizes harmonics generated by the converter onto the AC power line.

Power Good

Signal (typically a visible LED) that indicates the DC output of the primary channel of a converter is still present.

Power Rating

Specified power available at the converter output pins.

Power Supply

Internal assembly or external unit, whether open frame or cased, that powers up the downstream equipment. It converts AC to DC, or DC to DC (often called Converter or Adaptor) or DC to AC (also called Inverter).

Pre-Regulation

The regulation at the front end of a power supply, generally by a type of switching regulator, this is followed by output regulation, usually by a linear type regulator.

Primary Circuit

Input side of an isolated converted. See Secondary Circuit.

Programmable Power Supply

A power supply with an output controlled by an external resistor, voltage or digital code.

R

Radiated EMI

Also called Radio Frequency Interference (RFI). EMI is unwanted high frequency energy caused by the noise generators of the adaptors. That portion that is radiated through space is know as radiated EMI. Most Radiated EMI measurements are done between 30MHz and 300MHz. Also see EMI and RFI.

Rated Output Current

Maximum output current that can be continuously drawn from a converter under specified conditions.

Reflected Ripple Current

AC components measured at the input line. Given as a peak-to-peak or RMS value.

Regulation

Ability of a converter to maintain an output voltage within specified limits under varying conditions of input line and output load. Also see Linear Regulation.

RFI – Radio Frequency Interference

Electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. Also See EMI and Radiated EMI.

Remote Error Sensing or Remote Sensing

A feature found on some power supplies, which, by means of two extra wires between the supply and the load, permits the power supply to achieve its optimum regulation at the load terminals rather than at the power supply output terminals, thus compensating for the IR drop present in the current carrying leads connecting the load to its power supply. The current through the sensing leads is so small that in spite of the resistance of these leads, their voltage drop is negligible.

Remote Programming

A feature of some power supplies which permits control of the regulated output current of voltage by means of a remotely varied resistance or voltage.

Remote Shutdown

See Logic Inhibit/Enable.

Resolution

For an adjustable power supply, the smallest change in output voltage that can be realized by the adjustment.

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

Converter feature that prevents damage to internal components if a reverse voltage is inadvertently applied to the input or output terminals. It is sometimes referred to as Reverse Polarity Protection.

Ripple and Noise

The residual AC component which is superimposed on the DC output of a regulated power supply. Ripple and noise may be specified in terms of its RMS or (preferably) peak-to-peak value. When the peak-to-peak value is specified, it should be accompanied by the maximum bandwidth of the measuring instrument, typically DC to 20 MHz. Measuring ripple and noise with an instrument that has insufficient bandwidth may conceal high frequency spikes detrimental to the load.

RMS Value – Root Mean Square Value

The Root Mean Square (RMS) value of a voltage or current, expressed as Vrms or Irms.

S

Secondary Circuit

Output side of an isolated AC to DC or DC to DC converter. Also see Primary Circuit.

Sense Line

Output line used in a remote sensing connection to route the output voltage (at the load) back to the control feedback loop. Also see Remote Sensing.

Series Operation

Master/Slave configuration in which two or more isolated converters are connected to obtain a higher output voltage level (converter inputs connected in parallel) or wider input voltage range (converter inputs connected in series) than that obtainable from one module. Also see Master/Slave Operation.

Series Regulator

Linear regulator (internal or external to the converter) placed in series with the load to achieve a constant voltage across the load. This is the most popular method of linear regulation. Also see Linear Regulation, Post Regulation and Shunt Regulator.

Short Circuit Protection

See Current Limiting and Foldback Current Limiting.

Shunt Regulator

Linear regulator (internal or external to the converter) placed in parallel with the load to achieve a constant voltage across the load. Also see Linear Regulation, Post Regulation and Series Regulator.

Six-Sided Shielding

Converter packaging technique in which the unit is placed into a metal case. The metal shielding minimizes any noise radiation from the converter components. A continuous shielded case has the base (or header) welded on, further reducing potential noise leakage.

Soft Start

Converter input circuit that limits the inrush current at turn on.

Stability

This term refers to the instability in power supply output which occurs in the presence of constant load, constant line and constant ambient temperature for a stated period of time (usually 8 hours) following warm-up. This small output variation which is related in part to the internal temperature rise of the power supply, is the zero frequency component of noise which must be present in any DC amplifier or regulator, even though all input, output, environmental and control parameters are hold constant.

Standby Current

Current drawn by a converter when it has no load and has been shut down by a logic inhibit signal.

Step Change

Sudden change in a converter parameter. Typically used in referring to changes in output load or input line during converter testing.

Storage Temperature Range

Range of ambient temperatures over which a converter can be safely stored.

T

Temperature Coefficient

For a power supply operated at a constant load and under conditions of constant input AC line voltage, the change in output voltage (for a constant voltage supply) for each degree change in the ambient temperature.

Temperature Range

See Operating Temperature Range and Storage Temperature Range.

Thermal Conductivity

Given a material’s ability to conduct heat, this is the time rate for heat transfer (via conduction) across a unit material thickness of 1 meter and when the temperature differential of the two opposite faces is 1 deg. k.

Thermal Protection

Feature that shuts the converter down if the internal temperature exceeds the preset limits. Also called Thermal Shutdown. Also see OTP.

Topology

This refers to the way in which the power handling part of a power supply is configured. Choice of topology influences many of the basic characteristics of a converter.

Tracking

For a multiple output converter the parameter that gives the change in one output voltage caused by a change in the voltage level or load on another output.

TUV – Technischer Uberwachungs-Verein

Organization approved for testing products to VDE standards. US based companies often use TUV in place of VDE because they have established facilities in the US.

U

UL – Underwriters Laboratories

Independent organization that conducts safety testing of products to established standards.

Undershoot

Transient change in a converter output voltage that does not meet the lower limit of the voltage accuracy specification. Typically occurs at converter turns on/off or with some step change in output load or input line. Also see Voltage Accuracy.

UPS – Uninterruptible Power Supply

Power supply that will continue to operate after the loss of AC input power.

UNLO – Under Voltage Lock Out

A protection system for power converters where the converter is deliberately shut down if the input voltage drops below a pre-defined level. UVLO is usually needed with battery systems where the voltage decreases gradually with time rather than shutting off quickly.

V

VDE – Verband Deutsher Elektrotechniker

German organization that sets standards for product safety and noise emissions and tests and certifies products to those standards.

Voltage Balance

For multiple output converters, the percentage difference in voltage level of two outputs with opposite polarities and equal nominal values.

W

Warmup Drift

See Drift.

Warmup Time

Time required for a converter to operate within specifications after turn-on. This time normally precedes a long-term drift specification.

Withstand Voltage

Maximum voltage level that can be applied between circuits or components without causing a breakdown. Also see Breakdown Voltage and Isolation.

Z

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