US20160202294A1 - Hybrid closed-loop/open-loop magnetic current sensor - Google Patents
Hybrid closed-loop/open-loop magnetic current sensor Download PDFInfo
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- US20160202294A1 US20160202294A1 US15/076,218 US201615076218A US2016202294A1 US 20160202294 A1 US20160202294 A1 US 20160202294A1 US 201615076218 A US201615076218 A US 201615076218A US 2016202294 A1 US2016202294 A1 US 2016202294A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
- G01R15/185—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
Definitions
- the present disclosure relates to current sensors and more particularly to closed-loop non-contacting current sensing systems.
- Open-loop current sensing provides a cost effective solution in which a magnetic field generated by the flow of current through an electrical conductor is concentrated inside a magnetic core and a magnetic sensor measures the field and provides an output signal used for estimating the current flow.
- Open-loop approaches typically consume little power, and can use low sensitivity sensors for measuring high currents.
- the open-loop approach suffers from poor accuracy, typically due to nonlinearities of the core and/or the sensor.
- Closed-loop current sensing techniques may be employed with a magnetic core encircling an electrical conductor, where a secondary winding or compensation coil is provided on the core and driven by the sensor until the magnetic flux within the core is zero.
- the secondary current at this point is measured and is generally proportional to the primary current flowing in the electrical conductor of interest.
- the closed-loop approach generally provides improved accuracy compared with open-loop techniques, and is thus preferred in applications using the current measurement for regulation of host system performance or for power metering applications.
- closed-loop current sensing is generally restricted to the capabilities of the compensation coil driver circuitry, and accommodating a high sensed current range is expensive and consumes a significant amount of power.
- close-loop techniques are not economical for certain high current sensing applications, while open-loop techniques may not provide the required level of accuracy in current sensing at nominal or expected current levels.
- Hybrid closed-loop/open-loop techniques and apparatus are provided for non-contact current measurement by which the foregoing and other shortcomings can be mitigated or overcome.
- Integrated dual-sensor apparatus embodiments are disclosed to facilitate current measurement in situations where good accuracy is required over a nominal current range and significantly higher current levels can be measured with reduced accuracy requirements without significant cost and size impact, by providing the accuracy benefits of closed-loop current sensing techniques in combination with an open-loop sensor to accommodate some measure of current sensing during system overload conditions.
- disclosed embodiments may be employed to facilitate enhanced system integrity and self-testing by redundant current sensing capability.
- Hybrid closed-loop, open-loop magnetic current sensor apparatus including an integrated circuit having first and second current sensing circuits formed as part of the integrated circuit structure.
- a first current sensing circuit includes a first magnetic sensor along with a driver circuit to provide a compensation signal at least partially according to the first magnetic sensor output signal in a closed-loop magnetic circuit to drive a compensation coil associated with a core structure magnetically affected by measured current flowing in a conductor.
- the first current sensing circuitry moreover, includes a compensation sensing circuit providing a first current sensor signal at least partially according to the compensation signal from the driver circuit.
- the apparatus further includes a second current sensing circuit with a second magnetic sensor formed as part of the integrated circuit structure, which provides a second current sensor signal, and an output circuit providing an output signal representing the current flowing in the conductor at least partially according to the first current sensor signal and/or the second current sensor signal.
- the first magnetic sensor employed in the closed-loop magnetic circuit is a fluxgate sensor with corresponding excitation and sensing circuitry
- the second magnetic sensor can be a Hall sensor, such as a vertical Hall sensor in various embodiments.
- the driver circuit in certain embodiments provides a compensation signal in a first mode at a level representing the current flowing in the conductor to regulate the closed-loop magnetic circuit to a constant flux level over all or at least a portion of a first current range, and the driver may discontinue the compensation signal or provide compensation at a constant level in a second mode over a second current range in various embodiments.
- the output circuit in certain embodiments provides separate first and second outputs signals respectively representing the first and second current sensor signals, or may provide one output signal based on the first current sensor signal over the first current range and provide the output signal based on the second current sensor signal over at least a portion of the second range.
- the output circuit provides an output signal as a sum or other function of the first current sensor signal and the second current sensor signal, through analog circuitry and/or through operations on converted digital values based on the current sensor signals.
- Certain embodiments include a logic circuit comparing one or both of the first magnetic sensor output signal and the second current sensor signal with a corresponding threshold, and the logic circuit controls the output circuit in a first state to provide the output signal or signals based on the first current sensor signal when the compared signal is below the threshold, and in a second state to provide the output signal at least partially according to the second current sensor signal when the compared signal is greater than or equal to the corresponding threshold.
- a current sensing apparatus including a first current sensing circuit with a fluxgate sensor circuit providing a first magnetic sensor output signal according to a magnetic field, a driver circuit providing a compensation signal in a closed-loop magnetic circuit at least partially according to the first magnetic sensor output signal, and a compensation sensing circuit which provides a first current sensor signal at least partially according to the compensation signal from the driver circuit.
- the apparatus further includes a Hall sensor providing a second current sensor signal at least in part according to the magnetic field, as well as an output circuit that provides one or more output signals according to the first current sensor signal over at least a portion of a first current range and according to the second current sensor signal over a second current range.
- a hybrid closed-loop, open-loop magnetic current sensor in accordance with further aspects of the present disclosure, which includes a magnetically susceptible core structure accommodating an electrical conductor, a compensation coil with at least one winding around the core, and an integrated circuit with means for testing current flow in the conductor using a closed-loop magnetic circuit comprising a fluxgate sensor formed on or in the integrated circuit, as well as means for testing the current flow using an open-loop magnetic circuit with a Hall sensor formed on or in the integrated circuit.
- FIG. 1 is a schematic diagram illustrating an exemplary hybrid current sensing system with two magnetic sensors integrated into a single integrated circuit disposed within a magnetic core gap for closed-loop, open-loop current sensing according to one or more embodiments;
- FIG. 2 is a schematic diagram illustrating further details of the integrated magnetic sensors and associated excitation and sensing circuitry according to one or more embodiments;
- FIG. 3 is a partial front elevation view illustrating positioning of the first and second magnetic sensors and a portion of a corresponding integrated circuit within a gap of the magnetic core in the current sensor system of FIGS. 1 and 2 ;
- FIG. 4 is a schematic diagram illustrating an exemplary output circuit embodiment in the current sensing system of FIG. 1 providing a voltage output signal corresponding to a selected one of the closed-loop and open-loop sensor circuits;
- FIG. 5 is a schematic diagram illustrating another output circuit embodiment including an analog-to-digital converter providing a digital output corresponding to a selected one of the closed-loop and open-loop sensor circuits;
- FIG. 6 is a schematic diagram illustrating another output circuit embodiment in the current sensing system, providing separate first and second voltage outputs corresponding to the closed-loop and open-loop sensor circuits;
- FIG. 7 is a schematic diagram illustrating a further output circuit embodiment including separate outputs corresponding to the closed-loop and open-loop sensor circuits and a combined output;
- FIG. 8 is a waveform diagram illustrating various electrical signals in the current sensing system of FIG. 1 showing an embodiment in which closed-loop compensation coil driver circuitry is operational in a first current sensing range and is selectively disabled in a second higher current sensing range;
- FIG. 9 is a waveform diagram illustrating electrical signals in another embodiment of the current sensing apparatus in which the compensation coil driver circuitry provides a fixed level of compensation coil excitation in the second higher current sensing range.
- FIG. 1 an exemplary integrated closed-loop/open-loop current sensor apparatus 2 is shown in FIG. 1 for measuring a primary current I PRI flowing in a primary coil or conductor 4 magnetically interacting with a magnetic core 6 .
- the conductor 4 can be magnetically interfaced with the core 6 in any suitable fashion by which the core structure 6 is magnetically affected by the current flow I PRI in the conductor 4 , and the conductor 4 may be a single electrical conductor passing through the core 6 as shown in FIG. 1 , or can be a winding with one or more turns encircling portions of the core 6 , or other suitable magnetic interaction configuration by which the current I PRI flowing in the conductor 4 affects the magnetic flux in the core 6 .
- Multiple primary conductors 4 may be used in certain embodiments, for example, in ground fault sensing applications with a primary conductor 4 passing through the opening in the core 6 to direct current toward a circuit of a host system, and a return conductor 4 (not shown) providing a return current path from the powered circuit and extending through the core opening in the opposite direction, with the sensing apparatus 2 being used to monitor the net current flow (ideally 0) and to detect or identify fault conditions when the net current flow in the two primary conductors 4 deviates from zero, thereby indicating a suspected fault condition in the host system circuit.
- Multiple primary conductors 4 may also be used, each passing through the opening of the core structure 6 , for monitoring three-phase power systems, and/or to sense a summation of multiple current flows, or in a variety of other applications.
