CN116068352A - Reverse recovery measurement and graph - Google Patents

Abstract

A test and measurement instrument has: a user interface; one or more probes to be connected to a Device Under Test (DUT); and one or more processors configured to execute code that causes the one or more processors to: receiving waveform data from the DUT after the DUT is activated by application of power from a power source and application of at least first and second pulses from a source instrument; locating one or more reverse recovery regions in the waveform data; determining a reverse recovery time for the DUT from the reverse recovery zone; and displaying, on the user interface, a reverse recovery graph of the one or more reverse recovery regions, the reverse recovery graph automatically configured to display one or more of the reverse recovery regions and including at least one characteristic for the one or more reverse recovery regions annotated on the reverse recovery graph.

Description

Reverse recovery measurement and graph

Cross Reference to Related Applications

The present disclosure claims the benefit of indian provisional application No. 202121050042, entitled "Automated Double Pulse Test (DPT) Measurements with Reverse Recovery Plot for System Validation of Wide Brand Gap (WBG) Power Devices During In-Circuit Operation," filed on 1, 11, 2022, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to testing and measurement of semiconductor-based power devices.

Background

Semiconductor materials used in power electronics are transitioning from silicon to Wide Band Gap (WBG) semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), due to their superior performance at higher power levels in automotive and industrial applications.

GaN and SiC technologies enable smaller, faster, and more efficient designs. It is fully demonstrated that SiC or GaN based WBG devices require both static and dynamic measurements. The preferred test method for measuring the switching and diode reverse parameters of a MOSFET or IGBT is commonly performed using a Double Pulse Test (DPT) method.

WBG system validation was performed by comparing real-time waveforms for a wide range of voltage and heating values across a range of operating conditions during DPT experiments.

DPT is a well-defined method for measuring switching parameters and evaluating the dynamic behavior of a power device.

The IEC and JEDEC standards define dynamic testing of WBG power devices. DPT helps to determine key performance parameters of a switching device by measuring: switching parameters, diode reverse recovery energy and time, gate charge and capacitance analysis.

The customer operates in the circuitry of the DUT board without external stimulus and manifests the discrete MOSFET/IGBT components earlier in the workflow. In-circuit testing depicts a real-world scenario of DUT operation and is sometimes referred to as system verification. There is no standard measurement or test procedure for testing the DUT at the system verification stage.

In the case of conventional DPT settings, manually performing these tests under several permutations of test parameters and thereafter manually analyzing the experimental data is a time-consuming and error-prone process.

Currently, customers test WBG devices by: manually save waveforms, export to tools like Excel or LabVIEW; run their proprietary technology and document test reports; and iterating across multiple DUTs (tens to twenty). The planned delays also result in delayed time to market and loss of critical customers to the competitors.

One of the key challenges customers face during system validation of WBG reference designs is improving test time. Capturing the real-time waveform and analyzing in multiple runs takes longer. Validating and testing only one power device takes days. The key attributes are a plurality of measurements to be made, a plurality of DUTs to be tested; manual testing, analysis, and reporting resulting in delays.

Another key challenge is the lack of confidence in the test results. DPT testing requires automated measurement and control of instruments such as AFG, DUT boards, and measurement systems (mirrors) during dynamic testing because test engineers use their own code or tools for analysis resulting in ineffective control of test setup, probes do not meet bandwidth, dynamic range, common mode rejection ratio requirements, and oscilloscopes need to have multiple channels with deskew capability and high dynamic range.

Homemade solutions are dominant in this space and are custom settings that vary from company to company. Although it has fair coverage around the measurement results, from a system point of view, there is no standard-as technology and implementation may vary from company to company and from setup to setup. This results in low confidence in the test setup and presents challenges with respect to result correlation. There are no standards and accepted solutions available to verify operation in the circuitry of the DUT.

Existing test methods from T & M suppliers do not have a dedicated mirror-based solution for system validation. Thus, there is a need for an efficient test solution.

Drawings

Fig. 1 shows a circuit diagram of parasitic elements in a DPT power circuit.

Fig. 2 shows a schematic flow chart of the board verification flow.

Fig. 3 shows an embodiment of a schematic flow chart of a workflow.

