Variable voltage compliance for current output generator

An apparatus for delivering electrical neural stimulation therapy to a patient, comprising an implantable medical device and an external device, the implantable medical device comprising:

• a power supply, circuitry connected to the power supply and adapted to detect tissue/electrode interface impedances;
• and a current output pulse generator comprising a programmed amplitude of stimulation current, wherein the generator is adapted to deliver electrical neural stimulation therapy at the programmed amplitude, the generator further comprising:
• an adjustable compliance voltage source connected to the power supply, the voltage source adapted to provide different potentials for different tissue/electrode interface impedances and comprises:
• an adjustable voltage level;
• a supply capacitor;
• two variable current sources connected in parallel with the supply capacitor;
• and a plurality of switches connected to the current sources and supply capacitor, the switches adapted to control the delivery of electrical neural stimulation therapy, wherein the pulse generator is adapted to receive the detected impedances, maintain the programmed amplitude of stimulation current for the different tissue/electrode interface impedances and adjust the compliance voltage source by adjusting the voltage level based on the programmed amplitude of the stimulation current and the detected impedances.

An apparatus for delivering electrical neural stimulation therapy to a patient comprising:

• means for applying neural stimulation therapy comprising a programmed amplitude of stimulation current, wherein the means for applying uses a current output pulse generator comprising:
• an adjustable compliance voltage source, the voltage source comprising an adjustable voltage level and is adapted to provide different potentials for different tissue/electrode interface impedances;
• implantable means for detecting tissue/electrode interface impedances;
• and means for adjusting the voltage level of the adjustable compliance voltage source, the adjusting means including means for receiving the detected impedances and adapted to adjust the voltage level to a voltage amplitude to maintain the programmed amplitude of stimulation current for different tissue/electrode interface impedances by adjusting the voltage level based on the programmed amplitude of the stimulation current and the detected impedances;
• wherein the adjustable compliance voltage source is connected to the detecting means and the stimulating means.

A method for delivering electrical neural stimulation therapy to a patient, comprising:

• providing implantable circuitry adapted to detect tissue/electrode interface impedances;
• and providing a current output pulse generator comprising a programmed amplitude of stimulation current, wherein the generator is adapted to deliver electrical neural stimulation therapy at the programmed amplitude, the generator further comprising:
• an adjustable compliance voltage source connected to the power supply, the voltage source adapted to provide different potentials for different tissue/electrode interface impedances and comprises:
• an adjustable voltage level;
• a supply capacitor;
• two variable current sources connected in parallel with the supply capacitor;
• and a plurality of switches connected to the current sources and supply capacitor, the switches adapted to control the delivery of electrical neural stimulation therapy, wherein the pulse generator is adapted to receive the detected impedances, maintain the programmed amplitude of stimulation current for the different tissue/electrode interface impedances and adjust the compliance voltage source by adjusting the voltage level based on the programmed amplitude of the stimulation current and the detected impedances.

A method for delivering electrical neural stimulation therapy to a patient, comprising:

• applying electrical neural stimulation therapy at a programmed amplitude of stimulation current using a current output pulse generator, wherein the output pulse generator comprises:
• an adjustable compliance voltage source, the voltage source comprising an adjustable voltage level and is adapted to provide different potentials for different tissue/electrode interface impedances;
• detecting tissue/electrode interface impedances;
• using the detected impedances to determine an appropriate voltage level for the adjustable compliance voltage source to maintain the programmed amplitude of stimulation current for different tissue/electrode interface impedances;
• and adjusting the voltage level to the appropriate voltage amplitude based on the programmed amplitude of the stimulation current and the detected impedances.