High-voltage power supply device

Abstract

A high voltage power supply device is provided. Noise superimposed on an output voltage is reduced. One embodiment of the high voltage power supply device according to the present invention includes: a voltage generating portion that outputs a direct-current high voltage; a switching portion that outputs an output voltage of the voltage generating portion to a voltage output terminal when turned on, using a semiconductor switching element; a driving portion that drives a control terminal of the semiconductor switching element in the switching portion; and a control portion that controls turning on and turning off of the switching portion through the driving portion, the driving portion including: a high-frequency transformer having a primary winding and a secondary winding, a distribution of a parasitic capacitance per unit number of turns of the primary winding in an extension direction of the primary winding with respect to a midpoint of the primary winding being symmetrical between the primary winding and the secondary winding; a rectifying portion that rectifies an alternating current excited in the secondary winding of the high-frequency transformer; and a high-frequency exciting portion of a balanced output type that differentially excites the primary winding of the high-frequency transformer.

Description

Technical Field

[0001] This invention relates to a high-voltage power supply device. Background Technology

[0002] In mass spectrometry, various compounds in a sample are ionized, and the generated ions are separated and detected according to their mass-to-charge ratio (m / z). The compounds are then identified or quantified based on the detection signal. These compounds include those that readily undergo positive ionization and those that readily undergo negative ionization. Therefore, gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) systems typically have the capability to repeatedly perform measurements while alternately switching between positive and negative ion detection modes.

[0003] In both positive and negative ion measurement modes, it is necessary to switch the polarity of the voltages applied to various structural elements of the mass spectrometer, such as the ion source, mass separator, and ion detector. To rapidly switch between positive and negative ion measurement modes, it is essential to rapidly switch the polarity of each applied voltage. Therefore, a high-voltage power supply capable of rapidly switching the polarity of the output voltage is used.

[0004] As one type of high-voltage power supply device, the device described in Patent Document 1 is known. This high-voltage power supply device includes: a positive voltage generator that generates a positive DC high voltage +HV; a negative voltage generator that generates a negative DC high voltage -HV; a discharge diode connected in such a way that it is reverse-biased when the output voltages of the positive and negative voltage generators are output; a positive-side high-voltage switch that, when turned on, connects the output terminal of the positive voltage generator to a switching voltage output terminal, which is the voltage output terminal of the high-voltage power supply device; a negative-side high-voltage switch that, when turned on, connects the output terminal of the negative voltage generator to the aforementioned switching voltage output terminal; and an output capacitor connected in parallel with a load connected to the switching voltage output terminal to stabilize the load potential.

[0005] When outputting a positive high voltage to the load, the positive high voltage switch is turned on and the negative high voltage switch is turned off, activating the positive voltage generator and deactivating the negative voltage generator. Conversely, when outputting a negative high voltage to the load, the positive high voltage switch is turned off and the negative high voltage switch is turned on, deactivating the positive voltage generator and activating the negative voltage generator. In either case, the output capacitor and other components are charged using the power supplied to the load from either the positive or negative voltage generator. When switching the polarity of the output voltage, both voltage generators are temporarily deactivated, while both high voltage switches are turned on. As a result, the charge originally stored in the output capacitor or the rectifier capacitors included in each voltage generator is discharged through a discharge diode of one of the voltage generators.

[0006] In the aforementioned high-voltage power supply devices, it is simple to use DC-driven mechanical relays as high-voltage switches from a circuit perspective. However, mechanical relays are prone to malfunctions due to wear and tear of mechanical contacts, making it difficult to ensure high reliability over long periods. Furthermore, the switching speed is limited, making it difficult to handle the rapid changes in voltage polarity. Additionally, circuit design must account for chattering bounce. In contrast, by using semiconductor switching elements such as power MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) as high-voltage switches, most of these problems can be solved.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 6516062 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] In the use of semiconductor switching elements, a gate drive circuit is required to turn the element on / off. In high-voltage power supply devices, there exists a mixture of high-voltage circuits handling voltages of several hundred volts or higher and low-voltage control circuits handling voltages of several volts or lower. Therefore, gate drive circuits employing isolation methods are common for purposes such as protecting low-voltage circuits. One known example of such a circuit is a gate drive circuit comprising a transformer, an excitation circuit that excites the primary winding of the transformer with a high-frequency signal, and a rectifier circuit that rectifies the alternating current induced in the secondary winding of the transformer. In this gate drive circuit, when a current based on a high-frequency signal is supplied from the excitation circuit to the primary winding of the transformer, an alternating current is induced in the secondary winding of the transformer. The direct current obtained by rectifying this alternating current using the rectifier circuit is charged into a capacitor (and the parasitic capacitance of the gate, etc.) connected between the gate and source of the semiconductor switching element. When the charging voltage of this capacitor exceeds the gate threshold voltage of the semiconductor switching element, the semiconductor switching element is turned on.

