JPH0783221B2 - Power amplifier for generating magnetic attraction - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power amplifier for current amplification used in a magnetic attraction device such as a magnetic bearing device or a magnetic levitation device for non-contact levitation. .

[Conventional technology]

Magnetic bearing device that uses magnetic force as a supporting method that reduces friction and enables high-precision positioning, enables rotating bodies to rotate at high speed, and enables use in special environments such as vacuum. Magnetic levitation devices have become popular.

As one of the methods of generating this magnetic force, there is a method using an electromagnet, and a magnetic attraction force generated by supplying a current to an electromagnet coil is mainly used.

There are some methods for supplying the current, that is, a power amplifier, but they are required to have high efficiency and good responsiveness.

Among the methods that have been conventionally used, there is a first method disclosed in Japanese Patent Laid-Open No. 58-54220. This is a so-called push-pull linear amplifier,
In order to improve the responsiveness, the power supply voltage must be raised. If this is done, most of the supplied power will be consumed by the heat generated by the transistors, resulting in extremely poor efficiency, and transistors and cooling devices with extremely large heat capacities. However, there is a drawback that it becomes expensive. Further, if the power supply voltage is lowered in order to reduce heat generation, the current responsiveness deteriorates accordingly, and in some cases, the stabilization of the magnetic bearing control loop may be impaired.

As a second method instead of the method having such a big defect, the P method as disclosed in Japanese Patent Laid-Open No. 57-73223 is used.
A WM type amplifier was considered. According to this method, when the transistor is turned on, the current of the electromagnet coil follows the given DC power supply voltage V _DC , Start up related by.

However, when the transistor is turned off, the flywheel current circulates in a loop made with the diode, but the forward voltage V _d of the diode attenuates the current and V _d is 1 V.
Because it is Therefore, only very loose damping is possible.

This means that even if an attempt is made to control the current, it cannot be expected that the response will be high, and that the stabilization of the magnetic bearing control loop cannot be expected.

[Problems to be solved by the invention]

As described above, the conventional method has drawbacks such as poor responsiveness and poor efficiency. Therefore, the present invention intends to improve it dramatically.

[Means for solving problems]

In order to do so, the present invention configures one electromagnet coil with one switching element, one diode, and one current detection means.

That is, it is used in a magnetic attraction force generator that has two electromagnets that generate magnetic attraction forces in opposite directions. A PWM method magnetic attraction force that controls the current by turning on / off the switching element and modulating its pulse width. In the power amplifier for generation, a first switching element having an emitter connected to a positive DC power supply, a first diode having a cathode connected to the collector of the first switching element and an anode connected to a negative DC power supply, A first main circuit composed of a first electromagnet coil having one end connected to a connection point of a first switching element and a first diode and the other end connected to ground; and the first electromagnet coil and ground. First current detection means provided between the first electromagnet coil and detecting the current flowing through the first electromagnet coil, and a current command and a signal from the first current detection means. And a first current controller that receives a signal from the first subtractor to perform pulse width modulation to output a pulse, and a signal from the first current controller that receives a signal from the first current controller A first power amplifier composed of a first base drive circuit connected to the base of a first switching element in the first main circuit; and a second switching element having an emitter connected to a negative DC power supply, A second diode having an anode connected to the collector of the second switching element and a cathode connected to a positive DC power source, and one end connected to the connection point of the second switching element and the second diode and the other end connected A second main circuit composed of a second electromagnet coil connected to the ground;
The second electromagnet coil is provided between the ground and the second
A second current detecting means for detecting a current flowing through the electromagnet coil, a second subtractor for receiving and subtracting the current command and the signal from the second current detecting means, and a signal for the second subtractor. A second current controller which receives and pulse-modulates the pulse width and outputs a pulse, and which receives a signal from the second current controller and is connected to a base of a second switching element in the second main circuit It is composed of two power amplifiers of a second power amplifier composed of a second base drive circuit, and the first power amplifier follows the current command received by the first subtractor by the current of the first electromagnet coil. And the second power amplifier is controlled so that the current of the second electromagnet coil follows the current command received by the second subtractor, and in the main circuit of the first power amplifier, , By positive DC power supply The flywheel current of the given current of the first electromagnet coil is attenuated by the negative DC power supply, and the main circuit of the second power amplifier attenuates the current of the second electromagnet coil given by the negative DC power supply. Attenuate the flywheel current with a positive DC power supply so that the flywheel current is flowing through the electromagnet coils of both main circuits. The increase rate and the decrease rate of the current are made the same in the same manner as the voltage of the electromagnet coil, and the flywheel current is complemented between the two main circuits.

