High-voltage power supply device

Abstract

A high-voltage power supply device is provided, comprising: a first voltage generating unit that outputs a positive high voltage; a second voltage generating unit that outputs a negative high voltage; a first discharge diode connected to the voltage output end of the first voltage generating unit; a second discharge diode connected to the voltage output end of the second voltage generating unit; a first output circuit that connects a first switch and a protective resistor in series; a second output circuit that connects the second switch and the protective resistor in series; an output capacitor connected in parallel with a load; a control unit that controls the operation of the two voltage generating units and the opening and closing operation of the two switches when switching the polarity of the output voltage so that the two switches are temporarily turned on in a state where the operation of the two voltage generating units is stopped; a first limiting unit that limits the time rate of change of the voltage between the two ends of the switch when the first switch is turned on; and a second limiting unit that limits the time rate of change of the voltage between the two ends of the switch when the second switch is turned on.

Description

Technical Field

[0001] The present invention relates to a high-voltage power supply device, and more particularly to a high-voltage power supply device capable of switching the positive and negative polarities of an output. Background Art

[0002] In a mass spectrometer, various compounds in a sample are ionized, the resulting ions are separated and detected based on their mass-to-charge ratio (m / z), and the compounds are identified or quantified based on the detection signals. Some compounds are easily positively ionized, while others are easily negatively ionized. Therefore, gas chromatographs and liquid chromatographs generally have the ability to repeatedly perform measurements while alternating between positive and negative ion measurement modes.

[0003] In positive and negative ion measurement modes, the polarity of the voltages applied to various components of the mass spectrometer, such as the ion source, mass separator, and ion detector, must be switched. To quickly switch between positive and negative ion measurement modes, the polarity of each applied voltage must be switched quickly. Therefore, a high-voltage power supply capable of quickly switching the polarity of the output voltage is used.

[0004] One such high-voltage power supply device is known, as described in Patent Document 1. This high-voltage power supply device includes: a positive voltage generator that generates a positive high voltage +HV; a negative voltage generator that generates a negative high voltage -HV; a discharge diode connected so that when a voltage is output from the output terminals of the positive and negative voltage generators, the diode is reverse-biased by the voltage; a positive-side high-voltage switch; a negative-side high-voltage switch; a protective resistor inserted between the output terminals of each high-voltage switch and a common voltage output terminal to limit inrush current flowing through the high-voltage switches; and an output capacitor connected in parallel with a load connected to the common voltage output terminal to stabilize the potential of the load.

[0005] When outputting a positive high voltage to the load, the positive high voltage switch is turned on, while the negative high voltage switch is turned off. This places the positive voltage generator in an active state and the negative voltage generator in a deactivated state. When outputting a negative high voltage to the load, the positive high voltage switch is turned off, while the negative high voltage switch is turned on. This places the positive voltage generator in a deactivated state and the negative voltage generator in an active state. In either case, the power supplied to the load from either the positive or negative voltage generator is used to charge the output capacitor and other components. When switching the output voltage polarity, both voltage generators are deactivated, while both high voltage switches are turned on. This allows the charge accumulated in the output capacitor to be discharged through one of the discharge diodes. Furthermore, the charge accumulated in the capacitors of the rectifier circuit, smoothing circuit, and other components included in the positive and negative voltage generators is also discharged through one of the discharge diodes.

[0006] In the conventional high-voltage power supply device, the charge accumulated in the output capacitor and the like is quickly discharged by the discharge diode as described above, thereby shortening the time required to switch the polarity of the output voltage compared to the previously known power supply device.

[0007] Prior art literature

[0008] Patent Literature

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

[0010] Problems to be solved by the invention

[0011] There is a situation where, when a high voltage is applied to a load from a high-voltage power supply device such as the one described above, the load current changes dramatically depending on the load condition. For example, when a high voltage is applied from a high-voltage power supply device to an orthogonal acceleration unit in an orthogonal acceleration time-of-flight mass spectrometer (hereinafter referred to as "OA-TOFMS") for ion ejection, when the amount of ions introduced into the orthogonal acceleration unit increases dramatically, the load current of the high-voltage power supply device changes suddenly. When the output voltage changes with such a sudden change in the load current, the initial energy imparted to the ions in the orthogonal acceleration unit changes, resulting in a decrease in measurement accuracy such as mass accuracy. Therefore, it is desirable to suppress the change in the output voltage as much as possible even when the load current changes suddenly. In order to suppress the output voltage change when the load current changes suddenly in the above-mentioned conventional high-voltage power supply device, it is necessary to make the electrostatic capacitance of the output capacitor large or the resistance value of the protection resistor small to reduce the output impedance.

[0012] However, increasing the capacitance of the output capacitor increases both its discharge and charge times, resulting in a longer output voltage polarity reversal time. Furthermore, the increased size of the capacitor may necessitate an increase in the size of the power supply itself. On the other hand, reducing the resistance of the protective resistor increases the switching current flowing through the high-voltage switch, potentially making it more susceptible to failure or shortening its lifespan. Furthermore, selecting a high-voltage switch with a higher maximum current rating increases the size and cost of the switch.

