Ultra-low noise floating high voltage power supply for mass spectrometer ion detectors

Abstract

A high voltage power supply system for a mass spectrometer includes a ground referenced power supply having a first transformer with a primary winding and a secondary winding, the primary winding electrically coupled to a first AC power source, and a floating bias power supply having a second transformer with a primary winding and a secondary winding, the primary winding of the second transformer electrically coupled to a second AC power source. A return electrical path of the floating bias power supply is electrically coupled to the ground referenced power supply to bias an output voltage of the ground referenced power supply. A floating shield is disposed about the floating bias power supply and at least one resistive element is located in the return electrical path of the floating bias power supply to reduce noise coupled from the floating bias power supply to the ground referenced power supply.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 905,029, filed September 24, 2019, entitled “Ultra Low Noise Floated HighVoltage Supply for Mass Spectrometer Ion Detector,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to systems and methods for reducing noise coupling between two high-voltage power supplies, and more specifically, to systems and methods for reducing noise coupling between a floating bias power supply and a ground reference voltage power supply used in a mass spectrometry system. Background Technology

[0004] In mass spectrometry systems, high-voltage power supplies are used to apply voltage to various components of the system. For example, a high-voltage power supply is used in mass spectrometry analysis systems to apply a bias voltage to the ion detector. In some configurations, a floating high-voltage power supply is electrically coupled to a ground reference power supply, causing the floating high-voltage power supply to bias the output voltage of the ground reference power supply. In the conventional design of this configuration, current ripple can flow from the secondary winding of the floating high-voltage power supply to the output capacitor of the ground reference power supply, thus generating a ripple voltage at the output. This ripple voltage can increase noise in the ion detector, thus adversely affecting the signal-to-noise ratio of ion detection.

[0005] Therefore, there is a need for methods and systems for reducing noise in high-voltage power supplies, and more specifically, for methods and systems that can be used to reduce noise between two high-voltage power supplies in an electrically floating configuration with mass spectrometry applications. Summary of the Invention

[0006] In one aspect, a high-voltage power supply system for a mass spectrometer is disclosed. This high-voltage power supply system includes: a ground reference power supply having a first transformer including a primary winding and a secondary winding, the primary winding being electrically coupled to a first AC power supply; and a floating bias power supply having a second transformer including a primary winding and a secondary winding, the primary winding of the second transformer being electrically coupled to a second AC power supply. The return path of the floating bias power supply is electrically coupled to the ground reference power supply to bias the output voltage of the ground reference power supply. Additionally, a floating shield is disposed around the floating bias power supply, and at least one resistive element is disposed in the return path of the floating bias power supply to reduce noise coupled from the floating bias power supply to the ground reference power supply.

[0007] Floating shields can provide a low AC impedance path from the return path of the floating bias power supply to ground.

[0008] A resistive element disposed in the return path can be coupled in series with a capacitor to enhance the impedance of the return path, the capacitor being associated with the floating shield. In some embodiments, the resistance of the resistive element can be in the range of about 10 kΩ to about 1 MΩ, for example, in the range of about 100 kΩ to about 500 kΩ. In some embodiments, the capacitor associated with the floating shield can be in the range of about 6 pF to about 100 nF, for example, in the range of about 100 pF to about 50 nF.

[0009] In some embodiments, a Faraday shield is disposed in the transformer of a floating voltage power supply to reduce parasitic coupling between the secondary and primary windings of the transformer. In some embodiments, the Faraday shield can reduce this coupling by approximately 2 to approximately 100 times.

[0010] In some embodiments, the return electrical path is capacitively coupled to ground via at least one capacitor. In some embodiments, the capacitance of such a capacitor may be in the range of about 6 pF to about 100 nF.

[0011] In some embodiments, the ground reference power supply can provide an output voltage in the range of about 0 to about 20 kV (e.g., in the range of about 0 to 10 kV).

[0012] In some embodiments, a floating bias power supply can be coupled to the ion detector of the mass spectrometer to apply a high voltage to it.

[0013] In a related aspect, a mass spectrometer is disclosed, comprising: a mass analyzer; an ion detector disposed downstream of the mass analyzer; and a high-voltage power supply system configured to apply a high voltage to the ion detector. The high-voltage power supply system may include a ground reference voltage power supply having a first transformer including a primary winding and a secondary winding, the primary winding being electrically coupled to a first AC power supply. The high-voltage power supply system may also include a floating bias power supply having a second transformer including a primary winding and a secondary winding, the primary winding of the second transformer being electrically coupled to a second AC power supply. A return path of the floating bias power supply is electrically coupled to the ground reference voltage power supply to bias the output voltage of the ground reference power supply. A floating shield is disposed around the floating bias power supply, and at least one resistive element is disposed in the return path of the floating bias power supply to reduce noise coupled from the floating bias power supply to the ground reference voltage power supply.