In addition, the above two current control systems are separately provided by using two reactors to form the third and fourth current control systems to form a voltage control device.

That is, the voltage control device for the DC power supply includes a voltage detecting means for detecting the voltages of the positive and negative DC power supplies, an adder for adding the two detection signals, and a voltage for phase-compensating the added signals. A controller, a second adder for adding the reference current command signal and the voltage controller signal, a subtractor for subtracting the reference current command signal and the voltage controller signal, and the second adder And an output signal of the subtractor as a current command, and two power amplifiers having the same configuration as the first and second power amplifiers having a reactor instead of an electromagnet coil.

[Action]

With this configuration, in the case of the first power amplifier, when the switching element is turned on, a positive power supply voltage is applied to both ends of the electromagnet coil, When the switching element is turned off, the flywheel current of the electromagnet coil causes a current to flow from the negative DC power supply to the electromagnet coil through the diode, and negative current is applied to both ends of the electromagnet coil. Because it takes current The current decreases at the rate of change related by. The same operation is performed in the case of the second power amplifier as well, and the rise and fall of the current are approximately the same in both cases, so that the responsiveness can be improved even when the current is controlled.

Then, if the magnitudes of the currents of the two current control systems are different, in total, one power supply is discharged and the other power supply is charged, so the voltage changes, but the third and fourth current control Using the system, the operation opposite to the above is performed to make the power supply voltage constant.

〔Example〕

 FIG. 1 shows an embodiment of the present invention, in which OV is the main circuit and
And control circuit ground line, V Is the positive DC voltage of the main circuit
Source, V Is the negative DC power supply of the main circuit. V , V Haso
The voltage of is also shown.

The first switching element 14-1 is a PNP transistor here.
It is a transistor, but the emitter is V Connect to the base
1 to the base drive circuit 61, the collector of the first
At the cathode of the electromagnet coil 21 and the first diode 15-1
It is connected.

The anode of the first diode 15-1 is V Connected to
There is. The other end of the first electromagnet coil 21 has a first amplification
Connected to the device 51 and the first shunt 41, the first shunt 41
The other end of is connected to OV. These first amplifiers 51 and
The shunt 41 detects the electric current of the first electromagnet coil 21.
It constitutes a flow detecting means. Also, the first switching element
Child 14-1, first electromagnet coil 21, diode 15-1 and
The first shunt 41 constitutes a first main circuit.

The command signal I _S1 of the current of the electromagnet coil 21 and the first amplifier 5
The difference is obtained by the first subtractor 81 having the detection signal as an input, which is obtained as the output of 1, and the first current controller 71 operates with this as an input to turn on the first transistor 14-1. An off signal is sent to the first base drive circuit 61.

The first current controller 71 includes at least a phase compensation circuit, a comparator, and an oscillator, and the phase compensation circuit is usually a PID.
Although it is a compensation circuit, I (integration) and D (differentiation) may be omitted. Then, the comparator receives the output signal of the PID compensation circuit as input, compares it with the output of the oscillator, and outputs H _i or L _o.
However, a triangular wave or a sawtooth wave having a constant frequency amplitude may be used as the output of the oscillator. The first current controller 71 functions as a PWM controller.

