CN214856669U - Current excitation device for portable electrical impedance imaging system - Google Patents

Abstract

The utility model describes a current excitation device for portable electrical impedance imaging system, current excitation device includes signal generation module, filtering module and voltage current conversion module, signal generation module is used for generating the square wave signal that the range is adjustable and frequency adjustable, filtering module is used for converting square wave signal into sinusoidal signal, voltage current conversion module is used for generating the current excitation based on sinusoidal signal, signal generation module includes high frequency clock unit, frequency divider, accurate digital analog converter and analog switch, voltage current conversion module includes first conversion module and second conversion module, according to the utility model discloses, a current excitation device for portable electrical impedance imaging system that has lower consumption and circuit structure is comparatively simple is provided.

Description

Current excitation device for portable electrical impedance imaging system

Technical Field

The utility model relates to an electrical impedance imaging field on the whole, concretely relates to a current excitation device for portable electrical impedance imaging system.

Background

The electrical impedance imaging technology has wide application in the fields of industry, biology and the like. The electrical impedance imaging technology generally refers to applying a current with a certain frequency and amplitude to a measured object through an electrode group arranged on the surface of the measured object, measuring a response voltage at the same time, and finally obtaining an image capable of reflecting the electrical impedance distribution information in the measured object by using a corresponding imaging algorithm. However, with the rapid advance of electronic science and technology, the electrical impedance imaging technology also tends to be developed in the direction of miniaturization and portability; therefore, higher updating requirements are placed on the data acquisition system, particularly on the current excitation device for generating the current excitation source.

In a conventional electrical impedance imaging system, a sinusoidal current excitation signal can only be applied to an imaging target, a scheme of a Field Programmable Gate Array (FPGA) and a high-speed Digital-to-Analog converter (DAC) is usually adopted to generate a required sinusoidal voltage excitation signal, and a voltage-to-current Conversion circuit is constructed by using elements such as an operational amplifier. The chips such as the field programmable gate array FPGA, the high-speed digital-to-analog converter DAC and the operational amplifier have high power consumption, and the circuit structure is complex, so that the field programmable gate array FPGA, the high-speed digital-to-analog converter DAC and the operational amplifier are not suitable for being applied to a portable electrical impedance imaging system which needs low power consumption design.

SUMMERY OF THE UTILITY MODEL

The present invention has been made in view of the above-mentioned state of the art, and an object of the present invention is to provide a current excitation device for a portable electrical impedance imaging system having a low power consumption and a simple circuit structure.

To this end, the present invention provides, in a first aspect, a current excitation device for a portable electrical impedance imaging system, including a signal generation module, a filtering module and a voltage-current conversion module, wherein the signal generation module is configured to generate a square wave signal with adjustable amplitude and adjustable frequency, the filtering module is configured to convert the square wave signal into a sinusoidal signal, the voltage-current conversion module is configured to generate current excitation based on the sinusoidal signal, the signal generation 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 end, a second input end and a first common output end, an output end of the precision digital-to-analog converter is connected to the first input end, the second input end is grounded, and an output end of the high-frequency clock unit is connected to an input end of the frequency divider, the precise digital-to-analog converter is used for generating a stable voltage signal with adjustable amplitude, the high-frequency clock unit is used for generating a high-frequency clock, the frequency divider is used for dividing frequency based on the high-frequency clock so as to control the connection and disconnection between the first public output end and the first input end or the second input end to realize that the first public output end outputs the square wave signal with adjustable frequency, the input end of the filter module is connected with the first public output end, the output end of the filter module is connected with the voltage and current conversion module, the voltage and current conversion module comprises a first conversion module and a second conversion module, 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, one end of the first resistor is connected with 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 with the output end of the first low-power operational amplifier, the other end of the third resistor is a current excitation positive output end, the fourth resistor is connected with the positive phase input end and the current excitation positive output end of the first low-power operational amplifier, one end of the fifth resistor is connected with the positive phase input end of the first low-power operational amplifier, the other end of the fifth resistor is connected with the filtering module, the second conversion module comprises a second low-power operational amplifier, a sixth resistor and a seventh resistor, the sixth resistor is connected with 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-consumption operational amplifier is a current excitation negative output end, and the positive phase input end of the second low-power-consumption operational amplifier is grounded. In the utility model, the current excitation device comprises a signal generation module, a filtering module and a voltage-current conversion module, and the circuit structure is simpler; the precise digital-to-analog converter can be used for obtaining a stable voltage signal with adjustable amplitude so as to generate a square wave signal with adjustable amplitude and adjustable frequency at the first common output end, in addition, a filtering module is used for obtaining a sine type exciting current, and the voltage and current conversion module comprises a first low-power-consumption operational amplifier and a second low-power-consumption operational amplifier, so that the power consumption of the current exciting device can be reduced. Thus, a current excitation device having low power consumption and a simple circuit structure can be obtained.

