Magnetic sensors are used in a broad range of applications, such as Internet-of-Thing (IoT), medical devices, automotive, handheld devices (e.g., smart phones and tablets), and appliances. The magnetic sensors can support various types of measurements for those applications, such as measuring position/movement, electrical current, and torque. For many of these applications, it is desirable to have a magnetic sensor to have a low power consumption to improve battery life, and to have high sensitivity and high linearity to increase measurement precision.
An apparatus comprises: a first coil, a second coil, a control circuit, and a processing circuit. The second coil is magnetically coupled to the first coil. The control circuit has a control input and a signal output, and the signal output is coupled to the first coil. The control circuit is configured to: responsive to a state of the control input, select a field strength level from a set of discrete field strength levels; and provide a first signal representing the selected field strength level at the signal output. The processing circuit has processing inputs and a processing output, the processing inputs coupled to the second coil, the processing output is coupled to the control input. The processing circuit is configured to, responsive to a second signal across the processing inputs, set a state of the processing output representing a polarity of a magnetic field sensed by the second coil.
An apparatus comprises a control circuit and a processing circuit. The control circuit has a control input and a compensation magnetic field control output, and the control circuit configured to: responsive to a state of the control input, select a field strength level from a set of discrete field strength levels; and provide a first signal representing the selected field strength level at the compensation magnetic field control output. The processing circuit has a magnetic field sensing input and a processing output, the processing output coupled to the control input, and the processing circuit configured to, responsive to a second signal at the magnetic field sensing input, set a state of the processing output representing a polarity of a magnetic field.
In a method, a first one of a first signal is received from a first coil. The first one of the first signal represents at least one of: a polarity of a first magnetic field, or whether the first magnetic field saturates a region surrounded by the first coil. Responsive to the polarity of the first magnetic field, a field strength level is selected from a set of discrete field strength levels, and a second signal representing the selected field strength level is provided to a second coil that surrounds the region. After the second signal is provided, a second one of the first signal representing a polarity of a second magnetic field is received from the first coil. Responsive to the polarity of the second magnetic field, a third signal is provided to represent whether a strength of the first magnetic field exceeds the selected field strength level.
The same reference numbers or other reference designators are used in the drawings to designate the same or similar (functionally and/or structurally) features.
There are various types of magnetic sensors. One type of magnetic sensor is a Hall sensor, which can detect the presence and magnitude of a magnetic field using the Hall effect. A Hall sensor can include a strip of metal to conduct a current. The presence of a magnetic field perpendicular to the flow of the current in the strip can produce a voltage across the strip. The voltage is proportional to the strength of the magnetic field.
Another type of magnetic sensor is a fluxgate magnetic sensor. Compared with a Hall sensor, a fluxgate magnetic sensor can have a significantly higher sensitivity, lower drift, and lower noise, all of which can improve the measurement precision of the magnetic sensor. A fluxgate magnetic sensor can include an excitation coil and a sense coil. In some examples, the excitation coil and the sense coil can surround a core. The excitation coil and the sense coil can be magnetically coupled. An excitation circuit can provide a current pulse in the excitation coil, which generates internal magnetic fields to magnetically saturate the region surrounded by the excitation coil (e.g., a core or a core region) in alternating and opposing directions. Absent an external magnetic field, the internal magnetic fields can cancel each other. This can lead to a static magnetic flux across the sense coil, and no voltage is induced across the sense coil. If an external magnetic field is present and the external magnetic field propagates through the core region, there can be a net change in the magnetic flux across the sense coil, and the net change in the magnetic flux can induce a voltage across the sense coil. The polarity of the voltage can indicate the polarity of the external magnetic field, and the magnitude of the voltage can indicate the strength/magnitude of the external magnetic field.
In some examples, the fluxgate magnetic sensor can include an air core. In some examples, the core of the fluxgate magnetic sensor can include a highly permeable material, such as iron, to concentrate the magnetic field to be measured. The core can have various shapes and configurations, such as a rod shape or a ring shape. In some examples, the coil windings of the fluxgate magnetic sensor can be encapsulated in a magnetic molding compound to further concentrate the magnetic field to be measured. The magnetic molding compound can encapsulate the core, or can fill the core region surrounded by the excitation coil and by the sense coil.
