Power supply device

Abstract

To provide a power supply unit capable of detecting an abnormal state of a discharge switch to prevent erroneous discharge of a capacitor.SOLUTION: A power supply unit 1 includes a capacitor 3 charged by the charging operation of a charger 2, and a discharge switch 5 interposed in the discharge current path of a capacitor 3 so as to supply discharge current of the capacitor 3 to an inductive load L when the discharge switch 5 is in ON state. Also included are: a plurality of series-connected semiconductor switches Thy1 to Thy3 that constitute the discharge switch 5; voltage detection units 11 to 13 for detecting applied voltages V1 to V3 of the semiconductor switches Thy1 to Thy3; and a control unit 8 that determines whether or not the discharge switch 5 is in an abnormal state based on the values detected by the voltage detection units 11 to 13, and stops the charging operation if it is determined to be in an abnormal state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power supply device for supplying a large current to an inductive load.

Background Art

[0002] As a power supply device for supplying a large current to an inductive load such as a magnetic field generating device, a capacitor energy storage type power supply device is known (see, for example, Patent Document 1). The capacitor energy storage type power supply device includes a charger, a capacitor charged by the charging operation of the charger, a discharge switch interposed in the discharge current path of the capacitor, and a control unit that controls the charger.

[0003] The capacitor energy storage type power supply device can store a large amount of energy in the capacitor in advance by the charging operation of the charger, and supply the discharge current of the capacitor to the inductive load by turning on the discharge switch to discharge the capacitor.

[0004] A semiconductor switch such as a thyristor is used for the discharge switch. The discharge switch composed of a semiconductor switch may fail (mainly, a short circuit failure) due to the flow of a large current. For example, if the discharge switch has a short circuit failure and causes an accidental arcing during the charging operation of the charger, an unintended discharge current of the capacitor flows into the inductive load. Such an accidental discharge of the capacitor causes the generation of an unintended strong magnetic field in an inductive load such as a magnetic field generating device.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a power supply device capable of detecting an abnormal state of a discharge switch and preventing an accidental discharge of a capacitor.

Means for Solving the Problem

[0007] In order to solve the above problems, a power supply device according to the present invention includes: a capacitor charged by a charging operation of a charger; a discharge switch interposed in a discharge current path of the capacitor, and is a power supply device that supplies a discharge current of the capacitor to an inductive load when the discharge switch is in an on state, a plurality of semiconductor switches connected in series to form the discharge switch; a voltage detection unit that detects an applied voltage of each of the plurality of semiconductor switches; and a control unit that determines whether the discharge switch is in an abnormal state based on a detection value of the voltage detection unit, and stops the charging operation when it is determined that the discharge switch is in the abnormal state.

[0008] According to this configuration, since a voltage detection unit that detects an applied voltage of each of the plurality of semiconductor switches that form the discharge switch is provided, it is possible to detect an abnormal state of the discharge switch based on a detection value of the voltage detection unit. Further, according to this configuration, since the charging operation of the charger is stopped when an abnormal state is detected, it is possible to avoid an accidental arcing of the discharge switch and prevent an accidental discharge of the capacitor.

[0009] In the power supply device, a plurality of voltage equalizing resistors are provided in parallel with each of the plurality of semiconductor switches, the voltage detection unit includes a plurality of voltage detection means connected one-to-one to the plurality of semiconductor switches, and the control unit can be configured to calculate a difference between detection values of the plurality of voltage detection means, and determine that the discharge switch is in the abnormal state and stop the charging operation when the difference is equal to or greater than a predetermined threshold value.

[0010] In the power supply device, The control unit can be configured to continue the charging operation even if the difference is greater than 0 and less than the threshold value.

[0011] In the power supply device, The threshold value is preferably set to a value of 10% or more and 50% or less of the rated voltage of the capacitor.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a power supply device capable of detecting an abnormal state of a discharge switch and preventing an accidental discharge of a capacitor.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the power supply device according to the present invention will be described with reference to the accompanying drawings.

[0015] FIG. 1 shows a power supply device 1 according to an embodiment of the present invention. The power supply device 1 supplies a large current to an inductive load L connected to output terminals T1 and T2. For example, a strong magnetic field generating device is connected to a coil (not shown) on the secondary side of the inductive load L.