[0012] When using the gate drive circuit described above, high-frequency noise originating from the high-frequency signal generated by the excitation circuit is sometimes superimposed on the output voltage of the high-voltage power supply device. For example, when this noise is superimposed on the high voltage applied to the ion ejection section or flight tube in a time-of-flight mass spectrometer, there is a concern about performance degradation such as mass resolution or mass accuracy. One way to mitigate the high-frequency noise appearing in the output voltage is to increase the electrostatic capacitance of the output capacitor used to stabilize the output voltage. However, if the electrostatic capacitance of the output capacitor is increased, the amount of charge charged and discharged to the output capacitor when the polarity of the output voltage is reversed increases, which raises concerns about, for example, an increase in the polarity reversal time.

[0013] The present invention was made to solve the above-mentioned problems. Its main objective is to reduce the noise superimposed on the output voltage from the gate drive circuit of the semiconductor switching element in a high-voltage power supply device that uses a semiconductor switching element in the switching or on / off operation of the output voltage.

[0014] Solution for solving the problem

[0015] One embodiment of the high-voltage power supply device according to the present invention, which is made to solve the above-mentioned problems, comprises:

[0016] The voltage generator outputs a high DC voltage.

[0017] The switching section using a semiconductor switching element outputs the output voltage of the voltage generator to the voltage output terminal when it is turned on;

[0018] The driving unit drives the control terminals of the semiconductor switching elements in the switching unit; and

[0019] The control unit controls the conduction and deconduction of the switching unit via the drive unit.

[0020] The driving unit includes:

[0021] A high-frequency transformer having a primary winding and a secondary winding, wherein the parasitic capacitance per unit number of turns of the primary winding between the primary winding and the secondary winding is symmetrical about the midpoint of the primary winding in the direction of extension of the primary winding.

[0022] A rectifier section that rectifies the alternating current induced in the secondary winding of the high-frequency transformer; and

[0023] A balanced output type high-frequency excitation unit differentially excites the primary winding of the high-frequency transformer.

[0024] The effects of the invention

[0025] According to the above-described manner of the high-voltage power supply device of the present invention, common-mode noise generated at the voltage output terminal due to the excitation of the high-frequency transformer can be suppressed regardless of the size of the parasitic capacitance between the primary and secondary windings of the high-frequency transformer. This reduces the noise superimposed on the output voltage of the high-voltage power supply device, primarily caused by the gate drive circuit. Furthermore, it is not necessary to increase the electrostatic capacitance of the output capacitor to a required level, thus shortening the time required for polarity switching or voltage rise of the output voltage. Additionally, by suppressing the electrostatic capacitance of the output capacitor, its miniaturization and weight reduction can be achieved, which is also advantageous for the miniaturization and weight reduction of the high-voltage power supply device itself.

[0026] When the high-voltage power supply device described above is applied to high-voltage power supplies for ion emission or flight tubes in, for example, time-of-flight mass spectrometry analyzers, mass resolution or mass accuracy can be improved by reducing noise superimposed on the output voltage. Furthermore, by suppressing the electrostatic capacitance of the output capacitor, analysis time can be shortened, and measurements can be performed virtually simultaneously while switching between positive and negative ion measurement modes. Attached Figure Description

[0027] Figure 1 This is a schematic block diagram of a polarity-switching high-voltage power supply device as one embodiment of the present invention.

[0028] Figure 2 This is a schematic structural diagram of the gate drive unit in the polarity switching high-voltage power supply device of this embodiment.

[0029] Figure 3 This is a schematic diagram of the gate drive section using an unbalanced output type excitation section.

[0030] Figure 4 This is an illustration of the parasitic capacitance between the primary and secondary windings of a high-frequency transformer.

[0031] Figure 5 This is a schematic diagram illustrating the common-mode current flowing in the parasitic capacitance of the high-frequency transformer included in the gate drive section of the polarity-switching high-voltage power supply device of this embodiment (in the case where the primary winding of the high-frequency transformer is a separate primary winding).

[0032] Figure 6 This is a schematic diagram illustrating the common-mode current flowing in the parasitic capacitance of the high-frequency transformer included in the gate drive section of the polarity-switching high-voltage power supply device of this embodiment (in the case where the primary windings of multiple high-frequency transformers are connected in series).

[0033] Figure 7This is an illustration of the common-mode current flowing through the parasitic capacitance when the distribution of the parasitic capacitance of the high-frequency transformer is asymmetrical relative to the midpoint of the primary winding.

[0034] Figure 8 This is an illustration of the common-mode current flowing in the parasitic capacitance when using an unbalanced output type excitation unit and the distribution of the parasitic capacitance of the high-frequency transformer is symmetrical with respect to the midpoint of the primary winding.

[0035] Figure 9 This diagram illustrates an example of a high-frequency transformer in the polarity-switching high-voltage power supply device of this embodiment.

[0036] Figure 10 Examples of measured waveforms of output noise in conventional polarity-switching high-voltage power supply devices (A) and examples of measured waveforms of output noise in the polarity-switching high-voltage power supply device of this embodiment (B) are shown. Detailed Implementation

[0037] The structure and operation of one embodiment of the high-voltage power supply device according to the present invention will be described below in comparison with devices based on prior art.

[0038] [Overall structure and general operation of the polarity switching high-voltage power supply device in this embodiment]

[0039] Figure 1 This is a schematic block diagram of the polarity switching high-voltage power supply device of this embodiment.

