KR102093188B1 - Multi-Bit Charge Detecting Circuit for Bio Current Stimulator - Google Patents

Abstract

Provided is a multi-bit charge amount detecting circuit for a bio-stimulator. The multi-bit charge amount detecting circuit for a bio-stimulator of the present invention comprises: a first buffer which receives a first input as an input, and has a first switch to which an output terminal is connected; a second buffer which receives a second input as an input and has a second switch to which an output terminal is connected; and a capacitor which has one end connected to the first switch and an ADC, and has the other end connected to a third switch connected to the second switch and a ground. During a charge detection operation, the first switch and the second switch are turned on, and, during an output operation, the third switch is turned on.

Description

Multi-Bit Charge Detecting Circuit for Bio Current Stimulator

The present invention relates to a charge amount detection circuit used in the charge balance operation of the deep brain stimulator.

The bio-stimulator serves to transmit visual information to the optic nerve according to the purpose of the bio-stimulator through stimulation using a current or voltage, or to stabilize the hydronephrosis and motor nerves as brain stimulation for Parkinson's disease patients. Looking at the prior art, it is being studied for the purpose of semi-permanent use in vivo by transmitting power wirelessly and wirelessly transmitting data necessary for stimulation. It is preferable to design the biostimulator using a safer current stimulator. Since it is inserted and operated in a living body, it must be small in volume, and most importantly, it must be designed to prevent electric charges from accumulating in the cell and causing damage due to stimulation in the living body.

The conventional current stimulator according to the prior art controls the direction of the current by turning on / off the switch according to the signal of the controller and controls the magnitude of the current according to the input to the DAC.

Looking at the prior art, most of the control of the stimulator uses a microcontroller unit (MCU), so it is possible to use and design complex and diverse functions, but it has a disadvantage that the MCU occupies a large volume. The previously proposed stimulation process is to input the size and time of the cathodic waveform, calculate the size and time of the anodic waveform through the MCU, and the size, time, and magnitude of the cathodic waveform. It uses a method of controlling the stimulator by inputting both the size and time of the anodic waveform. And, after one stimulation and release, there is no charge accumulated through charge balance.

Technical problem to be achieved by the present invention is to create a quantum pole waveform of a different pulse width according to the voltage difference across the channel through the current stimulator including the proposed charge detection circuit can quickly drop the voltage across the channel below the safe voltage In providing circuits. In addition, it is guaranteed to always be below the safety voltage at the end of each stimulation, and it is intended to reduce the amount of computation in the rear stage by accurately producing the digital signal of the voltage difference at both ends without a high-end ADC.

In one aspect, the multi-bit charge detection circuit for a bio-stimulator proposed in the present invention receives a first input as an input, a first buffer connected to an output terminal to a first switch, a second input as an input, and a second It includes a second buffer connected to the output terminal to the switch and a capacitor connected to the first switch and ADC, and the other terminal connected to the third switch connected to the second switch and ground, and the first switch during charge detection operation. And the second switch is turned on, and the third switch is turned on during the output operation.

In the charge detection operation, the first input and the second input are stored in the form of a voltage in the capacitor, so that the voltage difference across the channel becomes the voltage difference across the capacitor.

During the output operation, the voltage stored in the capacitor is converted to a digital signal through the ADC and output.

During the charge balancing operation, a variable stimulus length is created according to the amount of charge remaining in the capacitor, and the voltage difference across the channel is detected and converted into a digital signal.

When the voltage difference across the channel is out of the safe range, a quantum pole waveform having a different pulse width is generated according to the voltage difference across the channel so that the voltage across the channel falls below the safety voltage.

In another aspect, an operation method of a multi-bit charge amount detection circuit for a bio-stimulator proposed in the present invention includes receiving a quantum pole through a first input and receiving a negative stimulus through a second input. When the switch and the second switch are turned on, the first input and the second input are stored in the form of a voltage in the capacitor to detect a voltage difference across the channel, and a charge detection operation step to detect the voltage difference across the channel and the third switch is turned on to store the ADC in the voltage stored in the capacitor. And an output operation step that is converted into a digital signal and output.

According to embodiments of the present invention, the current stimulator including the proposed charge detection circuit generates a quantum pole waveform having a different pulse width according to the voltage difference across the channel, so the voltage across the channel can be quickly dropped below the safety voltage. It is possible to ensure that the voltage is always below the safety voltage at the end of each stimulation. In addition, it is possible to reduce the amount of calculation in the rear stage by accurately generating the voltage difference between the two stages into a digital signal without a high specification ADC.

