Adaptive charge neutralization apparatus
The system addresses the inaccuracy in conventional charge neutralizers by using a control circuit to adjust the duty cycle of cations and anions based on balance voltage feedback, enhancing charge neutralization accuracy and reducing swing voltage for applications like semiconductor manufacturing.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- ILLINOIS TOOL WORKS INC
- Filing Date
- 2022-06-03
- Publication Date
- 2026-07-01
AI Technical Summary
Conventional charge neutralizers lack a feedback mechanism to accurately determine whether the predetermined balance of cations and anions is appropriate for the charge present on the target during operation, leading to potential inaccuracies in charge neutralization.
The system employs a control circuit to modulate a high-voltage, high-frequency AC signal using a DC offset signal to control the generation of cations and anions, adjusting the duty cycle based on balance voltage feedback to achieve a more accurate ion balance, reducing swing voltage to +/- 5V.
The system achieves a more accurate balance voltage, significantly improving charge neutralization accuracy and reducing swing voltage, making it suitable for applications sensitive to voltage and charge, such as semiconductor manufacturing.
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Abstract
Description
Technical Field
[0001] The present disclosure relates generally to ionization, and more particularly to methods and apparatus for adaptive charge neutralization.
Background Art
[0002] The ion emitter of a charge neutralization device generates both positive and negative ions and supplies them into the surrounding air or gas medium. To generate gas ions, the amplitude of the applied voltage must be high enough to create a corona discharge between at least two electrodes arranged as an ionization cell. In the ionization cell, at least one electrode is the ion emitter and the other can be a reference electrode.
Summary of the Invention
[0003] A method and apparatus for adaptive charge neutralization are disclosed, substantially as shown by and described in connection with at least one of the drawings, as more fully set forth in the claims. [[ID=2o]]
[0004] These features, aspects, and advantages of the present disclosure, as well as other features, aspects, and advantages, will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals represent like parts throughout.
Brief Description of the Drawings
[0005] [Figure 1] FIG. 1 shows an exemplary AC charge neutralization system configured to control ionization output based on balance voltage feedback, according to an aspect of the present disclosure. [Figure 2] FIG. 2 is a block diagram of an exemplary embodiment of the AC charge neutralization system of FIG. 1. [Figure 3] FIG. 3 shows an exemplary input signal to the emitter power supply of FIG. 2, which controls the output of positive and negative ions via a DC offset signal. [Figure 4]This figure shows an example of an output signal from the power supply to the emitter in Figure 2, which controls the balance voltage by outputting cations and anions when the pulse output is turned off. [Figure 5] This figure shows an example of an output signal from the power supply to the emitter in Figure 2, which controls the balance voltage by outputting cations and anions when the pulse output is turned on. [Figure 6] This flowchart illustrates an exemplary method for controlling the ionization output of the AC charge neutralization system shown in Figure 1 based on balanced voltage feedback. [Figure 7] This flowchart shows an example of a method for controlling the ion output from an ionizer power supply, such as the power supply shown in Figure 2. [Modes for carrying out the invention]
[0006] The drawings are not necessarily to exact scale. Where appropriate, similar or identical reference numbers are used to refer to similar or identical components.
[0007] Ionizers, or charge neutralizers, discharge static electricity that may be present on surfaces or substrates in manufacturing facilities, etc., by releasing positive and / or negative ions. The illustrated charge neutralization methods and apparatus disclosed can be used in a Class 1 cleanroom production environment and are particularly useful for semiconductor chip manufacturing.
[0008] Conventional charge neutralizers release a predetermined balance of cations and anions, which can be adjusted by an operator via software and / or an input device. However, conventional charge neutralizers lack a feedback mechanism to accurately determine whether the predetermined balance is appropriate for the charge present on the target during operation.
