POWER SUPPLY SYSTEM FOR A SERVO MOTOR

Abstract

This power supply system includes a servo amplifier; a power supply that switchably outputs voltages of at least two magnitudes; a servo amplifier control circuit that is connected to the power supply and controls the servo amplifier; a switch that opens and closes a current path between the power supply and the servo amplifier; a voltage comparison circuit that compares the voltage output from the power supply and a predetermined threshold value; and a switch control circuit that controls the opening and closing of the current path between the power supply and the servo amplifier by the switch according to the comparison result from the voltage comparison circuit.

Description

TECHNICAL FIELDThe present disclosure relates to a power supply system for a servomotor.GENERAL STATE OF THE ARTA servo amplifier that drives a servo motor in a machine such as an industrial robot or a machine tool is provided with a drive power supply that supplies electric power for driving the servo motor and a control power supply that supplies electric power for a circuit that controls the servo amplifier.LIST OF REFERENCESPATENT CHARACTERISTIC[PTL1] JP 2020-162193A[PTL 2] JP 2012-135164ASUMMARY OF THE INVENTIONTECHNICAL PROBLEMA power supply system is needed that interrupts energization by a drive power supply upon non-driving of a servo motor to ensure safety of a machine driven by a servo amplifier, while ensuring energization by a control power supply to monitor the state of the servo motor.SOLUTION OF PROBLEMAccording to an aspect of the present disclosure, a power supply system includes a servo amplifier, a power supply configured to output voltages having at least two kinds of magnitudes in a switchable manner, a servo amplifier control circuit connected to the power supply and configured to control the servo amplifier, switches configured to open and close a circuit between the power supply and the servo amplifier, a voltage comparison circuit configured to compare the voltage output from the power supply with a predetermined threshold, and a switch control circuit configured to control the opening and closing of the circuit between the power supply and the servo amplifier by the switches on the basis of a comparison result by the voltage comparison circuit.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a circuit diagram showing a power supply system according to an embodiment of the present disclosure. FIG. 2 is a circuit diagram showing a step-down chopper circuit provided in a servo amplifier control circuit in the power supply system according to the embodiment of the present disclosure. FIG. 3 is a flowchart showing an operation related to opening and closing of a switch in the power supply system according to an embodiment of the present disclosure. FIG. 4 is a circuit diagram showing a power supply system based on a conventional example in which a driving power supply and a control power supply are separately provided.DESCRIPTION OF EMBODIMENTSReferring to the drawings, a power supply system for a servomotor according to an embodiment will be described below. It should be noted that like components or components having like functions are denoted by like reference numerals in the following description. Overlapping description of the components may be omitted. In this disclosure, "connected" means "electrically connected.". When a switch is turned "on", it means that a circuit in which the switch is provided is closed; that is, by performing a turn-on operation on a switch, a circuit in which the switch is provided is connected and comes into a closed state. When a switch is turned "off", it means that a circuit in which the switch is provided is open; that is, by performing a turn-off operation on a switch, a circuit in which the switch is provided is interrupted and comes into an open state.The configuration of the power supply system according to the embodiment of the present disclosure of FIG. 1 is a circuit diagram showing a power supply system according to an embodiment of the present disclosure.As an example, a case where a three-phase motor 2 is driven by electric power supplied from a power supply system 1 will be described. The motor 2 is a servomotor. The motor 2 may be, for example, a synchronous motor or an induction motor. Examples of a machine provided with the motor 2 include an industrial robot and a machine tool.According to a first embodiment of the present disclosure, the power supply system 1 includes a servo amplifier 11, a power supply 12, a servo amplifier control circuit 13, a positive-side switch 14P, a negative-side switch 14N, a voltage comparison circuit 15, a switch control circuit 16, a positive-side potential detection unit 17P, a negative-side potential detection unit 17N, and a capacitor 18.The power supply 12 outputs DC voltages of at least two kinds of magnitudes in a switchable manner. Examples of the power supply 12 include a variable voltage source including a battery and an output changeover switch, a variable voltage source including a battery and a variable resistor, and a PWM rectifier that converts an AC power supplied from an AC power supply into a DC power and outputs the DC power. For example, when the power supply 12 is configured by a PWM rectifier, the power supply 12 includes a bridge circuit including switching elements and diodes each connected in an anti-parallel