Magnetic sensors, encoders and servo motors

Abstract

To provide a magnetic sensor capable of operating stably with less electric power.SOLUTION: Provided is a magnetic sensor comprising: a Hall element having first and second drive terminals and first and second detection terminals, and outputting a voltage, which is proportionate to a magnetic flux density across a drive current flowing from the first drive terminal to the second drive terminal, between the first and second detection terminals; a drive circuit for supplying the drive current to the Hall element; a signal processing circuit provided with a power supply terminal connected to the second drive terminal, for amplifying the voltage and processing the signal that corresponds to the amplified voltage; and a variable capacitance capacitor circuit connected to the second drive terminal, which a portion of the drive current flows to.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a magnetic sensor, an encoder, and a servo motor. [Background technology]

[0002] Patent Document 1 discloses a magnetic sensor in which one end of a magnetoelectric conversion element is connected to an output electrode of a constant current source and the other end is connected to a positive power supply electrode of one or more signal processing circuits etc. built into the magnetic sensor. Patent Document 1 discloses that the magnetoelectric conversion element and the signal processing circuit are connected in series to a voltage source.

[0003] Patent Document 2 discloses a position detector including a pulse wire. Patent Document 2 discloses that the position detector operates without external energy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2016-011878 [Patent Document 2] Special Publication No. 2006-523822 Summary of the Invention [Problem to be solved by the invention]

[0005] In the magnetic sensor described in Patent Document 1, a current imbalance occurs between the magnetoelectric conversion element and the signal processing circuit, which may reduce the stability of the operation of the magnetoelectric conversion element or the signal processing circuit. When operating without external energy, as in the position detector described in Patent Document 2, it is desirable to effectively utilize the generated energy.

[0006] An object of the present disclosure is to provide a magnetic sensor that can operate stably with low power consumption. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided a magnetic sensor comprising: a Hall element having first and second drive terminals and first and second detection terminals, and outputting a voltage between the first and second detection terminals that is proportional to the magnetic flux density across a drive current flowing from the first drive terminal to the second drive terminal; a drive circuit that supplies the drive current to the Hall element; a signal processing circuit that has a power supply terminal connected to the second drive terminal, amplifies the voltage, and processes a signal corresponding to the amplified voltage; and a variable capacitance capacitor circuit that is connected to the second drive terminal and through which a portion of the drive current flows. [Effects of the Invention]

[0008] The magnetic sensor of the present disclosure can operate stably with little power. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a servo motor system using an encoder according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the configuration of a servo motor using the encoder according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 7] FIG. 7 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the circuit configuration of the encoder according to the first embodiment. [Figure 9]FIG. 9 is a diagram illustrating the circuit configuration of an encoder according to the second embodiment. [Figure 10] FIG. 10 is a diagram illustrating the circuit configuration of an encoder according to the second embodiment. [Figure 11] FIG. 11 is a diagram illustrating the circuit configuration of an encoder according to the third embodiment. [Figure 12] FIG. 12 is a diagram illustrating the circuit configuration of an encoder according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, each embodiment of the present invention will be described with reference to the accompanying drawings. Note that, in the description of the specification and drawings relating to each embodiment, components having substantially the same or corresponding functional configurations may be designated by the same reference numerals, and redundant description may be omitted. Also, for ease of understanding, the scale of each part in the drawings may differ from the actual scale.

[0011] First Embodiment <Servo motor system 1> First, a description will be given of a servo motor system using an encoder 12 according to the first embodiment. Fig. 1 is a diagram illustrating a servo motor system 1 using an encoder 12 according to the first embodiment.

[0012] The servo motor system 1 includes a servo motor 10 and a servo controller 20. The servo controller 20 acquires at least one of position information and rotation information of the rotation shaft 11a from the servo motor 10. The servo controller 20 controls the servo motor 10 using at least one of the acquired position information and rotation information.

[0013] The servo motor 10 includes a motor 11 and an encoder 12. The motor 11 is connected to a servo controller 20 via a wire L1. The encoder 12 is connected to the servo controller 20 via a wire L2.

[0014] The motor 11 rotates the rotary shaft 11a in the direction of the arrow AR based on a command from the servo controller 20. Specifically, the motor 11 rotates the rotary shaft 11a based on power supplied from the servo controller 20. The servo controller 20 controls the motor 11 by supplying controlled power from a wiring L1. The motor 11 is, for example, an alternating current (AC) motor, a direct current (DC) motor, or the like.

[0015] The encoder 12 detects at least one of position information and rotation information of the rotating shaft 11a of the motor 11. The encoder 12 outputs the detected at least one of the position information and rotation information to the servo controller 20 via the wiring L2. The position information of the rotating shaft 11a is, for example, the angle of the rotation direction of the rotating shaft 11a. The rotation information of the rotating shaft 11a is, for example, the rotation speed of the rotating shaft 11a.

