JP2023062648A - Hall element sensor and operating method thereof - Google Patents

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

Field of the Invention The present invention relates to a current sensor and its operating method, in particular, using a silicon Hall element (hereinafter simply referred to as "Hall element") formed on an IC chip (i.e., on a silicon wafer) by IC technology to flow in a magnetic field or a conductor. The present invention relates to a Hall element sensor that detects current and a method of operating the same.

2. Description of the Related Art In new-model vehicles such as passenger cars, it is common to electrically control the opening/closing of rearview mirrors, door opening/closing, locking, and the like. That is, under the control of a controller (eg, a microprocessor), a number of electric motors and solenoids are energized to perform the operations described above. At that time, it is necessary to feed back to the controller whether or not the control signal causes the drive current to flow through the object to be controlled and the desired operation is actually performed. For this purpose, a large number of Hall element sensors are used in recent vehicles and the like in order to detect the drive current flowing through the conductor, which is the object to be controlled.

In general, Hall element sensors can be manufactured in a small size and at low cost using IC technology. As is well known, a Hall element is a sensor that uses the Hall effect to generate a voltage (potential difference) in the direction perpendicular to the current and magnetic field when a magnetic field is applied to a semiconductor (or conductor) through which current is flowing. be. Since a magnetic field corresponding to the current flowing through the conductor is generated around the conductor through which the current flows, the current flowing in the conductor can be sensed by placing the Hall element in this magnetic field.

In general, a silicon Hall element can be manufactured or mounted on an IC chip in a small size and at low cost, but has low sensitivity and causes an offset in a bridge circuit using it. In order to remove or suppress this offset, techniques such as spinning measurement, which will be described later, have been proposed. For example, it discloses a circuit that cancels the offset by rotating the direction of the driving current of the hall element and adding the signals with a sample-and-hold and an addition circuit. (See Patent Document 1).

Japanese Patent No. 3022957

Before describing the present invention, the spinning measurement technique in the Hall element will be described in some detail. As shown in FIG. 1A, the Hall element has four terminals A, B, C and D formed at positions corresponding to four vertices of a square. Then, a current (driving current) is passed in a selected direction from a bias source (not shown) to the selected pair of terminals, and a voltage output is obtained from the other terminals. FIG. 1(B) is a table showing the terminals and directions through which drive currents flow, the terminals for obtaining voltage outputs, and operating states (or angles).

In FIG. 1B, in the operating state of 0 deg, current flows from terminals A to C, and a magnetic field-dependent voltage Vhall is output from terminals B and D. FIG. In an operating state of 90 degrees, which is rotated 90 degrees to the right with respect to the operating state of 0 degrees, a current is passed from the terminal B to the terminal D, and a voltage Vhall depending on the magnetic field is output from the terminals C and A. In the operating state 180deg, which is rotated further 90deg to the right from the operating state 90deg, a current flows from the terminal C to the terminal A, and the voltage Vhall depending on the magnetic field is output from between the terminals D and B. Further, in the operating state of 270 deg, which is a further 90 deg clockwise rotation from the operating state of 180 deg (that is, corresponds to the above-described operating state of 0 deg to 90 deg counterclockwise rotation), a current flows from the terminal D to B, and from between the terminals A and C depends on the magnetic field. output the voltage Vhall.

Next, FIGS. 2(A)-(D) show the bias source and bias source in the four operating states 0 deg, 90 deg, 180 deg and 270 deg of the Hall element H described above with reference to FIGS. 1(A) and 1(B). Each shows a connection state of a differential amplifier (AMP). In FIG. 2, for convenience of explanation, the Hall element H is represented by four bridge-connected resistance values (or bridge resistance values) R1 to R4, the bias source is Iref, and the differential amplifier for amplifying the voltage output is AMP. is shown.

Assuming a zero magnetic field state from FIG.
VA={(R1+R3)//(R2+R4)}IREF
As a result, terminals B and D are respectively
VB={R4/(R2+R4)}*VA
VD={R3/(R1+R3)}*VA
becomes. 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 is generated under the condition of R1R4=R2R3, but the offset voltage Vofs is generated when R1R4≠R2R3 due to mismatch.

