JP2002174238A - Magnetic bearing control device and vacuum pump using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing control device provided with a compensating circuit capable of advancing the phase of a control signal of large amplitude and lowering gain when the control signal is inputted and a vacuum pump provided with the device. SOLUTION: Impedance circuits 15 and 16 having primary delay transmission functions are connected via diodes 5 and 6 biased in opposite directions in parallel with a resistor 18 applying negative feedback to an operational amplifier 2. The diodes 5 and 6 do not operate for a signal of small amplitude and the negative feedback is performed by the resistor 18. The diodes 5 and 6 are conducted for the signal of large amplitude and the negative feedback is applied by the impedances 15 and 16 together with the resistor 18. As a result, gain of the operational amplifier 2 is lowered and the phase of an output signal is advanced. Operating voltage of a limiter is set by bias voltage of the diodes 5 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing control device and a vacuum pump using the same, for example, a magnetic bearing control device for a vacuum pump having a rotor held by a magnetic bearing such as a turbo molecular pump, And a vacuum pump using the device.

[0002]

2. Description of the Related Art A control circuit for a magnetic bearing used in a turbo-molecular pump or the like uses a PID (Proportional) control signal for a frequency component of the whirling or vibration to suppress the vibration of the rotor due to whirling or disturbance of the rotor.
The phase difference is given by an integral differential circuit to enhance the damping effect.
As a result, the Bode diagram becomes as shown in FIG.
The gain 501 increases on the high frequency side, and the phase 502 advances and then delays as the frequency increases. As described above, in a control circuit of a magnetic bearing used in a turbo molecular pump or the like, a gain at a high frequency is increased. Therefore, when a disturbance having a large amplitude at a high frequency enters, a large electromagnet current needs to flow to suppress the disturbance.

However, since the output of a power amplifier for driving an electromagnet is limited, when a large-frequency disturbance occurs at a high frequency, the output of the power amplifier is saturated, and as a result, the current is controlled according to a target value. In some cases, the influence of disturbance could not be suppressed. Therefore, in order to suppress a large amplitude disturbance, it is necessary to reduce the gain of the control circuit at the time of large amplitude to prevent saturation of the power amplifier and to advance the phase of the control signal to enhance the damping effect. In the control circuit of the magnetic bearing,
Japanese Patent Laid-Open No. 7-167 discloses a compensation circuit for performing such compensation.
There is a correction circuit for a servo control circuit of an active magnetic bearing disclosed in No. 144.

FIG. 8 is a diagram showing the circuit configuration of a control circuit 400 disclosed in JP-A-7-167144. Control circuit 4
00 is installed, for example, between the PID control circuit and the driving power amplifier. The control circuit 400 includes the operational amplifier 11
0, first impedance circuit 100, second impedance circuit 200, and third impedance circuit 300
It is composed of First impedance circuit 100
Is a resistor 1 connected in series with the resistor 111
12 and a capacitor 113 are connected.
The second impedance circuit 200 has exactly the same configuration as the first impedance circuit, and the constants of the corresponding elements are the same.

The third impedance circuit 300 has a resistor 131 and a diode section 134 connected in series.
The diode portion 134 forms a limiter, and conducts when a difference between voltages applied to both ends is equal to or more than a predetermined value,
If it is smaller than a predetermined value, no conduction is made. For example, assuming that the operating voltage of the diode is 0.5 [V], the diode section 134 becomes conductive when the voltage becomes 1 [V] or more because two diodes are connected in series. The diode section 134 operates in both directions because the diodes are connected in parallel in opposite directions.

