Voltage-current conversion module

Abstract

The present disclosure describes a voltage-current conversion module, which is applied to a current excitation device of an electrical impedance imaging system. The voltage-current conversion module is used to generate current excitation based on a sinusoidal signal or a square wave signal. The voltage-current conversion module includes a first conversion module and a second conversion module. The output end of the first conversion module is a positive output end of current excitation, and the output end of the second conversion module is a negative output end of current excitation. The positive output end of current excitation and the negative output end of current excitation form current excitation. The first conversion module includes a first low-power operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The second conversion module includes a second low-power operational amplifier, a sixth resistor, and a seventh resistor. According to the present disclosure, a voltage-current conversion module with lower power consumption and a relatively simple circuit structure can be provided.

Description

[0001] This application is a divisional application of a patent application with application date of December 31, 2020, application number 2020116367849, and invention name "Current excitation device for portable electrical impedance imaging system". Technical Field

[0002] The present disclosure generally relates to the field of electrical impedance imaging, and more particularly to a voltage-to-current conversion module. Background Art

[0003] Impedance imaging technology has a wide range of applications in industry, biology and other fields. Impedance imaging technology usually refers to applying a current of a certain frequency and amplitude to the object under test through an electrode group installed on the surface of the object under test, and measuring the response voltage at the same time, and finally using the corresponding imaging algorithm to obtain an image that can reflect the internal impedance distribution information of the object under test. However, with the rapid development of electronic science and technology, impedance imaging technology has also tended to develop in the direction of miniaturization and portability; therefore, higher and newer requirements are put forward for its data acquisition system, especially for the current excitation device that generates the current excitation source.

[0004] In traditional electrical impedance imaging systems, only sinusoidal current excitation signals can be applied to the imaging target. Field Programmable Gate Array (FPGA) and high-speed digital to analog conversion (DAC) are usually used to generate the required sinusoidal voltage excitation signal, and components such as operational amplifiers are used to build voltage-current conversion circuits. Among them, chips such as field programmable gate arrays FPGA, high-speed digital to analog converters DAC and operational amplifiers have high power consumption and complex circuit structures, so they are not suitable for portable electrical impedance imaging systems that require low-power design. Summary of the invention

[0005] The present disclosure is made in view of the above-mentioned prior art conditions, and its purpose is to provide a current excitation device for a portable electrical impedance imaging system with lower power consumption and simpler circuit structure.

[0006] To this end, the first aspect of the present disclosure provides a current excitation device for a portable electrical impedance imaging system, which includes a signal generating module, a filtering module and a voltage-current conversion module. The signal generating module is used to generate a square wave signal with adjustable amplitude and frequency. The filtering module is used to convert the square wave signal into a sinusoidal signal. The voltage-current conversion module is used to generate current excitation based on the sinusoidal signal. The signal generating module includes a high-frequency clock unit, a frequency divider, a precision digital-to-analog converter and an analog switch. The analog switch has a first input terminal, a second input terminal and a first common output terminal. The output terminal of the precision digital-to-analog converter is connected to the first input terminal, the second input terminal is grounded, and the high-frequency clock The output end of the unit is connected to the input end of the frequency divider, the precision digital-to-analog converter is used to generate a stable voltage signal with adjustable amplitude, the high-frequency clock unit includes a high-precision crystal oscillator circuit for generating a high-frequency clock, the frequency divider performs frequency division based on the high-frequency clock to control the on-off between the first common output end and the first input end or the second input end so as to realize that the first common output end outputs the square wave signal with adjustable frequency, the input end of the filtering module is connected to the first common output end, the output end of the filtering module is connected to the voltage-current conversion module, the filtering module includes a first-order high-pass filter and a second-order active low-pass filter, the first-order high-pass filter is used to filter out the square wave signal The intermediate signal is obtained by filtering out the DC component in the intermediate signal, the second-order active low-pass filter is used to filter out the high-order harmonic components in the intermediate signal to obtain a sinusoidal signal, the voltage-current conversion module includes a first conversion module and a second conversion module, the first conversion module includes a first low-power operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, one end of the first resistor is connected to the negative phase input end of the first low-power operational amplifier, the negative phase input end and the output end of the first low-power operational amplifier are connected through the second resistor, one end of the third resistor is connected to the output end of the first low-power operational amplifier, the other end of the third resistor is a current excitation positive output end, and the fourth A resistor connects the positive phase input terminal of the first low-power operational amplifier and the current excitation positive output terminal, one end of the fifth resistor is connected to the positive phase input terminal of the first low-power operational amplifier, and the other end of the fifth resistor is connected to the filtering module. The second conversion module includes a second low-power operational amplifier, a sixth resistor and a seventh resistor. The sixth resistor connects the output terminal of the first low-power operational amplifier and the negative phase input terminal of the second low-power operational amplifier. The negative phase input terminal and the output terminal of the second low-power operational amplifier are connected through the seventh resistor. The output terminal of the second low-power operational amplifier is the current excitation negative output terminal, and the positive phase input terminal of the second low-power operational amplifier is grounded.In the present disclosure, the current excitation device includes a signal generation module, a filtering module and a voltage-current conversion module, and the circuit structure is relatively simple; a stable voltage signal with adjustable amplitude can be obtained by using a precision digital-to-analog converter, so as to generate a square wave signal with adjustable amplitude and frequency at the first common output terminal, and in addition, a sinusoidal excitation current is obtained by using the filtering module, and the voltage-current conversion module includes a first low-power operational amplifier and a second low-power operational amplifier, thereby reducing the power consumption of the current excitation device. Thus, a current excitation device with lower power consumption and a relatively simple circuit structure can be obtained.