[0013] The present invention has been made to solve such problems, and an object of the present invention is to provide a high-voltage power supply device capable of suppressing fluctuations in output voltage when a load current suddenly changes while minimizing increases in device size and cost.

[0014] Solutions for solving problems

[0015] One embodiment of a high-voltage power supply device according to the present invention, which has been developed to solve the above-mentioned problems, is a high-voltage power supply device that outputs a high voltage of positive and negative polarities in a switchable manner, comprising:

[0016] a first voltage generating unit that outputs a positive-polarity high voltage;

[0017] a second voltage generating unit that outputs a negative high voltage;

[0018] a first discharge diode connected to the voltage output terminal of the first voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage;

[0019] a second discharge diode connected to the voltage output terminal of the second voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage;

[0020] a first output circuit connected between a voltage output terminal of the first voltage generating unit and a polarity switching voltage output terminal common to both polarities, wherein a first switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor;

[0021] a second output circuit connected between the voltage output terminal of the second voltage generating unit and the polarity switching voltage output terminal, wherein a second switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor;

[0022] an output capacitor connected in parallel with a load connected to the polarity-switched voltage output terminal;

[0023] a control unit configured to control the operation of the first and second voltage generating units and the opening and closing operations of the first and second switches so as to temporarily turn on the first and second switches while stopping the operation of the first and second voltage generating units when switching the polarity of the voltage output from the polarity switching voltage output terminal;

[0024] a first limiting unit that limits a time rate of change of a voltage between both ends of the switch when the control unit turns the first switch on; and

[0025] The second limiting unit limits a time rate of change of a voltage between both ends of the second switch when the control unit turns the second switch on.

[0026] In the high-voltage power supply device of the above-mentioned embodiment involved in the present invention, the first switch and the second switch as voltage-controlled semiconductor switches can use one or more stages of power MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) connected in series, or one or more stages of IGBTs (Insulated Gate Bipolar Transistors) connected in series.

[0027] Effects of the Invention

[0028] In the high-voltage power supply device of the above-described embodiment according to the present invention, when the control unit causes the first or second switch to transition to conduction, the first or second limiting unit maintains the time rate of change of the voltage across the terminals of the first or second switch at a substantially constant rate. Consequently, the current flowing through the first or second switch during the transition to conduction is also substantially constant. This allows the current flowing through the switch due to charge released from the output capacitor, etc., during the transition to conduction to be limited, without relying on a protective resistor primarily designed to limit inrush current. Furthermore, the resistance value of the protective resistor can be determined independently of the maximum allowable switching power of the switch. As a result, the maximum rated current of the first and second switches can be suppressed while the resistance value of the protective resistor can be set lower than that of conventional devices. Furthermore, by reducing the resistance value of the protective resistor, the output impedance is reduced, thereby suppressing fluctuations in the output voltage during sudden changes in load current.

[0029] Thus, the high-voltage power supply device according to the present invention, as described above, eliminates the need for large semiconductor switches with higher maximum current ratings as the first and second switches, which would increase the size and cost of the device. This allows for suppressing fluctuations in output voltage during sudden changes in load current. Consequently, for example, when the high-voltage power supply device is used as the power source for the orthogonal ion accelerator in an OA-TOFMS, even if the amount of ions introduced into the orthogonal ion accelerator fluctuates significantly, fluctuations in the output voltage can be suppressed, thereby maintaining high mass accuracy and mass resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic circuit diagram of a polarity switching high-voltage power supply device as one embodiment of the present invention.

[0031] Figure 2 This is an example of a waveform diagram of the output voltage when the positive and negative polarities of the polarity switching high-voltage power supply device according to this embodiment are switched.

[0032] Figure 3 This is a diagram for explaining the operation of the polarity switching high-voltage power supply device according to this embodiment.

[0033] Figure 4 This is an equivalent circuit during stage [2] in the polarity switching high-voltage power supply device of this embodiment.

[0034] Figure 5 It will Figure 4 The equivalent circuit shown is further simplified to obtain an equivalent circuit.

[0035] Figure 6 This is a diagram showing an example of a circuit of a high-voltage switch section in the polarity switching high-voltage power supply device according to the present embodiment. DETAILED DESCRIPTION

[0036] Hereinafter, a polarity switching high-voltage power supply device as one embodiment of the high-voltage power supply device according to the present invention will be described in detail with reference to the accompanying drawings.

[0037] Figure 1 This is a schematic circuit diagram of the polarity switching high-voltage power supply device according to this embodiment. Figure 2 This is an example of a schematic waveform diagram of the output voltage when the positive and negative polarities of the polarity switching high-voltage power supply device according to the present embodiment are switched. Figure 3 This is a diagram for explaining the operation of the polarity switching high-voltage power supply device according to this embodiment.

