Compact current sensing for protection and wiring devices

Abstract

Systems and methods for sensing current utilize a wireless coil-based sensor circuit to detect current. The current sensing circuit includes a first conductive line segment carrying a mains AC current, and a second conductive line segment electrically coupled in parallel with the first line segment. A coil-less sensor is mounted between the two conductive wire segments proximate and substantially opposite the second conductive wire segment. Any suitable coil-free sensors may be used, including Hall effect sensors, tunneling magnetoresistance ("TMR") sensors, anisotropic magnetoresistance ("AMR") sensors, and other types of sensors that do not use coils to sense current. This arrangement results in the addition of the induced two magnetic fields at the coil-less sensor, which allows the sensor to produce a higher output voltage, providing a more precise current sensor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This international application claims priority to U.S. Provisional Application No. 63 / 421,545, filed on November 1, 2022, entitled “Compact Current Sensing for Protection and Wiring Devices,” and U.S. Application No. 18 / 215,087, filed on June 27, 2023, entitled “Compact Current Sensing for Protection and Wiring Devices,” and is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to circuit breakers, wiring devices, and other devices that monitor electrical current, and more particularly, to systems and methods for sensing electrical current that are more compact relative to existing solutions. Background Art

[0004] Modern protective devices (e.g., circuit breakers), wiring devices, and other devices that monitor current flow have components that enable a variety of functions that were previously unavailable in existing devices. For example, a microcontroller in an electronic circuit breaker allows the circuit breaker to function as both a ground fault circuit interrupt (GFCI) device and an arc fault circuit interrupt (AFCI) device. The GFCI function can detect a conductive path formed between an ungrounded current-carrying conductor and the earth, while the AFCI function can detect intermittent faults caused by worn or damaged insulation, loose connections, broken conductors, etc. The microcontroller detects such faults by constantly sensing and sampling the line currents and monitoring these currents.

[0005] In many electronic circuit breakers, the current sensor is a current transformer. This current transformer can be optimally configured for current sensing by adjusting the number of secondary winding turns or by using a ferrite core, etc. In some circuit breakers, a di / dt current sensor, also known as a "current rate of change" sensor or "current rise time" sensor or Rogowski coil, is used in place of a current transformer. A di / dt sensor provides an output signal (i.e., a voltage signal) that is proportional to the rate of change of its input signal (i.e., the line current).

[0006] However, using current transformers, di / dt sensors, and similar types of current sensors presents some design challenges. First, these current sensors take up a lot of space, making them difficult to integrate into already crowded electronic circuit breakers. This is especially true for miniature circuit breakers (MCBs), where internal space is extremely limited. Additional challenges often arise due to the increased mechanical complexity that typically accompanies these current sensors.

[0007] Therefore, there is a need for a method to reduce the internal spacing required for current sensors within protection devices, wiring devices, and other devices that monitor current. Summary of the invention

[0008] Embodiments of the present disclosure provide systems and methods for reducing the internal spacing required for current sensors within protection devices, wiring devices, and other devices that monitor current. In some embodiments, the systems and methods provide a current monitoring device, such as a circuit breaker or wiring device, that uses a coil-free sensor to detect current. Examples of coil-free sensors that can be used include Hall effect sensors, tunnel magnetoresistance ("TMR") sensors, anisotropic magnetoresistance ("AMR") sensors, and other types of sensors that do not use coils to sense current. The coil-free current sensor can detect the magnetic field generated by the current and provide an output voltage proportional to the detected magnetic field. Such coil-free current sensors are generally well known to those of ordinary skill in the art for their small package size and footprint.

