CN108227011B - Double-trapezoidal wave transmitting system with controllable falling edge and control method - Google Patents
Double-trapezoidal wave transmitting system with controllable falling edge and control method Download PDFInfo
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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
Technical Field
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.
Background
The traditional transient electromagnetic method can only excite and measure electromagnetic induction signals due to the limitation of a detection system, has single measurement parameters and single interpretation parameters, has lower accuracy of data interpretation and is a bottleneck for development of the current transient electromagnetic method. The multi-parameter combined detection is an effective method for improving the detection precision of the TEM, the induced polarization effect is a common phenomenon existing in the ground, and meanwhile, the interpretation precision of the transient electromagnetic and induced polarization signals to the ground can be effectively improved. The time domain electromagnetic induction method (TEM) is to generate a secondary field by excitation, and measure the secondary induction magnetic field to obtain the conductivity information of the underground medium; the induced polarization method (IP) is to energize the earth to generate an induced polarization field, and to measure the induced polarization field to obtain the polarization parameters of the underground medium. TEM and IP have obvious advantages for water resource and metal ore detection, and the induction field and the polarization field are found to exist simultaneously during low-frequency time domain electromagnetic detection. The induction field is attenuated rapidly in the early stage after the current is cut off, and the induction field and the polarization field coexist, so that the polarization field discharges; the late induction field is almost absent and is mainly a polarized field. The polarization charging effect exists on the falling edge of the emission current of the magnetic source, and under the condition that the emission current is the same in size, the polarization charging time is short, the induced polarization field is weak, and the method is suitable for induction field measurement; for long falling edge emission, the polarization charging time is longer, the induced polarization field intensity is suitable for polarization field measurement. Therefore, transmitting a set of trapezoidal wave currents with different off-times is a feasible method for simultaneously detecting the double fields of the IP and the TEM.
In order to accurately acquire the magnetic field signal excited by the emission current, the receiving system needs to be synchronized with the emitting system, and a GPS synchronization mode is often adopted under the condition of long distance between the emitting device and the receiving device, but in some areas with poor signals, such as remote mountain areas, jungles, urban areas with tall buildings shielding, and the like, the GPS signal is sometimes lost, and the conventional transient electromagnetic emitting system often fails to work due to the fact that the synchronous signal is not received.
Chinese patent CN105510979a discloses a transient electromagnetic transmitter circuit with parallel discharge of load, 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 can measure the induction field signal.
Chinese patent CN 105119588A discloses a transient electromagnetic pulse current transmitting circuit, which improves the current falling edge clamping voltage, shortens the falling edge time, improves the falling linearity, but still cannot realize simultaneous detection of the two parameters of resistivity and polarizability through an energy-feed constant voltage clamping circuit.
Disclosure of Invention
The invention provides a double-trapezoidal wave transmitting system with a controllable falling edge and a control method, which solve the problem that simultaneous detection of two parameters of resistivity and polarizability cannot be realized.
The present invention has been achieved in such a way that,
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 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.
Further, the transmitting bridge is composed of a high-power diode D1 and four power field effect transistors, wherein 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, the two series circuits are connected in parallel again, the connection position 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 stage of the high-power diode D1 is connected with the positive pole of the series battery pack, the negative pole is connected with the public end of the power field effect transistor S1 and the power field effect transistor S2, the negative pole 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 the positive or negative current trapezoidal waves are generated on the transmitting coil.
Further, the main 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.
Further, the low voltage transient suppression diode circuit comprises: the low-voltage transient suppression diode is characterized in that two ends of the low-voltage transient suppression diode are respectively connected with the power field effect tube S5 and the power field effect tube S6, the power field effect tube S5 and the power field effect tube S6 are respectively connected with the power field effect tube S7 and the power field effect tube S8, the whole is connected with two ends of the 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 controlled through the driving of a falling edge control signal of the master control circuit through an optocoupler, and the power field effect tube S5 and the power field effect tube S6 are connected with the power field effect tube S5 and the power field effect tube S6 through two control square waves of the master control circuit through a NOR gate.
