Auto-dimming LCD filter glass element

Abstract

The invention relates to an apparatus and a method related to detecting a silent electrical arc. The apparatus comprises an automatically dimming LCD element and circuitry for controlling the automatically dimming LCD element. A light detector detects an incident light intensity as a function of time and generates a detection signal based on the detected incident light intensity. Signal processing circuitry processes the detection signal to generate a silent electrical arc indication signal indicating a presence of a silent electrical arc when an amplitude of the detection signal in a predetermined frequency range characteristic of a silent electrical arc is above a predetermined threshold. Circuitry for activation activates dimming of the automatically dimming LCD element when the silent electrical arc indication signal indicates a presence of a silent electrical arc.

Description

TECHNICAL FIELD

[0001] The present invention relates to devices and methods related to automatically darkening liquid crystal display (LCD) type light filtering glass elements. More particularly, the present invention relates to devices and methods for controlling automatically darkening LCD light filtering glass elements used in protective welding helmets and welding face shields, particularly suitable for protecting a user during a tungsten inert gas (TIG) welding, also known as gas tungsten arc welding (GTAW), and / or during a plasma arc welding (PAW), and / or during a plasma cutting. BACKGROUND

[0002] Tungsten inert gas (TIG) welding, also known as gas tungsten arc welding (GTAW), is an arc welding process that uses a non-consumable tungsten electrode.

[0003] The arc produced during TIG welding not only emits visible light, but also UV (ultraviolet) and IR (infrared) radiation that is absorbed by the cornea and can even reach the retina of the eye. Any arc welding emits much more UV than sunlight. Therefore, automatically darkening LCD light filtering glass elements, in the art referred to as automatically darkening LCD elements, are used in welding helmets and welding face shields for protecting the eyes of a user during operation. As soon as the welding arc is triggered, the automatically darkening LCD element will automatically darken to protect the eyes of the user from the light radiation of the welding arc.

[0004] Plasma arc welding (PAW) is another known arc welding process in which an arc is formed between a non-consumable electrode and a workpiece. In addition to welding, a plasma arc can also be used to cut electrically conductive materials by means of a hot plasma-accelerated jet.

[0005] The darkening of the LCD light filtering glass is based on glass panels with embedded liquid crystal cells (LCCs). There can be more than one layer of LCCs, which can be further supplemented with polarizing filters. When the welding arc is triggered, a photo sensor is used to detect whether there is bright incoming light, and the LCCs in the LCD element are electrically activated to reduce the amount of light passing through the LCD light filtering glass, thus darkening the panel. When no welding is taking place, the LCCs are not activated, so that they are in a position that does not significantly reduce the amount of light passing through, so that the light lens allows a clear view and assessment of the welding piece and the surrounding area.

[0006] In practical situations, it has been found that a problem sometimes occurs that the TIG arc cannot activate the automatically darkening LCD element, thus exposing the eyes of the user to harmful light radiation. The intensity of the TIG arc, and thus the light emitted by it, is quite stable in nature compared to other common types of welding arcs, and in the case of a TIG arc whose intensity, and thus the light emitted by it, is particularly stable, it can be referred to as a silent TIG arc.

[0007] The stable plasma arc used in PAW or plasma cutting can have the same silent arc characteristics as the silent TIG arc. Therefore, the eyes of the user of the PAW or plasma cutting device can also be protected by an automatic darkening LCD element of a welding face shield or welding helmet. The PAW arc and the plasma arc used for plasma cutting are collectively referred to herein as plasma arc. In the following, the term "silent arc" refers to both the silent TIG arc and the silent plasma arc.

[0008] In other known arc welding methods, such as stick welding, MIG or MAG welding, the welding process itself, in particular the material transfer during the process, causes a huge variation of the current and voltage used to operate the welding, which is reflected in the light emitted by the welding arc, which shows a high variation in intensity. In TIG welding, the welding process itself does not cause such a variation due to material transfer, so the TIG welding arc is more stable than the arc used in stick welding, MIG and MAG welding. Several aspects of the welding process and equipment have an influence on the stability of the arc, but it is well known that TIG welding of some materials, such as high-grade steel or titanium, results in a particularly stable TIG arc.

[0009] In addition to the welding process itself, the stability of the light emission of the TIG arc is also influenced by the stability of the current. Currently, a so-called inverter technology is used, in which AC power is first rectified to DC and then switched (inverted) into a step-down transformer to generate the desired welding voltage and / or current, which is supplied for generating the arc. In the best case, the load current of the inverter power supply fluctuates very little, so that the load current achieved is stable. When a TIG arc is generated using a stable load current, the welding arc is also very stable and the light emission of the arc varies little. Such a very stable TIG welding arc can be referred to as a silent TIG arc.

