Patent ID: 12191849

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereinafter, configurations and operations of several embodiments of a high-voltage power supply device according to the present invention will be described in comparison with a device according to a prior art.

[Overall Configuration and Schematic Operation of Polarity Switching High-Voltage Power Supply Device of this Embodiment]

FIG.1is a schematic block configuration diagram of a polarity switching high-voltage power supply device of this embodiment.

The polarity switching high-voltage power supply device of this embodiment is provided with a positive voltage generation unit1, a negative voltage generation unit2, a positive electrode-side high-voltage switching unit3, a negative electrode-side high-voltage switching unit4, a positive electrode-side driver5, a negative electrode-side driver6, an output capacitor7, and a controller8.

The positive voltage generation unit1generates a DC high-voltage +HV of positive polarity. The negative voltage generation unit2generates a DC high-voltage −HV of negative polarity. The positive electrode-side high-voltage switching unit3includes a plurality of power MOSFETs31-3N. The negative electrode-side high-voltage switching unit4includes a plurality of power MOSFETs41-4N. The positive electrode-side driver5and the negative electrode-side driver6include a plurality of gate drivers51-5N and a plurality of gate drivers61to6N, respectively, for driving the plurality of power MOSFETs31-3N and the plurality of power MOSFETs41-4N, respectively. The output capacitor7is connected between a voltage output terminal9, which is a connecting end between the positive electrode-side high-voltage switching unit3and the negative electrode-side high-voltage switching unit4, and a ground (GND).

This polarity switching high-voltage power supply device is used to apply a voltage to a mass spectrometer, an electrophoresis device, or the like. The voltage values (absolute values) of the DC high-voltages +HV and −HV are usually 1 kV or higher, or about 400V-500 V at the lowest.

The positive voltage generation unit1and the negative voltage generation unit2may have any configurations as long as the positive voltage generation unit1and the negative voltage generation unit2can output a DC high-voltage +HV and a DC high-voltage −HV, respectively, under the control of the controller8. As one example, each of the positive voltage generation unit1and the negative voltage generation unit2may be configured as described in Patent Document 1. That is, they may be configured to include an excitation circuit for outputting a high-voltage high-frequency AC signal, a rectifier circuit for converting the high-frequency AC signal into a DC high-voltage, and a filter circuit for removing ripple voltages included in the DC high-voltage.

Further, a discharging diode may be provided so as to be connected in a direction to become a reverse biased state by a voltage outputted to the output terminal of each of the positive voltage generation unit1and the negative voltage generation unit2.

The positive electrode-side high-voltage switching unit3and the negative electrode-side high-voltage switching unit4are each configured by N pieces of power MOSFETs connected in series. The power MOSFETs31-3N included in the positive electrode-side high-voltage switching unit3are simultaneously turned on/off by the N pieces of the gate drivers51-5N. The power MOSFETs41-4N included in the negative electrode-side high-voltage switching unit4are simultaneously turned on/off by the N pieces of the gate drivers61-6N.

The controller8controls the voltage-output operations by the positive voltage generation unit1and the negative voltage generation unit2and also controls the gate drivers51-5N and61-61N. With this, the positive electrode-side high-voltage switching unit3and the negative electrode-side high-voltage switching unit4are respectively turned on/off. The controller8may be configured mainly by a microcomputer including, for example, a CPU, a RAM, a ROM, and the like.

In the polarity switching high-voltage power supply device of this embodiment, it is assumed that the positive voltage generation unit1is turned on (in an active state), the negative voltage generation unit2is turned off (in an inactive state), the positive electrode-side high-voltage switching unit3is turned on (in a conductive state), and the negative electrode-side high-voltage switching unit4is turned off (in a non-conductive state). At this time, the output voltage HVout of the voltage output terminal9is a positive DC high-voltage +HV.

