CN210837112U

CN210837112U - Sensitivity adjusting circuit of automatic light-changing welding mask

Info

Publication number: CN210837112U
Application number: CN201922454379.4U
Authority: CN
Inventors: 成江
Original assignee: Jiangsu Jiangxiang Optoelectronic Technology Co ltd
Current assignee: Jiangsu Jiangxiang Optoelectronic Technology Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2020-06-23
Anticipated expiration: 2029-12-30

Abstract

The utility model discloses an automatic become sensitivity regulating circuit of light welding face guard, including filter circuit and by integrated circuit U1, filter circuit is used for carrying out the filtering back output with the signal of telecommunication wave form that does not have stroboflash or extremely low stroboscopic light conversion come, integrated circuit U1 includes operational amplifier U1A and operational amplifier U1B, operational amplifier U1A's output is connected with operational amplifier U1B's negative input end, operational amplifier U1A is used for enlargiing the voltage signal through filter circuit, operational amplifier U1B is as the comparator, be used for exporting after comparing the voltage of the negative input end of input with the voltage of positive input end; the positive input end of U1B is connected with resistor R6 and one end of potentiometer W3 respectively, the other end of resistor R6 is connected with circuit supply voltage VCC, the other end of potentiometer W3 is connected with R14 and R17 and then grounded, and the threshold value is set by adjusting potentiometer W3. The utility model discloses can adjust circuit sensitivity to light when making the electric welder operate, adjust and set up convenient rate.

Description

Sensitivity adjusting circuit of automatic light-changing welding mask

Technical Field

The utility model relates to a welding mask technical field especially relates to sensitivity adjustment circuit of automatic darkening welding mask.

Background

The automatic dimming of the mask has a very important parameter: the sensitivity specifically defines that the quality of products produced by domestic manufacturers at present is uneven, but the aspects of sensitivity adjustment and the like are relatively deficient, the quality is lower, and the response is insensitive during welding, so that domestic electric welding masks can enter high-end professional markets when users needing further improvement to jump out of low grades, the eyes are free from being damaged by welding hard light during operation of electric welders, and the occurrence of electro-optic ophthalmia is avoided.

SUMMERY OF THE UTILITY MODEL

The utility model discloses one or more to above-mentioned current problem provides the sensitivity regulating circuit of automatic optically variable welding face guard.

According to an aspect of the utility model, the sensitivity regulating circuit of automatic light-changing welding face guard, sensitivity regulating circuit include signal conditioning circuit, signal conditioning circuit include filter circuit and by integrated circuit U1, filter circuit is used for carrying out the filtration back output with the signal of telecommunication wave form that does not have stroboflash or extremely low stroboflash light conversion come, and integrated circuit U1 includes operational amplifier U1A and operational amplifier U1B, operational amplifier U1A's output is connected with operational amplifier U1B's negative input end, operational amplifier U1A is used for will passing through the voltage signal of filter circuit amplifies, operational amplifier U1B is used as the comparator for the voltage of the negative input end of input is exported after with the voltage comparison of positive input end;

the positive electrode input end of the U1B is respectively connected with one end of a resistor R6, a capacitor C4 and a potentiometer W3, the other end of the resistor R6 is connected with a circuit power supply voltage VCC, the other end of the capacitor C4 is grounded, the other end of the potentiometer W3 is connected with the R14 and the R17 and then grounded, and a threshold value is set by adjusting the potentiometer W3.

In some embodiments, the filter circuit includes a capacitor C1, a capacitor C2, a resistor R2, and a resistor R3, the capacitor C1 and the resistor R2 are connected in series and then connected to one end of R3 and one end of C2, the other end of R3 is grounded, and the other end of C2 is connected to the negative input terminal of the operational amplifier U1A and the negative input terminal of the operational amplifier U1B, respectively.

In some embodiments, the negative input terminal of the U1A is connected to the output terminal thereof through a connecting resistor R4 to form negative feedback.

In some embodiments, the positive input terminal of U1A is connected to one terminal of a capacitor C3, one terminal of a resistor R13, and one terminal of a resistor R5, the other terminal of C3 is grounded, the other terminal of a resistor R13 is grounded, and the other terminal of a resistor R5 is connected to the circuit supply voltage VCC.

