Servo motor power supply system

Abstract

This power source system comprises: a servo amplifier; a power source that switchably outputs voltages of at least two sizes; a servo amplifier control circuit that is connected to the power source and that controls the servo amplifier; a switch that opens and closes an electrical path between the power source and the servo amplifier; a voltage comparison circuit that compares the voltage output by the power source and a threshold value prescribed in advance; and a switch control circuit that controls the opening and closing of the electrical path between the power source and the servo amplifier by the switch according to the comparison result from the voltage comparison circuit.

Description

Technical Field

[0001] The present disclosure relates to a power supply system for a servo motor.

Background Art

[0002] A servo amplifier that drives a servo motor in a machine such as an industrial robot or a machine tool is provided with a power supply for powering to drive the servo motor and a control power supply for powering a circuit for controlling the servo amplifier.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to ensure the safety of a machine driven by a servo amplifier, when the servo motor is not driven, while the energization by the driving power supply is cut off, a power supply system that ensures the energization by the control power supply to monitor the state of the servo motor is desired.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, the power supply system includes a servo amplifier, a power supply that can switchably output voltages of at least two magnitudes, a servo amplifier control circuit connected to the power supply and controlling the servo amplifier, a switch that opens and closes an electric circuit between the power supply and the servo amplifier, a voltage comparison circuit that compares the voltage output by the power supply with a predetermined threshold value, and a switch control circuit that controls the opening and closing of the electric circuit between the power supply and the servo amplifier by the switch according to the comparison result by the voltage comparison circuit. Power lines connected connected to the power supply and controlling the servo amplifier, a switch that opens and closes an electric circuit between the power supply Power lines connected and the servo amplifier, a voltage comparison circuit that compares the voltage output by the power supply with a predetermined threshold value, and a switch control circuit that controls the opening and closing of the electric circuit between the power supply and the servo amplifier by the switch according to the comparison result by the voltage comparison circuit. The switch control circuit controls the switch to open the circuit between the power supply and the servo amplifier if the voltage comparison circuit determines that the voltage output by the power supply is below a threshold, and controls the switch to close the circuit between the power supply and the servo amplifier if the voltage comparison circuit determines that the voltage output by the power supply is above the threshold. ru. [Brief explanation of the drawing]

[0006] [Figure 1] This is a circuit diagram showing a power supply system according to an embodiment of the present disclosure. [Figure 2] This is a circuit diagram showing a step-down chopper circuit provided in a servo amplifier control circuit within a power supply system according to one embodiment of the present disclosure. [Figure 3] This is a flowchart showing the operations related to the opening and closing of switches in a power supply system according to an embodiment of the present disclosure. [Figure 4] This is a circuit diagram showing a conventional power supply system in which the power supply and the control power supply are provided separately. [Modes for carrying out the invention]

[0007] The power supply system for the servo motor of this embodiment will be described below with reference to the drawings. In the following description, components having the same or similar functions will be denoted by the same reference numerals. Duplication of these components may be omitted. Here, "connected" means "electrically connected." "On" of a switch means that the circuit to which the switch is located is closed; that is, when the switch is turned on, the circuit to which the switch is located is connected and closed. "Off" of a switch means that the circuit to which the switch is located is open; that is, when the switch is turned off, the circuit to which the switch is located is interrupted and opened.

[0008] <Configuration of the power supply system according to the embodiment of this disclosure> Figure 1 is a circuit diagram showing a power supply system according to an embodiment of the present disclosure.

[0009] As an example, we will show a case where a three-phase AC motor 2 is driven by power supplied from a power supply system 1. Motor 2 is a servo motor. Motor 2 may be a synchronous motor or an induction motor, for example. Machines in which motor 2 is installed include, for example, industrial robots and machine tools.

[0010] According to the first embodiment of this disclosure, the power supply system 1 comprises a servo amplifier 11, a power supply 12, a servo amplifier control circuit 13, a positive switch 14P, a negative switch 14N, a voltage comparison circuit 15, a switch control circuit 16, a positive potential detection unit 17P, a negative potential detection unit 17N, and a capacitor 18.

