Fluorescence x-ray analyzer and power supply used therefor

Abstract

To improve accuracy of discharge detection in an analyzer including an X-ray generator.SOLUTION: A fluorescence X-ray analyzer includes an X-ray tube, a detector, a power supply device, and a control device. The power supply device includes a high voltage power supply unit 120 that generates a tube voltage, power supply wiring T4 that transmits the tube voltage from the high voltage power supply unit to a target, and a detection circuit 140. The detection circuit is configured to detect a voltage variation in the high voltage circuit including the X-ray tube. The detection circuit includes a resistor R10 having one end connected to a ground potential, resistors RF1-RF10 connected in series between the other end of the resistor R10 and the power supply wiring, capacitors CF1-CF10 connected in parallel with the resistors RF1-RF10, respectively, and a high-pass filter 142 connected to the other end of the resistor R10. The control device detects occurrence of discharge in the high voltage circuit on the basis of a signal from the detection circuit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an X-ray fluorescence analyzer and a power supply device used therein, and more particularly to discharge detection in a power supply device used in an X-ray fluorescence analyzer. [Background technology]

[0002] Conventionally, fluorescent X-ray analyzers have been known that irradiate a sample with X-rays and analyze the sample using fluorescent X-rays generated from the sample. Such X-ray analyzers use an X-ray generator such as that disclosed in Japanese Patent Laid-Open Publication No. 2010-212072 (Patent Document 1). In the X-ray generator, X-rays are generated by applying a tube voltage to an X-ray tube in which a cathode electrode and a target electrode are arranged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-212072 Summary of the Invention [Problem to be solved by the invention]

[0004] In X-ray generators, when a boosted high voltage is applied to the X-ray tube, unintentional discharges can occur in the high-voltage circuit, including the X-ray tube. When a discharge occurs, a current greater than that normally used flows instantaneously through the circuit, which can cause deterioration or failure of the power supply that applies high voltage to the X-ray tube or the X-ray tube.

[0005] To prevent deterioration and failure due to such discharges, X-ray generators are generally provided with an overcurrent protection circuit to protect the circuit from overcurrent caused by discharges. However, if a discharge occurs at a level that cannot be detected by the overcurrent detection mechanism included in the overcurrent protection circuit, the device may continue to be used without the protection circuit taking action. Furthermore, if intermittent discharges that cannot be detected by the overcurrent detection mechanism occur, this can accelerate deterioration of the power supply device or X-ray tube, ultimately leading to failure.

[0006] To increase the detection sensitivity, it is possible to lower the threshold value for detecting overcurrent in the overcurrent detection mechanism, but if the threshold value is lowered too much, current fluctuations within the normal operating range may cause the protection circuit to malfunction.In addition, it is possible to increase the response speed of the overcurrent protection circuit, but increasing the response speed may increase the risk of the protection circuit malfunctioning due to load fluctuations or noise.

[0007] Another method for detecting overcurrent occurrence is to indirectly detect the overcurrent by detecting a drop in the high-voltage output voltage during discharge. In this case, a differentiating circuit consisting of a resistor and a capacitor is typically used to detect the voltage drop. However, this requires connecting the differentiating circuit to a high-voltage line, which requires a high-voltage capacitor. This increases the component cost of the capacitor itself, and may also increase the cost of mounting and insulating molding materials. Furthermore, adding a capacitor increases the size of the power supply device.

[0008] The present disclosure has been made to solve such problems, and its purpose is to improve the accuracy of discharge detection in an analytical device equipped with an X-ray generator while suppressing increases in costs. [Means for solving the problem]

[0009] An X-ray fluorescence analyzer according to a first aspect of the present disclosure includes an X-ray tube, a detector, a power supply, and a control device. The X-ray tube includes a filament and a target and irradiates a sample with primary X-rays. The detector detects secondary X-rays generated from the sample. The power supply applies a tube voltage to the target. The control device detects the occurrence of a discharge in a high-voltage circuit including the X-ray tube. The power supply includes a high-voltage power supply unit that generates the tube voltage, a power supply line that transmits the tube voltage from the high-voltage power supply unit to the target, and a detection circuit connected to the power supply line. The detection circuit is configured to detect voltage fluctuations in the X-ray tube. The detection circuit includes a first resistor element having one end connected to a ground potential, a plurality of second resistor elements connected in series between the other end of the first resistor element and the power supply line, a plurality of capacitors connected in parallel to each of the plurality of second resistor elements, and a high-pass filter connected to the other end of the first resistor element. The control device detects the occurrence of a discharge in the high-voltage circuit based on a signal from the detection circuit.