[0009] In some embodiments, a current monitoring device incorporates a coil-free sensor into a highly compact current sensing circuit that can be used to monitor the current flowing through the device. The compact current sensing circuit includes two conductive segments, namely a first segment that carries the AC current of the mains, and a second segment that is electrically connected in parallel to the first segment. In some embodiments, the first segment or main segment can be a bus bar, and in some embodiments, the second segment can be a conductive trace on a printed circuit board (PCB). The coil-free sensor, which can be a TMR sensor in some embodiments, is then mounted between the two conductive segments near the second segment. In these embodiments, the conductive trace is formed on one side of the PCB, and the coil-free sensor is mounted on the other side of the PCB that is substantially opposite to the conductive trace, and the bus bar extends above the coil-free sensor in electrical parallel with the conductive trace. In some embodiments, the conductive trace can have a shape similar to the letter "S", so that the middle leg of the "S" carries a current that is parallel to the current in the bus bar but in the opposite direction. This arrangement results in the induction of two magnetic fields that are added at the coil-free sensor, which causes the sensor to produce a higher output voltage than a single magnetic field from the bus bar or conductive trace alone, thereby improving the overall sensing accuracy.

[0010] In some embodiments, a magnetic shield may be provided for the compact current sensing circuit to reduce electromagnetic noise. The magnetic shield may have any suitable shape that prevents or minimizes external electromagnetic fields from interfering with the operation of the compact current sensing circuit. Example shield shapes may include a shape generally similar to the letter "U", such as a rectangular or oval with an open top in some embodiments, and a shape with a closed or partially closed top, and in some embodiments may be attached to a PCB so that the middle leg of the coil-free sensor, bus bar, and conductive trace is within the shield. Such a shield may be made of a suitable high permeability material, which helps prevent external magnetic fields from reaching the middle leg of the sensor, bus bar, and conductive trace. The above components result in a further improvement in sensing accuracy. The output voltage from the coil-free sensor may then be processed and provided to a controller of the current monitoring device to monitor the current in the device.

[0011] In general, in one aspect, embodiments of the present disclosure relate to a compact current sensing circuit. The compact current sensing circuit particularly includes a main conductive line segment and a second conductive line segment, the second conductive line segment being opposite to the main conductive line segment and electrically connected to the main conductive line segment in parallel. The compact current sensing circuit also includes a coil-free sensor, which is installed between the main conductive line segment and the second conductive line segment, opposite to the second conductive line segment and close to the second conductive line segment. Thereafter, the current flowing through the main conductive line segment and the second conductive line segment induces a magnetic field added at the coil-free sensor.

[0012] In general, on the other hand, embodiments of the present disclosure relate to a current monitoring device. The current monitoring device includes, among other things, a controller and a compact current sensing circuit that is connected to provide a signal to the controller indicating a current flowing through the current monitoring device. The compact current sensing circuit includes a main conductive wire segment and a second conductive wire segment, the second conductive wire segment being conductively connected to the main conductive wire segment opposite to and electrically parallel to the main conductive wire segment. The compact current sensing circuit also includes a coil-free sensor that is installed between the main conductive wire segment and the second conductive wire segment, opposite to and adjacent to the second conductive wire segment. Thereafter, the current flowing through the main conductive wire segment and the second conductive wire segment induces a magnetic field that is added at the coil-free sensor, and the coil-free sensor is configured to provide a signal to the controller based on the magnetic field.

[0013] In general, in yet another aspect, embodiments of the present disclosure relate to a method of providing a compact current sensing circuit in a current monitoring device. The method includes, among other things, conductively coupling a main conductive wire segment to a second conductive wire segment opposite and electrically parallel to the main conductive wire segment. The method also includes mounting a coil-free sensor between the main conductive wire segment and the second conductive wire segment, opposite and proximate to the second conductive wire segment. Thereafter, current flowing through the main conductive wire segment and the second conductive wire segment induces a magnetic field that is added at the coil-free sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a block diagram illustrating an exemplary current monitoring device using a compact current sensing circuit according to an embodiment of the present disclosure;

[0015] Figure 2A and 2B is a schematic diagram illustrating an exemplary compact current sensing circuit according to an embodiment of the present disclosure;

[0016] Figure 3A and 3B is a schematic diagram illustrating an exemplary compact current sensing circuit in more detail according to an embodiment of the present disclosure;

[0017] Figures 4A-4C is a schematic diagram illustrating magnetic fields and magnetic shielding of an exemplary compact current sensing circuit according to an embodiment of the present disclosure;

