Patent Application
20200261727
The present disclosure relates generally to a multi-channel electric stimulator used in biomedical engineering, in particular, in neural prostheses, such as a deep brain stimulator, a cochlear prosthesis, and a retinal prosthesis, to stimulate a nerve using electric current.
The information disclosed in the Background of the Invention section is only for the enhancement of understanding of the background of the invention, and should not be taken as an acknowledgment or as any form of suggestion that this information forms a prior art that would already be known to those skilled in the art.
In general, a neural implant refers to an electronic device replacing the function of a damaged nerve or restricting undesirable neural activity by electrically stimulating the nerve. Such neural prostheses may include a cochlear prosthesis, a retinal prosthesis, a deep brain stimulator, and the like. A related-art is disclosed in Korean Patent Application No. 10-2007-0051150 (titled “Electric Stimulator”).
In such a neural implant,
This phenomenon in the nerve stimulation is undesirable, since an accurate level of stimulation is important. Thus, to prevent this phenomenon in the nerve stimulation, a length of time, during which voltages on both ends of the DAC are stabilized, is provided by adding a DAC switching state. However, this solution may not be effective when applied to the multi-channel electric stimulator having a large number of channels, and a new multi-channel electric stimulator for a neural implant is demanded.
Patent Document 1: Korean Patent Application No. 10-2007-0051150 (filed on May 26, 2007; titled “Electric Stimulator”)
Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention proposes a multi-channel electric stimulator for a neural implant. The multi-channel electric stimulator for a neural implant has a simple and effective structure, by which a biphasic current pulse can be prevented from having current noise induced digital-to-analog converter (DAC) switching noise when the multi-channel electric stimulator stimulates the nerve.
In order to achieve the above object, according to one aspect of the present invention, there is provided a multi-channel electric stimulator for a neural implant. The multi-channel electric stimulator supplies direct current to stimulate the nerve in the sequence of stimulation. When the nerve is stimulated using a nerve stimulation channel earlier in the sequence of stimulation among adjacent nerve stimulation channels, a nerve stimulation channel next in the sequence of stimulation among the adjacent nerve stimulation channels stands by, with an electric current thereof being modified into a direct current (DC) level.
More specifically, when none of two DACs connected to a multiplexer connected to a biphasic current pulse generator (BCG) are selected by the multiplexer and another pulse waveform is generated, electric current is modified to a current level to flow at a selected point in time. Accordingly, the magnitude of the electric current is modified before the standby operation, and the electric current is allowed to flow, with the magnitude thereof being determined, when a next stimulation pulse is generated.
According to embodiments, DAC switching noise induced by the occurrence of a biphasic current pulse is not transferred to the circuit, and thus no current noise induced by DAC switching noise is created in a biphasic current pulse.
In addition, it is possible to reduce stimulation pulse intervals as small as possible in the case of continuous interleaved sampling (CIS) stimulation, thereby providing an electric stimulation circuit having a higher pulse rate. Thus, it is possible to reduce inter-channel intervals, thereby performing CIS stimulation using more channels in a predetermined time.
Furthermore, the multi-channel electric stimulator can be effectively used in a cochlear prosthesis provided with a large number of channels.
The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:
Reference will now be made in greater detail to an exemplary embodiment of the present invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.
As illustrated in
In addition, the DC generator 300-1, 300-2, and 302 according to an exemplary embodiment includes a multiplexer 302 to alternately and sequentially select DC-supplying operations according to the nerve stimulation channels. In addition, the DC generator 300-1, 300-2, and 302 includes a DAC circuit comprised of a plurality of DACs. Due to the DAC circuit comprised of the plurality of DACs, the DC generator 300-1, 300-2, and 302 has an operation of controlling a channel to stand by, with the electric current thereof modified into a DC level, when selected for a point in time, at which another pulse is generated, without being selected by the multiplexer 302, and supplying direct current at a point in time, at which a next stimulation pulse is generated.
The DC generator 300-1, 300-2, and 302 is configured to supply direct current in response to nerve stimulation in the sequence of stimulation by causing a nerve stimulation channel next in the sequence of stimulation among adjacent nerve stimulation channels to stand by, with the electric current of the next nerve stimulation channel being modified into a DC level, in a case of nerve stimulation using a nerve stimulation channel earlier in the sequence of stimulation among the adjacent nerve stimulation channels. Due to the DC generator 300-1, 300-2, and 302, DAC switching noise is not transferred to the circuit. The DC generator 300-1, 300-2, and 302 determines the magnitude of nerve stimulation current.
The BCG 301 generates biphasic current pulses by switching direct current according to the nerve stimulation channels. The BCG 301 includes DC switches to generate biphasic current pulses according to the nerve stimulation channels. In addition, the BCG generates biphasic current pulses by performing switching using the switches differently according to the nerve stimulation channels. Accordingly, the nerve is stimulated by the biphasic current pulses.
The controller (not shown) controls the switching operation of the BCG 301, in the sequence of stimulation, which is set according to the nerve stimulation channels.