[0010] The main reason for the problem is that the control circuitry of the automatic darkening LCD element does not always distinguish the TIG arc and / or the plasma arc, in particular the silent TIG arc and / or the silent plasma arc, from the normal ambient light, so it does not activate the automatic darkening LCD element. Increasing the activation sensitivity of the automatic darkening LCD element by using a lower limit value for the brightness setting tends to cause the activation of the darkening mode even in the case of a normal ambient light that is bright, which can cause problems in actual use.

[0011] Therefore, there is a need for a device and a method for recognizing the presence of a TIG and / or plasma arc in all cases, which ensures that for all types of welding, in particular for TIG welding and PAW and for plasma cutting, the ambient light can be distinguished from the light emitted by the welding arc.

[0012] Description of the Related Art

[0013] Figure 1An exemplary graph of the optical radiation spectrum of light emitted by a TIG arc is shown. Significant components appear at wavelengths between 300 nm and 500 nm, falling within the ultraviolet (UV) and visible light range. The optical radiation spectrum of normal sunlight at sea level has a significantly wider bandwidth, extending from the ultraviolet (UV) to the infrared (IR) range, such as... Figure 2 As shown in the diagram, the maximum intensity of sunlight is higher than the wavelength of light emitted by the TIG arc. The light emission spectrum of an incandescent lamp is very similar to that of the sun, except that the peak of the light emission spectrum is at a wavelength of approximately 1000 nm. The spectral power of a typical power LED used for lighting is... Figure 3 As shown, it has a typical peak power value in the range of approximately 450 nm, and other high power value ranges in wavelengths above 500 nm.

[0014] Therefore, TIG arc light can be distinguished by detecting ultraviolet light at a wavelength of approximately 350 nm, where the spectral characteristics of TIG arcs differ from the spectral power of all typical ambient light sources. However, suitable and sufficiently reliable selective light sensors are often difficult to find and quite expensive.

[0015] Patent application US20060285330 discloses an automatic darkening filter.

[0016] Patent application US20100265421 discloses an automatic dimming filter device, which includes a shutter control system that switches between different states in response to changes in the intensity of incident light.

[0017] Patent application US20040178326 discloses a microprocessor-based automatic dimming goggle with anti-interruption function. Summary of the Invention

[0018] One objective is to provide an apparatus and method for automatically activating an auto-dimming LCD element. Preferably, this objective should be achieved in an energy-saving manner. In particular, the objective is to provide an apparatus and method for automatically activating an auto-dimming LCD element in the presence of a TIG arc. The objective of the invention is achieved by the apparatus according to the first aspect and the welding helmet or welding mask according to the other aspect. The objective of the invention is further achieved by the method according to the first method aspect.

[0019] Preferred embodiments of the present invention are disclosed in other aspects.

[0020] According to a first aspect, an apparatus is provided, including an auto-dimming LCD element and a circuit system for controlling the auto-dimming LCD element. The circuit system includes a photodetector configured to detect incident light intensity as a function of time and generate a detection signal based on the detected incident light intensity. The circuit system also includes a signal processing circuit system configured to process the detection signal to generate a silent arc indication signal indicating the presence of a silent arc when the amplitude of the detection signal in a predetermined frequency range characteristic of a silent arc is higher than a predetermined threshold. The circuit system further includes an activation circuit system configured to activate the dimming of the auto-dimming LCD element when the silent arc indication signal indicates the presence of a silent arc.

[0021] According to the second aspect, the signal processing circuit system includes: a high-pass filter configured to filter the detection signal, wherein the cutoff frequency of the high-pass filter is at the lower limit of the predetermined frequency range that is a characteristic of a silent arc, and wherein the cutoff frequency of the high-pass filter is higher than the corresponding frequency range of light intensity variations emitted by typical ambient light sources such as incandescent lamps, fluorescent lamps, and / or LED lamps; and a comparator configured to compare the amplitude of the filtered detection signal with a predetermined threshold to generate a silent arc indication signal.

[0022] According to the third aspect, the lower limit of the predetermined frequency range that is a characteristic of silent electric arcs is between 300 Hz and 400 Hz.

[0023] According to the fourth aspect, the signal processing circuit system further includes: a low-pass filter configured to perform low-pass filtering on the detection signal, the low-pass filter having a cutoff frequency between about 1 kHz and about 3 kHz; or a band-pass filter configured to perform both the high-pass filtering and the low-pass filtering.

[0024] According to the fifth aspect, the activation circuit system is also configured to activate the dimming of the auto-dark LCD element when the circuit system for controlling the auto-dark LCD element determines that there is incident light with an intensity exceeding a predetermined intensity threshold.

