Electromagnetic power supply device

Abstract

To provide an electromagnet power supply device that can further improve stability of output current.SOLUTION: There is provided an electromagnet power supply device comprising: a main circuit unit that is connected to an electromagnet and supplies current according to a stepwise changing current pattern to the electromagnet; a current detector that detects current flowing through the electromagnet; and a control unit that controls operation of the main circuit unit on the basis of the current pattern and a detection result of the current detector. The main circuit unit includes a forcing circuit and a flat maintenance circuit. The control unit makes the forcing circuit perform output operation of outputting voltage and stop operation of stopping output voltage; and, after making the forcing circuit perform the output operation, switches the forcing circuit from the output operation to the stop operation at timing when a current deviation, which represents a difference between a target current value represented by the current pattern and the present output current value detected by the current detector, reaches a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to an electromagnetic power supply. [Background technology]

[0002] Electromagnet power supply devices for voltage-source power conversion systems are known that supply an electromagnet with a current corresponding to a current pattern that changes stepwise. In such electromagnet power supply devices, two chopper circuits are connected in series. One chopper circuit operates during a period in which the current command value changes stepwise. This chopper circuit is called, for example, a forcing circuit. The other chopper circuit operates during a period in which the current command value is constant. This chopper circuit is called, for example, a flat-maintaining circuit.

[0003] In this way, by providing two chopper circuits connected in series, it is possible to obtain high responsiveness of the load current to changes in the current command value, and to control the load current with high precision for a constant current command value. Such an electromagnet power supply device is used, for example, in medical scanning electromagnets.

[0004] The forcing circuit performs an output operation to output voltage during the period when the current command value changes in a stepwise manner, and performs a stopping operation to stop the voltage output by making the output side conductive (bypass) during the period when the current command value is constant.

[0005] The forcing circuit switches from output operation to stopping operation when the current deviation, which represents the difference between the target current value and the current output current value, falls below a threshold. At this time, jitter caused by the sampling time of the current deviation may cause the timing of the forcing circuit's switching from output operation to stopping operation to be unstable, which could result in a decrease in the stability of the output current supplied to the electromagnet.

[0006] For this reason, it is desirable to further improve the stability of the output current in an electromagnetic power supply device. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 1-279311 Summary of the Invention [Problem to be solved by the invention]

[0008] The embodiments of the present invention provide an electromagnetic power supply device that can further improve the stability of the output current. [Means for solving the problem]

[0009] According to an embodiment of the present invention, there is provided a main circuit section connected to an electromagnet and supplying the electromagnet with a current corresponding to a current pattern that changes stepwise, a current detector that detects the current flowing through the electromagnet, and a control section that receives an input of the current pattern and controls the operation of the main circuit section based on the input current pattern and the detection result of the current detector, wherein the main circuit section has a forcing circuit that operates during a period when the current pattern changes stepwise, and a flat maintaining circuit that is connected in series with the forcing circuit and operates during a fixed period when the current pattern changes stepwise, and the control section causes the forcing circuit to perform an output operation that outputs a voltage during the period when the current pattern changes stepwise, and causes the forcing circuit to perform a stop operation that makes the output side conductive and stops outputting the voltage during the fixed period when the current pattern is ,before a current deviation representing the difference between the target current value represented by the current pattern and the current output current value detected by the current detector; a current deviation is acquired at a predetermined sampling period, and each time the current value of the current deviation is acquired, a time for the current deviation to reach the predetermined threshold is calculated based on the current value of the current deviation, a predetermined threshold, and a rate of change of the current deviation, and after causing the forcing circuit to perform the output operation, if the current deviation reaches the predetermined threshold before the next acquisition of the current value of the current deviation, at a timing when the calculated arrival time has elapsed from the timing of acquisition of the current value of the current deviation, An electromagnet power supply is provided that switches the forcing circuit from the output operation to the deactivated operation. [Effects of the Invention]

[0010] According to an embodiment of the present invention, an electromagnetic power supply device capable of further improving the stability of the output current is provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a circuit diagram schematically illustrating an electromagnetic power supply device according to an embodiment. [Figure 2] FIG. 2 is a circuit diagram schematically illustrating a main circuit section. [Figure 3] 3(a) and 3(b) are graphs that schematically show an example of the operation of the control unit. [Figure 4] 10 is a graph schematically illustrating an example of the operation of the control unit. [Figure 5] 10 is a graph schematically illustrating an example of the operation of the control unit. [Figure 6] 10 is a graph schematically showing an example of a reference operation of a control unit.

