JP7815864B2 - Power supply circuit, encoder, and power supply circuit control method - Google Patents

Description

This disclosure relates to a power supply circuit, an encoder, and a method for controlling the power supply circuit.

Patent Document 1 discloses a power generation detection device that does not require a power source or battery, and a rotation counter that uses this power generation detection device to count and record the number of rotations. Patent Document 1 also discloses that when the output voltage of the power-on reset circuit of the power generation detection device exceeds a threshold voltage, it activates a sequencer and records the detection results of the voltage detection circuit in a non-volatile logic circuit.

Patent Document 2 discloses a power generating device capable of generating a predetermined DC voltage even when the rotational speed of a rotating member fluctuates greatly. Patent Document 2 discloses that the power generating device includes multiple voltage conversion units that can convert the input voltage supplied from a rectifier circuit into a specified voltage and output it, and an output circuit unit that selectively outputs one of the output voltages of the multiple voltage conversion units.

Patent Document 3 discloses a rotation signal generator and rotation detection system that do not require power wiring or battery replacement. Patent Document 3 discloses that the rotation signal generator includes a rectifier that rectifies AC power output from a power generation unit to create a pulsating current, and a charging unit that converts the pulsating current obtained by the rectifier into DC and charges the power once charged in the charging unit, which is then supplied to a downstream transmitting unit.

Patent No. 6321918 Japanese Patent Application Laid-Open No. 2020-031488 Japanese Patent Application Laid-Open No. 2003-161638

When the power generated by the power generation element is first charged into a storage element and then supplied to the power supply circuit, if the energy is discharged to the power supply circuit when the charge stored in the storage element is insufficient, there may be a shortage of energy midway through depending on the load conditions. When there is a shortage of energy, the power supply voltage output from the power supply circuit may drop.

Furthermore, when the output from the power generating element fluctuates, control using a fixed threshold, as disclosed in Patent Document 1, may not be able to provide appropriate control.

The present disclosure aims to provide a power supply circuit, an encoder, and a method for controlling the power supply circuit that can utilize power supplied from a power generation element with high efficiency.

According to one aspect of the present disclosure, there is provided a power generating device having a power generating element that converts external energy into an electric pulse, a first terminal connected to a common potential, and a second terminal connected to the power generating element, a first storage element that stores electricity between the first terminal and the second terminal, a positive terminal connected to the second terminal, and a negative terminal, a rectifier that passes current from the positive terminal to the negative terminal, a third terminal connected to the common potential, a fourth terminal connected to the negative terminal, a second storage element that stores electricity between the third terminal and the fourth terminal, and a first storage element that connects to the second terminal. A power supply circuit is provided, which has an input terminal and a second input terminal connected to the negative terminal, a comparison element that outputs from an output terminal based on the potential difference between a first potential at the first input terminal and a second potential at the second input terminal, a stabilized power supply circuit, and a switch element that connects or disconnects the second terminal and the stabilized power supply circuit based on the output of the output terminal, and when the first potential becomes lower than the second potential after the electrical pulse is generated, the switch element connects the second terminal and the stabilized power supply circuit.

The power supply circuit, encoder, and power supply circuit control method disclosed herein enable highly efficient use of power supplied from the power generating element.

FIG. 1 is a diagram illustrating a servo motor system using an encoder according to this embodiment. FIG. 2 is a diagram illustrating the configuration of a servo motor using the encoder according to this embodiment. FIG. 3 is a diagram illustrating the circuit configuration of the encoder according to this embodiment. FIG. 4 is a diagram illustrating the circuit configuration of the encoder according to this embodiment. FIG. 5 is a diagram illustrating the processing of the encoder according to this embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the description of each embodiment and in the drawings, components having substantially the same or corresponding functional configurations may be designated by the same reference numerals, and redundant explanations may be omitted. Furthermore, to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

<Servo motor system 1>
First, a servo motor system 1 using an encoder 12 according to this embodiment will be described. Fig. 1 is a diagram illustrating a servo motor system 1 using an encoder 12 according to this embodiment.