[0010] A power supply device according to a second aspect of the present disclosure applies a tube voltage to an X-ray tube including a filament and a target. The power supply device includes a high-voltage power supply unit that generates the tube voltage, a power supply line that transmits the tube voltage from the high-voltage power supply unit to the target, and a detection circuit connected to the power supply line. The detection circuit is configured to detect voltage fluctuations in the high-voltage circuit including the X-ray tube. The detection circuit includes a first resistor element having one end connected to a ground potential, a plurality of second resistor elements connected in series between the other end of the first resistor element and the power supply line, a plurality of capacitors connected in parallel to each of the plurality of second resistor elements, a high-pass filter connected to the other end of the first resistor element, and a comparator configured to compare a signal that has passed through the high-pass filter with a reference value. [Effects of the Invention]

[0011] In the X-ray fluorescence analyzer according to the present disclosure, the output voltage from the high-voltage power supply is stepped down by a plurality of resistor elements, each of which has a capacitor connected in parallel, and the occurrence of a discharge is detected based on a signal that has passed through a high-pass filter. This circuit configuration makes it possible to improve the accuracy of discharge detection while suppressing increases in costs. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram schematically illustrating a power supply device and an X-ray tube of the fluorescent X-ray analyzer according to the embodiment. [Figure 2] FIG. 2 is a diagram illustrating details of the detection circuit of FIG. [Figure 3] FIG. 2 is a functional block diagram of the control device of FIG. [Figure 4] 4 is a flowchart of a discharge detection process executed by the control device. [Figure 5] 2 is a diagram for explaining a detection region of a discharge voltage in the detection circuit of FIG. 1. FIG. [Figure 6] FIG. 10 is a diagram illustrating details of a detection circuit according to a first modified example. [Figure 7] FIG. 10 is a diagram illustrating details of a detection circuit according to a second modification. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0014] [Embodiment Mode] (Configuration of X-ray fluorescence analyzer) 1 is a diagram schematically illustrating an X-ray fluorescence analyzer according to an embodiment. The X-ray fluorescence analyzer 10 is, for example, an energy dispersive X-ray fluorescence spectrometer (EDX). In this embodiment, an example will be described in which a power supply device 100 that generates primary X-rays is applied to the X-ray fluorescence analyzer 10.

[0015] As shown in FIG. 1, the X-ray fluorescence analyzer 10 includes a power supply 100, an X-ray tube 200, a detector 300, and a control device 400. The power supply 100 applies a voltage to the X-ray tube 200 to excite primary X-rays B1. The primary X-rays B1 are irradiated onto a sample S. The sample S irradiated with the primary X-rays B1 emits fluorescent X-rays B2. The fluorescent X-rays B2 emitted from the sample S are referred to as "secondary X-rays" in contrast to the primary X-rays. The detector 300 detects the fluorescent X-rays B2. This enables the X-ray fluorescence analyzer 10 to perform quantitative and / or qualitative analysis of the sample S. Note that although FIG. 1 illustrates the control device 400 as a separate element from the power supply 100, some or all of the functions of the control device 400 may be included in the power supply 100 or the high-voltage power supply unit 120.

[0016] A target TG1 and a filament F1 are arranged inside the X-ray tube 200. The target TG1 is an anode, and the filament F1 is a cathode. The target TG1 and the filament F1 are arranged at a distance from each other inside the X-ray tube 200. The power supply device 100 includes a filament power supply unit 110, a high-voltage power supply unit 120, a tube current control unit 130, overcurrent protection circuits 125 and 135, and a detection circuit 140.

[0017] The filament power supply unit 110 heats the filament F1 by supplying a current to the filament F1. In the following description, the current supplied from the filament power supply unit 110 to the filament F1 will be referred to as the "filament current."

[0018] The high-voltage power supply unit 120 applies a high voltage to the target TG1 in the X-ray tube 200. In the following description, the high voltage applied by the high-voltage power supply unit 120 will be referred to as the "tube voltage." The high-voltage power supply unit 120 generates a high voltage by boosting a DC voltage converted from a commercial power source using a rectifier, a converter, a Cockcroft-Walton circuit (none of which are shown), etc.

[0019] The high-voltage power supply unit 120 is connected to the target TG1 via a power line L4 and a resistor R4 provided on the power line L4. The high-voltage power supply unit 120 is also connected to the ground potential GND via a power line L5 and a resistor R5. Within the X-ray tube 200, the filament F1 is heated by the filament power supply unit 110, generating thermoelectrons. The generated thermoelectrons move toward the target TG1 due to the tube voltage applied between the filament F1 and the target TG1 by the high-voltage power supply unit 120, and finally collide with the target TG1. This collision of the thermoelectrons excites primary X-rays B1.

[0020] The filament power supply unit 110 is connected to the filament F1 by power lines L1 and L2. The power line L1 is connected to a terminal TF1 of the filament power supply unit 110 and a terminal T1 of the power supply device 100. The power line L2 is connected to a terminal TF2 of the filament power supply unit 110 and a terminal T2 of the power supply device 100. The terminal T1 is connected to one end of the filament F1, and the terminal T2 is connected to the other end of the filament F1.

[0021] Resistors R1 and R2 are connected in series between the power lines L1 and L2. One end of a power line L3 is connected to a connection node NP1 between the power lines L1 and L2. The other end of the power line L3 is connected to the ground potential GND via the resistor R3. Note that the one end of the power line L3 may be connected to either the power line L1 or the power line L2 instead of the connection node NP1.