[0018] Figures 5A-5D is a schematic diagram illustrating an exemplary current monitoring device employing an exemplary compact current sensing circuit according to an embodiment of the present disclosure;

[0019] Figure 6 is a schematic diagram illustrating another exemplary current monitoring device employing an exemplary compact current sensing circuit according to an embodiment of the present disclosure;

[0020] Figure 7 is a schematic diagram illustrating an exemplary received signal strength indicator (RSSI) circuit that may be used with an exemplary compact current sensing circuit according to an embodiment of the present disclosure; and

[0021] Figure 8 is a flow chart illustrating an exemplary method of monitoring current using an exemplary compact current sensing circuit according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] This specification and the accompanying drawings illustrate exemplary embodiments of the present disclosure and should not be considered as limiting, and the claims define the scope of the present disclosure, including equivalents. Various mechanical, compositional, structural, electrical and operational changes may be made without departing from the scope of the present specification and the claims (including equivalents). In some cases, well-known structures and techniques are not shown or described in detail to avoid confusing the present disclosure. In addition, elements and related aspects thereof described in detail with reference to one embodiment may be included in other embodiments in which they are not specifically shown or described, as long as feasible. For example, if an element is described in detail with reference to one embodiment, without describing with reference to a second embodiment, the element may still be required to be included in the second embodiment.

[0023] Reference now Figure 1, a block diagram of an exemplary current monitoring device 100 using a compact current sensing circuit according to an embodiment of the present disclosure is shown. The current monitoring device 100 in this example is a double-pole electronic circuit breaker 100, which is designed to monitor current and provide ground fault (GFCI) and / or arc fault (AFCI) protection. To this end, the circuit breaker 100 includes a plurality of functional components or modules, some of which are represented here as blocks, which will be discussed further below. Of course, it will be understood that within the scope of the present disclosure, each block shown here (and in subsequent figures) may be divided into multiple constituent blocks, or two or more blocks may be combined into a single block.

[0024] As can be seen, the circuit breaker 100 includes a ground fault sensing circuit 102, an arc fault sensing signal 104, a compact current sensing circuit 106, and a trip unit 108 in communication with a controller 110. The controller 110 is typically a microcontroller unit (MCU) and typically has at least one analog-to-digital converter (ADC) 112, a ground fault detection module 114, an arc fault detection module 116, and a wired and / or wireless interface module 118 therein. In some embodiments, the ADC 112 may also be a separate component from the controller 110. Other functional components and modules not explicitly shown may also be included within the scope of the present disclosure. Likewise, one or more explicitly shown functional components or modules may be removed without departing from the present disclosure.

[0025] The operation of the circuit breaker 100 is generally well known in the art, so only a brief description is provided here. Generally, the controller 110 receives input signals from the ground fault sensing circuit 102, the arc fault sensing circuit 104, the compact current sensing circuit 106, and other circuits capable of sensing the mains AC current or voltage in the line conductors (not explicitly shown) of the circuit breaker 100. The ADC 112 samples these signals at a certain sampling rate, which is high enough for the various functions provided by the circuit breaker 100. The ADC 112 converts each sample into a numerical value proportional to the sample amplitude and outputs these values ​​to other components and modules in the controller 110. The controller 110 then processes the data in a known manner to monitor the occurrence of fault conditions, such as ground faults, arc faults, short circuits, etc. When a fault condition is detected, the controller 110 sends a trip signal to the trip unit 108, which causes the trip unit 108 to immediately cut off the current flowing through the circuit breaker 100.

[0026] Figure 2A and 2Bis a perspective view showing an example of a compact current sensing circuit 106 according to an embodiment of the present disclosure. In the depicted example, the compact current sensing circuit 106 includes a first or main conductive wire segment 200, a pair of conductive shunt arms 202 and 204, and a second conductive wire segment 206. The conductive shunt arms 202 and 204 conductively couple the main conductive wire segment 200 to the second conductive wire segment 206 so that current can flow from the main conductive wire segment 200 through the second wire segment 206 and back to the main conductive wire segment 200.

