Switching power supply and power supply system

Abstract

To provide a switching power supply device that can prevent the device from becoming complicated in control and increasing in size.SOLUTION: A switching power supply device comprises: a switching unit 22 that includes at least one switching element; and a control unit 40B that controls the switching element to control an output current that is output from the switching unit 22. The control unit 40B performs a forcing control which performs raising or falling of an output current by turning on the switching element and turns off the switching element when the output current has increased to reach a first off-threshold value, and a re-on control which turns on the switching element again when the output current has reduced after the forcing control to reach an on-threshold value, and turns off the switching element again when the output current has increased to reach a second off-threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a switching power supply and a power supply system. [Background technology]

[0002] As a power supply system, an electromagnet power supply system that supplies excitation current to an electromagnet is known (see, for example, Patent Document 1). Conventional electromagnet power supply systems include a switching power supply device that comprises an IGBT unit composed of multiple IGBTs (insulated gate bipolar transistors), an FET unit composed of multiple FETs (field-effect transistors), and a control unit that controls each unit.

[0003] An IGBT unit includes multiple parallel-connected bridge circuits, each containing four bridge-connected IGBTs. Similarly, an FET unit includes multiple parallel-connected bridge circuits, each containing four bridge-connected FETs.

[0004] The control unit drives the IGBT unit and the FET unit when raising or lowering the output current to a predetermined target value, while stopping the IGBT unit and driving only the FET unit when maintaining the output current at the target value. By using the IGBT unit and the FET unit in this way, it is possible to supply an excitation current with a desired waveform (for example, a trapezoidal or stepped waveform) to the electromagnet.

[0005] However, the control unit controls the IGBT unit to quickly raise (or lower) the current and fine-tune the current for the FET unit. Therefore, it is necessary to use different control parameters for the IGBT unit and the FET unit (a control parameter suitable for IGBT on / off control and a control parameter suitable for FET on / off control). As a result, conventional switching power supplies have the problem of complex output current control. In addition, conventional switching power supplies have two units, the IGBT unit and the FET unit, which leads to an increase in the number of components and thus the size of the device. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-68469 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above circumstances, and its objective is to provide a switching power supply device and power supply system that can avoid increased control complexity and larger device size. [Means for solving the problem]

[0008] To solve the above problems, the switching power supply device according to the present invention is A switching section including at least one switching element, A control unit that controls the switching element and controls the output current output from the switching unit, A switching power supply device comprising, The control unit, Forcing control that turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, The invention is characterized by performing a re-on control, in which, after the forcing control, the switching element is turned on again when the output current decreases and reaches an on threshold, and the switching element is turned off again when the output current increases and reaches a second off threshold.

[0009] In this configuration, a single switching unit functions as both a circuit for raising (or lowering) the output current and a circuit for maintaining the output current. The output current can be controlled by forcing control and re-on control, which switch the switching element on and off. Therefore, this configuration avoids increased control complexity and larger device size.

[0010] The aforementioned switching power supply device is The switching section is further provided on the input side and includes a capacitor section containing at least one capacitor. The control unit, When the operation of the switching unit during the forcing control is a power operation in which current is supplied from the capacitor unit, the second off threshold is set to the same value as the first off threshold. When the switching unit operates during the forcing control in a regenerative operation that supplies current to the capacitor unit, the second off threshold can be configured to be set to a value closer to the on threshold than the first off threshold.

[0011] In the aforementioned switching power supply device, The control unit, A state determination unit that determines whether the output current is in a first state (rising in the positive region), a second state (falling in the positive region), a third state (falling in the negative region), or a fourth state (rising in the negative region), The system can be configured to include a threshold setting unit that sets the second off threshold to the same value as the first off threshold in the first and third states, sets the second off threshold to the same value as the second off threshold in the first state in the second state, and sets the second off threshold to the same value as the second off threshold in the third state in the fourth state.

[0012] In the switching power supply device, the switching unit includes a plurality of switching circuits connected in parallel, the switching circuit includes a plurality of the switching elements, the control unit can be configured to determine the number of the switching circuits to be simultaneously driven during the forcing control based on the change amount of the target value of the output current.

[0013] In the switching power supply device, the switching unit includes a plurality of switching circuits connected in parallel, the switching circuit includes a plurality of the switching elements, the control unit can be configured to make the number of the switching circuits to be simultaneously driven during the re-on control less than the number of the switching circuits to be simultaneously driven during the forcing control.

