A system for optimizing voltage distribution along high-voltage resistor strings in ICT high-voltage power supplies

Abstract

An insulated core transformer (ICT) high voltage DC power supply is disclosed. The power supply includes a plurality of printed circuit boards, each of which includes a secondary winding and a voltage doubler circuit. These voltage doubler circuits are arranged in series. The stacked printed circuit boards are surrounded by a plurality of grading rings. The last grading ring is electrically connected to the output voltage. High voltage resistors are then placed between adjacent grading rings to form a voltage divider. The voltage of the first grading ring may be used as part of a feedback system to regulate the output of the AC power supply. By placing high voltage resistors on the grading rings, a more uniform voltage gradient may be created.

Description

[Technical field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 166,413, filed February 3, 2021, the entire disclosure of which is incorporated herein by reference.

[0002] Field SUMMARY OF THE DISCLOSURE Embodiments of the present disclosure relate to a system for evenly distributing voltage along a high voltage resistor string in an isolation core transformer high voltage power supply. [Background technology]

[0003] background An isolated core transformer (ICT) high voltage power supply is a method of producing a high voltage DC output from an AC voltage. The input AC voltage is communicated to a primary winding.

[0004] In certain embodiments, there is a single secondary winding that multiplies the input voltage by a factor equal to the ratio of the number of turns in the secondary winding to the number of turns in the primary winding. The rectification and doubling of the voltage is done using a voltage circuit made up of diodes and capacitors. Typically, a voltage multiplier consists of two capacitors to store the voltage and two diodes, each of which allows current to flow in only one direction. The capacitors are arranged in series, which doubles the voltage.

[0005] In other embodiments, there are multiple secondary windings, each with its own voltage doubler circuit, arranged in series to generate the required higher DC voltage.

[0006] An ICT high voltage power supply includes multiple stacked printed circuit boards, with each printed circuit board comprising one stage of the high voltage power supply. For example, if the desired high voltage output is intended to be 125kV, there may be ten printed circuit boards stacked together, each producing 12.5kV. These printed circuit boards are connected in series to produce the high voltage output.

[0007] Additionally, in some embodiments, the AC voltage is controlled via closed loop control. The actual output voltage is compared to the desired output voltage and the AC voltage is adjusted accordingly. This may be accomplished by utilizing a voltage divider to generate a low DC voltage that is a predetermined percentage of the output voltage. For example, a voltage divider may be used to generate a 10V output from a 125kV output voltage. This 10V output is used as part of the feedback to control the AC voltage.

[0008] Due to the magnitude of the high voltage output, a voltage divider is usually created using multiple high voltage resistors and one or more low voltage resistors. For example, to generate a 10V output, five 400MΩ resistors are arranged in series to form a high voltage resistor string. One end of the high voltage resistor string may be connected to the output voltage, and the second end of the high voltage resistor string may be connected to a low voltage resistor, such as a 160kΩ resistor. The other end of the low voltage resistor may be grounded. If the output voltage is actually 125kV, the voltage across the low voltage resistor may be 10V. If the output voltage is different from the desired output, the voltage across the low voltage resistor will be different from this voltage.

[0009] However, in certain embodiments, due to stray capacitance, the voltages across multiple high voltage resistors may not be equal, resulting in some resistors consuming less power than the ideal voltage while other resistors consume more power than the ideal voltage.

[0010] This uneven voltage distribution across the resistors can cause voltage stress on these components, which can result in premature component failure. In addition to voltage stress, voltage measurement errors also occur because the currents going into and out of each resistor in the voltage divider may not be the same due to stray capacitance. This causes a difference between the actual output voltage and the measured output voltage.

[0011] It would therefore be advantageous to have a system and method for improving voltage uniformity between these components. It would further be beneficial if this approach were low cost and easy to implement. Summary of the Invention

[0012] An insulating core transformer (ICT) high voltage DC power supply is disclosed. The power supply includes a plurality of printed circuit boards, each of which includes a secondary winding and a voltage doubler circuit. These voltage doubler circuits are arranged in series. The stacked printed circuit boards are surrounded by a plurality of grading rings. The last grading ring is electrically connected to a high voltage output. High voltage resistors are then placed between adjacent grading rings to form a voltage divider. The voltage of the first grading ring may be used as part of a feedback system to regulate the output of the AC power supply. By placing high voltage resistors on the grading rings, a more uniform voltage gradient may be created.

