DSOX4PWR Power Measurement Application User's Guide s1 Notices © Agilent Technologies, Inc. 2007-2009, 2011-2012 No part of this manual may be reproduced in any form or by any means (including electronic storage and retrieval or translation into a foreign language) without prior agreement and written consent from Agilent Technologies, Inc. as governed by United States and international copyright laws. Manual Part Number Version 03.00.0000 Edition October 13, 2012 Available in electronic format only Agilent Technologies, Inc. 1900 Garden of the Gods Road Colorado Springs, CO 80907 USA Trademarks Microsoft®, MS-DOS®, Windows®, Windows 2000®, and Windows XP® are U.S. registered trademarks of Microsoft Corporation. Adobe®, Acrobat®, and the Acrobat Logo® are trademarks of Adobe Systems Incorporated. Warranty The material contained in this document is provided “as is,” and is subject to being changed, without notice, in future editions. 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U.S. Government users will receive no greater than Limited Rights as defined in FAR 52.227-14 (June 1987) or DFAR 252.227-7015 (b)(2) (November 1995), as applicable in any technical data. WA R N I N G A WARNING notice denotes a hazard. It calls attention to an operating procedure, practice, or the like that, if not correctly performed or adhered to, could result in personal injury or death. Do not proceed beyond a WARNING notice until the indicated conditions are fully understood and met. DSOX4PWR Power Measurement Application User's Guide Power Measurement Application—At a Glance The DSOX4PWR Power Measurement and Analysis for the InfiniiVision 4000 X- Series oscilloscopes lets you quickly and easily analyze switching power supply efficiency and reliability. Input Line Analysis AC Input Rectifier Block Output Analysis Transient Response Analysis Turn On Analysis Power Device Analysis Power Transfer and Isolation Output DC Output PWM Controller Modulation Analysis Regulation and Control Figure 1 Switch-Mode Power Supply (SMPS) Block Diagram and Types of Measurements With the Power Measurement Application, you can: • Measure switching loss and conduction loss at the switching device (to help improve efficiency). • Analyze dI/dt and dV/dt slew rate (for reliable operation). • Automate oscilloscope setup for ripple measurements (to eliminate tedious manual oscilloscope set up). • Perform pre- compliance testing to IEC 61000- 3- 2 standards (to reduce compliance testing time). • Analyze line power with total harmonic distortion, true power, apparent power, power factor, and crest factor tests (to quickly provide power quality information). • Measure output noise (ripple). • Analyze modulation using the on- time and off- time information of a Pulse Width Modulation (PWM) signal (to help characterize the active power factor). DSOX4PWR Power Measurement Application User's Guide 3 • Measure how well a circuit rejects ripple coming from the input power supply at various frequencies with the Power Supply Rejection Ratio (PSRR) measurement. The power measurement and analysis license, along with the oscilloscope, high- voltage differential probe, current probe, probe deskew fixture, and passive probe, form a complete power measurement system for power supply design and testing. Included with DSOX4PWR, at no additional charge, is a license for the U1881A PC- based power analysis software package which provides additional offline power measurements and report generation. This guide describes: • Chapter 1, “Prerequisites,” starting on page 9 • Chapter 2, “Getting Started,” starting on page 15 • Chapter 3, “Performing Power Analysis,” starting on page 25 • Chapter 4, “Automatic Power Measurements,” starting on page 63 4 DSOX4PWR Power Measurement Application User's Guide Contents Power Measurement Application—At a Glance 1 Prerequisites Safety 9 Oscilloscope Requirements 9 Bandwidth Requirements 10 Memory Requirements 10 Software Version Requirements 11 Probe Requirements 11 Voltage Probe 11 Current Probe 12 De-Skewing the Voltage and Current Probes 2 3 12 Getting Started Step 1: Access the Power Measurement Application Step 2: Perform channel deskew 16 Step 3: Select the type of power analysis 20 Step 4: Make DUT connections and set up signals 20 Step 5: Change the analysis settings (if available) 22 Step 6: Apply the analysis 22 Step 7: View the analysis results 3 15 23 Performing Power Analysis Input Measurements 25 Power Quality 25 DSOX4PWR Power Measurement Application User's Guide 5 Current Harmonics 29 Inrush Current 34 Switching Measurements Switching Loss 36 Slew Rate 41 Modulation 44 36 Output Measurements 47 Output Ripple 47 Turn On/Turn Off 49 Transient Response 52 Power Supply Rejection Ratio (PSRR) Efficiency 58 4 Automatic Power Measurements Power Factor Real Power 63 64 Apparent Power 64 Reactive Power 64 Crest Factor 65 Phase Angle 65 Output Ripple Input Power Efficiency 66 66 Peak Current Transient 65 65 Output Power 6 55 67 67 Turn On Time 67 Turn Off Time 67 DSOX4PWR Power Measurement Application User's Guide Power Loss 68 Power Loss/Cyc Energy Loss 68 68 Index DSOX4PWR Power Measurement Application User's Guide 7 8 DSOX4PWR Power Measurement Application User's Guide DSOX4PWR Power Measurement Application User's Guide 1 Prerequisites Safety 9 Oscilloscope Requirements 9 Probe Requirements 11 This chapter describes safety considerations and the necessary requirements for using the Power Measurement Application. Safety WA R N I N G When connecting to a circuit with hazardous voltages, make sure the probes and other components are used within their ratings. Refer to the probes' and other components' documentation. Oscilloscope Requirements The DSOX4PWR Power Measurement Application works with the 4000 X- Series digital storage oscilloscopes (DSO). • The InfiniiVision 4000 X- Series oscilloscopes come in 200 MHz, 350 MHz, 500 MHz, 1 GHz, and 1.5 GHz bandwidth models, with 2 Mpts or 4 Mpts of memory. Characteristics of the power supply under test determine the oscilloscope bandwidth and memory required. • “Bandwidth Requirements" on page 10 • “Memory Requirements" on page 10 s1 9 1 Prerequisites • “Software Version Requirements" on page 11 Bandwidth Requirements The bandwidth requirements of the oscilloscope and probe are driven by the slew rate (rise/fall times) of the switching device. For oscilloscopes with Gaussian response (typical for 1 GHz and lower bandwidth oscilloscopes), the oscilloscope's rise time is commonly related to the oscilloscope's bandwidth using the formula: rise time = 0.35/bandwidth To measure an input signal's rise time with ±5% error, the oscillosope's rise time must be 1/3 of the input signal's rise time. Therefore, the oscilloscope bandwidth required is: BW = [ 0.35 / (input signal rise time / 3) ] For example, a switching device whose rise time is 10 ns requires oscilloscope (and probe) bandwidth of 105 MHz. Memory Requirements The memory requirements of the oscilloscope depend on the time range and the types of signals to capture: memory depth = time range * sample rate • For switching device signals: If you need to capture the switching signals for the duration of half the mains cycle (60 Hz), with a slew rate of 50 ns (using a sampling rate that is four times the required bandwidth), memory depth = 8.333 ms * 21 MHz * 4 = 699972 points. With InfiniiVision 3000 X- Series oscilloscopes, the sampling rate is determined by time range setting. In the above case, the sample rate in High Resolution mode for the time range of 8.333 ms is 100 MSa/s; therefore, the memory depth needed is 833300 points. • For input AC line signals: You need to capture a few cycles in order to plot the FFT. Resolution of the FFT plot = sampling rate / data size. The expected harmonics are in multiples of 50/60 Hz. 10 DSOX4PWR Power Measurement Application User's Guide 1 Prerequisites Because the input signals have low frequency components, a high sampling rate is unnecessary. For example, the RTCA- DO- 160E specification states that a sampling rate of 100 kSa/s and higher should