In some embodiments, a diode group D6 composed of two diodes connected in series is connected in parallel to the resistor R4, the anode of the diode group D6 is connected to the negative input terminal of the U1A and the capacitor C2, the cathode of the diode group D6 is connected to the negative input terminal of the U1B, and the middle of the two diodes is connected to the capacitor C2.

In some embodiments, the positive input terminal of the U1B is further connected to a capacitor C4, and the other terminal of the capacitor C4 is grounded.

The utility model discloses a benefit: the utility model discloses a sensitivity regulating circuit of automatic darkening welding face guard, including filter circuit and by integrated circuit U1, filter circuit is used for carrying out the filtering back output with the signal of telecommunication wave form that does not have stroboflash or extremely low stroboscopic light conversion come, operational amplifier U1A's output is connected with operational amplifier U1B's negative input end, operational amplifier U1A is used for enlargiing the voltage signal through filter circuit, operational amplifier U1B is as the comparator, be used for exporting after the voltage comparison of the negative input end of input and the voltage of positive input end; the positive input end of U1B is connected with resistor R6 and one end of potentiometer W3 respectively, the other end of resistor R6 is connected with circuit supply voltage VCC, the other end of potentiometer W3 is connected with R14 and R17 and then grounded, and the threshold value is set by adjusting potentiometer W3. Therefore, the sensitivity of the circuit to light can be adjusted when the electric welder operates, the adjustment and the setting are convenient, and the working efficiency is further improved.

Drawings

FIG. 1 is a block diagram of a sensitivity adjustment circuit for an autodarkening welding helmet applied to a control circuit;

FIG. 2 is a circuit diagram of a sensitivity adjustment circuit for an autodarkening welding helmet applied to a control circuit;

FIG. 3 is a circuit diagram of a power circuit for applying the sensitivity adjustment circuit of the automatic darkening welding helmet to a control circuit;

FIG. 4 is a circuit diagram of a sensitivity adjustment circuit of the automatic darkening welding helmet applied to a photoelectric conversion circuit of a control circuit;

FIG. 5 is a circuit diagram of a signal conditioning circuit applied to a control circuit by the sensitivity adjustment circuit of the auto-darkening welding helmet;

FIG. 6 is a circuit diagram of an LCD drive frequency and drive timing circuit for the sensitivity adjustment circuit of the autodarkening welding helmet applied to a control circuit;

FIG. 7 is a circuit diagram of an LCD drive voltage regulator circuit for use with the control circuit of the sensitivity adjustment circuit of the autodimming welding helmet;

FIG. 8 is a circuit diagram of an LCD drive circuit for the sensitivity adjustment circuit of the automatic darkening welding helmet applied to a control circuit;

FIG. 9 is a circuit diagram of a positive and negative voltage switching circuit for the sensitivity adjustment circuit of the automatic darkening welding helmet applied to a control circuit;

fig. 10 is a circuit diagram of a negative voltage doubler circuit applied to a control circuit by a sensitivity adjustment circuit of an automatic dimming welding mask.

Detailed Description

The technical scheme of the application is further explained in detail with reference to the attached drawings.

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be used. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The terms "mounted," "disposed," "provided," "connected," and "sleeved" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

According to an aspect of the utility model, as shown in fig. 1-10, the utility model provides a sensitivity adjustment circuit of automatic darkening welding face guard is applied to automatic darkening welding face guard control circuit, and control circuit includes: the device comprises a power supply circuit 1, a photoelectric conversion circuit 2, a signal conditioning circuit 3, an LCD driving frequency and driving time sequence circuit 4, an LCD driving voltage adjusting circuit 5, an LCD driving circuit 6, a positive and negative voltage conversion circuit 7 and a negative voltage doubling circuit 8;

the power supply circuit 1 is electrically connected with other circuits in the circuit and provides electric energy;

the photoelectric conversion circuit 2 consists of an infrared photodiode and is used for detecting optical signals generated by electric welding and converting the optical signals into electric signals;

the signal conditioning circuit 3 is electrically connected with the output end of the photoelectric conversion circuit 2, amplifies the electric signal in the photoelectric conversion circuit 2, and adjusts the electric signal to enable the voltage of the optical signal to reach a threshold value to drive a post-stage circuit;

the LCD driving frequency and driving time sequence circuit 4 is electrically connected with the output end of the signal conditioning circuit 3 and is used for changing the LCD working frequency and outputting the LCD working frequency to the LCD driving circuit according to time sequence;