Fig. 4 shows an embodiment of measurement result grouping for a DPT flow.

Fig. 5 shows an embodiment of a schematic circuit diagram showing test points for measuring a switching parameter.

Fig. 6 shows an embodiment of an on-off transition in an Insulated Gate Bipolar Transistor (IGBT).

Figure 7 shows an image of Eon configuration and resulting badge on an embodiment of WBG-DPT solution.

FIG. 8 illustrates an annotated E using an embodiment of WBG solution on an oscilloscope with navigation _on A zone.

Fig. 9 shows an image of the reverse current captured on an oscilloscope using a Tektronix Current Probe (TCP) in an embodiment of the reverse recovery process.

Fig. 10 shows an embodiment of a schematic circuit diagram showing test points for measuring diode reverse recovery.

Fig. 11 shows a reverse recovery time (Trr) configuration page and measurement badge on an embodiment of the WBG-DPT solution.

Fig. 12 shows the reverse recovery region annotated on the waveform using an embodiment of the WBG-DPT solution.

Fig. 13 illustrates an embodiment of a scaled and annotated restored charge region.

Fig. 14 shows an embodiment of an overlapping reverse recovery graph for multiple pulses.

Fig. 15 illustrates an embodiment of overlapping recovered charge regions for multiple pulses on a reverse recovery graph.

FIG. 16 illustrates a single reverse recovery graph and its corresponding waveforms from an embodiment performing a reverse recovery test.

FIG. 17 illustrates a plurality of reverse recovery graphs, corresponding waveforms, and reverse recovery currents resulting from an embodiment performing a reverse recovery test.

Detailed Description

Various embodiments of the present disclosure provide for automated Double Pulse Test (DPT) measurements with reverse recovery graphs for system validation of Wide Bandgap (WBG) power devices during operation in circuits.

The measurement of the reverse recovery characteristics is severely dependent on the acquisition accuracy. With industry-leading probes developed by Tektronix, such as the Iso-Vu probe and Tektronix Current Probe (TCP), the system can measure reverse recovery characteristics that are close to the true characteristics of the device. The embodiments herein have several advantages. These include definitions of workflows that meet and debug new designs according to industry standards. Other advantages include automated measurement with validation and feedback, automation of source instrumentation, test and measurement instrumentation, and Devices Under Test (DUTs), and flexibility with respect to custom reference and configurable integration points in the measurement. Additional advantages include new graph types for reverse recovery representations with time slice overlap capability, analysis per cycle with annotations, and control of single and multiple pulse results and statistics.

The WBG test and measurement instrument based solution of the embodiments provides flexibility in workflow and performs complex measurements. These standards may include, but are not limited to, those set forth by various standards setting organizations, such as JEDEC (joint electronics engineering council) and IEC (international electrotechnical commission). The present solution (WBG-DPT) is very useful to designers and validation teams.

Power electronics systems involve switching a Power Semiconductor Device (PSD) by applying a control signal to control the flow of current. The dynamic performance of the PSD has a significant impact on the efficiency and power density of power converters and other power electronic systems.

Fig. 1 shows two main parasitic loops in a DPT power stage: a power loop 10 and a control loop 12.LS and LD are stray inductive elements in the main power loop. LG is the parasitic inductance associated with the gate loop. Parasitic capacitances (CGS, CGD, and CDS) in MOSFETs contribute to slower switching, thereby increasing switching losses. LD and LG are key contributors to parasitic ringing, but ringing due to fast switching is more sensitive to LD. This results in the system validating that in-circuit testing becomes critical to the designer, otherwise it ignores PCB effects during characterization.

The DUT is customized based on the target application. The PCB board is designed to be compact and to minimize the effects of circuit parasitics and loops thereof that affect the dynamic performance of the packaged board. The fast switching WBG(s) have high sensitivity to circuit parasitics, and therefore, measuring DPT switch and diode recovery parameters during operation in circuits as part of system validation is critical. The information obtained from the DPT analysis helps predict board thermoelectric performance that is very valuable in validating the design of the target application.