[0022] A protection circuit D1 including a Zener diode is connected between the power line L1 and the ground potential GND. Similarly, a protection circuit D2 including a Zener diode is connected between the power line L2 and the ground potential GND. The protection circuits D1 and D2 are circuits for protecting the filament power supply unit 110 and the tube current control unit 130 from excessive current generated by discharge when a discharge occurs in the X-ray tube 200.

[0023] The tube current control unit 130 performs feedback control of the output current from the filament power supply unit 110 based on the current flowing through the power line L3. More specifically, the tube current control unit 130 detects the tube current flowing through the power line L3 by converting it into a voltage value using a resistor R3. The tube current control unit 130 transmits the detected value of the tube current to the filament current control unit 111 and the overcurrent protection circuit 135.

[0024] The filament power supply unit 110 adjusts the filament current based on the tube current detected by the tube current control unit 130. The overcurrent protection circuit 135 is configured to determine whether or not an overcurrent occurs based on a comparison between the current value detected by the tube current control unit 130 and a threshold value, and to stop the output of the high-voltage power supply unit 120 if an overcurrent occurs.

[0025] Similarly, overcurrent protection circuit 125, which is arranged on the output side of high-voltage power supply unit 120, detects the current flowing through power line L5 by converting it into a voltage value using resistor R5. If an overcurrent state continues for a certain period of time, overcurrent protection circuit 125 stops the output of high-voltage power supply unit 120.

[0026] Detection circuit 140 is connected to power line L4 and is configured to detect the voltage applied to power line L4. As will be described later with reference to FIG. 2, detection circuit 140 steps down the voltage applied to power line L4 using a plurality of resistors connected in series and detects fluctuations in the stepped-down voltage. Detection circuit 140 is connected to control device 400 at terminal T3 of power supply device 100. Control device 400 detects the occurrence of a discharge in a high-voltage circuit including X-ray tube 200 based on the voltage fluctuation detected by detection circuit 140. Here, the high-voltage circuit is a general term for a circuit to which a high voltage output from high-voltage power supply unit 120 is applied, and includes X-ray tube 200, high-voltage power supply unit 120, and power line L4.

[0027] As mentioned above, devices that include an X-ray generator, such as an X-ray fluorescence analyzer, are generally equipped with an overcurrent protection circuit to protect the circuit from overcurrent caused by electrical discharge. However, if an electrical discharge occurs at a level that cannot be detected by the overcurrent detection mechanism included in the overcurrent protection circuit, the device may continue to be used without the protection circuit taking action. Furthermore, if electrical discharges that cannot be detected by the overcurrent detection mechanism occur intermittently, this can result in deterioration or failure of the power supply device or X-ray tube.

[0028] To detect such discharges, it is possible to increase the detection sensitivity by lowering the threshold value for detecting overcurrent in the overcurrent detection mechanism, but if the threshold value is lowered too much, current fluctuations within the normal operating range may cause false detection, which may result in malfunction of the protection circuit.In addition, it is possible to increase the response speed of the overcurrent protection circuit, but increasing the response speed may increase the risk of the protection circuit malfunctioning due to load fluctuations or noise.

[0029] Another method for detecting overcurrent occurrence is to detect a drop in the high-voltage output voltage during discharge. In this case, a differentiating circuit consisting of a resistor and a capacitor is typically used to detect the voltage drop. However, this requires connecting the differentiating circuit to the high-voltage line. Adding such a circuit separately to a conventional circuit requires a high-voltage capacitor. This increases the component cost of the capacitor itself, and may also increase the cost of mounting and insulating molding materials. Furthermore, adding a capacitor increases the size of the power supply device.

[0030] Therefore, in the X-ray fluorescence analyzer 10 of this embodiment, in addition to the conventional overcurrent protection circuit 125, a detection circuit 140 is provided for detecting voltage fluctuations in the power line L4 on the output side of the high-voltage power supply unit 120. By providing this detection circuit 140, it becomes possible to detect an abnormality due to an output short circuit using the overcurrent protection circuit 125 and to detect a momentary discharge using the detection circuit 140. In particular, in this embodiment, as will be described later with reference to FIG. 2, the detection circuit 140 is constructed using an existing feedback circuit for voltage control of the high-voltage power supply unit 120. Therefore, compared to when the detection circuit 140 is provided separately, it is possible to achieve the desired function with fewer additional components and at relatively low cost.

[0031] (Detection circuit configuration) Fig. 2 is a diagram showing details of detection circuit 140 in Fig. 1. Referring to Fig. 2, detection circuit 140 includes resistors R10, RF1 to RF10, capacitors C10, CF1 to CF10, a low-pass filter 141, a high-pass filter 142, an amplifier 143, a comparator (CMP) 144, a resistor R15, and an operational amplifier OP2. Note that the capacitors indicated by CS1 to CS10 in Fig. 2 are schematic representations of parasitic capacitances occurring between each resistor and ground potential GND, and no physical elements are actually arranged.

