Hall element sensor and its operating method

Abstract

To provide a Hall element sensor which provides high-precision output by effectively suppressing residual offset and AC noise generated during spinning measurement by a Hall element without using a large Hall element and additional circuitry with high-capacity filter capacitors and the like.SOLUTION: Residual offset and AC noise generated during spinning measurement by a Hall element sensor with four operating states (0 deg, 90 deg, 180 deg, and 270 deg) are effectively suppressed by measuring offset voltages in the four operating states, selecting a combination with less offset voltage difference among adjacent operating states, and repeating the spinning measurement in the combination.SELECTED DRAWING: Figure 4

Description

[[Technical Field]]

[0001] The present invention relates to a current sensor and an operating method thereof, and particularly to a Hall element sensor that detects a current flowing through a magnetic field or a conductor using a silicon Hall element (hereinafter simply referred to as "Hall element") formed by IC technology on an IC chip (i.e., on a silicon wafer), and an operating method thereof. [[Background Art]]

[0002] In new-type vehicles such as passenger cars, it is common to electrically control opening / closing of rearview mirrors, opening / closing of doors, locking and the like. That is, under the control of a controller (e.g., a microprocessor), driving currents are supplied to a large number of electric motors and solenoids to perform the above-described operations. In this case, it is necessary to feed back to the controller to check whether a driving current flows through the controlled object according to the control signal and the intended operation is actually performed. For this purpose, in order to detect the driving current flowing through the conductor that is the controlled object, a large number of Hall element sensors are used in recent vehicles and the like.

[0003] In general, Hall element sensors can be manufactured in a small size at low cost by IC technology. As is well known, a Hall element is a sensor that utilizes the Hall effect in which when a magnetic field is applied perpendicular to the current in a current-carrying semiconductor (or conductor), a voltage (potential difference) is generated in a direction perpendicular to both the current and the magnetic field. A magnetic field corresponding to the current flowing through the conductor is generated around the current-carrying conductor, so by arranging the Hall element in this magnetic field, the current flowing through the conductor can be detected.

[0004] In general, a silicon Hall element can be manufactured or mounted on an IC chip in a small size at low cost, but it has low sensitivity, and an offset occurs in the bridge circuit using the silicon Hall element. In order to remove or suppress this offset, techniques such as the spinning measurement described later have been proposed. For example, there has been disclosed a circuit that cancels an offset by rotating the direction of the driving current of a Hall element and adding signals by a sample-hold circuit and an adding circuit. See Patent Document 1. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 3022957 [Overview of the Initiative]

[0006] Before describing the present invention, we will briefly explain the spinning measurement technique in Hall elements. As shown in Figure 1(A), the Hall element has four terminals A, B, C, and D formed at positions corresponding to the four vertices of a square. A current (drive current) is passed from a bias source (not shown) in a selected direction to a selected pair of terminals, and a voltage output is obtained from the other terminals. Figure 1(B) is a table showing the terminals and direction through which the drive current flows, and the terminals and operating state (or angle) from which the voltage output is obtained.

[0007] In Figure 1(B), in operating state 0deg, current flows from terminal A to C, and a magnetic field-dependent voltage Vhall is output between terminals B and D. In operating state 90deg, which is 90deg to the right of operating state 0deg, current flows from terminal B to D, and a magnetic field-dependent voltage Vhall is output between terminals C and A. In operating state 180deg, which is another 90deg to the right of operating state 90deg, current flows from terminal C to A, and a magnetic field-dependent voltage Vhall is output between terminals D and B. Furthermore, in operating state 270deg, which is another 90deg to the right of operating state 180deg (i.e., equivalent to a 90deg left rotation from operating state 0deg as described above), current flows from terminal D to B, and a magnetic field-dependent voltage Vhall is output between terminals A and C.

[0008] Next, Figures 2(A) to 2(D) show the connection states of the bias source and differential amplifier (AMP) in the four operating states of the Hall element H described above: 0deg, 90deg, 180deg, and 270deg, with reference to Figures 1(A) and 1(B). In Figure 2, for the sake of explanation, the Hall element H is represented by four bridged resistors (or bridge resistances) R1 to R4, the bias source by Iref, and the differential amplifier that amplifies the voltage output by AMP.

