KR100676212B1 - Hall sensor driving circuit and pointing apparatus thereof - Google Patents

Abstract

A hall sensor driver circuit and a pointing device using the same are provided to exclude a power circuit generating static voltage for driving a hall sensor and to secure a self-amplification function by non-linearly increasing hall voltage by increasing magnetic flux density applied on the hall sensor. A hall sensor driver circuit(300) includes: a driving power source with predetermined voltage(Vcc); a hall sensor(U7) for detecting the change of peripheral magnetic flux density and changing output voltage(V2) of two output terminals correspondently to the detected magnetic flux density; an amplifier(U8) for receiving one of reference voltage(Vref) lower than the voltage of the driving power source and the output voltage of the hall sensor and outputting a control signal generated by amplifying the difference between the reference voltage and the output voltage of the hall sensor; and a switching element keeping the output voltage input to the amplifier correspondently to the reference voltage by controlling the flow of current input from the driving power source to the hall sensor according to the control signal.

Description

Hall sensor driving circuit and pointing device by the driving circuit

1A is a hall sensor driving circuit diagram according to a voltage driving method;

FIG. 1B is a graph showing Hall voltage measured according to the circuit of FIG. 1A;

2 is another conventional Hall sensor driving circuit diagram;

3 is a circuit diagram illustrating a hall sensor driving circuit according to an exemplary embodiment of the present disclosure;

4A and 4B are graphs showing Hall voltages measured according to the circuit of FIG. 3;

5 is a driving circuit for a plurality of Hall sensors, and according to another embodiment of the present invention;

6 is a block diagram of a pointing device by the Hall sensor driving circuit of the present invention.

The present invention relates to a Hall sensor driving circuit and a pointing device by the Hall sensor driving circuit. More specifically, the output voltage of one of the sensor output terminals is reduced in spite of a change in the magnetic flux acting on the Hall sensor. By driving the hall sensor to be kept constant, the present invention relates to a hall sensor drive circuit and a pointing device by the hall sensor drive circuit, which can simplify the drive circuit and widen the selection range of elements constituting the drive circuit.

The magnetic field sensor is a sensor for detecting a change in an external magnetic field, and includes a Hall sensor using a Hall effect and a magnetoresistive sensor using a magnetoresistive effect according to the physical phenomenon or effect used thereof.

A hall sensor is a sensor that uses a potential difference generated in a direction perpendicular to the current and the magnetic field, that is, a change in the hall voltage when a current flows in a semiconductor substrate or the like and applies a magnetic field in a direction perpendicular to the flow of the current. bridge) can be represented by the internal resistance of the structure.

The driving method of the Hall sensor is largely a constant current driving method for supplying a constant current and sensing a Hall voltage corresponding to a change in magnetic flux density, and a constant voltage driving method for driving the sensor by applying a constant voltage. Can be distinguished.

The constant voltage driving method, which is generally used because of better temperature characteristics than the constant current driving method, supplies driving power to two of the four terminals of the Hall sensor and detects the change in magnetic flux density by measuring the voltage of the remaining two terminals. .

FIG. 1A is a Hall sensor driving circuit diagram according to a voltage driving method, and FIG. 1B is a graph illustrating Hall voltage measured according to the circuit of FIG. 1A. 1A relates to a method of using the voltage between two output terminals.

Referring to the circuit of FIG. 1A, the driving voltage V _DD is supplied between the terminals 1 and 3 to the hall sensor U1. Referring to the graph of FIG. 1B, it can be seen that the voltage Va read at the terminal 2 of the hall sensor U1 and the voltage V _b read at the terminal 4 change based on the voltage V _DD / 2. The hall voltage V _H1 of the hall sensor U1 becomes V _b -Va, and as the magnetic flux density increases, the closer the distance to the magnet is, the larger the hall voltage V _H1 becomes.