[0013] According to one embodiment, a high voltage DC power supply for generating a DC voltage is disclosed, the high voltage DC power supply includes a primary winding and a plurality of stacked printed circuit boards including a first printed circuit board and a last printed circuit board, each printed circuit board includes a secondary winding having a first end and a second end, and a voltage multiplier circuit in communication with the secondary winding and having a high voltage output and a low voltage, the high voltage output of the first printed circuit board in communication with the low voltage of an adjacent second printed circuit board, the high voltage output of the last printed circuit board includes a DC voltage, a plurality of grading rings surround the plurality of stacked printed circuit boards, a last of the plurality of grading rings in communication with a DC voltage, a high voltage resistor is disposed between adjacent grading rings to form a voltage divider, a first terminal of the plurality of grading rings is connected to one terminal of a low voltage resistor, a second terminal of the low voltage resistor is grounded, and a voltage across the low voltage resistor represents a DC voltage.

[0014] In certain embodiments, at least one additional printed circuit board is disposed between the first printed circuit board and the last printed circuit board. In some embodiments, at least one additional grading ring is disposed between the first of the plurality of grading rings and the last of the plurality of grading rings. In some embodiments, the voltage generated by each voltage multiplier circuit is the same. In some embodiments, the high voltage DC power supply includes an AC power supply in communication with the primary winding and a feedback system in communication with the AC power supply. In certain embodiments, the voltage across the low voltage resistor is used by the feedback system to control the output of the AC power supply. In certain embodiments, a measurement error associated with the voltage across the low voltage resistor is reduced by at least a factor of three compared to an embodiment in which no grading rings are used. In some embodiments, at least one of the plurality of stacked printed circuit boards includes a plurality of voltage multiplier circuits. In certain embodiments, the voltage multiplier circuit includes a voltage doubler circuit. In certain further embodiments, the voltage doubler circuit includes a capacitor string including a plurality of capacitors arranged in series, where the negative end of a first capacitor of the capacitor string is at the lower voltage and the positive end of the last capacitor of the capacitor string is at the high voltage output, and a diode string including a plurality of diodes arranged in series, where the anode of the first diode of the diode string is connected to the low voltage and the cathode of the last diode of the diode string is connected to the high voltage output, wherein a first end of the secondary winding is electrically connected to the midpoint of the capacitor string and a second end of the secondary winding is electrically connected to the midpoint of the diode string.In some embodiments, each printed circuit board includes at least one additional secondary winding having a first end and a second end, and the voltage multiplier circuit includes a plurality of low voltage doubler circuits arranged in series to form a voltage multiplier circuit having a low voltage output at a first end and a high voltage output at a second end, each low voltage doubler circuit includes a positive end and a negative end and includes a first capacitor and a second capacitor arranged in series and a first diode and a second diode arranged in series, the positive end of the first capacitor is electrically connected to the cathode of the first diode and includes the positive end of the low voltage doubler circuit, the negative end of the second capacitor is electrically connected to the anode of the second diode and includes the negative end of the low voltage doubler circuit, the first end of each secondary winding is electrically connected to a trace connecting the first capacitor and the second capacitor, and the second end of each secondary winding is electrically connected to a trace connecting the first diode and the second diode.

