Capacitor Discharge Switching to Prevent Reverse Bias in Series Banks
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Solution Overview
Problem
Capacitors in cardiac therapy devices experience uneven discharge due to manufacturing tolerances, leading to potential reverse biasing and damage when coupled in series, especially after delivering high-voltage therapies like defibrillation.
Innovation Solution
The processing circuitry periodically interrupts the discharge of capacitors coupled in series and recharges them in parallel to a common voltage, repeating this process until the desired discharge voltage level is reached, ensuring equal voltage distribution across capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If capacitors are discharged in series to eliminate residual charge, then the discharge efficiency is improved, but manufacturing tolerances cause uneven voltage distribution leading to reverse biasing and potential capacitor damage
Solution Approach 1:
The discharge process is divided into multiple periodic cycles, each consisting of a discharge phase followed by a redistribution phase. During the discharge phase, capacitors are discharged in series to eliminate residual charge efficiently. During the redistribution phase, capacitors are reconfigured in parallel to allow automatic voltage equalization. This periodic switching between series and parallel configurations continues until all capacitors reach a safe voltage level, preventing reverse biasing while maintaining high discharge efficiency.
Solution Approach 2:
The system dynamically reconfigures the capacitor connections between series and parallel arrangements based on the discharge progress. The control circuitry monitors voltage levels and automatically switches the capacitor configuration to optimize both discharge efficiency and safety. This dynamic adaptation allows the system to exploit the advantages of both series (efficient discharge) and parallel (safe voltage distribution) configurations at different stages of the discharge process.
2Speed
If capacitors are discharged continuously without interruption, then the discharge speed is improved, but uneven voltage distribution due to manufacturing tolerances causes reverse biasing
Solution Approach 1:
The continuous discharge process is interrupted periodically by redistributing capacitor connections. The control circuitry monitors voltage levels across capacitors and automatically switches between discharge mode (series configuration for high speed) and redistribution mode (parallel configuration for safe voltage equalization). This periodic interruption prevents any single capacitor from being over-discharged and reverse-biased, while maintaining overall high discharge speed through efficient use of series configuration during discharge phases.
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 method prevents capacitors from being reverse biased, minimizing damage and maintaining capacitor performance by equalizing voltages across capacitors, thus ensuring reliable delivery of subsequent therapies like pacing.
Implementation Method 1
a plurality of capacitors... processing circuitry configured to discharge the plurality of capacitors... charge the one or more capacitors
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A processing circuitry is configured to discharge capacitors to a discharge voltage level, such as by repeatedly discharging the capacitors when coupled in series and partially recharging one or more capacitors of the capacitors when coupled in parallel until the voltage across the capacitors coupled in series is approximately equal to the discharge voltage level. To discharge the capacitors, the processing circuitry is configured to discharge the capacitors when coupled in series to respective intermediate threshold voltage levels of a plurality of intermediate threshold voltage levels, and to partially recharge the one or more capacitors, the processing circuitry is configured to, in response to a voltage across the capacitors coupled in series reaching the respective intermediate threshold voltage levels, charge the one or more capacitors to respective intermediate common voltage levels of a plurality of intermediate common voltage levels when coupled in parallel.