be sufficient. For a 60 Hz signal, to capture 10 cycles you need to capture a duration of 83.33 ms. The InfiniiVision 3000 X- Series oscilloscopes set the sampling rate to be 10 MSa/s for the above time range. The memory depth required is 83330 points with an FFT resolution of 4.77 Hz. Software Version Requirements Table 1 Oscilloscope Software Version Required Oscilloscope Family Software Version Required InfiniiVision 4000 X-Series 3.00 or later Probe Requirements • “Voltage Probe" on page 11 • “Current Probe" on page 12 • “De- Skewing the Voltage and Current Probes" on page 12 Voltage Probe You can use the following voltage probes: • Agilent N2791A differential probe, 25 MHz, 700 V dynamic range. • Agilent N2790A differential probe with AutoProbe interface, 100 MHz, 1.4 kV dynamic range. • Agilent N2792A differential probe, 200 MHz bandwidth, 20 V dynamic range. • Agilent N2793A differential probe, 800 MHz bandwidth, 15 V dynamic range. • Agilent N2891A high- voltage differential probe, 70 MHz bandwidth, 7 kV dynamic range. DSOX4PWR Power Measurement Application User's Guide 11 1 Prerequisites • Agilent 1141A differential probe, 200 MHz bandwidth, 400 V dynamic range. • Agilent 10070D passive probe 1:1, 20 MHz bandwidth, 400 V max. input (for power supply noise measurement and for Power Supply Rejection Ratio measurement). • Agilent N2870A passive probe, 1:1, 35 MHz bandwidth, 55 V max input (for power supply noise measurement and for Power Supply Rejection Ratio measurement). For voltage probe bandwidth requirements, see “Bandwidth Requirements" on page 10. The probe's voltage range required depends on the input signals to measure. An AC- DC switch mode power supply needs a high voltage range probe because the switching signals and input line signals can go up to 700 Vpp. For a DC- DC switch mode power supply, a smaller probe voltage range is sufficient because the signal amplitudes are much smaller. A passive probe is typically used to measure DC output and transient response. Current Probe You can use the following Agilent AC/DC current probes: • 1147B 50 MHz bandwidth, 15A peak. • N2893A 100 MHz bandwidth, 30A peak. • N2780A 2 MHz bandwidth, 500A peak. • N2781A 10 MHz bandwidth, 150A peak. • N2782A 50 MHz bandwidth, 30A peak. • N2783A 100 MHz bandwidth, 30A peak. For current probe bandwidth requirements, see “Bandwidth Requirements" on page 10. De-Skewing the Voltage and Current Probes To ensure accurate power loss measurements, use the U1880A deskew fixture to adjust the skew for any time delay differences between the current probe and voltage probe signal paths. 12 DSOX4PWR Power Measurement Application User's Guide Prerequisites 1 The procedure on de- skewing probes is described in Chapter 2, “Getting Started,” starting on page 15. Table 2 U1880A Deskew Fixture Environmental Characteristics Temperature Operating: –10 °C to +55 °C Non-operating: –20 °C to +60 °C Humidity Operating: 95% RH at 40 °C for 24 hr Non-operating: 90% RH at 65 °C for 24 hr Altitude Operating: to 4,570 m (15,000 ft) Non-operating: to 15,244 m (50,000 ft) Indoor use Rated for indoor use only DSOX4PWR Power Measurement Application User's Guide 13 1 14 Prerequisites DSOX4PWR Power Measurement Application User's Guide DSOX4PWR Power Measurement Application User's Guide 2 Getting Started Step 1: Access the Power Measurement Application 15 Step 2: Perform channel deskew 16 Step 3: Select the type of power analysis 20 Step 4: Make DUT connections and set up signals 20 Step 5: Change the analysis settings (if available) 22 Step 6: Apply the analysis 22 Step 7: View the analysis results 23 This chapter gives an overview of the steps you must take when first performing power measurements. Step 1: Access the Power Measurement Application To access the power measurements application on the oscilloscope: 1 Press the [Analyze] key. 2 Press Features; then, select Power Application. 3 Press Features again to enable power measurements. s1 15 2 Getting Started Next • "Step 2: Perform channel deskew" on page 16 Step 2: Perform channel deskew To make accurate power loss measurements, you must perform current and voltage channel deskew using the U1880A deskew fixture. The channel deskew procedure calibrates the time delay between current and voltage probes. You need to perform the deskew procedure once initially, and you should re- run the procedure when any part of the hardware setup changes (for example, a different probe, different oscilloscope channel, etc.) or when the ambient temperature changes. To perform the channel deskew: 1 First, demagnetize and zero- adjust the current probe. Refer to the current probe's documentation for instructions on how to do this. 16 DSOX4PWR Power Measurement Application User's Guide Getting Started 2 2 Make connections to the U1880A deskew fixture: Small Loop Large Loop For current probes: • • • • 1147B (50 MHz, 15A) N2893A (10 MHz, 15A) N2782A (50 MHz, 30A) N2783A (100 MHz, 30A) • N2780A (2 MHz, 500A) • N2781A (10 MHz, 150A) Connect high-voltage differential probe to either: • J5 (2.54 mm connector) • J6 and J7 (alligator type) • J2 (2.54 mm connector) • J3 and J4 (alligator type) a Connect D+ and D- of the high- voltage differential probe to the deskew fixture. b Connect the current probe to the current loop with the direction of the arrow pointing towards the current flow. c Make sure the switch on the deskew fixture is set to the appropriate side of the fixture (either "small loop" or "large loop"). d Connect the deskew fixture to a USB port on your oscilloscope or a PC using a USB cable. The USB port supplies power to the deskew fixture. 3 In the Power Application main menu, press Signals. DSOX4PWR Power Measurement Application User's Guide 17 2 Getting Started 4 In the Power Application Signals Menu, press the Voltage softkey and use the Entry knob to select the analog channel probing the voltage signal. 5 Press the Current softkey and use the Entry knob to select the analog channel probing the current signal. 6 Press the Deskew softkey. 7 In the Power Application Deskew Menu, press Auto Deskew. NOTE Use the lowest attenuation setting on the high voltage differential probes whenever possible because the voltage levels on the deskew fixture are very small. Using a higher attenuation setting may yield inaccurate skew values (and affect the measurements made) because the noise level is magnified as well. When the deskew process completes, you see a message indicating whether the deskew was successful, and if so, the settings being used. 18 DSOX4PWR Power Measurement Application User's Guide Getting Started 2 8 Press the Back Back/Up key twice to return to the Power Application main menu. The deskew values are saved in the oscilloscope until a factory default or secure erase is performed. The next time you run the Power Application, you can use the saved deskew values or perform the deskew again. Generally, you need to perform the deskew again when part of the test setup changes (for example, a different probe, different oscilloscope channel, etc.) or when the ambient temperature has changed. See Also Next • "U1880A Deskew Fixture User's Guide". • "Step 3: Select the type of power analysis" on page 20 DSOX4PWR Power Measurement Application User's Guide 19 2 Getting Started Step 3: Select the type of power analysis 1 In the Power Application main menu, press the Analysis softkey; then, turn the Entry knob to select the type of power analysis. The following types of power analysis are available: • Current Harmonics. • Efficiency. • Inrush Current. • Modulation. • Power Quality. • Switching Loss. • Transient Response. • Turn On/Turn Off. • Output Ripple. • Power Supply Rejection Ratio (PSRR). • Slew Rate Next • "Step 4: Make DUT connections and set up signals" on page 20 Step 4: Make DUT connections and set up signals For each type of power analysis, there is a Signals softkey and menu for specifying the oscilloscope channels being used and setting other related options. 1 In the Power Application main menu, press the Signals softkey. 