- FIG. 1 shows a single primary conductor 4
- the various concepts of the present disclosure are not limited to this exemplary situation.
- the core structure 6 includes a gap or opening in which first and second magnetic sensors 10 and 20 are disposed, where the magnetic sensors 10 and 20 in certain embodiments are integrated into, or otherwise formed as part of, a single integrated circuit structure 50 , which may include sensors 10 and 20 formed on and/or in a semiconductor structure and/or a printed circuit board structure to form a single integrated circuit structure (IC) 50 having both sensors 10 and 20 disposed proximate one another within the gap of the core structure 6 .
- IC integrated circuit structure
- Any suitable magnetic sensors 10 and 20 can be used, including without limitation to fluxgate sensors, Hall effect sensors, etc., which provide one or more signals or values indicative of a magnetic condition of the core 6 .
- the sensors 10 and 20 in certain embodiments are constructed so as to be sensitive, at least partially, to magnetic fields in a vertical direction 7 , which may be a direction generally parallel to a first surface or side 50 a of the integrated circuit structure 50 , with the integrated circuit structure 50 being generally disposed vertically within the core gap in certain non-limiting embodiments.
- the integrated circuit structure 50 includes first and second opposite sides 50 a and 50 b , respectively, and the circuit 50 is disposed within a slotted gap in the illustrated core structure 6 with the first side 50 a extending in a vertical (Y) direction generally parallel to the direction 7 of magnetic fields within the slotted portion of the core 6 .
- a first current sensing circuit 10 , 30 , 53 , 54 , 56 of FIG. 1 operates in a closed-loop magnetic circuit via the magnetic sensor 10 and a compensation coil 8 having first and second ends 8 a and 8 b to provide closed-loop current sensing to estimate the current I PRI flowing in the conductor 4 .
- This first current sensing circuitry includes the first magnetic sensor 10 , in this case a fluxgate sensor, formed on and/or in the integrated circuit structure 50 .
- the sensor 10 provides a first magnetic sensor output signal 39 via excitation and sensing circuitry 30 according to the magnetic field in the direction 7 generally parallel to the first side 50 a of the integrated circuit structure 50 (e.g., in the negative Y direction in the figures).
- FIG. 2 illustrates a partial schematic front view showing the top side of the integrated circuit structure 50 a with further details of a fluxgate sensor 10 formed on and/or in the integrated circuit structure 50 .
- the sensor 10 in this example includes a fluxgate core structure 12 fabricated on and/or in a semiconductor substrate or printed circuit board structure with suitable excitation and sense coil windings formed as conductive structures at least partially encircling the core structure, and excitation and sensing circuitry 30 includes suitable circuitry for providing excitation AC waveform to one or more excitation coils of the sensor 10 via the connections 18 and 19 .
- the circuit 30 in such embodiments further includes sensing circuitry 36 , 38 with any suitable rectification or demodulation circuitry and suitable integrator or other filtering circuits by which an output signal 39 is provided which indicates or otherwise represents the external magnetic field proximate the sensor 10 .
- the fluxgate sensor 10 includes a magnetically susceptible core structure 12 , such as may be formed on and/or in the IC structure 50 , with an excitation winding or coil 14 including excitation coil sections 14 a , 14 b , 14 c and 14 d wound around portions of the core 12 , and a centrally located sense winding 16 .
- the windings 14 and 16 are formed around corresponding portions of the core structure 12 using conductive portions on different layers of the IC assembly 50 , with solid lines showing winding portions above the corresponding core structure 12 and dashed-lines showing winding portions below the corresponding core structure 12 . Any number of excitation and sense windings 14 , 16 may be used in different embodiments.
- the fluxgate core structure 12 may be deposited and patterned as part of the fabrication of a semiconductor-based integrated circuit structure 50 , with the windings being fabricated using copper and/or aluminum layer formation and patterning steps.
- the integrated circuit structure 50 includes a printed circuit board substrate, with the core structure 12 being formed on one side of the structure, with windings being constructed using traces on various overlying an underlying layers with suitable vias for conductive interconnection.
- the illustrated magnetically susceptible core structure 12 includes two longitudinally opposite gaps 12 g separating bilaterally symmetrical core portions 12 a and 12 b .
- the core portions 12 a and 12 b may, but need not be symmetrical in all embodiments of the present disclosure.
- the coil windings in different embodiments can take on many different variations, which in general should not impact the excitation circuitry aspects of the present disclosure, and additional coils can be included on the fluxgate sensor.
- An H-bridge excitation circuit 32 provides an AC excitation current signal “ie” 18 to the excitation windings 14 via connections 18 a and 18 b to the respective first and second ends of the excitation coil 18 .
- Sensing circuitry 36 , 38 receives a sensor current signal “is” 19 via connections 19 a and 19 b to ends of the sense coil 16 , and provides the first magnetic sensor output signal 39 , such as a voltage signal in one example, based at least partially on the sensor signals 19 received from the sense winding 16 .
- the excitation circuit 32 provides alternating excitation current waveforms “ie” to the excitation windings 18 to alternately drive the core structure 12 through magnetic saturation and demagnetization in opposite polarities or directions, thereby inducing an electrical sense current flow “is” in the sensing coil 16 .
- the illustrated fluxgate sensor 10 is configured for sensing an external magnetic field generally in the vertical direction 7 (negative Y) direction in FIGS. 1-3 , with the fluxgate excitation and sensing circuit 30 including suitable demodulation circuitry 36 and an integrator 38 to provide the output signal 39 representing the magnitude of the external magnetic field proximate the sensor 6 .
- the circuitry 30 includes the integrator circuit 38 providing an analog output voltage signal 39 proportional to the sensed magnetic field along the corresponding sensing direction 7 of the fluxgate magnetic sensor 10 .
- the sensing circuitry 36 and 38 in certain embodiments is synchronized with the operation of the excitation circuit 32 by one or more control signals from a control circuit 34 which provides switching control signals to H-bridge transistors Q 1 -Q 4 of the excitation circuit 32 .
- the control circuit 34 in certain embodiments can be selectively enabled or disabled via an excitation and enable (XEN) signal 31 from on-board control logic 62 of FIG. 1 .
- the logic circuit 62 may receive an external mode control input signal 52 from a host system in certain embodiments, and may set the enabled/disabled state of the fluxgate excitation accordingly.
- This feature advantageously allows selective deactivation of the fluxgate excitation circuit 32 in certain modes of operation, for example, when the current I PRI in the conductor 4 is in a second range of operation beyond the nominal first range for which the fluxgate sensor 10 and the closed-loop sensing circuitry 10 , 30 , 53 , 54 , 56 is designed or sized.
- the first current sensing circuit further includes a driver circuit 54 also formed as part of the IC structure 50 , which receives the first magnetic sensor output signal 39 through an integrator/filter circuit 53 providing high DC gain and unity gain at high frequencies, and the driver 54 provides a compensation current signal I SEC in a closed-loop magnetic circuit to drive the compensation coil 8 of the current sensing core 6 .
- Compensation current signal I SEC is generated in the suitable fashion by the driver circuitry 54 , and in the illustrated closed-loop current sensing configuration is provided in a manner that regulates the flux within the main core structure 6 to attempt to cancel the flux corresponding to the primary current flow through the conductor 4 .
- a compensation sensing circuit RS, 56 is formed as part of the IC 50 and provides a first current sensor signal 58 at least partially according to the compensation signal I SEC from the driver circuit 54 , where the illustrated example provides an amplifier circuit 56 receiving a voltage signal proportional to the compensation current signal I SEC via a sense resistor RS, which may be adjustable or trimmable in certain embodiments as shown.
- the amount of compensation current required to equalize the magnetic flux within the main core structure 6 during regulated closed-loop operation will represent the sensed primary current I PRI flowing in the conductor 4 , and the output signal 58 from the compensation sensing circuit amplifier 56 is provided to an output circuit 60 as seen in FIG. 1 .
- a second current sensing circuit is formed in the integrated circuit structure 50 and includes a second magnetic sensor 20 , such as a Hall sensor in non-limiting example, along with an excitation and sensing circuit 40 which provides a second current sensor signal 46 at least partially according to the magnetic field in the first direction 7 .
- the Hall excitation and sensing circuitry 40 interfaces with the Hall sensor 20 by connections 48 and 49 , with excitation voltage being provided to the sensor 20 by connections 48 a and 48 b (VDD and a circuit ground in this case), and a Hall voltage output signal is provided to an amplifier 42 via connections 49 .
- the circuitry 40 further includes a gain/trim circuit 44 which provides an output voltage as the second current sensor signal 46 .
