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LISN:
Line Impedance Stabilization Network.
Load Regulation:
The change in output voltage, in percentage, as the load is varied from minimum to maximum, all other parameters held constant.
MIL-STD:
US military standards.
MIL-STD-202F:
Describes the test methods for determining a component 's resistance to the effects of natural elements and conditions. Typically used for small components such as resistors.
MIL-STD-202F, Method 103:
Describes Humidity Tests. 85% relative humidity, non condensing, 85°C ambient, 240 hours.
MIL-STD-202F, Method 107:
Defines Thermal Shock. 200 cycles, -40°C to 125°C, 15 minute dwell time.
MIL-STD-202F, Method 108:
Defines Accelerated Life. 100 hours, 60°C ambient, maximum power.
MIL-STD-461C:
Describes the design and documentation requirements for electromagnetic emission and susceptibility characteristics of electronic equipment. It covers four areas: Conducted Emissions, Conducted Susceptibility, Radiated Emissions and Radiated Susceptibility.
MIL-STD-462C:
Describes test methods used to verify the compliance with EMC limits set by MIL-STD-461C.
MIL-STD-704D:
Defines the conducted electrical power characteristics for aircraft systems at the interface between the power system and electronic equipment. It ensures the compatibility of aircraft equipment and ground support equipment.
MIL-STD-810E:
Environmental Test Methods and Engineering Guidelines.
Defines the methods for testing the effects of natural and induced environments on equipment used in military applications.
MIL-STD-883D, Method 2002.3:
Defines Mechanical Shock. Condition A, 500G, 1mSec, half sine, 5 shocks, 2 directions, 3 axes, 30 shocks total. Suitable for packaged, low power modules.
MIL-STD-883D, Method 2007.2:
Defines Mechanical Vibration. 4 four minute sweeps, 4 times each axis, total time 48 minute, 20 to 2000Hz logarithmically. Suitable for packaged, low power modules.
MIL-STD-1275A:
Describes the transient voltage characteristics and steady state limits for 28Vdc powered circuits used in military vehicles.
MIL-T-28800E:
Humidity, Vibration.
Minimum Load:
The minimum amount of output current required by a SMPS in order to maintain all specifications.
MOSFET:
Metal Oxide Silicon Field Effect Transistor.
MTBF:
Mean Time Between Failure. The failure rate of a SMPS expressed in hours, usually calculated using the MIL-HDBK-217F, at 25°C and a Ground Benign environment.
NEC:
National Electrical Code (USA).
NEMCO:
Norsk Electroteknisk Komite (Norway).
NFC:
National Fire Safety Code (USA).
NEMKO:
Norges Elektriske Materiell Kontroll (Norway).
Noise, Common Mode:
The component of noise which is common to both lines of input (or output) of a SMPS with respect to chassis.
Noise, Differential Mode:
The component of the noise measured between the two input or two output wires).
Off-Line SMPS:
A SMPS which operates off the AC line directly, without using a transformer prior to rectification and filtering.
Output Impedance:
The ratio of the change in output voltage to change in load current.
OVP:
Over Voltage Protection. A feature or circuit of a SMPS for protecting the SMPS and the load if an abnormal high voltage occurs to the output.
OVE:
Safety agency, Austria.
PARD:
Periodic and Random Deviation. A term used for the sum of all ripple and noise components measured over a specified frequency band, and stated either as Peak-to Peak or RMS values.
PFC:
Power Factor Correction.
Power Supply:
Usually a DC power source derived from an AC input voltage.
Power Supply, Programmable:
A Power Supply with the output (Voltage and/or current) controlled by an external analog signal (resistance, voltage, current) or digital code.
Prototype:
The term was originally applied to the first unit of a production run, which was used as the final check of a design before full production started.
Prototype, Engineering:
A prototype that is hand built outside the production line, but with the circuit, physical construction and PCBs close to the final product.
PWM:
Pulse Width Modulation. A method of voltage regulation used in SMPS where the output is controlled by varying only the width of a train of pulses.
Push-Pull Converter:
A SMPS topology which is using usually a center-tap transformer and two switches that are driven ON and OFF alternately.
Radiation, Heat Transfer:
A heat transfer that is due to electromagnetic (infrared) emission which is inherent with any physical object with a temperature above 0 K.
Rated Output Current:
The maximum load current a SMPS was designed to provide under specified conditions.
Recovery Time, Power Supply:
The time it takes for the output voltage of a Power Supply to settle within a tolerance band following a change in a resistive load.
Redundancy:
The ability of a system of multiple Power Supplies to continue to provide power to a common load if one or more Power Supplies of the system fail. The SMPS should be designed from start to be compatible with a redundant system design. The system designer should specify the level of redundancy for the system ("M" Power Supplies in a system of "N" may fail and the system will still provide adequate power to the load.
Regulation:
The ability of a SMPS to maintain an output voltage within specified limits under varying of input voltage and output load.
Reliability:
The ability of a SMPS to maintain its functionality and the specifications under stated conditions for a stated period of time.
Resolution, Output Voltage Adjustment:
The smallest change in the output voltage that can be realized by the adjustment.
Resonant Converter:
A SMPS topology in which a resonant tank circuit is used to transfer energy from input to the output.