On the other hand, it is assumed that the positive voltage generation unit1is turned off, the negative voltage generation unit2is turned on, the positive electrode-side high-voltage switching unit3is turned off, and the negative electrode-side high-voltage switching unit4is turned on. At this time, the output voltage HVout of the voltage output terminal9is a negative DC high-voltage −HV. The controller8controls on/off operations of the positive voltage generation unit1and the negative voltage generation unit2and on/off operations of the positive electrode-side high-voltage switching unit3and the negative electrode-side high-voltage switching unit4according to preset programs. With this, a DC high-voltage of +HV or −HV is outputted to the voltage output terminal9. At this time, the output capacitor7functions to stabilize the potential of a load (not shown) connected to the voltage output terminal9.

[Problems of Conventional Gate Drive Circuit]

As described above, the gate drivers51-5N and61-6N drive the gates (control terminals) of the power MOSFETs31-3N and41-4N. Hereinafter, the problems of the gate drive circuit according to the conventional art example ofFIG.3will be described.

FIG.4is an explanatory diagram of a stray capacitance between the primary winding512aand the secondary winding512bof the high-frequency transformer512used in the above-described gate driver150. Between the primary winding512aand the secondary winding512b, there exists a stray capacitance512ccorresponding to the sum of the plurality of distributed capacitances C1, C2, . . . , Cn.

As shown inFIG.4, when an excitation unit511, which is an unbalanced output type excitation unit, is connected to the primary winding512a, a common mode current flows the following path, i.e., the excitation unit511→the primary winding512a→the stray capacitance512c→the secondary winding512b→the secondary ground capacitor516→ground. As a result, common mode noise corresponding to the common mode current is generated in the secondary ground capacitor516.

That is, in a case where the gate driver150shown inFIG.3is applied to the high-voltage power supply device shown inFIG.1, a common mode current flows through the output node, i.e., the voltage output terminal9, through the stray capacitance512cbetween the primary winding512aand the secondary winding512bof the high-frequency transformer512. Therefore, the common mode noise is further superimposed on the output noise derived from the voltage generation units1and2, resulting in an increase in the noise of the output voltage.

It is now assumed to configure such that the gate driver150shown inFIG.3is applied to the high-voltage power supply device shown inFIG.1. In this case, the magnitude of the common mode noise observed at the voltage output terminal9is proportional to the amplitude of the excitation signal generated at the excitation unit511and the stray capacitance in the high-frequency transformer512and is inversely proportional to the capacitance of the output capacitor7. Therefore, for the purpose of reducing the common mode noise, it is considered to reduce the amplitude of the excitation signal and the stray capacitance of the high-frequency transformer512and increase the capacitance of the output capacitor7.

However, in the case of reducing the amplitude of the excitation signal, it is required to increase the number of turns of the primary winding512aand the secondary winding512bof the high-frequency transformer512in order to ensure a gate voltage required to keep the power MOSFET30in the on-state. However, this leads to an increase in the stray capacitance512cbetween the primary winding512aand the secondary winding512b. Further, in order to decrease the stray capacitance512cbetween the primary winding512aand the secondary winding512b, it is considered to increase the separation distance between the primary winding512aand the secondary winding512b.

Alternatively, it is considered to arrange an electrostatic shielding between the primary winding512aand the secondary winding512b. However, all of the above-described measures lead to an increase in size and cost of the high-frequency transformer512. On the other hand, when the capacitance of the output capacitor7is increased, the amount of the electric charge for charging/discharging the output capacitor7at the time of inverting the polarity of the output voltage increases. This may lead to, for example, an increase in the polarity inversion time, as previously described.

[Configuration and Operation of Gate Drive Circuit of this Embodiment]

FIG.2is a principle schematic circuit configuration diagram of the gate driver51-5N included in the positive electrode-side driver5in the polarity switching high-voltage power supply device of this embodiment that can solve the above-described problems. Although not described here, the principle schematic circuit configuration of the gate driver61-6N included in the negative electrode-side driver6is also basically the same. In the high-voltage power supply device shown inFIG.1, a configuration in which a plurality of power MOSFETs is connected in series is used.