[0016] The power supply device 1 includes a charger 2, a capacitor 3, a charging resistor 4, a discharge switch 5, a protection reactor 6, a clover circuit 7, a control unit 8, and a plurality (three in this embodiment) of voltage detection means 11 to 13.

[0017] The charger 2 is configured to output a DC voltage under the control of the control unit 8 and charge the capacitor 3 via the charging resistor 4. The capacitor 3 is composed of one or more capacitors. One end (+ side) of the capacitor 3 is connected to the high potential side of the charger 2 via the charging resistor 4, and the other end (- side) of the capacitor 3 is connected to the low potential side of the charger 2.

[0018] The discharge switch 5 is interposed in the discharge current path between the capacitor 3 and the output terminal T1. The discharge switch 5 is composed of a plurality of semiconductor switches connected in series, and in this embodiment, is composed of three thyristors Thy1 to Thy3 connected in series. Although not shown, a first voltage equalizing resistor is connected in parallel to the thyristor Thy1, a second voltage equalizing resistor is connected in parallel to the thyristor Thy2, and a third voltage equalizing resistor is connected in parallel to the thyristor Thy3.

[0019] Voltage detection means 11 to 13 are connected to the thyristors Thy1 to Thy3, respectively. The voltage detection means 11 detects the voltage across the thyristor Thy1 (applied voltage) V1, the voltage detection means 12 detects the voltage across the thyristor Thy2 (applied voltage) V2, and the voltage detection means 13 detects the voltage across the thyristor Thy3 (applied voltage) V3.

[0020] The protection reactor 6 is interposed between the discharge switch 5 and the output terminal T1 in the above discharge current path. The clover circuit 7 includes a series circuit composed of a diode 7a and a resistor 7b, and a resistor 7c connected in parallel to the diode 7a. One end (the cathode side of the diode 7a) is connected to the output terminal T1 via the protection reactor 6, and the other end (the resistor 7b side) is connected to the output terminal T2.

[0021] The control unit 8 controls the charging operation of the charger 2 and the discharge switch 5. The control unit 8 may be composed of a digital control circuit using a microcontroller or the like, or may be composed of a circuit combining an analog control circuit and a digital control circuit.

[0022] When the control unit 8 starts the charging operation of the charger 2, the charging voltage Vc of the capacitor 3 is applied to the thyristors Thy1 to Thy3 constituting the discharge switch 5. The control unit 8 determines whether the discharge switch 5 is in an abnormal state based on the detection values (both-end voltages V1 to V3) of the voltage detection means 11 to 13. When the control unit 8 determines that the discharge switch 5 is in an abnormal state, it stops the charging operation.

[0023] In this embodiment, the control unit 8 calculates the difference between the maximum value and the minimum value of the both-end voltages V1 to V3, and determines that it is in an abnormal state when the difference is equal to or greater than a predetermined threshold value, and stops the charging operation of the charger 2. Even if the difference is greater than 0, the control unit 8 continues the charging operation when it is smaller than the above threshold value. The above threshold value is set to a value of 20% of the rated voltage of the capacitor 3.

[0024] As described above, since the equalizing resistors are connected in parallel to the thyristors Thy1 to Thy3, the charging voltage Vc of the capacitor 3 is applied after being equalized to the thyristors Thy1 to Thy3. Therefore, when a difference equal to or greater than the threshold value occurs in the both-end voltages V1 to V3, it can be determined that the discharge switch 5 is in an abnormal state.

[0025] Figures 2 to 5 show the timing diagrams of the power supply device 1 and a conventional power supply device. The conventional power supply device is common to the power supply device 1 except that it does not detect an abnormal state of the discharge switch 5 during the charging operation and does not stop the charging operation of the charger 2. In each figure, (a) shows the charging voltage Vc of the capacitor 3 and the output terminal voltage Vo, (b) shows the voltages V1 to V3 across the thyristors Thy1 to Thy3, (c) shows the output current (the discharge current of the capacitor 3), (d) shows the state of the discharge switch 5, and (e) shows the state of the charger 2.

[0026] Figure 2 is a timing diagram when the discharge switch 5 is in a normal state, which is common to the power supply device 1 and the conventional power supply device. At time t 10 when the control unit 8 turns on the charger 2, the charger 2 starts the charging operation for the capacitor 3, and the charging voltage Vc of the capacitor 3 rises.