Further, 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 very 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 at the clamping voltage of the transmitting coil, so that the transmitting current is turned off quickly.
Further, 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, and at the moment of current turn-off, two control square waves of the main control circuit are both at a low 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.
Further, the system also comprises a double synchronization module, the GPS and Beidou double synchronization mode is adopted for synchronization, after the main control circuit receives the synchronization signals generated by the double synchronization module, the main control circuit generates two paths of transmitting bridge circuit control square wave signals and falling edge control square waves according to the set transmitting parameters, and the main control circuit is in driving connection with the optocoupler through a control signal output port.
Further, the system further comprises an absorption circuit, the absorption circuit comprises an absorption resistor, a power field effect transistor S9 and a power field effect transistor S10 which are arranged 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 a high level, the power field effect transistor S9 and the power field effect transistor S10 are conducted, the absorption resistor is connected at two ends of the transmitting coil in parallel, and the tail of the falling edge is absorbed to oscillate.
A method for controlling emission of a dual trapezoidal wave with a controllable falling edge, the method comprising:
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.
Further, 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.
Compared with the prior art, the invention has the beneficial effects that: 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 rate, and improves detection precision; and the GPS and Beidou double-synchronous mode is adopted, and the synchronous signals are complementary, so that the stability of the system in a poor signal area is improved.
Drawings
FIG. 1 is a diagram of an overall structure of a transmitting system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a falling edge control circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an absorption circuit provided by an embodiment of the present invention;
fig. 4 is a flowchart of a procedure of a master control circuit of a transmitting system according to an embodiment of the present invention
FIG. 5 is a waveform diagram of control timing of a transmitting system according to an embodiment of the present invention;
fig. 6 shows a screenshot of a dual trapezoidal wave emission current oscillograph with controllable falling edge, where 6a is a waveform diagram with fast falling edge and 6b is a waveform diagram with slow falling edge.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1 and fig. 5, the dual trapezoidal wave transmitting system with controllable falling edge provided by the invention mainly comprises a main control circuit 1, a dual synchronization module 2, a key 3, a liquid crystal display 4, an optocoupler driving combination 5, a transmitting bridge 6, a high-voltage transient suppression diode 7, a low-voltage transient suppression diode circuit 8, an absorption circuit 9, a transmitting coil 10, a serial battery pack 11, a lithium battery 12, a low-voltage power supply 13 and a high-voltage power supply 14, wherein the dual synchronization module 2 has a Beidou and GPS dual synchronization mode, and the low-voltage transient suppression diode circuit 8 comprises 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 together form a falling edge control circuit which is connected in parallel with two ends of the transmitting coil 10. The main control circuit 1 is respectively connected with the double-synchronous module 2, the key 3 and the liquid crystal display 4, 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, the series battery pack 11 is connected with the transmitting bridge 6 to provide power for 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 two ends of the transmitting coil 10, the transmitting system is powered by the lithium battery 12, the main control circuit 1, the double-synchronous module 2, the liquid crystal display 4 and the like are powered by the DC/DC obtained voltage source 13, and the driving voltage is provided for the optocoupler driving combination 5 by the DC/DC obtained high-voltage power source 14.