Assuming that the internal equivalent resistance R ₁ = R ₄ = 150 Hz and the internal equivalent resistance R ₂ = R ₃ = 50 Hz of the Hall sensor U1 as the magnetic flux acts on the Hall sensor U1, calculate the Hall voltage V _H1 . . Assume that the driving voltage V _DD is 1V. Voltage Va becomes 0.25V, the voltage V _b becomes 0.75V. Therefore, the hall voltage V _H1 = V _b -Va = 0.75-0.25 = 0.5V. When driving a Hall sensor whose internal equivalent resistance changes linearly with magnetic flux density, the Hall voltage V _H1 is linearly increased as the magnetic flux density increases because the driving voltage V _DD is fixed.

1B, the threshold voltage of the PMOS transistor and the threshold voltage of the NMOS transistor are shown. In the case of a PMOS transistor, it operates only when the voltage applied between the gate and the source is lower than the threshold voltage of the PMOS transistor, and in the case of an NMOS transistor, only when the voltage applied between the gate and the source is larger than the threshold voltage of the NMOS transistor. It will work. Therefore, depending on the threshold voltage value and the operating voltage value of the PMOS / NMOS transistor provided in the manufacturing process of the circuit for controlling the Hall sensor, the PMOS or NMOS transistor alone does not utilize the entire interval of the signal illustrated in the graph of FIG. 1B. Failure may occur. This relationship is illustrated in FIG. 1B by the relative position of the Hall sensor output voltage and the threshold voltages of the PMOS and NMOS transistors.

Therefore, in this case the Hall sensor U1 of the output voltage Va and V _b the detection circuit at the rear end of the input receiving process is the output voltage a or b intervals of even the use of PMOS and NMOS transistors at the same time, or the detection circuit in order to operate the power supply voltage if To increase the position of the PMOS threshold voltage, or to provide the desired threshold voltage of the PMOS / NMOS transistor.

FIG. 2 is another conventional Hall sensor driving circuit diagram, which shows a circuit for driving and detecting two Hall sensors U2 and U3 based on the method of FIG. 1A.

The sensor power supply circuit 201 for the hall sensors U2 and U3 is connected to the input terminals 1 and 3 of the hall sensors U2 and U3.

The sensor power supply circuit unit 201 generates a constant voltage for supplying the hall sensor, and the level of the constant voltage is determined by the characteristics of the sensor to be used, but typically uses a value of about 1V.

The differential amplifiers U4 and U5 are connected to the output terminals 2 and 4 of the hall sensors U2 and U3, respectively, to amplify and detect the hall voltage, which is the voltage between the terminals 2 and 4, corresponding to the change in the magnetic flux density. The differential amplifier U6 is provided to detect a relative difference in magnetic flux density detected by the two Hall sensors U2 and U3 and amplifies the difference in the output voltages of the differential amplifiers U4 and U5. This relative difference in magnetic flux density is caused by the position of the magnet in application to the pointing device.

Examining the circuit of FIG. 2, the output voltages of Hall sensors U2 and U3 will be displayed as shown in FIG. 1B in response to changes in magnetic flux density and the like. In the case of the differential amplifiers U4 and U5 that accept the output of the Hall sensor as an input, only the limited type of implementation described above is possible depending on the threshold voltage, the supply voltage (V _CC ) and the input signal of the transistor. Will be

An object of the present invention is to provide a Hall sensor driving circuit which can reduce the number of differential amplifiers for comparing a plurality of Hall sensor outputs by simplifying the plurality of Hall sensor driving circuits.

Another object of the present invention is to provide a Hall sensor driving circuit which can be implemented by using an NMOS transistor at an input terminal of a differential amplifier in generating a differential amplifier for forming a Hall sensor driving circuit.

Still another object of the present invention is to provide a Hall sensor driving circuit in which the magnitude of the output Hall voltage increases nonlinearly as the magnetic flux density acting on the Hall sensor increases, and a pointing device to which the driving circuit is applied.

In order to achieve the above object, the Hall sensor driving circuit according to the present invention detects a drive power supply having a predetermined voltage and a change in magnetic flux density around the sensor, and output voltages of two output terminals are respectively corresponding to the detected magnetic flux density. A hall sensor, an amplifier for receiving a reference voltage lower than the voltage of the driving power source, and an output voltage of the hall sensor and outputting a control signal amplifying the difference, and the hall sensor from the driving power source according to the control signal And a switching element for controlling the output voltage input to the amplifier to be maintained by converging to the reference voltage by controlling the flow of current input to the amplifier.

