Implanted Heart-Stimulation Device Charge Balance Control
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Solution Overview
Problem
Conventional implantable heart-stimulation devices face challenges in maintaining charge neutrality during multi-site stimulation, particularly in cardiac resynchronization therapy, where simultaneous stimulations with short stimulation periods and high charge transfer can lead to parasitic diode formation and current leakage, potentially damaging the device and affecting patient safety.
Innovation Solution
The implementation of an implantable heart-stimulation device with a control unit that performs repeated partial discharges of coupling capacitors in a temporally non-overlapping sequence until each capacitor's voltage is below a predetermined level, reducing the risk of charge loss and parasitic diode activation, thereby maintaining charge balance and preventing undesired device operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simultaneous stimulations with short stimulation periods and high charge transfer are applied during cardiac resynchronization therapy, then coordination therapy effectiveness is improved, but parasitic diode formation and current leakage occur causing charge imbalance
Solution Approach 1:
The control unit performs preliminary discharge of coupling capacitors before they reach voltage levels that would activate parasitic diodes. By proactively managing capacitor discharge in a temporally non-overlapping sequence, the system prevents charge leakage through parasitic diodes while maintaining the ability to deliver coordinated stimulation pulses to multiple heart sites
Solution Approach 2:
The discharge process of multiple coupling capacitors is segmented into temporally non-overlapping sequences. Instead of discharging all capacitors simultaneously or in overlapping time periods, the control unit divides the discharge operation into distinct time slots for each stimulation channel, preventing simultaneous voltage conflicts that could activate parasitic diodes
2Loss of time
If coupling capacitors are discharged simultaneously in multi-channel stimulation, then discharge time is reduced, but charge loss through parasitic diodes increases
Solution Approach 1:
The control unit implements periodic discharge cycles for coupling capacitors in a structured sequence. Each capacitor is discharged in alternating time periods rather than simultaneously, creating a rhythmic pattern of charge and discharge that maintains efficiency while preventing parasitic diode activation through controlled voltage management
3Power
If high voltage is applied to coupling capacitors during stimulation, then stimulation effectiveness is improved, but parasitic diode activation and current leakage increase
Solution Approach 1:
The control unit continuously monitors the voltage levels of coupling capacitors and adjusts discharge timing based on this feedback. When a capacitor approaches a voltage level that could activate parasitic diodes, the control unit triggers discharge for that specific channel, creating a closed-loop control system that maintains high stimulation effectiveness while preventing harmful voltage excursions
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 ensures charge neutrality is maintained after stimulation sequences, reducing the risk of device malfunction and potential harm to the patient by minimizing charge leakage and parasitic diode activation, even during high-stimulation conditions.
Implementation Method 1
a direct current blocking element, typically a capacitor, is arranged in series with the current path at the cathode, which capacitor is capable of being charged and discharged
Implementation Method 2
a parasitic p-n diode may be formed in the p-n junction. If a large enough bias is placed on the junction, a parasitic p-n diode is formed, and current will flow over the parasitic p-n diode
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to implantable medical devices, in particular to a implantable heart-stimulation device, a method for operating an implantable heart-stimulation device and a heart-stimulation system, wherein stimulation pulses are delivered via a plurality of stimulation channels to selected sites on or about a patient's heart via electrodes, and wherein coupling capacitors included in the stimulation channels are subsequently discharged through a sequence of temporally non-overlapping partial discharges of the respective coupling capacitors. By this configuration, the risk of charge neutrality of a stimulation channel not being maintained at the end of a stimulation sequence, comprising the delivery of stimulation pulses via stimulation channels, is reduced or eliminated.