[0014] In order to solve the above problems, a power supply system according to the present invention includes an AC / DC conversion device having an AC input terminal and a DC output terminal, converting an AC voltage input to the AC input terminal into a DC voltage, and outputting the DC voltage from the DC output terminal, and the switching power supply device of the present invention connected to the DC output terminal of the AC / DC conversion device.

Effect of the Invention

[0015] According to the present invention, it is possible to provide a switching power supply device and a power supply system capable of avoiding complication of control and enlargement of the device.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram showing a power supply system according to an embodiment of the present invention. [Figure 2] It is a diagram showing an inverter unit of a switching power supply device according to an embodiment of the present invention. [Figure 3] This is a block diagram of the control unit of a switching power supply according to one embodiment of the present invention. [Figure 4] This diagram illustrates the output current states and the stop thresholds for each state in the present invention. [Figure 5] The diagram shows the relationship between the output current value and the drive waveform of each drive unit, where (A) is the case when each drive unit is driven simultaneously during re-on control, and (B) is the case when each drive unit is driven in a shift manner during re-on control. [Figure 6] The diagram shows the relationship between the output current value, deviation signal, stop threshold, and re-on threshold, where (A) is the case when a single stop threshold X is set in the second state, and (B) is the case when two different stop thresholds X are set in the second state. [Modes for carrying out the invention]

[0017] Hereinafter, embodiments of the switching power supply device and power supply system according to the present invention will be described with reference to the attached drawings.

[0018] [Power System] Figure 1 shows a power supply system 1 according to one embodiment of the present invention. The power supply system 1 comprises an AC / DC conversion unit 10, an inverter unit 20, a transformer unit 30, a control unit 40A that controls the AC / DC conversion unit 10, a control unit 40B that controls the inverter unit 20, and terminals T1 to T3.

[0019] Terminal T1 is connected to an AC power source (not shown). Terminals T2 and T3 are connected to electromagnet 2. Power supply system 1 is an electromagnet power supply system that generates an excitation current based on the AC voltage supplied from the AC power source and supplies the generated excitation current to electromagnet 2.

[0020] The AC / DC conversion unit 10 and the control unit 40A correspond to the "AC / DC conversion device" of the present invention. The AC / DC conversion unit 10 has an AC input terminal connected to terminal T1 and a DC output terminal connected to the inverter unit 20, and performs an AC / DC conversion operation under the control of the control unit 40A, converting the AC voltage input to the AC input terminal into a DC voltage.

[0021] The AC / DC conversion unit 10 includes, for example, a transformer that transforms the AC voltage input to the AC input terminal, a switching circuit and / or rectifier circuit that transforms the transformed AC voltage into a DC voltage, and a filter circuit that removes noise from the DC voltage output from the switching circuit and / or rectifier circuit.

[0022] The inverter unit 20 and the control unit 40B correspond to the "switching power supply device" of the present invention. The output current output from the inverter unit 20 passes through the transformer unit 30, which is composed of at least one transformer, and is supplied as an excitation current to the electromagnet 2 connected between terminals T2 and T3.

[0023] [Switching power supply] A switching power supply device according to one embodiment of the present invention comprises an inverter unit 20 and a control unit 40B, as described above. The inverter unit 20 comprises a capacitor unit 21, a switching unit 22, input terminals T11 and T12, and output terminals T21 and T22.

[0024] The capacitor section 21 consists of at least one capacitor and is connected between input terminals T11 and T12. The switching section 22 includes a plurality (three in this embodiment) of switching circuits 22-1, 22-2, and 22-3 connected in parallel, as shown in Figure 2.

[0025] The switching circuits 22-1, 22-2, and 22-3 perform a powering operation in which current is supplied from the capacitor section 21, a regenerative operation in which current is supplied to the capacitor section 21, and a recirculation operation in which current is recirculated without passing through the capacitor section 21.

[0026] Switching circuit 22-1 is a full-bridge circuit consisting of switching elements Q1 to Q4. Switching circuit 22-1 includes a first leg and a second leg connected in parallel. In the first leg, a pair of switching elements Q1 and Q2 connected in series form the upper and lower arms, and in the second leg, a pair of switching elements Q3 and Q4 connected in series form the upper and lower arms. Diodes D1 to D4 are connected in parallel to the current paths of switching elements Q1 to Q4. Switching circuits 22-2 and 22-3 have the same circuit configuration as switching circuit 22-1.