In addition, in the current excitation device according to the first aspect of the present invention, the high-frequency clock unit may include a high-precision crystal oscillator circuit for generating a high-frequency clock. This makes it possible to obtain a high-frequency clock with high accuracy.

In addition, in the current excitation device according to the first aspect of the present invention, optionally, 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 configured to filter out a dc component in the square wave signal to obtain an intermediate signal, and the second-order active low-pass filter is configured to filter out a higher harmonic component in the intermediate signal to obtain a sinusoidal signal. Thus, the sinusoidal signal can be obtained by filtering out the direct current component and the harmonic component.

Additionally, in the current excitation device according to the first aspect of the present invention, optionally, the current excitation device further includes a following module and a change-over switch module, the filtering module and the following module pass through the change-over switch module, the change-over switch module is connected or disconnected with the voltage-current conversion module, the change-over switch module includes a first connection end, a second connection end and a second common output end, the output end of the filtering module is connected to the first connection end, the input end of the following module is connected to the first common output end, the output end of the following module is connected to the second connection end, and the second common output end passes through the fifth resistance connection to the voltage-current conversion module to the positive input end of the first low power consumption operational amplifier. Thereby, it can be facilitated to select both types of excitation currents, sinusoidal and square wave, to be generated.

In addition, in the current excitation device according to the first aspect of the present invention, optionally, the first-order high-pass filter includes a first capacitor and an eighth resistor, and 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. Therefore, the direct-current component in the square wave signal can be filtered by the first capacitor and the eighth resistor, and the higher harmonic component in the intermediate signal can be filtered by the third low-power-consumption operational amplifier, the second capacitor, the third capacitor, the first digital potentiometer and the second digital potentiometer.

In addition, in the current excitation device according to the first aspect of the present invention, optionally, the positive phase input terminal of the third low power consumption operational amplifier is connected to the ground of the third capacitor, the negative phase input terminal of the third low power consumption operational amplifier is connected to the output terminal of the third low power consumption operational amplifier, the positive phase input terminal of the third low power consumption operational amplifier is connected to the one end of the second digital potentiometer, the other end of the second digital potentiometer is connected to the one end of the first digital potentiometer and the one end of the second capacitor, the other end of the first digital potentiometer is connected to the ground of the eighth resistor, and the other end of the second capacitor is connected to the output terminal of the third low power consumption operational amplifier. Thus, the harmonic component in the intermediate signal can be filtered.

In addition, in the current excitation device according to the first aspect of the present invention, optionally, a cut-off frequency of the second-order active low-pass filter is adjusted by the first digital potentiometer and the second digital potentiometer. Thereby, the cut-off frequency of the second order active low pass filter can be adjusted based on the requirements.

