JPH1187138A - Degaussing power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the switching timing synchronized with the period of the a-c component in a rectified a-c current for each power feed time set to an integral multiple of the period of the a-c component. SOLUTION: This power source generates pulse signals, synchronized with the period of an a-c current not yet rectified from a period detector circuit 10 and changes the address designated to a memory circuit 22 each time the no. of the generated pulse signals agrees with a time-designated signal obtd. from the memory circuit 22 so as to have an operation signal from this circuit 22 output to an output synchronous circuit 24 which feeds a control signal synchronized with the pulse signal to a switching circuit 16, based on the pulse signal and operation signal, thereby feeding an exciting current to an excitation coil 18 from the switching circuit 16. Thus each feed time to the coil 18 is at an integral multiple of the period of the a-c component in a d-c current after rectification, and the switching time in the feeding direction is synchronized with the a-c component period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demagnetizing power supply for supplying a direct current to an exciting coil or the like of an electromagnetic chuck by alternately switching an energizing direction.

[0002]

2. Description of the Related Art As one type of this type of demagnetizing power supply,
There is a type in which a decaying alternating current of a predetermined voltage is supplied to an exciting coil to demagnetize an electromagnetic chuck and a workpiece (Japanese Patent Publication No. 61-1986).
19095).

[0003] This conventional device rectifies alternating current into direct current,
In the switching circuit, the polarity (that is, energizing direction) of the obtained DC is alternately switched, and the energizing time (switching cycle) to the exciting coil is gradually reduced, thereby generating an attenuated alternating current.

[0004] Attenuated alternating current is performed using a so-called demagnetization pattern that gradually reduces the time for energizing the exciting coil.
The degaussing pattern has an array of times for gradually reducing the energization time, and is created based on an integral multiple of the period T of a pulse signal of a constant frequency generated from a clock pulse generator in the power supply for degaussing.

However, in the conventional apparatus, the cycle T of the pulse signal, which is the basis for creating the demagnetization pattern, does not match the cycle of the rectified AC, and does not match the cycle t of the AC component in the rectified DC. Therefore, the energizing time to the exciting coil is not an integral multiple of the AC component cycle t, and the timing of polarity switching (energization direction switching) is not synchronized with the AC component cycle.

As a result, in the conventional device, even if the energizing time is the same, it is unavoidable that the output voltage of the switching circuit varies, and the current flowing through the exciting coil varies. . In particular, since such a variation has a large effect in the case of a short energization time, a large effect occurs at the last stage of the degaussing pattern, and a large variation occurs in the degaussing effect.

Further, in the conventional apparatus, an optimum demagnetization pattern can be selected according to the shape, material, size, etc. of the workpiece to be demagnetized, but the initial energization time, the attenuation ratio of the energization time, Every time the number of times of polarity switching is changed, a new degaussing pattern must be created and written to the memory, resulting in a very large memory capacity for the degaussing pattern.

[0008]

From the above, it is possible to set each energizing time to a cycle that is an integral multiple of the cycle of the rectified AC component in the DC, and to synchronize the switching timing with the cycle of such AC component. desirable.

It is also desirable to reduce the capacity of the memory by enabling the degaussing operation using one degaussing pattern to be performed in the middle of the degaussing pattern without executing the degaussing pattern from the beginning.

[0010]

A demagnetizing power supply device according to the present invention detects a period of an alternating current supplied to a rectifier circuit for converting an alternating current to a direct current and generates a pulse signal corresponding to the detected period. A memory circuit storing at least one demagnetization pattern including a plurality of operation designation signals for designating a direction of energization to the excitation coil and a plurality of time designation signals for designating a period of energization to the excitation coil; and a rectifier circuit. A processing circuit that outputs a control signal synchronized with the AC cycle to a switching circuit that switches an exciting current supplied to the exciting coil.

The processing circuit designates a predetermined address in the memory circuit, outputs a signal in the address from the memory circuit, counts pulse signals output from the cycle detection circuit, and counts the number of pulse signals from the memory circuit. The address designated to the memory circuit is changed each time the value matches the value corresponding to the obtained time designation signal, and a control signal is output based on the output operation designation signal and pulse signal.