circuit to the switching elements; and for example, each switching element is controlled on / off according to an obtained command, and outputs DC voltages having multiple kinds of magnitudes. Examples of the switching elements include a non-bipolar transistor such as an FET, a bipolar transistor, an IGBT, a thyristor, and a GTO. It should be noted that the type of switching element itself does not limit the present embodiment, and another type of switching element may be employed.For example, when the power supply 12 is configured to output DC voltages having two kinds of magnitudes, a high voltage (e.g., 48 V) and a low voltage (e.g., 24 V) in a switchable manner, the high voltage output from the power supply 12 is used as a drive voltage of the motor 2 and a drive voltage of the servo amplifier control circuit 13 when the motor 2 is driven by the servo amplifier 11. The low voltage output from the power supply 12 is used as the driving voltage of the servo amplifier control circuit 13 when the motor is not driven by the servo amplifier 11. It should be noted that the switching between the high voltage and the low voltage output from the power supply 12 is performed in connection with whether or not the motor 2 is driven. Whether or not the motor 2 is driven may be changed by a manual command operation performed by an operator using a control panel or the like or by a command output from a motor control unit (not shown) according to an operation program of the motor 2. The power supply 12 may be configured to output two or more kinds of quantities such as 100 V, 48 V, and 24 V. It should be noted that the numerical values listed in this disclosure and indicating the magnitude of the output voltage are only examples and may be other values.The capacitor 18 is connected between a positive-side DC line 19P extending from a positive-side output terminal of the power supply 12 and a negative-side DC line 19N extending from a negative-side output terminal. The capacitor 18 has the function of suppressing a ripple component in the DC output of the power supply 12 and the function of accumulating a DC power. Examples of the capacitor 18 include an electrolytic capacitor and a film capacitor.The servo amplifier 11 includes an inverter having a bridge circuit based on switching elements. Examples of the switching element include a non-bipolar transistor such as an FET, a bipolar transistor, an IGBT, a thyristor, and a GTO. It should be noted that the type of switching element itself does not limit the present embodiment, and another type of switching element may be employed. In the example illustrated in FIG. 1, a switching element in an upper arm of the U phase is denoted by Su 1, and a switching element in a lower arm of the U phase is denoted by Su 2. A switching element in an upper arm of the V phase is denoted by Sv 1, and a switching element in a lower arm of the V phase is denoted by Sv 2. A switching element in an upper arm of the W phase is denoted by Sw 1 and a switching element in a lower arm of the W phase is denoted by Sw 2. Although a switching element configured by a MOSFET will be described below by way of example, the embodiment of the present disclosure may also be applied by an IGBT, a thyristor, a GTO, or a transistor. When the switching element is implemented by an IGBT, the embodiment of the present disclosure is applied as a "collector" and an "emitter", respectively, by reading a "drain" representing a current inflow terminal and a "source" representing a current outflow terminal. When the switching element is implemented by a transistor, the embodiment of the present disclosure is applied as a "base", a "collector", and an "emitter", respectively, by reading a "gate" representing a control terminal, a "drain" representing a current inflow terminal, and a "source" representing a current outflow terminal. When the switching element is implemented by a thyristor or a GTO, the embodiment of the present disclosure is applied as an "anode" and a "cathode", respectively, by reading a "drain" representing a current supply terminal and a "source" representing a current discharge terminal.The servo amplifier 11 performs current conversion between a direct current power and an alternating current power, which is a drive current or a regenerative current, by driving each switching element on the basis of a PWM control method according to a switching command obtained from the servo amplifier control circuit. More specifically, the servo amplifier 11 converts a DC power supplied from the power supply 12 when the switches 14P and 14N are turned on into an AC power having a desired frequency for driving the motor 2 by bringing the internal switching elements to perform a switching operation according to a switching command obtained from the servo amplifier control circuit 13. Thus, the motor 2 operates based on, for example, variable frequency AC power. As long as a regenerative current can be generated when the motor 2 is decelerated, the regenerative alternating current generated in the motor 2 is converted into a direct current power and fed back to the direct current side by causing the internal switching elements to perform a switching operation in such a case according to a switching command obtained from the servo amplifier control circuit 13.The servo amplifier control circuit 13 generates a switching command for on / off control of each switching