RO Associates, Inc.
RO
Application Note 7
Rev -, September 21, 1994
Measuring Line And Load Regulation
Line regulation is the module's ability to maintain a
constant output voltage as the line (input) voltage
changes. Load regulation is the module's ability to
maintain a constant output voltage as the load current
changes.
Line and load regulation are two of the most common
types of converter measurements. Although
straightforward, there are some simple guidelines that
will help insure accurate readings.
To check the module for regulation, measure the
output voltage at the sense pins (+SENSE and
-SENSE). There is virtually no current flowing
through the sense leads, and consequently no
appreciable drop across them. Therefore, measuring at
the sense pins is equivalent to measuring at the point
where the sense leads are connected to the output
leads.
In contrast, there can be a significant voltage drop
between the module's output terminals and the load.
This voltage drop, which varies with load current, can
cause erroneous regulation values.
The remote sense terminals should always be
connected to the output either at the output terminals
or at the load. (Connect -SENSE to -OUT and
+SENSE to +OUT.)
Line Regulation Connect a DVM to the sense
terminals. Vary the input voltage from minimum to
maximum. The output voltage change, as a percentage
of nominal output voltage, is the line regulation. See
figure 7a.
+IN
+OUT
+SENSE
V
V
-IN
R
-SENSE
-OUT
Figure 7a Detail of line (input) regulation measurement
circuit
Load Regulation Connect a DVM to the sense
terminals. Vary the load current from zero to
maximum. The output voltage change, as a percentage
of nominal output voltage, is the load regulation. See
figure 7b.
+IN
+OUT
+SENSE
I
V
-IN
R
-SENSE
-OUT
Figure 7b Detail of load regulation measurement circuit
(800) 443-1450 • Fax: (408)744-1521 • Email: apps@roassoc.com • Web: www.roassoc.com
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AP-7
Measuring Line and Load Regulation
09-21-94
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RO Associates, Inc. • 246 Caspian Dr. • Sunnyvale, CA 94089 • (408) 744-1450