JP6995450B2 - Power supply - Google Patents

Description

An embodiment of the present invention relates to a power supply device for driving an electromagnet.

Various application devices have been developed that utilize the accelerated charged particle beam. In such an application device, it is necessary to deflect and scan the charged particle beam to irradiate the target area. The charged particle beam can be scanned by controlling the current flowing through the electromagnet as the charged particle passes through the electromagnet.

There is a power supply that accurately controls the current flowing through the electromagnet. Such a power supply device needs to control the current value with high accuracy in order to make the scanning range and the irradiation position of the charged particle beam accurate. In recent years, in addition to the above-mentioned requirements, there is a strong demand for shortening the scanning time, and the power supply device is required to stably follow the set current value (reference current value) that can be switched at high speed. ing.

Since the electromagnet has an inductive impedance, the current flowing through the electromagnet cannot be changed in steps even if the reference current value is changed in steps. At the time of transition of the reference current value, the deviation of the output current from the reference current value becomes large, and the output current may become unstable due to the ringing of the control amount.

There is a demand for a power supply device that enables highly accurate current value setting and that operates stably even when the reference current value changes.

Japanese Patent No. 3580254

The embodiment provides a power supply device capable of stably controlling an output current.

The power supply device according to the embodiment supplies an output current to the electromagnet according to a reference current signal transitioning between the first signal value and the second signal value different from the first signal value. This power supply device outputs the first voltage in the first period, which is the transition period from the first output current value corresponding to the first signal value to the second output current value corresponding to the second signal value. In periods other than the first period, a first power converter that outputs a second voltage having a voltage lower than the first voltage and a second having an output connected in series to the output of the first power converter. It includes a power converter and a control device for controlling the output current output by the second power converter. The control device presets a control amount generation means for generating and outputting a control amount according to a deviation between the reference current signal and an output current signal representing the output current, and an output of the control amount generation means. It includes a control amount limiting means for limiting within the limit value. The control amount generation means outputs a control amount smaller than the limit value of the control amount limiting means in the first period.

In the present embodiment, a power supply device capable of stably controlling the output current is realized.

It is a block diagram which illustrates the power supply device which concerns on embodiment. It is a block diagram illustrating a part of the power supply device of an embodiment. FIG. 3A is an example of an operation waveform showing the operation of the power supply device of the embodiment. FIG. 3B is an enlarged view of part A in FIG. 3A. It is an example of the operation waveform of each part of the power supply device of an embodiment. It is a block diagram which illustrates a part of the power supply device of a comparative example. It is an example of the operation waveform of the power supply device of the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
It should be noted that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between the parts, and the like are not necessarily the same as the actual ones. Further, even when the same part is represented, the dimensions and ratios may be different from each other depending on the drawing.
In addition, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram illustrating a power supply device according to an embodiment.
As shown in FIG. 1, the power supply device 10 of the embodiment is connected to the power supply 1. The power supply 1 is an AC power supply. The AC power source is preferably three-phase AC. The power supply device 10 includes output terminals 2a and 2b. An electromagnet 4, which is a load, is connected between the output terminals 2a and 2b. The electromagnet 4 deflects a charged particle beam emitted from an accelerator or the like and scans a set irradiation region. The power supply unit 10 receives a reference current signal Iref from a host control system (not shown). The power supply device 10 is operated by the power supply 1 and supplies an output current set according to the reference current signal Iref to the electromagnet 4.

The power supply device 10 includes two chopper units 14, 24 and a control device 30. A current detector 28 is provided at the outputs of the chopper units 14 and 24. The current detector 28 detects the output current supplied to the electromagnet 4 and supplies it to the control device 30 as an output current signal Iout. The control device 30 inputs the reference current signal Iref from the host control system and the output current signal Iout from the current detector 28, respectively, to generate a gate signal for driving the switching elements of the chopper units 14 and 24, and the chopper unit. Supply to 14 and 24.

The chopper units 14 and 24 both include an input / output non-isolated DC-DC converter circuit. In this example, the chopper units 14 and 24 have a full-bridge type circuit configuration capable of supplying positive and negative output currents in order to supply positive and negative output currents to the load electromagnets. When the direction of the output current supplied to the electromagnet is unidirectional, the circuit configuration may be, for example, a step-down chopper system, and an appropriate circuit format can be used according to input / output conditions and the like.