Fig. 2 shows an embodiment of a workflow from reference design to validation of the final product. A Device Under Test (DUT) has discrete components integrated into the test circuit with probe points provided. Typically by applying power from a power source, the system is put into operation. Test software sets the pulse(s) for application to the DUT. This may involve a source instrument such as an arbitrary waveform generator (AFG) or other waveform source. The DUT then undergoes testing and analysis to ensure that it meets desired results and/or criteria. Analysis and any post-processing of the results then completes the test.

Fig. 3 shows a workflow using an embodiment. Embodiments provide an automated process with minimal user intervention. The packaged characterized component 20 is mounted to an integrated circuit board/PCB 22. The power supply 24 is turned on to provide power and the source instrument (such as AFG) 28 provides pulses for testing. Test and measurement instrument 26 supports de-embedding of parasitic, inductive and S-parameter files and has a complete measurement set according to industry standards.

It should be noted that the discussion focuses on AFG as a source instrument and oscilloscopes or mirrors as test and measurement instruments, but that the discussion uses these for ease of understanding and is not intended to limit these elements to those specific examples in any way.

Embodiments herein allow for a large number of measurements for WBG devices. Fig. 4 shows a user interface showing the grouping of such measurements. As can be seen, the user interface presented by the test and measurement interface in this embodiment allows for selection of the device type, which is either a MOSFET (metal oxide semiconductor field effect transistor) or an Insulated Gate Bipolar Transistor (IGBT), both examples of wide bandgap devices. Test and measurement instruments support a number of power devices including, but not limited to, silicon carbide (SiC) and gallium nitride (GaN) MOSFETs, silicon devices, and GaN-HEMT (high electron mobility transistor) devices. The user may select the voltage and current source channels and the gate voltage channel. The user may also use the test setup to choose from one of several tests. These include, by way of example, switching parameter analysis, switching timing analysis, diode reverse recovery analysis, and capacitance analysis.

Fig. 5 shows an embodiment of a switching parameter measurement scenario. The semiconductor DUT resides in a low-side location (Q2) and forms a switch cell under test along with a freewheeling diode (FWD) in a high-side location (Q1).

Along with the gate voltage of Q2, the detector from test and measurement instrument 28 captures the switching voltage and current. The configuration of the probe connections to the test and measurement equipment 26 constitutes only an example. The probes are connected to the test and measurement instruments through ports 32, which ports 32 in turn communicate data to the processor 30. A user interface 34 having a menu thereon (such as the one shown in fig. 4) allows a user to interact with the testing process. The user interface herein includes a touch screen embodiment, but may include any combination of displays and controls, such as knobs or buttons. The processor may include: one or more processors executing code that causes the one or more processors to perform the methods of the embodiments.

As can be seen in the figure, an optional connection exists between the source instrument and the test and measurement instrument. As used herein, activation of a DUT means application of power from a power source and then application of pulses from a source instrument. The application of the source instrument may occur in synchronization with the test and measurement instrument using the optional connection/communication channel.

The system allows automation of the DPT process but still allows for variation. For example, the system may automatically set the pulse zone for the second pulse according to one of many industry standards. However, users have the flexibility to change the pulse zone based on their DUT operation. In the case of "automatic" selection, the user does not have to perform any setting of anything in the measurement configuration. The automatic setting performs both validation and measurement on the waveform.

For user selectable settings, fig. 7 shows an embodiment of a menu for these, if the user ignores placement in the second pulse zone, the measurement may fail. In this case, the measurement fails and the user will get feedback in the result badge. For example, if the second burst disk does not exist, the user will be notified because of a "valid E _on The region is not present on the second pulse … … ".

Using IGBTs as an example, the on and off parameters can be calculated by looking at the falling edge of the first pulse and the rising edge of the second pulse, as shown in fig. 6. One switching parameter analysis measures the energy dissipated inside the IGBT during the on-period of a single collector current pulse described in the following equation:

（1）

energy dissipated inside the IGBT during the off time plus the tail time of a single collector current pulse

（2）。

Fig. 8 shows an embodiment of the resulting waveform with annotated Eon regions, and the user can navigate the waveform by scrolling and zooming to see details of the displayed waveform data.