[0016] <Servo motor 10> Next, a description will be given of the configuration of the servo motor 10 using the encoder 12 according to the first embodiment. Fig. 2 is a diagram illustrating the configuration of the servo motor 10 using the encoder 12 according to the first embodiment.

[0017] [Motor 11] The motor 11 includes a disk 11d provided on the rotary shaft 11a facing the encoder 12, and a magnet 11m provided on the disk 11d. In addition to the rotary shaft 11a, the disk 11d, and the magnet 11m, the motor 11 also includes well-known elements such as bearings that support the rotary shaft 11a, windings that form a stator for rotating the rotary shaft 11a, an iron core, and permanent magnets that form a rotor, but a description of these elements will be omitted here.

[0018] Disk 11d is fixed to rotating shaft 11a. Disk 11d rotates together with rotating shaft 11a as rotating shaft 11a rotates in the direction of arrow AR. Magnet 11m is fixed to the surface of disk 11d on the encoder 12 side.

[0019] The magnet 11m is a permanent magnet made of neodymium or the like. The magnet 11m is provided so as to have an N pole and an S pole in a direction parallel to the surface of the disk 11d. When the magnet 11m rotates together with the disk 11d, the magnetic field on the encoder 12 side changes.

[0020] [Encoder 12] The encoder 12 detects at least one of position information and rotation information of the rotating shaft 11a based on the magnetic field that changes with the rotation of the magnet 11m. The encoder 12 also generates the power required to operate the encoder 12 based on the magnetic field that changes with the rotation of the magnet 11m.

[0021] Encoder 12 includes power generation unit 12g that generates power from a changing magnetic field, and Hall elements 12h1, 12h2, and 12h3 that measure the magnetic field. Power generation unit 12g, Hall elements 12h1, 12h2, and 12h3 are provided on the motor 11 side of encoder 12 so as to be easily affected by the magnetic field generated by magnet 11m.

[0022] [Generator 12g] The power generation unit 12g is, for example, a Wiegand wire, which is an energy harvest generator (EHG). The Wiegand wire generates a power generation pulse near the zero point where the external magnetic field reverses, regardless of the rate of change of the external magnetic flux. Therefore, the Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a.

[0023] By using an environmental power generator in the power generation unit 12g, the encoder 12 does not require a battery or external power source. In other words, the encoder 12 is a battery-less encoder. Because Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a, it is suitable for use as the power generation unit 12g of the encoder 12, which is a battery-less encoder.

[0024] [Hall element 12h1, Hall element 12h2, and Hall element 12h3] Each of the Hall elements 12h1, 12h2, and 12h3 detects a magnetic field that crosses a semiconductor element through which a drive current flows. In the encoder 12, each of the Hall elements 12h1, 12h2, and 12h3 mainly detects a magnetic field generated by the magnet 11m. Each of the Hall elements 12h2 and 12h3 is made of a semiconductor element such as indium antimonide (InSb) or gallium arsenide (GaAs).

[0025] As shown in Fig. 4 for Hall element 12h1, each of Hall elements 12h1, 12h2, and 12h3 includes a first drive terminal 12ha and a second drive terminal 12hb, and a first detection terminal 12hp and a second detection terminal 12hm. A drive current flows from the first drive terminal 12ha to the second drive terminal 12hb in each of Hall elements 12h1, 12h2, and 12h3. Each of Hall elements 12h1, 12h2, and 12h3 outputs a voltage between the first detection terminal 12hp and the second detection terminal 12hm that is proportional to the drive current and the magnetic flux density across the drive current.

[0026] Each of the Hall elements 12h1, 12h2, and 12h3 outputs a magnetic field detection signal to the signal processing circuit 12c (see FIG. 2). A constant current is supplied to each of the Hall elements 12h1, 12h2, and 12h3 from the drive circuit 12b. The current output of each of the Hall elements 12h1, 12h2, and 12h3 is connected to a positive power supply terminal V+ of the signal processing circuit 12c. The positive power supply terminal V+ of the signal processing circuit 12c is an example of a power supply terminal of the signal processing circuit 12c.

[0027] Each of the Hall elements 12h1, 12h2, and 12h3 is supplied with a current that is generated by the power generating unit 12g, rectified by the rectifier circuit 12a, and then made constant by the drive circuit 12b. The currents flowing out of each of the Hall elements 12h1, 12h2, and 12h3 are supplied to the signal processing circuit 12c.

[0028] By inputting the currents flowing out from the Hall elements 12h1, 12h2, and 12h3 to the signal processing circuit 12c, the encoder 12 can effectively utilize the power generated by the power generation unit 12g, which is an environmental power generator. Also, the encoder 12 can increase the drive currents supplied to the Hall elements 12h1, 12h2, and 12h3, respectively, compared to when the signal processing circuit 12c is connected in parallel with the Hall elements 12h1, 12h2, and 12h3.