[0009] The illustrated charge neutralization methods and apparatus disclosed herein adapt the output ion balance based on balance voltage feedback. The illustrated charge neutralization methods and apparatus disclosed herein modulate a high-voltage, high-frequency AC signal using a DC offset signal to control the generation of cations and anions. To improve the accuracy of the balance voltage obtained at the target by adapting the output ion balance, the illustrated charge neutralization methods and apparatus disclosed herein increase or decrease the duty cycle of the DC offset signal to adapt the modulation of the high-voltage, high-frequency AC signal. Compared to conventional charge neutralization apparatuses, the illustrated charge neutralization methods and apparatus disclosed herein are capable of achieving a more accurate balance voltage and substantially reducing the swing voltage. Some of the disclosed charge neutralization methods and apparatuses achieve a swing voltage of + / - 5V, which offers significant advantages for applications sensitive to voltage and charge, such as semiconductor manufacturing.
[0010] As used herein, "exceeding" the threshold voltage can occur in a positive direction (e.g., positive above the threshold) or a negative direction (e.g., negative below the threshold).
[0011] As used herein, "balance voltage" refers to the net voltage produced by ionization by the emitter.
[0012] The terms "ionization" and "charge neutralization" are used interchangeably in this specification.
[0013] An illustrated charge neutralization apparatus disclosed comprises a first emitter nozzle, a power supply configured to supply a high-frequency alternating current (AC) signal to the first emitter nozzle, and a control circuit, the control circuit being configured to provide a polarity signal to the power supply to generate a DC offset signal, wherein the power supply is configured to output a cation generation pulse or an anion generation pulse, to control the polarity signal to cause the power supply to provide a cation generation period and an anion generation period, to determine a balance voltage at the output of the first emitter nozzle, and to control the polarity signal to adjust the relative duration of the cation generation period and the anion generation period based on the balance voltage.
[0014] In some exemplary devices, the composite of the high-frequency AC signal and the DC offset signal has a peak voltage higher than the corona generation threshold voltage of the first emitter nozzle. In some exemplary devices, the composite of the high-frequency AC signal and the DC offset signal causes the voltage at the first emitter nozzle to exceed only one of either the anode corona generation threshold voltage or the cathode corona generation threshold voltage for each high-frequency AC cycle.
[0015] In some exemplary devices, the control circuit is configured to determine the balance voltage based on a feedback signal from the antenna. In some exemplary devices, the antenna is positioned adjacent to the ionization target. In some exemplary devices, the control circuit is configured to determine the balance voltage based on a feedback signal from a closed-loop controller.
[0016] In some exemplary devices, the power supply applies a signal obtained based on a composite of a high-frequency AC signal and a DC offset signal to a first emitter nozzle, and the resulting signal causes the voltage at the first emitter nozzle to exceed the anode corona generation threshold voltage or the cathode corona generation threshold voltage. In some exemplary devices, when the control circuit controls the polarity signal so as not to generate a DC offset in the power supply, the high-frequency AC signal does not exceed either the anode corona generation threshold voltage or the cathode corona generation threshold voltage.
[0017] In some exemplary devices, the emitter tip is silicon-based or titanium-based. Some exemplary devices include a plurality of emitter nozzles, including a first emitter nozzle. In some exemplary devices, the control circuit is configured to modulate a polarity signal based on a balance voltage to control the duty cycle of a cation generation pulse or anion generation pulse. In some exemplary devices, the control circuit is configured to determine the balance voltage based on a feedback signal from an antenna. In some exemplary devices, the first emitter nozzle includes an emitter tip held within a stainless steel sleeve, and the power supply is configured to apply a composite of a high-frequency AC signal and a DC offset signal to the emitter tip relative to the sleeve.
[0018] Figure 1 shows an exemplary AC charge neutralization system 100 configured to control the ionization output based on balance voltage feedback. The exemplary AC charge neutralization system 100 outputs cations and anions 102 to neutralize the charge on a target device or substrate 104.
[0019] To generate ions 102, the exemplary system 100 comprises one or more ion emitter nozzles 106, each of which is coupled to one or more power sources providing a high-voltage, high-frequency AC signal for the generation of ions 102. The system 100 may comprise any number of emitter nozzles 106 to distribute the ions 102 over a desired area or size on the target device or substrate 104. By alternately generating cations and anions, the exemplary system 100 effectively neutralizes any static charge present on the target device or substrate 104 while reducing or avoiding the charging of the target device or substrate 104 by the ions 102.