[0007] In addition, in the current excitation device involved in the first aspect of the present disclosure, optionally, the current excitation device also includes a follower module and a switching switch module, the filter module and the follower module are connected or disconnected with the voltage-current conversion module through the switching switch module, the switching switch module includes a first connection terminal, a second connection terminal and a second common output terminal, the output terminal of the filter module is connected to the first connection terminal, the input terminal of the follower module is connected to the first common output terminal, the output terminal of the follower module is connected to the second connection terminal, and the second common output terminal is connected to the positive phase input terminal of the first low-power operational amplifier of the voltage-current conversion module via the fifth resistor. In this way, it is convenient to select and generate two types of excitation currents, namely, sinusoidal and square waves.

[0008] In addition, in the current excitation device involved in the first aspect of the present disclosure, optionally, the first-order high-pass filter includes a first capacitor and an eighth resistor. Thus, the first capacitor and the eighth resistor can be used to filter out the DC component in the square wave signal.

[0009] In addition, in the current excitation device involved in the first aspect of the present disclosure, optionally, the second-order active low-pass filter includes a third low-power operational amplifier, a second capacitor, a third capacitor, a first digital potentiometer, and a second digital potentiometer. Thus, the third low-power operational amplifier, the second capacitor, the third capacitor, the first digital potentiometer, and the second digital potentiometer can be used to filter out high-order harmonic components in the intermediate signal.

[0010] In addition, in the current excitation device involved in the first aspect of the present disclosure, optionally, the non-phase input terminal of the third low-power operational amplifier is grounded through the third capacitor, the negative phase input terminal of the third low-power operational amplifier is connected to the output terminal of the third low-power operational amplifier, the non-phase input terminal of the third low-power operational amplifier is connected to one end of the second digital potentiometer, the other end of the second digital potentiometer is connected to one end of the first digital potentiometer and one end of the second capacitor, the other end of the first digital potentiometer is grounded through the eighth resistor, and the other end of the second capacitor is connected to the output terminal of the third low-power operational amplifier. In this way, the high-order harmonic components in the intermediate signal can be filtered out.

[0011] In addition, in the current excitation device involved in the first aspect of the present disclosure, optionally, the cutoff frequency of the second-order active low-pass filter is adjusted by the first digital potentiometer and the second digital potentiometer. Thus, the cutoff frequency of the second-order active low-pass filter can be adjusted based on demand.

[0012] To this end, the second aspect of the present disclosure provides a current excitation device for a portable electrical impedance imaging system, which includes a signal generating module, a following module and a voltage-current conversion module, wherein the signal generating module is used to generate a square wave signal with adjustable amplitude and adjustable frequency, the following module is used to perform impedance matching between the signal generating module and the voltage-current conversion module, the voltage-current conversion module is used to generate current excitation based on the square wave signal, the signal generating module includes a high-frequency clock unit, a frequency divider, a precision digital-to-analog converter and an analog switch, the analog switch has a first input terminal, a second input terminal and a first common output terminal, the precision digital-to-analog converter The output end of the converter is connected to the first input end, the second input end is grounded, the output end of the high-frequency clock unit is connected to the input end of the frequency divider, the precision digital-to-analog converter is used to generate a stable voltage signal with adjustable amplitude, the high-frequency clock unit includes a high-precision crystal oscillator circuit for generating a high-frequency clock, the frequency divider performs frequency division based on the high-frequency clock to control the on-off between the first common output end and the first input end or the second input end to realize that the first common output end outputs the square wave signal with adjustable frequency, the input end of the follower module is connected to the first common output end, and the output end of the follower module is connected to the A voltage-current conversion module, wherein the voltage-current conversion module comprises a first conversion module and a second conversion module, wherein the first conversion module comprises a first low-power operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, wherein one end of the first resistor is connected to the negative phase input end of the first low-power operational amplifier, and the negative phase input end and the output end of the first low-power operational amplifier are connected through the second resistor, one end of the third resistor is connected to the output end of the first low-power operational amplifier, and the other end of the third resistor is a current excitation positive output end, the fourth resistor is connected to the positive phase input end of the first low-power operational amplifier and the current excitation positive output end, one end of the fifth resistor is connected to the positive phase input end of the first low-power operational amplifier, and the other end of the fifth resistor is connected to the follower module, and the second conversion module comprises a second low-power operational amplifier, a sixth resistor and a seventh resistor, wherein the sixth resistor is connected to the output end of the first low-power operational amplifier and the negative phase input end of the second low-power operational amplifier, and the negative phase input end and the output end of the second low-power operational amplifier are connected through the seventh resistor, the output end of the second low-power operational amplifier is a current excitation negative output end, and the positive phase input end of the second low-power operational amplifier is grounded.In the present disclosure, the current excitation device includes a signal generation module, a follower module and a voltage-current conversion module. The circuit structure is relatively simple. A stable voltage signal with adjustable amplitude can be obtained by using a precision digital-to-analog converter, so as to generate a square wave signal with adjustable amplitude and frequency at the first common output terminal. In addition, the signal generation module and the voltage-current conversion module are impedance matched by using a follower module, and the follower module outputs a square wave type excitation current. The voltage-current conversion module includes a first low-power operational amplifier and a second low-power operational amplifier, thereby reducing the power consumption of the current excitation device. Thus, a current excitation device with lower power consumption and a relatively simple circuit structure can be obtained.