[0027] Although not explicitly shown, the main wire segment 200 is connected to the main AC line within the circuit breaker 100 so as to carry the main AC current therein, as indicated by the solid arrow line 212. The second wire segment 206 extends between the shunt arms 202 and 204 so as to carry the main AC current in electrical parallel with the main wire segment 200, also as indicated by the solid arrow line 212. The coil-free sensor 208 is positioned adjacent to the second wire segment 206 and is mounted in the space between the main wire segment 200 and the second wire segment 206.

[0028] In some embodiments, the first or main conductor segment 200 may be a bus bar and the second conductor segment 206 may be a conductive trace (eg, copper) on a printed circuit board (PCB) (see Figure 3A and 3B ). In these embodiments, the conductive trace 206 is a generally planar trace formed on one side of the PCB, and the coil-free sensor 208 is mounted on the other side of the PCB generally opposite the conductive trace 206. When viewed from the sensor 208, the bus bar 200 extends above the sensor 208 in electrical parallel with the conductive trace 206.

[0029] The coil-free sensor 208 may be any commercially available coil-free sensor suitable for a given application. As previously described, any sensor that does not require a coil to detect current may be used as the coil-free sensor 208, including Hall effect sensors, tunnel magnetoresistance ("TMR") sensors, anisotropic magnetoresistance ("AMR") sensors, and similar types of sensors. Examples of suitable commercially available TMR sensors are available from a number of coil-free sensor manufacturers, such as Crocus Technologies, Inc. of Milpitas, California, USA, and Infineon Technologies, Inc. of Neubiberg, Germany, among others. These TMR sensors are typically low-profile surface mount devices approximately 3 mm by 3 mm in size, suitable for particularly compact applications.

[0030] In some embodiments, conductive trace 206 may have a shape similar to the letter "S" (or an inverted "S", depending on the viewing point) such that the middle leg 206b of the "S" carries a current that is physically parallel to, but in the opposite direction to, the current in bus bar 200. According to the right-hand rule of magnetic field induction, this results in the magnetic field induced by the current in the middle leg 206b having a direction opposite to the magnetic field induced by the current in the other two legs 206a and 206c, as shown by dashed arrow line 214.

[0031] In some embodiments, a magnetic shield 210 may be mounted on the compact current sensing circuit 106 to reduce electromagnetic noise. In some embodiments, the magnetic shield 210 may have a shape roughly similar to the letter "U", such as a rectangular or oval shape with an open top, or a shape with a closed or partially closed top, and in some embodiments, may be attached to the PCB so that the bus bar 200, the middle leg 206b of the conductive trace 206, and the coil-free sensor 208 are within the shield 210. Such a shield 210 may be made of a suitable high magnetic permeability material that can help prevent external magnetic fields from reaching the bus bar 200, the middle leg 206b of the conductive trace 206, and the coil-free sensor 208. The specific size and spacing of the shield 210 may be selected as needed based on the specific requirements of a given application.

[0032] Figure 3A and 3B 300 , and a side view and a bottom view, respectively, of an exemplary compact current sensing circuit 106 according to an embodiment of the present disclosure are shown in greater detail. As can be seen here, in some embodiments, the conductive trace 206 is formed (e.g., by etching, photolithography, etc.) on one side of the PCB 300, and the coil-free sensor 208 is mounted on the other side of the PCB 300 that is generally opposite to the conductive trace 206. More specifically, the coil-free sensor 208 is disposed on the PCB 300, generally opposite to the middle leg 206b of the conductive trace 206, so as to optimize exposure to the magnetic field induced by the current in the leg 206b. The bus bar 200 is also located above the coil-free sensor 208, physically parallel to the middle leg 206b of the conductive trace 206. As previously described, the specific dimensions and spacing of the bus bar 200, the conductive trace 206, and the coil-free sensor 208 can be selected as needed according to the specific requirements of a given application.

