Power Measurement and Analysis Software
Features & Benefits
- Hi Power Finder and Magnetic Property Pinpoint the Sources of Reliability Problems
- Power Loss Measurements at the Switching Device and Magnetic Component Improve Switching Power Supply Efficiency
- Sophisticated Report Generation Saves Time
- Customizable Safe Operating Area Mask Testing with Linear and Log Scale for Reliability Testing
- In-circuit Bpeak, Permeability, and Coercive Force Measurements Determine the Reliability of the Magnetic Component
- Automatic Ripple Measurement Setup Eliminates Manual Processes
- Spectral Analysis Locates Ripple and Noise on the Output Voltage and EMI Issues with the Switching Power Supply
- Precompliance Testing to the EN61000-3-2, EN61000-3-2 AM14, and MIL 1399 (400 Hz) Standards Reduces Compliance Test Time and Risk
- Automated THD, True Power, Apparent Power, Power Factor, and Crest Factor Features Eliminate Tedious Manual Calculations
- Modulation Analysis quickly provides Accurate Active Power Factor Characterization
- Automatic Deskew ensures Accurate, Time-correlated Results
- Correct Scale Factor and Unit Display while using Third-party Current Probes Eliminates Manual Calculations and Human Error
- Power Loss Measurement at Switching Device and Magnetic Component
- Characterization of Power Semiconductor Devices
- Optimal Drive Characterization of Synchronous Rectifiers
- Measurement and Analysis of Ripple and Noise
- Precompliance Testing to IEC Standard EN61000-3-2, EN61000-3-2 AM14, MIL Standard 1399 (400 Hz), and up to 100 Harmonics
- Debugging Active Power Factor Correction Circuits
DPOPWR Power Measurement and Analysis software transforms Tektronix Windows oscilloscopes into sophisticated analysis tools that quickly measure and analyze power dissipation in power supply switching devices and magnetic components, and then generates detailed test reports in customizable formats. DPOPWR, used with an MSO/DPO5000, DPO7000 or MSO/DSA/DPO70000 Series oscilloscope and differential voltage and current probes, forms a complete measurement system for power supply design and test.
DPOPWR provides a number of specific measurements to characterize power supplies: Magnetic Component Analysis, Switching Component Analysis, Input Analysis, and Output Analysis. Finally, DPOPWR provides a convenient report generator to document the test results.
Magnetic Component Analysis
Magnetic components are an important part of any power supply system. Inductors and transformers are used as energy storage devices in both switch-mode and linear power supplies. Some power supplies also use inductors in filters at their output. Given their important role in the system, it is essential to characterize these magnetic components to determine the power supply's stability and overall efficiency.
Inductors exhibit increasing impedance with frequency, impeding higher frequencies more than lower frequencies. This behavior is known as inductance and is measured in units of Henries. The inductance can be measured automatically with DPOPWR.
Magnetic Power Loss
Figure 1 – Total magnetic power loss measurement for an inductor.
An analysis of magnetic power losses is essential to accurately characterize the efficiency, reliability, and performance of a switching supply. DPOPWR measures the total magnetic power loss (which includes core losses and copper losses) as shown in Figure 1.
Figure 2 – B-H plot using DPOPWR.
The properties of magnetic materials are described by the magnetic flux density (B), magnetic field intensity strength (H), and the magnetic permeability of a material (μ). B-H curve plots are often used to verify the saturation (or lack thereof) of the magnetic elements in a switching supply and provide a measure of the energy lost per cycle in a unit volume of core material. DPOPWR measures the voltage across the magnetic element and the current flowing through it, and plots B versus H, as shown in Figure 2.
Switching Component Analysis
The accurate calculation and evaluation of energy loss in power supplies has become even more critical with the drive to higher power conversion efficiency and greater reliability.
Switching Loss Measurements
Figure 3 – DPOPWR switching loss measurements.
Although almost all components of a power supply contribute to energy losses, the majority of energy losses in a switch-mode power supply (SMPS) occur when the switching transistor transitions from an OFF to an ON state (turn-on loss) and vice versa (turn-off loss). By measuring the voltage drop across the switching device and the current flowing through the switching device, DPOPWR measures the switching losses as shown in Figure 3.
Hi Power Finder
Figure 4 – DPOPWR Hi Power Finder.
Dynamically changing loads can cause a switching power to exceed its voltage and current limits, and in turn, its power rating. The DPOPWR Hi Power Finder is a unique feature which analyzes the power loss in switching components, ensuring that the instantaneous power remains within the specified limits. The Hi Power Finder is shown in Figure 4.