[0025] According to the sixth aspect, the circuit system is configured to have a) an active state, wherein the circuit system is active and the auto-dimming LCD element is dimmed; b) a standby state, wherein the circuit system is active and is capable of activating the dimming of the auto-dimming LCD element within approximately 0.1 to 1 ms from receiving an indication of the presence of a silent arc, and upon determining that there is incident light with an intensity exceeding a predetermined intensity threshold; and c) an idle state, wherein at least a portion of the circuit system is set to a low-power state, in which it consumes less power than in the active state.

[0026] According to the seventh aspect, the circuit system further includes a motion detector, wherein the circuit system is configured to move from an idle state to a standby state when the motion detector detects that the amount of movement of the device within a predetermined time period exceeds a predetermined movement threshold, and wherein the circuit system is configured to move from a standby state to an idle state when the motion sensor detects that the amount of movement of the device within a predetermined time period does not exceed the predetermined movement threshold.

[0027] According to the eighth aspect, the circuit system further includes a voltage multiplier configured to generate a trigger voltage for triggering activation of an auto-dimming LCD element, wherein a) in a standby state of the circuit system, the voltage multiplier is configured to operate periodically to generate the trigger voltage, and the circuit system further includes at least one capacitor configured to temporarily store the trigger voltage when the voltage multiplier is turned off during periodic trigger voltage generation operation, and b) in an idle state of the circuit system, the operation of the voltage multiplier is disabled.

[0028] According to the ninth aspect, the circuit system used for control is implemented using CMOS logic.

[0029] According to another aspect, a welding helmet or welding mask is provided, including an auto-dimming LCD element according to any of the foregoing aspects and a circuit system for controlling the auto-dimming LCD element.

[0030] According to a first method aspect, a method for controlling an auto-dimming LCD element is provided, the method comprising: i) detecting an incident light intensity as a function of time and generating a detection signal based on the detected incident light intensity; ii) processing the detection signal to generate a silent arc indication signal indicating the presence of a silent arc when the amplitude of the detection signal in a predetermined frequency range characteristic of a silent arc is higher than a predetermined threshold; and iii) activating the dimming of the auto-dimming LCD element when the silent arc indication signal indicates the presence of a silent arc.

[0031] According to the second method aspect, processing the detection signal includes high-pass filtering the detection signal to extract a portion of the detection signal within a predetermined frequency range that is a characteristic of a silent electric arc, wherein the predetermined frequency range is higher than the corresponding frequency range of light intensity variations emitted by typical ambient light sources such as incandescent lamps, fluorescent lamps, and / or LED lamps, and comparing the amplitude of the filtered detection signal with a predetermined threshold to generate a silent electric arc indication signal.

[0032] According to the third method, the lower limit of the predetermined frequency range that serves as a characteristic of silent electric arcs is between 300 Hz and 400 Hz.

[0033] According to the fourth method aspect, the method further includes low-pass filtering the detection signal, wherein the low-pass filtering defines an upper limit of a predetermined frequency range, which is between about 1 kHz and about 3 kHz.

[0034] According to the fifth method aspect, the method further includes activating the dimming of the auto-darkening LCD element when it is determined that there is incident light with an intensity exceeding a predetermined intensity threshold.

[0035] According to the sixth method aspect, the method further includes setting the circuit system implementing the method to one of the following: a) an active state, wherein the circuit system is active and the auto-dimming LCD element is dimmed; b) a standby state, wherein the circuit system is active and is capable of activating the dimming of the auto-dimming LCD element within approximately 0.1 to 1 ms from receiving an indication of the presence of a silent arc, and upon determining that there is incident light with an intensity exceeding a predetermined intensity threshold; and c) an idle state, wherein at least a portion of the circuit system is set to a low-power state, in which it consumes less power than in the active state.

[0036] According to the seventh method aspect, when it is determined that the amount of movement within a predetermined time period exceeds a predetermined movement threshold, the circuit system is moved from an idle state to a standby state, and when it is detected that the amount of movement of the device within a predetermined time period does not exceed the predetermined movement threshold, the circuit system is moved from a standby state to an idle state.

[0037] According to an eighth aspect of the method, the method further includes generating a trigger voltage for triggering the activation of the auto-dimming LCD element, wherein a) in a standby state, the trigger voltage is generated periodically, and the trigger voltage is temporarily stored in at least one capacitor during a shutdown period of the periodic trigger voltage generation operation, and b) in an idle state of the circuit system, no trigger voltage is generated.

[0038] This invention is based on the following idea: utilizing the light intensity variation characteristics of silent TIG arcs and / or silent plasma arcs to detect and indicate the presence of silent TIG arcs and / or silent plasma arcs, and using this information to activate the dimming of an auto-dark LCD element. This operation can supplement the traditional activation of auto-dark LCD elements by detecting the presence of bright incident light and activating dimming when the detected brightness exceeds a brightness threshold.

