Underground transient electromagnetic turn-off circuit and use method

Abstract

The invention provides an underground transient electromagnetic turn-off circuit and a use method, and the circuit comprises a transmitting antenna which is used for transmitting a transient electromagnetic primary field; the transmitting power supply is used for supplying power to the transmitting bridge circuit; the cut-off diode is used for cutting off a follow current loop of the transmitting antenna and shortening the turn-off time of the transmitting current after the bridge circuit is turned off; the transmitting bridge circuit is used for providing bipolar square wave current for the transmitting antenna under the control of the MCU, and after the transmitting current is turned off, the cut-off diode cuts off a follow current loop from the current in the transmitting coil to the field-effect tube and the transmitting power supply, so that the transmitting current is turned off quickly, the influence of a primary field on shallow stratum information is reduced, and the transmission efficiency is improved. And the intensity of the secondary field signal is improved.

Description

Technical Field

[0001] The present invention relates to the field of mine geophysical exploration, and in particular to an underground transient electromagnetic shutdown circuit and a use method thereof. Background Art

[0002] Transient electromagnetic method is a method that uses an ungrounded return line or a grounded line source to emit a pulse magnetic field underground, and uses a coil or a grounding electrode to observe the secondary induced eddy current field caused in the underground medium during the interval of a pulse magnetic field. According to the scope of application, transient electromagnetic method includes aviation, ground, ocean, and mine transient electromagnetic method. Mine transient electromagnetic method is widely used in the field of coal mine underground excavation front, roadway roof and floor, working face roof and floor, and side wall water hazard detection. It is a time domain method.

[0003] Transient electromagnetic detection technology in mines is mainly used for the detection of water bodies that cause disasters in underground projects. The speed of the emission current shutdown time affects the detection of shallow stratum information by the transient electromagnetic instrument and the strength of the secondary field signal excited. Existing mine transient electromagnetic detectors mainly use resistor-capacitor energy storage absorption circuits and high-voltage clamping shutdown technology. Although the shutdown time of the former is faster than that of the bare bridge, the shutdown time with the coil still reaches hundreds of milliseconds; the latter has a shorter shutdown time, but the cost is higher than the former. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a downhole transient electromagnetic shutdown circuit and a method of use, so as to realize high-speed shutdown of emission current in a low-cost manner.

[0005] To achieve the above object, according to one aspect of the present invention, a downhole transient electromagnetic shutdown circuit is provided, and the following technical solutions are adopted:

[0006] A downhole transient electromagnetic shutdown circuit comprises: a transmitting power supply, wherein the positive pole of the transmitting power supply is connected to the positive pole of a truncation diode, the negative pole of the truncation diode is connected to the drain pole of an upper bridge arm field effect transistor of a transmitting bridge circuit, and the negative pole of the transmitting power supply is connected to the negative pole of the truncation diode of the lower bridge arm of the transmitting bridge circuit; the transmitting bridge circuit comprises: a transmitting antenna; a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm respectively connected to the transmitting antenna; wherein the drain poles of the field effect transistors of the first bridge arm and the second bridge arm are connected to the negative pole of the truncation diode, and the negative poles of the truncation diodes of the third bridge arm and the fourth bridge arm are connected to the negative pole of the transmitting power supply; and the first bridge arm and the second bridge arm form an upper bridge arm, and the third bridge arm and the fourth bridge arm form a lower bridge arm, and the four bridge arms each comprise: a field effect transistor and a truncation diode, and the source pole of the field effect transistor is connected to the positive pole of the truncation diode of the bridge arm.

[0007] Furthermore, in the underground transient electromagnetic shutdown circuit, the cutoff diodes in the transmitting bridge circuit all adopt low voltage drop germanium Schottky diodes.

[0008] On the other hand, the present invention provides a method for using a downhole transient electromagnetic shutdown circuit, the construction method includes the downhole transient electromagnetic shutdown circuit described in the first aspect, and an additional microcontroller unit MCU for controlling the emission current is provided, and the field effect tube is turned on and off by controlling the preset timing logic, so as to provide a bipolar square wave emission circuit for the transmitting antenna, thereby realizing transient electromagnetic primary field emission;

[0009] When the transmitting current needs to be shut down, the microcontroller unit MCU turns off all field effect tubes, and at the same time the cut-off diode cuts off the current loop from the transmitting antenna to the field effect tube and the transmitting power supply, thereby achieving high-speed shutdown of the transmitting current, reducing the shutdown time and reducing interference to the shallow bottom layer.