[0027] The same type of switching element is used as the switching elements Q1 to Q4 in switching circuits 22-1, 22-2, and 22-3, and in this embodiment, IGBTs (isolated gate bipolar transistors) are used. That is, the switching section 22 of this embodiment consists only of IGBT units and, unlike conventional switching power supplies, does not have FET units.

[0028] In this embodiment, the number of switching circuits is set to three, but it may be four or more. Furthermore, it is not limited to a full-bridge configuration; a half-bridge configuration with one row of legs is also acceptable, as is a configuration with three or more parallel legs. In addition, if the same type of switching element is used, a switching element other than an IGBT may be used.

[0029] The control unit 40B controls the output current output from the switching unit 22 by performing forcing control and re-on control to switch the switching elements Q1 to Q4 of the switching circuits 22-1, 22-2, and 22-3 on and off. Forcing control is a control that raises or lowers the output current. Re-on control is a control that maintains the output current after the rise or fall, and is performed after the forcing control.

[0030] During forcing control, the control unit 40B turns on some of the switching elements Q1 to Q4 to raise or lower the output current, and when the output current reaches a predetermined off threshold (corresponding to the "first off threshold" of the present invention), it turns off the switching elements Q1 to Q4.

[0031] During re-on control, when the output current decreases after forcing control and reaches a predetermined on threshold, the control unit 40B turns on some of the switching elements Q1 to Q4 again. When the output current increases as a result and reaches a predetermined off threshold (corresponding to the "second off threshold" of the present invention), the control unit 40B turns off the switching elements Q1 to Q4 again. By repeatedly turning on and off in this manner, the control unit 40B maintains the output current within a predetermined range including the target value (current setting value).

[0032] Figure 3 shows a block diagram of the control unit 40B. The control unit 40B consists of a digital circuit D and an analog circuit A, and includes a target value reading unit 41, a state determination unit 42, a deviation signal generation unit 43, a threshold setting unit 44, a comparison unit 45, a re-on determination unit 46, a processing unit 47, a first drive unit 48-1, a second drive unit 48-2, and a third drive unit 48-3. In this embodiment, the deviation signal generation unit 43 and the comparison unit 45 are composed of analog circuit A, and the other functional units are composed of digital circuit D.

[0033] The control unit 40B receives the target value Iref of the output current of the inverter unit 20, a strobe signal, and the current value (measured value) of the output current from an external source. The current value (measured value) of the output current is input, for example, from a current sensor installed between the inverter unit 20 and the transformer unit 30, or from a current sensor installed between the transformer unit 30 and terminals T2 and T3.

[0034] The target value reading unit 41 receives the target value Iref and a strobe signal as input. The target value reading unit 41 reads and stores the target value Iref at a timing corresponding to the strobe signal, and outputs the stored target value Iref to the state determination unit 42, the deviation signal generation unit 43, and the threshold setting unit 44.

[0035] The state determination unit 42 calculates the change amount △Iref of the target value Iref and performs a state determination regarding the state of the output current. For example, the state determination unit 42 calculates the change amount △Iref by subtracting the target value Iref read at the Nth position of the strobe signal from the target value Iref read at the (N+1)th position of the strobe signal. As shown in Figure 4, the state of the output current includes a rising edge in the positive region (first state), a falling edge in the positive region (second state), a falling edge in the negative region (third state), and a rising edge in the negative region (fourth state).

[0036] The state determination unit 42 determines, for example, that the system is in the first state when the target value Iref is positive and the change amount △Iref is positive; the system is in the second state when the target value Iref is positive and the change amount △Iref is negative; the system is in the third state when the target value Iref is negative and the change amount △Iref is negative; and the system is in the fourth state when the target value Iref is negative and the change amount △Iref is positive. If the change amount △Iref is zero, the state determination unit 42 determines that re-on control is in progress and maintains the previous determination result. The state determination unit 42 outputs the change amount △Iref and the determination result to the threshold setting unit 44 and the processing unit 47.