element, and applies the command to the gate terminal of the switching element. The servo amplifier control circuit 13 controls the motor 2 to be able to operate according to a predetermined operation pattern by controlling the current conversion by the inverter in the servo amplifier 11 according to a predetermined operation program. It should be noted that the configuration of the servo amplifier control circuit 13 defined in this disclosure is only an example, and the configuration of the servo amplifier control circuit 13 may be defined by including members such as a position command generation unit, a torque command generation unit, and a switching command generation unit, for example.The servo amplifier control circuit 13 is supplied with electric power from the power supply 12 via the positive-side DC line 19P and the negative-side DC line 19N. As described above, the power supply 12 outputs DC voltages having at least two kinds of magnitudes in a switchable manner. Therefore, direct current voltages of at least two kinds of magnitudes are input to the servo amplifier control circuit 13. On the other hand, the driving voltage of each circuit in the servo amplifier control circuit 13 is always constant regardless of the magnitude of the output voltage of the power supply 12. The servo amplifier control circuit 13 is provided with a voltage conversion circuit configured to convert the voltage input from the power supply 12 into a drive voltage for driving the servo amplifier control circuit.For example, when the power supply 12 is configured to output a high voltage of 48 V and a low voltage of 24 V in a switchable manner, either 48 V or 24 V are input to the servo amplifier control circuit 13. The voltage conversion circuit in the servo amplifier control circuit 13 converts the voltage of 48 V or 24 V from the power supply 12 into a drive voltage (e.g., 5 V or 10 V) for driving the servo amplifier control circuit. Examples of the voltage conversion circuit in the servo amplifier control circuit 13 include a step-down chopper circuit, a step-up chopper circuit, a step-up / step-down chopper circuit, and a circuit including a combination of a switching element and a voltage dividing resistor.For example, a case will be described in which the voltage conversion circuit in the servo amplifier control circuit 13 is implemented with a step-down chopper circuit. FIG. 2 is a circuit diagram showing a step-down chopper circuit provided in the servo amplifier control circuit in the power supply system according to the embodiment of the present disclosure. As illustrated in FIG. 2, the servo amplifier control circuit 13 is provided with, for example, a step-down chopper circuit including a switching element 31, a diode 32, and an inductor 33 as the voltage conversion circuit 21. Examples of the switching element 31 include a non-bipolar transistor such as an FET, a bipolar transistor, an IGBT, a thyristor, and a GTO. It should be noted that the type of switching element 31 itself does not limit the present embodiment, and another type of switching element may be employed.The impedance of a circuit in a stage following the voltage conversion circuit 21 in the servo amplifier control circuit 13 is denoted by Z in in FIG. 2. The input voltage E in of the voltage conversion circuit 21 is a DC voltage supplied from the power supply 12 of, for example, 48 V or 24 V. In the voltage conversion circuit 21, power is stored in the inductor 33 when the switching element 31 is turned on, and power stored in the inductor 33 is released when the switching element 31 is turned off. The output voltage of the voltage conversion circuit 21 increases with the increase in the on-time of the switching element 31, and the output voltage of the voltage conversion circuit 21 decreases with the decrease in the on-time of the switching element 31. By controlling the duty ratio of the switching element 31, the output voltage (e.g., 5 V or 10 V) for driving the servo amplifier control circuit is output from the voltage conversion circuit 21.Now, the description returns to FIG. 1. The positive-side switch 14P and the negative-side switch 14N are provided as switches that open and close a circuit between the power supply 12 and the servo amplifier 11. In other words, in the circuit, the positive-side switch 14P that opens and closes a circuit between the positive-side DC line 19P extending from the positive-side output terminal of the power supply and the positive-side input terminal of the servo amplifier 11 is provided. In the circuit, the negative-side switch 14N that opens and closes a circuit between the negative-side DC line 19N extending from the negative-side output terminal of the power supply 12 and a negative-side input terminal of the servo amplifier 11 is provided. Upon receiving an on command from the switch control circuit 16, the positive-side switch 14P and the negative-side switch 14N perform a closing operation, thereby closing the circuit between the power supply 2 and the servo amplifier 11. Upon receiving an off command from the switch control circuit 16, the positive-side switch 14P and the negative-side switch 14N perform an opening operation, thereby opening the circuit between the power supply 2 and the servo amplifier 11.The positive-side potential detection unit 17P detects a positive-side potential of the positive-side DC power line 19P extending from the positive-side output