[0011] The power supply 12 outputs DC voltages of at least two different magnitudes in a switchable manner. Examples of the power supply 12 include, for example, a variable voltage source having a battery and an output selector switch, a variable voltage source having a battery and a variable resistor, and a PWM rectifier that converts AC power supplied from an AC power source into DC power for output. For example, when the power supply 12 is configured as a PWM rectifier, the power supply 12 consists of a bridge circuit of switching elements and diodes connected in antiparallel thereto, and each switching element is controlled on or off in response to a received command to output DC voltages of multiple magnitudes. Examples of switching elements include unipolar transistors such as FETs, bipolar transistors, IGBTs, thyristors, GTOs, etc. However, the type of switching element itself is not limited to this embodiment, and other switching elements may be used.

[0012] For example, if the power supply 12 is configured to output two types of DC voltages, high voltage (e.g., 48V) and low voltage (e.g., 24V), the high voltage output by the power supply 12 is used as the drive voltage for the motor 2 and the servo amplifier control circuit 13 when the motor 2 is driven by the servo amplifier 11. The low voltage output by the power supply 12 is used as the drive voltage for the servo amplifier control circuit 13 when the motor 2 is not driven by the servo amplifier 11. The switching between the high and low voltages output by the power supply 12 is linked to whether or not the motor 2 is driven. The switching between whether or not the motor 2 is driven can be done manually by an operator using a control panel or the like, or it can be commanded by a motor control unit (not shown) according to the motor 2's operation program. The power supply 12 may also be configured to output two or more types of voltages, such as 100V, 48V, and 24V. The numerical values ​​indicating the magnitude of the output voltage of the power supply 12 listed here are merely examples, and other values ​​may be used.

[0013] A capacitor 18 is connected between the positive DC power line 19P extending from the positive output terminal of the power supply 12 and the negative DC power line 19N extending from the negative output terminal. The capacitor 18 has the function of suppressing the pulsation component of the DC output of the power supply 12 and the function of storing DC power. Examples of capacitors 18 include electrolytic capacitors and film capacitors.

[0014] The servo amplifier 11 has an inverter consisting of a bridge circuit of switching elements. Examples of switching elements include unipolar transistors such as FETs, bipolar transistors, IGBTs, thyristors, and GTOs. However, the type of switching element itself is not limited to this embodiment, and other switching elements may be used. In the example shown in Figure 1, the switching element of the upper U-phase arm is Su1, and the switching element of the lower U-phase arm is Su2. Also, the switching element of the upper V-phase arm is Sv1, and the switching element of the lower V-phase arm is Sv2. The switching element of the upper W-phase arm is Sw1, and the switching element of the lower W-phase arm is Sw2. Below, as an example, the case in which the switching elements are composed of MOSFETs will be described, but the embodiments of this disclosure are also applicable to IGBTs, thyristors, GTOs, or transistors. Furthermore, when the switching elements are composed of IGBTs, the current inflow terminal "drain" is read as "collector," and the current outflow terminal "source" is read as "emitter," and the embodiments of this disclosure are applied accordingly. Furthermore, when the switching element is composed of a transistor, the embodiments of this disclosure apply by replacing the control terminal "gate" with "base," the current inflow terminal "drain" with "collector," and the current outflow terminal "source" with "emitter." Also, when the switching element is composed of a thyristor or GTO, the embodiments of this disclosure apply by replacing the current inflow terminal "drain" with "anode," and the current outflow terminal "source" with "cathode."

[0015] The servo amplifier 11 converts power between DC power and AC power, which is the drive power or regenerative power of the motor 2, by driving each switching element on and off based on a PWM control method based on switching commands received from the servo amplifier control circuit 13. More specifically, the servo amplifier 11 switches its internal switching elements based on switching commands received from the servo amplifier control circuit 13, and converts the DC power supplied from the power supply 12 when switches 14P and 14N are ON into AC power having a desired frequency for driving the motor 2. As a result, the motor 2 operates, for example, based on AC power with a variable frequency. In addition, regenerative power may be generated when the motor 2 is decelerated, and the servo amplifier 11 switches its internal switching elements based on switching commands received from the servo amplifier control circuit 13, converting the AC regenerative power generated by the motor 2 into DC power and returning it to the DC side.