[0037] The deviation signal generation unit 43 calculates the difference between the target value Iref and the current value (measured value), and outputs a deviation signal related to this difference to the comparison unit 45 and the re-on determination unit 46.

[0038] The threshold setting unit 44 sets the stop threshold X for turning off the switching elements Q1 to Q4, with X = Iref × A + B, for each state of the output current. As shown in Figure 4, the threshold setting unit 44 sets the stop threshold X for the first state as X = Iref × A1 + B1, the stop threshold X for the second state as X = Iref × A2 + B2 during forcing control and as X = Iref × A1 + B1 during re-on control. The threshold setting unit 44 also sets the stop threshold X for the third state as X = Iref × A3 + B3, the stop threshold X for the fourth state as X = Iref × A4 + B4 during forcing control and as X = Iref × A3 + B3 during re-on control. Here, the eight coefficients A1 to A4 and B1 to B4 are constants with different values ​​from each other.

[0039] The threshold setting unit 44 determines which of the first to fourth states the output current is in based on the determination result input from the state determination unit 42. If the determination result is the second or fourth state, it determines whether to use forcing control or re-on control based on the comparison result of the comparison unit 45 (whether or not the deviation signal has reached the stop threshold X), which will be described later. For example, if the determination result is the second state, the threshold setting unit 44 determines that it is forcing control in the second state from the time the determination result is input until the deviation signal reaches the stop threshold X, and determines that it is re-on control in the second state from the time the deviation signal reaches the stop threshold X until the change amount △Iref is zero. If the determination result is the fourth state, the threshold setting unit 44 determines that it is forcing control in the fourth state from the time the determination result is input until the deviation signal reaches the stop threshold X, and determines that it is re-on control in the fourth state from the time the deviation signal reaches the stop threshold X until the change amount △Iref is zero.

[0040] The threshold setting unit 44 has pre-stored the eight coefficients A1 to A4 and B1 to B4, and based on the above determination, selects a coefficient corresponding to the current state of the output current, calculates the stop threshold X from the target value Iref, and sets the stop threshold X. The threshold setting unit 44 outputs the set stop threshold X to the comparison unit 45.

[0041] The comparison unit 45 compares the input deviation signal with the stop threshold X at predetermined intervals and outputs the comparison result (whether or not the deviation signal has reached the stop threshold X) to the threshold setting unit 44 and the processing unit 47. The comparison unit 45 includes, for example, a comparator, and outputs a high-level comparison result signal via the A / D converter when the deviation signal has reached the stop threshold X, and outputs a low-level comparison result signal via the A / D converter when the deviation signal has not reached the stop threshold X.

[0042] The re-on determination unit 46 stores a preset re-on threshold k and compares the input deviation signal with the re-on threshold k at predetermined intervals, outputting the comparison result (whether or not the deviation signal has reached the re-on threshold k) to the processing unit 47. For example, the re-on determination unit 46 outputs a high-level comparison result signal when the deviation signal has reached the re-on threshold k, and outputs a low-level comparison result signal when the deviation signal has not reached the re-on threshold k.

[0043] The processing unit 47 controls the on / off timing of switching elements Q1 to Q4 during forcing control and re-on control, determines the number of switches 22-1, 22-2, and 22-3 to be driven, and performs shift control to sequentially drive (shift drive) the switches 22-1, 22-2, and 22-3.

[0044] Regarding timing control, the processing unit 47 determines the on / off timing of each switching element Q1 to Q4 in switching circuits 22-1, 22-2, and 22-3 based on the determination result of the state determination unit 42, the comparison result of the comparison unit 45 (whether or not the deviation signal has reached the stop threshold X), and the comparison result of the re-on determination unit 46 (whether or not the deviation signal has reached the re-on threshold k), and generates an on / off control signal related to that timing. When generating the on / off control signal, the processing unit 47 reflects the determination result of the drive count determination and the control processing of the shift control. The processing unit 47 outputs the generated on / off control signal to the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3.

[0045] Regarding the determination of the number of drives, the processing unit 47 determines the number of switches 22-1, 22-2, and 22-3 to be driven simultaneously during forcing control based on the change amount ΔIref input from the state determination unit 42. For example, the processing unit 47 determines the number of drives to be 3 if the absolute value of the change amount ΔIref exceeds a predetermined value, and determines the number of drives to be 2, 1, or 0 if the absolute value of the change amount ΔIref is less than or equal to the predetermined value. If the change amount ΔIref is small, there is a risk that the output current will overshoot by a large amount exceeding the target value Iref if the switching elements Q1 to Q4 of switches 22-1, 22-2, and 22-3 are turned on simultaneously during forcing control. However, by adjusting the number of drives to 2 or less, the output current can be suppressed and the overshoot can be avoided.

