JP3778909B2 - Magnetic field sensor, magnetic field detection device, and magnetic field detection method - Google Patents

Description

  The present invention relates to a magnetic field sensor, a magnetic field detection method, and a magnetic field detection apparatus that can detect the intensity of a magnetic field without depending on the polarity of the magnetic field.

  In recent years, a demand for a magnetic field sensor as a position sensor such as an open / close detection device and a rotation detection device mounted on a small electronic device such as a folding mobile phone, a notebook personal computer, or a digital still camera is increasing. In a magnetic field sensor mounted on a portable small electronic device, it is necessary to reduce both circuit scale and current consumption.

  In general, the magnetic field sensor is configured to be monolithically integrated using a bipolar transistor or a CMOS device. Such a magnetic field sensor includes a magnetoelectric conversion element that generates a voltage proportional to a magnetic field or magnetic flux density, an amplifier that amplifies the output voltage of the magnetoelectric conversion element, and a comparator that compares the output voltage of the amplifier with a predetermined reference voltage. A determination result as to whether or not the intensity of the magnetic field detected by the magnetoelectric conversion element (hereinafter referred to as a detected magnetic field) is larger than a predetermined magnetic field intensity is output to the outside. As the magnetoelectric conversion element, a Hall element that outputs a voltage corresponding to the strength of the magnetic field passing through the element or the density of the magnetic flux, or a magnetoresistance whose resistance value changes depending on the strength of the magnetic field is used.

  In order to obtain an accurate comparison result according to the strength of the magnetic field from the magnetic field sensor, the offset signal included in the signal output from the amplifier is suppressed, and the variation in the signal output from the amplifier for each magnetic field sensor (product) Must be kept small. There are mainly two factors that cause the offset signal. One is an offset signal component of the magnetoelectric conversion element due to the influence of the stress or the like of the sealing package, and the other is an input offset signal component of the amplifier.

  A method for compensating the offset signal component of the magnetoelectric transducer is disclosed in US Pat. No. 4,037,150. That is, among the output terminals of the magnetoelectric conversion element having four geometrically equivalent terminals, the potential difference between the two pairs of output terminals located diagonally is expressed by the first phase and the first phase in the synchronization signal that triggers detection. The two phases are alternately switched and output, and the output value is summed. The effective signal component is doubled because it is in phase, and the offset signal component is canceled because it is in antiphase.

  One of the factors that determine the superiority or inferiority of the magnetic field sensor is whether or not the magnetic field can be detected regardless of the polarity of the magnet incorporated in the product, that is, whether or not the magnetic field sensor can be handled in accordance with both polarities. If the magnetic field strength can be determined regardless of the polarity of the magnet, it is not necessary to manage the direction of the magnet when the magnet is arranged in a position sensor or the like in which the magnet and the Hall IC are incorporated.

Hereinafter, a conventional magnetic field sensor disclosed in Japanese Patent Laid-Open No. 7-83699 that performs magnetic field strength determination that can handle both polarities will be described with reference to the drawings.
FIG. 4 shows a configuration example of a conventional magnetic field strength determination circuit that can handle both polarities. As shown in FIG. 4, the conventional magnetic field sensor includes a magnetoelectric conversion element (a Hall element in the conventional example) 101, a voltage amplifier 102 that amplifies the output voltage of the magnetoelectric conversion element 101, and an output voltage from the voltage amplifier 102. The first Schmitt trigger circuit 103A that receives and outputs an output voltage that varies depending on the threshold value, and the second Schmitt trigger that receives the output voltage from the voltage amplifier 102 by inverting the polarity of the input signal of the first Schmitt trigger circuit 103A. The circuit 103B includes a logic latch circuit 104 that receives and latches output signals from the first Schmitt trigger circuit 103A and the second Schmitt trigger circuit 103B.

The operation of the conventional magnetic field sensor configured as described above will be described.
First, in proportion to the magnetic flux density passing through the magnetoelectric conversion element 101, the Hall voltage generated at the output terminal of the magnetoelectric conversion element 101 is amplified by the amplifier 102 to obtain an amplified voltage VH.
Next, the amplified voltage VH is input to the first Schmitt trigger circuit 103A and the second Schmitt trigger circuit 103B, and whether or not the value of the amplified voltage VH is larger than the set voltage value is output. To do. The first Schmitt trigger circuit 103A and the second Schmitt trigger circuit 103B are equivalent, and the two Schmitt trigger circuits detect the magnetic field strength levels of the N polarity and the S polarity by inverting the polarities of the input signals. This is performed separately at 103A and 103B.

Next, output values of the first Schmitt trigger circuit 103 </ b> A and the second Schmitt trigger circuit 103 </ b> B are input to the logic latch circuit 104. Thereafter, the logic latch circuit 104 outputs an output value obtained by performing an operation on the output values of the two Schmitt trigger circuits 103A and 103B corresponding to the magnetic field intensities of N polarity and S polarity. Here, the output value from the logic latch circuit 104 is a binary value indicating whether the strength of the detected magnetic field is greater than the strength of the set magnetic field regardless of the polarity.
U.S. Pat. No. 4,037,150 JP 7-83699 A

  However, the conventional magnetic field sensor requires two sets of Schmitt trigger circuits as voltage comparison circuits in order to detect the magnetic field intensity corresponding to both polarities regardless of the magnetic field polarity. It has a problem that it is difficult to reduce both of them.

  The present invention solves the above-described conventional problems, and provides a low-power-consumption magnetic field sensor, a magnetic field detection device, and a magnetic field detection method with a simple configuration that detects the intensity of a magnetic field of both polarities regardless of the polarity of the magnetic field. For the purpose.

  In order to solve the above problems, the present invention has the following configuration. According to the first aspect of the present invention, a signal corresponding to the applied magnetic field output from the magnetoelectric conversion element is input, and the first period, the fourth period, the second period, and the second period of the signal from the outside are input. A first switch unit that switches and outputs the signals so as to have opposite polarities in the period of 3; an amplifier that amplifies an output signal of the first switch unit and outputs a signal to an output terminal pair; and an output of the amplifier A first memory element having both ends connected to a terminal pair, and one of the output terminal pair and one terminal of the first memory element are inserted and connected, and interlocked with the first period and the third period The second switch unit that closes and opens in conjunction with the second period and the fourth period, and at least one signal at both ends of the second switch unit in the second period, Outputting a first polarity signal corresponding to the magnitude of the applied magnetic field; A switch output terminal for outputting a signal having a polarity opposite to the first polarity corresponding to the magnitude of the applied magnetic field, which is at least one of the signals at both ends of the second switch section in a period of 4; It is a magnetic field sensor provided with.