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.

Servo motor 10 includes motor 11 and encoder 12. Motor 11 is connected to servo controller 20 via wiring L1. Encoder 12 is connected to servo controller 20 via wiring L2.

The motor 11 rotates the rotary shaft 11a in the direction of the arrow AR based on commands 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 the wiring L1. The motor 11 is, for example, an AC (Alternating Current) motor, a DC (Direct Current) motor, etc.

The encoder 12 detects fluctuations in the magnetic field to detect at least one of position information and rotation information of an object, such as the rotating shaft 11a of the motor 11. The encoder 12 also outputs the detected position information and/or rotation information to the servo controller 20 via wiring L2. Note that 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.

<Servo motor 10>
Next, the configuration of the servo motor 10 using the encoder 12 according to this embodiment will be described. Fig. 2 is a diagram illustrating the configuration of the servo motor 10 using the encoder 12 according to this embodiment. Note that lines with arrows indicate the flow of power or current supply.

[Motor 11]
The motor 11 includes a disk 11d provided on the rotary shaft 11a on the side of 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.

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 facing the encoder 12.

Magnet 11m is a permanent magnet made of neodymium or the like. Magnet 11m is arranged so that it has a north pole and a south pole parallel to the surface of disk 11d. When magnet 11m rotates together with disk 11d, the magnetic field on the encoder 12 side changes.

[Encoder 12]
The encoder 12 will now be described. By describing the encoder 12, the power supply circuit 12d included in the encoder 12 and a method for controlling the power supply circuit 12d will be described. 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. Furthermore, the encoder 12 generates the power required to operate the encoder 12 based on the magnetic field that changes with the rotation of the magnet 11m.

The encoder 12 includes a power generating element 12g, a rectifier circuit 12a, a switching circuit 12b, a stabilized power supply circuit 12c, a drive circuit 12e, a Hall element 12h, a signal processing circuit 12f, and a control circuit 12p. The power generating element 12g, rectifier circuit 12a, switching circuit 12b, and stabilized power supply circuit 12c are collectively referred to as the power supply circuit 12d. The drive circuit 12e, Hall element 12h, and signal processing circuit 12f are collectively referred to as the analog processing circuit 12m.

The encoder 12 includes a power generating element 12g that generates electricity using changes in magnetic flux caused by movement, and a Hall element 12h that measures the magnetic field. The power generating element 12g and the Hall element 12h are each located on the motor 11 side of the encoder 12 so that they are easily affected by the magnetic field generated by the magnet 11m.

[Power generating element 12g]
The power generating element 12g is an element that generates electricity by converting external energy into an electric pulse. The power generating element 12g is, for example, a Wiegand wire that is an energy harvest generator (EHG).

Wiegand wire generates an electrical pulse near the zero point where the external magnetic field reverses, regardless of the rate of change of the external magnetic flux. Therefore, Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a. Wiegand wire generates a stable electrical pulse (voltage pulse) even with gradual changes in magnetic flux caused by slow rotation (movement). Wiegand wire generates an electrical pulse when the magnetic field reverses.

By using an environmental power generator in the power generating element 12g, the encoder 12 does not require a battery or external power source. In other words, the encoder 12 is a battery-less encoder. Wiegand wire generates a constant amount of power regardless of the rotation speed of the rotating shaft 11a, and produces a stable power generation waveform even at low rotation speeds in particular. This makes it suitable for use as the power generating element 12g of the battery-less encoder 12.

Note that the power generating element 12g is not limited to a Wiegand wire; for example, it may be a coil or the like that generates power from changes in the magnetic field.