The processing circuit outputs a signal at a predetermined address from the memory circuit, and each time the number of pulse signals output from the cycle detection circuit matches a value corresponding to the time designation signal obtained from the memory circuit, The address designated to the circuit is changed, and the state is returned to the original state each time the number of output pulse signals of the cycle detection circuit matches the value corresponding to the time designation signal from the memory circuit. Thereby, the operation designating signal and the time designating signal are sequentially output from the memory circuit.

The processing circuit outputs a control signal synchronized with the AC cycle before rectification to the switching circuit based on the operation designation signal output from the memory circuit and the pulse signal output from the cycle detection circuit. . Such a control signal can be generated by an AND condition between the operation specifying signal and the pulse signal. As a result, the switching circuit supplies the rectified DC to the exciting coil by switching its polarity alternately.
The degaussing operation ends when the operation of the degaussing pattern starting from a predetermined address is completed.

As described above, the pulse signal synchronized with the AC cycle before rectification is generated from the cycle detection circuit, and each time the number of generated pulse signals matches the time designation signal obtained from the memory circuit, the memory circuit If the address specified in (1) is changed, each energizing time to the exciting coil by the switching circuit becomes a cycle of an integral multiple of the cycle of the rectified AC component in the DC, and the timing of the switching of the energizing direction becomes such an AC. Synchronizes with the cycle of the component.

The processing circuit receives an address signal for specifying an address storing a signal to be output to the memory circuit, a time specifying signal and a pulse signal, and receives the received pulse signal. Counting means for outputting an address change signal for changing the address signal output from the address specifying means to the next address signal according to the degaussing pattern each time the counted value reaches a value corresponding to the received time specifying signal; Output synchronizing means for outputting the control signal based on the operation designating signal and the pulse signal. The counting means is returned to the original state each time the number of output pulse signals of the cycle detection circuit matches the value corresponding to the time designation signal from the memory circuit.

The power supply unit further includes an initial address setting device for selectively setting an initial address of a demagnetization pattern to be used, and the processing circuit sets the initial address set in the initial address setting means to the memory circuit. Each time the number of pulse signals matches the value corresponding to the time designation signal obtained from the memory circuit, the address designated to the memory circuit can be changed.

When the initial address setting device is used, the processing circuit sets the initial address set in the initial address setting device as a start address in the degaussing pattern including the initial address set in the initial address setting device in the middle. The degaussing operation can be executed from the start address. According to this configuration, the demagnetizing operation is not performed from the beginning (first term) of one demagnetizing pattern, and an arbitrary term (for example,
Since it can be executed from the item i), one demagnetization pattern stored in the memory can be used in common for a plurality of types of degaussing, and as a result, the number of degaussing patterns stored in the memory circuit is small. Also, it is possible to demagnetize various types of degaussing objects having different materials and sizes.

However, the processing circuit may perform degaussing by a degaussing pattern starting from the address set as the initial address and starting from the beginning of the degaussing pattern. In this case, it is preferable that a plurality of demagnetization patterns corresponding to the material and size of the workpiece to be demagnetized are stored in a memory circuit, and the initial address setting device is used for selecting a desired demagnetization pattern.

The power supply device further includes a switching number setting device for setting the number of switching of the energizing direction, and the processing circuit further counts the number of energizing to the exciting coil based on a control signal or an operation designating signal. A second counting means for generating an operation stop signal for stopping the operation of the processing circuit when the count value reaches a value set in the switching number setting device can be included. With this configuration, the number of times of switching the energizing direction can be set according to the material and size of the degaussing target, and the switching can be performed in the middle of one degaussing pattern. One demagnetization pattern can be used in common for a plurality of types of demagnetization. As a result, even if the number of demagnetization patterns stored in the memory circuit is small, various types of demagnetization objects having different materials and sizes can be used. Can be demagnetized.

The counting means receives the time designation signal and the pulse signal, counts the received pulse signals, and outputs a carry signal each time the counted value reaches a value corresponding to the received time designation signal; An address change signal for changing an address designation signal output from the address designation means to a next address designation signal according to a demagnetization pattern based on a carry signal from the count means, and outputting an address change signal for clearing a count value of the count means. Generating means.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a degaussing power supply device 10 converts an AC current from an AC power supply 12 into a rectifier circuit 14.
The present invention is applied to an apparatus that performs a so-called loop attenuation demagnetization method in an electromagnetic chuck that rectifies the DC current into a DC current and supplies the rectified DC current to an exciting coil 18 via a switching circuit 16.

