Capacitor-Based AC-DC Step-Up Converter for Implantable Devices

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Solution Overview

Problem

Current biomedical implantable devices face inefficiencies in generating high output voltages for functional electrical stimulation due to power losses in regulators and rectifiers, and the use of bulky inductors in boost converters, which are size-constrained and power-inefficient.

Innovation Solution

A timing-controlled capacitor-based AC-DC step-up converter that generates multiple regulated positive and negative output voltages directly from a low induced voltage, minimizing power dissipation by controlling switch on/off times and eliminating the need for linear regulators, using a unique circuit structure and switching protocol.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If linear regulators are used to regulate high AC induced voltage, then high output voltage is obtained, but power loss increases due to regulator inefficiency

Engineering Contradiction:

Improveoutput voltageVSAvoidpower loss in regulators

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces linear regulators (electrical/thermal system) with a capacitor-based voltage multiplier circuit that uses capacitive energy storage and transfer mechanisms. This substitution eliminates the resistive power losses inherent in linear regulation by using reactive energy transfer instead of dissipative voltage dropping.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using high-voltage capacitors charged during specific phases of the AC cycle and then connected in series to multiply the output voltage. This parameter change approach allows efficient voltage transformation without the continuous power dissipation characteristic of linear regulators.

Inventive Principle:

Principle #35Parameter changes

2Power

If boost converters are used to up convert low voltage, then high output voltage is obtained, but device size increases due to bulky inductor requirements

Engineering Contradiction:

Improveoutput voltageVSAvoidconverter size

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The patent replaces the inductor-based magnetic energy storage mechanism of boost converters with a capacitor-based electric energy storage mechanism. This substitution eliminates the need for bulky magnetic components while achieving the same voltage step-up function through capacitive voltage multiplication.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental energy storage parameter from magnetic (inductor) to electric (capacitor), enabling voltage transformation without requiring large magnetic components. This parameter change allows the use of compact capacitor-based voltage multipliers instead of inductor-based boost converters.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If switched capacitor DC-DC converters are used for voltage regulation, then multiple output voltages are obtained, but power loss increases during voltage regulation

Engineering Contradiction:

Improvemultiple output voltagesVSAvoidpower loss in voltage regulation

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent segments the voltage regulation function into multiple independent capacitor-based voltage multiplier circuits, each capable of providing different output voltages. This segmentation allows each circuit to operate independently at optimal efficiency points, reducing the power losses associated with single-circuit multi-tap regulation.

Inventive Principle:

Principle #1Segmentation

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 minimizes overall power dissipation and achieves high power conversion efficiency by directly converting low induced voltages into high output voltages within implantable medical devices, reducing the size and power consumption of the converters.

Implementation Method 1

a timing controlled capacitor based AC-DC step up converter

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the second terminal being coupled to a first positive converter output through an active rectifier

Methodology Applied

Scientific EffectRectification: Diode

Implementation Method 3

said first switch controller comprises an integrator configured to integrate the difference between a function of the first positive converter output and a predetermined first reference voltage to provide thereby a first control signal

Methodology Applied

Scientific EffectIntegration:

Data Source

PatentUS8797771B1Capacitor based AC to DC step up converter

Publication Date: 2014.08.05 ALFRED E MANN FOUND FOR SCI RES

AI summary

An AC-DC step-up converter circuit architecture for generating multiple output voltages, both positive and negative, in an implantable biomedical device is disclosed. Switches and active rectifiers are used inside the converter for charging capacitors from the AC source and delivering currents to the loads. Regulated output voltages with high power efficiency are obtained by controlling the on/off times of the switches using feedback loops that include integrator circuits configured to provide control parameters related to the various output voltages and their associated predetermined reference voltages.