Terminology

Below you will find a list of common DC/DC and AC/DC power supply terminology which may appear in the Fabrimex data sheets. The terminology, with a brief corresponding explanation is in alphabetical order.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

A

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Ambient Temperature (Ta)

The temperature in the medium around a component is measured some distance from the power supply, usually a few cm, to be considered uniform. However, ambient temperature is per definition imprecise . Therefore temperature ratings for converters are usually given for case temperatures (Tc).

Category: A
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Approval

Many power supplies have to meet certain standards. If so, these are listed in the data sheet. However, many standards apply only on an apparatus level. Then Fabrimex will not list this under "approvals" in the data sheet, but the adherence to that standard can be found in the relevant technical parameter

Category: A

B

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Boost Converter

The Boost Converter (step-up) is a commonly used building block in converter design without galvanic isolation. When the switch (Q) is conductive, the inductor (L) is charged. After opening the switch  the energy is transferred from the inductor to the load.


Advantage:
+ Very few componets
+ Good cost / performance ratio

Disadvantage:
- Moderate conversion ratio

The output-to-input voltage ratio is always greater than one and is ideally equal to the inverse of one minus the duty conduction cycle of the switch during continuous operation. The boost topology also requires an output energy storage capacitor to support the load current while the switch is on.

Category: B
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Brownout

Partial power outage. The input voltage drops below the minimum input voltage of a connected load. The result is a drop of the output voltage below the nominal value.

Category: B
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Buck Converter

The Buck Converter (step-down) is another commonly used building block in converter designs without galvanic separation. In its basic form, without a transformer, the output voltage is always less than the input voltage.


Advantage:
+ Very few componets
+ Good cost / performance ratio

Disadvantage:
- Moderate conversion ratio

When the transistor (Q) is switched on, energy is transferred from the input source to charge the inductor  (L) and the output. When the switch is turned off, the inductors polarity is reversed and the energy is transferred to the output capacitor and the load. The output-to-input voltage ratio is ideally equal to the conduction duty cycle of the switch for continuous operation. Since most applications severely limit the amount of pulsating current that can be drawn from the converter’s input source, some form of low pass filter is generally inserted on the input side of the switch.

Category: B
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Burn-In

The process of operating newly manufactured power supplies for some period of time prior to delivery. The intent is to stabilize the electronics and eliminate infant mortality by aging the device. The time period and conditions (input voltage cycling, load switching, temperature, etc.) can be varied.

Category: B
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Burst

High-frequency and low-power impulse, capacitive coupled via an electrical field.

Category: B

C

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Case Temperature (Tc)

The temperature of a converter measured at its hottest spot on the base plate or case.  Temperature ratings for converters are usually given for the case temperature (Tc), as ambient temperature per definition is imprecise. The case temperature for an operating converter is ordinarily higher than the ambient temperature.

Category: C
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Convection Cooling

Cooling without forced air flow, also referred to as ‘natural convection’. The only air flow is induced by temperature differences rather than by mechanical means.

Category: C
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Converter Regulated

A DC/DC converter where the output voltage value, independent of the load and input voltage, is regulated within specified limits.

Category: C
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Converter Unregulated

A DC/DC converter where the output voltage value changes depending on the load and input voltage.

Category: C
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Crow Bar

An over voltage protection circuit which monitors the output voltage of a power supply and rapidly creates a low resistance path, usually a thyristor, across the output when a predetermined voltage is exceeded.

Category: C
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Current Limit

A protection of the power supply where the output current is limited to a value above the nominal output current, usually between 110% to 150% of the nominal output current.

Category: C
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Current Limit Characteristic

There are three main current limiting characteristics. All three drop the output voltage when the rated current is exceeded:

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Hicc-Up Mode

Current Limit

Category: C

D

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Derating

Temperature derating allows the operating temperature to exceed the specified values if the output power is reduced as predetermined (reciprocal, the output power may exceed the specified nominal power if the operating temperature is reduced as predetermined).

Category: D
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Dynamic Load Response

Voltage jump at the output caused by a jump in the load current. See also: Load Transient Recovery Time, Load Transient Error Band.

Category: D

E

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Efficiency

Ratio between output power and input power as a factor or a percentage.

Category: E
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EMC (in general)

The electromagnetic compatibility (EMC) of equipment is understood to mean

  • the limitation of the transmission of electromagnetic interference to a level that guarantees trouble-free operation of other equipment in the environment (EMC conducted and / or radiated).
  • the ensuring of a sufficiently high resistance to externally acting electromagnetic interference so that correct operation is guaranteed at the intended place of use under the electromagnetic interference conditions to be expected there (EMC irradiated).
Category: E
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EMC Conducted

Electromagnetic interference caused by the power supply and which is transmitted via the circuit path or connected cables.