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

The sum of the output (sensitivity voltage) Vhall depending on the magnetic field and the offset voltage Vofs generated by the above-described mismatch is the Hall element output VOH. The device output is shown in Table 1 below. From Table 1, by calculating the difference between 0 deg and 90 deg ÷ 2, the difference between 90 deg and 180 deg ÷ 2, the difference between 180 deg and 270 deg ÷ 2, and the difference between 270 deg and 0 deg ÷ 2, the offset can be canceled and only the sensitivity voltage can be extracted. . This is the principle of spinning measurement. In FIG. 1B, FIG. 2 and Table 1, the direction of the terminal for obtaining the voltage output when rotated by 90 degrees is reversed, so the polarity of the sensitivity voltage is alternately switched, and this is called sensitivity modulation. If the terminal direction for obtaining the voltage output when rotated by 90 degrees is not reversed, the polarity of the offset voltage is alternately switched as shown in Table 2. This is called offset modulation. In offset modulation, by 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, the offset can be canceled and only the sensitivity voltage can be extracted.

However, in reality, the PN junction formed between the Hall plate and the back gate of the Hall element has a change in depletion layer width due to the dependence of the reverse bias voltage. In the case of a type semiconductor, in the 0 deg state, the thickness of the hole plate on the bottom side (terminal B side) where the voltage is low is thinner than the thickness of the hole plate on the top side (terminal A side) where the voltage is high. Therefore, the resistance values of the top-side resistors R1 and R2 are increased, and the resistance values of the bottom-side resistors R3 and R4 are decreased. Due to this effect, the occurrence of offset changes depending on whether the resistor mismatch occurs on the top side or on the bottom side. As an example, consider a spinning measurement when there is a mismatch in R1. Here, it is assumed that the offset is Vofs1 when the resistor mismatch occurs on the top side, and the offset is Vofs2 when it is on the bottom side. In the 0 deg and 270 deg states, the resistor mismatch occurs on the top side, so the offset is Vofs1. In the 90 deg and 180 deg states, the resistor mismatch occurs on the bottom side, so the offset is Vofs2. Therefore, a residual offset occurs in the spinning measurement in the combination of 0deg and 90deg, the residual offset becomes zero in the spinning measurement in the combination of 90deg and 180deg, the residual offset occurs in the spinning measurement in the combination of 180deg and 270deg, and the combination of 270deg and 0deg. The spinning measurement at has zero residual offset. Similarly, offset voltages when mismatches occur in R2, R3, and R4 can also be considered, which are summarized in Table 3. From Table 3, it can be seen that the offset occurs differently when there is a mismatch in R1 and R4 and when there is a mismatch in R2 and R3. Moreover, since mismatches occur randomly during manufacturing and are also affected by stress changes, it is not known at which of R1, R2, R3, and R4 mismatches will occur. In addition, as described above, since the residual offset alternately occurs in the order of 0→present→zero→present during spinning measurement, it appears as AC noise in the Hall output.

In the prior art, there was a problem that residual offset and AC noise were generated during spinning measurement due to the reverse bias voltage dependence of the PN junction formed between the Hall plate and the back gate terminal.

The Hall element sensor of the present invention measures the offset voltages of the four operating states (0deg, 90deg, 180deg and 270deg) in the Hall element sensor having four operating states, and measures the offset voltage difference among the adjacent operating states. By selecting a combination with a small , and repeating the spinning measurement in said combination, the residual offset and AC noise generated during the spinning measurement are effectively suppressed.

According to the Hall element sensor and its operation method of the present invention, there is no need to use a large Hall element for suppressing the mismatch, or to use an additional circuit such as a large-capacity filter capacitor for suppressing the AC noise. , has a significant effect of effectively suppressing the residual offset and AC noise generated during the spinning measurement of the Hall element.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of a general semiconductor Hall element, (A) is a model diagram of a Hall element, (B) is a table|surface explaining four operation states of a Hall element. It is explanatory drawing of the operating state of the Hall element sensor which uses a Hall element as shown in FIG. 1, (A) is operating state 0deg, (B) is operating state 90deg, (C) is operating state 180deg, (D) indicates an operating state of 270deg. 1 is a block diagram showing the basic configuration of a Hall element sensor according to the present invention; FIG. FIG. 2 is a timing chart diagram showing the Hall element sensor and its operation method according to Embodiment 1 of the present invention. It is a timing chart figure which shows the hall element sensor in Embodiment 2 of this invention, and its operation method.

FIG. 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 comprises a Hall element 101, a switch matrix 102, a bias generator 103, a control circuit 104, a Hall sensitivity measuring circuit 105 and a Hall offset measuring circuit .