[0029] The encoder 12 can improve the signal-to-noise ratio and sensitivity of each of the Hall elements 12h1, 12h2, and 12h3 by increasing the drive current supplied to each of the Hall elements 12h1, 12h2, and 12h3. Furthermore, the encoder 12 can reduce the power consumption of the entire circuit.

[0030] In the above description, the encoder 12 is provided with three Hall elements, but the number of Hall elements is not limited to 3. The encoder 12 may be provided with one or two Hall elements, or may be provided with four or more Hall elements.

[0031] The encoder 12 includes a rectifier circuit 12a, a drive circuit 12b, a signal processing circuit 12c, a variable capacitor circuit 12d, and a current bypass circuit 12e. Each element will be described in detail below with reference to the diagrams of Figures 3 to 8 illustrating the circuit configuration of the encoder 12 according to the first embodiment.

[0032] The Hall elements 12h1, 12h2, and 12h3, the drive circuit 12b, the signal processing circuit 12c, the variable capacitor circuit 12d, and the current bypass circuit 12e are collectively referred to as the magnetic sensor 12m. That is, the encoder 12 includes the magnetic sensor 12m. The magnetic sensor 12m may include at least either the variable capacitor circuit 12d or the current bypass circuit 12e.

[0033] [Rectifier circuit 12a] Rectifier circuit 12a rectifies the power generated by power generating unit 12g to generate a positive voltage. Rectifier circuit 12a includes full-wave rectifier circuit 12a1 and smoothing capacitor 12a2.

[0034] The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses generated by the power generating unit 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, when the power generating unit 12g is a Wiegand wire, the power generating unit 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generating unit 12g into positive pulses.

[0035] The smoothing capacitor 12a2 smoothes the positive pulses generated by the full-wave rectifier circuit 12a1. The smoothing capacitor 12a2 is provided between the output terminal of the full-wave rectifier circuit 12a1 and ground. By smoothing the positive pulses by the smoothing capacitor 12a2, a voltage of a substantially constant voltage value is output from the rectifier circuit 12a to the line Lv. The line Lv has a potential difference VT with respect to the ground.

[0036] [Driver circuit 12b] The drive circuit 12b converts the power supplied from the rectifier circuit 12a into a drive current and supplies it to each of the Hall elements 12h1, 12h2, and 12h3. The drive circuit 12b includes a constant current circuit 12b1 and a current mirror circuit 12b2.

[0037] The encoder 12 includes, between the wiring Lv and the wiring Lm, a current mirror circuit 12b2, a Hall element 12h1, and a constant current circuit 12b1, in this order from the wiring Lv. The encoder 12 also includes, between the wiring Lv and the wiring Lm, a current mirror circuit 12b2, and a Hall element 12h2 or a Hall element 12h3, in this order from the wiring Lv. The wiring Lv has a potential difference VH with respect to the wiring Lm.

[0038] The encoder 12 detects the positional relationship with the relatively moving magnet based on the magnitude of the output voltages of the Hall elements 12h1, 12h2, and 12h3. Therefore, it is desirable that a constant, equal-value drive current flows through each of the Hall elements 12h1, 12h2, and 12h3. The encoder 12 includes a constant current circuit 12b1 that supplies a constant current to the Hall element 12h1. The encoder 12 also includes a current mirror circuit 12b2 that uses the drive current from the constant current circuit 12b1 as a reference to supply a constant, equal-value drive current to each of the Hall elements 12h1, 12h2, and 12h3.

[0039] (Constant current circuit 12b1) The constant current circuit 12b1 supplies drive power to the Hall element 12h1 so that a constant current flows as a drive current through the Hall element 12h1. Fig. 7 is a diagram showing the circuit configuration of the constant current circuit 12b1.

[0040] Constant current circuit 12b1 includes transistor 12b11, current detection resistor 12b12, and differential amplifier 12b13. Constant current circuit 12b1 also includes resistor 12b14, Zener diode 12b15, and capacitor 12b16.

[0041] Transistor 12b11 is controlled so that a constant current flows through Hall element 12h1. The gate terminal of transistor 12b11 is connected to the output terminal of differential amplifier 12b13. Differential amplifier 12b13 outputs a voltage based on the potential difference between the positive terminal and the negative terminal from its output terminal. Constant current circuit 12b1 is controlled so that a constant current based on the voltage input to the positive terminal and the resistance value of current detection resistor 12b12 flows between the source and gate of transistor 12b11.

[0042] Although the encoder 12 according to this embodiment includes the constant current circuit 12b1 on the low-voltage side of the Hall element 12h1, the constant current circuit 12b1 may also be provided on the high-voltage side of the Hall element 12h1. That is, the encoder 12 may include, between the wiring Lv and the wiring Lm, the current mirror circuit 12b2, the constant current circuit 12b1, and the Hall element 12h1, in this order from the wiring Lv.