The invention according to claim 2 includes a first terminal pair and a second terminal pair, the magnetoelectric conversion element outputting a signal corresponding to the applied magnetic field, and the first terminal pair of the magnetoelectric conversion element And a signal of the second terminal pair and an external signal defining the first, second, third, and fourth periods are input, and the magnetoelectric conversion element in the first period and the fourth period A first switch unit that outputs a signal of the first terminal pair and outputs a signal of the second terminal pair of the magnetoelectric transducer in the second period and the third period, and an output of the first switch part An amplifier that amplifies the signal and outputs a signal to an output terminal pair; a first storage element having both ends connected to the output terminal pair of the amplifier; one of the output terminal pair and one of the first storage elements; The second period is inserted and connected between the terminals and closed in conjunction with the first period and the third period of the signal applied from the outside. A second switch unit to open in conjunction with the beauty fourth period, the switch output terminal for outputting at least one signal of the second switch portion at both ends, a magnetic field sensor, characterized in that it comprises a.
In the present specification, the first, second, third, and fourth periods occur once or repeatedly in this order.

  The invention according to claim 18 is the first selection signal generator for generating the first selection signal in the first period and the fourth period, and the second selection in the second period and the third period. A second selection signal generator for generating a signal, a third selection signal generator for generating a third selection signal in the first period and the third period, and in the second period and the fourth period A fourth selection signal generator for generating a fourth selection signal; a magnetoelectric transducer that includes a first terminal pair and a second terminal pair; and outputs a signal corresponding to the applied magnetic field; The signal of the first terminal pair and the signal of the second terminal pair of the conversion element and the first selection signal and the second selection signal are individually input, and the first period and the fourth period A first terminal that outputs a signal of the first terminal pair of the magnetoelectric conversion element and outputs a signal of the second terminal pair of the magnetoelectric conversion element in the second period and the third period. A switch unit; an amplifier that amplifies an output signal of the first switch unit and outputs a signal to an output terminal pair; a first storage element having both ends connected to the output terminal pair of the amplifier; and the output terminal Inserted and connected between one terminal of the pair and one terminal of the first memory element, inputs the third selection signal, and closes in the first period and the third period, and the second period and the fourth period A second switch portion that is open to the second switch portion and one terminal of the second switch portion, the fourth selection signal is input, the second switch portion is opened during the first period and the third period, and the second period and the second period The voltage of at least one of the fifth switch section closed during the period 4 and the second switch section is input via the fifth switch section, and the result of comparison with a predetermined value is output. A comparator, an output signal of the comparator in a second period, and a fourth period A judging circuit for outputting a logical sum signal of the output signal of the comparator definitive a magnetic field detecting device, characterized in that it comprises a.

According to the nineteenth aspect of the present invention, a signal corresponding to the applied magnetic field output from the magnetoelectric conversion element is input, and the first period and the fourth period are reversed in the second period and the third period. The switching step for switching to polarity and outputting, the amplification step for amplifying and outputting the signal output in the switching step, and the voltage output in the amplification step in the first period and the third period A signal component corresponding to the magnetic field of the holding step held in the first storage element, the voltage output in the amplification step in the second period and the fourth period, and the voltage held in the first storage element An addition step in which the addition voltages in the addition step having opposite polarities are input in the second period and the fourth period, and a comparison step for outputting a result of comparison with a predetermined value; Said comparison in period An output signal of the step, a magnetic field detection method characterized by having a determination step of outputting a logical sum signal of the output signal of the comparing step in the fourth period.
By providing this configuration, the offset voltage component generated in the output of the magnetoelectric conversion element is removed using the symmetry of the structure of the magnetoelectric conversion element, and the offset voltage associated with the amplifier is removed to obtain the output signal of the magnetoelectric conversion element. It can be taken out.
The presence or absence of a signal can be determined regardless of whether the magnetic field polarity is N or S.

  A third aspect of the present invention is the magnetic field sensor according to the second aspect, wherein the second switch section includes an output terminal pair.

The invention according to claim 4 is the magnetic field sensor according to claim 2, further comprising a comparator that inputs a signal of the switch output terminal and outputs a result of comparison with a predetermined value. It is a magnetic field sensor.
By providing a comparator that inputs a signal from the switch output terminal and outputs a result of comparison with a predetermined value, the magnetic field sensor outputs a highly accurate binary detection signal.

  According to a fifth aspect of the present invention, in the magnetic field sensor according to the fourth aspect, a different voltage is added to the signal of the switch output terminal in accordance with the output signal of the comparator. With this configuration, the comparator is provided with hysteresis, so that the magnetic field or magnetic flux can be detected stably.

  The invention according to claim 6 is the magnetic field sensor according to claim 2, wherein the magnetic field sensor is inserted and connected between one terminal of the second switch unit and one input terminal of the comparator, and the signal applied from the outside A fifth switch unit that opens in conjunction with the first period and the third period and closes in conjunction with the second period and the fourth period; The other switch part is connected to one of the comparator input terminal pair via a second storage element, and the other of the second switch part is connected to the other of the comparator input terminal pair via a second storage element. It is a magnetic field sensor. The threshold voltage can be stored in the second memory element, and the threshold can be set in the comparator with a simple configuration.

  The invention according to claim 7 is the magnetic field sensor according to claim 6, further comprising a third switch portion having one end connected to one of both ends of the second storage element, and both ends of the second storage element. A first switch having one end connected to the other, a voltage source for applying a first voltage to the other of the third switch, and a voltage value different from the first voltage value for the other of the fourth switch And a voltage source for applying a voltage, wherein the third and fourth switch sections are closed during the first period of the signal. Thus, the threshold voltage can be stored in the second memory element with a simple configuration, and the threshold can be set in the comparator.

  The invention according to claim 8 is the magnetic field sensor according to claim 7, wherein one of the first voltage value and the second voltage value is made different according to a signal given from the outside. is there. By adding different voltages to the signal at the switch output terminal according to the output signal of the comparator, the magnetic field sensor can perform detection with hysteresis added.