Referring to
Although a fluxgate magnetic sensor can have a high sensitivity, it can also exhibit significant non-linearity in measuring a large external magnetic field, which can saturate the cores/core regions of fluxgate magnetic sensor, as shown in
Referring to
Sensor system 700 can perform a feedback operation to iteratively estimate the external magnetic field strength. Specifically, compensation coil 704 can receive a compensation current (labelled Icomp) from compensation circuit 706 and generate a compensation magnetic field having a strength of Bcomp responsive to the compensation current. The compensation magnetic field can have an opposite polarity to the external magnetic field having a strength of Bext, so that the core magnetic field in core 201/202 having a net strength of a difference between Bext and Bcomp (Bext−Bcomp). As part of the feedback mechanism, compensation circuit 706 can receive result signal 116 from processing circuit 104. Result signal 116 can include a digital value representing the net strength Bext−Bcomp. Compensation circuit 706 can include a digital-to-analog converter (DAC) to generate compensation current Icomp iteratively based on result signal 116 until the net strength Bext−Bcomp reaches zero. Compensation circuit 706 can then provide an output signal 710 representing the final value of Icomp as an estimation/measurement of the external magnetic field strength Bext. Because the core magnetic field has a reduced net strength Bext−Bcomp, the core is less likely to be saturated even when a large external magnetic field is present. The core magnetic field can be within a range where the output of the fluxgate magnetic sensor is more linear (e.g., below B0 of
Referring to
Towards the end of measurement cycle 1, processing circuit 104 can process the Vsense pulses and provide an output voltage V1 as part of result signal 116 to compensation circuit 706. Compensation circuit 706 may determine that output voltage V1 represents a magnetic field strength of BCOMP0 instead of Bext from the transfer characteristic graph represented by graph 808. Accordingly, compensation circuit 706 can provide a compensation current Icomp0 to compensation coil 704, which can then generate a compensation magnetic field having the strength of Bcomp0. The compensation magnetic field can combine with the external magnetic field, so that the core/combined magnetic field strength is reduced to become Bext−Bcomp0.
In measurement cycle 2, sense coil 204 can generate Vsense pulses representing the net strength Bext−Bcomp0. Towards the end of measurement cycle 2, processing circuit 104 can process the Vsense pulses and provide an output voltage V2 as part of result signal 116 to compensation circuit 706. Based on the output voltage V2, compensation circuit 706 determines that the previous compensation current Icomp0 does not generate sufficient magnetic field to completely cancel out Bext, and increase the compensation current to Icomp1 to further reduce the output voltage of processing circuit 104. Compensation circuit 706 can determine Icomp1 by first determining the additional amount of compensation current to increase the compensation magnetic field strength by Bext−Bcomp0, and adding the amount of compensation current to Icomp0. Compensation circuit 706 can provide compensation current Icomp1 to compensation coil 704, which can then generate a compensation magnetic field having the strength of Bcomp1. The compensation magnetic field can combine with the external magnetic field, so that the core/combined magnetic field strength is reduced to become Bext−Bcomp1.
In subsequent measurement cycles, compensation circuit 706 can continue increasing the compensation current to further reduce core magnetic field strength. Convergence is reached in cycle N−1 where the core/combined magnetic field strength is below a threshold, which indicates that the external magnetic field and the compensation magnetic field have almost the same strength, and the strength difference is below the threshold. Compensation circuit 706 can then provide output signal 710 based on the final compensation current value to represent a measurement of the external magnetic field strength Bext.
Although the feedback operation described in
The compensation magnetic field generated by compensation coil 203 can combine with the external magnetic field to provide a combined/core magnetic field, which can be sensed by sense coil 204. Processing circuit 104 can provide result signal 116 representing a polarity of the core magnetic field, which can also indicate whether the external magnetic field strength exceeds or is below the compensation magnetic field strength. Control circuit 902 can also maintain a record of previously-selected strength levels and their compensation current settings. Responsive to result signal 116, control circuit 902 can select a different compensation current setting from mapping table 906 to increase the compensation magnetic field strength if the external magnetic field strength exceeds the compensation magnetic field strength.