[0014] Further understanding of various aspects of this disclosure can be obtained by referring to the following detailed description in conjunction with the relevant diagrams briefly described below. Attached Figure Description

[0015] Figure 1A high-voltage power supply system according to an embodiment of this teaching is schematically depicted.

[0016] Figure 2 schematically depicted Figure 1 Selected portions of the high-voltage power supply system depicted in the text.

[0017] Figure 3 An example of a controller that can be used to synchronize the phase of an AC voltage generated by an AC voltage source that applies AC voltage to the primary winding of a transformer of a floating bias power supply with a ground reference voltage power supply is schematically depicted.

[0018] Figure 4 A mass spectrometer in which a high-voltage power supply system according to the present disclosure can be employed is schematically depicted. Detailed Implementation

[0019] This disclosure provides methods and systems for reducing noise coupling between two high-voltage power supplies in an electrically floated configuration for mass spectrometry applications. In this configuration, one power supply returns to a reference ground, and the second power supply uses the output of another power supply as a return reference. It is well known that connecting two power supplies in this manner can produce undesirable effects such as ripple or noise coupling from the floated power supply to the grounded reference power supply. Such ripple or noise can lead to performance degradation of the mass spectrometry system. As discussed in detail below, the methods and systems of this disclosure can significantly reduce such ripple or noise coupling and thus improve the performance of the high-voltage power supply system, for example, when used in a mass spectrometry analysis system.

[0020] Figure 1 and Figure 2 A power supply system 10 according to an embodiment of the present disclosure is schematically depicted, comprising a ground reference voltage power supply 100 (also referred to herein as a ground reference power supply or pad power supply) and a floating bias power supply 200 (also referred herein as a bias power supply), the floating bias power supply 200 being electrically coupled to the ground reference power supply 100 to apply a bias thereto in a manner discussed in more detail below. The floating bias power supply 200 may apply a bias to the ion detector 406 of the mass spectrometer 400, and the pad power supply 100 may apply a voltage to the pad element 408 of the mass spectrometer, as discussed in more detail below.

[0021] The floating bias power supply 200 includes a transformer 202, which includes a primary winding 202a and a secondary winding 202b. The primary winding 202a receives AC voltage from the AC power supply 204 via a capacitor C1. In this embodiment, the primary winding 202a of the transformer is coupled to the AC voltage source 204. The secondary winding of the transformer can boost the AC voltage applied to the primary winding by the AC source and apply the boosted voltage to downstream components of the floating bias power supply, as discussed below.

[0022] In this embodiment, the Faraday shield 210 is disposed in the transformer of the floating bias power supply between its primary and secondary windings to suppress parasitic coupling between the primary and secondary windings.

[0023] Additionally, a floating metal shield 220 is disposed around the bias source 200. As discussed in more detail below, the floating metal shield 220 provides a low-impedance path between one terminal and the other terminal of the secondary winding of the transformer of the floating bias power supply, which can help suppress noise current returning to the second terminal via the path through the pad voltage source.

[0024] The pad voltage power supply 100 also includes a transformer 102, which includes a primary winding 102a that receives AC voltage from an AC voltage source 104 and a secondary winding 102b that boosts the voltage of the primary winding and applies the boosted voltage to downstream components of the pad voltage power supply. In this embodiment, the primary winding 102a is coupled to the AC voltage source 104 via a capacitor C16.

[0025] Continue to refer to Figure 1 and Figure 2 Electrical connection path 110 electrically connects bias power supply 200 to ground reference voltage power supply 100 so that bias can be applied to ground reference voltage power supply via floating bias power supply. In this embodiment, electrical connection path 110 includes a return electrical path 222 for floating bias power supply, referred to herein as the "return electrical path".

[0026] Electrical connection path 110 extends from terminal A of the secondary winding 202b of the transformer of the floating bias power supply 200 via parasitic capacitor C9 to electrical ground, and then through electrical ground to terminal D of capacitor C21 associated with the pad power supply. Connection path 110 also extends from terminal C of capacitor C21 via return electrical path 222 of the floating bias power supply to terminal B of the secondary winding of the transformer of the floating bias power supply.