The switching element is preferably a metal oxide semiconductor field effect transistor (MOSFET).

According to another embodiment of the present invention, a pointing device of a portable digital device including a display unit on which a predetermined pointer is displayed may include a magnet moving a predetermined space, and formed on one side of the space, thereby providing displacement of the magnet. At least one Hall sensor driver for detecting and a pointing control unit for moving the pointer of the display unit in a manner corresponding to the movement of the magnet.

Hereinafter, the present invention will be described in detail with reference to the drawings.

3 is a circuit diagram illustrating a hall sensor driving circuit according to an exemplary embodiment of the present invention.

The Hall sensor driving circuit 300 of the present invention may be manufactured as a single semiconductor chip together with the Hall sensor U7, and the Hall sensor U7 is operated by the driving power of the entire chip to separate the hall sensor U7. There is no need to provide the sensor power supply circuit portion, so that the circuit and the wiring can be simplified.

In addition, the present invention may be included in a multi chip package (MCP) or a multi chip module (MCP) that is manufactured in one package together with other semiconductor modules using the output of the hall sensor U7.

In addition, in order to detect an external magnetic flux density, the magnetic flux sensing circuit including the plurality of Hall sensors may be included in the driving circuit for the plurality of Hall sensors.

Referring to FIG. 3, the hall sensor U7 may have four terminals and may be represented by a combination of internal equivalent resistors having a bridge shape. In addition, hereinafter, the internal resistances R1 to R4 of the hall sensor U7 change in response to the change of the magnetic flux density, and the following description will be given on the assumption that the resistance R1 becomes larger than the resistance R2.

The driving voltage Vcc of the hall sensor driving circuit 300 is connected to the input terminal 1 of the hall sensor U7 through the transistor M1. The voltage Vcc may be output through a predetermined power supply unit (not shown), and if the Hall sensor driving circuit 300 of the present invention is made of one semiconductor chip together with a predetermined other circuit, an external separate circuit The driving voltage Vcc can be received through.

Here, the voltage Vcc is a driving voltage of the entire Hall sensor driving circuit 300, and the transistor M1 may be a P-type or an N-type as a metal-oxide semiconductor field effect transistor (MOSFET).

In FIG. 3, the transistor M1 shows a PMOS transistor. If the transistor M1 to a NMOS transistor, it should be configured as opposed to Figure 3 the input of amplifier U8, the reference voltage V _ref is to be input to the + terminal of amplifier U8.

The amplifier U8 receives a predetermined reference voltage V _ref as a − terminal and an output voltage V ₂ of the terminal 2 of the hall sensor U 7 through the + terminal. The output voltage of amplifier U8 is connected to the gate of transistor M1 to control transistor M1. The reference voltage V _ref is an output voltage value when the output voltage (here, V ₂ ) of one of the output terminals of the hall sensor U7 (terminal 2 in FIG. 3) is to be maintained at a constant value V _ref . In general, it is preferable to have near half of the supply voltage specified in the specification of the driving hall sensor.

As the Hall sensor driving circuit 300 of the present invention starts to operate, the voltage V ₂ will be lower or higher than the reference voltage V _ref . However, the amplification circuit by the amplifier U8 receives the voltage V ₂ feedback and controls the drive current of the transistor M1 so that the voltage V ₂ converges to the reference voltage.

Therefore, the output voltage V ₂ of the terminal 2 of the hall sensor U7 maintains the reference voltage V _ref . Then, the output voltage of the Hall sensor U7 terminal 4 of V ₄ is a variation of, and changes in response to changes in magnetic flux, such a change in voltage of V ₄ is the internal resistance of the Hall sensor U7 R ₁ to R _4, which acts on the Hall sensor U7 Is determined by

When no magnetic flux acts on the hall sensor U7, the internal resistances R ₁ to R ₄ maintain the same value, so that the voltage V ₄ becomes equal to the voltage V ₂ , which is equal to the reference voltage V _ref . Thus, V ₂ = V ₄ = V _ref holds.