terminal of the power supply 12. The negative-side potential detection unit 17N detects a negative-side potential of the negative-side DC power line 19N extending from the negative-side output terminal of the power supply 12. The potential difference between the positive side potential of the positive side DC power line 19P and the negative side potential of the negative side DC power line 19N is the magnitude of the voltage output from the power supply 12. The detection results by the positive-side potential detection unit 17P and the negative-side potential detection unit 17N are sent to the voltage comparison circuit 15.The voltage comparing circuit 15 compares the voltage output from the power supply 12 with a predetermined threshold value. As described above, the power supply 12 outputs voltages of at least two magnitudes in a switchable manner. The voltage comparison circuit 15 determines the value of the voltage output from the power supply 12 using the threshold value. The comparison result by the voltage comparison circuit 13 is sent to the switch control circuit 16. For example, when the power supply 12 is configured to output a high voltage of 48 V and a low voltage of 24 V in a switchable manner, either 48 V or 24 V are output from the power supply 12. In this case, for example, by setting the threshold value to be 36 V and comparing the threshold value of 36 V with the voltage output from the power supply 12 in the voltage comparison circuit 15, which is output from the power supply 102 from 48 V and 24 V can be determined. In other words, the voltage comparison circuit 15 determines that the power supply 12 outputs the voltage of 24 V when the voltage output from the power supply 12 is equal to or lower than the threshold value of 36 V, and determines that the power supply 12 outputs the voltage of 48 V when the voltage output from the power supply 12 is higher than the threshold value of 36 V. The examples of the numerical values described in this disclosure are only examples and may be other values. It should be noted that the threshold may be stored in a rewritable storage unit (not shown) and may be rewritten by an external device, allowing the threshold to be changed to an appropriate value as required even after being set.The switch control circuit 16 controls the opening and closing of the circuit between the power supply 12 and the servo amplifier 11 through the positive-side switch 14P and the negative-side switch 14N on the basis of the comparison result by the voltage comparison circuit 15.When it is determined by the voltage comparison circuit 15 that the voltage output from the power supply 12 is equal to or lower than the threshold value, the switch control circuit 16 sends an off command to the positive-side switch 14P and the negative-side switch 14N. When the positive-side switch 14P and the negative-side switch 14N receive the off command, they perform the opening operation and open the circuit between the power supply 12 and the servo amplifier 11. Since the positive-side switch 14P and the negative-side switch 14N are in the open state, the voltage output from the power supply 12 is not input to the servo amplifier 11, but is input to the servo amplifier control circuit 13, on the other hand. Accordingly, since the motor 2 is not driven but the servo amplifier control circuit 13 itself operates, various kinds of processing including processing for monitoring the state of the motor 2 can be executed and safety of the machine is ensured.When it is determined by the voltage comparison circuit 15 that the voltage output from the power supply 12 is larger than the threshold value, the switch control circuit 16 sends an on command to the positive-side switch 14P and the negative-side switch 14N. When the positive-side switch 14P and the negative-side switch 14N receive the on command, they perform the closing operation and close the circuit between the power supply 12 and the servo amplifier 11. Since the positive-side switch 14P and the negative-side 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, and the motor 2 can be driven by the servo amplifier 11.The above-described voltage comparison circuit 15 may include a comparator circuit, and the switch control unit 16 controls the positive-side switch 14P and the negative-side switch 14N on the basis of the output of the converter circuit in this case. Alternatively, the above-described voltage comparison circuit 15 may have a circuit configuration in which a computation processing device, a memory, and an analog-to-digital converter are combined.In the power supply system 1, at least one processor that is a computing processing device is provided. Examples of the calculation processing device include an IC, an LSI, a CPU, an MPU, and a DSP. The calculation processing device may include the voltage comparison circuit 15, the switch control circuit 16, the motor control circuit (not shown), and another processing circuit. For example, each unit included in the computation processing circuit may be a functional module provided by a program executed on a processor. For example, when the voltage comparison circuit 15, the switch control circuit 16, the motor control circuit, and the other processing circuit are constructed in a program form, the function of each unit can be provided by operating the arithmetic processing apparatus according to the program. The program for executing