[0033] Figures 4A-4Care cross-sectional elevation views illustrating magnetic fields generated by various components of a compact current sensing circuit 106 and exemplary shields that may be used therewith according to embodiments of the present disclosure. In these figures, magnetic field lines are represented by dashed elliptical lines, respectively, and the direction of each magnetic field is represented by a solid arrow. Thus, magnetic field line 400 represents the magnetic field induced by the current in bus bar 200, while magnetic field lines 402, 404, and 406 represent the magnetic field induced by the current in each leg 206a, 206b, and 206c of conductive trace 206, respectively. As indicated by the solid arrows, magnetic field lines 400 of the magnetic field induced by the current in bus bar 200 and magnetic field lines 404 of the magnetic field induced by the current in middle leg 206b are additive at coil-free sensor 208.

[0034] The above arrangement enables the coil-free sensor 208 to generate a higher output voltage in response to the two added magnetic fields 400 and 404 compared to a single magnetic field from any leg 206a, 206b, or 206c of the bus bar 200 or the conductive trace 206 alone, thereby improving overall sensing accuracy. In addition, a magnetic shield can be provided to help prevent external magnetic fields from reaching the bus bar 200, the middle leg 206b of the conductive trace 206, and the coil-free sensor 208, thereby further improving overall sensing accuracy. As previously described, the magnetic shield can have any suitable shape depending on the particular application, including in some embodiments a shape roughly similar to the letter "U", such as a rectangular shape 210a with an open top ( Figure 4A ), or an oval shape 210b with an open top ( Figure 4B ), or the shield may have a closed or partially closed top shape 210c ( Figure 4C The output voltage from the coilless sensor 208 may then be processed and provided to the controller 110 of the circuit breaker 100 (see Figure 1 ) to monitor the current in the circuit breaker.

[0035] Figures 5A-5D is a schematic diagram showing an example of the disclosed compact current sensing circuit used in a current monitoring device. In these and other figures, L and L' represent the main line and the second line, respectively, while L1 and L2 are different phases of a two-phase current source, and N represents a neutral line.

[0036] First reference Figure 5A, an exemplary circuit breaker 500a is shown in which the compact current sensing circuit ("CCSC") disclosed herein may be used. The circuit breaker 500a is a typical single-pole circuit breaker that includes a high-frequency analog front end 502, a microcontroller unit 504, and a power supply 506, among other components. These components and their operation are generally well known to those of ordinary skill in the art, and therefore a detailed description is omitted herein. Mains AC current is provided to the circuit breaker 500a from a utility or other suitable AC current source 516 via a switch or relay 508. According to an embodiment of the present disclosure, the mains AC current is sensed using a compact current sensing circuit 512, which operates as shown and described previously herein. The output voltage from the sensor circuit 512 is then provided to the microcontroller unit 504 to monitor the current in the circuit breaker 500 in a known manner.

[0037] Figure 5B An example of a compact current sensing circuit disclosed herein for use with a double-pole circuit breaker 500b is shown. The double-pole circuit breaker 500b, as shown in FIG. Figure 5A 500a, has a high frequency analog front end 502, a microcontroller unit 504 and a power supply 506, among other components. In this example, the mains AC current is provided to the two poles from a two-phase AC current source 516' through two trip latches 510 and 510', respectively. As shown, two compact current sensing circuits 512 and 514 are used to sense the AC current flowing through the two trip latches 510 and 510', one for each pole. The output voltage from each sensor circuit 512 and 514 is then provided to the microcontroller unit 504 to monitor the current.

[0038] Figure 5C FIG. 5 shows an example of a compact current sensing circuit disclosed herein used with another double-pole circuit breaker 500c. The double-pole circuit breaker 500c here is similar to Figure 5B 500b, except that in this example, the AC current from the mains AC current source 516 flows through two switches or relays 508 and 508', respectively. The AC current flowing through the two switches or relays 508 and 508' is again sensed using two compact current sensing circuits 512 and 514, respectively, one for each pole. The output voltage from each sensor circuit 512 and 514 is then provided to the microcontroller unit 504 for monitoring purposes.

