CN117686758A - Shunt for counteracting mutual inductance - Google Patents

Abstract

The shunt resistor has: a substrate having a conductive structure for carrying a current in a current path; a resistive portion in electrical contact with the conductive structure; and one or more cancellation inductance leads electrically connected to the conductive structure and the resistive portion, the one or more cancellation inductances configured to cancel inductance effects across the resistive portion in a voltage measurement. The modular tip interconnect has: a connector at a first end of the interconnect configured to connect to a probe tip of a test and measurement instrument; and the shunt resistor at the second end of the interconnect is configured to connect to a Device Under Test (DUT).

Description

Shunt for counteracting mutual inductance

Cross Reference to Related Applications

The present disclosure claims the benefit of U.S. provisional application No. 63/405,837 entitled "CURRENT stunt WITH CANCELING MUTUAL INDUCTANCE," filed on 9 and 12 of 2022, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to test and measurement systems, and more particularly to systems for measuring current in a Device Under Test (DUT).

Background

U.S. patent application publication No. 20210318361A1, published at 10/14/2021, describes an isolated differential shunt probe for measuring current in a Device Under Test (DUT), the contents of which are hereby incorporated by reference into the present disclosure in its entirety. The shunt uses a voltage drop across a shunt resistor and techniques for minimizing shunt inductance. Similarly, U.S. patent application Ser. No. 18/198,800, filed on 5/17/2023, and U.S. patent application Ser. No. 18/225,034, filed on 7/21/2023, describe different approaches to shunts for test and measurement instruments, both of which are incorporated herein by reference in their entirety.

Developing and testing switching power supplies, motor drives, battery chargers, wireless chargers, photovoltaic inverters, and other related power electronics typically involve current measurement. One common method of measuring current involves placing a low value resistor (commonly referred to as a "shunt" or "shunt resistor") in series with the path of the current to be measured. Measuring the voltage drop across the shunt allows the current to be determined based on the known resistance of the shunt.

One method commonly used is to place a series resistor (or "shunt") in the current path, measure the voltage drop caused by the current, and divide by the resistance. This approach works well for DC and lower frequencies, but since for frequencies above f _c The inductive voltage drop across the shunt exceeds the resistive voltage drop, and therefore the method is affected at higher frequencies:

when measuring large currents, a relatively small shunt resistance R is required to keep the voltage drop and power consumption of the shunt within reasonable limits, which results in an available bandwidth f _c Too low.

Another way to increase the available bandwidth of the shunt is to add a cancellation mutual inductance M in the wire-laying (address) of the voltage measurement wires of conventional shunts _c ：

This does not require a specific return current path, thereby minimizing the insertion inductance. Is cumbersome to implement because the return current path must still be known in order to determine the lead placement to achieve cancellation (M _C =l). This cancellation method is also affected at high frequencies due to the skin effect. When the skin depth approaches the shunt thickness, the physical position of the current path through the shunt will shift, changing M in the equation above _C Values of L and R.

Examples of the present disclosure address these and other deficiencies of the prior art.

Drawings

Fig. 1 shows a diagram of an embodiment of a shunt resistor with current and measurement paths.

Fig. 2-5 illustrate embodiments of a substrate having shunt resistors and inductance canceling leads.

Fig. 6 shows an alternative embodiment of a shunt resistor with inductance canceling leads.

Fig. 7-8 illustrate an embodiment of a shunt resistor with a via connection.

Fig. 9-11 show different views of an embodiment of a shunt with a through hole.

Fig. 12 shows an embodiment of a tip extension with an interconnect.

Fig. 13 illustrates an embodiment of an interconnect for a square pin connector.

Fig. 14 illustrates an embodiment of an interconnect with a flexible circuit substrate.

Figure 15 illustrates an embodiment of an interconnect with a device under test.