[0032] Resistors RF1 to RF10 and resistor R10 are connected in series in this order between power line L4 and ground potential GND. Resistors RF1 to RF10 are resistors for stepping down the voltage applied to power line L4. Resistor R10 is a voltage dividing resistor R10 for setting the voltage at connection node N10 between resistor RF10 and resistor R10.

[0033] The connection node N10 is connected to a terminal T3 for output to the detection circuit 140 via a low-pass filter 141, a high-pass filter 142, a resistor R15, an operational amplifier OP2, an amplifier 143 and a comparator 144.

[0034] In order to improve the efficiency of the high-voltage power supply unit 120 by sufficiently reducing the current flowing through the resistors RF1 to RF10 relative to the current flowing through the power line L4, it is necessary to set the resistance value of each of the resistors RF1 to RF10 to a high resistance. As an example, if the resistance value of each of the resistors RF1 to RF10 is set to 200 MΩ and the resistance value of the resistor R10 is set to 75 kΩ, the high voltage of 5 kV to 65 kV applied to the power line L4 can be reduced to approximately several volts at the connection node N10. Note that while FIG. 2 illustrates a configuration using ten resistors as the step-down resistors RF1 to RF10, the number of resistors may be any number other than ten as long as the voltage can be reduced to the desired level.

[0035] The capacitors CF1 to CF10 are connected in parallel to the resistors RF1 to RF10, respectively. The capacitor C10 is connected in parallel to the resistor R10 between the connection node N10 and the ground potential GND.

[0036] The low-pass filter 141 includes a resistor R11 having one end connected to the connection node N10 and a capacitor C11 connected between the other end of the resistor R11 and the ground potential GND. The low-pass filter 141 passes signals in a frequency band lower than a cutoff frequency determined by the resistor R11 and the capacitor C11. The signal that passes through the low-pass filter 141 is supplied to the high-pass filter 142 and is also used as a feedback control signal FBK in the high-voltage power supply unit 120.

[0037] The high-pass filter 142 includes a capacitor C12 having one end connected to the other end of the resistor R11, and a resistor R12 connected between the other end of the capacitor C12 and the ground potential GND. The high-pass filter 142 passes signals in a frequency band higher than the cutoff frequency determined by the resistor R12 and the capacitor C12.

[0038] The operational amplifier OP2 is a voltage follower type operational amplifier. The non-inverting input of the operational amplifier OP2 is connected to the other end of the capacitor C12 in the high-pass filter 142 via a resistor R15. The inverting input of the operational amplifier OP2 is connected to the output terminal of the operational amplifier OP2. The operational amplifier OP2 functions as a buffer and serves to isolate the circuits following the amplifier 143. The resistor R15 is a protective resistor that prevents excessive current from flowing through the operational amplifier OP2.

[0039] If the high-pass filter 142 and the amplifier 143 are directly connected, the resistor R12 of the high-pass filter 142 and the resistor R13 of the amplifier 143 appear to be electrically parallel, and the combined resistance of the resistors R12 and R13 may result in the cutoff frequency of the high-pass filter 142 not being as designed. Therefore, in the circuit of Figure 2, an operational amplifier OP2 is disposed between the high-pass filter 142 and the amplifier 143 to electrically isolate the high-pass filter 142 and the amplifier 143. Note that if the resistance values ​​of the resistors are designed taking the above-mentioned conditions into consideration, the operational amplifier OP2 is not necessarily required.

[0040] The amplifier 143 includes an operational amplifier OP1 and resistors R13 and R14. One end of the resistor R13 is connected to the output terminal of the operational amplifier OP2, and the other end of the resistor R13 is connected to one end of the resistor R14. The other end of the resistor R13 is also connected to the inverting input of the operational amplifier OP1. The non-inverting input of the operational amplifier OP1 is connected to the ground potential GND, and the output terminal is connected to the other end of the resistor R14. In other words, the operational amplifier OP1 and the resistors R13 and R14 form an inverting amplifier. The other end of the resistor R14 is further connected to the comparator 144.

[0041] Comparator 144 compares the signal that has passed through low-pass filter 141, high-pass filter 142, and amplifier 143 with a reference potential. For example, comparator 144 outputs a Hi (first state) signal when the signal is lower than the reference potential, and outputs a Lo (second state) signal when the signal is higher than the reference potential. When the output signal from comparator 144 changes from Hi to Lo, detection circuit 140 detects that a discharge has occurred in the high-voltage circuit including X-ray tube 200. Note that the output signal of comparator 144 may be set to Lo when the input signal is lower than the reference potential, and to Hi when the input signal is higher than the reference potential.

[0042] (Discharge detection process) Next, the discharge detection process executed by the control device 400 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a functional block diagram of the control device 400 of Fig. 1. Fig. 4 is a flowchart for explaining the discharge detection process executed by the control device 400.

[0043] The control device 400 includes a counter circuit 410, a comparison circuit 420, and a notification circuit 430. The circuits included in the control device 400 are realized by, for example, a programmable logic controller (PLD) and / or a central processing unit (CPU).