The first impedance circuit is connected in series to the inverting input terminal of the operational amplifier 110, and constitutes a differentiating circuit together with the operational amplifier 110. The negative feedback circuit 150 of the operational amplifier 110 is
0 and the impedance circuit 300 are connected in parallel. Here, assuming that the operating voltage of the diode section 134 is Vth, when the amplitude of the output signal of the operational amplifier 110 is smaller than Vth, the diode section 134 does not conduct, and only the second impedance circuit 200 acts as a negative feedback circuit. I do. In this case, the negative feedback circuit 200 and the operational amplifier 110 form a first-order delay circuit. Therefore, when the amplitude of the output signal of the operational amplifier 110 is smaller than Vth, the change in the phase caused by the primary advance circuit due to the operation of the impedance circuit 100 is reduced by the impedance circuit 200.
Is compensated by the first-order lag effect due to the action of

When the output voltage of the operational amplifier 110 is equal to or higher than Vth, the diode portion 134 conducts and the negative feedback circuit 1
50 is the impedance circuit 200 and the impedance 30
0 is synthesized. In this case, the resistor 131 is connected in parallel to the impedance circuit 200, and the gain of the operational amplifier 110 decreases, and the phase of the negative feedback signal is delayed by the negative feedback circuit 150. The phase advances with respect to the signal. As described above, when the amplitude of the control signal of the driving power amplifier exceeds a predetermined value, the control circuit 400 acts to reduce the amplitude of the control signal and advance the phase.

[0008]

However, the control circuit 40
0 indicates that the operation start voltage of the limiter function is
Since it is determined by the operating voltage of the constant voltage diode of No. 4, a diode having a different operating voltage must be purchased and used every time the operating point is changed, which increases the procurement cost, adjustment cost, and production cost. Further, since the operating voltage of the diode is a discrete value such as 3.3 [V] or 4.7 [V], a control circuit having an intermediate characteristic cannot be formed. Further, since the same filter characteristics must be realized in the impedance circuit 100 and the impedance circuit 200, the control circuit 40 must be improved in accuracy of the resistor 111 and the capacitor 113.
The characteristics of 0 vary.

Therefore, an object of the present invention is to realize a limiter that can more freely set a limiter voltage without using a constant voltage characteristic of a diode, and to provide a small-amplitude control signal in which a limiter circuit does not operate. An object of the present invention is to provide a magnetic bearing control device that does not affect the filter characteristics with variations in capacitors and resistors, and a vacuum pump using the device.

[0010]

In order to achieve the above object, the present invention provides an operational amplifier having a predetermined gain and converting an electric signal input from an input section as an output signal, and the operational amplifier. A resistor that applies negative feedback to
A first impedance circuit having a first reference voltage value to be compared with the voltage value of the output signal, and having a first limiter that operates when the output signal is larger than the first reference voltage value; When the first limiter is operated, the first impedance circuit is connected in parallel to the resistor, and first connection means for adjusting a gain of the operational amplifier; and a voltage value of the output signal; A second limiter having a second reference voltage value to be compared and having a second limiter that operates when the output signal is smaller than the second reference voltage value
And second connection means for connecting the second impedance circuit to the resistor in parallel when the second limiter operates and adjusting the gain of the operational amplifier. A magnetic bearing control device having a compensating circuit is provided (first configuration). In the first configuration, by appropriately configuring the first impedance and the second impedance circuit, the gain of the operational amplifier can be adjusted, and also the phase of the output signal from the operational amplifier can be adjusted. Further, in the first configuration, the first limiter and the second limiter are:
The first reference voltage value at which the first limiter operates and the second reference voltage value at which the second limiter operates are constituted by diodes each biased by a predetermined voltage in the opposite direction, It can be configured so as to be defined by the operating voltage of each of the diodes (second configuration). Further, the first impedance circuit and the second impedance circuit in the first configuration or the second configuration are configured such that a second resistor is connected in series to a component in which a capacitor and a first resistor are connected in parallel. And a DC voltage applying means for applying a DC voltage to the first impedance circuit and the second impedance circuit, wherein the diode is connected in the reverse direction. The bias voltage for biasing the DC voltage applied by the DC voltage application means is defined by a voltage dividing ratio of the DC voltage applied by the first resistor and the second resistor. 3
Configuration). Further, the electric signal input from the input unit in any one of the first to third configurations is a control signal of a power amplifier that supplies an exciting current of an electromagnet forming a magnetic bearing. When the voltage value of the control signal is higher than the first reference voltage value, the phase of the control signal is advanced in the first impedance circuit, and the gain of the operational amplifier is reduced. When the voltage value is smaller than the second reference voltage value, the control signal is compensated by advancing the phase of the control signal and lowering the gain of the operational amplifier in the second impedance circuit. (Fourth configuration). Further, in any one of the first to fourth configurations, an operating voltage of the first limiter and an operating voltage of the second limiter may be set according to an installation posture of the magnetic bearing. (Fifth configuration). The change of the operating voltage of the limiter can be performed, for example, by setting the resistance values of the resistors used in the first impedance circuit and the second impedance circuit to appropriate values. . In order to achieve the above object, the present invention uses the magnetic bearing control device according to any one of the first to fifth configurations, wherein the magnetic bearing control device is used. Provide a vacuum pump. This vacuum pump can be a turbo-molecular pump using a magnetic bearing device for holding the rotor.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a circuit diagram showing a circuit configuration of a nonlinear circuit 1 used as a compensation circuit of a magnetic bearing control device according to an embodiment of the present invention. The nonlinear circuit 1 includes an operational amplifier 2, a signal input unit 3, a signal output unit 4, a resistor 18, and a capacitor 4. The gain of the operational amplifier 2 was 100 [dB], the resistance of the resistor 18 was 10 [kΩ], and the capacitance of the capacitor 4 was 100 [pF]. The inverting input terminal of the operational amplifier 2 is connected to the signal input unit 3 via the resistor 17.
The non-inverting input terminal is grounded.