the output end of the LCD driving voltage regulating circuit 5 is electrically connected with the LCD driving circuit and is used for setting the LCD driving voltage between two poles of the LCD;

the positive and negative voltage conversion circuit 7 is used for converting positive voltage in the circuit into negative voltage required by the circuit and outputting the negative voltage to the LCD driving voltage regulating circuit 5, and square wave voltage signals are output to the negative voltage doubling circuit 8;

the negative voltage doubling circuit 8 is used for generating pulse voltage by multiplying the signal received from the positive and negative voltage conversion circuit 7 for multiple times and outputting the pulse voltage to the LCD driving circuit 6;

and the LCD driving circuit 6 is used for matching with other circuits and outputting the received pulse voltage, the LCD driving voltage and the LCD working frequency to the LCD according to a time sequence.

In this embodiment, the signal conditioning circuit 3 includes a filter circuit and an integrated circuit U1, the filter circuit is configured to filter an electrical signal waveform converted from light without stroboflash or extremely low stroboflash and output the filtered electrical signal waveform, the integrated circuit U1 includes an operational amplifier U1A and an operational amplifier U1B, an output terminal of the operational amplifier U1A is connected to a negative input terminal of the operational amplifier U1B, the operational amplifier U1A is configured to amplify a voltage signal passing through the filter circuit, and the operational amplifier U1B is used as a comparator configured to compare an input voltage at the negative input terminal with an input voltage at the positive input terminal and output the amplified voltage;

the positive input end of U1B is connected with resistor R6 and one end of potentiometer W3 respectively, the other end of resistor R6 is connected with circuit supply voltage VCC, the other end of potentiometer W3 is connected with R14 and R17 and then grounded, and the threshold value is set by adjusting potentiometer W3.

In this embodiment, the filter circuit includes a capacitor C1, a capacitor C2, a resistor R2, and a resistor R3, the capacitor C1 and the resistor R2 are connected in series and then connected to one end of R3 and one end of C2, the other end of R3 is grounded, and the other end of C2 is connected to the negative input terminal of the operational amplifier U1A and the negative input terminal of the operational amplifier U1B, respectively. The negative input end of the U1A is connected with the output end of the U1A through a connecting resistor R4 to form negative feedback. The positive input end of U1A is connected with one end of a capacitor C3, one end of a resistor R13 and one end of a resistor R5, the other end of C3 is grounded, the other end of a resistor R13 is grounded, and the other end of the resistor R5 is connected with a circuit supply voltage VCC.

A diode group D6 formed by two diodes connected in series is connected in parallel to the resistor R4, the anode of the diode group D6 is connected with the negative input end of the U1A and the capacitor C2, the cathode of the diode group D6 is connected with the negative input end of the U1B, and the middle of the two diodes is connected with the capacitor C2. The positive input end of the U1B is also connected with a capacitor C4, and the other end of the capacitor C4 is grounded.

In this embodiment, the LCD driving frequency and driving timing circuit includes U4, U4 is composed of three schmitt trigger circuits with 2 inputs, each of which is a 2-input nand gate with schmitt trigger function, and is respectively a nand gate U4B, a nand gate U4A, and a nand gate U4C;

the nand gate U4B is used for signal inversion, and when the input signal is at high level, the output is at low level, whereas when the input is at low level, the output is at high level;

the NAND gate U4A is used as a self-oscillation circuit, the U4A, the R8 and the C7 form an oscillation circuit, square wave signals are generated, and the frequency of the square wave is determined by the capacitance value of the capacitor C7 and the resistance value of the resistor R8;

the nand gate U4C is used for signal inversion, and the output of the nand gate U4C is controlled by the output of U4A and is inverted from the output of U4A.

The output end of the NAND gate U4B is connected with the resistor R11 and the cathode of the diode D7, the anode of the diode D7 is connected with the other end of the resistor R11, the resistor R11 and the diode D7 are connected in parallel and then connected with the gating signal A0 end of the MC14052BG and the capacitor C6, and the other end of the capacitor C6 is grounded.

The input end of the nand gate U4B is connected with the anode of the diode D1 and one end of the potentiometer W2, the other end of the potentiometer W2 is connected with the resistor R7, the other end of the potentiometer W2 is grounded, the input end of the nand gate U4B is also connected with the filter capacitor C5, the output end of the nand gate U4B is connected with one input end of the nand gate U4A, the other end of the resistor R7 is connected with the output end of the U1B, and the anode of the diode D1 is connected with the output end of the U1B.