[0038] like Figure 1As shown, the polarity switching high-voltage power supply device of this embodiment includes a positive voltage generating unit 1A for generating a positive polarity high voltage +HV, a negative voltage generating unit 1B for generating a negative polarity high voltage -HV, a positive side discharge diode 2A, a negative side discharge diode 2B, a positive side high voltage switch unit 3A, a negative side high voltage switch unit 3B, a positive side protection resistor 5A, a negative side protection resistor 5B and an output capacitor 4.

[0039] Positive voltage generator 1A includes an excitation circuit 1A1 that outputs a high-voltage, high-frequency AC signal, a rectifier circuit 1A2 that converts the high-frequency AC signal into a high-voltage DC signal, and a filter circuit 1A3 that removes ripple voltage from the high-voltage DC signal. Similar to positive voltage generator 1A, negative voltage generator 1B includes an excitation circuit 1B1 that outputs a high-voltage, high-frequency AC signal, a rectifier circuit 1B2 that converts the high-frequency AC signal into a high-voltage DC signal, and a filter circuit 1B3 that removes ripple voltage from the high-voltage DC signal.

[0040] Discharge diodes 2A and 2B are connected so that when a voltage is output from the output terminals of positive voltage generator 1A and negative voltage generator 1B, respectively, they become reverse biased. Discharge diodes 2A and 2B function to discharge charge accumulated in capacitor 21A and 21B in rectifier circuit 1A2 and 1B2, capacitor 31A and 31B in filter circuit 1A3 and 1B3, and output capacitor 4.

[0041] The positive-side high-voltage switch section 3A includes a power MOSFET 3A1, which is a type of voltage-controlled semiconductor switch; a constant current source 3A2 connected between the source terminal (hereinafter sometimes referred to as the "S terminal") and the gate terminal (hereinafter sometimes referred to as the "G terminal") of the power MOSFET 3A1; and a feedback capacitor 3A3 connected between the drain terminal (hereinafter sometimes referred to as the "D terminal") and the G terminal of the power MOSFET 3A1. Similar to the positive-side high-voltage switch section 3A, the negative-side high-voltage switch section 3B includes a power MOSFET 3B1, which is a type of voltage-controlled semiconductor switch; a constant current source 3B2 connected between the S and G terminals of the power MOSFET 3B1; and a feedback capacitor 3B3 connected between the D and G terminals of the power MOSFET 3B1.

[0042] The voltage output terminal for outputting the positive-polarity DC high voltage generated by the positive voltage generator 1A is connected to the D terminal of the power MOSFET 3A1. A protective resistor 5A is connected between the S terminal of the power MOSFET 3A1 and the common voltage output terminal 6. The voltage output terminal for outputting the negative-polarity DC high voltage generated by the negative voltage generator 1B is connected to the S terminal of the power MOSFET 3B1. A protective resistor 5B is connected between the D terminal of the power MOSFET 3B1 and the common voltage output terminal 6. Protective resistors 5A and 5B primarily function to limit surge currents generated when, for example, an unintended discharge occurs in the load 100, preventing the flow of currents exceeding the rated currents of the power MOSFETs 3A1 and 3B1. Output capacitor 4 is connected between the common voltage output terminal 6 and the ground potential and stabilizes the potential of the load 100.

[0043] The control unit 7 controls the operation of the excitation circuits 1A1 and 1B1 and activates / deactivates (ON / OFF) the constant current sources 3A2 and 3B2 via the driver 8, thereby driving the power MOSFETs 3A1 and 3B1 on / off, respectively. The control unit 7 can be configured as a microcomputer, for example, including a CPU, RAM, and ROM. In this case, for example, a program corresponding to a series of control sequences for outputting a voltage waveform (described later) relative to the passage of time can be stored in the ROM, and the CPU can execute this program to output a control signal. Alternatively, the same functions can be achieved using hardware circuits such as a digital signal processor, rather than a microcomputer.

[0044] Next, refer to Figure 2 、 Figure 3 The output operation of the voltage waveform in the polarity switching high-voltage power supply device of this embodiment will be described.

[0045] exist Figure 3 In the embodiment, stage [1] is a state where a positive high voltage +HV is stably output from the common voltage output terminal 6 to the load 100, and stage [5] is a state where a negative high voltage -HV is stably output from the common voltage output terminal 6 to the load 100. When the polarity of the output voltage is reversed from positive to negative, the state changes from the positive voltage stable output state of stage [1] to the negative voltage stable output state of stage [5] through stages [2] → [3] → [4] in sequence. On the other hand, when the polarity of the output voltage is reversed from negative to positive, the state changes from the negative voltage stable output state of stage [5] to the positive voltage stable output state of stage [1] through stages [6] → [7] → [8] in sequence. Figure 2 The periods [1] to [8] in the voltage waveform shown are Figure 3Corresponding to stage [1] to stage [8].