The signal output unit 4 of the operational amplifier 2 is connected to a power amplifier of an electromagnet of a magnetic bearing, not shown, and outputs a control signal compensated by the nonlinear circuit 1. The output terminal and the inverting input terminal of the operational amplifier 2 are connected via a resistor 18 to form a negative feedback circuit. As will be described later, the operational amplifier 2 is feedback-controlled by the resistor 18 when the diodes 5 and 6 are not conducting, and the gain is determined by the ratio between the resistor 18 and the resistor 17.

The capacitor 4 is inserted to cut high frequency noise of the input signal. Since the high frequency noise is bypassed by the capacitor 4, the high frequency noise is not amplified by the operational amplifier 2.

Further, the nonlinear circuit 1 includes impedance circuits 15 and 16. As will be described later, when the voltage Vo of the output signal of the operational amplifier 2 exceeds a predetermined value Vth1, the diode 6 conducts and the impedance circuit 16
Is added to the negative feedback circuit of the operational amplifier 2 to operate. When Vo falls below a predetermined value -Vth2, the diode 5 conducts and the impedance 15 is added to the negative feedback circuit to operate. As described later, the operating voltage Vt of the impedance circuit 16 is
h1 and the operating voltage −Vth2 of the impedance circuit 15
Can be individually set by appropriately selecting the resistance values of the resistors 8, 9, 10, and 11. Note that, in the present embodiment, Vth1 is -Vth2 to +1.15 [V].
Is set to −1.15 [V], and the amplitude of the output signal is ± 1.
When the voltage becomes 15 [V] or more, the impedance circuits 15, 1
6 are configured to operate.

The resistors 8, 9, 10, and 11 are connected in series.
[V] and -15 [V].
The resistance values of the resistors 8, 9, 10, and 11 are 270, respectively.
[KΩ], 20 [kΩ], 20 [kΩ], 270 [k
Ω], and the potentials at points A and B are +1 [V],
The voltage is divided to -1 [V]. The point C is connected to the output terminal of the operational amplifier 2, and the potential at the point C is divided to 0 [V].

The impedance circuit 16 includes a resistor 10,
It comprises a resistor 11, a capacitor 12, and a diode 6. The resistor 11 and the capacitor 12 are connected in parallel, and the resistor 10 is connected to them in series. Point B is connected to the inverting input terminal of operational amplifier 2 via diode 6 and resistor 18. The forward direction of the diode is from point B to the inverting input terminal. The operating voltage of the diode 6 is, for example,
When the voltage is 0.5 [V], the potential at the point B increases, and the potential difference acting on both ends of the diode 6 becomes 0.5 [V] in the forward direction.
When this occurs, the diode 6 conducts, and a feedback signal is sent from the point B to the inverting input terminal. The potential at point B is low,
When the voltage applied to the diode 6 in the forward direction is less than 0.5 [V], the diode 6 does not conduct, and the impedance circuit 16 does not act on the operational amplifier 2. Note that the resistance value of the resistor 19 is 20 [kΩ], and the resistor 19 is inserted to make the amount of negative feedback appropriate.

