A program-controlled zero-current phase-changing charging device for nuclear magnetic resonance water detector

Abstract

The present invention relates to the field of nuclear magnetic resonance detection technology, and in particular to a program-controlled zero-current phase-changing charging device for a nuclear magnetic resonance water detector, comprising an energy storage capacitor, two ends of which are connected to two ends of a rectifier bridge, and the other two ends of the rectifier bridge are connected to two ends of the secondary side of a transformer; an IGBT bridge; a current sensor, sensing the magnitude of the current of the matching capacitor on the IGBT bridge; a drive circuit, controlling the switching of four IGBT transistors on the IGBT bridge; a microcontroller, receiving the magnitude of the current transmitted by the current sensor, and controlling the drive circuit to switch the working state of the IGBT bridge when the current of the matching capacitor passes through the zero point. Compared with the existing nuclear magnetic power supply, it can adapt to a larger frequency range, is more suitable for working circuits with large capacitors, and can reduce switching losses compared with conventional PWM control with lower frequency. At the same time, constant resonance is achieved at the front end of the charging circuit.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear magnetic resonance detection, and in particular to a program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water detector. Background Art

[0002] The use of MRS (Magnetic Resonance Sounding) technology to detect groundwater is currently the only direct groundwater detection method in the world. It has the advantages of high resolution, high water finding efficiency, rich information and unique interpretation.

[0003] At present, most nuclear magnetic resonance power supplies use PWM control mode for charging and storing electrical energy in capacitors. However, the capacitance of nuclear magnetic resonance systems is large, which will cause large fluctuations in frequency. The frequency range of conventional PWM control methods is generally small, which is not suitable for this large capacitor energy storage method. In addition, conventional PWM switching power supplies work in hard switching mode. When the switch tube is turned on and off with hard switching technology, the voltage of the switch tube cannot drop to zero immediately, and there is a falling edge. At the same time, the current of the switch tube will have a rising edge. At this time, the voltage and current overlap, and switching losses are generated.

[0004] In order to reduce the size and weight of the converter, the switching frequency must be increased, but at high frequencies, the switching losses will become greater. Summary of the invention

[0005] The present invention provides a program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water detector, which can adapt to a larger frequency range than the existing nuclear magnetic resonance power supply, is more suitable for working circuits with large capacitance, and can reduce switching losses compared to conventional PWM control with lower frequencies. At the same time, constant resonance is achieved at the front end of the charging circuit.

[0006] The present invention is achieved in this way.

[0007] A program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water detector, comprising:

[0008] The energy storage capacitor has two ends connected to the two ends of the rectifier bridge, and the other two ends of the rectifier bridge are connected to the two ends of the secondary side of the transformer;

[0009] The IGBT bridge circuit includes a first IGBT transistor, a second IGBT transistor, a third IGBT transistor and a fourth IGBT transistor, wherein the collector of the first IGBT transistor is connected to a power supply terminal, the emitter of the first IGBT transistor is connected to the collector of the second IGBT transistor, the emitter of the second IGBT transistor is grounded, the collector of the third IGBT transistor is connected to the power supply terminal, the emitter of the third IGBT transistor is connected to the collector of the fourth IGBT transistor, and the emitter of the fourth IGBT transistor is grounded; the emitter of the first IGBT transistor and the emitter of the third IGBT transistor are connected to the primary side of the transformer and the tuning capacitor C2 connected in series with the primary side;

[0010] Current sensor, which senses the current of the tuning capacitor on the IGBT bridge circuit;

[0011] The driving circuit controls the switching of the four IGBT transistors on the IGBT bridge circuit;

[0012] The microcontroller receives the current from the current sensor and controls the drive circuit to switch the working state of the IGBT bridge circuit when the current of the tuning capacitor passes through the zero point.

[0013] Furthermore, a voltage sensor is included to sense the voltage of the energy storage capacitor and transmit the data to the microcontroller. When the capacitor is fully charged, the microcontroller controls the drive circuit to stop charging.

[0014] Furthermore, the current sensor is placed at the front end of the IGBT bridge circuit and is connected in series with the primary side of the transformer and the tuning capacitor when the IGBT is turned on.