- the second sensor 20 operates in open-loop fashion to provide the output signal 46 generally proportional to the sensed magnetic field along the direction 7 , and can be any suitable sensor type and form.
- the second sensor 20 is a vertical Hall structure formed on/in a semiconductor substrate portion of the integrated circuit structure 50 for magnetic sensitivity along the vertical direction (negative Y direction) 7 in FIGS. 1-3 .
- the illustrated design is formed on/in an n-portion of a semiconductor substrate (e.g., silicon), with a p-type ring structure 28 isolating an interior region in which n+ structures 22 , 24 and 26 are configured to extend along the sensitivity direction 7 .
- the vertical Hall configuration provides for connection of the positive excitation voltage via connection 48 a to a central n+structure 22 , and a negative excitation connection (ground) is made to the outermost left and right n+structures 24 a and 24 b as shown in FIG. 2 .
- a voltage signal Hall voltage
- the output of the amplifier 42 is provided through the gain/trim circuit 44 to generate the second current sensor signal 46 at least partially according to the magnetic field in the direction 7 .
- the first and second current sensor signals 58 and 46 thus represent an open loop measured current (Imo) and a closed loop measured current (Imc), respectively, and the signals are provided to the output circuit 60 as seen in FIG. 1 .
- the output circuit 60 provides one or more output signals 66 representing the current I PRI flowing in the conductor 4 at least partially according to one or both of the current sensor signals 58 and 46 .
- the output circuit 60 is operable in different modes according to a mode selection signal (SEL) 64 from the logic circuit 62 .
- SEL mode selection signal
- FIG. 4 shows one exemplary output circuit embodiment 60 , in which a single voltage output signal 66 is provided as an output voltage Vout corresponding to a selected one of the closed-loop and open-loop sensor circuit output signals 58 and 46 .
- the logic circuit 62 provides the control signal 64 to operate the output circuit in a first mode for a first range of current (e.g., a nominal current range from 0% through 100%) and operates the output circuit 60 in a second mode for a second range of current (e.g., and overcurrent range from 100% through 500% in one non-limiting example).
- a first range of current e.g., a nominal current range from 0% through 100%
- a second range of current e.g., and overcurrent range from 100% through 500% in one non-limiting example
- the output circuit 60 in this case includes a switch circuit 61 operable according to the mode selection signal 64 from the logic 62 in order to connect the output 66 to the first current sensor signal 58 in the first operating mode, and to connect the output 66 to the second current sensor signal 46 in the second mode.
- FIG. 5 illustrates another embodiment of the output circuitry 60 , in this case including an analog-to-digital converter 68 (ADC) with an analog input connectable via the switch 61 to receive the first current sensor voltage signal 58 in a first mode or the second current sensor voltage signal 46 in the second mode, with the logic circuit 62 again operating the switch 61 via the mode selection control signal 64 .
- ADC analog-to-digital converter
- the logic 62 advantageously provides high accuracy current sensing via the closed-loop magnetic circuit and the closed-loop current sensing configuration using the first sensor 10 and associated excitation and sensing circuitry 30 as well as the driver circuit 54 and the compensation sensing circuitry RS, 56 when the current I PRI flowing in the conductor 4 is in its normal expected operating range (the first range).
- the logic 62 changes the state of the switch 61 via the control signal 64 to instead employ the Hall sensor 20 and associated sensing circuitry 40 to provide the output 66 via signal 46 , thereby extending the effect of operating range of the overall sensing apparatus 2 , possibly with reduced accuracy.
- the provision of the second sensor 10 and associated circuitry 40 is a relatively small increase in the overall size, cost and complexity of the system 2 compared with potentially over designing the size and power consumption of the closed-loop sensing apparatus including a fluxgate sensor 10 , circuitry 30 and the compensation driver circuitry 54 in order to provide such extended sensing range.
- the disclosed approach is significantly smaller and more economical and efficient than providing two separate sensor circuits.
- the integrated closed-loop/open-loop hybrid apparatus 2 of the present disclosure presents a significant advance in non-contacting current sensing, particularly for applications in which a host system is normally expected to operate in a predefined nominal range, with the possibility of higher current operation for which some measure of current sensing capability is desired.
- the disclosed hybrid structure 2 also advantageously provides a solution for applications in which it is desirable to provide redundant sensing and the capability for self-testing, for example, to facilitate safe operation of the host system.
- the output circuitry 60 provides a first output signal 66 a representing the first current sensor signal 58 , and also provides a second output signal 66 b representing the second current sensor signal 46 .
- the two outputs 66 a and 66 b each provide an indication of the sensed current within the conductor 4 throughout the entire normal operating range (e.g., 0% through 100%), and thus redundant sensing capability is provided using a single integrated circuit structure 50 , at considerably higher power efficiency and lower cost and size than would be the case if multiple magnetic sensors are separately provided in a gap of the core structure 6 .
- the provision of separate outputs 66 a and 66 b facilitates the option of self-testing, if desired, for safe reliable operation of the host system.
- FIG. 7 shows a further output circuit embodiment 60 , also including separate outputs 66 a (Vout 1 ) and 66 b (Vout 2 ) corresponding respectively to the closed-loop and open-loop sensor circuits, as well as a combined output 66 c (Vout 3 ) provided using a summing amplifier circuit 69 to effectively provide the combined output 66 c as the sum of the first current sensor signal 58 and the second current sensor signal 46 .
- the summing amplifier circuit 69 may be modified in certain embodiments to adjust the relative summation of the two signals 58 and 46 , for example, to accommodate various offsets or gains associated with individual ones of the current sensor signals 58 and 46 .
- FIGS. 4-7 are just a few of the possible output circuit configurations 60 which could be employed in the hybrid closed-loop/open-loop integrated current sensing apparatus 2 in accordance with the various aspects of the present disclosure.
- many different switching circuits could be provided for selectively controlling a single output pin voltage 66 in various operating modes of the apparatus 2
- on-board analog-to-digital converters 68 may be provided in one or more output signal paths.
- the apparatus 2 may include a microprocessor or other programmable or programmed logic to perform various control and/or reporting functions based on converted digital values corresponding to one or both of the signals 58 , 46 in certain embodiments.
- analog circuitry may be provided in the output 60 to perform various functions, wherein the summing amplifier circuitry 69 in FIG. 7 is but one example.
- FIGS. 1 and 8 waveform diagrams or graphs are shown illustrating exemplary operation of the sensing apparatus 2 in one embodiment in which the logic circuitry 62 detects transition from the nominal current sensing operating range into a higher current (second) operating range through threshold comparison of one or both of the first magnetic sensor output signal 39 from the fluxgate sensing circuitry 30 and/or the second current sensor signal 46 from the hall excitation and sensing circuitry 40 .
- Certain implementations may initiate the operating mode change via the output circuit mode select signal 64 , and the logic circuit 62 selectively disables operation of the fluxgate excitation circuit 32 ( FIG. 1 ) via the excitation enable signal 31 according to the operating range of the sensing apparatus 2 in this example.
- FIG. 8 illustrates an exemplary primary current signal 72 showing the current I PRI flowing in the conductor 4 of FIG. 1 in operation of the host system over time, with a transition from a first or nominal expected operating range (0%-100%) to a significantly higher current level (e.g., approximately 450% in the illustrated example) beginning at time T 1 , and returning to the normal operating range at time T 2 .
- a first or nominal expected operating range 0%-100%
- a significantly higher current level e.g., approximately 450% in the illustrated example
- FIG. 8 further illustrates a graph 74 showing the first magnetic sensor output signal 39 (e.g., a fluxgate sensor voltage output signal 39 (Vfg)) and a corresponding first threshold 75 (shown in dashed lines form in FIG. 8 ), with the logic circuit 62 in one embodiment comparing the first sensor output signal 39 with the corresponding first threshold 75 in generally continuous fashion, and actuating transition from a first operating mode to a second operating mode when the signal 39 is greater than or equal to the threshold 75 , and operating in the normal (first) operating mode when the signal 39 is below the threshold 75 .
- Vfg fluxgate sensor voltage output signal 39
- the fluxgate output signal 39 is generally close to 0 due to the closed-loop operation of the driver circuit 54 and the compensation coil 8 , with the driver circuitry 54 effectively regulating the flux in the main core 6 such that the sensor signal 39 from the fluxgate sensing circuitry 30 remains close to zero during the normal operating range.
- Graph 76 in FIG. 8 further illustrates the first current sensor signal 58 (which is also provided as the first voltage output 66 a in the output circuit embodiments of FIGS. 6 and 7 ), which rises generally in proportion to the corresponding primary current curve 72 until time T 1 , as well as after time T 2 in this example.