The chopper unit (first power converter) 14 includes input terminals 15a and 15b and output terminals 16a and 16b. The power supply 1 is connected to the input of the rectifier 12 via the transformer 11. The output of the rectifier 12 is connected to the input terminals 15a and 15b of the chopper unit 14 via the filter 13.

In the chopper unit 14, when supplying a voltage corresponding to the output voltage of the rectifier 12 input to the full bridge circuit via the input terminals 15a and 15b to the output terminals 16a and 16b, and when bypassing the output terminals 16a and 16b. To switch between. When supplying a voltage corresponding to the output voltage of the rectifier 12 input to the full bridge circuit to the output terminals 16a and 16b, the switching element on the high side side of one leg of the full bridge circuit is turned on and the other is turned on. Turn on the switching element on the low side of the leg. When bypassing the output terminals 16a and 16b, for example, the switching element on the high side side of the full bridge circuit is switched from on to off, and the full bridge circuit is operated in reflux.

The chopper unit (second power converter) 24 includes input terminals 25a and 25b and output terminals 26a and 26b. The power supply 1 is connected to the input of the rectifier 22 via the transformer 21. The output of the rectifier 22 is connected to the input terminals 25a and 25b of the chopper unit 24 via the filter 23.

The chopper unit 24 outputs a voltage corresponding to the output voltage of the rectifier 22 input to the full bridge circuit via the input terminals 25a and 25b from the output terminals 26a and 26b.

One output terminal 16a of the chopper unit 14 is connected to one terminal of the electromagnet 4 via the output terminal 2a of the power supply device 10. One output terminal 26a of the chopper unit 24 is connected to the other output terminal 16b of the chopper unit 14. The other output terminal 26b of the chopper unit 24 is connected to the other terminal of the electromagnet 4 via the output terminal 2b of the power supply device 10.

The control device 30 controls the chopper unit 14 so as to switch and output the value of the voltage output by the chopper unit 14. The reference current signal Iref transitions from one reference current value (first signal value) to the next reference current value (second signal value). At this time, the output current signal Iout has a period (first period) in which the value corresponding to one reference current value is changed to the value corresponding to the next reference current value. During this transition period, the chopper unit 14 outputs a voltage corresponding to the DC voltage input to the full bridge circuit to the output terminals 16a and 16b.

In the period other than the transition period of the output current signal Iout, the chopper unit 14 causes the full bridge circuit to recirculate to bypass the output terminals 16a and 16b, and outputs 0V between the output terminals 16a and 16b. The chopper unit 14 may output a sufficiently low voltage, not limited to 0V, in a period other than the transition period of the output current signal Iout. A sufficiently low voltage is, for example, a voltage value lower than the voltage output by the chopper unit 24 during this period.

The control device 30 generates a gate signal that appropriately drives the switching element of the chopper unit 24, and controls the value of the output current output by the chopper unit 24 so as to follow the reference current signal Iref.

AC voltage isolated by transformers 11 and 21 is supplied to the rectifiers 12 and 22, and is converted into rectified and smoothed DC voltage by the rectifiers 12 and 22 and the filters 13 and 23, respectively. That is, electrically isolated DC voltages are input to the chopper units 14 and 24, respectively, and are connected in series on the output side to supply electric power to the electromagnet 4. As for the turns ratio of the transformers 11 and 21, the number of turns of the transformer 11 is sufficiently larger than the turn number ratio of the transformer 21. That is, the input voltage of the chopper unit 14 is sufficiently higher than the input voltage of the chopper unit 24, and the chopper unit 14 can output a voltage sufficiently higher than that of the chopper unit 24.

FIG. 2 is a block diagram illustrating a part of the power supply device of the embodiment.
As shown in FIG. 2, the control device 30 includes a PI controller 32, a limiter 33, and a stop signal generation circuit 38. The components of FIG. 2 are used to control the chopper unit 24. Since the specific elements for controlling the chopper unit 14 are not directly related to the configuration and operation of the present embodiment, detailed description thereof will be omitted.

The adder / subtractor 31 inputs the reference current signal Iref and the output current signal Iout to supply the current deviation to the PI controller 32. The PI controller (control amount generation means) 32 proportionally integrates the input current deviation and outputs it as a control amount.

The limiter (control amount limiting means) 33 limits the size of the controlled amount to the upper limit value UL or the lower limit value LL when the magnitude of the input controlled amount exceeds the upper limit value UL or the lower limit value LL. The upper limit value UL and the lower limit value LL are set in advance.