[0015] Furthermore, the microcontroller determines the states of the four IGBT transistors according to the state of the driving circuit. When the first IGBT transistor and the fourth IGBT transistor are turned on, the current flows to the first IGBT transistor, and then flows to the rectifier bridge through the transformer to charge the energy storage capacitor, and then flows out through the rectifier bridge, the transformer, the tuning capacitor and the fourth IGBT transistor. The tuning capacitor is in a charging state. When the tuning capacitor is fully charged, the current drops to 0. When the current sensor detects zero current, the microcontroller controls the driving circuit to drive the first IGBT transistor and the fourth IGBT transistor to turn off, and the second IGBT transistor and the fourth IGBT transistor are turned on. The current flows to the third IGBT transistor, flows through the tuning capacitor, and then flows to the rectifier bridge through the transformer to charge the energy storage capacitor. The current then flows out through the current bridge, the transformer, and the second IGBT transistor. The capacitor voltage cannot change suddenly, and the tuning capacitor begins to discharge. When the tuning capacitor is fully discharged, the current drops to 0, and the microcontroller switches the state of the IGBT bridge again to complete a program-controlled zero current switching process.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The magnitude of the electric energy current provided by the power supply of the present invention is kept within a constant range, so the program-controlled power supply can also play a certain protective role on the circuit. At the same time, the program-controlled power supply is more flexible than the traditional power supply and is more suitable for the nuclear magnetic resonance water finder.

[0018] The present invention adopts zero current control mode, which reduces the volume and weight of the converter and the switching loss compared with the traditional charging device. Since it does not need to artificially give PWM signals like the traditional PWM control, it reduces the volume and weight of the converter. Therefore, it is very suitable for use in the case where the nuclear magnetic resonance water detector is a large capacitor energy storage.

[0019] The program-controlled zero-current commutation charging power supply of the present invention contains two groups of IGBT transistors, which can protect the circuit. When the current of the power supply is released, the group of IGBT transistors can shunt and suppress the current, and when the current is zero, the working states of the two groups of IGBT transistors are switched. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a programmable zero-current commutation charging power supply provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The structural schematic diagram of a program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water detector provided by an embodiment of the present invention is as follows: Figure 1 As shown, including:

[0023] The energy storage capacitor C2 has two ends connected to the two ends of the rectifier bridge H, and the other two ends of the rectifier bridge H are connected to the two ends of the secondary side of the transformer 39; the rectifier bridge H includes four diodes connected end to end to form four nodes, wherein the first node and the third node are respectively connected to the two ends of the secondary side of the transformer 39, the second node and the fourth node are connected to the two ends of the energy storage capacitor C2, and the secondary winding of the transformer 39 has the same polarity as the source winding.

[0024] The IGBT bridge circuit includes a first IGBT transistor 35, a second IGBT transistor 38, a third IGBT transistor 37 and a fourth IGBT transistor 36. The collector of the first IGBT transistor 35 is connected to the power supply terminal through a busbar, the emitter of the first IGBT transistor 35 is connected to the collector of the second IGBT transistor 38, the emitter of the second IGBT transistor 38 is grounded, the collector of the third IGBT transistor 37 is connected to the power supply terminal, the emitter of the third IGBT transistor 37 is connected to the collector of the fourth IGBT transistor 36, and the emitter of the fourth IGBT transistor 36 is grounded; the emitter of the first IGBT transistor 35 and the emitter of the third IGBT transistor 37 are connected to the main side of the transformer 39 and the matching capacitor C2 connected in series with the main side. The IGBT bridge circuits form a pair of bridge arms in pairs, and are alternately turned on in pairs according to the diagonal relationship. When a pair of IGBT transistors is turned on, the current passes through an IGBT, flows through the transformer and the matching capacitor to boost the voltage, and then is rectified by the rectifier bridge H to output a direct current to charge the energy storage capacitor C1.

[0025] A current sensor 31 senses the current of the tuning capacitor C2 on the IGBT bridge circuit;

[0026] A driving circuit 34 controls the switching of four IGBT transistors on the IGBT bridge circuit;

[0027] The microcontroller 33 receives the current value transmitted by the current sensor 31 and controls the driving circuit 34 to switch the working state of the IGBT bridge circuit when the current of the tuning capacitor C2 passes through the zero point.

[0028] The voltage sensor 40 senses the voltage of the energy storage capacitor C1 and transmits the data to the microcontroller 33. When the capacitor is fully charged, the microcontroller 33 controls the driving circuit 34 to stop charging.

[0029] The current sensor 31 is connected to the microcontroller 33 via a first analog-to-digital converter 32, and the voltage sensor 40 is connected to the microcontroller 33 via a second analog-to-digital converter 41. The first analog-to-digital converter 32 receives the current size transmitted by the current sensor 31 and converts the analog current into a digital current; the second analog-to-digital converter 41 receives the voltage size transmitted by the voltage sensor 40 and converts the analog voltage into a digital voltage.

[0030] The value of the energy storage capacitor C1 in the present invention is 0.1-0.2F.

[0031] The current flows out from the power part of the charging device and is transmitted to the IGBT bridge circuit. At this time, the current sensor 31 senses the current signal, and the analog signal is converted into a digital signal through the first analog-to-digital converter 32. The microcontroller 33 analyzes and judges it. When the current passes through zero, the microcontroller 33 controls the drive circuit 34 to switch the working states of the first IGBT crystal 35, the fourth IGBT transistor 36, the third IGBT transistor 37, and the second IGBT transistor 38.