[0009] From Figure 2, assuming a zero magnetic field state, in the operating state 0deg, the voltage at terminal A is: VA={(R1+R3) / / (R2+R4)}IREF Therefore, terminals B and D are, VB = {R4 / (R2+R4)} * VA VD = {R3 / (R1+R3)} * VA Therefore, the offset voltage Vofs, which is the voltage difference between terminals B and D, is Vofs = VB - VD = IREF(R1R4 - R2R3) / (R1 + R2 + R3 + R4). Therefore, no offset voltage occurs when R1R4 = R2R3, but if R1R4 ≠ R2R3 due to a mismatch, an offset voltage Vofs will occur.

[0010] Similarly, assuming a zero magnetic field state, and considering the offset voltage at the operating state of 90 degrees, the output between terminals C and A is VC-VA=Vofs, between terminals D and B at the operating state of 180 degrees is VD-VB=Vofs, and between terminals A and C at the operating state of 270 degrees is VA-VC=Vofs.

[0011] The Hall element output VOH is the sum of the magnetic field-dependent output (sensitivity voltage) Vhall and the offset voltage Vofs generated by the mismatch described above. Therefore, the Hall element outputs for the four operating states (0deg, 90deg, 180deg, 270deg) are shown in Table 1 below. From Table 1, by calculating the difference between 0deg and 90deg ÷ 2, the difference between 90deg and 180deg ÷ 2, the difference between 180deg and 270deg ÷ 2, and the difference between 270deg and 0deg ÷ 2, the offset can be canceled out, and only the sensitivity voltage can be extracted. This is the principle of spinning measurement. In Figure 1(B), Figure 2, and Table 1, the terminal direction for obtaining the voltage output when rotated by 90deg is reversed, so the polarity of the sensitivity voltage switches alternately, which is called sensitivity modulation. If the terminal direction for obtaining the voltage output when rotated by 90deg is not reversed, the polarity of the offset voltage switches alternately, as shown in Table 2, which is called offset modulation. In offset modulation, calculating the average of 0deg and 90deg, the average of 90deg and 180deg, the average of 180deg and 270deg, and the average of 270deg and 0deg can cancel out the offset and extract only the sensitive voltage. [Table 1] [Table 2]

[0012] However, in reality, the PN junction formed between the hole plate and back gate of a Hall element exhibits a change in depletion layer width due to the reverse bias voltage dependence. For example, if the hole plate is an N-type semiconductor and the back gate is a P-type semiconductor, in the 0-degree state, the hole plate thickness on the lower voltage side (terminal B side) is thinner than the hole plate thickness on the higher voltage side (terminal A side). Consequently, the resistance values ​​of resistors R1 and R2 on the top side become higher, and the resistance values ​​of R3 and R4 on the bottom side become lower. This effect causes the offset to change depending on whether the resistance mismatch occurs on the top side or the bottom side. As an example, consider spinning measurement when there is a mismatch in R1. Here, we assume that the offset when the resistance mismatch occurs on the top side is Vofs1, and the offset when it occurs on the bottom side is Vofs2. In the 0deg and 270deg states, the resistance mismatch occurs on the top side, so the offset is Vofs1. In the 90deg and 180deg states, the resistance mismatch occurs on the bottom side, so the offset is Vofs2. Therefore, a residual offset occurs in the spinning measurement with the 0deg and 90deg combination, zero residual offset in the spinning measurement with the 90deg and 180deg combination, a residual offset occurs in the spinning measurement with the 180deg and 270deg combination, and zero residual offset in the spinning measurement with the 270deg and 0deg combination. Similarly, the offset voltage when a mismatch occurs in R2, R3, and R4 can be considered, and this is summarized in Table 3. From Table 3, it can be seen that the way the offset occurs differs when there is a mismatch in R1 and R4 compared to when there is a mismatch in R2 and R3. Furthermore, mismatches occur randomly during manufacturing and are also affected by stress changes, so it is impossible to know which of R1, R2, R3, or R4 the mismatch will occur in. Also, as mentioned above, during spinning measurements, residual offset alternates between zero and present, so it appears as AC noise in the Hall output. [Table 3] Problems to be Solved by the Invention