The invention according to claim 9, in the magnetic field sensor of claim 2, wherein the first memory element is a magnetic field sensor, which is a capacitor.
A tenth aspect of the present invention is the magnetic field sensor according to the seventh aspect, wherein the second memory element is a capacitor.
By using a capacitor as a memory element, a small magnetic field sensor suitable for IC implementation can be realized.

  An eleventh aspect of the present invention is the magnetic field sensor according to the second aspect, wherein the signal of the switch output terminal is further inputted and the signal values of the second period and the fourth period of the signal given from the outside are inputted. It is a magnetic field sensor provided with the determination circuit which outputs the signal which determined this.

  According to a twelfth aspect of the present invention, in the magnetic field sensor according to the eleventh aspect, the determination circuit inputs the signal of the comparator output terminal to the D input terminal, and the first clock signal to the clock input terminal. A first flip-flop that inputs and holds a signal within the second period and outputs it to a Q output terminal, the comparator output terminal, and the Q output terminal of the first flip-flop are individually input terminals. A NOR logic circuit that inputs to a pair and outputs a NOR logic output; an output of the NOR logic circuit is input to a D input terminal; and a second clock signal is input to a clock input terminal; And a second flip-flop that holds the signal and outputs it to the output terminal, and outputs a second flip-flop output terminal signal.

According to a thirteenth aspect of the present invention, in the magnetic field sensor according to the eleventh aspect, the determination circuit inputs the signal of the comparator output terminal to the D input terminal, and the first clock signal to the clock input terminal. A first flip-flop that inputs and holds a signal within the second period and outputs it to a Q output terminal; a signal of the comparator output terminal is input to a D input terminal; and a second clock signal Are input to the clock input terminal, the second flip-flop that holds the signal within the fourth period and outputs it to the output terminal, and the Q outputs of the first and second flip-flops are individually input terminal pairs. And a NOR logic circuit that outputs a NOR logic output, and outputs the NOR logic circuit output.
By providing a determination circuit that inputs a signal from the switch output terminal and outputs a signal that determines the signal value of the second period and the fourth period of the signal applied from the outside, the polarity of the magnetic field is N or S. Even so, the presence or absence of a signal can be determined.

  According to a fourteenth aspect of the present invention, in the magnetic field sensor according to the second aspect, the first switch section outputs a first voltage terminal that outputs a first voltage, and a second voltage terminal that outputs a second voltage. The first, second, third and fourth input terminals, the first and second output terminals, and the first voltage terminal and the first input terminal are inserted and connected to open and close in response to a signal given from the outside. Inserted between the first switch element, the second switch element inserted and connected between the first voltage terminal and the second input terminal, and opened and closed in response to an external signal, and inserted between the second voltage terminal and the third input terminal A third switch element connected and opened and closed according to a signal applied from the outside; a fourth switch element inserted and connected between the second voltage terminal and the fourth input terminal and opened and closed according to a signal applied from the outside; Inserted and connected between the first output terminal and the first input terminal. A fifth switch element that opens and closes in response to a signal applied from the unit, a sixth switch element that is inserted and connected between the first output terminal and the second input terminal, and that opens and closes in response to a signal applied from the outside; A seventh switch element inserted and connected between the output terminal and the third input terminal and opened / closed according to a signal given from the outside, and a signal inserted and connected between the second output terminal and the fourth input terminal and given from the outside And an eighth switch element that opens and closes, one of the first terminal pair of the magnetoelectric conversion element is connected to the first input terminal, and one of the second terminal pair of the magnetoelectric conversion element is connected to the second input terminal The other of the first terminal pair of the magnetoelectric conversion element is connected to the third input terminal, and the other of the second terminal pair of the magnetoelectric conversion element is connected to the fourth input terminal. It is a magnetic field sensor.

According to a fifteenth aspect of the present invention, in the magnetic field sensor according to the fourteenth aspect, the first, third, sixth, and eighth switch elements are closed during first and fourth periods of an externally applied signal, The magnetic field sensor is characterized in that the second, fourth, fifth and seventh switches are closed during the second and third periods of the signal applied from the outside.
The first switch unit is composed of eight switch elements, and two sets of output terminal pairs of the magnetoelectric conversion elements are switched in the first period, the fourth period, the second period, and the third period. With this configuration, the offset signal component of the magnetoelectric conversion element can be canceled.

A sixteenth aspect of the present invention is the magnetic field sensor according to the second aspect, wherein the magnetoelectric conversion element is a Hall element.
The invention according to claim 17 is the magnetic field sensor according to claim 2, wherein the magnetoelectric conversion element is a magnetic resistance.
By using a Hall element or a magnetic resistance as the magnetoelectric conversion element, a small-sized magnetic field sensor suitable for IC implementation can be realized.
The invention according to claim 20 is characterized in that the first switch section further includes a signal generator that outputs a signal for determining the first, second, third and fourth periods. A magnetic field sensor according to claim 1 or 2.

  According to the magnetic field sensor of the present invention, one voltage comparator can cope with both polarities regardless of the polarity of the magnetic field, the magnetic field strength can be detected with a simple configuration, and the current consumption can be reduced.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments that specifically show the best mode for carrying out the present invention will be described below with reference to the drawings.

Embodiment 1
A magnetic field sensor according to Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 1 is a block diagram showing the configuration of the magnetic field detection apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a magnetic field sensor of Embodiment 1, and 3 is a signal generator.
The signal generator 3 includes a first selection signal generator 4, a second selection signal generator 5, a third selection signal generator 6, a fourth selection signal generator 9, and a first clock signal generator 7. And a second clock signal generator 8. In addition, the signal generator 3 can also be comprised with a microcomputer. The first selection signal generator 4 outputs a first selection signal a. The second selection signal generator 5 outputs a second selection signal b. The third selection signal generator 6 outputs a third selection signal c. The fourth selection signal generator 9 outputs a fourth selection signal d. The first clock signal generator 7 and the second clock signal generator 8 output a first clock signal CK1 and a second clock signal CK2, respectively. The four selection signals and the two clock signals are generated according to the timing chart shown in FIG.