each kind of processing in the voltage comparison circuit 15, the switch control circuit 16, the motor control circuit, and the other processing circuit may be provided in a form recorded 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 circuit, and the other processing circuit may be provided as a semiconductor integrated circuit in which a program providing the function of each unit is written.In the power supply system 1, at least one storage that is a storage device is provided. Examples of the memory include an electrically erasable / writable nonvolatile memory such as an EEPROM (registered trademark) and high-speed readable / writable random access memories such as a DRAM and an SRAM. For example, the storage device may have a structure such as an HDD or an SSD. A program for operating the voltage comparison circuit 15, the switch control circuit 16, the motor control circuit, and the other processing circuit may be stored in the memory. Results of the potential detection obtained by the positive-side potential detection unit 17P and the negative-side potential detection unit 17N may be stored in the memory. A comparison result by the voltage comparison circuit 15 may be stored in the memory. Various kinds of data required when the motor is driven may be stored in the memory.Operation of Power Supply System According to Embodiment of the Present DisclosureFIG. 3 is a flowchart illustrating an operation related to opening and closing of a switch in the power supply system according to the embodiment of the present disclosure.The power supply 12 outputs a voltage from among DC voltages having at least two kinds of magnitudes. In step S 101, the positive-side potential detection unit 17P detects the positive-side potential of the positive-side DC power line 19P extending from the positive-side output terminal of the power supply 12. The negative-side potential detection unit 17N detects the negative-side potential of the negative-side DC power line 19N extending from the negative-side output terminal of the power supply 12. Thereby, the magnitude of the voltage output from the power supply 12 is detected. The detection results by the positive-side potential detection unit 17P and the negative-side potential detection unit 17N are sent to the voltage comparison circuit 15.In step S 102, the voltage comparison circuit 15 compares the voltage output from the power supply 12 with the predetermined threshold value. When it is determined by the voltage comparing circuit 15 that the voltage output from the power supply 12 is equal to or lower than the threshold at step S 102, the processing proceeds to step S 103. When it is determined by the voltage comparing circuit 15 that the voltage output from the power supply 12 is not equal to or lower than the threshold (i.e., it is determined that the voltage output from the power supply 12 is greater than the threshold) at step S 102, the processing proceeds to step S 104.In step S 103, the switch control circuit 16 sends an off command to the positive-side switch 14P and the negative-side switch 14N. When the positive-side switch 14P and the negative-side switch 14N receive the off command, they perform the opening operation and open the circuit between the power supply 12 and the servo amplifier 11. Accordingly, since the motor 2 does not operate but the servo amplifier control circuit 13 itself operates, various kinds of processing including processing for monitoring the state of the motor 2 can be executed and safety of the machine is ensured.In step S 104, the switch control circuit 16 sends an on command to the positive-side switch 14P and the negative-side switch 14N. When the positive-side switch 14P and the negative-side switch 14N receive the on command, they perform the closing operation and close the circuit between the power supply 12 and the servo amplifier 11.FIG. 4 is a circuit diagram showing a power supply system based on a conventional example in which a driving power supply and a control power supply are separately provided.In a power supply system 100 based on the conventional example, in which a drive power supply 112- 1 and a control power supply 112- 2 are separately provided, a positive-side power switch 114P and a negative-side power switch 114N are provided on the output side of the drive power supply 112- 1 to prevent supply of electric power from the drive power supply 112- 1 to a servo amplifier 111 when a motor 2 is not driven. The positive-side current switch 114P is connected to a positive-side input terminal of the servo amplifier 111 through a positive-side drive current line 116P-1. The negative-side current switch 114N is connected to a negative-side input terminal of the servo amplifier 111 through a negative-side drive current line 116N-1. The positive-side terminal and the negative-side terminal of the control power supply 112- 2 are connected to the servo amplifier control circuit 113 through a positive-side control current line 116P- 2 and a negative-side control current line 116N- 2, respectively. Thus, according to the conventional example, a total of four power lines, the positive-side drive power line 116P- 1, the negative-side drive power line 116N- 1, the positive-side control power line 116P- 2, and the negative-side control power line 116N- 2, are required between the drive power supply 112- 1 and the control power supply 112- 2, and the servo amplifier 111 and the