To this end, the second aspect of the present invention provides a current excitation device for a portable electrical impedance imaging system, comprising a signal generation module, a following module and a voltage-current conversion module, wherein the signal generation module is configured to generate a square wave signal with adjustable amplitude and adjustable frequency, the following module is configured to perform impedance matching on the signal generation module and the voltage-current conversion module, the voltage-current conversion module is configured to generate current excitation based on the square wave signal, the signal generation module comprises 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 end, a second input end and a first common output end, an output end of the precision digital-to-analog converter is connected to the first input end, the second input end is grounded, an output end of the high-frequency clock unit is connected to an input end of the frequency divider, the precise digital-to-analog converter is used for generating a stable voltage signal with adjustable amplitude, the high-frequency clock unit is used for generating a high-frequency clock, the frequency divider is used for dividing frequency based on the high-frequency clock so as to control the connection and disconnection between the first public output end and the first input end or the second input end to realize that the first public output end outputs the square wave signal with adjustable frequency, the input end of the following module is connected with the first public output end, the output end of the following module is connected with the voltage and current conversion module, the voltage and current conversion module comprises a first conversion module and a second conversion module, 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, one end of the first resistor is connected with 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 with the output end of the first low-power operational amplifier, the other end of the third resistor is a current excitation positive output end, the fourth resistor is connected with the positive phase input end and the current excitation positive output end of the first low-power operational amplifier, one end of the fifth resistor is connected with the positive phase input end of the first low-power operational amplifier, the other end of the fifth resistor is connected with the following module, the second conversion module comprises a second low-power operational amplifier, a sixth resistor and a seventh resistor, the sixth resistor is connected with 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-consumption operational amplifier is a current excitation negative output end, and the positive phase input end of the second low-power-consumption operational amplifier is grounded. The utility model discloses in, current excitation device includes that signal generation module, follow module and voltage current conversion module circuit structure are comparatively simple, utilizes accurate digital analog converter can obtain range adjustable steady voltage signal to generate the square wave signal that range is adjustable and frequency adjustable at first public output, in addition, utilizes and follows the module and carry out impedance matching to signal generation module and voltage current conversion module, follows the exciting current of module output square wave type, voltage current conversion module includes first low-power consumption operational amplifier and second low-power consumption operational amplifier, can reduce current excitation device's consumption from this. Thus, a current excitation device having low power consumption and a simple circuit structure can be obtained.

In addition, in the current excitation device according to the first or second aspect of the present invention, optionally, the high-frequency clock unit includes a high-precision crystal oscillator circuit for generating a high-frequency clock, the follower module is configured by an operational amplifier, and the division coefficient of the frequency divider is set by a program. Thus, a high-frequency clock with high accuracy can be obtained, the frequency division coefficient of the frequency divider can be adjusted as required, and impedance matching can be performed by the follower block including the operational amplifier.

In addition, in the current excitation device according to the first or second aspect of the present invention, optionally, the frequency divider outputs a square wave drive signal having a duty ratio of 50%.

According to the utility model discloses, a have lower consumption and the comparatively simple electric current excitation device who is used for portable electrical impedance imaging system of circuit structure.

Drawings

Embodiments of the invention will now be explained in further detail by way of example only with reference to the accompanying drawings, in which:

fig. 1 is a block diagram showing a current excitation device for a portable electrical impedance imaging system according to a first embodiment of the present invention.

Fig. 2 is a circuit diagram showing a signal generation module according to a first embodiment of the present invention.

Fig. 3 is a circuit diagram showing a filter module according to a first embodiment of the present invention.

Fig. 4 is a circuit diagram showing a voltage-current conversion module according to a first embodiment of the present invention.

Fig. 5 is a circuit diagram showing a portable electrical impedance imaging system according to a first embodiment of the present invention.

Fig. 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 invention.

Fig. 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 invention.

Fig. 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 invention.

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 invention.

Fig. 10 is a circuit diagram illustrating an isoelectric point generation module according to an example of the present invention.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals, and redundant description thereof is omitted. The drawings are schematic and the ratio of the dimensions of the components and the shapes of the components may be different from the actual ones.

It should be noted that the terms "first", "second", "third" and "fourth" etc. in the description and claims of the present invention and the above-mentioned drawings are used for distinguishing different objects, and are not used for describing a specific order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

The utility model relates to a current excitation device for a portable electrical impedance imaging system. The utility model relates to a current excitation device for portable electrical impedance imaging system can be referred to as current excitation device for short. The utility model discloses a current excitation device has lower consumption and circuit structure comparatively simple. The portable electrical impedance imaging system to which the current excitation device of the present invention is applied may be, for example, a battery-powered portable electrical impedance imaging system.