Detailed Description

Embodiments of the present disclosure include implementations of shunt structures, including details regarding management of cancellation mutual inductance, interconnection, and kelvin sensing. As described above, one way to increase the available bandwidth of the shunt is to add a cancellation mutual inductance M in the wire laying of the voltage measurement wires of conventional shunts _c ：

This does not require a specific return current path, thus minimizing the insertion inductance, but is cumbersome to implement, since the return current path still has to be known in order to determine the lead placement to achieve cancellation (M _C =l). This cancellation method is also affected at high frequencies due to the skin effect. When the skin depth approaches the shunt thickness, the physical location of the current path through the shunt will shift, thereby changing M _C Values of L and R.

Embodiments of the present disclosure utilize a Kelvin sensing configuration of resistor voltage drops. No measured signal current flows through the canceling inductance measuring sensor. For high current applications, the contact resistance may create a large gain error in the intended current measurement, which is where kelvin sensing becomes important.

Fig. 1 shows a diagram of a shunt resistor and associated current and measurement paths according to an embodiment. The structure of the shunt resistor generally includes a resistive material 16, the resistive material 16 being located between two conductive structures 14. The current path follows arrow 10 and the voltage drop across resistive material 16 allows the current to be measured. The measurement path is shown as thicker black arrows 15 and 17 between the canceling inductance lead 18 and the contact 19. Path 13, a thinner gray dashed line, shows the e.dl path from one contact 19 down to the down lead 18, up the current path through the resistive material, through the other lead 18, up to the other contact 19. The term E.dl refers to the potential:

the E.dl path portion in the resistive material region picks up both the desired I.R voltage drop of the resistor and the undesirable L.di/dt induced spike term from the magnetic field surrounding the current path 10. However, the E.dl path also picks up the cancellation mutual inductance term M.di/dt from portions of the two leads 18 of the path. These are also surrounded by a magnetic field. The remainder of the E.dl path (i.e., along the substrate side and traces on the printed circuit board or flex circuit) is perpendicular to the current flow. Thus, these parts do not pick up any further magnetic coupling from the current flow. The following discussion sets forth various embodiments of shunt resistors with canceling inductance measurement leads (which may be more simply referred to as measurement leads).

Fig. 2 shows an embodiment of a shunt resistor or "shunt". This embodiment includes a ceramic substrate co-fabricated with a resistor and canceling inductance measurement leads. In the following discussion, the term "reside" refers to a portion residing on and in contact with a portion on which it rests. Furthermore, the different embodiments below may show substrates and components having different orientations (such as facing up or down with respect to the page). Embodiments do not limit the orientation of any embodiment to any particular orientation.

In the embodiment of fig. 2, the shunt takes the form of a substrate with the shunt resistor features painted or printed on the substrate. In this embodiment, the substrate may comprise ceramic or other material co-fabricated with the resistor and the inductance canceling leads. The substrate 12 provides one or more surfaces on which the elements of the shunt resistor reside. In the embodiment of fig. 2, the conductive structure 14 includes an end cap. The conductive structure contacts either side of the resistive portion 16. The sense leads 18 allow the voltage drop across the resistive portion 16 to be measured. This embodiment of the shunt resistor includes an insulator 20 between the sense lead 18 and the resistive portion 16. One of the advantages in this context is the precise placement of the cancellation inductance, thus enabling ultra-high Bandwidth (BW) precise measurements.

In one embodiment, individual features are painted and/or printed on multiple sides to take advantage of the precise and microscopic geometry of the ceramic substrate. In one embodiment, the pen may allow painting of 3-D circuitry. Exxelia Micropen is an example of a manufacturer that can paint a circuit on a 3D shape. By utilizing the accuracy of the ceramic substrate and circuit placement techniques, frequency optimization and measurement accuracy are obtained. The method may be applied to any or all embodiments.

Fig. 3 and 4 illustrate another embodiment of a shunt configuration according to some embodiments of the present disclosure. In fig. 3, the resistive portion 16 resides on one surface of the substrate 12 and the leads 18 are located on a second surface opposite the first surface, as shown in fig. 4. This embodiment does not use an insulator other than the substrate itself.

In fig. 5, the conductive structure 14, the resistive portion 16, and the leads 18 all reside on one surface of the substrate 12. Conductive structures 14 reside on the surface of substrate 12 at opposite ends. A lead 18 extends from each connector to the resistive portion 16. This embodiment uses an insulator 20 between the resistive portion 16 and the leads 18.