  In the magnetic field sensor 1, 11 is a magnetoelectric conversion element, 12 is a voltage amplifier, 17 is a first storage element, 16 is a switch circuit (first switch unit), 13 is a Schmitt trigger circuit, and 15 is a logic latch circuit (determination circuit). ) And 54 are inverters, and 19 is a second inverter. In the first embodiment, the magnetoelectric conversion element 11 is a Hall element.

  The switch circuit 16 includes eight switches 21A, 21B, 22A, 22B, 23A, 23B, 24A, and 24B. A power supply voltage is applied to one of the terminal pairs of the magnetoelectric transducer 11 via the switch circuit 16, and the other is grounded. At this time, a signal voltage generated at the other terminal pair of the magnetoelectric conversion element 11 is applied to the input terminal of the voltage amplifier 12.

  Specifically, the first switch 21A (first switch element) has one end connected to the first external terminal located at the first apex angle among the four apex angles of the magnetoelectric conversion element 11, The other end is connected to the power supply voltage input terminal and is closed in synchronization with the first selection signal a. The second switch 21B (second switch element) has one end connected to a second external terminal located at a second apex angle adjacent to the first apex angle of the magnetoelectric conversion element 11, and the other end connected to a power source. It is connected to the voltage input terminal and is closed in synchronization with the second selection signal b. The third switch 22A (third switch element) has one end connected to a third external terminal located at a third apex angle opposite to the first apex angle of the magnetoelectric transducer 11, and the other end grounded. The terminal is connected and is closed in synchronization with the first selection signal a. The fourth switch 22B (fourth switch element) has one end connected to a fourth external terminal located at a fourth apex angle opposite to the second apex angle of the magnetoelectric transducer 11, and the other end grounded. The terminal is connected and is closed in synchronization with the second selection signal b.

  The fifth switch 23 </ b> A (fifth switch element) has one end connected to the second external terminal of the magnetoelectric conversion element 11 and the other end connected to the non-inverting input terminal of the voltage amplifier 12. The closed state is synchronized with a. The sixth switch 23B (sixth switch element) has one end connected to the first external terminal of the magnetoelectric conversion element 11, the other end connected to the non-inverting input terminal of the voltage amplifier 12, and the second selection signal. The closed state is synchronized with b. The seventh switch 24A (seventh switch element) has one end connected to the fourth external terminal of the magnetoelectric conversion element 11, the other end connected to the inverting input terminal of the voltage amplifier 12, and the first selection signal a. Synchronously with the closed state. The eighth switch 24B (eighth switch element) has one end connected to the third external terminal of the magnetoelectric conversion element 11, the other end connected to the inverting input terminal of the voltage amplifier 12, and the second selection signal b. Synchronously with the closed state.

  In this configuration, when the first selection signal a is High, the switches 21A and 22A are conductive, one end of the switch 23A is connected to the non-inverting input terminal of the voltage amplifier 12, and one end of the switch 24A is connected to the voltage amplifier 12. Connected to the inverting input terminal. When the second selection signal b is High, the switches 21B and 22B are turned on, one end of the switch 23B is connected to the non-inverting input terminal of the voltage amplifier 12, and one end of the switch 24B is connected to the inverting input terminal of the voltage amplifier 12. Connected. The polarities of the voltages applied between the input terminals of the voltage amplifier 12 are opposite to each other between the period when the first selection signal a is High and the period when the second selection signal b is High.

  One end of a switch 18C (second switch unit) and one end of a switch 20D (fifth switch unit) are connected to the non-inverting output terminal of the voltage amplifier 12, and the other end of the switch 18C is connected to the first storage element 17. One end and the terminal 101 are connected. The other end of the first memory element 17 is connected to the inverting output terminal of the voltage amplifier 12. The other end of the switch 20D is connected to the output terminal 100, and the voltage between the output terminals 100 and 101 is applied to the Schmitt trigger circuit 13. The switch 18C is closed in synchronization with the third selection signal c, and the switch 20D is closed in synchronization with the fourth selection signal d.

The Schmitt trigger circuit 13 includes a comparator 130, a second storage element 33, a switch 34C (third switch unit), a switch 35C (fourth switch unit), a first MOS switch 36, and a second MOS switch 37. , A voltage source 38 and a first inverter 39.
One end (one electrode) of the second memory element 33 is connected to the terminal 100, and the other end (other electrode) is connected to the non-inverting input terminal of the comparator 130. The switch 34C has one end connected to one electrode of the second memory element 33 and the other end connected to one end of the first MOS switch 36 and the second MOS switch 37, and is synchronized with the third selection signal c. Closed. The switch 35C has one end connected to the other electrode of the second storage element 33 and the non-inverting input terminal of the comparator 130, and the other end connected to a setting voltage source 38 for setting a hysteresis value (setting magnetic field). The closed state is synchronized with the selection signal c.

  One end of each of the first MOS switch 36 and the second MOS switch 37 is connected to the other end of the switch 34 </ b> C, and the other end is connected to a different terminal of the setting voltage source 38. The output voltage of the terminal of the setting voltage source 38 to which the other end of the first MOS switch 36 is connected is higher than the output voltage of the terminal of the setting voltage source 38 to which the other end of the second MOS switch 37 is connected. . The output voltage of the terminal of the setting voltage source 38 to which the other end of the switch 35C is connected is lower than the output voltage of the terminal of the setting voltage source 38 to which the other end of the second MOS switch 37 is connected.

The inverting input terminal of the comparator 130 is connected to the terminal 101. The output terminal of the comparator 130 becomes the output terminal of the Schmitt trigger circuit 13.
The first inverter 39 has an input terminal connected to the output terminal of the logic latch circuit 15 (determination circuit), an output terminal connected to the PMOS gate electrode of the first MOS switch 36, and the second MOS switch 37. Connected to the gate electrode of the NMOS. The NMOS gate electrode of the first MOS switch 36 and the PMOS gate electrode of the second MOS switch 37 are connected to the output terminal of the logic latch circuit 15.

  The logic latch circuit 15 has a D input terminal connected to the output terminal of the comparator 130, a first flip-flop 51 that receives the first clock signal CK1 at the clock terminal, and an output from the comparator 130 at one input terminal. A two-input NOR logic circuit 52 that receives the signal and receives the output signal from the first flip-flop 51 at the other input terminal, a D input terminal receives the output signal from the NOR logic circuit 52, and a second at the clock terminal. And a second flip-flop 53 receiving the clock signal CK2. The output terminal of the second flip-flop 53 becomes the output terminal of the logic latch circuit 15.