2 In the Power Application Signals Menu, connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. 20 DSOX4PWR Power Measurement Application User's Guide 2 Getting Started 3 In the above example, you would press the Voltage and Current softkeys and make sure the proper analog channel is selected. NOTE Be sure to select the proper attenuation factor used for the voltage probe. The attenuation factor multiplied by the probe's maximum output voltage gives the maximum input signal. For example, the N2791A probe's maximum output voltage is ±7V, so a 100:1 attenuation ratio gives a maximum input signal of ±700V. NOTE Also, be sure to select the proper attenuation factor used for the current probe. 4 If other softkeys are present for setting related options, like the Cycles softkey in the above example, use them to specify the appropriate settings. DSOX4PWR Power Measurement Application User's Guide 21 2 Getting Started 5 If it is present, press the Auto Setup softkey to automatically scale and position the voltage and current channels and perhaps set the time/div. 6 Press the menu. Next Back Back/Up key to return to the Power Application main • "Step 5: Change the analysis settings (if available)" on page 22 Step 5: Change the analysis settings (if available) If there are settings available for the type of power analysis chosen, there will be a Settings softkey or other softkeys in the Power Application main menu. To specify the power analysis settings: 1 In the Power Application main menu, press the Settings softkey or other softkeys to make the appropriate settings for the type of analysis being performed. For example, the Current Harmonics settings menu looks like: For descriptions of the settings available for each type of power analysis, see Chapter 3, “Performing Power Analysis,” starting on page 25. 2 When you have fininshed changing the settings, return to the Power Application main menu (perhaps by pressing the necessary). Next Back Back/Up key if • "Step 6: Apply the analysis" on page 22 Step 6: Apply the analysis Each type of power analysis provides an Apply softkey for starting the analysis. 1 In the Power Application main menu, press Apply. 22 DSOX4PWR Power Measurement Application User's Guide Getting Started Next 2 • "Step 7: View the analysis results" on page 23 Step 7: View the analysis results Once a power analysis has completed, you can view the results in the following ways: • By viewing the power analysis results on screen. • By adding automatic power measurements. Viewing Power Analysis Results on Screen Adding Automatic Power Measurements Power analysis results are displayed on the oscilloscope screen. For example, here is a Current Harmonics analysis result: Just like adding automatic measurements of voltage (peak- to- peak, max, min, etc.) and time (frequency, period, rise time, fall time, etc.), you can also add automatic power measurements. See Chapter 4, “Automatic Power Measurements,” starting on page 63. DSOX4PWR Power Measurement Application User's Guide 23 2 Getting Started See Also To learn more about the individual types of power analysis, their input signals, their settings, and their results, see: • Chapter 3, “Performing Power Analysis,” starting on page 25 24 DSOX4PWR Power Measurement Application User's Guide DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis Input Measurements 25 Switching Measurements 36 Output Measurements 47 This chapter describes the types of power analysis you can perform with the Power Measurement Application, the proper probing connections to the device under test, signal setup, settings, and results. Input Measurements • "Power Quality" on page 25 • "Current Harmonics" on page 29 • "Inrush Current" on page 34 Power Quality The Power Quality analysis shows the quality of the AC input line. Some AC current may flow back into and back out of the load without delivering energy. This current, called reactive or harmonic current, gives rise to an "apparent" power which is larger than the actual power consumed. Power quality is gauged by these measurements: power factor, apparent power, true power, reactive power, crest factor, and phase angle of the current and voltage of the AC line. Signals Setup 1 With the Power Quality analysis selected in the Power Application main menu, press the Signals softkey. s1 25 3 Performing Power Analysis 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. Figure 2 Typical Configuration for Input Line Analysis Tests a Connect D+ of the voltage probe to the live wire of the AC input. b Connect D- of the voltage probe to the neutral wire of the AC input. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the live wire of the AC input with the direction of the arrow pointing towards the current flow. e Connect the voltage and current probes to the oscilloscope input channels. 3 Press the Voltage and Current softkeys and make sure the proper analog channel is selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Cycles softkey; then, turn the Entry knob to select the desired number of cycles to capture in one acquisition. 6 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage and current channels. Also displayed it the power waveform which is the math multiply operator of the voltage and current waveforms. 26 DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis 7 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Type: softkey; then, turn the Entry knob to select the type of measurement to make in the power quality analysis: • Power Factor — Ratio of the actual power to the apparent power. • Real (Actual) Power — The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction. • Apparent Power — The portion of power flow due to stored energy, which returns to the source in each cycle. • Reactive Power — The difference between apparent power and real power due to reactance. DSOX4PWR Power Measurement Application User's Guide 27 3 Performing Power Analysis • Crest Factor — Crest factor is the ratio between the instantaneous peak current/voltage required by the load and the RMS current/voltage (RMS stands for Root Mean Square, which is a type of average). • Phase Angle — In the power triangle (the right triangle where apparent_power2 = real_power2 + reactive_power2), phase angle is the angle between the apparent power and the real power, indicating the amount of reactive power. Analysis Results To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. The voltage and current waveforms are displayed as well as the input power waveform (waveform math multiply of the voltage and current). Also displayed are the power quality measurements you have selected and applied: • "Power Factor" on page 63 28 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 • "Real Power" on page 64 • "Apparent Power" on page 64 • "Reactive Power" on page 64 • "Crest Factor" on page 65 • "Phase Angle" on page 65 Power quality measurements are calculated using the captured voltage and current waveforms over the number of cycles specified. Automatic Measurements You can add these relevant automatic measurements using the [Meas] key and menu. Automatic Voltage measurements (refer to oscilloscope User's Guide for more information): • AC - RMS Current Harmonics Switching power supplies draw a range of harmonics from the AC mains. Standard limits are set for these harmonics because these harmonics can travel back to the supply grid and cause problems with other devices on the grid. Use the Current Harmonics analysis to test a switching power supply's current harmonics to pre- compliance standard of IEC61000- 3- 2 (Class A, B, C, or D). The analysis presents up to 40 harmonics. Signals Setup 1 With the Current Harmonics analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. DSOX4PWR Power Measurement Application User's Guide 29 3 Performing Power Analysis Figure 3 Typical Configuration for Input Line Analysis Tests a Connect D+ of the voltage probe to the live wire of the AC input. b Connect D- of the voltage probe to the neutral wire of the AC input. