Current sensing system and current sensing method

A current sensing system uses a Hall effect device. A conductor carrying a target current is shaped in a way such that two regions with opposite magnetic field directions crossed there through are created at a silicon die which contains the Hall effect devices placed in a mirror way. The Hall effect devices react the magnetic field to generate a Hall voltage when a bias current is applied, which is then processed by a process circuit and an operational unit, so that a differential signal indicative of the target current is generated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of European Patent Application No. 17157945.1, filed Feb. 24, 2017, which is incorporated herein by reference in its entirety

TECHNICAL FIELD

The present invention generally relates to sensor, and more particularly but not exclusively relates to current sensing system and current sensing method.

BACKGROUND OF THE INVENTION

Hall effect devices are used in various applications. One application that Hall effect devices are used is in the area of current sensors. A typical integrated planar Hall effect device is shown inFIG. 1A. As shown inFIG. 1A, the Hall effect device has two pairs of connectors (a first pair of connectors C1& C2, and a second pair of connectors C3& C4).FIG. 1Bschematically shows the Hall effect device inFIG. 1Awith a cross-section view along the CP slice. As shown inFIG. 1B, the connectors are N-type highly doped regions (N+) formed in an N-type well region (N-well), which is formed on a P-type substrate (P-sub). When a magnetic field B is applied perpendicular to a plane of the Hall effect device, and a current is applied to one pair of the connectors (e.g. C1& C2), a Hall voltage will be generated in the other pair of the connectors (e.g. C3& C4). A depletion layer which functions as an isolation layer is generated at the junction of the N-well and the P-sub when the current is applied to the Hall effect device and an appropriate voltage level is applied to the P-sub with respect to the voltage level of the connectors.

However, the accuracy of current sensing based on Hall effect devices may suffer from parasitic field and temperature drifts of the magnetic field B, and parasitic spikes due to switching of power switches in a power stage. Efforts such as spinning current technique which controls the current applied to the Hall effect device and the resulted Hall voltage to be spinning between the two pairs of the connectors are adopted to alleviate the current sense accuracy issues, but further improvement is still needed.

SUMMARY

It is an object of the present invention to provide an improved current sensor, which solves the above problems.

In accomplishing the above and other objects, there has been provided, in accordance with an embodiment of the present invention, a current sensing system, comprising: a silicon die; and a conductor, part of the conductor shaped to carry a target current in a way such that a first magnetic region and a second magnetic region are created at the silicon die, and magnetic fields with opposite directions respectively crosses through the first magnetic region and the second magnetic region, the silicon die having N Hall effect devices in each of the magnetic regions, half of the N Hall effect devices in each of the magnetic regions being placed at one side of a mid-line, another half of N Hall effect devices in each of the magnetic regions being placed at the other side of the mid-line, the two halves of the Hall effect blocks being placed symmetrically with each other along the mid-line, N being a positive even number, each Hall effect device being applied with a bias current to provide a Hall voltage, wherein the silicon die further comprises: two process circuits, configured to respectively process the Hall voltages from each side of the mid-line, to generate two processed signals; and an operational unit, configured to execute a subtraction operation or an add operation on the two processed signals to generate an operational signal.

In addition, there has been provided, in accordance with an embodiment of the present invention, a current sensing method, comprising: shaping part of a conductor to create a first magnetic region and a second magnetic region at a silicon die when a target current is flowing through the conductor, and magnetic fields with opposite directions crossing through the first magnetic region and the second magnetic region; placing N Hall effect devices in each of the magnetic regions at a silicon die, half of the N Hall effect devices in each of the magnetic regions being placed in one side of a mid-line, another half of N Hall effect devices in each of the magnetic regions being placed in the other side of the mid-line, the two halves of the Hall effect devices being placed in a mirrored way to each other along the mid-line, N being a positive even number; applying a bias current to the Hall effect device in each of the magnetic regions with spinning scheme, so that a Hall voltage is generated by each of the Hall effect devices; processing the Hall voltages at each side of the mid-line to generate two processed signals; and executing a subtraction operation or an add operation on the processed signals to generate an operational signal.

