CN108227011B - A dual trapezoidal wave emission system and control method with controllable falling edge - Google Patents

Abstract

The invention relates to the field of transient electromagnetic emission, in particular to a double-trapezoidal wave emission system with a controllable falling edge and a control method. The system comprises: the device comprises a main control circuit, an optocoupler driving circuit, a transmitting bridge circuit, a high-voltage transient suppression diode, a low-voltage transient suppression diode circuit, a series battery pack and a transmitting coil, wherein: the main control circuit is connected with the transmitting bridge circuit through an optocoupler drive, and the transmitting bridge circuit is connected with the transmitting coil; the series battery pack is connected with the transmitting bridge circuit to provide power for transmitting, and the high-voltage transient suppression diode and the low-voltage transient suppression diode circuit are connected in parallel at two ends of the transmitting coil. The invention can simultaneously generate a group of trapezoidal wave emission currents with different turn-off times, which are respectively used for exciting and measuring induction field signals and polarization responses, realizes simultaneous detection of resistivity and polarization ratio, and improves detection precision.

Description

A dual trapezoidal wave emission system and control method with controllable falling edge

technical field

The invention relates to the field of transient electromagnetic emission, in particular to a dual trapezoidal wave emission system and control method with controllable falling edges.

Background technique

Due to the limitations of the detection system, the traditional transient electromagnetic method can only stimulate and measure electromagnetic induction signals, and the measurement parameters are single, the interpretation parameters are single, and the accuracy of data interpretation is low, which is the bottleneck in the development of the current transient electromagnetic method. Multi-parameter joint detection is an effective method to improve the accuracy of TEM detection. The induced polarization effect is a common phenomenon existing in the earth. Simultaneous detection of transient electromagnetic and induced polarization signals can effectively improve the interpretation accuracy of the earth. The time-domain electromagnetic induction method (TEM) is to generate a secondary field by exciting the ground, and measure the secondary induced magnetic field to obtain the conductivity information of the underground medium; the induced polarization method (IP) is to generate an induced polarization field by electrifying the ground. The polarizability parameters of the subsurface medium are obtained by measuring the excited polarization field. Both TEM and IP have obvious advantages in the detection of water resources and metal mines. During low-frequency time-domain electromagnetic detection, it is found that the induction field and the polarization field exist at the same time. In the early stage after the current is turned off, the induction field decays rapidly, which is manifested as the coexistence of the induction field and the polarization field, and the polarization field discharges; in the late stage, there is almost no induction field, mainly the polarization field. There is a polarization charging effect on the falling edge of the emission current of the magnetic source. In the case of the same emission current, for short falling edge emission, the polarization charging time is short and the excitation polarization field is weak, which is suitable for induction field measurement; for long falling edge emission , the polarization charging time is longer, and the excitation polarization field strength is suitable for polarization field measurement. Therefore, emitting a set of trapezoidal wave currents with different off-times is a feasible method for simultaneous detection of IP and TEM dual fields.

In order to enable the receiving system to accurately collect the magnetic field signal excited by the transmitting current during detection, it is necessary to synchronize the receiving and transmitting systems. For the situation where the transmitting and receiving devices are far apart, GPS synchronization is often used. However, in some areas with poor signals, such as In remote mountainous areas, jungles, urban areas covered by tall buildings, etc., GPS signals may sometimes be lost. Conventional transient electromagnetic emission systems often fail to work because they cannot receive synchronous signals.

Chinese patent CN105510979A discloses a transient electromagnetic transmitter circuit for load parallel discharge, which shortens the discharge time of the load coil and reduces the turn-off delay of the transmitter by changing the connection mode of the load coil, but only for the induction field signal to measure.

Chinese patent CN 105119588 A discloses a transient electromagnetic method pulse current transmitting circuit, which improves the current falling edge clamping voltage through the energy feeding constant voltage clamping circuit, shortens the falling edge time, and improves the falling edge linearity, but It is still impossible to realize the simultaneous detection of the dual parameters of resistivity and polarizability.

Contents of the invention

The invention provides a dual trapezoidal wave emission system and control method with controllable falling edges, which solves the problem that the dual parameters of resistivity and polarizability cannot be detected simultaneously.