The AC power supply 12 is a commercial AC power supply, and the rectifier circuit 14 is a full-wave rectifier circuit or a half-wave rectifier circuit. The switching circuit 16 is a polarity switching circuit including a pair of relays for switching the direction of current supply to the exciting coil (that is, DC polarity) and an energizing circuit for driving these relays in synchronization. Alternatively, for example, the switching circuit 16
As described in JP-A-198436, a bridge circuit using a plurality of transistors may be included. The excitation coil 18 is an excitation coil for selectively setting a magnetic attraction surface, that is, a work surface of the electromagnetic chuck to an excited state and a non-excited state.

In the following description, the rectifier circuit 14
It is assumed that the circuit is a full-wave rectifier circuit that converts a power supply voltage as shown in FIG. 2A into a DC voltage as shown in FIG.

The demagnetizing power supply 10 detects the cycle of the AC supplied from the AC power supply 12 to the rectifier circuit 14 by using the cycle detecting circuit 2.
0, a control signal S for driving the switching circuit 16 based on the pulse signal S1 output from the cycle detection circuit 20 and the operation designation signal S2 output from the memory circuit 22.
3 is generated in the output synchronization circuit 24. Pulse signal S
1 is a synchronization pulse synchronized with the AC from the AC power supply 12.

The cycle detection circuit 20 detects a zero point of the input AC voltage (or current) and outputs a pulse signal S1 corresponding to the zero point. As such a cycle detection circuit 20, a general zero point detector that generates a pulse signal at a zero point position of an input voltage using a photocoupler can be used. The pulse signal S1 output from the cycle detection circuit 20 is as shown in FIG.
As shown in FIG. 2, the waveform has a waveform synchronized with the AC power supply voltage AC shown in FIG. 2A and synchronized with the AC voltage component in the rectified DC voltage DC shown in FIG. 2B.

The memory circuit 22 stores one or more degaussing patterns. Each degaussing pattern is information for causing the exciting coil 18 to generate an attenuated alternating magnetic field for degaussing. Each demagnetization pattern includes a plurality of instruction signals composed of a combination of an operation designation signal S2 for designating the energization direction of the switching circuit 16 and a time designation signal S4 for designating the energization time to the excitation coil 18.

The operation designation signal S2 is a signal for designating the polarity of the direct current supplied to the exciting coil 18, and is used as a signal for alternately switching the energizing direction (polarity).
On the other hand, the time designation signal S4 is
8 is a signal for designating the actual supply time.

FIG. 2D shows an example of the operation designating signal S2, and FIG. 2E shows an example of the control signal S3. FIG.
As shown in (D), the operation designation signal S2 has a time width slightly longer than the actual energization time (control signal S3) to the excitation coil 18.

The time designation signal S4 is the number of the pulse signals S1. Therefore, in the case of Japan, the frequency of the commercial AC power supply is 50 Hz or 60 Hz, so that the pulse signal S
One energization time can be designated by the number of occurrences of one.

Each degaussing pattern is also provided between the start of the degaussing operation and the energizing period that is temporally adjacent (between the adjacent positive exciting period and reverse exciting period, and when the energizing direction is switched). Includes an excitation pause period in which excitation is temporarily suspended. Each excitation suspension period is for temporarily stopping the supply of current to the excitation coil 18 and is designated by an excitation suspension signal. Each excitation pause signal is composed of a combination of a pause instruction signal for instructing the output synchronizing circuit 24 to stop energizing the excitation coil 18 and a time designation signal S4 for specifying the excitation pause period.

Each degaussing pattern also includes an end instruction period for instructing the end of the degaussing operation. This end instruction period is indicated by an end signal S10 output at the end (last) of the degaussing operation.

The instruction signal, each excitation pause signal and the end signal are recorded at one address, or are recorded separately at two or more consecutive addresses. Each of the excitation pause signal and the end signal may be considered as a kind of instruction signal because they are for designating or instructing the suspension of the excitation.

