JP2000182827A - Power source unit for electromagnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable demagnetizing a variety of workpieces by using a memory circuit of small capacity. SOLUTION: This power source unit is equipped with an initial address setting apparatus 70 for setting the initial address for starting demagnetization, and which can not only start demagnetization operation from the first term of a demagnetization pattern but also set the address of an arbitrary term of the demagnetization pattern as the initial address. Thereby demagnetization operation can be started from an arbitrarily set term.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device suitable for controlling an electromagnet used in a magnetic attraction device, a demagnetization device, and the like.

[0002]

2. Description of the Related Art As one of power supplies for an electromagnetic chuck,
In some cases, a decaying alternating magnetic field is generated in an exciting coil of an electromagnet to demagnetize an electromagnetic chuck and a workpiece. In this device, a so-called demagnetization pattern for generating an attenuated alternating magnetic field is created and stored in a memory circuit.
The degaussing pattern is read from the memory circuit and used as needed.

The demagnetization pattern differs depending on the shape, material, size, etc. of the workpiece to be demagnetized, that is, degaussed. Therefore, an optimal degaussing pattern according to the workpiece is selected. For this reason, in this type of conventional apparatus, it is necessary to create a new degaussing pattern and write a plurality of degaussing patterns to the memory circuit every time the shape, material, size, etc. of the workpiece are changed. Yes, the memory capacity becomes very large.

[0004]

Therefore, it is important for a power supply device for an electromagnet to enable demagnetization of various types of workpieces with a small-capacity memory circuit.

[0005]

A power supply device for an electromagnet according to the present invention comprises a rectifying / smoothing means for rectifying and smoothing an alternating current, and a polarity switching circuit for receiving an output of the rectifying / smoothing means and outputting an exciting current to be supplied to an exciting coil. Polarity switching means, a demagnetization processing means for generating a degaussing pattern for generating the decaying alternating magnetic field in the exciting coil, and a signal processing for receiving the degaussing pattern from the degaussing processing means and controlling the polarity switching means. Means.

The degaussing processing means stores at least one of the degaussing patterns including a plurality of operation designating signals for designating a direction of the exciting current and a plurality of time designating signals for designating the duration of the exciting current. A memory circuit, an address designating circuit for designating a predetermined address to the memory circuit, and an initial address setting device for selectively setting an address in the degaussing pattern as a degaussing start address.

The signal processing means includes a signal generating circuit for receiving the operation designating signal and the time designating signal and generating a switching control signal for controlling the polarity switching circuit; A polarity switching driver for controlling the switching circuit is provided.

At the time of degaussing, any address in the degaussing pattern, for example, any i-th address from the first term to the last x-th term
The term is set in the initial address setting device, and the demagnetization pattern from the i-th term to the final x-th term is executed. Thus, according to the workpiece, not only can the degaussing from the first term of the predetermined degaussing pattern be started, but also the degaussing from the middle term of the degaussing pattern can be started.

Therefore, according to the present invention, the same degaussing pattern can be commonly used for a plurality of types of degaussing, and a large-capacity memory circuit can degauss many types of workpieces.

The demagnetization processing means further includes a switching number setting device for setting the number of switching of the energizing current in the energizing direction;
A switching frequency counting circuit that counts the switching frequency and, when the count value reaches a value set in the polarity switching frequency setting device, generates an operation stop signal for stopping the degaussing operation. With this configuration, the demagnetization can be stopped after the set number of times of demagnetization is executed without executing until the end of the demagnetization pattern. As a result, even if the number of degaussing patterns stored in the memory circuit is small, more types of degaussing targets can be degaussed.

[0011] The apparatus further includes voltage detecting means disposed between the rectifying and smoothing means and the exciting coil, wherein the signal processing means further comprises a voltage setting section for setting a target voltage;
A voltage comparison circuit for comparing the set target voltage with a voltage detection signal from the voltage detection means; and a pulse signal having a pulse width corresponding to an output signal of the voltage comparison circuit for controlling the voltage adjustment means. A pulse width control circuit, wherein the polarity switching means further includes a voltage adjustment circuit having a transistor for adjusting the voltage to the excitation coil, and controls on / off of the transistor based on the pulse signal. And a voltage adjustment driver that performs the adjustment. In this way, stable demagnetization at the target voltage can be performed, and the excitation coil can be protected from overvoltage.