The present invention is achieved like this,

A dual trapezoidal wave emission system with controllable falling edges, said system comprising:

Main control circuit, optocoupler driving circuit, transmitting bridge, high-voltage transient suppression diode, low-voltage transient suppressing diode circuit, series battery pack and transmitting coil, wherein: the main control circuit is connected to the transmitting bridge through optocoupler driving, The transmitting bridge is connected to the transmitting coil; the series battery pack is connected to the transmitting bridge to provide power for transmitting, and the high-voltage transient suppression diode and the low-voltage transient suppression diode circuit are connected in parallel at both ends of the transmitting coil.

Further, the transmitting bridge is composed of a high-power diode D1 and four power FETs, wherein the power FET S1 is connected in series with the power FET S3, the power FET S2 is connected in series with the power FET S4, and the two A series circuit is connected in parallel again, the connection of the power field effect transistor S1 and the power field effect transistor S3 is connected with the output of the transmission circuit as the output of the transmission circuit at the connection of the power field effect transistor S2 and the power field effect transistor S3, and the high-power diode D1 The positive stage is connected to the positive pole of the series battery pack, the negative pole is connected to the common terminal of the power field effect transistor S1 and the power field effect transistor S2, the negative pole of the series battery pack is connected to the common terminal of the power field effect transistor S3 and the power field effect transistor S4, and the main control The four control signals of the circuit respectively control the conduction of the four power field effect transistors, thereby controlling the generation of positive or negative current trapezoidal waves on the transmitting coil.

Further, the main control circuit generates two transmission bridges, the first control square wave and the second control square wave, and the first control square wave is driven by an optocoupler to generate two control signals for controlling the power field effect transistor S1 and The power field effect transistor S4, the second control square wave is driven by the optocoupler to generate two control signals for controlling the power field effect transistor S2 and the power field effect transistor S3 respectively.

Further, the low-voltage transient suppression diode circuit includes: a low-voltage transient suppression diode. After the two ends of the low-voltage transient suppression diode are respectively connected to the power field effect transistor S5 and the power field effect transistor S6, the power field effect transistor S5 and the power field effect transistor S5 are connected to each other. The effect tube S6 is connected with the power FET S7 and the power FET S8 respectively, and the whole is connected in parallel at both ends of the transmitting coil, the power FET S5, the power FET S6, the power FET S7 and the power FET S8 , wherein the power field effect transistor S7 and the power field effect transistor S8 are both driven and controlled by the optocoupler through the falling edge control signal of the main control circuit, and the power field effect transistor S5 and the power field effect transistor S6 are controlled by the two control square waves of the main control circuit It is connected with power field effect transistor S5 and power field effect transistor S6 through a NOR gate.

Furthermore, when the falling edge control signal is at a low level, the power field effect transistor S7 and the power field effect transistor S8 are disconnected, and the transmitting coil generates a voltage overshoot with a high amplitude in the same direction as the current due to the existence of the inductance. Released by the high-voltage transient suppression diode connected in parallel at both ends of the transmitting coil, when the voltage at both ends of the transmitting coil is higher than the clamping voltage of the high-voltage transient suppression diode, the high-voltage transient suppression diode conducts and clamps the voltage at both ends of the transmitting coil at its On the clamping voltage, the emission current can be turned off quickly.

Furthermore, when the falling edge control signal is at a high level, the power field effect transistor S7 and the power field effect transistor S8 are turned on, and at the moment the current is turned off, the two control square waves of the main control circuit are both at low level, and the NOR gate The output signal is high level, the power field effect transistor S5 and the power field effect transistor S6 are turned on, the low-voltage transient suppression diode is connected in parallel at both ends of the transmitting coil, and the clamping voltage of the low-voltage transient suppression diode is very low. When the voltage overshoot is higher than When the low-voltage transient suppression diode breaks down the voltage, the low-voltage transient suppression diode conducts and clamps the voltage at both ends of the coil to a very low voltage to realize the slow shutdown of the emission current.