[ first embodiment ] to provide a liquid crystal display device

Fig. 1 is a block diagram showing a current excitation device 1 for a portable electrical impedance imaging system according to a first embodiment of the present invention. In some examples, as shown in fig. 1, the current excitation device 1 may include a signal generation module 10, a filtering module 20, and a voltage-to-current conversion module 30. The signal generation module 10 may be used to generate an amplitude-adjustable and frequency-adjustable square wave signal. The filtering module 20 may be used to convert a square wave signal into a sinusoidal signal. The voltage to current conversion module 30 may be used to generate a current excitation based on the sinusoidal signal.

Fig. 2 is a circuit diagram showing the signal generation module 10 according to the first embodiment of the present invention. In some examples, as described above, signal generation module 10 may be used to generate square wave signals that are adjustable in amplitude and adjustable in frequency.

In some examples, as shown in fig. 2, the signal generation module 10 may include a high frequency clock unit 11.

In some examples, the high frequency clock unit 11 may generate a high frequency clock. Specifically, the high-frequency clock unit 11 may include a high-precision crystal oscillator circuit. A high precision crystal oscillator circuit may be used to generate the high frequency clock. In this case, a high-frequency clock with high accuracy can be obtained.

In some examples, the frequency of the high frequency clock may be, for example, 8MHz or 33MHz (megahertz). The frequency of the high frequency clock of the examples of the present invention is not limited thereto.

In some examples, as shown in fig. 2, signal generation module 10 may include a frequency divider 12.

In some examples, the input of divider 12 may be connected to the output of a high frequency clock unit.

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

In some examples, divider 12 may have a division factor.

In some examples, divider 12 may divide based on a high frequency clock. Thereby, frequency adjustment can be achieved. In other words, the frequency divider 12 can divide the high frequency clock by a division coefficient.

In some examples, the division factor of divider 12 may be set by a program. Thus, the frequency division coefficient of the frequency divider can be adjusted on demand.

In some examples, frequency divider 12 may output a square wave drive signal with a 50% duty cycle.

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

In some examples, the frequency of the drive signal may be affected by a frequency division factor and the frequency of the high frequency clock. In some examples, if the division coefficient of the frequency divider 12 is set by a program, adjustment of the frequency of the drive signal can be achieved.

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

In some examples, divider 12 may control switching between the first common output and the first input or the second input (described later). In this case, the frequency dividers 12 with different frequency division coefficients can realize that the first common output end outputs the square wave signal with adjustable frequency by controlling the on-off between the first common output end and the first input end or the second input end. In other words, the frequency divider 12 may divide 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, so as to enable the first common output terminal to output the square wave signal with adjustable frequency. For example, the frequency divider 12 may 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, so that the first common output terminal outputs the square wave signal with adjustable frequency.

In some examples, as shown in fig. 2, the signal generation module 10 may include a precision digital-to-analog converter 13. A precision digital-to-analog converter 13 may be used to generate the voltage signal.

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 may generate a constant voltage signal.

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 may generate constant voltage signals having different voltage values according to the demand. In this case, the precision digital-to-analog converter 13 is capable of generating a regulated voltage signal with adjustable amplitude.

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

In some examples, as shown in fig. 2, the signal generation 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 end is communicated with the first input end, the first common output end can be disconnected with the second input end; if the first common output is disconnected from the first input, the first common output may be connected to the second input. I.e. the analog switch 14 may be an alternative switch.

In some examples, the first input may be connected to an output of the precision digital-to-analog converter 13. The second input terminal may be connected to ground. Here, the ground means actual ground. In other words, the first input terminal may input the stable voltage signal. The second input terminal may input a ground level signal.

In some examples, the first common output may be switched on and off with the first input or the second input by control of the frequency divider 12. In other words, the first common output terminal may be controlled by the driving signal generated by the frequency divider 12 to switch on and off with the first input terminal or the second input terminal. In this case, the first common output terminal may output a square wave signal that is adjustable in amplitude and adjustable in frequency.

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

In some examples, the first common output may be connected to an input of a filtering module 20 (described later).

Fig. 3 is a circuit diagram showing the filter module 20 according to the first embodiment of the present invention.