It can be seen from the following equation 1 that the diode 6 conducts when the output voltage Vo of the operational amplifier 2 is 1.15 [V] or more.

[0018]

(15 [V] +0.5 [V]) ０．５270 [kΩ] × 20 [kΩ] = 1.15 [V] (1)

That is, the output Vo of the operational amplifier 2 is 1.15
When the voltage is equal to or higher than [V], the diode 6 operates, the impedance 16 is added to the negative feedback circuit, and the output Vo becomes 1.1.
If it is less than 5, the diode 6 does not operate, and the impedance circuit 16 is disconnected from the negative feedback circuit. Thus, by applying a bias to the diode in the reverse direction, a limiter that operates at a predetermined voltage value can be formed. The operating voltage of this limiter is determined by the resistors 8, 9, 1
It can be set by appropriately selecting the resistance values of 0 and 11 and the voltages of the constant voltage power supplies 13 and 14, and can be set without depending on the operating voltage of the diode.

As will be described later, the impedance circuit 1
6 has a first-order lag transfer function, and has an impedance circuit 1
The negative feedback signal Vfb from 6 is a signal whose phase is delayed as compared with the input signal Vi of the operational amplifier 2. Since Vfb is input to the inverting input terminal of the operational amplifier 2 via the resistor 19, the phase of the output signal of the operational amplifier 2 advances. Further, when the diode 6 conducts, the resistor 18 and the impedance circuit 16 are connected in parallel, so that the resistance of the negative feedback circuit is reduced by the resistor 18 alone compared to when negative feedback is applied. In effect, the gain of the operational amplifier 2 decreases. From the above description, it can be seen that when the output voltage Vo of the operational amplifier 2 becomes 1.15 [V] or more, the output signal of the operational amplifier 2 advances in phase and decreases in gain.

The impedance circuit 15 includes a resistor 9, a resistor 8, a capacitor 7, and a diode 5. The resistor 8 and the capacitor 7 are connected in parallel, and the resistor 9 is connected in series with them. Point A is connected via a diode 5 to the inverting input terminal of the operational amplifier 2. The direction from point A to the inverting input terminal is the opposite direction. The operating voltage of the diode 5 is, for example,
Assuming that the potential at the point A drops to 0.5 [V], when the potential difference between both ends of the diode 5 becomes equal to or more than 0.5 [V] in the forward direction, the diode 5 conducts and is inverted from the point A. A feedback signal is sent to the input terminal. When the potential at the point A is high and the voltage applied to the diode 5 in the forward direction is smaller than 0.5 [V], the diode 5 does not conduct, and the impedance circuit 15 does not operate on the operational amplifier 2.

When the calculation is performed in the same manner as in the case of the impedance circuit 16, the output voltage Vo of the operational amplifier 2 is -1.15.
It can be seen that the diode 5 operates when the voltage is lower than [V]. When Vo becomes −1.15 [V] or less, the impedance circuit 15 is added to the negative feedback circuit, and the phase of the output signal of the operational amplifier 2 advances, and the gain decreases, as in the case of the impedance 16. Output voltage Vo is -1.1
When the voltage is 5 [V] or more, the impedance circuit 15 does not operate with respect to the negative feedback circuit, and the negative feedback circuit includes only the resistor 18.

From the above description, it can be seen that the voltage Vo of the output signal is-
When the output voltage Vo is in the range from 1.15 [V] to 1.15 [V], the nonlinear circuit 1 performs a normal operation, and when the output voltage Vo is −1.15 or less, or +1.15 or more, the nonlinear circuit 1 performs nonlinear operation. The gain of the circuit 1 decreases, and the phase of the control signal advances.
Thus, when the amplitude of the output signal becomes larger than the predetermined value, the nonlinear circuit 1 performs a nonlinear operation so that the gain decreases and the phase of the signal advances.

FIG. 2 is a diagram showing the impedance circuit 16 for an AC component. It is assumed that the diode 6 is operating and there is no voltage drop due to the diode 6. The resistance values of the resistors 10 and 11 are R3, R4,
Assuming that the capacitance of the capacitor 12 is C2, the potential Vf at the point B
b is expressed by the following equation 2 using the output Vo of the operational amplifier 2.