The memory circuit 22 sequentially stores one or more demagnetization patterns as described above in successive addresses for each demagnetization pattern so that the direction of energization to the exciting coil 18 is alternated and the energization time is reduced. doing. One example of the demagnetization pattern stored in the memory circuit 22 is shown in FIGS. The time designation signal S4 in the memory circuit 22 is supplied to the counting circuit 26.

As shown in FIG. 2D, the operation designating signal S2 has a time width slightly longer than the actual energizing time to the exciting coil 18, and has a number of pulses corresponding to the time designating signal S4. It disappears when the signal S1 is generated.
As shown in FIG. 2E, the output synchronization circuit 24 has a time width from when the first pulse signal S1 is received after receiving the operation specifying signal S2 to when the operation specifying signal S2 disappears.

The counting circuit 26 receives the time designation signal S4 from the memory circuit 22, presets the received time designation signal S4, starts counting the pulse signals S1 from the cycle detection circuit 20, and counts the number of received pulse signals. When the (count value) reaches the value corresponding to the time designation signal S4, the pulse-like carry signal S5 is output to the address change signal generation circuit 28 to return to the initial state. Execute.

The address change signal generating circuit 28 amplifies the received carry signal S5, and converts the amplified signal to an address change signal S6 for advancing an address designated to the memory circuit 22 to a successive address of the selected degaussing pattern. As a reset signal S7 for returning the counting circuit 26 to the initial state.

The counting circuit 26 is reset each time it receives the reset signal S7 from the address change signal generating circuit 28, and returns to the initial state. The counting circuit 26 may be reset by the carry signal S5 output by itself.

The address designating circuit 30 is a so-called address circuit for designating an address to output a signal to the memory circuit 22. In addition to the address change signal S6, the address specifying circuit 30 includes an initial address S8 set in the initial address setting unit 32, a degauss start signal S9 supplied to the terminal 34, and an end signal S10 output from the memory circuit 22. And receive.

The initial address setting unit 32 designates the first address of a degaussing operation according to a predetermined degaussing pattern, and switches such as a digital switch and a rotary switch are used. The degaussing start signal S9 is a signal for instructing the start of the degaussing operation, and is input by a changeover switch (not shown) provided in the apparatus. The end signal S10 is
A signal instructing that the degaussing operation based on the degaussing pattern is completed when one degaussing process is completed, and is output from the memory circuit 22.

The addressing circuit 30 outputs a degauss start signal S
9 is input to the terminal 34, first, an address signal S11 corresponding to the initial address S8 is output from the memory circuit 22 so that a signal in an address corresponding to the initial address S8 set in the initial address setting device 32 is output from the memory circuit 22. To supply. Thereafter, the addressing circuit 30
Each time the address change signal S6 is input, the address signal S11 supplied to the memory circuit 22 is advanced to the next address.

As the addressing circuit 30 as described above, the initial address signal S8 is preset by the input of the degaussing start signal S9, and thereafter, each time the signal S6 is received, the step is advanced, and the end signal S10 is received. A counter that stops operation and returns to the initial state can be used.

In the power supply device 10, when the power is turned on, the direct current DC shown in FIG. 2B is output from the rectifier circuit 14, and the pulse signal S1 shown in FIG. 20.

When the switch (not shown) is switched to the positive excitation in the state where the power is turned on, the power supply 10 energizes the excitation coil 18 in the positive direction. As a result, the magnetic working surface of the electromagnetic chuck is in an excited state, and the workpiece is magnetically attracted to the magnetic working surface.

When the changeover switch is turned off in a state where the power is turned on, the power supply 10 stops energizing the exciting coil 18. As a result, the magnetic working surface of the electromagnetic chuck is in a non-excited state, and the workpiece can be removed from the magnetic working surface.

However, since the magnetism remaining on the workpiece differs depending on the material of the workpiece, it may not be possible to remove the workpiece from the magnetic working surface only by turning off the changeover switch. Also, depending on the workpiece, it is desired to remove residual magnetism. In such a case, the changeover switch is switched to degaussing, thereby degaussing the workpiece and the electromagnetic chuck.

