A methane detection circuit, instrument, and method based on catalytic element fault detection

Abstract

This application provides a methane detection circuit, instrument, and method based on a catalytic element with fault detection functions for poor soldering and open circuits. The circuit includes a catalytic element, a methane signal acquisition and amplification circuit, a poor soldering detection circuit, and an MCU. The catalytic element is a methane signal acquisition element. The methane signal acquisition and amplification circuit amplifies the methane signal acquired by the catalytic element. The poor soldering detection circuit consists of an electronic switch and a comparator, and the signal is combined with the signal from the methane signal acquisition and amplification circuit, then output to the MCU for methane concentration calculation after passing through the electronic switch. This application solves the problem of incorrect methane concentration detection by the catalytic element due to poor soldering or poor contact of components in the circuit. No detection errors will occur after poor soldering, open circuits, or poor contact of circuit components. Even after a poor soldering or open circuit, the fault can be identified, or the methane concentration can still be measured normally.

Description

Technical Field

[0001] This application relates to the field of circuit fault detection technology, and in particular to a methane detection circuit, instrument and method based on catalytic element fault detection. Background Technology

[0002] Catalytic elements, based on the principle of catalytic combustion, are widely used in coal mine methane detection sensors to continuously detect methane concentration and transmit the data to the ground detection center in real time. Methane detection is the core and lifeline of the coal mine safety monitoring system, so the measurement must be accurate and reliable, and false alarms and misreports must not occur under any circumstances.

[0003] The catalytic element consists of a detection element and a compensation element. It uses a Wheatstone bridge for measurement and is usually powered by a power supply. The output pin of the catalytic element can output a voltage signal proportional to the methane concentration. This signal is usually amplified by an operational amplifier to obtain the methane concentration value. Since the catalytic element needs to be replaced periodically, the catalytic element and the amplification circuit are usually made into a single component and then connected to the main control acquisition unit. When replacing, only the component needs to be replaced, and the whole unit does not need to be replaced.

[0004] However, methane detection components may become loose due to vibration, impact, or other factors, leading to poor contact with the main control and thus incorrect methane detection results. Specifically, if components in the internal circuitry of the methane detection component have poor soldering, open circuits, or inadequate soldering, the measurement results may be accurate in the short term. However, over time, vibration, shaking, and aging can cause previously poorly soldered components to become open circuits or have poor contact, resulting in incorrect methane detection results. In some cases, poor soldering or open circuits may result in an actual methane concentration that is very low, causing a measured value that is very high, leading to false alarms, triggering power outages in related equipment, and causing serious consequences. Conversely, poor soldering or open circuits may result in an actual methane concentration that is very high, causing a detected value of 0, failing to trigger an alarm and creating a safety hazard. Regardless of the type of erroneous detection result, it will have extremely serious consequences. Summary of the Invention

[0005] This application provides a methane detection circuit, instrument, and method based on catalytic element fault detection, which solves the technical problem that existing methane detection circuits are prone to inaccurate methane detection and false alarms due to poor contact, cold solder joints, open circuits, etc.

[0006] Technical solution

[0007] According to one aspect of this application, a methane detection circuit based on catalytic element fault detection is provided, comprising:

[0008] A catalytic element is used to detect methane concentration and output a corresponding electrical signal. The detection element and the compensation element within the catalytic element have a common connection point D.

[0009] A methane signal acquisition and amplification circuit is used to differentially amplify the electrical signal and output a methane concentration analog voltage, with its reference ground terminal connected to point D.

[0010] A cold solder joint detection circuit includes a comparator and an electronic switch. The first input terminal of the comparator is connected to point D, the second input terminal of the comparator is connected to a fixed reference voltage, and the output terminal of the comparator is connected to the control terminal of the electronic switch. The first signal input terminal of the electronic switch is connected to the output terminal of the methane signal acquisition and amplification circuit, the second signal input terminal of the electronic switch is grounded, and the output terminal of the electronic switch is connected to the input terminal of the MCU. When the potential at point D is within the normal range relative to the fixed reference voltage, the electronic switch activates the first signal input terminal; when the potential at point D is abnormal relative to the fixed reference voltage, the electronic switch activates the second signal input terminal.