[0010] Furthermore, a method for using an underground transient electromagnetic shutdown circuit is provided, wherein the microcontroller unit MCU also includes a fault detection and protection mechanism, which can automatically cut off the emission current and send out an alarm signal when overcurrent or overvoltage is detected in the circuit.

[0011] In combination with the above method, a downhole transient electromagnetic shutdown method using a circuit is provided, wherein the cutoff diode is a fast recovery diode having a low recovery time and a high reverse breakdown voltage, thereby ensuring effective current cutoff during the high-speed shutdown process.

[0012] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0014] Figure 1 A schematic diagram of a downhole transient electromagnetic emission current high-speed shutdown circuit provided by an embodiment of the present invention;

[0015] Figure 2 A flow chart of a method for using a downhole transient electromagnetic emission current high-speed shutdown circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention will be described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0017] In a specific embodiment, Figure 1 As shown, a downhole transient electromagnetic shutdown circuit provided by the present invention includes the following devices:

[0018] Icon: 1-transmitting power supply; 2-cutoff diode; 3-field effect transistor; 4-cutoff diode; 5-field effect transistor; 6-cutoff diode; 7-transmitting antenna; 8-field effect transistor; 9-cutoff diode; 10-field effect transistor; 11-cutoff diode.

[0019] Figure 1 A schematic structural diagram of a downhole transient electromagnetic shutdown device provided by the present invention.

[0020] according to Figure 1 The present invention provides a downhole transient electromagnetic shutoff device, comprising: a transmitting antenna 7, which is composed of a multi-turn overlapping loop, and the two ends of the loop are respectively connected to the transmitting bridge circuit, and is used to transmit a transient electromagnetic primary field; a transmitting power supply 1, which is connected to a truncation diode 2, and is used to provide power for the transmitting bridge circuit; the transmitting bridge circuit is composed of a truncation diode 4, a truncation diode 6, a truncation diode 9, a truncation diode 11 and a field effect transistor 3, a field effect transistor 5, a field effect transistor 8, and a field effect transistor 10. The field effect transistors 3, 5, 8, and 10 are used to provide a bipolar square wave current transmitting circuit for the transmitting antenna 7 through opening and closing in a certain timing under the control of the MCU; the truncation diodes 4, 6, 9, and 1 are on each arm of the transmitting bridge circuit, and are used to cut off the freewheeling circuit of the current in the transmitting antenna to the field effect transistors 3, 5, 8, 10 and the transmitting power supply 1 after the transmitting current is turned off.

[0021] The bridge circuit includes five cutoff diodes, wherein the positive electrode of the transmitting power supply is connected to the positive electrode of diode 2, the negative electrode of diode 2 is connected to the drain electrodes of field effect transistors 3 and 5, the source electrode of field effect transistor 3 is connected to the positive electrode of diode 4, the source electrode of field effect transistor 5 is connected to the positive electrode of diode 6, the negative electrode of diode 4 is connected to the positive electrode of transmitting antenna 7, the negative electrode of diode 6 is connected to the negative electrode of transmitting antenna 7, the drain electrode of field effect transistor 8 is connected to the positive electrode of transmitting antenna 7, the drain electrode of field effect transistor 10 is connected to the negative electrode of transmitting antenna 7, the source electrode of field effect transistor 8 is connected to the positive electrode of diode 9, the source electrode of field effect transistor 10 is connected to the positive electrode of diode 11, and the negative electrodes of diodes 9 and diodes 11 are connected to the negative electrode of the transmitting power supply.

[0022] In addition to the above structure, the present invention also provides a method for using a downhole transient electromagnetic shutdown circuit, the device comprising:

[0023] In the first aspect, a method for using an underground electrical shutdown circuit is described as follows: Figure 2 As shown:

[0024] S110: Initialize the system;

[0025] S120: emission current starts;

[0026] S130: current is turned off;

[0027] S140: The cut-off diode cuts off the emission current follow-through;

[0028] S150: Fault detection and protection mechanism;

[0029] S160: The system restarts current transmission.

[0030] In step S110, it specifically includes starting the micro-control unit and performing a system self-check; after the self-check is completed, the preset timing logic parameters are initialized to verify whether all field effect tubes and cut-off diodes are in normal working state.

[0031] After successfully verifying the working status, enter step S120 and start the transmitting current. The specific operation includes that the micro-control unit controls the field effect transistors to turn on in sequence according to the preset timing logic, providing a bipolar square wave transmitting circuit for the transmitting antenna and generating a transient electric primary field.

