Voltage/current control system for a human tissue stimulator

• US 5,522,865 A
• Filed: 10/12/1994
• Issued: 06/04/1996
• Est. Priority Date: 09/22/1989
• Status: Expired due to Term

• Current Assignee: Alfred E. Mann Foundation For Scientific Research
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Schulman, Joseph H., Gord, John C., Wolfe, James H., Strojnik, Primoz, Whitmoyer, David I.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/322,068
• Time in Patent Office: 601 Days
• Field of Search: 607/55, 607/56, 607/57, 607/32, 607/60
• US Class Current: 607/56
• CPC Class Codes: A61N 1/36038 Cochlear stimulation
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• CPC Class Codes: H04R 2460/03 Aspects of the reduction of energy consumption in hearing devices
• CPC Class Codes: H04R 25/505 using digital signal processing

Abstract

A tissue stimulating system includes an external transmitter for transmitting a data signal to an implanted stimulator. The implanted stimulator includes a processor for generating stimulation signals for application to a plurality of tissue stimulating electrodes through respective isolated output channels. The implanted stimulator also includes a power supply that extracts a raw power signal from the data signal. A voltage downconverter generates at least four separate voltages from the extracted raw power signal by alternately connecting at least four capacitors in series across the raw power signal, thereby providing at least four output voltages, and then connecting the capacitors in parallel to transfer the charge stored thereon to a storage capacitor, which serves as the power source for portions of the stimulator. A selected one of the output voltages from the voltage downconverter is applied to an isolated refresh voltage capacitor in each output channel, where it controls a voltage controlled current source. The processor selectively monitors the electrodes and/or voltages generated in the stimulator and generates status indicating/measurement signals for transmission to the external transmitter. The external processor receives and processes the status indicating/measurement signals and uses the information therefrom to control the amount of power transmitted to the stimulator.

Claims

1. An implanted human tissue stimulator comprising:

receiver means for receiving a data signal from an external transmitter, the data signal comprising a series of data frames containing an end of frame signal, each data frame comprising a plurality of data words, each data word defining an amplitude for a tissue stimulating signal for a different output channel of the tissue stimulator, and a command word for controlling a processor means in the tissue stimulator;

power supply means coupled to said receiver means for extracting a raw power signal from the data signal and generating at least one power supply voltage from the raw power signal and distributing the at least one power supply voltage throughout the human tissue stimulator to provide operating power for the human tissue stimulator;

a plurality of output channels, each having a tissue stimulating electrode connected thereto; and

processor means for serially processing the plurality of data words and command word in each data frame received by the receiver means, said processor means comprising

a command detector means responsive to the command words received by said receiver means for controlling the functions of the processor means,

data word latching means for successively storing the data words received in a data frame by said receiver means, and

switch means for successively coupling amplitude voltages representative of output signals from the data word latching means to successive ones of the output channels; and

wherein

each of the plurality of output channels includes;

refresh voltage controller means for generating an isolated refresh voltage for the output channel, said refresh voltage controller means including at least one flying capacitor and means for alternately connecting the at least one flying capacitor to receive the at least one power supply voltage from the power supply means and then disconnecting the at least one flying capacitor from the power supply means to provide the isolated refresh voltage for the output channel, and

a voltage controlled current source powered by the isolated refresh voltage provided by the refresh voltage controller means for amplitude controlling, in accordance with the amplitude voltages coupled from the switch means, tissue stimulating signals to the stimulating electrode of the output channel.

2. The implanted human tissue stimulator of claim 1 wherein the power supply means comprises:

a downconverter clock means for generating a two-phase non-overlapping pair of clock signals,

voltage downconverter means for generating at least four different output voltages from the raw power signal, said voltage downconverter means including

a group of at least four capacitors,

a storage capacitor, and

means driven by the two-phase non-overlapping pair of clock signals for establishing a pattern of connections between and among the group of at least four capacitors such that during a phase 1 of the pair of clock signals the at least four capacitors are connected in series across the raw power signal, at which time the at least four different output voltages are made available on outputs from the voltage downconverter means to the refresh voltage controller means for each of the output channels, and such that during a phase 2 of the pair of clock signals the group of at least four capacitors are connected in parallel and deliver charge to the storage capacitor, which storage capacitor comprises a power source for the processor means.