[0011] The MCU calculates the methane concentration or determines the fault state based on the voltage at the output terminal of the electronic switch. When the MCU collects a 0V voltage, it determines that it is in a fault state; otherwise, it calculates and outputs the corresponding methane concentration based on the non-zero voltage collected by the MCU.

[0012] Preferably, the methane signal acquisition and amplification circuit includes an operational amplifier, the negative input terminal of which is connected to point D through a voltage divider resistor network, and the positive input terminal of which is connected to the methane signal output terminal of the catalytic element.

[0013] Preferably, the methane signal acquisition and amplification circuit is configured to output a preset methane concentration analog voltage greater than 0V when there is no methane gas.

[0014] Preferably, the cold solder joint detection circuit includes a resistor voltage divider network, which is disposed between the power supply and ground to generate the fixed reference voltage.

[0015] Preferably, the electronic switch is an analog electronic switch.

[0016] Preferably, it further includes a power control circuit, which includes a MOSFET. The gate of the MOSFET is connected to the control I / O port of the MCU. The level of the control I / O port of the MCU is preset to be different from the level when the methane concentration exceeds the standard as calculated by the MCU. The source and drain of the MOSFET are connected in series in the power supply circuit of the catalytic element. The MOSFET is used to cut off the power supply to the catalytic element when the methane concentration is highly exceeded according to the level output by the control I / O port of the MCU.

[0017] Preferably, when a poor solder joint or disconnection occurs at the grounding point of the second signal input terminal of the electronic switch, the electronic switch activates the first signal input terminal.

[0018] A second aspect of this application provides a methane detection instrument, including a methane detection circuit based on catalytic element fault detection according to the first aspect of this application.

[0019] A third aspect of this application provides a methane detection circuit detection method based on catalytic element fault detection, applied to the methane detection circuit described in the first aspect of this application, comprising the following steps:

[0020] The potential of the common connection point D between the detection element and the compensation element inside the catalytic element is used as the reference potential for the methane signal acquisition and amplification circuit.

[0021] The methane signal output from the catalytic element is differentially amplified by a methane signal acquisition and amplification circuit to output a simulated voltage of methane concentration.

[0022] The comparator compares the potential of point D with a fixed reference voltage to determine whether the position of point D is abnormal, and generates a control signal.

[0023] The electronic switch is controlled according to the control signal. When the potential of D is normal, the electronic switch selects the methane concentration analog voltage and outputs it to the MCU. When the potential of D is abnormal, the electronic switch selects the ground voltage 0V and outputs it to the MCU.

[0024] The MCU collects the output voltage of the electronic switch. If the output voltage is 0V, it is determined to be a fault; otherwise, the methane concentration is calculated based on the output voltage.

[0025] Preferably, the method further includes:

[0026] A MOSFET is connected in series in the power supply circuit of the catalytic element, and the switching of the MOSFET is controlled according to whether the methane concentration output by the MCU exceeds the limit. When the methane concentration exceeds the preset range, the power supply to the catalytic element controlling the MOSFET is cut off.

[0027] Beneficial effects

[0028] In this embodiment, a methane detection circuit based on a catalytic element with functions for detecting solder joint defects and open circuit faults is used. The circuit includes: a catalytic element, a methane signal acquisition and amplification circuit, a solder joint defect detection circuit, and an MCU. The catalytic element is a methane signal acquisition element. The methane signal acquisition and amplification circuit amplifies the methane signal acquired by the catalytic element. The solder joint defect detection circuit consists of an electronic switch and a comparator. After the signal is combined with the signal from the methane signal acquisition and amplification circuit, it is output to the MCU for acquisition and calculation of the methane concentration via an electronic switch.

[0029] This application addresses the issue of incorrect methane concentration detection by catalytic elements due to poor soldering or contact of components in the circuit. It prevents detection errors even after circuit components have poor soldering, open circuits, or poor contact. When a circuit has poor soldering or open circuit, it can be identified as a fault or the methane concentration can still be measured normally. Attached Figure Description

[0030] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1 This is a logic diagram of a methane detection circuit based on catalytic element fault detection according to an embodiment of this application.

[0032] Figure 2 This is a schematic diagram of a methane detection circuit based on catalytic element fault detection according to an embodiment of this application.

