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

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.

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.

DC/DC Converter
An electrical device that accepts an unregulated DC input and generates a regulated DC output, usually of a different voltage typically achieved by high frequency switching action employing inductive and capacitive filter elements.

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

Efficiency
The ratio of total output power to input power, expressed in percentage. Normally specified at full load and nominal input voltage.

EMI
Abbreviation for Electromagnetic Interference, which is the generation of unwanted noise during the operation of a power supply or other electrical or electronic equipment.

High Line Input
The maximum steady-state input voltage applied between the + and – input pins.

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 in applying a high voltage between two isolated test points.

Input Filter
A low-pass or band-reject filter at the input of a power supply that reduces line noise fed to the supply. This filter may be internal or external to the power supply.

Input Voltage Range
The high and low input voltage limits within which a DC/DC converter meets its specifications.

Isolation
The electrical separation between input and output of a power supply by means of the power transformer. The isolation resistance (normally in megaomhs) and the isolation capacitance (normally in picofarads) are generally specified and are a function of materials and spacing employed throughout the power supply.

Isolation Voltage
The maximum Ac or Dc voltage may be continuously applied from input to output and/or chassis of a power supply.

LFM
Linear Feet per Minute. A measure of the velocity of air. Used in distributed power systems to give the air flow over a baseplate or heatsink surface area. LFM is equal to m/s multiplied by 196.8.

Line Regulation
The change in output voltage when the input voltage is changed from minimum to maximum, expressed as a percentage of the output voltage.

Load Regulation
The change in output voltage when the load on the output is changed, expressed as a percentage of the output voltage.

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

Minimum Load
The minimum load current required for a converter to operate within specification.

MTBF
Mean Time Between Failure. The failure rate of a power supply, expressed in hours, established by the actual operation or calculation from a known standard such as MIL-HDBK-217F.

Nominal Input
The center value for the input voltage range.

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

Operating Temperature
The ranges of ambient or case temperatures within which a DC/DC converter can be safely operated and meet its specifications.

Output Voltage
The nominal value of the DC voltage at the output terminals of a power supply.

Output Voltage Accuracy
For a fixed output supply, the tolerance in percentage of the output voltage with respect to its nominal value under all minimum or maximum conditions.

Over Voltage Protection
A power supply protection feature shuts down the supply, crowbars or clamps the output when its output voltage exceeds a preset level.

Over Temperature Protection
When the case temperature is too high, the converter will shut down operation. Thermal shutdown halts the PWM operation placing the converter in a low current drain mode until the case temperature decreases.

Output Trim
Output voltage trimming allows the user to change the output voltage of the module. The output trim can be either a fixed resistor or a trimpot. Any value from zero ohm to infinity may be used to trim the output voltage when fixed resistors are used. A 10K, 1 or 10 Turn trimpot is usually specified for continuous trimming. This pin may be safely left floating if it is not used.

Pi Filter
A commonly used filter at the input of a switching supply or DC/DC converter to reduce reflected ripple current. The filter usually consists of two parallel capacitors and a series inductor.

Primary
The input section of an isolated DC/DC converter.

Pulse Frequency Modulation (PFM)
A switching power conversion technique at a fixed operating duty cycle (or width) where the switching frequency is modulated to control power transfer for regulating power supply outputs.

Pulse Width Modulation (PWM)
A switching power conversion technique at a fixed operating frequency where the duty cycle (or width) of the switching period is modulated to control power transfer for regulating power supply outputs.

Push-Pull Converter
A switch mode power supply topology which uses a center-tapped transformer and two power switches which are driven on and off alternatively.

Rated Output Current
The maximum load current which a power supply was designed to provide at a specified ambient temperature.

Reflected Ripple Current
The rms or peak-to-peak AC current generated at the input of the DC/DC converter 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 change conditions of input voltage and/or load.

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”.

Ripple and Noise
The magnitude of AC voltage on the output of a DC/DC converter expressed in millivolts peak-to-peak or RMS at a specified band width. DC/DC converters output noise usually have two components: a 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.

Secondary
The output section of an isolated DC/DC converter.

Short-Circuit Input Current
The maximum input current that a converter will source with its output shorted.

Standby Current
The input current drawn by a power supply when shuts down by a control input (remote on/off).

Storage Temperature
The range of ambient temperature within a power supply which may be safely stored, non-operating, with no degradation in its subsequent operation.

Switching Frequency
The rate which the DC voltage is switched on and off in a DC/DC converter.

Temperature Coefficient
The average percentage change in output voltage per degree centigrade change in ambient temperature over a specified temperature range.

Transient Recovery Time
The time required for the output voltage of a power supply to settle within specified output accuracy limits following a step change in output load current or a step change in input voltage.

Unit Weight
This is the weight of the converter in gram.

Voltage Balance
The difference in magnitudes, in percentage, between two output voltages of a dual output power supply where the voltages have equal nominal values with opposite polarities.