Category: E
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EMC Irradiated

Electromagnetic interference caused by externally acting factors which penetrate the power supply.

Category: E
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EMC Radiated

Electromagnetic interference caused by the power supply and which is transmitted via the surrounding medium (air).

Category: E

F

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Flyback Converter

The Flyback Converter is used in circuits with galvanic isolation for lower power ranges. In the basic Flyback Converter, when the transistor is turned on, the current increases linearly in the transformer (T) primary and is stored in a magnetic field. When the switch (Q) turns off the transformer, its polarity is reversed and causes a current flow in the secondary, transferring energy to the output capacitor and the load.


Advantage:
+ Few components
+ Good cost / performance ratio

Disadvantage:
- Sensitive to production process
- for low power only

Since the transformer assumes the roles of both an energy storage device and a transformer, only one magnetic component is needed.

Category: F
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This current limiting characteristic decreases the output current and voltage simultaneously as the overload increases to protect the load.

When in current limiting mode, the converter usually has to be re-started to escape the current limiting mode.

 

Category: F
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Forward Converter

The Forward Converter is a circuit with galvanic isolation for low power. Contrary to the Flyback, the Forward Converter is not storing energy in the transformer. The secondary winding is in  opposite direction, compared to  the Flyback. It carries the current immediately to the secondary side. The energy is  stored in the succeeding inductor.

Advantage:
+ Less component stress
+ 'simple' components

Disadvantage:
- More components
- Only low power

 

Category: F
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Full Bridge Converter

The Full Bridge topology is a derivate of the Forward Converter, intended for  higher power, also with galvanic isolation. The transformer (T) is alternately connected to the full input voltage. Two of the four transistors (Q) are building one branch (Q1/Q4 or Q2/Q3), and each branch is driven alternated. Similar to the Forward Converter, the transformer transfers the energy directly to the inductor on the secondary side.


Advantage:
+ Less component stress
+ 'simple' components
+ Higher power

Disadvantage:
- Needs 4 transistors

 

Category: F

G

H

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Half Bridge Converter

The Half Bridge topology is a derivate of the Forward Converter for mid power, also with galvanic isolation. The transformer (T) is connected to the midpoint between the two capacitors (C1/C2). The two transistors are driven alternated and charge the transformer with different polarities. Similar to the Forward Converter, the transformer transfers the energy directly to the inductor on the secondary side.


Advantage:
+ Less componet stress
+ 'Simler' components

Disadvantage:
- 2 capacitors, 2 transistors and more transformer windings needed
- Mid Power

Since the transformer assumes the roles of both an energy storage device and a transformer, only one magnetic component is needed.

Category: H
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Hold-Up Time

The amount of time that a power supply's output remains within the specified output voltage range after its input  voltage ceases.

Category: H

I

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Input Voltage Range

The range of input voltage values for which a power supply operates within specified limits.

Category: I
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Inrush Current

The maximum input current drawn by a power supply when turned on. The lower the current, the less thermal shock the system experiences.

Category: I
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Isolation Resistance

The resistance between input and output, primarily a function of the transformer used. The isolation resistance is useful when the leakage current between input and output has to be established.

Category: I
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Isolation Voltage

Also known as galvanic isolation voltage. The maximum AC or DC voltage which can be applied to the power supply between input and output while the specified isolation resistance is maintained. Primarily a function of the transformer used.

Category: I

J

K

L

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Leakage Current

A term relating to current flowing between the AC supply wires and earth ground. Leakage current usually refers to the 50/60 Hertz current which flows through the EMI filter capacitors which are connected between the AC lines and ground.

Category: L
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Line Regulation

The maximum deviation, in percentage of nominal, of the output voltage when the input voltage varies from minimum to maximum.

 

Category: L
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Load Regulation

The maximum deviation, in percentage of nominal, of the output voltage when the load varies from a determined minimum to maximum. 

 

Category: L
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Load Transient Error Band

Defined output voltage range outside the specified range, caused be a jump in the load current.

Category: L
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Load Transient Recovery Time

Time needed to enter the specified output voltage range after a jump in the load current. 

 

Category: L

M

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MTBF

MTBF (Mean Time Between Failures) is a factor to express the likelihood of failures and the unit is in operating hours. This factor is a statistical factor and can not be applied to a single power supply only, but has to applied to a multitude.

1st Failure = MTBF / quantity [h]

There are several MTBF standards, such as the MIL-HDBK-217 and the Belcore standard. The MTBF values of different standards can not be directly compared to each other.

Category: M

N

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Natural Convection

See convection cooling.

Category: N
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No Load Current

Also referred to as ‘standby current’, is the input current the power supply will consume when no load is connected to the output.