When the changeover switch is switched to degaussing while the power is turned on, the degaussing start signal S9 is input to the addressing circuit 30.
0 is an address signal S corresponding to the initial address S8.
11 is output to the memory circuit 22. As a result, the excitation pause signal is output from the memory circuit 22 to the cycle detection circuit 24 instead of the operation designation signal S2, so that the excitation coil 18 is not energized. Further, since the time designation signal S4 is output to the counting circuit 26, the counting circuit 26 presets the time designation signal S4 and starts counting the pulse signal S1.

The count value of the counting circuit 26 is the time designation signal S4
, A carry signal S5 is output from the counting circuit 26, and the address change signal generating circuit 28
Output signals S6 and S7. Thereby, the counting circuit 26 is reset, and the address specifying circuit 30 advances the address signal S11 output to the memory circuit 22 by one.

When the first excitation pause signal is stored at a plurality of addresses, power supply device 10 executes the above-described steps a plurality of times.

When the first address storing the instruction signal including the operation designation signal S2 and the time designation signal S4 is designated by the address signal S11, the power supply 10 shifts to the first excitation step. The first excitation step is performed as follows.

First, since an instruction signal in the address corresponding to the address signal S11 is output from the memory circuit 22, the counting circuit 26 presets the time designation signal S4 in the output instruction signal and counts the pulse signal S1. To start. The output synchronizing circuit 24 outputs a control signal S3 to the switching circuit 16 based on the pulse signal S1 and the operation signal S2. Thereby, during the first excitation step, the excitation coil 18
Is energized in a predetermined direction, and the electromagnetic chuck is in a forward or (reverse) excitation state.

Next, when the count value of the counting circuit 26 reaches the value designated by the time designation signal S4, the carry signal S
5 is output from the counting circuit 26, and the signals S6 and S7 are output from the address change signal generating circuit 28. Thereby, the counting circuit 26 is reset, and the addressing circuit 3
0 advances the address signal S11 output to the memory circuit 22 by 1.

When the operation designating signal S2 and the time designating signal S4 are stored in a plurality of addresses, the power supply 10
Performs the above operation a plurality of times. When the first address storing the intermediate excitation pause signal is specified by the address signal S11, the power supply device 10 shifts to the intermediate excitation pause step.

As a result, when the operation designating signal S2 ends, as shown in FIG. 2, it synchronizes with the generation of the pulse signal S1 and also synchronizes with the AC component from the AC source from the power source and the AC component in the rectified DC component. I do.

As shown in FIG. 2 (E), the control signal S3 is output from when the first pulse signal S1 is supplied after the operation specifying signal S2 is supplied until the operation specifying signal S2 disappears. . For this reason, at the time of disappearance, it synchronizes with the generation of the pulse signal, and synchronizes with the AC component from the power supply and the AC component in the rectified DC and DC. And rectified by the AC component in the DC.

In the intermediate excitation pause step, first, the excitation pause signal in the address corresponding to the address signal S11 is output from the memory circuit 22, so that the output synchronization circuit 2
Numeral 4 suspends energization of the excitation coil 18, and the operation designation signal counting circuit 26 presets the supplied time instruction signal S4 and starts counting pulse signals.

Next, when the count value of the counting circuit 26 reaches the value specified by the time specifying signal S4, the carry signal S5 is output from the counting circuit 26, and the signals S6 and S7 are output from the address change signal generating circuit 28. Counting circuit 2
6 is reset, and the addressing circuit 30 advances the address signal S11 output to the memory circuit 22 by one.

When the intermediate excitation pause signal is stored at a plurality of addresses, the power supply device 10 executes the above operation a plurality of times, and then proceeds to the second excitation step. The second excitation step is performed in the same manner as the second first excitation step, except that the direction of energization to the excitation coil 18 is different. Thereafter, the intermediate excitation pause step is executed again.

The above-described first and second excitation steps are executed a plurality of times with an intermediate excitation pause step between them.
When such a process is performed a plurality of times, the power supply device 10
It shifts to the last end step.

This end step is started when the address storing the end signal S10 is designated by the address signal S11. The end signal S10 in the address corresponding to the address signal S11 is output from the memory circuit 22 to the address designating circuit 30, whereby the power supply 1
0 ends the degaussing operation and returns to the standby state.