[0012] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In the present specification and the drawings, elements similar to those described above with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted as appropriate.

[0013] FIG. 1 is a circuit diagram that schematically illustrates an electromagnetic power supply device according to an embodiment. As shown in FIG. 1, the electromagnet power supply device 10 includes a main circuit unit 12 and a control unit 14. The main circuit unit 12 is connected to an electromagnet 2, which is a load, and supplies the electromagnet 2 with a current according to a current pattern that changes stepwise. The main circuit unit 12 operates the electromagnet 2 by supplying the current. The main circuit unit 12 is, for example, a voltage-type power conversion device. The control unit 14 controls the operation of the main circuit unit 12. More specifically, the control unit 14 controls the operation of the main circuit unit 12 to supply current to the electromagnet 2.

[0014] The main circuit section 12 has a forcing circuit 16 and a flat maintenance circuit 18. The flat maintenance circuit 18 is connected in series with the forcing circuit 16. The forcing circuit 16 operates during a period when the current pattern (current command value) changes stepwise. The flat maintenance circuit 18 operates during a period when the current pattern (current command value) is constant.

[0015] For example, reactors 21 and 22 are provided on the output side of the forcing circuit 16. For example, reactors 23 and 24 are provided on the output side of the flat maintenance circuit 18. The reactors 21 to 24 are, for example, reactors for smoothing ripples. The flat maintenance circuit 18 is connected in series with the forcing circuit 16 via, for example, reactors 22 and 23. The forcing circuit 16 and the flat maintenance circuit 18 (main circuit section 12) are connected to the electromagnet 2 via the reactors 21 and 24.

[0016] The electromagnet power supply device 10 further includes, for example, a DC power supply 30 and a DC power supply 40. The forcing circuit 16 is connected to the electromagnet 2, which is a load, and is also connected to the DC power supply 30. The forcing circuit 16 operates to change the current supplied to the electromagnet 2 in a step-like manner by switching between supplying and stopping the DC voltage supplied from the DC power supply 30 to the electromagnet 2. The current supplied from the main circuit unit 12 to the electromagnet 2 changes in a step-like manner when the forcing circuit 16 is outputting a DC voltage.

[0017] The DC power supply 30 includes, for example, a transformer 31, a rectifier 32, a reactor 33, and a capacitor 34. The rectifier 32 is connected to the AC power supply 4 via the transformer 31. The rectifier 32 rectifies the AC power supplied from the AC power supply 4 and converts it into rectified power. The reactor 33 and the capacitor 34 smooth the rectified power converted by the rectifier 32 and convert it into DC power. In this way, the DC power supply 30 supplies the DC power to the forcing circuit 16.

[0018] The flat maintenance circuit 18 is connected to the electromagnet 2, which is a load, and is also connected to a DC power supply 40. The flat maintenance circuit 18 controls the current supplied to the electromagnet 2 to be a constant current according to a current command value represented by a current pattern by switching between supplying and stopping the supply of DC voltage supplied from the DC power supply 40 to the electromagnet 2.

[0019] The DC power supply 40 includes, for example, a transformer 41, a rectifier 42, a reactor 43, and a capacitor 44. The configuration of the DC power supply 40 is similar to that of the DC power supply 30, and therefore a detailed description thereof will be omitted. As a result, the DC power supply 40 supplies DC power to the flat maintenance circuit 18.

[0020] The configuration of the DC power supplies 30, 40 is not limited to the above, and any configuration may be used that is capable of supplying DC power to the forcing circuit 16 and the flat maintenance circuit 18. Furthermore, the electromagnet power supply device 10 does not necessarily have to include the DC power supplies 30, 40. The forcing circuit 16 and the flat maintenance circuit 18 may receive DC power from an external DC power supply.

[0021] FIG. 2 is a circuit diagram that schematically illustrates the main circuit section. As shown in FIG. 2, the forcing circuit 16 has four full-bridge connected switching elements 50a to 50d and four rectifying elements 52a to 52d connected in anti-parallel to the four switching elements 50a to 50d, respectively.