The main control circuit 1 is a singlechip taking ARM as a processor and comprises a double-synchronous module communication port, a key input interface, a liquid crystal display screen interface and a control signal output port. The key 3 and the liquid crystal display 4 are connected with the main control circuit 1 through a key input interface and a liquid crystal display interface to form a man-machine interaction interface. And setting parameters such as pulse width, period, falling edge emission mode and the like of an emission waveform through a human-computer interaction interface. The double synchronization module 2 is connected with the main control circuit 1 through a double synchronization module communication port, and is synchronous through a GPS and Beidou double synchronization mode, when the main control circuit 1 receives a synchronization signal generated by the double synchronization module 2, the main control circuit 1 generates a first control square wave U1 and a second control square wave U2 of the two paths of transmitting bridge circuits 6 according to set transmitting parameters, the control time sequences of the two square waves have a phase difference, when the first control square wave U1 is high, current positively flows, when the second control square wave U2 is high, current negatively flows, and the falling edge control square wave U3 and the absorption circuit control square wave U4 are controlled. The main control circuit 1 is connected with the optocoupler driving combination 5 through a control signal output port, the first control square wave U1 generates two paths of control signals (Q1 and Q4) through the optocoupler driving combination 5, and the first control square wave U2 generates two paths of control signals (Q2 and Q3) through the optocoupler driving combination.
Referring to fig. 2, the optocoupler driving combination 5 is connected to the transmitting bridge 6, the transmitting bridge 6 is composed of a high-power diode D1 and four power field effect transistors, 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, the two series circuits are connected in parallel, the junction of the power field effect transistor S1 and the power field effect transistor S3 is connected in parallel with the junction of the power field effect transistor S2 and the power field effect transistor S4 as the output of the transmitting circuit is connected to the transmitting coil 10, the positive electrode of the high-power diode D1 is connected with the positive electrode of the series battery pack 11, the negative electrode of the series battery pack 11 is connected with the common end of the power field effect transistor S1 and the power field effect transistor S2. The control signals Q1, Q2, Q3, Q4 control the power field effect transistors S1, S2, S3, S4 to turn on, respectively. When the control time sequence of the first control square wave U1 is high level and the time 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, the power field effect transistor S2 and the power field effect transistor S3 are turned off, and a forward current trapezoidal wave is generated on the transmitting coil 10; when the control time sequence of the first control square wave U1 is low level and the control time sequence of the second control square wave U2 is high level, the power field effect transistor S2 and the power field effect transistor S3 are turned on, the power field effect transistor S1 and the power field effect transistor S4 are turned off, and negative current trapezoidal waves are generated on the transmitting coil 10.
The low-voltage transient suppression diode circuit 8 is composed of a power field effect tube, 2 NOR gates (G1 and G2), 4 optocouplers and a low-voltage transient suppression diode 15, wherein a first control signal U1 and a second control signal U2 of the transmitting bridge circuit 6 are used as inputs of the NOR gates (G1 and G2), the output of the NOR gate is connected with the power field effect tube S5 and the power field effect tube S6 through the optocouplers, a falling edge control signal U3 is driven to the power field effect tube S7 and the power field effect tube S8 through the optocouplers, two ends of the low-voltage transient suppression diode 15 are respectively connected with the power field effect tube S5 and the power field effect tube S6, and two ends of the low-voltage transient suppression diode 15 are respectively connected with the power field effect tube S7 and the power field effect tube S8 and are integrally connected with two ends of the transmitting coil 10 in parallel.
When the falling edge control signal U3 is at a low level, the power field effect transistor S7 and the power field effect transistor S8 are disconnected, the transmitting coil 10 generates a voltage overshoot with a very high amplitude in the same direction as the current due to the presence of the inductor, and the voltage overshoot cannot be released through the freewheeling diode of the power field effect transistor forming the transmitting bridge 6 due to the presence of the diode D1, so that the voltage overshoot can only be released through the high-voltage transient suppression diodes 7 connected in parallel to the two 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-suppressing diode 7, the high voltage transient-suppressing diode 7 is turned on and clamps the voltage across the transmitting coil 10 to its clamping voltage. The voltage and current change across the inductive load is represented by formula (1):
wherein U is the voltage at two ends of the load, L is the load inductance value, and di/dt is the rate of change of the current flowing through the load. According to the formula, under the condition that the load is unchanged, the voltage at two ends of the load is in direct proportion to the current change rate. The transmitting coil 10 can be equivalently connected in series with an inductor and a resistor, and the clamping voltage of the high-voltage transient suppression diode 7 is very high, so that the transmitting current drops quickly, and the transmitting current is turned off quickly.