[0032] After the startup is completed, the process enters step S130, where the microcontroller unit controls the field effect tubes to be turned off one by one.

[0033] Entering step S140, the cut-off diode ensures that the current loop is quickly disconnected, ensuring that the continuous current to the field effect transistor and the transmitting power supply in the transmitting antenna is effectively cut off.

[0034] After shutdown, the fault detection and protection step S150 is entered. The micro-control unit continuously monitors the current and voltage parameters in the circuit. When overcurrent and overvoltage are detected, the emergency shutdown procedure is executed and an alarm signal is issued.

[0035] When there is no abnormality, the process proceeds to step S160. After the shutdown procedure is completed, the micro-control unit performs a self-check, resets the system and the device, and prepares for the next cycle of current emission operation.

[0036] A microcontroller unit MCU is added to control the emission current. By controlling the preset timing logic to turn on and off the field effect tube, a bipolar square wave emission circuit is provided for the transmitting antenna to realize transient electromagnetic primary field emission.

[0037] When the transmitting current needs to be shut down, the microcontroller unit MCU turns off all field effect tubes, and at the same time, the cut-off diode cuts off the current loop from the transmitting antenna to the field effect tube and the transmitting power supply, thereby realizing high-speed shutdown of the transmitting current, reducing the shutdown time and reducing interference with the secondary field signal of the shallow formation.

[0038] In addition, the microcontroller unit MCU also includes a fault detection and protection mechanism, which can automatically cut off the transmission current and send out an alarm signal when it detects overcurrent or overvoltage in the circuit.

[0039] The cut-off diode is a fast recovery diode with short recovery time and high reverse breakdown voltage, ensuring effective current cut-off during high-speed shutdown. The diodes in the bridge circuit are all high-current, low-voltage-drop germanium Schottky diodes.

[0040] The present invention only uses 5 large-current low-voltage-drop germanium Schottky diodes. After the transmitting current is turned off, the diodes cut off the freewheeling loop of the current in the transmitting coil to the field-effect transistor and the transmitting power supply. At a low cost, the transmitting current can be quickly turned off, reducing the influence of the primary field on the shallow formation information and improving the strength of the secondary field signal.

[0041] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A downhole transient electromagnetic shutdown circuit, characterized in that: include: A transmitting power supply, wherein the positive electrode of the transmitting power supply is connected to the positive electrode of a cut-off diode, the negative electrode of the cut-off diode is connected to the drain of a transmitting bridge circuit, and the negative electrode of the transmitting power supply is connected to the negative electrode of the cut-off diode of the lower bridge arm of the transmitting bridge circuit; The transmitting bridge includes: Transmitting antenna; The first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm of the transmitting bridge are respectively connected; The drains of the first bridge arm and the second bridge arm are connected to the cathode of the cut-off diode behind the transmitting power supply, and the cathodes of the cut-off diodes of the third bridge arm and the fourth bridge arm are connected to the cathode of the transmitting power supply; Furthermore, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all include: a field effect tube and a cut-off diode, and the source of the field effect tube is connected to the anode of the cut-off diode.

2. The downhole transient electromagnetic shutdown circuit according to claim 1, characterized in that: The cut-off diodes in the transmitting bridge circuit all use low voltage drop germanium Schottky diodes.

3. A method for using a downhole transient electromagnetic shutdown circuit, characterized in that: Constructing a downhole transient electromagnetic shutdown circuit as claimed in any one of claims 1 to 2; A microcontroller unit MCU is added to control the emission current. By controlling the preset timing logic to turn on and off the field effect tube, a bipolar square wave emission circuit is provided for the transmitting antenna to realize transient electromagnetic primary field emission. When the transmitting current needs to be shut down, the microcontroller unit MCU turns off all field effect tubes, and at the same time, the cut-off diode cuts off the current loop from the transmitting antenna to the field effect tube and the transmitting power supply, thereby realizing high-speed shutdown of the transmitting current, reducing the shutdown time and reducing interference with the secondary field signal of the shallow formation.

4. A method for using a downhole transient electromagnetic shutdown circuit according to claim 3, characterized in that: The micro-control unit MCU also includes a fault detection and protection mechanism, which can automatically cut off the transmission current and send out an alarm signal when overcurrent or overvoltage is detected in the circuit.

5. According to the circuit method for underground transient electromagnetic shutdown described in claim 4, the cut-off diode is a fast recovery diode with a low recovery time and a high reverse breakdown voltage, ensuring that the current is effectively cut off during the high-speed shutdown process.

Images