Hello, I’m Ed Brorein, an applications specialist for Agilent Technologies systems product division.
Today I’ll be talking about how to test the load regulation of a voltage regulator.
This will be quickly and easily accomplished using an N6782A Source/Measure module for
functional test. This module will both source and sync current, so it’s an ideal as both
a voltage source and an electronic load. Together with the N6705B DC Power Analyzer main frame,
it forms an ideal platform for testing components like DC voltage regulators and
other power management circuitry.
Here I have wired up a three pin linear regulator. I have set it up for 10 volts operation.
And I have its input connected to one channel of the N6705B where there is a DC power module
installed to power it. And the output is connected to channel two of the DC power analyzer mainframe,
again, where our second module is acting as an electronic load to load its output.
And I’m also using the 14585 Control and Analysis software. This software provides
an easy way to control and set up the N6705B mainframe as well as display the results.
Pretty much everything you can do on this software, you can do on the front panel of
the N6705B mainframe as well. Here on our diagram, we have a display of
DC load regulation. And DC load regulation is the change of the output voltage from a
high level to a low level, and its response to the DC loading going from a minimum current
to a maximum current. And what we have here is an N6782A as a source module providing
a fixed 15 volts into the voltage regulator and we have a second load module, an N6782
drawing a pulse current out of the output of the voltage regulator. The N6782 has high
speed digitizing read-back for its output voltage and current, so it will directly capture
our current and voltage wave forms so we can measure the load regulation response for the
load regulator very easily. Here we have the 14585 Control and Analysis
software user interface controlling the DC power analyzer mainframe and the first thing
we need to do is set up our instrument control. So here on the right, I’ll pull up a control
panel for setting the instrument settings, and let me set up Output 2 here.
And we need to set up Output 2 as an electronic load. As you can see, we have set it up for
CC load operation. We have a pull down menu here that allows us to quickly set up outputs
for any kind of configuration we need whether it’s a source or a load for example.
We have set it up for minus 50 milliamps of DC bias drain current. It’s negative because
it’s operating as a load, not a source. We’ll go to Output 1 and we’ll set it
up as a voltage source. Here we have set it up as a 2 channel, 2 quadrant power supply
in voltage priority to provide 15 volts of bias to our device under test. So now we have
set up the DC bias conditions for the device under test, but for load regulation, we need
to set up a pulse loading conditions on our load or our second output and for that, we
need to use an ARB function or an arbitrary waveform function which we do have built
in this platform for that purpose. So I’ll go into our ARB setup screen and here we
are able to setup ARB functions on the outputs for this kind of application. And down at
the bottom here, I’m applying the ARB sequence to Output 2 current to be able to pull a
pulse load current from our device under test. So here is our pulsed ARB waveform and it
starts out at a minus 50 milliamps, that’s our DC quiescent bias condition and we’re
pulsing down to minus 500 milliamps, that’s our full load condition and then we go back
to our quiescent state again. And I’m pulsing a very short duration that’s a 5 percent
duty cycle in order to minimize the heating effect on our device under test. So now we
are done setting up our load conditions and now we need to set up our measurement conditions.
For that, I’ll need to go back into our oscilloscope screen and set up our measurement
conditions. So, we’re now back into our oscilloscope display screen. And what I have
here down on the bottom is I have set up our vertical and horizontal scaling factors.
I have two milliseconds per division. Here I am setting up and selecting Output 2 voltage
and current because we want to measure the load voltage and load current. And I have
set up my triggering accordingly to capture the wave forms of the current and voltage.
So now that I have set up our measurement conditions, all I need to do now is run it
to capture our results. In order to do that I’ll first start up the oscilloscope function
capture by clicking on this icon. It’s now in a starting mode, but it’s waiting for
a trigger and as soon as I start up our ARB function it will provide the current that
will start the trigger. And now you can see we have captured our voltage and current waveforms
of the output loading of this device under test to capture load regulation. And what
we have here is on the top, we have our load current pulsing down to 500 milliamps of full
load condition and then we have our output voltage in response to that load condition.
And so, I need to measure the DC levels at both no load and full load condition. So,
we have markers for that purpose and let me place the markers on an unloaded portion of
the wave form. And so, I have captured a portion of that
wave form and if I go down to the numerical results here, I will see that I have an average
current of 10.029 volts. Now, let me move the markers to the loaded portion.
And I see I now have 10.015 volts roughly, that equates to roughly 14 milli-volts of
load regulation which out of 10 volts output is 0.14 percent, which is about what you would
expect for a linear regulator. And so this is an approach you can take for testing the
load regulation of a DC voltage regulator made easy and quick using an N6782 Source/Measure
module for functional tests, the N6705 DC Power Analyzer, and the 14585 software.
Thank you.