[0020] The system 100 in Figure 1 alternately generates cations and anions by controlling the output voltage of nozzle 106 to output cation and anion periods. The relative duration of the cation and anion periods can be controlled based on a desired balance. In contrast to conventional charge neutralization systems, the exemplary system 100 achieves a balance voltage within + / - 5V by measuring the balance voltage via antenna 108 and adjusting the ion balance based on the measurement. For example, the system 100 can adjust the relative duration of the cation and anion periods to adjust the output balance. Antenna 108 can be positioned near target 104 so that antenna 108 measures the balance voltage that indicates the output of system 100. Using feedback from antenna 108, system 100 repeatedly (e.g., continuously) adjusts the relative balance of the cation generation period and the anion generation period.
[0021] FIG. 2 is a block diagram of an exemplary embodiment of the AC charge neutralization system 100 of FIG. 1. The example of FIG. 2 includes an in-line ionizer 200 having a high voltage high frequency (HVHF) power supply 202, and the power supply 202 outputs an HVHF signal to an emitter assembly 204 having a plurality of emitters 206. In some examples, the emitters 206 are silicon-based or titanium-based. Based on the HVHF signal from the power supply 202, the emitters 206 generate and output positive and negative ions.
[0022] The HVHF power supply 202 includes a DC-DC converter 208, an AC HV inverter 210, a DC offset generator 212, and an AC HV amplifier 214. The DC-DC converter 208 outputs a DC signal to the inverter 210, and the inverter 210 generates an AC signal. The DC offset generator 212 selectively generates a DC offset signal based on the polarity control signals 216, 218. When the positive polarity control signal 216 is active, the DC offset generator 212 generates a positive DC offset. Conversely, when the negative polarity control signal 218 is active, the DC offset generator 212 generates a negative DC offset. When neither of the polarity control signals 216, 218 is active, the DC offset generator 212 does not generate a DC offset. The DC offset voltage, regardless of its polarity, is combined with the AC signal output by the AC HV inverter 210 to generate a combined signal.
[0023] The AC HV amplifier 214 amplifies the voltage of the combined signal output by the DC offset generator 212.
[0024] The exemplary ionizer 200 includes a control circuit section 220 that controls the HVHF power supply 202. The exemplary control circuit section 220 can include a general-purpose microprocessor, a microcontroller, a system-on-chip (SoC), an application-specific integrated circuit (ASIC), and / or any other type of digital and / or analog circuit section.
[0025] The control circuit unit 220 comprises at least one controller or processor that controls the operation of the ionizer 200. The control circuit unit 220 receives and processes a plurality of inputs related to the system's performance and requirements. The control circuit unit 220 may comprise one or more microprocessors, for example, one or more "general-purpose" microprocessors, one or more dedicated microprocessors and / or ASICs, and / or any other type of processing device. For example, the control circuit unit 220 may comprise one or more digital signal processors (DSPs).
[0026] The illustrated control circuit unit 220 may include one or more storage devices and one or more memory devices. The storage device(s) (e.g., non-volatile storage) may include ROM, flash memory, hard drive, and / or any other suitable optical medium, magnetic medium, and / or solid-state storage medium, and / or combination thereof. The storage device stores data (e.g., ionization configuration data), instructions, and / or any other suitable data. The memory device(s) may include volatile memory such as random access memory (RAM), and / or non-volatile memory such as read-only memory (ROM). The memory device(s) and / or storage device(s) may store a variety of information and can be used for a variety of purposes. For example, the memory device(s) and / or storage device(s) may store processor-executable instructions (e.g., firmware or software) executed by the control circuit unit 220.
[0027] The illustrated control circuit unit 220 outputs a target voltage level signal to the DC-DC converter 208 to control the DC output voltage to the AC HV inverter 210, and controls the output by controlling polarity signals 216 and 218 to the DC offset generator 212. By controlling the polarity signals 216 and 218, the illustrated control circuit unit 220 can control the balance of cations and anions output by the emitter 204.