[0013] In the prior art, due to the reverse bias voltage dependency of the PN junction formed between the Hall plate and the back gate terminal, there has been a problem that residual offset and AC noise occur during spinning measurement. Means for Solving the Problems

[0014] The Hall element sensor of the present invention is a Hall element sensor having four operating states (0deg, 90deg, 180deg, and 270deg), wherein the offset voltages of the four operating states are measured, a combination of adjacent operating states with a small offset voltage difference is selected, and spinning measurement on the combination is repeated, thereby effectively suppressing residual offset and AC noise that occur during spinning measurement. Effects of the Invention

[0015] According to the Hall element sensor and the operating method thereof of the present invention, there is a remarkable effect that residual offset and AC noise occurring during spinning measurement of the Hall element can be effectively suppressed without using a large Hall element for suppressing the mismatch or adding an additional circuit such as a large-capacity filter capacitor for suppressing the AC noise. Brief Description of the Drawings

[0016] [Figure 1] It is an explanatory diagram of a general semiconductor Hall element, wherein (A) is a schematic diagram of the Hall element, and (B) is a table diagram explaining four operating states of the Hall element. [Figure 2] It is an explanatory diagram of operating states of a Hall element sensor using the Hall element as shown in FIG. 1, wherein (A) shows the operating state of 0deg, (B) shows the operating state of 90deg, (C) shows the operating state of 180deg, and (D) shows the operating state of 270deg. [Figure 3] It is a block diagram showing the basic configuration of the Hall element sensor according to the present invention. [Figure 4]It is a timing chart showing the Hall element sensor and the operation method thereof according to Embodiment 1 of the present invention. [Figure 5] It is a timing chart showing the Hall element sensor and the operation method thereof according to Embodiment 2 of the present invention. Mode for Carrying Out the Invention

[0017] Figure 3 is a block diagram showing the basic configuration of the Hall element sensor according to the present invention. The Hall element sensor of the present invention includes a Hall element 101, a switch matrix 102, a bias generation unit 103, a control circuit 104, a Hall sensitivity measurement circuit 105, and a Hall offset measurement circuit 106.

[0018] The Hall element 101 is at least one silicon Hall element formed on or mounted on a semiconductor chip. The bias generation unit 103 is a constant voltage source or constant current source that selectively and in a selected direction flows a predetermined current to a pair of terminals at selected diagonal positions of the Hall element 101. The driving method of the Hall element may be voltage mode or current mode. The switch matrix 102 is preferably an electronic switch matrix made of MOS semiconductors. The control circuit 104 is a logic circuit or microprocessor that switches the direction in which current flows to the Hall element and the terminal pair from which voltage is extracted from the Hall element to supply a control signal to the switch matrix 102 to transition between spin states of 0deg, 90deg, 180deg, and 270deg, controls the Hall sensitivity measurement circuit 105 to cancel the offset voltage included in the Hall output VOH modulated by the spinning measurement, controls the Hall offset measurement circuit 106 to measure the offset voltage of the four spin states (0deg, 90deg, 180deg, and 270deg), and receives the four offset voltages Vofs=(a1, a2, a3, a4) output from the Hall offset measurement circuit 106 corresponding to each spin state as input, selects a combination from the four offset voltages that minimizes the offset voltage difference between adjacent operating states, and controls the system to repeat the spinning measurement in the selected combination. Here, the spinning measurement method may be sensitivity modulation or offset modulation. The Hall sensitivity measurement circuit 105 is a circuit that operates to cancel the offset voltage from the Hall output VOH modulated by spinning measurement. The Hall sensitivity measurement circuit 105 may consist only of analog circuits including an amplification circuit, a filter circuit, a demodulation circuit, etc., or it may be an analog-digital mixed circuit configuration in which the Hall output VOH signal is converted to a digital signal by an analog-to-digital converter and then the offset is canceled by digital signal processing.The Hall offset measurement circuit 106 measures the offset voltage for four spin states (0deg, 90deg, 180deg, 270deg) using an amplifier and an analog-to-digital converter, and outputs four offset voltages Vofs=(a1, a2, a3, a4) corresponding to each spin state. The Hall offset measurement circuit 106 may directly measure the offset, or it may control the switch matrix 102 to measure the resistance between adjacent terminals of the Hall element, and estimate the offset voltage from the results obtained from the four resistance values ​​(R1, R2, R3, R4). The Hall offset measurement circuit 106 may be mounted inside the Hall IC, or it may be mounted outside the chip (e.g., on a tester).