A second inverter 19 as an output buffer that receives the output signal of the second flip-flop 53 is connected to the subsequent stage of the logic latch circuit 15 via the inverter 54. The output terminal of the second inverter 19 becomes the output terminal of the magnetic field sensor 1.
In Embodiment 1, the first memory element 17 and the second memory element 33 are capacitors. Hereinafter, the first memory element 17 and the second memory element 33 are referred to as a capacitor 17 and a capacitor 33, respectively.

Hereinafter, the operation of the magnetic field sensor configured as described above will be described.
FIG. 2 is a timing chart of a synchronization signal applied to the magnetic field sensor according to Embodiment 1 of the present invention. In FIG. 2, a state in which the first selection signal a is High, the second selection signal b is Low, the third selection signal c is High, and the fourth selection signal d is Low is a first period. A state in which the first selection signal a is Low, the second selection signal b is High, the third selection signal c is Low, and the fourth selection signal d is High is a second period. The third period is a state in which the first selection signal a is Low, the second selection signal b is High, the third selection signal c is High, and the fourth selection signal d is Low. A state in which the first selection signal a is High, the second selection signal b is Low, the third selection signal c is Low, and the fourth selection signal d is High is a fourth period.

  In the first period, the switches 21A, 22A, 23A, 24A, 18C, 34C, and 35C are turned on. In the first period, the switches 21A and 22A are turned on to apply a potential to the magnetoelectric conversion element 11, and the switches 23A and 24A are turned on to supply the output signal of the magnetoelectric conversion element 11 to the input terminal pair of the voltage amplifier 12. The voltage applied to the input terminal pair of the voltage amplifier 12 in the first period is the sum of the effective signal component and the offset signal component of the magnetoelectric transducer 11. Since the switch 18C is closed by the third selection signal c and the switch 20D is opened by the fourth selection signal d, the signal voltage amplified by the voltage amplifier 12 is applied to both ends of the capacitor 17.

  On the other hand, since the switches 34C and 35C are closed, the voltage of the voltage source 38 is applied to each terminal of the capacitor 33. The voltage source 38 outputs a voltage obtained by dividing the power supply voltage by the resistors 140 to 145. The voltage at the connection between the resistors 142 and 143 is applied to the other end of the switch 35C. A voltage is applied to the other end of the switch 34C via the first MOS switch 36 or the second MOS switch 37. When the voltage at the input of the first inverter 39 is high, the first MOS switch 36 is conductive, and when the voltage at the input of the first inverter 39 is low, the second MOS switch 37 is conductive. When the first MOS switch 36 is turned on, the voltage at the connection between the resistor 140 and the resistor 141 is applied to the switch 34C. When the second MOS switch 37 is turned on, the voltage at the connection between the resistor 141 and the resistor 142 is applied. In this way, a predetermined voltage is applied across the capacitor 33. The voltage applied across the capacitor 33 corresponds to a threshold value for detecting the strength of the detected magnetic field.

  In the second period, the switches 21A, 22A, 23A, 24A, 18C, 34C, and 35C are opened. The switches 21B and 22B are turned on to apply a potential to the magnetoelectric conversion element 11. The switches 23B and 24B are turned on, and the output signal of the magnetoelectric conversion element 11 is given to the input terminal pair of the voltage amplifier 12. On the other hand, since the switch 18C is opened by the third selection signal c and the switch 20D is closed by the fourth selection signal d, the signal voltage amplified by the voltage amplifier 12 is connected to the capacitor 17 and the capacitor 33 in series. Given to both ends.

  The polarity of the effective signal component applied to the input terminal pair of the voltage amplifier 12 in the second period is opposite to the polarity of the effective signal component applied to the input terminal pair of the voltage amplifier 12 in the first period. On the other hand, the polarity of the offset signal component of the magnetoelectric conversion element 11 is the same in the first period and the second period.

  When the switch 18C is opened, the voltage at the connection portion between the capacitor 17 and the inverted output terminal of the voltage amplifier 12 is relatively positive with respect to the connection portion (terminal 101) between the switch 18C and the capacitor 17. And In this state, the polarity of the voltage at the non-inverted output terminal is output with a positive value with respect to the inverted output terminal of the voltage amplifier 12. Accordingly, in the second period, the signal of the first period and the signal of the second period are added and output between the terminal 100 and the terminal 101. The voltage at the terminal 100 is higher than the voltage at the terminal 101.

  If the offset voltage of the voltage amplifier 12 is always present in the voltage extracted from the output terminal pair by amplifying the voltage of the input terminal pair of the voltage amplifier 12, the offset voltage of the switch 18C is changed between the first period and the second period. The polarity is opposite to both ends. The output voltage between the terminal 100 and the terminal 101 in the second period does not include this because the offset voltage component is substantially canceled. The offset signal component of the magnetoelectric conversion element 11 given to the input terminal pair of the voltage amplifier 12 has the same polarity in the first period and the second period. Between the output terminals 100 and 101, the offset signal component of the magnetoelectric conversion element 11 has a reverse polarity in the first period and the second period. The output voltage between the terminal 100 and the terminal 101 in the second period does not include this because the offset signal component is substantially canceled.

  In this way, in the output voltage between the terminal 100 and the terminal 101 in the second period, the offset voltage component of the magnetoelectric conversion element 11 and the voltage amplifier 12 is canceled, and the effective signal component is doubled.

Next, a voltage obtained by subtracting the voltage (threshold value) across the capacitor 33 from the sum of the output voltage of the voltage amplifier 12 and the voltage of the capacitor 17 is applied to the input terminal pair of the comparator 130.
When the voltage value given to the comparator 130 (the voltage value obtained by subtracting the voltage of the inverting leading terminal from the voltage of the non-inverting input terminal) is zero or more (for example, when a magnetic field of S polarity with an intensity higher than the threshold is detected), The comparator 130 outputs a High value that is one value of the binary voltage. Note that in the first period, the voltage across the capacitor 33 (the voltage obtained by subtracting the voltage at the inverting input terminal from the voltage at the non-inverting input terminal of the comparator 130) is negative, and the output of the comparator 130 is low. .