[0028] The exemplary control circuit 220 further receives a balance voltage input 222 from a remote ion balance sensor, such as the antenna 108 in Figure 1. The exemplary control circuit 220 may further include a balance detector connected to an antenna located near the ionization target, or may receive input from a balance detector. The balance detector can be implemented using a Simco-Ion® Novx-based control system, such as the Novx 3352 Closed-loop Ionizer Controller or the Novx 3362 Closed-loop Ionizer Controller. In other examples, the control circuit 220 or the ionizer 200 may include a balance detector that receives a feedback signal directly from the antenna 108.
[0029] The illustrated control circuit 220 may perform a PID controller and / or other type of filtering to filter the balance voltage measurements received via antenna 108. In some examples, the balance voltage input 222 is determined using an analog-to-digital converter (ADC) circuit configured to receive an input signal from antenna 108, and the control circuit 220 applies one or more filters and / or control loops to the balance voltage input 222 to adjust the balance value that controls the polarity signals 216, 218. The control circuit 220 periodically receives the balance voltage input 222 in response to one or more event types and / or at any other time, at the same frequency that the ADC or other circuit may sample and deliver the balance voltage input 222.
[0030] To generate an airflow or gasflow, a pressurized air source, a pressurized nitrogen source, or a pressurized argon source can be connected to the inline ionizer 200 via an inlet. In another example, the emitter assembly 204 allows the ambient airflow to transport ions toward the output of the emitter assembly 204. The airflow or gasflow, if present, entrains cations and anions and transports the ions toward a target (e.g., target 104 in Figure 1) through the ionizer outlet.
[0031] Figure 3 shows exemplary input signals to the power supply 202 in Figure 2, which control the cation and anion outputs via a DC offset signal. The exemplary control circuit 220 compares the count signal 302 with a balance value 304 set by the control circuit 220 based on a balance setpoint and balance voltage input 222. The exemplary control circuit 220 can control the count signal to increase and decrease based on the control circuit 220's clock signal to maintain consistent timing. When the count signal 302 is less than the balance value 304, the control circuit 220 controls the negative polarity signal 218 to be active and the positive polarity signal 216 to be inactive. Conversely, when the count signal is greater than the balance value 304, the control circuit 220 controls the negative polarity signal 218 to be inactive and the positive polarity signal 216 to be active. Therefore, the positive polarity signal 216 remains active for a longer period as the balance value decreases (e.g., the measured positive balance value decreases or the negative balance value increases), and the negative polarity signal 218 remains active for a longer period as the balance value increases (e.g., the measured positive balance value increases or the negative balance value decreases). In some examples, the control circuit 220 may further implement a pulse signal 306 to control the power supply 202. For example, the pulse signal 306 can be used to control the output of the AC HV inverter 210 to switch the AC high frequency signal on and off. While the polarity signals 216 and 218 may be active at a given time, a low value (e.g., off) of the pulse signal 306 turns off the output of the power supply 202 until the pulse signal 306 is changed to a high value (e.g., on). By using the pulse signal 306, the ionization swing voltage can be reduced without significantly affecting the decay time in some types of applications where achieving both decay time requirements and swing voltage requirements is difficult. In addition or alternatively, the pulse signal 306 can be used to suppress ion recombination.
[0032] In the example shown in Figure 3, the pulse signal 306 has a specific duration and duty cycle that can be controlled based on the clock signal of the control circuit unit 220. However, in other examples, the duration and / or duty cycle of the pulse signal 306 can be adjusted as desired, for example, to achieve a specific ionization rate.
[0033] In some cases, the control circuit 220 may output a warning or alert if the balance value 304 reaches and / or remains at an upper or lower limit. In such cases, there may be errors in the balance voltage measurement, and / or the ionizer 200 may not be able to provide sufficient ionization for the application.
[0034] Figure 4A shows an example output signal 400 from power supply 202 to emitter 206 in Figure 2, which outputs cations and anions to control the balance voltage, with the pulse output (e.g., pulse signal 306 in Figure 3) turned off. Figure 4B shows a more detailed view of a portion of the output signal 400 exhibiting high frequencies. In the example in Figure 4A, the output signal 400 has a defined emitter period 402, which includes a negative portion 404, a positive portion 406, and one or more off portions 408. The off portions 408 may include one or more predetermined periods occurring between the sequential negative and positive portions, at the beginning of the emitter period 402, and / or at the end of the emitter period 402, in order to provide sufficient time for the power supply 202 to switch.
