Powering system for constant current neural stimulators
A powering system for constant current neural stimulators provides adaptive supply voltage for neural stimulators to decrease power dissipation by taking advantage of varying voltage compliance of constant current stimulation. The powering system includes an adaptive voltage supply generator, a monitoring circuit, a charge pump, a step-down converter, and a rechargeable battery.
1 . A powering system, providing an adaptive supply voltage for constant current neural stimulators comprising;
an adaptive voltage supply generator, configured to be connected to an energy source to output desired voltage levels and to decrease an average supply voltage, and wherein the adaptive voltage supply generator is configured to generate a necessary voltage compliance with energy sources having varying voltage levels and provide the necessary voltage compliance to a switch matrix, the switch matrix is configured to create a necessary stimulation signal for a stimulation electrode;
a monitoring circuit, for measuring an electrode voltage compliance and control the voltage supply generator and the monitoring circuit comprises:
a voltage subtracting circuit, wherein the voltage subtracting circuit continuously provides an electrode's voltage difference to the voltage supply generator and enable the voltage supply generator to adapt the voltage supply generator to any changes, wherein the any changes occur during a stimulation by tracking an electrode voltage,
a digitalizing circuit to change a number of charge pump stages operational
a charge pump, tracking the electrode voltage by a control of the number of the charge pump stages utilized and a control of a frequency;
a step-down converter, configured to be connected to the energy source to power the monitoring circuit and power a control circuitry to bring down a power loss and wherein the step-down converter is configured to decrease a power dissipation of the control circuitry; and
a rechargeable battery.
2 . The powering system according to claim 1 , further comprising an energy harvester system, wherein the energy harvester system is configured to charge the rechargeable battery.
3 . The powering system according to claim 1 , wherein the adaptive voltage supply generator is structured to be controlled by the number of the charge pump stages for the necessary voltage compliance.
4 . The powering system according to claim 1 , wherein the adaptive voltage supply generator is structured for a fine tuning of the necessary voltage compliance by pulse frequency modulation (PFM) control.
5 . The powering system according to claim 1 , wherein a charge pump circuit comprises a level shifter to handle switches, wherein the switches connect the charge pump stages to an output.
6 . The powering system according to claim 1 , wherein the adaptive voltage supply generator utilizes a three-stage charge pump.
7 . The powering system according to claim 1 , wherein an adaptive voltage supply and the step-down converter use a battery as an energy source.
8 . The powering system according to claim 1 , wherein the step-down converter comprises a switched-capacitor converter.
9 . The powering system according to claim 1 , wherein the step-down converter is one of the group consisting of a resonant converter, a multi-level switching converter and a linear converter.
10 . The powering system according to claim 1 , wherein an external source is a wireless power transmitter.
11 . An operation method of the powering system according to claim 1 , comprising;
generating control signals via the control circuitry to start the charge pump and pull an output of the charge pump to a maximum;
generating the control signals via the control circuitry for the switch matrix to start a simulation period;
enabling of a voltage sampling circuitry and a creation of a scaled electrode voltage with an offset;
using the scaled electrode voltage as a reference voltage for a pulse frequency modulation control and to create signals for a stage number control;
allowing the charge pump output to drop from the maximum to a value determined by the scaled electrode voltage and track the charge pump output;
pulling the charge pump output via the control circuitry to the maximum with signals from the control circuitry before the stimulation period ends to provide a sufficient voltage for a subsequent stimulation period; and
keeping the charge pump output at the maximum until a start signal for a next stimulation period is given.