Further, the system also includes a dual synchronization module, which uses GPS and Beidou dual synchronization mode for synchronization. When the main control circuit receives the synchronization signal generated by the dual synchronization module, the main control circuit generates two transmission bridges according to the set transmission parameters. Control the square wave signal and the falling edge control square wave, the main control circuit is connected with the optocoupler driver through the control signal output port.

Further, the system also includes an absorption circuit, the absorption circuit includes an absorption resistor, a power field effect transistor S9 and a power field effect transistor S10 at both ends of the absorption resistance, and an optocoupler drive of the power field effect transistor, and the absorption circuit passes through The absorption circuit control signal generated by the main control circuit is controlled. After the current is turned off, the absorption circuit control signal becomes high level, the power field effect transistor S9 and the power field effect transistor S10 are turned on, and the absorption resistance is connected in parallel at both ends of the transmitting coil , to absorb falling shocks along the tail.

A double trapezoidal wave emission control method with controllable falling edge, said method comprising:

Step 1 According to the detection requirements, combined with the conductivity and polarization characteristics of the measurement area, use the soft loading method to set the period and duty cycle parameters of the emission current, configure the parameters into the two timers of the main control circuit, and use pulse width modulation The technology controls the launch bridge through optocoupler drive;

Step 2. The main control circuit outputs a square wave after receiving the synchronization signal, and then drives to control the transmitting bridge to generate a bipolar trapezoidal wave with an adjustable period and duty cycle on the transmitting coil;

Step 3: During the turn-off period of the first set of trapezoidal waves, the high-voltage transient suppression diode connected in parallel on the transmitting coil is pierced by the voltage overshoot, and the voltage at both ends of the transmitting coil is clamped at a high voltage, which can realize fast turn-off on the falling edge;

Step 4 During the turn-off period of the second set of trapezoidal waves, by controlling the conduction of the low-voltage transient suppression diode circuit connected in parallel on the transmitting coil, the voltage at both ends of the transmitting coil is clamped at a low voltage, which can realize slow turn-off at the falling edge.

Further, in step 2, the process of the main control circuit outputting a square wave after receiving the synchronization signal is: the dual synchronization mode of the GPS synchronization signal and the Beidou synchronization signal is started at the same time, and the first second pulse uses the GPS synchronization signal to trigger the external interruption of the main control circuit , to stimulate the main control circuit to output the control square wave signal of the transmitting bridge, and the second second pulse uses the Beidou synchronization signal to trigger the external interruption of the main control circuit, and so on. When the external interruption of the main control circuit is triggered twice consecutively by the Beidou synchronization signal, Then it is determined that the GPS synchronization signal is lost. At this time, the main control circuit only uses the Beidou synchronization signal as the synchronization pulse; when the external interruption of the main control circuit is triggered twice consecutively by the GPS synchronization signal, it is determined that the Beidou synchronization signal is lost. The GPS signal is used as the synchronization pulse.

Compared with the prior art, the present invention has the beneficial effect that: the present invention can simultaneously generate a set of trapezoidal wave emission currents with different off-times, which are respectively used for excitation and measurement of induction field signals and polarization responses, and realize resistivity and polarization Simultaneous detection of dual parameters of rate improves the detection accuracy; GPS and Beidou dual synchronization mode is adopted, and the synchronization signals are complementary, which improves the stability of the system working in areas with poor signals.

Description of drawings

Fig. 1 is the overall structural diagram of the transmitting system provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of the falling edge control circuit provided by the embodiment of the present invention;

Fig. 3 schematic diagram of the absorbing circuit provided by the embodiment of the present invention;

Figure 4 is the program flow chart of the main control circuit of the transmitting system provided by the embodiment of the present invention

FIG. 5 is a timing waveform diagram of the transmission system control provided by the embodiment of the present invention;