When the magnetic flux acts on the hall sensor U7, the resistances R ₁ to R ₄ change in response to the change of the magnetic flux. However, due to the characteristics of the Hall sensor, the resistors R ₁ and R ₄ always maintain the same value, and the resistors R ₂ and R ₃ always maintain the same value.

Accordingly, when the voltage V ₄ is obtained, the following Equation 1 is obtained.

Here, the resistors R ₁ and R ₂ are not fixed constants and have the same value when no magnetic flux exists, and when R ₁ increases due to the Hall Effect when magnetic flux exists, R _{1. When 2} becomes smaller and R ₁ becomes smaller, a change in magnitude occurs in a direction in which R ₂ increases, and since the magnitude change is proportional to the intensity of the magnetic flux, the voltage V ₄ does not change linearly with respect to the reference voltage. In addition, the value of R1 / R2, which is a proportional constant of the equation, is characterized by having a larger value as the magnetic flux density increases.

If the resistance R ₁ becomes larger than the resistance R ₂ in response to the change of the magnetic flux density, the voltage V ₄ becomes larger than the reference voltage V _ref , and the hall voltage V _H2 is expressed by Equation 2 below.

For example, assume that the reference voltage V _ref is 0.5V, the resistance R ₁ = R ₄ = 150 mV, and the resistance R ₂ = R ₃ = 50 mV. The voltage V ₂ becomes 0.5V, the preamplifier V ₄ becomes 1.5V by the equation (1), and the hall voltage V _H2 becomes 1.0V.

This is compared with the conventional circuit of FIG. 1A as follows. In the case of FIG. 1A, there is no reference voltage, and the driving power source V _DD is applied to the terminal 1 of the hall sensor U1 as it is. Therefore, the magnitude of the Hall voltage V _H1 may be influenced by the fixed V _DD regardless of the change in the magnetic flux density. However, when that is the V _DD is the case is not applied the magnetic flux output voltage _{Va = V b = V DD /} 2 to be equal to the reference voltage V _ref, the Hall voltage V _H1 is a 0.5V as previously calculated .

Therefore, the Hall sensor driving circuit 300 according to the present invention basically includes an amplifier function having an amplification factor proportional to a change in magnetic flux density.

Furthermore, when the reference voltage V _ref is higher than the threshold voltage of the NMOS transistor, the voltage V ₄ is always higher than V _ref . Therefore, the transistor constituting the input terminal of the amplifier (not shown) to which the voltage V ₄ can be input can use only the NMOS transistor without using the PMOS transistor and the NMOS transistor together.

In addition, in designing an amplifier to which the voltage V ₄ is input by using the Hall sensor driving circuit 300 of the present invention, a manufacturing process characterized by a high threshold voltage and an operating environment characterized by a low power supply voltage (for an amplifier) Even under a simple structure, an amplifier can be designed.

According to another exemplary embodiment of the present disclosure, the amplifier U8 and the transistor M1 of FIG. 3 may be included in a separate circuit (eg, a sensor power circuit unit) for supplying a hall sensor driving power. However, one feature of the present invention is that the amplifier U8 and the transistor M1 are formed so that a constant voltage (for example, V ₂ = V _ref ) is maintained at one of the output terminals of the hall sensor. In addition, the amplifier U8 and the transistor M1 may be formed by being included in a separate circuit together with another configuration.

4A and 4B are graphs showing Hall voltages measured according to the circuit of FIG. 3.

Referring to FIG. 4A, the horizontal axis of the Hall voltage graph is a magnetic flux density. Therefore, as the horizontal axis converges to zero, the distance between the magnet and the hall sensor U7 increases.

In FIG. 4A, the resistors R ₁ and R ₂ change in response to a change in the magnetic flux, but basically assume that R ₁ > R ₂ as shown in FIG. 1B. In the graphs, voltages V ₂ and V ₄ were displayed, and hall voltages V _H2 were also displayed. Hall voltages V _H1 shown in the graphs correspond to V _H1 in FIG. 1B for comparison.