[0044] In step (hereinafter, step will be abbreviated as S) 100, control device 400 uses counter circuit 410 to count the number of times the output signal from comparator 144 in detection circuit 140 switches from Hi to Lo, i.e., the number of times a discharge occurs in the high-voltage circuit including X-ray tube 200. Then, in S110, control device 400 next uses comparison circuit 420 to compare the count value of counter circuit 410 with a predetermined reference value, and determines whether the count value exceeds the reference value.

[0045] If the count value is equal to or less than the reference value (NO in S110), the control device 400 retains the count value and skips the subsequent processing. If the count value exceeds the reference value (YES in S110), the control device 400 proceeds to S120, determines that a discharge abnormality has occurred, and outputs a signal to the notification circuit 430. The notification circuit 430 is configured with a display device capable of visually displaying information such as a lamp or LCD screen, or a device capable of outputting a buzzer or audio output, and notifies the user visually and / or audibly that a predetermined number of discharges have occurred (S130). This allows the user to know of signs of abnormality and / or deterioration in the X-ray generator.

[0046] The determination of the discharge abnormality is not limited to the determination based on the comparison of the count value with the reference value, but may be based on, for example, the fluctuation of the count number per hour. Specifically, if it is detected that the count number per hour is on the rise, it may be determined that the discharge abnormality has occurred.

[0047] (Detection circuit features) 2, a tenth-order low-pass filter is formed by the resistors RF1 to RF10 and their parasitic capacitances CS1 to CS10 connected in series. In this case, due to the time constant of the low-pass filter formed by each resistor and the parasitic capacitance, a change in the feedback signal FBK is delayed when the output of the high-voltage power supply unit 120 fluctuates.

[0048] As a result, feedback control slows the response speed of the high-voltage power supply unit 120 and the detection circuit 140, resulting in greater fluctuations in the output from the high-voltage power supply unit 120 due to input or load fluctuations or disturbances. This increases the variability in the intensity of the X-rays emitted from the X-ray tube, which can affect the stability of the analysis results. Furthermore, if the response of the high-voltage power supply unit 120 slows, it takes longer to reach the desired output when the output voltage of the high-voltage power supply unit 120 is changed, resulting in a longer time required for analysis.

[0049] On the other hand, if a discharge or output short circuit occurs, the charge stored in each parasitic capacitance flows through resistors RF1 to RF10 into power line L4. At this time, a higher voltage is applied to resistors RF1 to RF10 that are closer to power line L4, which can cause the resistors to malfunction or deteriorate. Because resistors RF1 to RF10 are components that affect the accuracy and stability of the output voltage of high-voltage power supply unit 120, malfunction or deterioration of any of these resistors can also affect analysis accuracy.

[0050] In particular, the high-voltage parts of the power supply device 100 are generally sealed with a dielectric (molding material) that has a higher dielectric constant than air in order to ensure a substantial separation distance, which increases the parasitic capacitance of the molding material and makes the effects of the above problems more pronounced.

[0051] To solve this problem, in the power supply device 100 according to the embodiment, capacitors CF1 to CF10 are connected in parallel to resistors RF1 to RF10, respectively. By making the capacitance values ​​of these parallel-connected capacitors CF1 to CF10 sufficiently larger than the parasitic capacitances CS1 to CS10, the influence of the parasitic capacitances CS1 to CS10 can be ignored, and the high-frequency gain of the voltage fluctuation can be increased. This reduces the aforementioned decrease in response speed and the influence of high voltage application to resistors RF1 to RF10 when a discharge occurs. As an example, assuming that the parasitic capacitance generated in each resistor is a maximum of 10 pF, the influence of the parasitic capacitance can be reduced by setting the capacitance of capacitors CF1 to CF10 to approximately 100 pF.

[0052] In order to improve the detection sensitivity in detecting electric discharges, it is necessary to set the reference potential set in the comparator 144 as low as possible so that small voltage fluctuations can be detected. On the other hand, it is necessary to prevent voltage fluctuations during normal operation of the X-ray generator from being erroneously detected as electric discharges.

[0053] The following two factors are considered to be factors that cause voltage fluctuations during normal operation. The first is voltage fluctuations that occur when the output voltage is intentionally changed, such as during the boost operation when the X-ray generator is started up and when the output voltage setting of the high-voltage power supply unit 120 is changed. The second is voltage fluctuations caused by ripples that accompany the switching operation of a boost power conversion device included in the high-voltage power supply unit 120.

[0054] In the detection circuit 140 according to the embodiment, the voltage fluctuations accompanying the normal operation are separated by frequency using the low-pass filter 141 and the high-pass filter 142 to prevent erroneous detection. Generally, intentional changes in the output voltage generally result in voltage fluctuations that are slower than voltage fluctuations during discharge, and therefore the influence of these voltage fluctuations is removed by the high-pass filter 142. Furthermore, voltage fluctuations accompanying ripples depend on the switching frequency of the power conversion device and have a frequency that is relatively higher than voltage fluctuations during discharge, and therefore the influence of these voltage fluctuations is removed by the low-pass filter 141.