Furthermore, there has been provided, in accordance with an embodiment of the present invention, a current sensing system, comprising: a silicon die; and a conductor, part of the conductor shaped to carry a target current in a way such that a first magnetic region and a second magnetic region are created at the silicon die, and magnetic fields with opposite directions respectively crosses through the first magnetic region and the second magnetic region, the silicon die having a first portion and a second portion, each portion including: at least two Hall effect devices placed at the first and second magnetic regions, respectively, each Hall effect device being applied with a bias current to provide a Hall voltage, wherein the Hall effect devices in the first portion are laid in a mirrored way with the Hall effect devices in the second portion; and a process circuit, configured to process the Hall voltage to generate a processed signal; and wherein the silicon die further comprises: an operational unit, configured to execute a subtraction operation or an add operation on the processed signals to generate an operational signal.

The use of the similar reference label in different drawings indicates the same of like components.

DETAILED DESCRIPTION

Embodiments of circuits for current sensing system are described in detail herein. In the following description, some specific details, such as example circuits for these circuit components, are included to provide a thorough understanding of embodiments of the invention. One skilled in relevant art will recognize, however, that the invention can be practiced without one or more specific details, or with other methods, components, materials, etc.

The following embodiments and aspects are illustrated in conjunction with circuits and methods that are meant to be exemplary and illustrative. In various embodiments, the above problem has been reduced or eliminated, while other embodiments are directed to other improvements.

FIG. 2schematically shows a current sensing system in accordance with an embodiment of the present invention. As shown inFIG. 2, the current sensing system comprises: a silicon die101; and a conductor102, wherein part of the conductor102is shaped to carry a target current in a way such that two magnetic regions (a first magnetic region11and a second magnetic region12) with opposite magnetic fields B crossed therethrough are created at the silicon die101. As shown inFIG. 2, when the current flows through the conductor102in the shown direction, the magnetic field B crossing through the first magnetic region11has a direction pointing into the plane (labeled as cross), and the magnetic field B crossing through the second magnetic region12has a direction pointing out of the plane (labeled as a dot). However, one of ordinary skill should realize that the current flowing through the conductor102may have another direction, so that the first magnetic region11is with a magnetic field B crossing through the silicon101with a direction pointing out of the plane, and the second magnetic region12is with a magnetic field B crossing through the silicon101with a direction pointing into the plane. The target current is the current that needs to be sensed. The silicon die101has N Hall effect devices13in each of the magnetic regions, wherein N is a positive even number. Half of the Hall effect devices in each of the magnetic regions are placed at one side of a mid-line1010, and another half of the Hall effect devices in each of the magnetic region are placed at the other side of the mid-line1010. That is, the number of Hall effect devices in each of the magnetic regions is a multiple of 2 (i.e. 2, 4, 6, 8, etc), and the total number of Hall effect devices in the silicon die101is a multiple of 4 (i.e., 4, 8, 12, 16, etc). The two halves of the Hall effect devices are placed in a mirrored way (i.e., each half is symmetrically placed with a corresponding other half) to each other along the mid-line1010, which will be further shown and discussed further with reference toFIG. 6andFIG. 8.

The mid-line1010is a line along which the first magnetic region11and the second magnetic region12can be “folded” and divided into two symmetric halves, respectively.

In one embodiment, the Hall effect device is coupled to a switch box to perform so-called spinning current, which will be discussed further with reference toFIG. 4.

In one embodiment, the silicon die101is with a surface mount package. However, in other embodiments, the silicon die101can be with any other suitable packages.

In one embodiment, the conductor102comprises a lead frame, which is shaped as shown inFIG. 2.

In one embodiment, the conductor102has four fingers (lead fingers)1021,1022,1023and1024, with two fingers (e.g.,1021and1022) flowing into the target current, and the other two finger (e.g.1023and1024) flowing out the target current.

FIG. 3schematically shows a Hall effect device in accordance with an embodiment of the present invention. As shown inFIG. 3, the Hall effect device comprises two pairs of connectors (31&33and32&34). In the example ofFIG. 3, a bias current is applied from connector31to connector33in a vertical magnetic field B pointing into the plane. As a result, a Hall voltage is generated between connectors32and34, wherein connector32is with a positive polarity, and connector34is with a negative polarity. For illustration purpose, the Hall effect device inFIG. 3Bwill be illustrated as inFIG. 3Ain the following discussion.