[0022] Similarly, the flat maintenance circuit 18 has four full-bridge connected switching elements 54a to 54d, and four rectifying elements 56a to 56d connected in anti-parallel to the four switching elements 54a to 54d, respectively.

[0023] In other words, the forcing circuit 16 and the flat maintaining circuit 18 are chopper circuits. In other words, the forcing circuit 16 is a first chopper circuit, and the flat maintaining circuit 18 is a second chopper circuit.

[0024] In the forcing circuit 16, the connection point between the upper (high-side) switching element 50a and the lower (low-side) switching element 50c, and the connection point between the upper switching element 50b and the lower switching element 50d, respectively, form a pair of output points 16a and 16b. Similarly, in the flat maintaining circuit 18, the connection point between the upper switching element 54a and the lower switching element 54c, and the connection point between the upper switching element 54b and the lower switching element 54d, respectively, form a pair of output points 18a and 18b.

[0025] Output point 18a of flat maintenance circuit 18 is connected to output point 16b of forcing circuit 16 via reactors 22 and 23. As a result, the output side of flat maintenance circuit 18 is connected in series with the output side of forcing circuit 16. Output point 16a of forcing circuit 16 is connected to one end of electromagnet 2 via reactor 21. Output point 18b of flat maintenance circuit 18 is connected to the other end of electromagnet 2 via reactor 24. As a result, the output sides of forcing circuit 16 and flat maintenance circuit 18, which are connected in series, are connected to electromagnet 2, and power output from forcing circuit 16 and flat maintenance circuit 18 is supplied to electromagnet 2.

[0026] Each of the switching elements 50a-50d, 54a-54d has a pair of main terminals and a control terminal. Depending on the voltage input to the control terminal, each of the switching elements 50a-50d, 54a-54d switches between an ON state in which current flows between the pair of main terminals and an OFF state in which current is blocked between the pair of main terminals. The OFF state does not necessarily have to be a state in which current flow between the main terminals is completely blocked, but may be a state in which a weak current flows between the main terminals to the extent that it does not affect the operation of the main circuit unit 12. The ON state is, in other words, a first state in which current flows between the main terminals, and the OFF state is, in other words, a second state in which current flows between the main terminals in a smaller amount than in the first state.

[0027] Each of the switching elements 50a to 50d, 54a to 54d may be a self-excited semiconductor switching element such as an IGBT (Insulated Gate Bipolar Transistor), but the switching elements 50a to 50d, 54a to 54d are not limited to this and may be any switching element that can be controlled to switch between an on state and an off state.

[0028] In the forcing circuit 16 and flat maintenance circuit 18 of the full-bridge circuit, the direction of the current supplied to the electromagnet 2 can be controlled by switching the switching elements 50a to 50d, 54a to 54d. However, the configurations of the forcing circuit 16 and the flat maintenance circuit 18 are not limited to those described above, and any configuration may be used as long as it is possible to appropriately supply a current to the electromagnet 2 according to a current pattern that changes stepwise.

[0029] The control unit 14 is connected to the control terminals of each of the switching elements 50a to 50d, 54a to 54d, and controls the operation of the forcing circuit 16 and the flat maintaining circuit 18 by controlling the switching between the on state and the off state of each of the switching elements 50a to 50d, 54a to 54d.

[0030] The control unit 14 controls the switching between the on and off states of each of the switching elements 50a to 50d of the forcing circuit 16, thereby controlling the operation of changing the current supplied to the electromagnet 2 in a stepwise manner.

[0031] Furthermore, control unit 14 causes forcing circuit 16 to perform an output operation that outputs a voltage during a period in which the current pattern changes stepwise, and also causes forcing circuit 16 to perform a stop operation that makes the output side conductive (bypass) and stops the output of voltage during a period in which the current pattern is constant. The output operation is, in other words, a forcing operation.

[0032] In this example, the pair of output points 16a, 16b can be brought into a conductive state by turning on the upper switching elements 50a, 50b and turning off the lower switching elements 50c, 50d, or conversely, turning off the upper switching elements 50a, 50b and turning on the lower switching elements 50c, 50d.