As shown in c of FIG. 4A, when no magnetic flux acts on the hall sensor U7, the voltage V ₄ becomes equal to the voltage V ₂ , which is equal to the reference voltage V _ref . As the magnet approaches the hall sensor U7, when the magnetic flux density acting on the hall sensor U7 is increased, the hall voltage V _H2 increases nonlinearly. Thus, the graph of FIG. 4A shows that the Hall sensor driving circuit 300 of the present invention basically has an amplifier function of Hall voltage.

However, it is preferable that the magnetic flux density acting on the hall sensor by the approach of the magnet is usually about 50 × 10 ⁻³ T [tesla] or less in consideration of the influence of the magnetic flux on other electric elements. When such magnetic flux density acts on the hall sensor U7, the hall voltage V _H2 in accordance with the drive circuit 300 applied to the hall sensor currently commercialized is usually 100 mV or less.

As mentioned above, when the reference voltage V _ref is made higher than the threshold voltage of the NMOS transistor, the voltage V ₄ is always higher than V _ref . Therefore, the transistor constituting the input terminal of the amplifier (not shown) to which the voltage V ₄ can be input can use only the NMOS transistor without using the PMOS transistor and the NMOS transistor together.

FIG. 4B may occur when the voltage V ₄ is fed back and kept constant instead of the voltage V ₂ . In this case, since the resistance R ₁ = R ₄ and the resistance R ₂ = R ₃ , the resistance R ₂ becomes smaller as the magnetic flux increases, so the output voltage V ₂ is lower than the voltage V ₄ to be fixed to the reference voltage V _ref . You lose. However, in the case of FIG. 4B, the absolute value of the hall voltage V _H2 is the same as that of FIG. 4A.

In addition, FIG. 4B may occur when the direction of the magnetic flux density acting on the hall sensor U7 is opposite to FIG. 4A.

As mentioned above, when the reference voltage V _ref is lower than the threshold voltage of the PMOS transistor, the voltage V ₂ is always lower than V _ref . Therefore, the transistors constituting the input terminal of the amplifier (not shown) to which the voltage V ₂ can be input can use only the PMOS transistors without using the PMOS transistors and the NMOS transistors together.

5 is a driving circuit for a plurality of Hall sensors according to another embodiment of the present invention.

The Hall sensor driving circuit 500 of FIG. 5 includes at least two Hall sensors and detects a difference in magnetic flux densities sensed by the two Hall sensors. The Hall sensor driving circuit 500 includes a magnet (not shown) that moves between (or near) two Hall sensors U9 and U10, and may be used in an apparatus for detecting the position and movement of the magnet.

Referring to FIG. 5, there are two Hall sensors U9 and U10, and there are amplifiers U11 and U12 for maintaining the voltage at terminal 2 as the reference voltage V _ref for the Hall sensors U9 and U10, respectively.

Accordingly, the block composed of the Hall sensor U9, the transistor M2 and the amplifier U11 and the block composed of the Hall sensor U10, the transistor M3 and the amplifier U12 operate in the same manner as the Hall sensor driving circuit 300 of FIG. Corresponds to the configuration of FIG.

The output voltages of the output terminals 4 of the hall sensors U9 and U10 are input to the amplifier U13, respectively. This allows the amplifier U13 to detect the change in magnetic flux by comparing the outputs of the two Hall sensors U9 and U10.

As mentioned above, in designing the amplifier U13 which receives the output voltages of the output terminals 4 of the Hall sensors U9 and U10, the manufacturing process characterized by the high threshold voltage and the low power supply voltage (for the amplifier U13) are characterized. Even under the operating environment, a simple amplifier can be designed.

In addition, compared with the conventional Hall sensor driving circuit 200 of FIG. 2, the output voltage of the Hall sensor driving circuit 500 of the present invention is fixed to V _ref of each of the two Hall sensors. The corresponding configuration may be omitted. The amplifiers U11 and U12, unlike FIG. 2, may be recognized as being a newly added configuration in FIG. 5, but the configurations of the amplifiers U11 and U12 may be included in the sensor power supply circuit portion 201 of FIG. Compared to the U4 and U5 amplifiers, the structure is simpler.

Furthermore, the Hall sensor driving circuit of the present invention may be included in a predetermined pointing device that controls to move the pointer displayed on the predetermined display device in response to the movement of the magnet moving above the Hall sensor driving circuit.