The first base drive circuit 61 has isolated inputs and outputs.
From the first current controller 71 to the first transistor 14-1.
When receiving the ON signal of V Lower potential to the first tran
It is given to the base of Dista 14-1 and turned on. Also the first
The off signal of the first transistor 14-1 from the flow controller 71.
When receiving V The same potential as that of the first transistor 14-1
And turn it off.

This is the first current controller 71, the first base drive circuit 6
1, a first amplifier 51, the first main circuit and a first subtractor 81
Thus, a first current control system that makes the current of the first electromagnet coil 21 follow I _s1 , that is, a PWM-type first power amplifier is configured.

The second switching element 14-2 is an NPN transistor here.
It is a transistor, but the emitter is V Connect to the base
The second base drive circuit 62 is connected, and the collector is connected to the second base drive circuit 62.
On the anode of the electromagnet coil 22 and the second diode 15-2
It is connected. And the second diode 15-2
V is V It is connected to the. Also the second electromagnet coil
The other end of 22 is connected to the second amplifier 52 and the second shunt 42.
And the other end of this second shunt 42 is connected to OV
There is. This is the second amplifier 52 and the second shunt 42
Current detection means for detecting the current of the electromagnet coil 22 of
is doing.

Also, the second transistor 14-2 and the second electromagnet coil 2
The second main circuit is composed of the second diode 15-2 and the second shunt 42. A difference is obtained by the second subtracter 82 which receives the command signal I _s2 of the current of the second electromagnet coil 22 and the detection signal obtained as the output of the second amplifier 52, and the difference is obtained as the input. The current controller 72 works,
The on / off signal of the second transistor 14-2 is sent to the second base drive circuit 62. This is the second current controller 72
And the second base drive circuit have substantially the same contents as the first current controller 71 and the first base drive circuit, respectively.

The second base drive circuit 62 is connected to the second current controller 72.
When the on signal of the second transistor 14-2 is received, V
Apply a higher potential to the base of the second transistor 14-2
And turn it on.

Also, from the second current controller 72 to the second transistor 14-2
When the off signal of The same potential as the second transition
Give it to the base of Star 14-2 and turn it off. Here,
A second current controller 72, a second base drive circuit 62 and
With the second amplifier 52, the second main circuit, and the second subtractor 82,
Set the current of the second electromagnet coil 22 to I_s2The second to follow
The current control system, that is, the PWM type second power amplifier
I am configuring.

In the above configuration, the current command I_s1Is given,
At that time, the current of the first electromagnet coil 21 was zero.
Try. At that time, the input signal of the first current controller 71 is +.
The first current controller 71 operates to activate the first transistor 14
-2 ON signal is sent to the first base drive circuit 61.
In response to this, the first base drive circuit 61 changes to V Than
Applying a low potential to the base of the first transistor 14-1,
The first transistor 14-1 is turned on. First electromagnet
Coil 21 has approximately V Because the voltage ofThe current increases accordingly.

Then, the current increases and the output of the first amplifier 51 increases.
Is I_s1When it becomes larger, the input signal of the first current controller 71
Becomes negative, and the first base drive circuit 61
The off signal of the register 14-1 is sent. The first to receive this
The base drive circuit 61 is V The same potential as the first tran
First transistor 14-
1 is turned off. The first transistor 14-1 is turned off
Then, the emitter-collector current becomes zero, but the first
The magnet coil 21 is an inductance and the flywheel
Because current flows, V From the first diode 15-1, the first
Current to OV via 1 electromagnet coil 21 and 1st shunt 41
Flows. The first electromagnet coil 21 has approximately V
Since the potential ofThe current decreases accordingly.

When the current decreases and the output of the first amplifier 51 becomes smaller than I _s1 , the above-mentioned movement is repeated, and the current flowing through the first electromagnet coil 21 follows I _s1 .