[0043] (Current mirror circuit 12b2) The current mirror circuit 12b2 is a circuit that passes a drive current of the same magnitude as the drive current flowing through the Hall element 12h1, i.e., a mirror current based on the drive current flowing through the Hall element 12h1, through the Hall elements 12h2 and 12h3. The encoder 12 includes a constant current circuit 12b1 for the Hall element 12h1. The encoder 12 uses the current mirror circuit 12b2 to pass a drive current of the same magnitude as the drive current flowing through the Hall element 12h1 through the Hall elements 12h2 and 12h3. By using the current mirror circuit 12b2, the encoder 12 can reduce the overall circuit size.

[0044] 8 is a diagram showing the circuit configuration of the current mirror circuit 12b2. The current mirror circuit 12b2 includes a transistor 12b21, a transistor 12b22, and a transistor 12b23. The emitter terminals of the transistors 12b21, 12b22, and 12b23 are connected to a line Lv. The collector terminals of the transistors 12b21, 12b22, and 12b23 are connected to the drive terminals of the Hall elements 12h1, 12h2, and 12h3, respectively.

[0045] The base terminals of the transistors 12b21, 12b22, and 12b23 are connected to each other, and the base terminal of the transistor 12b21 is connected to the collector terminal of the transistor 12b21.

[0046] The transistors 12b21, 12b22, and 12b23 connected as described above make the values ​​of the drive currents flowing through the Hall elements 12h1, 12h2, and 12h3 equal to each other.

[0047] The Hall element 12h1 is an example of a first Hall element, and the Hall element 12h2 or the Hall element 12h3 is an example of a second Hall element.

[0048] [Signal processing circuit 12c] The signal processing circuit 12c uses the detection results of the Hall elements 12h1, 12h2, and 12h3 to detect at least one of position information and rotation information regarding the rotating shaft 11a of the motor 11. Fig. 4 is a diagram illustrating the circuit configuration of the signal processing circuit 12c.

[0049] The positive power supply terminal V+ of the signal processing circuit 12c is connected to the wiring Lm. That is, the positive power supply terminal V+ of the signal processing circuit 12c is connected to the second drive terminals 12hb of the Hall elements 12h1, 12h2, and 12h3. The wiring Lm has a potential difference VL with respect to the ground.

[0050] The connection of the positive power supply terminal V+ of the signal processing circuit 12c to the second drive terminal 12hb includes both a case where the positive power supply terminal V+ is directly connected to the second drive terminal 12hb and a case where the positive power supply terminal V+ is indirectly connected to the second drive terminal 12hb via a circuit. For example, even when the positive power supply terminal V+ of the signal processing circuit 12c is connected to the second drive terminal 12hb of the Hall element 12h1 via the constant current circuit 12b1, the positive power supply terminal V+ of the signal processing circuit 12c is still said to be connected to the second drive terminal 12hb of the Hall element 12h1.

[0051] The signal processing circuit 12c includes a logic circuit 12c1, a plurality of differential amplifiers 12c2, and a plurality of comparators 12c3, the number of which is equal to the number of Hall elements.

[0052] (Logic circuit 12c1) Based on the input from comparator 12c3, logic circuit 12c1 detects at least one of position information and rotation information, such as the rotation position and rotation speed, of rotating shaft 11a of motor 11. Furthermore, logic circuit 12c1 records at least one of the detected position information and rotation information of rotating shaft 11a of motor 11, or transmits it to an external control system, for example, servo controller 20.

[0053] Logic circuit 12c1 is, for example, a microcomputer, an ASIC (application specific integrated circuit), etc. Logic circuit 12c1 may also be, for example, an FPGA (field-programmable gate array), a PLD (programmable logic device), etc. Furthermore, logic circuit 12c1 may include a nonvolatile memory such as a ferroelectric memory.

[0054] To supply power for operating the logic circuit 12c1, the logic circuit 12c1 includes a positive power supply terminal V+ and a negative power supply terminal V-. The positive power supply terminal V+ of the logic circuit 12c1 is connected to the wiring Lm. That is, the positive power supply terminal V+ of the logic circuit 12c1 is connected to the second drive terminals 12hb of the Hall elements 12h1, 12h2, and 12h3. The negative power supply terminal V- of the logic circuit 12c1 is grounded.

[0055] (Differential amplifier 12c2) Each of the differential amplifiers 12c2 amplifies the voltage between the first detection terminal 12hp and the second detection terminal 12hm of each of the Hall elements 12h1, 12h2, and 12h3, and outputs the amplified voltage to the corresponding comparator 12c3.