[0012] The present invention further comprises a current detecting means disposed between the rectifying and smoothing means and the exciting coil, and the signal processing means further comprises a current setting section for setting a maximum allowable value of the exciting current. A current comparison circuit that compares the maximum allowable value with a current detection signal from the current detection unit, and generates an abnormal signal when the current detection signal is equal to or greater than the maximum allowable value. The pulse width of the pulse signal can be changed by receiving the signal. In this way, the exciting coil can be protected from overcurrent.

The polarity switching circuit and the voltage adjustment circuit are integrally formed as voltage adjustment switching means, the voltage adjustment switching means including a bridge circuit using a plurality of transistors, and the polarity switching driver and the voltage adjustment circuit. The driver and the voltage adjustment switching driver can be integrally configured.

[0014] The apparatus further includes an output presence / absence and disconnection detection means disposed between the polarity switching circuit and the excitation coil, and the signal processing means further receives an output signal from the output presence / absence and disconnection detection means. An error detection / judgment circuit that judges the occurrence of an output presence / absence error and a disconnection error, and outputs an error occurrence signal when an error occurs, and a notifying device that receives the error occurrence signal and notifies the occurrence of the error can be provided. . By doing so, it is possible to quickly and easily know that the output presence / absence error or the disconnection error has occurred, and it is safe.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an electromagnet power supply 10 generates an exciting current based on a commercial alternating current supplied to an input terminal 12, and supplies the exciting current to an exciting coil 14 of the electromagnet. Supply.

The power supply device 10 rectifies and smoothes the alternating current supplied to the terminal 12 in a rectifying / smoothing circuit 16, and
The smoothed DC is applied to the voltage adjustment circuit 18 and the current detection circuit 2
0, the polarity switching circuit 22 and the voltage detection circuit 24 are supplied to the exciting coil 14 as a demagnetizing exciting current through the order.

The power supply 10 includes the circuits 16 to 24 described above.
A signal processing circuit 26 for generating a switching control signal for controlling the polarity switching circuit 22 and a pulse signal for adjusting the excitation voltage, and a degaussing process for generating a degaussing pattern for generating an attenuated alternating magnetic field. Circuit 28, a polarity switching driver 30 for operating the polarity switching circuit 22 using the switching control signal, and the voltage adjusting circuit 1 using the pulse signal.
And a voltage regulation driver 32 for operating the power supply 8.

The rectifying / smoothing circuit 16 rectifies the AC supplied to the terminal 12 by a bridge circuit 34 composed of appropriate electronic components such as diodes, and connects the rectified output to the output terminal of the bridge circuit 34 in parallel. Capacitor 3
6 is a known circuit for smoothing.

The voltage adjusting circuit 18 has a power transistor 38 connected in series to the output of the rectifying / smoothing circuit 16 and a diode 40 connected in parallel to the output of the rectifying / smoothing circuit 16. The power transistor 38 is turned on / off by the voltage adjustment driver 32, thereby adjusting the excitation voltage.

The current detecting circuit 20 is a known circuit for detecting the actual value of the output current of the rectifying / smoothing circuit 16 by the resistor 42, and the signal between the terminals of the resistor 42 as a current detecting signal to the signal processing circuit 26. Supply.

The polarity switching circuit 22 is a known circuit for switching the direction (polarity) of the exciting current to the exciting coil 14 for demagnetization, ie, demagnetization, and a pair of contacts 4 of a relay.
4. Both contacts 44 are driven synchronously by the polarity switching driver 30. The polarity switching driver 30 controls energization to a relay corresponding to the contact 44 based on a switching control signal output from the signal processing circuit 26.

The voltage detecting circuit 24 has a pair of diodes 46 and 48 whose positive terminals are connected to a supply path of the exciting current from the polarity switching circuit 22 to the exciting coil 14, and negative terminals of both diodes 46 and 48. A pair of resistors 50 and 52 are connected in series with the ground, and a capacitor 54 is connected in parallel with one resistor 52. The voltage detection circuit 24 supplies the voltage between the terminals of one resistor 52 to the signal processing circuit 26 as a voltage detection signal.

The signal processing circuit 26 includes a reference value setting unit 56 for setting a maximum allowable value of the exciting current and a target voltage. The reference value setting unit 56 includes a voltage setting unit that sets a target voltage of the exciting current, and a current setting unit that sets a maximum allowable value of the exciting current. The set target voltage and the maximum allowable value are supplied to a signal generation circuit 58 in the signal processing circuit 26.

The target voltage and the maximum permissible value are supplied from the signal generation circuit 58 to the voltage comparison circuit 60 and the current comparison circuit 62, respectively. In the comparison circuits 60 and 62, the voltage detection signal and the current detection circuit from the voltage detection circuit 24 are supplied. 20 is compared with the current detection signal.

