Charge Pump K-Factor Control for Implantable Pacemaker Battery Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing cardiac pacemakers face challenges in efficiently delivering pacing voltages that vary over time due to battery voltage fluctuations, leading to increased battery current draw and reduced battery life, as they typically operate with a limited number of discrete K-factor modes.
Innovation Solution
The proposed solution involves a charge pump architecture that adds K-factors of 0.75x and 1.25x, utilizing a 2-phase clock to minimize additional capacitors and clock phases, allowing for automatic switching of K-factors based on the charged hold capacitor voltage to optimize current drain and extend battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a limited number of discrete K-factor modes are used, then device complexity is reduced, but battery current draw increases and battery life decreases
Solution Approach 1:
The charge pump circuit dynamically adjusts the K-factor by selectively activating different capacitor configurations based on real-time battery voltage conditions. The system transitions from static discrete K-factor modes to a dynamic continuous adjustment mechanism, allowing the output voltage to precisely track the battery voltage variations and minimize current draw at all operating points.
Solution Approach 2:
The invention changes the electrical parameters of the charge pump by varying the effective capacitance ratio through switchable capacitor connections. By changing the configuration of capacitors in series/parallel combinations, the system achieves continuous K-factor adjustment rather than being limited to fixed discrete values, thereby optimizing energy efficiency across the entire battery discharge curve.
2Device complexity
If a limited number of discrete K-factor modes are used, then device complexity is reduced, but battery life is reduced
Solution Approach 1:
The system continuously adapts the charge pump ratio to match instantaneous battery voltage conditions, preventing energy waste from operating at suboptimal K-factors. This dynamic adaptation extends battery life by ensuring maximum efficiency at every stage of battery discharge, rather than being constrained to fixed operating points.
Solution Approach 2:
The charge pump control mechanism incorporates feedback from the battery voltage sensing to automatically select the optimal capacitor configuration. This closed-loop control ensures the system always operates at the most efficient point for the current battery state, maximizing overall battery utilization and extending operational duration.
3Measurement precision
If additional capacitors and clock phases are added to increase K-factor precision, then pacing voltage matching improves, but device complexity increases
Solution Approach 1:
The charge pump capacitors serve multiple functions: they determine the K-factor ratio, store energy for pulse delivery, and provide voltage regulation. By making the capacitors multi-functional, the system achieves precise voltage matching without requiring additional dedicated components, thus avoiding increased complexity while improving precision.
Solution Approach 2:
The invention merges the voltage regulation function with the energy storage function by using the same capacitor network for both purposes. The switchable capacitor configurations simultaneously achieve precise K-factor control and maintain adequate energy reserves, eliminating the need for separate regulation components and reducing overall device complexity.
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 enables a significant reduction in battery current drain and increases battery longevity by allowing more precise matching of pacing voltages to available battery voltages, thereby improving the efficiency and duration of cardiac pacing therapy.
Implementation Method 1
A charge pump in the implantable medical device charges a hold capacitor to a voltage equal to a K-factor multiplied by a battery voltage
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An implantable medical device (IMD) includes a hold capacitor configured to deliver an electrical therapy pulse, and charge pump circuitry configured to transfer energy from the battery to the hold capacitor. The charge pump circuitry comprises a plurality of capacitors, and switching circuitry configured to put the charge pump circuitry into a K-factor mode selected from a group of K-factor modes by opening and closing a combination of switches connected to the plurality of capacitors.