However, inFIG.2, in the same manner as inFIG.3, it is assumed to drive a single power MOSFET30. Accordingly, each of the power MOSFETs31-3N inFIG.1corresponds to the power MOSFET30inFIG.2, and each of the gate drivers51-5N inFIG.1corresponds to the gate driver50inFIG.2. InFIG.2, the substantially same constituent element as that shown inFIG.3is assigned by the same reference numeral. That is, the rectifier505and subsequent constituent elements are substantially the same as in this embodiment and a conventional device.

The gate driver50includes an excitation unit501, a high-frequency transformer502, a rectifier505including rectifying diodes503and a rectifying capacitor504, and a discharging resistor506. The excitation unit501is not an unbalanced output type excitation unit shown inFIG.3but a balanced output type oscillation circuit that outputs two high-frequency signals in which the wave shapes are inverted to each other (i.e., the polarities are reversed).

Although the detailed structure will be described later, the high-frequency transformer502is configured as follows. That is, the distribution of the stray capacitance per number of unit turns of the primary winding502abetween the primary winding502aand the secondary winding502balong the extension direction of the primary winding502ais configured to be symmetrical to the midpoint P of the primary winding502a. It should be noted that, of course, the symmetry is not necessarily perfect due to manufacturing errors, variations, and the like.

Hereinafter, a high-frequency transformer having such properties will be referred to as a stray capacitance distribution symmetric type high-frequency transformer, and a high-frequency transformer not having such properties will be referred to as a stray capacitance distribution asymmetric type high-frequency transformer.

The two outputs of the excitation unit501are connected to both ends of the primary winding502aof the high-frequency transformer502. Thus, when the excitation unit501is turned on, the excitation unit501excites both ends of the primary winding502adifferentially. With this, the AC current induced in the secondary winding502bof the high-frequency transformer502is rectified by the rectifier505to charge the rectifying capacitor504(and the parasitic capacitance between the gate and the source of the power MOSFET30). When this charging voltage exceeds the gate threshold voltage of the power MOSFET30, the power MOSFET30is turned on.

When the excitation unit501is turned off, the electric charges accumulated in the rectifying capacitor504and the parasitic capacitance are mainly discharged through the discharging resistor506, thereby turning off the power MOSFET30.

The principle that the common mode noise generated in the output voltage is reduced by using the gate driver50having the above-described configuration in the high-voltage power supply device shown inFIG.1will be described with reference toFIG.5.

FIG.5is a principle explanation diagram of a common mode current flowing through the stray capacitance of the high-frequency transformer502in a case where the primary winding502aof the stray capacitance distribution symmetric type high-frequency transformer502is excited by the balanced output type excitation unit501differentially (see (A) ofFIG.5).

(B), (C), and (D) ofFIG.5each show a graph in which the number of turns Np of the primary winding502ais represented by the Y-axis (vertical axis). Further, the X-axis (horizontal axis) shown in (B) ofFIG.5represents the stray capacitance (AC/An) per number of unit turns of the primary winding502abetween the primary winding502aand the secondary winding502b. The X-axis (horizontal axis) shown in (C) ofFIG.5represents the instantaneous value (first-order differential value: dVc/dt) of the common mode voltage applied to the primary winding502a. The X-axis (horizontal axis) shown in (D) ofFIG.5represents the instantaneous value (first-order differential value: ΔIc/dt) of the common mode current flowing through the stray capacitance.

The common mode current flowing between the primary winding502aand the secondary winding502bcan be determined as follows. That is, the common mode current can be determined by multiplying each stray capacitance to a minute number of turns of the primary winding502aby the instantaneous value of the common mode voltage applied to the stray capacitance and integrating the product along the Y-axis (number of turns).