Control circuit 902 can also stop the comparison operation and the measurement operation if the external magnetic field strength is between two consecutive compensation magnetic field strength levels in mapping table 906, or if the entire set of compensation current settings has been traversed and the external magnetic field strength exceeds the maximum magnetic field strength level in mapping table 906. Control circuit 902 can then provide an output signal 912 as a measurement of the external magnetic field strength. Output signal 912 can indicate, for example, a range of the external magnetic field strength (e.g., between two consecutive compensation magnetic field strength levels in mapping table 906), or whether the external magnetic field strength exceeds the maximum magnetic field strength level in mapping table 906.
In some examples, control circuit 902 (and sensor system 900) can switch between an active state and a sleep state. In the active state, control circuit 902 can enable processing circuit 104, excitation circuit 210, and DAC 904 to measure an external magnetic field strength. In the sleep state, control circuit 902 can disable processing circuit 104, excitation circuit 210, and DAC 904 to reduce power consumption. Control circuit 902 can enter the sleep state after completing a measurement of the external magnetic field strength, and can exit the sleep state to start a new measurement responsive to a wake-up signal 914. In some examples, control circuit 902 can receive wake-up signal 914 as a periodic signal (e.g., a clock signal) to exit the sleep state periodically, so that sensor system 900 can detect and measure an external magnetic field periodically. In some examples, control circuit 902 can receive wake-up signal 914 from a user-controllable input interface (e.g., a mechanical switch) and can exit the sleep state responsive to a user input.
The magnetic field measurement operations of sensor system 900 can reduce response time and power consumption, while providing measurements with improved linearity and accuracy. Specifically, instead of iteratively determining the strength of a compensation magnetic field that matches (and completely cancels) the external magnetic field, as described in
Also, compared with a case where no compensation magnetic field is generated to at least partially cancel the external magnetic field, as described in
In some examples, sensor system 900 can be configured as an omnipolar switch that can change states according to the strength and polarity of an external magnetic field. The state of the omnipolar switch can provide a measurement of the magnetic field. The omnipolar switch can also have built-in hysteresis. The switch can enter an on state if an external magnetic field of sufficient strength is present. After the switch is turned on, it can remain in the on-state until the magnetic field is removed, and the switch can enter an off state. The switch can remain in the off state until an external magnetic field of sufficient strength is again present.
Also, the switch can have built-in hysteresis and can have different switching thresholds depending on whether the external magnetic field strength increases or decreases. For example, for an increasing external magnetic field, if the external magnetic field strength increases above Bth1, the switch can change from the S1 state to the S0 state. The switch can stay in the S1 state when the decreasing external magnetic field strength is between Bth0 and Bth1. Also, for a decreasing external magnetic field, if the external magnetic field strength decreases below Bth0, the switch can change from the S0 state to the S1 state. The switch can stay in the S0 state when the increasing external magnetic field strength is between Bth0 and Bth1.
Referring to
In step 1104, sensor system 900 can provide zero compensation current to compensation coil 704, so that compensation coil 704 does not generate a compensation magnetic field. An external magnetic field that enters the core/core region can become the first core magnetic field, and the first core magnetic field can have the same strength as the external magnetic field. For example, control circuit 902 can provide control signal 910 indicating zero compensation current Icomp to DAC 904, which then provides zero Icomp to compensation coil 704. An external magnetic field can enter cores 202a/202b as the first core magnetic field.
In step 1106, sensor system 900 can provide a first excitation current pulse to excitation coil 203, such as the excitation current pulses illustrated in
As described above, the excitation current pulse can induce an internal magnetic field that saturates cores 202a/202b. If cores 202a/202b are not saturated by the external magnetic field prior to sensor system 900 providing the first excitation current pulse to excitation coil 203, voltage pulses can be induced on terminals s1 and s2, as illustrated in
In step 1108, sensor system 900 can detect transitions in the Vs1 and Vs2 voltages and determine whether voltage pulses are detected at terminals s1 and s2. For example, processing circuit 104 can provide result signal 116 to indicate whether voltage pulse is detected, which can also indicate whether the core (or the core region) is saturated.