[0039] The advantage of this invention lies in its improved activation reliability of the auto-dimming LCD element, thereby enhancing eye protection for the user during TIG welding as well as during PAW and plasma cutting. This invention further improves the energy efficiency of the circuitry used to control the auto-dimming LCD element, thereby increasing battery life and, consequently, the operational life of the welding helmet or welding mask. Attached Figure Description

[0040] The invention will now be described in more detail with reference to preferred embodiments and the accompanying drawings, in which...

[0041] Figure 1 The diagram illustrates the light radiation spectrum emitted by the TIG arc.

[0042] Figure 2 The diagram illustrates the light radiation spectrum of normal sunlight.

[0043] Figure 3 The diagram illustrates the light radiation spectrum of a high-power LED.

[0044] Figure 4 The diagram illustrates the intensity characteristics of light emitted by a TIG arc.

[0045] Figure 5 The illustration shows the intensity characteristics of light emitted by an LED light source.

[0046] Figure 6 The diagram illustrates a circuit system used to detect the presence of TIG arcs.

[0047] Figure 7 The diagram illustrates an example implementation of a circuit system used for detection and filtering.

[0048] Figure 8 Another implementation example of a circuit system used for detection and filtering is illustrated.

[0049] Figure 9 The diagram illustrates the intensity variations of light emitted from various light sources.

[0050] Figure 10 The diagram illustrates the detection signal, which represents the intensity of incident light emitted by the TIG silent arc before and after filtering. Detailed Implementation

[0051] The invention is described below in conjunction with TIG welding. However, the same findings also apply to plasma arcs under selected conditions, therefore this solution is equally applicable to PAW and plasma cutting.

[0052] Figure 4 The diagram illustrates the intensity characteristics of light emitted by a silent TIG arc. The upper figure (40) shows the intensity in the time domain, in other words, as a function of time, while the lower figure (41) shows the intensity variation in the frequency domain. In this figure, the vertical line (42) is located at 295 Hz on the lower scale to show that the intensity of light emitted by a silent TIG arc also varies significantly at frequencies above 300 Hz.

[0053] Figure 5The intensity characteristics of light emitted by an LED light source are illustrated. In the time domain shown in Figure (50) above, a clear sinusoidal variation in intensity can be detected. This is also clearly visible in the intensity variation of light emitted by an LED lamp in the frequency domain, as shown in Figure (51) below, with a dominant peak at approximately 100 Hz, a distinct overtone at 200 Hz, and another weak overtone at 300 Hz. The vertical line marker (52) in this figure is located at the 115 Hz frequency on the scale below. The intensity variation of light emitted by an incandescent lamp exhibits a clearer frequency dependence, with a single peak at 100 Hz and no significant intensity variation at higher frequencies. The intensity variation of light emitted by a fluorescent lamp typically has a dominant peak at 100 Hz, but also a distinct overtone at 200 Hz.

[0054] Sunlight is known to be stable, with no significant changes in intensity over short periods. Therefore, there is no distinct frequency component in the intensity of sunlight.

[0055] Based on the above findings, the inventors discovered that light from a silent TIG arc can be distinguished from ambient light by detecting the frequency component of the intensity variation of the detected incident light occurring above approximately 300 Hz. The same principle applies to plasma arcs used in PAW and plasma cutting. The ideal solution is a high-pass filter with a sharp cutoff frequency that attenuates any frequency at or below 300 Hz and shows almost no attenuation after 301 Hz. Testing revealed that a high-pass filter with 50 to 60 dB attenuation at 100 Hz and no significant attenuation at 400 Hz or higher can adequately distinguish the intensity variation of incident light from ambient light sources and silent arcs. In practice, the lower limit of the useful frequency range falls between 300 Hz and 400 Hz, and the cutoff frequency of the high-pass filter also falls within this range. Theoretically, there is no fixed upper limit to the useful frequency range for silent arc detection purposes, but in practice, some higher frequency interference exists in the kHz range, which is preferably filtered out to avoid false positives and thus improve detection reliability. The need for low power consumption also often limits the upper limit of the frequency range of active high-pass filters.

[0056] Although the initial testing and design of the exemplary embodiments were conducted in Europe with a grid frequency of 50 Hz, it should be noted that in countries with a grid frequency of 60 Hz, the characteristic intensity variation frequencies of typical ambient light sources are also different, as these are typically integer multiples of the grid frequency. Therefore, for use in countries with a 60 Hz grid frequency, typical ambient light sources may have characteristic light intensity variations at frequencies such as 120 Hz, 240 Hz, and 360 Hz, in which case the high-pass filter preferably has a cutoff frequency higher than approximately 360 Hz.

[0057] One alternative is to replace the high-pass filter with a specific band-stop filter at typical frequencies of ambient light intensity variation: 100Hz, 200Hz, and optionally 300Hz in countries with a 50Hz grid frequency, or 120Hz, 240Hz, and optionally 360Hz in countries with a 60Hz grid frequency. However, implementing such a band-pass filter is far more complex than a simple active high-pass filter and can be more power-intensive.