[Hall element 12h]
The Hall element 12h detects a magnetic field that crosses a semiconductor element through which a drive current flows. In the encoder 12, the Hall element 12h mainly detects a magnetic field generated by the magnet 11m. The Hall element 12h is made of a semiconductor element such as indium antimonide (InSb) or gallium arsenide (GaAs). The Hall element 12h outputs a voltage proportional to the drive current and the magnetic flux density that crosses the drive current.

The Hall element 12h outputs a magnetic field detection signal to the signal processing circuit 12f. A constant current Idr is supplied to the Hall element 12h from the drive circuit 12e.

The Hall element 12h is supplied with the electric power generated by the power generating element 12g, which is rectified by the rectifier circuit 12a and then converted to a constant current (constant current Idr) by the drive circuit 12e.

Note that although the encoder 12 is equipped with one Hall element, the number of Hall elements is not limited to one. The encoder 12 may be equipped with multiple Hall elements. Furthermore, the magnetic field measurement is not limited to a Hall element, as long as it is an element capable of detecting magnetism (magnetic detection element). For example, a magnetoresistance effect element or the like may be used instead of the Hall element 12h.

The circuit configuration of the encoder 12 will be described with reference to Figure 3. Figure 3 is a diagram illustrating the circuit configuration of the encoder 12 according to this embodiment.

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

The full-wave rectifier circuit 12a1 rectifies the positive and negative pulses of the voltage Vgn generated by the power generating element 12g into positive pulses. The full-wave rectifier circuit 12a1 is a so-called diode bridge circuit. For example, if the power generating element 12g is a Wiegand wire, the power generating element 12g generates positive and negative pulses. The full-wave rectifier circuit 12a1 converts the positive and negative pulses generated by the power generating element 12g into positive pulses.

The first capacitor 12a2 has a first terminal T1 and a second terminal T2. The first terminal T1 is connected to a common potential. The second terminal T2 is connected to the power generating element 12g via the full-wave rectifier circuit 12a1. The first capacitor 12a2 stores the power generated by the power generating element 12g.

The first capacitor 12a2 smooths the positive pulse generated by the full-wave rectifier circuit 12a1. The first capacitor 12a2 is connected between the output terminal of the full-wave rectifier circuit 12a1 and the common potential. By smoothing the positive pulse by the first capacitor 12a2, a smoothed voltage Vrc is output from the rectifier circuit 12a.

[Switching circuit 12b]
The switching circuit 12b connects or disconnects the rectifier circuit 12a and the stabilized power supply circuit 12c. In other words, the switching circuit 12b connects or disconnects the rectifier circuit 12a and the stabilized power supply circuit 12c.

Before the power generating element 12g generates an electrical pulse, the switching circuit 12b opens the connection between the rectifier circuit 12a and the stabilized power supply circuit 12c. That is, before the power generating element 12g generates an electrical pulse, the switching circuit 12b disconnects the rectifier circuit 12a from the stabilized power supply circuit 12c. Then, after the power generating element 12g generates an electrical pulse and the voltage of the electrical pulse rectified by the rectifier circuit 12a reaches its maximum, the switching circuit 12b closes the connection between the rectifier circuit 12a and the stabilized power supply circuit 12c. That is, after the power generating element 12g generates an electrical pulse and the voltage of the electrical pulse rectified by the rectifier circuit 12a reaches its maximum, the switching circuit 12b connects the rectifier circuit 12a to the stabilized power supply circuit 12c.

The specific configuration of the switching circuit 12b will be explained using Figure 4. Figure 4 is a diagram explaining the circuit configuration of the encoder 12 according to this embodiment, and in particular the switching circuit 12b.

The switching circuit 12b includes a second capacitor 12b1, a rectifier 12b2, a comparison element 12b5, and a switch element 12b6. The rectifier 12b2 includes a first rectifier element 12b3 and a second rectifier element 12b4.

The second capacitor 12b1 stores a portion of the power generated by the power generating element 12g. The second capacitor 12b1 is connected to the rectifier circuit 12a via the rectifier 12b2.