The anode of the diode D1 is further connected to VCC through capacitors C8 and R12 in sequence, and the other end of R12 is connected to the pin 8 of the input end of the NAND gate U4C.

The pin 9 of the input end of the not gate U4C is connected with the output end of the not gate U4A, the other input end of the not gate U4A is connected with one end of a capacitor C7 and one end of a resistor R8, the other end of the capacitor C7 is grounded, the other end of the resistor R8 is connected with the pin 9 of the input end of the not gate U4C, and the output end of the not gate U4C is connected with the gating signal A1 end of the MC14052 BG.

In the present embodiment, the LCD driving voltage adjusting circuit 5 includes a low power consumption operational amplifier U2, and the output terminal and the negative input terminal of the low power consumption operational amplifier U2 are connected to the input terminal of the LCD driving circuit 6;

the positive input end of the low-power-consumption operational amplifier U2 is connected with one end of a potentiometer W1B, the other end of the potentiometer W1B is connected with a circuit power supply voltage VCC through a pull-up resistor R15, and the output end of the low-power-consumption operational amplifier U2 is connected with the input end of the LCD driving circuit 6 to provide driving voltage for the LCD driving circuit 6. The LCD driving circuit 6 adopts an output chip U3, the U3 adopts a two-way 4-channel digital control analog switch MC14052BG, and the output ends Za and Zb of the output chip U3 are connected with the LCD.

The low power consumption operational amplifier U2 is of model SGM 8521. The output end of the low-power consumption operational amplifier U2 is connected with the Y3A pin and the Y2B pin of the output chip U3. The input end of the low-power consumption operational amplifier U2 is also connected with a grounded capacitor C9 and a grounded resistor VR 1. The input terminal of the low power consumption operational amplifier U2 is also connected to the Y3B pin of the output chip U3 through a resistor R10. The output terminal of the positive-negative voltage conversion circuit 7 is connected to one terminal of the resistor R10 and the Y3B pin of the output chip U3.

In this embodiment, the positive-negative voltage conversion circuit 7 includes an integrated voltage conversion chip U6, the U6 is an ICL7660AIBAZ chip, the 5 pins corresponding to VOUT of U6 are connected to the GND terminal of the low power consumption operational amplifier U2 through two serially connected diodes, the anode of the diode is connected to the GND terminal of the low power consumption operational amplifier U2, the cathode of the diode is connected to the 5 pins corresponding to VOUT of U6, the pin 2 corresponding to CAP + of U6 is connected to the input terminal of the negative voltage doubling circuit 8, and the pin 4 corresponding to CAP of U6 is connected to the input terminal of the negative voltage doubling circuit 8 through a capacitor E1.

In this embodiment, the negative voltage doubling circuit is configured to generate a pulse voltage by multiple voltage doubling, the negative voltage doubling circuit 8 includes U4D and a voltage doubling rectifying unit, U4D is a 2-input nand gate having a schmitt trigger function, 2 inputs of U4D are connected, and both an output and an input of U4D are connected to a control input of the voltage doubling rectifying unit; the positive and negative voltage conversion circuit 7 is used for converting a positive voltage in the circuit into a negative voltage required by the circuit and outputting the negative voltage square wave voltage signal to the negative voltage doubling circuit 8.

The voltage-doubling rectifying unit comprises a bootstrap booster circuit consisting of 8 diodes and 7 capacitors, and the output of the voltage-doubling rectifying circuit is connected to the negative level VEE end of an output chip U3 of the LCD driving circuit 6. 8 diodes are formed with A, B, C, D, E, F, G crossing points, B, D, F are connected to the output end of U4D through a corresponding capacitor, A, C, E, G are connected to the input end of U4D through a corresponding capacitor, crossing points A, C, E, G are connected with a capacitor E1 through a corresponding capacitor, the cathode of the diode is connected with the output end and the input end of U4D, and the anode of the last diode is connected with the VEE pin of the LCD driving circuit U3 as the output end of the voltage-doubling rectifying unit.