[0015] According to another embodiment, a high voltage DC power supply for generating a DC voltage is disclosed. The high voltage DC power supply includes a primary winding and a plurality of stacked printed circuit boards, including a first printed circuit board and a last printed circuit board, each printed circuit board includes a secondary winding having a first end and a second end, and a voltage multiplier circuit in communication with the secondary winding and having a high voltage output and a low voltage, the high voltage output of the first printed circuit board in communication with the low voltage of an adjacent second printed circuit board, the high voltage output of the last printed circuit board includes a DC voltage, a plurality of grading rings surround the plurality of stacked printed circuit boards, a last of the plurality of grading rings in communication with the DC voltage, a high voltage resistor is disposed between adjacent grading rings to form a voltage divider, and a first of the grading rings is grounded. In certain embodiments, at least one additional printed circuit board is disposed between the first of the plurality of grading rings and the last of the plurality of grading rings. In some embodiments, the voltage generated by each voltage multiplier circuit is the same. In some embodiments, at least one of the plurality of stacked printed circuit boards includes a plurality of voltage multiplier circuits. In certain embodiments, the voltage multiplier circuit includes a voltage doubler circuit. In certain further embodiments, the voltage doubler circuit includes a capacitor string including a plurality of capacitors arranged in series, where a negative end of a first capacitor of the capacitor string is at a lower voltage and a positive end of a last capacitor of the capacitor string is at a high voltage output, and a diode string including a plurality of diodes arranged in series, where an anode of a first diode of the diode string is connected to a low voltage and a cathode of a last diode of the diode string is connected to a high voltage output, and a first end of a secondary winding is electrically connected to a midpoint of the capacitor string and a second end of the secondary winding is electrically connected to a midpoint of the diode string.In some embodiments, each printed circuit board includes at least one additional secondary winding having a first end and a second end, and the voltage multiplier circuit includes a plurality of low voltage doubler circuits arranged in series to form a voltage multiplier circuit having a low voltage at a first end and a high voltage output at a second end, each low voltage doubler circuit includes a positive end and a negative end and includes a first capacitor and a second capacitor arranged in series, and a first diode and a second diode arranged in series, the positive end of the first capacitor is electrically connected to the cathode of the first diode and includes the positive end of the low voltage doubler circuit, the negative end of the second capacitor is electrically connected to the anode of the second diode and includes the negative end of the low voltage doubler circuit, the first end of each secondary winding is electrically connected to a trace connecting the first capacitor and the second capacitor, and the second end of each secondary winding is electrically connected to a trace connecting the first diode and the second diode.

[0016] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief description of the drawings]

[0017] [Figure 1] 1 is a representative schematic diagram illustrating a high voltage power supply with voltage non-uniformity compensation according to one embodiment. [Diagram 2] 2 illustrates a layout of voltage generators located on each of the printed circuit boards in the high voltage power supply of FIG. 1 according to one embodiment. [Diagram 3] 2 illustrates a layout of voltage generators disposed on each of the printed circuit boards in the high voltage power supply of FIG. 1 according to another embodiment. [Figure 4] 2 illustrates an expanded view of a resistor string used with the high voltage power supply of FIG. 1 according to one embodiment. [Diagram 5] FIG. 13 illustrates a resistive voltage divider disposed on a grading ring according to one embodiment. [Figure 6] FIG. 13 illustrates a resistive voltage divider disposed on a grading ring according to another embodiment. [Figure 7] FIG. 7 shows the voltage distribution across a resistive divider in a high voltage power supply compared to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] This disclosure describes systems and methods for producing a more uniform voltage distribution across a voltage divider and reducing voltage measurement errors in an ICT high voltage DC power supply. Additionally, this disclosure describes a system for producing a more uniform voltage distribution across multiple grading rings surrounding an ICT high voltage DC power supply.

[0019] FIG. 1 illustrates a first embodiment of an ICT high voltage DC power supply 1. The ICT high voltage DC power supply 1 includes a primary winding 20. The primary winding 20 may be connected to an AC voltage power supply 10. The primary winding 20 passes through one or more openings in each of a plurality of stacked printed circuit boards 30. For example, as shown in FIG. 1, the primary winding 20 rests on a bottom bar of ferrite. Each of the printed circuit boards 30 (PCBs) includes one or more secondary windings 31 in proximity to the ferrite bottom bar that couples the magnetic flux. The secondary windings 31 on each PCB communicate with a voltage multiplier circuit located on that printed circuit board 30, as described in more detail below. Furthermore, in certain embodiments, each printed circuit board 30 may have two voltage multiplier circuits, each in communication with one or more secondary windings 31. Furthermore, the output of a voltage multiplier circuit on one PCB may serve as an input voltage to a voltage multiplier circuit located on an adjacent PCB. In other words, the output of a voltage multiplier circuit on one printed circuit board 30 is cascaded in series with voltage multiplier circuits on other printed circuit boards formed in a stack to form a high voltage output. Each printed circuit board generates an independent voltage and is cascaded in series to produce the high voltage output. In certain embodiments, the voltage multiplier circuit includes a voltage doubler circuit.