The second capacitor 12b1 has a third terminal T3 and a fourth terminal T4. The third terminal T3 is connected to a common potential. The fourth terminal T4 is connected to the second terminal T2 of the first capacitor 12a2 via the rectifier 12b2. The second capacitor 12b1 stores a portion of the power generated by the power generating element 12g. It is desirable that the storage capacity of the first capacitor 12a2 be greater than that of the second capacitor 12b1.

The rectifier 12b2 allows current to flow in one direction and prevents current from flowing in the other direction. The rectifier 12b2 has a positive terminal Tp and a negative terminal Tm. The rectifier 12b2 includes a first rectifying element 12b3 and a second rectifying element 12b4 between the positive terminal Tp and the negative terminal Tm. The first rectifying element 12b3 and the second rectifying element 12b4 are connected in series between the positive terminal Tp and the negative terminal Tm, in other words, between the second terminal T2 of the first capacitor 12a2 and the fourth terminal T4 of the second capacitor 12b1.

Each of the first rectifying element 12b3 and the second rectifying element 12b4 is, for example, a diode. When current flows through the rectifier 12b2, a voltage drops across each of the first rectifying element 12b3 and the second rectifying element 12b4. Therefore, when current flows through the rectifier 12b2, the voltage Vt at the fourth terminal T4 of the second capacitor 12b1 is lower than the voltage Vrc at the second terminal T2 of the first capacitor 12a2.

Note that in the above example, a diode was used as the rectifying element, but the rectifying element is not limited to a diode. For example, instead of a diode, a transistor such as a diode-connected MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) may be used as the rectifying element.

The comparison element 12b5 compares the potential difference between the voltage Vrc at the second terminal T2 of the first capacitor 12a2 and the voltage Vt at the fourth terminal T4 of the second capacitor 12b1, and outputs the comparison result. The comparison element 12b5 is a so-called comparator.

The positive terminal (first input terminal Ip1) of the comparison element 12b5 is connected to the second terminal T2 of the first capacitor 12a2. The negative terminal (second input terminal Ip2) of the comparison element 12b5 is connected to the fourth terminal T4 of the second capacitor 12b1. The output terminal Op1 of the comparison element 12b5 is connected to the switch element 12b6. The positive power supply terminal Pp1 of the comparison element 12b5 is connected to the second terminal T2 of the first capacitor 12a2. The negative power supply terminal Pm1 of the comparison element 12b5 is connected to a common potential.

The switch element 12b6 opens and closes the connection between the rectifier circuit 12a and the stabilized power supply circuit 12c based on the output of the comparison element 12b5. The switch element 12b6 is, for example, an analog switch. When the switch element 12b6 requires power, the power supply terminal of the switch element 12b6 is connected to the second terminal T2 of the first capacitor 12a2 to input the voltage Vrc.

It is desirable that the response speed of the comparison element 12b5 and the switch element 12b6 be faster than the rise time of the electrical pulse supplied from the power generation element 12g.

[Stabilized power supply circuit 12c]
The stabilized power supply circuit 12c converts the voltage output from the rectifier circuit 12a into a substantially constant voltage and outputs the voltage. The stabilized power supply circuit 12c includes a regulator 12c1. The regulator 12c1 is, for example, an LDO (Low Dropout) regulator.

The stabilized power supply circuit 12c outputs a substantially constant voltage Vdd when a voltage of a predetermined magnitude is input.

[Drive circuit 12e]
The drive circuit 12e is a so-called constant current circuit that supplies a constant current Idr to the Hall element 12h. The drive circuit 12e operates as a constant current source. The encoder 12 drives the Hall element 12h with the constant current Idr. The drive circuit 12e supplies drive power to the Hall element 12h so that a constant current flows through the Hall element 12h as a drive current.

The drive circuit 12e is driven by the voltage Vdd supplied from the stabilized power supply circuit 12c.

