Constant current circuit for human electrical stimulation

Abstract

This invention provides a constant current circuit for human body electrical stimulation, comprising: an MCU having a first port and a second port for selectively outputting digital voltage signals; a first link comprising a first digital-to-analog converter and a first operational amplifier connected in sequence, wherein the first digital-to-analog converter can convert the received digital voltage signal into a positive analog voltage signal and output it externally, and the output terminal of the first operational amplifier is electrically connected to a current output terminal; a second link comprising a second digital-to-analog converter and a second operational amplifier connected in sequence, wherein the second digital-to-analog converter can convert the received digital voltage signal into a negative analog voltage signal and output it externally, and the output terminal of the second operational amplifier is electrically connected to the current output terminal; and a switch selector selectively conducting the electrical connection between the first link and the current output terminal and selectively conducting the electrical connection between the second operational link and the current output terminal.

Description

Technical Field

[0001] This utility model relates to the field of medical device technology, and in particular to a constant current circuit for human electrical stimulation. Background Technology

[0002] Electrical stimulation is a beneficial method for neuromuscular rehabilitation and can be used to treat many diseases. For example, electrical stimulation of the radial and median nerves at the wrist can relieve essential tremor; electrical stimulation of the brain has been widely used in motor disorders such as Parkinson's disease and congenital torticollis, and can even be used as an adjunct treatment for epilepsy; patients with sequelae of cerebral hemorrhage and cerebral thrombosis who experience limited limb movement, numbness on one side of the body, or impaired motor function can all benefit from electrical stimulation and limb function rehabilitation training to promote functional recovery.

[0003] Because the impedance of human skin varies considerably depending on the individual, time, condition, humidity, and temperature, the current generated when stimulating the human body with a voltage source will fluctuate significantly depending on the skin impedance. The safe current that the human body can tolerate is only 10mA; the higher the current intensity, the greater the risk of death; the longer the duration, the greater the possibility of death. Therefore, to avoid injury or even accidental death to the user due to fluctuating current during electrical stimulation, a constant current method is usually used for electrical stimulation. Utility Model Content

[0004] The purpose of this invention is to provide a novel constant current circuit for human electrical stimulation.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a constant current circuit for human electrical stimulation, the constant current circuit having a current output terminal for externally outputting current, the constant current circuit comprising: an MCU having a first port and a second port for selectively outputting digital voltage signals; a first link coupled between the MCU and the current output terminal, the first link comprising a first digital-to-analog converter and a first operational amplifier electrically connected in sequence, the first digital-to-analog converter being electrically connected to the first port of the MCU and capable of receiving digital voltage signals from the first port, the first digital-to-analog converter converting the received digital voltage signals into positive analog voltage signals for external output, and the output terminal of the first operational amplifier being electrically connected to the... A current output terminal; a second link, coupled between the MCU and the current output terminal, the second link including a second digital-to-analog converter and a second operational amplifier electrically connected in sequence, the second digital-to-analog converter being electrically connected to a second port of the MCU and capable of receiving digital voltage signals from the second port, the second digital-to-analog converter converting the received digital voltage signals into negative analog voltage signals and outputting them externally, the output terminal of the second operational amplifier being electrically connected to the current output terminal; and a switch selector, the switch selector being signal-connected to the MCU and configured to selectively conduct the electrical connection between the first link and the current output terminal and selectively conduct the electrical connection between the second link and the current output terminal.

[0006] In the above technical solution, preferably, the first link further includes a first load resistor coupled between the first operational amplifier and the switch selector. More preferably, the first link further includes a first gain resistor coupled between the first digital-to-analog converter and the positive input terminal of the first operational amplifier, a second gain resistor coupled between the ground terminal and the negative input terminal of the first operational amplifier, a third gain resistor coupled between the negative input terminal and the output terminal of the first operational amplifier, and a fourth gain resistor coupled between the positive input terminal of the first operational amplifier and the downstream end of the first load resistor.

[0007] In the above technical solution, preferably, the second link further includes a second load resistor coupled between the second operational amplifier and the switch selector. More preferably, the second link further includes a fifth gain resistor coupled between the second digital-to-analog converter and the positive input terminal of the second operational amplifier, a sixth gain resistor coupled between the ground terminal and the negative input terminal of the second operational converter, a seventh gain resistor coupled between the negative input terminal and the output terminal of the second operational amplifier, and an eighth gain resistor coupled between the positive input terminal of the second operational amplifier and the downstream end of the second load resistor.