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 conducted, the first control signal U1 and the second control signal U2 are at a low level at the moment of current cut-off, the output signal U4 of the nor gate (G1 and G2) 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 15 is connected in parallel at two ends of the transmitting coil 10, the clamping voltage of the low-voltage transient suppression diode 15 is very low, and 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 conducted and clamps the voltages at two ends of the coil at a very low voltage, so that the slow cut-off of the transmitting current is realized. And a group of trapezoidal wave emission currents with different turn-off times are obtained by controlling the falling edge control signal U3.
Referring to fig. 3, the absorption circuit 9 is composed of an absorption resistor 31, an optocoupler driving and power field effect transistor S9, and a power field effect transistor S10, wherein the absorption resistor 31 is required to satisfy the condition shown in the formula (2):
wherein L is the inductance value of the transmitting coil 10, C stray Is the transmit circuit stray capacitance value. The absorption circuit control signal U5 is driven to the power field effect transistor S9 and the power field effect transistor S10 through the optocoupler, the power field effect transistor S9 and the power field effect transistor S10 are respectively connected in parallel with two ends of the absorption resistor 31, the whole absorption circuit control signal U5 is connected with the transmitting coil 10 in parallel, the control output signal U5 is changed from low level to high level after the current is cut off, the power field effect transistor S9 and the power field effect transistor S10 are controlled to be conducted through the optocoupler output control signals (Q9 and Q10) so that the absorption resistor 31 is connected with the transmitting coil 10 in parallel, tail oscillation of transmitting current is effectively absorbed, and the controllable falling edge double-trapezoidal wave transmitting current with good quality is obtained.
Referring to fig. 4, the control method of double trapezoidal waves with controllable falling edges provided by the invention,
1) According to the detection requirements, combining the conductivity and polarization characteristics of the measurement area, setting parameters such as a period, a duty ratio and the like of a transmitting current in a soft loading mode through a man-machine interaction interface formed by a key (3) and a liquid crystal display screen (4), configuring the parameters into two timers of a main control circuit 1, and controlling a transmitting bridge circuit 6 through an optocoupler driving combination 5 by utilizing a pulse width modulation technology;
2) The transmitting system adopts a GPS and Beidou double-synchronization mode for synchronization. The double synchronization module 2 is provided with a GPS and Beidou double synchronization mode and is connected with the main control circuit 1. The GPS and Beidou double-synchronous mode is started simultaneously, the first second pulse adopts a GPS synchronous signal to trigger the external interruption of the main control circuit (1), the main control circuit 1 is excited to output a control square wave signal of the transmitting bridge circuit 6, and the second pulse adopts a Beidou synchronous signal to trigger the external interruption of the main control circuit 1, so that the operation is repeated. When the external interrupt of the main control circuit 1 is triggered by the Beidou synchronous signal twice continuously, the GPS synchronous signal is judged to be lost, and the main control circuit 1 takes the Beidou signal only as a synchronous pulse; when the external interrupt of the main control circuit 1 is triggered by the GPS synchronizing signal twice continuously, the Beidou synchronizing signal is judged to be lost, and the main control circuit 1 takes the GPS signal as a synchronizing pulse. The working mode of double synchronization complementation of the GPS and the Beidou is adopted, so that the working stability of the system in the area with poor signals is improved.