[0027] In this embodiment, two resistors, R5 and R7, are positioned in the return path of the floating bias power supply to mitigate noise injected into the pad power supply from the floating bias power supply. Although two resistors are depicted in this embodiment, one or more resistors may be used in other embodiments. In some embodiments, the combined resistance of resistors R5 and R7 may be in the range of, for example, from about 10 kΩ to about 1 MΩ, such as from about 100 kΩ to about 500 kΩ, or from about 200 kΩ to about 400 kΩ.

[0028] In some embodiments, resistors R5 and R7 disposed in the return path of the floating bias power supply can reduce noise injected from the floating bias power supply to the pad power supply by approximately 20 to approximately 100 times (e.g., in the range of approximately 30 to approximately 90 times, or in the range of approximately 40 to approximately 80 times, or in the range of approximately 50 to approximately 70 times). For example, resistors R5 and R7 help reduce the noise injected from the floating bias power supply to the pad power supply to a level of less than approximately 60 mVpp (millivolt peak-to-peak).

[0029] By considering the inherent characteristic of voltage transformers—the parasitic coupling between their primary and secondary windings—the role of the various components according to this disclosure in reducing noise coupling between the floating bias power supply and the pad power supply can be further understood. This parasitic coupling between the primary and secondary windings of the transformer of the floating bias power supply is described herein as capacitor C9, and the corresponding parasitic coupling between the primary and secondary windings of the transformer of the pad power supply is represented herein by capacitor C24. Furthermore, an inherent side effect of placing the floating bias power supply within the metal floating shield 220 connected to the return terminal of the bias transformer TX1 is the existence of parasitic capacitance between terminal A of the secondary winding of the floating bias power supply transformer and the outer casing. This parasitic capacitance is represented herein by capacitor C40 and is connected in parallel with the secondary winding of transformer 202.

[0030] The capacitive coupling between the secondary winding of the pad transformer and ground is represented by capacitor C41 in this paper.

[0031] In the pad power supply, capacitors C24 and C41 are connected in parallel with inter-winding capacitor C17, which is significantly larger than C24 and C41. These capacitors slightly increase the capacitive load on transformer TX2, but do not have any adverse effect on the circuit's function.

[0032] In contrast, in a floating bias power supply, capacitor C9 provides a path for the voltage signal present at terminal A of the secondary winding 202b of the bias power supply transformer 202 to ground. This path allows AC current to flow to ground through C9. If resistors R7 and R5 were not present, the current would return via C9 to terminal B of the secondary winding of transformer 202 through parallel-connected capacitors C10 and C21 (see [link to relevant documentation]). Figure 2More specifically, because C21 has a much larger capacitance than C10, most of this AC current will return to terminal B of the secondary winding of the bias transformer 202 via capacitor C21 of the pad voltage power supply. Therefore, this AC current can generate an AC voltage ripple across capacitor C21. Typically, the impedance of capacitor C21 is much lower than that of capacitors C9 and C10. For example, the typical impedances of C21, C10, and C9 are as follows: C21 is approximately 1400 ohms, C10 is approximately 10 kilohms, and C9 is greater than approximately 1 kilohm. Nevertheless, due to the typically high amplitude signal at terminal A of the secondary winding of the transformer of the floating bias power supply and the C9 / C21 voltage divider configuration, the current circulating along this path can generate an AC voltage ripple across C21 whose amplitude will undesirably appear at the output of the pad power supply.

[0033] To reduce the AC current cycling through C21, resistors R5 and R7, exhibiting high resistance, are added to the return path 222 between C10 and C21. By adding these resistors, most of the current via C9 is forced to return to ground via C10, which is the capacitor of the floating shield box, at terminal B of transformer 202. The AC voltage at terminal A of transformer 202 can create a ripple voltage across C10, which is attenuated by the ratio C10 / C9 and further attenuated by the filtering effect of the network R7+R5 and C21.

[0034] The use of the transformer Faraday shield 210, the floating metal shield 220, and the current-reducing resistors R5 and R7 can reduce the amplitude of unwanted current injected into the pad power supply via the bias source. Specifically, in some embodiments, the transformer Faraday shield can reduce the capacitance of capacitor C9, for example, by about 5 to 10 times, which in turn increases the impedance of C9 and reduces the amplitude of the current returning through that capacitor. This reduces the magnitude of unwanted ripple at the pad power supply output.