- FIG. 8 further provides a graph 78 illustrating the second current sensor signal 46 (which is also provided as the second output Vout 2 66 b in the output circuitry embodiments of FIGS. 6 and 7 ), which shows operation of the Hall sensor in providing an output 46 generally tracking the primary current curve 72 of graph 70 , including tracking in the over-current operation from T 1 through T 2 .
- the graph 78 further illustrates a second threshold 79 (shown in dashed line in the figure) which is set at approximately 100% of the nominal operating range for the apparatus 2 , where the logic circuit 62 may compare the second current sensor signal 46 with this second threshold 79 for selective mode switching in certain embodiments.
- a second threshold 79 shown in dashed line in the figure
- the logic circuit 62 in this example advantageously compares the current flowing through the conductor 4 by threshold comparison of either the fluxgate output voltage (signal 39 in graph 74 ) and/or the second current sensor signal 46 (graph 78 ) with a corresponding threshold 75 , 79 .
- the logic circuit 62 provides the control signal 64 in a first state (e.g., prior to time T 1 FIG. 8 ) to cause the output circuit 62 provide the output signal 66 (e.g., output circuit 60 in FIG. 4 or FIG. 5 above) based on the first current sensor signal 58 when the first magnetic sensor output signal 39 and/or the second current sensor signal 46 is below the corresponding threshold 75 , 79 .
- the logic circuitry 62 in this example provides the control signal 64 in the second state to cause the output circuit 62 provide the output signal 66 at least partially according to the second current sensor signal 46 when the first magnetic sensor output signal 39 or the second current sensor signal 46 are greater than or equal to the corresponding threshold 75 , 79 .
- This operation is shown in the graph 86 of FIG. 8 , in which the logic circuit 62 asserts the output circuit select signal 64 at time T 1 (switching the output 66 to track the second current sensor signal 46 ), and then reverts back to using the first current sensor signal 58 at T 2 .
- the logic circuit 62 in certain embodiments enables the fluxgate excitation circuitry via the enable signal 31 (e.g., allowing the control circuit 34 in FIG. 2 to operate the H bridge excitation circuit 32 ) while the primary current is within the first or normal operating range, and once the signal 39 meets or exceeds the threshold 75 (or the signal 46 meets or exceeds the threshold 79 ), the logic circuitry 62 disables operation of the fluxgate excitation circuitry 32 , with the enable signal 31 going low at time T 1 in the example of FIG. 8 . Once the sensed current drops again into the primary sensing range, the logic circuitry 62 again asserts the fluxgate enable signal 31 at time T 2 as shown in the graph 80 of FIG. 8 .
- the contribution of the first magnetic sensor output signal 39 to the magnetic condition of the sensing court structure 6 is turned off such that this contribution will not offset or disturb the measurement provided by the Hall sensing system 20 , 40 in the second range of operation of the hybrid current sensing apparatus 2 .
- This is seen in graph 82 of FIG. 8 , showing a curve 84 illustrating the secondary current flow I SEC through the compensation coil 8 , which generally tracks the profile of the primary current flow curve 72 of graph 70 until the fluxgate excitation is turned off at T 1 , and then resumes tracking the primary current after T 2 .
- Graph 88 in FIG. 8 illustrates the final output voltage ( 66 in the example of FIG. 4 ), where the overall output of the apparatus 2 generally tracks the primary current curve 72 of graph 70 , due to the selective operation of the logic circuitry 62 and the provision of two separate sensors in the integrated circuit structure 50 .
- the apparatus 2 provides an accurate indication of the level of current flow through the primary conductor 4 even during the time period T 1 -T 2 during which the primary current exceeds the normal operating range.
- FIG. 9 further graphs 90 , 94 , 96 , 98 , 100 , 102 , 106 and 108 illustrate system signals in operation according to a similar primary current profile curve 92 (graph 90 ) in which the driver circuit 54 is operative in a first mode to provide the compensation signal ( 104 in graph 102 ) at a level representing the primary current flowing in the conductor 4 to regulate the flux density in the closed-loop magnetic circuit to a constant level over at least a portion of the first current range.
- the driver 54 then provides the compensation signal I SEC at a second constant level (e.g., approximately 70% in this example) over the second current range, with the logic circuit 62 in this case maintaining the fluxgate excitation circuit in the enabled mode (excitation enable signal 31 shown in graph 100 ) throughout operation of the system 2 .
- the first current sensor signal 58 shown in graph 96 of FIG. 9 generally tracks the primary current curve 92 of graph 90 until T 1 , and then reverts to a corresponding constant level (e.g., 70% in this case) from T 1 through T 2 .
- this constant compensation signal may be accomplished in certain embodiments by the logic circuit 62 setting operation of the control circuit 34 to provide a constant pulse width modulated excitation signal via switching control signals provided to the H-bridge circuit 32 in FIG. 2 .
- the logic circuit 62 switches again to the first operating mode, with the driver 56 again providing the compensation signal level 104 (I SEC ) which generally tracks the primary current after T 2 due to the closed-loop operation.
- I SEC compensation signal level
- the output select control signal 64 is again asserted by the logic circuitry 62 at T 1 and then discontinued at T 2 based on the threshold comparison of signal 39 or signal 46 , and the graph 108 illustrates the single output 66 (based on the switched selection in the example of FIGS. 4 and 5 ) as well as the exemplary combined output 66 c (from the summation circuitry 69 in the example of FIG. 7 ), which track the sensed primary current curve 92 of graph 90 .
- the apparatus provides an integrated dual-sensor solution by which an extended operating range is achieved without requiring the driver circuit 54 and the fluxgate sensor circuitry 10 , 30 to be designed for the higher second current range, while advantageously providing the accuracy benefits of the closed-loop sensing operation during the normal expected operating range with the ability to provide a current sensing output signal representing the primary current flow through the conductor 4 during overcurrent conditions.
- the various concepts of the present disclosure are not limited to embodiments using fluxgate sensors 10 or Hall secondary sensors 20 , although these particular configurations are advantageous in certain respects.
- Hall sensors are easily integrated into the fabrication of the integrated circuit structure 50 , and vertical Hall sensors may be constructed for magnetic sensitivity along the plane of the integrated circuit side 50 a , thereby being sensitive in the same direction as the fluxgate sensor 10 .
- This facilitates easy mounting within a gap of the current sensing core structure 6 , for example, as seen in FIGS. 1 and 3 above.
- Hall sensors can provide generally linear operation to yield adequate current sensor output signals at significantly high values, for example, where the secondary sensor 20 can be constructed to produce fairly accurate signals in a second range that significantly exceeds the highest value of the first sensing range.
- the secondary sensor 20 and associated excitation and sensing circuitry 40 may provide a suitable output 66 at significant multiples of the first operating range, including without limitation 1000% in certain implementations.
- the disclosed sensing apparatus 2 advantageously facilitates provision of a second separate measurement path for redundancy, which is particularly useful in safety-critical applications, for example, as shown in FIGS. 6 and 7 above. This, in turn, provides a solution for current measurement applications in which redundancy and/or self-testing is desirable to facilitate correct measurement of a sensed current, without requiring the added cost, complexity, and power consumption associated with use of two current sensors in parallel.
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Abstract
Hybrid magnetic current sensors and sensing apparatus are presented with closed-loop and open-loop circuitry employs first and second integrated magnetic sensors to sense a magnetic field in a magnetic core structure gap to provide high accuracy current measurement via a closed-loop magnetic circuit with the first sensor in a nominal current range as well as open-loop current measurement using the second sensor in an extended second range to accommodate over-current conditions in a host system as well as to provide redundant current sensing functionality.
Description
- This application is a divisional of U.S. patent application Ser. No. 14/193,023 filed Feb. 28, 2014, which claims priority to and the benefit of U.S. Provisional Patent Application Ser. No. 61/863,294 that was filed on Aug. 7, 2013, the entirety of both are incorporated by reference herein.
- The present disclosure relates to current sensors and more particularly to closed-loop non-contacting current sensing systems.
