Power supply device for inductive loads

Abstract

To provide a power supply device for an inductive load capable of stabilizing a raised pulse-like current in a short time.SOLUTION: A power supply device 10A for an inductive load includes a control unit 40A for controlling a second current source 30 based on a preset target current value Iref1 and a load current value Iload that is a current value of a pulse-like current. A PWM control unit 45 of the control unit 40A is configured to: (1) in a phase with a pulse-like current being raised, generate a PWM control signal Vpwm related to a duty of a driving signal based on a deviation between the load current value Iload and a load current value obtained by adjusting the load current value Iload in accordance with a predetermined rule; and (2) in a phase with the pulse-like current being maintained, generate the PWM control signal Vpwm based on a deviation between the target current value Iref1 and the load current value Iload.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power supply device for an inductive load that applies a pulsed large current that rises steeply to an inductive load such as an electromagnet.

Background Art

[0002] Accelerators used in fields such as physical and chemical experiments and medicine are equipped with a power supply device for an inductive load for applying a pulsed large current to an electromagnet, which is an inductive load. As a conventional power supply device for an inductive load, for example, as described in Patent Document 1, there is known one including a first current source that raises a pulsed current to the top and a second current source that maintains the raised pulsed current at the top.

[0003] This conventional power supply device for an inductive load supplies only the first discharge current of a first capacitor charged in advance to the inductive load in order to maintain the pulsed current at the top with high accuracy, and the second current source is configured so that the second discharge current of a second capacitor charged in advance can be supplied to the electromagnet together with the first discharge current.

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above-described conventional power supply device for an inductive load could not prevent overshoot and undershoot that occur in the pulsed current immediately after rising. In other words, in the above-described conventional power supply device for an inductive load, it took a long time for the raised pulsed current to stabilize.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power supply device for an inductive load capable of stabilizing a rising pulsed current in a short time.

Means for Solving the Problems

[0007] In order to solve the above problems, a power supply device for an inductive load according to the present invention applies a pulsed current to the inductive load, and includes a first current source that raises the pulsed current to the top, a second current source that maintains the raised pulsed current at the top, and a control unit that controls at least the second current source based on a preset target current value and a load current value that is the current value of the pulsed current. The control unit includes a drive signal generation unit that generates a drive signal for turning on / off a switching element that constitutes the second current source, and a PWM control unit that gives a PWM control signal regarding the duty of the drive signal to the drive signal generation unit. The PWM control unit generates a PWM control signal based on (1) a deviation between the load current value and a value obtained by adjusting the load current value according to a predetermined rule in a phase where the pulsed current is rising, and (2) a deviation between the target current value and the load current value in a phase where the pulsed current is maintained. The drive signal generation unit has a configuration in which (1) in a phase where the pulsed current is rising, a drive signal is generated without depending on the PWM control signal, and (2) in a phase where the pulsed current is maintained, a drive signal is generated based on the PWM control signal.

[0008] In this configuration, in the phase when the pulsed current is rising, the PWM control unit outputs a PWM control signal generated based on a minute deviation between the load current value and the value obtained by adjusting the load current value according to a predetermined rule, while the drive signal generation unit generates a drive signal without relying on this. Also, in this configuration, in the phase when the pulsed current is maintained, the PWM control unit outputs a PWM control signal generated based on the deviation between the target current value and the load current value, and the drive signal generation unit generates a drive signal based on this. That is, in this configuration, when switching from the phase where the pulsed current is rising to the phase where the pulsed current is maintained, a PWM control signal based on a minute deviation is always input to the drive signal generation unit. Therefore, according to this configuration, when the phase is switched, an inappropriate duty drive signal affected by the previous PWM control signal is not generated, and the rising pulsed current can be stabilized earlier.

[0009] It is preferable that the power supply device for inductive load performs adjustment by multiplying the load current value by a coefficient of 1.00 or more and 1.01 or less determined in advance.

[0010] The power supply device for inductive load can be used, for example, as a device that applies a pulsed current to an electromagnet as an inductive load.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a power supply device for inductive load that can stabilize a rising pulsed current in a short time.

Brief Description of the Drawings

[0012]

Figure 1

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Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the inductive load power supply device according to the present invention will be described with reference to the accompanying drawings.