Fig. 6 is a screenshot of the dual trapezoidal wave emission current oscilloscope with controllable falling edge provided by the embodiment of the present invention, 6a is a waveform diagram of a fast falling edge, and 6b is a waveform diagram of a slow falling edge.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Referring to Fig. 1 in conjunction with Fig. 5, the double trapezoidal wave emission system with controllable falling edge provided by the present invention is mainly composed of a main control circuit 1, a dual synchronization module 2, a button 3, a liquid crystal display 4, an optocoupler drive combination 5, Transmitting bridge circuit 6, high-voltage transient suppression diode 7, low-voltage transient suppression diode circuit 8, absorption circuit 9, transmitting coil 10, series battery pack 11, lithium battery 12, low-voltage power supply 13 and high-voltage power supply 14, in which the double synchronous module 2 has a Beidou and GPS dual synchronization mode, and the low-voltage transient suppression diode circuit 8 is composed of a low-voltage transient suppression diode 15 and a series of switching devices. The high-voltage transient suppression diode 7 and the low-voltage transient suppression diode circuit 8 jointly constitute a falling edge control circuit, and are connected in parallel at both ends of the transmitting coil 10 . The main control circuit 1 is connected with the dual synchronization module 2, the key 3, and the liquid crystal display 4 respectively, and is connected with the transmitting bridge 6 through the optocoupler driving combination 5, the transmitting bridge 6 is connected with the transmitting coil 10, and the battery pack 11 is connected in series with the transmitting The bridge 6 is connected to provide power for the transmission. The high-voltage transient suppression diode 7, the low-voltage transient suppression diode circuit 8 and the absorption circuit 9 are connected in parallel at both ends of the transmission coil 10. The transmission system uses a lithium battery 12 for power supply, and obtains a low-voltage power supply through DC/DC 13 supplies power to the main control circuit 1, dual synchronization module 2, liquid crystal display 4, etc., and obtains a high-voltage power supply 14 through DC/DC to provide driving voltage for the optocoupler driving combination 5.

The main control circuit 1 is a single-chip microcomputer with ARM as the processor, including a dual synchronization module communication port, a key input interface, a liquid crystal display interface, and a control signal output port. The keys 3 and the liquid crystal display 4 are connected to the main control circuit 1 through the key input interface and the liquid crystal display interface to form a human-computer interaction interface. Through the human-computer interaction interface, set the transmission waveform pulse width, cycle, falling edge transmission mode and other parameters. The dual synchronization module 2 is connected to the main control circuit 1 through the communication port of the dual synchronization module, and uses GPS and Beidou dual synchronization mode for synchronization. When the main control circuit 1 receives the synchronization signal generated by the dual synchronization module 2, the main control circuit 1 follows the set The transmission parameters generate the first control square wave U1 and the second control square wave U2 of the two transmission bridges 6. The control timing of these two square waves has a phase difference. When the first control square wave U1 is high, the current is positive When the second control square wave U2 is high, the current flows negatively, the falling edge controls the square wave U3 and the absorbing circuit controls the square wave U4. The main control circuit 1 is connected to the optocoupler drive combination 5 through the control signal output port, the first control square wave U1 is driven by the optocoupler to generate two control signals (Q1, Q4), and the first control square wave U2 is generated by the optocoupler drive Two control signals (Q2, Q3).

Referring to Fig. 2, the optocoupler driving combination 5 is connected to the transmitting bridge 6, and the transmitting bridge 6 is composed of a high-power diode D1 and four power field effect transistors, and the power field effect transistor S1 is connected in series with the power field effect transistor S3. The power field effect transistor S2 is connected in series with the power field effect transistor S4, and the two series circuits are then connected in parallel. The output of the transmitting circuit is connected to the transmitting coil 10, the positive pole of the high-power diode D1 is connected to the positive pole of the series battery pack 11, the negative pole is connected to the common end of the power field effect transistor S1 and the power field effect transistor S2, and the negative pole of the series battery pack 11 is connected to the power field The common end of the effect transistor S3 and the power field effect transistor S4 is connected. The control signals Q1, Q2, Q3, and Q4 respectively control the conduction of the power field effect transistors S1, S2, S3, and S4. When the control timing of the first control square wave U1 is high level and the timing sequence of the second control square wave U2 is low level, the power field effect transistor S1 and the power field effect transistor S4 are turned on, and the power field effect transistor S2 and the power field effect transistor S3 is turned off, and a positive current trapezoidal wave is generated on the transmitting coil 10; when the first control square wave U1 controls the timing sequence to be low level and the second control square wave U2 is high level, the power FET S2 and the power FET The tube S3 is turned on, the power field effect transistor S1 and the power field effect transistor S4 are turned off, and a negative current trapezoidal wave is generated on the transmitting coil 10 .

