CN107703468B - Driving circuit of gradient power amplifier of nuclear magnetic resonance apparatus - Google Patents
Driving circuit of gradient power amplifier of nuclear magnetic resonance apparatus Download PDFInfo
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- CN107703468B CN107703468B CN201710969313.1A CN201710969313A CN107703468B CN 107703468 B CN107703468 B CN 107703468B CN 201710969313 A CN201710969313 A CN 201710969313A CN 107703468 B CN107703468 B CN 107703468B
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- 238000005481 NMR spectroscopy Methods 0.000 title claims abstract description 14
- 230000005540 biological transmission Effects 0.000 claims abstract description 40
- 229920006395 saturated elastomer Polymers 0.000 claims description 6
- 238000002595 magnetic resonance imaging Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 238000013467 fragmentation Methods 0.000 description 1
- 238000006062 fragmentation reaction Methods 0.000 description 1
- 238000013421 nuclear magnetic resonance imaging Methods 0.000 description 1
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 description 1
- 238000010827 pathological analysis Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/385—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using gradient magnetic field coils
- G01R33/3852—Gradient amplifiers; means for controlling the application of a gradient magnetic field to the sample, e.g. a gradient signal synthesizer
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- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
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Abstract
A driving circuit of a gradient power amplifier of a nuclear magnetic resonance instrument relates to the gradient power amplifier. The zero-crossing comparator, the adder circuit and the transmission gate are arranged; the input end of the zero-crossing comparator is connected with a pulse input signal of 0 to +/-5V, and the output end of the zero-crossing comparator is connected with the control end of the transmission gate of the positive and negative signal path; the adder circuit is provided with 3 adders under positive and negative signal paths, and the non-inverting input ends of the adders are commonly connected with input signals; the output end of the adder is connected with the input end of the transmission gate; the transmission gates are provided with 3 transmission gates under the positive and negative signal paths, the control ends of the 3 transmission gates are connected with the output ends of the zero-crossing comparator, the on-off of the transmission gates is controlled by the output of the zero-crossing comparator, the input ends of the 3 transmission gates are connected with the adder, the output ends of the 3 transmission gates are connected with the IGBT of the amplifying circuit, and the working state of the IGBT is controlled by the output state of the output adder.
Description
Technical Field
The present invention relates to gradient power amplifiers, and more particularly to a drive circuit for a Nuclear Magnetic Resonance (NMR)/Magnetic Resonance Imaging (MRI) gradient power amplifier.
Background
Nuclear magnetic resonance (Nuclear Magnetic Resonance, NMR), also known as magnetic resonance (Magnetic Resonance, MR), is a phenomenon in which nuclei undergo energy level fragmentation in a static magnetic field and undergo energy level transition under the excitation of an applied radio frequency magnetic field. The method is mainly used for measuring nuclear magnetic moment, electromagnetic polar moment and spin. Nuclear magnetic resonance imaging (Magnetic Resonance Imaging, MRI) is used for determining molecular structure, analysis of living organisms in tissues and living tissues, pathological analysis, nondestructive detection of products, medical diagnosis, etc. Furthermore, NMR/MRI can also be used to observe some dynamic process variations.
One of the core components of nuclear magnetic resonance NMR/MRI using the technology is a gradient power amplifier, the gradient power amplifier emits a strong and variable gradient pulse in a very short time (microsecond to millisecond level), a driving current of hundreds of amperes is provided for a gradient coil load, and the load current follows a computer spectrometer to generate pulse sequence reference signals in three directions of an X axis, a Y axis and a Z axis, so that a magnetic field with a variable gradient is generated, and dynamic change of a main magnetic field is realized.