The positive and negative voltage conversion circuit 7 comprises an integrated voltage conversion chip U6, a U6 adopts a chip ICL7660AIBAZ, a pin 2 corresponding to CAP + of the U6 is connected with the input end of the negative voltage doubling circuit 8, and a pin 4 corresponding to CAP-of the U6 is connected with the input end of the negative voltage doubling circuit 8 through a capacitor E1.

In this embodiment, the LCD driving circuit 6 uses an output chip U3, the U3 uses a dual 4-channel digital control analog switch MC14052BG, and the output terminals Za and Zb of the output chip U3 are connected to the LCD.

In this embodiment, the power circuit 1 includes a power voltage stabilizing circuit, the power voltage stabilizing circuit includes a power voltage stabilizing chip U5, a transistor J6, a collector of the transistor J6 is connected to an anode of the battery BAT, a cathode of the battery BAT is grounded, a base of the transistor J6 is connected to an anode of the solar battery, a cathode of the solar battery is grounded, a collector of the transistor J6 is connected to an input terminal of the power voltage stabilizing chip U5, the power voltage stabilizing chip U5 employs a low dropout linear regulator HT7130-1, an output terminal of the power voltage stabilizing chip U5 is connected to one end of a capacitor E5 and a switch W1B, the other end of the capacitor E5 is grounded, and the other end of the switch W1B is connected to a power supply voltage VCC of the circuit.

In this embodiment, the power supply circuit 1 further includes a battery under-voltage reminding circuit, the battery under-voltage reminding circuit includes a low-voltage detection chip U7, a resistor R9, a light emitting diode LED1, the low-voltage detection chip U7 adopts a chip XC61CC2502MR, a pin 1 of the chip XC61CC2502MR is connected to one end of the resistor R9, a pin 3 of the chip XC61CC2502MR is connected to the battery voltage VBAT and the anode of the light emitting diode LED1, the cathode of the light emitting diode LED1 is connected to the other end of the resistor R9, and a pin 2 of the chip XC61CC2502MR is grounded.

In embodiment 1, a linear voltage stabilizing chip U5 with low power consumption is adopted in a power supply voltage stabilizing circuit, so as to reduce power consumption caused by voltage stabilization; as shown in the figure, T + and T-are respectively connected with the anode and the cathode of the solar cell, and the whole machine enters a working state only when light exists, so that the useless loss of the electric quantity of the cell is further reduced; the switch W1B adopts a resistance switch two-in-one potentiometer, and the switch of W1B can manually cut off the output of the voltage stabilizing chip.

Embodiment 2, battery under-voltage reminds circuit adopts dedicated low-voltage to detect the chip, and low-voltage detection chip U7 adopts chip XC61CC2502MR, and when the voltage that supplies the chip is not enough, LED can shine, reminds the user to change the battery.

In embodiment 3, the photoelectric conversion circuit is composed of an infrared photodiode, and converts an infrared light signal in the electric welding light into an electric signal, so that the following circuit can drive the LCD black screen in time accordingly, thereby protecting the naked eyes of the welder from being irradiated by strong light.

In embodiment 4, the signal conditioning circuit includes a filter circuit composed of C1, C2, R2, and R3, and filters out electrical signal waveforms converted from lights without stroboflash or extremely low stroboflash, such as sunlight and fluorescent light, the post-stage circuit does not respond, does not drive the LCD black screen, and only responds to stroboflash light signals of about 50HZ to hundreds of HZ, and the voltage of the stroboflash light signals of 50HZ to hundreds of HZ needs to reach a certain threshold value to drive the post-stage, which is set by the user adjusting potentiometer W3.

Embodiment 5, LCD driving frequency and driving sequence circuit, driving LCD not only needs to apply certain voltage, but also changes the voltage polarity of two pins of LCD, namely the working frequency of LCD from time to avoid that the liquid crystal in LCD can not return to the initial state after the liquid crystal distortion time is too long, the R8 and C7 parameters determine the working frequency of LCD.

The response time is typically several milliseconds to tens of milliseconds due to the technical bottleneck of the LCD. After the electric welding light is generated, the circuit drives the LCD with the voltage set by the user, when the LCD is stabilized to the set darkness level, the driving voltage of the LCD is higher, the darkness level is darker, and the electric welding light penetrates through the LCD to stab eyes of the user within the time of several milliseconds to tens of milliseconds. It is necessary to apply a very high, short duration pulsed voltage before driving the LCD with the user-set LCD driving voltage for fast response of the LCD. This circuit thus cooperates with the following U3 chip to achieve this function

Embodiment 7, an LCD driving voltage setting circuit, the darkness of an LCD is related to the voltage applied between its two poles. The LCD driving voltage setting circuit is realized by a potentiometer W1BB, and the voltage division of W1BB is performed by using a voltage division circuit of 1: 1 operational amplifier for enhancing and outputting to LCD driving circuit

In the embodiment 7, in the positive and negative voltage conversion circuit, part of the circuit needs negative voltage, and only one 3V button battery is needed for the power supply of the whole machine, and a negative voltage charge pump chip is needed to realize positive and negative conversion. Compared with other types of negative voltage circuits, the negative voltage circuit of the charge pump has the advantages of extremely high efficiency and extremely low static power consumption.

Embodiment 8, the negative voltage doubling circuit generates a pulse voltage, obtains a signal from the positive/negative voltage conversion circuit, and generates a negative voltage of about-20V after multiple voltage doubling.

In embodiment 9, the LCD driving circuit, in cooperation with other modules, outputs the pulse voltage, the LCD driving voltage for setting the darkness by the user, the LCD operating frequency, and the like to the LCD according to the time sequence.

The working principle is as follows:

1) in the static state:

static means no stroboscopic light or dark environment, where the LCD is not driven. The reason is as follows:

the light without strobing is converted by the photodiode in the photoelectric conversion circuit 2 to form a dc voltage, but the isolation of C1 prevents the processing of the subsequent circuits.

In dark light, the photodiode in the photoelectric conversion circuit 2 does not generate voltage, and no voltage signal is sent to a subsequent circuit.

In both cases, the voltage obtained at the inverting input of the operational amplifier U1A in the signal conditioning circuit 3 approaches zero.

Different from the traditional inverse operational amplifier circuit, in order to solve the problem of offset voltage inherent to the operational amplifier when the operational amplifier is powered by a single power supply, the forward input end of the operational amplifier is raised, namely R13/R13+ R5 VCC, and the value of the input voltage is about 328mv, so that the static output voltage of the inverse operational amplifier circuit is also changed into R13/R13+ R5 VCC which is about 328 mv. In terms of gain, the gain of the inverting operational amplifier circuit still follows the rule of a basic inverting operational amplifier, namely:

Vo＝-R4/Xc2＝-R4*2πfc；

since the voltage obtained at the inverting input of the current operational amplifier U1A is close to zero, the output will not change after U1A, and the static voltage output, i.e., R13/R13+ R5 VCC, is still maintained at about 328 mv. U1B is also an operational amplifier, but is used as a comparator here, and the reference voltage is introduced to the positive input terminal, and the range can be adjusted by W3. The variation range of the reference voltage is W3min + R14+ R17/R6+ W3min + R14+ R17 VCC to W3max + R14+ R17/R6+ W3max + R14+ R17 VCC by calculation, and the variation range is about 380mv-600mv by substituting the component values in the figure.

The voltage of the reverse input end of the U1B of the comparator is R13/R13+ R5 VCC, which is less than the minimum reference voltage W3min + R14+ R17/R6+ W3min + R14+ R17 VCC of the forward input end, and is about 380 mv. Therefore, the output of the comparator U1B is high, approaching VCC.

Since the U1B outputs high level, it is transmitted to the LCD driving frequency and driving sequence circuit 4, and after charging the C5 through R7 and W2, the voltage that C5 will get to VCC is sent to the nand gate U4B, and the U4B is equivalent to an inverter because two input pins are short-circuited, and the output is low level, and is divided into two paths to control the back stage circuit.

Wherein the first path: after the output end of the nand gate U4B passes through R11, D7 and C6, the voltage across the capacitor C6 is zero, and then the U3 in the LCD driving circuit adopts MC14052BG as a two-way 4-to-1 analog switch, and the gating signal a1 of the two-way 4-to-1 analog switch is 0.

And a second path: the output of the nand gate U4B is fed into one of the inputs of the nand gate U4A, as shown in the nand gate truth table: there are 0 out of 1 and all 1 out of 0, so the output of U4A must be high.

The high level of the output of U4A is fed into one of the inputs of NAND gate U4C, and the other end is connected to the junction of R12 and C8. From the previous analysis, it is known that the potential on the right side of the capacitor C8 is VCC, so that both ends of the series connection of R12 and C8 are substantially connected to VCC, and it is found that the potential on the left side of C8 is almost equal to the potential on the right side of C8, and then VCC is equal to high level.

Then, at this time, both input terminals of the nand gate U4C are at high level, the output thereof must be at low level 0, and the low level is transmitted to the gate pin a0 of the two-way 1-out-of-4 analog switch U3, so that a0 is 0

The analysis shows that: the two-way 4-to-1 analog switch U3 gates signals: a0 ═ a1 ═ 0, and the logical control relationship of MC14052BG shows that: Y0A and Za are turned on to GND, Y0B and Zb are turned on to GND, and Za and Zb are connected to two electrodes of LCD respectively, so the difference of voltage between two electrodes of LCD is 0, so it will not become dark.

2) In the state of stroboscopic light irradiation

Under the flash light irradiation state, the negative voltage doubling circuit 8 can generate a pulse high voltage to the LCD driving circuit, a short-time strong voltage is applied to enable the LCD to be quickly blackened, a voltage corresponding to the required LCD darkness is applied through the LCD driving voltage adjusting circuit 5, and the polarity of two pins of the LCD is switched at a certain frequency by matching with the LCD driving frequency and the driving time sequence circuit 4, so that the LCD cannot return to the original position after the direct-current voltage is applied for a long time. The principle is as follows:

at the moment of strong light irradiation, voltages are generated across the light emitting diodes D10 and D11 in the photoelectric conversion circuit 2, but since the voltages across the capacitors cannot change abruptly, the voltage signals generated by the diodes D11 and D12 can be quickly coupled to D6 through the capacitors C1 and C2 and injected into the reverse input end of the comparator U1B. When the voltage at the reverse input end of the comparator U1B is greater than that at the positive input end of the comparator, the output of U1B is low.

The low level output by U1B changes the right side of the capacitor C8 to low level through D1, and at this time VCC charges the capacitor C8 through the resistor R12, but it takes a certain time t equal to RC, so that the potential on the left side of the current C8 still approaches to 0V on the right side, and one input terminal of the nand gate U4C is 0. According to the truth table of the NAND gate, 0 goes out of 1, all 1 goes out of 0, and the output of the NAND gate U4C is definitely high, so that the gating signal A0 of the two-way 4-to-1 analog switch in the LCD driving circuit 6 is 1.

At this time, both input ends of the nand gate U4B are 0, the output is high, VCC charges the capacitor C6 through the resistor R11, but this requires a certain time t equal to RC, so the voltage across the current C6 still approaches to 0, that is, the gate signal a1 of the two-way 4-to-1 analog switch in the LCD driving circuit 6 is 0.

In summary, the two-way 1-by-4 analog switch U3 gates the signal a0 equal to 1 and a1 equal to 0, and then obtains the following results according to the logic control relationship of the MC14052 BG: Y1A and Za turn on being VCC, Y1B and Zb turn on being VEE, Za and Zb connect two electrodes of LCD respectively, and the LCD two-pole voltage difference is VCC in MC14052BG minus the voltage of VEE, VEE is the negative high voltage that negative voltage doubling circuit exported VEE in U3, from this, LCD obtains this voltage and darkens fast.

3) After the instant of strong light irradiation

After the moment of strong light irradiation, if the light is stroboscopic, the ac voltage generated at the two ends of the leds D10 and D11 is coupled to the input end of the inverting operational amplifier U1A through C1 and C2, and after proportional amplification, the static voltage at the positive input end of the inverting operational amplifier U1A is output to the inverting input end of the comparator U1B. At this time, the voltage of the reverse input end of the comparator U1B is greater than that of the forward input end, the voltage range of the forward input end is W3min + R14+ R17/R6+ W3min + R14+ R17 VCC to W3max + R14+ R17/R6+ W3max + R14+ R17 VCC, and the range is known to be about 380mv to 600mv by substituting the component values in the figure, the output of the comparator U1B continues to maintain the previous low level output, and the nand gate U4B of the LCD driving frequency and driving timing circuit 4 outputs high level.

At this time, the capacitor C6 connected to the gate pin a1 of the U3 of the LCD driver circuit 6 is charged by the high level output from the nand gate U4B and the resistor R11, and becomes high, that is, a1 is 1.

When VCC charges through the resistor R12, the pin 8 of the input terminal of the nand gate U4C goes high in the capacitor C8, and the pin 1 of the input terminal of the not gate U4A is connected to the output of the U4B, so the pin 1 input of the not gate U4A is also high. And U4A, R8 and C7 form an oscillating circuit. I.e., the square wave signal oscillated by the output of U4A, when pin 8 of U4C is already at a high level, the output of U4C is inverted with respect to the output of nand gate U4A, i.e., the level of gate signal a0 in LCD driver circuit 6 is controlled by the output of U4A and is in opposite phase.

In summary, it is found that the gate signal a1 of the two-way 4-to-1 analog switch in the LCD driving circuit 6 is 1, and a0 is constantly changing. Thus, the resulting voltages for the LCD are: the output voltage of U2 in the LCD driving voltage adjusting circuit 5 is subtracted by the output voltage of U6 in the positive-negative voltage converting circuit 7, but the polarity is changed continuously.

4) After the stroboscopic light is cancelled

After the strobe light is removed, the circuit state is restored to the static state after a delay, and the LCD becomes transparent.

The delay is generated because: when the output of the nand gate U4B changes from low to high, the capacitor C5 needs to be fully charged through R7 and W2 before the latter circuit becomes the same as in the quiescent state, so that the LCD does not become transparent immediately after the strobe light is deactivated, but becomes transparent after the capacitor C5 is fully charged.

The above are only some embodiments of the present invention. For those skilled in the art, without departing from the inventive concept, several modifications and improvements can be made, which are within the scope of the invention.

Claims

1. The sensitivity adjusting circuit of the automatic light-changing welding mask is characterized by comprising a signal conditioning circuit (3), wherein the signal conditioning circuit (3) comprises a filter circuit and an integrated circuit U1, the filter circuit is used for filtering and outputting an electric signal waveform converted from light without stroboflash or extremely low stroboflash, the integrated circuit U1 comprises an operational amplifier U1A and an operational amplifier U1B, the output end of the operational amplifier U1A is connected with the negative input end of the operational amplifier U1B, the operational amplifier U1A is used for amplifying a voltage signal passing through the filter circuit, and the operational amplifier U1B is used as a comparator and used for comparing the voltage of the input negative input end with the voltage of the positive input end and outputting the voltage;

the positive electrode input end of the U1B is respectively connected with one end of a resistor R6 and one end of a potentiometer W3, the other end of the resistor R6 is connected with a circuit power supply voltage VCC, the other end of the potentiometer W3 is connected with R14 and R17 and then grounded, and a threshold value is set by adjusting the potentiometer W3.

2. The sensitivity adjusting circuit of the automatic dimming welding mask as claimed in claim 1, wherein the filter circuit comprises a capacitor C1, a capacitor C2, a resistor R2 and a resistor R3, the capacitor C1 and the resistor R2 are connected in series and then connected with one end of R3 and one end of C2, the other end of R3 is grounded, and the other end of C2 is connected with the negative input end of an operational amplifier U1A and the negative input end of an operational amplifier U1B respectively.

3. The sensitivity adjusting circuit of the automatic dimming welding mask as claimed in claim 1, wherein the negative input terminal of the U1A is connected with the output terminal of the U1A through a connecting resistor R4 to form negative feedback.

4. The sensitivity adjusting circuit of the automatic dimming welding mask as claimed in claim 3, wherein the positive input terminal of the U1A is connected with one terminal of a capacitor C3, one terminal of a resistor R13 and one terminal of a resistor R5, the other terminal of the C3 is grounded, the other terminal of the resistor R13 is grounded, and the other terminal of the resistor R5 is connected with a circuit supply voltage VCC.

5. The sensitivity adjusting circuit of an automatic dimming welding mask as claimed in claim 1, wherein a diode group D6 composed of two diodes connected in series is connected in parallel to the resistor R4, the anode of the diode group D6 is connected with the negative input end of the U1A and the capacitor C2, the cathode of the diode group D6 is connected with the negative input end of the U1B, and the middle of the two diodes is connected with the capacitor C2.

6. The sensitivity adjusting circuit of the automatic dimming welding mask as claimed in claim 1, wherein the positive input end of the U1B is further connected with a capacitor C4, and the other end of the capacitor C4 is grounded.