- Contactless current sensing is employed in a variety of applications for safely measuring current flow, particularly for high current levels. Open-loop current sensing provides a cost effective solution in which a magnetic field generated by the flow of current through an electrical conductor is concentrated inside a magnetic core and a magnetic sensor measures the field and provides an output signal used for estimating the current flow. Open-loop approaches typically consume little power, and can use low sensitivity sensors for measuring high currents. However, the open-loop approach suffers from poor accuracy, typically due to nonlinearities of the core and/or the sensor. Closed-loop current sensing techniques may be employed with a magnetic core encircling an electrical conductor, where a secondary winding or compensation coil is provided on the core and driven by the sensor until the magnetic flux within the core is zero. The secondary current at this point is measured and is generally proportional to the primary current flowing in the electrical conductor of interest. The closed-loop approach generally provides improved accuracy compared with open-loop techniques, and is thus preferred in applications using the current measurement for regulation of host system performance or for power metering applications. However, closed-loop current sensing is generally restricted to the capabilities of the compensation coil driver circuitry, and accommodating a high sensed current range is expensive and consumes a significant amount of power. Thus, close-loop techniques are not economical for certain high current sensing applications, while open-loop techniques may not provide the required level of accuracy in current sensing at nominal or expected current levels. Moreover, certain current sensing applications require redundancy and/or self-test capabilities to ensure correct measurement, but provision of two or more current sensors in parallel significantly impacts cost and system complexity, as well as occupying more space in a host system. Accordingly, a need remains for improved current sensing systems and apparatus.
- Hybrid closed-loop/open-loop techniques and apparatus are provided for non-contact current measurement by which the foregoing and other shortcomings can be mitigated or overcome. Integrated dual-sensor apparatus embodiments are disclosed to facilitate current measurement in situations where good accuracy is required over a nominal current range and significantly higher current levels can be measured with reduced accuracy requirements without significant cost and size impact, by providing the accuracy benefits of closed-loop current sensing techniques in combination with an open-loop sensor to accommodate some measure of current sensing during system overload conditions. Moreover, disclosed embodiments may be employed to facilitate enhanced system integrity and self-testing by redundant current sensing capability.
- Hybrid closed-loop, open-loop magnetic current sensor apparatus is provided in certain embodiments, including an integrated circuit having first and second current sensing circuits formed as part of the integrated circuit structure. A first current sensing circuit includes a first magnetic sensor along with a driver circuit to provide a compensation signal at least partially according to the first magnetic sensor output signal in a closed-loop magnetic circuit to drive a compensation coil associated with a core structure magnetically affected by measured current flowing in a conductor. The first current sensing circuitry, moreover, includes a compensation sensing circuit providing a first current sensor signal at least partially according to the compensation signal from the driver circuit. The apparatus further includes a second current sensing circuit with a second magnetic sensor formed as part of the integrated circuit structure, which provides a second current sensor signal, and an output circuit providing an output signal representing the current flowing in the conductor at least partially according to the first current sensor signal and/or the second current sensor signal.
- In certain embodiments, the first magnetic sensor employed in the closed-loop magnetic circuit is a fluxgate sensor with corresponding excitation and sensing circuitry, and the second magnetic sensor can be a Hall sensor, such as a vertical Hall sensor in various embodiments. The driver circuit in certain embodiments provides a compensation signal in a first mode at a level representing the current flowing in the conductor to regulate the closed-loop magnetic circuit to a constant flux level over all or at least a portion of a first current range, and the driver may discontinue the compensation signal or provide compensation at a constant level in a second mode over a second current range in various embodiments. The output circuit in certain embodiments provides separate first and second outputs signals respectively representing the first and second current sensor signals, or may provide one output signal based on the first current sensor signal over the first current range and provide the output signal based on the second current sensor signal over at least a portion of the second range. In various embodiments, moreover, the output circuit provides an output signal as a sum or other function of the first current sensor signal and the second current sensor signal, through analog circuitry and/or through operations on converted digital values based on the current sensor signals. Certain embodiments include a logic circuit comparing one or both of the first magnetic sensor output signal and the second current sensor signal with a corresponding threshold, and the logic circuit controls the output circuit in a first state to provide the output signal or signals based on the first current sensor signal when the compared signal is below the threshold, and in a second state to provide the output signal at least partially according to the second current sensor signal when the compared signal is greater than or equal to the corresponding threshold.
- A current sensing apparatus is provided in accordance with further aspects of the disclosure, including a first current sensing circuit with a fluxgate sensor circuit providing a first magnetic sensor output signal according to a magnetic field, a driver circuit providing a compensation signal in a closed-loop magnetic circuit at least partially according to the first magnetic sensor output signal, and a compensation sensing circuit which provides a first current sensor signal at least partially according to the compensation signal from the driver circuit. The apparatus further includes a Hall sensor providing a second current sensor signal at least in part according to the magnetic field, as well as an output circuit that provides one or more output signals according to the first current sensor signal over at least a portion of a first current range and according to the second current sensor signal over a second current range.
- A hybrid closed-loop, open-loop magnetic current sensor is provided in accordance with further aspects of the present disclosure, which includes a magnetically susceptible core structure accommodating an electrical conductor, a compensation coil with at least one winding around the core, and an integrated circuit with means for testing current flow in the conductor using a closed-loop magnetic circuit comprising a fluxgate sensor formed on or in the integrated circuit, as well as means for testing the current flow using an open-loop magnetic circuit with a Hall sensor formed on or in the integrated circuit.
- The following description and drawings set forth certain illustrative implementations of the disclosure in detail, which are indicative of several exemplary ways in which the various principles of the disclosure may be carried out. The illustrated examples, however, are not exhaustive of the many possible embodiments of the disclosure. Other objects, advantages and novel features of the disclosure will be set forth in the following detailed description when considered in conjunction with the drawings, in which:
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FIG. 1 is a schematic diagram illustrating an exemplary hybrid current sensing system with two magnetic sensors integrated into a single integrated circuit disposed within a magnetic core gap for closed-loop, open-loop current sensing according to one or more embodiments; -
FIG. 2 is a schematic diagram illustrating further details of the integrated magnetic sensors and associated excitation and sensing circuitry according to one or more embodiments; -
FIG. 3 is a partial front elevation view illustrating positioning of the first and second magnetic sensors and a portion of a corresponding integrated circuit within a gap of the magnetic core in the current sensor system ofFIGS. 1 and 2 ; -
FIG. 4 is a schematic diagram illustrating an exemplary output circuit embodiment in the current sensing system ofFIG. 1 providing a voltage output signal corresponding to a selected one of the closed-loop and open-loop sensor circuits; -
FIG. 5 is a schematic diagram illustrating another output circuit embodiment including an analog-to-digital converter providing a digital output corresponding to a selected one of the closed-loop and open-loop sensor circuits; -
FIG. 6 is a schematic diagram illustrating another output circuit embodiment in the current sensing system, providing separate first and second voltage outputs corresponding to the closed-loop and open-loop sensor circuits; -
FIG. 7 is a schematic diagram illustrating a further output circuit embodiment including separate outputs corresponding to the closed-loop and open-loop sensor circuits and a combined output; -
FIG. 8 is a waveform diagram illustrating various electrical signals in the current sensing system ofFIG. 1 showing an embodiment in which closed-loop compensation coil driver circuitry is operational in a first current sensing range and is selectively disabled in a second higher current sensing range; and -
FIG. 9 is a waveform diagram illustrating electrical signals in another embodiment of the current sensing apparatus in which the compensation coil driver circuitry provides a fixed level of compensation coil excitation in the second higher current sensing range. - One or more embodiments or implementations are hereinafter described in conjunction with the drawings, wherein like reference numerals are used for reference to like elements throughout, and wherein the various features are not necessarily drawn to scale.