As shown in (B) ofFIG.5, the distribution of the stray capacitance of the primary winding502aper the number of unit turns between the primary winding502aand the secondary winding502bof the high-frequency transformer502in the extension direction of the primary winding502ais symmetrical to the X-axis. Further, as shown in (C) ofFIG.5, the instantaneous value of the common mode voltage applied to the primary winding502ais a point-symmetric to the origin 0.

Therefore, when the instantaneous value of the common mode current obtained by multiplying both of them is integrated along the Y-axis, it becomes 0 (zero). This is indicated by the fact that, in the graph shown in (D) ofFIG.5, the hatched portion above the X-axis and the hatched portion below the X-axis are opposite in polarity and has the same area. That is, in the gate driver50, the common mode current is canceled in the high-frequency transformer502, which makes it possible to avoid generation of common mode noise regardless of the magnitude of the impedance between the secondary winding502band the ground.

As shown inFIG.1, in a case where one high-voltage switching unit3,4is configured by a plurality of power MOSFETs connected in series, it may be configured as shown in (A) ofFIG.6. That is, the same number of the primary windings of stray capacitance distribution symmetric type high-frequency transformers as that of the power MOSFETs (in the example shown inFIG.6, three primary windings502a1,502a2, and502a3) are connected in series. Both ends of the series circuit are excited by a single balanced output type excitation unit501differentially.

(B) to (D) ofFIG.6are graphs similar to (B) to (D) ofFIG.5corresponding to the circuit shown in (A) ofFIG.6. As shown in (B) ofFIG.6, the distribution of the stray capacitance per number of unit turns of the primary winding502abetween the primary winding and the secondary winding in the extension direction of the primary winding502ain each high-frequency transformer is symmetrical to the X-axis.

As shown in (C) ofFIG.6, the instantaneous value of the common mode voltage applied to the series circuit of the three primary windings502a1,502a2, and502a3is point symmetric to the origin 0 corresponding to the midpoint of the center located high-frequency transformer. Therefore, when the instantaneous value of the common mode current obtained by multiplying both of them is integrated along the Y-axis, it becomes 0 (zero).

This indicates the fact in (D) ofFIG.6as follows. That is, in the graph corresponding to the high-frequency transformer located in the center, the hatched portion above the X-axis and the hatched portion below the X-axis are opposite in polarity and have the same area. The hatched portion of the graph located above the center graph and the hatched portion of the graph located below the center graph are opposite in polarity and have the same area.

That is, also in this configuration, the common mode current is canceled, which makes it possible to avoid generation of common mode noise regardless of the magnitude of the impedance between the secondary winding of each high-frequency transformer and the ground, in the same manner as in the case shown inFIG.5.

FIG.7is an example for comparing the cases shown inFIG.5andFIG.6.FIG.7is a principle explanatory diagram of the common mode current flowing through the stray capacitance of the high-frequency transformer512in a case where the primary winding512aof the stray capacitance distribution asymmetric type high-frequency transformer512as used in the configuration shown inFIG.3is excited by the balanced output type excitation unit501(see (A) ofFIG.7). (B) to (D) ofFIG.7are graphs similar to (B) to (D) ofFIG.5corresponding to the circuit shown in (A) ofFIG.7.

As shown in (C) ofFIG.7, the instantaneous value of the common mode voltage applied to the primary winding512ais point-symmetric to the origin 0. However, as shown in (B) ofFIG.7, the distribution of the stray capacitance per number of unit turns of the primary winding512abetween the primary winding512aand the secondary winding512bin the extension direction of the primary winding502ais asymmetric to the X-axis. Therefore, even if the instantaneous value of the common mode current, which is the product of both of them, is integrated along the Y-axis. It will not become 0 (zero).

This is indicated by the fact that, in the graph shown in (D) ofFIG.7, although the hatched portion above the X-axis and the hatched portion below the X-axis are opposite in polarity but their areas are not equal to each other. That is, unlike the cases shown inFIG.5andFIG.6, the common mode current will not be canceled, thereby causing common mode noise corresponding to the magnitude of the impedance between the secondary winding512band the ground.