[0058] Figure 6 An exemplary implementation of a circuit system for detecting the presence of a silent electric arc is illustrated. The circuit system includes: a photodetector (60) that provides a detection signal (160) corresponding to the intensity of the detected incident light, and a signal processing circuit system for processing the detection signal (160) to generate a TIG arc indication signal (162) indicating the presence of a TIG arc.

[0059] Typically, the detection signal is an electrical signal, but other types of detection signals can also be used. When using a welding helmet or welding mask with an automatic dimming LCD element and its control circuitry, the photodetector (60) preferably operates continuously, such that the detection signal provides information about the intensity of the incident light as a function of time.

[0060] The signal processing circuitry may include: a high-pass filter (61) for filtering out any detection signals with frequencies typical of ambient light sources, and a comparator (62) for providing a silent arc indication signal (162) indicating whether a silent arc has been detected. As is known in the art, the output of the comparator (62) may be considered a digital signal.

[0061] The cutoff frequency of the high-pass filter (61) can be selected to fall within a selected lower limit of the aforementioned useful frequency range, specifically characterized by the intensity variation of light emitted by a silent arc. This is achieved by defining the cutoff frequency of the high-pass filter (61) so that it can effectively filter out frequency components in the detection signal that are typical for ambient light sources (such as LEDs or incandescent lamps) but allow frequencies characteristic of a silent arc to pass through. In a preferred, non-limiting embodiment, the cutoff frequency is about 300 Hz, but any cutoff frequency within the aforementioned useful frequency range can be selected. The high-pass filter (61) generates a high-pass filtered detection signal, which can be further passed through a low-pass filter (not shown) to remove other unwanted frequency components. The resulting filtered detection signal (161) includes frequencies characteristic of the intensity variation of light emitted by a silent arc, but not typical for any common ambient light source. Instead of separate high-pass and low-pass filters, the detection signal (160) can be filtered using a band-pass filter with a passband suitable for this purpose to produce the filtered detection signal (161). Depending on the implementation, the high-pass filtered detection signal can thus be used as the detection signal (161).

[0062] The filtered detection signal (161) is then fed to a comparator (62), which compares the voltage amplitude of the filtered detection signal with a predetermined threshold. If the amplitude of the filtered detection signal exceeds the predetermined threshold, a silent arc indicator signal (162) at the output of the comparator (62) indicates that a silent arc has been detected. If the amplitude is below the predetermined threshold, it is considered that no silent arc has been detected. As is known in the art, the comparator outputs a digital signal with two alternative values. This silent arc indicator signal (162) can then be used to control the activation circuitry of an auto-dimming LCD element, which can also be referred to as the dimming of the auto-dimming LCD element.

[0063] The control circuitry system that activates the auto-dimming LCD element preferably incorporates a hysteresis to prevent the auto-dimming LCD element from flickering between its "on" and "dimmed" states. The hysteresis can be implemented, for example, by introducing a delay for deactivating the auto-dimming LCD element. Therefore, a brief interruption of a silent arc or any other welding or plasma cutting arc will not immediately deactivate the auto-dimming LCD element. In an exemplary implementation, a delay of approximately 1 second can be applied before deactivation occurs, after which a silent arc and / or any other type of welding arc is no longer detected.

[0064] For other types of welding arcs, it is generally sufficient to detect the brightness of the incident light and use the presence of bright incident light as the primary physical quantity upon which the auto-darkening LCD element is based. To achieve a universal auto-darkening LCD element applicable to various types of welding equipment, the circuit system is preferably further configured to detect the presence of bright incident light generated by any other type of welding arc and detected by a photodetector or another photodetector. Such circuit systems for detecting the presence of a welding arc based on the detection of bright incident light are well known in the art and can be readily combined with the circuit system of the present invention for controlling a multi-purpose auto-darkening LCD element.

[0065] In practical implementation, in addition to filtering, the signal from the photodetector (60) may also need to be amplified. Any suitable amplifier circuit system known in the art can be used.

[0066] Figure 7 The illustration shows a possible, non-limiting implementation example of a circuit system for detecting the intensity of incident light and for filtering a detection signal that can be used to detect the presence of a silent electric arc, particularly a silent TIC arc. The photodetector (60) is implemented using a photodiode to provide the detection signal (160), and the high-pass filter (61) is implemented using an active two-stage filter circuit system to provide the filtered detection signal (161). The output of the high-pass filter can be further fed through a low-pass filter (not shown) before using a comparator (not shown) to determine whether a silent arc has been detected as described above. The output of the comparator can be used as an indication signal to indicate the presence of a silent arc to the circuitry controlling the activation of an auto-dimming LCD element.