[0020] FIG. 2 illustrates a first embodiment of a voltage doubler circuit 32 that may be disposed on each printed circuit board 30. The printed circuit board 30 may be a conventional printed circuit board having multiple layers, with conductive layers separated from one another by insulating material such as FR4. In a particular embodiment, the printed circuit board 30 may include two conductive layers, a top side and a bottom side. Electrical traces may be disposed on these layers of the printed circuit board. Vias may be used to connect the traces on the top side to the traces on the bottom side. These electrical traces are used to electrically connect the various components disposed on the printed circuit board. In other embodiments, there may be more than two conductive layers.

[0021] The voltage doubler circuit 32 also includes a capacitor string. The string includes a number of capacitors 100 arranged in series. Each of the capacitors may have the same capacitance and voltage rating. A first end of the capacitor string is connected to the lower voltage 34 and a second end of the capacitor string is connected to the higher voltage 35. The voltage doubler circuit 32 also includes a string of diodes. The diode string includes a number of diodes 110 arranged in series as well. A first end of the diode string is connected to the lower voltage 34 and a second end of the diode string is connected to the higher voltage 35. The cathode of one diode is connected to the anode of the adjacent diode in the diode string. Thus, the anode of the first diode is connected to the lower voltage 34 and the cathode of the last diode in the diode string is connected to the higher voltage 35. During the positive portion of the AC cycle, the diodes located between the midpoint and the higher voltage 35 conduct current, charging the capacitors located between the midpoint and the higher voltage 35. During the negative portion of the AC cycle, the diodes placed between the midpoint and the lower voltage 34 conduct current, charging the capacitors placed between the midpoint and the lower voltage 34. Thus, the cathode of each diode is at a higher voltage than the anode of that diode.

[0022] In a particular embodiment, the number of diodes 110 and capacitors 100 are equal. In other embodiments, the number of diodes 110 and capacitors 100 may be different. The number of capacitors 100 and diodes 110 may be even such that there are an equal number of diodes and capacitors on either side of the midpoint. A first end of the secondary winding 31 is electrically connected to the midpoint of the capacitor string. A second end of the secondary winding 31 is electrically connected to the midpoint of the diode string. The midpoint means that there are the same number of capacitors 100 (and diodes 110) between the first end and the midpoint as there are between the midpoint and the second end.

[0023] 2 shows twelve capacitors 100 and twelve diodes 110, the disclosure is not limited to this embodiment. Rather, the number of capacitors 100 and diodes 110 is not limited by the disclosure. Furthermore, the number of capacitors 100 and diodes 110 need not be the same.

[0024] FIG. 3 shows a second embodiment of a high voltage doubler circuit 301 that may be disposed on each printed circuit board 30. In this embodiment, there are multiple secondary windings 31. Each secondary winding 31 is in communication with an associated low voltage doubler circuit 350. Each low voltage doubler circuit 350 includes two capacitors 360a, 360b arranged in series and two diodes 370a, 370b arranged in series. A first end of the secondary winding 31 is in electrical contact with a trace connecting the two capacitors 360a, 360b. A second end of the secondary winding 31 is in electrical contact with a trace connecting the anode of the diode 370a to the cathode of the diode 370b. The positive end of the capacitor 360a is electrically connected to the cathode of the diode 370a. The negative end of the capacitor 360b is electrically connected to the anode of the diode 370b.

[0025] The low-voltage doubler circuits 350 are connected in series to form the high-voltage doubler circuit 301. In other words, the cathode of the diode 370a of one low-voltage doubler circuit 350 is in electrical contact with the anode of the diode 370b of an adjacent low-voltage doubler circuit 350. Each low-voltage doubler circuit 350 is electrically connected in series to at least one other low-voltage doubler circuit 350 to form the high-voltage doubler circuit 301.

[0026] The input to the first low voltage doubler circuit 350 is electrically connected to the low voltage 34 , while the output of the last low voltage doubler circuit 350 is electrically connected to the high voltage 35 .

