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These definitions should be considered relevant to a SMPS, and may not apply identically to other technical areas. While definitions already available in other publications (standards, dictionaries, manufacturer's data books, technical notes, manuals) were considered, the following terminology represents the personal view of the author, and might be slightly different from what a particular user of this document may be used to.
Absolute Maximum Ratings, Component:
Specifications which, if exceeded, could cause permanent damage to the component. These are not continuous ratings, and proper operation is not implied.
Ae, Effective Area:
For a magnetic core with a given geometry, is the magnetic cross-sectional area of a hypothetical toroidal core of the same material that will be the magnetic equivalent to the given core.
Ambient Temperature (1):
The temperature of the objects and of the still air surrounding the SMPS, measured at a minimum of 4" (100mm) from the supply.
Ambient Temperature (2):
According to MIL-STD-810E: The test unit shall be surrounded by an envelope of air, except at necessary support points. The gradient throughout this envelope shall be within 2°C of the test temperature and shall not exceed 1°C per meter.
Ampere Turns (NI):
The product of current flowing in a winding times number of turns.
ATP:
Acceptance Test Procedure.
BABT:
The British Approvals Board for Telecommunications. An independent organization that approves telecom equipment for UK market. BABT grants approvals and accredits testing laboratories.
Behavioral Model:
Model of a circuit block expressed in mathematical relationship. The highest level of simulation hierarchy.
BJT:
Bipolar Junction Transistor.
BOM:
Bill of Material.
Boost:
A basic SMPS topology in which energy is stored in a inductor when a switch is ON, and is transferred to the output when the switch is OFF. It converts an unregulated input voltage to a regulated output voltage higher than the input.
Breadboard:
The first physical implementation of a circuit. It may be incomplete and may have no resemblance to the final product.
BS:
British Standard.
BSI:
British Standards Institution (United Kingdom). A institution that develops standards and tests products for compliance.
Buck:
A basic SMPS topology in which a series switch chops the input voltage and applies the pulses to an averaging LC filter. The Buck regulator will produce a lower output voltage than the input.
Buck-Boost:
See Flyback.
Burn-In:
The procedure of operating a SMPS for some period of time with the intent to eliminate the infant mortality and stabilizing the SMPS by aging. Temperature cycling and power cycling may also be applied during burn-in.
C1, Core Constant:
The summation of the magnetic path length of each section of the circuit divided by the corresponding area of the same section.
CENELEC:
Comite pour Europeen de Normalisation Electronic (European Committee for Electrotechnical Standardization). An organization that includes 17 European countries, and develops standards that are published as EC Directive.
CE Mark:
Indicating compliance with all relevant European Union directives.
CFM:
Cubic Feet per Minute.
CISPR:
Committee International Special des Perturbations Radioelectriques.
Common:
A conductive path used for more than two circuits. Also known as Return. Not to be used for defining the Ground terminal.
Constant Current:
A mode of operation when the Output Current is regulated for changes in output load.
Constant Voltage:
A mode of operation when Output Voltage is regulated for changes in output load.
Convection:
A heat transfer mode that occurs at the interface between a solid surface and surrounding still air.
Convection, Natural:
When a warm surface is surrounded by cooler natural moving air.
Convection, Forced:
When a air flow is created around and along the warm surface by a fan or other mechanical means.
Converter (DC/DC):
A SMPS that converts a DC input voltage to a different DC output voltage.
Cross Regulation:
In a multiple output power supply is the percentage in voltage change at one output caused by a load change at another output.
Crowbar:
An overvoltage protection circuit which places an almost short circuit is placed across the points where the overvoltage was detected.
CSA:
Canadian Standards Association. A independent organization that set standards and conducts safety testing for Canadian market.
CSA 22.2 No. 950:
See UL1950.
Cuk:
A buck-boost derived SMPS topology that can produce very low output ripple.
Curie Temperature:
The transition temperature above which a ferromagnetic material becomes diamagnetic.
Current Mode Control:
A control method which is using a dual loop circuit to adjust the PWM operation.
Current, Maximum Rated Output:
The maximum output current which a SMPS was designed to provide at a specified set of conditions, such as: ambient temperature, intake air temperature, elevation, airflow restrictions, heat radiated by other components of the environment, output voltage, output power.
DEMKO:
Dansk Electroteknisk Komite. (Denmark).
Derating:
The specified reduction in an operating parameter to improve reliability. Generally for a SMPS, it is the reduction in maximum available output power at temperature above the ambient, input voltages below the nominal, etc.
DF:
Dissipation Factor.
DHHS:
Department of Health and Human Services (USA).
Drift:
The change in output voltage of a SMPS over a specified period of time, following a warm-up period, with all other operating parameters such as input voltage, load and ambient temperature held constant.
ECO:
Engineering Change Order.
