Teledyne Power Analyzer Package User Manual
Operator's
Manual
Power Analysis Software
Power Analysis Software Operator's Manual
© 2013 Teledyne LeCroy, Inc. All rights reserved.
Unauthorized duplication of Teledyne LeCroy documentation materials other than for internal sales and distribution purposes is strictly prohibited. However, clients are encouraged to distribute and duplicate Teledyne LeCroy documentation
for their own internal educational purposes.
Power Analysis and Teledyne LeCroy are registered trademarks of Teledyne LeCroy, Inc. Windows is a registered trademark of Microsoft Corporation. Other product or brand names are trademarks or requested trademarks of their respective holders. Information in this publication supersedes all earlier versions. Specifications are subject to change without
notice.
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Contents
Power Analysis Software Overview 2
Software Overview 3
Required Equipment 3
Method of Operation 4
Power Analysis Software Dialogs 4
Deskew Voltage and Current Channels 6
Power Device Analysis 9
Device Analysis Preliminary Setup 9
Set Up Device Analysis Input Channels 11
Identify Switching Zone 12
Device Losses Test 13
Device Safe Operating Area Test 15
Device B-H Curve Test 16
Device Dynamic On-resistance Test 17
Device dv/dt Test 18
Control Loop Analysis 19
Control Loop Analysis Preliminary Setup 19
Set Up Control Loop Analysis Source Channel 21
Closed Loop Test 22
Line Power Analysis 23
Line Power Analysis Preliminary Setup 23
Set Up Line Power Analysis Source Channels 23
Line Power Test 25
Line Harmonics Test 26
Performance Analysis 28
Performance Efficiency Test 28
Performance Ripple Test 30
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Power Analysis Software
Power Analysis Software Overview
The Power Analyzer Software (PAS) option helps measure and analyze the operating characteristics of
power-conversion devices and circuits for off-line, DC-DC and DC-AC power circuit designs. It provides
automatic detection and measurement of turn-on and turn-off switching device losses, as well as conduction losses. Areas of power loss are clearly delineated by a color-coded waveform overlay, and tools
are provided to reduce measurement errors. A streamlined user interface guides you through the various stages of analysis.
PAS consists of these major analysis areas:
l Device Analysis covers the measurement of switching device performance such as device instant-
aneous power, switching losses, safe operating area (SOA), saturation voltage, dynamic on-resistance, dv/dt or di/dt, and saturation hysteresis curves of magnetic devices. With PAS, these
device measurements can be made either on a test stand or in circuit while the devices are operating in a power conversion system.
l Control Loop Analysis covers the acquisition and analysis of information contained in a power con-
version circuit’s modulated control signal. It analyzes modulation changes in pulse width (PWM),
duty cycle, frequency, or period as the feedback loop responds to changes in line and/or load, as
well as during start-up and shut-down.
l Line Power Analysis covers the measurement of line voltage and current applied to an off-line
power conversion device. Real power, apparent power, power factor, crest factor, and line harmonics are measured. Analysis of line harmonic content is included to assist the design and evaluation engineer in designing for pre-compliance to EN 61000-3-2 requirements.
l Performance Analysis computes the efficiency of the power supply and adds the measurements to
determine the amount of ripple a power source generates.
All Teledyne LeCroy voltage and current probes are integrated with the software, and measurements are
automatic and precise. Documentation and Flashback to prior power-circuit analyses can be accomplished through LabNotebook.
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Software Overview
Required Equipment
You will need this equipment to utilize the Power Analysis Software.
Oscilloscope
Power Analyzer Software option operates on any Teledyne LeCroy Windows-based oscilloscope. For analysis of phenomenon requiring the acquisition of many cycles, an oscilloscope with a minimum memory
of 1 Mpt per channel is recommended. Steady-state analysis can be accomplished with shorter record
lengths. Two acquisition channels are adequate for most measurements, but a four-channel oscilloscope
is recommended if you would like to analyze multiple devices or use complex triggering. To see the small
signal details hidden in large signals, such as a saturation voltage, or ripple transient analysis, a 12-bit
oscilloscope is recommended.
Probes
Voltage Probes. A wide range of voltage probes are available and are integrated within this software.
Proper section of the following probes should match circuit details, including: single-ended passive,
single-ended high voltage, differential high-voltage, active single and differential high-frequency, and 50
Ohm transmission line probe. Differential voltage probes will support your measurement environment
including isolating your circuits from line power, measuring currents with current sensing resisters, and
viewing switching transients in power supply ripple measurements.
