Hi. My name is Bob Zollo with Agilent Technologies, and today I’d like to share with you some
new equipment that’s designed for testing DC to DC converters. What I have in front
of me here is a demo board that has a DC to DC converter in the center, and the measurement
we’re going to make on this DC to DC converter is an efficiency measurement. Which is,
of course, very important to have efficient DC to DC converters because an efficient DC to DC
converter means that the device that it’s inside of like a handset or some kind of wireless
device will have a longer runtime off its battery if the DC to DC converter is efficient.
Now normally to do an efficiency test on a DC to DC converter you need quite a bit of
test equipment in your R&D lab, so what you need is a power supply on the input side of
the DC to DC converter to power it up. You’d need an e-load on the output side of the
DC to DC converter, and that would need to be a programmable load that can be swept so you
can measure the efficiency at different operating points. And you’d also need a volt meter,
an oscilloscope, or a datalogger or something that can acquire the data as you’re doing
that sweep. And you also need to accurately measure current because the measuring of the
current is going to be critical to coming up with an accurate efficiency measurement.
And therefore, you’d need some current shunts or something like that. Now, that test setup
is quite complicated. It takes a long time to set up and to get good measurements from.
The N6705B DC Power Analyzer is a single integrated instrument that can make those same measurements,
a much faster setup time, and much more accurately. So it simplifies the measurements that you’ll be
making on a DC to DC converter. Now this is a modular system. We have two modules installed
in it, an N6781 battery drain analyzer SMU in channel one and similarly an N6781A battery
drain analyzer in channel number two. Now, channel number one will be connected to the
input side of the DC to DC converter, sourcing the power, and channel number two will be
on the output side of the DC to DC converter acting as an e-load, absorbing the power.
But the critical function of that e-load side is it’s going to sweep from low power to
high power, so you can actually measure the efficiency across the entire operating range
of the DC to DC converter, and that’s the measurement that we’ll be making. So let
me refer you to this block diagram here. What we have is the DC to DC converter. This is
a 2.5 volt in, 3.2 volt out, operating at about 1 amp. So the input side is an SMU set
to 2.5 volts constant voltage. The output side is the e-load set to 3.2 volts, but it’s
going to be sweeping the load current from low current of about 0 amps up to full current
of 1 amp and then we’ll be plotting the input power versus the output power to measure
efficiency. We’re going to use some software to do that. It’s the 14585A software, and
I’m going to bring up that software right now. So on the screen here is a datalogger
screen. It’s a grid, and it’s going to take ten seconds do this sweep and we’re
going to see the power in, power out, and a formula which is another feature of this
software. It allows you to do calculations on the traces, and we’re going to have a
formula that is the efficiency, the ratio of power in to power out so that we can see
the efficiency of the DC to DC converter. Now again, the key to this is going to be
sweeping the load. And another function of this software is the ability to generate arbitrary
waveforms. That arbitrary waveform is applied to the load side to change the load on the
output. So we’re going to do a sweep that looks like this. It’s going to take ten
seconds. It’s going to start at low current and sweep up to high current. Now, this looks
backwards because it’s starting high and going low, but this is a load and everything’s
negative. So it’s going to start at zero and sweep down to negative one, which means
pulling full current out of the output side of the DC to DC converter. So what we’re
going to do now is we’re going to start the datalogger, and then we’re going to
start the arbitrary waveform generator. And because this is an integrated instrument,
one of the key features is since they’re both in one box, we can cause the datalogger
to be triggered when you start the arbitrary waveform generator. Now, normally you’d
have separate instruments and you’d have to be pushing buttons on all of them. Because
they’re integrated, they can work together. So we’ve already got the instrument all
set up. It’s pulling current on the load side. It’s sourcing power on the source side.
I will arm the datalogger, and then I will start the arbitrary waveform generator.
It’s going to take ten seconds. You’ll start to see the traces going by up there.
And in a few seconds it’ll be done, and I’ll be able to describe those traces to you.
Okay. Fantastic. We’re done. So now there’s ten seconds of sweep time across
the screen here. Now, what I’m showing in these two colors, the top trace, the yellow
trace is the input power starting at zero power and sweeping up as more power is pulled
out of the device under test up to its full output power of a few watts. And the same
thing on the output side. This is starting at zero power and as the arbitrary waveform
generator sweeps, it begins pulling more and more power. And again, because current is
negative coming out of the device, it looks like the power is going down, not going up.
And here we are at full power here. The pink trace is a formula. It’s the ratio of these
two, and as you can see, it starts off a little bit down and then it reaches some peak power
right around here. And as you begin pulling more and more power out of the device under
test, the efficiency actually goes down. So what this says is this device is most efficient
right around here. Now, I have markers on the screen. Let me move one of these markers
on to see. Right now marker number two is saying we’re sitting at about 83 percent
efficiency. Right there it’s telling us that. But as we start to sweep up into this
higher efficiency area, maybe right about here, we’re achieving about 93 percent efficiency.
So as an R&D engineer, I can very quickly produce this test. I can sweep through and
make measurements across my sweep of efficiency and be able to determine where my most efficient
operating point is. And I can do all that in a single integrated package without having
to do a lot of setup. Thank you.