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the live wire of the AC input with the direction of the arrow pointing towards the current flow. e Connect the voltage and current probes to the desired oscilloscope channels. 3 Press the Voltage and Current softkeys and make sure the proper analog channels are selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Cycles softkey; then, turn the Entry knob to select the desired number of cycles to capture in one acquisition. 6 Press the Auto Setup softkey to automatically scale and position the voltage and current channels and set the appropriate time/div. Also set automatically is the Hanning FFT window (for better frequency resolution and low spectral leakage). If you choose to set up signals manually, you can select other FFT windows for analysis, such as the 30 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 Blackman- Harris window (for minimal spectral leakage) or the Hamming window (for better frequency resolution and moderate spectral leakage). 7 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Settings softkey. 2 In the Power Application Current Harmonics Menu, make the appropriate settings. Table 3 Current Harmonics Analysis Settings Setting Description Line Frequency Enter the line frequency. Current Harmonics Standard Select the standard to perform compliance testing on the current harmonics. • IEC 61000-3-2 Class A — for balanced three-phase equipment, household appliances (except equipment identified as Class D), tools excluding portable tools, dimmers for incandescent lamps, and audio equipment. • IEC 61000-3-2 Class B — for portable tools. • IEC 61000-3-2 Class C — for lighting equipment. Class C requires a power factor calculation that happens when the Apply softkey (in the Power Application main menu) is pressed. For this reason, you are only allowed to select Class C when the Power Application is disabled — it forces you to press Apply (again) to perform the analysis. • IEC 61000-3-2 Class D — for equipment having a specified power according less than or equal to 600 W, of the following types: personal computers and personal computer monitors, television receivers. Display Choose how to display harmonics: • Table. • Bar Chart. • Off — Harmonics measurement results are not displayed. DSOX4PWR Power Measurement Application User's Guide 31 3 Performing Power Analysis After the analysis has been performed, you can return to the settings menu to change the display type and, if results are displayed in Bar Chart or Table form, press the Scroll Harmonics softkey and use the Entry knob to scroll current harmonics analysis results. 3 When you have fininshed changing the settings, press the key to return to the Power Application main menu. Analysis Results Back Back/Up To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. Table 4 Current Harmonics Test Results FFT waveform 32 Shows the frequency components in the input current. The FFT is calculated using the Hanning window. DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis Table 4 3 Current Harmonics Test Results (continued) Harmonic, Actual Value (RMS), Limit (RMS), Margin, Pass/Fail Status For the first 40 harmonics, these values are displayed: • Actual Value (RMS) — the measured value in the units specified by the Harmonics Unit parameter. • Limit (RMS) — the limit specified by the selected Current Harmonics Standard parameter. • Margin — the margin specified by the selected Current Harmonics Standard parameter. • Pass/Fail Status — whether the value passes or fails according to the selected Current Harmonics Standard. Rows in the table or bars in the chart are color-coded according to pass/fail values. Marginal results are greater than 85% of the limit but less than 100% of the limit. THD (Total Harmonic Distortion) Where: • Xn = voltage or current of each harmonic • X1 = fundamental voltage or current value Saving Harmonics Test Results To save current harmonics test results to a USB storage device 1 Press the [Save/Recall] key. 2 In the Save/Recall Menu, press the Save softkey. 3 In the Save Menu, press the Format softkey and turn the Entry knob to select Power Harmonics data (*.csv) . 4 Press the softkey in the second position and use the Entry knob to navigate to the save location. See the oscilloscope User's Guide for information on navigating storage locations. 5 Finally, press the Press to Save softkey. A message indicating whether the save was successful is displayed. Automatic Measurements You can add these relevant automatic measurements using the [Meas] key and menu. Automatic Power App measurements: • "Apparent Power" on page 64 DSOX4PWR Power Measurement Application User's Guide 33 3 Performing Power Analysis • "Crest Factor" on page 65 Automatic Voltage measurements (refer to oscilloscope User's Guide for more information): • AC - RMS Inrush Current The Inrush current analysis measures the peak inrush current of the power supply when the power supply is first turned on. Signals Setup 1 With the Inrush analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. Figure 4 Typical Configuration for Inrush Current Analysis Tests a Connect D+ of the voltage probe to the live wire of the AC input. b Connect D- of the voltage probe to the neutral wire of the AC input. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the live wire of the AC input with the direction of the arrow pointing towards the current flow. e Connect the voltage and current probes to the oscilloscope input channels. 3 Press the Voltage and Current softkeys and make sure the proper analog channels are selected. 34 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Expected softkey; then, turn the Entry knob to specify the expected inrush current amplitude. This sets the vertical scale of the channel probing current. 6 Press the Max Vin softkey; then, turn the Entry knob to specify the maximum input voltage. This sets the vertical scale of the channel probing voltage. 7 Press the menu. Analysis Results Back Back/Up key to return to the Power Application main To perform the analysis, press Apply in the Power Application main menu. Follow the onscreen instructions. When the analysis has completed, results are displayed. DSOX4PWR Power Measurement Application User's Guide 35 3 Performing Power Analysis The voltage and current waveforms are displayed. Also displayed is this automatic power measurements: • "Peak Current" on page 67 Switching Measurements • "Switching Loss" on page 36 • "Slew Rate" on page 41 • "Modulation" on page 44 Switching Loss The Switching Loss analysis calculates the power dissipated in the switching cycles across the switching device. Typical power losses include: • Switching losses that occur during switching of Vds and Id. 36 DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis • Conduction losses that occur when the switching device (MOSFET) is ON. turn-OFF switching period ON state OFF state turn-ON switching period ON state Id(t) ON state forward voltage drop current probe null offset switching level t Vds(t) 0 P(t) = Vds(t) * Id(t) t 0 conduction loss Figure 5 switching loss false losses due to probe null offset switching loss conduction loss Loss Occurrence in the Power Device Design engineers use this information to improve the power conversion efficiency of the power supply. Switching loss is also used to quantify the power loss that is transferred to the heat sink of the power device. Signals Setup 1 With the Switching Loss analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. DSOX4PWR Power Measurement Application User's Guide 37 3 Performing Power Analysis Figure 6 Typical Configuration for Power Device Analysis Tests a Connect D+ of the voltage probe to the source of the MOSFET. b Connect D- of the voltage probe to the drain of the MOSFET. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the drain of the MOSFET with the direction of the arrow pointing towards the current flow. e Connect the voltage and current probes to the oscilloscope input channels. 3 Press the Voltage and Current softkeys and make sure the proper analog channel is selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage and current channels. 