The voltage comparison circuit 60 outputs a signal corresponding to the difference between the target voltage and the voltage detection signal to the pulse width control circuit 64. On the other hand, the current comparison circuit 62 outputs an abnormal signal to the pulse width control circuit 64 when the current detection signal exceeds the maximum allowable value.

The pulse width control circuit 64 includes a voltage adjustment circuit 1
And a pulse signal having a pulse width corresponding to the output signal of the voltage comparison circuit 60 to the voltage adjustment driver 32 at all times. When an abnormal signal is input from the controller, a signal for preventing generation of a pulse signal is output to the voltage adjustment driver 32.

Each time a pulse signal is supplied from the pulse width control circuit 64, the voltage adjustment driver 32 turns on the transistor 38 for a time corresponding to the pulse width. As a result, the transistor 38 is turned on for a time proportional to the pulse width of the pulse signal from the pulse width control circuit 64, and the actual value of the exciting current becomes equal to or less than the maximum allowable value, and the actual value of the voltage becomes the target value. Is controlled so that

The degaussing circuit 28 includes a memory circuit 66 in which at least one degaussing pattern is stored. As shown in FIG. 2, the demagnetization pattern is a pattern in which the time width gradually decreases and the polarity alternates.
It has the excitation state up to the term (final term).

The demagnetization pattern is such that the excitation is temporarily performed between the start of the degaussing operation and the temporally adjacent energizing period (between the adjacent positive excitation period and non-exciting period, and when the energizing direction is switched). Includes a suspension period of excitation. During the excitation suspension period, energization of the excitation coil 14 is temporarily interrupted.
The degaussing pattern also includes an end instruction period that means when the degaussing operation ends.

Each item of the demagnetization pattern is composed of a combination of an operation designating signal for designating a direction (polarity) of energizing the exciting coil 14 and a time designating signal for designating the energizing time to the exciting coil 14. Each item is stored at a predetermined address of the memory circuit 66, and when the corresponding address is designated by the address designating circuit 68, the memory circuit 6
6 to the signal generation circuit 58.

The first address output from the address specifying circuit 68 is the initial address set in the initial address setting unit 70. The address designating circuit 68 changes the output address each time an address change command is supplied from the signal generating circuit 58. Addressing circuit 6
The address change in 8 is performed every time an address change command is output until an operation stop signal is supplied from the switching number counting circuit 72 to the address designating circuit 68 or until the last term of the degaussing pattern.

The address set in the initial address setting unit 70 is an arbitrary term in the degaussing pattern to start degaussing,
For example, it is an address corresponding to the i-th term, and is set in advance by the operator according to the demagnetized object.

The switching number counting circuit 72 includes the exciting coil 14
This circuit counts the number of times of switching of the direction (polarity) of the excitation current to the motor, and outputs an operation stop signal to the addressing circuit 68 when the count reaches the value set in the polarity switching number setting unit 74. I do.

In the illustrated example, the switching frequency counting circuit 72
The fact that the term of the demagnetization pattern is supplied from the memory circuit 66 to the signal generation circuit 58 is counted. However, the switching number counting circuit 72 is provided with the polarity switching circuit 2 from the switching driver 30.
2 may be counted (see FIG. 1).
, The address change command output from the signal generator 58 to the address designating circuit 68 may be counted.

The polarity switching number setting circuit 74 is a circuit for setting the number of times of switching of the direction of the exciting current supplied to the exciting coil 14 for degaussing, and is preset by an operator according to the object to be degaussed.

At the time of degaussing, first, a degaussing start command is inputted from the terminal 76 to the address designating circuit 68. As a result, the address specifying circuit 68 takes in the initial address set in the initial address setting device 70 and outputs the initial address to the memory circuit 66. If the initial address is not set in the initial address setting device 70, the address specifying circuit 68 outputs the address of the first term of the demagnetization pattern as the initial address.

Next, the operation designation signal and the time designation signal of the term of the demagnetization pattern corresponding to the initial address are output from the memory circuit 66 to the signal generation circuit 58, and the signal generation circuit 58 receives the supplied operation designation signal and time designation signal. Is output to the polarity switching driver 30. As a result, the polarity switching driver 30 switches the polarity switching circuit 22 in the direction specified by the supplied switching control signal, and maintains the state for the time specified by the switching control signal. As a result, the exciting current is supplied to the exciting coil 14 in a predetermined direction for a predetermined time.