[0040] The polarity-switching high-voltage power supply device of this embodiment includes: a positive voltage generating unit 1 that generates a positive DC high voltage +HV; a negative voltage generating unit 2 that generates a negative DC high voltage -HV; a positive-side high-voltage switching unit 3 that includes multiple power MOSFETs 31 to 3N; a negative-side high-voltage switching unit 4 that also includes multiple power MOSFETs 41 to 4N; a positive-side driving unit 5 and a negative-side driving unit 6, wherein the positive-side driving unit 5 includes multiple gate driving units 51 to 5N that drive the multiple power MOSFETs 31 to 3N respectively, and the negative-side driving unit 6 includes multiple gate driving units 61 to 6N that drive the multiple power MOSFETs 41 to 4N respectively; an output capacitor 7 connected between a voltage output terminal 9 and ground (GND), wherein the voltage output terminal 9 is the connection terminal between the positive-side high-voltage switching unit 3 and the negative-side high-voltage switching unit 4; and a control unit 8.

[0041] This polarity-switching high-voltage power supply device is used to apply voltage to mass spectrometry analysis devices or electrophoresis devices. The absolute values ​​of the DC high voltage +HV and -HV are usually above 1kV, and even if they are low, they are around 400V to 500V or higher.

[0042] The positive voltage generator 1 and the negative voltage generator 2 can be configured to output DC high voltages +HV and -HV respectively, as long as they are controlled by the control unit 8. Their structures can be arbitrary. For example, as described in Patent Document 1, the positive voltage generator 1 and the negative voltage generator 2 can be configured to include: an excitation circuit that outputs a high-frequency AC signal; a rectifier circuit that converts the high-frequency AC signal into a DC high voltage; and a filter circuit that removes pulsating voltages contained in the DC high voltage. Additionally, a discharge diode may be included, connected in an orientation that reverses the voltage output by the positive voltage generator 1 and the negative voltage generator 2.

[0043] The positive-side high-voltage switching section 3 and the negative-side high-voltage switching section 4 are both high-voltage switching sections in which N power MOSFETs are connected in series. The power MOSFETs 31 to 3N included in the positive-side high-voltage switching section 3 are simultaneously switched on / off driven by N gate driving sections 51 to 5N. The power MOSFETs 41 to 4N included in the negative-side high-voltage switching section 4 are simultaneously switched on / off driven by N gate driving sections 61 to 6N.

[0044] The control unit 8 controls the voltage output operation of the positive voltage generator 1 and the negative voltage generator 2, and controls the gate drive units 51-5N and 61-61N, thereby driving the positive side high voltage switch unit 3 and the negative side high voltage switch unit 4 to turn on / off respectively. The control unit 8 can be configured around a microcomputer, such as a CPU, RAM, or ROM.

[0045] In the polarity-switching high-voltage power supply device of this embodiment, when the positive voltage generator 1 is turned on (operation state), the negative voltage generator 2 is turned off (stop state), the positive side high-voltage switch 3 is turned on (conduction state), and the negative side high-voltage switch 4 is turned off (non-conduction state), the output voltage HVout of the voltage output terminal 9 is a positive DC high voltage +HV. On the other hand, when the positive voltage generator 1 is turned off, the negative voltage generator 2 is turned on, the positive side high-voltage switch 3 is turned off, and the negative side high-voltage switch 4 is turned on, the output voltage HVout of the voltage output terminal 9 is a negative DC high voltage -HV. The control unit 8 controls the on / off operation of the positive voltage generator 1 and the negative voltage generator 2, as well as the on / off operation of the positive side high-voltage switch 3 and the negative side high-voltage switch 4, according to a preset program, thereby outputting a DC high voltage of +HV or -HV at the voltage output terminal 9. At this time, the output capacitor 7 has the function of stabilizing the potential of a load (not shown) connected to the voltage output terminal 9.

[0046] [The structure and problems of previous gate drive circuits]

[0047] As described above, the gate drive units 51-5N and 61-6N drive the gates (control terminals) of the power MOSFETs 31-3N and 41-4N to enable them to turn on / off. Here, the structure of the gate drive circuit of the prior art and its problems will be explained.

[0048] Figure 3 This is a schematic diagram of the conventional gate drive section.

[0049] The gate drive section 150 includes an excitation section 511, a high-frequency transformer 512, a rectifier section 505 including a rectifier diode 503 and a rectifier capacitor 504, and a discharge resistor 506.

[0050] When the excitation unit 511 is turned on, the high-frequency signal voltage output by the excitation unit 511 is applied to the primary winding 512a of the high-frequency transformer 512, and a high-frequency current flows through the primary winding 512a. Consequently, the alternating current generated in the secondary winding 512b of the high-frequency transformer 512 is rectified by the rectifier unit 505, charging the rectifier capacitor 504 (and the parasitic capacitance between the gate and source of the power MOSFET 30). When this charging voltage exceeds the gate threshold voltage of the power MOSFET 30, the power MOSFET 30 is turned on. When the excitation unit 511 is turned off, the charge stored in the rectifier capacitor 504 and the parasitic capacitance is mainly discharged through the discharge resistor 506, and the power MOSFET 30 is turned off.