The second current control system is V The first phone that is using
It goes without saying that the same operation as the flow control system is performed.

V in either case And V Keep the same size
And the rise and fall of the current are almost the same,
The responsiveness of the person can be increased. But,
Current flowing in the electromagnet coils of the first and second current control systems
Are different, one of the power supplies will discharge more and the other will
The power supply has a large amount of charge. Power supply with high discharge
Is charged from the original power supply, so the voltage drops.
The power supply that has a large amount of charge is
Can not be discharged to the power supply of the
Will end up. To prevent this, first, second
With the same configuration as the current control system of
4 current control system and voltage control system
It This is shown in Fig. 3, and the first used there.
The control system shown in FIG. 2 has been rewritten.

In the figure, 93 and 94 are third and fourth current control circuits, 23 and 24 are third and fourth main circuits, and dummy reactors 13 are used for 23 and 24 in the center of FIG. . Reference numerals 21 and 22 on the right side of the figure are main circuits including electromagnet coils of magnetic bearings, and the current control circuit is omitted.

V , V Are positive and negative DC power supplies, respectively, and
A smoothing capacitor is provided between the switch and OV. 3
1,32 is V , V Voltage detector that detects the voltage of
Signal added by adder 4 is input to voltage controller 5.
ing.

Although 5 is a PiD controller, i (integral compensation) and D (differential compensation) may be omitted.

I _s0 is a first current control system composed of a third current controller 93 and a third main circuit 23, and a second current control system composed of a fourth current control circuit 94 and a fourth main circuit 24. This is a command signal for the reference current of the current control system, and I _s0 and the signal of the voltage controller 5 are added by the adder 6 to become the input signal of the third current control circuit 93, and I _s0 and the voltage controller 5 The signal is subtracted by the subtractor 7 and becomes the input signal of the fourth current control circuit 94.

With such a configuration, | V ｜ ＜ | V ｜
See. Then, it will be detected by the voltage detectors 31 and 32.
V , V When the signals of 1 are added by the adder 4, it becomes negative.
Then, the voltage controller 5 also outputs − in response to the signal, and
I by the calculator 6_s0Signal I added with_s1Is I_s0Less than
And the subtractor 7 causes I_s0And the subtracted signal I_s2
Is I_s0Get bigger.

Therefore, the reactor current of the third main circuit 23 decreases, the reactor current of the fourth main circuit 24 increases, and the sum of the acceleration current and the flywheel current of each reactor is V _−.
Is equal to the current flowing from V to V ₊ .

This means that the voltage of V ₊ increases and the magnitude of V ₋ decreases.

On the other hand, | V ｜ ＞ | V Let's say. Then,
V detected by the voltage detectors 31 and 32 , V Signal of
When it is added by the adder 4, it becomes +. Depending on the signal
The pressure controller 5 also outputs +, and the adder 6 outputs I_s0And addition
Signal I_s1Is I_s0Becomes larger, and by subtractor 7
I_s0And the subtracted signal I_s2Is I_s0It gets smaller.

Therefore, the current of the reactor of the third main circuit 23 increases,
4 the main circuit 24 reactor current is reduced, each rear
If you add the acceleration current of the kutor and the flywheel current,
V To V Is equal to the current flowing to.

As a result of the above operation, the operation of the magnetic bearing power amplifier
R V , V Even if the magnitude of V fluctuates, V And V of
The size is kept constant.

That is, according to the present invention, by connecting one end of a diode for passing a flywheel current to a power source having a polarity opposite to that of the power source of a transistor (switching element) to which the diode is connected, the electromagnet applied when the flywheel power source is flowing The coil voltage is made to be the same as the electromagnet voltage when the flywheel current is not flowing, and the current increase rate and decrease rate are made the same so that the levitation control of the magnetic bearing can be performed without problems. It is a thing.

[Modification]

The switching elements may be FETs or other types of elements.