Current Probes. The measurements described in Power Device Analysis require precision wide-bandwidth current probes with DC measurement capability. We recommend Teledyne LeCroy:
l AP015 or CP030 DC-to-50 MHz, 30-ampere current probe
l CP031 DC-to-100 MHz, 30-ampere current probe
l CP150 and CP500 high-current probes
Other, higher current probes are also available from Teledyne LeCroy.
Teledyne LeCroy ProBus probes automatically use correct units and scaling for power measurements
when used with the Power Analyzer software. When other probes are used, the Power Analyzer Software
provides methods for entering the correct units and scaling.
When a channel is selected as the current input within the software, its units are automatically changed
to Amperes. When a differential probe is used to measure the voltage across a shunt resistor, the Power
Analyzer software will support the proper amps/div scaling when the resistor value is entered.
Differential Amplifier
Measuring high-side gate drive signals in an off-line application and capturing a device saturation voltage
to measure conduction loss or Rds(on) are challenging to do. These require a voltage probing solution
that has high CMRR, fast overdrive recovery, voltage clamping (so the oscilloscope is not overdriven),
compensation flatness, gain/ amplification to see small signal details, and precise offset generation to see
the switching device’s turn-off performance. The Teledyne LeCroy DA1855A and its associated DXC Series
Passive Differential Probes are required.
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Deskew Signal Source
To assist with eliminating propagation delay differences among voltage and current probes used for
device testing, the DCS015 dekew calibrated source is recommended. This source has time-coincident
voltage and current signals used to adjust deskew values within the oscilloscope channel controls and
Power Analyzer software.
Method of Operation
The general process for using the software to conduct power analysis is:
1. Set up DUT test circuit, consider isolation requirements, attach probes, and setup oscilloscope trigger
This includes all physical circuit setup and oscilloscope setup for timebase and acquisition triggers. We
show recommended connections, probing points, and trigger events for each type of analysis in the preliminary setup topics.
2. Set up voltage and current source channels
Make all Vertical settings on the channels to be used for a test and perform all necessary preliminary
adjustments to ensure measurement accuracy.
Because signals associated with power devices are relatively fast, it is important to determine whether
the propagation time for the current and voltage signal paths are the same. Signal delay characteristics of
the voltage and current probes, as well as the distance the signals must travel from the probe tips to the
input of the oscilloscope, can cause time-coincident points on the voltage and current signals to be
sampled by the oscilloscope at different times. Even a small time difference can cause significant errors to
occur in the measurements. Therefore, we recommend performing a preliminary deskew procedure and
repeating it whenever you change to the physical characteristics of the probes or the bandwidth/filter settings of the input channels.
Likewise, Fine DC Adjust voltage channels to remove any residual charge that may be in the probes.
3. Select analysis type, tests to be performed, and measurements to be displayed
This step comprises most of the work you will do in the Power Analyzer Software. Once the source channels are set up, various tests can be performed on the same inputs. The software automatically calculates your selected power measurements and displays them on screen, with test-appropriate trace
annotations and overlays to help you see significant portions of the input waveforms.
Power Analysis Software Dialogs
The Power Analysis Software presents a series of dialogs for setting up measurements specific to testing
switched-mode power supplies ad devices. Generally, the order of the tabs presents the order in which
you proceed to use the software, working from left to right.
Power Analysis Dialog
The first tab is the Power Analysis dialog. This is the main set of controls where you select the Voltage
and Current Source input channels, the Analysis Type, and the specific Tests to run.
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The Power Analysis dialog is also where you control the display of Statistics or Histicons within the Power
Analysis Measurements table, and Clear Sweeps to reset the measurement counter.
The Grid control allows you to quickly change the grid style. The default setting, PowerAuto, displays the
correct number and style of grids for the selected power test. This setting is only available when Power
Analysis is enabled.
Quickly return to the Power Analysis dialog from any other dialog by selecting the leftmost section of the
Power Analysis measurement table.
Input Settings Dialog
The second tab opens the Input Settings dialog, which allows you to adjust the Fine DC Offset and
Deskew values of your probes to increase measurement accuracy.
You can view the result of adjusting Fine DC Offset and Deskew by checking View on the Input Settings
dialog. This is a convenience to assist with fine adjustment; it's not necessary to keep this trace open.
Deskew values are duplicated on the Channel dialog, and the Power Analysis Software incorporates the
Fine DC Offset value in its measurement results.
You also use the Input Settings dialog to select the type of device used to measure current in ProbeType.
Setup Source buttons on the Input Settings dialog enable you to quickly access the source Channel
setup dialogs, where you can adjust input bandwidth limits, set up filters, AutoZero voltage probes, or
DeGauss current probes.