[0019] Embodiment 1 Figure 4 is a timing chart diagram showing a Hall element sensor and its operating method in Embodiment 1 of the present invention. Figure 4(A) shows the case where there is a mismatch in R2 in Figure 2 and sensitivity modulation is performed, Figure 4(B) shows the case where there is a mismatch in R1 in Figure 2 and sensitivity modulation is performed, Figure 4(C) shows the case where there is a mismatch in R2 in Figure 2 and offset modulation is performed, and Figure 4(D) shows the case where there is a mismatch in R1 in Figure 2 and offset modulation is performed.

[0020] The Hall element sensor and its operation according to the present invention are divided into a Hall offset measurement period and a Hall sensor operation period for spinning measurement. During the Hall offset measurement period, the control circuit 104 generates a control signal CONTROL3 so that the Hall element 101 switches between four states (0deg, 90deg, 180deg, 270deg). The switch matrix 102, which receives the control signal CONTROL3, switches the connections of the four terminals VA, VB, VC, and VD of the Hall element. At this time, the Hall offset measurement circuit 105 measures the offset voltages of the four spin states (0deg, 90deg, 180deg, 270deg) using an amplifier and an analog-to-digital converter based on the control signal CONTROL2 from the control circuit 104, and outputs four offset voltages Vofs=(a1, a2, a3, a4) corresponding to each spin state to the control circuit 104. The Hall offset measurement may be performed continuously, not only during the Hall offset measurement period but also during the Hall sensor operation period, or it may be performed only when the power is started up, or only during testing after the Hall IC is manufactured. Furthermore, noise immunity may be improved by performing the Hall offset measurement multiple times and taking the average value, or the Hall offset measurement may be performed multiple times, and it may be determined from the absolute value and fluctuation range of the offset measurement results that there is no abrupt change in the offset voltage due to an external magnetic field, and only the offset measurement results in a state close to zero magnetic field may be used.

[0021] During the Hall sensor operation period, the control circuit 104 selects, from the measurement results of the four offset voltages Vofs=(a1, a2, a3, a4), the first combination of operating states with the smallest offset voltage difference among adjacent operating states, and the second combination of operating states with the next smallest offset voltage difference. If there is a mismatch in R2 as shown in Figures 4(A) and (C), the control circuit 104 outputs a control signal CONTROL1 to the Hall sensitivity measurement circuit 105 to cancel the offset using the combinations of 0deg and 90deg and 180deg and 270deg, and the Hall sensitivity measurement circuit 105 repeatedly cancels the offset using the combinations of 0deg and 90deg and 180deg and 270deg. If there is a mismatch in R1 as shown in Figures 4(B) and (D), the control circuit 104 outputs a control signal CONTROL1 to the Hall sensitivity measurement circuit 105 so that offset cancellation is performed for the combinations of 90deg and 180deg and 270deg and 0deg. The Hall sensitivity measurement circuit 105 then performs offset cancellation for the combinations of 90deg and 180deg and 270deg and 0deg.

[0022] Embodiment 2 Figure 5 is a block diagram showing a Hall element sensor and its operating method in Embodiment 2 of the present invention. Figure 5(A) shows the case where there is a mismatch in R2 in Figure 2 and sensitivity modulation is performed, Figure 5(B) shows the case where there is a mismatch in R1 in Figure 2 and sensitivity modulation is performed, Figure 5(C) shows the case where there is a mismatch in R2 in Figure 2 and offset modulation is performed, and Figure 5(D) shows the case where there is a mismatch in R1 in Figure 2 and offset modulation is performed.

[0023] The Hall element sensor and its operation according to the present invention are divided into a Hall offset measurement period and a Hall sensor operation period for spinning measurement. The operation during the Hall offset measurement period is the same as in Embodiment 1 described above, so it will be omitted here.