[0051] Figure 4 This is an explanatory diagram of the parasitic capacitance between the primary winding 512a and the secondary winding 512b of the high-frequency transformer 512 used in the gate drive section 150 described above. There exists a parasitic capacitance 512c between the primary winding 512a and the secondary winding 512b, which is equivalent to the sum of multiple distributed capacitances C1, C2…Cn. (As shown...) Figure 4 As shown, when an unbalanced output type excitation unit 511 is connected to the primary winding 512a, the common-mode current flows along the path of excitation unit 511 → primary winding 512a → parasitic capacitance 512c → secondary winding 512b → secondary grounding capacitor 516 → ground. Consequently, common-mode noise corresponding to the common-mode current is generated in the secondary grounding capacitor 516.

[0052] That is, in the case of Figure 3 The gate drive unit 150 shown is applied to Figure 1In the case of the high-voltage power supply device shown, the common-mode current flows to the output node, that is, the voltage output terminal 9, through the parasitic capacitance 512c between the primary winding 512a and the secondary winding 512b of the high-frequency transformer 512. The common-mode noise is superimposed on the output noise originating from the voltage generating units 1 and 2, resulting in an increase in the noise of the output voltage.

[0053] In Figure 3 The gate drive unit 150 shown is applied to Figure 1 In the structure of the high-voltage power supply device shown, the magnitude of the common-mode noise observed at the voltage output terminal 9 is directly proportional to the amplitude of the excitation signal generated by the excitation unit 511 and the parasitic capacitance in the high-frequency transformer 512, and inversely proportional to the electrostatic capacitance of the output capacitor 7. Therefore, to reduce the common-mode noise, it is only necessary to reduce the amplitude of the excitation signal and the parasitic capacitance of the high-frequency transformer 512, and increase the electrostatic capacitance of the output capacitor 7.

[0054] However, when the amplitude of the excitation signal is small, in order to ensure the gate voltage required to maintain the power MOSFET 30 in the ON state, the turns ratio of the primary winding 512a to the secondary winding 512b of the high-frequency transformer 512 needs to be large, which leads to an increase in the parasitic capacitance 512c between the primary winding 512a and the secondary winding 512b. Alternatively, to reduce the parasitic capacitance 512c between the primary winding 512a and the secondary winding 512b, it is sufficient to increase the phase distance between the primary winding 512a and the secondary winding 512b, or to provide electrostatic shielding between them. However, these measures both result in a larger and more expensive high-frequency transformer 512. On the other hand, when the electrostatic capacitance of the output capacitor 7 is large, the amount of charge charged and discharged to the output capacitor 7 during polarity reversal of the output voltage increases, which, as already described, may lead to, for example, an increase in the polarity reversal time.

[0055] [Structure and operation of the gate drive circuit in this embodiment]

[0056] Figure 2 This is a schematic circuit diagram of the gate drive units 51 to 5N included in the positive-side drive unit 5 of the polarity-switching high-voltage power supply device of this embodiment, which can solve the above-mentioned problems. Although the description is omitted here, the schematic circuit structure of the gate drive units 61 to 6N included in the negative-side drive unit 6 is basically the same. Figure 1 The high-voltage power supply device shown uses a structure that connects multiple power MOSFETs in series, but in Figure 2 Nakaya and Figure 3 Similarly, consider the case where a single power MOSFET 30 is driven. Therefore, Figure 1The power MOSFETs 31 to 3N in the circuit are respectively connected to... Figure 2 The power MOSFET 30 in the diagram corresponds to... Figure 1 Each gate driving section 51 to 5N in the middle is respectively connected to Figure 2 The gate drive section 50 corresponds to this. Furthermore, in... Figure 2 In the middle, to and Figure 3 The structural elements that are substantially the same are marked with the same symbols. That is to say, the structural elements of the rectifier section 505 and its subsequent stages in the device of this embodiment are substantially the same as those in the conventional device.

[0057] The gate drive unit 50 includes an excitation unit 501, a high-frequency transformer 502, a rectifier unit 505 including a rectifier diode 503 and a rectifier capacitor 504, and a discharge resistor 506. The excitation unit 501 is not... Figure 3 The excitation section shown is not an unbalanced output type, but a balanced output type oscillator circuit with two high-frequency signals whose output waveforms are reversed (that is, opposite in polarity).

[0058] Although the detailed construction will be described later, the high-frequency transformer 502 is configured such that the parasitic capacitance per unit number of turns of the primary winding 502a between the primary winding 502a and the secondary winding 502b is symmetrical about the midpoint P of the primary winding 502a along its extension direction. Of course, this symmetry may not be perfectly symmetrical due to manufacturing errors or deviations. Furthermore, high-frequency transformers with this characteristic will be referred to as high-frequency transformers with symmetrical parasitic capacitance distribution, while those without this characteristic will be referred to as high-frequency transformers with asymmetrical parasitic capacitance distribution.