[0056] To supply power for operating the differential amplifier 12c2, the differential amplifier 12c2 has a positive power supply terminal V+ and a negative power supply terminal V-. The positive power supply terminal V+ of the differential amplifier 12c2 is connected to the wiring Lm. That is, the positive power supply terminal V+ of the differential amplifier 12c2 is connected to the second drive terminals 12hb of the Hall elements 12h1, 12h2, and 12h3. The negative power supply terminal V- of the differential amplifier 12c2 is grounded.

[0057] (Comparator 12c3) Each of the plurality of comparators 12c3 compares the output of the corresponding differential amplifier 12c2 with a reference voltage ref and outputs the comparison result to the logic circuit 12c1. The comparator 12c3 binarizes the output of the corresponding differential amplifier 12c2.

[0058] Each comparator 12c3 has a positive power supply terminal V+ and a negative power supply terminal V- to supply power for operating it. The positive power supply terminal V+ of the comparator 12c3 is connected to the wiring Lm. That is, the positive power supply terminal V+ of the comparator 12c3 is connected to the second drive terminals 12hb of the Hall elements 12h1, 12h2, and 12h3. The negative power supply terminal V- of the comparator 12c3 is grounded.

[0059] [Variable capacitor circuit 12d] In the encoder 12, the power consumed by the Hall elements 12h1, 12h2, and 12h3 and the drive circuit 12b provided between the wires Lv and Lm is different from the power consumed by the signal processing circuit 12c provided between the wire Lm and the ground. Therefore, it is necessary to consider the case where the power consumed between the wires Lv and Lm is different from the power consumed between the wire Lm and the ground.

[0060] A case will be described in which the power consumed by Hall elements 12h1, 12h2, and 12h3 and drive circuit 12b in encoder 12 is greater than the power consumed by signal processing circuit 12c. Encoder 12 includes variable capacitor circuit 12d for storing surplus power not consumed by signal processing circuit 12c. Figure 5 is a diagram showing the circuit configuration of variable capacitor circuit 12d.

[0061] A portion of the drive current flowing through the Hall elements 12h1, 12h2, and 12h3 flows through the variable capacitor circuit 12d. The variable capacitor circuit 12d is a circuit that changes its capacitance depending on the voltage applied to its internal capacitor. The variable capacitor circuit 12d in FIG. 5 switches between two levels of capacitance. The variable capacitor circuit 12d increases its capacitance when the voltage applied to its internal capacitor exceeds a predetermined voltage value.

[0062] In the encoder 12, when the power consumed by the Hall elements 12h1, 12h2, and 12h3 and the drive circuit 12b is greater than the power consumed by the signal processing circuit 12c, the voltage on the line Lm increases. When the voltage on the line Lm increases, the variable capacitor circuit 12d increases its capacitance, allowing the encoder 12 to efficiently store surplus power in the variable capacitor circuit 12d. Furthermore, when the power consumption in the signal processing circuit 12c increases, the encoder 12 can supply power from the variable capacitor circuit 12d to the signal processing circuit 12c.

[0063] The variable capacitor circuit 12d includes a capacitor 12d1 and a capacitor 12d2. The capacitor 12d1 has a small capacitance. The capacitor 12d2 has a larger capacitance than the capacitor 12d1. When the voltage applied to the capacitors is lower than a predetermined voltage, the variable capacitor circuit 12d has the capacitance of the capacitor 12d1. When the voltage applied to the capacitors is higher than the predetermined voltage, the variable capacitor circuit 12d has the capacitance obtained by adding the capacitances of the capacitors 12d1 and 12d2.

[0064] The variable capacitor circuit 12d includes transistors 12d3 and 12d4, and resistors 12d6, 12d7, 12d8, and 12d9 for changing the capacitance, and a diode 12d5 for discharging the capacitor 12d2.

[0065] In the variable capacitor circuit 12d, when the voltage on the line Lm is lower than the set voltage, the transistors 12d3 and 12d4 are turned off, and therefore the variable capacitor circuit 12d is a circuit including the capacitor 12d1 between the line Lm and the ground.

[0066] The set voltage is determined by the voltage divided by resistors 12d6 and 12d7 and the voltage at which transistor 12d3 turns on. When the voltage on line Lm becomes higher than the set voltage, transistor 12d3 turns on. When transistor 12d3 turns on, transistor 12d4 turns on due to the voltage divided by resistors 12d8 and 12d9. When transistor 12d4 turns on, variable capacitor circuit 12d becomes a circuit in which capacitors 12d1 and 12d2 are connected in parallel between line Lm and ground.

[0067] Furthermore, when the voltage of the capacitor 12d2 becomes higher than the voltage of the capacitor 12d1, the power stored in the capacitor 12d2 is discharged from the capacitor 12d2 via the diode 12d5.

[0068] As described above, the variable capacitor circuit 12d can realize a power storage device (variable capacitor) whose capacitance changes depending on the voltage level of the line Lm.