One or more processors in the test and measurement instrument provide the ability to improve measurement accuracy by performing signal conditioning on the incoming waveform data. The incoming data from the DUT will typically be analog signal data that undergoes analog-to-digital conversion prior to analysis. Signal conditioning may include voltage or current limiting, application of anti-aliasing filters, amplification, filtering, and many other conditioning. Signal conditioning will typically mitigate the effects of noise to ensure that measurement results have a higher accuracy than they would have without signal conditioning. Other noise control techniques may include the use of hysteresis band control loops or filters.

Additionally, while the discussion above mentions user input identifying the analysis to be performed by the DUT as user entered input, the user input may also include: the user uses a programming interface to provide an automated script or other form of programming to perform testing and analysis in an automated manner. This holds true for all aspects of the DPT test including reverse recovery discussed below.

During the initiation of the second pulse of the double pulse test, the freewheeling diode in forward conduction mode is switched to reverse blocking mode. The current in the diode will drop below zero and return to 0 ampere at this point as shown in fig. 9. The time it takes for the system to recover back to 0 amperes (referred to as the reverse recovery time Trr) and the resulting recovered charge Qrr comprise several of the important reverse characteristics for the system to analyze. Using embodiments, a user may perform Trr measurements on a single current waveform or may use a gate-source voltage as an edge qualifier. Fig. 10 shows an embodiment of a test setup.

The reverse recovery time may be found using the formula:

（3）

wherein the method comprises the steps oft _a Is the time it takes for the reverse current to drop from 0 ampere to the maximum reverse current during the second pulse, andt _b the time at which the extrapolated tangent drawn as the reverse current rises toward 0 ampere intercepts the zero current axis.

After the user provides the appropriate input to the measurement, ta is determined using a robust edge detection technique on the waveform with edges at zero amps within the hysteresis band. For tb, a tangent is drawn for reverse time analysis when the reverse current is restored from its maximum reverse current toward the zero current axis. In some standards, the tangent line should pass through the points of 90% and 25% of the maximum reverse current (Irm). For novice users, the solution provides an automatic level of configuration by the oscilloscope according to industry standards.

The ability to configure these percentage levels is valuable because the recovery of current may occur very suddenly or mildly based on the system. In an embodiment of the WBG solution, the user may configure the tangent to pass through different starting and ending percentages of Irm. The line equations for A% and B% passing through Irm at times t1 and t2, respectively, are found by:

（4）。

the tangential time to zero current axis intercept is at:

（5）。

using this intercept time, the tb reverse recovery time is found by subtracting the time for the current to reach Irm from tint (trm)

（6）。

As noted from equation 5, tint is independent of Irm. As the configuration of the start and end points of the tangent line changes, the total reverse recovery time (Trr) changes. The new configuration facility provides a powerful tool for analyzing nonlinear reverse recovery regions based on visual feedback and mirror measurement feedback. In embodiments herein of WBG solutions, the point through which the line should pass may be provided as an absolute value or as a percentage of Irm. These configurations will help engineers judge the nature of the current recovery and quantify them using the measurements. FIG. 11 illustrates an embodiment of a user interface that allows a user to select an extrapolated level of current for the first and second pulses if the user selects Customs, or uses an automatic value if the user selects Auto. Fig. 11 also shows a measurement badge concerning Trr measurement.

Further, since the reverse recovery time parameter includes time sensitive information, the proposed solution will provide a new graph in an application called reverse recovery graph. Fig. 12 shows the captured waveforms. The process scales into the waveform by automatically finding the inversion region and annotates the relevant inversion characteristic parameters annotated as shown. Embodiments find the inversion region on the captured waveform by means of edge techniques and measurement settings. After drawing the scaled version of the waveform, the mirror will mark the region of interest with a dashed line and annotate the appropriate reverse recovery feature.

Conventional solutions do not have the ability to automatically scale to the reverse recovery area and annotate them with parameters like the following: irm, the time taken to reach Irm (ta), the intercept of the time axis by the tangent (tb), the total reverse time (trr), and other relevant parameters that determine the reverse recovery time of the system.