Next, when the address switching command is supplied from the signal generation circuit 58 to the address designating circuit 68, the address designating circuit 68 designates the next address to the memory circuit 66 and outputs the operation designation signal and the operation designation signal in the next address. The time designation signal is output from the memory circuit 66 to the signal generation circuit 58 and the switching counting circuit 72.

Accordingly, the signal generation circuit 58 outputs a new switching control signal corresponding to the supplied operation designation signal and time designation signal to the polarity switching driver 30, and the polarity switching driver 30 newly switches the polarity switching circuit 22. The switching is performed in the direction specified by the switching control signal, and the state is maintained for the time specified by the new switching control signal. As a result, the exciting current is supplied to the exciting coil 14 in a direction opposite to the previous time for a predetermined time.

By repeating the above process a plurality of times, the exciting coil 14 receives the exciting current in which the conduction time gradually decreases and the polarity alternates, and generates an alternating magnetic field that gradually decreases. Thereby, the degaussing object is gradually degaussed.

During the demagnetization, the switching number counting circuit 72 counts the number of polarity switching, and outputs an operation stop signal to the addressing circuit 68 when the counted value reaches the number set in the polarity switching number setting device 74. I do. Thereby, the address specifying circuit 68 ends the address specification and ends the degaussing operation.

Before the count value of the switching frequency counting circuit 72 reaches the number of times set in the polarity switching frequency setting device 74, the operation designation signal and the time designation signal of the last term (the x-th term) of the demagnetization pattern are transmitted from the memory circuit 66. When output is performed and when the number of times of switching is not set in the number-of-times-of-switching setting unit 74, the power supply device 10 performs the degaussing operation after terminating the excitation by the operation specifying signal and the time specifying signal of the last term (the x-th term). finish.

During the degaussing operation, the excitation voltage is detected by the voltage detection circuit 24, and a signal corresponding to the difference between the voltage detection signal and the target voltage is output from the voltage comparison circuit 60 to the pulse width control circuit 64. A pulse signal having a pulse width having a pulse width corresponding to the difference between the voltage detection signal and the target voltage is supplied from the pulse width control circuit 64 to the voltage adjustment driver 32, and the transistor 38 is turned on for a time corresponding to the pulse width of the pulse signal. To be. Thereby, the exciting current is adjusted to the target voltage.

During the degaussing operation, the exciting current is detected by the current detecting circuit 20, and the current detecting signal is compared with the maximum allowable value by the current comparing circuit 62. When the current detection signal exceeds the maximum allowable value, an abnormal signal is supplied from the current comparison circuit 62 to the pulse width control circuit 64, so that the pulse width control circuit 64 does not output a pulse signal.
As a result, the transistor 38 is not turned on,
The exciting current is not supplied to the exciting coil 14, and the exciting current is maintained at a value equal to or less than the maximum allowable value.

As described above, if the degaussing operation can be started not only from the first term of the degaussing pattern but also from any i-th term, the same degaussing pattern can be commonly used for a plurality of types of degaussing. A large-capacity memory circuit can demagnetize various types of workpieces. Also, if the number of polarity switchings can be specified, degaussing can be stopped after executing the set number of switchings without performing until the end of the degaussing pattern. Even if the number of patterns is small, it is possible to degauss more types of degaussing objects, and it is possible to degauss more types of workpieces with a small-capacity memory circuit.

The power supply device 10 is an example of a power supply device for a demagnetizing device, but may be used as a power supply device for an electromagnetic chuck. When the power supply device 10 is used as a power supply device for an electromagnetic chuck, an excitation command for attracting a workpiece to the chuck can be input from the terminal 78 to the signal processing circuit 26, for example, to the signal generation circuit 58.

When the excitation command is input to the signal generation circuit 58, the circuits other than the demagnetization processing circuit 28 operate. The circuits that operate at this time operate in the same manner as when demagnetizing, except that the polarity switching driver 30 maintains the switching circuit 22 so as to supply the exciting current to the exciting coil 14 in one direction.

When the workpiece is released from the chuck, a degauss start command is input to the addressing circuit 68 from the terminal 76, and all the circuits operate as described above.

Referring to FIG. 3, an electromagnet power supply 80
Is a voltage adjusting circuit 18 in the power supply device 10 shown in FIG.
And the polarity switching circuit 22 together with the voltage adjustment switching circuit 82
As a single unit. Voltage adjustment switching circuit 82
Are four transistors 84a, 84b, 84c, 84
It is a bridge circuit using d and four diodes.