6 is a block diagram of a pointing device by the Hall sensor driving circuit of the present invention. Hereinafter, the pointing device will be described with reference to FIG. 6.

Referring to FIG. 6, the pointing device 600 includes a magnet 601, a hall sensor driver 603, and a pointing controller 605.

The pointing device 600 of FIG. 6 may be included in various digital devices, and in response to a user's manipulation, the pointing device 600 may move a pointer on a display unit (not shown) included in the digital device. Preferably, the pointing device 600 may be included in a portable digital device.

The magnet 601 may be provided to move a predetermined space.

The hall sensor driver 603 is formed at one side of a space in which the magnet 601 moves, detects a displacement of the magnet, and outputs a control command corresponding to the displacement to the pointing controller 605.

The Hall sensor driver 603 may correspond to the Hall sensor driver circuit of FIGS. 3 and 5, and although only one Hall sensor driver 603 is illustrated in FIG. 6, a plurality of Hall sensor driver 603 may be included.

The pointing controller 605 controls the pointer of the display unit (not shown) to move according to a control command received from the hall sensor driver 603.

Non-linearity of the Hall voltage V _H2 output from the Hall sensor driver 603 brings an acceleration effect of the movement of the pointer. For example, as the magnet 601 gets closer to the Hall sensor (as the magnetic flux density increases), the Hall voltage V _H2 output from the Hall sensor increases nonlinearly, so that the movement of the pointer does not become an equivalent speed, and the speed is gradually increased. Will increase. That is, acceleration is added to the movement of the pointer.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the above-described specific embodiment, the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

As described above, the hall sensor driving circuit according to the present invention does not require a separate power supply circuit for generating a constant voltage to drive the hall sensor.

The hall sensor driving circuit includes amplification function by itself by non-linearly increasing the hall voltage output as the magnetic flux density acting on the hall sensor increases.

The hall sensor driving circuit outputs the voltage output from the output terminal of the hall sensor only in one form of increasing or decreasing based on a predetermined reference voltage. Therefore, in designing the input terminal of the amplifier receiving the output of the hall sensor, the transistor used can be composed of only one of the NMOS or PMOS transistor. Furthermore, in designing an amplifier receiving the output of the hall sensor, it is possible to design an amplifier having a simple structure even in a manufacturing process characterized by a high threshold voltage and an operating environment featuring a low power supply voltage.

In the case of the pointing device using the Hall sensor driving circuit of the present invention, a function of increasing the moving speed of the pointer as the magnet approaches the Hall sensor may be basically implemented according to the nonlinear characteristic of the Hall voltage.

Claims (3)

A driving power source having a predetermined voltage; A hall sensor which senses a change in magnetic flux density around and changes output voltages of two output terminals in response to the detected magnetic flux density; An amplifier for receiving one of a reference voltage lower than a voltage of the driving power supply and an output voltage of the hall sensor and outputting a control signal amplifying the difference; And And a switching element controlling the output voltage input to the amplifier to be maintained by converging to the reference voltage by controlling a flow of current input from the driving power source to the hall sensor according to the control signal. Hall sensor drive circuit. The method of claim 1, And said switching element is a metal oxide semiconductor field effect transistor (MOSFET). In the pointing device of a portable digital device comprising a display unit on which a predetermined pointer is displayed, A magnet moving a predetermined space; At least one hall sensor driver formed at one side of the space to detect a displacement of the magnet; And And a pointing controller for moving the pointer of the display unit in a manner corresponding to the movement of the magnet. The hall sensor driving unit, A driving power source having a predetermined voltage; A hall sensor which senses a change in magnetic flux density according to the movement of the magnet and changes output voltages of two output terminals in response to the detected magnetic flux density; An amplifier for applying a reference voltage smaller than the voltage of the driving power source to one of the two input terminals, and outputting a control signal amplified between the two input terminals by being connected to one of the output terminals of the hall sensor; And And a switching element controlling the output voltage of the output terminal connected to the amplifier to be maintained by converging to the reference voltage by controlling the flow of current input from the driving power source to the hall sensor according to the control signal. Pointing device.

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