Reverse recovery charge is an important parameter for determining the reverse characteristics of a system. The recovered charge Qrr can be approximated by the area under the reverse current-time curve. The charge region represents the energy that must be dissipated with a reverse voltage in the power switch side of the circuit. The user should provide the reverse current waveform as input to the measurement and have the option of providing the gate voltage as an edge qualifier, since the gate sources are typically cleaner, as they come directly from the IC.

Qrr is defined as the integral of the reverse current flowing through the diode as shown in fig. 13 during the second pulse of the double pulse test:

（7）

wherein t is ₀ Is the time during which the reverse current falls below the zero current axis during the second pulse, and t _i Is the integration time until which the opposite charge is found.

The integration time for finding the reverse charge will depend on Irm. The integration time is found by: the current waveform is scanned until the current reaches a certain percentage of Irm during the current rise towards the zero current axis. Some industry standards set the latter percentage of Irm at 2% during recovery towards the zero current axis.

Since each system design has its own tolerance on the reverse charge, the solution causes the facility to configure the integration time (ti) by providing a percentage of the maximum reverse current (Irm). This new configuration capability caters for nonlinear recovery area analysis. In an embodiment of the WBG solution, the Irm value up to which integration should be completed may be provided as an absolute value or as a percentage of Irm. The new reverse recovery plot for this measurement will identify the reverse recovery region from the captured waveform, annotate the time considered for the integration in equation (7), and fill the total charge region.

The only way for the new reverse recovery graph is its capacity to consider multiple sets of double pulses and provide visual and measurement results on each set. The user may configure the measurements in the WBG solution to query the results on every first or second pulse or all pulses of the set of double pulses. In the case of multiple pulses, the edge definition Fu Boxing provided to the measurement is used as a reference to find the pulse position. Fig. 14 shows an example of a display of a plurality of reverse recovery graphs and a plurality of reverse recovery regions. It should be noted that although the graph only shows pulse 1 and pulse 2, as noted in the illustration, there may be up to N pulses. The measurement badge or legend will show the current pulse results, along with the average result of all the pulses. In the reverse recovery graph of fig. 14, the time zone annotated for the current annotation zone is a solid line for pulse 1. Fig. 15 shows a plurality of graphs with reverse recovery zones.

Fig. 16 and 17 show embodiments of graphs having their corresponding waveforms and reverse recovery currents. Fig. 16 shows a single graph and fig. 17 shows a plurality of graphs.

An embodiment of the WBG application presents multiple pulses on a single graph, annotating the reverse current (Irr) recovery region along with other recovery regions in the background for comparison. Since there are multiple regions of interest in a single acquisition, the instrument uses a single current waveform to slice each region of interest and overlap them in the graph. The instrument also has the ability to display multiple regions from multiple graphs as a covering as shown in fig. 17. The plurality of regions may result from a single acquisition or from multiple acquisitions.

The user interface allows the user to navigate the waveform. In addition to scaling into the region of interest, the user may filter the results by selecting a first pulse, a second pulse, each odd pulse, each even pulse, a plurality of pulses different than odd and even, and so forth. Navigation allows the user to move to the next, previous, minimum, maximum, etc. As the user navigates, the annotations update to reflect the scaled region. Highlighting of the zoomed region of interest may involve using a different color, thickening the line, etc. The instrument also has the ability to analyze the signal in both the forward direction (left to right in the figure) and the backward direction (right to left in the figure) to handle oscillations at the region of interest.

This new graph type in the oscilloscope will provide coverage of multiple varying time sliced waves from a single waveform. The graph also provides the ability to navigate each of these regions and the measurements on the mirror updated accordingly. The following oscilloscope applications are not currently available in the market: which may provide such navigational features on a single waveform containing multiple reversal areas highlighting the reversal characteristics.

A further extension of the reverse recovery graph is: a configurable visual masking limit is provided such that each inversion region is under a specific limit. The mirror will run the measurements and notify of any limit violations. This masking feature on the graph will help in maintaining the ideal reverse recovery zone where the system limits the maximum recovery time, maximum reverse current, etc.

