Biomedical Electro-Stimulator Circuit Constant Current Charging
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Solution Overview
Problem
Biomedical electro-stimulators, such as pacemakers, face inefficiencies in energy charging due to resistive losses, which shorten battery life and require frequent surgical replacements, especially since existing charging circuits do not allow for precise control of charging current, leading to suboptimal energy efficiency.
Innovation Solution
A biomedical electro-stimulator circuit that employs an energy converter to maintain a substantially constant charging current over the charging period, minimizing resistive losses and extending battery life, utilizing an inductive or capacitive energy converter with a control circuit to regulate the charging current, ensuring efficient energy transfer to the storage capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional charging circuit with exponential current decay is used, then the charging process is simple, but resistive losses increase and battery lifetime decreases
Solution Approach 1:
The charging circuit dynamically adjusts the charging current to maintain a substantially constant value throughout the charging period, transitioning from static exponential decay to dynamic constant current control. This is achieved through feedback mechanisms that continuously regulate the current based on capacitor voltage, minimizing resistive losses while managing circuit complexity through controlled dynamics.
Solution Approach 2:
The invention changes the key parameter of charging current from a decaying exponential profile to a substantially constant profile. By controlling the current parameter to remain stable throughout charging rather than allowing it to decay, the circuit achieves lower resistive losses (I²R losses) while using energy-efficient switching regulators instead of linear regulators to manage the parameter change.
2Measurement precision
If a linear voltage regulator is used to control charging voltage, then voltage control is precise, but power consumption increases
Solution Approach 1:
The invention replaces the linear voltage regulator (analog/mechanical approach) with a switching regulator system. Instead of using continuous analog voltage regulation that dissipates power as heat, the circuit uses pulsed width modulation (PWM) or similar switching techniques to control charging voltage, achieving precise voltage control with significantly reduced power consumption through efficient switching operation.
Solution Approach 2:
The charging circuit employs periodic switching action to control the charging process. By using periodic pulse-width modulation or similar periodic control mechanisms, the circuit achieves precise voltage control through averaged effects over time, reducing instantaneous power dissipation while maintaining accurate voltage regulation through feedback control during each switching cycle.
3Duration of action of stationary object
If the battery is made larger to extend lifetime, then battery lifetime increases, but device size increases
Solution Approach 1:
The invention changes the operational parameters of the charging circuit to achieve substantially constant current charging, which optimizes energy transfer efficiency and minimizes resistive losses. This parameter optimization extends battery lifetime by maximizing the useful energy stored per charging cycle, thereby extending device operation without requiring increased battery capacity or 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
The solution provides a power-efficient charging scheme that prolongs battery life by minimizing resistive losses and allowing precise control of charging voltage without the need for a linear voltage regulator, suitable for miniature implantable devices.
Implementation Method 1
An inductive DC-DC converter (inductive boost converter), which can be modeled in steady state as a variable voltage source, charges a storage capacitor by converting energy from a battery
Implementation Method 2
Biomedical electro-stimulators, such as cardiac pacemakers or neural stimulators, are often based on providing electric stimulation pulses to the human tissue with an electrode by discharge from a storage or holding capacitor in the electro-stimulator circuit
Data Source
AI summary
A power efficient biomedical electro-stimulator circuit BSC is provided. The circuit BSC includes a charging circuit arranged to control charging of a storage capacitor C based on electric energy from an energy source ES, e.g. a battery. The charging circuit includes an energy converter EC that applies a charging current I to the storage capacitor C, this charging current I being substantially constant over a charging period T, thereby providing a power efficient charging. In preferred embodiments, the energy converter EC is an inductive energy converter, e.g. a DC-DC converter, with a control circuit serving to provide an almost constant charging current during the charging period. In another embodiment, the energy converter EC is an energy converter that charges the storage capacitor via a series resonator, e.g. a series connection of an inductor and a capacitor. The proposed biomedical electro-stimulator circuit is advantageous for devices such as pacemakers, and neural stimulation etc. which can benefit of increased battery lifetime due to an efficient charging scheme.