Hall element 101 is at least one silicon Hall element formed or mounted on a semiconductor chip. The bias generation unit 103 is a constant voltage source or a constant current source that selectively supplies a predetermined current in a selected direction to a pair of terminals at selected diagonal positions of the Hall element 101 . A method of driving the Hall element may be a voltage mode or a current mode. Switch matrix 102 is an electronic switch matrix preferably constructed from MOS semiconductors. The control circuit 104 supplies the switch matrix 102 with a control signal that switches the direction of the current flow to the Hall element and the terminal pair that extracts the voltage from the Hall element, thereby transitioning the spin states of 0 deg, 90 deg, 180 deg, and 270 deg, Control the Hall sensitivity measurement circuit 105 to cancel the offset voltage contained in the Hall output VOH modulated by the spinning measurement, and measure the offset voltage of the four spin states (0deg, 90deg, 180deg, 270deg). , the Hall offset measurement circuit 106 is controlled, four offset voltages Vofs=(a1, a2, a3, a4) corresponding to each spin state output from the Hall offset measurement circuit 106 are input, and the four offset voltages A logic circuit or a microprocessor that selects a combination from which the offset voltage difference between adjacent operating states is small and repeats the spinning measurement in the 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 the spinning measurement. The Hall sensitivity measurement circuit 105 may be composed only of an analog circuit including an amplifier circuit, a filter circuit, a demodulator circuit, etc., or may convert the Hall output VOH signal into a digital signal with an analog-to-digital converter and convert it into a digital signal. An analog-digital mixed circuit configuration that cancels the offset in signal processing may be used. Hall offset measurement circuit 106 measures the offset voltages of four spin states (0deg, 90deg, 180deg, 270deg) with an amplifier and an analog-to-digital converter, and obtains four offset voltages Vofs=(a1, a2 , a3, a4). The Hall offset measurement circuit 106 may directly measure the offset, but it controls the switch matrix 102 to measure the resistance between adjacent terminals of the Hall element, and the four resistance values ( R1, R2, R3, R4) may be used to estimate the offset voltage. The Hall offset measuring circuit 106 may be mounted inside the Hall IC, or may be mounted outside the chip (tester, etc.).

Embodiment 1
FIG. 4 is a timing chart showing the Hall element sensor and its operating method according to Embodiment 1 of the present invention. FIG. 4A shows a mismatch in R2 in FIG. 2, and in the case of sensitivity modulation operation, FIG. 4(D) shows the case of mismatch in R1 in FIG. 2 and offset modulation.

The Hall element sensor of the present invention and its operation are divided into a Hall offset measurement period and a Hall sensor operation period for performing spinning measurement. During the Hall offset measurement period, the control circuit 104 generates the control signal CONTROL3 so that the Hall element 101 is switched between four states (0deg, 90deg, 180deg, 270deg), and the switch matrix 102 to which the control signal CONTROL3 is input, The connections of the four terminals VA, VB, VC, and VD of the Hall element are switched. 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 according to the control signal CONTROL2 from the control circuit 104, Four offset voltages Vofs=(a1, a2, a3, a4) corresponding to each spin state are output to the control circuit 104 . The Hall offset measurement may be performed not only during the Hall offset measurement period but also during the Hall sensor operation period. good. Further, the Hall offset measurement may be performed a plurality of times and the average value may be taken to improve the noise resistance. It is also possible to determine that there is no abrupt change in the offset voltage due to the magnetic field, and to use only the offset measurement result in a state close to the zero magnetic field state.

During the Hall sensor operation period, the control circuit 104 selects the first operation state having the smallest offset voltage difference among the adjacent operation states from the measurement results of the four offset voltages Vofs=(a1, a2, a3, a4). A combination and a second operating state combination having a smaller offset voltage difference at the next point are selected. If there is a mismatch in R2 as shown in FIGS. 4A and 4C, the control circuit 104 holds the control signal CONTROL1 so as to cancel the offset in the combination of 0deg and 90deg and the combination of 180deg and 270deg. It is output to the sensitivity measurement circuit 105, and the Hall sensitivity measurement circuit 105 repeats offset cancellation with a combination of 0deg and 90deg and a combination of 180deg and 270deg. When there is a mismatch in R1 as shown in FIGS. 4B and 4D, the control circuit 104 outputs the control signal CONTROL1 with Hall sensitivity so as to cancel the offset with a combination of 90deg and 180deg and a combination of 270deg and 0deg. It is output to the measurement circuit 105, and the Hall sensitivity measurement circuit 105 performs offset cancellation with a combination of 90deg and 180deg and a combination of 270deg and 0deg.

Embodiment 2
FIG. 5 is a block diagram showing a Hall element sensor and its operating method according to Embodiment 2 of the present invention. FIG. 5A shows a mismatch in R2 in FIG. 2, and in the case of sensitivity modulation operation, FIG. In the case of offset modulation operation with a mismatch in R2, FIG. 5D shows the case of offset modulation with a mismatch in R1 in FIG.

The Hall element sensor of the present invention and its operation are divided into a Hall offset measurement period and a Hall sensor operation period for performing spinning measurement. The operation during the hole offset measurement period is the same as that of the first embodiment described above, so the description thereof is omitted.