Aspects of the disclosure may operate on specially created hardware, on firmware, digital signal processors, or on specially programmed general-purpose computers including processors operating according to programmed instructions. The term controller or processor as used herein is intended to include microprocessors, microcomputers, application Specific Integrated Circuits (ASICs), and special purpose hardware controllers. One or more aspects of the present disclosure may be embodied in computer-usable data and computer-executable instructions, such as in one or more program modules, executed by one or more computers (including monitoring modules) or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer-executable instructions may be stored on a non-transitory computer-readable medium such as a hard disk, an optical disk, a removable storage medium, a solid state memory, a Random Access Memory (RAM), and the like. As will be appreciated by one of skill in the art, the functionality of the program modules may be combined or distributed as desired in various aspects. In addition, the functionality may be embodied in whole or in part in firmware or hardware equivalents (such as integrated circuits, FPGAs, and the like). Particular data structures may be used to more efficiently implement one or more aspects of the present disclosure, and such data structures are contemplated within the scope of the computer-executable instructions and computer-usable data described herein.

In some cases, the disclosed aspects may be implemented in hardware, firmware, software, or any combination thereof. The disclosed aspects may also be implemented as instructions carried by or stored on one or more non-transitory computer-readable media, which may be read and executed by one or more processors. Such instructions may be referred to as a computer program product. As discussed herein, computer-readable media means any medium that can be accessed by a computing device. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media.

Computer storage media means any medium that can be used to store computer readable information. By way of example, and not limitation, computer storage media may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital Video Disk (DVD), or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, and any other volatile or non-volatile, removable or non-removable media implemented in any technology. Computer storage media exclude signals themselves and signal transmissions in the form of transients.

Communication media means any medium that can be used for communication of computer readable information. By way of example, and not limitation, communication media may include coaxial cables, fiber optic cables, air, or any other medium suitable for the communication of electrical, optical, radio Frequency (RF), infrared, acoustic, or other types of signals.

In addition, the written description refers to particular features. It should be understood that the disclosure in this specification includes all possible combinations of those particular features. For example, where a particular feature is disclosed in the context of a particular aspect, that feature may also be used as much as possible in the context of other aspects.

Moreover, when a method having two or more defined steps or operations is referred to in this application, the defined steps or operations may be performed in any order or simultaneously unless the context excludes those possibilities.

Example

Illustrative examples of the disclosed technology are provided below. Embodiments of the technology may include one or more of the examples described below and any combination.

Example 1 is a test and measurement instrument, comprising: a user interface; one or more probes to be connected to a Device Under Test (DUT); and one or more processors configured to execute code that causes the one or more processors to: receiving waveform data from the DUT after the DUT is activated by application of power from a power source and application of at least first and second pulses from a source instrument; locating one or more reverse recovery regions in the waveform data; determining a reverse recovery time for the DUT from the reverse recovery zone; and displaying, on the user interface, a reverse recovery graph of the one or more reverse recovery regions, the reverse recovery graph automatically configured to display one or more of the reverse recovery regions and including at least one characteristic for the one or more reverse recovery regions annotated on the reverse recovery graph.

Example 2 is the test and measurement instrument of example 1, wherein the one or more processors are further configured to: a user input specifying a configuration for determining the reverse recovery time is received.

Example 3 is the test and measurement instrument of example 2, wherein the user input is one of an automatic setting for an extrapolated level or a user-specified setting for an extrapolated level for a tangent line.

Example 4 is the test and measurement instrument of example 3, wherein the code that causes the one or more processors to display a reverse recovery graph comprises code that causes the one or more processors to: displaying at least one of a tangent line generated from the automatic setting and a tangent line generated from a user-specified setting.

Example 5 is the test and measurement instrument of any one of examples 1 to 4, wherein the code that causes the one or more processors to display the reverse recovery graph comprises code that causes the one or more processors to: the reverse recovery graph is displayed with a legend.

Example 6 is the test and measurement instrument of any one of examples 1 to 5, wherein the one or more processors are further configured to execute code that causes the one or more processors to: a recovered charge from the one or more reverse recovery regions is determined.

Example 7 is the test and measurement instrument of example 6, wherein the code that causes the one or more processors to display the reverse recovery graph comprises code that causes the one or more processors to: the recovered charge is displayed as a recovered charge region for the one or more reverse recovery regions.