[0046] Regarding shift control, the processing unit 47 performs shift control during re-on control. For example, during forcing control, the processing unit 47 simultaneously drives switching circuits 22-1, 22-2, and 22-3 to quickly raise (or lower) the output current, while during re-on control, it drives switching circuits 22-1, 22-2, and 22-3 sequentially one by one. This allows the switching frequencies of switching elements Q1 to Q4 to be adjusted, thereby reducing output current ripple.

[0047] In this embodiment, switching circuits 22-1, 22-2, and 22-3 are driven one at a time during shift control, but they may be driven two at a time. However, it is preferable that the number of switching circuits 22-1, 22-2, and 22-3 driven simultaneously during shift control is less than or equal to the number of switching circuits 22-1, 22-2, and 22-3 driven simultaneously during forcing control.

[0048] The first drive unit 48-1 generates drive signals to turn the switching elements Q1 to Q4 of the switching circuit 22-1 on and off based on the on / off control signal, and outputs these signals to the switching elements Q1 to Q4 of the switching circuit 22-1. For example, if the drive signal output to switching element Q1 is at a high level, switching element Q1 is turned on, and if the drive signal is at a low level, switching element Q1 is turned off. The same applies to switching elements Q2 to Q4.

[0049] The second drive unit 48-2 generates drive signals to turn the switching elements Q1 to Q4 of the switching circuit 22-2 on and off based on the on / off control signal, and outputs them to the switching elements Q1 to Q4 of the switching circuit 22-2. Similarly, the third drive unit 48-3 generates drive signals to turn the switching elements Q1 to Q4 of the switching circuit 22-3 on and off based on the on / off control signal, and outputs them to the switching elements Q1 to Q4 of the switching circuit 22-3.

[0050] Figure 5 shows the relationship between the current value (measured value) of the output current of the inverter unit 20 and the drive waveforms of the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3. Figure 5(A) shows the case when shift control is not performed, and (B) shows the case when shift control is performed. Note that in Figure 5, the control delay time is not considered.

[0051] In Figure 5(A), the control unit 40B controls time t 10 ~t 11 Forcing control is performed at time t 11 Re-on control is performed thereafter. During forcing control, the control unit 40B simultaneously raises the drive waveforms of the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3 to a high level, thereby simultaneously driving the switching circuits 22-1, 22-2, and 22-3. Time t 10 ~t 11 During this period, in switching circuits 22-1, 22-2, and 22-3, switching elements Q1 and Q4 are ON, and switching elements Q2 and Q3 are OFF. Time t at the time of re-ON control. 13 ~t14 The same applies to the period.

[0052] Time t 11 When the current value reaches a predetermined off threshold value (when the deviation signal reaches the stop threshold value X) at time t, the control unit 40B sets the drive waveforms of the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3 to the low level and stops the driving of the switching circuits 22-1, 22-2, and 22-3. As a result, the switching elements Q1 to Q4 turn off, and the control mode switches from forcing control to re-on control.

[0053] When the control unit 40B turns off the switching elements Q1 to Q4 and then turns them on again, a predetermined standby time is provided to avoid failure due to the loss relationship of the switching elements Q1 to Q4 in the switching circuits 22-1, 22-2, and 22-3. The standby time is calculated by the processing unit 47. The standby time becomes longer as the number of switching circuits 22-1, 22-2, and 22-3 to be driven simultaneously during re-on control increases. For example, when the number of drives is 3, the standby time is from time t 11 ~t 12 is longer than the period.

[0054] Therefore, even when the current value reaches the on threshold value (even when the deviation signal reaches the re-on threshold value k) at time t 12 , the control unit 40B cannot set the drive waveforms of the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3 to the high level and cannot drive the switching circuits 22-1, 22-2, and 22-3. When the standby time has elapsed at time t 13 , the control unit 40B can set each drive waveform to the high level and can drive the switching circuits 22-1, 22-2, and 22-3.