[Signal processing circuit 12f]
The signal processing circuit 12f processes the detection signal from the Hall element 12h to detect the direction of the magnetic field of the magnet 11m. The signal processing circuit 12f will be described with reference to FIG.

The signal processing circuit 12f includes a differential amplifier 12f1 and a comparator 12f2.

(Differential amplifier 12f1)
The differential amplifier 12f1 amplifies the potential difference between the voltage Vh+ and the voltage Vh− output from the Hall element 12h to generate a voltage Vd, and outputs the amplified voltage Vd to the comparator 12f2. The differential amplifier 12f1 is supplied with power of the voltage Vdd from the stabilized power supply circuit 12c.

(Comparator 12f2)
The comparator 12f2 compares the voltage Vd output from the differential amplifier 12f1 with a reference potential (reference potential Vref) and outputs the comparison result to the control circuit 12p. The comparator 12f2 is a so-called comparator. The comparator 12f2 includes a differential amplifier 12f2a and resistors 12f2b, 12f2c, and 12f2d. The differential amplifier 12f2a receives power at voltage Vdd from the stabilized power supply circuit 12c. The differential amplifier 12f2a compares the voltage Vd output from the differential amplifier 12f1 with a reference potential Vref generated by dividing the voltage Vdd using resistors 12f2c and 12f2d, and outputs the comparison result to the control circuit 12p as a magnetic pole signal Smg, which is a voltage signal. The resistor 12f2b is a feedback resistor.

[Control circuit 12p]
Based on the input from the signal processing circuit 12f, the control circuit 12p calculates at least one of position information and rotation information, such as the rotation position and rotation speed, of the rotating shaft 11a of the motor 11. The control circuit 12p also records at least one of the detected position information and rotation information of the rotating shaft 11a of the motor 11, and transmits it to an external control system, for example, a servo controller 20.

The control circuit 12p may be, for example, a microcomputer or an ASIC (application-specific integrated circuit). The control circuit 12p may also be, for example, an FPGA (field-programmable gate array) or a PLD (programmable logic device). Furthermore, the control circuit 12p may include non-volatile memory such as a ferroelectric memory. The control circuit 12p may also be connected to an external non-volatile memory such as a ferroelectric memory.

The control circuit 12p has at least a terminal PWR and a terminal SIG.

The terminal PWR of the control circuit 12p is a terminal to which positive power is supplied. Power at voltage Vdd is supplied to terminal PWR from the stabilized power supply circuit 12c. The control circuit 12p operates when power is supplied to terminal PWR.

The terminal SIG of the control circuit 12p is a terminal to which a signal is input from the outside. The terminal SIG is connected to the signal processing circuit 12f. The magnetic pole signal Smg, which is the detection result detected by the signal processing circuit 12f, is input from the terminal SIG. The magnetic pole signal Smg is a signal that indicates the direction of the magnetic field detected by the Hall element 12h.

<Operation of Encoder 12>
The operation of the encoder 12 will now be described. FIG. 5 is a diagram illustrating the processing of the encoder 12 according to this embodiment. FIG. 5(a) shows the output voltage of the power generating element 12g, the voltage Vrc at the second terminal T2 of the first capacitor 12a2, and the voltage Vt at the fourth terminal T4 of the second capacitor 12b1. FIG. 5(b) shows the voltage at the output terminal Op1 of the comparison element 12b5. FIG. 5(c) shows the voltage Vdd output from the stabilized power supply circuit 12c.

In Figures 5(a), 5(b), and 5(c), the vertical axis represents voltage and the horizontal axis represents time. The same point on the horizontal axis in Figures 5(a), 5(b), and 5(c) represents the same time.

When the rotating shaft 11a of the motor 11 rotates and the magnetic field fluctuates in the power generating element 12g, the power generated by the power generating element 12g is supplied. Note that if the power generating element 12g is a Wiegand wire, it may output a positive pulse or a negative pulse. Therefore, in the encoder 12 according to this embodiment, the rectifier circuit 12a converts this into a positive pulse.