[0013] In addition, in the current excitation device involved in the first aspect or the second aspect of the present disclosure, optionally, the frequency division coefficient of the frequency divider is set by a program, thereby being able to adjust the frequency division coefficient of the frequency divider based on demand.

[0014] In addition, in the current excitation device involved in the first aspect or the second aspect of the present disclosure, optionally, the frequency divider outputs a square wave driving signal with a duty cycle of 50%.

[0015] In addition, in the current excitation device involved in the first aspect or the second aspect of the present disclosure, optionally, the follower module is composed of an operational amplifier. Thus, impedance matching can be performed using the follower module composed of the operational amplifier.

[0016] According to the present disclosure, a current excitation device for a portable electrical impedance imaging system is provided, which has lower power consumption and a relatively simple circuit structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments of the present disclosure will now be explained in further detail, by way of example only, with reference to the accompanying drawings, in which:

[0018] Figure 1 4 is a block diagram showing a current excitation device for a portable electrical impedance imaging system according to a first embodiment of the present disclosure.

[0019] Figure 2 1 is a circuit diagram showing a signal generating module according to the first embodiment of the present disclosure.

[0020] Figure 3 is a circuit diagram showing a filter module according to a first embodiment of the present disclosure.

[0021] Figure 4 1 is a circuit diagram showing a voltage-current conversion module according to a first embodiment of the present disclosure.

[0022] Figure 5 1 is a circuit diagram showing a portable electrical impedance imaging system according to a first embodiment of the present disclosure.

[0023] Figure 6 is a block diagram showing a current excitation device for a portable electrical impedance imaging system according to a second embodiment of the present disclosure.

[0024] Figure 7 is a circuit diagram showing a current excitation device for a portable electrical impedance imaging system according to a second embodiment of the present disclosure.

[0025] Figure 8 is a block diagram showing a current excitation device for a portable electrical impedance imaging system according to a third embodiment of the present disclosure.

[0026] Fig. 9 is a circuit diagram showing a current excitation device for a portable electrical impedance imaging system according to a third embodiment of the present disclosure.

[0027] Fig.10 is a circuit diagram showing an equipotential point generating module involved in an example of the present disclosure. DETAILED DESCRIPTION

[0028] Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same symbols are assigned to the same components, and repeated descriptions are omitted. In addition, the accompanying drawings are only schematic diagrams, and the ratio of the dimensions of the components or the shapes of the components may be different from the actual ones.

[0029] It should be noted that the terms "first", "second", "third" and "fourth" etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0030] The present disclosure relates to a current excitation device for a portable electrical impedance imaging system. The current excitation device for a portable electrical impedance imaging system involved in the present disclosure can be referred to as a current excitation device. The current excitation device of the present disclosure has low power consumption and a relatively simple circuit structure. The portable electrical impedance imaging system to which the current excitation device involved in the present disclosure is applied can be, for example, a portable electrical impedance imaging system powered by a battery.

[0031] [First embodiment]

[0032] Figure 1is a block diagram showing a current excitation device 1 for a portable electrical impedance imaging system according to a first embodiment of the present disclosure. Figure 1 As shown, the current excitation device 1 may include a signal generating module 10, a filtering module 20 and a voltage-current conversion module 30. The signal generating module 10 may be used to generate a square wave signal with adjustable amplitude and adjustable frequency. The filtering module 20 may be used to convert the square wave signal into a sinusoidal signal. The voltage-current conversion module 30 may be used to generate current excitation based on the sinusoidal signal.

[0033] Figure 2 is a circuit diagram showing a signal generating module 10 involved in the first embodiment of the present disclosure. In some examples, as described above, the signal generating module 10 can be used to generate a square wave signal with adjustable amplitude and adjustable frequency.