6 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Settings softkey. 2 In the Power Application Switching Loss Menu, make the appropriate settings. 38 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis Table 5 3 Switching Loss Analysis Settings Setting Description V Ref Enter the switching level for the switching edges. The value is in percentage of the maximum switch voltage. You can adjust this value to ignore noise floors. This value specifies the threshold that is used to determine the switching edges. I Ref Enter the switching level for the start of switching edges. The value is in percentage of the maximum switch current. You can adjust this value to ignore noise floors or null offset that is difficult to eliminate in current probes. This value specifies the threshold that is used to determine the switching edges. DSOX4PWR Power Measurement Application User's Guide 39 3 Performing Power Analysis Table 5 Switching Loss Analysis Settings (continued) Setting Description Conduction Choose how to calculate conduction: • Voltage waveform — The Power waveform uses the original data, and the calculation is: P = V x I • Rds(on) — The Power waveform includes error correction: • In the On Zone (where the voltage level is below V Ref) – the Power calculation is: P = Id2 x Rds(on) Specify Rds(on) using the additional softkey. • In the Off Zone (where the current level is below I Ref) – the Power calculation is: P = 0 Watt. • Vce(sat) — The Power waveform includes error correction: • In the On Zone (where the voltage level is below V Ref) – the Power calculation is: P = Vce(sat) x Ic Specify Vce(sat) using the additional softkey. • In the Off Zone (where the current level is below I Ref) – the Power calculation is: P = 0 Watt. 3 When you have fininshed changing the settings, press the key to return to the Power Application main menu. Analysis Results Back Back/Up To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. 40 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 The voltage and current waveforms are displayed, as well as the power waveform (waveform math multiply of the voltage and current). Also displayed are these automatic power measurements and statistics: • "Power Loss" on page 68 • "Power Loss/Cyc" on page 68 • "Energy Loss" on page 68 Automatic Measurements You can add these relevant automatic measurements using the [Meas] key and menu. Automatic Time measurements (refer to oscilloscope User's Guide for more information): • Frequency Slew Rate The Slew Rate analysis measures the rate of voltage or current change during switching. DSOX4PWR Power Measurement Application User's Guide 41 3 Performing Power Analysis Signals Setup 1 With the Slew Rate analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. Figure 7 Typical Configuration for Power Device Analysis Tests a Connect D+ of the voltage probe to the source of the MOSFET. b Connect D- of the voltage probe to the drain of the MOSFET. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the drain of the MOSFET with the direction of the arrow pointing towards the current flow. e Connect the voltage and current probes to the oscilloscope input channels. 3 Press the Voltage and Current softkeys and make sure the proper analog channel is selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage and current channels. 6 Press the menu. 42 Back Back/Up key to return to the Power Application main DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis Settings Analysis Results 1 In the Power Application main menu, press the Source softkey; then, turn the Entry knob to select either dV/dt or dI/dt as the source for the slew rate analysis. To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. The voltage and current waveforms are displayed along with a differentiate math function waveform that shows the slew rate. Max and Min measurements on the differentiate math function waveform are added and displayed. DSOX4PWR Power Measurement Application User's Guide 43 3 Performing Power Analysis Table 6 Slew Rate Test Results dV/dt [ y(n) - y(n-1) ] / [ x(n) - x(n-1) ], measures the slew rate of Vds of the power device (MOSFET). dI/dt [ y(n) - y(n-1) ] / [ x(n) - x(n-1) ], measures the slew rate of Id of the power device (MOSFET). Modulation The Modulation analysis measures the control pulse signal to a switching device (MOSFET) and observes the trending of the pulse width, duty cycle, period, frequency, etc. of the control pulse signal in response to different events. Signals Setup 1 With the Modulation analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. Figure 8 Continuous Mode Connection for Modulation Analysis Tests a Connect D+ of the voltage probe to the gate of the MOSFET. b Connect D- of the voltage probe to the source of the MOSFET. c On the voltage probe, select the appropriate attenuation ratio. d Connect the current probe to the drain of the MOSFET. e Connect the voltage and current probes to oscilloscope input channels. 44 DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis 3 Press the Voltage and Current softkeys and make sure the proper analog channels are selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Duration softkey; then, turn the Entry knob to specify the time to capture signals. This sets the time scale of the oscilloscope. 6 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage and current channels. 7 Adjust the trigger level to capture waveforms at the same place in each cycle (in other words, stabilize the waveform display). 8 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Source softkey; then, turn the Entry knob to select either Voltage or Current as the source for the modulation analysis. 2 Press the Type: softkey; then, turn the Entry knob to select the type of measurement to make in the modulation analysis: • Average • RMS - AC • Ratio • Period • Frequency • +Width • - Width • Duty Cycle • Rise Time DSOX4PWR Power Measurement Application User's Guide 45 3 Performing Power Analysis • Fall Time Analysis Results To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. The Measurement Trend math waveform vizualization is used to plot the measurement variation for each cycle of the modulation waveforms. Automatic Measurements You can add these relevant automatic measurements using the [Meas] key and menu. Automatic Voltage measurements (refer to oscilloscope User's Guide for more information): • Average • AC - RMS • Ratio Automatic Time measurements (refer to oscilloscope User's Guide for more information): 46 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 • Period • Frequency • +Width • - Width • Duty Cycle • Rise Time • Fall Time Output Measurements • "Output Ripple" on page 47 • "Turn On/Turn Off" on page 49 • "Transient Response" on page 52 • "Power Supply Rejection Ratio (PSRR)" on page 55 • "Efficiency" on page 58 Output Ripple The Output Ripple analysis measures the ripple noise of the power supply output. Signals Setup 1 With the Output Ripple analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. DSOX4PWR Power Measurement Application User's Guide 47 3 Performing Power Analysis Figure 9 Typical Configuration for Output Voltage Ripple Test a Connect the voltage probe (passive or differential) to the DC output of the power supply. b Connect the voltage probe to an oscilloscope input channel. 3 Press the Voltage softkey and make sure the proper analog channel is selected. 4 Make sure the proper probe attenuation factor is set in the oscilloscope for the voltage probe. 5 Press the Duration softkey; then, turn the Entry knob to select the time scale of the measurement. 6 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage channel as well as the time scale. 7 Press the menu. Analysis Results Back Back/Up key to return to the Power Application main To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. 