H-Bridge Therapy Circuit with Low-Side Current Control
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Solution Overview
Problem
Existing implantable defibrillators face challenges in delivering controlled current outputs for pacing and induction pulses due to the limitations of current voltage boosting circuitry, which often require separate and complex circuits for different therapy levels, increasing complexity, cost, and space requirements.
Innovation Solution
The proposed solution involves an electronic circuit design for an implantable medical device that includes an H-bridge with latching switches and a current controlling circuit with a feedback mechanism, allowing for controlled current delivery through a sense resistor and bypass path, enabling efficient switching between different therapy outputs without the need for multiple separate circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate voltage boosting circuitry is used for different therapy levels, then controlled current outputs for pacing and induction pulses can be achieved, but device complexity increases
Solution Approach 1:
The H-bridge circuit is designed to perform multiple functions: it can deliver both high-power defibrillation shocks and controlled current pacing/induction pulses through a single circuit architecture. The circuit includes switching elements (MOSFETs or IGBTs) and energy storage capacitors that can operate in different modes to provide different therapy types, eliminating the need for separate dedicated circuits for each therapy level.
Solution Approach 2:
The patent combines previously separate voltage boosting and controlled current delivery functions into a unified H-bridge circuit. The energy storage capacitors are charged through the H-bridge switching action, and the same circuit components are used for both charging and controlled discharge, merging multiple functions into a single integrated system.
2Reliability
If multiple separate circuits are used for different therapy outputs, then reliable controlled current delivery is achieved, but cost increases
Solution Approach 1:
The H-bridge circuit serves as a universal platform that can reliably deliver different therapy types (defibrillation, pacing, induction) through controlled switching sequences. The circuit includes protection mechanisms and controlled current paths that ensure reliable operation across different therapy modes without requiring separate dedicated circuits for each function.
3Adaptability or versatility
If multiple separate circuits are used for different therapy outputs, then therapy versatility is achieved, but device volume increases
Solution Approach 1:
The patent merges multiple therapy delivery functions into a single H-bridge circuit architecture. The same physical components (switching elements, capacitors, inductors) are used across different therapy modes, significantly reducing the overall device volume compared to having separate dedicated circuits for defibrillation, pacing, and induction functions.
Solution Approach 2:
The H-bridge circuit is designed as a universal therapy delivery platform that can provide multiple therapy types through different switching configurations and control modes, eliminating the need for multiple separate circuit boards or components and thereby reducing the overall implantable device volume.
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 design enables efficient and controlled delivery of both pacing and defibrillation therapies using a single circuit, reducing complexity and cost while maintaining effective power transfer, thus addressing the limitations of existing voltage boosting technologies.
Implementation Method 1
a transformer configured to selectively transfer energy from the battery to the high power capacitor
Implementation Method 2
a feedback circuit configured to receive a signal indicating a voltage drop across the sense resistor
Data Source
AI summary
Improved devices, circuits and methods of operation in implantable stimulus systems. An implantable defibrillator may comprise a charging circuit using a transformer to store and build up energy on an HV capacitor or capacitor stack, with the HV capacitor in turn coupled to an H-bridge output circuit having low and high sides for issuing therapy. In the output current path, a current controlling circuitry is placed between the H-bridge and ground, allowing the greater flexibility in the selection of switching devices, and drivers for such devices, in the H-bridge circuit and/or enabling circuits between the H-bridge and the HV capacitor or other therapy circuit.