The low-voltage transient suppression diode circuit 8 is composed of a power FET, 2 NOR gates (G1, G2), 4 optocoupler drivers and a low-voltage transient suppression diode 15, wherein the first control signal U1, The second control signal U2 is used as the input of the NOR gate (G1, G2), and the output of the NOR gate is connected with the power field effect transistor S5 and the power field effect transistor S6 through the optocoupler, and the falling edge control signal U3 is driven by the optocoupler to give power FET S7, power FET S8, the two ends of the low-voltage transient suppression diode 15 are respectively connected with the power FET S5 and the power FET S6, and both ends are connected with the power FET S7 and the power FET S8, The whole is then connected in parallel at both ends of the transmitting coil 10 .

When the falling edge control signal U3 is at low level, the power field effect transistor S7 and the power field effect transistor S8 are disconnected, and the transmitting coil 10 will generate a voltage overshoot with a high amplitude in the same direction as the current due to the existence of inductance. Due to the existence of the diode D1, the voltage overshoot cannot be released through the freewheeling diode of the power field effect transistor forming the transmitting bridge 6, so it can only be released through the high voltage transient suppression diode 7 connected in parallel at both ends of the transmitting coil 10. When the voltage across the transmitting coil 10 is higher than the clamping voltage of the high-voltage transient suppression diode 7 , the high-voltage transient suppression diode 7 conducts and clamps the voltage across the transmitting coil 10 at its clamping voltage. The expression of the voltage and current changes at both ends of the inductive load is shown in formula (1):

Among them, U is the voltage across the load, L is the inductance value of the load, and di/dt is the change rate of the current flowing through the load. According to the formula, when the load is constant, the voltage across it is proportional to the rate of change of the current. The transmitting coil 10 can be equivalent to a series connection of an inductor and a resistor, and the high-voltage transient suppression diode 7 has a very high clamping voltage, so that the transmitting current drops rapidly, and the transmitting current is quickly turned off.

When the falling edge control signal U3 is at a high level, the power field effect transistor S7 and the power field effect transistor S8 are turned on, and the moment the current is turned off, the first control signal U1 and the second control signal U2 are both at a low level, or the NOR gate (G1, G2) The output signal U4 is high level, the power field effect transistor S5 and the power field effect transistor S6 are turned on, the low voltage transient suppression diode 15 is connected in parallel at both ends of the transmitting coil 10, and the low voltage transient suppression diode 15 clamps the voltage Very low, when the voltage overshoot is higher than the breakdown voltage of the low-voltage transient suppression diode 15, the low-voltage transient suppression diode 15 is turned on and the voltage across the coil is clamped at a very low voltage to realize the slow shutdown of the emission current . A set of trapezoidal wave emission currents with different off-times can be obtained by controlling the falling edge control signal U3.

Referring to Fig. 3, the absorbing circuit 9 is composed of the absorbing resistor 31, the optocoupler drive and the power field effect transistor S9, and the power field effect transistor S10. The absorbing resistor 31 must meet the conditions shown in formula (2):

Wherein, L is the inductance value of the transmitting coil 10, and C _stray is the stray capacitance value of the transmitting circuit. The absorbing circuit control signal U5 is driven by the optocoupler to the power field effect transistor S9 and the power field effect transistor S10, and the power field effect transistor S9 and the power field effect transistor S10 are respectively connected in parallel to both ends of the absorbing resistor 31, and then connected in parallel with the transmitting coil 10 as a whole After the current is turned off, the control output signal U5 changes from low level to high level, and the power field effect transistor S9 and power field effect transistor S10 are controlled by the optocoupler output control signal (Q9, Q10) to make the absorption resistor 31 and The transmitting coils 10 are connected in parallel to effectively absorb the tail oscillation of the transmitting current, and obtain a controllable falling-edge dual trapezoidal wave transmitting current of good quality.