[0046] like Figure 3 As shown in (a), in stage [1], the positive-side excitation circuit 1A1 remains in the ON (operating) state, and the positive-side high-voltage switch unit 3A remains in the ON (conducting) state. The DC high voltage +HV generated by the positive voltage generating unit 1A passes through the positive-side high-voltage switch unit 3A and the positive-polarity protection resistor 5A, and is applied to the output capacitor 4 and the load 100. As shown in the figure, the current is supplied to the load 100.

[0047] like Figure 3 As shown in (b), in stage [2], the control unit 7 sets the positive polarity excitation circuit 1A1 to the OFF (stop) state, keeps the positive side high voltage switch unit 3A in the ON (conduction) state, and switches the negative side high voltage switch unit 3B from the OFF (cut-off) state to the ON (conduction) state, that is, makes it conduct. If the negative side high voltage switch unit 3B is turned on, then when it is about to be turned on, the charge accumulated in the capacitor 21A included in the positive side rectifier circuit 1A2, the capacitor 31A included in the positive side filter circuit 1A3, and the output capacitor 4 is in accordance with Figure 3 The current path indicated by the dot-dash line in (b) is discharged through the protective resistors 5A and 5B and the negative electrode discharge diode 2B.

[0048] The aforementioned conduction transition of the negative-side high-voltage switch section 3B is performed while the time-dependent rate of change (slew rate) of the drain-source voltage of the power MOSFET 3B1 is maintained substantially constant by the operation of the feedback capacitor 3B3 and constant current source 3B2, which constitute the negative-side high-voltage switch section 3B. Therefore, regardless of the resistance values ​​of the protective resistors 5A and 5B, an excessive discharge current does not flow through the power MOSFET 3B1. The reason why the time-dependent rate of change of the drain-source voltage of the power MOSFET 3B1 is maintained constant by the operation of the feedback capacitor 3B3 and constant current source 3B2 will be explained in detail later. Furthermore, during the discharge of the aforementioned current path, most of the energy accumulated in the capacitor 21A included in the positive-side rectifier circuit 1A2, the capacitor 31A included in the positive-side filter circuit 1A3, and the output capacitor 4 is dissipated (converted into heat) by the power MOSFET 3B1.

[0049] like Figure 3As shown in (c), in stage [3], the control unit 7 switches the positive-side high-voltage switch unit 3A from the ON state to the OFF state (towards cutoff) by stopping the operation of the constant current source 3A2. In addition, the details will be described later, but at this time, the charge accumulated between the gate and source of the power MOSFET 3A1 is discharged through the bleeder resistor (not shown) connected in parallel with the constant current source 3A2. After the gate voltage drops, the power MOSFET 3A1 can be transferred to the OFF state. On the other hand, the negative-side high-voltage switch unit 3B maintains the ON state.

[0050] like Figure 3 As shown in (d), in stage [4], the control unit 7 turns on the negative-side excitation circuit 1B1. This charges the output capacitor 4 to negative polarity, causing the absolute value of the output voltage to increase. When the output voltage reaches the desired voltage value, the process transitions to stage [5].

[0051] like Figure 3 As shown in (e) of FIG5 , in stage [5], the negative-side excitation circuit 1B1 remains in the ON (operating) state, and the negative-side high-voltage switch unit 3B remains in the ON (conducting) state. At this time, the DC high voltage -HV generated by the negative voltage generating unit 1B passes through the negative-side high-voltage switch unit 3B and the negative-side protective resistor 5B, and is applied to the output capacitor 4 and the load 100.

[0052] like Figure 3 As shown in (f), in stage [6], the control unit 7 sets the excitation circuit 1B1 on the negative side to the OFF (stop) state, keeps the high voltage switch unit 3B on the negative side in the ON (conduction) state, and switches the high voltage switch unit 3A on the positive side from the OFF (cut-off) state to the ON (conduction) state, that is, turns it on. The charge accumulated in the capacitor 21B included in the rectifier circuit 1B2 on the negative side, the capacitor 31B included in the filter circuit 1B3 on the negative side, and the output capacitor 4 is in accordance with Figure 3 The current path indicated by the dot-dash line in (f) is discharged after passing through the protective resistors 5A and 5B and the positive electrode side discharge diode 2A.

[0053] The conduction transition of the positive-side high-voltage switch section 3A is performed while maintaining the time rate of change (slew rate) of the drain-source voltage of the power MOSFET 3A1 constant through the operation of the feedback capacitor 3A3 and constant current source 3A2 that comprise the positive-side high-voltage switch section 3A. Therefore, regardless of the resistance values ​​of the protective resistors 5A and 5B, an excessive discharge current does not flow through the power MOSFET 3A1. Furthermore, during the discharge in the aforementioned current path, most of the energy accumulated in the capacitor 21B included in the negative-side rectifier circuit 1B2, the capacitor 31B included in the negative-side filter circuit 1B3, and the output capacitor 4 is dissipated by the power MOSFET 3A1.