[0033] The control unit 14 controls the switching between the on and off states of each of the switching elements 54a to 54d of the flat maintenance circuit 18, thereby controlling the current supplied to the electromagnet 2 to be a constant current according to the current pattern when the current pattern is in a constant period. The control unit 14 controls the current supplied to the electromagnet 2 to be a constant current according to the current pattern, for example, by quickly switching between the on and off states of each of the switching elements 54a to 54d. The control unit 14 controls the current supplied to the electromagnet 2 to be a constant current according to the current pattern, for example, by performing ACR (Auto Current Regulator) control on the flat maintenance circuit 18.

[0034] 1, the electromagnet power supply device 10 further includes a current detector 60. The current detector 60 detects the current flowing through the electromagnet 2 and inputs the detection result to the control unit 14.

[0035] 3(a) and 3(b) are graphs that schematically show an example of the operation of the control unit. Fig. 3(a) schematically shows an example of a current pattern input to the control unit 14 and an example of an output current supplied from the main circuit unit 12 to the electromagnet 2. Fig. 3(b) shows an enlarged view of the area surrounded by the dashed line in Fig. 3(a).

[0036] As shown in FIGS. 3(a) and 3(b), a current pattern that changes stepwise is input to the control unit 14. The current pattern is input to the control unit 14 as needed, for example, from a higher-level controller via communication. In other words, the control unit 14 receives the current pattern input from an external device such as a higher-level controller by communicating with the external device. The current pattern is, in other words, a current command value that indicates the magnitude of the current to be supplied to the electromagnet 2. In other words, the control unit 14 receives the current command value input from the external device by communicating with the external device.

[0037] The current pattern (current command value) may be input to the control unit 14 in advance, for example, and stored in a storage unit of the control unit 14 or another storage unit connected to the control unit 14. The method for inputting the current pattern to the control unit 14 is not limited to the above, and any method that can appropriately input the current pattern to the control unit 14 may be used.

[0038] The control unit 14 controls the operation of the main circuit unit 12 (the forcing circuit 16 and the flat maintaining circuit 18) based on the input current pattern and the detection result of the current detector 60.

[0039] The control unit 14 causes the forcing circuit 16 to perform a stop operation to make the output side conductive during a period when the current pattern is constant, and also controls the operation of the flat maintenance circuit 18 based on the detection results of the current detector 60 so that the current supplied to the electromagnet 2 becomes a constant current according to the current pattern.

[0040] As shown in Figure 3(a), when changing the polarity of the current supplied to the electromagnet 2, the control unit 14 changes the polarity of the voltage output from the flat maintenance circuit 18 depending on whether a current of positive polarity is supplied to the electromagnet 2 or a current of negative polarity is supplied to the electromagnet 2.

[0041] FIG. 4 is a graph schematically illustrating an example of the operation of the control unit. As shown in FIGS. 3( a), 3(b), and 4, the control unit 14 causes the forcing circuit 16 to perform an output operation to output a voltage when the current pattern changes stepwise. The control unit 14 changes the polarity of the voltage output from the forcing circuit 16 depending on whether the current supplied to the electromagnet 2 is lower than the current pattern or higher than the current pattern. For example, when the current supplied to the electromagnet 2 is lower than the current pattern and the current supplied to the electromagnet 2 is to be increased toward a target current value, the control unit 14 causes the forcing circuit 16 to output a voltage with a positive polarity. On the other hand, when the current supplied to the electromagnet 2 is higher than the current pattern and the current supplied to the electromagnet 2 is to be decreased toward a target current value, the control unit 14 causes the forcing circuit 16 to output a voltage with a negative polarity.

[0042] When the forcing circuit 16 is caused to perform an output operation, the flat maintenance circuit 18 may continue to control the current supplied to the electromagnet 2 to be constant, or may perform a stop operation to make the output side conductive.

[0043] 3(b) and 4, the forcing-on period during which the forcing circuit 16 performs an output operation is represented by the period indicated by arrow (1), and the flat operation period during which the flat maintenance circuit 18 performs an operation to control the current to a constant level is represented by the period indicated by arrow (2). Note that in Fig. 3(b), in consideration of the response delay between the timing of a change in the current pattern and the timing of operating the forcing circuit 16, the timing of the start of the forcing-on period is shown slightly delayed from the timing of a change in the current pattern.