[0055] As an example, if the capacitance CCW value of the Cockcroft-Walton circuit included in the high-voltage power supply unit 120 is 144 pF, the capacitance value of each of capacitors CF1 to CF10 is 100 pF, and the resistance value of resistor R4 is 50 kΩ, the frequency of the voltage fluctuation at the output terminal of the high-voltage power supply unit 120 when a discharge occurs is approximately 21 kHz. On the other hand, changes in the output voltage setting are gradual changes of about 16 Hz, and the frequency of the ripple voltage is, for example, approximately 60 kHz.

[0056] Therefore, for example, by setting the cutoff frequency of high-pass filter 142 to 1.6 kHz and the cutoff frequency of low-pass filter 141 to 30 kHz, it is possible to detect voltage fluctuations due to discharge while eliminating the effects of voltage fluctuations caused by changes in the output voltage setting and the effects of voltage fluctuations caused by ripples. Note that the cutoff frequency of low-pass filter 141 may be set to approximately 16 kHz in practice, as long as it is possible to eliminate the effects of ripple voltage.

[0057] FIG. 5 is a diagram for explaining a discharge voltage detection region in the detection circuit of FIG. 1. In FIG. 5, the horizontal axis represents frequency, and the vertical axis represents the voltage of the signal input to the comparator 144. In FIG. 5, the line LN11 indicates the passing characteristics of the low-pass filter 141, and the line LN12 indicates the passing characteristics of the high-pass filter 142.

[0058] The cut-off frequency f1 of the high-pass filter 142 is lower than the cut-off frequency f2 of the low-pass filter 141 (f1 < f2). As shown in FIG. 5, the low-pass filter 141 and the high-pass filter 142 constitute a band-pass filter having a frequency band from f1 to f2 as the passing band. That is, the region RG1 in FIG. 5 is a region where voltage fluctuations can occur with changes in the output voltage, and the region RG2 is a region where voltage fluctuations can occur due to the ripple voltage. By appropriately adjusting the cut-off frequencies f1 and f2 as in the above example and setting the region RG3 for detecting the discharge voltage, it is possible to detect voltage fluctuations due to discharge while eliminating the influence of voltage fluctuations associated with changes in the output voltage setting and the influence of voltage fluctuations associated with the ripple.

[0059] The "power line L4" in the embodiment corresponds to the "power supply wiring" in the present disclosure. The "resistor R10" in the embodiment corresponds to the "first resistor element" in the present disclosure. Each of the "resistors RF1 to RF10" in the embodiment corresponds to the "second resistor element" in the present disclosure.

[0060] <Modification Example 1> FIG. 6 is a diagram showing details of the detection circuit 140A of Modification Example 1. In the detection circuit 140A, the resistor R10 and the capacitor C10 in FIG. 2 are replaced with a resistor R10A and a capacitor C10A, respectively, and the amplifier 143 is deleted. In FIG. 6, the description of the elements overlapping with FIG. 2 will not be repeated.

[0061] 6, capacitor C10A has a smaller capacitance than capacitor C10. In the case of detecting a discharge, the voltage fluctuation is instantaneous, in other words, a high-frequency signal, so the response of the detection circuit to the high-frequency signal (high-frequency gain) becomes important. In the case of a high-frequency signal, voltage is divided by a capacitor rather than a resistor, so by making the capacitance of capacitor C10A smaller than that of capacitor C10, the potential at connection node N10 becomes higher than in the case of detection circuit 140.

[0062] Therefore, by appropriately adjusting the capacitance value of capacitor C10A, it is possible to omit amplifier 143. This reduces the number of components, which contributes to cost reduction.

[0063] In the above example, the high frequency gain is increased by making the capacitance value of capacitor C10A smaller than that of capacitor C10, but instead, the high frequency gain may be increased by making the capacitance values ​​of capacitors CF1A to CF10A larger.

[0064] <Variation 2> Fig. 7 is a diagram showing details of detection circuit 140B of Modification 2. Detection circuit 140B has a configuration in which low-pass filter 141 in Fig. 2 is deleted. In Fig. 7, descriptions of elements that overlap with those in Fig. 2 will not be repeated.

[0065] 7 is applicable to devices in which the level of ripple voltage is relatively small in the boost circuit of the high-voltage power supply unit 120. In this case as well, the reduction in the number of parts can contribute to cost reduction.

[0066] In addition, in the detection circuit 140B, as in the first modification, it is also possible to remove the amplifier 143 by adjusting the capacitor C10.

[0067] The high-pass filter 142 is provided to prevent erroneous detection when there is a gradual change in the output voltage from the high-voltage power supply unit 120. However, in the discharge detection process of the control device 400, it is also possible to omit the high-pass filter 142 by masking discharge detection during the period from when the X-ray generator is started up to when the voltage rises to a predetermined voltage, or during the period when the voltage setting value is changed.