Fig. 6 shows a shunt resistor with different component sequences. In this embodiment, leads 18 reside on substrate 12. The substrate has a conductive structure 14 in the form of a via that can traverse from one side of the substrate to the other. An insulator 20 then resides over the leads 18, with the resistive portion 16 being the outermost layer of the shunt. This embodiment may well surface mount the resistor to a test board or other circuit board where the connection through the through hole allows contact with the leads on the "top" or upper side of the substrate.

Fig. 7 and 8 show an alternative substrate consisting of a thin film. Fig. 7 shows one side of the film with pads such as 30. The other side of the film shown in fig. 8 shows leads 18. This embodiment utilizes a squeegee technique and through holes traversing the substrate and enables accurate placement of the canceling inductance leads.

The use of vias has advantages in the routing of the sense leads. Fig. 9-11 illustrate another embodiment of a substrate having a through hole. FIG. 9 illustrates castellated vias and allows for viewing of the path between the sense leads and the resistive portion. In fig. 9, the first conductive path runs from the pad 40 residing on the resistive portion 16 through the via up to the trace 42, the trace 42 traversing to the via 44 contacting the first sense lead 46. The second conductive path runs from the pad 50 in contact with the other side of the resistive portion 16 up through the via 52 to the via 54 in contact with the end 58 of the other sense lead 56. Note that the term "traveling" is not meant to imply any type of flow or direction. Since the parameter being sensed is a voltage, no current can flow in these first and second conductive paths in this structure. The current flow on DUT60 is shown in the direction of arrow 62, i.e., between pads 40 and 50 through resistive portion 16. Fig. 10 and 11 show alternative views of this configuration, with fig. 10 showing vias on DUT60 as part of substrate 12 and fig. 11 showing a side view.

The measured counter or counter inductance, kelvin sense shunt resistor of the various embodiments may be integrated in many different contact schemes. One embodiment integrates a shunt resistor with the probe tip extension. Fig. 12 illustrates an embodiment of a probe tip extension of an integrated shunt resistor. The probe tip extension 70 has a probe connector 72, a transmission path 74 (typically a cable of some sort), and a probe tip 76, the probe tip 76 including a shunt resistor or being connected to a connector having a shunt resistor such as 77 or 78.

In some embodiments, the probe tip extension has a shunt identification signal for signaling back to the attached oscilloscope, adding custom mathematics and adjusting the display of various measurement characteristics. By way of example, the transmission path 74 may be a dual-axis, differential pair, or flex circuit differential pair, but may include many other ways.

According to various embodiments, the modular tip interconnect at the shunt resistor end of the tip extension may have a variety of configurations. Fig. 13 shows a plug-in connector (sometimes referred to as a "chiplet") for connecting to square pins. The tip 76 will be inserted into an intermediate structure, such as the male connector 77 of fig. 12. This would then connect to an adapter or connector 80, with the adapter or connector 80 being mounted to the customer DUT82. It should be noted that the term "customer DUT" includes a test board or circuit that is mounted directly to the DUT itself or to the DUT resident thereon.

The modular tip interconnect may include wires or molded flex wires to help manage measuring inductance using inductance cancellation on the kelvin sense shunt resistor. Returning to fig. 12, the interconnect 78 may include a flexible PCB on which the sense leads fall, as shown in fig. 14. In this example, the transmission path 74 of fig. 12 includes twisted pair connectors 90. The connections to shunt resistor 92 may include wire holes that shape flex circuits 94 and 96.

As further shown in FIG. 15, the DUT interconnects may take a variety of forms. The resistor may be soldered directly to the DUT through a soldering tip, as shown at 100. The resistors may be connected using a clip as shown at 102 or a Browser at 104. The resistor may be mounted to a provided PCB and the PCB will mate with the device through a square pin header at 106.

In this way, the shunt resistor provides a means to allow the measurement of the voltage drop across the resistor without adversely affecting the accuracy of the measurement. In addition, the above configuration provides for counteracting mutual inductance in the measurement path to provide a more accurate measurement.