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

In some examples, as shown in fig. 5, the input of the filtering module 20 may be connected to a first common output. The output terminal of the filtering module 20 may be connected to a voltage-current conversion module 30 (described later).

In some examples, as shown in fig. 3, the filtering module 20 may include a first order high pass filter a. The first-order high-pass filter a can be used for filtering out the dc component in the square wave signal to obtain an intermediate signal.

In some examples, as shown in fig. 3, the first order high pass filter a may include a first capacitor 21 and an eighth resistor 22. In this way, the first capacitor 21 and the eighth resistor 22 can filter out the dc component in the square wave signal.

In some examples, one end of the first capacitor 21 is an input terminal of the filtering module 20. The other terminal of the first capacitor 21 is connected to ground via an eighth resistor 22 (see fig. 3).

In some examples, as shown in fig. 3, the filtering module 20 may include a second-order active low-pass filter B. The second-order active low-pass filter B can be used to filter out higher harmonic components in the intermediate signal to obtain a sinusoidal signal.

In some examples, as shown in fig. 3, 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 filter out harmonic components in the intermediate signal.

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

In some examples, as shown in fig. 3, the non-inverting input terminal of the third low power operational amplifier 23 is grounded through a 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 non-inverting input terminal of the third low power operational amplifier 23 is connected to one terminal 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 connected to ground through an eighth resistor 22. The other end of the second capacitor 24 is connected to the output end of the third low power operational amplifier 23.

In some examples, the second order active low pass filter B may have a cut-off frequency.

In some examples, the cut-off frequency of the second-order active low-pass filter B may be adjusted by the first and second digital potentiometers 26 and 27. Thereby, the cut-off frequency of the second order active low pass filter can be adjusted based on the requirements. In this case, the second-order active low-pass filter B may employ a digital potentiometer to adjust the cutoff frequency by programming.

In some examples, the output of the third low power operational amplifier 23 may be the output of the filtering module 20. The output of the filtering module 20 may output a sinusoidal signal.

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.

Fig. 4 is a circuit diagram showing a voltage-current conversion module 30 according to a first embodiment of the present invention. Fig. 5 is a circuit diagram showing a portable electrical impedance imaging system according to a first embodiment of the present invention.

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

In some examples, as shown in fig. 4, the voltage-to-current conversion module 30 may include a first conversion module C. The input of the voltage-to-current conversion module 30 may be an input of the first conversion module C. The output of the voltage-to-current conversion module 30 is a differential output. In particular, the output of the voltage to current conversion module 30 may include a current-driven positive output and a current-driven negative output. The current excitation positive output and the current excitation negative output may form a current excitation. The current-driven positive output may be the output of the first conversion module C. The current-driven negative output may be an output of the second conversion module D.

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

In some examples, as shown in fig. 4, 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.

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 may constitute a current pump. Thereby, the first conversion module C can be made to have a high output impedance characteristic.

In some examples, as shown in fig. 4, 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 consumption operational amplifier 31 are connected through a second resistor 34. One end of the third resistor 35 is connected to the output end of the first low power operational amplifier 31. The other end of the third resistor 35 is a current-driven positive output terminal. The fourth resistor 36 connects the non-inverting input terminal of the first low power consumption operational amplifier 31 and the current-driven positive output terminal I⁺. One end of the fifth resistor 37 is connected to the non-inverting input terminal of the first low power operational amplifier 31. The other end of the fifth resistor 37 may be an input terminal of the first conversion module C.

In some examples, as shown in fig. 5, the other end of the fifth resistor may be connected to the filtering module 20. In this case, the output terminal of the voltage current conversion module 30 may output a sinusoidal type excitation current.

In some examples, as shown in fig. 4, the voltage-to-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.

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 constitute an inverting amplifier. This can extend the dynamic range of the excitation signal.

In some examples, as shown in fig. 4, the sixth resistor 38 connects the output terminal of the first low power operational amplifier 31 and the negative phase input terminal of the second low power operational amplifier 32. The negative phase input terminal and the output terminal of the second low power consumption operational amplifier 32 are connected through a seventh resistor 39. The output terminal of the second low power consumption operational amplifier 32 is a current-driven negative output terminal I^-And the non-inverting input terminal of the second low power operational amplifier 32 is grounded.