[0027] When the discharge switch 5 is in a normal state, that is, when no short-circuit fault occurs in the thyristors Thy1 to Thy3, the charging voltage Vc of the capacitor 3 is evenly applied across the thyristors Thy1 to Thy3. For example, when the charging voltage Vc of the capacitor 3 reaches Y [V], the voltages V1, V2, and V3 across the thyristors Thy1 to Thy3 all become Y / 3 [V].

[0028] At time t 20 when the control unit 8 turns on the discharge switch 5 (conducts the thyristors Thy1 to Thy3), an output terminal voltage Vo of Y [V] is generated at the output terminals T1 and T2, and the discharge current of the capacitor 3 is supplied as the output current to the inductive load L.

[0029] Figure 3 is a timing diagram when the discharge switch 5 is in an abnormal state (the thyristor Thy1 has a short-circuit fault), which is the timing diagram of the conventional power supply device.

[0030] When the thyristor Thy1 has a short - circuit fault, the charging voltage Vc of the capacitor 3 is not equalized. Even when the charging voltage Vc of the capacitor 3 reaches Y[V], the voltage V1 across the thyristor Thy1 remains 0[V]. On the other hand, the voltage V2 across the thyristor Thy2 and the voltage V3 across the thyristor Thy3 each become Y / 2[V].

[0031] In this case, since mis - arcing of the discharge switch 5 and mis - discharging of the capacitor 3 do not occur, at time t 20 when the control unit 8 turns on the discharge switch 5 (conducts the thyristors Thy2 and Thy3), the discharge current of the capacitor 3 is supplied to the inductive load L. However, if the power supply device 1 continues to operate with the thyristor Thy1 in a short - circuit fault state, the thyristors Thy2 and Thy3 may deteriorate, leading to a risk of failure (mainly short - circuit failure) of the thyristors Thy2 and Thy3.

[0032] Figure 4 is a timing diagram when the discharge switch 5 is in an abnormal state (the thyristors Thy1 and Thy2 have short - circuit faults), and it is a timing diagram of a conventional power supply device.

[0033] When the thyristors Thy1 and Thy2 have short - circuit faults, the charging voltage Vc of the capacitor 3 is not equalized. The voltage V1 across the thyristor Thy1 and the voltage V2 across the thyristor Thy2 remain 0[V]. On the other hand, the thyristor Thy3 is in an over - voltage state because all of the charging voltage Vc of the capacitor 3 is applied to it.

[0034] At time t 12 if a short - circuit fault due to over - voltage occurs in the thyristor Thy3, all of the thyristors Thy1 - Thy3 will be in a conducting state, resulting in mis - arcing of the discharge switch 5. As a result, the discharge current of the capacitor 3 flows into the inductive load L at an unintended timing. Such mis - discharging of the capacitor 3 causes the generation of an unintended strong magnetic field in the inductive load L such as a magnetic field generating device.

[0035] FIG. 5 is a timing diagram when the discharge switch 5 is in an abnormal state (the thyristor Thy1 has a short-circuit fault), and is a timing diagram of the power supply device 1 according to the present embodiment.

[0036] When the thyristor Thy1 has a short-circuit fault, the charging voltage Vc of the capacitor 3 is not equalized, and the voltage V1 across the thyristor Thy1 remains at 0 [V]. On the other hand, the voltage V2 across the thyristor Thy2 and the voltage V3 across the thyristor Thy3 tend to rise so that they become Y / 2 [V] when the charging voltage Vc of the capacitor 3 reaches Y [V].

[0037] In the process of the rise, the control unit 8 of the power supply device 1 determines whether the discharge switch 5 is in an abnormal state based on the detection values (the voltages V1, V2, V3 across both ends) of the voltage detection means 11 to 13. Specifically, the control unit 8 calculates the difference between the maximum value and the minimum value of each detection value (the voltages V1, V2, V3 across both ends), and determines that it is in an abnormal state when the difference is equal to or greater than a predetermined threshold value (in this embodiment, a value of 20% of the rated voltage of the capacitor 3).

[0038] Time t 11 When the difference between the voltages V2, V3 across both ends and the voltage V1 across both ends reaches 20% of the rated voltage of the capacitor 3, the control unit 8 determines that the discharge switch 5 is in an abnormal state. Note that the control unit 8 that has determined that the discharge switch 5 is in an abnormal state may determine that the thyristor Thy1 with the smallest detected value at the time of determination has a short-circuit fault.