servo amplifier control circuit 113.On the other hand, according to the embodiment of the present disclosure, as illustrated in FIG. 1, only a total of two power lines, the positive-side DC power line 19P and the negative-side DC power line 19N, are sufficient for connection between the power supply 12 and the servo amplifier 11 and the servo amplifier control circuit 13. For example, the effect of reduction in wiring increases when the servo amplifiers 11 are placed close to the motor 2 in an industrial robot and the servo amplifiers 11 are linked.Although the present disclosure has been described above in detail, the present disclosure is not limited to each embodiment described above. Various additions, substitutions, changes, partial omissions, and the like can be made to the embodiments without departing from the scope of the present disclosure derived from the contents described in the claims and their equivalents. In addition, the embodiments may be implemented in combination. For example, the operation order or the processing order is exemplified in the above embodiments, but is not limited thereto. The above also applies when a numerical value or mathematical expression has been used in the description of the above-mentioned embodiments.Supplementary NotesWith respect to the above-mentioned embodiments and their modification examples, the following supplementary notes are further disclosed.Supplementary Note 1A power supply system includes a servo amplifier 11; a power supply 12 configured to output voltages of at least two kinds of magnitudes in a switchable manner; a servo amplifier control circuit 13 connected to the power supply 12 and configured to control the servo amplifier 11; switches 14P and 14N configured to open and close a circuit between the power supply 12 and the servo amplifier 11; a voltage comparison circuit 15 configured to compare the voltage output from the power supply 12 with a predetermined threshold; and a switch control circuit 16 that controls the opening and closing of the circuit between the power supply 12 and the servo amplifier 11 by the switches 14P and 14N on the basis of a comparison result by the voltage comparison circuit 15.Supplementary Note 2In the power supply system according to Supplementary Note 2, the switch control circuit 16 is configured to control the switches 14P and 14N in such a manner that the circuit between the power supply 12 and the servo amplifier 11 is opened when it is determined by the voltage comparison circuit 15 that the voltage output from the power supply 12 is equal to or lower than the threshold value, and controls the switches 14P and 14N in such a manner that the circuit between the power supply 12 and the servo amplifier 11 is closed when it is determined by the voltage comparison circuit 15 that the voltage output from the power supply 12 is higher than the threshold value.Supplementary Note 3In the power supply system according to Supplementary Note 1 or 2, the servo amplifier control circuit 13 includes a voltage conversion circuit 21 configured to convert the voltage input from the power supply 12 into a drive voltage for driving the servo amplifier control circuit 13.LIST OF REFERENCE CHARACTERS1 Power supply system 2 Motor 11 Servo amplifier 12 Power supply 13 Servo amplifier control circuit 14P Positive-side switch 14N Negative-side switch 15 Voltage comparison circuit 16 Switch control circuit 17P Positive-side potential detection unit 17N Negative-side potential detection unit 18 Capacitor 19P Positive-side DC line 19N Negative-side DC line 21 Voltage conversion circuit 31 Switching element 32 Diode 33 Inductor Su 1, Su 2, Sv 1, Sv 2, Sw 1, Sw 2 Switching elementReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2020-162193A

[0002] JP 2012-135164A

[0002]

Claims

A power supply system comprising: a servo amplifier; a power supply configured to output voltages of at least two kinds of magnitudes in a switchable manner; a servo amplifier control circuit connected to the power supply and configured to control the servo amplifier; switches configured to open and close a circuit between the power supply and the servo amplifier; a voltage comparison circuit configured to compare the voltage output from the power supply with a predetermined threshold; and a switch control circuit configured to control the opening and closing of the circuit between the power supply and the servo amplifier by the switches on the basis of a comparison result by the voltage comparison circuit.The power supply system according to claim 1, wherein the switch control circuit controls the switches in such a manner that the circuit between the power supply and the servo amplifier is opened when it is determined by the voltage comparison circuit that the voltage output from the power supply is equal to or less than the threshold value, and controls the switches in such a manner that the circuit between the power supply and the servo amplifier is closed when it is determined by the voltage comparison circuit that the voltage output from the power supply is greater than the threshold value.The power supply system according to claim 1 or 2, wherein the servo amplifier control circuit includes a voltage conversion circuit configured to convert the voltage input from the power supply into a drive voltage for driving the servo amplifier control circuit.

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