[0033] Figure 3 This is a schematic flowchart of a methane detection method based on catalytic element fault detection according to an embodiment of this application. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] like Figure 2 The diagram shown is a schematic of a methane detection circuit based on catalytic element fault detection according to the present invention. Figure 1 The diagram shown is a logic diagram of a methane detection circuit based on catalytic element fault detection according to the present invention. The following is a description of its operation in conjunction with... Figure 1 and Figure 2 The embodiments of the present invention will be described in detail below.

[0036] like Figure 2 As shown, the circuit includes:

[0037] A catalytic element is used to detect methane concentration and output a corresponding electrical signal. The detection element and the compensation element within the catalytic element have a common connection point D.

[0038] Specifically, Figure 2In this circuit, the catalytic element is denoted as U3. Internally, it employs a Wheatstone bridge structure, including a detection element and a compensation element connected in series. Their common connection point is node D. During operation, the power supply terminal of catalytic element U3 is connected to the supply voltage via R2. The differential voltage output from the signal output terminal of catalytic element U3 is proportional to the methane concentration. The common connection point D serves as the reference point for the methane signal acquisition and amplification circuit; it is a virtual ground, not the actual system ground. Its potential stabilizes at a preset DC bias value during normal operation, which in this embodiment is 1.2V.

[0039] A methane signal acquisition and amplification circuit is used to differentially amplify the electrical signal and output a simulated voltage of methane concentration. Its reference ground terminal is connected to point D.

[0040] like Figure 2 As shown, the methane signal acquisition and amplification circuit mainly consists of operational amplifier U2 and its peripheral resistors R1, R3, R4, R5, R6, R7, and R8. The negative input terminal of operational amplifier U2 is connected to the common connection point D of the catalytic element through a voltage divider network formed by resistors R5 and R6. Simultaneously, resistors R3 and R4, after voltage division from the power supply, are also connected to the negative input terminal, collectively setting the static operating point of the amplification circuit. The positive input terminal of the operational amplifier is connected to the methane signal output terminal of the catalytic element U3 through resistors R7 and R8. Thus, operational amplifier U2 constitutes a subtraction amplifier, outputting the differential amplification result of the methane signal relative to point D. Furthermore, the above configuration ensures that the output voltage of the methane signal acquisition and amplification circuit is always greater than 0V during normal operation, even when there is no methane, outputting a very small preset positive value, creating a clear distinction between the actual methane signal and the signal when there is no methane signal during subsequent fault detection.

[0041] A cold solder joint detection circuit includes a comparator and an electronic switch. The first input terminal of the comparator is connected to point D, the second input terminal of the comparator is connected to a fixed reference voltage, and the output terminal of the comparator is connected to the control terminal of the electronic switch. The first signal input terminal of the electronic switch is connected to the output terminal of the methane signal acquisition and amplification circuit, the second signal input terminal of the electronic switch is grounded, and the output terminal of the electronic switch is connected to the input terminal of the MCU. When the potential at point D is within the normal range relative to the fixed reference voltage, the electronic switch activates the first signal input terminal; when the potential at point D is abnormal relative to the fixed reference voltage, the electronic switch activates the second signal input terminal.

[0042] like Figure 2As shown, the cold solder joint detection circuit consists of comparator U5, electronic switch U6, resistors R10, R12, R13, R14, and capacitor C3. The non-inverting input of comparator U5 is the first input, and the inverting input is the second input. The first input is directly connected to the common connection point D. Resistors R12 and R13 are connected in series between the power supply and AGND. The midpoint between resistors R12 and R13 generates a fixed reference voltage, which in this embodiment is 1.0V. This reference voltage is connected to the second input of comparator U5. The output of comparator U5 is connected to the control pin of electronic switch U6. The first signal input of electronic switch U6 is connected to the output of the methane signal acquisition and amplification circuit; the second signal input of electronic switch U6 is connected to the actual system ground AGND; and the output of electronic switch U6 is connected to the analog input pin of the MCU.