[0039] Figure 5DAn alternative circuit breaker 500d is shown, in which the compact current sensing circuit disclosed herein can be used. The circuit breaker 500d is also a double-pole circuit breaker, but includes separate group components for each pole. Therefore, the circuit breaker 500d has two high-frequency analog front ends 502 and 502', two microcontroller units 504 and 504' and two power supplies 506 and 506' and other components. As mentioned above, these components and their operation are generally known to those of ordinary skill in the art, and for the sake of economy, detailed description is omitted. The mains AC current from the AC current source 516 is again provided to each pole of the circuit breaker 500d through two switches or relays 508 and 508', respectively. The mains AC current is sensed again using two compact current sensing circuits 512 and 514, one circuit for each pole. The output voltage from each sensor circuit 512 and 514 is then provided to the microcontroller unit 504 and 504' to monitor the current.

[0040] Figure 6 is a schematic diagram illustrating an example of the compact current sensing circuit disclosed herein used in another current monitoring device 600 . Figure 6 The current monitoring device 600 in the example is a wiring device 600 that includes an electrical socket 602 that is commonly used to plug in various electrical appliances. Mains AC current is supplied via a branch circuit (not explicitly shown) through a switch or relay 604 operated by a relay unit 606. The relay unit 606 is in turn controlled by a controller 606 that monitors the current through the socket 602. According to an embodiment of the present disclosure, a compact current sensing circuit 610 as shown and described herein is used to sense the flow of current. The output voltage from each sensor circuit 610 is then provided to the controller 606 to monitor the current flowing through the socket 602.

[0041] Embodiments of the present disclosure also provide many other advantages. For example, in existing designs, RSSI (receiver signal strength indicator) and line current are typically connected to di / dt sensors. However, the embodiments described herein can be used to allow RSSI to be captured from the voltage between the line (L) and the neutral (N), or for high frequency (HF) signals generated from branch circuits, from the low impedance path between L and N. That is, the compact current sensing circuit disclosed herein can be used to obtain line current from a coil-free sensor (such as a TMR sensor). This provides a compact design for current AFCI devices. For series devices, a single RSSI signal path and two sensors can be used to measure current from two different bus bars and mechanical subassemblies. This allows for a simplified design in which a single microcontroller is used and the same AFD algorithm for a bipolar configuration is utilized. In addition, both line currents are isolated, so no isolation circuit is required. This also allows more available space for other sensors, such as ground fault (GF) sensors or communication circuits. In wiring devices, energy monitoring elements that typically require shunt sensors and high-sensitivity ADCs can be replaced with coil-free sensors that provide current measurement signals to a communications controller, resulting in cost savings over existing designs.

[0042] Figure 7 An example of an RSSI circuit 700 is shown, which can be used in a current monitoring device to capture RSSI from the voltage between the line (L) and the neutral line (N). The RSSI circuit 700 in this example includes a bandpass filter 702 and a voltage amplifier 704, connected as shown. In some embodiments, one of the inputs of the bandpass filter 702 is provided by the line (L) through a capacitor C1, and the other input of the bandpass filter 702 is provided by the neutral line (N) through a second capacitor C2. In some embodiments, capacitors C1 and C2 can have approximately equal capacitance. A diode arrangement Dp including two diodes connected in reverse parallel can be connected to the input of the bandpass filter 702 to limit the voltage on the bandpass filter 702 to a diode voltage drop. The output of the bandpass filter 702 is then fed to the input of the voltage amplifier 704, and the output voltage from the amplifier 704 is then fed to the MCU (specifically its ADC) of the current monitoring device. This RSSI circuit 700 allows RSSI to be captured from the voltage between the line (L) and the neutral line (N) without the need for a separate di / dt sensor.

[0043] Reference now Figure 8, a flow chart 800 is shown illustrating an exemplary method for detecting and monitoring current using the exemplary compact current sensing circuit described herein according to an embodiment of the present disclosure. The method generally begins by providing a compact current sensing circuit that can be used to detect and monitor current. Thus, at 802, a main conductive wire segment is conductively coupled to a second conductive wire segment that is opposite and electrically parallel to the main conductive wire segment. In some embodiments, the main conductive wire segment can be a bus bar and the second conductive wire segment can be a conductive trace on a printed circuit board (PCB). In some embodiments, the conductive coupling can be accomplished by a pair of conductive shunt arms that connect the main conductive wire segment to the second conductive wire segment.