1 is a view showing a cell and electrode model according to an embodiment of the present invention.
2 is a view showing a current stimulator according to an embodiment of the present invention.
3 is a view showing a charge balancing algorithm according to an embodiment of the present invention.
4 is a view showing a current stimulation waveform according to an embodiment of the present invention.
5 is a view showing a charge amount detector during a sampling operation and an output operation according to an embodiment of the present invention.
6 is a flowchart illustrating an operation of a multi-bit charge amount detection circuit for a bio-stimulator according to an embodiment of the present invention.
7 is a view showing a simulation result waveform according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a cell and electrode model according to an embodiment of the present invention.

The reason for the charge balancing operation can be explained from the equivalent model of the electrode. 1 is an equivalent model that mimics the electrical characteristics of cells and electrodes, and is connected to CH_N and CH_P in FIG. 2.

The equivalent resistance of the biological tissue varies depending on the position of the probe and the stimulation site directly contacting the biological tissue for stimulation, but it is generally seen as about 100KΩ, and this resistance is Rs in FIG. 1. When the probe of the stimulator is directly applied to stimulate this biological tissue, a capacitance is generated by the probe, which is about 100 nF on average. The parallel parasitic resistance Re of this capacitor is about 10 MΩ, which means that if the capacitor is charged through stimulation, it cannot be discharged by itself within a short time.

When current flows from CH_P to CH_N for current stimulation, Re has a much larger impedance than Ce, so most of the current flows to Ce, and this current forms a voltage across the capacitor. After the stimulation is over, a voltage is generated between the channels by the capacitor. When the voltage exceeds 50 mV, problems that may cause damage to biological tissues, such as electrolysis of water and a change in pH concentration, may occur. Therefore, it is important to keep the charge balance after stimulation below 50 mV.

2 is a view showing a current stimulator according to an embodiment of the present invention.

In order to perform the current stimulation with the charge balancing algorithm according to an embodiment of the present invention, the current stimulation must be possible in a dual phase and a stimulator capable of adjusting the magnitude of the current is required. The current stimulator determines the intensity of the stimulation current by receiving the DAC output as the gate voltage as M1, and M2 ~ M5 operate as a switch to determine the direction of the current.

FIG. 2 (a) shows the state in which the switches S5 and S3 are closed to flow the anode stimulation current from CH_N to CH_P, that is, to the cell. FIG. 2 (b) shows that S4 and S2 are closed to close the quantum pole current (Cathode) stimulation current) from CH_P to CH_N.

At this time, the Op-Amp applied to the M2 and M3 gate terminals makes the voltage of the drain terminal of M1 to 80mV by using the principle of virtual ground, making M1 operate in the deep triode region and the gate voltage of M1 as the current source (VDAC) To operate linearly.

3 is a view showing a charge balancing algorithm according to an embodiment of the present invention.

According to an embodiment of the present invention, by applying a positive pulse of a flexible length in accordance with the amount of charge between the two electrodes to apply a variable pulse width algorithm that quickly balances the charge to create an improved stimulation pattern than the prior art. The charge balancing algorithm proposed in the present invention is initially in a standby state, and when data is received from an external device, it proceeds with negative stimulation, and when the negative stimulation ends, it has a delay period and the amount of charge across the electrodes. To confirm. Check the amount of charge at both ends of the electrode and apply the quantum pole (Cathode Stimulation) by varying the pulse length of the current to match the charge balance according to the voltage level. Through charge detection, it is repeatedly performed until the voltage at both ends of the electrode is less than 50 mV, and when it is less than 50 mV, the stimulation is terminated and it returns to the standby state.

4 is a view showing a current stimulation waveform according to an embodiment of the present invention.

The stimulation current waveform by the algorithm applied in FIG. 4 is shown. The current stimulation consists of negative stimulation and charge balancing, and the charge balancing operation includes cathode stimulation and charge detecting.

In the charge amount detection section, the current does not flow, and at this time, the voltage difference across the cells is measured to determine whether it is below the safety voltage (50 mV), and if it is greater than the safety voltage, the quantum pole of different pulse length is repeated according to the V_electrode value in FIG. When it is less than the safe zone, the charge balancing operation ends.

The circuit proposed in the present invention is a charge amount detection circuit that calculates a voltage difference across the channel during charge detection. The prior art charge detection circuit is a circuit that only determines whether it is within or outside the safe voltage range, but the proposed circuit determines how far it is out of the safe voltage range and adjusts the length of the quantum pole as shown in FIG. 4 according to the value. You can do it.

5 is a view showing a charge amount detector during a sampling operation and an output operation according to an embodiment of the present invention.