[0059] The two outputs of the excitation unit 501 are respectively connected to the two ends of the primary winding 502a of the high-frequency transformer 502. Therefore, when the excitation unit 501 is turned on, it differentially excites the two ends of the primary winding 502a. As a result, the alternating current generated in the secondary winding 502b of the high-frequency transformer 502 is rectified by the rectifier unit 505 and charges the rectifier capacitor 504 (and the parasitic capacitance between the gate and source of the power MOSFET 30). When the charging voltage exceeds the gate threshold voltage of the power MOSFET 30, the power MOSFET 30 is turned on. When the excitation unit 501 is turned off, the charge stored in the rectifier capacitor 504 and the parasitic capacitance is mainly discharged through the discharge resistor 506, and the power MOSFET 30 is turned off.

[0060] use Figure 5 To illustrate by Figure 1 The high-voltage power supply device shown uses the gate drive unit 50 with the above structure to reduce common-mode noise generated in the output voltage.

[0061] Figure 5 This refers to the case where the primary winding 502a of a high-frequency transformer 502 with symmetrical parasitic capacitance distribution is differentially excited using a balanced output type excitation unit 501 (see reference). Figure 5 A schematic diagram illustrating the principle of common-mode current flowing in the parasitic capacitance of the high-frequency transformer 502 (A).

[0062] Figure 5 Figures (B), (C), and (D) are all graphs with the number of turns Np of the primary winding 502a as the Y-axis (vertical axis). Additionally, Figure 5 The X-axis (horizontal axis) of the graphs shown in (B), (C), and (D) represents the parasitic capacitance per unit number of turns of the primary winding 502a (ΔC / Δn), the instantaneous value of the common-mode voltage applied to the primary winding 502a (first derivative: dVc / dt), and the instantaneous value of the common-mode current flowing through the parasitic capacitance (first derivative: ΔIc / dt). The common-mode current flowing between the primary winding 502a and the secondary winding 502b can be calculated by multiplying each parasitic capacitance corresponding to a small number of turns of the primary winding 502a by the instantaneous value of the common-mode voltage applied to that parasitic capacitance and integrating the product along the Y-axis (number of turns).

[0063] like Figure 5 As shown in (B), the parasitic capacitance per unit number of turns of the primary winding 502a between the primary winding 502a and the secondary winding 502b of the high-frequency transformer 502 is symmetrical about the X-axis in the direction of extension of the primary winding 502a. Additionally, as... Figure 5 As shown in (C), the instantaneous value of the common-mode voltage applied to the primary winding 502a is point-symmetric with respect to the origin 0. Therefore, when the instantaneous value of the common-mode current, obtained by multiplying these two values, is integrated along the Y-axis, it becomes zero. This is in Figure 5 The following is illustrated in the graph shown in (D): the shaded area above the X-axis and the shaded area below the X-axis have opposite polarities and the same area. That is, in this gate drive section 50, the common-mode current in the high-frequency transformer 502 is eliminated, and the generation of common-mode noise can be avoided regardless of the magnitude of the impedance between the secondary winding 502b and ground.

[0064] In such Figure 1 In the case where the high-voltage switching sections 3 and 4 are structured by connecting multiple power MOSFETs in series, as shown, the following structure can be configured: Figure 6 As shown in (A), the same number of power MOSFETs (in) Figure 6In the example, the primary windings of a high-frequency transformer with symmetrical parasitic capacitance distribution (the three primary windings 502a1, 502a2, and 502a3) are connected in series, and the two ends of the series circuit are differentially excited by a balanced output type excitation unit 501.

[0065] Figure 6 (B) to (D) are related to Figure 6 The circuit shown in (A) corresponds to the same Figure 5 The same charts as (B) to (D). Figure 6 As shown in (B), the parasitic capacitance per unit number of turns of the primary winding 502a between the primary and secondary windings in each high-frequency transformer is symmetrical about the X-axis along the extension direction of the primary winding 502a. Figure 6 As shown in (C), the instantaneous value of the common-mode voltage applied to the series circuit of the three primary windings 502a1, 502a2, and 502a3 is point-symmetric with respect to the origin 0, which corresponds to the midpoint of the high-frequency transformer located in the center. Therefore, when the instantaneous value of the common-mode current, obtained by multiplying these two values, is integrated along the Y-axis, it becomes zero. This is in Figure 6 This is reflected in (D) as follows: In the graph corresponding to the central high-frequency transformer, the shaded areas above and below the X-axis have opposite polarities and the same area. Similarly, the shaded areas in the graph above the central transformer and the shaded areas in the graph below the central transformer have opposite polarities and the same area. That is, in this structure, common-mode current is also eliminated, and... Figure 5 Similarly, the generation of common-mode noise can be avoided regardless of the impedance between the secondary windings of each high-frequency transformer and ground.

[0066] Figure 7 It is used with Figure 5 and Figure 6 A contrasting example is using a balanced output type exciter 501 to excite something like... Figure 3 The diagram illustrates the principle of the common-mode current flowing in the parasitic capacitance of the high-frequency transformer 512 in the case of the primary winding 512a of the asymmetric high-frequency transformer 512 with the parasitic capacitance distribution used in the structure shown in (refer to (A)). Figure 7 (B) to (D) are related to Figure 7 The circuit shown in (A) corresponds to the same Figure 5 The same charts (B) to (D).