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

The utility model discloses in, current excitation device 1 can include signal generation module 10, filtering module 20 and voltage-to-current conversion module 30, and circuit structure is comparatively simple, utilizes accurate digital analog converter can obtain the steady voltage signal of range adjustable to generate the square wave signal that range is adjustable and frequency-adjustable at first public output. In addition, the sinusoidal type excitation current is obtained by the filter 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, whereby the power consumption of the current excitation device 1 can be reduced. Thus, the current excitation device 1 having low power consumption and a simple circuit configuration can be obtained.

[ second embodiment ]

Fig. 6 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 invention. Fig. 7 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 invention.

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

In the second embodiment, as shown in fig. 6 or fig. 7, the output terminal of the signal generating module 10 (i.e., the first common output terminal of the analog switch 14) is connected to the input terminal of the follower module 40. Otherwise, the signal generating module 10 of the second embodiment is the same as that of the first embodiment, and specific reference may be made to the description of the first embodiment.

In some examples, as shown in fig. 6 or 7, the output of the follower module 40 is connected to the input of the voltage-to-current conversion module 30. The output of the follower module 40 outputs a square wave signal.

In some examples, the follower module 40 may be constituted by an operational amplifier.

In some examples, the follower module 40 may be a voltage follower circuit formed of an operational amplifier. In this case, the output terminal of the signal generation block 10 is connected to the non-inverting input terminal of the operational amplifier in the voltage follower circuit.

In some examples, as shown in fig. 6 or fig. 7, the input terminal of the voltage-current conversion module 30 (i.e., the other terminal of the fifth resistor) is connected to the output terminal of the follower module 40. I.e. the voltage-to-current conversion module 30 generates a square-wave type current excitation based on the square-wave signal. Otherwise, the voltage-current conversion module 30 of the second embodiment is the same as that of the first embodiment, and specific reference may be made to the description of the first embodiment.

In this embodiment, the current excitation device 1 may include a signal generation 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 adjustable frequency at a first common output end, in addition, the following module 40 is used to perform impedance matching on the signal generation module 10 and the voltage-current conversion module 30, the following module 40 outputs an excitation current of a square wave type, and the voltage-current conversion module 30 includes a first low-power operational amplifier and a second low-power operational amplifier, thereby being capable of reducing the power consumption of the current excitation device 1. Thus, the current excitation device 1 having low power consumption and a simple circuit configuration can be obtained.

[ third embodiment ] according to the present invention

Fig. 8 is a block diagram showing the current excitation device 1 for a portable electrical impedance imaging system according to the third embodiment of the present invention. 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 invention.

In the third embodiment, the current excitation device 1B for the portable electrical impedance imaging system may be simply referred to as the current excitation device 1B. As shown in fig. 8 or fig. 9, the current excitation device 1B may include a signal generation module 10, a filtering module 20, a following module 40, a switch module 50, and a voltage-current conversion module 30. The signal generating module 10, the filtering module 20, the following module 40, the switch module 50 and the voltage-current converting module 30 may be described in detail with reference to the contents of the first and second embodiments.

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

In the third embodiment, as shown in fig. 8 or 9, the switch module 50 may include a first connection terminal, a second connection terminal, and a second common output terminal. The output of the filtering module 20 may be connected to the first connection terminal. The input of the follower module 40 may be connected to a first common output. The output terminal connection of the follower module 40 may be a 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-to-current conversion module 30 via a fifth resistor. Thereby, it can be facilitated to select both types of excitation currents, sinusoidal and square wave, to be generated.

In the third embodiment, if the first connection terminal is connected to the second common output terminal, the second connection terminal may be disconnected from the second common output terminal, and the second common output terminal may output the sinusoidal signal output by the filtering module 20. If the first connection end is disconnected from the second common output end, the second connection end may be connected to the second common output end, and the second common output end may output the square wave signal output by the following module 40.

In some examples, the toggle module 50 may be program controlled. In this case, one of the sinusoidal signal output by the filtering module 20 or the square wave signal output by the following module 40 can be selected to be input to the voltage-to-current conversion module 30, thereby realizing switching of the excitation signal type.