Efficiency:
The ratio of total output power to the active input power, expressed as a percentage. This is normally specified at full load, nominal input voltage and 25C ambient temperature.
EMC, Electromagnetic Compatibility:
The ability of a device to function satisfactorily in its electromagnetic environment without introducing intolerable disturbances to that environment or to other devices therein.
EMI:
Electromagnetic Interference. Unwanted energy, generated from the SMPS which may be conducted or radiated.
EN:
Euro Norme.
ESL:
Equivalent Series Inductance. The value of a inductance in series with an ideal capacitor , which duplicates the performance of a real capacitor.
ESR:
Equivalent Series Resistance. The value of a resistance in series with an ideal capacitor, which duplicates the performance of a real capacitor.
EUT:
Equipment Under Test.
Faraday Shield:
An electrostatic shield between input and output windings of a transformer. This is used to reduce primary to secondary coupling capacitance, which in turn will reduce output common mode noise.
FCC:
Federal Communications Commission (USA).
Feed Forward:
A control technique whereby the line regulation of a SMPS is improved by directly sensing the input voltage.
FET:
Field Effect Transistor.
Flux Density, Magnetic:
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, Soldering:
A substance added during soldering to a metal surface which, when heated, will prevent oxidation and help the flowing of the solder.
Flyback Converter:
A isolated Buck-Boost SMPS topology in which, during the first period of a switching cycle the energy is stored in a inductance and during the second period this energy is transferred to a different winding of the same inductor and into the load.
Foldback Current Limiting:
An overcurrent protection circuit where the output current decreases with increasing overload, reducing the stress on SMPS components.
Forward Converter:
A Buck-derived SMPS topology in which energy is transferred to the secondary of a transformer winding and into the load, when the switching transistor is ON.
Fourier analysis:
The use of the Fourier series to evaluate the harmonic components of a complex wave.
Fourier Series:
A mathematical series that shows any periodic function to be a combination of sine and cosine terms.
Full Bridge Converter:
A SMPS topology in which four transistors are connected in a bridge configuration to drive the primary of a transformer.
GaAs:
Gallium Arsenide.
Ground Benign:
Ideal laboratory environment.. Applies to test and medical equipment, laboratory instruments, etc.
Ground Fixed:
Less than ideal environment. Applies to rack mount equipment, or used in a unheated building, etc.
Ground Mobile:
Applies to equipment installed in wheeled or tracked vehicles.
Half Bridge Converter:
A SMPS topology, similar with full bridge, in which only two transistors are used, the other two being replaced by capacitors.
H.A.L.T.:
Highly Accelerated Life Testing.
H.A.S.S.:
Highly Accelerated Stress Sampling.
Heat Sink:
Usually a metal plate, extrusion, etc. that is used to transfer heat away from sensitive components.
Hiccup Mode:
An operating mode for a SMPS triggered by a fault condition, in which the SMPS cycles ON and OFF.
Hi-Pot Test:
High Potential Test. A test to determine if the breakdown voltage of a circuit or component exceeds the minimum requirement.
Holdover Time:
See Hold-Up Time.
Hold-Up Time:
The time during which a SMPS output voltage remains within specifications, following the loss of input power.
Hot Plug-In:
A SMPS capability of being connected or disconnected from the power buses (input and output) without damages.
IEC:
The International Electrotechnical Commission. An organization that sets standards for electronic products and components. Does not conduct any testing.
IMQ:
Safety agency, Italy.
Inrush Current:
The peak instantaneous input current drawn by a SMPS at turn-on.
Insulation, Basic (IEC Definition):
Insulation, the failure of which could cause a risk of electric shock.
Insulation, Double (IEC Definition):
Insulation comprising both Basic Insulation and Supplementary Insulation.
Insulation, Reinforced (IEC Definition):
Insulation which provides protection against electric shock not less than that provided by Double Insulation. It may comprise several layers which can not be tested singly as Supplementary Insulation or Basic Insulation.
Insulation, Supplementary (IEC Definition):
Independent insulation applied in addition to Basic Insulation in order to provide protection against electrical shock in the event of a failure of Basic Insulation.
Inverter:
A power source with DC input and AC output.
ISO:
International Standards Organization.
Isolation Voltage:
The maximum AC or DC voltage which may be continuously applied between two section of a SMPS.
Laplace Transform:
A mathematical operation that reduces the work of solving certain differential equations to solving algebraic equations.
le, Effective Length:
For a magnetic core with a given geometry, is the magnetic path length of a hypothetical toroidal core of the same material that will be the magnetic equivalent to the given core.
Lifetime (SMPS):
The time during which a SMPS will maintain its electrical specifications and a reasonable MTBF.
Line Regulation:
The change in output voltage, in percentage, as the input voltage is varied over its specified limits, with all other parameters held constant. |