  In the third period, the switches 21B, 22B, 23B, 24B, 18C, 34C, and 35C are turned on. Similarly to the second period, the switches 21B and 22B are turned on to apply a potential to the magnetoelectric conversion element 11. The switches 23B and 24B are turned on, and the output signal of the magnetoelectric conversion element 11 is given to the input terminal pair of the voltage amplifier 12. Since the switch 18C is closed by the third selection signal c and the switch 20D is opened by the fourth selection signal d, the signal voltage amplified by the voltage amplifier 12 is applied to both ends of the capacitor 17.

  In the fourth period, the switches 21B, 22B, 23B, 24B, 18C, 34C, and 35C are opened. Similarly to the first period, the switches 21 </ b> A and 22 </ b> A are turned on to apply a potential to the magnetoelectric conversion element 11. The switches 23A and 24A are turned on, and the output signal of the magnetoelectric conversion element 11 is given to the input terminal pair of the voltage amplifier 12. Since the switch 18C is opened by the third selection signal c and the switch 20D is closed by the fourth selection signal d, the signal voltage amplified by the voltage amplifier 12 is applied to both ends of the series connection of the capacitor 17 and the capacitor 33. Given.

  The polarity of the effective signal component applied to the input terminal pair of the voltage amplifier 12 in the fourth period is opposite to the polarity of the effective signal component applied to the input terminal pair of the voltage amplifier 12 in the third period. On the other hand, the polarity of the offset signal component of the magnetoelectric conversion element 11 is the same in the third period and the fourth period.

  The polarity of the signal applied to the voltage amplifier 12 in the first and second periods and the polarity of the signal applied in the third and fourth periods are opposite to each other. If the voltage of the terminal 100 is lower than the voltage of the terminal 101 in the second period, the voltage of the terminal 100 is higher than the voltage of the terminal 101 in the fourth period. In the fourth period, the comparator 130 outputs High when the input voltage value is zero or more. When an S-polar magnetic field is detected in the second period, an N-polar magnetic field is detected in the fourth period. In either one of the second period and the fourth period, the time (detection cycle) from the first period to the fourth period is sufficiently shorter than the fluctuation period of the detection magnetic field to be detected. It can be determined whether or not the magnetic field strength of the detected magnetic field is greater than a predetermined value. The magnetic field sensor according to the first embodiment can determine whether the strength of the detected magnetic field is greater than a predetermined value regardless of the polarity of the detected magnetic field.

  The output of the comparator 130 is given to the logic latch circuit 15. The logic latch circuit 15 is supplied with the first clock signal CK1 and the second clock signal CK2 for latching the output signal of the comparator 130 within the second period and the fourth period, respectively. The logic latch circuit 15 latches the input signal when the clock signal falls.

  First, a value corresponding to the output state of the comparator 130 is held at the Q output of the first flip-flop 51 by the first clock signal CK1. The Q output signal and the output signal of the comparator 130 are applied to the NOR logic circuit 52. When both values are low, the output of the NOR logic circuit 52 is high. The output of the NOR logic circuit 52 is held at the output of the second flip-flop 53 by the second clock signal CK2.

  If the output of the comparator 130 is High in either the second or fourth period, the Q output signal of the second flip-flop 53 is Low. Further, if the output of the comparator 130 is Low in both the second and fourth periods, the Q output signal of the second flip-flop 53 is High. The Q output signal of the second flip-flop 53 is taken out as the output signal of the logic latch circuit 15.

The output signal of the logic latch circuit 15 includes an input part of the inverter 54, an input part of the first inverter 39 in the Schmitt trigger circuit 13, an NMOS gate electrode of the first MOS switch 36, and a PMOS of the second MOS switch 37. To the gate electrode. The output signal of the inverter 54 is given to the input part of the second inverter 19.
When the output of the logic latch circuit 15 is High, a current drive signal directed to the outside is taken out from the output of the second inverter 19. When the output of the logic latch circuit 15 is Low, a current signal directed from the outside to the output portion of the second inverter 19 is given.

  If the output of the logic latch circuit 15 is High, the voltage at the input of the first inverter 39 becomes High, the first MOS switch 36 is turned on, and the switch 34C connected to the first MOS switch 36 is connected. The voltage at the connection between the resistor 140 and the resistor 141 is applied to the other end of the resistor. When the output of the logic latch circuit 15 is Low, the voltage of the input part of the first inverter 39 becomes Low, the second MOS switch 37 becomes conductive, and the switch 34C connected to the second MOS switch 37 is connected. A voltage at a connection portion between the resistor 141 and the resistor 142 is given to the end.

  From the above, when no magnetic field (or magnetic flux) is detected in any of the second and fourth periods, the voltage at the connection of the resistors 140 and 141 is applied to one of the capacitors 33, and the second or fourth period. When the magnetic field (or magnetic flux) is detected at, the voltage at the connection portion of the resistors 141 and 142 is applied to one of the capacitors 33. Thus, by making the voltage value applied to one of the capacitors 33 different according to the output signal, the comparison level of the comparator 130 can be provided with hysteresis.

The magnetic field detection apparatus of the first embodiment can output a binary value indicating whether or not the intensity of the detected magnetic field is greater than a predetermined value regardless of the polarity of the detected magnetic field.
The magnetic field detection device according to the first embodiment gives a high hysteresis voltage to the comparator 130 in a state where no magnetic field is detected, and gives a low hysteresis voltage to the comparator 130 once detected. Therefore, the magnetic field can be detected stably.
Since the magnetic field detection apparatus of the first embodiment has only one voltage comparator, current consumption is small and the circuit scale is small.

<< Embodiment 2 >>
FIG. 3 is a circuit diagram showing a configuration of the magnetic field detection apparatus according to the second embodiment of the present invention. The magnetic field detection apparatus according to the first embodiment is obtained by replacing the magnetic field sensor 1 with the magnetic field sensor 2. The magnetic field sensor 2 of the second embodiment is obtained by replacing the logic latch circuit 15 of the magnetic field sensor 1 (FIG. 1) of the first embodiment with a logic latch circuit 150. In other respects, the magnetic field sensor of the second embodiment is the same as that of the first embodiment. In FIG. 3, the same blocks as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The output part of the comparator 130 of the Schmitt trigger circuit 13 is connected to the D input terminals of the first flip-flop 510 and the second flip-flop 511. The clock input terminal of the first flip-flop 510 is supplied with the first clock signal CK1. Further, the second clock signal CK <b> 2 is supplied to the clock input terminal of the second flip-flop 511. The Q output signals of the first flip-flop 510 and the second flip-flop 511 are supplied to the NOR logic circuit 520. When the signals detected by the first clock signal CK1 and the second clock signal CK2 are both low, the output of the logic latch circuit 150 is high. When one of the signals detected by the first clock signal CK1 and the second clock signal CK2 is High, the output of the logic latch circuit 150 is Low.