[0027] Regardless of which voltage doubler circuit is used, the higher voltage 35 of one printed circuit board 30 is electrically connected to the lower voltage 34 of an adjacent printed circuit board in the stack. In some embodiments, the voltage generated by the voltage doubler circuit on each printed circuit board is the same.

[0028] Thus, the output of the voltage doubler circuit of each PCB is in series with the voltage doubler circuit of the adjacent PCB, cascading the voltage doubler circuits. For example, if ten PCBs are stacked, the output voltage may be 125 kV if the voltage doubler circuit on each PCB produces 12.5 kV. Of course, a different number of PCBs may be used and the voltage produced by each voltage doubler circuit may be different from the above example. The PCB that produces the output voltage may be referred to as the last printed circuit board. This last printed circuit board is the last PCB in the series. The first printed circuit board in the series may be referred to as the first printed circuit board. If the printed circuit boards are stacked vertically, as shown in Figure 1, the first PCB may be the bottom printed circuit board and the last PCB may be the top printed circuit board. Of course, the stack may be flipped so that the last PCB is the bottom printed circuit board.

[0029] Although the above description refers to voltage doubler circuits, it will be understood that these voltage doubler circuits do not have to double the voltage. For example, a voltage tripler circuit, a voltage quadruple circuit, or a rectifier circuit may be used.

[0030] Referring again to FIG. 1, surrounding the stacked printed circuit boards 30 are a number of grading rings 40. The grading rings 40 are used to reduce the corona effect emitted by the ICT high voltage DC power supply 1. The grading rings 40 also serve to create a more uniform potential along the stacked printed circuit boards 30. The grading rings 40 are made of a conductive material such as metal. The grading rings may be circular rings and may have an inner diameter larger than the dimensions of the printed circuit boards 30.

[0031] The last grading ring of the multiple grading rings 40 communicates with an output voltage that may be generated by a last printed circuit board. Thus, the voltage applied to the last grading ring is equal to the output voltage of the ICT high voltage DC power supply 1. The first grading ring may communicate with a first printed circuit board, which may be the bottom printed circuit board, as described in more detail below. In certain embodiments, at least one grading ring is disposed between the last grading ring and the first grading ring. In some embodiments, multiple grading rings are disposed between the last grading ring and the first grading ring.

[0032] The number of grading rings 40 may be different from the number of printed circuit boards 30.

[0033] High voltage resistors 50 are used to electrically connect adjacent grading rings 40. For example, if there are six grading rings 40, there will be five high voltage resistors 50 arranged in series, which are used to form a voltage divider on the grading rings 40. The resistance value of each high voltage resistor 50 may be the same. These high voltage resistors 50 form a high voltage resistor string.

[0034] These high voltage resistors 50 may be attached directly to the grading rings 40, as best shown in FIG. 4. For example, the terminals of each high voltage resistor 50 may be clamped or otherwise fixed to two adjacent grading rings 40. The grading rings 40 and the high voltage resistors 50 act as a shielding capacitance to compensate for stray capacitance. The high voltage resistors 50 are positioned on the grading rings 40 such that leakage from stray capacitance is nearly or completely neutralized by the grading rings 40 and the voltage difference along the voltage divider is nearly uniform.

[0035] FIG. 5 shows a block diagram showing ten stacked printed circuit boards 30 and six grading rings 40. The last grading ring 40a is electrically connected to the output voltage generated by the last printed circuit board 30a. High voltage resistors 50 are used to connect adjacent grading rings such that there is a high voltage resistor between each pair of adjacent grading rings 40. The first grading ring 40b is electrically connected to the first printed circuit board 30b. Note that none of the other grading rings 40 are in communication with the voltage generated by the other printed circuit boards. In certain embodiments, at least one printed circuit board is disposed between the last printed circuit board 30a and the first printed circuit board 30b. In some embodiments, multiple printed circuit boards are disposed between the last printed circuit board 30a and the first printed circuit board 30b.