The direction of energization of the exciting coil 18 is alternately switched in the forward direction and the reverse direction for each exciting step. Also,
The excitation time is gradually reduced. As a result, FIG.
As shown in FIG. 7, an attenuated alternating voltage having alternating polarities and gradually attenuating is supplied from the output synchronization circuit 24 to the exciting coil 18.

As described above, when the control signal S3 is synchronized with the pulse signal S1, the start and end of energization of the excitation coil 18 are synchronized with the AC component in the DC and DC. If the time is the same, the same current is always supplied to the exciting coil, so that degaussing can be ensured.

In the power supply circuit 10, the address specified first for the memory circuit may be fixed. In this case, the address setting device 32 that can selectively set the initial address may not be used, or the setting value of the address setting device 32 may be fixed.

However, it is preferable that the initial address setting unit 32 can be selectively set. If you do that,
Without performing the degaussing operation from the beginning (first term) of one degaussing pattern, as shown in FIG. 3B, an arbitrary term in the middle (for example, i)), one degaussing pattern stored in the memory can be used in common for a plurality of types of degaussing, and as a result, even if the number of degaussing patterns stored in the memory circuit is small. , Various types of degaussing objects having different materials and sizes can be degaussed.

A plurality of demagnetization patterns corresponding to the material and size of a workpiece to be demagnetized may be stored in a memory circuit, and the initial address setting device 32 may be used for selecting a desired demagnetization pattern. Good. In this case, the degaussing operation using the degaussing pattern with the address set in the initial address setting unit 32 as the start address (first address) is executed from the beginning of the degaussing pattern.

Referring to FIG. 4, power supply device 40 further includes a polarity switching number setting device 42 for setting the number of switching of the energizing direction, and excitation coil 18 based on operation designating signal S2 (or control signal S3). Counting circuit 4 for counting the number of times electricity is supplied to
4 is included. The counting circuit 44 generates an operation stop signal S12 for stopping the operation of the power supply device 10 when the counted value reaches the value set in the polarity switching number setting device 42. The operation stop signal S12 is supplied to the addressing circuit 30.

In the power supply device 40, when the start address (for example, the i-th term) of the degaussing operation is set in the initial address setting unit 32 and the number of switching (for example, n) is set in the polarity switching number setting unit 42, When the degaussing start signal S9 is input to the addressing circuit, the addressing circuit 30 starts the degaussing operation from the i-th term, as shown in FIG.

The above-described degaussing operation is started by outputting an address signal S11 corresponding to the address where the information of the i-th term is stored from the address specifying circuit 30 to the memory circuit 22. When the number of times of polarity switching becomes n, the operation stop signal S12 is supplied to the addressing circuit 30.
The addressing circuit 30 ends the degaussing operation and returns to the standby state, similarly to the case where the end signal S10 is supplied thereto.

According to the above, the number of times of switching of the energizing direction can be set in accordance with the material and size of the demagnetizing object, and the switching can be performed in the middle of one demagnetizing pattern. One demagnetization pattern stored in the memory can be used in common for a plurality of types of demagnetization. As a result, even if the number of demagnetization patterns stored in the memory circuit is small, various types of materials and sizes different from each other can be used. The object to be demagnetized can be demagnetized.

FIGS. 5 and 6 show two relays CR1 and C
One embodiment of a degaussing pattern used in a power supply device using R2 as a switching means in a switching circuit is shown. In the degauss pattern shown in FIG. 5, the upper and lower parts of the address and data are indicated by hexadecimal numbers each having 4 bits. For example,
The address FF corresponds to 1111 and 1111.

The upper 4 bits (for example, the “3” bit of data 3F) in the data are bits that specify the energized state (non-energized and energized direction) of the relay.
The bit (for example, the “F” bit of the data 3F) is a bit that specifies the number of generations of the pulse signal S1.

Therefore, for example, the addresses FD, F
C, FB, and FA mean that the reverse excitation is performed while the 58 pulse signals S1, which are the sum of the lower 4 bits, are generated. In this case, the energization time is determined by setting the cycle of the pulse signal S1 to t.
Then, it becomes 58t.