[0034] In some examples, such as Figure 2 As shown, the signal generating module 10 may include a high-frequency clock unit 11 .

[0035] In some examples, the high-frequency clock unit 11 may include a high-precision crystal oscillator circuit. The high-precision crystal oscillator circuit may be used to generate a high-frequency clock. In this case, a high-precision high-frequency clock may be obtained.

[0036] In some examples, the frequency of the high-frequency clock may be, for example, 8 MHz or 33 MHZ (megahertz). However, the frequency of the high-frequency clock in the examples of the present disclosure is not limited thereto.

[0037] In some examples, such as Figure 2 As shown, the signal generating module 10 may include a frequency divider 12 .

[0038] In some examples, an input terminal of the frequency divider 12 may be connected to an output terminal of the high frequency clock unit.

[0039] In some examples, frequency divider 12 may include a timer or dedicated circuitry integrated by a microprocessor.

[0040] In some examples, frequency divider 12 may have a frequency division factor.

[0041] In some examples, the frequency divider 12 can perform frequency division based on the high-frequency clock. Thus, frequency adjustment can be achieved. In other words, the frequency divider 12 can divide the high-frequency clock using a frequency division coefficient.

[0042] In some examples, the frequency division coefficient of the frequency divider 12 can be set by a program, so that the frequency division coefficient of the frequency divider can be adjusted based on demand.

[0043] In some examples, the frequency divider 12 may output a square wave driving signal with a duty cycle of 50%.

[0044] In some examples, the frequency divider 12 can generate a driving signal. That is, the output end of the frequency divider 12 can output the driving signal. Specifically, the frequency divider 12 can divide the high frequency clock by a frequency division coefficient to generate the driving signal. The driving signal can be, for example, a square wave driving signal.

[0045] In some examples, the frequency of the driving signal may be affected by the frequency division coefficient and the frequency of the high frequency clock. In some examples, if the frequency division coefficient of the frequency divider 12 is set by a program, the frequency of the driving signal can be adjusted.

[0046] In some examples, the drive signal may be used to drive an analog switch 14 (described later).

[0047] In some examples, the frequency divider 12 can control the on-off between the first common output terminal and the first input terminal or the second input terminal (described later). In this case, the frequency divider 12 with different frequency division coefficients can control the on-off between the first common output terminal and the first input terminal or the second input terminal to realize the first common output terminal outputs a square wave signal with adjustable frequency. In other words, the frequency divider 12 can divide the frequency based on the high-frequency clock to control the on-off between the first common output terminal and the first input terminal or the second input terminal to realize the first common output terminal outputs a square wave signal with adjustable frequency. For example, the frequency divider 12 can divide the frequency based on the frequency division coefficient and the high-frequency clock to control the on-off between the first common output terminal and the first input terminal or the second input terminal to realize the first common output terminal outputs a square wave signal with adjustable frequency.

[0048] In some examples, such as Figure 2 As shown, the signal generating module 10 may include a precision digital-to-analog converter 13. The precision digital-to-analog converter 13 may be used to generate a voltage signal.

[0049] In some examples, the voltage signal generated by the precision digital-to-analog converter 13 is stable, that is, the precision digital-to-analog converter 13 can generate a constant voltage signal.

[0050] In some examples, the amplitude of the voltage signal generated by the precision digital-to-analog converter 13 is adjustable. Specifically, the precision digital-to-analog converter 13 can generate a constant voltage signal with different voltage values ​​according to requirements. In this case, the precision digital-to-analog converter 13 can generate a stable voltage signal with adjustable amplitude.

[0051] In some examples, the amplitude of the voltage signal generated by the precision digital-to-analog converter 13 can be adjusted by program control.

[0052] In some examples, such as Figure 2As shown, the signal generating module 10 may include an analog switch 14. The analog switch 14 may have a first input terminal, a second input terminal and a first common output terminal. If the first common output terminal is connected to the first input terminal, the first common output terminal may be disconnected from the second input terminal; if the first common output terminal is disconnected from the first input terminal, the first common output terminal may be connected to the second input terminal. That is, the analog switch 14 may be a two-choice switch.

[0053] In some examples, the first input terminal may be connected to the output terminal of the precision digital-to-analog converter 13. The second input terminal may be grounded. Here, grounding refers to actual grounding. In other words, a stable voltage signal may be input to the first input terminal. A ground level signal may be input to the second input terminal.

[0054] In some examples, the first common output terminal can be connected and disconnected with the first input terminal or the second input terminal by the control of the frequency divider 12. In other words, the first common output terminal can be controlled by the drive signal generated by the frequency divider 12 to achieve connection and disconnection with the first input terminal or the second input terminal. In this case, the first common output terminal can output a square wave signal with adjustable amplitude and adjustable frequency.

[0055] In some examples, since the second input terminal is grounded, the first common output terminal can output a stable voltage signal whose high level is output by the precision digital-to-analog converter 13 and a stable amplitude square wave signal whose low level is 0V.