The transistors of the voltage adjustment switching circuit 82
On / off is controlled by a voltage adjustment switching driver 86 integrally formed by combining the polarity switching driver 30 and the voltage adjustment driver 32 in FIG. 1, so that the excitation voltage is adjusted to the target voltage and the excitation current is maximized. Adjust so as not to exceed the allowable value.

The voltage adjustment switching driver 86 receives a switching control signal corresponding to the demagnetization pattern from the signal generation circuit 58 and controls on / off of the transistor of the voltage adjustment switching circuit 82. As a result, an attenuated alternating magnetic field according to the degaussing pattern is generated from the exciting coil 14.

The power supply device 80 uses a commercially available insulated DC current sensor (DCCT) as the current detection circuit 88, and the current detection circuit 88 is disposed on the output side of the voltage adjustment switching circuit 82. A voltage detection circuit 90 using a pair of resistors 50 and 52 connected in series is arranged between the rectifying and smoothing circuit 16 and the voltage adjustment switching circuit 82.

The power supply device 80 further includes an output presence / absence detection circuit 92 and a disconnection detection circuit 94 disposed between the voltage adjustment switching circuit 82 and the exciting coil 14. The output presence / absence detection circuit 92 is connected to the positive side of the output of the voltage adjustment switching circuit 82, and the disconnection detection circuit 94 is connected to the negative side of the voltage adjustment switching circuit 82.

The two circuits 92 and 94 have the same circuit configuration using a pair of resistors connected in series with each other. For this reason, at the time of demagnetization, the positive side and the negative side of the output of the voltage adjustment switching circuit 82 are switched by the polarity switching operation. In that case, the two circuits 92 and 94 alternate their roles.

When the output voltage is obtained by the output presence / absence detection circuit 92, the output of the voltage adjustment switching circuit 82 is present, and when the output is also obtained by the disconnection detection circuit 94, there is no disconnection in the exciting coil. The output presence / absence detection signal and disconnection detection signal of both circuits 92 and 94 are supplied to an error detection determination circuit 96 and used for error determination.

The determination as to whether the detection signal is an output presence / absence detection signal or a disconnection detection signal is made by an error detection determination circuit 96 in synchronization with the switching control signal using the switching control signal from the signal generating circuit 56. It is done.

When an error is determined by the error detection determination circuit 96, an error signal is supplied from the error detection determination circuit 96 to the notification device 98, and the notification device 98 notifies the error by sounding a buzzer, lighting a lamp, or the like. Done.

The current detection signal and the voltage detection signal of the current detection circuit 88 and the voltage detection circuit 90 are also used in the error detection determination circuit 9.
6 to be used for determining an overcurrent error and an overvoltage error. In both cases of the overcurrent error and the overvoltage error, an error occurrence signal is reported by the error reporting device 98.

The power supply 80 includes a regenerative voltage absorbing circuit 100 for absorbing a regenerative voltage generated when the exciting current is turned on / off by the voltage adjustment switching circuit 82. The regenerative voltage absorption circuit 100 is arranged between the voltage detection circuit 90 and the voltage adjustment switching circuit 82, and is composed of a resistor 102 and a transistor 104 connected in series to each other.

The series connection circuit of the resistor 102 and the transistor 104 is connected in parallel to the rectifying / smoothing circuit 16. The transistor 104 is controlled by a driver 106, and the driver 106
6 is controlled by a signal generation circuit 58 which receives an error generation signal from the control signal generator 6.

When a high regenerative voltage is generated, a voltage detection signal is supplied from the voltage detection circuit 90 to the error detection determination circuit 96, and an error signal is output from the error detection determination circuit 96. As a result, the signal generation circuit 58 outputs an ON instruction signal to the driver 106, and the driver 106 turns ON the transistor 104.

When the transistor 104 is turned on, a current flows through the resistor 102 and the transistor 104.
The regenerative voltage is absorbed by the resistor 102 and the transistor 104, thereby preventing the destruction of the capacitor 36 of the rectifying / smoothing circuit 16 due to the regenerative voltage.

When an error signal is generated from the error detection judgment circuit 96, the error signal is transmitted to the signal generation circuit 58.
To temporarily suspend the demagnetization.

In FIG. 3, the reference numerals in the circles mean that the parts having the same reference numerals are electrically connected to each other.
A broken line shows an example in which the number of times of polarity switching in the switching number counting circuit 72 is performed using an output signal of the voltage adjustment switching driver 86. In the example shown by a broken line, two output signals are passed through the OR gate 108. ing.