Referring to Fig. 4, the control method of double trapezoidal wave with controllable falling edge provided by the present invention,

1) According to the detection requirements, combined with the conductivity and polarization characteristics of the measurement area, the human-computer interaction interface composed of the button (3) and the LCD screen (4) adopts a soft loading method to set parameters such as the cycle and duty cycle of the emission current , configure the parameters into the two timers of the main control circuit 1, and use the pulse width modulation technology to control the transmitting bridge 6 through the optocoupler driving combination 5;

2) The launch system adopts GPS and Beidou dual synchronization mode to synchronize. The dual synchronization module 2 has GPS and Beidou dual synchronization modes, and is connected with the main control circuit 1 . The GPS and Beidou dual synchronization modes are started at the same time. The first second pulse uses the GPS synchronization signal to trigger the external interrupt of the main control circuit (1), which excites the main control circuit 1 to output the control square wave signal of the transmitting bridge 6. The second second pulse uses The Beidou synchronization signal triggers an external interrupt of the main control circuit 1, and so on and on. When the external interruption of the main control circuit 1 is triggered twice consecutively by the Beidou synchronization signal, it is determined that the GPS synchronization signal is lost. At this time, the main control circuit 1 only uses the Beidou signal as the synchronization pulse; When it is triggered twice, it is determined that the Beidou synchronization signal is lost. At this time, the main control circuit 1 only uses the GPS signal as the synchronization pulse. The dual synchronous and complementary working mode of GPS and Beidou improves the stability of the system working in poor signal areas.

In the present embodiment, the switching devices of the transmitting bridge circuit 6, the low-voltage transient suppression diode circuit 8 and the absorbing circuit 9 select power field effect transistors, select a rectangular loop with a side length of 25m as the transmitting coil 10, and measure the resistance of the transmitting coil 10 0.2Ω, inductance of 0.2mH, select a battery with a voltage of 12V as the battery pack 11 connected in series to supply power, and use a 1Ω non-inductive resistor in series with the transmitting coil 10 to sample the transmitting current. The voltage of group 11 selects SMCJ13CA high-voltage transient suppression diode 7 and SMCJ5CA low-voltage transient suppression diode 15 . After receiving the synchronization signal, the main control circuit 1 outputs the first control square wave U1 and the second control square wave U2. The first control square wave U1 is driven to generate signals Q1 and Q4 to control the power field effect of the transmitting bridge 6. The tube S1 and the power FET S4 are turned on to generate a positive current on the transmitting coil 10; the second control square wave U2 is driven to generate signals Q2 and Q3 to control the power FET S2 of the transmitting bridge 6 , The power field effect transistor S3 is turned on, and a negative current is generated on the transmitting coil 10 . By controlling the first control square wave U1 and the second control square wave U2, a bipolar trapezoidal wave with a cycle and an adjustable duty cycle can be generated on the transmitting coil 10;

3) During the off period of the first group of trapezoidal waves, the first group of trapezoidal waves refers to: a positive trapezoidal wave and a negative trapezoidal wave are a group of trapezoidal waves. During the first positive wave turn-off and the first negative wave turn-off, the high-voltage transient suppression diode 7 is pierced by the voltage overshoot, and the voltage across the transmitting coil 10 is clamped at a high voltage, which can realize fast turn-off on the falling edge off; the current linear fast turn-off fall time calculation formula is shown in formula (3):

Among them, I is the current value of the flat top of the transmitter, L _COIL is the inductance value of the transmitter coil 10, which can be obtained by calculation or measurement, and U _HTVS is the clamping voltage of the high voltage transient suppression diode 7. In the formula, for SMCJ13CA high-voltage transient suppression diode 7, U _HTVS is 21.5V.

4) During the second set of trapezoidal wave off period, the second set of trapezoidal wave off period refers to the second positive wave off period and the second negative wave off period, the main control circuit 1 generates a falling edge control signal U3 , and then driven by the optocoupler to generate signal Q7 and signal Q8, respectively controlling the conduction of power field effect transistor S7 and power field effect transistor S8. At this time, the first control square wave U1 and the second control square wave U2 are both at low level, The output signal U4 of the NOR gate is high level, and then the signal Q5 and the signal Q6 are generated by the optocoupler to control the conduction of the power field effect transistor S5 and the power field effect transistor S6 respectively. The two ends of the coil 10 clamp the voltage at the two ends of the transmitting coil 10 to a low voltage, which can realize slow turn-off at the falling edge. The formula for calculating the current linear slow turn-off fall time is shown in formula (4):

Where U _LTVS is the clamping voltage of the low-voltage transient suppression diode 15, U _Dedio is the voltage drop of the freewheeling diode of the switching device, and U _MOS is the forward voltage drop when the switching device is turned on. In the formula, for the SMCJ5CA low-voltage transient suppression diode (11), U _HTVS is 9.2V; for the power FET, U _Dedio is 0.7V, and U _MOS is very small and can be ignored.