The stop signal generation circuit (stop signal generation means) 38 inputs the reference current signal Iref and the output current signal Iout to generate the stop signal RST. The output of the stop signal generation circuit 38 is connected to, for example, the reset input of the PI controller 32. The stop signal generation circuit 38 supplies the stop signal RST to the PI controller 32.

The stop signal generation circuit 38 includes, for example, a comparator, and compares the magnitude of the reference current signal Iref with the magnitude of the output current signal Iout. The stop signal generation circuit 38 outputs an H-level stop signal RST when the magnitude of the reference current signal Iref is equal to or greater than the magnitude of the output current signal Iout. The stop signal generation circuit 38 outputs an L-level stop signal RST when the magnitude of the reference current signal Iref is smaller than the magnitude of the output current signal Iout.

In the example of the embodiment, since the current flowing through the electromagnet is in both positive and negative directions, the stop signal generation circuit 38 compares the magnitude of the absolute value of the reference current signal Iref with the magnitude of the absolute value of the output current signal Iout. , Generate a stop signal RST.

When the stop signal RST of the L level is input from the stop signal generation circuit 38, the PI controller 32 executes PI control of the current deviation and outputs a control amount according to the current deviation. When the H level stop signal RST is input from the stop signal generation circuit 38, the PI controller 32 stops the execution of PI control and outputs 0 regardless of the input current deviation.

The control amount output from the limiter 33 is input to the comparator 35 via the adder 34. The control amount is compared with the carrier signal generated by the carrier signal generation circuit 36 in the comparator 35. The carrier signal is, for example, a triangular wave. The comparator 35 generates and outputs a gate signal Vg, which is a PWM signal, based on the control amount and the comparison result of the carrier signal. Although not shown, the generated gate signal is converted into a gate drive signal that appropriately drives each of the four switching elements of the chopper unit 24 via a gate drive circuit or the like, and is supplied to the chopper unit 24.

An output of a coefficient device 37 having a preset gain is connected to the adder 34. A reference current signal Iref is input to the coefficient device 37. The coefficient device 37 adds a voltage feedforward to the control amount output from the PI controller 32 by the adder 34 so that the current value supplied to the electromagnet 4 reaches the target value at an early stage.

The best result can be obtained when the magnitude of the output of the PI controller 32 when the stop signal RST is input is 0, but the output is not limited to 0 and may be a sufficiently small value. For example, the value is sufficiently smaller than the upper and lower limit values of the limiter 33.

Further, the stop signal RST may be generated during the period in which the reference current signal Iref transitions from the value in one period to the value in the next period, regardless of the magnitude relationship between the reference current signal Iref and the output current signal Iout. It may be generated. For example, it may be set in advance based on the rate of change of the output current flowing through the electromagnet 4.

The operation of the power supply device 10 of the embodiment will be described.
First, the entire operation including the chopper units 14 and 24 of the power supply device 10 will be described.
FIG. 3A is an example of an operation waveform showing the operation of the power supply device of the embodiment. FIG. 3B is an enlarged view of part A in FIG. 3A.
In FIGS. 3A and 3B, the horizontal axis is time t, the vertical axis is the reference current signal Iref and the output current signal Iout, and the time changes of the reference current signal Iref and the output current signal Iout are the same graph. Shown inside. In the figure, the solid line represents the output current signal Iout, and the alternate long and short dash line represents the reference current signal Iref.

As shown in FIG. 3A, the reference current signal Iref transitions between different target current values depending on the scanning condition of the charged particle beam. In the figure, almost constant current values are the respective target current values. For each target current value, a period during which the value becomes constant is set in the host control system or the like. The output current signal Iout transitions according to the reference current signal Iref or to follow the reference current signal Iref.

As shown in FIG. 3B, in the period T1, the reference current signal transitions from the current reference current value to the next reference current value, and the output current signal Iout rises according to the reference current signal Iref. The rate of change of the current of the output current signal Iout is suppressed by the inductance of the electromagnet 4. The product of the rate of change of the output current flowing through the electromagnet 4 and the inductance is the voltage applied to both ends of the electromagnet 4. Therefore, by sufficiently increasing the voltage value output by the power supply device 10, the period T1 which is the transition period between the target current values of the output current signal Iout can be shortened.

The chopper unit 14 outputs a high voltage during the period T1 and causes the full bridge circuit to recirculate to bypass the output during the other period.

Over the period T2, that is, the entire period, the chopper unit 24 outputs the PWM-controlled output current signal Iout so as to follow the reference current signal Iref.