48 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 The output voltage waveforms is displayed along with this automatic power measurement: • "Output Ripple" on page 65 Turn On/Turn Off The Turn On analysis determines how fast a turned on power supply takes to reach 90% of its steady state output. The Turn Off analysis determines how fast a turned off power supply takes to reduce its output voltage to 10% of maximum. Signals Setup 1 With the Turn On/Turn Off analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. DSOX4PWR Power Measurement Application User's Guide 49 3 Performing Power Analysis Figure 10 Typical Configuration for Turn On/Off Analysis Tests a Connect D+ of the input voltage probe to the live wire of the AC input. b Connect D- of the input voltage probe to the neutral wire of the AC input. c On the input voltage probe, select the appropriate attenuation ratio. d Connect the output voltage probe (passive or differential) to the DC output of the power supply. e Connect the voltage probes to the oscilloscope input channels. 3 Press the Input V and Output V softkeys and make sure the proper analog channels are selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage probes. 5 Press the Duration softkey; then, turn the Entry knob to select the time scale of the measurement. 6 Press the Max Vin softkey; then, turn the Entry knob to specify the maximum input voltage. Enter the maximum (peak- to- peak) source voltage amplitude. The source voltage will be used to trigger the oscilloscope in "Turn On Time" test. 50 DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis This value is used to adjust the vertical scale of the channel probing the oscilloscope input voltage. 7 Press the Steady Vout softkey; then, turn the Entry knob to specify the expected steady state output DC voltage of the power supply. This value is used to adjust the vertical scale of the channel probing the oscilloscope output voltage. 8 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Test softkey; then, turn the Entry knob to select whether turn on or turn off analysis is performed: • Turn On — measures the time taken to get the output voltage of the power supply after the input voltage is applied. • Turn Off — measures the time taken for the output voltage of the power supply to turn off after the input voltage is removed. Analysis Results To perform the analysis, press Apply in the Power Application main menu. Follow the instructions on screen. When the analysis has completed, results are displayed. DSOX4PWR Power Measurement Application User's Guide 51 3 Performing Power Analysis The input and output voltage waveforms are displayed. Also displayed is this automatic power measurements: • "Turn On Time" on page 67 • "Turn Off Time" on page 67 Transient Response The Transient Response analysis determines how fast a power supply's output voltage responds to change at the output load. This time is from when the output voltage first exits the settling band to when it last enters the settling band. Signals Setup 1 With the Transient Response analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. 52 DSOX4PWR Power Measurement Application User's Guide 3 Performing Power Analysis Figure 11 Typical Configuration for Power Output Transient Response a Connect the voltage probe (passive or differential) to the DC output of the power supply. b Connect the voltage probe to an oscilloscope input channel. c Connect the current probe to the output load of the power supply. The change in the load current will be used to trigger the oscilloscope to capture the transients. d Connect the current probe to an oscilloscope input channel. 3 Press the Voltage and Current softkeys and make sure the proper analog channel is selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Duration softkey; then, turn the Entry knob to select the time scale of the measurement. 6 Press the Overshoot softkey; then, turn the Entry knob to specify the % of overshoot of the output voltage. This value will be used to determine the settling band value for the transient response and to adjust the vertical scale of the oscilloscope. 7 Press the Steady Vout softkey; then, turn the Entry knob to specify the expected steady state output DC voltage of the power supply. DSOX4PWR Power Measurement Application User's Guide 53 3 Performing Power Analysis This value is used along with the overshoot percentage to specify the settling band for the transient response and to adjust the vertical scale of the oscilloscope. 8 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Settings softkey. 2 In the Power Application Transient Menu, make the appropriate settings. Table 7 Transient Response Analysis Settings Setting Description Initial I Enter the initial load current value. The initial load current will be used as a reference and to trigger the oscilloscope. New I Enter the new load current value. The new load current will be used as a reference and to trigger the oscilloscope. 3 When you have fininshed changing the settings, press the key to return to the Power Application main menu. Analysis Results Back Back/Up To perform the analysis, press Apply in the Power Application main menu. Follow the instructions on screen. When the analysis has completed, results are displayed. 54 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 The voltage and current waveforms are displayed. There are start and end time stamps that mark the measured area. Also displayed is this automatic power measurements: • "Transient" on page 67 Power Supply Rejection Ratio (PSRR) The Power Supply Rejection Ratio (PSRR) test is used to determine how well a voltage regulator rejects ripple noise over different frequency range. This analysis provides a signal from the oscilloscope's waveform generator that sweeps its frequency. This signal is used to inject ripple to the DC voltage that feeds the voltage regulator. The AC RMS ratio of the input over the output is measured and is plotted over the range of frequencies. DSOX4PWR Power Measurement Application User's Guide 55 3 Performing Power Analysis There are many different ways to measure PSRR. Because the oscilloscope has a higher noise floor and lower sensitivity than a network analyzer, it is difficult to measure PSRR any better than - 60 dB. The PSRR test using the oscilloscope is usually acceptable for spot- checking overall PSRR behavior of a power supply under test. Signals Setup 1 With the Power Supply Rejection Ratio (PSRR) analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. Figure 12 Typical Configuration for Power Supply Rejection Ratio Analysis a Connect one voltage probe (passive or differential) to the input of the low- dropout (LDO) regulator (and ground). b Connect a second voltage probe (passive or differential) to the output of the low- dropout (LDO) regulator (and ground). c Connect the waveform generator output to the modulated power supply. One example of a modulated power supply is the "TS200" Option 1A from Accel Instruments. You can also use an injection transformer to inject the oscilloscope's WaveGen signal to a power supply output that is connected to the low- dropout (LDO) regulator. In this case, the injection transformer and power supply combination replaces a modulated power supply (like TS200). 3 Press the Input V and Output V softkeys and make sure the proper analog channels are selected. 56 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis 3 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage probes. 5 Press the menu. Settings Back Back/Up key to return to the Power Application main 1 In the Power Application main menu, press the Settings softkey. 2 In the Power Application PSRR Menu, make the appropriate settings. Table 8 Switching Loss Analysis Settings Setting Description Min Freq Sets the start sweep frequency value. The measurement is displayed on a log scale, so you can select from decade values. Max Freq Sets the end sweep frequency value. The measurement is displayed on a log scale, so you can select from decade values in addition to the maximum frequency of 20 MHz. Max Ratio Specifies the vertical scale of the PSRR math waveform. Amplitude Sets the amplitude value for the waveform generator. Output Load Sets the waveform generator expected output load impedance. 