Cochlea Implant Charge Balancing via Voltage Measurement
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Solution Overview
Problem
Cochlea implants face challenges in ensuring electrical safety due to potential failures of DC blocking capacitors, which can lead to unbalanced electrical stimulation, and there is no effective method to estimate the status of these capacitors or control the ratio between positive and capacitive discharges, affecting patient safety and stimulation efficiency.
Innovation Solution
A cochlea implant system that includes a pulse generating unit, an electrode array, a capacitor unit, and a resistive load to control the ratio between positive and capacitive discharges, with a measurement and evaluation unit to assess the status of capacitors and adapt to different recipient impedances, ensuring stable and efficient stimulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC blocking capacitors are used to ensure charge balancing, then patient safety is improved by preventing unbalanced stimulation, but the reliability deteriorates when capacitors fail (open or leaky), compromising safety
Solution Approach 1:
The patent implements a feedback mechanism by measuring the actual charge delivered to the cochlea and using this information to adjust subsequent pulses. The system measures the voltage across the capacitor and the current through the electrode to calculate the actual charge, then uses this feedback to compensate for any imbalance, ensuring safe stimulation even if the capacitor degrades over time
Solution Approach 2:
The patent replaces the passive mechanical/electrical capacitor-based charge balancing system with an active control system using measurement and adjustment circuitry. Instead of relying solely on the capacitor's physical properties to balance charge, the system actively measures and controls the charge delivery through electronic feedback, substituting passive component reliability with active control reliability
2Reliability
If capacitor values are increased to improve charge balancing, then stimulation safety is improved, but the device complexity increases due to additional measurement and control circuitry
Solution Approach 1:
The patent makes the existing measurement circuitry (ADC, voltage sensors) perform multiple functions: it continues to monitor electrode voltages for stimulation control while simultaneously measuring capacitor charge for safety verification. This multi-functionality avoids adding dedicated safety measurement circuitry, thereby limiting the increase in device complexity while maintaining high safety standards
3Reliability
If self-check methods are implemented to monitor capacitor status, then device reliability is improved, but the difficulty of detecting and measuring capacitor failures increases due to implantation depth
Solution Approach 1:
The patent uses the electrode and the cochlear fluid as intermediaries to indirectly measure capacitor status. Instead of trying to directly access and measure the capacitor (which would require surgical access), the system measures the electrical properties (voltage, current, impedance) of the electrode-capacitor-cochlea pathway, using these intermediate measurements to infer capacitor health status
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system reliably controls the ratio between positive and capacitive discharges, preventing tissue damage and ensuring stable stimulation efficiency by identifying and addressing capacitor failures, and adapting to individual patient impedance, thereby enhancing patient safety and treatment effectiveness.
Implementation Method 1
a capacitor unit connected to the at least one of the plurality of electrodes, where the capacitor unit is configured to receive the first electrical pulse and generate a capacitive discharge of the first electrical pulse
Implementation Method 2
a resistive load connected in series to the capacitor unit and the at least one of the plurality of electrodes, where the cochlea implant system is configured to control a ratio between the positive charge and the capacitive discharge of the first electrical pulse by changing a value of the resistive load
Data Source
AI summary
A method and a cochlea implant system for providing reliably control and stability of the ratio between the positive charge and the capacitive discharge of an electrical pulse are disclosed. The system includes an external unit configured to receive acoustical sound and process the acoustical sound into a coded audio signal, and an implantable unit configured to receive the coded audio signal. The system further comprises a pulse generating unit configured to generate a first electrical pulse of a first pulse duration and a second electrical pulse of a second pulse duration different from the first pulse duration based on the coded audio signal. The system still further comprises an electrode array including a plurality of electrodes, wherein at least one of the plurality of electrodes is configured to receive at least the first electrical pulse and the second electrical pulse, and a capacitor connected to the at least one of the plurality of electrodes. The system still further comprises a measurement unit configured to measure, across the connection of the at least one of the plurality of electrodes and the capacitor, a first voltage based on the first electrical pulse and a second voltage based on the second electrical pulse. The system still further comprises an evaluation unit configured to calculate a voltage difference between the measured first and second voltages.