On the other hand,FIG.8is another example for comparing the cases shown inFIG.5andFIG.6.FIG.8is a principle explanatory diagram of the common mode current flowing through the stray capacitance of the high-frequency transformer in a case where the primary winding502aof the stray capacitance distribution symmetric type high-frequency transformer502as shown inFIG.2is excited by the unbalanced output type excitation unit511as used inFIG.3(see (A) ofFIG.8). (B) to (D) ofFIG.8are similar graphs corresponding to (B) to (D) ofFIG.5corresponding to the circuit shown in (A) ofFIG.8.

As shown in (B) ofFIG.8, the distribution of the stray capacitance per number of unit turns of the primary winding502abetween the primary winding502aand the secondary winding502bin the extension direction of the primary winding502ais symmetrical to the X-axis. However, as shown in (C) ofFIG.8, the instantaneous value of the common mode voltage applied to the primary winding502ais not point-symmetrical to the origin 0. Therefore, the instantaneous value of the common mode current, which is the product of both of them, will not become 0 (zero) even if it is integrated along the Y-axis.

This is shown by the fact that in the graph shown in (D) ofFIG.8, the hatched portion above the X-axis and the hatched portion below the X-axis are not opposite in polarity (are the same in polarity). That is, the common mode current will not be canceled, thereby causing common mode noise corresponding to the magnitude of the impedance between the secondary winding502band the ground.

As is apparent from the above description, in order to avoid or reduce occurrence of common mode noise at the voltage output terminal9of the high-voltage power supply device, it is required to configure as follows. That is, as shown inFIG.2, it is required to use the stray capacitance distribution symmetric type high-frequency transformer502as a high-frequency transformer and excite both ends of the primary winding502adifferentially by the balanced output type excitation unit501.

Further, when driving a plurality of power MOSFETs connected in series, it may be configured such that as shown in (A) ofFIG.6, the primary windings502aof a plurality of stray capacitance distribution symmetric type high-frequency transformers502are connected in series, and both ends of the series circuit is excited by the balanced output type excitation unit501differentially. Of course, the balanced output type excitation unit501may be provided for each of the plurality of stray capacitance distribution symmetric type high-frequency transformers502.

[Specific Example of High-Frequency Transformer]

FIG.9AandFIG.9Beach show an example of a specific structure of a stray capacitance distribution symmetric type high-frequency transformer502, which can be used in the polarity switching high-voltage power supply device according to this embodiment.FIG.9Ais a plan view of the high-frequency transformer502, andFIG.9Bis a cross-sectional view taken along the A-AA line inFIG.9A.

In the high-frequency transformer502, the core502cis formed in a toroidal shape (doughnut shape), and a secondary winding502bis wound around the core502c. Further, a straight primary winding502acovered with an insulating member502dpenetrates substantially the center of the opening formed in the center of the core502c, the opening being circular in top view. The number of turns of the secondary winding502bmay be appropriately adjusted according to the required voltage, amplitude of the excitation signal, and the like.

In the high-frequency transformer502having the above-described structure, it is simple in the structure and it is possible to make the distribution of the stray capacitance of primary winding502aper number of unit turns of the primary winding502abetween the primary winding502aand the secondary winding502bin the extension direction of the primary winding502asymmetrical to the midpoint P of the primary winding502a.

It should be noted that the primary winding502apenetrating through the opening may be offset from the center of the opening of the core502cas long as the primary winding502ais not greatly inclined with respect to the center of the core502c. Even in such a case, it is possible to substantially secure the symmetry of the distribution of the stray capacitance of the primary winding502ain the extension direction of the primary winding502a. Further, it should be noted that the specific configuration of the high-frequency transformer502is not limited to that shown inFIG.9.