[0032] For example, first, the first IGBT crystal 35 and the fourth IGBT transistor 36 are turned on, and the current flows to the first IGBT crystal 35 through the bus, and then flows to the rectifier bridge H through the transformer 39, and then charges the energy storage capacitor C1, and then flows out through the current bridge H, the transformer 39, the tuning capacitor C2, and the fourth IGBT transistor 36. At this time, the tuning capacitor C2 is in a charging state. When the tuning capacitor C2 is fully charged, it is equivalent to an open circuit, and the current drops to 0. When the current sensor detects zero current, the first IGBT crystal 35 and the fourth IGBT transistor 36 are turned off, and the third IGBT transistor 37 and the second IGBT transistor 38 are turned on. The current flows to the third IGBT transistor 37 through the bus, flows through the tuning capacitor C2, and then flows to the rectifier bridge H through the transformer 39, and then charges the energy storage capacitor C1, and then flows out through the current bridge H, the transformer 39, and the second IGBT transistor 38. The capacitor voltage cannot change suddenly, so the tuning capacitor C2 starts to discharge. When the tuning capacitor C2 is fully discharged, it is equivalent to an open circuit again, and the state of the IGBT bridge is switched again. So far, a program-controlled zero current switching process is completed. In this process, the primary side of the transformer 39 and the tuning capacitor C2 form a series resonant circuit. Since the circuit reaches a zero current state every time the tuning capacitor C2 is just fully charged, the state will be switched. That is, the electric energy of the tuning capacitor C2 and the magnetic energy of the primary inductance of the transformer 39 are always exchanged, so the resonant circuit is always in a resonant state, achieving constant resonance.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. A program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water detector, characterized in that: include: The energy storage capacitor has two ends connected to the two ends of the rectifier bridge, and the other two ends of the rectifier bridge are connected to the two ends of the secondary side of the transformer; The IGBT bridge circuit includes a first IGBT transistor, a second IGBT transistor, a third IGBT transistor and a fourth IGBT transistor, wherein the collector of the first IGBT transistor is connected to a power supply terminal, the emitter of the first IGBT transistor is connected to the collector of the second IGBT transistor, the emitter of the second IGBT transistor is grounded, the collector of the third IGBT transistor is connected to the power supply terminal, the emitter of the third IGBT transistor is connected to the collector of the fourth IGBT transistor, and the emitter of the fourth IGBT transistor is grounded; the emitter of the first IGBT transistor and the emitter of the third IGBT transistor are connected to the primary side of the transformer and the tuning capacitor C2 connected in series with the primary side; Current sensor, which senses the current of the tuning capacitor on the IGBT bridge circuit; The driving circuit controls the switching of the four IGBT transistors on the IGBT bridge circuit; The microcontroller receives the current from the current sensor and controls the drive circuit to switch the working state of the IGBT bridge circuit when the current of the tuning capacitor passes through the zero point; The microcontroller determines the state of the four IGBT transistors according to the state of the driving circuit. When the first IGBT transistor and the fourth IGBT transistor are turned on, the current flows to the first IGBT transistor, and then flows to the rectifier bridge through the transformer to charge the energy storage capacitor, and then flows out through the rectifier bridge, the transformer, the tuning capacitor and the fourth IGBT transistor. The tuning capacitor is in a charging state. When the tuning capacitor is fully charged, the current drops to 0. When the current sensor detects zero current, the microcontroller controls the driving circuit to drive the first IGBT transistor and the fourth IGBT transistor to turn off, and the second IGBT transistor and the fourth IGBT transistor are turned on. The current flows to the third IGBT transistor, flows through the tuning capacitor, and then flows to the rectifier bridge through the transformer to charge the energy storage capacitor. The current then flows out through the rectifier bridge, the transformer, and the second IGBT transistor. The capacitor voltage cannot change suddenly, and the tuning capacitor starts to discharge. When the tuning capacitor is fully discharged, the current drops to 0, and the microcontroller switches the state of the IGBT bridge again to complete a program-controlled zero current switching process.

2. A program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water finder according to claim 1, characterized in that: It also includes a voltage sensor, which senses the voltage of the energy storage capacitor and transmits the data to the microcontroller. When the capacitor is fully charged, the microcontroller controls the drive circuit to stop charging.

3. A program-controlled zero-current phase-change charging device for a nuclear magnetic resonance water finder according to claim 1, characterized in that: The current sensor is placed at the front end of the IGBT bridge circuit and is connected in series with the primary side of the transformer and the tuning capacitor when the IGBT is turned on.

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