3. The implanted human tissue stimulator of claim 2 wherein the raw power signal extracted from the data signal by the power supply means has a nominal value of V volts dc, and wherein the group of at least four capacitors of said voltage downconverter means comprises four equal capacitors, with an equal voltage of V/4 appearing across each of the four capacitors during phase 1 such that in combination V volts appears across all four capacitors connected in series during phase 1, 3 V/4 volts appears across three of the four capacitors connected in series during phase 1, V/2 volts appears across two of the four capacitors connected in series during phase 1, and V/4 volts appears across one of the four capacitors connected in series during phase 1, and with a charge of V/4 volts being delivered to the storage capacitor during phase 2.

4. The implanted human tissue stimulator of claim 3 wherein the raw power signal of the power supply means has a nominal value of 14 volts dc, whereby the voltage downconverter means generates voltages of 14 volts, 10.5 volts, 7.0 volts and 3.5 volts.

5. The implanted human tissue stimulator of claim 2 wherein the means for alternatively connecting and disconnecting the flying capacitor within the refresh voltage controller means of each of said plurality of output channels includes means for applying a selected one of the at least four different output voltages made available to it from the voltage downconverter means to the flying capacitor during phase 1, and for disconnecting the flying capacitor from the selected one of the at least four different output voltages and connecting it to a refresh voltage source capacitor during phase 2, the voltage on the refresh voltage source capacitor comprising the isolated refresh voltage used by the voltage controlled current source,

whereby the flying capacitor of each of said plurality of output channels, alternately connected to the selected power supply voltage and to the refresh voltage source capacitor, provides electrical isolation of the refresh voltage for that output channel.

6. The implanted human tissue stimulator of claim 5 wherein the downconverter clock means generates a squarewave output signal from which the two-phase non-overlapping pair of clock signals that define phase 1 and phase 2 are derived, said squarewave output signal having a frequency of at least 137.5 KHz.

7. The implanted human tissue stimulator of claim 2 further including back telemetry means for:

(a) measuring the raw power signal and the voltage on the storage capacitor, and (b) transmitting the voltages thus measured to a non-implanted location remote from the implanted tissue stimulator.

8. A tissue stimulating system, comprising:

external transmitter means for transmitting data to a multi-channel implanted tissue stimulator, the data comprising a series of frames containing an end of frame signal, a plurality of data words each defining an amplitude for a tissue stimulating signal for a different output channel of the stimulator, and a command word for processor means in the stimulator; and

an implanted stimulator including;

receiver means for receiving the data,

a plurality of output channels, each having a tissue stimulating electrode connected thereto, and

processor means for serially processing the data words and command words from the receiver and including

a command detector responsive to the command words for controlling the functions of the processor,

data word latching means for successively storing the data words, and

switch means for successively coupling voltages representative of output signals from the data word latching means to successive ones of the output channels;

power supply means coupled to the receiver means for generating at least one power supply voltage for powering the operation of said implanted stimulator, including said processor means; and

wherein

each output channel includes;

a refresh voltage controller for generating an isolated refresh voltage from said at least one power supply voltage for the output channel, said refresh voltage controller including a flying capacitor and means for alternately connecting the flying capacitor to receive the at least one power supply voltage from the power supply means and then disconnecting the flying capacitor from the power supply means to provide the isolated refresh voltage for the output channel, and

a voltage controlled current source powered by the isolated refresh voltage for amplitude controlling, in accordance with the voltages coupled from the switch means, tissue stimulating signals to the stimulating electrode of the output channel.