[0067] Figure 8 The illustration shows another non-limiting implementation example of a circuit system for detecting the intensity of incident light and for filtering the detection signal, which could be used to detect the presence of a silent electric arc. Figure 7 Compared to the circuit system, this high-pass filter (61) circuit system is designed specifically for power saving.

[0068] Figure 9 The diagram illustrates the filtered detection signal (161) at the output of an exemplary high-pass filter (61), where a photodetector (60) detects different types of light emission sources. Graph 81 represents the high-pass filtered detection signal at the output of the high-pass filter (61) based on a 10A DCTIG arc operated with an inverter power supply. Graph 82 represents the corresponding filtered detection signal based on light emitted by a fluorescent lamp, graph 83 represents the corresponding filtered detection signal based on light emitted by an incandescent lamp, and graph (84) represents the corresponding filtered detection signal based on light emitted by an LED lighting device.

[0069] Graph 81 indicates that the detected signal (81) representing the intensity of incident light emitted by the silent arc includes at least one higher frequency component. In the exemplary system, this higher frequency component is caused by an inverter used to generate a DC power signal for operating TIG welding. If this component is generated in a used welding apparatus, the higher frequency component can be further filtered out, for example, by using a low-pass filter that filters out the inverter frequency. The exact inverter frequency to be filtered out is a design option and depends on the source and characteristics of such higher frequency components, such as the implementation of the inverter apparatus used. In the exemplary system, a low-pass filter with a cutoff frequency of approximately 3 kHz is used.

[0070] Figure 10 The detection signal is illustrated in the time domain, representing the intensity of incident light emitted by the silent arc before (81) and after (81') further low-pass filtering. The low-pass filtering effectively removes distorted high-frequency components from the detection signal (81), where the presence of frequency components above 300 Hz is clearly visible, and the remaining filtered detection signal (81') is ready to be used to determine whether a silent arc has been detected, for example, using the comparator explained above. Depending on the implementation, the low-pass filter cutoff frequency can be, for example, between 1 kHz and 3 kHz, preferably between 2 kHz and 3 kHz. In some embodiments, the high-pass and low-pass filters can be implemented as a combined bandpass filter with suitable upper and lower cutoff frequencies.

[0071] Although the above description uses TIG welding, especially silent TIG arc, as an example, the same principle applies to plasma arcs used in PAW or plasma cutting.

[0072] When designing actual products, the energy efficiency of the automatic dimming LCD element and the circuitry controlling its operation is another aspect to consider. Active photodiodes, detection circuitry, and filtering circuitry all consume energy. While welding helmets or welding masks with automatic dimming LCD elements require electrical power to operate, battery operation is preferable, eliminating the need for external power connection cables. Energy efficiency helps extend battery life.

[0073] In standby mode, the auto-dimming LCD element does not dim. The photodetector, its associated amplifier, and the control logic consume power. To facilitate rapid dimming operation of the auto-dimming LCD element, a voltage peak of approximately 20V to 30V, referred to here as the trigger voltage, is fed to the LCD element. The auto-dimming LCD element needs to dim before the human eye can actually detect the light emitted by the arc. Therefore, activation of the auto-dimming LCD element should occur within 0.1ms to 1ms after the arc appears. Thus, the trigger voltage becomes readily available. In practice, the trigger voltage is obtained from a battery of approximately 3V to 6V carried in the welding helmet or welding mask, and is therefore not readily available. Energy is consumed during standby mode to enable the rapid generation of the trigger voltage. In operation, when the auto-dimming LCD element is dim, only approximately 2V to 3V is needed to maintain the auto-dimming LCD element in its active dimming state. The power consumption of an active, dimming auto-dimming LCD element is higher than that of its standby state because the glass-based LCD element is equivalent to a lossy capacitor and requires a constant energy supply to remain active. A typical current consumption of an active auto-dimming LCD element is approximately 100μA-200μA or even more. The current consumption of the control logic depends on the implementation. Traditional CMOS logic has low standby current consumption, typically less than 1μA. If a processor is used to implement the control logic, it may require operating currents as high as 100μA-200μA even in standby mode.

[0074] To minimize power consumption and maximize battery life, all power-consuming components in the welding helmet or glasses can be optimized.

[0075] To minimize the power consumption of the photodiode used as a photodetector, it is beneficial to operate it in photovoltaic mode (also known as zero-bias mode), allowing it to operate without an external power supply. In photovoltaic mode, the photodiode generates a voltage when exposed to light. Photodiodes can also be used in photoconductive mode or avalanche diode mode, both of which use reverse bias, but these modes require generating a reverse bias voltage, which consumes energy.