[0054] like Figure 3 As shown in (g), in stage [7], the control unit 7 switches the negative-side high-voltage switch unit 3B from the ON state to the OFF state, that is, turns it to the OFF state. On the other hand, the positive-side high-voltage switch unit 3A remains in the ON state.

[0055] like Figure 3 As shown in (h), in stage [8], the control unit 7 turns on the positive-side excitation circuit 1A1. This charges the output capacitor 4 to positive polarity, causing the output voltage to rise. When the output voltage reaches the desired voltage value, the process transitions to stage [1].

[0056] As mentioned above, in Figure 2 In the output voltage waveform shown, the periods [1] to [8] correspond to the aforementioned stages [1] to [8]. The time required to reverse the polarity of the output voltage from positive to negative, or vice versa, from negative to positive, i.e., the polarity reversal time tR, is the sum of the discharge time td, which is the time ts during which the high voltage switch units 3A and 3B are turned off, and the charging time tc. The discharge time td is the time during which the energy stored in the capacitors 21A, 31A, 21B, and 31B, respectively included in the rectifier circuits 1A2 and 1B2 and the filter circuits 1A3 and 1B3 of the voltage generating units 1A and 1B, and the output capacitor 4, is consumed in the power MOSFETs 3A1 and 3B1, thereby reducing the output voltage. The charging time tc is the time during which the excitation circuits 1A1 and 1B1 of the voltage generating units 1A and 1B are activated, thereby increasing the output voltage to the desired voltage value. The discharge time td is determined by the product of the output voltage and the inverse of the time rate of change (slew rate) of the voltage of the power MOSFETs 3A1 and 3B1.

[0057] Figure 4 This is an equivalent circuit during stage [2] in the polarity switching high-voltage power supply device of this embodiment. Figure 5 Ignore Figure 4The equivalent circuit shown is a further simplified equivalent circuit in which the combined capacitance of capacitor 21A of rectifier circuit 1A2, capacitor 31A of filter circuit 1A3, and output capacitor 4 is rewritten as Co. These equivalent circuits will be used to explain why the time rate of change of the drain-source voltage is substantially constant during the conduction transition of a power MOSFET.

[0058] Here, the direction of the current that increases the voltage between both ends of the feedback capacitor 3B3 is defined as charging, and the direction of the current that decreases the voltage between both ends is defined as discharging.

[0059] exist Figure 5 In this case, the power MOSFET 3B1 is initially in the OFF state, so a voltage equal to that of the output capacitor 4 is applied to the feedback capacitor 3B3. In this state, when the constant current source 3B2 is switched from inactive (OFF) to active (ON), the feedback capacitor 3B3 is discharged by the current supplied by the constant current source 3B2. This causes the gate-drain voltage of the power MOSFET 3B1 to decrease, while the gate-source voltage to increase. When this gate-source voltage reaches the gate threshold voltage Vth of the power MOSFET 3B1, the power MOSFET 3B1 begins to transition to conduction. As a result, the drain-source voltage of the power MOSFET 3B1 decreases. However, this causes a current to flow from the G terminal to the D terminal in the feedback capacitor 3B3 based on the rate of change of its voltage. This results in negative feedback being applied in the direction of decreasing the gate voltage.

[0060] When the current value generated by the constant current source 3B2 is set to Ig, the electrostatic capacitance of the feedback capacitor 3B3 is set to Cr, and it is assumed that the forward transfer admittance of the power MOSFET 3B1 is very large, the following equation holds.

[0061] Ig=Cr×(dVo / dt)

[0062] Right now,

[0063] dVo / dt=Ig / Cr…(1)

[0064] Equation (1) means that if the current value Ig and the electrostatic capacitance Cr are constant, the time change rate (slew rate) of the drain voltage is fixed.

[0065] On the other hand, the drain current Id of the power MOSFET 3B1 is:

[0066] Id=Co×(dVo / dt)

[0067] Therefore, according to the above formula (1), the following formula can be written:

[0068] Id=(Co / Cr)×Ig…(2)

[0069] Equation (2) means that if the capacitance Co is known, the drain current Id of the power MOSFET 3B1 can be kept constant based on the electrostatic capacitance Cr and the current value Ig, regardless of the resistance value of the protection resistor 5B.

[0070] The above description is an example of the operation for turning on power MOSFET 3B1 in stage [2]. However, the same operation is also applied to turning on power MOSFET 3A1 in stage [6]. That is, the time rate of change of the drain voltage of power MOSFET 3A1 can be made constant, thereby maintaining the drain current of power MOSFET 3A1 constant regardless of the resistance value of protection resistor 5A.

[0071] Here, the advantages of the polarity switching high-voltage power supply device of this embodiment over the conventional power supply device described in Patent Document 1 are specifically described. The comparison items are the resistance value and discharge time of the protective resistor under the same conditions. The conditions are as follows.

[0072] <Condition 1> The output voltages ±HV of the positive and negative voltage generating units 1A and 1B are set to ±10 kV.