[0069] Although the variable capacitor circuit 12d uses a total of two capacitors, the capacitor 12d1 and the capacitor 12d2, the number of capacitors is not limited to two, and three or more capacitors may be provided.

[0070] [Current bypass circuit 12e] Next, a case will be described in which the power consumed by the signal processing circuit 12c in the encoder 12 is greater than the power consumed by the Hall elements 12h1, 12h2, and 12h3 and the drive circuit 12b. The encoder 12 includes a current bypass circuit 12e for bypassing the power (current) shortage in the signal processing circuit 12c in the Hall elements 12h1, 12h2, and 12h3 and the drive circuit 12b. Figure 6 is a diagram showing the circuit configuration of the current bypass circuit 12e.

[0071] The current bypass circuit 12e is a circuit that bypasses the Hall elements 12h1, 12h2, and 12h3 when the power consumed by the signal processing circuit 12c becomes insufficient.

[0072] For example, if the current consumption of the signal processing circuit 12c momentarily increases, power is supplied from the variable capacitor circuit 12d, for example. However, if the power supply from the variable capacitor circuit 12d is not enough, the voltage of the signal processing circuit 12c drops due to the current shortage.

[0073] When the signal processing circuit 12c is short of power, the encoder 12 uses the current bypass circuit 12e to create a current bypass route that does not flow through the Hall elements 12h1, 12h2, and 12h3, and supplies the desired power to the signal processing circuit 12c.

[0074] The current bypass circuit 12e controls the voltage of the line Lm to a predetermined voltage value. The current bypass circuit 12e includes a differential amplifier 12e1, a transistor 12e2, and a diode 12e3. The encoder 12 also includes a Zener diode 12f that is connected to the line Lv via a resistor 12r and is grounded. The positive terminal of the differential amplifier 12e1 is connected to the terminal of the Zener diode 12f on the line Lv side. The negative terminal of the differential amplifier 12e1 is connected to the line Lm.

[0075] The differential amplifier 12e1 controls the transistor 12e2 to pass a current from the line Lv to the line Lm via the transistor 12e2 so that the potential of the line Lm coincides with the potential of the Zener diode 12f on the line Lv side. Then, the current bypass circuit 12e allows a current to flow from the line Lv to the line Lm, bypassing the Hall elements 12h1, 12h2, and 12h3.

[0076] The diode 12e3 is a diode for preventing backflow.

[0077] <Actions and Effects> The encoder 12 (magnetic sensor 12m) according to the first embodiment includes the variable capacitor circuit 12d or the current bypass circuit 12e, which can eliminate the imbalance in power consumption between the Hall element connected in series to the power supply and the signal processing circuit that processes the signal from the Hall element. Therefore, the encoder 12 (magnetic sensor 12m) according to the first embodiment can operate stably with little power.

[0078] For example, if the sum of the currents flowing through the Hall element and the drive circuit that drives the Hall element is smaller than the current used in the signal processing circuit, the voltage required for the signal processing circuit cannot be secured. Also, when the current required for the signal processing circuit is needed, the current required for the signal processing circuit will be insufficient due to the Hall element and the drive circuit that drives the Hall element.

[0079] According to the encoder 12 (magnetic sensor 12m) of the first embodiment, when there is surplus power consumed by the signal processing circuit 12c, the power can be stored in the variable capacitor circuit 12d, whose capacitance changes depending on the voltage. Therefore, the surplus power can be reused without being wasted. Furthermore, according to the encoder 12 of the first embodiment, when power is required by the signal processing circuit 12c, a drop in the voltage of the power supplied to the signal processing circuit 12c can be detected, and the Hall element can be bypassed to supply the power to the signal processing circuit 12c.

[0080] According to the encoder 12 (magnetic sensor 12m) of this embodiment, even if there is an imbalance in power consumption between the Hall element and the signal processing circuit that processes the signal from the Hall element, the imbalance can be eliminated and the encoder 12 can operate. Furthermore, according to the encoder 12 of this embodiment, the Hall element and the signal processing circuit that processes the signal from the Hall element can operate with power efficiency by using a common current.

[0081] In the above description, the Hall element is provided on the side with a higher potential and the signal processing circuit is provided on the side with a lower potential, but the order is not limited to the above. For example, the Hall element may be provided on the side with a lower potential and the signal processing circuit on the side with a higher potential.

[0082] Furthermore, although the servo motor 10 according to this embodiment includes the magnet 11m in the motor 11, a magnet that rotates together with the rotary shaft 11a may be provided inside the encoder 12 instead of the magnet 11m.