[0044] At 804, the coil-free sensor is mounted between the main conductive line segment and the second conductive line segment, opposite to and adjacent to the second conductive line segment. In embodiments where the second conductive line segment is a planar trace on a PCB, the coil-free sensor is mounted on one side of the PCB, and the conductive trace is formed on another side of the PCB that is substantially opposite to the coil-free sensor. At 806, a magnetic shield is optionally provided around the coil-free sensor. In some embodiments, the magnetic shield can have a shape roughly similar to the letter "U" with an open top, or the shield can be closed or partially closed. Similarly, in some embodiments, the second conductive line segment can have a shape similar to the letter "S".

[0045] At 808, current from the mains AC current source is allowed to flow through the main conductive wire segment, and thus through the second conductive wire segment. The current induces a magnetic field around the main conductive wire segment and the second conductive wire segment. Due to the position and shape of the second conductive wire segment, the magnetic field induced by the current in the middle leg of the second conductive wire segment is added to the magnetic field induced by the current in the main conductive wire segment at the coil-free sensor. The added magnetic field allows the coil-free sensor to produce a higher output voltage than would otherwise be possible, thereby achieving greater sensing accuracy.

[0046] At 810, the output from the coil-free sensor is sampled, for example, by an analog-to-digital converter and pre-processed (e.g., filtered, etc.). At 812, the sampled output from the coil-free sensor is provided to a controller unit, such as a microcontroller unit, which further processes the output in a known manner for monitoring and detection purposes.

[0047] Thus, it can be seen that the embodiments disclosed herein provide many benefits and advantages. For example, the disclosed embodiments simplify the assembly process in manufacturing because the coil-free sensor can be assembled with other surface mount components during PCB module assembly. The busbar assembly is also simplified because it does not need to be inserted through a core / winding based sensor, and the resulting improved gap allows the busbar to be simply soldered in place. Lower manufacturing costs can also be achieved because the coil-free sensor is a true sensor and therefore does not require additional active components, such as amplifiers or integrators. The disclosed embodiments are particularly ideal solutions for AFCI and EM (electromagnetic) applications in AFCI and series AFCI and wiring devices where space is a major constraint. These embodiments provide a compact design, compared to core-based sensors that increase the complexity of manufacturing and also require more space.

[0048] In addition, the design of the PCB traces along with the bus bar assembly improves the magnetic field around the sensor, thereby increasing the SNR (signal-to-noise ratio) and improving the sensitivity of the sensor. As mentioned above, the PCB traces are in an "S" shape, carrying current in the opposite direction of the bus bar. This produces a magnetic field in the same direction on both sides of the sensor, resulting in a stronger magnetic field than the magnetic field from the trace or bus bar alone.

[0049] The U-shaped shield made of high permeability material allows for good crosstalk isolation from external magnetic fields with minimal or no effect on AFD (arc fault detection) or energy monitoring. This shield prevents the opposing magnetic field generated by current passing through adjacent parallel traces from canceling the magnetic field generated by the trace below the sensor. The shield essentially reserves space around the sensor for the desired magnetic field for current measurement.

[0050] The PCB traces and busbars carry current on both sides of the coil-less sensor. The busbar carries most of the current, but the PCB traces are closer to the sensor. Both the busbar and the PCB traces generate magnetic fields that add up toward the center of the sensor instead of canceling each other out. This increases the total magnetic field generated by both current paths.

[0051] Sensors such as the TMR sensor are true current sensors and not di / dt sensors (such as Rogowski coils). Therefore, there is no need to integrate the sensor signal to derive the true current. The assembly of the busbar and TMR sensor can be fully automated and does not require complex handling. The U-shaped magnetic shield is designed to completely isolate any external magnetic field and is easily integrated into the assembly process with minimal space requirements. In AFCI applications, line current can be measured without the need for a di / dt sensor and the associated integrator, whether using a 1-pole / 2-pole or series design. A low-pass filter is sufficient for the AFD and the signal can be sampled directly with the microcontroller's ADC peripheral.