[0043] Under normal operating conditions, the potential at point D is higher than the reference voltage, and comparator U5 outputs a high level. This level causes electronic switch U6 to switch its internal contacts to the first signal input terminal, thereby transmitting the methane concentration analog voltage output by operational amplifier U2 to the MCU. If a cold solder joint or open circuit occurs, such as a disconnection at point D, the potential at that point will drop to near 0V. At this time, the potential at point D is lower than the reference voltage, and the output of comparator U5 flips, controlling electronic switch U6 to switch to the second signal input terminal, i.e., outputting 0V to the MCU.

[0044] The MCU calculates the methane concentration or determines the fault state based on the voltage at the output terminal of the electronic switch. When the MCU collects a 0V voltage, it determines that it is in a fault state; otherwise, it calculates and outputs the corresponding methane concentration based on the non-zero voltage collected by the MCU.

[0045] Specifically, the MCU can periodically read the output voltage of electronic switch U6. If it reads 0V, the MCU determines that there is a cold solder joint or open circuit fault, stops the methane concentration conversion, and reports the sensor fault to the host computer via the communication interface. If it reads a non-zero voltage, the MCU calculates the actual methane concentration value according to the preset concentration-voltage curve for display or alarm purposes.

[0046] In some preferred embodiments, the methane signal acquisition and amplification circuit is configured to output a preset methane concentration analog voltage greater than 0V when there is no methane gas.

[0047] Specifically, such as Figure 2 As shown, by reasonably setting the resistance values ​​of resistors R3, R4, R5, and R6, the operational amplifier U2 can output a preset DC voltage when the catalyst element U3 has no methane output. This makes the voltage values ​​at the input terminal of the MCU completely different between the normal methane-free state and the fault state, thereby avoiding misjudgment of the fault.

[0048] In some preferred embodiments, the solder joint detection circuit includes a resistor divider network disposed between the power supply and ground to generate the fixed reference voltage.

[0049] Specifically, such as Figure 2 As shown, resistors R12 and R13 are connected in series between the power supply VCC and AGND, with the midpoint being the reference voltage. By adjusting the ratio of R12 and R13, the reference voltage can be set to any desired voltage value. In this embodiment, the reference voltage is set to 1V, placing it between the normal potential (approximately 1.2V) and the fault potential (0V) at point D, thereby ensuring that comparator U5 reliably flips.

[0050] In some preferred embodiments, the electronic switch is an analog electronic switch, specifically a low on-resistance analog switching device such as CD4066 or MAX4614. This type of switch allows analog signals to pass through and offers advantages such as fast switching speed and low power consumption.

[0051] In some preferred embodiments, a power control circuit is further included. The power control circuit includes a MOSFET, the gate of which is connected to the control I / O port of the MCU. The level of the control I / O port of the MCU is preset to be different from the level when the methane concentration exceeds the standard as calculated by the MCU. The source and drain of the MOSFET are connected in series in the power supply circuit of the catalyst element. The MOSFET is used to cut off the power supply to the catalyst element when the methane concentration is highly exceeded according to the level output by the control I / O port of the MCU.

[0052] Specifically, such as Figure 2 As shown, the power control circuit consists of a MOSFET U4, resistors R9, R11, R2, capacitor C2, and diode D1. MOSFET U4 is an N-channel enhancement-mode MOSFET, and its gate is connected to a general-purpose I / O port of the MCU through resistor R11. The level of this I / O port is determined by the MCU based on the real-time calculated methane concentration. When the concentration is below a preset safety threshold, the I / O port outputs a high level, turning on MOSFET U4 and connecting the power supply circuit for catalyst element U3. Conversely, when the concentration exceeds the safety threshold, the I / O port outputs a low level, turning off MOSFET U4 and cutting off the power supply circuit for catalyst element U3, thus preventing overheating and damage to catalyst element U3 at excessively high concentrations. It should be noted that in this embodiment, MOSFET U4 can also be a P-channel MOSFET, with the corresponding control level logic reversed: a high level when the concentration exceeds the threshold and a low level when the concentration is within the threshold.

[0053] In some preferred embodiments, when a poor solder joint or disconnection occurs at the grounding point of the second signal input terminal of the electronic switch, the electronic switch activates the first signal input terminal.