Safe Operating Area
Figure 5 – DPOPWR Safe Operating Area (SOA) display.
The Safe Operating Area (SOA) plot is a graphical technique for evaluating a switching device to ensure that it is not being stressed beyond its maximum specifications. SOA testing can be used to validate performance over a range of operating conditions, including load variations, temperature changes, and variations in input voltages. Limit testing can also be used with SOA plots to automate the validation. An example of an SOA plot is shown in Figure 5.
Power quality measurements and current harmonics are two common sets of measurements made on the input section of a power supply to analyze the effects of the power supply on the power line.
Figure 6 – DPOPWR power quality measurements.
Power quality refers to a power supply's ability to function properly with the electric power that is supplied to it. These measurements help understand the effects of distortions caused by nonlinear loads, including the power supply itself. The measurements include RMS voltage and current, true and apparent power, crest factor, line frequency, and power factor, as shown in Figure 6.
Figure 7 – DPOPWR current harmonics measurements, including up to 100 harmonics.
Because a switching power supply presents a nonlinear load to the power line, the input voltage and current waveforms are not identical. Current is drawn for some portion of the input cycle, causing the generation of harmonics on the input current waveform. Excessive harmonic energy can affect the operation of other equipment connected to the power line, as well as increase the cost of delivering the electric power. Therefore, power supply designers can use the DPOPWR current harmonics measurements to assure pre-compliance of their designs to industry standards (such as IEC61000-3-2 and MIL Standard 1399) before investing in the official compliance testing. An example of the current harmonics graph display of up to 100 harmonics is shown in Figure 7.
The ultimate goal of a DC-output power supply is to transform input power into one or more DC-output voltages. Especially for switching power supplies, the most important output measurements are line ripple, switching ripple, spectral analysis, and turn-on time.
Line and Switching Ripple
The quality of a power supply's DC output should be clean with minimal noise and ripple. Line ripple measures the amount of AC-output signal related to the input line frequency. Switching ripple measures the amount of AC signal related to the switching frequency. The output line ripple is usually twice the line frequency; whereas the switching ripple is typically coupled with noise and in the kHz frequency range. DPOPWR greatly simplifies the separation of line ripple from switching ripple.
Figure 8 – DPOPWR output spectral analysis measurements.
Spectral Analysis is used to analyze the frequency components that contribute to the electromagnetic interference (EMI) of the power supply. It also measures the noise/ripple at the output DC voltage frequency range. Like the oscilloscope's FFT, the DPOPWR Spectral Analysis displays the magnitudes of the output signal's frequency components versus frequency, allowing the identification of each of the AC components, as shown in Figure 8.
Turn-on time is defined as the time it takes from when the power supply is turned on to when a valid, usable output is available. DPOPWR automates this measurement on up to three outputs simultaneously.
Data collection, archiving, and documentation are often tedious but necessary tasks in the design and development process. DPOPWR is equipped with a report generation tool that makes the documentation of measurement results easy and effortless. Instead of simply generating standard reports for all measurements, DPOPWR allows you to customize report templates and layout.
Power Device Analysis
Switching Analysis - Switching Loss, Hi Power Finder, Safe Operating Area (SOA), SOA Mask Editor with Mask Testing, Dynamic ON Resistance, di/dt, dv/dt.
Modulation Analysis - Pulse Width, Duty Cycle, Period, and Frequency Variation versus Time.
Magnetic Loss, Inductance, Maximum Magnetic Flux Density, Permeability, Remanence Flux Density, Coercive Force.
Input Analysis - True Power, Apparent Power, Power Factor, Crest Factor, Current Harmonics, THD, precompliance testing for EN61000-3-2, EN61000-3-2 AM14, and MIL Standard 1399 (400 Hz) standards.
Output Analysis - Ripple due to line frequency and switching frequency, Turn-on Time, Spectral Analysis (automated spectral analysis by setting start frequency, stop frequency, and resolution bandwidth).
Create template, custom report layout, and report generation.
Tektronix Oscilloscopes and Probes Supported
For a complete listing of compatible probes for each oscilloscope, please refer to http://www.tek.com/probes for specific information on the recommended models of probes and any necessary probe adapters.
Power Measurement and Analysis Software.
New Instrument Orders
Power Bundle for MSO/DPO5000 and DPO7000 Series. Bundle includes P5205A, TCP0030, DPOPWR, TPA-BNC adapter, deskew fixture 067-1686-xx
Additional information about power analysis is available at www.tek.com/applications/design_analysis/power.html.
DPOPWR solution updates and up-to-date software upgrades are available at www.tek.com/downloads.