A time shared stimulator which employs a single pulse generator to provide non-simultaneous independently controllable multiple outputs. A train of pulses in which the power level of successive pulses may be controlled is produced from the pulse generator output. Switching circuitry connects the pulse train to a series of output electrodes. A trigger signal, which is generated on the trailing edge of each pulse generator pulse, is applied to the switching circuitry to route successive pulses in the pulse train to different ones of the pulse output electrodes. BACKGROUND OF THE INVENTION The application of electrical pulses to various portions of the body for such purposes as pain alleviation and nerve stimulation is well-known. Such pulses have been applied transcutaneously by external stimulators as well as internally with implantable devices. One form which the implantable devices have taken is an RF-powered implantable stimulator, an example of which is a well-known bilateral dorsal column stimulator used for pain alleviation. When the pain to be suppressed is diffuse and bilateral, stimulation of the cord dorsum with a single electrode placed off midline several millimeters, was found to be inadequate to abolish bilateral pain in the ipsilateral side. To overcome this problem, a second electrode was added with both stimuli being produced at the same amplitude and time. The resulting bilateral stimulator requires four leads and tends to cause an undesirable cross-stimulus spread of nerve depolarization which may occur when the biological volume conductor is excited at two different sites simultaneously. Also, since the ammplitude difference between causing pain and alleviating pain may be very small, an output amplitude determined by the highest threshold of the two electrode sites was found to have the potential to cause pain or discomfort in the lower threshold electrode site. SUMMARY OF THE INVENTION The present invention provides a time shared stimulator in which a train of pulses is produced. These pulses are connected to a plurality of output electrodes by switching circuitry. A trigger signal, which is generated upon the trailing edge of each of the pulses in the pulse train, is applied to the switching circuitry to route successive pulses in the pulse train to successive one of the output electrodes. From this it can be seen that the difficulties resulting from the simultaneous stimulation of the prior art devices is eliminated by providing a stimulator in which the stimuli are non-simultaneous. In addition, the present invention provides a means for independently regulating the power level of alternate pulses in the pulse train such that the pulses applied to each of the electrodes can be independently regulated thereby enabling an adjustment of the stimulation applied to a certain site in conformity with the threshold of that site. Also, the present invention may be operated as an RF-powered implantable stimulator in which the amplitude of each stimuli may be remotely adjusted through an RF link. The stimulator of the present invention requires only three leads to operate in a dual bipolar electrode mode and may be operated as a dual isolated output monopolar system.
A system for coupling a plurality of physiological signals across an isolation barrier. A plurality of physiological signals received at a number of signal inputs on the isolated side of the barrier are sampled during separate time periods and coupled to the primary winding of a transformer. The direction of signal flow through the primary winding is reversed during each said period. A pair of serial pulses of opposed polarities are induced in the secondary winding for each sampled signal. The pairs of serial pulses induced in the secondary winding are reconverted to the plurality of physiological signals on the non-isolated side of the barrier.
A method and apparatus for applying electrical stimulation to areas of the nervous system wherein the method permits precise pulse dosage control over prescribed time intervals to be exercised by the administering physician, and the apparatus is organized to provide the desired pulse dosage by means of selectable duty cycle on/off modulation of a pulse train having selectable pulse repetition rates and pulse widths. Digital circuitry is used in a pulse counting technique to implement the generation of pulse sequences such that direct quantitative control may be exercised.
An independently rate-adjustable multiple channel controller-transmitter for a nerve stimulator to be used in conjunction with an implanted stimulation pulse output unit includes a rate generating circuit (40,41,43,44) for producing asynchronous trigger signals of independently adjustable rate and width, a transmitting circuit (46,47,48,49) for generating bursts of RF energy at separate frequencies in response to the trigger signals, and a rate control circuit (50) for preventing excitation of the transmitting circuit by more than one trigger signal at a time. In the event that two or more trigger signals coincide at the transmitting circuit (46,47,48,49), the rate control circuit (50) blocks and delays the latter occurring trigger signals with only minor and insignificant effect on trigger signal rate.
An electrical stimulation system for selectively stimulating portions of the body. The system includes an external device for alternately transmitting stimulus signals and control signals to an implantable receiver. The receiver includes a plurality of output devies adapted to apply the stimulus signals to the body and circuitry for routing the stimulus signal to the output devices under the control of the control signals. In a preferred embodiment, the control signals are formed of an alterably preselected number of pulse signals with the routing circuitry routing each of the stimulus signals to the output devices in predetermined correspondance with the number of pulse signals within a different one of the control signals. The system of the present invention may be employed to sequentially stimulate several stimulation sites, with the stimulation sites being selected to combat the same or different body disfunctions. Alternatively, the system of the present invention may be employed to repetitively stimulate the same stimulation sites while allowing an alteration in the stimulation sites to combat nerve fatigue or to provide a more effective electrode configuration, for example.
An apparatus for generating electrical pulses which are suitable for application to selected areas of the user's body for pain control or muscle stimulation. The current level, pulse width, pulse rate, voltage level and pulse configuration are all controlled to produce the desired effects. The apparatus includes a timing circuit which emits pulses of selected width and repetition rate. The pulses from the timing circuit energize a switching circuit which selectively connects the primary of a pulse transformer to a power source. The transformer is so constructed and arranged that it operates near saturation, thereby effectively operating as a current limiter, which helps to prevent spikes in the electrical pulse output of the apparatus.