[0044] After causing forcing circuit 16 to perform an output operation, control unit 14 switches forcing circuit 16 from output operation to stop operation at the timing when a current deviation representing the difference between a target current value represented by the current pattern and the current output current value detected by current detector 60 reaches a predetermined threshold. In other words, control unit 14 switches from a forcing-on period to a flat operation period at the timing when the current deviation reaches the predetermined threshold. In other words, control unit 14 switches forcing circuit 16 from output operation to stop operation at the timing when the current supplied to electromagnet 2 reaches the target current value.

[0045] The threshold value may be set to zero deviation according to the target current value, or may be set to switch to a stopping operation earlier, taking into account overshoot (undershoot) of the current deviation due to a delay in the operation of the forcing circuit 16, etc. For example, as shown in FIG. 4, when switching the forcing circuit 16 from output operation to stopping operation, it may be required that the current deviation be within a predetermined range. The predetermined range is, for example, within ±0.1% of the rated current value. The rated current value is the current supplied to the electromagnet 2 when the forcing circuit 16 performs an output operation. In such a case, the threshold value may be set appropriately, taking into account overshoot of the current deviation, etc., so that the current deviation falls within the predetermined range.

[0046] FIG. 5 is a graph schematically illustrating an example of the operation of the control unit. 5, the control unit 14 acquires the current deviation value at a predetermined sampling period. In other words, the control unit 14 acquires the detected value of the current flowing through the electromagnet 2 from the current detector 60 at a predetermined sampling period. The control unit 14 acquires the detected value of the current flowing through the electromagnet 2 from the current detector 60 at a predetermined sampling period, for example, and acquires the current deviation value at the predetermined sampling period by calculating the difference between the detected current value and the target current value each time the control unit 14 acquires the detected current value from the current detector 60. The control unit 14 calculates the current deviation value at the predetermined sampling period, for example, using the following formula. Current deviation = Target current - Current detection value

[0047] Each time the control unit 14 acquires the current deviation's current value, the control unit 14 calculates the time it takes for the current deviation to reach the threshold value based on the current deviation's current value, the threshold value, and the rate of change of the current deviation. The control unit 14 calculates the threshold value arrival time using, for example, the following formula. Time to reach threshold = (current deviation - threshold) ÷ rate of change of current deviation

[0048] For example, if the current deviation is 2A, the threshold is 1A, and the rate of change of the current deviation is 1A / μs, the time it takes to reach the threshold can be calculated as (2A-1A)÷1A / μs=1μs.

[0049] The sign of the current deviation may change depending on whether the current pattern is increasing or decreasing and the direction in which current is supplied to the electromagnet 2 (current polarity). Therefore, the current deviation is, more specifically, the absolute value of the current deviation. Similarly, the sign of the rate of change of the current deviation may also change depending on whether the current pattern is increasing or decreasing. The rate of change of the current deviation is, more specifically, the absolute value of the slope of the change in the current deviation.

[0050] As shown in FIG. 5, after causing the forcing circuit 16 to perform an output operation, if the current deviation reaches a predetermined threshold before the next acquisition of the current value of the current deviation, the control unit 14 switches the forcing circuit 16 from the output operation to the stop operation at the timing when the arrival time calculated from the timing of acquisition of the current value of the current deviation has elapsed.

[0051] When the output voltage output from main circuit unit 12 to electromagnet 2 is V, the output current output from main circuit unit 12 to electromagnet 2 is i, the inductance component of electromagnet 2 is L, the resistance component of electromagnet 2 is R, and the rate of change of output current i output to electromagnet 2 is di / dt, the output voltage V can be expressed by the following equation. Note that when forcing circuit 16 is performing an output operation, output voltage V is, in other words, the output voltage of forcing circuit 16. V=L·di / dt+R·i By modifying the above equation, the rate of change di / dt can be expressed by the following equation: That is, the rate of change of the current deviation can be calculated by the following equation. di / dt=(VR·i) / L

[0052] The output voltage V, output current i, inductance component L, and resistance component R can be obtained as design values ​​of the electromagnet power supply device 10. Therefore, the rate of change of the current deviation can be a predetermined value calculated in advance using the above formula. The control unit 14 stores the pre-calculated rate of change of the current deviation in, for example, an internal storage unit or an external storage unit connected via wiring, and calculates the threshold arrival time based on the stored rate of change of the current deviation.