Example 8 is the test and measurement instrument of example 6, wherein the code that causes the one or more processors to determine the recovered charge comprises code that causes the one or more processors to: a predetermined percentage of the maximum reverse current is used.

Example 9 is the test and measurement instrument of example 6, wherein the code that causes the one or more processors to determine the recovered charge comprises code that causes the one or more processors to: a user interface is presented for a user to input a desired percentage of the maximum reverse current.

Example 10 is the test and measurement instrument of any of examples 1 to 9, wherein the code that causes the one or more processors to display a reverse recovery graph for one or more reverse recovery zones comprises code that causes the one or more processors to: a plurality of reverse recovery zones are shown.

Example 11 is the test and measurement instrument of example 10, wherein the code that causes the one or more processors to display the plurality of reverse recovery zones comprises code that causes the one or more processors to display the plurality of reverse recovery zones as an overlay, wherein the overlay comprises one of: an overlay having each reverse recovery area of the scaled area annotated and highlighted with a tangent line; an overlay from multiple reverse recovery areas within a single acquisition of waveform data from the DUT; and an overlay from a plurality of reverse recovery regions from multiple acquisitions of waveform data by the DUT.

Example 12 is a method of providing reverse recovery measurements for a Device Under Test (DUT), comprising: receiving waveform data from the DUT through a probe after the DUT is activated by application of power from a power source and application of first and second pulses from a source instrument; locating one or more reverse recovery regions in the waveform data; determining a reverse recovery time for the DUT for the one or more reverse recovery zones; and displaying, on the user interface, a reverse recovery graph of the one or more reverse recovery regions, the reverse recovery graph automatically configured to display the one or more reverse recovery regions and including at least one characteristic of the one or more reverse recovery regions annotated on the reverse recovery graph.

Example 13 is the method of example 12, further comprising: user input specifying a selection for determining the reverse recovery time is received.

Example 14 is the method of example 13, wherein the selecting comprises one of an automatic setting for an extrapolated level or a user-specified setting for an extrapolated level for a tangent line.

Example 15 is the method of example 14, wherein displaying the reverse recovery graph further comprises: displaying at least one of a tangent line generated from the automatic setting and a tangent line generated from a user-specified setting.

Example 16 is the method of example 12, further comprising: a recovered charge from the one or more reverse recovery regions is determined.

Example 17 is the method of any one of examples 12 to 16, wherein displaying the reverse recovery graph comprises: the recovered charge is displayed as a recovered charge region.

Example 18 is the method of any one of examples 12 to 17, wherein displaying the reverse recovery graph comprises: a plurality of reverse recovery zones are shown.

Example 19 is the method of example 18, wherein displaying the plurality of reverse recovery regions comprises: a plurality of reverse recovery regions and corresponding recovered charge regions are shown.

Example 20 is the method of any one of examples 12 to 18, wherein displaying the plurality of reverse recovery regions comprises: in the case of highlighting and annotating the selected region, a plurality of reverse recovery regions and user controls are displayed to allow the user to zoom into the selected recovery region within a series of reverse recovery regions and to navigate the plurality of reverse recovery regions to selected other recovery regions.

All of the features disclosed in the specification, including the claims, abstract and drawings, and all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in the specification, including the claims, abstract, and drawings, may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Although specific embodiments have been illustrated and described herein for purposes of description, it will be appreciated that various modifications may be made without deviating from the spirit and scope of the disclosure. Accordingly, the invention should not be limited except as by the appended claims.

Claims (20)

1. A test and measurement instrument comprising:

a user interface;

one or more probes to be connected to a Device Under Test (DUT); and

one or more processors configured to execute code that causes the one or more processors to:

receiving waveform data from the DUT after the DUT is activated by application of power from a power source and application of at least first and second pulses from a source instrument;

locating one or more reverse recovery regions in the waveform data;

determining a reverse recovery time for the DUT from the reverse recovery zone; and

displaying, on the user interface, a reverse recovery graph of the one or more reverse recovery regions, the reverse recovery graph automatically configured to display one or more of the reverse recovery regions and including at least one characteristic for the one or more reverse recovery regions annotated on the reverse recovery graph.