[0054] Since the second signal input is connected to the system's actual ground, AGND, if there is a cold solder joint or a break at that connection point, the second signal input will be floating instead of a stable 0V. To avoid the MCU acquiring an uncertain voltage in this situation, the comparator U5 in the cold solder joint detection circuit still uses point D as the judgment criterion. As long as the voltage at point D is normal, comparator U5 controls the electronic switch U6 to select the data from the first signal input. Therefore, even if the AGND connected to the second signal input is disconnected, the methane signal acquisition and amplification circuit can still operate normally, and the MCU can still correctly read the methane concentration. Thus, a cold solder joint on AGND will not cause a false alarm in the system, nor will it cause methane detection to fail.

[0055] Based on the same inventive concept as the above method embodiments, this application also provides a methane detection instrument, including a methane detection circuit based on catalytic element fault detection as described in the foregoing embodiments.

[0056] The methane detector can be a portable methane alarm or a fixed methane sensor probe. The instrument integrates the circuits described in the above embodiments and, together with a housing, display module, audible and visual alarm, and communication interface, forms a complete product. Due to the use of a detection circuit with self-testing capabilities for poor soldering and open circuits, even if soldering aging or poor contact occurs during long-term use, the instrument can report the fault immediately rather than outputting an incorrect concentration value, significantly improving the reliability of the coal mine safety monitoring system.

[0057] The circuits in the above embodiments, by setting the reference ground of the methane signal acquisition and amplification circuit to the common connection point D inside the catalytic element, and by causing the amplification circuit to output a preset non-zero voltage when there is no methane, clearly distinguish at the physical level between a fault-induced 0V and normal methane-free conditions. The MCU only needs to detect 0V to determine the fault, making the judgment logic simple and reliable. The cold solder joint detection circuit uses a comparator and an electronic switch to monitor the integrity of multiple critical connection points in real time. A break at any point will cause the electronic switch to automatically switch the MCU input to 0V, avoiding the output of incorrect concentration values. Even when the AGND itself has a cold solder joint, the circuit can still maintain normal methane concentration measurement and will not be paralyzed due to poor grounding. The power control circuit actively cuts off the power supply to the catalytic element when the concentration exceeds the limit, protecting sensitive components and avoiding secondary risks that may arise from continuous power supply during a fault.

[0058] Based on the same inventive concept as the circuit embodiments described above, such as... Figure 3As shown, this application also provides a methane detection circuit detection method based on catalyst element fault detection, applied to the methane detection circuits of the above embodiments, including the following steps:

[0059] Step S101: Use the potential of the common connection point D of the detection element and the compensation element inside the catalytic element as the reference potential of the methane signal acquisition and amplification circuit.

[0060] Step S102: Differential amplification of the methane electrical signal output by the catalytic element is performed through the methane signal acquisition and amplification circuit to output the methane concentration analog voltage.

[0061] Step S103: Compare the potential of D with a fixed reference voltage using a comparator to determine whether the position of point D is abnormal, and generate a control signal.

[0062] Step S104: Control the selection of the electronic switch according to the control signal. When the potential of D is normal, the electronic switch selects the methane concentration analog voltage and outputs it to the MCU. When the potential of D is abnormal, the electronic switch selects the ground voltage 0V and outputs it to the MCU.

[0063] Step S105: The MCU collects the output voltage of the electronic switch. If the output voltage is 0V, it is determined to be a fault; otherwise, the methane concentration is calculated based on the output voltage.

[0064] In some preferred embodiments, the method further includes:

[0065] A MOSFET is connected in series in the power supply circuit of the catalytic element, and the switching of the MOSFET is controlled according to whether the methane concentration output by the MCU exceeds the limit. When the methane concentration exceeds the preset range, the power supply to the catalytic element controlling the MOSFET is cut off.

[0066] Through the above steps, this method achieves real-time health monitoring of the catalytic element and key nodes of its surrounding circuitry. Compared to conventional simple methane detection methods, this method can proactively adjust the output to 0V after faults such as poor soldering or open circuits occur, enabling the MCU to clearly identify the fault state and avoiding false alarms or missed alarms caused by outputting incorrect concentrations due to faults. Furthermore, this method can maintain normal operation even when the AGND has a poor solder joint, and automatically cuts off power when the concentration exceeds the limit, comprehensively improving the safety and robustness of the methane detection system.