[0036] The first grading ring 40b is electrically connected to a low-voltage resistor 38 that may be disposed on the first printed circuit board 30b. For example, one terminal of the low-voltage resistor on the first printed circuit board 30b may communicate with the first grading ring 40b, while the second terminal of the low-voltage resistor communicates with ground. Alternatively, one terminal of the low-voltage resistor 38 may be disposed on or near the first grading ring 40b, while the second terminal of the low-voltage resistor is grounded. In these embodiments, the first grading ring 40b is not grounded, but is at a voltage generated by a voltage divider that includes a high-voltage resistor 50 disposed on the grading ring 40b and a low-voltage resistor 38 that communicates with the first grading ring 40b. For example, if the high voltage resistors 50 disposed on the grading ring 40 are each 400 MΩ and the low voltage resistors 38 are 160 kΩ, then the voltage on the first grading ring 40b may be 10,000V.

[0037] In this embodiment, the voltage of the first grading ring 40b may be used as part of a feedback system 500 that controls the magnitude of the AC voltage power supply 10. The feedback system 500 may include a controller, such as a proportional controller, a proportional-derivative (PD) controller, a proportional-integral-derivative (PID) controller, or other types of controllers. For example, if the voltage of the first grading ring 40b is lower than an expected value, the feedback system 500 may increase the voltage output from the AC voltage power supply 10. Conversely, if the voltage of the first grading ring 40b is greater than an expected value, the feedback system 500 may decrease the voltage output from the AC voltage power supply 10.

[0038] According to another embodiment shown in FIG. 6, the first grading ring 40b is electrically grounded. This can be done via a connection to the first printed circuit board 30b. In this way, the voltage of each grading ring 40 is equal to N *4, the output voltage of the grading ring 40 is connected to the output of the printed circuit board 30. The output voltage of the grading ring 40 is approximately equal to (output voltage) / M-1, where M is the number of grading rings 40 and N is the position of the grading ring in the series. Specifically, the first grading ring 40b has an N value of 0 and the last grading ring 40a has an N value of M-1. Again, as discussed above with respect to FIG. 4, only the last grading ring 40a is in communication with the output voltage of the printed circuit board 30. The remaining grading rings are connected only to adjacent grading rings through high voltage resistors 50, except for the first grading ring 40b, which is also grounded.

[0039] As an example, if the output voltage is 125 kV and there are six grading rings, the voltages of the grading rings 40 may be 0, 25 kV, 50 kV, 75 kV, 100 kV, and 125 kV, respectively. In this embodiment, the grading rings 40 do not provide feedback to the AC voltage power supply 10. Rather, in this embodiment, the high voltage resistors 50 function to create a more uniform voltage gradient across the stacked printed circuit boards 30.

[0040] The system described herein has many advantages. A simulation was performed for a high voltage power supply with an output of 125 kV. Ten printed circuit boards were used, each with a voltage doubler circuit. In one embodiment, no grading ring 40 was used, and the high voltage resistors 50 described above were placed on one or more of the printed circuit boards. There were five high voltage resistors 50, each with a resistance of 400 MΩ. In addition, a low voltage resistor 38 with a resistance of 160 kΩ was also placed on one of the printed circuit boards. As explained above, these six resistors form a voltage divider. Due to stray capacitance, the voltage across each high voltage resistor 50 in the high voltage resistor string is not uniform. Rather, the voltage drop across the high voltage resistor 50 closest to the high voltage output is greatest because more current passes through it. The voltage across each high voltage resistor 50 in the high voltage resistor string may decrease as one moves away from the high voltage output. For example, the voltages simulated across each resistor are as follows: 125.0kV; 85.21kV; 57.34kV; 32.10kV; 14.837kV; and 9.394V.

[0041] This voltage across each high voltage resistor is shown in Figure 7 as line 700. This means increased voltage stress on the high voltage resistors near the high voltage outputs, which can lead to premature failure.

[0042] Additionally, using this embodiment, the voltage measured across low voltage resistor 38 is less than the theoretical value. For example, if the output voltage is 125 kV, the voltage measured across low voltage resistor 38 could theoretically be 10,000 V. However, in this embodiment, as discussed above, the simulated voltage was only 9.4 V. This difference in voltage can impact the ability to accurately generate the required high voltage output.