[0016] The servo amplifier control circuit 13 generates switching commands to control the on / off state of each switching element and applies them to the gate terminals of each switching element. The servo amplifier control circuit 13 controls the power conversion of the inverter in the servo amplifier 11 according to a predetermined operating program, thereby controlling the motor 2 to operate according to a predetermined operating pattern. Note that the configuration of the servo amplifier control circuit 13 defined here is merely an example, and the configuration of the servo amplifier control circuit 13 may be defined to include terms such as a position command generation unit, a torque command generation unit, and a switching command generation unit.

[0017] Power is supplied to the servo amplifier control circuit 13 from the power supply 12 via the positive-side DC power line 19P and the negative-side DC power line 19N. As described above, the power supply 12 can output DC voltages of at least two different magnitudes. Therefore, at least two different magnitudes of DC voltages are input to the servo amplifier control circuit 13. On the other hand, the driving voltage of each circuit within the servo amplifier control circuit 13 is always constant regardless of the magnitude of the output voltage of the power supply 12. Therefore, the servo amplifier control circuit 13 is provided with a voltage conversion circuit that converts the voltage input from the power supply 12 into a driving voltage for driving the servo amplifier control circuit.

[0018] For example, when the power supply 12 is configured to be able to switchably output a high voltage of 48V and a low voltage of 24V, either 48V or 24V is input to the servo amplifier control circuit 13. The voltage conversion circuit within the servo amplifier control circuit 13 converts the input voltage of 48V or 24V from the power supply 12 into a driving voltage (such as 5V or 10V, etc.) for driving the servo amplifier control circuit. Examples of the voltage conversion circuit within the servo amplifier control circuit 13 include, for example, a step-down chopper circuit, a step-up chopper circuit, a buck-boost chopper circuit, and a combination circuit of a switching element and a voltage-dividing resistor.

[0019] As an example, an example in which the voltage conversion circuit within the servo amplifier control circuit 13 is configured as a step-down chopper circuit will be described. FIG. 2 is a circuit diagram showing the step-down chopper circuit provided in the servo amplifier control circuit within the power supply system according to an embodiment of the present disclosure. As shown in FIG. 2, the servo amplifier control circuit 13 is provided with a step-down chopper circuit as the voltage conversion circuit 21, for example, including a switching element 31, a diode 32, and an inductor 33. Examples of the switching element 31 include unipolar transistors such as FETs, bipolar transistors, IGBTs, thyristors, GTOs, etc. However, the type of the switching element 31 itself does not limit this embodiment, and other switching elements may also be used.

[0020] In FIG. 2, the impedance of the circuit 40 after the voltage conversion circuit 21 in the servo amplifier control circuit 13 is set as Z in The input voltage E in of the voltage conversion circuit 21 is a DC voltage of, for example, 48V or 24V supplied from the power supply 12. In the voltage conversion circuit 21, energy is stored in the inductor 33 when the switching element 31 is on, and the energy stored in the inductor 33 is released when the switching element 31 is off. The longer the on-time of the switching element 31, the higher the output voltage of the voltage conversion circuit 21, and the shorter the on-time of the switching element 31, the lower the output voltage of the voltage conversion circuit 21. By controlling the duty ratio of the switching element 31, an output voltage (such as 5V or 10V) for driving the servo amplifier control circuit is output from the voltage conversion circuit 21.

[0021] Returning to the explanation of FIG. 1. As switches for opening and closing the circuit between the power supply 12 and the servo amplifier 11, a positive-side switch 14P and a negative-side switch 14N are provided. That is, a positive-side switch 14P for opening and closing the circuit is provided in the circuit between the positive-side DC power line 19P extending from the positive-side output terminal of the power supply 12 and the positive-side input terminal of the servo amplifier 11. Also, a negative-side switch 14N for opening and closing the circuit is provided in the circuit between the negative-side DC power line 19N extending from the negative-side output terminal of the power supply 12 and the negative-side input terminal of the servo amplifier 11. The positive-side switch 14P and the negative-side switch 14N perform a closing operation when receiving an on command from the switch control circuit 16, and close the circuit between the power supply 12 and the servo amplifier 11. Also, the positive-side switch 14P and the negative-side switch 14N perform an opening operation when receiving an off command from the switch control circuit 16, and open the circuit between the power supply 12 and the servo amplifier 11.

