H-Bridge Current Control for Implantable Defibrillators
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Solution Overview
Problem
Existing implantable defibrillators face challenges in delivering controlled current outputs for pacing and induction pulses, as current H-Bridge circuitry is primarily designed for high-power defibrillation and lacks efficient mechanisms for controlled current delivery, leading to increased complexity and cost with separate boosting circuits.
Innovation Solution
The implementation of a current monitoring and control subcircuit within the H-Bridge circuit, utilizing a bootstrap circuit and high voltage isolation components, allows for controlled current flow during pacing and induction by modulating the current through feedback signals, reducing the need for separate boosting circuits and simplifying the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate boosting circuit is added to provide controlled current outputs for pacing and induction pulses, then the device can deliver precise controlled current outputs, but the device complexity and cost increase
Solution Approach 1:
The patent combines the controlled current output functionality with the existing H-Bridge defibrillation circuitry by adding a current monitoring subcircuit and current control subcircuit. The current control subcircuit couples the high power capacitor to the H-Bridge and uses feedback from the current monitoring subcircuit to control current through the H-Bridge, enabling both defibrillation and controlled current pacing/induction functions through a single integrated circuit rather than requiring separate boosting circuits.
Solution Approach 2:
The H-Bridge circuit is designed to serve multiple functions: it can deliver high-power defibrillation shocks and also provide controlled current outputs for pacing and induction pulses. The current control subcircuit enables the same H-Bridge infrastructure to be used for different therapeutic applications by modulating current flow based on feedback signals.
2Power
If traditional H-Bridge circuitry is used for high-power defibrillation, then high-power therapy delivery is achieved, but controlled current delivery capability is lost
Solution Approach 1:
The patent implements a feedback mechanism where the current monitoring subcircuit measures current through the H-Bridge and provides feedback signals to the current control subcircuit. This feedback enables the system to regulate and control current delivery for pacing and induction while maintaining the capability to deliver high-power defibrillation shocks when needed.
Solution Approach 2:
The system dynamically switches between different operational modes: high-power defibrillation mode and controlled current mode for pacing/induction. The current control subcircuit can modulate the H-Bridge switching to provide precise current control when required, while maintaining the ability to deliver uncontrolled high-power shocks for defibrillation.
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 solution enables efficient and controlled current delivery for both defibrillation and pacing, reducing the complexity and cost of the device while maintaining high-power therapy capabilities, thereby improving the usability of implantable defibrillators in various therapeutic applications.
Implementation Method 1
a DC:DC conversion circuit configured to charge the at least one high power capacitor using current drawn from the at least one battery
Implementation Method 2
An H-Bridge circuit is often used to provide the switching capability. The switches of an H-Bridge, which may take the form of junction or field effect transistors, silicon controlled rectifiers, or other suitable circuitry, may be used in an ON/OFF manner
Implementation Method 3
a current monitoring subcircuit coupled to the first and second low side legs, the current monitoring subcircuit adapted to receive current through both of the first and second low side legs
Implementation Method 4
a current control subcircuit coupling the high power capacitor to the first and second high side legs, the current control subcircuit configured to receive a feedback signal from the current monitoring subcircuit to control current through the H-bridge
Implementation Method 5
the current control subcircuit comprises a bootstrap circuit coupled to a first transistor that is configured to enable current flow to the H-bridge from the at least on high power capacitor
Data Source
AI summary
Improved devices, circuits and methods of operation in implantable stimulus systems. An implantable defibrillator may comprise an H-bridge output circuit having low and high sides, with a current controlling circuit coupled to the high side of the H-bridge output circuit and a current monitoring circuit coupled to the low side of the H-bridge output circuit. A bootstrap design or a DC isolating circuit or circuit element may be used in the current controlling circuit.