[0053] In this way, the rate of change of the current deviation depends on the output voltage of the forcing circuit 16. In other words, the rate of change of the current deviation depends on the output voltage of the DC power supply 30. In the electromagnet power supply 10, the time of the forcing-on period (the time during which the output current is changed in a stepwise manner) may be predetermined. In this case, the rate of change of the current deviation is determined according to the time of the predetermined forcing-on period. In other words, the output voltage of the forcing circuit 16 and the output voltage of the DC power supply 30 are determined according to the time of the predetermined forcing-on period. The time of the forcing-on period may also be called, for example, the excitation speed.

[0054] The rate of change of the current deviation may be calculated based on the previous current deviation value, the current current deviation value, and the sampling period, each time the current current deviation value is acquired. That is, the rate of change of the current deviation may be calculated using the following formula each time the current current deviation value is acquired. Current deviation change rate = (current deviation value from previous time - current deviation value from current time) / sampling period

[0055] However, there is a possibility that noise due to measurement errors or the like may be superimposed on the current value of the current deviation detected by the current detector 60. For this reason, it is preferable that the rate of change of the current deviation be a predetermined value calculated in advance based on the output voltage V, the output current i, the inductance component L, and the resistance component R. This makes it possible, for example, to suppress the influence of measurement errors and more appropriately calculate the time it takes for the current deviation to reach the threshold value. Furthermore, it is also possible to reduce the calculation load on the control unit 14.

[0056] FIG. 6 is a graph schematically showing an example of a reference operation of the control unit. In the example shown in FIG. 6, after the control unit 14 causes the forcing circuit 16 to perform an output operation, each time the control unit 14 acquires the current value of the current deviation, it determines whether the acquired current value of the current deviation has reached a threshold value, and switches the forcing circuit 16 from an output operation to a stop operation in response to determining that the threshold value has been reached.

[0057] In the reference operation shown in Fig. 6, due to jitter caused by the sampling period of the current deviation, the timing at which forcing circuit 16 is switched from output operation to stopped operation may be delayed from the timing at which it should be switched to stopped operation (the point at which it should be turned off) when the current value of the current deviation reaches a threshold value. In other words, in the reference operation, the timing at which forcing circuit 16 is switched from output operation to stopped operation may vary within the range from the timing at which the current deviation is sampled to the timing at which the next current deviation is sampled.

[0058] Thus, in the reference operation, the timing at which forcing circuit 16 switches from output operation to stopping operation (forcing-off timing) is unstable, and as a result, the behavior of the overshoot of the current deviation when switching from output operation to stopping operation may be unstable. For example, when forcing circuit 16 switches from output operation to stopping operation, there is a possibility that the current deviation will not fall within a predetermined range, which is set to, for example, within ±0.1% of the rated current value.

[0059] For example, as shown in FIG. 3(a), the cycle of the current pattern change (the cycle from one forcing-on period to the next) may be relatively high, at several tens of kilohertz or more, and the duration of the forcing-on period may also need to be short, on the order of a few microseconds. In such a case, if the sampling period for acquiring the current deviation value is set to about 1 microsecond, the sampling period becomes too long relative to the change in the current deviation, and the problem of variation in the timing for switching the forcing circuit 16 from output operation to stop operation becomes significant. In the reference operation, if the cycle of the current pattern change is high, there is a high possibility that the current deviation will not fall within a predetermined range when forcing is turned off.

[0060] One possible solution is to increase the sampling period for acquiring the current deviation value. However, increasing the sampling period while maintaining high resolution of the current deviation value in the control unit 14 would complicate the configuration of the control unit 14. For example, new components such as an AD converter would have to be developed, which would increase the manufacturing costs of the control unit 14.