[0024] During the Hall sensor operation period, the control circuit 104 selects the combination of the first operating state with the smallest offset voltage difference from among the adjacent operating states, based on the four offset voltages Vofs = (a1, a2, a3, a4). If multiple combinations of the first operating state with the smallest offset are detected, the one with the smallest absolute value of the offset is selected. In the case of a mismatch in R2, as shown in Figures 5(A) and (C), the combination of 0deg and 90deg has the smallest offset voltage difference. Therefore, the control circuit 104 generates a control signal CONTROL3 to spin the Hall element 101 only with the 0deg and 90deg combination to cancel the offset, and the switch matrix 102, which receives the control signal CONTROL3, switches the connections of the four terminals VA, VB, VC, and VD of the Hall element. The control circuit 104 generates a control signal CONTROL1 to cancel the offset using the combination of 0deg and 90deg, and the Hall sensitivity measurement circuit 105, which receives the control signal CONTROL1, repeatedly cancels the offset using the combination of 0deg and 90deg. In the case of a mismatch in R1, as shown in Figures 5(B) and (D), the offset voltage difference is smallest with the combination of 270deg and 0deg, so the control circuit 104 generates a control signal CONTROL3 to spin the Hall element 101 with the combination of 270deg and 0deg to cancel the offset, and the switch matrix 102, which receives the control signal CONTROL3, switches the connections of the four terminals VA, VB, VC, and VD of the Hall element. Also, the control circuit 104 generates a control signal CONTROL1 to cancel the offset using the combination of 270deg and 0deg, and the Hall sensitivity measurement circuit 105, which receives the control signal CONTROL1, repeatedly cancels the offset using the combination of 270deg and 0deg.

[0025] As shown in Embodiments 1 and 2, the Hall element sensor and its operating method of the present invention, in a Hall element sensor having four operating states (0deg, 90deg, 180deg, and 270deg), measures the offset voltage of the four operating states, selects a combination of adjacent operating states with a small offset voltage difference, and repeats spinning measurements in the selected combination, thereby effectively suppressing residual offset and AC noise generated during spinning measurements. [Industrial applicability]

[0026] The Hall element sensor and its operating method of the present invention effectively suppress residual offset and AC noise generated during Hall element spinning measurement without using large Hall elements or additional circuits such as large-capacity filter capacitors. This has a significant effect on miniaturizing and improving the accuracy of Hall element sensors, and because it can be manufactured compactly and inexpensively using IC technology, it can be used in a wide range of applications, including current sensors for variable speed control of electric motors. [Explanation of Symbols]

[0027] 101 Hall element 102 Switch Matrix 103 Bias generation unit 104 Control circuits 105 Hall Sensitivity Measurement Circuit 106 Hall offset measurement circuit

Claims

1. A Hall element having two pairs of terminals at each diagonal position of a square, wherein a drive current is passed through one pair of terminals and a voltage is output from the other pair of terminals, wherein the spinning current operation method of the Hall element is configured such that there are four operating states of 90 deg, 180 deg, and 270 deg, with the state in which a drive current is passed through any pair being the reference (0 deg), and the output voltage of the zero magnetic field state in the four operating states is measured by an amplifier and an analog-to-digital converter. A method for operating a Hall element, characterized in that, among the four operating states, among adjacent operating states (0 deg and 90 deg, 90 deg and 180 deg, 180 deg and 270 deg, 270 deg and 0 deg), the output voltages of the first adjacent operating state (for example, 0 deg and 90 deg) with the smallest difference in the absolute values ​​of the output voltages in the zero magnetic field state are added together and divided by 2 to take the average value, and the output voltages of the second adjacent operating state with the next smallest difference in the absolute values ​​of the output voltages in the zero magnetic field state are added together and divided by 2 to take the average value.

2. A method for operating a Hall element, characterized in that, among the adjacent operating states described in claim 1, a first adjacent operating state is selected that has the smallest difference in the absolute values ​​of the output voltages in the zero magnetic field state, a spinning current operation is performed only in the first adjacent operating state, and the average value is taken by adding the output voltages of the adjacent operating states and dividing by 2.

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