[0035] The floating metal shielding provides an alternating low-impedance path from the secondary winding terminal B of the floating bias power supply to the grounding capacitor (C10) of 220, which in turn provides an alternating low-impedance path for the current flowing through capacitor C9. Resistors R7 and R4 advantageously reduce and preferably suppress the current flowing through capacitor C21, thus reducing voltage ripple on the pad.

[0036] As discussed above, the floating metal shield 220 adds a parasitic capacitor C10 to ground. This capacitor creates a new path for current flowing through capacitor C9 back to terminal B of the secondary winding of the transformer of the floating bias power supply, exhibiting an impedance significantly higher (e.g., approximately 10 to 20 times greater) than the path extending from C9 to C21. Therefore, capacitor C10 does not substantially increase the amplitude of the voltage ripple across C21. Additionally, resistors R5 and R7 increase the impedance of the return path 222 (e.g., from several thousand ohms to several hundred kilohms), thus reducing the amplitude of the voltage ripple across C21 by, for example, 10 to 100 times, and in some cases, more. In other words, in many embodiments, the current flowing through capacitor C9 will use capacitor C10 as the return path, so most of any voltage ripple will occur across capacitor C10, which is not present at the output of the pad voltage source.

[0037] Additionally, in some embodiments, the phases of the AC signals applied by AC voltage sources 104 and 204 to the transformers 102 and 202, which are respectively bias source and ground reference voltage source, can be synchronized, such that the voltage ripple generated by the floating bias source 200 will be subtracted from the voltage ripple generated by the pad power supply, thereby reducing the overall ripple at the output of the pad power supply.

[0038] As an example and reference Figure 1 The controller 12, communicating with AC voltage sources 104 and 204, can synchronize the phase of the AC voltages generated by those voltage sources to ensure that the voltage ripple generated by the floating bias power supply 200 is subtracted from the voltage ripple generated by the pad voltage source 100. The controller 12 can be implemented in hardware, firmware, and / or software using techniques known in the art as disclosed in this disclosure. For example, Figure 3 An example implementation of a controller 12 is schematically depicted, including a processor 14, random access memory (RAM) 16, read-only memory (ROM) 18, and a communication bus 20 that enables communication between the processor and other components. The controller 12 may also include a communication module 22 that enables communication between the controller 12 and AC voltage sources 104 and 204. Instructions for synchronizing the phase of the AC voltages can be stored in the ROM 18 and passed by the processor to the RAM 16 for execution during runtime.

[0039] Refer again Figure 1In the floating bias power supply, capacitors C2 and C6, together with diodes D1 and D2, form a conventional double voltage multiplier, which reduces the need for transformer 210 in the floating bias power supply used to multiply the AC voltage applied to its primary winding. The floating bias power supply 200 also includes a filter formed by resistors R1 and R2 and capacitors C7 and C8. This filter is a differential filter used to reduce the differential voltage at the output of the bias power supply.

[0040] Continue to refer to Figure 1 The pad power supply 100 includes a quadruple voltage multiplier formed by diodes D3, D4, D5, and D6 and capacitors C39, C30, C11, and C12, which are uniformly provided in a conventional multiplier configuration. The quadruple voltage multiplier reduces the need for the transformer 100 of the pad power supply for amplifying the voltage of the primary winding of the transformer applied to the pad power supply by the AC voltage source 104.

[0041] As described above, the high-voltage power supply system according to this disclosure can be used in various mass spectrometers, such as those with time-of-flight mass analyzers, quadrupole mass analyzers, and others. For example, such a high-voltage power supply system can be used to provide ion acceleration and / or apply the necessary voltage to the ion detector of the mass spectrometer.

[0042] See the diagram for reference. Figure 4 as well as Figure 1 The mass spectrometer 400 according to an embodiment of the present disclosure includes an ion source 402 for generating ions, a mass analyzer 404 for analyzing ions, and an ion detector 406 for detecting ions, as well as other components. In this embodiment, a high-voltage power supply system 100 can apply a bias voltage to the ion detector of the mass spectrometer and to the pad elements of the mass spectrometer. More specifically, as Figure 1 As depicted, in this embodiment, the output voltage of a floating bias power supply is used to bias the ion detector, and the output voltage of a ground reference voltage power supply is used to bias the pad element of the mass spectrometer.

[0043] The mass analyzer 404 can be any suitable mass analyzer used in mass spectrometry systems known in the art. For example, the mass analyzer 404 can be a time-of-flight mass analyzer, a quadrupole mass analyzer, a tandem quadrupole-quadrupole mass analyzer, and others.