- Referring to
FIGS. 1-3 , an exemplary integrated closed-loop/open-loopcurrent sensor apparatus 2 is shown inFIG. 1 for measuring a primary current IPRI flowing in a primary coil orconductor 4 magnetically interacting with amagnetic core 6. Theconductor 4 can be magnetically interfaced with thecore 6 in any suitable fashion by which thecore structure 6 is magnetically affected by the current flow IPRI in theconductor 4, and theconductor 4 may be a single electrical conductor passing through thecore 6 as shown inFIG. 1 , or can be a winding with one or more turns encircling portions of thecore 6, or other suitable magnetic interaction configuration by which the current IPRI flowing in theconductor 4 affects the magnetic flux in thecore 6. Multipleprimary conductors 4 may be used in certain embodiments, for example, in ground fault sensing applications with aprimary conductor 4 passing through the opening in thecore 6 to direct current toward a circuit of a host system, and a return conductor 4 (not shown) providing a return current path from the powered circuit and extending through the core opening in the opposite direction, with thesensing apparatus 2 being used to monitor the net current flow (ideally 0) and to detect or identify fault conditions when the net current flow in the twoprimary conductors 4 deviates from zero, thereby indicating a suspected fault condition in the host system circuit. Multipleprimary conductors 4 may also be used, each passing through the opening of thecore structure 6, for monitoring three-phase power systems, and/or to sense a summation of multiple current flows, or in a variety of other applications. Thus, while the illustrated configuration inFIG. 1 shows a singleprimary conductor 4, the various concepts of the present disclosure are not limited to this exemplary situation. Thecore structure 6 includes a gap or opening in which first and secondmagnetic sensors magnetic sensors integrated circuit structure 50, which may includesensors sensors core structure 6. Any suitablemagnetic sensors core 6. - As shown in
FIG. 3 , thesensors vertical direction 7, which may be a direction generally parallel to a first surface orside 50 a of theintegrated circuit structure 50, with theintegrated circuit structure 50 being generally disposed vertically within the core gap in certain non-limiting embodiments. As seen inFIG. 3 , moreover, theintegrated circuit structure 50 includes first and secondopposite sides circuit 50 is disposed within a slotted gap in the illustratedcore structure 6 with thefirst side 50 a extending in a vertical (Y) direction generally parallel to thedirection 7 of magnetic fields within the slotted portion of thecore 6. In this embodiment, a firstcurrent sensing circuit FIG. 1 operates in a closed-loop magnetic circuit via themagnetic sensor 10 and a compensation coil 8 having first andsecond ends conductor 4. This first current sensing circuitry includes the firstmagnetic sensor 10, in this case a fluxgate sensor, formed on and/or in theintegrated circuit structure 50. Thesensor 10 provides a first magneticsensor output signal 39 via excitation andsensing circuitry 30 according to the magnetic field in thedirection 7 generally parallel to thefirst side 50 a of the integrated circuit structure 50 (e.g., in the negative Y direction in the figures). -
FIG. 2 illustrates a partial schematic front view showing the top side of theintegrated circuit structure 50 a with further details of afluxgate sensor 10 formed on and/or in theintegrated circuit structure 50. Thesensor 10 in this example includes afluxgate core structure 12 fabricated on and/or in a semiconductor substrate or printed circuit board structure with suitable excitation and sense coil windings formed as conductive structures at least partially encircling the core structure, and excitation and sensingcircuitry 30 includes suitable circuitry for providing excitation AC waveform to one or more excitation coils of thesensor 10 via theconnections circuit 30 in such embodiments further includessensing circuitry 36, 38 with any suitable rectification or demodulation circuitry and suitable integrator or other filtering circuits by which anoutput signal 39 is provided which indicates or otherwise represents the external magnetic field proximate thesensor 10. - As seen in
FIG. 2 , thefluxgate sensor 10 includes a magneticallysusceptible core structure 12, such as may be formed on and/or in theIC structure 50, with an excitation winding or coil 14 includingexcitation coil sections core 12, and a centrally located sense winding 16. In the illustrated example, thewindings 14 and 16 are formed around corresponding portions of thecore structure 12 using conductive portions on different layers of theIC assembly 50, with solid lines showing winding portions above thecorresponding core structure 12 and dashed-lines showing winding portions below thecorresponding core structure 12. Any number of excitation andsense windings 14, 16 may be used in different embodiments. In certain implementations, for example, thefluxgate core structure 12 may be deposited and patterned as part of the fabrication of a semiconductor-basedintegrated circuit structure 50, with the windings being fabricated using copper and/or aluminum layer formation and patterning steps. In other possible non-limiting embodiments, theintegrated circuit structure 50 includes a printed circuit board substrate, with thecore structure 12 being formed on one side of the structure, with windings being constructed using traces on various overlying an underlying layers with suitable vias for conductive interconnection. The illustrated magneticallysusceptible core structure 12 includes two longitudinallyopposite gaps 12 g separating bilaterallysymmetrical core portions gap 12 g is used, or a single gap may be provided, or more than twosuch gaps 12 g may be included in thecore structure 12. Furthermore, thecore portions - An H-
bridge excitation circuit 32 provides an AC excitation current signal “ie” 18 to the excitation windings 14 viaconnections excitation coil 18.Sensing circuitry 36, 38 receives a sensor current signal “is” 19 viaconnections sense coil 16, and provides the first magneticsensor output signal 39, such as a voltage signal in one example, based at least partially on the sensor signals 19 received from the sense winding 16. In one non-limiting form of operation, theexcitation circuit 32 provides alternating excitation current waveforms “ie” to theexcitation windings 18 to alternately drive thecore structure 12 through magnetic saturation and demagnetization in opposite polarities or directions, thereby inducing an electrical sense current flow “is” in thesensing coil 16. - The illustrated
fluxgate sensor 10 is configured for sensing an external magnetic field generally in the vertical direction 7 (negative Y) direction inFIGS. 1-3 , with the fluxgate excitation andsensing circuit 30 includingsuitable demodulation circuitry 36 and an integrator 38 to provide theoutput signal 39 representing the magnitude of the external magnetic field proximate thesensor 6. Specifically, when thecore structure 12 is exposed to an external magnetic field within the gap of the currentsensing core structure 6, thefluxgate core structure 12 is more easily saturated in alignment with that field, and less easily saturated in opposition to the external field. In one possible implementation, thecircuitry 30 includes the integrator circuit 38 providing an analogoutput voltage signal 39 proportional to the sensed magnetic field along the correspondingsensing direction 7 of the fluxgatemagnetic sensor 10. Moreover, thesensing circuitry 36 and 38 in certain embodiments is synchronized with the operation of theexcitation circuit 32 by one or more control signals from acontrol circuit 34 which provides switching control signals to H-bridge transistors Q1-Q4 of theexcitation circuit 32. As seen inFIG. 2 , moreover, thecontrol circuit 34 in certain embodiments can be selectively enabled or disabled via an excitation and enable (XEN) signal 31 from on-board control logic 62 ofFIG. 1 . Thelogic circuit 62 may receive an external modecontrol input signal 52 from a host system in certain embodiments, and may set the enabled/disabled state of the fluxgate excitation accordingly. This feature advantageously allows selective deactivation of thefluxgate excitation circuit 32 in certain modes of operation, for example, when the current I PRI in theconductor 4 is in a second range of operation beyond the nominal first range for which thefluxgate sensor 10 and the closed-loop sensing circuitry - As best seen in
FIG. 1 , the first current sensing circuit further includes adriver circuit 54 also formed as part of theIC structure 50, which receives the first magneticsensor output signal 39 through an integrator/filter circuit 53 providing high DC gain and unity gain at high frequencies, and thedriver 54 provides a compensation current signal ISEC in a closed-loop magnetic circuit to drive the compensation coil 8 of thecurrent sensing core 6. Compensation current signal ISEC is generated in the suitable fashion by thedriver circuitry 54, and in the illustrated closed-loop current sensing configuration is provided in a manner that regulates the flux within themain core structure 6 to attempt to cancel the flux corresponding to the primary current flow through theconductor 4. A compensation sensing circuit RS, 56 is formed as part of theIC 50 and provides a firstcurrent sensor signal 58 at least partially according to the compensation signal ISEC from thedriver circuit 54, where the illustrated example provides anamplifier circuit 56 receiving a voltage signal proportional to the compensation current signal ISEC via a sense resistor RS, which may be adjustable or trimmable in certain embodiments as shown. In this manner, the amount of compensation current required to equalize the magnetic flux within themain core structure 6 during regulated closed-loop operation will represent the sensed primary current IPRI flowing in theconductor 4, and theoutput signal 58 from the compensationsensing circuit amplifier 56 is provided to anoutput circuit 60 as seen inFIG. 1 . - As further shown in
FIG. 1 , a second current sensing circuit is formed in theintegrated circuit structure 50 and includes a secondmagnetic sensor 20, such as a Hall sensor in non-limiting example, along with an excitation andsensing circuit 40 which provides a secondcurrent sensor signal 46 at least partially according to the magnetic field in thefirst direction 7. As seen inFIG. 2 , the Hall excitation andsensing circuitry 40 interfaces with theHall sensor 20 byconnections 48 and 49, with excitation voltage being provided to thesensor 20 byconnections amplifier 42 viaconnections 49. In this example, moreover, thecircuitry 40 further includes a gain/trim circuit 44 which provides an output voltage as the secondcurrent sensor signal 46. - The