The power supply 80 includes circuits 82, 86, 88,
1 operates in the same manner as the power supply 10 shown in FIG. 1 except that the 90, 92, 94, 96, 100, 106 and the notification device 98 operate as described above.

The power supply 80 also sends an excitation command for attracting the workpiece to the chuck from the terminal 78 to the signal generation circuit 58.
May be used for the electromagnet power supply device. Also in this case, when the workpiece is attracted to the chuck, the demagnetization processing circuit 2
When the circuits other than 8 operate and release the workpiece from the chuck, all the circuits operate as described above because the degaussing start command is input to the addressing circuit 68 from the terminal 76.

The regenerative voltage absorbing circuit 100 may be arranged in the power supply device 10 shown in FIG. 1, and the line voltage absorbing circuit may be operated when an overvoltage occurs. Also, the notification device 98 is shown in FIG.
May be provided to the power supply device 10 to notify various errors.

The present invention is not limited to the above embodiment, but can be variously modified without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit showing an embodiment of a power supply device for an electromagnet according to the present invention.

FIG. 2 is a diagram showing one embodiment of a demagnetization pattern.

FIG. 3 is a block diagram of an electric circuit showing another embodiment of the power supply device for an electromagnet according to the present invention.

[Explanation of symbols]

 10, 80 Power supply unit 12 AC input terminal 14 Excitation coil

Claims (6)

[Claims] 1. An electromagnet power supply device for generating an attenuated alternating magnetic field for demagnetization in an exciting coil, comprising: a rectifying / smoothing means for rectifying and smoothing an alternating current; A polarity switching circuit that includes a polarity switching circuit that outputs an excitation current to be supplied, and a polarity switching driver that controls the polarity switching circuit; A memory circuit storing at least one degaussing pattern including a designation signal and a plurality of time designation signals for designating an energizing time of the exciting current, an address designating circuit for designating a predetermined address to the memory circuit, and the degaussing pattern Degaussing processing means including an initial address setting device for selectively setting the middle address as a degaussing start address; and the operation designating signal. And a signal processing circuit including a signal generation circuit for generating a switching control signal for controlling the polarity switching circuit in response to the time designation signal, wherein the polarity switching driver performs the polarity switching based on the switching control signal. A power supply for electromagnets that controls the circuit. 2. The demagnetization processing means further includes a switching number setting device for setting the number of switching of the exciting current in the energizing direction, and counting the switching number, and setting the counted value in the polarity switching number setting device. The power supply device according to claim 1, further comprising: a switching frequency counting circuit that generates an operation stop signal that stops the operation of degaussing when the value reaches the set value. A voltage setting unit configured to set a target voltage; a voltage setting unit configured to set a target voltage; and a voltage setting unit configured to set a target voltage. A voltage comparison circuit for comparing a voltage with a voltage detection signal from the voltage detection means, and a pulse width control for generating a pulse signal having a pulse width corresponding to an output signal of the voltage comparison circuit for controlling the voltage adjustment means A voltage adjustment circuit having a transistor for adjusting a voltage to the excitation coil, and a voltage adjustment driver for controlling on / off of the transistor based on the pulse signal. 2. The method according to claim 1, further comprising:
Or the power supply device according to 2. And a current setting unit configured to set a maximum allowable value of the exciting current, further comprising: a current detecting unit disposed between the rectifying and smoothing unit and the exciting coil. A current comparison circuit that compares the set maximum allowable value with a current detection signal by the current detection unit and generates an abnormal signal when the current detection signal is equal to or greater than the maximum allowable value; The power supply device according to claim 3, wherein a pulse width of the pulse signal is changed by receiving the abnormal signal. 5. The voltage switching circuit and the voltage adjustment circuit are integrally formed as voltage adjustment switching means, the voltage adjustment switching means includes a bridge circuit using a plurality of transistors, and the polarity switching driver and the voltage switching circuit The power supply device according to claim 3 or 4, wherein the voltage adjustment driver is integrally configured as a voltage adjustment switching driver. 6. An output presence / absence and disconnection detecting means disposed between the polarity switching circuit and the excitation coil, wherein the signal processing means further includes an output presence / absence and an output signal of the disconnection detection means. An error detection determination circuit that receives the output presence / absence error and determines the occurrence of a disconnection error, and outputs an error generation signal when an error occurs, and a notification device that receives the error generation signal and reports the occurrence of the error.
The power supply device according to claim 1.