[0073] <Condition 2> The capacitance of output capacitor 4, which includes the load capacitance, is set to 10 nF. The capacitances of capacitors 21A, 31A, 21B, and 31B included in voltage generating units 1A and 1B are sufficiently small compared to the capacitance of output capacitor 4 and can be ignored. Furthermore, the resistance of load 100 is sufficiently large compared to the output impedance of the power supply device, so the current flowing through load 100 is negligible.

[0074] <Condition 3> The maximum switching power of the power MOSFETs 3A1 and 3B1 is set to 100W.

[0075] <Condition 4> The maximum on-state current of the power MOSFETs 3A1 and 3B1 is set to 1A.

[0076] In conventional power supply devices, the maximum switching power of the power MOSFET is limited by the resistance value of the protection resistor. That is, in conventional power supply devices, the lower limit of the resistance value of the protection resistor is:

[0077] R <min>=10[kV] 2 / 100[W]=1[MΩ]

[0078] In addition, in the conventional power supply device, the discharge time td is:

[0079] td=3×τ=3×1[MΩ]×10[nF]=30[ms]

[0080] In contrast, in the polarity switching high-voltage power supply device of this embodiment, the maximum on-state current 1A of the power MOSFETs 3A1 and 3B1 is constrained by the resistance values ​​of the protection resistors 5A and 5B. That is, in this power supply device, the lower limit of the resistance value of the protection resistors is:

[0081] R <min>=10[kV] / 1[A]=10[kΩ]

[0082] In addition, the maximum switching power is 100W, so,

[0083] Id=100[W] / 10[kV]=10[mA]

[0084] Therefore, the discharge time td is:

[0085] td=10[nF]×10[kV] / 10[mA]=10[ms]

[0086] Thus, in the high-voltage power supply device of this embodiment, the discharge time can be shortened to 1 / 3 of the discharge time of the conventional high-voltage power supply device, and the resistance value of the protective resistor can be set to 1 / 100 of the resistance value of the protective resistor of the conventional high-voltage power supply device.

[0087] In the polarity switching power supply device of the present embodiment, circuits having various known structures can be employed as the constant current sources 3A2 and 3B2 constituting the high voltage switching units 3A and 3B. Figure 6 An example of this circuit is shown in FIG.

[0088] The constant current source in this example is a general constant current source using a PNP transistor. The emitter terminal of transistor Q1 is connected to resistor R2, and a Zener diode ZD3 is connected between the other terminal of resistor R2 and the base terminal of transistor Q1. In addition, the base terminal of transistor Q1 is connected to resistor R1. When transistor Q1 is turned on, ic = (V ZD -V be ) / R2(where V ZD is the Zener voltage of Zener diode ZD3, V be The collector current (which is the base-emitter voltage of transistor Q1) is used as a constant current. Furthermore, resistors R3 and R4 connected between the drain and source of power MOSFET 3A1 are used to reduce the effects of imbalance in the applied voltage to each MOSFET stage when the MOSFET is turned off, caused by variations in the drain-source off-state current of the power MOSFETs, when multiple power MOSFETs are connected in series in multiple stages as described later.

[0089] In addition, Figure 6 In the circuit shown, the drive signal supplied from the driver 8 is transmitted via a pulse transformer TR1, rectified by the rectifier circuit RC, a bridge circuit composed of Schottky barrier diodes, and then supplied to the base terminal of transistor Q1. This causes transistor Q1 to transition to the ON state. Conversely, when the drive signal from the driver 8 ceases, the voltage application to the emitter and base terminals of transistor Q1 ceases, turning transistor Q1 off. Consequently, the charge accumulated between the gate and source of the power MOSFET 3A1 is dissipated in resistor R1 via the collector and base of transistor Q1 and Schottky barrier diode SD2, ultimately turning the power MOSFET 3A1 off. In other words, in this circuit, resistor R1 acts as the aforementioned bleeder resistor. Thus, in this circuit, the driver 8 is connected to the power circuit including the power MOSFET via the pulse transformer TR1, providing the advantage of electrically isolating the driver 8 from the power circuit.

[0090] [Modification]

[0091] The polarity switching high-voltage power supply device of the above-described embodiment is merely an example of the present invention, and various modifications such as the following are possible.

[0092] In the polarity-switching high-voltage power supply device of the above-described embodiment, a single power MOSFET is used as the semiconductor switch in the high-voltage switching units 3A and 3B. However, due to the withstand voltage, multiple power MOSFETs can also be connected in series in multiple stages. In this case, it is preferable to provide a constant current source and a feedback capacitor for each power MOSFET, and to make the time rate of change of the drain-source voltage constant in each power MOSFET during the conduction transition. In addition, as the semiconductor switch, a voltage-controlled semiconductor switch other than a power MOSFET can also be used. Specifically, a single insulated gate bipolar transistor (IGBT) or multiple IGBTs connected in series in multiple stages can also be used. When an IGBT is used as the semiconductor switch, it is self-evident that the drain, source, and gate of the power MOSFET correspond to the collector, emitter, and base, respectively. Even when an IGBT is used, the operation is the same as when a power MOSFET is used.