In step 1110, sensor system 800 can determine whether saturation of the core (or the core region) is detected when zero compensation magnetic field is provided. If saturation is detected, control circuit 902 can provide output signal 912 representing that the switch is in a first state (e.g., an off state, or S0 state in
But if saturation is not detected (in step 1110), sensor system 900 can proceed to compare the external magnetic field strength with one or more threshold strengths. Specifically, referring to
In step 1124, sensor system 900 can provide a first compensation magnetic field having a second polarity opposite to the first polarity and having a first strength level. Specifically, referring to
In step 1126, sensor system 900 can provide a second excitation current pulse to excitation coil 203, such as the excitation current pulses illustrated in
The second excitation current pulse can induce an internal magnetic field that saturates cores 202a/202b, and the second core magnetic field can introduce pulse width mismatches between the voltage pulses Vs1 and Vs2. The pulse width of the Vsense pulses (or a voltage resulted from integrating the Vsense pulses) represents the output of fluxgate magnetic sensor 702 in measuring the second core magnetic field. Referring to
In step 1128, sensor system 900 can determine whether the second core magnetic field has the first polarity or the second polarity, based on result signal 116. As described above, if Bext (external magnetic field strength or first core magnetic field strength) exceeds Bth0, the second core magnetic field can have the first polarity. But if Bext is below Bth0, the second core magnetic field can have the second polarity.
In step 1130, if result signal 116 indicates that the external magnetic field strength is below the first strength level (e.g., result signal 116 indicating the second polarity), control circuit 902 can provide output signal 912 representing that the switch is in a second state (e.g., an on state, or S1 state in
But if result signal 116 indicates that the external magnetic field strength is above the first strength level (e.g., result signal 116 indicating the first polarity), and that a compensation magnetic field having the first strength level has previously been provided, control circuit 902 can proceed to compare the external magnetic field strength with a second strength level Bth1. Referring to
Specifically, control circuit 902 can refer to mapping table 906 and select a second compensation current setting I1 for the second strength level Bth1. Control circuit 902 can then provide control signal 910 indicating the second polarity and including the second compensation current setting I1 to DAC 904. DAC 904 can then provide a compensation current Icomp to compensation coil 704 responsive to control signal 910, and compensation coil 704 can generate the second compensation magnetic field having the second polarity. Referring to
In step 1144, sensor system 900 can provide a second excitation current pulse to excitation coil 203, such as the excitation current pulses illustrated in
The third excitation current pulse can induce an internal magnetic field that saturates cores 202a/202b, and the third core magnetic field can introduce pulse width mismatches between the voltage pulses Vs1 and Vs2. The pulse width of the Vsense pulses (or a voltage resulted from integrating the Vsense pulses) represents the output of fluxgate magnetic sensor 702 in measuring the third core magnetic field. Referring to
In step 1146, sensor system 900 can determine whether the third core magnetic field has the first polarity or the second polarity, based on result signal 116. As described above, if Bext (external magnetic field strength or first core magnetic field strength) exceeds Bth1, the second core magnetic field can have the first polarity. But if Bext is below Bth1, the second core magnetic field can have the second polarity.
In step 1148, if result signal 116 indicates that the external magnetic field strength is below the second strength level (e.g., result signal 116 indicating the second polarity), control circuit 902 can maintain the state of the switch, in step 1150. This can provide the built-in hysteresis where the switch state is maintained as the external magnetic field strength increases or decreases to be within the range between Bth0 and Bth1. For example, if the prior switch state is S1 and the external magnetic field is becoming stronger with time, control circuit 902 can maintain the switch state at S1 when the external magnetic field strength is within the range between Bth0 and Bth1. Also, if the prior switch state is S0 and the external magnetic field is becoming weaker with time, control circuit 902 can maintain the switch state at S0 when the external magnetic field strength is within the range between Bth0 and Bth1. Control circuit 902 can then reenter the sleep state in step 1152, and the third measurement cycle ends.