[0068] [Note] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0069] (Item 1) An X-ray fluorescence analyzer according to one embodiment includes an X-ray tube, a detector, a power supply, and a control device. The X-ray tube includes a filament and a target and irradiates a sample with primary X-rays. The detector detects secondary X-rays generated from the sample. The power supply applies a tube voltage to the target. The control device detects the occurrence of a discharge in a high-voltage circuit including the X-ray tube. The power supply includes a high-voltage power supply unit that generates the tube voltage, a power supply line that transmits the tube voltage from the high-voltage power supply unit to the target, and a detection circuit connected to the power supply line. The detection circuit is configured to detect voltage fluctuations in the X-ray tube. The detection circuit includes a first resistor element having one end connected to a ground potential, multiple second resistor elements connected in series between the other end of the first resistor element and the power supply line, multiple capacitors connected in parallel to each of the multiple second resistor elements, and a high-pass filter connected to the other end of the first resistor element. The control device detects the occurrence of a discharge in the high-voltage circuit based on a signal from the detection circuit.

[0070] According to the X-ray fluorescence analyzer of paragraph 1, the tube voltage supplied from the high-voltage power supply to the X-ray tube is stepped down using multiple second resistor elements, each with a capacitor connected in parallel, and the occurrence of a discharge in the high-voltage circuit including the X-ray tube is detected based on a signal obtained by passing the stepped-down signal through a high-pass filter. Stepping down the tube voltage using second resistor elements with capacitors connected in parallel eliminates the influence of the low-pass filter formed by the second resistor elements and parasitic capacitance, enabling high-response detection of voltage fluctuations in the tube voltage, i.e., the occurrence of a discharge. Furthermore, passing the stepped-down signal through a high-pass filter prevents erroneous detection of gradual voltage fluctuations that may occur during normal analytical operation as a discharge. Because relatively low-voltage components can be used for the elements used in the detection circuit, the accuracy of discharge detection can be improved while suppressing increases in cost.

[0071] (Item 2) In the fluorescent X-ray analyzer described in item 1, the detection circuit further includes an amplifier that is provided in a path connecting the other end of the first resistor element and the control device, and that amplifies the signal that has passed through the high-pass filter.

[0072] According to the X-ray fluorescence analyzer of paragraph 2, the signal obtained by reducing the tube voltage using the second resistive element is amplified by an amplifier after passing through a high-pass filter, thereby increasing the voltage level of the reduced signal, making it possible to detect discharge even when voltage fluctuations are small.

[0073] (Item 3) In the fluorescent X-ray analyzer described in item 1, the detection circuit further includes a low-pass filter provided in a path connecting the other end of the first resistor element and the control device and connected in series with the high-pass filter. The cutoff frequency of the high-pass filter is lower than the cutoff frequency of the low-pass filter.

[0074] According to the X-ray fluorescence analyzer of paragraph 3, by applying a low-pass filter having a cutoff frequency higher than that of the high-pass filter, it is possible to remove the influence of noise with a frequency higher than that of the discharge, such as the ripple voltage generated in the high-voltage power supply, thereby further improving the accuracy of discharge detection.

[0075] (Item 4) In the fluorescent X-ray analyzer described in item 3, the detection circuit further includes an amplifier that amplifies a signal that has passed through a high-pass filter and a low-pass filter provided in a path connecting the other end of the first resistive element and the control device.

[0076] According to the X-ray fluorescence analyzer of paragraph 4, the signal obtained by reducing the tube voltage using the second resistive element is passed through a high-pass filter and a low-pass filter, and then amplified by an amplifier, thereby increasing the voltage level of the reduced signal, making it possible to detect discharge even when the voltage fluctuation is small.

[0077] (Item 5) In the fluorescent X-ray analyzer according to any one of Items 1 to 4, the detection circuit further includes a comparator configured to compare the signal that has passed through the high-pass filter with a reference value. The control device detects the occurrence of a discharge in the high-voltage circuit based on the output signal from the comparator.

[0078] (Item 6) In the fluorescent X-ray analyzer described in Item 5, the comparator changes the output signal from the first state to the second state when the signal that has passed through the high-pass filter exceeds a reference value. The control device determines that a discharge has occurred when the output signal from the comparator changes to the second state.

[0079] (Item 7) In the fluorescent X-ray analyzer described in item 6, the control device notifies the user when a predetermined number of discharges have occurred.

[0080] According to the X-ray fluorescence analyzer of paragraph 7, by notifying the user when a predetermined number of discharges have occurred, the user can properly recognize signs of abnormality or deterioration in the X-ray generator.

[0081] (Item 8) A power supply device according to one aspect applies a tube voltage to an X-ray tube including a filament and a target. The power supply device includes a high-voltage power supply unit that generates the tube voltage, a power supply line that transmits the tube voltage from the high-voltage power supply unit to the target, and a detection circuit connected to the power supply line. The detection circuit is configured to detect voltage fluctuations in the high-voltage circuit including the X-ray tube. The detection circuit includes a first resistive element having one end connected to a ground potential, a plurality of second resistive elements connected in series between the other end of the first resistive element and the power supply line, a plurality of capacitors connected in parallel to each of the plurality of second resistive elements, a high-pass filter connected to the other end of the first resistive element, and a comparator configured to compare a signal that has passed through the high-pass filter with a reference value.