[0022] The positive potential detection unit 17P detects the positive potential in the positive DC power line 19P extending from the positive output terminal of the power supply 12. The negative potential detection unit 17N detects the negative potential in the negative DC power line 19N extending from the negative output terminal of the power supply 12. The potential difference between the positive potential in the positive DC power line 19P and the negative potential in the negative DC power line 19N becomes the magnitude of the voltage output by the power supply 12. The detection results from the positive potential detection unit 17P and the negative potential detection unit 17N are sent to the voltage comparison circuit 15.

[0023] The voltage comparison circuit 15 compares the voltage output by the power supply 12 with a predetermined threshold. As described above, the power supply 12 outputs DC voltages of at least two different magnitudes in a switchable manner. The voltage comparison circuit 15 uses the threshold to determine which voltage value was output from the power supply 12. The comparison result from the voltage comparison circuit 15 is sent to the switch control circuit 16. For example, if the power supply 12 is configured to output a high voltage of 48V and a low voltage of 24V in a switchable manner, then either 48V or 24V will be output from the power supply 12. In this case, by setting the threshold to, for example, 36V, the voltage comparison circuit 15 can determine whether the power supply 12 output 48V or 24V by comparing the threshold of 36V with the voltage output by the power supply 12. In other words, the voltage comparison circuit 15 determines that the power supply 12 has output a voltage of 24V if the voltage output by the power supply 12 is less than or equal to the threshold of 36V, and determines that the power supply 12 has output a voltage of 48V if the voltage output by the power supply 12 is greater than the threshold of 36V. The numerical examples shown here are merely examples, and other values ​​may be used. The threshold may be stored in a rewritable memory unit (not shown) and rewritable by an external device, which would allow the threshold to be changed to an appropriate value as needed, even after it has been set.

[0024] The switch control circuit 16 controls the opening and closing of the circuit between the power supply 12 and the servo amplifier 11 using the positive switch 14P and the negative switch 14N, according to the comparison result from the voltage comparison circuit 15. More details are as follows.

[0025] When the voltage comparison circuit 15 determines that the voltage output by the power supply 12 is below a threshold, the switch control circuit 16 sends an off command to the positive switch 14P and the negative switch 14N. Upon receiving the off command, the positive switch 14P and the negative switch 14N open up, opening the circuit between the power supply 12 and the servo amplifier 11. When the voltage output by the power supply 12 is determined to be below a threshold, it corresponds to not driving the motor 2, so the power supply 12 outputs a low voltage (e.g., 24V). Since the positive switch 14P and the negative switch 14N are in the open state, the voltage output from the power supply 12 is not input to the servo amplifier 11, but it is input to the servo amplifier control circuit 13. Therefore, although the motor 2 is not driven, the servo amplifier control circuit 13 itself operates, so it can perform various processes, including monitoring the state of the motor 2, and the safety of the machine is ensured.

[0026] Furthermore, if the voltage comparison circuit 15 determines that the voltage output by the power supply 12 is greater than a threshold, the switch control circuit 16 sends an ON command to the positive switch 14P and the negative switch 14N. Upon receiving the ON command, the positive switch 14P and the negative switch 14N close, closing the circuit between the power supply 12 and the servo amplifier 11. When the voltage output by the power supply 12 is determined to be greater than a threshold, it corresponds to driving the motor 2, so a high voltage (e.g., 48V) is output from the power supply 12. Since the positive switch 14P and the negative switch 14N are in the closed state, the voltage output from the power supply 12 is input to the servo amplifier 11 and the servo amplifier control circuit 13, enabling the servo amplifier 11 to drive the motor 3.

[0027] The voltage comparison circuit 15 described above may also have a comparator circuit, in which case the switch control unit 16 controls the positive switch 14P and the negative switch 14N based on the output of the converter circuit. Alternatively, the voltage comparison circuit 15 described above may have a circuit configuration that combines an arithmetic processing unit, memory, and an analog-to-digital converter.