Also, if result signal 116 indicates that the external magnetic field strength is above the second strength level (e.g., result signal 116 indicating the first polarity), control circuit 902 can provide output signal 912 representing that the switch is in the first state (e.g., an off state, or S0 state in
Also, polarity detection circuit 1304 can include a demodulator 1314, a differential integrator 1316 including an amplifier 1318 and capacitors 1320a and 1320b, and a comparator 1322. Demodulator 1314 can convert the Vs1 and Vs2 voltage pulses to a particular polarity based on the polarities of the excitation current pulses, which reflect the excitation direction. Differential integrator 1316 can be reset by a reset signal 1321 at the beginning of a measurement cycle. After the reset signal is released, differential integrator 1316 can integrate the converted Vs1 and Vs2 voltage pulses to generate differential signals 1324a and 1324b. The relative magnitudes of differential signals 1324a and 1324b can reflect the polarity of the core magnetic field. Comparator 1322 can compare differential signals 1324a and 1324b and generate a comparison signal 1326. The state of comparison signal 1326 can indicate the polarity of core magnetic field. In some examples, comparator 1322 can include a dynamic latch-based/clocked comparator. Comparator 1322 can perform a comparison and generate comparison signal 1326 in every measurement cycle (e.g., after 2nd excitation pulse), and then hold the state of comparison signal 1326. Processing circuit 104 can include saturation signal 1306 and comparison signal 1326 as result signal 116.
Referring to
After determining that cores 202a/202b are not saturated by the external magnetic field in the first measurement cycle, control circuit 902 can start a second measurement cycle (labelled “cycle 2”), which spans between times T2 and T4. In the second measurement cycle, control circuit 902 determines the polarity of the external magnetic field, and cause DAC 904 to provide zero compensation current (Icomp), so that compensation coil 704 provides no compensation magnetic field. Control circuit 902 causes excitation circuit 210 to provide a second pair of excitation current pulses having opposite polarities to excitation coil 203. The external magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T2 and integrates the Vsense voltage pulses. The differential output of integrator 1316 reduces during the integration to below zero, and the output of comparator 1322 can remain in the first state (a de-asserted state), which indicates a first polarity of the external magnetic field. The switch state represented by output signal 912 of control circuit 902 can remain in the prior switch state (S0 in
Also, before the end of the second measurement cycle, control circuit 902 can select −I0 from mapping table 906 based on the polarity of the external magnetic field. Control circuit 902 can then transmit control signal 910 indicating −I0 to DAC 904 at time T3. DAC 904 can then provide a compensation current of −I0 to compensation coil 704 to generate a compensation magnetic field having the strength of Bth0 and having a second polarity opposite to the first polarity of the external magnetic field. The compensation magnetic field can subtract from the external magnetic field to generate a core magnetic field having a net strength of difference between Bext and Bth0 (Bext−Bth0). The core magnetic field can have the same polarity as the external magnetic field if Bext exceeds Bth0. The core magnetic field can have opposite polarity to the external magnetic field if Bext is below Bth0.
Control circuit 902 can then start a third measurement cycle (labelled “cycle 3”) at time T4, to determine the polarity of the core magnetic field. Control circuit 902 causes excitation circuit 210 to provide a third pair of excitation current pulses having opposite polarities to excitation coil 203. The core magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T4 and integrates the Vsense voltage pulses. In the example of
Referring to
Before the end of the first measurement cycle, at time T2, control circuit 902 can select −I0 from mapping table 906 based on the first polarity of the external magnetic field. Control circuit 902 can then transmit control signal 910 indicating −I0 to DAC 904 at time T2. DAC 904 can then provide a compensation current of −I0 to compensation coil 704 to generate a first compensation magnetic field having the strength of Bth0 and having a second polarity opposite to the first polarity of the external magnetic field. The first compensation magnetic field can subtract from the external magnetic field to generate a first core magnetic field having a net strength of Bext−Bth0. The first core magnetic field can have the same first polarity as the external magnetic field if Bext exceeds Bth0. The first core magnetic field can have the second polarity (opposite to the first polarity of the external magnetic field) if Bext is below Bth0.