In the above embodiment, the output synchronization circuit 2
4, a counting circuit 26, an address change signal generating circuit 28 and an address specifying circuit 30, or a counting circuit 44 in addition to the above.
U). When replacing them with a computer, an internal memory of the computer may be used as the memory circuit 22.

The present invention is not limited to the above embodiment. For example, the present invention can be applied not only to a demagnetizing power supply device used for an electromagnetic chuck, but also to a power supply device used for a general demagnetizing device.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a waveform of an electric signal in the device of FIG.

FIG. 3 is a diagram illustrating an example of a waveform of an excitation voltage supplied to an excitation coil in the device of FIG. 1;

FIG. 4 is a block diagram of an electric circuit showing another embodiment of the power supply device according to the present invention.

FIG. 5 is a diagram showing one embodiment of a part of a degaussing pattern stored in a memory circuit.

FIG. 6 is a diagram showing a remaining portion of the degaussing pattern following the degaussing pattern shown in FIG.

[Explanation of symbols]

 10, 40 Power supply device for degaussing 12 Commercial AC power supply 14 Rectifier circuit 16 Switching circuit 18 Exciting coil

Claims (6)

[Claims] 1. A demagnetizing device for supplying a direct current output from a rectifier circuit for rectifying an alternating current in a switching circuit to the exciting coil by alternately switching an energizing direction in order to generate an attenuated alternating magnetic field for demagnetizing in the exciting coil. A power supply,
A cycle detection circuit that detects a cycle of an alternating current supplied to the rectifier circuit and generates a pulse signal corresponding to the cycle, a plurality of operation designation signals that designate a direction of energization to the excitation coil, and A memory circuit storing at least one demagnetization pattern including a plurality of time designation signals designating an energization period; and a processing circuit outputting a control signal synchronized with the AC cycle to the switching circuit; Specifies a predetermined address to the memory circuit, causes the signal in the address to be output from the memory circuit, counts pulse signals output from the cycle detection circuit, and obtains the number of pulse signals from the memory circuit. Change the address specified to the memory circuit each time the value matches the value corresponding to the specified time specifying signal, and output the operation specifying signal and A degaussing power supply device that outputs the control signal based on the pulse signal. 2. The processing circuit according to claim 1, wherein said processing circuit receives an address signal for designating an address storing a signal to be output to said memory circuit, and receives said time designation signal and said pulse signal; Address change that counts the received pulse signal and changes the address signal output from the addressing means to the next address signal according to the degaussing pattern each time the counted value reaches a value corresponding to the received time designation signal. 2. The degaussing power supply device according to claim 1, further comprising: a counting unit that outputs a signal; and an output synchronizing unit that outputs the control signal based on the operation designation signal and the pulse signal. 3. The processing circuit according to claim 1, further comprising an initial address setting device for selectively setting an initial address of a demagnetization pattern to be used, wherein said processing circuit specifies an initial address set in said initial address setting means in said memory circuit. 3. The degaussing power supply device according to claim 1, wherein an address designated to said memory circuit is changed each time the number of pulse signals matches a value corresponding to a time designation signal obtained from said memory circuit. 4. The processing circuit according to claim 1, wherein, among the degauss patterns including the initial address set in the initial address setting device, the initial address set in the initial address setting device is set as a start address, and the processing circuit is executed from the start address. The power supply for degaussing according to claim 3. 5. The apparatus according to claim 1, further comprising: a switching frequency setting device for setting a switching frequency of the energizing direction, wherein the processing circuit further counts the number of energizing operations to the exciting coil based on the control signal or the operation designating signal. 5. The apparatus according to claim 2, further comprising a second counting means for generating an operation stop signal for stopping operation of the processing circuit when the count value reaches a value set in the switching number setting device. Power supply for degaussing. 6. The counting means receives the time designation signal and the pulse signal, counts the received pulse signal, and each time the count value reaches a value corresponding to the received time designation signal, a carry signal is provided. And changing the addressing signal output from the addressing means to the next addressing signal according to the demagnetization pattern based on the carry signal from the counting means, and clearing the count value of the counting means. And an address change signal generating means for outputting an address change signal.
6. The power supply for degaussing according to 4 or 5.