[0055] In this way, when the shift control is not executed, there is a period (time t 12 ~t 13This occurs during a certain period. Therefore, if shift control is not performed, the output current ripple will increase.

[0056] In Figure 5(B), the control unit 40B controls time t 20 ~t 21 Forcing control is performed at time t 21 Re-on control is performed from this point onward. The forcing control is the same as in the case of Figure 5(A).

[0057] time t 21 When the current value reaches a predetermined off threshold (when the deviation signal reaches the stop threshold X), the control unit 40B lowers the drive waveforms of the first drive unit 48-1, the second drive unit 48-2, and the third drive unit 48-3 to a low level, stopping the driving of the switching circuits 22-1, 22-2, and 22-3. As a result, the switching elements Q1 to Q4 are turned off, and the control mode is switched from forcing control to re-on control.

[0058] During re-on control, the control unit 40B performs shift control and sequentially drives the switching circuits 22-1, 22-2, and 22-3 one by one. That is, the control unit 40B, at time t 22 ~t 23 During this period, the drive waveform of the first drive unit 48-1 is set to a high level to drive the switching circuit 22-1, and at time t 24 ~t 25 During this period, the drive waveform of the second drive unit 48-2 is set to a high level to drive the switching circuit 22-2, and at time t 26 During the following period, the drive waveform of the third drive unit 48-3 is set to a high level to drive the switching circuit 22-3. While the switching circuits 22-1, 22-2, and 22-3 are being driven, the switching elements Q1 and Q4 are turned on, and the switching elements Q2 and Q3 are turned off.

[0059] In Figure 5(B), since the number of switching circuits 22-1, 22-2, and 22-3 driven simultaneously during re-on control is 1, the waiting time is shorter than in Figure 5(A). As a result, switching elements Q1 and Q4 can be turned on at the timing when the current value reaches the on threshold. Furthermore, because the waiting time is shorter, the on threshold and off threshold can be brought closer to the target value Iref than in Figure 5(A), thereby reducing output current ripple.

[0060] Figure 6(A) shows the stop threshold X in the comparative example, and Figure 6(B) shows the stop threshold X in this embodiment. The comparative example is the same as this embodiment except for the setting of the stop threshold X after time t2. That is, in the comparative example, a single stop threshold X (X=Iref×A2+B2) is set after time t2, whereas in this embodiment, two different stop thresholds X (X=Iref×A2+B2 and X=Iref×A1+B1) are set after time t2. Note that in Figure 6, output current ripple included in the current value is not shown for clarity.

[0061] In Figures 6(A) and 6(B), during the period from time t0 to t2, the output current is in a state where it is rising in the positive region (first state), and during the period from time t2 onward, the output current is in a state where it is falling in the positive region (second state). The control unit 40B performs forcing control during the period from time t0 to t1 and from time t2 to t3, and performs re-on control during the period from time t1 to t2 and from time t3 onward.

[0062] During forcing control, the control unit 40B controls the switching circuits 22-1, 22-2, and 22-3 to stop driving (turn off switching elements Q1 and Q4) when the deviation signal reaches the stop threshold X. However, a control delay occurs, so in reality, the increase in the current value stops at time t1 after a predetermined delay time has elapsed. A similar delay time occurs during re-on control. In this embodiment, the coefficients A1 to A4 and B1 to B4 of the stop threshold X are set considering the above delay time so that the output current value matches the target value Iref.

[0063] The switching unit 22 performs power operation during the period from time t0 to t1, alternates between recirculation operation and power operation during the period from time t1 to t2, performs regenerative operation during the period from time t2 to t3, and alternates between recirculation operation and power operation from time t3 onward.

[0064] In the comparative example shown in Figure 6(A), the stop threshold X is X = Iref × A2 + B2 during the period after time t2. As described above, during the period after time t2, the switching unit 22 operates in a regenerative mode during forcing control, but during re-on control, the switching unit 22 operates in a recirculating mode and a power mode. Therefore, if a single stop threshold X (X = Iref × A2 + B2) is set, the control amount during re-on control becomes large, and the output current ripple increases.