Control circuit 902 can then start a second measurement cycle (labelled “cycle 2”), which spans between times T3 and T5. In the second measurement cycle, control circuit 902 determines the polarity of the first core external magnetic field. Control circuit 902 causes excitation circuit 210 to provide a second pair of excitation current pulses having opposite polarities to excitation coil 203. The first core magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T3 and integrates the Vsense voltage pulses, and the differential output of integrator 1316 reduces during the integration to below zero. The output of comparator 1322 can remain in the first state (a de-asserted state), which indicates that the first core magnetic field has the first polarity. The switch state represented by output signal 912 of control circuit 902 can remain in the prior switch state (S1 in
Before the end of the second measurement cycle, at time T4, control circuit 902 can select −I1 from mapping table 906 based on the first polarity of the first core magnetic field. Control circuit 902 can then transmit control signal 910 indicating −I1 to DAC 904 at time T4. DAC 904 can then provide a compensation current of −I1 to compensation coil 704 to generate a second compensation magnetic field having the strength of Bth1 and having the second polarity. The second compensation magnetic field can subtract from the external magnetic field to generate a second core magnetic field having a net strength of difference between Bext and Bth1 (Bext−Bth1). The second core magnetic field can have the same first polarity as the external magnetic field if Bext exceeds Bth1. The second core magnetic field can have the second polarity (opposite to the first polarity of the external magnetic field) if Bext is below Bth1.
Control circuit 902 can then start a third measurement cycle (labelled “cycle 3”) at time T5, to determine the polarity of the second core magnetic field. Control circuit 902 causes excitation circuit 210 to provide a third pair of excitation current pulses having opposite polarities to excitation coil 203. The core magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T5 and integrates the Vsense voltage pulses. In the example of
Referring to
Before the end of the first measurement cycle, at time T2, control circuit 902 can select −I0 from mapping table 906 based on the first polarity of the external magnetic field. Control circuit 902 can then transmit control signal 910 indicating −I0 to DAC 904 at time T2. DAC 904 can then provide a compensation current of −I0 to compensation coil 704 to generate a first compensation magnetic field having the strength of Bth0 and having a second polarity opposite to the first polarity of the external magnetic field. The first compensation magnetic field can subtract from the external magnetic field to generate a first core magnetic field having a net strength of Bext−Bth0. The first core magnetic field can have the same first polarity as the external magnetic field if Bext exceeds Bth0. The first core magnetic field can have the second polarity (opposite to the first polarity of the external magnetic field) if Bext is below Bth0.
Control circuit 902 can then start a second measurement cycle (labelled “cycle 2”), which spans between times T3 and T5. In the second measurement cycle, control circuit 902 determines the polarity of the first core external magnetic field. Control circuit 902 causes excitation circuit 210 to provide a second pair of excitation current pulses having opposite polarities to excitation coil 203. The first core magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T3 and integrates the Vsense voltage pulses, and the differential output of integrator 1316 reduces during the integration to below zero, and the output of comparator 1322 can remain in the first state (a de-asserted state), which indicates that the first core magnetic field has the first polarity. The switch state represented by output signal 912 of control circuit 902 can remain in the prior switch state (S1 in
Before the end of the second measurement cycle, at time T4, control circuit 902 can select −I1 from mapping table 906 based on the first polarity of the first core magnetic field. Control circuit 902 can then transmit control signal 910 indicating −I1 to DAC 904 at time T4. DAC 904 can then provide a compensation current of −I1 to compensation coil 704 to generate a second compensation magnetic field having the strength of Bth1 and having the second polarity. The second compensation magnetic field can subtract from the external magnetic field to generate a second core magnetic field having a net strength of Bext−Bth1. The second core magnetic field can have the same first polarity as the external magnetic field if Bext exceeds Bth1. The second core magnetic field can have the second polarity (opposite to the first polarity of the external magnetic field) if Bext is below Bth1.
Control circuit 902 can then start a third measurement cycle (labelled “cycle 3”) at time T5, to determine the polarity of the second core magnetic field. Control circuit 902 causes excitation circuit 210 to provide a third pair of excitation current pulses having opposite polarities to excitation coil 203. The core magnetic field can introduce Vsense voltage pulses across sense coil 204. Differential integrator 1316 exits the reset state at T5 and integrates the Vsense voltage pulses. In the example of
In step 1702, the control circuit can receive a first one of a first signal from a first coil, in which the first one of the first signal indicates at least one of: a polarity of a first magnetic field, or whether the first magnetic field saturates a region surrounded by the first coil.