The charge detector is an important block to determine if the voltage difference across the channel after stimulation is less than 50mV, which is a safe range, to determine whether additional charge balancing operation is necessary. However, the charge detector used in the conventional algorithms of pulse insertion and offset adjustment simply determines whether the voltage difference between the two ends is less than 50 mV. Therefore, it is unsuitable for use in an algorithm that generates different pulse waveforms depending on the magnitude of the voltage difference between both ends applied in the present invention. Therefore, the present invention proposes a new charge amount detector that can be used in a pulse width modulation algorithm.

The proposed charge detector first separated the charge measurement operation from the channel by receiving both ends of the channel as a buffer input to measure the voltage at both ends without affecting the channel. To find the potential difference between the two ends, there may be a method of converting each potential into a digital signal using two ADCs and digitally subtracting the potentials at both ends to check. However, this requires two ADCs with high effective bits and an additional subtractor, which requires a lot of power and chip area. However, the proposed charge detector converts the potential difference at both ends into a 5-bit thermometer code with one capacitor and one ADC as shown in FIG. 5.

Fig. 5 (a) is a circuit diagram during charge detection operation, and Fig. 5 (b) is a circuit diagram during output operation.

The operation of the charge amount detection circuit can be divided into a charge detection operation and an output operation. In the charge detection operation, S1 and S2 are closed during the charge detection operation as shown in FIG. 5 (a), and CH_P and CH_N are received as input and stored in the form of voltage in the capacitor C through the buffer. If the voltage across the capacitor is VP and VN, VP = CH_P and VN = CH_N. Therefore, the voltage difference across the channel is VP-VN, which is the voltage difference across the capacitor.

In the output operation as shown in FIG. 5 (b), S1 and S2 are opened and S3 is closed to lower VN to 0, and the VP value is converted into a digital signal through an ADC and output. The circuit used for the measurement according to the embodiment of the present invention was designed to output 5 bits. For example, it receives the VP as an ADC input and sends it to B <4: 0>, a 5-bit thermometer code output, to convert it into a digital signal. The proposed charge detector can measure the potential difference between two channels with only one capacitor and one ADC, thus consuming less area and power.

Through the proposed circuit, it is possible to create a variable stimulus length according to the amount of charge remaining during charge balancing operation, and it is possible to accurately detect the voltage difference across the channel and convert it into a digital signal without a high-end ADC.

6 is a flowchart illustrating an operation of a multi-bit charge amount detection circuit for a bio-stimulator according to an embodiment of the present invention.

The proposed method of operation of the multi-bit charge detection circuit for the bio-stimulator receives the quantum pole through the first input and the negative stimulus through the second input (610), the first switch and the second switch are on The first input and the second input are stored in the form of a voltage in the capacitor to detect the voltage difference across the channel, the charge detection operation step 620 and the third switch are turned on so that the voltage stored in the capacitor is converted into a digital signal through the ADC. And an output operation step 630 which is converted and output.

The current stimulation consists of negative stimulation and charge balancing, and the charge balancing operation includes cathode stimulation and charge detecting.

In the charge balancing operation including the charge detection operation step, a variable stimulus length is generated according to the amount of charge remaining in the capacitor, and a voltage difference across the channel is detected and converted into a digital signal.

When the voltage difference across the channel is out of the safe range, a quantum pole waveform having a different pulse width is generated according to the voltage difference across the channel so that the voltage across the channel falls below the safety voltage.

According to an embodiment of the present invention, by applying a positive pulse of a flexible length in accordance with the amount of charge between both electrodes to apply a variable pulse width algorithm that quickly balances the charge to create an improved stimulation pattern than the prior art. The charge balancing algorithm proposed in the present invention is initially in a standby state, and when data is received from an external device, negative stimulation proceeds, and when the negative stimulation is over, a period of rest is used to check the amount of charge across the electrodes. Check the amount of charge across the electrodes and apply the quantum pole by varying the pulse length of the current to match the charge balance according to the voltage level. Through the detection of the amount of charge, it is repeatedly performed until the voltage at both ends of the electrode is less than 50 mV, and when it is less than 50 mV, the stimulation is terminated and the state returns to the standby state.

7 is a view showing a simulation result waveform according to an embodiment of the present invention.

After the negative stimulation is over, the charge is detected and the length of the quantum pole pulse is determined according to the output bit. Since the potential difference across the channel decreases as the quantum pole progresses, the quantum pole pulse gradually decreases, and it is confirmed that the stimulus is terminated when the safety voltage is finally lower than the safety voltage.