In this embodiment, the switching devices of the transmitting bridge 6, the low-voltage transient suppression diode circuit 8 and the absorbing circuit 9 are power field effect transistors, a rectangular loop with a side length of 25m is selected as the transmitting coil 10, the resistance of the transmitting coil 10 is measured to be 0.2 Ω, the inductance is 0.2mH, a storage battery with a voltage of 12V is selected as the serial battery pack 11 for supplying power, a 1 Ω non-inductive resistor is adopted to be serially connected into the transmitting coil 10 for sampling the transmitting current, and the SMCJ13CA high-voltage transient suppression diode 7 and the SMCJ5CA low-voltage transient suppression diode 15 are selected according to the breakdown voltage of the switching devices of the transmitting bridge 6 and the voltage of the serial battery pack 11. The main control circuit 1 receives the synchronous signals and outputs a first control square wave U1 and a second control square wave U2, the first control square wave U1 is positive and generates signals Q1 and Q4 through driving, the power field effect tube S1 and the power field effect tube S4 of the transmitting bridge circuit 6 are controlled to be conducted, and forward current is generated on the transmitting coil 10; the second control square wave U2 is positive and is driven to generate signals Q2 and Q3, the power field effect transistor S2 and the power field effect transistor S3 of the transmitting bridge 6 are controlled to be conducted, and negative current is generated on the transmitting coil 10. The first control square wave U1 and the second control square wave U2 can be controlled to generate a bipolar trapezoidal wave with adjustable period and duty ratio on the transmitting coil 10;
3) During the off period of the first set of trapezoidal waves, the first set of trapezoidal waves refers to: one positive trapezoidal wave and one negative trapezoidal wave are a set 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 broken down by voltage overshoot, and the voltages at the two ends of the transmitting coil 10 are clamped at high voltage, so that the falling edge fast turn-off can be realized; the calculation formula of the current linear fast turn-off falling time is shown as (3):
wherein I is the current value of the emission flat top end, L COIL For transmitting the inductance value of the transmitting coil 10, the inductance value may be obtained by calculation or measurement, U HTVS The voltage is clamped for the high voltage transient suppression diode 7. In-middle pair SMCJ13CA high-voltage transient suppression diode 7, U HTVS 21.5V.
4) In the second group of trapezoidal wave turn-off periods, the second group of trapezoidal wave turn-off periods refer to the second positive wave turn-off period and the second negative wave turn-off period, the main control circuit 1 generates a falling edge control signal U3, and then generates a signal Q7 and a signal Q8 through optical coupling driving, and respectively controls the power field effect transistor S7 and the power field effect transistor S8 to be conducted, at the moment, the first control square wave U1 and the second control square wave U2 are both in low level, the NOR gate output signal U4 is in high level, and then generates a signal Q5 and a signal Q6 through optical coupling driving, and respectively controls the power field effect transistor S5 and the power field effect transistor S6 to be conducted, at the moment, the low voltage transient suppression diode 15 is connected at two ends of the transmitting coil 10 in parallel, and the voltage at two ends of the transmitting coil 10 is clamped on low voltage, and the falling edge slow turn-off can be realized. The calculation formula of the current linear slow turn-off falling time is shown as (4):
wherein U is LTVS Clamping voltage for low voltage transient suppression diode 15, U Dedio For the voltage drop of the freewheeling diode of the switching device, U MOS Is the forward voltage drop when the switching device is on. In the formula, for SMCJ5CA low-voltage transient suppression diode (11), U HTVS 9.2V; for power field effect transistor, U Dedio Is 0.7V, U MOS And is very small and negligible.
By controlling the clamping voltages 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, the bipolar combined trapezoidal wave with controllable transmitting falling edges is realized in one current period.
Fig. 6 (a) and 6 (b) are dual-trapezoidal wave emission current oscillographs with controllable falling edges, namely a trapezoidal wave emission current with a fast falling edge and a trapezoidal wave emission current with a slow falling edge, so that the effectiveness of the invention is fully verified.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
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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| CN111352164B (en) * | 2020-03-20 | 2021-04-23 | 吉林大学 | Transient electromagnetic detection system with large transmitting magnetic moment and short turn-off time |
| CN113866835B (en) * | 2021-11-10 | 2023-07-14 | 吉林大学 | Electromagnetic emission system combining time domain three waveforms and control method |
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