[0056] In some examples, the first common output terminal may be connected to an input terminal of a filter module 20 (described later).

[0057] Figure 3 is a circuit diagram showing the filter module 20 according to the first embodiment of the present disclosure.

[0058] In some examples, the filtering module 20 may be used to convert a square wave signal into a sinusoidal signal.

[0059] In some examples, such as Figure 5 As shown, the input end of the filter module 20 can be connected to the first common output end. The output end of the filter module 20 can be connected to the voltage-current conversion module 30 (described later).

[0060] In some examples, such as Figure 3 As shown, the filtering module 20 may include a first-order high-pass filter A. The first-order high-pass filter A may be used to filter out a DC component in a square wave signal to obtain an intermediate signal.

[0061] In some examples, such as Figure 3As shown, the first-order high-pass filter A may include a first capacitor 21 and an eighth resistor 22. Thus, the first capacitor 21 and the eighth resistor 22 can be used to filter out the DC component in the square wave signal.

[0062] In some examples, one end of the first capacitor 21 is the input end of the filter module 20. The other end of the first capacitor 21 is grounded through the eighth resistor 22 (see Figure 3 ).

[0063] In some examples, such as Figure 3 As shown, the filtering module 20 may include a second-order active low-pass filter B. The second-order active low-pass filter B may be used to filter out high-order harmonic components in the intermediate signal to obtain a sinusoidal signal.

[0064] In some examples, such as Figure 3 As shown, the second-order active low-pass filter B may include a third low-power operational amplifier 23, a second capacitor 24, a third capacitor 25, a first digital potentiometer 26, and a second digital potentiometer 27. Thus, the third low-power operational amplifier 23, the second capacitor 24, the third capacitor 25, the first digital potentiometer 26, and the second digital potentiometer 27 can be used to filter out the high-order harmonic components in the intermediate signal.

[0065] In some examples, the third low power operational amplifier 23 may be a low voltage, low power operational amplifier.

[0066] In some examples, such as Figure 3 As shown, the positive phase input terminal of the third low power operational amplifier 23 is grounded through the third capacitor 25. The negative phase input terminal of the third low power operational amplifier 23 is connected to the output terminal of the third low power operational amplifier 23. The positive phase input terminal of the third low power operational amplifier 23 is connected to one end of the second digital potentiometer 27. The other end of the second digital potentiometer 27 is connected to one end of the first digital potentiometer 26 and one end of the second capacitor 24. The other end of the first digital potentiometer 26 is grounded through the eighth resistor 22. The other end of the second capacitor 24 is connected to the output terminal of the third low power operational amplifier 23.

[0067] In some examples, the second-order active low-pass filter B can have a cutoff frequency.

[0068] In some examples, the cutoff frequency of the second-order active low-pass filter B can be adjusted by the first digital potentiometer 26 and the second digital potentiometer 27. Thus, the cutoff frequency of the second-order active low-pass filter can be adjusted based on demand. In this case, the second-order active low-pass filter B can use a digital potentiometer to adjust the cutoff frequency through a program.

[0069] In some examples, the output end of the third low power operational amplifier 23 may be the output end of the filter module 20. The output end of the filter module 20 may output a sinusoidal signal.

[0070] In some examples, the filtering module 20 including the first-order high-pass filter A and the second-order active low-pass filter B may be referred to as a band-pass filtering circuit.

[0071] Figure 4 is a circuit diagram showing the voltage-current conversion module 30 according to the first embodiment of the present disclosure. Figure 5 1 is a circuit diagram showing a portable electrical impedance imaging system according to a first embodiment of the present disclosure.

[0072] In some examples, the voltage-to-current conversion module 30 may be used to generate a current excitation based on a sinusoidal signal.

[0073] In some examples, such as Figure 4 As shown, the voltage-current conversion module 30 may include a first conversion module C. The input end of the voltage-current conversion module 30 may be the input end of the first conversion module C. The output of the voltage-current conversion module 30 is a differential output. Specifically, the output end of the voltage-current conversion module 30 may include a current excitation positive output end and a current excitation negative output end. The current excitation positive output end and the current excitation negative output end may form current excitation. The current excitation positive output end may be the output end of the first conversion module C. The current excitation negative output end may be the output end of the second conversion module D.

[0074] In some examples, the signal output by the voltage-current conversion module 30 may be referred to as an excitation signal. The excitation signal output by the voltage-current conversion module 30 may have a wide output dynamic range.

[0075] In some examples, such as Figure 4 As shown, the first conversion module C may include a first low power operational amplifier 31 , a first resistor 33 , a second resistor 34 , a third resistor 35 , a fourth resistor 36 and a fifth resistor 37 .

[0076] In some examples, the first low power operational amplifier 31, the first resistor 33, the second resistor 34, the third resistor 35, the fourth resistor 36 and the fifth resistor 37 in the first conversion module C can form a current pump. Thus, the first conversion module C can have a high output impedance characteristic.