[0093] Furthermore, in the polarity switching high-voltage power supply device of the above embodiment, a combination of constant current sources 3A2, 3B2 and feedback capacitors 3A3, 3B3 is used to maintain a substantially constant time rate of change of the drain-source voltage when power MOSFETs 3A1, 3B1 are switched to conduction. However, the same function can be achieved using other configurations. For example, a feedback circuit using an OP amplifier (operational amplifier) ​​or the like can be used to monitor the drain-source voltage of power MOSFETs 3A1, 3B1 in real time and control the gate-source voltage so that the time rate of change of this voltage remains constant at a target value.

[0094] In addition, the structure of the excitation circuits 1A1 and 1B1 included in the positive and negative voltage generating units 1A and 1B is not considered as long as they can output high-voltage AC signals, but typically, they can be configured to include an AC-DC converter that converts commercial AC power into DC power, switching elements such as power MOSFET that switches the DC current generated by the AC-DC converter, and a transformer including a primary coil that supplies the switched current.

[0095] Furthermore, the present invention is not limited to the above-described embodiment and various modifications, and any modifications, additions, or alterations appropriately made within the scope of the gist of the present invention are naturally encompassed by the scope of the claims of the present application.

[0096] [Various methods]

[0097] It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following aspects.

[0098] (Item 1) One embodiment of a high-voltage power supply device according to the present invention is a high-voltage power supply device that outputs a high voltage of positive and negative polarities in a switchable manner, comprising:

[0099] a first voltage generating unit that outputs a positive-polarity high voltage;

[0100] a second voltage generating unit that outputs a negative high voltage;

[0101] a first discharge diode connected to the voltage output terminal of the first voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage;

[0102] a second discharge diode connected to the voltage output terminal of the second voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage;

[0103] a first output circuit connected between a voltage output terminal of the first voltage generating unit and a polarity switching voltage output terminal common to both polarities, wherein a first switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor;

[0104] a second output circuit connected between the voltage output terminal of the second voltage generating unit and the polarity switching voltage output terminal, wherein a second switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor;

[0105] an output capacitor connected in parallel with a load connected to the polarity-switched voltage output terminal;

[0106] a control unit configured to control the operation of the first and second voltage generating units and the opening and closing operations of the first and second switches so as to temporarily turn on the first and second switches while stopping the operation of the first and second voltage generating units when switching the polarity of the voltage output from the polarity switching voltage output terminal;

[0107] a first limiting unit that limits a time rate of change of a voltage between both ends of the switch when the control unit turns the first switch on; and

[0108] The second limiting unit limits a time rate of change of a voltage between both ends of the second switch when the control unit turns the second switch on.

[0109] (Second item) In the high-voltage power supply device described in the first item, it can be set as follows: the first switch and the second switch are both MOSFETs, and the first limiting part and the second limiting part are each constructed to include: a feedback capacitor connected between the gate and the drain of the MOSFET, and a constant current source connected between the gate and the source of the MOSFET and supplying current from the source side to the gate, thereby limiting the time rate of change of the voltage between the drain and the source during the conduction transition of the MOSFET.

[0110] (Item 3) In the high-voltage power supply device described in the first item, it can be set as follows: the first switch and the second switch are switches obtained by connecting a plurality of MOSFETs in series in multiple stages, and the first limiting part and the second limiting part are each constructed as follows: a feedback capacitor connected between the gate and the drain of each MOSFET, and a constant current source connected between the gate and the source of each MOSFET and supplying current from the source side to the gate, thereby limiting the time change rate of the voltage between the drain and the source during the conduction transition of each MOSFET.

[0111] (Item 4) In the high-voltage power supply device described in the first item, it can be set as follows: the first switch and the second switch are both IGBTs, and the first limiting part and the second limiting part are each constructed as: a feedback capacitor connected between the base and the collector of the IGBT, and a constant current source connected between the base and the emitter of the IGBT and supplying current from the emitter side to the base, thereby limiting the time rate of change of the voltage between the collector and the emitter during the conduction transition of the IGBT.

[0112] (Item 5) In the high-voltage power supply device described in the first item, it can be set as follows: the first switch and the second switch are switches obtained by connecting a plurality of IGBTs in series in multiple stages, and the first limiting part and the second limiting part are each constructed as follows: a feedback capacitor connected between the base and the collector of each IGBT, and a constant current source connected between the base and the emitter of each IGBT and supplying current from the emitter side to the base, thereby limiting the time change rate of the voltage between the collector and the emitter during the conduction transition of each IGBT.