[0014] [Embodiment] FIG. 1 shows an inductive load power supply device 10A according to an embodiment of the present invention. The inductive load power supply device 10A is for applying a load current I, which is a pulsed large current, to an inductive load (an electromagnet in this embodiment) 50. As shown in the figure, it includes a first current source 20, a second current source 30, and a control unit 40A for controlling them.

[0015] The first current source 20 includes a first capacitor C1 charged with a DC voltage of several thousand volts, four switching elements SW1, SW2, SW3, SW4 connected in an H-bridge, and diodes D1, D2, D3, D4 connected in anti-parallel to each of the switching elements SW1, SW2, SW3, SW4.

[0016] The switching elements SW1, SW2, SW3, and SW4 form a bridge circuit section. The connection point of the switching elements SW1 and SW2 is the first output terminal, and the connection point of the switching elements SW3 and SW4 is the second output terminal. The first capacitor C1 is connected in parallel to the bridge circuit section.

[0017] The switching elements SW1, SW2, SW3, and SW4 are made of IGBT (Insulated Gate Bipolar Transistor), which is a type of power semiconductor device. The gates, which are the control terminals of the switching elements SW1, SW2, SW3, and SW4, are connected to a control unit 40A (a first drive signal generation unit 42 described later). Note that the diodes D1, D2, D3, and D4 may be built-in to the switching elements SW1, SW2, SW3, and SW4 or may be externally attached.

[0018] The second current source 30 includes a second capacitor C2 charged with a DC voltage of several hundred volts, four switching elements SW5, SW6, SW7, and SW8 connected in an H-bridge configuration, and diodes D5, D6, D7, and D8 connected in anti-parallel to the respective switching elements SW5, SW6, SW7, and SW8.

[0019] The switching elements SW5, SW6, SW7, and SW8 form a bridge circuit section. The connection point of the switching elements SW5 and SW6 is the third output terminal, and the connection point of the switching elements SW7 and SW8 is the fourth output terminal. The second capacitor C2 is connected in parallel to the bridge circuit section.

[0020] The switching elements SW5, SW6, SW7, and SW8 are made of IGBT, similar to the switching elements SW1, SW2, SW3, and SW4. The gates, which are the control terminals of the switching elements SW5, SW6, SW7, and SW8, are connected to a control unit 40A (a second drive signal generation unit 43 described later). Note that the diodes D5, D6, D7, and D8 may be built-in to the switching elements SW5, SW6, SW7, and SW8 or may be externally attached.

[0021] The first output terminal of the first current source 20 is connected to the fourth output terminal of the second current source 30 via an inductive load 50. Also, the second output terminal of the first current source 20 is directly connected to the third output terminal of the second current source 30.

[0022] The control unit 40A controls the first current source 20 and the second current source 30 based on a preset target current value Iref1 and a load current value Iload which is the current value of the load current I. As shown in FIG. 1, the control unit 40A includes a storage unit 41, a first drive signal generation unit 42, a second drive signal generation unit 43, a phase control unit 44, a PWM control unit 45, an adjustment unit 46, a signal switching unit 47, and a deviation signal output unit 48.

[0023] The storage unit 41 is composed of a non-volatile or volatile memory that stores the target current value Iref1 set by the user.

[0024] The first drive signal generation unit 42 generates drive signals (gate signals) for turning on / off the switching elements SW1, SW2, SW3, SW4 that constitute the first current source 20 based on a phase control signal Vphase described later.

[0025] The second drive signal generation unit 43 generates drive signals (gate signals) for turning on / off the switching elements SW5, SW6, SW7, SW8 that constitute the second current source 30 based on the phase control signal Vphase described later and a PWM control signal Vpwm described later.

[0026] The phase control unit 44 generates a phase control signal Vphase to be supplied to the first drive signal generation unit 42 and the second drive signal generation unit 43 based on the target current value Iref1, the load current value Iload, and an output start command (not shown) from the user, which are stored in the storage unit 41. Specifically, the phase control unit 44 generates: (1) a phase control signal Vphase indicating phase 1 until it receives the output start command; (2) a phase control signal Vphase indicating phase 2 from when it receives the output start command until the load current value Iload matches the target current value Iref1; (3) a phase control signal Vphase indicating phase 3 from when phase 2 ends until a predetermined time has elapsed; and (4) a phase control signal Vphase indicating phase 4 from when phase 3 ends until the load current value Iload becomes zero.