According to embodiments of the present invention, the current stimulator including the proposed charge detection circuit generates a quantum pole waveform having a different pulse width according to the voltage difference across the channel, so the voltage across the channel can be quickly dropped below the safety voltage. It is possible to ensure that the voltage is always below the safety voltage at the end of each stimulation. In addition, it is possible to reduce the amount of calculation in the rear stage by accurately generating the voltage difference between the two stages into a digital signal without a high-end ADC.

The device described above may be implemented with hardware components, software components, and / or combinations of hardware components and software components. For example, the devices and components described in the embodiments include, for example, a processor, controller, arithmetic logic unit (ALU), digital signal processor (micro signal processor), microcomputer, field programmable array (FPA), It may be implemented using one or more general purpose computers or special purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may run an operating system (OS) and one or more software applications running on the operating system. In addition, the processing device may access, store, manipulate, process, and generate data in response to the execution of the software. For convenience of understanding, a processing device may be described as one being used, but a person having ordinary skill in the art, the processing device may include a plurality of processing elements and / or a plurality of types of processing elements. It can be seen that may include. For example, the processing device may include a plurality of processors or a processor and a controller. In addition, other processing configurations, such as parallel processors, are possible.

The software may include a computer program, code, instruction, or a combination of one or more of these, and configure the processing device to operate as desired, or process independently or collectively You can command the device. Software and / or data may be interpreted by a processing device, or to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. Can be embodied in The software may be distributed on networked computer systems, and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the medium may be specially designed and constructed for the embodiments or may be known and usable by those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs, DVDs, and magnetic media such as floptical disks. -Hardware devices specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language code that can be executed by a computer using an interpreter, etc., as well as machine language codes produced by a compiler.

As described above, although the embodiments have been described by a limited embodiment and drawings, those skilled in the art can make various modifications and variations from the above description. For example, the described techniques are performed in a different order than the described method, and / or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form from the described method, or other components Alternatively, even if replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (8)

A first buffer receiving the first input as an input and having an output terminal connected to the first switch;
A second buffer receiving the second input as an input and having an output terminal connected to the second switch; And
Capacitor with one end connected to the first switch and ADC, and the other end connected to the second switch and the third switch connected to ground.
Including,
The first switch and the second switch are turned on during the charge detection operation, and the third switch is turned on during the output operation,
During the charge balancing operation, a variable stimulus length is created according to the amount of charge remaining in the capacitor, and the voltage difference across the channel is detected to be converted into a digital signal,
If the voltage difference across the channel is outside the safety range, determine the degree of deviation and create a quantum pole waveform of different pulse width according to the voltage difference across the channel so that the voltage across the channel falls below the safety voltage.
In order to measure the voltage at both ends without affecting the channel, both ends of the channel are received as inputs through the first buffer and the second buffer, separating the charge measurement operation from the channel, and the potential difference between both ends is measured by a capacitor and one ADC. Convert to
When it is in the standby state and receives data, it proceeds with negative stimulation, and when the negative stimulation has ended, it has a rest period and checks the amount of charge across the electrodes. Multi-bit charge detection circuit that applies quantum pole (Cathode Stimulation) by varying the pulse length. According to claim 1,
In the charge detection operation, the first input and the second input are stored in the form of a voltage in the capacitor so that the voltage difference across the channel becomes the voltage difference across the capacitor.
Multi-bit charge detection circuit. According to claim 1,
During output operation, the voltage stored in the capacitor is converted to a digital signal through the ADC and output.
Multi-bit charge detection circuit. delete delete Receiving a quantum pole through a first input and a negative stimulus through a second input;
A charge detection operation step in which the first switch and the second switch are turned on so that the first input and the second input are stored in a capacitor in the form of a voltage to detect a voltage difference across the channel; And
An output operation step in which the voltage stored in the capacitor is converted to a digital signal through the ADC when the third switch is turned on and output.
Including,
During the charge balancing operation, a variable stimulus length is created according to the amount of charge remaining in the capacitor, and the voltage difference across the channel is detected to be converted into a digital signal,
If the voltage difference across the channel is outside the safety range, determine the degree of deviation and create a quantum pole waveform of different pulse width according to the voltage difference across the channel so that the voltage across the channel falls below the safety voltage.
In order to measure the voltage at both ends without affecting the channel, both ends of the channel are received as inputs through the first buffer and the second buffer, separating the charge measurement operation from the channel, and the potential difference between both ends is measured by a capacitor and one ADC. Convert to
When it is in the standby state and receives data, it proceeds with negative stimulation, and when the negative stimulation has ended, it has a rest period and checks the amount of charge across the electrodes. Applying a quantum pole (Cathode Stimulation) by varying the pulse length
Multi-bit charge detection method. delete delete

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