9. The system of claim 8 further including clock control means for connecting the isolated refresh voltage and the voltage-controlled current source to the processor means only during times when voltages are coupled from the switch means to otherwise isolate each output channel from the rest of the output channels and from the processor means.

10. The system of claim 9 wherein said power supply means includes means for generating a plurality of power supply voltages, and wherein the flying capacitor of each output channel functions as a refresh voltage storage means for selectively storing as the isolated refresh voltage one of the plurality of power supply voltages.

11. The system of claim 10 further including clock control means for selectively connecting and disconnecting the flying capacitor to and from a selected one of the plurality of power supply voltages generated by the power supply means, with the voltage stored on said flying capacitor comprising the isolated refresh voltage when the flying capacitor is disconnected from the power supply means.

12. The system of claim 8 wherein each output channel further includes output switching means for controlling the direction of current flow between its output terminals, the stimulating electrodes being between the output terminals, and the output switching means being responsive to a polarity signal in each data word for controlling the direction of the tissue stimulating signal to the stimulating electrode connected to the output channel.

13. The system of claim 8 wherein:

each output channel includes an output switching means having two output terminals,

the system further includes an indifferent electrode; and

the processor includes output mode determining means connected to the output switching means of each channel and responsive to a monopolar command word from the external transmitter for an output channel for controlling the output switching means of the channel to connect its stimulating electrode to one of the output terminals of the output switching means and another of the output terminals to the indifferent electrode, and responsive to a bipolar command word from the external transmitter for the output channel for controlling the output switching means to connect its stimulating electrode between the output terminals of the output switching means.

14. The system of claim 13 wherein the output mode determining means includes means responsive first to monopolar command words for certain channels and then to a command word from the external transmitter to disconnect the indifferent electrode from the other output terminals of the output switching means.

15. The system of claim 13 wherein the output mode determining means is responsive to a discharge resistor control command word from the external transmitter for controlling the output switching means to connect a discharge resistor between the output terminals of the output switching means.

16. The system of claim 13 wherein the processor includes a pulse width control means connected to the output switching means and responsive to pulse width command words from the external transmitter for selectively turning the output channels on and off to create pulses of controlled duration at the output terminals of the output channel.

17. The system of claim 16 wherein the pulse width control is responsive to a global disconnect command from the external transmitter for turning off the output channels.

18. The system of claim 8 wherein said power supply means includes means for generating a plurality of power supply voltages for powering the output channels, and for applying the plurality of power supply voltages to the refresh voltage controller of each output channel;

and wherein said system further comprises;

monitor means in the processor means for monitoring the refresh voltage requirements of the output channel and for generating status indicating signals indicative of such requirements;

telemetry means for transmitting the status indicating signals to the external transmitters;

means in the external transmitter for receiving the refresh voltage status indicating signals and for generating and transmitting command words to the implanted stimulator indicative of the required refresh voltage levels for the various output channels; and

means in the command detector and responsive to the refresh voltage command words for controlling the refresh voltage controller to develop the required isolated refresh voltages in the output channels.

19. The system of claim 8 wherein the implanted stimulator further includes:

monitor means for selectively monitoring at least one voltage in the output channels, processor means, and from an external source, and for generating therefrom status indicating/measurement signals; and

telemetry means for transmitting the status indicating/measurement signals to the external transmitter for processing.

20. The system of claim 19 wherein:

the external transmitter includes means for generating different command words for detection by the command detector,

the command detector includes means for detecting the command words and in response to certain of the command words instituting the measurement of voltages in the processor, output channels and external source indicated by the command words, and

the external transmitter includes means for modifying the command words in response to the status indicating/measurement signals.

21. The system of claim 20 wherein the status indicating/measurement signals comprise a measurement of at least one of the following voltages:

direct current power, regulated direct current power, processor means reference voltages, output channel output voltages, electrode voltages, voltage across output channel current sources, voltages across current sampling resistors related to stimulus currents, and voltages derived from an external device connected to the stimulator.