[0027] The PWM control unit 45 generates a PWM control signal Vpwm regarding the duty of the drive signal output from the second drive signal generation unit 43 based on a deviation signal described later.

[0028] When organizing the states of the switching elements SW1, SW2, SW3, SW4, SW5, SW6, SW7, and SW8 in each phase, it becomes as shown in the following table.

Table 1

[0029] In phase 1, the first drive signal generation unit 42 generates a drive signal to turn off the switching elements SW1, SW2, SW3, and SW4, and the second drive signal generation unit 43 generates a drive signal to turn off the switching elements SW5, SW6, SW7, and SW8. In this phase, no load current I flows through the inductive load 50.

[0030] In Phase 2, the first drive signal generation unit 42 generates drive signals to turn on the switching elements SW1 and SW4 and turn off the switching elements SW2 and SW3, and the second drive signal generation unit 43 generates drive signals to turn on the switching element SW8 and turn off the switching elements SW5, SW6, and SW7. In this phase, the first capacitor C1 discharges through the path of "first capacitor C1 → switching element SW1 → inductive load 50 → switching element SW8 → diode D6 → switching element SW4 → first capacitor C1", and the load current I flows.

[0031] In Phase 3, the first drive signal generation unit 42 generates drive signals to turn on the switching element SW4 and turn off the switching elements SW1, SW2, and SW3, and the second drive signal generation unit 43 generates drive signals to turn on the switching element SW5, turn off the switching elements SW6 and SW7, and turn on / off the switching element SW8 with an on-duty corresponding to the PWM control signal Vpwm. In this phase, when the switching element SW8 is on, the load current I flows through the path of "second capacitor C2 → switching element SW5 → switching element SW4 → diode D2 → inductive load 50 → switching element SW8 → second capacitor C2". Also, in this phase, when the switching element SW8 is off, the load current I refluxes through the path of "inductive load 50 → diode D7 → switching element SW5 → switching element SW4 → diode D2 → inductive load 50".

[0032] In Phase 4, the first drive signal generation unit 42 generates drive signals to turn off the switching elements SW1, SW2, SW3, and SW4, and the second drive signal generation unit 43 generates drive signals to turn off the switching elements SW5, SW6, SW7, and SW8. In this phase, the energy stored in the inductive load 50 is regenerated to the first capacitor C1 and the second capacitor C2 through the path of "inductive load 50 → diode D7 → second capacitor C2 → diode D6 → diode D3 → first capacitor C1 → diode D2 → inductive load 50". At this time, the load current I gradually decreases.

[0033] The adjustment unit 46 adjusts the load current value Iload and outputs the adjusted current value to the signal switching unit 47. In this embodiment, the adjustment is performed by multiplying Iload by a coefficient α that is predetermined to be 1.00 or more and 1.01 or less. Therefore, in this embodiment, the target current value Iref1 and the adjusted load current value α×Iload are input to the signal switching unit 47.

[0034] The signal switching unit 47 switches the value to be output as Iref2 based on the phase control signal Vphase generated by the phase control unit 44. Specifically, when the phase control signal Vphase indicates phase 2, the signal switching unit 47 outputs the adjusted load current value α×Iload as Iref2, and in other cases (that is, when the phase control signal Vphase indicates phases 1, 3, or 4), the signal switching unit 47 outputs the target current value Iref1 as Iref2.

[0035] The deviation signal output unit 48 outputs a deviation signal corresponding to the deviation between the load current value Iload and Iref2 to the PWM control unit 45. Specifically, in phase 2, the deviation signal output unit 48 outputs a deviation signal corresponding to the deviation "α×Iload - Iload", and in other phases, the deviation signal output unit 48 outputs a deviation signal corresponding to the deviation "Iref1 - Iload".

[0036] Therefore, during phase 2 when the pulsed current rises, a deviation signal corresponding to a minute deviation of 0 or more and 0.01×Iload or less is input to the PWM control unit 45. And the PWM control unit 45 to which such a deviation signal is input outputs a PWM control signal Vpwm such that the duty of the drive signal output by the second drive signal generation unit 43 does not become extremely large or small.