[0035] During the negative portion 404, the negative polarity signal 218 is active, and the emitter 206 generates anions and emits them toward the target 104. During the positive portion 406, the positive polarity signal 216 is active, and the emitter 206 generates positive ions and emits them toward the target 104. During the off portion 408, neither polarity signals 216 nor 218 are active, and the emitter 206 does not generate anions. This is because the output signal 400 generated from the power supply 202 is not sufficient to exceed either the positive threshold voltage 410 or the negative threshold voltage 412. The positive portion 406 and / or the negative portion 404 may have their respective duty cycles relative to the emitter period 402.
[0036] In response to the balance voltage input 222, the exemplary control circuit 220 can adjust the duty cycle of the negative portion 404 and / or positive portion 406 by adjusting the balance signal 304 in Figure 3, thereby adjusting the polarity signals 216, 218.
[0037] The control circuit unit 220 can respond to changes in the balance value 304 by determining the corresponding durations of the negative portion 404 and / or the positive portion 406.
[0038] Figure 5A shows an example output signal 500 from power supply 202 to emitter 206 in Figure 2, which outputs cations and anions to control the balance voltage, with the pulse output (e.g., pulse signal 306 in Figure 3) turned on. Figure 5B shows a more detailed view of a portion of the output signal 500 exhibiting high frequency. The example output signal 500 is similar to the output signal 400 in Figure 4A, except that the HV output signal to emitter 204 is turned off based on pulse signal 306.
[0039] Figure 6 is a flowchart illustrating an exemplary method 600 for controlling the ionization output of the AC charge neutralization system shown in Figures 1 and 2 based on balanced voltage feedback.
[0040] In block 602, the exemplary HVHF power supply 202 generates a high-voltage, high-frequency AC signal. For example, the DC-DC converter 208 and the AC high-voltage inverter 210 generate a high-voltage, high-frequency AC signal. In block 604, the control circuit 220 sets a balance value based on a desired ion output balance. For example, the control circuit 220 can set an initial balance value 304 based on balance inputs that control the negative portion 404 and / or the positive portion 406.
[0041] In block 606, the control circuit 220 determines the cation duty cycle (e.g., the positive portion 406 of the emitter period 402) and the anion duty cycle (e.g., the negative portion 404 of the emitter period 402) based on the balance value 304. For example, the control circuit 220 can calculate the cation duty cycle and the anion duty cycle based on the balance value 304 (within a predetermined range) and a predetermined off time 408. In some other examples, the control circuit 220 does not calculate the cation duty cycle and the anion duty cycle, but instead controls the polarity signal (e.g., in real time) based on a comparison of the balance value 304 with the count signal 302.
[0042] In block 608, the control circuit unit 220 controls the ion output from the power supply 202 based on the cation duty cycle and the anion duty cycle. An exemplary method for implementing block 608 is disclosed below with reference to Figure 7.
[0043] In block 610, the control circuit 220 measures the balance voltage. For example, the control circuit 220 can receive a balance voltage input 222 indicating the balance voltage. In block 612, the control circuit 220 updates the balance value 304 based on the measured balance voltage and balance setpoint. For example, the control circuit 220 can adjust the balance value 304 by applying the measured balance voltage and balance setpoint to a PID controller. The PID controller, or other control loop, adjusts the commanded balance value 304 based on the difference between the measured balance voltage and the balance setpoint.
[0044] After updating the balance values (block 612), control returns to block 606, which continues to update the cation duty cycle and anion duty cycle, and output the HVHF signal to emitter 206.
[0045] Figure 7 is a flowchart illustrating an exemplary method 700 for controlling the ion output from an ionizer power supply, such as the power supply 202 in Figure 2. The exemplary method 700 can be performed by the control circuit unit 220 in Figure 2 to implement block 608 in Figure 6. Before performing method 700, the exemplary control circuit unit 220 has already determined the cation duty cycle and anion duty cycle based on the balance signal 304.