Return:
The name for the Common terminal.
Reverse Voltage Protection:
A feature which protects a SMPS against a reverse voltage applied at the input or output terminals.
RFI:
Radio Frequency Interference.
Ripple and Noise, Output:
The magnitude of the AC voltage on the output of a SMPS expressed usually in milivolts peak-to-peak or RMS, within a specified bandwidth.
Ripple Current, Reflected:
The AC current generated at the input of a SMPS generated by the switching operation, stated as peak-to-peak or RMS.
Royer Converter:
A self-oscillating push-pull converter used in low cost, low power designs.
Secondary Side:
Output side of an isolated SMPS.
SEMKO:
Svenska Elektriska Kommissionen (Sweeden).
Sensing, Remote:
A technique of regulating the output voltage of a SMPS at the load, by using a separate pair of leads for voltage sensing.
SETI:
Electrical Inspectorate Finland (Finland).
SEV:
Schweizerischer Elektrotechnischer Verein (Switzerland).
Short Circuit Protection:
A feature which limits the output current of a SMPS to a safe value under a short circuit condition, so that the SMPS will not be damaged.
Single Fault Condition (IEC Definition):
Condition in which one means for protection against hazard is defective. Note: If a Single Fault Condition results unavoidably in another Single Fault Condition, the two failures are considered as one Single Fault Condition.
SMT:
Surface Mount Technology.
Snubber:
A component or a circuit, active or passive, dissipative or regenerative used in a SMPS to reduce components stress by limiting peak voltage or current, dV/dt, dI/dt.
Soft Start:
A feature of a SMPS which, which, at start-up, gradually rise the output voltage of a SMPS to its final value, therefore protecting both the power supply and the load.
Stability, Long Term:
The output voltage change of a SMPS, in percentage, usually due only to time, with all other factors held constant. Some time other factors are also included.
Temperature, Ambient:
The temperature of the objects (not necessary the temperature of the intake air), surrounding the SMPS.
Temperature Coefficient:
The average percentage variation in the output voltage of a SMPS due to temperature variation (specified as parts per million per degree Centigrade, over a specified temperature range).
Temperature, Intake Air:
The temperature of the intake air used to cool a SMPS. Usually the main task for the intake air would be to cool the heatsink(s), and the magnetics. A secondary task would be to cool other components such as ICs, resistors, capacitors.
Temperature, Operating Ambient:
The temperature interval within which a SMPS would operate with reasonable electrical specifications and reliability. It should not be considered, unless specified such, that a SMPS will be able to deliver the full output power over the entire operating temperature range, or that the SMPS will maintain the same electrical specifications over the entire operating temperature range.
Transfer Function:
A mathematical expression that shows how two entities or events occurring in different places or at different times are related.
Transient Recovery Time:
Time required for a converter output to return to within specified limits, following a step change in output load current.
TUV:
Technisher Uberwachungs-Verein (Germany). A testing agency only, authorized to approve products to VDE standards.
UL:
Underwriters Laboratories, Inc.. An independent, non-profit US organization that tests products for safety (USA).
UL94:
UL standard, Flammability of Plastic Materials.
UL1012:
UL standard, Power Supplies.
UL 1262:
UL standard, Laboratory Equipment.
UL1950:
Safety of Information Technology Equipment.
UPS:
Uninterruptible Power Supply. A Power Supply which continues to supply power during a loss of the AC input voltage.
VDE:
Verband Deutscher Elektrotechniker (Association of German Electrical Engineers). A private German organization that sets standards for product safety and noise emissions and also tests and certifies equipment to those standards.
Warm-up Drift:
The initial change in output voltage of a SMPS from turn-on until it reaches thermal equilibrium at nominal line, full load and 25C ambient temperature.
Warm-up Time:
The time needed, after turn-on, for a SMPS to reach thermal equilibrium at nominal line, full load and 25C ambient temperature. Usually estimated to be about 30 minutes.
Winding, Split Bobbin:
A method of winding a transformer whereby the primary and secondary are wound side-by-side on a bobbin with an insulation barrier between the two windings.
X Capacitors:
RFI Capacitor used in positions where if failed would not be hazardous to anyone who touches the case of the equipment. The X capacitors are connected across the line conductors. There are three sub-classes of X capacitors: X1, X2 and X3. The most common is X2 sub-class, used for IEC-664 Installation Category II. The X2 capacitors are rated for peak pulse voltage in service of less or equal to 2.5KV.
Y Capacitors:
RFI Capacitor used in positions where if failed could be hazardous to somebody who touches the case of the equipment. The Y capacitors are connected between power lines and chassis/earth. There are four sub-classes of Y capacitors: Y1, Y2, Y3 and Y4. The most common is Y2 sub-class, used across a Basic or Supplementary insulation. The Y2 capacitors are rated for nominal working voltages less or equal to 250Vac and for peak impulse voltage before endurance test of less or equal to 5KV. Because Safety Standards stipulate maximum current towards earth for different applications, the capacitance of Y capacitors must be limited to a certain value depending on the type of equipment in which the capacitor is used.
Zero Voltage Switching:
Technique in which the power switch(es) in a SMPS turns on when there is zero voltage across it, in order to minimizes switching transient noise and switching losses. |