IGBT (Insulated Gate Bipolar Transistor), i.e. insulated gate bipolar transistor, is a dual-mechanism composite device formed by combining a MOSFET (insulated gate field effect transistor) and a BJT (bipolar transistor). It has the advantages of high input impedance of MOSFET, low on-state voltage drop of GTR and low on-state resistance. The MOSFET has small driving power, high switching speed, large conduction voltage drop and small current carrying density. The GTR saturation voltage is reduced and the current carrying density is high, but the drive current is high. IGBTs combine the advantages of both devices, with low drive power and reduced saturation voltage. In the fields of motor control, medium-high frequency switching power supply, especially in the fields of medium-high power and low loss, the IGBT has great advantages. The power amplifier can be used for designing a gradient power amplifier, an amplifying circuit is formed by utilizing a push-pull circuit structure, and positive and negative voltage signals are converted into hundreds of ampere current signals by controlling the working state of an IGBT. This requires a driving circuit that can effectively place the IGBT in a desired operating state under control of the signal to ensure proper operation of the push-pull circuit.
Disclosure of Invention
The invention aims at providing a driving circuit of a gradient power amplifier of a nuclear magnetic resonance apparatus aiming at the circuit requirement of the gradient power amplifier of the nuclear magnetic resonance apparatus.
The invention is provided with a zero-crossing comparator, an adder circuit and a transmission gate;
the zero-crossing comparator is provided with two opposite zero-crossing comparators, the input ends of the two opposite zero-crossing comparators are connected with each other and are connected with pulse input signals of 0 to +/-5V, and the output ends of the two opposite zero-crossing comparators are respectively connected with the control ends of the transmission gates of the positive and negative signal paths;
the adder circuit is provided with 3 adders under positive and negative signal paths, the 3 adders respectively add-20V, -9V and +5V 3 state voltages to the inverting input ends of the adders, and the non-inverting input ends of the adders are commonly connected with input signals; the output end of the adder is connected with the input end of the transmission gate;
the transmission gates are provided with 3 transmission gates under positive and negative signal paths, the control ends of the 3 transmission gates are connected with the output ends of the zero-crossing comparator, the on-off of the transmission gates is controlled by the output of the zero-crossing comparator, the input ends of the 3 transmission gates are connected with the adder, the output ends of the 3 transmission gates are connected with the IGBT of the amplifying circuit, and the working state of the IGBT is controlled by the output state of the output adder.
The invention can effectively distinguish 0 to +5V voltage and 0 to-5V voltage by utilizing the zero-crossing comparator, and respectively controls the IGBTs in the amplifying circuit through the adder circuit and the transmission gate in the positive and negative signal paths under the two input signals, so that 4 IGBTs forming a push-pull bridge structure in the amplifying circuit work in a required state to finish the function of converting 0 to +5V into hundreds of amperes of current.
Drawings
FIG. 1 is a block diagram of the overall structure of an embodiment of the present invention;
fig. 2 is an output characteristic curve of an amplifying circuit IGBT transistor;
fig. 3 is an overall circuit diagram of an embodiment of the present invention coupled to an amplifying circuit.
Detailed Description
Referring to fig. 1, the embodiment of the present invention is provided with two opposite zero-crossing comparators 1 receiving input signals, the outputs of which are connected to a positive signal path transmission gate 3 and a negative signal path transmission gate 4, respectively. When the input signal is positive voltage, the positive signal path transmission gate 3 is turned on, and the output state of the adder circuit 2 of the positive signal path is added to the IGBT of the amplifying circuit 5; when the input signal is a negative voltage, the negative signal path transfer gate 4 is turned on, and the output state of the adder circuit 2 of the negative signal path is added to the IGBT of the amplifying circuit 5.
Referring to fig. 2, the output characteristic diagram of the IGBT shows that the IGBT is in an amplified state when the voltage is 20V, in a saturated state when the voltage is 9V, and in an off state when the voltage is-5V.