FIG. 4schematically shows a spinning Hall effect device (i.e., a Hall effect device coupled with a switch box) in accordance with an embodiment of the present invention. In the example ofFIG. 4, the spinning Hall effect device comprises: a Hall device as a sensing element having two pairs of connectors (31&33, and32&34), with one pair of connectors configured to receive a bias current, and the other pair of connectors configured to generate a Hall voltage in response to the bias current and a vertical magnetic field B; and a switch box (SB), configured to control the bias current running in the Hall device and the sensed Hall voltage to be spinning between the two pairs of the connectors. In the example ofFIG. 4, the spinning direction is clockwise, which means that in the immediately coming cycle, the bias current will be applied from connector34to connector32(i.e. the bias current will be shifted to connectors34&32from connectors31&33), and the Hall voltage will be generated between connectors31and33. For illustration purpose, the spinning Hall effect device inFIG. 4Bwill be illustrated as inFIG. 4Ain the following discussion.

FIG. 5schematically shows a spinning Hall effect device with a detailed configuration of the switch box in accordance with an embodiment of the present invention. In the example ofFIG. 5, the switch box includes: a first switch pair (M1& M2), coupled between a current source11and two connectors (31&34) of the Hall effect device; a second switch pair (M3& M4), coupled between two connectors (32&33) of the Hall effect device and ground; a third switch pair (M5& M6), coupled between two connectors (31&34) of the Hall effect device and a first output terminal V+; and a fourth switch pair (M7& M8), coupled between two connectors (32&33) of the Hall effect device and a second output terminal V−, wherein a voltage difference between the first output terminal V+ and the second output terminal V− is the Hall voltage, and wherein each switch pair has one switch controlled by a control signal (CLK), and the other switch controlled by an inverted signal of the control signal (CLK). In that way the Hall signal is modulated with the control signal (CLK). The operation principle of the switch box is well known in the art, which will not be discussed for briefly.

FIG. 6schematically shows a circuit configuration of the silicon die101in accordance with an embodiment of the present invention. In the example ofFIG. 6, the silicon die101has two portions (a first portion1011and a second portion1012) having a same circuit configuration at the two sides of the mid-line1010, respectively. Each portion includes: two Hall effect devices, placed in the first magnetic region11and the second magnetic region12, respectively, each Hall effect device configured to provide a Hall voltage (or called as a differential signal) in response to a spinning current applied thereto; and a process circuit14, configured to process the Hall voltages to generate a processed signal.

Continue referring toFIG. 6, the first portion1011has a first Hall effect device1311& a second Hall effect device1321, while the second portion1012has a first Hall effect device1312& a second Hall effect device1322. The first Hall effect devices1311and1312are laid in a mirror way (i.e. they are placed symmetrically with each other along the mid-line1010), and with mirror bias current directions and mirror spinning current schemes. Likewise, the second Hall effect devices1321and1322are also laid in a mirror way and with mirror bias current directions and mirror spinning current schemes. Specifically, in the example ofFIG. 6, the bias current applied to the first Hall effect devices1311in the first portion1011rotates clockwise and has an initial current direction pointing from bottom left corner to top right corner, whereas the bias current applied to the first Hall effect device1312in the second portion1012rotates counterclockwise and has an initial current direction pointing from top left corner to bottom right corner. The second Hall effect device1321in the first portion1011rotates clockwise and has an initial current direction pointing from bottom right corner to top left corner, whereas the second Hall effect device1322in the second portion1012rotates counterclockwise and has an initial current direction pointing from top right corner to bottom left corner.

The switch box which provides the bias current to the Hall effect devices is placed anywhere at the corresponding Hall effect device proximity. In one embodiment, it may be placed inside the magnetic region. In other embodiments, it may be placed outside the magnetic region.

Due to the Hall effect devices in each of the magnetic regions are laid in a mirror way and with mirror bias current directions and mirror spinning current schemes with each other as discussed above, the Hall voltages generated at two sides of the mid-line1010are with opposite polarities with each other, whereas parasitic signals generated due to switching of switches in a power stage have the same polarities.