[0065] On the other hand, in this embodiment shown in Figure 6(B), the stop threshold X during the period from time t2 to t3 (during forcing control and regenerative operation) is X = Iref × A2 + B2, but the stop threshold X during re-on control from time t3 onward is X = Iref × A1 + B1. The stop threshold X from time t3 onward (X = Iref × A1 + B1) is the same value as the stop threshold X during the period from time t0 to t2, and is closer to the re-on threshold k than the stop threshold X during the period from time t2 to t3 (X = Iref × A2 + B2). Therefore, in this embodiment, the control amount during re-on control can be reduced compared to the comparative example, and the output current ripple can be reduced.

[0066] In Figure 6(B), the case where different stop thresholds X are set in the second state is explained, but the same applies when different stop thresholds X are set in the fourth state. That is, in the fourth state, the operation of the switching unit 22 during forcing control is regenerative operation, but the operation of the switching unit 22 during re-on control is recirculation operation and power operation. In this embodiment, the stop threshold X in the fourth state is set to X = Iref × A4 + B4 during forcing control and to X = Iref × A3 + B3 during re-on control, so that the control amount can be reduced and the output current ripple can be reduced.

[0067] As described above, in the switching power supply device and power supply system 1 according to this embodiment, one switching unit 22 functions as a circuit for raising (lowering) the output current and a circuit for maintaining the output current, and the output current can be controlled by forcing control and re-on control that turn the switching elements Q1 to Q4 on and off. Therefore, according to the switching power supply device and power supply system 1 according to this embodiment, it is possible to supply an output current with a desired waveform (for example, a trapezoidal or stepped waveform) to the electromagnet 2 while avoiding increased control complexity and increased device size.

[0068] Furthermore, in the switching power supply and power supply system 1 according to this embodiment, the stop threshold X for the second state is set to X = Iref × A2 + B2 during forcing control and to X = Iref × A1 + B1 during re-on control, and the stop threshold X for the fourth state is set to X = Iref × A4 + B4 during forcing control and to X = Iref × A3 + B3 during re-on control. Therefore, according to the switching power supply and power supply system 1 according to this embodiment, the control amount during re-on control in the second and fourth states can be reduced, and the output current ripple can be reduced.

[0069] Furthermore, in the switching power supply device and power supply system 1 according to this embodiment, the control unit 40B performs a drive count determination to determine the number of switching circuits 22-1, 22-2, and 22-3 to be driven simultaneously during forcing control. Therefore, according to the switching power supply device and power supply system 1 according to this embodiment, the output current can be suppressed and overshoot can be avoided by reducing the number of drives when the change amount ΔIref is small.

[0070] Furthermore, in the switching power supply device and power supply system 1 according to this embodiment, the control unit 40B simultaneously drives the switching circuits 22-1, 22-2, and 22-3 during forcing control to quickly raise (or lower) the output current, while simultaneously performing shift control to shift drive the switching circuits 22-1, 22-2, and 22-3 during re-on control. Therefore, according to the switching power supply device and power supply system 1 according to this embodiment, the switching frequencies of the switching elements Q1 to Q4 can be adjusted during re-on control, and the output current ripple can be reduced.

[0071] [Differentiation] Although embodiments of the switching power supply device and power supply system according to the present invention have been described above, the present invention is not limited to the above embodiments.

[0072] The switching power supply device according to the present invention comprises a switching unit including at least one switching element, and a control unit that controls the switching element and controls the output current output from the switching unit, wherein the control unit can be appropriately configured to perform forcing control, which turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, and re-on control, which turns on the switching element again when the output current decreases after forcing control and reaches an on threshold, and turns off the switching element again when the output current increases and reaches a second off threshold.

[0073] In the above embodiment, the stop threshold X for the first state is set as X = Iref × A1 + B1, and the stop threshold X for the second state is set as X = Iref × A2 + B2 during forcing control and as X = Iref × A1 + B1 during re-on control. However, the stop threshold X for the first state may be set to different values ​​for forcing control and re-on control. Furthermore, the stop threshold X during re-on control in the second state can be set arbitrarily as long as it is closer to the re-on threshold k than the stop threshold X during forcing control in the second state.

[0074] Similarly, in the above embodiment, the stop threshold X for the third state is set as X = Iref × A3 + B3, and the stop threshold X for the fourth state is set as X = Iref × A4 + B4 during forcing control and as X = Iref × A3 + B3 during re-on control. However, the stop threshold X for the third state may be set to different values ​​for forcing control and re-on control. Furthermore, the stop threshold X during re-on control of the fourth state can be set arbitrarily as long as it is closer to the re-on threshold k than the stop threshold X during forcing control of the fourth state.

