Technical data

Constant-voltage/constant current (CV/CC) power supply: a power
supply that operates as a constant-voltage power supply
or a constant-current power supply, depending on load
conditions. The supply acts as a constant-voltage source
for comparatively large values of load resistance and as a
constant-current source for comparatively small values of
load resistance.
Constant-Voltage/Constant-Current Output Characteristics
Constant-voltage/current limiting (CV/CL) power supply: a power
supply similar to a constant-voltage/constant-current supply
except that at comparatively small values of load resistance,
its output current is limited instead of being stabilized.
Crest factor: the ratio of the zero-to-peak value to the rms
value of a waveform. This term is often used to specify the
maximum peak amplitude that an ac power supply can source
(relative to its maximum rms rating) without distortion.
Crowbar: see overvoltage protection.
Current limiting: the action, under overload or short-circuit
conditions, of limiting the output current of a constant-
voltage supply to some predetermined maximum value (fixed
or adjustable) and automatically restoring the output voltage
to its normal value when the overload or short circuit is
removed. There are three types of current limiting:
•
by constant-voltage/constant-current crossover
•
by decreasing the output voltage as the current increases
•
by decreasing both voltage and current as the load resistance
decreases.
DFI: a TTL compatible output signal that can be used as an
alarm and automatically initiates an action for multiple power
supply or electronic load shutdown. The DFI signal is com-
monly connected to RI of the next supply. (See RI)
Downprogramming: the ability of a power supply to discharge its
output capacitors independently of load. The use of an active
down programming device can reduce the fall time of the out-
put voltage.
Drift: the maximum change of a power supply output or load
input voltage or current during an 8-hour period following a
30-minute warmup, with all influence and control quantities
maintained constant during the warm-up time and the period
of drift measurement. Drift includes both periodic and
random deviations over the bandwidth from zero frequency
(dc) to a specified upper frequency limit.
Efficiency: expressed in percent, efficiency is the total output
power of the supply divided by the active input power. Unless
otherwise specified, Agilent measures efficiency at maximum
rated output power and at worst case conditions of the ac
line voltage.
Electromagnetic interference (EMI): any type of electromagnetic
energy that could degrade the performance of electrical
equipment. The EMI generated by a power supply can be
propagated either by conduction (via the input and output
leads) or bt radiation from the units’ case. The terms “noise”
and “radio-frequency interference” (RFI) are sometimes
used in the same context.
Electronic Load: an active device which absorbs power. Loads
are used for the testing of the power producing products.
Foldback: immediate shutdown of the power supply output
when a crossover between constant voltage and constant
current mode occurs. Both the voltage and current levels
are reduced (folded back).
Harmonics: the occurrence of this type of distortion is based
upon the mathematical principle that all periodic waveforms
are made up of a series of sine waves. As a result, harmonic
distortion is produced at frequencies that are integer
multiples of the fundamental or desired signal frequency.
When viewed in the frequency domain, harmonics have an
amplitude (often expressed in db), frequency, and phase
characteristic relative to the fundamental.
Isolation: the maximum voltage (including output voltage)
either output terminal may be floated from earth ground.
Load cross regulation: the affect on one output of a multiple
output power supply when another output is programmed
from zero to full rated current.
Load Effect: also known as “load regulation”. Load effect is
the change in the steady-state value of the stabilized output
voltage or current resulting from a full-load change in the load
current of a constant-voltage supply or the load voltage of a
constant-current supply, with all other influence quantities
maintained constant.
Load effect transient recovery time: the time interval between a
specified step change in the load current of a constant-voltage
supply (usually a full-load or 5-amp change, whichever is
smaller) or in the load voltage of a constant-current supply
and the instant when the stabilized output quantity returns to
and stays within a specified transient recovery band.
Load Effect Transient Recovery Waveforms
(Constant – Voltage Operation)
Load
Increase Decrease
Load Effect
Transient
Recovery
Band
Load Effect
Transient
Recovery
Time
E
OUT
t
I
OUT
or
(Constant – Current Operation)
E
S
I
S
0
0
I
OUT
R
L
⬎R
C
⬎
∆I
∆E
∆I
∆E
E
OUT
Open
Circuit
Load
Constant Voltage
Operating Region
Constant Current
Operating Region
Short Circuit Load
R
L
=R
C
R
L
=
R
L
R
C
70 APPLICATIONS INFORMATION
Power Products Terms (cont’d)
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