In the example ofFIG. 6, the silicon die101further comprises: an operational unit15, configured to receive the processed signals from the first portion1011and the second portion1012, to execute a subtraction operation or an add operation on the two processed signals to generate an operational signal (OS). In the example ofFIG. 6, the operational unit15is shown as placed in the first portion1011. However, one of ordinary skill in the art should realize that the operational amplifier15may be placed in either portion.

In one embodiment, the operation unit15comprises a subtractor.

In the example ofFIG. 6, the process circuit14in each of the portions comprises: an operational amplifier (or called as a differential difference amplifier)141, configured to respectively sum the Hall voltages generated by the half Hall effect devices in the first magnetic region11at one side of the mid-line1010(i.e. by the half Hall effect devices placed in both of the first magnetic region11and the corresponding portion), and the Hall voltages generated by the half Hall effect devices in the second magnetic region12at one side of the mid-line1010(i.e. by the half Hall effect devices placed in both of the second magnetic region12and the corresponding portion), and to amplify a difference between the summed results to generate an amplified signal SA; a peak to peak detector142, coupled to the operational amplifier141to receive the amplified signal SA, to generate a peak-peak signal (P-P) indicative of the difference between a maximum value and a minimum value of the amplified signal SA; a sample and hold circuit143, coupled to the peak to peak detector142to receive the peak-peak signal (P-P), to generate a sample-hold signal (S/H); and a filter144, coupled to the sample and hold circuit143to receive the sample-hold signal (S/H), to generate the processed signal (SF) based on the sample-hold signal (S/H).

During the operation of the system, when the target current is applied to the conductor102, due to the shape of the conductor, two magnetic fields with opposite directions crossed therethrough are generated in the magnetic regions11and12, respectively. So in each portion, the Hall voltages generated in the first magnetic region11and the second magnetic region12are with opposite polarities with each other. In addition, as discussed hereinbefore, the Hall voltages in each side of the mid-line1010are with opposite polarities, too. The Hall voltages are then processed by the process circuit14and the operational unit15. Thus the operational signal (OS) provided by the operational unit15reflects the magnetic field intensity of the magnetic regions, which is generated by the target current. So the operational signal (OS) is indicative of the target current. Thus current sense is achieved by the current sensing system discussed above.

FIG. 7schematically shows a “mirror” layout example in accordance with an embodiment of the present invention.

FIG. 8schematically shows a circuit configuration of the silicon die101with four Hall effect devices in each of the magnetic regions in accordance with an embodiment of the present invention. In each of the magnetic regions, two Hall effect devices are placed in the first portion1011, and the other two Hall effect devices are placed in the second portion1012; the two Hall effect devices in the first portion1011and the two Hall effect devices in the second portion1012are laid in a mirrored way to each other along the mid-line1010, and with mirrored bias current directions and mirrored spinning current schemes. Each of the Hall effect devices is placed along the boundary (shown as dashed arc line) of the conductor102and is configured to provide a Hall voltage (or called as a differential signal). The other circuits of the silicon die101in the example ofFIG. 8are similar to that inFIG. 6.

In one embodiment, the two Hall effect devices placed in each quarter (e.g. the upper half of the first magnetic region11in the first portion1011, the lower half of the first magnetic region11in the second portion1012, the upper half of the second magnetic region12in the first portion, or the lower half of the second magnetic region12in the second portion1012) are applied with opposite bias current directions and opposite spinning current schemes.

Specifically, as shown inFIG. 8, in the first magnetic region11, the Hall effect device1311has a bias current rotating clockwise and with an initial current direction pointing from bottom left corner to top right corner, its mirrored Hall effect device1312has a bias current rotating counterclockwise and with an initial current direction pointing from top left corner to bottom right corner; the Hall effect device1313has a bias current rotating counterclockwise and with an initial current direction pointing from top left corner to bottom right corner, its mirrored Hall effect device1314has a bias current rotating clockwise and with an initial current direction pointing from bottom left corner to top right corner.

In second the magnetic region12, the Hall effect device1321has a bias current rotating clockwise and with an initial current direction pointing from bottom right corner to top left corner, its mirrored Hall effect device1322has a bias current rotating counterclockwise and with an initial current direction pointing from top right corner to bottom left corner; the Hall effect device1323has a bias current rotating counterclockwise and with an initial current direction pointing from top right corner to bottom left corner, its mirrored Hall effect device1324has a bias current rotating clockwise and with an initial current direction pointing from bottom right corner to top left corner.