[0067] like Figure 7 As shown in (C), the instantaneous value of the common-mode voltage applied to the primary winding 512a is point-symmetric with respect to the origin 0. However, as Figure 7As shown in (B), the parasitic capacitance per unit number of turns of the primary winding 502a between the primary winding 512a and the secondary winding 512b is asymmetrical with respect to the X-axis along the extension direction of the primary winding 502a. Therefore, even when integrating the instantaneous value of the common-mode current obtained by multiplying the two together along the Y-axis, it does not become zero. This is in Figure 7 This is illustrated in the graph shown in (D) by the following: the shaded areas above and below the X-axis, although opposite in polarity, have different areas. That is, in this case, unlike... Figure 5 and Figure 6 The common-mode current is not eliminated, resulting in common-mode noise corresponding to the impedance between the secondary winding 512b and ground.

[0068] on the other hand, Figure 8 It is used with Figure 5 and Figure 6 Another example of comparison is the use of, for example Figure 3 The unbalanced output type exciter 511 used is used to excite such as Figure 2 A schematic diagram illustrating the common-mode current flowing through the parasitic capacitance of a high-frequency transformer, specifically in the case of the primary winding 502a of a high-frequency transformer 502 with a symmetrical parasitic capacitance distribution (refer to (A)). Figure 8 (B) to (D) are related to Figure 8 The circuit shown in (A) corresponds to the same Figure 5 The same charts (B) to (D).

[0069] like Figure 8 As shown in (B), the parasitic capacitance per unit number of turns of the primary winding 502a between the primary winding 502a and the secondary winding 502b is symmetrical about the X-axis in the direction of extension of the primary winding 502a, but as... Figure 8 As shown in (C), the instantaneous value of the common-mode voltage applied to the primary winding 502a is not point-symmetric with respect to the origin 0. Therefore, even if the instantaneous value of the common-mode current obtained by multiplying the two is integrated along the Y-axis, it does not become zero. This is in Figure 8 As illustrated in graph (D), the shaded area above the X-axis is not of opposite polarity (they are of the same polarity) as the shaded area below the X-axis. That is, in this case, the common-mode current is not eliminated, resulting in common-mode noise corresponding to the magnitude of the impedance between the secondary winding 502b and ground.

[0070] Based on the above explanation, it is clear that in order to avoid or reduce the generation of common-mode noise at the voltage output terminal 9 of the high-voltage power supply device, it is necessary to... Figure 2As shown, a high-frequency transformer 502 with symmetrical parasitic capacitance distribution is used as the high-frequency transformer, and the two ends of the primary winding 502a are differentially excited using a balanced output type excitation section 501. Alternatively, when driving multiple power MOSFETs connected in series, this can also be done as follows: Figure 6 As shown in (A), the primary windings 502a of multiple high-frequency transformers 502 with symmetrical parasitic capacitance distribution are connected in series, and the two ends of the series circuit are differentially excited by a balanced output type excitation unit 501. Of course, a balanced output type excitation unit 501 can also be provided for each of the multiple high-frequency transformers 502 with symmetrical parasitic capacitance distribution.

[0071] [Specific examples of high-frequency transformers]

[0072] Figure 9 This is an example of the specific structure of a high-frequency transformer 502 with a parasitic capacitance distribution that can be used in the polarity switching high-voltage power supply device of this embodiment. (A) is a top view, and (B) is a cross-sectional view along line A-AA in (A).

[0073] In this high-frequency transformer 502, the core 502c is in a ring shape, and a secondary winding 502b is wound on the core 502c. Furthermore, a straight primary winding 502a, covered by an insulating member 502d, passes approximately at the center of a circular opening in the center of the core 502c. The number of turns of the secondary winding 502b can be appropriately adjusted according to the required voltage or the amplitude of the excitation signal.

[0074] In the high-frequency transformer 502 constructed as described above, it is possible to make the distribution of the parasitic capacitance per unit number of turns of the primary winding 502a between the primary winding 502a and the secondary winding 502b symmetrical with respect to the midpoint P of the primary winding 502a in the direction of extension of the primary winding 502a.

[0075] Furthermore, the primary winding 502a, which passes through the opening of core 502c, can be offset from the center of the opening, as long as it is not significantly tilted relative to the central axis of core 502c. In this case, the symmetry of the distribution of the parasitic capacitances in the extending direction of the primary winding 502a can be substantially ensured. Additionally, the specific construction of the high-frequency transformer 502 is not limited to... Figure 9 The structure shown in the figure.