The base drive circuit may not have the input and output isolated.

The current detection may be performed by a Hall element.

The first and second power supply control systems may be used individually or in different numbers of combinations.

A combination of the first power supply control system and the voltage control system using the fourth current control system can also be used.

It is also possible to use a combination of the second current control system and the voltage control system using the third current control system.

Also, the oscillator used for the current controller can be shared.

In the embodiment, the power amplifier that supplies a current to two electromagnet coils of the electromagnets used in the magnetic bearing and the magnetic levitation apparatus has been described, but it is also applicable to a power amplifier having three or more electromagnets as follows. That is, the stator electromagnet of the radial magnetic bearing is required to have at least three electromagnet coils in order to enable control in two directions orthogonal to each other. As is known in Japanese Patent Publication No. 61-66219, as one of the methods of arranging the three electromagnet coils, an electromagnet having a large magnetic attraction force is arranged right above and two small electromagnets are arranged on both lower sides. However, when controlling up and down, it is necessary to support the weight of the rotor on the upper side, so a large magnet works and pulls, and on the lower side, it is possible to control by pulling with the resultant force of two magnets. When controlling left and right, pull on the right side by the combined force of the upper electromagnet supporting the rotor weight and the lower right electromagnet, and on the left side the upper electromagnet supporting the rotor weight and the left electromagnet Control by pulling with the resultant force.

The size of the upper electromagnet and the size of the sum of the currents of the two lower electromagnets are set to be approximately the same, and the first power amplifier described in the embodiment is used as the power amplifier that supplies the current to the upper electromagnet. Two of the second power amplifiers described in the embodiments are used as the power amplifiers that supply current to the magnet. By doing so, the flywheel current of each electromagnet coil can be returned to each DC power supply and the balance of both DC power supply voltages can be maintained, as in the embodiment.

In the case of a magnetic bearing provided with four electromagnets, 2 described in the embodiment is used.
It is easy to understand that it is sufficient to add another pair of power amplifiers, and even if there are four or more power amplifiers, power amplifiers can be added in the same manner.

〔The invention's effect〕

Since the responsiveness of the current control can be enhanced, the responsiveness of the control loop of the magnetic attraction force generator can be enhanced. That is, the rigidity of the magnetic attraction force generator can be increased, and the stability of the control loop can be improved.

Only one transistor, one diode, and one shunt are required for one electromagnet, which is simple and low cost. Moreover, since only one base drive circuit is required, the synchronization of signals required when two base drive circuits are used is unnecessary and the design is easy.

That is, it is easy to increase the carrier frequency of PWM to improve the response. Moreover, since the recovery current of the diode, that is, the surge current does not flow in the shunt used for the current detection, it is not detected and has a merit that the trouble is released.

Because of the added voltage control circuit, fluctuations in the power supply voltage can be suppressed and stable current control can be performed.

The above effect is particularly large in a system using a large number of electromagnet coils.

[Brief description of drawings]

1 to 3 are block diagrams of embodiments of the present invention. 14-1 ...... First transistor 14-2 ...... Second transistor 21 ...... First electromagnet coil 22 ...... Second electromagnet coil 15-1 ...... First diode 15-2 ...... Second Diode 41 ...... first shunt 42 ...... second shunt 51 …… first amplifier 52 …… second amplifier 61 …… first base drive circuit 62 …… second base drive circuit 71 …… ... 1st current controller 72 ... 2nd current controller 81 ... 1st subtractor 82 ... 2nd subtractor 4 ... adder 5 ... voltage controller 6 ... adder 7 ... … Subtractor 8 …… Capacitor 9 …… Current controller 10 …… Amplifier 11 …… Base driver 12 …… Shunt 13 …… Reactor 14 …… Transistor 15 …… Diode 31,32 …… Voltage detector 21 …… No. 1st main circuit 22 ...... 2nd main circuit 23 ...... 3rd main circuit 24 ...... 4th main circuit 91 ...... 1st current control Road 92 ...... second current control circuit 93 ...... third current control circuit 94 ...... fourth current control circuit

