H-Bridge Charge Equalization Delay for Clear Evoked Potential Sensing
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Solution Overview
Problem
Electrical charge equalization during stimulation in medical devices can overlay evoked potentials, leading to measurement artifacts, particularly in close proximity stimulation and derivation locations, where artifacts can obscure the neurophysiological response.
Innovation Solution
Incorporating a capacitive element in the bridge branch of an H-bridge circuit to delay the discharge of the capacitive element after stimulation current pulses, creating a time window for interference-free measurement of physiological signals without direct influence from the stimulation current or discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct charge equalization is performed immediately after stimulation current pulses, then electrolysis is prevented and charge balance is maintained, but measurement artifacts occur that obscure evoked potentials
Solution Approach 1:
The patent applies preliminary action by performing charge equalization before the measurement period rather than immediately after stimulation. The capacitor is charged during stimulation, then the switching elements isolate the capacitor from the load during the measurement window, allowing evoked potentials to be recorded without contamination from discharge artifacts. The charge equalization is completed in a subsequent phase after measurements are taken.
2Measurement precision
If charge equalization is delayed to avoid measurement artifacts, then evoked potentials can be measured clearly, but electrolysis risk increases due to prolonged charge imbalance
Solution Approach 1:
The patent implements periodic action through a cyclic operation mode where stimulation and measurement phases are repeated in sequence. During each cycle, the capacitor is charged during stimulation, isolated during measurement to prevent artifacts, then discharged in the next cycle to maintain charge balance. This periodic alternation between charging and discharging phases allows both clear evoked potential detection and prevention of electrolysis through regular charge equalization.
3Reliability
If a capacitor is used for charge equalization, then charge balance is improved, but measurement artifacts occur due to capacitor discharge current
Solution Approach 1:
The patent applies segmentation by dividing the circuit into distinct functional sections controlled by switching elements. The capacitor is isolated in one circuit section during measurement while another section records evoked potentials. The switching elements act as separators that prevent the discharge current from the capacitor from reaching the measurement circuit, thus eliminating measurement artifacts while maintaining charge balance functionality.
4Measurement precision
If switching elements are used to control charge equalization timing, then measurement clarity is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the switching elements to perform multiple roles: they control capacitor charging during stimulation, isolate the capacitor during measurement to prevent artifacts, and enable discharge during subsequent phases. The same switching elements manage both charge equalization and measurement protection functions, reducing the need for additional separate components and simplifying the overall circuit architecture.
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
This approach allows for the unambiguous identification and analysis of neurophysiological responses by reducing the amplitude and duration of stimulation artifacts, thereby enhancing the clarity of sensory and motor evoked potentials and reducing the number of averaging procedures required for signal recording.
Implementation Method 1
Incorporating a capacitive element in the bridge branch of an H-bridge circuit to delay the discharge of the capacitive element after stimulation current pulses
Data Source
AI summary
An arrangement for electrical charge equalization after generation of stimulation current pulse(s), containing a bridge circuit, switching elements, a bridge branch between two legs of the bridge circuit, into which a load resistance is introducible, and a power source for generating a stimulation current pulse, connected to the legs of the bridge circuit that enables an electrical current via one leg through the bridge branch and through a leg connected to the other end of the bridge branch with corresponding switch position. A capacitive element is in the bridge branch for generating a current for electrical charge equalization for current introduced by stimulation current pulse(s) and is configured such that, between one or more stimulation current pulses and a discharge of the capacitive element via stimulation electrode(s), a delay time window is maintained, which is used for measuring electrical physiological signals induced as a reaction to the stimulation current pulse(s).