By controlling the clamping voltage of the high-voltage transient suppression diode 7 and the low-voltage transient suppression diode 15, the two ends of the transmitting coil 10 are kept at high voltage and low voltage, and finally a bipolarity with controllable emission falling edge is realized in one current cycle Combine trapezoidal waves.

Fig. 6 (a) and Fig. 6 (b) are the double trapezoidal wave emission current oscilloscope screenshots of controllable falling edge, respectively fast falling edge trapezoidal wave emission current and slow falling edge trapezoidal wave emission current, fully verifying the effectiveness of the present invention sex.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (6)

1. A dual trapezoidal wave transmitting system with controllable falling edges, the system comprising:

the device comprises a main control circuit, an optocoupler driving circuit, a transmitting bridge circuit, a high-voltage transient suppression diode, a low-voltage transient suppression diode circuit, a series battery pack and a transmitting coil, wherein: the main control circuit is connected with the transmitting bridge circuit through an optocoupler drive, and the transmitting bridge circuit is connected with the transmitting coil; the series battery pack is connected with the transmitting bridge circuit to provide power for transmission, and the high-voltage transient suppression diode and the low-voltage transient suppression diode circuit are connected in parallel at two ends of the transmitting coil;

the transmitting bridge comprises a high-power diode D1 and four power field effect transistors, wherein the power field effect transistor S1 is connected with the power field effect transistor S3 in series, the power field effect transistor S2 is connected with the power field effect transistor S4 in series, the two series circuits are connected in parallel again, the connection part of the power field effect transistor S1 and the power field effect transistor S3 is connected with the transmitting coil as the output of the transmitting circuit, the positive electrode of the high-power diode D1 is connected with the positive electrode of the series battery pack, the negative electrode of the series battery pack is connected with the public end of the power field effect transistor S1 and the power field effect transistor S2, the negative electrode of the series battery pack is connected with the public end of the power field effect transistor S3 and the power field effect transistor S4, and the four control signals of the main control circuit respectively control the four power field effect transistors to be conducted, so that positive or negative current trapezoidal waves are generated on the transmitting coil;

the low voltage transient suppression diode circuit includes: the low-voltage transient suppression diode is characterized by comprising a low-voltage transient suppression diode, wherein two ends of the low-voltage transient suppression diode are respectively connected with a power field effect tube S5 and a power field effect tube S6, the power field effect tube S5 and the power field effect tube S6 are respectively connected with a power field effect tube S7 and a power field effect tube S8, the whole is connected with two ends of a transmitting coil in parallel, the power field effect tube S5, the power field effect tube S6, the power field effect tube S7 and the power field effect tube S8 are respectively driven and controlled by a falling edge control signal of a main control circuit through an optocoupler, two control square waves of the main control circuit are used as input of a NOR gate, and output of the NOR gate is connected with the power field effect tube S5 and the power field effect tube S6 through the optocoupler;

when the falling edge control signal is at a low level, the power field effect transistor S7 and the power field effect transistor S8 are disconnected, the transmitting coil generates a voltage overshoot with a high amplitude in the same direction as the current due to the existence of an inductor, the voltage overshoot is released through the high-voltage transient suppression diodes connected in parallel at the two ends of the transmitting coil, and when the voltage at the two ends of the transmitting coil is higher than the clamping voltage of the high-voltage transient suppression diodes, the high-voltage transient suppression diodes are conducted and clamp the voltage at the two ends of the transmitting coil on the clamping voltage of the transmitting coil, so that the transmitting current is quickly turned off;

when the falling edge control signal is at a high level, the power field effect transistor S7 and the power field effect transistor S8 are conducted, the two control square waves of the main control circuit are low in level, the NOR gate output signal is at a high level, the power field effect transistor S5 and the power field effect transistor S6 are conducted, the low-voltage transient suppression diode is connected in parallel at two ends of the transmitting coil, the clamping voltage of the low-voltage transient suppression diode is very low, and when the voltage overshoot is higher than the breakdown voltage of the low-voltage transient suppression diode, the low-voltage transient suppression diode is conducted and clamps the voltages at two ends of the coil at a very low voltage, so that the slow turn-off of the transmitting current is realized.

