Self-Oscillating Cascode Generator for Low-Loss Electrosurgery
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Solution Overview
Problem
Existing electrosurgical generators face challenges in achieving high efficiency with simple structures, particularly in delivering high power at high frequencies above 100 kHz while minimizing switching losses and avoiding voltage overloading of components.
Innovation Solution
A power generator design featuring a resonant circuit between cascode circuits, which forms a self-oscillating generator with push-pull operation, minimizing switching losses and maintaining frequency stability and spectral purity, and using a cascode circuit configuration with transistors that can withstand high voltages without degrading the resonant circuit quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If externally controlled switches are used to excite resonant circuits in electrosurgical generators, then the generator can deliver high power at high frequencies, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent implements a feedback mechanism where the resonant circuit itself controls the switching of the cascode circuits. The oscillation signal from the resonant circuit is fed back to the control electrodes of the input transistors, creating a self-oscillating system that automatically synchronizes switching with the resonant frequency, thereby minimizing switching losses while delivering high power
Solution Approach 2:
The generator is designed as a self-oscillating system where the resonant circuit generates its own oscillation signal that automatically controls the switching of the power transistors. This eliminates the need for external control signals and ensures that switching occurs at the optimal moment in the resonant cycle, minimizing energy loss
2Device complexity
If simple generator structures are used, then device complexity is reduced, but achieving high efficiency and frequency stability becomes difficult
Solution Approach 1:
The patent merges the oscillation generation function and the power amplification function into a single integrated circuit structure. The cascode circuits are directly coupled to the resonant circuit, and the feedback path combines the oscillation signal with the control signals, creating a unified system that achieves both simplicity and frequency stability
Solution Approach 2:
The patent replaces complex external control mechanisms with an electronic feedback system. Instead of using separate control circuits and external switches, the system uses electronic feedback from the resonant circuit to directly control the transistor switching, achieving frequency stability through electronic means rather than mechanical or external control
3Productivity
If high-frequency current is used for electrosurgery, then cutting and coagulation effectiveness is improved, but neuromuscular irritation increases if frequency is not sufficiently high
Solution Approach 1:
The patent is designed to operate at frequencies well above 100 kHz, which is the threshold for avoiding neuromuscular irritation. The resonant circuit and cascode configuration enable efficient generation and delivery of high-frequency current that effectively cuts and coagulates tissue without causing harmful neuromuscular stimulation
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 enables the generation of high-frequency alternating voltage with minimal switching losses, achieving high efficiency and frequency stability suitable for electrosurgical applications, with reduced voltage stress on control electrodes and minimal need for additional protection components.
Implementation Method 1
A power generator design featuring a resonant circuit between cascode circuits, which forms a self-oscillating generator
Implementation Method 2
The cascode circuits are connected to one another in a feedback-coupling manner and, together with the resonant circuit, form a self-oscillating generator. The two cascode circuits work in push-pull mode, with switching losses in the two cascode circuits being minimized by the mutual positive feedback.
Implementation Method 3
A power generator design featuring a resonant circuit between cascode circuits, which forms a self-oscillating generator with push-pull operation, minimizing switching losses and maintaining frequency stability and spectral purity, and using a cascode circuit configuration with transistors that can withstand high voltages without degrading the resonant circuit quality.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The power generator (22) according to the invention is self-oscillating. It comprises two cascode circuits (31, 32) whose outputs (A1, A2) are connected to a parallel resonant circuit (23) to drive it in push-pull mode. The input transistors (33, 35) of the cascode circuits (31, 32) are cross-coupled, while the control electrodes of the output transistors (34, 36) are at a fixed potential. The power oscillator 22 is self-controlled, so that the transistors (33) to (36) exhibit minimal switching losses.