Periodic And Random Deviation (PARD) - deviation about the
mean, which is the composite peak-to-peak envelope of ripple and noise which
exists on the output of a power conversion equipment.
Phase margin - the open loop difference in phase between an
input signal and the corresponding return signal in a closed-loop feedback
system at the frequency where the amplitude difference is zero. The phase
margin is usually expressed in degrees and is one measure of feedback loop
Phasors - a vectorial descriptor of the angular displacement
between the voltage and current in a circuit and usually has to do with phase
margins or power factor as it relates to power or power supplies.
Platform power - that power provided to systems or
subsystems by the vehicle/ship/aircraft/ satellite upon which it is
Point-of-Load - a collocated deployment technique of
distributed post regulators which provide a dedicated regulated output(s) to
individual functional elements or components of a system or subsystem.
Power On Reset (POR) - a power supply signal indicating that
its output(s) are in tolerance and used for the initialization of logic in the
next higher assembly.
Post regulator - a circuit or control element located after
or down-stream of the primary conditioning of energy to provide particularly
well regulated or quiet (low noise) current to sensitive loads.
Power - the product of in-phase voltage and current in a
device or (for resistive devices) the product of the square of the current times
the resistance through which the current is flowing.Power is expressed in
Power factor - a unit of measure, usually given in decimal,
which is the ratio of active power in Watts to the apparent power in VA (rms
voltage times rms current).
Power supply - an apparatus that has as its input raw and
unregulated voltage which it conditions, steps up or down, and regulates for use
by electrical loads.
Power System - the entire collection of equipments and
distribution medium which conditions and carries the energy from the prime
source to the utilizing loads.
Prime power - that power source from which all of the
platform power is derived (i.e., the prime source).
Pulse Width Modulator (PWM) - a device that takes analog
signals and generates electrical pulses of controlled width.
Radio Frequency Interference (RFI) - see EMI in this
Rectifier - an element or component that allows current to
flow in but one direction, usually used for changing an AC source into a DC
Reference- a standard cell or component quantity which
establishes the standard to which something else (e.g., output voltage) is
Regulation - the control process of an output voltage or
current which maintains it within predetermined bounds while other parametrics
are changing (e.g., temperature/load/line/ aging/radiation).
Remote sense - the carrying of the point of regulation to a
distance beyond the output of a power supply to include error correction
associated with voltage drops in the distribution.
Ripple -that portion of an
AC component residing upon a DC output voltage.
Secondary input power - usually an alternative energy source
from which a system can be powered when the prime source is unavailable.
Silicon Controlled Rectifier (SCR) - a regenerative
semiconductor which, after being gated 6c on" generally remains turned "on"
or"saturated" until the anode current or anode/cathode voltage decays to
zero. The anode current must reverse to clear the outer two junctions so
the device will regain its forward blocking capability.
Soft start - a circuit technique employed (usually in the
front end) of a power conversion apparatus to limit the inrush current at turn
on (see inrush in this glossary).
Switching power supply - provides a regulated DC output
voltage. The switching/regulating device(s) consists of one or more
semiconductors typically driven at a frequency below I MHz. The developed
square wave is magnetically coupled to the output and rectified/filtered to
establish the user voltage. A sample of the output voltage is isolated and
fed back to the endput to control the ON/OFF period of the switching
semiconductors. This feedback control, along with an internal reference,
establishes the set point for the output voltage and regulates against both
input line and output load perturbations.
Synchronous rectifier - a circuit technique by which a field
effect transistor (FET) is substituted for the rectifying diode(s) to facilitate
increased rectification efficiencies at low voltages.