[0083] Second Embodiment <Encoder 112> A constant voltage circuit may be provided to supply power to a signal processing circuit that processes signals from the Hall elements. An encoder 112 (see FIG. 9) according to the second embodiment further includes a constant voltage circuit 112j in addition to the components of the encoder 12 according to the first embodiment. Moreover, the encoder 112 according to the second embodiment includes a signal processing circuit 112c and a magnetic sensor 112m instead of the signal processing circuit 12c and the magnetic sensor 12m of the encoder 12 according to the first embodiment.

[0084] The Hall elements 12h1, 12h2, and 12h3, the drive circuit 12b, the signal processing circuit 112c, the variable capacitor circuit 12d, the current bypass circuit 12e, and the constant voltage circuit 112j are collectively referred to as the magnetic sensor 112m. That is, the encoder 112 includes the magnetic sensor 112m. The magnetic sensor 112m may include at least either the variable capacitor circuit 12d or the current bypass circuit 12e.

[0085] [Constant voltage circuit 112j] The encoder 112 includes a constant voltage circuit 112j for supplying constant voltage power to the signal processing circuit 112c. The constant voltage circuit 112j is provided between the line Lm and the signal processing circuit 112c. The constant voltage circuit 112j and the signal processing circuit 112c are connected via the line Lvc.

[0086] The constant voltage circuit 112j is, for example, a low-dropout regulator. The constant voltage circuit 112j converts the power supplied from the line Lm into power of a predetermined constant voltage and outputs it. Since signal processing circuits generally operate at a constant voltage, it is desirable for the encoder 112 to include the constant voltage circuit 112j.

[0087] It is desirable that the constant voltage circuit 112j has a small drop voltage and a small operating current. The output voltage of the constant voltage circuit 112j is determined taking into consideration the need to ensure the signal-to-noise ratio of the signal processing circuit 112c, low power consumption, the voltage generated by the power generating unit 12g, and the voltage drops across the Hall elements 12h1, 12h2, and 12h3.

[0088] [Signal processing circuit 112c] The signal processing circuit 112c includes a plurality of level converters 112c4 (see FIG. 10) in addition to the configuration of the signal processing circuit 12c (see FIG. 4).

[0089] In the signal processing circuit 112c, the positive power supply terminals V+ of the logic circuit 12c1, the differential amplifier 12c2, and the comparator 12c3 are connected to a line Lvc, which has a potential difference VL with respect to the ground.

[0090] (Level converter 112c4) Each of the plurality of level converters 112c4 is connected to the first detection terminal 12hp and the second detection terminal 12hm of each of the Hall elements 12h1, 12h2, and 12h3, and converts the potential difference between the first detection terminal 12hp and the second detection terminal 12hm of each of the Hall elements 12h1, 12h2, and 12h3, and outputs the converted potential difference to the corresponding differential amplifier 12c2.

[0091] The level converter 112c4 is connected to the lines Lv, Lm, and Lvc to convert the voltage levels, and performs level conversion based on the potential difference between the lines Lv and Lm and the potential difference between the line Lvc and ground.

[0092] <Actions and Effects> According to the encoder 112 (magnetic sensor 112m) of the second embodiment, in addition to the effects and advantages of the encoder 12 (magnetic sensor 12m) of the first embodiment, the signal processing circuit 112c can be operated stably by operating at a constant voltage.

[0093] Third Embodiment <Encoder 212> The encoder 212 according to the third embodiment (see FIG. 11) includes a signal processing circuit 212c and a magnetic sensor 212m instead of the signal processing circuit 112c and the magnetic sensor 112m of the encoder 112 according to the second embodiment. In the signal processing circuit 212c of the encoder 212 according to the third embodiment, voltage level conversion is performed on the digital signal after conversion by the comparator 12c3.

[0094] The Hall elements 12h1, 12h2, and 12h3, the drive circuit 12b, the signal processing circuit 212c, the variable capacitor circuit 12d, the current bypass circuit 12e, and the constant voltage circuit 112j are collectively referred to as the magnetic sensor 212m. That is, the encoder 212 includes the magnetic sensor 212m. The magnetic sensor 212m may include at least either the variable capacitor circuit 12d or the current bypass circuit 12e.

[0095] [Signal processing circuit 212c] The signal processing circuit 212c includes a plurality of level converters 212c5 (see FIG. 12) in addition to the configuration of the signal processing circuit 112c (see FIG. 10). In the signal processing circuit 212c, the positive power supply terminal V+ of the logic circuit 12c1 is connected to a line Lvc. The line Lvc has a potential difference VL with respect to the ground.

[0096] (Level converter 112c4) Each of the plurality of level converters 112c4 is connected to the first detection terminal 12hp and the second detection terminal 12hm of each of the Hall elements 12h1, 12h2, and 12h3, and converts the potential difference between the first detection terminal 12hp and the second detection terminal 12hm of each of the Hall elements 12h1, 12h2, and 12h3, and outputs the converted potential difference to the corresponding differential amplifier 12c2.