[0008] In the above technical solution, preferably, the constant current circuit further includes a load resistor coupled between the switch selector and the current output terminal.

[0009] The constant current circuit provided by this utility model has a first link for outputting positive current and a second link for outputting negative current. In actual operation, a digital voltage signal can be continuously applied to the first and second links via an MCU, and the electrical connection between the first link and the current output terminal, and between the second link and the current output terminal, can be selectively established via a switch. Understandably, the frequency of the current output by this constant current circuit is limited only by the operating time and frequency of the switch selector, and is not affected by the frequency of the MCU and the various digital-to-analog converters, thus adapting to higher-frequency medical applications. Attached Figure Description

[0010] Figure 1 This is the constant current stimulation circuit that the applicant used earlier;

[0011] Figure 2 This embodiment provides a constant current circuit for human electrical stimulation.

[0012] Figure 3 A circuit diagram of an operational amplifier circuit that can be implemented according to this embodiment;

[0013] Figure 4 for Figure 2 The diagram shows the electrical signal of the constant current circuit during electrical stimulation. Detailed Implementation

[0014] To explain in detail the technical content, structural features, achieved objectives and effects of this application, the technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings.

[0015] In this application, the term "electrical connection" means that two objects are directly electrically connected or indirectly electrically connected through conductive components (such as resistors or selectively conducting switches).

[0016] In this application, the term "coupled" refers to a physical connection method that enables an electrical connection. For example, "the second link further includes a second load resistor coupled between the second operational amplifier and the switch selector" means that the second circuit also includes a second load resistor located between the second operational amplifier and the switch selector, and the second operational amplifier, the second load resistor, and the switch selector are electrically connected in sequence.

[0017] Figure 1 The circuit shown is a constant current stimulation circuit previously used by the applicant, which can apply a continuous rated current to stimulate specific parts of the human body. As shown in the figure, the constant current circuit includes an MCU (Microcontroller Unit) as a power supply, a digital-to-analog converter that converts the digital voltage signal output by the MCU into an analog voltage signal, an operational amplifier that amplifies (or reduces) the analog voltage signal output by the digital-to-analog converter by a certain gain before outputting it externally, and a load resistor that transmits the analog voltage signal output by the operational amplifier to the stimulated object with a constant current.

[0018] When this constant current circuit operates, the voltage accuracy of the MCU's output is relatively low. The voltage stimulation signal received by the analog-to-digital converter (ADC) is converted into positive and negative voltages with a reference voltage of zero. However, the ADC in this constant current circuit requires a certain amount of time to switch from a positive to a negative output value (this time is often called settling time, which is the time required for the ADC output to change from one steady state to another). Furthermore, the MCU and ADC in this type of constant current circuit typically operate at relatively low frequencies. Due to these two limitations, this type of constant current circuit exhibits significant distortion in therapeutic paradigms with higher output current frequencies. This, to some extent, reduces the therapeutic effect of electrical stimulation on the human body.

[0019] Figure 2 This invention illustrates a constant current circuit that can apply a continuous rated current to a specific location on the human body (such as a nerve, acupoint, or muscle). Specifically, the constant current circuit includes a power supply module, a first link, a second link, and a switch selector. The first and second links are configured to accept voltage from the power supply module and convert the received voltage into currents of opposite polarities to be delivered to the current output terminal. Figure 2 The medium current output terminal is located downstream of the switch selector. When performing electrical stimulation in this constant current circuit, the current output terminal contacts the stimulation point of the human body through methods such as application to provide constant current stimulation to the human body.

[0020] In this embodiment, the power supply module is an MCU, which has at least two selectively output digital voltage signals V. mcuThe first and second ports. It should be noted that all voltages output by the MCU are positive.

[0021] The first link is coupled between the MCU and the current output terminal, and includes a first digital-to-analog converter electrically connected to a first port on the MCU. Figure 2 (referred to as DAC+ in the text) The first digital-to-analog converter is configured to accept a digital voltage signal from a first port on the MCU and convert the digital voltage signal into a positive analog voltage signal with a reference voltage of zero (i.e., an analog voltage signal with a potential higher than zero).

[0022] The second link is coupled between the MCU and the current output terminal, and includes a second digital-to-analog converter electrically connected to a second port on the MCU. Figure 2 (Indicated by DAC-), the second digital-to-analog converter is configured to accept a digital voltage signal from a second port on the MCU and convert the digital voltage signal into a negative analog voltage signal with a reference voltage of zero (i.e., an analog voltage signal with a potential below zero).