2. The system of claim 1, wherein the master control circuit generates two paths of first control square waves and second control square waves of the transmitting bridge, the first control square waves are driven by the optocoupler to generate two paths of control signals for controlling the power field effect transistor S1 and the power field effect transistor S4 respectively, and the second control square waves are driven by the optocoupler to generate two paths of control signals for controlling the power field effect transistor S2 and the power field effect transistor S3 respectively.

3. The system of claim 1, further comprising a dual synchronization module, wherein the dual synchronization module is synchronized by using a GPS and a beidou, and when the master control circuit receives the synchronization signal generated by the dual synchronization module, the master control circuit generates two paths of transmitting bridge control square wave signals and a falling edge control square wave according to the set transmitting parameters, and the master control circuit is in driving connection with the optocoupler through a control signal output port.

4. The system of claim 1, further comprising an absorption circuit, wherein the absorption circuit comprises an absorption resistor, a power field effect transistor S9 and a power field effect transistor S10 at two ends of the absorption resistor, and an optocoupler driving of the power field effect transistor, the absorption circuit is controlled by an absorption circuit control signal generated by the main control circuit, after the current is turned off, the absorption circuit control signal becomes high level, the power field effect transistor S9 and the power field effect transistor S10 are turned on, the absorption resistor is connected at two ends of the transmitting coil in parallel, and the absorption falling edge tail oscillates.

5. A method for controlling emission of a double trapezoid wave with a controllable falling edge, which adopts the double trapezoid wave emission system with the controllable falling edge as set forth in any one of claims 1 to 4, and the method is characterized in that:

step 1, according to the detection requirement, combining the conductivity and polarization characteristics of a measurement area, adopting a soft loading mode to set the period and duty ratio parameters of the emission current, configuring the parameters into two timers of a main control circuit, and controlling an emission bridge circuit through optocoupler driving by utilizing a pulse width modulation technology;

step 2, the main control circuit receives the synchronous signal and outputs a square wave, and then the square wave is driven to control the transmitting bridge circuit to generate a bipolar trapezoidal wave with adjustable period and duty ratio on the transmitting coil;

step 3, during the turn-off period of the first group of trapezoidal waves, the high-voltage transient suppression diode connected in parallel on the transmitting coil is broken down by voltage overshoot, and the voltages at two ends of the transmitting coil are clamped on the high voltage, so that the fast turn-off of the falling edge can be realized;

and 4, during the turn-off period of the second group of trapezoidal waves, the low-voltage transient suppression diode circuit connected in parallel on the transmitting coil is controlled to be conducted, and the voltage at two ends of the transmitting coil is clamped at the low voltage, so that the slow turn-off of the falling edge can be realized.

6. The method of claim 5, wherein in step 2, the process of outputting the square wave after the master control circuit receives the synchronization signal is: the GPS synchronization signal and the Beidou synchronization signal double synchronization mode are started simultaneously, the first second pulse adopts the GPS synchronization signal to trigger the external interruption of the main control circuit to excite the main control circuit to output a control square wave signal of the transmitting bridge, the second pulse adopts the Beidou synchronization signal to trigger the external interruption of the main control circuit, so that the process is repeated, when the external interruption of the main control circuit is continuously triggered twice by the Beidou synchronization signal, the GPS synchronization signal is judged to be lost, and at the moment, the main control circuit only takes the Beidou synchronization signal as the synchronization pulse; when the external interruption of the main control circuit is triggered by the GPS synchronizing signal twice continuously, the Beidou synchronizing signal is judged to be lost, and the main control circuit only takes the GPS signal as a synchronizing pulse.

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