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 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 functions 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 effectively implement one or more aspects of the present disclosure, and such data structures are contemplated within the scope of 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 are readable and executable by one or more processors. Such instructions may be referred to as a computer program product. As discussed herein, computer-readable media refers to 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 refers to 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 does not include signals themselves and the transitory forms of signal transmission.

Communication media refers to any medium that can be used for the 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.

The previously described versions of the disclosed subject matter have many advantages that have been described or will be apparent to those of ordinary skill. Even so, such advantages or features are not required in all versions of the disclosed apparatus, systems or methods.

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

Furthermore, 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.

All of the features disclosed in this specification (including any accompanying 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 any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Example

Illustrative examples of the disclosed technology are provided below. Embodiments of the present technology may include one or more examples described below, as well as any combination thereof.

Example 1 is a shunt resistor, comprising: a substrate having a conductive structure for carrying a current in a current path; a resistive portion in electrical contact with the conductive structure; and one or more cancellation inductance leads electrically connected to the conductive structure and the resistive portion, the one or more cancellation inductance leads configured to cancel an inductance effect across the resistive portion in a voltage measurement.

Example 2 is the shunt resistor of example 1, wherein: the conductive structure includes caps on opposite ends of the substrate; the resistive portion resides on and contacts the substrate; an insulator resides on and in contact with the resistive portion; and the one or more canceling inductance leads reside on and in contact with the insulator, each lead extending from one of the covers at an opposite end of the substrate.

Example 3 is the shunt resistor of any one of examples 1 or 2, wherein: the resistive portion resides on a first surface of the substrate opposite a second surface of the substrate; an insulator on the second surface of the substrate; and the one or more canceling inductance leads reside on the second surface of the substrate and are electrically connected to the conductive structure.

Example 4 is the shunt resistor of any one of examples 1 to 3, wherein: the conductive structure includes pads on either end of the surface of the substrate; the resistive portion resides on and contacts the substrate between the conductive structures; an insulator resides on and in contact with the resistive portion; and the one or more cancellation inductor leads extend from the bond pad and reside on and in contact with the insulator.

Example 5 is the shunt resistor of any one of examples 1 to 4, wherein: the conductive structure resides on the first surface of the substrate; the one or more canceling inductance leads are electrically connected to the conductive structure on the first surface of the substrate; an insulator resides on the one or more cancellation inductor leads; and the resistive portion resides on and in contact with the insulator.

Example 6 is the shunt resistor of any one of examples 1 to 5, wherein the conductive structure comprises a via traversing from the first surface of the substrate to the second surface of the substrate.

Example 7 is the shunt resistor of any one of examples 1 to 6, wherein the conductive structure comprises a castellated via.

Example 8 is the shunt resistor of any one of examples 1 to 7, wherein the substrate comprises an insulating film, wherein the resistive portion resides on one surface of the film, and the lead resides on a second surface of the film opposite the first surface.

Example 9 is the shunt resistor of any one of examples 1 to 8, wherein at least one of the resistive portion, the conductive structure, and the lead is formed on the substrate in one of painting or printing.

Example 10 is a modular tip interconnect, comprising: a connector at a first end of the interconnect configured to connect to a probe of a test and measurement instrument; and a shunt resistor at a second end of the interconnect configured to be connected to a Device Under Test (DUT), the shunt resistor comprising: a substrate having a conductive structure for carrying a current in a current path; a resistive portion in electrical contact with the conductive structure; and one or more cancellation inductance leads electrically connected to the conductive structure and the resistive portion, the one or more cancellation inductance leads configured to cancel an inductance effect across the resistive portion in a voltage measurement.

Example 11 is the modular tip interconnect of example 10, further comprising a cable between the connector and the shunt resistor.

Example 12 is the modular terminal interconnect of example 11, wherein the cable comprises one of a differential cable, a coaxial cable, or a twisted pair cable.

Example 13 is the modular tip interconnect of any of examples 10 to 12, wherein the shunt resistor resides in an intermediate structure between the cable and the DUT.

