Power Supply Glossary of Terms

For a better understanding of power terms and specifications.

If you are new to the world of power supplies or are just trying to keep up with the latest terms and buzz words, our Power Supply Glossary of Terms should be a great help.  If you see any new ones that we missed, please let us know!

Capacitive Load – A load connected to the output of a power supply that causes capacitive reactance to draw current.

Current Limited – A circuit in which, if a maximum current value reached (or approaches a short circuit), voltage source voltage will drop as power demand increases.

Earth Leakage – Leakage from an active circuit to ground.

Efficiency – The difference between power consumed at the input of a power supply and that available at the output, usually stated in percent.

EMI Emissions – Non-desired electromagnetic emissions or interference.

EN55022 – A European standard defined by the European Committee for Electrotechnical Standardization (CENELEC) for the limit of acceptable conducted and radiated noise in a power circuit, which also corresponds to limits set by the FCC.

Energy Star – A program of the US Government (Environmental Protection Agency and Department of Energy) which sets standards for the operating efficiency of various kinds of manufactured products.  For electrical and electronic products, it defines the maximum amount of power which can be consumed in an idle state in order to meet certification.  Energy Star

Input Voltage Range – The nominal input power range that will allow a power supply to deliver its rated output.

Input Surge Withstand – The amount of momentary surge voltage, above the normal input range, that can be applied to the input without causing an interruption in operation.

Isolation – The maximum voltage applied to the input of a power supply that can be isolated from the output of that supply, in the event of a failure.

Line Regulation – The maximum amount of variation of output voltage as input voltage varies, stated in percent.

Load Regulation – The amount of variation of the output that occurs with variations of the load from minimum to maximum, stated in percent.

Line-Synchronous Switching Technology – A patented Bias Power circuit design that prevents input noise from reaching the power output.

No Load Consumption – The amount of input power consumed by a power supply under a no-output load condition.

Operating Relative Humidity – The range of humidity that a power supply can tolerate and continue to meet its rated specifications.

Operation Temperature (or Operating Temperature)
– The range of ambient temperature that the power supply can operate within at rated specifications.

Output Power – The rated maximum amount of power available at the output of the power supply.

Package Size – The nominal physical dimensions of the power supply enclosure.

Reliability – A relative indication of the likelihood of a device failing, under rated operating conditions.

Ripple Vo – The amount of repetitive variation in the output of the power supply.

Safety Compliance – An indication of adherence to standards defined by major third-party testing organizations.

Short Circuit Protection – Protection of a power supply not to be damaged if the output circuit is short circuited or connected to a very low impedance source.

Standby Power – An auxiliary source of power, intended to power timing and control circuitry in an appliance or electronic device, when power to primary operating circuits has been “switched off.”

Storage Temperature – The maximum range of temperature that the power supply can safely be kept in storage when no circuit power is applied.

Switching Frequency – In a switching power supply, the operating frequency of the power oscillator circuit which is fed to the power transformer.

UL1950/EN60950 – Parallel safety standards issues by Underwriters Laboratories and European Committee for Electrotechnical Standardization (CENELEC) to ensure safe design and construction of DC power sources.

Voltage Limited
— The maximum amount of voltage available at the power supply output.