[0028] Furthermore, the power supply system 1 includes at least one processor, which is an arithmetic processing unit. Examples of arithmetic processing units include ICs, LSIs, CPUs, MPUs, and DSPs. The arithmetic processing unit may have a voltage comparison circuit 15, a switch control circuit 16, a motor control unit (not shown), and other processing circuits. Each of these parts of the arithmetic processing unit may be a functional module realized by a program executed on the processor. For example, if the voltage comparison circuit 15, the switch control circuit 16, the motor control unit, and other processing circuits are constructed in program form, the functions of each part can be realized by operating the arithmetic processing unit according to this program. The programs for executing each of the processes of the voltage comparison circuit 15, the switch control circuit 16, the motor control unit, and other processing circuits may be provided in the form of a recording on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the voltage comparison circuit 15, the switch control circuit 16, the motor control unit, and other processing circuits may be realized as semiconductor integrated circuits on which programs realizing the functions of each part are written.

[0029] Furthermore, the power supply system 1 is provided with at least one memory, which is a storage device. The memory may be an electrically erasable and recordable non-volatile memory such as EEPROM (registered trademark), or a high-speed read / write random access memory such as DRAM or SRAM. The storage device may also have a configuration such as an HDD or SSD. The memory may store programs for operating the voltage comparison circuit 15, the switch control circuit 16, the motor control unit, and other processing circuits. The memory may also store potential detection results obtained by the positive potential detection unit 17P and the negative potential detection unit 17N. The memory may also store comparison results from the voltage comparison circuit 15. The memory may also store various data necessary for motor driving.

[0030] <Operation of the power supply system according to the embodiment of this disclosure> Figure 3 is a flowchart showing the operation related to the opening and closing of a switch in a power supply system according to an embodiment of the present disclosure.

[0031] The power supply 12 outputs a DC voltage of at least two different magnitudes. In step S101, the positive potential detection unit 17P detects the positive potential in the positive DC power line 19P extending from the positive output terminal of the power supply 12. The negative potential detection unit 17N detects the negative potential in the negative DC power line 19N extending from the negative output terminal of the power supply 12. This allows the magnitude of the voltage output by the power supply 12 to be detected. The detection results from the positive potential detection unit 17P and the negative potential detection unit 17N are sent to the voltage comparison circuit 15.

[0032] In step S102, the voltage comparison circuit 15 compares the voltage output by the power supply 12 with a predetermined threshold. If the voltage comparison circuit 15 determines in step S102 that the voltage output by the power supply 12 is below the threshold, the process proceeds to step S103. If the voltage comparison circuit 15 does not determine in step S102 that the voltage output by the power supply 12 is below the threshold (i.e., the voltage output by the power supply 12 is greater than the threshold), the process proceeds to step S104.

[0033] In step S103, the switch control circuit 16 sends an off command to the positive switch 14P and the negative switch 14N. Upon receiving the off command, the positive switch 14P and the negative switch 14N open up, opening the circuit between the power supply 12 and the servo amplifier 11. As the positive switch 14P and the negative switch 14N are open, the voltage output from the power supply 12 is not input to the servo amplifier 11, but it is input to the servo amplifier control circuit 13. Therefore, although the motor 2 does not operate, the servo amplifier control circuit 13 itself operates, allowing it to perform various processes, including monitoring the state of the motor 2, and ensuring the safety of the machine.

[0034] In step S104, the switch control circuit 16 sends an ON command to the positive switch 14P and the negative switch 14N. Upon receiving the ON command, the positive switch 14P and the negative switch 14N close, closing the circuit between the power supply 12 and the servo amplifier 11. As the positive switch 14P and the negative switch 14N are closed, the voltage output from the power supply 12 is input to the servo amplifier 11 and the servo amplifier control circuit 13, enabling the servo amplifier 11 to drive the motor 3.

[0035] Figure 4 is a circuit diagram showing a conventional power supply system in which the power supply and the control power supply are provided separately.