[0075] The power supply system of the present invention is not limited to an electromagnet power supply system, and the configuration can be appropriately modified as long as it includes an AC / DC converter having an AC input terminal and a DC output terminal, which converts an AC voltage input to the AC input terminal into a DC voltage and outputs it from the DC output terminal, and a switching power supply device of the present invention connected to the DC output terminal of the AC / DC converter. [Explanation of symbols]

[0076] 1. Power System 2 Electromagnets 10 AC / DC conversion section 20 Inverter section 21 Capacitor section 22 Switching section 22-1~22-3 Switching Circuits 30 Transformer section 40A, 40B Control Unit 41 Target value reading unit 42 State determination unit 43 Deviation signal generation unit 44. Threshold setting section 45 Comparison Section 46 Re-on determination unit 47 Processing Unit 48-1 First drive unit 48-2 Second drive unit 48-3 Third drive unit

Claims

1. A switching unit including at least one switching element, A control unit that controls the switching element and controls the output current output from the switching unit, A switching power supply device comprising, The control unit, Forcing control that turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, After the forcing control, when the output current decreases and reaches an on threshold, the switching element is turned on again, and when the output current increases and reaches a second off threshold, the switching element is turned off again, a re-on control is performed. The switching section is further provided on the input side and includes a capacitor section containing at least one capacitor. The control unit, When the operation of the switching unit during the forcing control is a power operation in which current is supplied from the capacitor unit, the second off threshold is set to the same value as the first off threshold. When the switching unit operates during the forcing control in a regenerative operation that supplies current to the capacitor unit, the second off threshold is set to a value closer to the on threshold than the first off threshold. A switching power supply device characterized by the following features.

2. A switching unit including at least one switching element, A control unit that controls the switching element and controls the output current output from the switching unit, A switching power supply device comprising, The control unit, Forcing control that turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, After the forcing control, when the output current decreases and reaches an on threshold, the switching element is turned on again, and when the output current increases and reaches a second off threshold, the switching element is turned off again, a re-on control is performed. A state determination unit that determines whether the output current is in a first state (rising in the positive region), a second state (falling in the positive region), a third state (falling in the negative region), or a fourth state (rising in the negative region), The system includes a threshold setting unit that sets the second off threshold to the same value as the first off threshold in the first and third states, sets the second off threshold to the same value as the second off threshold in the first state in the second state, and sets the second off threshold to the same value as the second off threshold in the third state in the fourth state. A switching power supply device characterized by the following features.

3. A switching unit including at least one switching element, A control unit that controls the switching element and controls the output current output from the switching unit, A switching power supply device comprising, The control unit, Forcing control that turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, After the forcing control, when the output current decreases and reaches an on threshold, the switching element is turned on again, and when the output current increases and reaches a second off threshold, the switching element is turned off again, a re-on control is performed. The switching unit comprises a plurality of switching circuits connected in parallel, The switching circuit comprises a plurality of the switching elements, The control unit determines the number of switching circuits to be driven simultaneously during the forcing control based on the amount of change in the target value of the output current. A switching power supply device characterized by the following features.

4. A switching unit including at least one switching element, A control unit that controls the switching element and controls the output current output from the switching unit, A switching power supply device comprising, The control unit, Forcing control that turns on the switching element to raise or lower the output current, and turns off the switching element when the output current increases and reaches a first off threshold, After the forcing control, when the output current decreases and reaches an on threshold, the switching element is turned on again, and when the output current increases and reaches a second off threshold, the switching element is turned off again, a re-on control is performed. The switching unit comprises a plurality of switching circuits connected in parallel, The switching circuit comprises a plurality of the switching elements, The control unit reduces the number of switching circuits driven simultaneously during the re-on control to less than the number of switching circuits driven simultaneously during the forcing control. A switching power supply device characterized by the following features.

5. An AC / DC converter having an AC input terminal and a DC output terminal, which converts an AC voltage input to the AC input terminal into a DC voltage and outputs it from the DC output terminal, A switching power supply device according to any one of claims 1 to 4, connected to the DC output terminal of the AC / DC converter, is provided. A power supply system characterized by the following features.

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