[0052] It should be understood that the above description is intended to be illustrative, not restrictive. After reading and understanding the above description, many other implementation examples are apparent. Although the present disclosure describes specific examples, it should be appreciated that the systems and methods of the present disclosure are not limited to the examples described herein, but can be implemented by modification within the scope of the appended claims. Therefore, the description and drawings should be considered illustrative, not restrictive. Therefore, the scope of the present disclosure should be determined with reference to the appended claims and the full scope of the equivalents of these claims.

Claims

1. A compact current sensing circuit comprising: Main conductor segment; a second conductive line segment, opposite to the main conductive line segment and conductively coupled to the main conductive line segment in electrical parallel thereto; as well as a coil-free sensor mounted between the main conductive line segment and the second conductive line segment, opposite to and adjacent to the second conductive line segment; Therein, the current flowing through the main conductive line segment and the second conductive line segment induces a magnetic field that is added at the coil-free sensor. 2 . The compact current sensing circuit of claim 1 , further comprising a magnetic shield surrounding the coil-less sensor.

3. The compact current sensing circuit according to claim 2, wherein: The magnetic shield surrounding the coil-less sensor has a shape roughly similar to the letter "U" or a closed or partially closed rectangular shape.

4. The compact current sensing circuit according to claim 1, wherein: The main conductor segments are bus bars.

5. The compact current sensing circuit according to claim 1, wherein: The second conductive line segment is a conductive trace on a printed circuit board (PCB).

6. The compact current sensing circuit according to claim 5, wherein: The conductive traces on the PCB have a shape similar to the letter "S". 7 . The compact current sensing circuit of claim 1 , further comprising a pair of shunt arms conductively coupling the main conductive line segment to the second conductive line segment.

8. A current monitoring device, comprising: Controller; A compact current sensing circuit connected to provide a signal to a controller indicative of a current flowing through a current monitoring device, the compact current sensing circuit comprising: Main conductor segment; a second conductive line segment opposite the main conductive line segment and conductively coupled to the main conductive line segment in electrical parallel thereto; and a coil-free sensor mounted between the main conductive line segment and the second conductive line segment, opposite to and adjacent to the second conductive line segment; The current flowing through the main conductive line segment and the second conductive line segment induces a magnetic field that is summed at the coil-free sensor, and the coil-free sensor is configured to provide the signal to the controller based on the magnetic field.

9. The current monitoring device according to claim 8, wherein: The current monitoring device is a circuit breaker and further includes a trip unit controlled by the controller based on a signal provided to the controller by the coil-less sensor.

10. The current monitoring device according to claim 8, wherein: The current monitoring device is a wiring device and further includes a relay unit controlled by the controller based on a signal provided to the controller by the coil-less sensor.

11. The current monitoring device of claim 8, further comprising a magnetic shield surrounding the coil-less sensor.

12. The current monitoring device according to claim 8, wherein: The main conductor segments are bus bars.

13. The current monitoring device according to claim 8, wherein: The second conductive line segment is a conductive trace on a printed circuit board (PCB).

14. The current monitoring device of claim 8, further comprising a pair of shunt arms electrically coupling the main conductive line segment to the second conductive line segment.

15. A method of providing a compact current sensing circuit in a current monitoring device, comprising: Conductively coupling the main conductive line segment to a second conductive line segment opposite and electrically connected in parallel with the main conductive line segment; and The coil-free sensor is installed between the main conductive line segment and the second conductive line segment, opposite to and close to the second conductive line segment; Therein, the current flowing through the main conductive line segment and the second conductive line segment induces a magnetic field that is added at the coil-free sensor.

16. The method of claim 15, further comprising providing a magnetic shield around the coil-free sensor.

17. The method according to claim 16, wherein: The magnetic shield surrounding the coil-less sensor has a shape roughly similar to the letter "U" or a closed or partially closed rectangular shape.

18. The method according to claim 15, wherein: The main conductor segments are bus bars.

19. The method according to claim 15, wherein: The second conductive line segment is a conductive trace on a printed circuit board (PCB).

20. The method according to claim 19, wherein: The conductive traces on the PCB have a shape similar to the letter "S".

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