Example 14 is the modular tip interconnect of any of examples 10-13, wherein the shunt resistor is connected to an interconnect on the DUT.

Example 15 is the modular tip interconnect of example 14, wherein the interconnect to the DUT comprises one of a wire or a molded flex circuit.

Example 16 is the modular tip interconnect of example 15, wherein the leads fall on the flexible circuit.

Example 17 is the modular tip interconnect of examples 10-16, wherein the shunt resistor is soldered directly to the DUT.

Although specific examples of the invention 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 invention. Accordingly, the invention should not be limited except as by the appended claims.

Claims (17)

1. A shunt resistor comprising:

a substrate having a conductive structure for carrying a current in a current path;

a resistive portion in electrical contact with the conductive structure; and

one or more cancellation inductance leads electrically connected to the conductive structure and the resistive portion, the one or more cancellation inductance leads configured to cancel inductance effects across the resistive portion in a voltage measurement.

2. The shunt resistor of claim 1, wherein:

the conductive structure includes caps on opposite ends of the substrate;

the resistive portion resides on and contacts the substrate;

an insulator resides on and in contact with the resistive portion; and is also provided with

The one or more canceling inductance leads reside on and in contact with the insulator, each lead extending from one of the covers at an opposite end of the substrate.

3. The shunt resistor of claim 1, wherein:

the resistive portion resides on a first surface of the substrate opposite a second surface of the substrate;

an insulator on the second surface of the substrate; and is also provided with

The one or more canceling inductance leads reside on the second surface of the substrate and are electrically connected to the conductive structure.

4. The shunt resistor of claim 1, wherein:

the conductive structure includes pads on either end of the surface of the substrate;

the resistive portion resides on and contacts the substrate between the conductive structures;

an insulator resides on and in contact with the resistive portion; and is also provided with

The one or more cancellation inductor leads extend from the bond pad and reside on and contact the insulator.

5. The shunt resistor of claim 1, wherein:

the conductive structure resides on the first surface of the substrate;

the one or more canceling inductance leads are electrically connected to the conductive structure on the first surface of the substrate;

an insulator resides on the one or more cancellation inductor leads; and is also provided with

The resistive portion resides on and contacts the insulator.

6. The shunt resistor of claim 1, wherein the conductive structure comprises a via traversing from a first surface of the substrate to a second surface of the substrate.

7. The shunt resistor of claim 1, wherein the conductive structure comprises a castellated via.

8. The shunt resistor of claim 1, wherein the substrate comprises an insulating film, wherein the resistive portion resides on one surface of the film and the lead resides on a second surface of the film opposite the first surface.

9. The shunt resistor of claim 1, wherein at least one of the resistive portion, the conductive structure, and the lead is formed onto the substrate in one of a painting or printing.

10. A modular tip interconnect, comprising:

a connector at a first end of the interconnect configured to connect to a probe of a test and measurement instrument; and

a shunt resistor at a second end of the interconnect configured to be connected to a Device Under Test (DUT), the shunt resistor comprising:

a substrate having a conductive structure for carrying a current in a current path;

a resistive portion in electrical contact with the conductive structure; and

one or more cancellation inductance leads electrically connected to the conductive structure and the resistive portion, the one or more cancellation inductance leads configured to cancel inductance effects across the resistive portion in a voltage measurement.

11. The modular tip interconnect of claim 10, further comprising a cable between the connector and the shunt resistor.

12. The modular terminal interconnect of claim 11, wherein the cable comprises one of a differential cable, a coaxial cable, or a twisted pair cable.

13. The modular tip interconnect of claim 10, wherein the shunt resistor resides in an intermediate structure between the cable and the DUT.

14. The modular tip interconnect of claim 10, wherein the shunt resistor is connected to an interconnect on the DUT.

15. The modular tip interconnect of claim 14, wherein the interconnect to the DUT comprises one of a wire or a molded flex circuit.

16. The modular tip interconnect of claim 15, wherein the leads fall on the flexible circuit.

17. The modular tip interconnect of claim 10, wherein the shunt resistor is soldered directly to the DUT.