[0037] Also, during Phase 3 in which the pulsed current is maintained at the top, a deviation signal corresponding to the deviation “Iref1 - Iload” is input to the PWM control unit 45. Then, the PWM control unit 45 to which such a deviation signal is input outputs a PWM control signal Vpwm that causes the load current value Iload to match the target current value Iref1. More specifically, if the load current value Iload is greater than the target current value Iref1, the PWM control unit 45 reduces the duty of the drive signal output by the second drive signal generation unit 43, that is, the on-duty of the switching element SW8, by lowering the voltage value of the PWM control signal Vpwm. Conversely, if the load current value Iload is less than the target current value Iref1, the PWM control unit 45 increases the duty of the drive signal output by the second drive signal generation unit 43, that is, the on-duty of the switching element SW8, by raising the voltage value of the PWM control signal Vpwm.

[0038] Here, as understood from Table 1, the second drive signal generation unit 43 does not require the PWM control signal Vpwm in Phases 1, 2, and 4. In other words, the second drive signal generation unit 43 generates a drive signal without relying on the PWM control signal Vpwm in Phases 1, 2, and 4. Providing the signal switching unit 47 so that a PWM control signal Vpwm corresponding to a minute deviation is input to the second drive signal generation unit 43 during Phase 2 helps prevent an inappropriate duty drive signal affected by the immediately preceding PWM control signal Vpwm from being output from the second drive signal generation unit 43 to the switching elements SW5, SW6, SW7, SW8 (particularly, the switching element SW8) when switching from Phase 2 to Phase 3, which would cause a large overshoot in the load current I.

[0039] Figures 2 to 5 show the results of a simulation in which the power supply device 10A for an inductive load was operated with the target current value Iref1 set to 2.1 kA. Figure 2 shows the simulation results when the coefficient α used in the adjustment unit 46 is 1.0000, Figure 3 shows the simulation results when the coefficient α is 1.0010, Figure 4 shows the simulation results when the coefficient α is 1.0022, and Figure 5 shows the simulation results when the coefficient α is 1.0030. (A) in each figure is a waveform diagram of the voltage at the first output terminal of the first current source 20 with respect to the fourth output terminal of the second current source 30 (i.e., the voltage generated in the inductive load 50), (B) is a waveform diagram of Iref2 output by the signal switching unit 47, (C) is a waveform diagram of the PWM control signal Vpwm output by the PWM control unit 45, (D) is a waveform diagram of the load current I (Iload), and (E) is an enlarged waveform diagram of I (Iload) and Iref2. Also, the horizontal axis in each figure is the time (unit: s) based on the simulation start time. In this simulation, it is assumed that a switch from phase 1 to phase 2 occurs due to an output start command being issued at time 0.20 s, and a switch from phase 2 to phase 3 occurs when the load current value Iload matches the target current value Iref1 at approximately time 0.22 s.

[0040] Figures 2 to 5 show that when the coefficient α is changed, the voltage value of the PWM control signal Vpwm immediately before phase 3 changes (see (C) in each figure), indicating a difference in the rising manner of the load current I (Iload) (see (E) in each figure).

[0041] Specifically, in FIG. 2 where the coefficient α is set to 1.0000, the load current I (Iload) rises with a delay from Iref2 and stabilizes at 2.1 kA, which is the target current value Iref1, at around time 0.26 s. Also in FIG. 3 where the coefficient α is 1.0010, the load current I (Iload) rises with a delay from Iref2 and stabilizes at 2.1 kA at around time 0.25 s. In FIG. 4 where the coefficient α is 1.0022, the load current I (Iload) rises almost without delay from Iref2 and stabilizes at 2.1 kA at around time 0.225 s. Further, in FIG. 5 where the coefficient α is 1.0030, the load current I (Iload) rises so as to exceed Iref2 and stabilizes at 2.1 kA at around time 0.25 s.

[0042] For comparison, a similar simulation was also performed on the inductive load power supply device 10C equipped with the control unit 40C instead of the control unit 40A. As shown in FIG. 6, the control unit 40C is different from the control unit 40A in that the deviation signal output unit 48 always outputs a deviation signal corresponding to the deviation between the load current value Iload and the target current value Iref1.