[0025]

Vfb = R3 ÷ ｛(R3 + R4) + jω × R3 × R4 × C2｝ × Vo (2)

J is an imaginary unit, and ω is the frequency of the input signal. As can be seen by replacing jω with s in Equation 2, the impedance 16 has a first-order lag transfer function.

FIG. 3 shows a case where the nonlinear circuit 1 is used as a compensation circuit of a magnetic bearing control device, and when a large amplitude disturbance occurs at a high frequency in the rotor, the rotor is compensated by the nonlinear circuit 1 and the compensation is not performed. This is a comparison of the output current of the power amplifier. The horizontal axis represents time, and the vertical axis represents current value. The waveform 31 is a waveform inserted for comparison, in which the input signal is amplified with the same gain as that of the small signal and has the same phase as the input signal. A portion indicated by a solid line of the waveform 32 represents a current flowing through the electromagnet when the phase adjustment and the gain adjustment are not performed. The portion indicated by the dotted line indicates the portion where the power amplifier was saturated and was not output.

The phase of the waveform 32 is delayed as compared with the phase of the waveform 31, and the power amplifier is saturated at the portion indicated by the dotted line. That is, the waveform 32 has a phase behind the input signal, and the current cannot be controlled as desired. A waveform 33 represents the output current of the power amplifier when the control signal is compensated by the nonlinear circuit 1. Since the phase is advanced from the waveform 31 and the gain of the operational amplifier 2 decreases, the amplitude of the control signal decreases and the power amplifier does not saturate.

FIG. 4 shows experimental data using the nonlinear circuit according to the present invention. The vertical axis represents voltage, and the horizontal axis represents time. In the nonlinear circuit used in this experiment, the output amplitude was about 2
The limiter is set to operate when the voltage exceeds [V]. Waveform 38 represents the input signal to the non-linear circuit. Waveforms 39, 40, and 41 are the waveforms of the output signal with respect to the input signal represented by waveform 38. The waveform 39 has an amplitude within 2 [V] and the same phase as the input waveform 38. The waveforms 40 and 41 have an amplitude of 2 [V] or more, and it can be seen that the phase is advanced from the input signal.

FIG. 5 shows a non-linear circuit 1 according to the present embodiment.
FIG. 3 is a diagram showing an installation example in the case of installing a magnetic bearing control device used in a turbo-molecular pump, for example. Here, the turbo molecular pump will be described. The turbo molecular pump is, for example, a vacuum pump that discharges a process gas from a chamber of a semiconductor manufacturing apparatus or is installed in a vacuum device that requires a high vacuum. In a turbo molecular pump, a rotor is installed inside a casing that forms an outer casing. A plurality of rotor blades are mounted on the rotor in a plurality of stages radially from the axis of the rotor. The rotor blade is attached to the rotor shaft at a predetermined inclination with respect to a plane perpendicular to the axis of the rotor.

A large number of stator blades are attached to the casing toward the inside of the casing so as to be different from the rotor blades. The stator blade is attached to the stator at a predetermined inclination with respect to a plane perpendicular to the axis of the rotor. The rotor can rotate at a high speed of about 30,000 per minute. When the rotor rotates, the rotor blades also rotate, and by the action of the rotor blades and the stator blades, gas is sucked from the intake port of the turbo-molecular pump and discharged from the exhaust port.

The rotor has a magnetic bearing that holds the rotor in the radial direction and a magnetic bearing that holds the rotor in the thrust direction. A magnetic bearing that holds the rotor in the radial direction is arranged so that a plurality of electromagnets face each other around the rotor,
Due to the magnetic force exerted on the rotor by these electromagnets, the rotor magnetically floats in the radial direction and is held in a space without contact. Similarly, the magnetic bearing that holds the rotor in the thrust direction also causes the rotor to magnetically levitate in the thrust direction by the magnetic force of the electromagnet, and holds the rotor in a space without contact.