second sensor 20 operates in open-loop fashion to provide theoutput signal 46 generally proportional to the sensed magnetic field along thedirection 7, and can be any suitable sensor type and form. In the illustrated embodiment, moreover, thesecond sensor 20 is a vertical Hall structure formed on/in a semiconductor substrate portion of theintegrated circuit structure 50 for magnetic sensitivity along the vertical direction (negative Y direction) 7 inFIGS. 1-3 . The illustrated design is formed on/in an n-portion of a semiconductor substrate (e.g., silicon), with a p-type ring structure 28 isolating an interior region in which n+structures 22, 24 and 26 are configured to extend along thesensitivity direction 7. In this case, the vertical Hall configuration provides for connection of the positive excitation voltage viaconnection 48 a to a central n+structure 22, and a negative excitation connection (ground) is made to the outermost left and right n+structures FIG. 2 . By this orientation, magnetic fields in thedirection 7 within the gap of the currentsensing core structure 6 will create a voltage signal (Hall voltage) betweenn+ sensing structures sensing amplifier 42 via theconnections 49 as shown inFIG. 2 . The output of theamplifier 42 is provided through the gain/trim circuit 44 to generate the secondcurrent sensor signal 46 at least partially according to the magnetic field in thedirection 7. - Referring now to
FIGS. 1 and 4-7 , the first and second current sensor signals 58 and 46 thus represent an open loop measured current (Imo) and a closed loop measured current (Imc), respectively, and the signals are provided to theoutput circuit 60 as seen inFIG. 1 . Theoutput circuit 60, in turn, provides one or more output signals 66 representing the current IPRI flowing in theconductor 4 at least partially according to one or both of the current sensor signals 58 and 46. In certain embodiments, moreover, theoutput circuit 60 is operable in different modes according to a mode selection signal (SEL) 64 from thelogic circuit 62.FIG. 4 shows one exemplaryoutput circuit embodiment 60, in which a singlevoltage output signal 66 is provided as an output voltage Vout corresponding to a selected one of the closed-loop and open-loop sensor circuit output signals 58 and 46. In this embodiment, thelogic circuit 62 provides thecontrol signal 64 to operate the output circuit in a first mode for a first range of current (e.g., a nominal current range from 0% through 100%) and operates theoutput circuit 60 in a second mode for a second range of current (e.g., and overcurrent range from 100% through 500% in one non-limiting example). In one possible implementation, theoutput circuit 60 in this case includes aswitch circuit 61 operable according to themode selection signal 64 from thelogic 62 in order to connect theoutput 66 to the firstcurrent sensor signal 58 in the first operating mode, and to connect theoutput 66 to the secondcurrent sensor signal 46 in the second mode. -
FIG. 5 illustrates another embodiment of theoutput circuitry 60, in this case including an analog-to-digital converter 68 (ADC) with an analog input connectable via theswitch 61 to receive the first currentsensor voltage signal 58 in a first mode or the second currentsensor voltage signal 46 in the second mode, with thelogic circuit 62 again operating theswitch 61 via the modeselection control signal 64. By this operation in controlling theoutput circuits 60 ofFIGS. 4 and 5 , therefore, thelogic 62 advantageously provides high accuracy current sensing via the closed-loop magnetic circuit and the closed-loop current sensing configuration using thefirst sensor 10 and associated excitation andsensing circuitry 30 as well as thedriver circuit 54 and the compensation sensing circuitry RS, 56 when the current IPRI flowing in theconductor 4 is in its normal expected operating range (the first range). - For operation at higher current levels (e.g., 100%-500%), the
logic 62 changes the state of theswitch 61 via thecontrol signal 64 to instead employ theHall sensor 20 and associatedsensing circuitry 40 to provide theoutput 66 viasignal 46, thereby extending the effect of operating range of theoverall sensing apparatus 2, possibly with reduced accuracy. It is noted, however, that the provision of thesecond sensor 10 and associatedcircuitry 40 is a relatively small increase in the overall size, cost and complexity of thesystem 2 compared with potentially over designing the size and power consumption of the closed-loop sensing apparatus including afluxgate sensor 10,circuitry 30 and thecompensation driver circuitry 54 in order to provide such extended sensing range. Also, the disclosed approach is significantly smaller and more economical and efficient than providing two separate sensor circuits. Consequently, the integrated closed-loop/open-loop hybrid apparatus 2 of the present disclosure presents a significant advance in non-contacting current sensing, particularly for applications in which a host system is normally expected to operate in a predefined nominal range, with the possibility of higher current operation for which some measure of current sensing capability is desired. - Referring also to
FIGS. 6 and 7 , the disclosedhybrid structure 2 also advantageously provides a solution for applications in which it is desirable to provide redundant sensing and the capability for self-testing, for example, to facilitate safe operation of the host system. In the example ofFIG. 6 , for instance, theoutput circuitry 60 provides afirst output signal 66 a representing the firstcurrent sensor signal 58, and also provides asecond output signal 66 b representing the secondcurrent sensor signal 46. In this embodiment, for example, the twooutputs conductor 4 throughout the entire normal operating range (e.g., 0% through 100%), and thus redundant sensing capability is provided using a singleintegrated circuit structure 50, at considerably higher power efficiency and lower cost and size than would be the case if multiple magnetic sensors are separately provided in a gap of thecore structure 6. In addition, the provision ofseparate outputs -
FIG. 7 shows a furtheroutput circuit embodiment 60, also includingseparate outputs 66 a (Vout1) and 66 b (Vout2) corresponding respectively to the closed-loop and open-loop sensor circuits, as well as a combinedoutput 66 c (Vout3) provided using a summingamplifier circuit 69 to effectively provide the combinedoutput 66 c as the sum of the firstcurrent sensor signal 58 and the secondcurrent sensor signal 46. The summingamplifier circuit 69 may be modified in certain embodiments to adjust the relative summation of the twosignals - The examples of
FIGS. 4-7 are just a few of the possibleoutput circuit configurations 60 which could be employed in the hybrid closed-loop/open-loop integratedcurrent sensing apparatus 2 in accordance with the various aspects of the present disclosure. For example, many different switching circuits could be provided for selectively controlling a singleoutput pin voltage 66 in various operating modes of theapparatus 2, and on-board analog-to-digital converters 68 may be provided in one or more output signal paths. Moreover, theapparatus 2 may include a microprocessor or other programmable or programmed logic to perform various control and/or reporting functions based on converted digital values corresponding to one or both of thesignals output 60 to perform various functions, wherein the summingamplifier circuitry 69 inFIG. 7 is but one example. - Referring now to
FIGS. 1 and 8 , waveform diagrams or graphs are shown illustrating exemplary operation of thesensing apparatus 2 in one embodiment in which thelogic circuitry 62 detects transition from the nominal current sensing operating range into a higher current (second) operating range through threshold comparison of one or both of the first magneticsensor output signal 39 from thefluxgate sensing circuitry 30 and/or the secondcurrent sensor signal 46 from the hall excitation andsensing circuitry 40. Certain implementations may initiate the operating mode change via the output circuit modeselect signal 64, and thelogic circuit 62 selectively disables operation of the fluxgate excitation circuit 32 (FIG. 1 ) via the excitation enablesignal 31 according to the operating range of thesensing apparatus 2 in this example. Thegraph 70 inFIG. 8 illustrates an exemplary primarycurrent signal 72 showing the current IPRI flowing in theconductor 4 ofFIG. 1 in operation of the host system over time, with a transition from a first or nominal expected operating range (0%-100%) to a significantly higher current level (e.g., approximately 450% in the illustrated example) beginning at time T1, and returning to the normal operating range at time T2. -
FIG. 8 further illustrates agraph 74 showing the first magnetic sensor output signal 39 (e.g., a fluxgate sensor voltage output signal 39 (Vfg)) and a corresponding first threshold 75 (shown in dashed lines form inFIG. 8 ), with thelogic circuit 62 in one embodiment comparing the firstsensor output signal 39 with the correspondingfirst threshold 75 in generally continuous fashion, and actuating transition from a first operating mode to a second operating mode when thesignal 39 is greater than or equal to thethreshold 75, and operating in the normal (first) operating mode when thesignal 39 is below thethreshold 75. As seen in thegraph 74, moreover, thefluxgate output signal 39 is generally close to 0 due to the closed-loop operation of thedriver circuit 54 and the compensation coil 8, with thedriver circuitry 54 effectively regulating the flux in themain core 6 such that thesensor signal 39 from thefluxgate sensing circuitry 30 remains close to zero during the normal operating range. -
Graph 76 inFIG. 8 further illustrates the first current sensor signal 58 (which is also provided as thefirst voltage output 66 a in the output circuit embodiments ofFIGS. 6 and 7 ), which rises generally in proportion to the corresponding primarycurrent curve 72 until time T1, as well as after time T2 in this example.FIG. 8 further provides agraph 78 illustrating the second current sensor signal 46 (which is also provided as thesecond output Vout2 66 b in the output circuitry embodiments ofFIGS. 6 and 7 ), which shows operation of the Hall sensor in providing anoutput 46 generally tracking the primarycurrent curve 72 ofgraph 70, including tracking in the over-current operation from T1 through T2. Thegraph 78 further illustrates a second threshold 79 (shown in dashed line in the figure) which is set at approximately 100% of the nominal operating range for theapparatus 2, where thelogic circuit 62 may compare the secondcurrent sensor signal 46 with thissecond threshold 79 for selective mode switching in certain embodiments. - Referring also to the