Measured Examples

FIG.10Ashows a measured waveform of noise observed at the voltage output terminal9in a prior art. That is, the measured waveform of the noise is observed at the voltage output terminal9in a case where in the polarity inversion high-voltage power supply device shown inFIG.1, ten (10) pieces of power MOSFETs are connected in series for each of the high-voltage switching units3and4, and the primary windings502aof the high-frequency transformers502having the structure shown inFIG.9AandFIG.9Bare connected in series and excited by the unbalanced output type excitation unit511.

On the other hand,FIG.10Bshows a measured waveform of noise observed at the voltage output terminal9according to one aspect of the present invention. That is, the measured waveform of the noise is observed at the voltage output terminal9in a case where in the polarity inversion high-voltage power supply device shown inFIG.1, ten (10) pieces of power MOSFETs are connected in series for each of the high-voltage switching units3and4, and the primary windings502aof the high-frequency transformers502having the structure shown inFIG.9AandFIG.9Bare connected in series and excited by the balanced output type excitation unit501. In both cases, the applied voltage to the primary winding502aof the high-frequency transformer502was 1.2 Vp-p, the output capacitor7was 1 nF, and the exciting frequency of the excitation unit501or511was 330 kHz.

InFIG.10A, common mode noise having the exciting frequency was clearly observed, and the amplitude thereof was about 30 mVp-p. In contrast, as shown inFIG.10B, in the device according to one aspect of the present invention, the amplitude of the common mode noise was reduced to 4 mVp-p, which was reduced to about ⅛ of the case shown inFIG.10A. In this way, the effectiveness of the high-voltage power supply device according to the above-described embodiment can also be confirmed from the actual measurements.

In the above-described high-voltage power supply devices according to the embodiments, although a power MOSFET is used as a semiconductor switching element constituting the high-voltage switching unit3,4, it is obvious that other semiconductor switching element, such as, e.g., IGBT, may be used. Further, it is also obvious that a single power MOSFET or IGBT may be used instead of using a plurality of power MOSFETs or IGBTs connected in series.

Further, it should be noted that the circuits of the high-voltage power supply devices of the embodiments described inFIG.1,FIG.2, (A) ofFIG.6, etc., are simplified or equivalent circuits, and various modifications and additions can be made.

It should further be noted that any modifications, additions, and changes may be made appropriately within the scope of the present invention and the scope of the claims.

Various Aspects

It will be appreciated by those skilled in the art that the above-described exemplary embodiments are illustrative of the following aspects.

(Item 1)

A high-voltage power supply device according to one aspect of the present invention includes:a voltage generation unit configured to output a DC high-voltage;a switching unit using a semiconductor switching element, the switching unit being configured to output an output voltage by the voltage generation unit to a voltage output terminal when the switching unit is in a conduction state;a driver configured to drive a control terminal of the semiconductor switching element in the switching unit; anda controller configured to control conduction/non-conduction of the switching unit via the driver,wherein the driver includes:a high-frequency transformer provided with a primary winding and a secondary winding, a distribution of a stray capacitance per number of unit turns of the primary winding between the primary winding and the secondary winding in an extension direction of the primary winding being symmetrical to a midpoint of the primary winding;a rectifier configured to rectify an AC current induced in the secondary winding of the high-frequency transformer; anda balanced output type high-frequency excitation unit configured to excite the primary winding of the high-frequency transformer differentially.

According to the high-voltage power supply device as recited in the above-described Item 1, it is possible to suppress the common mode noise caused by the excitation of the high-frequency transformer appearing at the voltage output terminal, regardless of the magnitude of the stray capacitance between the primary winding and the secondary winding of the high-frequency transformer. With this, it is possible to reduce the noise caused mainly by the gate drive circuit, the noise being superimposed on the output voltage of the high-voltage power supply device. Further, there is no need to increase the capacitance of the output capacitor more than necessary, and therefore, it is possible to shorten the time required for switching the polarity of the output voltage and for rising the edge of the output voltage. Further, by suppressing the capacitance of the output capacitor, the capacitor can be reduced in size and weight, which is advantageous for reducing the size and weight of the high-voltage power supply device.