[0076] [Actual Test Example]

[0077] Figure 10 (A) is the measured waveform of noise observed at the voltage output terminal 9 in the following conditions, that is, in the prior art: Figure 1The polarity-reversing high-voltage power supply device shown in the figure uses 10 power MOSFETs connected in series as high-voltage switching units 3 and 4, respectively. Figure 9 The primary winding 502a of the high-frequency transformer 502 shown in the diagram is connected in series and excited using an unbalanced output type excitation unit 511. On the other hand, Figure 10 (B) is the measured waveform of noise observed at voltage output terminal 9 in the following condition, that is, in one embodiment of the invention: Figure 1 The polarity-reversing high-voltage power supply device shown in the figure uses 10 power MOSFETs connected in series as high-voltage switching units 3 and 4, respectively. Figure 9 The primary winding 502a of the high-frequency transformer 502 shown in the figure is connected in series and excited by a balanced output type excitation unit 501. The applied voltage to the primary winding 502a of the high-frequency transformer 502 is 1.2Vp-p, the output capacitor 7 is 1nF, and the excitation frequency of the excitation unit 501 or 511 is 330kHz.

[0078] exist Figure 10 In (A), common-mode noise with an excitation frequency and an amplitude of approximately 30 mVp-p is clearly observed. In contrast, as... Figure 10 As shown in (B), in one embodiment of the device of the present invention, the amplitude of the common-mode noise is 4mVp-p, which is reduced to Figure 10 Approximately 1 / 8 of (A). Thus, the effectiveness of the high-voltage power supply device described above can also be confirmed based on actual measurement results.

[0079] In the high-voltage power supply device of the above embodiment, a power MOSFET is used as the semiconductor switching element constituting the high-voltage switching sections 3 and 4, but it is obvious that other semiconductor switching elements such as IGBTs can be used. Furthermore, it is obvious that a single power MOSFET or IGBT can be used, rather than a structure in which multiple power MOSFETs or IGBTs are connected in series.

[0080] in addition, Figure 1 , Figure 2 , Figure 6 The circuit structure in the high-voltage power supply device described in the above embodiments (A) is a simplified circuit structure or an equivalent circuit structure, and it is obviously possible to make various modifications or additions.

[0081] Furthermore, all other points are equally important; any appropriate modifications, additions, or alterations made within the scope of the spirit of this invention are also included in the claims of this application, which is to be expected.

[0082] [Various methods]

[0083] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following methods.

[0084] (First item) One embodiment of the high-voltage power supply device according to the present invention comprises:

[0085] The voltage generator outputs a high DC voltage.

[0086] The switching section using a semiconductor switching element outputs the output voltage of the voltage generator to the voltage output terminal when it is turned on;

[0087] The driving unit drives the control terminals of the semiconductor switching elements in the switching unit; and

[0088] The control unit controls the conduction and deconduction of the switching unit via the drive unit.

[0089] The driving unit includes:

[0090] A high-frequency transformer having a primary winding and a secondary winding, wherein the parasitic capacitance per unit number of turns of the primary winding between the primary winding and the secondary winding is symmetrical about the midpoint of the primary winding in the direction of extension of the primary winding.

[0091] A rectifier section that rectifies the alternating current induced in the secondary winding of the high-frequency transformer; and

[0092] A balanced output type high-frequency excitation unit differentially excites the primary winding of the high-frequency transformer.

[0093] According to the high-voltage power supply device described in the first item, common-mode noise generated at the voltage output terminal due to the excitation of the high-frequency transformer can be suppressed regardless of the size of the parasitic capacitance between the primary and secondary windings of the high-frequency transformer. This reduces the noise superimposed on the output voltage of the high-voltage power supply device, primarily caused by the gate drive circuit. Furthermore, it is not necessary to increase the electrostatic capacitance of the output capacitor to a required level, thus shortening the time required for polarity switching or voltage rise of the output voltage. Additionally, by suppressing the electrostatic capacitance of the output capacitor, its miniaturization and weight reduction can be achieved, which is also beneficial for the miniaturization and weight reduction of the high-voltage power supply device itself.

[0094] (Second item) In the high-voltage power supply device described in the first item, it can be set as follows:

[0095] The voltage generating unit includes a first voltage generating unit that outputs a positive high-voltage DC voltage and a second voltage generating unit that outputs a negative high-voltage DC voltage.

[0096] The switching unit includes a first switching unit that outputs the output voltage of the first voltage generator to the voltage output terminal when the switch is turned on, and a second switching unit that outputs the output voltage of the second voltage generator to the voltage output terminal when the switch is turned on.

[0097] According to the high-voltage power supply device described in the second item, it is possible to appropriately switch between positive and negative DC high voltage output from the voltage output terminal. Furthermore, it is possible to reduce noise superimposed on the output voltage.

[0098] (Third item) In the high-voltage power supply device described in the first or second item, it can be configured such that a plurality of semiconductor switching elements in the switching section are connected in series, and the driving section includes a circuit that drives the control terminals of the plurality of semiconductor switching elements respectively.

[0099] According to the high-voltage power supply device described in item three, even with a high output voltage, semiconductor switching elements with low rated voltage can be used. This allows for comprehensive cost reduction of the device. Furthermore, readily available semiconductor switching elements can be used to achieve a high output voltage.

[0100] (Fourth item) In any of the first to third items of the high-voltage power supply device, the high-frequency transformer may be configured to include: a core in the shape of an annular ring; a primary winding with an opening through the center of the core; and a secondary winding wound around the core.