[0036] In a conventional power supply system 100, which provides separate power supply 112-1 and control power supply 112-2, a positive power switch 114P and a negative power switch 114N are provided on the output side of the power supply 112-1 to prevent power from being supplied to the servo amplifier 111 from the power supply 112-1 when the motor 2 is not being driven. The positive power switch 114P is connected to the positive input terminal of the servo amplifier 111 via the positive power line 116P-1. The negative power switch 114N is connected to the negative input terminal of the servo amplifier 111 via the negative power line 116N-1. In addition, the positive and negative terminals of the control power supply 112-2 are connected to the servo amplifier control circuit 113 via the positive control power line 116P-2 and the negative control power line 116N-2, respectively. Thus, according to conventional examples, a total of four power lines are required between the power supply 112-1 and the control power supply 112-2 and the servo amplifier 111 and the servo amplifier control circuit 113: the positive power line 116P-1, the negative power line 116N-1, the positive control power line 116P-2, and the negative control power line 116N-2.

[0037] In contrast, according to the embodiment of the present disclosure, as shown in Figure 1, only two power lines are required between the power supply 12 and the servo amplifier 11 and servo amplifier control circuit 13: a positive DC power line 19P and a negative DC power line 19N. Therefore, according to the embodiment of the present disclosure, not only is the safety of the machine ensured when the motor 2 is running and stopped, but power wiring can also be reduced. For example, if the servo amplifier 11 is placed near the motor 2 in an industrial robot and the servo amplifiers 11 are daisy-chained, the effect of reducing power wiring becomes even greater.

[0038] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the spirit of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0039] <Note> The following additional information is disclosed regarding the above embodiments and modifications.

[0040] (Note 1) Servo amplifier 11 and A power supply 12 that outputs at least two different voltage levels in a switchable manner, A servo amplifier control circuit 13, which is connected to the power supply 12 and controls the servo amplifier 11, Switches 14P and 14N open and close the electrical circuit between the power supply 12 and the servo amplifier 11, A voltage comparison circuit 15 compares the voltage output by the power supply 12 with a predetermined threshold value, A switch control circuit 16 controls the opening and closing of the electrical circuit between the power supply 12 and the servo amplifier 11 using switches 14P and 14N, according to the comparison results from the voltage comparison circuit 15. A power supply system equipped with the following features. (Note 2) The power supply system as described in Appendix 1, wherein the switch control circuit 16 controls switches 14P and 14N to open the circuit between the power supply 12 and the servo amplifier 11 when the voltage comparison circuit 15 determines that the voltage output by the power supply 12 is below a threshold, and controls switches 14P and 14N to close the circuit between the power supply 12 and the servo amplifier 11 when the voltage comparison circuit 15 determines that the voltage output by the power supply 12 is greater than a threshold. (Note 3) The power supply system according to Appendix 1 or 2, wherein the servo amplifier control circuit 13 has a voltage conversion circuit 21 that converts the voltage input from the power supply 12 into a drive voltage for driving the servo amplifier control circuit 13. [Explanation of Symbols]

[0041] 1. Power System 2 motors 11 Servo Amplifier 12 Power supply 13. Servo Amplifier Control Circuit 14P positive switch 14N Negative Switch 15 Voltage comparison circuit 16 Switch control circuit 17P Positive side potential detection unit 17N Negative side potential detection unit 18 Capacitors 19P Positive DC power line 19N negative DC power line 21 Voltage conversion circuit 31 Switching elements 32 diodes 33 Inductors Su1, Su2, Sv1, Sv2, Sw1, Sw2 switching elements

Claims

1. Servo amplifier and A power supply that can switch between outputting at least two different voltage levels, A servo amplifier control circuit, connected to the power line connected to the aforementioned power supply, controls the servo amplifier, A switch for opening and closing the circuit between the power line connected to the power supply and the servo amplifier, A voltage comparison circuit that compares the voltage output by the power supply with a predetermined threshold, A switch control circuit controls the opening and closing of the circuit between the power supply and the servo amplifier by the switch, according to the comparison result by the voltage comparison circuit, Equipped with, The switch control circuit controls the switch to open the circuit between the power supply and the servo amplifier when the voltage comparison circuit determines that the voltage output by the power supply is less than or equal to the threshold, and controls the switch to close the circuit between the power supply and the servo amplifier when the voltage comparison circuit determines that the voltage output by the power supply is greater than the threshold.

2. The power supply system according to claim 1, wherein the servo amplifier control circuit has a voltage conversion circuit that converts a voltage input from the power supply into a drive voltage for driving the servo amplifier control circuit.

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