Line Lg in Figure 5(a) shows the electrical pulse output from power generating element 12g. Note that in Figure 5(a), this shows a positive pulse. As power generating element 12g begins to generate electricity from time t1, line Lg gradually becomes larger.

The electrical pulses generated and output by the power generating element 12g are stored in the first capacitor 12a2. Line Lc1 in Figure 5(a) shows the voltage (voltage Vrc) at the second terminal T2 of the first capacitor 12a2. The first capacitor 12a2 is charged, and the voltage at the second terminal T2 gradually increases from time t2.

A portion of the electrical pulses generated and output by the power generating element 12g is stored in the second capacitor 12b1. Line Lc2 in Figure 5(a) shows the voltage (voltage Vt) at the fourth terminal T4 of the second capacitor 12b1. Because the second capacitor 12b1 is connected to the first capacitor 12a2 via the rectifier 12b2, the voltage at the fourth terminal T4 of the second capacitor 12b1 is lower than the voltage at the second terminal T2 of the first capacitor 12a2 by the amount of the voltage drop across the rectifier 12b2. Therefore, the second capacitor 12b1 is charged, and the voltage at the fourth terminal T4 gradually increases from time t3, which is slightly later than time t2.

As the first capacitor 12a2 is charged with power from the power generating element 12g, the voltage at the fourth terminal T4 increases as the voltage from the power generating element 12g increases. At time tmax, when the voltage at the power generating element 12g reaches its maximum, the voltage at the second terminal T2 also reaches its maximum at approximately the same time. After the voltage at the second terminal T2 reaches its maximum, the voltage gradually decreases.

Similar to the first capacitor 12a2, the second capacitor 12b1 is charged with power from the power generating element 12g, and the voltage at the fourth terminal T4 rises as the voltage from the power generating element 12g rises. At time tmax, when the voltage at the power generating element 12g reaches its maximum, the voltage at the fourth terminal T4 also reaches its maximum value at approximately the same time. After the voltage at the fourth terminal T4 reaches its maximum value, the voltage gradually decreases.

Because the comparison element 12b5 and other elements are connected to the second terminal T2 of the first capacitor 12a2, the power stored in the first capacitor 12a2 is consumed, and the voltage at the second terminal T2 gradually decreases. Meanwhile, the second capacitor 12b1 is hardly discharged, and the voltage at the fourth terminal T4 hardly changes.

Therefore, at time ts, the potential at the second terminal T2 and the voltage at the fourth terminal T4 are reversed. When the potential at the fourth terminal T4 becomes higher than the potential at the second terminal T2, the comparison element 12b5 outputs a positive logic voltage v1. When the comparison element 12b5 outputs a positive logic voltage v1, the switch element 12b6 closes the connection between the rectifier circuit 12a and the stabilized power supply circuit 12c.

At time ts, when the rectifier circuit 12a and the stabilized power supply circuit 12c are connected, a predetermined voltage v2 is output from the stabilized power supply circuit 12c, as shown by line Lrg in Figure 5(c).

The voltage at the second terminal of the first capacitor 12a2 gradually decreases, and at time t4, the stabilized power supply circuit 12c can no longer secure the voltage required to output voltage v2, causing the output from the stabilized power supply circuit 12c to gradually decrease.

Then, at time t5, the output of the comparison element 12b5 drops, opening the connection between the rectifier circuit 12a and the stabilized power supply circuit 12c and disconnecting them.

<Actions and Effects>
The power supply circuit and encoder disclosed herein enable highly efficient use of power supplied from the power generating element. According to the power supply circuit 12d of this embodiment, the first capacitor 12a2 is connected to the stabilized power supply circuit 12c after the first capacitor 12a2 has been sufficiently charged by the electric pulses supplied from the power generating element 12g. That is, while the first capacitor 12a2 is being charged by the electric pulses supplied from the power generating element 12g, the first capacitor 12a2 is charged and not discharged. While the first capacitor 12a2 is being charged by the electric pulses supplied from the power generating element 12g, the first capacitor 12a2 is charged intensively, thereby enabling efficient charging of the first capacitor 12a2.