In addition, the DC generator 300-1, 300-2, and 302 according to an exemplary embodiment illustrated in
In a case of nerve stimulation according to the nerve stimulation channels comprised of two channels, including a first channel that is first in the sequence of stimulation, and a second channel that is next in the sequence of stimulation, the multiplexer 302 connects the first channel to a DAC and supplies direct current to the first channel, with first priority according to the set sequence of stimulation. Here, when the multiplexer 302 is selected by another DAC, the second channel stands by, with the electric current thereof being previously modified into a DC level. Afterwards, the second channel is connected to the DAC, with second priority according to the set sequence of stimulation, and direct current is supplied to the second channel. In the same manner, when selected by the multiplexer 302, another DAC causes the first channel to stand by, with the electric current thereof being previously modified into a DC level. Accordingly, DC supplying operations are alternately and sequentially selected in the set sequence of stimulation, according to the nerve stimulation channels.
Each of the DAC circuits 300-1 and 300-2 includes a plurality of DACs according to DC levels. In addition, since each of the DAC circuits 300-1 and 300-2 is comprised of the plurality of DACs, when a channel is not selected by the multiplexer 302 and another pulse waveform is generated, the DAC circuits 300-1 and 300-2 cause the channel to stand by, with the electric current of the channel being modified into a level of direct current to be supplied at a point in time at which the channel will be selected. The point in time is a point in time at which another stimulation biphasic current pulse is generated according to an exemplary embodiment. Afterwards, when a next stimulation biphasic current pulse is generated, the DAC circuits 300-1 and 300-2 allow current to flow by determining the magnitude of current, due to the plurality of DACs. Consequently, DAC switching noise is not transferred to the circuit.
In addition, in the DAC according to an exemplary embodiment illustrated in
Specifically, each of the plurality of DACs of the DAC circuits according to an exemplary embodiment includes a clock circuit (not shown) to generate a DC level change clock at a point in time, at which another pulse is generated, not selected by the multiplexer, and to generate a digital signal generation clock when selected. In addition, each of the DAC circuits according to an exemplary embodiment includes a digital terminal (not shown) that causes a channel to stand by, with the electric current of the channel being modified into a DC level, at the DC level change clock when selected by the multiplexer and converts direct current into an analog signal by determining the magnitude of the direct current and allowing the direct current to flow at the digital signal generation clock.
The clock circuit (not shown) generates a DC level change clock at a point in time, at which another stimulation biphasic current pulse is generated, without being selected by the multiplexer. In addition, fundamentally, the clock circuit (not shown) outputs a digital signal generation clock when selected by the multiplexer.
The digital terminal (not shown) synchronizes the direct current with the DC level change clock, so that the direct current stands by, with the direct current being modified to a DC level that is to be supplied when selected by the multiplexer. In addition, the digital terminal (not shown) synchronizes the direct current with the digital signal generation clock and causes the direct current to flow by determining the magnitude of the direct current. Consequently, the digital terminal (not shown) converts the direct current of the digital signal, generated as above, into an analog signal, in response to the switching of the BCG.
As illustrated in
As illustrated in
In addition, in the case of nerve stimulation according to the nerve stimulation channels, the multiplexer alternately and sequentially selects DC supplying operations in the set sequence of stimulation according to the nerve stimulation channels (S502).
Then, when a channel is not selected by the multiplexer, the double-buffering two DAC circuits cause the channel to stand by, with the electric current of the channel being modified into a current level to be supplied at a point in time at which another stimulation biphasic current pulse is generated. In addition, when the channel is selected by the multiplexer, the DAC circuits allow direct current to flow by determining the magnitude of the direct current at a point in time at which a next stimulation biphasic current pulse is generated (S503). The above-described operations according an exemplary embodiment are performed whenever channels are changed. More particularly, the two DACs alternately repeats the operation of previously modifying the magnitude of electric current and the operation of supplying direct current by determining the magnitude of the D current in response to generation of a stimulation pulse. The operations performed as described above are based on the concept of double buffering according to an exemplary embodiment.
Accordingly, DAC switching noise is not transferred to the circuit.
In addition, a biphasic current pulse for nerve stimulation is generated by switching the above-described direct current, in response to the switching of the BCB.
Consequently, the nerve stimulated is, thereby replacing the function of a damaged nerve or restricting undesirable neural activity.
As set forth above, according to exemplary embodiments, in a case of nerve stimulation using a nerve stimulation channel earlier in the sequence of stimulation among adjacent nerve stimulation channels, a nerve stimulation channel next in the sequence of stimulation among the adjacent nerve stimulation channels stands by, with the electric current thereof being modified into a DC level, and direct current is supplied in response to nerve stimulation in the sequence of stimulation.
For example, when none of the two DACs connected to the multiplexer connected to the BCG is selected another pulse waveform is generated, electric current is modified to a current level to flow at a point in time of selection. Thus, the channel is caused to stand by, with the magnitude of electric current thereof being modified. When a next stimulation pulse is generated, the magnitude of electric current is determined and the electric current is allowed to flow, so that DAC switching noise is not transferred to the circuit. Accordingly, it is possible to reduce stimulation pulse intervals as small as possible in the case of continuous interleaved sampling (CIS) stimulation, thereby providing an electric stimulation circuit having a higher pulse rate. Thus, it is possible to reduce inter-channel intervals, thereby performing CIS stimulation using more channels in a predetermined time.
Although the exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present invention as disclosed in the accompanying claims.
It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.
As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.