graphs FIG. 8 , thelogic circuit 62 in this example advantageously compares the current flowing through theconductor 4 by threshold comparison of either the fluxgate output voltage (signal 39 in graph 74) and/or the second current sensor signal 46 (graph 78) with acorresponding threshold logic circuit 62 provides thecontrol signal 64 in a first state (e.g., prior to time T1FIG. 8 ) to cause theoutput circuit 62 provide the output signal 66 (e.g.,output circuit 60 inFIG. 4 orFIG. 5 above) based on the firstcurrent sensor signal 58 when the first magneticsensor output signal 39 and/or the secondcurrent sensor signal 46 is below the correspondingthreshold logic circuitry 62 in this example provides thecontrol signal 64 in the second state to cause theoutput circuit 62 provide theoutput signal 66 at least partially according to the secondcurrent sensor signal 46 when the first magneticsensor output signal 39 or the secondcurrent sensor signal 46 are greater than or equal to thecorresponding threshold graph 86 ofFIG. 8 , in which thelogic circuit 62 asserts the output circuitselect signal 64 at time T1 (switching theoutput 66 to track the second current sensor signal 46), and then reverts back to using the firstcurrent sensor signal 58 at T2. - As further seen in the
graph 80, moreover, thelogic circuit 62 in certain embodiments enables the fluxgate excitation circuitry via the enable signal 31 (e.g., allowing thecontrol circuit 34 inFIG. 2 to operate the H bridge excitation circuit 32) while the primary current is within the first or normal operating range, and once thesignal 39 meets or exceeds the threshold 75 (or thesignal 46 meets or exceeds the threshold 79), thelogic circuitry 62 disables operation of thefluxgate excitation circuitry 32, with the enablesignal 31 going low at time T1 in the example ofFIG. 8 . Once the sensed current drops again into the primary sensing range, thelogic circuitry 62 again asserts the fluxgate enablesignal 31 at time T2 as shown in thegraph 80 ofFIG. 8 . In this example, therefore, the contribution of the first magneticsensor output signal 39 to the magnetic condition of thesensing court structure 6 is turned off such that this contribution will not offset or disturb the measurement provided by theHall sensing system current sensing apparatus 2. This is seen ingraph 82 ofFIG. 8 , showing acurve 84 illustrating the secondary current flow ISEC through the compensation coil 8, which generally tracks the profile of the primarycurrent flow curve 72 ofgraph 70 until the fluxgate excitation is turned off at T1, and then resumes tracking the primary current after T2. -
Graph 88 inFIG. 8 illustrates the final output voltage (66 in the example ofFIG. 4 ), where the overall output of theapparatus 2 generally tracks the primarycurrent curve 72 ofgraph 70, due to the selective operation of thelogic circuitry 62 and the provision of two separate sensors in theintegrated circuit structure 50. Thus, theapparatus 2 provides an accurate indication of the level of current flow through theprimary conductor 4 even during the time period T1-T2 during which the primary current exceeds the normal operating range. - Referring also to
FIG. 9 ,further graphs driver circuit 54 is operative in a first mode to provide the compensation signal (104 in graph 102) at a level representing the primary current flowing in theconductor 4 to regulate the flux density in the closed-loop magnetic circuit to a constant level over at least a portion of the first current range. Thedriver 54 then provides the compensation signal ISEC at a second constant level (e.g., approximately 70% in this example) over the second current range, with thelogic circuit 62 in this case maintaining the fluxgate excitation circuit in the enabled mode (excitation enablesignal 31 shown in graph 100) throughout operation of thesystem 2. In this manner, the firstcurrent sensor signal 58 shown ingraph 96 ofFIG. 9 generally tracks the primarycurrent curve 92 ofgraph 90 until T1, and then reverts to a corresponding constant level (e.g., 70% in this case) from T1 through T2. The provision of this constant compensation signal may be accomplished in certain embodiments by thelogic circuit 62 setting operation of thecontrol circuit 34 to provide a constant pulse width modulated excitation signal via switching control signals provided to the H-bridge circuit 32 inFIG. 2 . At T2, in this example, thelogic circuit 62 switches again to the first operating mode, with thedriver 56 again providing the compensation signal level 104 (ISEC) which generally tracks the primary current after T2 due to the closed-loop operation. As seen in thegraph 106 ofFIG. 9 , the outputselect control signal 64 is again asserted by thelogic circuitry 62 at T1 and then discontinued at T2 based on the threshold comparison ofsignal 39 orsignal 46, and thegraph 108 illustrates the single output 66 (based on the switched selection in the example ofFIGS. 4 and 5 ) as well as the exemplary combinedoutput 66 c (from thesummation circuitry 69 in the example ofFIG. 7 ), which track the sensed primarycurrent curve 92 ofgraph 90. - As seen above, therefore, the apparatus provides an integrated dual-sensor solution by which an extended operating range is achieved without requiring the
driver circuit 54 and thefluxgate sensor circuitry conductor 4 during overcurrent conditions. In this regard, the various concepts of the present disclosure are not limited to embodiments usingfluxgate sensors 10 or Hallsecondary sensors 20, although these particular configurations are advantageous in certain respects. For instance, Hall sensors are easily integrated into the fabrication of theintegrated circuit structure 50, and vertical Hall sensors may be constructed for magnetic sensitivity along the plane of theintegrated circuit side 50 a, thereby being sensitive in the same direction as thefluxgate sensor 10. This facilitates easy mounting within a gap of the currentsensing core structure 6, for example, as seen inFIGS. 1 and 3 above. - Moreover, Hall sensors can provide generally linear operation to yield adequate current sensor output signals at significantly high values, for example, where the
secondary sensor 20 can be constructed to produce fairly accurate signals in a second range that significantly exceeds the highest value of the first sensing range. Thus, while the examples illustrated above describe a second operating range from approximately 100% through approximately 500% of a nominal first operating range, other embodiments are possible in which thesecondary sensor 20 and associated excitation andsensing circuitry 40 may provide asuitable output 66 at significant multiples of the first operating range, including without limitation 1000% in certain implementations. This provides a significant solution for many applications in which the safe measurement of large currents is needed in a normal operating range, with thefluxgate system Hall sensor circuitry sensing apparatus 2 advantageously facilitates provision of a second separate measurement path for redundancy, which is particularly useful in safety-critical applications, for example, as shown inFIGS. 6 and 7 above. This, in turn, provides a solution for current measurement applications in which redundancy and/or self-testing is desirable to facilitate correct measurement of a sensed current, without requiring the added cost, complexity, and power consumption associated with use of two current sensors in parallel. - The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In addition, although a particular feature of the disclosure may have been disclosed with respect to only one of multiple implementations, such feature may be combined with one or more other features of other embodiments as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.
Claims (1)
1. A hybrid closed-loop, open-loop magnetic current sensor, comprising:
a magnetically susceptible core structure with an opening to accommodate an electrical conductor conducting a current to magnetically interact with the core structure;
a compensation coil having at least one winding around a portion of the core structure;
an integrated circuit positioned at least partially within a gap of the core structure and connected to the compensation coil, the integrated circuit comprising means for testing the current flowing in the electrical conductor using a closed-loop magnetic circuit comprising a first sensor formed on or in the integrated circuit within the gap of the core structure, and means for testing the current flowing in the electrical conductor using an open-loop magnetic circuit comprising a second sensor formed on or in the integrated circuit within the gap of the core structure.
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US15/076,218 US20160202294A1 (en) | 2013-08-07 | 2016-03-21 | Hybrid closed-loop/open-loop magnetic current sensor |
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US201361863294P | 2013-08-07 | 2013-08-07 | |
US14/193,023 US9291648B2 (en) | 2013-08-07 | 2014-02-28 | Hybrid closed-loop/open-loop magnetic current sensor |
US15/076,218 US20160202294A1 (en) | 2013-08-07 | 2016-03-21 | Hybrid closed-loop/open-loop magnetic current sensor |
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US14/193,023 Division US9291648B2 (en) | 2013-08-07 | 2014-02-28 | Hybrid closed-loop/open-loop magnetic current sensor |
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US20160202294A1 true US20160202294A1 (en) | 2016-07-14 |
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US14/193,023 Active 2034-06-03 US9291648B2 (en) | 2013-08-07 | 2014-02-28 | Hybrid closed-loop/open-loop magnetic current sensor |
US15/076,218 Abandoned US20160202294A1 (en) | 2013-08-07 | 2016-03-21 | Hybrid closed-loop/open-loop magnetic current sensor |
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Also Published As
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US20150042325A1 (en) | 2015-02-12 |
CN104345204B (en) | 2019-03-19 |
CN104345204A (en) | 2015-02-11 |
US9291648B2 (en) | 2016-03-22 |
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