[0043] However, when the grading ring 40 is introduced and a high voltage resistor 50 is placed on the grading ring 40, as shown in Figure 5, the voltage uniformity is greatly improved. For example, the voltage across a simulated voltage divider is: 125.0kV; 98.960kV; 75.340kV; 48.66kV; 24.34kV; and 9.876V.

[0044] The voltage across high voltage resistor 50 is shown in FIG. 7 as line 710. Specifically, the measurement error using grading ring 40 is less than 0.125V instead of an error of 0.6V. This is a reduction in measurement error by a factor of four. In other embodiments, the measurement error may be reduced by at least a factor of three.

[0045] In addition, the voltage across each high voltage resistor 50 will be more uniform, and the voltage across the low voltage resistor 38 will be much closer to the theoretical value. Therefore, component reliability will be improved and control of the high voltage output may be more precise. This is due to the effect of the shield capacitance created by the grading ring 40.

[0046] Additionally, placing high voltage resistors 50 between adjacent grading rings 40 also creates a more uniform potential gradient along the grading rings. For example, in certain embodiments, the voltage of each voltage doubler circuit may vary depending on design, loading, or other parameters. By using only high voltage outputs and connecting the grading rings using multiple high voltage resistors, a more uniform voltage gradient can be created on the grading rings 40 than would otherwise be possible.

[0047] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, in addition to those described herein, various other embodiments and modifications of the present disclosure will become apparent to those skilled in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and variations are intended to be included within the scope of the present disclosure. Furthermore, although the present disclosure is described herein in connection with specific implementations in specific environments for specific purposes, those skilled in the art will recognize that its usefulness is not limited thereto, and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in light of the full scope and spirit of the present disclosure as described herein.

Claims

1. 1. A high voltage DC power supply for generating a DC voltage, comprising: A primary winding; A plurality of stacked printed circuit boards, including a first printed circuit board and a last printed circuit board, each printed circuit board comprising: a secondary winding having a first end and a second end; and the plurality of stacked printed circuit boards including a voltage multiplier circuit electrically connected to the secondary winding, the voltage multiplier circuit having a high voltage output and a low voltage, the high voltage output of a first printed circuit board being electrically connected to the low voltage of an adjacent second printed circuit board, the high voltage output of the last printed circuit board including the DC voltage; a plurality of grading rings surrounding the plurality of stacked printed circuit boards, the last of the plurality of grading rings being electrically connected to a DC voltage; a high voltage resistor disposed between adjacent grading rings forming a voltage divider, a first of the plurality of grading rings being connected to one terminal of a low voltage resistor, a second terminal of the low voltage resistor being grounded, a voltage across the low voltage resistor being based on the DC voltage, a value of the high voltage resistor, and a value of the low voltage resistor; a high voltage DC power supply for generating a DC voltage,

2. 10. The high voltage DC power supply of claim 1 including at least one additional printed circuit board disposed between said first printed circuit board and said last printed circuit board.

3. 2. The high voltage DC power supply of claim 1 including at least one additional grading ring disposed between the first of the plurality of grading rings and the last of the plurality of grading rings.

4. 2. The high voltage DC power supply of claim 1, wherein the voltage produced by each voltage multiplier circuit is the same.

5. 10. The high voltage DC power supply of claim 1, further comprising: an AC power source electrically connected to said primary winding; and a feedback system electrically connected to said AC power source.

6. 6. The high voltage DC power supply of claim 5, wherein the voltage across said low voltage resistor is used by said feedback system to control the output of said AC power supply.

7. 7. The high voltage DC power supply of claim 6, wherein a measurement error associated with the voltage across the low voltage resistor is reduced by at least a factor of three compared to an embodiment in which the multiple grading rings are not used.

8. 10. The high voltage DC power supply of claim 1, wherein at least one of said plurality of stacked printed circuit boards includes a plurality of voltage multiplier circuits.

9. 2. The high voltage DC power supply of claim 1, wherein said voltage multiplication circuit comprises a voltage doubler circuit.