[0076] As mentioned above, a trigger voltage is required to dim the auto-dimming LCD element quickly enough to protect the user's eyes. Due to the high response speed requirement, the trigger voltage needs to be generated in advance so that it is readily available when needed. A typical available energy source is a 3V to 6V battery, and the trigger voltage can be generated based on the battery voltage using a voltage multiplier. Conventional voltage multipliers consume hundreds of microamps of current. The total power consumption of the voltage multiplier can be reduced, for example, by operating it periodically. In periodic operation, the voltage multiplier operates only periodically. The voltage multiplier operates actively during its active period, and there are off periods between active periods during which the generated trigger voltage is stored in one or more capacitors, from which the generated trigger voltage is immediately available. The exact periodicity of the periodic trigger voltage generation operation, as well as the design and proportions of the required circuitry components, are design options.

[0077] By utilizing CMOS circuitry and low-power comparators, the power consumption of the operating logic can be kept low. If the control operation is so complex as to require a microprocessor, then the microprocessor used should be able to be placed in a low-power idle state without using auto-dimming LCD elements, since even low-power microprocessors typically consume hundreds of microamps of current when active. However, future developments in low-power microprocessor technology could provide devices capable of performing all necessary signal and data processing steps in a power-efficient manner and thus suitable for implementing the functions of the circuitry according to the embodiments.

[0078] Since welding helmets or masks are used only about 5% of the time in practice, motion sensors can be used to detect whether the helmet or mask is moving, indicating whether it is in use. If no movement is detected during a predetermined time period, the helmet or mask can be placed in a deactivated state, also known as an idle state. Any known type of motion sensor can be used to detect movement, such as an accelerometer or a gyroscope. In practice, any known type of accelerometer is preferred for motion detection. While gyroscopes are technically equally useful, they require more power and are more expensive. During the idle state, the photodetector, parts of the control logic, and / or trigger voltage generation can be deactivated when the helmet or mask is not in use and are only activated when the motion sensor detects sufficient movement of the helmet within a predefined time period. Therefore, only the motion sensor and the monitoring signal from the circuitry of the motion sensor need to be active in the idle state. When movement is detected, a standby state is activated, preparing the auto-dimming LCD elements to be active to protect the user's eyes. In standby mode, arc detection is activated, and the automatic dimming LCD element is activated and dims when an arc is detected based on the incident light characteristics described above. Conversely, if no further movement is detected within a predefined time period after use, the device is moved from standby mode to idle mode to save power.

[0079] The batteries commonly used in welding helmets are lithium batteries with a total capacity of 200–600 mAh. Many welding helmets also include one or more solar panels as an additional power source. Under normal ambient light, solar panels typically generate only a small amount of energy (if any). During welding, a well-designed and sufficiently large solar panel can generate hundreds of microamps of current from the incident light energy from the welding arc itself, which may be sufficient to generate all the energy needed to operate the auto-dimming LCD element and the circuitry in the welding helmet or visor used to control and operate it. Battery life can exceed one year when total standby current consumption is kept below 20 μA and active current consumption is less than 150 μA. Using low-power motion sensors can further reduce standby current.

[0080] It will be apparent to those skilled in the art that the basic idea of ​​this invention can be implemented in various ways as technology advances. Therefore, this invention and its embodiments are not limited to the examples described above, but can be varied within the scope of the claims.

Claims

1. An apparatus for controlling an auto-dimming LCD element, the apparatus comprising an auto-dimming LCD element and a circuit system for controlling the auto-dimming LCD element, wherein a silent arc refers to a situation where the intensity of light emitted by an arc used for TIG welding, plasma arc welding, or plasma cutting is stable, wherein the circuit system comprises: - A photodetector is configured to detect the intensity of incident light as a function of time, and to generate a detection signal based on the detected incident light intensity. The circuit system is characterized by: - A signal processing circuit system is configured to process a detection signal to generate a silent arc indication signal indicating the presence of a silent arc when the amplitude variation of the detection signal within a predetermined frequency range characteristic of a silent arc exceeds a predetermined threshold, wherein the lower limit of the predetermined frequency range is between 300 Hz and 400 Hz. - The activation circuit system is configured to activate the dimming of the auto-dark LCD element when a silent arc indicator signal indicates the presence of a silent arc.

2. The apparatus according to claim 1, wherein the signal processing circuit system comprises: - A high-pass filter is configured to perform high-pass filtering on the detection signal, wherein the cutoff frequency of the high-pass filter is at the lower limit of the predetermined frequency range that is a characteristic of the silent electric arc, and wherein the cutoff frequency of the high-pass filter is higher than the corresponding frequency range of intensity variations of light emitted by a typical ambient light source, and - A comparator is configured to compare the amplitude of the filtered detection signal with a predetermined threshold to generate a silent arc indication signal.

3. The apparatus according to claim 2, wherein the ambient light source is an incandescent lamp, a fluorescent lamp, and / or an LED lamp.

4. The apparatus of claim 2, wherein the signal processing circuit system further comprises: A low-pass filter is configured to perform low-pass filtering on the detection signal, and the low-pass filter has a cutoff frequency between 1 kHz and 3 kHz. Alternatively, a bandpass filter may be configured to perform both the high-pass filter and the low-pass filter.