[0067] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

Claims

1. A methane detection circuit based on catalytic element fault detection, characterized in that, include: A catalytic element is used to detect methane concentration and output a corresponding electrical signal. The detection element and the compensation element within the catalytic element have a common connection point D. A methane signal acquisition and amplification circuit is used to differentially amplify the electrical signal and output a methane concentration analog voltage, with its reference ground terminal connected to point D. A cold solder joint detection circuit includes a comparator and an electronic switch. The first input terminal of the comparator is connected to point D, the second input terminal of the comparator is connected to a fixed reference voltage, and the output terminal of the comparator is connected to the control terminal of the electronic switch. The first signal input terminal of the electronic switch is connected to the output terminal of the methane signal acquisition and amplification circuit, the second signal input terminal of the electronic switch is grounded, and the output terminal of the electronic switch is connected to the input terminal of the MCU. When the potential at point D is within the normal range relative to the fixed reference voltage, the electronic switch activates the first signal input terminal; when the potential at point D is abnormal relative to the fixed reference voltage, the electronic switch activates the second signal input terminal. The MCU calculates the methane concentration or determines the fault state based on the voltage at the output terminal of the electronic switch. When the MCU collects a 0V voltage, it determines that it is in a fault state; otherwise, it calculates and outputs the corresponding methane concentration based on the non-zero voltage collected by the MCU.

2. The circuit according to claim 1, characterized in that, The methane signal acquisition and amplification circuit includes an operational amplifier. The negative input terminal of the operational amplifier is connected to point D through a voltage divider resistor network, and the positive input terminal of the operational amplifier is connected to the methane signal output terminal of the catalytic element.

3. The circuit according to claim 1, characterized in that, The methane signal acquisition and amplification circuit is configured to output a preset methane concentration analog voltage greater than 0V when there is no methane gas.

4. The circuit according to claim 1, characterized in that, The cold solder joint detection circuit includes a resistor voltage divider network, which is located between the power supply and ground to generate the fixed reference voltage.

5. The circuit according to claim 1, characterized in that, The electronic switch is an analog electronic switch.

6. The circuit according to claim 1, characterized in that, It also includes a power control circuit, which includes a MOSFET. The gate of the MOSFET is connected to the control I / O port of the MCU. The level of the control I / O port of the MCU is preset to be different from the level when the methane concentration exceeds the standard, as calculated by the MCU. The source and drain of the MOSFET are connected in series in the power supply circuit of the catalyst element. The MOSFET is used to cut off the power supply to the catalyst element when the methane concentration is highly exceeded, according to the level output by the control I / O port of the MCU.

7. The circuit according to claim 1, characterized in that, When a poor solder joint or disconnection occurs at the grounding point of the second signal input terminal of the electronic switch, the electronic switch activates the first signal input terminal.

8. A methane detection instrument, characterized in that, Includes a methane detection circuit based on catalytic element failure detection as described in any one of claims 1 to 7.

9. A methane detection circuit detection method based on catalytic element fault detection, applied to the methane detection circuit according to any one of claims 1 to 7, characterized in that, Includes the following steps: The potential of the common connection point D between the detection element and the compensation element inside the catalytic element is used as the reference potential for the methane signal acquisition and amplification circuit. The methane signal output from the catalytic element is differentially amplified by a methane signal acquisition and amplification circuit to output a simulated voltage of methane concentration. The comparator compares the potential of point D with a fixed reference voltage to determine whether the position of point D is abnormal, and generates a control signal. The electronic switch is controlled according to the control signal. When the potential of D is normal, the electronic switch selects the methane concentration analog voltage and outputs it to the MCU. When the potential of D is abnormal, the electronic switch selects the ground voltage 0V and outputs it to the MCU. The MCU collects the output voltage of the electronic switch. If the output voltage is 0V, it is determined to be a fault; otherwise, the methane concentration is calculated based on the output voltage.

10. The method according to claim 9, characterized in that, Also includes: A MOSFET is connected in series in the power supply circuit of the catalytic element, and the switching of the MOSFET is controlled according to whether the methane concentration output by the MCU exceeds the limit. When the methane concentration exceeds the preset range, the power supply to the catalytic element controlling the MOSFET is cut off.

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