2. The test and measurement instrument of claim 1, wherein the one or more processors are further configured to: a user input specifying a configuration for determining the reverse recovery time is received.

3. The test and measurement instrument of claim 2, wherein the user input is one of an automatic setting for an extrapolated level or a user-specified setting for an extrapolated level for a tangent line.

4. The test and measurement instrument of claim 3, wherein the code that causes the one or more processors to display a reverse recovery graph includes code that causes the one or more processors to: displaying at least one of a tangent line generated from the automatic setting and a tangent line generated from a user-specified setting.

5. The test and measurement instrument of claim 1, wherein the code that causes the one or more processors to display the reverse recovery graph comprises code that causes the one or more processors to: the reverse recovery graph is displayed with a legend.

6. The test and measurement instrument of claim 1, wherein the one or more processors are further configured to execute code that causes the one or more processors to: a recovered charge from the one or more reverse recovery regions is determined.

7. The test and measurement instrument of claim 6, wherein the code that causes the one or more processors to display the reverse recovery graph includes code that causes the one or more processors to: the recovered charge is displayed as a recovered charge region for the one or more reverse recovery regions.

8. The test and measurement instrument of claim 6, wherein the code that causes the one or more processors to determine the recovered charge includes code that causes the one or more processors to: a predetermined percentage of the maximum reverse current is used.

9. The test and measurement instrument of claim 6, wherein the code that causes the one or more processors to determine the recovered charge includes code that causes the one or more processors to: a user interface is presented for a user to input a desired percentage of the maximum reverse current.

10. The test and measurement instrument of claim 1, wherein the code that causes the one or more processors to display a reverse recovery graph for one or more reverse recovery zones comprises code that causes the one or more processors to: a plurality of reverse recovery zones are shown.

11. The test and measurement instrument of claim 10, wherein the code that causes the one or more processors to display a plurality of reverse recovery zones comprises code that causes the one or more processors to display a plurality of reverse recovery zones as an overlay, wherein the overlay comprises one of: an overlay having each reverse recovery area of the scaled area annotated and highlighted with a tangent line; an overlay from multiple reverse recovery areas within a single acquisition of waveform data from the DUT; and an overlay from a plurality of reverse recovery regions from multiple acquisitions of waveform data by the DUT.

12. A method of providing reverse recovery measurements for a Device Under Test (DUT), comprising:

receiving waveform data from the DUT through a probe after the DUT is activated by application of power from a power source and application of first and second pulses from a source instrument;

locating one or more reverse recovery regions in the waveform data;

determining a reverse recovery time for the DUT for the one or more reverse recovery zones; and

displaying a reverse recovery graph of the one or more reverse recovery regions on the user interface, the reverse recovery graph automatically configured to display the one or more reverse recovery regions and including at least one characteristic of the one or more reverse recovery regions annotated on the reverse recovery graph.

13. The method of claim 12, further comprising: user input specifying a selection for determining the reverse recovery time is received.

14. The method of claim 13, wherein the selecting comprises one of an automatic setting for an extrapolated level or a user-specified setting for an extrapolated level for a tangent line.

15. The method of claim 14, wherein displaying the reverse recovery graph further comprises: displaying at least one of a tangent line generated from the automatic setting and a tangent line generated from a user-specified setting.

16. The method of claim 12, further comprising: a recovered charge from the one or more reverse recovery regions is determined.

17. The method of claim 18, wherein displaying the reverse recovery graph comprises: the recovered charge is displayed as a recovered charge region.

18. The method of claim 12, wherein displaying the reverse recovery graph comprises: a plurality of reverse recovery zones are shown.

19. The method of claim 18, wherein displaying a plurality of reverse recovery areas comprises: a plurality of reverse recovery regions and corresponding recovered charge regions are shown.

20. The method of claim 18, wherein displaying a plurality of reverse recovery areas comprises: in the case of highlighting and annotating the selected region, a plurality of reverse recovery regions and user controls are displayed to allow the user to zoom into the selected recovery region within a series of reverse recovery regions and to navigate the plurality of reverse recovery regions to selected other recovery regions.

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