3 When you have fininshed changing the settings, press the key to return to the Power Application main menu. Analysis Results Back Back/Up To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. DSOX4PWR Power Measurement Application User's Guide 57 3 Performing Power Analysis The input and output voltage waveforms and the PSRR math waveform are displayed. Tracking X and Y cursors are also displyed to show the ratio dB values at various frequencies. Efficiency Efficiency analysis tests the overall efficiency of the power supply by measuring the output power over the input power. This analysis requires a 4- channel oscilloscope because input voltage, input current, output voltage, and output current are measured. Signals Setup 1 With the Efficiency analysis selected in the Power Application main menu, press the Signals softkey. 2 Connect your probes to the device under test and to the oscilloscope as shown in the connection diagram. 58 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis Figure 13 3 Typical Configuration for Efficiency Analysis Tests a Connect D+ of the input voltage probe to the live wire of the AC input. b Connect D- of the input voltage probe to the neutral of the AC input. c On the input voltage probe, select the appropriate attenuation ratio. d Connect the input current probe to the live wire of the AC input with the direction of the arrow pointing towards the current flow. e Connect D+ of the output voltage probe to the input path of the load. f Connect D- of the output voltage probe to the return path of the load. g On the output voltage probe, select the appropriate attenuation ratio. h Connect the output current probe to the input path of the load with the direction of the arrow pointing towards the current flow. i Connect the voltage and current probes to the oscilloscope input channels. 3 Press the Input V, Input I, Output V, and Output I softkeys and make sure the proper analog channels are selected. 4 Make sure the proper probe attenuation factors are set in the oscilloscope for the voltage and current probes. 5 Press the Duration softkey; then, turn the Entry knob to specify the time to capture signals. This sets the time scale of the oscilloscope. DSOX4PWR Power Measurement Application User's Guide 59 3 Performing Power Analysis 6 Press the Auto Setup softkey to automatically set the vertical scale and position of the voltage and current channels. 7 Press the menu. Analysis Results Back Back/Up key to return to the Power Application main To perform the analysis, press Apply in the Power Application main menu. When the analysis has completed, results are displayed. The input voltage, input current, output voltage, and output current waveforms are displayed, as well as the input power waveform (waveform math multiply of the input voltage and current). Also displayed are these automatic power measurements and statistics: • "Input Power" on page 65 • "Output Power" on page 66 • "Efficiency" on page 66 60 DSOX4PWR Power Measurement Application User's Guide Performing Power Analysis Automatic Measurements 3 You can add these relevant automatic measurements using the [Meas] key and menu. Automatic Power App measurements: • "Real Power" on page 64 • "Apparent Power" on page 64 • "Reactive Power" on page 64 • "Power Factor" on page 63 • "Phase Angle" on page 65 Automatic Voltage measurements (refer to oscilloscope User's Guide for more information): • AC - RMS • DC - RMS • Maximum • Minimum • Peak- Peak Automatic Time measurements (refer to oscilloscope User's Guide for more information): • Frequency • Phase DSOX4PWR Power Measurement Application User's Guide 61 3 62 Performing Power Analysis DSOX4PWR Power Measurement Application User's Guide DSOX4PWR Power Measurement Application User's Guide 4 Automatic Power Measurements Power Factor 63 Real Power 64 Apparent Power 64 Reactive Power 64 Crest Factor 65 Phase Angle 65 Output Ripple 65 Input Power 65 Output Power 66 Efficiency 66 Peak Current 67 Transient 67 Turn On Time 67 Turn Off Time 67 Power Loss 68 Power Loss/Cyc 68 Energy Loss 68 Power Factor Ratio of the actual AC line power to the apparent power. Real Power / Apparent Power The power factor measurement is made using two source inputs, the voltage waveform and the current waveform, and it also requires a math multiply waveform of the voltage and current waveforms. s1 63 4 Automatic Power Measurements Real Power The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction. The real power measurement is made on one source input that represents power. This is typically a math multiply waveform of the voltage and current waveforms. Apparent Power The portion of AC line power flow due to stored energy, which returns to the source in each cycle. IRMS * VRMS The apparent power measurement is made using two source inputs, the voltage waveform and the current waveform. Reactive Power The difference between apparent power and real power due to reactance. Using the power triangle (the right triangle where apparent_power2 = real_power2 + reactive_power2): Measured in VAR (Volts- Amps- Reactive) 64 DSOX4PWR Power Measurement Application User's Guide 4 Automatic Power Measurements The reactive power measurement is made using two source inputs, the voltage waveform and the current waveform, and it also requires a math multiply waveform of the voltage and current waveforms. Crest Factor Crest factor is the ratio between the instantaneous peak AC line current/voltage required by the load and the RMS current/voltage. Select the voltage source for V crest factor: Vpeak / VRMS Select the current source for I crest factor: Ipeak / IRMS Phase Angle In the power triangle (the right triangle where apparent_power2 = real_power2 + reactive_power2), phase angle is the angle between the apparent power and the real power, indicating the amount of reactive power. Small phase angles equate to less reactive power. The phase angle measurement is made using two source inputs, the voltage waveform and the current waveform, and it also requires a math multiply waveform of the voltage and current waveforms. Output Ripple VMax - VMin The output ripple measurement is made on one source input that is the output voltage waveform. Input Power Input V * Input I DSOX4PWR Power Measurement Application User's Guide 65 4 Automatic Power Measurements The input power measurement is made using two source inputs, the input voltage waveform and the input current waveform, and it also requires a math multiply waveform of the voltage and current waveforms. The input power measurement requires that you specify the channels probing the input voltage, input current, output voltage, and output current in the Power Application Signals Menu and that you perform the automated signals setup by pressing the Auto Setup softkey in the same menu. Output Power Output V * Output I The output power measurement is made using two source inputs, the output voltage waveform and the output current waveform, and it also requires a math multiply waveform of the voltage and current waveforms. The output power measurement requires that you specify the channels probing the input voltage, input current, output voltage, and output current in the Power Application Signals Menu and that you perform the automated signals setup by pressing the Auto Setup softkey in the same menu. Efficiency Output power / input power. The efficiency measurement is made on one source input that represents input power. This is typically a math multiply waveform of the input voltage and input current waveforms. This measurement also requires the output voltage waveform and the output current waveform specified in the signals setup for the Efficiency power analysis. The efficiency measurement requires that you specify the channels probing the input voltage, input current, output voltage, and output current in the Power Application Signals Menu and that you perform the automated signals setup by pressing the Auto Setup softkey in the same menu. 66 DSOX4PWR Power Measurement