[0077] In some examples, such as Figure 4As shown, one end of the first resistor 33 is connected to the negative phase input terminal of the first low power operational amplifier 31. The other end of the first resistor 33 is grounded. The negative phase input terminal and the output terminal of the first low power operational amplifier 31 are connected through the second resistor 34. One end of the third resistor 35 is connected to the output terminal of the first low power operational amplifier 31. The other end of the third resistor 35 is the current excitation positive output terminal. The fourth resistor 36 is connected to the positive phase input terminal of the first low power operational amplifier 31 and the current excitation positive output terminal I + One end of the fifth resistor 37 is connected to the non-inverting input end of the first low power operational amplifier 31. The other end of the fifth resistor 37 may be an input end of the first conversion module C.

[0078] In some examples, such as Figure 5 As shown, the other end of the fifth resistor can be connected to the filter module 20. In this case, the output end of the voltage-current conversion module 30 can output a sinusoidal excitation current.

[0079] In some examples, such as Figure 4 As shown, the voltage-current conversion module 30 may include a second conversion module D. The second conversion module D may include a second low power operational amplifier 32 , a sixth resistor 38 and a seventh resistor 39 .

[0080] In some examples, the second low power operational amplifier 32 , the sixth resistor 38 , and the seventh resistor 39 in the second conversion module D may form an inverting amplifier, thereby extending the dynamic range of the excitation signal.

[0081] In some examples, such as Figure 4 As shown, the sixth resistor 38 is connected to the output end of the first low-power operational amplifier 31 and the negative phase input end of the second low-power operational amplifier 32. The negative phase input end and the output end of the second low-power operational amplifier 32 are connected through the seventh resistor 39. The output end of the second low-power operational amplifier 32 is the current excitation negative output end I - , the non-inverting input terminal of the second low power operational amplifier 32 is grounded.

[0082] In some examples, the first low power operational amplifier 31 and the second low power operational amplifier 32 may be low voltage, low power operational amplifiers.

[0083] In the present disclosure, the current excitation device 1 may include a signal generating module 10, a filtering module 20 and a voltage-current conversion module 30. The circuit structure is relatively simple. A stable voltage signal with adjustable amplitude can be obtained by using a precision digital-to-analog converter, so as to generate a square wave signal with adjustable amplitude and frequency at the first common output terminal. In addition, a sinusoidal excitation current is obtained by using the filtering module 20, and the voltage-current conversion module 30 includes a first low-power operational amplifier 31 and a second low-power operational amplifier 32, thereby reducing the power consumption of the current excitation device 1. Thus, a current excitation device 1 with lower power consumption and a relatively simple circuit structure can be obtained.

[0084] [Second embodiment]

[0085] Figure 6 2 is a block diagram showing a current excitation device 1 for a portable electrical impedance imaging system according to a second embodiment of the present disclosure. Figure 7 1 is a circuit diagram showing a current excitation device 1A for a portable electrical impedance imaging system according to a second embodiment of the present disclosure.

[0086] In the second embodiment, the current excitation device 1A for the portable electrical impedance imaging system can be referred to as the current excitation device 1A. The current excitation device 1A can include a signal generating module 10, a following module 40 and a voltage-current conversion module 30. Among them, the signal generating module 10 can be used to generate a square wave signal with adjustable amplitude and adjustable frequency. The following module 40 can be used to perform impedance matching on the signal generating module 10 and the voltage-current conversion module 30. The voltage-current conversion module 30 can be used to generate current excitation based on the square wave signal.

[0087] In a second embodiment, if Figure 6 or Figure 7 As shown, the output end of the signal generating module 10 (ie, the first common output end of the analog switch 14) is connected to the input end of the follower module 40. Otherwise, the signal generating module 10 of the second embodiment is consistent with that of the first embodiment, and the details can be referred to the description of the first embodiment.

[0088] In some examples, such as Figure 6 or Figure 7 As shown, the output end of the follower module 40 is connected to the input end of the voltage-current conversion module 30. The output end of the follower module 40 outputs a square wave signal.

[0089] In some examples, the follower module 40 may be implemented by an operational amplifier.

[0090] In some examples, the follower module 40 may be a voltage follower circuit formed by an operational amplifier. In this case, the output end of the signal generating module 10 is connected to the non-inverting input end of the operational amplifier in the voltage follower circuit.

[0091] In some examples, such as Figure 6 or Figure 7 As shown, the input end of the voltage-current conversion module 30 (i.e., the other end of the fifth resistor) is connected to the output end of the follower module 40. That is, the voltage-current conversion module 30 generates a square wave type current excitation based on the square wave signal. In addition, the voltage-current conversion module 30 of the second embodiment is consistent with that of the first embodiment, and the details can be referred to the description of the first embodiment.