The magnetic field detection device of the second embodiment has the same effects as the magnetic field detection device of the first embodiment.
In the first and second embodiments, the magnetoelectric conversion element 11 is a Hall element, but may be a magnetoresistive element or other magnetoelectric conversion element.
In the magnetic field sensor 1 of the first embodiment and the magnetic field sensor 2 of the second embodiment, the magnetoelectric conversion element 11 and the second inverter 19 may be provided outside the magnetic field sensor.
The first switch unit 16 may be configured to include the signal generator 3.

  The magnetic field sensor, the magnetic field detection method, and the magnetic field detection device of the present invention are useful as a magnetic field sensor, a magnetic field detection method, and a magnetic field detection device that can detect the strength of the magnetic field without depending on the polarity of the magnetic field.

The block diagram which shows the structure of the magnetic field detection apparatus of Embodiment 1 of this invention. Timing chart of synchronization signal applied to magnetic field sensor of embodiment 1 and embodiment 2 of the present invention The block diagram which shows the structure of the magnetic field detection apparatus of Embodiment 2 of this invention. Configuration diagram showing a conventional magnetic field strength determination circuit that can handle both polarities

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Magnetic field sensor 3 Signal generator 4 1st selection signal generator 5 2nd selection signal generator 6 3rd selection signal generator 7 1st clock signal generator 8 2nd clock signal generator 9 Fourth selection signal generator 11 Magnetoelectric conversion element 12 Voltage amplifier 13 Schmitt trigger circuit 15, 150 Logic latch circuit (determination circuit)
16 switch circuit (first switch part)
17 1st memory element 18C switch (2nd switch part)
19 Second inverter 20D Switch (fifth switch part)
21A First switch (first switch element)
21B Second switch (second switch element)
22A Third switch (third switch element)
22B Fourth switch (fourth switch element)
23A Fifth switch (fifth switch element)
23B Sixth switch (sixth switch element)
24A Seventh switch (seventh switch element)
24B Eighth switch (eighth switch element)
33 Second storage element 34C Switch (third switch unit)
35C switch (fourth switch)
36 First MOS switch 37 Second MOS switch 38 Voltage source 39 First inverter 54 Inverter 51, 510 First flip-flop 52, 520 NOR logic circuit 53, 511 Second flip-flop 100, 101 Output terminal 101 Magnetoelectric conversion element 102 Voltage amplifier 103A First Schmitt trigger circuit 103B Second Schmitt trigger circuit 104 Logic latch circuit 130 Comparator 140-145 Resistance

Claims (20)