[0023] The first link also includes a first operational amplifier electrically connected to the first digital-to-analog converter. Figure 2 (Indicated by OPA+), the first operational amplifier receives a positive analog voltage signal from the first digital-to-analog converter and amplifies (or reduces) the positive analog voltage signal based on a certain gain factor before outputting it externally. The first operational amplifier includes a positive input terminal electrically connected to the positive input terminal of the first digital-to-analog converter, a negative input terminal electrically connected to the ground terminal (i.e., at zero potential; in this embodiment, the zero potential can be provided by a human body receiving electrical stimulation or by the zero potential port on the MCU), and an output terminal for outputting an analog voltage signal. To more accurately control the analog voltage signal output by the first operational amplifier, i.e., to improve the current accuracy of the constant current circuit's output, the gain factor of the first operational amplifier in this embodiment is less than 1, thereby allowing for a larger voltage variation at the MCU output.

[0024] The first link also includes a first load resistor electrically connected to the first operational amplifier. Figure 2 China and Israel R shunt (Illustrated), the first load resistor is used to transmit the analog voltage signal output from the first operational amplifier to the stimulated object in the form of a constant current. Combined with... Figure 3 Here, a feasible operational amplifier circuit is provided. For example... Figure 3As shown, the first link also includes a first gain resistor R1 coupled between the first digital-to-analog converter and the positive input port of the first operational amplifier, a second gain resistor R2 coupled between the ground terminal and the negative input port of the first operational amplifier, a third gain resistor R3 coupled between the output terminal and the negative input terminal of the first operational amplifier, and a fourth gain resistor R4 coupled between the downstream end of the first load resistor (i.e., the end of the first load resistor closer to the current output section). (The formula is used to...) (where V) p V is the output voltage of the first digital-to-analog converter. n The ground electrode has zero potential; R1, R2, R3, R4 and R shunt These represent the resistance values ​​of the first, second, third, and fourth gain resistors, as well as the first load resistor. Understandably, by adjusting the input voltage V... p The output current I can be adjusted by varying the values ​​of the gain resistors. stimulate .

[0025] The second link also includes a second operational amplifier that is electrically connected to the second digital-to-analog converter. Figure 2 (Indicated by OPA+), this second operational amplifier receives a negative analog voltage signal from the second digital-to-analog converter and amplifies (or reduces) the positive analog voltage signal based on a certain gain factor before outputting it. The second operational amplifier includes a positive input terminal electrically connected to the second digital-to-analog converter, a negative input terminal electrically connected to ground, and an output terminal for outputting the analog voltage signal. To more accurately control the analog voltage signal output by the second operational amplifier, i.e., to improve the current accuracy of the constant current circuit's output, the gain factor of the second operational amplifier in this embodiment is less than 1, thereby allowing for a larger voltage variation at the MCU output.

[0026] The second link also includes a second load resistor electrically connected to the second operational amplifier. Figure 2 China and Israel R shunt (Illustrated), the second load resistor is used to transmit the analog voltage signal output by the second operational amplifier to the stimulated object in a constant current. Similarly, an operational amplifier circuit that can be implemented is provided here. The second link also includes a fifth gain resistor coupled between the second digital-to-analog converter and the positive input port of the second operational amplifier, a sixth gain resistor coupled between the ground terminal and the negative input port of the second operational amplifier, a seventh gain resistor coupled between the output terminal and the negative input terminal of the second operational amplifier, and an eighth gain resistor coupled between the downstream ends of the second load resistor. To avoid redundancy, the circuit diagram and current conversion formula of this operational amplifier circuit are not provided here; the reader can refer to the operational amplifier circuit of the first link described above.

[0027] The switch selector is connected to and controlled by the MCU signal. The switch selector is configured to selectively conduct the electrical connection between the first link and the current output terminal and selectively conduct the electrical connection between the second link and the current output terminal.