In the present invention, the circuit elements according to the above embodiments may be powered by a low voltage power supply. In addition, the current excitation device 1 of the present invention consumes less current.

Fig. 10 is a circuit diagram illustrating an isoelectric point generation module 60 according to an example of the present invention. In some examples, the current excitation device 1 may be powered by two power sources. In this case, the grounding in the individual modules of the current excitation device 1 may be "grounded" in the usual sense. I.e. the ground in the individual modules of the current excitation device 1 may be the actual ground.

In some examples, the current excitation device 1 may be powered by a single power supply. In this case, the grounding in the various modules of the current excitation device 1 (except for the signal generation module 10) may be "virtual ground" (i.e., "isoelectric point"). In other words, the ground in each module of the current excitation device 1 may be a virtual ground.

In some examples, the voltage of the isoelectric point may be any voltage between the supply voltage and 0V. In some examples, the voltage of the isoelectric point may be half of the supply voltage.

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

In some examples, as shown in fig. 10, the isoelectric point generation 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 supply voltage may be denoted VCC. One terminal of the tenth resistor 62 may be connected to the 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 divide the power supply voltage VCC in fig. 10 to obtain an equipotential voltage.

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

In some examples, as shown in fig. 10, the negative input of the operational amplifier 64 may be connected to the output of the operational amplifier 64. In this case, the operational amplifier 64 can constitute an impedance conversion circuit, thereby increasing the driving capability of the equipotential voltage.

In some examples, the output of the operational amplifier 64 is an isoelectric point. For example, in the case of a single power supply mode, the output terminal of the operational amplifier 64 may be used to connect to the "virtual ground" of the voltage-to-current conversion module 30; the output of the operational amplifier 64 may be used to connect to the ground of the filter circuit 20. In this case, the excitation current of the output of the voltage-to-current conversion module 30 may be relative to an isoelectric point.

While the present invention has been described in detail in connection with the drawings and the examples, it is to be understood that the above description is not intended to limit the present invention in any way. The present invention may be modified and varied as necessary by those skilled in the art without departing from the true spirit and scope of the invention, and all such modifications and variations are intended to be included within the scope of the invention.

Claims (10)

1. A current excitation device for a portable electrical impedance imaging system is characterized by comprising a signal generation module, a filtering module and a voltage-current conversion module, wherein the signal generation module is used for generating square wave signals with adjustable amplitude and adjustable frequency, the filtering module is used for converting the square wave signals into sine signals, the voltage-current conversion module is used for generating current excitation based on the sine signals, the signal generation module comprises a high-frequency clock unit, a frequency divider, a precise digital-to-analog converter and an analog switch, the analog switch is provided with a first input end, a second input end and a first common output end, the output end of the precise digital-to-analog converter is connected with the first input end, the second input end is grounded, and the output end of the high-frequency clock unit is connected with the input end of the frequency divider, the precise digital-to-analog converter is used for generating a stable voltage signal with adjustable amplitude, the high-frequency clock unit is used for generating a high-frequency clock, the frequency divider is used for dividing frequency based on the high-frequency clock so as to control the connection and disconnection between the first public output end and the first input end or the second input end to realize that the first public output end outputs the square wave signal with adjustable frequency, the input end of the filter module is connected with the first public output end, the output end of the filter module is connected with the voltage and current conversion module, the voltage and current conversion module comprises a first conversion module and a second conversion module, 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, one end of the first resistor is connected with 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 with the output end of the first low-power operational amplifier, the other end of the third resistor is a current excitation positive output end, the fourth resistor is connected with the positive phase input end and the current excitation positive output end of the first low-power operational amplifier, one end of the fifth resistor is connected with the positive phase input end of the first low-power operational amplifier, the other end of the fifth resistor is connected with the filtering module, the second conversion module comprises a second low-power operational amplifier, a sixth resistor and a seventh resistor, the sixth resistor is connected with 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-consumption operational amplifier is a current excitation negative output end, and the positive phase input end of the second low-power-consumption operational amplifier is grounded.