Application User's Guide 4 Automatic Power Measurements Peak Current The Peak Current can be a positive or negative value, so the result is the larger of the measured maximum or minimum. The peak current measurement is made on one source input that is the current waveform. Transient Transient response time = t2 – t1, where: • t1 = The first time a voltage waveform exits the settling band. • t2 = The last time it enters into the settling band. • Settling band = +/- overshoot % of the steady state output voltage. The transient measurement is made using X cursors on the output voltage signal. Turn On Time Turn On time = t2 - t1, where: • t1 = AC input voltage rises to 10% of its maximum amplitude (Start Time). • t2 = DC output voltage rises to 90% of its maximum amplitude (End Time). The turn on time measurement is made using X cursors on two source inputs, the input voltage waveform and the output voltage waveform. Turn Off Time Turn Off time = t2 - t1, where: • t1 = AC input voltage goes below 10% of its positive peak (or negative peak which ever occurs first) (Start Time). DSOX4PWR Power Measurement Application User's Guide 67 4 Automatic Power Measurements • t2 = DC output voltage drops to 10% of its steady state value (End Time). The turn on time measurement is made using X cursors on two source inputs, the input voltage waveform and the output voltage waveform. Power Loss Pn = Vdsn * Idn, where n is each sample. The power loss measurement is made on one source input that represents power. This is typically a math multiply waveform of the voltage and current waveforms. Power Loss/Cyc Pn = (Vdsn * Idn) * (Time range of zoom window) * (Counter measurement of the voltage of the switching signal), where n is each sample. The power loss per cycle measurement is made on one source input that represents power. This is typically a math multiply waveform of the voltage and current waveforms. This measurement operates when in zoom mode and the counter measurement is installed on the voltage of the switching signal. Energy Loss = (Vdsn * Idn) * sample size, where n is each sample. The energy loss measurement is made on one source input that represents power. This is typically a math multiply waveform of the voltage and current waveforms. 68 DSOX4PWR Power Measurement Application User's Guide Index Symbols % overshoot, 53 current probe attenuation factor parameter, 21 current switching level, 39 Hanning window, 30 harmonic, 33 high-voltage differential probe, 11 Numerics D I 10070D passive probe, 12 1141A differential probe, 12 1147B current probe, 12 4000 X-Series oscilloscopes, 11 deskew (channel), performing, 16 deskew fixture (U1880A), 12, 17 device under test, connection to, 20 dI/dt, 3, 44 dI/dt test results, 44 differential probe, high-voltage, 11 duration for turn on/off analysis, 50 duration of Efficiency analysis, 59 duration of load change, 53 duration of Modulation analysis, 45 duration of output ripple analysis, 48 Duty Cycle, power modulation analysis, 45 dV/dt, 3, 44 dV/dt test results, 44 I crest factor, 65 IEC 61000-3-2 standard, 3, 31 initial load current, 54 input power, 65 inrush current, 34 inrush current analysis, 34 inrush current analysis signals, 34 inrush current test results, 35 A accessing the Power Measurement Application, 15 apparent power, 3, 27, 64 at a glance, 3 Average, power modulation analysis, 45 B bandwidth (oscilloscope) requirements, 10 Blackman-Harris window, 31 block diagram, switch-mode power supply, 3 C channel deskew, performing, 16 conduction, 40 conduction loss, 3, 37 configuration (test) parameters, 22 connection to device under test, 20 crest factor, 3, 28, 65 current harmonics, 29 current harmonics analysis settings, 31 current harmonics analysis signals, 29 current harmonics plot parameter, 31 current harmonics standard parameter, 31 current harmonics test results, 32 current probe, 12 E L line frequency parameter, 31 load transient response test results, 54 M efficiency analysis signals, 58 efficiency, power app automatic measurement, 66 energy loss, 68 expected inrush current, 35 maximum source voltage, 50 memory (oscilloscope) requirements, 10 modulation, 44 modulation analysis, 3 modulation analysis settings, 45 modulation analysis signals, 44 F N Fall Time, power modulation analysis, 46 FFT waveform (plot), 32 Frequency, power modulation analysis, 45 N2780A current probe, 12 N2781A current probe, 12 N2782A current probe, 12 N2783A current probe, 12 N2790A high-voltage differential probe, 11 N2791A high-voltage differential probe, 11 N2792A differential probe, 11 N2793A differential probe, 11 N2870A passive probe, 12 G getting started, 15 H Hamming window, 31 DSOX4PWR Power Measurement Application User's Guide 69 Index N2891A high-voltage differential probe, 11 N2893A current probe, 12 negative pulse width, power modulation analysis, 45 new load current parameter, 54 noise floor, 39 notices, 2 null offset, 39 number of cycles, 26, 30 prerequisites, 9 probe (oscilloscope) requirements, 11 probe (oscilloscope), current, 12 probe (oscilloscope), high-voltage differential, 11 probe (oscilloscope), passive, 12 PSRR (Power Supply Rejection Ratio), 4 PWM (pulse width modulation), 3 O Ratio, power modulation analysis, 45 Rds (dynamic ON resistance) waveform, 40 reactive power, 27, 64 real (actual) power, 27, 64 requirements, current probe, 12 requirements, deskew fixture, 12 requirements, high-voltage differential probe, 11 requirements, oscilloscope, 9 requirements, oscilloscope bandwidth, 10 requirements, oscilloscope memory, 10 requirements, oscilloscope probe, 11 requirements, oscilloscope software version, 11 requirements, passive probe, 12 results (test), viewing, 23 ripple measurements, 3 Rise Time, power modulation analysis, 45 RMS - AC, power modulation analysis, 45 running tests, 22 oscilloscope bandwidth requirements, 10 oscilloscope memory requirements, 10 oscilloscope probe requirements, 11 oscilloscope requirements, 9 oscilloscope software version requirements, 11 output noise, 3 output power, 66 output ripple, 65 output ripple analysis signals, 47 output voltage ripple, 47 output voltage ripple test results, 48 overall efficiency, 58 overall efficiency test results, 60 overall system efficiency, 66 overview, 3 P parameters, test configuration, 22 passive probe, 12 peak current, 67 percent overshoot, 53 Period, power modulation analysis, 45 phase angle, 28, 65 positive pulse width, power modulation analysis, 45 power factor, 3, 27, 63 power loss, 68 power loss per cycle, 68 power measurements, more about, 25 power quality, 3, 25 power quality analysis settings, 27 power quality analysis signals, 25 power quality test results, 28 pre-compliance testing, 3 70 R switching loss analysis signals, 37 switching loss test results, 40 switch-mode power supply block diagram, 3 T test configuration, 22 test results, viewing, 23 test selection, 20 tests, running, 22 THD (total harmonic distortion), 33 total harmonic distortion, 3 trademarks, 2 transient response, 52 transient response analysis, 52 transient response analysis settings, 54 transient response analysis signals, 52 transient response time, 67 true power, 3 turn off time, 51, 67 turn off time test results, 51 turn on time, 51, 67 turn on time test results, 51 turn on/off analysis, 49 turn on/off analysis settings, 51 turn on/off analysis signals, 49 U U1880A deskew fixture, 12, 17 V S safety, 9 selecting tests, 20 slew rate analysis settings, 43 slew rate analysis signals, 42 slew rate of Id in power device, 44 slew rate of Vds in power device, 44 slew rate power analysis, 41 software (oscilloscope) version requirements, 11 software version (oscilloscope) requirements, 11 steady state DC output voltage, 51, 53 switching loss, 3, 36 switching loss analysis settings, 38 V crest factor, 65 viewing test results, 23 viewing waveforms, 23 voltage (high) differential probe, 11 voltage probe attenuation factor parameter, 21 voltage switching level, 39 W waveforms, viewing, 23 window parameter (FFT analysis), 30 DSOX4PWR Power Measurement Application User's Guide