[0028] In other embodiments, the first and second load resistors can be omitted, and the technical effect of transmitting the analog voltage signals output by the first and second operational amplifiers to the stimulated object with a constant current can be achieved by coupling a load resistor between the switch selector and the current output terminal. Combined with Figure 4 The working principle of the constant current circuit provided in this embodiment is explained below: When the constant current circuit performs human electrical stimulation, the first and second interfaces of the MCU output two different digital voltage signals of varying high and low values ​​(this embodiment uses 2.65V and 0.65V digital voltage signals output by the first and second interfaces of the MCU for explanation; similarly, the values ​​below are for illustrative purposes only and are not limitations on the values ​​in this embodiment); the first digital-to-analog converter of the first link converts the 2.65V digital voltage signal into a 1V analog voltage signal and sends it to the first operational amplifier; the second digital-to-analog converter of the second link converts the 0.65V digital voltage signal into a -1V analog voltage signal and sends it to the second operational amplifier; the first operational amplifier and the first load resistor of the first link convert the 1V analog voltage signal into a 5mA stimulation current for external transmission; the second operational amplifier and the second resistive load of the second link convert the -1V analog voltage signal into a -5mA stimulation current for external transmission; the MCU controls the switch selector with a tremor stimulation paradigm, so that the first and second interfaces alternately conduct according to a certain pattern, and a stimulation current I that conforms to the stimulation paradigm can be obtained after passing through the switch selector. simulate .

[0029] Understandably, in the process of human electrical stimulation, the constant current circuit provided by this invention continuously applies digital voltage signals to the first and second links via the MCU. The first and second links continuously convert the digital voltage signals into stimulation current, and finally, the electrical connections between the first link and the current output terminal, and between the second link and the current output terminal, are selectively connected via switches. During this process, the frequency of the current output by the constant current circuit is limited only by the operating time and frequency of the switch selector, and is not affected by the frequency of the MCU and the various digital-to-analog converters, thus adapting to higher-frequency medical procedures.

[0030] The above embodiments are only for illustrating the technical concept and features of this application, and are intended to enable those skilled in the art to understand the content of this application and implement it accordingly. They should not be construed as limiting the scope of protection of this application. All equivalent changes or modifications made in accordance with the spirit of this application should be included within the scope of protection of this application.

Claims

1. A constant current circuit for electrical stimulation of the human body, said constant current circuit having a pair of current output terminals for external output of current, characterized in that The constant current circuit includes: The MCU has a first port and a second port that can selectively output digital voltage signals. The first link is coupled between the MCU and the current output terminal. The first link includes a first digital-to-analog converter and a first operational amplifier connected in sequence. The first digital-to-analog converter is electrically connected to a first port of the MCU and can receive digital voltage signals from the first port. The first digital-to-analog converter can convert the received digital voltage signals into positive analog voltage signals and output them externally. The output terminal of the first operational amplifier is electrically connected to the current output terminal. A second link, coupled between the MCU and the current output terminal, includes a second digital-to-analog converter and a second operational amplifier electrically connected in sequence. The second digital-to-analog converter is electrically connected to a second port of the MCU and can receive digital voltage signals from the second port. The second digital-to-analog converter can convert the received digital voltage signals into negative analog voltage signals and output them externally. The output terminal of the second operational amplifier is electrically connected to the current output terminal. A switch selector is signal-connected to the MCU and configured to selectively enable the electrical connection between the first link and the current output terminal and to selectively enable the electrical connection between the second link and the current output terminal.

2. The constant current circuit of claim 1, wherein, The first link also includes a first load resistor coupled between the first operational amplifier and the switch selector.

3. The constant current circuit of claim 2, wherein, The first link further includes a first gain resistor coupled between the first digital-to-analog converter and the positive input terminal of the first operational amplifier, a second gain resistor coupled between the ground terminal and the negative input terminal of the first operational amplifier, a third gain resistor coupled between the negative input terminal and the output terminal of the first operational amplifier, and a fourth gain resistor coupled between the positive input terminal of the first operational amplifier and the downstream end of the first load resistor.

4. The constant current circuit of claim 1, wherein, The second link further includes a second load resistor coupled between the second operational amplifier and the switch selector.

5. The constant current circuit of claim 4, wherein, The second link further includes a fifth gain resistor coupled between the second digital-to-analog converter and the positive input terminal of the second operational amplifier, a sixth gain resistor coupled between the ground terminal and the negative input terminal of the second operational amplifier, a seventh gain resistor coupled between the negative input terminal and the output terminal of the second operational amplifier, and an eighth gain resistor coupled between the positive input terminal of the second operational amplifier and the downstream end of the second load resistor.

6. The constant current circuit of claim 1, wherein, It also includes a load resistor coupled between the switch selector and the current output terminal.

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