[0113] In the high-voltage power supply devices described in items 1 through 5, when the control unit causes the first or second switch, such as a power MOSFET or IGBT, to transition to conduction, the first or second limiting unit maintains the time rate of change of the voltage across the first or second switch at a substantially constant rate. Consequently, the current flowing through the first or second switch is also constant during the transition. This allows limiting the current flowing through the switch due to charge released from the output capacitor, etc., during the transition, without relying on a protective resistor primarily designed to limit inrush current. Consequently, the resistance value of the protective resistor can be determined independently of the maximum allowable switching power of the switch. As a result, the maximum rated current of the first and second switches can be suppressed while the resistance value of the protective resistor can be set lower than that of conventional devices. Furthermore, by reducing the resistance value of the protective resistor, the output impedance is reduced, thereby suppressing fluctuations in the output voltage during sudden changes in load current.

[0114] Thus, according to the high-voltage power supply device described in any one of items 1 to 5, fluctuations in output voltage during sudden changes in load current can be suppressed without using a large high-voltage switch with a higher maximum current rating, which would increase the size and cost of the device. Thus, for example, when the high-voltage power supply device described in any one of items 1 to 5 is used as a power source for the orthogonal ion accelerator in an OA-TOFMS, even if the amount of ions introduced into the orthogonal ion accelerator fluctuates significantly, changes in the output voltage can be suppressed, thereby maintaining high mass accuracy and mass resolution.

[0115] Description of Reference Numerals

[0116] 1A: Positive voltage generating unit; 1B: Negative voltage generating unit; 1A1, 1B1: Excitation circuit; 1A2, 1B2: Rectification circuit; 1A3, 1B3: Filter circuit; 2A, 2B: Discharge diode; 3A, 3B: High voltage switching unit; 3A1, 3B1: Power MOSFET; 3A2, 3B2: Constant current source; 3A3, 3B3: Feedback capacitor; 4: Output capacitor; 5A, 5B: Protection resistor; 6: Common voltage output terminal; 7: Control unit; 8: Drive unit; 100: Load.< / min> < / min>

Claims

1. A high-voltage power supply device that outputs a high voltage of positive and negative polarity in a switchable manner, the high-voltage power supply device comprising: a first voltage generating unit that outputs a positive-polarity high voltage; a second voltage generating unit that outputs a negative high voltage; a first discharge diode connected to the voltage output terminal of the first voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage; a second discharge diode connected to the voltage output terminal of the second voltage generating unit in such a direction that the diode becomes reverse biased by the voltage when the voltage output terminal outputs a high voltage; a first output circuit connected between a voltage output terminal of the first voltage generating unit and a polarity switching voltage output terminal common to both polarities, wherein a first switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor; a second output circuit connected between the voltage output terminal of the second voltage generating unit and the polarity switching voltage output terminal, wherein a second switch serving as a voltage-controlled semiconductor switch is connected in series with a protective resistor; an output capacitor connected in parallel with a load connected to the polarity-switched voltage output terminal; a control unit configured to control the operation of the first and second voltage generating units and the opening and closing operations of the first and second switches so as to temporarily turn on the first and second switches while stopping the operation of the first and second voltage generating units when switching the polarity of the voltage output from the polarity switching voltage output terminal; a first limiting unit that limits a time rate of change of a voltage between both ends of the switch when the control unit turns the first switch on; and The second limiting unit limits a time rate of change of a voltage between both ends of the second switch when the control unit turns the second switch on.

2. The high-voltage power supply device according to claim 1, wherein: The first switch and the second switch are both metal oxide semiconductor field effect transistors (MOSFETs), The first limiting part and the second limiting part are each constructed as follows: a feedback capacitor connected between the gate and the drain of the MOSFET, and a constant current source connected between the gate and the source of the MOSFET and supplying current from the source side to the gate, thereby limiting the time rate of change of the voltage between the drain and the source during the conduction transition of the MOSFET.

3. The high-voltage power supply device according to claim 1, wherein: The first switch and the second switch are switches obtained by connecting a plurality of MOSFETs in series in multiple stages. The first limiting part and the second limiting part are each constructed as follows: a feedback capacitor connected between the gate and the drain of each MOSFET, and a constant current source connected between the gate and the source of each MOSFET and supplying current from the source side to the gate, thereby limiting the time rate of change of the voltage between the drain and the source during the conduction transition of each MOSFET.

4. The high-voltage power supply device according to claim 1, wherein: The first switch and the second switch are both insulated gate bipolar transistors (IGBTs), The first limiting part and the second limiting part are each constructed to include a feedback capacitor connected between the base and the collector of the IGBT, and a constant current source connected between the base and the emitter of the IGBT and supplying current from the emitter side to the base, thereby limiting the time rate of change of the voltage between the collector and the emitter during the conduction transition of the IGBT.

5. The high-voltage power supply device according to claim 1, wherein: The first switch and the second switch are switches obtained by connecting a plurality of IGBTs in series in multiple stages. The first limiting part and the second limiting part are each constructed as follows: a feedback capacitor connected between the base and the collector of each IGBT, and a constant current source connected between the base and the emitter of each IGBT and supplying current from the emitter side to the base side, thereby limiting the time change rate of the voltage between the collector and the emitter during the conduction transition of each IGBT.

Images