In the power supply device 10, the outputs of the chopper unit 14 capable of outputting a high voltage and the chopper unit 24 that outputs a voltage lower than that of the chopper unit 14 are connected in series. Therefore, a sufficiently high voltage can be applied to the electromagnet 4 during the period T1.

FIG. 4 is an example of the operation waveform of each part of the power supply device of the embodiment.
The uppermost figure of FIG. 4 shows the time change of the reference current signal Iref and the output current signal Iout on the same graph. The reference current signal Iref is shown by a long-dashed line, and the output current signal Iout is shown by a solid line.
The second figure from the top of FIG. 4 shows the time change of the current deviation input to the PI controller 32.
The third figure from the top of FIG. 4 shows the time change of the control amount output from the limiter 33.
The lowermost figure of FIG. 4 shows the time change of the stop signal RST output by the stop signal generation circuit 38.
The four figures of FIG. 4 are drawn with a common time axis.

As shown in FIG. 4, the reference current signal Iref is the reference current level of the previous period until the time t1, and transitions to the new reference current level at the time t1. In this example, the reference current level after the time t1 is set to a larger value than the reference current level in the period before the time t1.

At time t1, the output current signal Iout begins to rise in response to the reference current signal Iref. However, since the output current of the power supply device 10 flows through the inductance of the electromagnet 4, the output current signal Iout rises following the reference current signal Iref even if the reference current signal Iref transitions in a stepped manner. Can't. The rate of change di / dt of the output current is determined by the inductance value L of the electromagnet 4 and the voltage V applied to both ends of the electromagnet 4 (V / L).

The stop signal generation circuit 38 compares the reference current signal Iref with the output current signal Iout, and detects Iref ≧ Iout at time t1, so that the H level stop signal RST is output.

The current deviation is the difference between the reference current signal Iref and the output current signal Iout, and is the maximum at time t1. However, at time t1, since the H level stop signal RST is input, the PI controller 32 outputs almost 0 regardless of the value of the current deviation.

Since the state of Iref ≧ Iout is continued until the time t2, the PI controller 32 outputs almost 0 regardless of the magnitude of the current deviation.

At time t2, the magnitude of the output current signal Iout becomes larger than that of the reference current signal Iref. The stop signal generation circuit 38 outputs an L-level stop signal RST. Therefore, the PI controller 32 executes a normal operation and outputs a signal corresponding to the current deviation.

At time t2 to time t3, some ringing occurs in the output current signal Iout, but it is suppressed to a sufficiently small level.

The effect of the power supply device 10 of the embodiment will be described while comparing with the operation of the power supply device of the comparative example.
FIG. 5 is a block diagram illustrating a part of the power supply device of the comparative example.
As shown in FIG. 5, the control device 130 of the power supply device of the comparative example is different from the case of the embodiment in that the stop signal generation circuit 38 is not included. In other respects, the control device 130 is the same as in the embodiment.

FIG. 6 is an example of the operation waveform of the power supply device of the comparative example.
The uppermost figure of FIG. 6 shows the time change of the reference current signal Iref and the output current signal Iout on the same graph. The reference current signal Iref is shown by a long-dashed line, and the output current signal Iout is shown by a solid line.
The second figure of FIG. 6 shows the time change of the current deviation input to the PI controller 32.
The lowermost figure of FIG. 6 shows the time change of the control amount output by the limiter 33.
The three figures of FIG. 6 are drawn with a common time axis.

As shown in FIG. 6, by time t11, the reference current signal Iref is the reference current level of the previous period, and at time t11, the reference current signal transitions to the new reference current level. In this example, as in the case of the embodiment, the reference current level after the time t11 is set to a larger value than the reference current level in the period before the time t11.

At time t11, the output current signal Iout begins to rise in response to the reference current signal Iref. The output current signal Iout increases at the rate of change (di / dt = V / L) of the output current determined by the inductance of the electromagnet 4 and the voltage applied across the electromagnet 4. Since this rate of change is smaller than the rate of change of the reference current signal Iref, the magnitude of the current deviation becomes the largest at time t11.

The magnitude of the current deviation gradually decreases as the output current signal Iout rises after time t11. The magnitude of the current deviation becomes 0 at time t12 when the magnitude of the output current signal Iout becomes equal to the magnitude of the reference current signal Iref.

Within the period from time t11 to time t12, the PI controller 32 outputs a signal according to the magnitude of the current deviation. The broken line in the figure is the control amount output by the PI controller 32, and this signal is input to the limiter 33. The limiter 33 limits the signal exceeding the upper limit value UL to the upper limit value UL. The limiter 33 outputs a control amount limited to the upper limit value UL or less.