In the example ofFIG. 8, the operational amplifier141in each of the first and the second portions is configured to respectively sum the Hall voltages generated by the half Hall effect devices in the first magnetic region11at one side of the mid-line1010(both in the first magnetic region11and in the first portion1011), and the Hall voltages generated by the half Hall effect devices in the second magnetic region12at one side of the mid-line1010(both in the second magnetic region12and in the first portion1011), and to amplify a difference between the summed results to generate an amplified signal SA. That is:
VSA=A×[(V1311+V1313)−(V1321+V1323)]
wherein A represents a gain of the operational amplifier141, VSArepresents the voltage of the amplified signal SA, V1311represents the Hall voltage generated by the Hall effect device1311, V1313represents the Hall voltage generated by the Hall effect device1313, V1321represents the Hall voltage generated by the Hall effect device1321, and V1323represents the Hall voltage generated by the Hall effect device1323.

FIG. 9schematically shows the variation of bias current direction applied to the four Hall effect devices in the first portion1011ofFIG. 8during 4 phases in one cycle in accordance with an embodiment of the present invention. As shown inFIG. 9, the bias current applied to the Hall effect device1311has a current direction from bottom left corner to top right corner at phase1; it shifts from top left corner to bottom right corner at phase2, shifts from top right corner to bottom left corner at phase3, and shifts from bottom right corner to top left corner at phase4.

The bias current applied to the Hall effect device1321has a current direction from bottom right corner to top left corner at phase1; it shifts from bottom left corner to top right corner at phase2, shifts from top left corner to bottom right corner at phase3, and shifts from top right corner to bottom left corner at phase4.

The bias current applied to the Hall effect device1323has a current direction from top right corner to bottom left corner at phase1; it shifts from top left corner to bottom right corner at phase2, shifts from bottom left corner to top right corner at phase3, and shifts from bottom right corner to top left corner at phase4.

The bias current applied to the Hall effect device1313has a current direction from top left corner to bottom right corner at phase1; it shifts from bottom left corner to top right corner at phase2, shifts from bottom right corner to top left corner at phase3, and shifts from top right corner to bottom left corner at phase4.

FIG. 10schematically shows a circuit configuration of the silicon die101with four Hall effect devices in each of the magnetic regions in accordance with another embodiment of the present invention. In the example ofFIG. 10, each of the magnetic regions also has two Hall effect devices placed in the first portion1011and the other two Hall effect devices placed in the second portion1012. The two Hall effect devices in the first portion1011and the two Hall effect devices in the second portion1012are laid in a mirror way to each other along the mid-line1010, and with mirror bias current directions and mirror spinning current schemes. The silicon die101in the example ofFIG. 10is similar to the silicon die101in the example ofFIG. 8, with a difference that the biased current and the spinning direction applied to the Hall effect devices in the second magnetic region12are with another scheme.

Specifically, as shown inFIG. 10, in the first magnetic region11, the Hall effect device1311has a bias current rotating clockwise and with an initial current direction pointing from bottom left corner to top right corner, its mirrored Hall effect device1312has a bias current rotating counterclockwise and with an initial current direction pointing from top left corner to bottom right corner; the Hall effect device1313has a bias current rotating counterclockwise and with an initial current direction pointing from top left corner to bottom right corner, its mirrored Hall effect device1314has a bias current rotating clockwise and with an initial current direction pointing from bottom left corner to top right corner, which are same to that in the example ofFIG. 8. In the second the magnetic region12, the Hall effect device1321has a bias current rotating counterclockwise and with an initial current direction pointing from bottom right corner to top left corner, its mirrored Hall effect device1322has a bias current rotating clockwise and with an initial current direction pointing from top right corner to bottom left corner; the Hall effect device1323has a bias current rotating clockwise and with an initial current direction pointing from top right corner to bottom left corner, its mirrored Hall effect device1324has a bias current rotating counterclockwise and with an initial current direction pointing from bottom right corner to top left corner.