10. The voltage doubler circuit comprises: a capacitor string including a plurality of capacitors arranged in series, the negative end of a first capacitor of the capacitor string being a low voltage output and the positive end of a last capacitor of the capacitor string being a high voltage output; a diode string including a plurality of diodes arranged in series, an anode of a first diode of the diode string being connected to the low voltage and a cathode of a last diode of the diode string being connected to the high voltage output, the first end of the secondary winding being electrically connected to a midpoint of the capacitor string, and the second end of the secondary winding being electrically connected to the midpoint of the diode string; 10. The high voltage DC power supply of claim 9, comprising:

11. each printed circuit board includes at least one additional secondary winding having a first end and a second end; The voltage multiplier circuit comprises:

2. The high voltage DC power supply of claim 1, comprising a plurality of low voltage doubler circuits arranged in series to form the voltage multiplier circuit having the low voltage at a first end and the high voltage output at a second end, each low voltage doubler circuit including a positive end and a negative end, and including a first capacitor and a second capacitor arranged in series, and a first diode and a second diode arranged in series, a positive end of the first capacitor electrically connected to a cathode of the first diode and comprising the positive end of the low voltage doubler circuit, a negative end of the second capacitor electrically connected to an anode of the second diode and comprising the negative end of the low voltage doubler circuit, a first end of a respective secondary winding electrically connected to a trace connecting the first capacitor and the second capacitor, and a second end of the respective secondary winding electrically connected to a trace connecting the first diode and the second diode.

12. 1. A high voltage DC power supply for generating a DC voltage, comprising: A primary winding; A plurality of stacked printed circuit boards, including a first printed circuit board and a last printed circuit board, each printed circuit board comprising: a secondary winding having a first end and a second end; and the plurality of stacked printed circuit boards including a voltage multiplier circuit electrically connected to the secondary winding and having a high voltage output and a low voltage, the high voltage output of a first printed circuit board being electrically connected to the low voltage of an adjacent second printed circuit board, the high voltage output of the last printed circuit board including the DC voltage; a plurality of grading rings surrounding the plurality of stacked printed circuit boards, a last ring of the plurality of grading rings being electrically connected to the DC voltage, high voltage resistors being disposed between adjacent grading rings to form a voltage divider, and a first of the plurality of grading rings being grounded; a high voltage DC power supply including

13. 13. The high voltage DC power supply of claim 12 including at least one additional printed circuit board disposed between said first printed circuit board and said last printed circuit board.

14. 13. The high voltage DC power supply of claim 12 including at least one additional grading ring disposed between the first of the plurality of grading rings and the last of the plurality of grading rings.

15. 13. The high voltage DC power supply of claim 12, wherein the voltage produced by each voltage multiplier circuit is the same.

16. 13. The high voltage DC power supply of claim 12, wherein at least one of said plurality of stacked printed circuit boards includes a plurality of voltage multiplier circuits.

17. 13. The high voltage DC power supply of claim 12, wherein the voltage multiplication circuit comprises a voltage doubler circuit.

18. The voltage doubler circuit comprises: a capacitor string including a plurality of capacitors arranged in series, the negative end of a first capacitor of the capacitor string being at the low voltage output and the positive end of a last capacitor of the capacitor string being at the high voltage output; a diode string including a plurality of diodes arranged in series, an anode of a first diode of the diode string being connected to the low voltage and a cathode of a last diode of the diode string being connected to the high voltage output, the first end of the secondary winding being electrically connected to a midpoint of the capacitor string, and the second end of the secondary winding being electrically connected to the midpoint of the diode string; 20. The high voltage DC power supply of claim 17, comprising:

19. each printed circuit board includes at least one additional secondary winding having a first end and a second end; The voltage multiplier circuit comprises:

13. The high voltage DC power supply of claim 12, comprising a plurality of low voltage doubler circuits arranged in series to form the voltage multiplier circuit having the low voltage at a first end and the high voltage output at a second end, each low voltage doubler circuit including a positive end and a negative end, and including a first capacitor and a second capacitor arranged in series, and a first diode and a second diode arranged in series, a positive end of the first capacitor electrically connected to a cathode of the first diode and comprising the positive end of the low voltage doubler circuit, a negative end of the second capacitor electrically connected to an anode of the second diode and comprising the negative end of the low voltage doubler circuit, a first end of a respective secondary winding electrically connected to a trace connecting the first capacitor and the second capacitor, and a second end of the respective secondary winding electrically connected to a trace connecting the first diode and the second diode.

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