[0097] The level converter 112c4 is connected to the lines Lv, Lm, and Lvc to convert the voltage levels, and performs level conversion based on the potential difference between the lines Lv and Lm and the potential difference between the lines Lv and Lvc.

[0098] In the signal processing circuit 212c, the positive power supply terminals V+ of the differential amplifier 12c2 and the comparator 12c3 are connected to the line Lv, and the negative power supply terminals V− of the differential amplifier 12c2 and the comparator 12c3 are connected to the line Lvc.

[0099] (Level converter 212c5) Each of the plurality of level converters 212c5 is connected to a corresponding comparator 12c3, and each of the plurality of level converters 212c5 converts the potential of the corresponding comparator 12c3 and outputs the converted potential to the logic circuit 12c1.

[0100] The level converter 212c5 is connected to the lines Lv and Lvc to convert the voltage level, and performs level conversion based on the potential difference between the lines Lv and Lvc and the potential difference between the line Lv and ground.

[0101] <Actions and Effects> According to the encoder 212 (magnetic sensor 212m) of the third embodiment, in addition to the effects and advantages of the encoder 112 (magnetic sensor 112m) of the second embodiment, the circuit can be simplified. Furthermore, according to the encoder 212 (magnetic sensor 212m) of the third embodiment, power consumption can be reduced.

[0102] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0103] 1. Servo motor system 10 Servo motor 11 Motor 12, 112, 212 encoder 12a rectifier circuit 12b Drive circuit 12b1 Constant current circuit 12b2 current mirror circuit 12c, 112c, 212c signal processing circuit 12c1 Logic Circuit 12c2 differential amplifier 12c3 comparator 12d Variable Capacitor Circuit 12e Current Bypass Circuit 12g Power generation unit 12h1 Hall element 12h2 Hall element 12h3 Hall element 12ha 1st drive terminal 12hb 2nd drive terminal 12hm Second detection terminal 12hp 1st detection terminal 12m, 112m, 212m magnetic sensor 20 Servo Controller V+ Positive power supply terminal

Claims

1. a Hall element having first and second drive terminals and first and second detection terminals, and outputting a voltage between the first and second detection terminals that is proportional to a magnetic flux density across a drive current that flows from the first drive terminal to the second drive terminal; a drive circuit that supplies the drive current to the Hall element; a signal processing circuit including a power supply terminal connected to the second drive terminal, amplifying the voltage and processing a signal corresponding to the amplified voltage; a variable capacitance capacitor circuit connected to the second drive terminal, through which a portion of the drive current flows, and which increases its capacitance when the voltage at the second drive terminal increases; Equipped with Magnetic sensor.

2. a current bypass circuit provided in parallel with the Hall element, connected to the second drive terminal, and controlling the voltage at the second drive terminal to be a predetermined voltage value; The magnetic sensor according to claim 1 .

3. a Hall element having first and second drive terminals and first and second detection terminals, and outputting a voltage between the first and second detection terminals that is proportional to a magnetic flux density across a drive current that flows from the first drive terminal to the second drive terminal; a drive circuit that supplies the drive current to the Hall element; a signal processing circuit including a power supply terminal connected to the second drive terminal, amplifying the voltage and processing a signal corresponding to the amplified voltage; a current bypass circuit provided in parallel with the Hall element, connected to the second drive terminal, and configured to control a voltage at the second drive terminal to a predetermined voltage value; Equipped with Magnetic sensor.

4. A plurality of the Hall elements are provided, The drive circuit a constant current circuit that supplies a constant current to a first Hall element that is one of the Hall elements; a current mirror circuit that supplies a mirror current equal to the constant current flowing through the first Hall element to a second Hall element different from the first Hall element of the Hall elements; The magnetic sensor according to claim 1 .

5. the signal processing circuit includes a differential amplifier connected to the first detection terminal and the second detection terminal and amplifying the voltage, and a positive power supply terminal of the differential amplifier is connected to the second drive terminal; The magnetic sensor according to claim 1 .

6. the power supply terminal is connected to the second drive terminal via a constant voltage circuit; The magnetic sensor according to claim 1 .

7. the signal processing circuit includes a logic circuit, and a positive power supply terminal of the logic circuit is connected to the second drive terminal; The magnetic sensor according to claim 1 .

8. A magnetic sensor comprising the magnetic sensor according to any one of claims 1 to 7. Encoder.

9. A motor; 9. An encoder according to claim 8, Servo motor.

10. the motor includes a magnet that rotates together with a rotation shaft; the encoder further includes a power generating unit that generates power by a change in a magnetic field caused by the magnet, The electric power generated by the power generation unit is supplied to the first drive terminal.

10. The servo motor according to claim 9.

11. The Hall element detects the magnetic field of the magnet.

11. The servo motor according to claim 10.

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