FIG. 11schematically shows the variation of bias current direction applied to the four Hall effect devices in the first portion1011ofFIG. 10during 4 phases in one cycle in accordance with an embodiment of the present invention. As shown inFIG. 11, the bias current applied to the Hall effect device1311has a current direction from bottom left corner to top right corner at phase1; it shifts from top left corner to bottom right corner at phase2, shifts from top right corner to bottom left corner at phase3, and shifts from bottom right corner to top left corner at phase4.

The bias current applied to the Hall effect device1321has a current direction from bottom right corner to top left corner at phase1; it shifts from top right corner to bottom left corner at phase2, shifts from top left corner to bottom right corner at phase3, and shifts from bottom left corner to top right corner at phase4.

The bias current applied to the Hall effect device1323has a current direction from top right corner to bottom left corner at phase1; it shifts from bottom right corner to top left corner at phase2, shifts from bottom left corner to top right corner at phase3, and shifts from top left corner to bottom right corner at phase4.

The bias current applied to the Hall effect device1313has a current direction from top left corner to bottom right corner at phase1; it shifts from bottom left corner to top right corner at phase2, shifts from bottom right corner to top left corner at phase3, and shifts from top right corner to bottom left corner at phase4.

In this sense, the direction of the current for a given Hall effect device is always different from the currents of the others Hall effect devices.

Furthermore, the present invention provides a current sensing method.FIG. 12schematically shows a flow chart1000of a current sensing method in accordance with an embodiment of the present invention. The method comprising:

Step1001, shaping part of a conductor to create a first magnetic region and a second magnetic region with opposite magnetic field directions crossed therethrough at a silicon die when a target current is flowing through the conductor. In one embodiment, the conductor includes four fingers, with two fingers flowing into the target current, and the other two fingers flowing out the target current.

Step1002, placing N Hall effect device in each of the magnetic regions at the silicon die, half of the N Hall effect devices in each of the magnetic regions being placed in one side of a mid-line, another half of N Hall effect devices in each of the magnetic regions being placed in the other side of the mid-line, the two halves of the Hall effect devices being placed in a mirrored way to each other along the mid-line, N being a positive even number. In one embodiment, the mid-line is a line along which the first magnetic region and the second magnetic region can be “folded”, and divided into symmetric sections. In one embodiment, the Hall effect devices are placed along the boundary of the conductor.

Step1003, applying a bias current to the Hall effect device in each of the magnetic regions with spinning scheme, so that a Hall voltage is generated by each of the Hall effect device. In one embodiment, the Hall effect devices at one side of the mid-line are applied with mirrored bias current direction and mirrored spinning current scheme with the Hall effect devices at the other side of the mid-line.

Step1004, processing the Hall voltages at each side of the mid-line to generate two processed signals. And

Step1005, executing a subtraction operation or an add operation on the processed signals to generate an operational signal.

In one embodiment, the step of processing the Hall voltages comprises: respectively summing the Hall voltages of the half Hall effect devices in the first magnetic region at one side of the mid-line, and the Hall voltages of the half Hall effect devices in the second magnetic region at one side of the mid-line; amplifying a difference between the summed results to generate an amplified signal; detecting a difference between a maximum value and a minimum value of the amplified signal to generate a peak-peak signal; sampling and holding the peak-peak signal to generate a sample-hold signal; and filtering the sample-hold signal to generate the processed signal.

Several embodiments of the foregoing current sensing system and method provide better current sense compared to conventional technique. Unlike the conventional technique, several embodiments of the foregoing current sensing system shape part of the conductor in a way such that two regions with opposite magnetic field directions crossed therethrough are created at the silicon die. In addition, several embodiments of the foregoing current sensing system adopt differential (mirror) layout with mirror bias current and mirror spinning current scheme, which benefits from dv/dt (voltage variation) suppression of primary current loop, and immunes to parasitic magnetic fields, parasitic electric spikes due to switching and thermal drift of the electronics.

It is to be understood in these letters patent that the meaning of “A” is coupled to “B” is that either A and B are connected to each other as described below, or that, although A and B may not be connected to each other as described above, there is nevertheless a device or circuit that is connected to both A and B. This device or circuit may include active or passive circuit elements, where the passive circuit elements may be distributed or lumped-parameter in nature. For example, A may be connected to a circuit element that in turn is connected to B.

This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the art to make and use the invention. The patentable scope of the invention may include other examples that occur to those skilled in the art.