[0039] The control unit 8 that has determined that the discharge switch 5 is in an abnormal state stops the charging operation of the charger 2. Thereby, it is possible to avoid the thyristors Thy2 and Thy3 from deteriorating or malfunctioning.

[0040] Ultimately, according to the power supply device 1 according to the present embodiment, it is possible to detect an abnormal state of the discharge switch 5 and prevent mis-discharge of the capacitor 3. Further, since the threshold value for determining whether the discharge switch 5 is in an abnormal state is set to a relatively low value of 20% of the rated voltage of the capacitor 3, an abnormal state can be detected at an early stage.

[0041] [Modification Example] As described above, the embodiments of the power supply device according to the present invention have been described, but the present invention is not limited to the above embodiments.

[0042] Fig. 6 shows a circuit diagram of the discharge switch 5' according to the modification example. The discharge switch 5' can be used instead of the discharge switch 5 of the above embodiment. The discharge switch 5' is composed of a plurality of semiconductor switches (thyristors Thy11~Thy14, Thy21~24) connected in a bridge configuration.

[0043] The discharge switch 5' can switch between positive current and negative current for output. When outputting positive current, thyristors Thy11~Thy14 are set to the conducting state, while when outputting negative current, thyristors Thy21~24 are set to the conducting state.

[0044] Voltage detection means 21~28 and a voltage equalizing resistor (not shown) are connected to the thyristors Thy11~Thy14, Thy21~24. The determination of the abnormal state of the discharge switch 5' is performed in the same manner as in the above embodiment.

[0045] [Other Modification Examples] The power supply device according to the present invention includes a capacitor charged by the charging operation of a charger and a discharge switch interposed in the discharge current path of the capacitor, and is a power supply device that supplies the discharge current of the capacitor to an inductive load when the discharge switch is in the on state. If it includes a plurality of semiconductor switches connected in series that constitute the discharge switch, a voltage detection unit that detects the applied voltage of each of the plurality of semiconductor switches, and a control unit that determines whether the discharge switch is in an abnormal state based on the detection value of the voltage detection unit and stops the charging operation when it determines that it is in an abnormal state, the configuration can be changed as appropriate.

[0046] Semiconductor switches other than thyristors may be used.

[0047] The voltage detection unit preferably includes a plurality of voltage detection means connected one-to-one to a plurality of semiconductor switches, but the number of semiconductor switches and the number of voltage detection means may be different.

[0048] In the above embodiment, the threshold value for determining whether the discharge switch 5 is in an abnormal state is set to a relatively low value of 20% of the rated voltage of the capacitor 3, but the threshold value can be changed as appropriate. For example, according to the number of semiconductor switches constituting the discharge switch 5, etc., the threshold value may be set to a value of 10% or more and 50% or less of the rated voltage of the capacitor 3.

Explanation of reference numerals

[0049] 1 Power supply device 2 Charger 3 Capacitor 4 Charging resistor 5 Discharge switch 6 Protection reactor 7 Clover circuit 8 Control unit 11~13,21~28 Voltage detection means

Claims

1. a capacitor charged by the charging operation of a charger; and a discharge switch interposed in the discharge current path of the capacitor, wherein when the discharge switch is in an on state, it is a power supply device that supplies the discharge current of the capacitor to an inductive load, and a plurality of semiconductor switches connected in series to form the discharge switch; a voltage detection unit that detects the applied voltage of each of the plurality of semiconductor switches; a control unit that determines whether the discharge switch is in an abnormal state based on the detection value of the voltage detection unit, and stops the charging operation when it is determined that the discharge switch is in the abnormal state; a plurality of voltage equalizing resistors connected in parallel to each of the plurality of semiconductor switches; the voltage detection unit includes a plurality of voltage detection means connected one-to-one to the plurality of semiconductor switches; the control unit calculates the difference between the detection values of the plurality of voltage detection means, and determines that the discharge switch is in an abnormal state and stops the charging operation when the difference is equal to or greater than a predetermined threshold value A power supply device characterized by the above.

2. The control unit continues the charging operation when the difference is greater than 0 and less than the threshold value. The power supply device according to claim 1, characterized by the above.

3. The threshold value is set to a value of 10% or more and 50% or less of the rated voltage of the capacitor. The power supply device according to claim 1 or 2, characterized by the above.

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