The position of the rotor is detected by a displacement sensor for detecting the displacement of the rotor in the radial direction and a displacement sensor for detecting the displacement of the rotor in the thrust direction. The magnetic bearing control device always keeps the rotor position at a predetermined position. Thus, the exciting current of the electromagnet constituting the magnetic bearing is adjusted.
In this embodiment, a turbo molecular pump is used as an example of the vacuum pump. However, the present invention is not limited to this.
Other vacuum pumps using magnetic bearings may be used.

As described above, the magnetic bearing of the turbo-molecular pump is constituted by a plurality of electromagnets and a plurality of displacement sensors, but in the following description, a single electromagnet is used for simplicity. A description will be given using an electromagnet 45 and a single sensor 41 as a displacement sensor. The configuration using the electromagnet 45 and the sensor 41 described below can be applied to individual electromagnets constituting a magnetic bearing of a turbo molecular pump.

The sensor 41 is installed around the rotor of the magnetic bearing device and detects the position of the rotor. Sensor 41
Are usually installed in plural numbers, and detect the radial and axial displacement of the rotor. The PID control circuit 42 generates a control signal for adjusting the magnetic force of the electromagnet 45 so as to hold the rotor at a predetermined position from the detection signal of the sensor 41.

The output signal of the PID control circuit 42 is input to the compensation circuit 43. In this case, the non-linear circuit 1 is used as the compensation circuit 43. When the amplitude of the input control signal is smaller than a predetermined value, the non-linear circuit 1 amplifies the control signal with a predetermined gain, and outputs the amplified control signal to the power amplifier without changing the phase. When the amplitude of the control signal is equal to or larger than a predetermined value, the phase of the control signal is advanced and the gain is reduced. The control signal compensated by the nonlinear circuit 1 is input to the power amplifier 44, and the power amplifier 44 supplies an exciting current to the electromagnet of the magnetic bearing according to the control signal. Further, as shown in FIG. 6, the compensation circuit 43 includes the sensor 41 and the PID control circuit 4.
It may be installed between two.

In the nonlinear circuit 1, the impedance circuit 1
Although the constants of the corresponding elements of 5 and 16 are made the same and configured symmetrically, the operating voltages of the impedance circuits 15 and 16 can be set individually by changing the resistance values of the resistors 8, 9, 10 and 11. . For example, impedance 15 is
It operates when the output voltage of the operational amplifier 2 is -0.8 [V] or less, and the impedance 16 operates when the output voltage of the operational amplifier 2 is 1.6 [V] or more. You can also. Further, by changing the capacitances C1 and C2 of the capacitors 7 and 8, only the phase can be adjusted.

As described above, if the operating points of the impedances 15 and 16 can be set individually, the nonlinear circuit 1 can be made to function effectively, for example, when it is used in a control circuit of a magnetic bearing of a horizontally held rotor. Can be. That is, when the rotor is held horizontally, the rotor bears its own weight on the magnetic bearing, and when disturbance occurs in the rotor, the amplitude below the rotor holding position becomes larger than the amplitude above the rotor holding position. There is. At this time, if the amplitude at which the limiter of the nonlinear circuit 1 operates is set separately above and below the rotor, the vibration can be effectively reduced and the vibration can be suppressed. In the non-linear circuit 1, the operating voltages of the impedance circuits 15 and 16 can be individually set according to the installation posture of the magnetic bearing, for example, when the rotor is installed obliquely with respect to the ground.

[0039]

According to the present invention, the rotor of the magnetic bearing is
When a high-frequency large-amplitude disturbance occurs, it can be effectively suppressed. Since the operating voltage of the limiter is obtained by dividing the voltage supplied from the constant voltage power supply by the resistor, the limiter voltage can be set more freely without using the constant voltage characteristics of the diode. For a small-amplitude input signal in which the limiter circuit does not operate, variations in capacitors and resistors do not affect the filter characteristics.
Further, according to the present invention, it is possible to provide a vacuum pump capable of effectively suppressing the occurrence of high-frequency large-amplitude disturbance in the rotor of the magnetic bearing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a nonlinear circuit used as a compensation circuit of a magnetic bearing control circuit according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an impedance circuit added to a negative feedback circuit with respect to an AC component.