[0046] In block 702, the control circuit 220 generates a positive polarity control signal 216 based on the cation duty cycle to control the DC offset (for example, of the DC offset generator 212). For example, the control circuit 220 can keep the positive polarity control signal 216 active (e.g., on) and the negative polarity control signal 218 inactive (e.g., off) for the duration of the cation duty cycle.
[0047] In block 704, the DC offset generator 212 combines a high-voltage high-frequency AC signal (e.g., from the AC HV inverter 210) with a DC offset to control the ion output balance. For example, the DC offset generator 212 combines a high-voltage high-frequency AC signal with a DC offset generated based on a positive polarity control signal 216. For example, the AC HV amplifier 214 amplifies the combined DC offset and AC HVHF signal output to the emitter 206.
[0048] In block 706, power supply 202 outputs a combined signal to generate cations over the duration of the cation duty cycle. For example, emitter 206 generates cations while DC offset generator 212 generates a positive DC offset based on positive polarity signal 216.
[0049] Following the cation duty cycle (e.g., blocks 702-706), in block 708, the control circuit 220 generates a negative polarity control signal 216 based on the anion duty cycle to control the DC offset (e.g., of the DC offset generator 212). For example, the control circuit 220 may keep the negative polarity control signal 218 active (e.g., on) and the positive polarity control signal 216 inactive (e.g., off) for the duration of the anion duty cycle.
[0050] In block 710, the DC offset generator 212 combines a high-voltage high-frequency AC signal (e.g., from the AC HV inverter 210) with a DC offset to control the ion output balance. For example, the DC offset generator 212 combines a high-voltage high-frequency AC signal with a DC offset generated based on a negative polarity control signal 218. For example, the AC HV amplifier 214 amplifies the combined DC offset and AC HVHF signal output to the emitter 206.
[0051] In block 712, power supply 202 outputs a combined signal to generate anions over the duration of the anion duty cycle. For example, emitter 206 generates anions while DC offset generator 212 generates a negative DC offset based on negative polarity signal 218.
[0052] The cation duty cycle and the anion duty cycle can be separated by an off period (e.g., off period 408) and / or interrupted by a periodic pulse based on the pulse signal 306 in Figure 3.
[0053] The method and system can be implemented in hardware, software, and / or a combination of hardware and software. The method and / or system can be implemented centrally in at least one computing system, or distributedly, with different elements distributed across several interconnected computing systems. Any type of computing system or other device adapted to perform the method described herein is suitable. A typical combination of hardware and software may include a general-purpose computing system, along with a program or other code that, when loaded and executed, controls the computing system to perform the method described herein. Another typical embodiment may include an application-specific integrated circuit or chip. Some embodiments may include a non-temporary machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, etc.) which stores one or more lines of machine-executable code, thereby causing a machine to perform a process such as that described herein. As used herein, the term “non-temporary machine-readable medium” includes all types of machine-readable storage media and is defined as being free from propagated signals.
[0054] As used herein, the terms “circuit” and “circuit section” mean physical electronic components (i.e., hardware) and any software and / or firmware ("code") that can constitute the hardware, that the hardware can execute, and / or that can otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may include a first “circuit” when executing one or more first lines of the code, and a second “circuit” when executing one or more second lines of the code. As used herein, “and / or” means any one or more items in the list linked by “and / or”. For example, “x and / or y” means any element in the set of three elements {(x), (y), (x,y)}. In other words, “x and / or y” means “one or both of x and y”. As another example, “x, y and / or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x,z), (y,z), (x,y,z)}. In other words, “x, y and / or z” means “one or more of x, y and z.” As used herein, the term “exemplary” means to serve as an unrestricted example, case, or illustration. As used herein, the term “for example” begins a list of one or more unrestricted examples, cases, or illustrations. As used herein, whenever a circuit section includes the hardware and code (if any) necessary to perform a certain function, the circuit section is “operable” to perform that function, regardless of whether the performance of that function is disabled or not (e.g., by a user-configurable setting, factory trim, etc.).
