Hello, I’m Ed Brorein, an applications specialist for Agilent Technologies systems product division
and today I’ll talk about how to test the line regulation of a DC voltage regulator.
This testing is made quick and easy using an N6782 source/measure module for functional testing.
This device can source and sync current, so it performs as both a source and electronic
load for testing voltage regulators and other similar components.
Together with the N6705B DC Power Analyzer mainframe and 14585B Software, this forms
a platform for testing power components. Here I have wired up a three pin voltage regulator
and it’s set up for 10 volts of output. And I have the input side of the voltage regulator
connected to channel one of our DC power analyzer mainframe. And I have the output connected
to channel two of the DC power analyzer. The DC power analyzer has two N6782 Source/Measure
modules to provide both power and loading for testing the line regulation of the voltage regulator.
Here in my diagram, I have both the output
voltage of the regulator and the input voltage of the regulator displayed and line regulation
is the change in output voltage and response to the change in input voltage of the regulator.
Here we have the regulator connected to the N6705B DC Power Analyzer. Again, channel one,
we have one module providing bias to the device under test. And we have the second N6782 acting
as an electronic load to load the output of the voltage regulator. And we’ll use the
first source to provide a voltage square wave to the input of the voltage regulator and
we’ll use the second load, the second module as a load and it will be measuring the output
voltage of the regulator. These modules have built-in high speed digitizing read back for
voltage and current making it easy to capture voltage and current wave forms for the device
under test. Here we have the 14585A Control and Analysis Software user interface, which
is being used to control the N6705 DC Power Analyzer. It’s a quick and easy way to set up
and display results from the power analyzer. Although, everything you see here in the software
can be done directly on the front panel of the DC Power Analyzer as well.
The first thing we need to do is set up the DC bias conditions for our sourcing and loading
for the device under test. And to do that, I first need to go over on the right of our
software and click on our instrument control panel to bring up the settings and controls
for the modules. First what I’m going to do is set up output one,
so let me click on output one and then I’m going to set its voltage and current
parameters and here it’s set to be a two quadrant DC power supply. We have set it for
voltage priority, because we want a voltage source and we have set it up for 13 volts
output, that’s our minimum input line voltage for the regulator as the low line condition.
Now we want to set up output two, so let me select output two. And here, now we have
our source conditions. Output two is acting as an electronic load so again, here we have
selected CC load conditions. As you can see, we have a list of preconfigured conditions
for quickly and easily setting up the particular operation for the particular module we are using.
We have set it up for minus 50 milliamps of drain current. You can see its negative
current because it’s in a loading operation. So we are now completed setting up our steady
state biasing conditions. We now need to set up our arbitrary waveform conditions, to be
able to pulse the line voltage high and low. For that, we have our ARB function and I can
go up here and I can click on the ARB screen tab and bring up the ARB settings.
What we need to do is apply the voltage square wave to the input one voltage so going down to
the bottom of the screen here, I have selected a sequence being applied to input one voltage
and as you can see, I’m using a square waveform and the square waveform is stepping from 13 volts
up to 18 volts, 18 volts representing the high line condition.
And I’m using a one-hertz frequency, that’s to provide plenty of steady state at each
level to be able to get a good DC reading on the line regulation. So now, we have completed
setting up our ARB function. I need to set up my measurement conditions. And for that,
I am going to use the data logger for capturing and displaying the results, so I’m going
to click on my data logger selecting screen button and now we are in data logging display mode.
And what I want to do is capture input voltage and output voltage, so I have selected
V1 input voltage and V2 the output voltage to capture for line regulation testing.
I’ve set up for 200 milliseconds per division, we are using a one-hertz signal and I’ve
set up my other acquisition parameters accordingly. I’m triggering on the ARB run button in
order to capture the waveform. So, all I need to do is first start the data logger by clicking
on the start button down here on the bottom lower corner and then I need to start up the
ARB function and that will start the capture.
And so, you can see, I have captured up here
the yellow trace, the input voltage, the line condition going from a low line condition
of 13 volts up to a high line condition of 18 volts and below it the green trace is the
output voltage response, the line regulation of the voltage regulator, here is a voltage
for the low line condition and here is a voltage for the high line condition and to be able
to measure that I’ll use my markers which I have up on the ends of the graph and let
me first move them to a portion of the curve that has high line voltage being applied,
and so down in the numerical results, I find that I have an average voltage on the output
of 10.033 volts roughly. Now let me move the markers to a low line condition.
And now I find down here again in the numerical
results, I now have about 10.028 volts so I’m seeing about 5 millivolts of line regulation
which is roughly about .05 percent of the output of a 10 volt regulator which is very
typical of a linear regulator performance and so this is a way you can test the line
regulation of a voltage regulator, easily accomplished using the N6782 DC Source/Measure module for
functional tests together with the N6705B DC Power Analyzer and 14585A Software.
Thank you.