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CONSTANT
CURRENT SOURCE
A regulated
power supply that delivers a constant current to a load, even when the
load resistance changes.
CONSTANT
VOLTAGE SOURCE
A regulated
power supply that delivers a constant voltage to a load even when the load
resistance changes.
CURRENT
LIMITING
Ability to limit
maximum current output at a preset value. This feature helps protect the
load from overcurrent damage.
ISOLATION
Floating output,
no reference to any voltage.
LINE
REGULATION
How much the
load voltage or current changes when the power supply is operated at
varying line voltages throughout a given range. Typically stated as a
percentage of the total voltage or current available from the supply. A
rating of "0%" would mean perfect regulation.
LOAD
REGULATION
How much the
load voltage or current changes between operating the power supply at
no-load and full-load conditions. Typically stated as a percentage of the
total voltage or current available from the supply. A rating of
"0%" would mean perfect regulation.
OVERLOAD
PROTECTION
Means by which a
power supply is protected from permanent damage due to short circuits,
excessive loads, or reverse polarities connected across the load
terminals.
Protection may
be as simple as a fuse (which can be economically replaced), or may be
electronic protection circuitry which automatically monitors load
conditions as well as power supply component temperatures.
POWER
CONSUMPTION
The input power
that is required by the power supply at a full load output condition.
POWER
REQUIREMENTS
The line voltage
that the power supply requires to operate. High quality power supplies
have a selector switch that permits operation from 110,120, 220 , and 240
VAC sources.
RECOVERY TIME
The time that it
takes a power supply to regulate its output after an abrupt change, such
as from full load to no load.
REGULATION
The ability to
maintain a constant voltage or current at the load despite changes in line
voltage or load resistance.
RIPPLE
CURRENT
The portion of
unfiltered AC current at the output of a filtered power supply.
RIPPLE
VOLTAGE
The portion of
unfiltered AC voltage and noise present at the output of a filtered power
supply, operated at full load. Typically stated as rms and peak-to-peak AC
voltage (with zero ripple voltage would represent a perfect power supply).
RMS VALUE
(root mean square value)
The effective
value of an AC or periodic voltage or current. The amount of work
accomplished by a given rms value equals the amount of work accomplished
by an equal DC value. The rms value can be obtained by first squaring the
ordinates of the wave, then finding the average value of the squared wave,
finally taking the square root of the average found. The rms value of a
pure sine wave is 0.707 times the peak value (RMS = Vp x 0.707), while the
rms value of a square wave is 0.5 times the peak value Vp = Peak Value =
Vpp/2 .
TRACKING
Two power
supplies (within one case) that are electrically coupled so that both can
be varied by using only one knob.
TEMPERATURE
COEFFICIENT
The change in
power supply output voltage that is caused by temperature change. It is
usually expressed in millivolts per degree.
VA
Abbreviation for
Volt-Ampere. Unit of input power delivered to a load. For electronic
equipment, the "VA" load imposed on the isolation transformer or
AC power supply is simply the load voltage multiplied by the load current,
or the wattage rating of the load.
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