NOTE: When selecting Device Analysis, Losses Test and a Conduction Loss calculation method measuring
Vsat with a 2nd voltage probe, a third set of controls will become available for Deskew and DC Fine
Adjust. These controls are made available for use with a probe or amplifier solution that incorporates
voltage clamping and fast overdrive recovery, such as the DA1855A/DXC100A.
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Zone Identification Dialog
This tab appears only when the Analysis Type is Device. The Zone Identification dialog is used to set up
device switching measurement zones, which adds a set of color overlays and annotations to the Power
Analysis trace.
Other Dialogs
Tabs for other dialogs, such as Device Power, appear only when the corresponding Analysis Type and
Test are selected. They contain rescale controls that allow you to “zoom” the result trace to view more or
less waveform detail . The controls are the same as found on any Zoom dialog, although in this case they
will alter the appearance of the Power Analysis trace instead of opening a new zoom trace.
Deskew Voltage and Current Channels
Use this Deskew procedure to check propagation delay differences between the current and voltage channels. This is very important if these signals are going to be used to make instantaneous power Losses,
Safe Operating Area, or Dynamic On-resistance measurements.
This process can be used to characterize and correct the delay difference between more than one current
and one voltage channel. For instance, if you plan to use one voltage channel and alternate measurements between two current channels, the relationship between the voltage channel and each of the
current channels can be characterized. The same is true if you are using a differential amplifier to capture
voltage at key event points. The amount of deskew required for each combination should be recorded
for later use.
Throughout this procedure, the Voltage source channel is used as the reference trace. Adjust all other
traces to this reference.
1. Recall the oscilloscope's factory default settings.
2. Connect the:
l Voltage probe to Channel 1
l Current probe to Channel 2
l DCS015 Deskew Calibration Source to the EXT input.
3. Set Channel 1 scale to 1 V/div. If using a differential probe on Channel 1, also AutoZero the probe.
4. Set Channel 2 scale to 20 mA/div. DeGauss the current probe.
NOTE: It's good practice to leave the current probe disconnected from the test circuit due to the excitation signal used to DeGauss the probe.
5. Connect the voltage and current probes to the DCS015. Be sure to match the proper voltage probe
polarization and current probe direction to the DCS015.
6. Set the oscilloscope timebase to 20 ns/div and zero delay.
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7. Set the oscilloscope trigger to Channel 1, negative edge, at a level of 2 Volts.
8. Choose Display > Single Grid, then adjust Offset on Channel 1 and Channel 2 so that the voltage
and current waveforms are on top on each other in the middle of the display.
9. Choose Analysis > Power Analysis to open the Power Analysis Software.
10. On the Power Analysis dialog, select C1 as the Voltage source, and C2 as the Current source.
11. On the Input Settings dialog, adjust the Current Deskew value until the slope of the current probe
intersects the voltage waveform at the upper knee of the falling edge.
Tip: You can do this by selecting the Deskew field, then turning the Front Panel Horizontal knob.
12. Repeat the deskew procedure for the differential amplifier or any other probes you have connected
to other channels.
NOTE: The Deskew values you obtain using this procedure are only valid for this particular setup. It is
recommended to repeat the deskew procedure if you change probes, cables, or bandwidth/filter settings
on any channel.
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Power Analysis Software
Falling edge of voltage and current traces before deskew adjustment.
Falling edge of voltage and current traces after deskew adjustment.
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Power Device Analysis
Device Analysis Preliminary Setup
The Device Analysis tests let you make difficult measurements on devices while they operate in circuit.
The exact setup for each measurement will differ depending on what device type is to be analyzed and
where it is located in the circuit.
Test Circuit Setup
Examples in this section are based on connections to an off-line flyback power supply circuit. Measurements are made on devices such as power transistors, snubber diodes, or similar devices in other
topologies.
A typical setup used to analyze the power MOS-FET in an off-line switching power supply is:
l A differential high-voltage probe is connected to Vds on the oscilloscope’s Channel 1.
l A current probe is connected to the drain current, Id, using a current loop into Channel 2.
l A differential amplifier, with a matched differential probe pair, is used to connect to either Vds or
Vgs into Channel 3. This amplifier will need to have voltage clamping and fast over drive recovery
in order to see the saturation voltage and have high CMRR to capture the high-side gates in an offline application.
The example in the figure below uses the oscilloscope’s Channel 4 to acquire a trigger signal indicating
when the load changes from maximum to minimum. You could also use the oscilloscope’s EXT trigger
input.
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