Category: N

O

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Open Frame

AC/DC and DC/DC modules where the components are in direct contact to the air flow as opposed to potted or enclosed modules. Advantage of open frame modules is the exposed surface area to the airflow which is larger then of a potted module.

Category: O
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Operating Temperature

The temperature range the power supply will operate within (including start up), inside of the specified limits. The operating temperature can be defined as ambient temperature (Ta) or case temperature (Tc).

Category: O
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Output Voltage Accuracy

The maximum deviation, in percentage of nominal, of the output voltage at nominal conditions.

Category: O
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Output Voltage Trim

Also known as “output voltage adjustment” and is used to make small adjustments to the nominal output voltage, usually ±10%. For board mounted modules it usually is an external adjustment, a resistance connected to a pin. Other power supplies may feature a potentiometer which can be adjusted mechanically with a screw driver.

Category: O
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Overvoltage Protection

A protective feature which either shuts down the power supply or crowbars the output in the event of an over voltage condition at the output.

Category: O

P

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Polarity Protection

A feature which protects the input of the DC/DC converter if the applied polarity has been interchanged.

Category: P
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Potting

A method of packaging board mounted modules as opposed to open frame modules. Advantage of potted modules is the thermal capacity characteristic of the potting which will transfer the heat from hot spots efficiently. Further the potting protects against mechanical influences.

Category: P
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Power Dissipation (Pd)

Also referred to as 'thermal power' , is the difference between input and output power. The power dissipation is converted to heat inside the power supply. To keep internal die-junction temperatures within normal operating specifications maximum power dissipation limits are specified. Power dissipation is calculated as follows:

Category: P
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Push-Pull Converter

The Push-Pull topolgy is a derivate of the Forward Converter for mid power, also with galvanic isolation. The two transistors (T) are driven alternated. Thus, the magnetic filed-flow through the windings is also alternated. Similar to the Forward Converter, the energy is stored in the succeeding inductor (L).

Advantages:
+ Medium number of components
+ Medium cost/performance ratio

Disadvantages:
- Sensitive to production process
- Bigger transformer
- 2 Transistors

 

Category: P
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PWM

Pulse width modulation (PWM) regulates the output voltage  in switching power supplies whereby the output voltage is controlled by varying the width, but not the height, of a train of pulses which trigger a power switch.

Category: P

Q

R

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Rca, Rth

See Thermal Resistance.

Category: R
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Remote Sense

A feature where the voltage drop between the power supply and the load is automatically compensated if the sense is connected to the load. 

Category: R
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Ripple & Noise

Ripple is the triangle waveform on top of the output voltage, generated by the PWM. Therefore the ripple presents the same frequency as the power supplies switching frequency.

Noise are the spikes at a given bandwidth on the output voltage as a result of conducted line noise, internal switching transients and other random noise.

Category: R

S

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Short Circuit Protection

Protection against damage to the power supply if the load becomes shorted. When ‘continuous’ short circuit protection, the power supply will resume operation automatically once the short circuit is removed. The main short circuit characteristics are ‘hiccup mode’ and ‘current limit’.

Hicc-Up Mode

Current Limit

 

 

Category: S
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Soft Start

Mit einem Soft Start lässt sich der Einschaltstrom in der Anlaufphase begrenzen, wodurch die Ausgangsspannung stufenweise auf das festgelegte Niveau ansteigt.

Category: S
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Stand-by Current

See No Load Current.

Category: S
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Start-Up Time

The time required until the output voltage reaches a certain percentage of nominal after input voltage has been switched on.

Category: S
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Step-Up Converter

See Boost Converter.

Category: S
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Storage Temperature

The minimum temperature range the power supply can be stored at without derogating the power supplies specification.

Category: S
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Surge

Low-frequency and high-power impulse, inductive coupled via an magnetic field.

Category: S
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Switching Frequency

The rate at which the internal DC voltage is switched on and off during the pulse width modulation process in a switching power supply. The switching frequency can be fixed or  variable.

Category: S

T

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Temperature Coefficient

The temperature coefficient is the relative change of the nominal output voltage when the temperature is changed by 1 K (Kelvin).

Category: T
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Thermal Resistance (Rca, Rth)

The measure of a material’s ability to resist heat flow. The formula for Thermal Resistance is:

where (L) is the material’s thickness and (k) is the material’s Thermal Conductivity constant. The higher a material’s R-value, the better its thermal insulation.

Category: T
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Thermal Shutdown

A protection feature where the critical internal temperature is monitored and the power supply shut down if a preset value is exceeded. The  thermal protection is not intended for continuous use as the shut down is initiated at a temperature > operating temperature.

Category: T

U

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Undervoltage Lockout

Preset input voltage values when the power supply will turn on (power up) and when it will shut down (power down).

Category: U

V

W

X

Y

Z