Resonant-H Electrosurgical Generator Feedback for Heat and Harmonics
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Solution Overview
Problem
Existing electrosurgical power amplifiers are inefficient, leading to excessive heat generation and maintenance issues, and they often introduce undesirable harmonics due to low conversion efficiency and quality factor changes in tuned resonance circuits.
Innovation Solution
A generator system with a gain stage and a class resonant-H amplifier, featuring a voltage source, sensors, and a controller to manage operational parameters, which includes a class A/B amplifier in a push-pull configuration and a pulse width modulated switch, optimizing output voltage and reducing heat sink needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a class A/B power amplifier is used to achieve surgical signal output, then the output power is sufficient, but the conversion efficiency is low and excessive heat is generated
Solution Approach 1:
The patent changes the operating parameters of the amplifier by transitioning from a conventional class A/B architecture to a class resonant-H architecture. This involves modifying the biasing conditions, operating point, and circuit topology to achieve resonant operation, which fundamentally alters the efficiency characteristics while maintaining the required output power capability for electrosurgical applications.
Solution Approach 2:
The patent employs periodic switching action characteristic of resonant switching mode power amplifiers. The class resonant-H amplifier utilizes periodic on/off switching of power devices in conjunction with resonant tanks to transfer energy to the load, replacing the continuous linear operation of class A/B amplifiers. This periodic action enables high efficiency by minimizing dissipative losses during energy transfer.
2Loss of energy
If a class resonant-H amplifier is used to improve conversion efficiency, then heat generation is reduced, but the quality factor changes with load making it difficult to maintain desired voltage or current
Solution Approach 1:
The patent implements feedback control mechanisms to monitor and adjust the amplifier's operating parameters in real-time. By sensing the actual output conditions and load variations, the feedback system dynamically compensates for quality factor changes, maintaining stable voltage or current output despite varying load conditions. This closed-loop control ensures consistent performance across different operating points.
Solution Approach 2:
The patent employs dynamic parameter adjustment where the amplifier's operating characteristics are continuously adapted to match load conditions. The resonant-H architecture allows dynamic tuning of the resonant frequency and impedance matching networks to maintain optimal quality factor and output stability as the load varies during electrosurgical procedures.
3Loss of energy
If a tuned resonance circuit is used to achieve high efficiency, then energy conversion is improved, but undesirable harmonics are introduced due to quality factor changes
Solution Approach 1:
The patent introduces intermediary filtering elements and impedance matching networks between the resonant amplifier stage and the load. These intermediary components act as mediators that selectively pass the fundamental frequency while attenuating harmonic frequencies. The resonant tanks and output filters serve as intermediaries that decouple the harmonic generation in the amplifier from the load, preventing radiofrequency interference while maintaining efficient energy transfer.
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 system achieves higher efficiency and reduced heat generation, minimizing thermal stress and improving reliability by maintaining desired voltage and current levels, while reducing radiofrequency interference.
Implementation Method 1
A class resonant-H RF electrosurgical generator may be utilized
Data Source
AI summary
A generator for use with an electrosurgical device is provided. The generator has a gain stage electrically disposed between a first voltage rail and a second voltage rail, wherein the gain stage includes an input and an output. A voltage source operably coupled to the gain stage input and configured to provide an input signal thereto responsive to a drive control signal is also provided. The generator also has one or more sensors configured to sense an operational parameter of the amplifier and to provide a sensor signal corresponding thereto and a controller adapted to receive the sensor signal(s) and in response thereto provide a drive control signal to the voltage source. The generator has an amplifier output configured to supply an output voltage corresponding to the first voltage rail and the second voltage rail when the output of the gain stage falls between a voltage of the first voltage rail and a voltage of the second voltage rail and is configured to supply a peak voltage output when the voltage output is falls greater than the voltage of the first voltage rail or less than the voltage of the second voltage rail.