[0092] In this embodiment, the current excitation device 1 may include a signal generating module 10, a following module 40 and a voltage-current conversion module 30. The circuit structure is relatively simple. A stable voltage signal with adjustable amplitude can be obtained by using a precision digital-to-analog converter, so as to generate a square wave signal with adjustable amplitude and frequency at the first common output terminal. In addition, the signal generating module 10 and the voltage-current conversion module 30 are impedance matched by using the following module 40. The following module 40 outputs a square wave type excitation current. The voltage-current conversion module 30 includes a first low-power operational amplifier and a second low-power operational amplifier, thereby reducing the power consumption of the current excitation device 1. Thus, a current excitation device 1 with lower power consumption and a relatively simple circuit structure can be obtained.

[0093] [Third specific implementation method]

[0094] Figure 8 is a block diagram showing a current excitation device 1 for a portable electrical impedance imaging system according to a third embodiment of the present disclosure. Fig. 9 is a circuit diagram showing a current excitation device 1B for a portable electrical impedance imaging system according to a third embodiment of the present disclosure.

[0095] In the third embodiment, the current excitation device 1B for the portable electrical impedance tomography system may be simply referred to as the current excitation device 1B. Figure 8 or Fig. 9 As shown, the current excitation device 1B may include a signal generating module 10, a filtering module 20, a following module 40, a switching module 50 and a voltage-current conversion module 30. The specific description of the signal generating module 10, the filtering module 20, the following module 40, the switching module 50 and the voltage-current conversion module 30 may refer to the contents of the first embodiment and the second embodiment described above.

[0096] The third embodiment is mainly different from the first embodiment and the second embodiment in that the filter module 20 and the follower module 40 can be connected or disconnected with the voltage-current conversion module 30 by switching the switch module 50. Specifically, if the filter module 20 is connected with the voltage-current conversion module 30 by switching the switch module 50, the follower module 40 can be disconnected from the voltage-current conversion module 30. If the follower module 40 is connected with the voltage-current conversion module 30 by switching the switch module 50, the filter module 20 can be disconnected from the voltage-current conversion module 30.

[0097] In a third embodiment, if Figure 8 or Fig. 9 As shown, the switching switch module 50 may include a first connection terminal, a second connection terminal and a second common output terminal. The output terminal of the filter module 20 may be connected to the first connection terminal. The input terminal of the follower module 40 may be connected to the first common output terminal. The output terminal of the follower module 40 may be connected to the second connection terminal. The second common output terminal may be connected to the non-inverting input terminal of the first low-power operational amplifier 31 of the voltage-current conversion module 30 via a fifth resistor. Thus, it is convenient to select and generate two types of excitation currents, sinusoidal and square waves.

[0098] In the third embodiment, if the first connection terminal is connected to the second common output terminal, the second connection terminal can be disconnected from the second common output terminal, and the second common output terminal can output the sinusoidal signal output by the filter module 20. If the first connection terminal is disconnected from the second common output terminal, the second connection terminal can be connected to the second common output terminal, and the second common output terminal can output the square wave signal output by the follower module 40.

[0099] In some examples, the switch module 50 can be controlled by a program. In this case, the sine wave signal output by the filter module 20 or the square wave signal output by the follower module 40 can be selected to be input into the voltage-current conversion module 30, thereby realizing the switching of the excitation signal type.

[0100] In the present disclosure, the circuit elements involved in the above-mentioned various embodiments can be powered by a low-voltage power supply. In addition, the current excitation device 1 of the present disclosure consumes less current.

[0101] Fig.10 is a circuit diagram showing an equipotential point generating module 60 involved in an example of the present disclosure. In some examples, the current excitation device 1 can be powered by a dual power supply. In this case, the grounding in each module of the current excitation device 1 can be a "grounding" in the usual sense. That is, the grounding in each module of the current excitation device 1 can be an actual grounding.

[0102] In some examples, the current excitation device 1 can be powered by a single power supply. In this case, the grounding in each module of the current excitation device 1 (except the signal generating module 10) can be connected to a "virtual ground" (i.e., an "equipotential point"). In other words, the grounding in each module of the current excitation device 1 can be a virtual ground.

[0103] In some examples, the voltage of the equipotential point may be any voltage between the power supply voltage and 0 V. In some examples, the voltage of the equipotential point may be half of the power supply voltage.

[0104] In some examples, the isoelectric point may be provided by the isoelectric point generation module 60 .

[0105] In some examples, such as Fig.10 As shown, the equipotential point generating module 60 may include a ninth resistor 61, a tenth resistor 62, a fourth capacitor 63 and an operational amplifier 64. One end of the ninth resistor 61 may be connected to a power supply voltage. The other end of the ninth resistor 61 may be connected to a non-inverting input terminal of the operational amplifier 64. The power supply voltage may be represented by VCC. One end of the tenth resistor 62 may be connected to a non-inverting input terminal of the operational amplifier 64. The other end of the tenth resistor 62 may be actually grounded. The ninth resistor 61 and the tenth resistor 62 may be connected to each other. Fig.10 The power supply voltage VCC is divided to obtain the equipotential point voltage.