5. The apparatus according to any one of the preceding claims, wherein the activation circuit system is further configured to activate the dimming of the auto-dark LCD element when the circuit system for controlling the auto-dark LCD element determines that there is incident light with an intensity exceeding a predetermined intensity threshold.

6. The apparatus of claim 5, wherein the circuit system is configured to have a) Active state, where the circuit system is active and the LCD elements automatically dim. b) Standby state, wherein the circuitry is active and capable of activating the dimming of the auto-dimming LCD element within 0.1 to 1 ms from receiving an indication of the presence of a silent arc, and upon determining that incident light with an intensity exceeding a predetermined intensity threshold is present. c) Idle state, in which at least part of the circuit system is set to a low-power state, in which it consumes less power than in the active state.

7. The apparatus of claim 6, wherein the circuit system further comprises a motion detector, wherein the circuit system is configured to move from an idle state to a standby state when the motion detector detects that the amount of movement of the device within a predetermined time period exceeds a predetermined movement threshold, and wherein the circuit system is configured to move from a standby state to an idle state when the motion sensor detects that the amount of movement of the device within a predetermined time period does not exceed the predetermined movement threshold.

8. The apparatus of claim 6, wherein the circuit system further comprises a voltage multiplier configured to generate a trigger voltage for triggering activation of the auto-dimming LCD element, wherein a) In the standby state of the circuit system, the voltage multiplier is configured to operate periodically to generate a trigger voltage, and the circuit system further includes at least one capacitor configured to temporarily store the trigger voltage when the voltage multiplier is turned off during periodic trigger voltage generation operation. b) The operation of the voltage multiplier is disabled when the circuit system is idle.

9. The apparatus according to any one of claims 1 to 4, wherein the circuitry for control is implemented using CMOS logic.

10. The apparatus of claim 1, wherein the apparatus is a welding helmet or welding mask.

11. A method for controlling an automatically dimming LCD element, wherein a silent arc refers to a situation where the intensity of light emitted by an arc used for TIG welding, plasma arc welding, or plasma cutting is stable, the method comprising: - Detect the incident light intensity as a function of time, and generate a detection signal based on the detected incident light intensity; The method is characterized by comprising: - Process the detection signal to generate a silent arc indication signal indicating the presence of a silent arc when the amplitude variation of the detection signal within a predetermined frequency range characteristic of a silent arc is higher than a predetermined threshold, wherein the lower limit of the predetermined frequency range is between 300 Hz and 400 Hz. - When the silent arc indicator signal indicates the presence of a silent arc, the automatic dimming LCD element is activated to dim.

12. The method of claim 11, wherein processing the detection signal comprises: - The detection signal is high-pass filtered to extract a portion of the detection signal within a predetermined frequency range that is characteristic of a silent electric arc, wherein the predetermined frequency range is higher than the corresponding frequency range of intensity variations of light emitted by typical ambient light sources, and - The amplitude of the filtered detection signal is compared with a predetermined threshold to generate a silent arc indication signal.

13. The method of claim 12, wherein the ambient light source is an incandescent lamp, a fluorescent lamp, and / or an LED lamp.

14. The method of claim 11 or 12 further comprises low-pass filtering the detection signal, wherein the low-pass filtering defines an upper limit of a predetermined frequency range, the upper limit being between 1 kHz and 3 kHz.

15. The method according to any one of claims 11 to 13, further comprising activating the dimming of the auto-darkening LCD element when it is determined that there is incident light having an intensity exceeding a predetermined intensity threshold.

16. The method of any one of claims 15, further comprising configuring the circuit system implementing the method as one of: a) Active state, where the circuit system is active and the LCD elements automatically dim. b) Standby state, wherein the circuitry is active and capable of activating the dimming of the auto-dimming LCD element within 0.1 to 1 ms from receiving an indication of the presence of a silent arc, and upon determining that incident light with an intensity exceeding a predetermined intensity threshold is present. c) Idle state, in which at least part of the circuit system is set to a low-power state, in which it consumes less power than in the active state.

17. The method of claim 16, wherein when it is determined that the amount of movement within a predetermined time period exceeds a predetermined movement threshold, the circuit system is moved from an idle state to a standby state, and when it is detected that the amount of movement of the device within a predetermined time period does not exceed the predetermined movement threshold, the circuit system is moved from a standby state to an idle state.

18. The method of claim 16, further comprising generating a trigger voltage for triggering activation of the auto-dimming LCD element, wherein... a) In standby mode, a trigger voltage is periodically generated, and the trigger voltage is temporarily stored in at least one capacitor during the off-period of the periodic trigger voltage generation operation. b) No trigger voltage is generated when the circuit system is idle.

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