Specifically, the first magnetic field can be a first core magnetic field sensed by sense coil 204. The first core magnetic field can result from an external magnetic field propagating through a core (or a region) surrounded by the first coil (e.g., cores 202a/202b) having a strength of Bext. In some examples, the control circuit may control compensation coil 704 to generate a first compensation magnetic field having a strength of Bth0 and an opposite polarity to the external magnetic field prior to step 1702, and the first core magnetic field can be a combination of the external magnetic field and the first compensation magnetic field and have a net strength of Bext−Bth0. The first signal can include comparison signal 1326 from comparator 1322 and/or saturation signal 1306 from saturation detection circuit 1302.
In step 1704, responsive to the first one of the first signal, the control circuit can select a magnetic field strength level from a set of magnetic field strength levels for generating a compensation magnetic field, and provide a second signal representing the selected magnetic field to a second coil that surrounds the region.
Specifically, the second coil can be compensation coil 704. In some examples, if the first one of the first signal indicates the core/core region is not saturated by the first magnetic field, and no compensation magnet field is present, control circuit 902 can select a magnetic field strength level (e.g., Bth0 or Bth1 of
In step 1706, after providing the second signal, the control circuit can receive a second one of the first signal representing a polarity of a second magnetic field from the first coil.
Specifically, the second magnetic field can result from a combination of the external magnetic field and one of the first or second compensation magnetic fields, and the second magnetic field can have a net strength of Bext−Bth0 or Bext−Bth1. The second one of the first signal can indicate whether Bext exceeds Bth0, or whether Bext exceeds Bth1.
In step 1708, responsive to the polarity of the second magnetic field, the control circuit can provide a third signal representing whether a strength of the first magnetic field (or the external magnetic field) exceeds the selected magnetic field strength.
Specifically, as described above, sensor system 900 can implement a fluxgate ominipolar switch having a transfer characteristic similar to the one illustrated in
Any of the methods described herein may be totally or partially performed with a computing system, such as a processor, a microcontroller, etc., which can be configured to perform the steps. Thus, embodiments can be directed to computing systems configured to perform the steps of any of the methods described herein, potentially with different components performing a respective steps or a respective group of steps. Although presented as numbered steps, steps of methods herein can be performed at a same time or in a different order. Additionally, portions of these steps may be used with portions of other steps from other methods. Also, all or portions of a step may be optional. Additionally, any of the steps of any of the methods can be performed with modules, units, circuits, or other means for performing these steps.
In this description, the term “couple” may cover connections, communications or signal paths that enable a functional relationship consistent with this description. For example, if device A provides a signal to control device B to perform an action, then: (a) in a first example, device A is directly coupled to device B; or (b) in a second example, device A is indirectly coupled to device B through intervening component C if intervening component C does not substantially alter the functional relationship between device A and device B, so device B is controlled by device A via the control signal provided by device A.
A device that is “configured to” perform a task or function may be configured (e.g., programmed and/or hardwired) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or reconfigurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construction and/or layout of hardware components and interconnections of the device, or a combination thereof.
A circuit or device that is described herein as including certain components may instead be adapted to be coupled to those components to form the described circuitry or device. For example, a structure described herein as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors and/or inductors), and/or one or more sources (such as voltage and/or current sources) may instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and/or integrated circuit (IC) package) and may be adapted to be coupled to at least some of the passive elements and/or the sources to form the described structure either at a time of manufacture or after a time of manufacture, such as by an end-user and/or a third party.
Certain components may be described herein as being of a particular process technology, but these components may be exchanged for components of other process technologies. Circuits described herein are reconfigurable to include the replaced components to provide functionality at least partially similar to functionality available prior to the component replacement. Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in series and/or parallel to provide an amount of impedance represented by the shown resistor. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series or in parallel between the same two nodes as the single resistor or capacitor.
Uses of the phrase “ground voltage potential” in this description include a chassis ground, an Earth ground, a floating ground, a virtual ground, a digital ground, a common ground, and/or any other form of ground connection applicable to, or suitable for, the teachings of this description. In this description, unless otherwise stated, “about,” “approximately” or “substantially” preceding a parameter means being within +/−10 percent of that parameter.
Modifications are possible in the described examples, and other examples are possible, within the scope of the claims.