Claims (6)

[Claims] 1. A device for generating magnetic attraction forces in directions opposite to each other.
Used in a magnetic attraction force generator with two electromagnets, a PWM type magnetic attraction force generation power amplifier that turns on / off a switching element and modulates its pulse width to control the current. A connected first switching element, a first diode having a cathode connected to the collector of the first switching element and an anode connected to a negative DC power supply, and a connection point of the first switching element and the first diode A first main circuit composed of a first electromagnet coil having one end connected to the other end and the other end connected to the ground, and a current provided between the first electromagnet coil and the ground and flowing through the first electromagnet coil A first current detecting means for detecting the current, a first subtractor for subtracting by receiving the current command and the signal of the first current detecting means, and a signal of the first subtractor. A first current controller that receives and pulse-width-modulates a pulse and outputs a pulse, and receives a signal from the first current controller and is connected to a base of a first switching element in the first main circuit. A first power amplifier composed of a first base drive circuit, a second switching element having an emitter connected to a negative DC power supply, an anode connected to the collector of the second switching element, and a cathode connected to the positive DC power supply. A second main circuit composed of a second diode connected to the second switching element, and a second electromagnet coil having one end connected to the connection point of the second switching element and the second diode and the other end connected to the ground. When,
The second electromagnet coil is provided between the ground and the second
A second current detecting means for detecting a current flowing through the electromagnet coil, a second subtractor for receiving and subtracting the current command and the signal from the second current detecting means, and a signal for the second subtractor. A second current controller which receives and pulse-modulates the pulse width and outputs a pulse, and which receives a signal from the second current controller and is connected to a base of a second switching element in the second main circuit It is composed of two power amplifiers of a second power amplifier composed of a second base drive circuit, and the first power amplifier follows the current command received by the first subtractor by the current of the first electromagnet coil. And the second power amplifier is controlled so that the current of the second electromagnet coil follows the current command received by the second subtractor, and in the main circuit of the first power amplifier, , By positive DC power supply The flywheel current of the given current of the first electromagnet coil is attenuated by the negative DC power supply, and the main circuit of the second power amplifier is designed to reduce the current of the second electromagnet coil given by the negative DC power supply. Attenuate the flywheel current with a positive DC power supply so that when the flywheel current is flowing through the electromagnet coils of both main circuits, the voltage of the electromagnet coils is when the flywheel current is not flowing. A power amplifier for generating a magnetic attraction force, characterized in that the increase rate and the decrease rate of the current are made to be the same as the voltage of the electromagnet coil, and the flywheel currents are mutually complemented between the two main circuits. . 2. The power amplifier for magnetic attraction force generation according to claim 1, wherein the magnetic attraction force generation device is a magnetic attraction force generation device having three or more electromagnet coils. 3. The power amplifier for magnetic attraction force generation according to claim 1, wherein the current detecting means uses a shunt resistor or a hall element. 4. The power amplifier for generating magnetic attraction force according to claim 1, wherein the switching element is a transistor. 5. The power amplifier for generating magnetic attraction force according to claim 1, wherein the DC power source is provided with a voltage control device. 6. A voltage control device for the DC power supply, wherein the voltage detection means for detecting the positive and negative DC power supply voltages, an adder for adding the two detection signals, and a phase for receiving the added signal A voltage controller for compensation, a second adder for adding the reference current command signal and the signal of the voltage controller, a subtractor for subtracting the reference current command signal and the signal of the voltage controller, and the second 2. The two power amplifiers having the same configuration as the first and second power amplifiers according to claim 1, wherein the output signals of the adder and the subtractor are received as current commands, and the reactor has a reactor instead of the electromagnet coil. The magnetic attraction force generating power amplifier according to claim 5, characterized in that: