Flame sensing circuit and gas combustion device

Abstract

The utility model relates to flame detection technical field discloses flame perception circuit and gas combustion equipment, the utility model is applied to the gas combustion equipment with controller, flame perception circuit includes: flame detection electrode, in analog signal detection circuit, the first input of first operational amplifier is connected with flame detection electrode, second input is grounded, and the output is connected with the analog signal receiving port of controller, in AD conversion circuit, the first input of second operational amplifier is connected with comparison voltage input unit, second input is connected with the output of analog signal detection circuit, and the output is connected with the digital signal receiving port of controller. In the utility model, flame perception circuit can combine AD conversion circuit and analog signal detection circuit, realizes the fast and accurate of combustion state detection.

Description

Technical Field

[0001] This utility model relates to the field of flame detection technology, and in particular to a flame sensing circuit and a gas combustion device. Background Technology

[0002] To ensure safe combustion in gas products, flame ionization current is typically detected to determine the combustion state. In related technologies, a threshold is usually set in the processor, and the collected flame ionization signal is compared with this threshold to determine the presence of a flame. However, this method can only simply determine the presence of a flame; it cannot analyze the specific state of the flame. This can lead to false positives due to momentary fluctuations in flame intensity, resulting in inaccurate flame detection. Utility Model Content

[0003] The first technical problem solved by this invention is to provide a flame sensing circuit that helps to achieve rapid and accurate flame detection.

[0004] The second technical problem solved by this invention is to provide a gas combustion device that helps to achieve rapid and accurate flame detection.

[0005] The first technical problem mentioned above is solved by the following technical solution:

[0006] A flame sensing circuit is applied to a gas combustion device with a controller; the flame sensing circuit includes:

[0007] Flame detection electrode, used to receive flame ionization signals;

[0008] The analog signal detection circuit includes a first operational amplifier; wherein, the first input terminal of the first operational amplifier is connected to the flame detection electrode, the second input terminal is grounded, and the output terminal is connected to the analog signal receiving port of the controller.

[0009] The analog-to-digital converter circuit includes: a second operational amplifier and a comparison voltage input unit; wherein, the first input terminal of the second operational amplifier is connected to the comparison voltage input unit, the second input terminal is connected to the output terminal of the analog signal detection circuit, and the output terminal is connected to the digital signal receiving port of the controller;

[0010] The comparison voltage input unit inputs a preset comparison voltage to the second operational amplifier;

[0011] The second operational amplifier is used to compare the detection voltage of the flame ion signal output by the first operational amplifier with a preset comparison voltage to obtain and output the detection signal.

[0012] Compared with the prior art, the flame sensing circuit of this utility model has the following advantages: It employs a first operational amplifier to form an analog signal detection circuit, which detects the detection voltage of the flame ion signal, thereby obtaining an analog signal characterizing the strength of the flame ion signal; it employs a second operational amplifier and a comparison voltage input unit to form an analog-to-digital conversion circuit, which further compares the detected voltage with a preset comparison voltage, thereby accurately determining the digital signal characterizing the presence or absence of the flame ion signal based on the comparison with the preset comparison voltage; simultaneously, this flame sensing circuit can output both analog and digital signals through the analog signal detection circuit and the analog-to-digital conversion circuit, enabling the analog-to-digital conversion circuit to quickly detect changes in the combustion state of the gas combustion device. This information is reflected in the output digital signal. For example, when the combustion state changes from burning to extinguishing, the output digital signal quickly changes from a low level to a high level. This allows the controller to quickly detect the presence or absence of a flame in the gas combustion device based on the digital signal output by the analog-to-digital converter circuit. Since the controller only uses the digital signal for judgment, it is relatively stable and less susceptible to interference. The analog signal detection circuit can accurately detect changes in flame size, continuously outputting an analog signal that reflects the current flame size. Therefore, the controller can accurately determine the flame size of the gas combustion device through the analog signal output by the analog signal detection circuit. Thus, this flame sensing circuit, combined with the analog-to-digital converter circuit and the analog signal detection circuit, achieves rapid and accurate detection of the combustion state. Furthermore, the gas proportional valve can be closed promptly based on the digital signal detected by the analog-to-digital converter circuit, and the opening degree of the gas proportional valve can be adjusted based on the analog signal detected by the analog signal detection circuit. Therefore, this invention provides a hardware architecture that helps to simultaneously achieve rapid and accurate flame detection in combustion devices.

[0013] In one embodiment, the voltage comparison input unit includes a first resistor and a second resistor;

[0014] In this configuration, one end of the first resistor is connected to the power supply, and the other end is connected to both the first input terminal of the second operational amplifier and one end of the second resistor.

[0015] The other end of the second resistor is connected to ground.

[0016] In one embodiment, the analog-to-digital conversion circuit further includes a third resistor;

[0017] One end of the third resistor is connected to the second input terminal of the second operational amplifier, and the other end of the third resistor is connected to the output terminal of the first operational amplifier.

[0018] In one embodiment, the analog-to-digital conversion circuit further includes a first capacitor;

[0019] One end of the first capacitor is connected to the first input terminal of the second operational amplifier, and the other end is connected to ground.

[0020] In one embodiment, the analog signal detection circuit further includes a fourth resistor and a fifth resistor;

[0021] Among them, one end of the fourth resistor is connected to the first input terminal of the first operational amplifier and one end of the fifth resistor, and the other end is connected to the flame detection electrode.

[0022] The other end of the fifth resistor is connected to the output of the first operational amplifier.

[0023] In one embodiment, the analog signal detection circuit further includes a second capacitor;

[0024] One end of the second capacitor is connected to the other end of the fourth resistor and the flame detection electrode, while the other end is connected to ground.

[0025] In one embodiment, the analog signal detection circuit further includes a sixth resistor;

[0026] One end of the sixth resistor is connected to the output of the first operational amplifier, and the other end is connected to the analog signal receiving port of the controller.

[0027] In one embodiment, the circuit also includes an AC power supply and a third capacitor;

[0028] One end of the AC power supply is connected to one end of the third capacitor, and the other end is connected to ground.

[0029] The other end of the third capacitor is connected to both the first input terminal of the first operational amplifier and the flame detection electrode.

[0030] In one embodiment, the circuit further includes a seventh resistor and an eighth resistor;

[0031] Among them, one end of the seventh resistor is connected to the flame detection electrode, and the other end is connected to one end of the eighth resistor and the other end of the third capacitor respectively;

[0032] The other end of the eighth resistor is connected to the first input terminal of the first operational amplifier.

[0033] The second technical problem mentioned above is solved by the following technical solution:

[0034] A gas burner device includes a flame sensing circuit, a controller, and a proportional valve as described in any of the above embodiments; the digital signal receiving port of the controller is electrically connected to the output terminal of the analog-to-digital conversion circuit, the analog signal receiving port of the controller is electrically connected to the output terminal of the analog signal detection circuit, and the control terminal of the controller is electrically connected to the gas proportional valve. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of a flame sensing circuit according to an embodiment of the present invention;

[0037] Figure 2 This is a circuit diagram of a flame sensing circuit according to an embodiment of the present invention.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1. Analog signal detection circuit; 2. Analog-to-digital conversion circuit; 21. Comparison voltage input unit. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0042] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0043] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] To ensure safe combustion in gas products, flame ionization current is typically detected to determine the combustion state. In related technologies, a threshold is usually set in the processor, and the collected flame ionization signal is compared with this threshold to determine the presence of a flame. However, this method can only simply determine the presence of a flame; it cannot analyze the specific state of the flame. This can lead to false positives due to momentary fluctuations in flame intensity, resulting in low accuracy and reliability in flame detection. Furthermore, this method is susceptible to interference from the controller's power supply module, placing high demands on the controller chip and further reducing the accuracy and reliability of flame detection.

[0045] Based on this, the present invention provides a flame sensing circuit. A first operational amplifier is used to construct an analog signal detection circuit to detect the detection voltage of the flame ion signal, thereby obtaining an analog signal characterizing the strength of the flame ion signal. A second operational amplifier and a comparison voltage input unit are used to construct an analog-to-digital converter circuit to further compare the detected voltage with a preset comparison voltage, thereby accurately determining the digital signal characterizing the presence or absence of the flame ion signal based on the comparison with the preset comparison voltage. Simultaneously, this flame sensing circuit can output both analog and digital signals through the analog signal detection circuit and the analog-to-digital converter circuit. When the combustion state of the gas combustion device changes, the analog-to-digital converter circuit can quickly detect the change in combustion state and reflect it. In the output digital signal, for example, when the combustion state changes from burning to extinguishing, the output digital signal quickly changes from low level to high level. This allows the controller to quickly detect the presence or absence of a flame in the gas combustion device based on the digital signal output by the analog-to-digital converter circuit. Since the controller only uses the digital signal for judgment, it is relatively stable and less susceptible to interference. Meanwhile, the analog signal detection circuit can accurately detect changes in flame size, continuously outputting an analog signal reflecting the current flame size. Thus, the controller can accurately determine the flame size of the gas combustion device through the analog signal output by the analog signal detection circuit. Therefore, this flame sensing circuit, combined with the analog-to-digital converter circuit and the analog signal detection circuit, achieves rapid and accurate detection of the combustion state. Furthermore, the gas proportional valve can be closed promptly based on the digital signal detected by the analog-to-digital converter circuit, and the opening of the gas proportional valve can be adjusted based on the analog signal detected by the analog signal detection circuit. Therefore, this invention provides a hardware architecture that helps to simultaneously achieve rapid and accurate flame detection in combustion devices.

[0046] The following is combined with Figures 1 to 2 The following describes embodiments of the present invention.

[0047] According to an embodiment of the present invention, a flame sensing circuit is provided, which can be applied to a gas combustion device with a controller to detect the flame ion signal of the gas combustion device.

[0048] Figure 1 This is a schematic diagram of the structure of a flame sensing circuit according to an embodiment of the present invention, as shown below. Figure 1As shown, the flame sensing circuit includes: a flame detection electrode J1, an analog signal detection circuit 1, and an analog-to-digital converter circuit 2. The analog signal detection circuit 1 is connected to the flame detection electrode J1 to detect the strength of the flame ion signal and obtain a detection voltage. The input terminal of the analog-to-digital converter circuit 2 is connected to the output terminal of the analog signal detection circuit 1 to detect the presence or absence of the flame ion signal based on the detection voltage output by the analog signal detection circuit 1, obtaining a detection signal. Simultaneously, the output terminal of the analog signal detection circuit 1 is connected to the analog signal receiving port of the controller, and the output terminal of the analog-to-digital converter circuit 2 is connected to the digital signal receiving port of the controller, enabling the controller to combine the measured voltage and the detection signal to accurately determine the flame combustion state, thereby improving the accuracy and reliability of flame detection.

[0049] Figure 2 This is a circuit diagram of a flame sensing circuit according to an embodiment of the present invention, as shown below. Figure 2 As shown, in the flame sensing circuit, the flame detection electrode J1 is used to receive the flame ionization signal. The analog signal detection circuit 1 includes a first operational amplifier U1; wherein the first input terminal of the first operational amplifier U1 is connected to the flame detection electrode J1, the second input terminal is grounded, and the output terminal is connected to the analog signal receiving port of the controller. The analog-to-digital conversion circuit 2 includes a second operational amplifier U2 and a comparison voltage input unit 21; wherein the first input terminal of the second operational amplifier U2 is connected to the comparison voltage input unit 21, the second input terminal is connected to the output terminal of the analog signal detection circuit 1, and the output terminal is connected to the digital signal receiving port of the controller; the comparison voltage input unit 21 inputs a preset comparison voltage to the second operational amplifier U2; the second operational amplifier U2 is used to compare the detection voltage of the flame ionization signal output by the first operational amplifier U1 with the preset comparison voltage to obtain and output a detection signal.

[0050] In one embodiment, such as Figure 2 As shown, the comparison voltage input unit 21 includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the power supply, and the other end is connected to both the first input terminal of the second operational amplifier U2 and one end of the second resistor R2. The other end of the second resistor R2 is grounded. The first resistor R1 and the second resistor R2 act as voltage dividers, dividing the power supply voltage to obtain a preset comparison voltage, which is then input to the first input terminal of the second operational amplifier U2. By adjusting the voltage division ratio of the first resistor R1 and the second resistor R2, the magnitude of the preset comparison voltage can be adjusted, thereby dynamically adjusting the detection reference of the analog-to-digital converter circuit 2 according to detection requirements and accuracy requirements.

[0051] In one embodiment, such as Figure 2As shown, the analog-to-digital converter circuit 2 also includes a third resistor R3; one end of the third resistor R3 is connected to the second input terminal of the second operational amplifier U2, and the other end of the third resistor R3 is connected to the output terminal of the first operational amplifier U1.

[0052] In one embodiment, such as Figure 2 As shown, the analog-to-digital converter circuit 2 also includes a first capacitor C1; one end of the first capacitor C1 is connected to the first input terminal of the second operational amplifier U2, and the other end is connected to ground.

[0053] In one embodiment, the first input terminal of the second operational amplifier U2 corresponds to the negative input terminal, and the second input terminal of the second operational amplifier U2 corresponds to the positive input terminal. The second operational amplifier U2, the comparison voltage input unit 21, the first capacitor C1, and the third resistor R3 constitute a comparator, which compares the detection voltage output by the analog signal detection circuit 1 with the preset comparison voltage obtained by voltage division by the comparison voltage input unit 21. When the detection voltage is greater than the preset comparison voltage, a high-level detection signal is output, and when the detection voltage is less than the preset comparison voltage, a low-level detection signal is output. This avoids misjudging the flame ionization signal by the controller when there is no flame ionization signal and the analog signal detection circuit 1 detects a very low detection voltage due to interference.

[0054] In one embodiment, such as Figure 2 As shown, the analog signal detection circuit 1 further includes a fourth resistor R4 and a fifth resistor R5; wherein, one end of the fourth resistor R4 is connected to the first input terminal of the first operational amplifier U1 and one end of the fifth resistor R5, and the other end is connected to the flame detection electrode J1; the other end of the fifth resistor R5 is connected to the output terminal of the first operational amplifier U1.

[0055] In one embodiment, the first input terminal of the first operational amplifier U1 corresponds to the negative input terminal, and the second input terminal of the first operational amplifier U1 corresponds to the positive input terminal. The first operational amplifier U1, the fourth resistor R4, and the fifth resistor R5 constitute an inverting amplifier to amplify the flame ionization signal and obtain the detection voltage.

[0056] In one embodiment, such as Figure 2 As shown, the analog signal detection circuit 1 also includes a second capacitor C2; one end of the second capacitor C2 is connected to the other end of the fourth resistor R4 and the flame detection electrode J1, and the other end is connected to ground.

[0057] In one embodiment, such as Figure 2As shown, the analog signal detection circuit 1 also includes a sixth resistor R6; one end of the sixth resistor R6 is connected to the output terminal of the first operational amplifier U1, and the other end is connected to the analog signal receiving port of the controller. The sixth resistor R6 acts as a current-limiting resistor, controlling the detection voltage output by the first operational amplifier U1 within the analog signal receiving range of the controller.

[0058] In one embodiment, such as Figure 2 As shown, the circuit also includes an AC power supply S1 and a third capacitor C3; one end of the AC power supply S1 is connected to one end of the third capacitor C3, and the other end is grounded; the other end of the third capacitor C3 is connected to the first input terminal of the first operational amplifier U1 and the flame detection electrode J1.

[0059] In one embodiment, such as Figure 2 As shown, the circuit also includes a seventh resistor R7 and an eighth resistor R8; one end of the seventh resistor R7 is connected to the flame detection electrode J1, and the other end is connected to one end of the eighth resistor R8 and the other end of the third capacitor C3; the other end of the eighth resistor R8 is connected to the first input terminal of the first operational amplifier U1.

[0060] In one embodiment, such as Figure 2 As shown, when the first operational amplifier U1, the fourth resistor R4, and the fifth resistor R5 constitute an inverting amplifier, the other end of the eighth resistor R8 is connected to the other end of the fourth resistor R4 and one end of the second capacitor C2. The eighth resistor R8 serves as the front-end resistor of the inverting amplifier and forms a filter circuit with the second capacitor C2 to filter out the spike interference of the flame ion signal and form a stable flame signal value.

[0061] In one embodiment, when there is no combustion flame, i.e., no flame ionization signal is formed, the AC power supply S1, through the third capacitor C3 and the seventh resistor R7, does not form a current loop. At this time, no signal enters the analog signal detection circuit 1 and the analog-to-digital conversion circuit 2. Both the analog signal receiving port and the digital signal receiving port of the controller are at a low level, and the controller determines that there is no combustion flame. When a combustion flame is present, the AC power supply S1, coupled through the third capacitor C3, provides power to the analog signal detection circuit 1 and the analog-to-digital conversion circuit 2. The analog signal detection circuit 1 amplifies the detected flame ionization signal and outputs it to the analog signal receiving port of the controller. Simultaneously, the analog-to-digital conversion circuit 2 compares the detection voltage output by the analog signal detection circuit 1 with a preset comparison voltage. When the detection voltage is greater than the preset comparison voltage, the analog-to-digital conversion circuit 2 outputs a high-level detection signal; otherwise, it outputs a low-level detection signal. The controller determines whether a burning flame exists based on two signals received from the analog signal receiving port and the digital signal receiving port. If both signals received from the analog signal receiving port and the digital signal receiving port are at a high level, then a burning flame is determined to exist. If the signal received from the analog signal receiving port is at a high level while the signal received from the digital signal receiving port is at a low level, then it is determined that there is a misjudgment caused by interference in the current analog signal detection circuit 1, or that the current flame intensity is too low to meet the combustion standard, and therefore no burning flame is determined to exist.

[0062] The flame sensing circuit provided by this utility model employs a first operational amplifier to form an analog signal detection circuit, which detects the detection voltage of the flame ion signal to obtain an analog signal characterizing the strength of the flame ion signal. A second operational amplifier and a comparison voltage input unit form an analog-to-digital converter circuit, which further compares the detected voltage with a preset comparison voltage, thereby accurately determining the digital signal characterizing the presence or absence of the flame ion signal based on the comparison with the preset comparison voltage. Simultaneously, this flame sensing circuit can output both analog and digital signals through the analog signal detection circuit and the analog-to-digital converter circuit. When the combustion state of the gas combustion device changes, the analog-to-digital converter circuit can quickly detect the change in combustion state and reflect it in the output. In digital signals, for example, when the combustion state changes from burning to extinguishing, the output digital signal rapidly changes from low to high level. This allows the controller to quickly detect the presence or absence of a flame in the gas combustion device based on the digital signal output by the analog-to-digital converter (ADC). Since the controller only relies on the digital signal for judgment, it is relatively stable and less susceptible to interference. Meanwhile, the analog signal detection circuit can accurately detect changes in flame size, continuously outputting an analog signal reflecting the current flame size. Thus, the controller can accurately determine the flame size of the gas combustion device using the analog signal output by the analog signal detection circuit. Therefore, this flame sensing circuit, combining the ADC and analog signal detection circuits, achieves rapid and accurate detection of the combustion state. Furthermore, the gas proportional valve can be closed promptly based on the digital signal detected by the ADC, and its opening can be adjusted based on the analog signal detected by the analog signal detection circuit. Therefore, this invention provides a hardware architecture that facilitates both rapid and accurate flame detection in combustion devices.

[0063] According to an embodiment of the present invention, another aspect provides a gas burner device, including a flame sensing circuit, a controller, and a proportional valve as described in any of the above embodiments; the digital signal receiving port of the controller is electrically connected to the output terminal of the analog-to-digital conversion circuit, the analog signal receiving port of the controller is electrically connected to the output terminal of the analog signal detection circuit, and the control terminal of the controller is electrically connected to the gas proportional valve.

[0064] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0065] The specific embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. A flame sensing circuit, characterized by, Applied to gas combustion equipment with a controller; The flame sensing circuit includes: Flame detection electrode, used to receive flame ionization signals; The analog signal detection circuit (1) includes a first operational amplifier; wherein, the first input terminal of the first operational amplifier is connected to the flame detection electrode, the second input terminal is grounded, and the output terminal is connected to the analog signal receiving port of the controller. The analog-to-digital conversion circuit (2) includes: a second operational amplifier and a comparison voltage input unit (21); wherein, the first input terminal of the second operational amplifier is connected to the comparison voltage input unit (21), the second input terminal is connected to the output terminal of the analog signal detection circuit (1), and the output terminal is connected to the digital signal receiving port of the controller to output a high level or a low level to the controller; The comparison voltage input unit (21) inputs a preset comparison voltage to the second operational amplifier; The second operational amplifier is used to compare the detection voltage of the flame ion signal output by the first operational amplifier with the preset comparison voltage to obtain and output the detection signal.

2. The circuit of claim 1, wherein, The comparison voltage input unit (21) includes a first resistor and a second resistor; Wherein, one end of the first resistor is connected to the power supply, and the other end is connected to both the first input terminal of the second operational amplifier and one end of the second resistor; The other end of the second resistor is connected to ground.

3. The circuit of claim 1, wherein, The analog-to-digital converter circuit (2) also includes a third resistor; One end of the third resistor is connected to the second input terminal of the second operational amplifier, and the other end of the third resistor is connected to the output terminal of the first operational amplifier.

4. The circuit of claim 1, wherein, The analog-to-digital conversion circuit (2) also includes a first capacitor; One end of the first capacitor is connected to the first input terminal of the second operational amplifier, and the other end is connected to ground.

5. The circuit of claim 1, wherein, The analog signal detection circuit (1) further includes a fourth resistor and a fifth resistor; Wherein, one end of the fourth resistor is connected to both the first input terminal of the first operational amplifier and one end of the fifth resistor, and the other end is connected to the flame detection electrode; The other end of the fifth resistor is connected to the output of the first operational amplifier.

6. The circuit of claim 5, wherein, The analog signal detection circuit (1) also includes a second capacitor; One end of the second capacitor is connected to the other end of the fourth resistor and the flame detection electrode, while the other end is connected to ground.

7. The circuit of claim 5, wherein, The analog signal detection circuit (1) also includes a sixth resistor; One end of the sixth resistor is connected to the output of the first operational amplifier, and the other end is connected to the analog signal receiving port of the controller.

8. The circuit of claim 1, wherein, The circuit also includes an AC power supply and a third capacitor; One end of the AC power supply is connected to one end of the third capacitor, and the other end is connected to ground; The other end of the third capacitor is connected to both the first input terminal of the first operational amplifier and the flame detection electrode.

9. The circuit of claim 8, wherein, The circuit also includes a seventh resistor and an eighth resistor; One end of the seventh resistor is connected to the flame detection electrode, and the other end is connected to one end of the eighth resistor and the other end of the third capacitor. The other end of the eighth resistor is connected to the first input terminal of the first operational amplifier.

10. A gas combustion apparatus, characterized by, Includes the flame sensing circuit, controller, and gas proportional valve as described in any one of claims 1-9; the digital signal receiving port of the controller is electrically connected to the output terminal of the analog-to-digital conversion circuit (2), the analog signal receiving port of the controller is electrically connected to the output terminal of the analog signal detection circuit (1), and the control terminal of the controller is electrically connected to the gas proportional valve.

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