FIG. 3 is a diagram comparing output currents of a power amplifier when a non-linear amplifier circuit according to the present embodiment is used and when it is not used.

FIG. 4 shows experimental data obtained by using the nonlinear amplifier circuit according to the embodiment.

FIG. 5 is a diagram showing an installation example in which the nonlinear amplification circuit according to the present embodiment is installed in a control device of a magnetic bearing device as an example.

FIG. 6 is a diagram showing another installation example in which the nonlinear amplification circuit according to the present embodiment is installed in a control device of a magnetic bearing device as an example.

FIG. 7 is a diagram schematically showing a Bode diagram of a control circuit of a conventional magnetic bearing.

FIG. 8 is a circuit diagram showing a conventional compensation circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-linear circuit 2 Operational amplifier 3 Signal input part 4 Signal output part 5 Diode 6 Diode 7 Capacitor 8 Resistor 9 Resistor 10 Resistor 11 Resistor 12 Capacitor 13 Constant voltage power supply 14 Constant voltage power supply 15 First impedance circuit 16 First 2 impedance circuit 17 resistor 18 resistor 31 current waveform 32 current waveform 33 current waveform 41 sensor 42 PID control circuit 43 compensation circuit 44 power amplifier 45 electromagnet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03F 1/34 H03F 1/34 F term (Reference) 3H022 AA01 BA06 CA16 CA50 DA09 3H031 DA02 EA12 FA13 3J102 AA01 BA03 BA16 CA02 CA22 CA25 DB01 DB05 DB10 DB11 DB25 DB26 DB37 GA06 5J090 AA01 AA47 CA11 CA14 DN02 FA01 FA19 HA00 HA19 HA25 HA29 HA42 KA00 KA11 MA13 MN01 NN12 SA00 TA01 TA03 TA06

Claims (6)

[Claims] An operational amplifier having a predetermined gain and converting an electric signal input from an input unit as an output signal, a resistor for applying a negative feedback to the operational amplifier, a voltage value of the output signal, A first impedance circuit having a first reference voltage value to be compared and having a first limiter that operates when the output signal is greater than the first reference voltage value; and When operated, the first impedance circuit is connected in parallel to the resistor, a first connection means for adjusting a gain of the operational amplifier, and a second reference voltage for comparing with a voltage value of the output signal. A second impedance circuit having a second limiter that operates when the output signal is smaller than the second reference voltage value; and a second impedance circuit that operates when the second limiter operates. Of the impedance circuit connected in parallel with the resistor, the magnetic bearing controller having a configured compensation circuit from the second connecting means for adjusting the gain of the operational amplifier. 2. The first limiter and the second limiter each include a diode biased at a predetermined voltage in a reverse direction, and the first reference voltage value at which the first limiter operates, 2. The magnetic bearing control device according to claim 1, wherein the second reference voltage value at which the second limiter operates is defined by an operating voltage of each of the diodes. 3. 3. The first impedance circuit and the second impedance circuit each include a first-order delay formed by connecting a second resistor in series to a component in which a capacitor and a first resistor are connected in parallel. And a DC voltage applying means for applying a DC voltage to the first impedance circuit and the second impedance circuit, wherein the bias voltage for biasing the diode in the reverse direction is The magnetic bearing according to claim 1, wherein a DC voltage applied by the DC voltage applying unit is defined by a voltage division ratio of the first resistor and the second resistor. 4. Control device. 4. The electric signal input from the input unit,
The control signal is a control signal of a power amplifier that supplies an exciting current of an electromagnet constituting a magnetic bearing, and when the voltage value of the control signal is larger than the first reference voltage value, the control signal is supplied to the first impedance circuit. When the voltage value of the control signal is smaller than the second reference voltage value, the phase of the control signal is advanced by the second impedance circuit and the operation is performed. 4. The magnetic bearing control device according to claim 1, wherein the control signal is compensated by lowering a gain of the amplifier. 5. The apparatus according to claim 1, further comprising changing means for changing at least one of an operating voltage of said first limiter and an operating voltage of said second limiter in accordance with an installation posture of said magnetic bearing. The magnetic bearing control device according to any one of claims 1 to 4. 6. A vacuum pump using the magnetic bearing control device according to any one of claims 1 to 5.