A signal corresponding to the applied magnetic field output from the magnetoelectric conversion element is input, and the polarity is reversed between the first period, the fourth period, the second period, and the third period of the signal from the outside. A first switch unit for switching and outputting,
An amplifier that amplifies the output signal of the first switch unit and outputs a signal to the output terminal pair;
A first storage element having both ends connected to the output terminal pair of the amplifier;
Inserted and connected between one of the output terminal pair and one terminal of the first memory element, closed in conjunction with the first period and the third period, the second period and the fourth period A second switch that opens in conjunction with the
In the second period, a signal having a first polarity corresponding to the magnitude of the applied magnetic field, which is at least one signal at both ends of the second switch unit, is output, and in the fourth period, A switch output terminal for outputting a signal having a polarity opposite to the first polarity corresponding to the magnitude of the applied magnetic field, at least one of the signals at both ends of the second switch unit;
A magnetic field sensor comprising: A magnetoelectric transducer that includes a first terminal pair and a second terminal pair and outputs a signal corresponding to an applied magnetic field;
A first terminal pair signal and a second terminal pair signal of the magnetoelectric conversion element, and an external signal defining the first, second, third, and fourth periods are input, and the first period And a first switch unit that outputs a signal of the first terminal pair of the magnetoelectric conversion element in the fourth period and outputs a signal of the second terminal pair of the magnetoelectric conversion element in the second period and the third period When,
An amplifier that amplifies the output signal of the first switch unit and outputs a signal to the output terminal pair;
A first storage element having both ends connected to the output terminal pair of the amplifier;
Inserted and connected between one of the output terminal pair and one terminal of the first memory element, closed in conjunction with the first period and the third period of the signal applied from the outside, and the second period and the fourth period A second switch that opens in conjunction with the period of
A switch output terminal for outputting at least one signal at both ends of the second switch section;
A magnetic field sensor comprising: The magnetic field sensor according to claim 2.
The magnetic field sensor, wherein the second switch section includes an output terminal pair. The magnetic field sensor according to claim 2, further comprising:
A magnetic field sensor comprising a comparator that inputs a signal from the switch output terminal and outputs a result of comparison with a predetermined value. 5. The magnetic field sensor according to claim 4, wherein different voltages are added to the signal at the switch output terminal according to the output signal of the comparator. 3. The magnetic field sensor according to claim 2, wherein a first period and a third period of a signal supplied from the outside are inserted and connected between one terminal of the second switch unit and one input terminal of the comparator. And a fifth switch portion that opens in conjunction with the second period and closes in conjunction with the second period and the fourth period, and one of the two ends of the second switch section is input to the comparator through the fifth switch section. A magnetic field sensor, wherein the magnetic field sensor is connected to one of a pair of terminals, and the other of the second switch sections is connected to the other of the pair of comparator input terminals via a second storage element. The magnetic field sensor according to claim 6, further comprising:
A third switch unit having one end connected to one of both ends of the second storage element;
A fourth switch unit having one end connected to the other of the two ends of the second storage element;
A voltage source for applying a first voltage to the other of the third switch units;
A voltage source that applies a voltage different from the first voltage value to the other of the fourth switch units,
The magnetic field sensor, wherein the third and fourth switch portions are closed during the first period of the signal. 8. The magnetic field sensor according to claim 7, wherein one of the first voltage value and the second voltage value is made different according to a signal given from outside. In the magnetic field sensor of claim 2, wherein the magnetic field sensor, wherein the first storage element is a capacitor. 8. The magnetic field sensor according to claim 7, wherein the second memory element is a capacitor. The magnetic field sensor according to claim 2, further comprising:
A magnetic field sensor comprising: a determination circuit that inputs a signal from the switch output terminal and outputs a signal obtained by determining a signal value of a second period and a fourth period of a signal supplied from the outside. The magnetic field sensor according to claim 11, wherein the determination circuit includes:
The comparator output terminal signal is input to the D input terminal, the first clock signal is input to the clock input terminal, and the signal is held and output to the Q output terminal within the second period. Flip-flops,
A NOR logic circuit that individually inputs the comparator output terminal and the Q output terminal of the first flip-flip to an input terminal pair and outputs a NOR logic output;
A second flip-flop that inputs the output of the NOR logic circuit to the D input terminal, inputs the second clock signal to the clock input terminal, holds the signal within the fourth period, and outputs it to the output terminal With
A magnetic field sensor for outputting a second flip-flop output terminal signal. The magnetic field sensor according to claim 11, wherein the determination circuit includes:
The comparator output terminal signal is input to the D input terminal, the first clock signal is input to the clock input terminal, and the signal is held and output to the Q output terminal within the second period. Flip-flops,
A signal at the comparator output terminal is input to the D input terminal, a second clock signal is input to the clock input terminal, and the signal is held and output to the output terminal within the fourth period. Flip-flops,
A NOR logic circuit that individually inputs Q outputs of the first and second flip-flops to an input terminal pair and outputs a NOR logic output;
A magnetic field sensor which outputs the NOR logic circuit output. The magnetic field sensor according to claim 2.
The first switch unit is
A first voltage terminal for outputting a first voltage;
A second voltage terminal for outputting a second voltage;
First, second, third and fourth input terminals;
First and second output terminals;
A first switch element that is inserted and connected between the first voltage terminal and the first input terminal and that opens and closes in response to an external signal;
A second switch element inserted and connected between the first voltage terminal and the second input terminal, and opened and closed according to a signal given from the outside;
A third switch element inserted and connected between the second voltage terminal and the third input terminal and opened and closed according to a signal given from the outside;
A fourth switch element inserted and connected between the second voltage terminal and the fourth input terminal, and opened and closed according to a signal given from the outside;
A fifth switch element that is inserted and connected between the first output terminal and the first input terminal and that opens and closes in response to a signal applied from the outside;
A sixth switch element that is inserted and connected between the first output terminal and the second input terminal and that opens and closes in response to a signal applied from the outside;
A seventh switch element that is inserted and connected between the second output terminal and the third input terminal and that opens and closes in response to a signal applied from the outside;
An eighth switch element that is inserted and connected between the second output terminal and the fourth input terminal and that opens and closes in response to a signal given from the outside;
One of the first terminal pairs of the magnetoelectric transducer is connected to the first input terminal;
One of the second terminal pairs of the magnetoelectric transducer is connected to the second input terminal;
Connecting the other of the first terminal pair of the magnetoelectric transducer to the third input terminal;
The magnetic field sensor, wherein the other of the second terminal pair of the magnetoelectric transducer is connected to the fourth input terminal. 15. The magnetic field sensor according to claim 14, wherein the first, third, sixth, and eighth switch elements are closed during first and fourth periods of an externally applied signal, and the second, fourth, fifth, and The magnetic field sensor, wherein the seventh switch is closed during the second and third periods of the signal applied from the outside. The magnetic field sensor according to claim 2, wherein the magnetoelectric conversion element is a Hall element. The magnetic field sensor according to claim 2, wherein the magnetoelectric conversion element is a magnetic resistance. A first selection signal generator for generating a first selection signal in a first period and a fourth period;
A second selection signal generator for generating a second selection signal in the second period and the third period;
A third selection signal generator for generating a third selection signal in the first period and the third period;
A fourth selection signal generator for generating a fourth selection signal in the second period and the fourth period;
A magnetoelectric transducer that includes a first terminal pair and a second terminal pair and outputs a signal corresponding to an applied magnetic field;
The first terminal pair signal and the second terminal pair signal of the magnetoelectric transducer, and the first selection signal and the second selection signal are individually input, and the first period and the fourth period are input. A first switch unit that outputs a signal of the first terminal pair of the magnetoelectric conversion element to a second terminal and a signal of the second terminal pair of the magnetoelectric conversion element in a second period and a third period;
An amplifier that amplifies the output signal of the first switch unit and outputs a signal to the output terminal pair;
A first storage element having both ends connected to the output terminal pair of the amplifier;
Inserted and connected between one of the output terminal pairs and one terminal of the first memory element, inputs the third selection signal, closes in the first period and the third period, the second period and the second period A second switch portion that opens during a period of 4;
A fifth switch which is connected to one terminal of the second switch unit, inputs a fourth selection signal, opens in the first period and the third period, and closes in the second period and the fourth period; And
A comparator that inputs the voltage of at least one of both ends of the second switch unit via the fifth switch unit and outputs a result of comparison with a predetermined value;
A determination circuit that outputs a logical sum signal of the output signal of the comparator in a second period and the output signal of the comparator in a fourth period;
A magnetic field detection device comprising: A signal corresponding to the applied magnetic field output from the magnetoelectric conversion element is input, and the signals are switched so as to have opposite polarities in the first period, the fourth period, the second period, and the third period. A switching step to
An amplification step of amplifying and outputting the signal output in the switching step;
A holding step of holding the voltage output in the amplification step in the first storage element in the first period and the third period;
An addition step of adding a signal component corresponding to the magnetic field of the voltage output in the amplification step and the voltage held in the first storage element in the second period and the fourth period;
A comparison step of inputting an addition voltage in the addition step having opposite polarities to each other in the second period and the fourth period, and outputting a result of comparison with a predetermined value;
A determination step of outputting a logical sum signal of the output signal of the comparison step in the second period and the output signal of the comparison step in the fourth period;
A magnetic field detection method comprising: The signal generator which outputs the signal which determines the said 1st, 2nd, 3rd, and 4th period to the said 1st switch part is further provided, The Claim 1 or Claim 2 characterized by the above-mentioned. Magnetic field sensor.

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