[0106] In some examples, such as Fig.10 As shown, one end of the fourth capacitor 63 can be connected to the non-inverting input terminal of the operational amplifier 64. The other end of the fourth capacitor 63 can be actually grounded. In some examples, the fourth capacitor 63 can be a filter capacitor. In this case, the noise in the equipotential point voltage can be filtered out by the fourth capacitor 63.

[0107] In some examples, such as Fig.10 As shown, the negative phase input terminal of the operational amplifier 64 can be connected to the output terminal of the operational amplifier 64. In this case, the operational amplifier 64 can form an impedance conversion circuit, thereby increasing the driving capability of the equipotential point voltage.

[0108] In some examples, the output end of the operational amplifier 64 is the equipotential point. For example, under the condition of a single power supply mode, the output end of the operational amplifier 64 can be used to connect to the "virtual ground" of the voltage-current conversion module 30; the output end of the operational amplifier 64 can be used to connect to the "virtual ground" of the filter circuit 20. In this case, the excitation current output by the voltage-current conversion module 30 can be relative to the equipotential point.

[0109] Although the present disclosure is specifically described above in conjunction with the accompanying drawings and embodiments, it is to be understood that the above description does not limit the present disclosure in any form. Those skilled in the art may modify and change the present disclosure as needed without departing from the essential spirit and scope of the present disclosure, and these modifications and changes all fall within the scope of the present disclosure.

Claims

1. A voltage-to-current conversion module, applied to a current excitation device of an electrical impedance tomography system, characterized in that: The voltage-current conversion module is used to generate current excitation based on a sinusoidal signal or a square wave signal. The voltage-current conversion module includes a first conversion module and a second conversion module. The output end of the first conversion module is a current excitation positive output end, and the output end of the second conversion module is a current excitation negative output end. The first conversion module includes a first low-power operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor. The negative phase input end of the first low-power operational amplifier is grounded through the first resistor, and the negative phase input end and the output end of the first low-power operational amplifier are connected through the second resistor. One end of the third resistor is connected to the output end of the first low-power operational amplifier, and the other end of the third resistor is the current excitation positive output end. The output terminal of the current excitation positive output terminal is connected to the positive phase input terminal of the first low-power operational amplifier through the fourth resistor, one end of the fifth resistor is connected to the positive phase input terminal of the first low-power operational amplifier, and the other end of the fifth resistor receives the sinusoidal signal or the square wave signal. The second conversion module includes a second low-power operational amplifier, a sixth resistor and a seventh resistor. The negative phase input terminal of the second low-power operational amplifier is connected to the output terminal of the first low-power operational amplifier through the sixth resistor, the negative phase input terminal and the output terminal of the second low-power operational amplifier are connected through the seventh resistor, the positive phase input terminal of the second low-power operational amplifier is grounded, and the output terminal of the second low-power operational amplifier is the current excitation negative output terminal.

2. The voltage-to-current conversion module according to claim 1, characterized in that: The sinusoidal signal is obtained by filtering out the DC component in the initial square wave signal to obtain an intermediate signal, and filtering out the high-order harmonic components in the intermediate signal; or The square wave signal is a square wave type excitation current obtained by impedance matching the initial square wave signal.

3. The voltage-to-current conversion module according to claim 2, characterized in that: The impedance matching is achieved by a voltage follower circuit composed of an operational amplifier.

4. The voltage-to-current conversion module according to claim 2, characterized in that: The initial square wave signal is generated by a signal generating module in the current excitation device, and the amplitude and frequency of the initial square wave signal are adjustable.

5. The voltage-to-current conversion module according to claim 1, characterized in that: The current excitation positive output terminal and the current excitation negative output terminal form the current excitation.

6. The voltage-to-current conversion module according to claim 1, characterized in that: The first low-power operational amplifier, the first resistor, the second resistor, the third resistor, the fourth resistor, and the fifth resistor form a current pump, and the current pump enables the first conversion module to have a high output impedance characteristic.

7. The voltage-to-current conversion module according to claim 1, wherein: The second low-power operational amplifier, the sixth resistor, and the seventh resistor form an inverting amplifier, and the inverting amplifier is used to expand the dynamic range of the excitation signal.

8. The voltage-to-current conversion module according to claim 1, characterized in that: The voltage-to-current conversion module generates a square wave type current excitation based on the square wave signal; or The voltage-to-current conversion module generates a sinusoidal type current excitation based on the sinusoidal signal.

9. The voltage-to-current conversion module according to claim 1, characterized in that: The current excitation device adopts a single power supply mode, the grounding of the voltage-current conversion module is connected to the equipotential point, and the excitation current output by the voltage-current conversion module is relative to the equipotential point.

10. The voltage-to-current conversion module according to claim 1, characterized in that: The non-phase input terminal of the first low-power operational amplifier is connected to a switching module in the current excitation device, and the switching module is used to select and generate two types of excitation currents: sinusoidal and square waves.

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