2. Current excitation device according to claim 1,

the high frequency clock unit includes a high precision crystal oscillator circuit for generating a high frequency clock.

3. Current excitation device according to claim 1,

the filtering module comprises a first-order high-pass filter and a second-order active low-pass filter, the first-order high-pass filter is used for filtering direct-current components in the square wave signals to obtain intermediate signals, and the second-order active low-pass filter is used for filtering higher harmonic components in the intermediate signals to obtain sinusoidal signals.

4. Current excitation device according to claim 1,

the current excitation device further comprises a following module and a change-over switch module, the filtering module and the following module are connected or disconnected with the voltage and current conversion module through the change-over switch module, the change-over switch module comprises a first connecting end, a second connecting end and a second public output end, the output end of the filtering module is connected with the first connecting end, the input end of the following module is connected with the first public output end, the output end of the following module is connected with the second connecting end, and the second public output end is connected with the positive phase input end of the first low power consumption operational amplifier of the voltage and current conversion module through the fifth resistor.

5. Current excitation device according to claim 3,

the first-order high-pass filter comprises a first capacitor and an eighth resistor, and the second-order active low-pass filter comprises a third low-power operational amplifier, a second capacitor, a third capacitor, a first digital potentiometer and a second digital potentiometer.

6. Current excitation device according to claim 5,

the positive phase input end of the third low-power-consumption operational amplifier is grounded through the third capacitor, the negative phase input end of the third low-power-consumption operational amplifier is connected with the output end of the third low-power-consumption operational amplifier, the positive phase input end of the third low-power-consumption operational amplifier is connected with one end of the second digital potentiometer, the other end of the second digital potentiometer is connected with 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 with the output end of the third low-power-consumption operational amplifier.

7. Current excitation device according to claim 5,

the cut-off frequency of the second-order active low-pass filter is adjusted through the first digital potentiometer and the second digital potentiometer.

8. A current excitation device for a portable electrical impedance imaging system is characterized by comprising a signal generation module, a following module and a voltage-current conversion module, wherein the signal generation module is used for generating square wave signals with adjustable amplitude and adjustable frequency, the following module is used for carrying out impedance matching on the signal generation module and the voltage-current conversion module, the voltage-current conversion module is used for generating current excitation based on the square wave signals, the signal generation module comprises a high-frequency clock unit, a frequency divider, a precise digital-to-analog converter and an analog switch, the analog switch is provided with a first input end, a second input end and a first public output end, the output end of the precise digital-to-analog converter is connected with the first input end, the second input end is grounded, and the output end of the high-frequency clock unit is connected with the input end of the frequency divider, the precise digital-to-analog converter is used for generating a stable voltage signal with adjustable amplitude, the high-frequency clock unit is used for generating a high-frequency clock, the frequency divider is used for dividing frequency based on the high-frequency clock so as to control the connection and disconnection between the first public output end and the first input end or the second input end to realize that the first public output end outputs the square wave signal with adjustable frequency, the input end of the following module is connected with the first public output end, the output end of the following module is connected with the voltage and current conversion module, the voltage and current conversion module comprises a first conversion module and a second conversion module, 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, one end of the first resistor is connected with 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 with the output end of the first low-power operational amplifier, the other end of the third resistor is a current excitation positive output end, the fourth resistor is connected with the positive phase input end and the current excitation positive output end of the first low-power operational amplifier, one end of the fifth resistor is connected with the positive phase input end of the first low-power operational amplifier, the other end of the fifth resistor is connected with the following module, the second conversion module comprises a second low-power operational amplifier, a sixth resistor and a seventh resistor, the sixth resistor is connected with 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-consumption operational amplifier is a current excitation negative output end, and the positive phase input end of the second low-power-consumption operational amplifier is grounded.

9. Current excitation device according to claim 4 or 8,

the high-frequency clock unit comprises a high-precision crystal oscillator circuit used for generating a high-frequency clock, the following module is composed of an operational amplifier, and the frequency division coefficient of the frequency divider is set by a program.

10. Current excitation device according to claim 4 or 8,

the frequency divider outputs a square wave drive signal with a duty cycle of 50%.

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