Referring to fig. 3, when the input signal is positive voltage, two opposite zero-crossing comparators 1 are turned over by a comparator with its non-inverting input end receiving a control signal, and output 10V voltage to provide a switching signal for the positive signal path transmission gate 3; when the input signal is negative voltage, the comparator with the inverting input end receiving the signal is inverted to output 10V voltage, and the switch signal is provided for the negative signal path transmission gate 4. The adder circuits 2 of the positive and negative signal paths are respectively provided with 3 adders, voltages of-20V, -9V and +5V are respectively applied to inverting input ends of the 3 adders, and meanwhile, non-inverting input ends of the 3 adders are connected with input signals, so that state voltages of 20V,9V and-5V and the input signals can be respectively transmitted to the positive signal path transmission gate 3 and the negative signal path transmission gate 4 which are respectively connected. The amplifying circuit 5 works under a push-pull bridge type structure, and the normal working state is that when the input voltage is 0 to +5V, the T1 pipe is in an amplifying state, the T4 pipe is saturated, and the T2 and the T3 are cut off; when the input voltage is 0 to-5V, the T2 tube is in an amplifying state, the T3 tube is saturated, and the T1 and the T4 are cut off. When the input signal is 0 to +5V, a comparator receiving the signal at the same-direction input end is used for overturning, 10V voltage is output, a transmission gate 3 of a positive signal path is conducted, the output state of an adder circuit 2 is respectively added to an IGBT of an amplifying circuit, a T1 pipe is in an amplifying state, a T4 pipe is saturated, and T2 and T3 are cut off; when the input signal is 0 to-5V, a comparator with an inverted input end receiving the signal is used for overturning, 10V voltage is output, a transmission gate 4 of a negative signal path is conducted, the output state of an adder is respectively added to an IGBT of an amplifying circuit, a T2 pipe is in an amplifying state, a T3 pipe is saturated, and T1 and T4 are cut off. Thus, the amplifying circuit can normally work under the push-pull bridge structure to complete the function of converting an input signal of 0 to +/-5V into a current signal of hundreds of amperes. In fig. 3, a symbol T0 is a gradient coil.
Claims (1)
1. The driving circuit of the gradient power amplifier of the nuclear magnetic resonance apparatus is characterized by being provided with a zero-crossing comparator, an adder circuit and a transmission gate;
the zero-crossing comparator is provided with two opposite zero-crossing comparators, the input ends of the two opposite zero-crossing comparators are connected with each other and are connected with pulse input signals of 0 to +/-5V, and the output ends of the two opposite zero-crossing comparators are respectively connected with the control ends of the transmission gates of the positive and negative signal paths;
the adder circuit is provided with 3 adders under positive and negative signal paths, the 3 adders respectively add-20V, -9V and +5V 3 state voltages to the inverting input ends of the adders, and the non-inverting input ends of the adders are commonly connected with input signals; the output end of the adder is connected with the input end of the transmission gate;
the transmission gates are provided with 3 transmission gates under positive and negative signal paths, the control ends of the 3 transmission gates are connected with the output ends of the zero-crossing comparator, the on-off of the zero-crossing comparator is controlled by the output of the zero-crossing comparator, the input ends of the 3 transmission gates are connected with the adder, the output ends of the 3 transmission gates are connected with the IGBT of the amplifying circuit, and the working state of the IGBT is controlled by the output state of the output adder;
when the voltage is 20V, the amplifying state is realized, when the voltage is 9V, the saturated state is realized, and when the voltage is-5V, the cut-off state is realized;
when the input signal is positive voltage, the comparator which receives the control signal by the non-inverting input terminal is turned over to output 10V voltage, and a switch signal is provided for the positive signal path transmission gate; when the input signal is negative voltage, the comparator receiving the signal at the inverting input end is turned over to output 10V voltage, and a switch signal is provided for the negative signal path transmission gate; the adder circuits of the positive and negative signal paths are respectively provided with 3 adders, voltages of-20V, -9V and +5V are respectively applied to the inverting input ends of the 3 adders, meanwhile, the non-inverting input ends of the 3 adders are connected with input signals, and state voltages of 20V,9V and-5V and the input signals are respectively transmitted to the positive signal path transmission gate and the negative signal path transmission gate which are respectively connected, and the amplifying circuit works under a push-pull bridge structure.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201710969313.1A CN107703468B (en) | 2017-10-18 | 2017-10-18 | Driving circuit of gradient power amplifier of nuclear magnetic resonance apparatus |
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| CN201710969313.1A CN107703468B (en) | 2017-10-18 | 2017-10-18 | Driving circuit of gradient power amplifier of nuclear magnetic resonance apparatus |
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| CN107703468B true CN107703468B (en) | 2023-12-01 |
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| US8760851B2 (en) * | 2010-12-21 | 2014-06-24 | Fastcap Systems Corporation | Electrochemical double-layer capacitor for high temperature applications |
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