(Item 2)

In the high-voltage power supply device as recited in the above-described Item 1, it may be configured such thatthe voltage generation unit includes:a first voltage generation unit configured to output a DC high-voltage of positive polarity; anda second voltage generation unit configured to output a DC high-voltage of negative polarity, andthe switching unit includes:a first switching unit configured to output an output voltage of the first voltage generation unit to the voltage output terminal when the first switching unit is in a conduction state; anda second switching unit configured to output an output voltage of the second voltage generation unit to the voltage output terminal when the second switching unit is in a conduction state.

According to the high-voltage power supply device described in the above-described Item 2, it is possible to output the DC high-voltage of positive polarity and the DC high-voltage of negative polarity from the voltage output terminal while appropriately switching therebetween. This enables the reduction of the noise superimposed on the output voltage.

(Item 3)

In the high-voltage power supply device as recited in the above-described Item 1 or 2, it may be configured such that the switching unit is composed of a plurality of semiconductor switching elements connected in series, and the driver includes a plurality of circuits for driving corresponding control terminals of the plurality of semiconductor switching elements.

According to the high-voltage power supply device described in the above-described Item 3, even in a case where the output voltage is high, a semiconductor switching element with a lower rated voltage can be used. This makes it possible to comprehensively reduce the cost of the device. Further, the output voltage can be increased by using a semiconductor switching element that is easily available.

(Item 4)

In the high-voltage power supply device as recited in any one of the above-described Items 1 to 3, it may be configured such that the high-frequency transformer includes a core of a toroidal shape, a primary winding penetrating through a central opening of the core, and a secondary winding wound around the core.

According to the high-voltage power supply device of the above-described Item 4, with a simple configuration, the distribution of the stray capacitance per number of unit turns of the primary winding between the primary winding and the secondary winding in the extension direction of the primary winding can be made symmetric to the midpoint of the primary winding.

(Item 5)

In the high-voltage power supply device as recited in the above-described Item 3, it may be configured such that the high-frequency transformer includes a core of a toroidal shape, a primary winding penetrating through a central opening of the core, and a secondary winding wound around the core,a plurality of primary windings of a plurality of high-frequency transformers respectively corresponding to the plurality of semiconductor switching elements are connected in series, the plurality of primary windings being included in the drivers for driving the corresponding plurality of semiconductor switching elements, andthe plurality of primary windings connected in series are excited by the high-frequency excitation unit differentially.

According to the high-voltage power supply device described in the above-described Item 5, even in a case where a large number of semiconductor switching elements are connected in series to form a switching unit, the configuration of the driver can be simplified. As a result, the cost of the device can be reduced, and it is advantageous to reduce the size and weight of the apparatus.

(Item 6)

In the high-voltage power supply device as recited any one of the above-described Items 1 to 5, it may be configured such that the primary winding and the secondary winding of the high-frequency transformer are electrically insulated by an insulating coating of the primary winding.

(Item 7)

In the high-voltage power supply device as recited in any one of the above-described Items 1 to 6, it may be configured such that the semiconductor switching element is either one of a power MOSFET and an IGBT.

DESCRIPTION OF SYMBOLS

1: Positive voltage generation unit2: Negative voltage generation unit3: Positive electrode-side high-voltage switching unit4: Negative electrode-side high-voltage switching unit30,31-3N,40,41-4N: Power MOSFET5: Positive electrode-side driver50,51-5N,60,61-6N: Gate driver501: Excitation unit502: High-frequency transformer502a,502a1,502a2,502a3: Primary winding502b: Secondary winding502c: Core502d: Insulating member505: Rectifier503: Rectifying diode504: Rectifying capacitor506: Discharging resistor6: Negative electrode-side driver7: Output capacitor8: Control unit9: Voltage output terminal