[0043] FIG. 7 shows the results of a simulation in which the inductive load power supply device 10C was operated with the target current value Iref1 set to 2.1 kA. (A) in the figure is a waveform diagram of the voltage generated in the inductive load 50, (B) is a waveform diagram of Iref1 input to the deviation signal output unit 48, (C) is a waveform diagram of the PWM control signal Vpwm output by the PWM control unit 45, (D) is a waveform diagram of the load current I (Iload), and (E) is an enlarged waveform diagram of I (Iload) and Iref1. Also, the horizontal axis in the figure is the time (unit: s) based on the simulation start time. In this simulation as well, it is assumed that the switching from phase 1 to phase 2 occurs due to the output start command being issued at time 0.20 s, and the switching from phase 2 to phase 3 occurs when the load current value Iload matches the target current value Iref1 at around time 0.22 s.

[0044] Figure 7 shows that when the voltage value of the PWM control signal Vpwm is much larger than the voltage value (about 2.5V) of the PWM control signal Vpwm suitable for maintaining the load current value Iload at the target current value Iref1 (2.1 kA), a switching from phase 2 to phase 3 occurred, resulting in a large overshoot in the load current I (Iload) immediately after the switching, and the load current I (Iload) did not stabilize until around time 0.27 s.

[0045] Figure 8 is a superposition of the waveform of the load current I (Iload) of the power supply device 10A for inductive loads according to the embodiment (coefficient α = 1.0000 to 1.0030) and the waveform of the load current I (Iload) of the power supply device 10C for inductive loads according to the comparative example. The figure shows that according to the power supply device 10A for inductive loads according to the embodiment (particularly, the power supply device 10A with the coefficient α set to 1.0022), the rising load current I (Iload) can be stabilized in a relatively short time.

[0046] As described above, the embodiments of the power supply device for inductive loads according to the present invention have been described, but the configuration of the present invention is not limited thereto.

[0047] [Modification Example] For example, the coefficient α used in the adjustment unit 46 can be changed within a range of 1.00 or more and 1.01 or less. Even when the coefficient α is about 1.01, the rising load current I (Iload) can be stabilized in a shorter time than in the comparative example. It should be noted that the optimal value of the coefficient α (1.0022 in the embodiment) is considered to change according to the inductance of the inductive load 50 and the target current value Iref1.

[0048] The adjustment unit 46 may adjust the load current value Iload by adding a predetermined value greater than 0.

[0049] The first current source 20 may omit the switching elements SW2 and SW3 that do not turn on through phases 1 to 4. Similarly, the second current source 30 may omit the switching elements SW6 and SW7 that do not turn on through phases 1 to 4.

[0050] Also, the power supply device for an inductive load according to the present invention may include a plurality of first current sources 20 in order to more steeply raise a pulsed current, like the power supply device 10B for an inductive load shown in FIG. 9.

Explanation of Reference Numerals

[0051] 10A, 10B Power supply device for inductive load 20 First current source 30 Second current source 40A Control unit 41 Storage unit 42 First drive signal generation unit 43 Second drive signal generation unit 44 Phase control unit 45 PWM control unit 46 Adjustment unit 47 Signal switching unit 48 Deviation signal output unit 50 Inductive load

Claims

1. A power supply device for an inductive load that applies a pulsed current to an inductive load, a first current source that raises the pulsed current to its peak, a second current source that maintains the raised pulsed current at the peak, a control unit that controls at least the second current source based on a preset target current value and a load current value that is the current value of the pulsed current, comprising: the control unit includes a drive signal generation unit that generates a drive signal for turning on / off a switching element that constitutes the second current source, and a PWM control unit that supplies a PWM control signal regarding the duty of the drive signal to the drive signal generation unit, the PWM control unit: (1) generates the PWM control signal based on a deviation between the load current value and a value obtained by adjusting the load current value according to a preset rule during a phase in which the pulsed current is being raised; (2) generates the PWM control signal based on a deviation between the target current value and the load current value during a phase in which the pulsed current is being maintained, the drive signal generation unit: (1) generates the drive signal without relying on the PWM control signal during a phase in which the pulsed current is being raised; (2) generates the drive signal based on the PWM control signal during a phase in which the pulsed current is being maintained A power supply device for an inductive load, characterized by the above.

2. The adjustment is to multiply the load current value by a preset coefficient of 1.00 or more and 1.01 or less. The power supply device for an inductive load according to claim 1, characterized by the above.

3. Applying the pulsed current to an electromagnet as the inductive load. The power supply device for an inductive load according to claim 1 or claim 2, characterized by the above.

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