[0061] In contrast, in the electromagnet power supply device 10 according to this embodiment, each time the control unit 14 acquires the current value of the current deviation, it calculates the time until the current deviation reaches the threshold value based on the current value of the current deviation, the threshold value, and the rate of change of the current deviation, and after causing the forcing circuit 16 to perform an output operation, if the current deviation reaches the predetermined threshold value before the next acquisition of the current value of the current deviation, it switches the forcing circuit 16 from output operation to stop operation at the timing when the calculated arrival time has elapsed from the timing of acquisition of the current value of the current deviation.

[0062] This stabilizes the timing at which forcing circuit 16 switches from output operation to stopping operation, and also stabilizes the behavior of overshoot in the current deviation when switching from output operation to stopping operation. For example, when forcing circuit 16 switches from output operation to stopping operation, the current deviation can be appropriately kept within a predetermined range.

[0063] Therefore, it is possible to provide an electromagnet power supply device 10 that can further improve the stability of the output current supplied to the electromagnet 2. For example, even when the cycle of change in the current pattern is high, it is possible to reduce the need to increase the sampling cycle and improve the stability of the output current with a relatively simple configuration.

[0064] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0065] 2...electromagnet, 4...AC power supply, 10...electromagnet power supply device, 12...main circuit section, 14...control section, 16...forcing circuit, 18...flat maintenance circuit, 21-24...reactor, 30, 40...DC power supply, 31, 41...transformer, 32, 42...rectifier, 33, 43...reactor, 34, 44...capacitor, 50a-50d, 54a-54d...switching element, 52a-52d, 56a-56d...rectifying element, 60...current detector

Claims

1. a main circuit section connected to the electromagnet and supplying a current to the electromagnet according to a current pattern that changes stepwise; a current detector for detecting a current flowing through the electromagnet; a control unit that receives the current pattern and controls the operation of the main circuit unit based on the input current pattern and the detection result of the current detector; Equipped with The main circuit section includes: a forcing circuit that operates during a period in which the current pattern changes stepwise; a flat-maintaining circuit connected in series with the forcing circuit, the flat-maintaining circuit operating for a fixed period of time; and the control unit causes the forcing circuit to perform an output operation to output a voltage when the current pattern is changing stepwise, and causes the forcing circuit to perform a stop operation to make an output side conductive and stop the output of the voltage when the current pattern is in a fixed period; acquires a present value of a current deviation that represents a difference between a target current value represented by the current pattern and a present output current value detected by the current detector at a predetermined sampling period; and each time the present value of the current deviation is acquired, calculates a time period for the current deviation to reach the predetermined threshold based on the present value of the current deviation, a predetermined threshold, and a rate of change of the current deviation; and after causing the forcing circuit to perform the output operation, if the current deviation reaches the predetermined threshold before the next acquisition of the present value of the current deviation, switches the forcing circuit from the output operation to the stop operation at a timing when the arrival time calculated from the timing of acquisition of the present value of the current deviation has elapsed.

2. a main circuit section having a forcing circuit and a flat maintaining circuit, and supplying a current to the electromagnet according to a target current value that changes stepwise; a current detector for detecting a current flowing through the electromagnet; a control unit that controls the operation of the main circuit unit based on the target current value and the current value detected by the current detector; Equipped with The control unit When the target current value changes, the forcing circuit is controlled to output a voltage so that the current flowing through the electromagnet becomes the target current value; acquiring a current deviation, which is a difference between the target current value and the current value detected by the current detector, at a predetermined sampling period; each time the current deviation is acquired, a time required for the current deviation to reach the predetermined threshold is calculated based on the current deviation, a predetermined threshold, and a rate of change of the current deviation; If the current deviation reaches the predetermined threshold value before the next sampling period, stopping the output of voltage from the forcing circuit at the timing when the time calculated from the timing of acquiring the current deviation has elapsed until the current deviation reaches the predetermined threshold value; an electromagnet power supply device that, when the output of voltage from the forcing circuit is stopped, controls the flat maintaining circuit to supply a constant current to the magnet based on the target current value until the target current value changes.

3. 3. The electromagnet power supply device according to claim 1, wherein the control unit calculates a time until the current deviation reaches the predetermined threshold value by using a rate of change of the current deviation that is calculated in advance based on an output voltage output from the main circuit unit to the electromagnet, an output current output from the main circuit unit to the electromagnet, an inductance component of the electromagnet, and a resistance component of the electromagnet.

Images