During the Hall sensor operation period, the control circuit 104 selects a combination of the first operation state with the smallest offset voltage difference among the adjacent operation states from the four offset voltages Vofs=(a1, a2, a3, a4). select. If multiple combinations of the smallest first operating states are detected, the one with the smallest absolute value of the offset is selected. When there is a mismatch in R2 as shown in FIGS. 5A and 5C, the combination of 0deg and 90deg has the smallest offset voltage difference. , the control circuit 104 generates a control signal CONTROL3 so as to cancel the offset, and the switch matrix 102 to which the control signal CONTROL3 is input switches connection of the four terminals VA, VB, VC, and VD of the Hall element. The control circuit 104 generates the control signal CONTROL1 so as to cancel the offset with a combination of 0deg and 90deg, and the Hall sensitivity measurement circuit 105 to which the control signal CONTROL1 is input repeats the offset cancellation with a combination of 0deg and 90deg. When there is a mismatch in R1 as shown in FIGS. 5B and 5D, the combination of 270deg and 0deg has the smallest offset voltage difference. The control circuit 104 generates the control signal CONTROL3 so as to cancel the offset, and the switch matrix 102 to which the control signal CONTROL3 is input switches connection of the four terminals VA, VB, VC, and VD of the Hall element. Further, the control circuit 104 generates the control signal CONTROL1 so as to cancel the offset with the combination of 270deg and 0deg, and the Hall sensitivity measurement circuit 105 to which the control signal CONTROL1 is input repeats the offset cancellation with the combination of 270deg and 0deg.

As shown in Embodiments 1 and 2, the Hall element sensor and the operating method thereof according to the present invention provide a Hall element sensor having four operating states (0deg, 90deg, 180deg and 270deg). By measuring the offset voltage in the operating state, selecting a combination with a small offset voltage difference from adjacent operating states, and repeating the spinning measurement in the combination, the residual offset and AC noise generated during the spinning measurement can be effectively removed. suppress to

The Hall element sensor and its operation method of the present invention effectively suppresses the residual offset and AC noise generated when measuring the spinning of the Hall element without using an additional circuit such as a large Hall element or a large-capacity filter capacitor. Therefore, it has a remarkable effect on miniaturization and high accuracy of the Hall element sensor, and it can be manufactured in a small size and at a low cost by IC technology. is available.

101 Hall element 102 Switch matrix 103 Bias generator 104 Control circuit 105 Hall sensitivity measurement circuit 106 Hall offset measurement circuit

Claims (10)

In the method for operating a Hall element sensor, wherein two pairs of terminals are provided at diagonal positions and four operating states (0 deg, 90 deg, 180 deg and 270 deg) are selected by switching a switch. A Hall element sensor and its operating method characterized by measuring offset voltages in four operating states, selecting a combination with a small offset voltage difference from adjacent operating states, and repeating spinning measurement in said combination. A combination of a first operating state having the smallest offset voltage difference and a combination of a second operating state having the next smallest offset voltage difference are selected from among the adjacent operating states, and the first operating state is selected. and the spinning measurement in the second operating state combination are repeated. 3. The Hall element sensor and method of operation of claim 2, comprising averaging the spinning measurement results in the first operating state combination and the spinning measurement results in the second operating state combination. measuring offset voltages for the four operating states between spinning measurements in the first operating state combination and spinning measurements in the second operating state combination; 3. The Hall element sensor and method of operation of claim 2, comprising updating the combination of the second operating states. 2. The method according to claim 1, wherein a combination of a third operating state having a smallest offset voltage difference is selected from among the adjacent operating states, and the spinning measurement of the combination of the third operating states is repeated. Hall element sensor and method of operation thereof. 2. The Hall element sensor and its operating method according to claim 1, further comprising estimating the offset voltages in said four operating states from resistance values between adjacent terminals of the Hall element. 2. The Hall element sensor and the operating method thereof according to claim 1, comprising updating the combination of the first operating state and the combination of the second operating state at power-on. 2. The Hall element sensor and method of operation of claim 1, comprising updating the first operating state combination and the second operating state combination when testing the Hall element sensor. After measuring the offset voltages in the four operating states multiple times and judging the zero magnetic field state from the absolute values and fluctuation widths of the offset voltages, a combination with a small offset voltage difference between the four operating states is selected. The Hall element sensor and method of operation thereof of claim 1, comprising: 2. The Hall element according to claim 1, comprising selecting a combination with a small offset voltage difference between the four operating states by using measurement data obtained by measuring the offset voltages of the four operating states multiple times and averaging them. Sensor and method of operation.

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