[0082] (Item 9) An X-ray fluorescence analyzer according to one embodiment includes an X-ray tube, a detector, a power supply, and a control device. The X-ray tube includes a filament and a target and irradiates a sample with primary X-rays. The detector detects secondary X-rays generated from the sample. The power supply applies a tube voltage to the target. The control device detects the occurrence of a discharge in a high-voltage circuit including the X-ray tube. The power supply includes a high-voltage power supply unit that generates the tube voltage, a power supply line that transmits the tube voltage from the high-voltage power supply unit to the target, and a detection circuit connected to the power supply line. The detection circuit is configured to detect voltage fluctuations in the high-voltage circuit. The detection circuit includes a first resistor element having one end connected to a ground potential, multiple second resistor elements connected in series between the other end of the first resistor element and the power supply line, and multiple capacitors connected in parallel to each of the multiple second resistor elements. The control device detects the occurrence of a discharge in the high-voltage circuit based on the signal from the detection circuit when the rate of change of the signal from the detection circuit is greater than or equal to a predetermined value.

[0083] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0084] 10 X-ray fluorescence analyzer, 100 power supply, 110 filament power supply unit, 111 filament current control unit, 120 high-voltage power supply unit, 125, 135 overcurrent protection circuit, 130 tube current control unit, 140, 140A, 140B detection circuit, 141 low-pass filter, 142 high-pass filter, 143 amplifier, 144 comparator, 200 X-ray tube, 300 detector, 400 control device, 410 counter circuit, 420 comparison circuit, 430 notification circuit, B1 primary X-ray, B2 fluorescent X-ray, C10 to C12, C10A, CF1 to CF10 capacitors, CF1 to CF10 capacitors, CS1 to CS10 parasitic capacitance, D1, D2 protection circuit, f1, f2 cutoff frequency, F1 filament, GND ground potential, L1 to L5 power line, N10, NP1 Connection node, OP1, OP2 operational amplifier, R1 to R5, R10 to R15, R10A, RF1 to RF10 resistors, RG1 to RG3 area, S sample, T1 to T3, TF1, TF2 terminals, TG1 target.

Claims

1. an X-ray tube including a filament and a target for irradiating a sample with primary X-rays; a detector for detecting secondary X-rays generated from the sample; a power supply device that applies a tube voltage to the target; a control device that detects the occurrence of a discharge in a high voltage circuit including the X-ray tube; The power supply device a high-voltage power supply unit that generates the tube voltage; a power supply wiring that transmits the tube voltage from the high-voltage power supply unit to the target; a detection circuit connected to the power supply wiring and configured to detect voltage fluctuations in the high voltage circuit; The detection circuit a first resistor element having one end connected to a ground potential; a plurality of second resistor elements connected in series between the other end of the first resistor element and the power supply wiring; a plurality of capacitors connected in parallel to the plurality of second resistor elements, respectively; a high-pass filter connected to the other end of the first resistor element, The control device detects the occurrence of a discharge in the high voltage circuit based on a signal from the detection circuit.

2. 2. The X-ray fluorescence analysis apparatus according to claim 1, wherein the detection circuit further includes an amplifier provided in a path connecting the other end of the first resistor element and the control device, the amplifier amplifying the signal that has passed through the high-pass filter.

3. the detection circuit further includes a low-pass filter that is provided in a path connecting the other end of the first resistance element and the control device and is connected in series with the high-pass filter; The X-ray fluorescence analyzer according to claim 1 , wherein the cutoff frequency of the high-pass filter is lower than the cutoff frequency of the low-pass filter.

4. 4. The X-ray fluorescence analysis apparatus according to claim 3, wherein the detection circuit further includes an amplifier that amplifies the signal that has passed through the high-pass filter and the low-pass filter and that is provided in a path connecting the other end of the first resistance element and the control device.

5. the detection circuit further includes a comparator configured to compare the high-pass filtered signal with a reference value; 5. The X-ray fluorescence analyzer according to claim 1, wherein the control device detects occurrence of discharge in the high voltage circuit based on an output signal from the comparator.

6. the comparator changes an output signal from a first state to a second state when the signal that has passed through the high-pass filter exceeds the reference value; 6. The X-ray fluorescence analysis apparatus according to claim 5, wherein the control device determines that a discharge has occurred when the output signal from the comparator is in the second state.

7. The X-ray fluorescence analyzer according to claim 6 , wherein the control device notifies a user when a predetermined number of discharges have occurred.

8. A power supply device that applies a tube voltage to an X-ray tube including a filament and a target, The power supply device a high-voltage power supply unit that generates the tube voltage; a power supply wiring that transmits the tube voltage from the high-voltage power supply unit to the target; a detection circuit connected to the power supply wiring and configured to detect voltage fluctuations in a high voltage circuit including the X-ray tube; The detection circuit a first resistor element having one end connected to a ground potential; a plurality of second resistor elements connected in series between the other end of the first resistor element and the power supply wiring; a plurality of capacitors connected in parallel to the plurality of second resistor elements, respectively; a high-pass filter connected to the other end of the first resistor; a comparator configured to compare the high-pass filtered signal with a reference value.

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