[0055] While the Method and / or System has been described with reference to certain specific embodiments, those skilled in the art will understand that various modifications and substitutions can be made without departing from the scope of the Method and / or System. For example, blocks and / or components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. In addition, many modifications can be made without departing from the scope of the Disclosure to adapt the teachings of the Disclosure to specific circumstances or materials. Therefore, the Method and / or System is not limited to the specific embodiments disclosed. Instead, the Method and / or System includes all embodiments that fall within the scope of the appended claims, either literally or under the doctrine of equivalents. The inventions disclosed herein include the following: [Aspect 1] A device for neutralizing electric charge, The first emitter nozzle, A power supply configured to supply a high-frequency alternating current (AC) signal to the first emitter nozzle, It comprises a control circuit section, The aforementioned control circuit unit is A polarity signal is provided to the power supply to generate a DC offset signal, wherein the power supply outputs a cation generation pulse or an anion generation pulse based on the composite of the high-frequency AC signal and the DC offset signal. Controlling the polarity signal so that the power supply provides a cation generation period and an anion generation period, Determining the balance voltage at the output of the first emitter nozzle, A device configured to control the polarity signal to adjust the relative duration of the cation generation period and the anion generation period based on the balance voltage. [Aspect 2] The apparatus according to embodiment 1, wherein the composite of the high-frequency AC signal and the DC offset signal has a peak voltage higher than the corona generation threshold voltage of the first emitter nozzle. [Aspect 3] The apparatus according to embodiment 1, wherein the composite of the high-frequency AC signal and the DC offset signal causes the voltage of the first emitter nozzle to exceed only one of the anode corona generation threshold voltage or the cathode corona generation threshold voltage for each high-frequency AC cycle. [Aspect 4] The apparatus according to embodiment 1, wherein the control circuit unit is configured to determine the balance voltage based on a feedback signal from the antenna. [Aspect 5] The apparatus according to embodiment 4, wherein the antenna is positioned adjacent to the ionization target. [Aspect 6] The apparatus according to embodiment 1, wherein the control circuit is configured to determine the balance voltage based on a feedback signal from a closed-loop controller. [Aspect 7] The apparatus according to the embodiment, wherein the power supply applies a signal obtained based on the composite of the high-frequency AC signal and the DC offset signal to the first emitter nozzle, and the voltage of the first emitter nozzle exceeds the anode corona generation threshold voltage or the cathode corona generation threshold voltage based on the obtained signal. [Aspect 8] The apparatus according to embodiment 7, wherein when the control circuit controls the polarity signal so as not to generate the DC offset in the power supply, the high-frequency AC signal does not exceed either the anode corona generation threshold voltage or the cathode corona generation threshold voltage. [Aspect 9] The apparatus according to embodiment 1, wherein the emitter tip is silicon-based or titanium-based. [Aspect 10] The apparatus according to embodiment 1, further comprising a plurality of emitter nozzles, including the first emitter nozzle. [Aspect 11] The apparatus according to embodiment 1, wherein the control circuit unit is configured to modulate the polarity signal based on the balance voltage in order to control the duty cycle of the cation generation pulse or the anion generation pulse. [Aspect 12] The control circuit unit is configured to determine the balance voltage based on the feedback signal from the antenna. manner The apparatus described in 11. [Aspect 13] The apparatus according to embodiment 1, wherein the first emitter nozzle comprises an emitter tip held within a stainless steel sleeve, and the power supply is configured to apply the composite of the high-frequency AC signal and the DC offset signal to the emitter tip relative to the sleeve.
Claims
[Claim 1] A device for neutralizing electric charge, The first emitter nozzle, A power supply configured to supply a high-frequency alternating current (AC) signal to the first emitter nozzle, It comprises a control circuit section, The aforementioned control circuit unit is A polarity signal is provided to the power supply to generate a DC offset signal, wherein the power supply outputs a cation generation pulse or an anion generation pulse based on the composite of the high-frequency AC signal and the DC offset signal. Controlling the polarity signal so that the power supply provides a cation generation period and an anion generation period, Based on a feedback signal from an antenna positioned adjacent to the ionization target, the balance voltage at the output of the first emitter nozzle is determined, A device configured to control the polarity signal to adjust the relative duration of the cation generation period and the anion generation period based on the balance voltage.