[0101] According to the high-voltage power supply device described in item four, it is possible to make the distribution of the parasitic capacitance per unit number of turns of the primary winding between the primary winding and the secondary winding symmetrical with respect to the midpoint of the primary winding in a simple construction.

[0102] (Fifth item) In the high-voltage power supply device described in the third item, the high-frequency transformer can be configured to include: a ring-shaped core; a primary winding with an opening through the center of the core; and a secondary winding wound around the core.

[0103] The primary windings of multiple high-frequency transformers, each corresponding to one of the multiple semiconductor switching elements, included in the driving unit that drives the multiple semiconductor switching elements are connected in series, and these series-connected primary windings are differentially excited by the high-frequency excitation unit.

[0104] According to the high-voltage power supply device described in item five, even when a large number of semiconductor switching elements are connected in series to form the switching section, the structure of the drive section can be simplified. This reduces the cost of the device and facilitates its miniaturization and weight reduction.

[0105] (Sixth item) In any of the high-voltage power supply devices described in items one through five, it can be configured such that the primary winding and secondary winding of the high-frequency transformer are electrically insulated from each other by an insulating layer on the primary winding.

[0106] (Seventh item) In any of the high-voltage power supply devices described in the first to sixth items, the semiconductor switching element can be configured to be a power MOSFET or an IGBT.

[0107] Explanation of reference numerals in the attached figures

[0108] 1: Positive voltage generating section; 2: Negative voltage generating section; 3: Positive side high voltage switching section; 4: Negative side high voltage switching section; 30, 31~3N, 40, 41~4N: Power MOSFETs; 5: Positive side drive section; 50, 51~5N, 60, 61~6N: Gate drive section; 501: Excitation section; 502: High frequency transformer; 502a, 502a1, 502a2, 502a3: Primary winding; 502b: Secondary winding; 502c: Core; 502d: Insulating component; 505: Rectifier section; 503: Rectifier diode; 504: Rectifier capacitor; 506: Discharge resistor; 6: Negative side drive section; 7: Output capacitor; 8: Control section; 9: Voltage output terminal.

Claims

1. A high-voltage power supply device, comprising: The voltage generator outputs a high DC voltage. The switching section using a semiconductor switching element outputs the output voltage of the voltage generator to the voltage output terminal when it is turned on; The driving unit drives the control terminals of the semiconductor switching elements in the switching unit; as well as The control unit controls the conduction and deconduction of the switching unit via the drive unit. The driving unit includes: A high-frequency transformer having a primary winding and a secondary winding, wherein the distribution of the parasitic capacitance per unit number of turns of the primary winding between the primary winding and the secondary winding is symmetrical with respect to the midpoint of the primary winding in the direction of extension of the primary winding. A rectifier section that rectifies the alternating current induced in the secondary winding of the high-frequency transformer; and A balanced output type high-frequency excitation unit differentially excites the primary winding of the high-frequency transformer. The high-frequency excitation unit is a balanced output type oscillator circuit that outputs two high-frequency signals with waveforms that are reversed vertically. The primary winding is differentially excited by supplying the two high-frequency signals to both ends of the primary winding of the high-frequency transformer.

2. The high-voltage power supply device according to claim 1, wherein, The voltage generating unit includes a first voltage generating unit that outputs a positive high-voltage DC voltage and a second voltage generating unit that outputs a negative high-voltage DC voltage. The switching unit includes a first switching unit that outputs the output voltage of the first voltage generator to the voltage output terminal when the switch is turned on, and a second switching unit that outputs the output voltage of the second voltage generator to the voltage output terminal when the switch is turned on.

3. The high-voltage power supply device according to claim 1, wherein, In the switching section, multiple semiconductor switching elements are connected in series, and the driving section includes circuits that drive the control terminals of the multiple semiconductor switching elements respectively.

4. The high-voltage power supply device according to claim 1, wherein, The high-frequency transformer includes: a ring-shaped core; a primary winding with an opening through the center of the core; and a secondary winding wound around the core.

5. The high-voltage power supply device according to claim 2, wherein, The high-frequency transformer includes: a ring-shaped core; a primary winding with an opening through the center of the core; and a secondary winding wound around the core.

6. The high-voltage power supply device according to claim 3, wherein, The high-frequency transformer includes: a ring-shaped core; a primary winding with an opening through the center of the core; and a secondary winding wound around the core.

7. The high-voltage power supply device according to claim 3, wherein, The high-frequency transformer includes: a ring-shaped core; a primary winding with an opening through the center of the core; and a secondary winding wound around the core. The primary windings of multiple high-frequency transformers, each corresponding to one of the multiple semiconductor switching elements, included in the driving unit that drives the multiple semiconductor switching elements are connected in series, and these series-connected primary windings are differentially excited by the high-frequency excitation unit.

8. The high-voltage power supply device according to claim 1, wherein, The primary winding and secondary winding of the high-frequency transformer are electrically insulated from each other by the insulating cladding of the primary winding.

9. The high-voltage power supply device according to any one of claims 1 to 8, wherein, The semiconductor switching element is a metal-oxide-semiconductor field-effect transistor, i.e., a MOSFET, or an insulated-gate bipolar transistor, i.e., an IGBT.

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