From time t12 to time t13, the energy corresponding to the upper limit value UL becomes surplus, so that large ringing occurs according to the surplus energy.

As described above, in the power supply device of the comparative example, the change rate di / dt of the output current is smaller than the change rate of the reference current signal Iref, so that a large current deviation is input to the PI controller 32. Since the PI controller 32 outputs a signal having a magnitude corresponding to the input current deviation, it is suppressed by the limiter 33 at the upper limit value UL.

Although the control amount is limited by the limiter 33, a finite value is output. Since the finite value does not need to be output as a control amount, the control amount causes ringing until the excess energy is released. If the period during which ringing occurs becomes long, it takes time to reach the target value, and it becomes difficult to appropriately set the irradiation period of the charged particle beam.

In addition, ringing of the controlled amount may cause unstable operation when performing PWM control. For example, the gate signal generated by the control device 130 has a narrow pulse width or a wide pulse width unlike the original pulse width, so that the chopper unit 24 may perform unstable operations such as hunting operation. There is.

In the power supply device 10 of the embodiment, the control device 30 has a stop signal generation circuit 38. In the stop signal generation circuit 38, when the magnitude of the reference current signal Iref is equal to or greater than the magnitude of the output current signal Iout, the PI controller 32 outputs almost 0. Therefore, since the surplus energy is hardly accumulated in the period when the magnitude of the reference current signal Iref is equal to or larger than the magnitude of the output current signal Iout, the occurrence of ringing due to the surplus energy is suppressed at the timing when the PI control is started. Can be done. Therefore, the subsequent PWM control can be stably continued.

In order to use the charged particle beam irradiation device for medical purposes and the like, it is required to scan the charged particle beam at high speed in order to minimize the treatment time. In addition, since it is necessary to irradiate the affected area with pinpoint, it is necessary to accurately set the scanning range and the irradiation position.

Therefore, in order to improve the scanning speed, it is necessary to apply a high voltage to the electromagnet 4 to increase the rate of change di / dt of the current flowing through the electromagnet 4. Then, in order to realize an accurate irradiation position, it is required to control the output current flowing through the electromagnet 4 with high accuracy.

In the power supply device 10 of the embodiment, during the period when a high voltage is applied to the electromagnet 4 by the chopper unit 14, the PWM control operation by the chopper unit 24 is avoided, ringing of the control amount due to unnecessary control is reduced, and high accuracy is achieved. It is possible to achieve both a high output current setting and a high-speed target value transition.

According to the embodiment described above, it is possible to realize a power supply device capable of stably controlling the output current even if the set current value changes at high speed.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention and its equivalents described in the claims. In addition, each of the above-described embodiments can be implemented in combination with each other.

1 power supply, 4 electric magnets, 10 power supplies, 11,21 transformers, 12, 22 rectifiers, 13, 23 filters, 14, 24 chopper units, 28 current detectors, 30 controllers, 31 adders / subtractors, 32 PI controllers, 33 limiter, 34 adder, 35 comparator, 36 carrier signal generation circuit, 37 coefficient device, 38 stop signal generation circuit

Claims (4)

A power supply device that supplies an output current to an electromagnet according to a reference current signal that transitions between a first signal value and a second signal value different from the first signal value.
The first voltage is output in the first period, which is the transition period from the first output current value corresponding to the first signal value to the second output current value corresponding to the second signal value, and other than the first period. In the period, a first power converter that outputs a second voltage having a voltage lower than the first voltage, and
A second power converter having an output connected in series with the output of the first power converter.
A control device that controls the output current output by the second power converter, and
Equipped with
The control device is
A control amount generation means that generates and outputs a control amount according to the deviation between the reference current signal and the output current signal representing the output current.
A control amount limiting means that limits the output of the control amount generation means within a preset limit value, and a control amount limiting means.
Including
The control amount generation means is a power supply device that outputs a control amount smaller than the limit value of the control amount limiting means during the first period. The power supply device according to claim 1, wherein the control amount generating means outputs 0 in the first period. The power supply device according to claim 1 or 2, wherein the control device detects the first period based on the magnitude of the reference current signal and the magnitude of the output current signal. The power supply device according to claim 3, wherein the control device includes a stop signal generating means for detecting the first period by comparing the magnitude of the reference current signal with the magnitude of the output current signal.

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