[0044] Those skilled in the art will understand that various changes can be made to the above embodiments without departing from the scope of the invention.

Claims

1. A high-voltage power supply system for a mass spectrometer, comprising: A ground reference power supply, the ground reference power supply having a first transformer including a primary winding and a secondary winding, the primary winding being electrically coupled to a first AC power supply. A floating bias power supply, the floating bias power supply having a second transformer including a primary winding and a secondary winding, the primary winding of the second transformer being electrically coupled to a second AC power supply. The return path of the floating bias power supply is electrically coupled to the ground reference power supply to bias the output voltage of the ground reference power supply. A floating shield, the floating shield being disposed around the floating bias power supply, and At least one resistive element is disposed in the return path of the floating bias power supply to reduce noise coupled from the floating bias power supply to the ground reference power supply.

2. The high-voltage power supply system according to claim 1, wherein, The floating shield provides a low AC impedance path from the return electrical path of the floating bias power supply to ground.

3. The high-voltage power supply system according to claim 2, wherein, The at least one resistive element is coupled in series with a capacitor to enhance the impedance of the return electrical path, the capacitor being associated with the floating shield.

4. The high-voltage power supply system according to claim 3, wherein, The resistance of the at least one resistive element is in the range of about 10 kΩ to about 1 MΩ.

5. The high-voltage power supply system according to claim 4, wherein, The resistance of the at least one resistive element is in the range of about 100 kΩ to about 1 MΩ.

6. The high-voltage power supply system according to claim 3, wherein, The capacitance associated with the floating shield is in the range of about 6 pF to about 100 nF.

7. The high-voltage power supply system according to claim 6, wherein, The capacitance associated with the floating shield is in the range of about 100 pF to about 50 nF.

8. The high-voltage power supply system according to claim 1 further includes a Faraday shield, the Faraday shield being disposed in the second transformer to reduce parasitic coupling between the primary winding and the secondary winding of the second transformer.

9. The high-voltage power supply system according to claim 8, wherein, The Faraday shield reduces the coupling by at least about 2 pF.

10. The high-voltage power supply system according to claim 8, wherein, The Faraday shield reduces the coupling by approximately 2 to approximately 100 times.

11. The high-voltage power supply system according to claim 1, wherein, The return electrical path is capacitively coupled to ground via at least one capacitor.

12. The high-voltage power supply system according to claim 1, wherein, The ground reference power supply provides an output voltage in the range of approximately 0 to approximately 20 kV.

13. The high-voltage power supply system according to claim 10, wherein, The floating bias power supply provides a bias voltage in the range of approximately 0 to approximately 10 kV.

14. The high-voltage power supply system according to claim 1, wherein, The floating bias power supply is coupled to the ion detector of the mass spectrometer to apply a bias voltage to the ion detector.

15. A mass spectrometer, comprising: Quality analyzer An ion detector, wherein the ion detector is disposed downstream of the mass analyzer, and A high-voltage power supply system configured to apply a high voltage to the ion detector. The high-voltage power supply system includes: A ground reference power supply, the ground reference power supply having a first transformer including a primary winding and a secondary winding, the primary winding being electrically coupled to a first AC power supply. A floating bias power supply, the floating bias power supply having a second transformer including a primary winding and a secondary winding, the primary winding of the second transformer being electrically coupled to a second AC power supply. The return path of the floating bias power supply is electrically coupled to the ground reference power supply to bias the output voltage of the ground reference power supply. A floating shield, the floating shield being disposed around the floating bias power supply, and At least one resistive element is disposed in the return path of the floating bias power supply to reduce noise coupled from the floating bias power supply to the ground reference power supply.

16. The mass spectrometer according to claim 15, wherein, The floating shield provides a low AC impedance path from the return electrical path of the floating bias power supply to ground.

17. The mass spectrometer according to claim 15, wherein, The at least one resistive element is coupled in series with a capacitor to enhance the impedance of the return electrical path, the capacitor being associated with the floating shield.

18. The mass spectrometer according to claim 17, wherein, The resistance of the at least one resistive element is in the range of about 10 kΩ to about 1 MΩ.

19. The mass spectrometer according to claim 18, wherein, The capacitance associated with the floating shield is in the range of about 6 pF to about 100 nF.

20. The mass spectrometer according to claim 15, wherein, The return electrical path is capacitively coupled to ground via at least one capacitor.

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