Furthermore, when the first capacitor 12a2 is sufficiently charged, power is supplied from the first capacitor 12a2 to the stabilized power supply circuit 12c, thereby stabilizing the output from the stabilized power supply circuit 12c.

Furthermore, with the power supply circuit and encoder disclosed herein, charging of the first capacitor 12a2 begins after the electrical pulse supplied from the power generating element 12g reaches its maximum. Because charging of the first capacitor 12a2 begins after the electrical pulse supplied from the power generating element 12g reaches its maximum, the first capacitor 12a2 can be charged stably and efficiently even if, for example, the magnitude of the electrical pulse supplied from the power generating element 12g fluctuates.

Note that the first capacitor 12a2 is an example of a first storage element, the second capacitor 12b1 is an example of a second storage element, the voltage Vrc is an example of a first potential, and the voltage Vt is an example of a second potential.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

1 Servo motor system 10 Servo motor 11 Motor 12 Encoder 12a Rectifier circuit 12a1 Full-wave rectifier circuit 12a2 First capacitor 12b Switching circuit 12b1 Second capacitor 12b2 Rectifier 12b3 First rectifier element 12b4 Second rectifier element 12b5 Comparison element 12b6 Switch element 12c Stabilized power supply circuit 12c1 Regulator 12d Power supply circuit 12e Drive circuit 12f Signal processing circuit 12g Power generation element 12h Hall element 12m Analog processing circuit 12p Control circuit 20 Servo controller

Claims (7)

a power generating element that converts external energy into an electrical pulse;
a first storage element having a first terminal connected to a common potential and a second terminal connected to the power generating element, storing electricity between the first terminal and the second terminal;
a rectifier having a positive terminal connected to the second terminal and a negative terminal, and causing a current to flow from the positive terminal to the negative terminal;
a third terminal connected to the common potential, a fourth terminal connected to the negative terminal, and a second storage element that stores electricity between the third terminal and the fourth terminal;
a comparison element having a first input terminal connected to the second terminal and a second input terminal connected to the negative terminal, and outputting from an output terminal based on a potential difference between a first potential at the first input terminal and a second potential at the second input terminal;
A stabilized power supply circuit;
a switch element that connects or disconnects the second terminal and the stabilized power supply circuit based on an output from the output terminal;
Equipped with
when the first potential becomes lower than the second potential after the electric pulse is generated, the switch element connects the second terminal and the stabilized power supply circuit.
power circuit. The storage capacity of the first storage element is greater than the storage capacity of the second storage element.
2. The power supply circuit according to claim 1. the response speed of the comparison element and the switch element is faster than the rise time of the electrical pulse;
3. The power supply circuit according to claim 1. The power supplies of the comparison element and the switch element are connected to the second terminal.
The power supply circuit according to any one of claims 1 to 3. The power generating element is a Wiegand wire.
The power supply circuit according to any one of claims 1 to 4. A power supply circuit comprising:
Encoder. a power generating element that converts external energy into an electrical pulse;
a first storage element having a first terminal connected to a common potential and a second terminal connected to the power generating element, storing electricity between the first terminal and the second terminal;
a rectifier having a positive terminal connected to the second terminal and a negative terminal, and causing a current to flow from the positive terminal to the negative terminal;
a third terminal connected to the common potential, a fourth terminal connected to the negative terminal, and a second storage element that stores electricity between the third terminal and the fourth terminal;
A stabilized power supply circuit;
A control method for a power supply circuit comprising:
connecting the second terminal to the stabilized power supply circuit when a first potential at the second terminal becomes lower than a second potential at the fourth terminal after the electric pulse is generated;
A method for controlling a power supply circuit.