Self-Oscillating Cascode Generator for Low-Loss Electrosurgery
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Solution Overview
Problem
Existing electrosurgical generators require complex configurations and external power sources, leading to inefficiencies and potential voltage overload issues, particularly at high frequencies above 100 kHz.
Innovation Solution
A self-oscillating generator circuit with a resonant circuit between the outputs of two cascode circuits, which operate in push-pull mode with positive feedback, minimizing switching losses and allowing for high-frequency stability and spectral purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If external power sources and complex configurations are used in existing electrosurgical generators, then sufficient power output for high-frequency operation is achieved, but device complexity and potential voltage overload issues increase
Solution Approach 1:
The patent combines the power generation function and voltage regulation function into a single integrated self-oscillating generator circuit. The cascode circuits with resonant circuit generate and regulate voltage simultaneously, eliminating the need for separate external power sources and complex voltage regulation stages, thus reducing device complexity while maintaining sufficient power output for electrosurgical applications
Solution Approach 2:
The generator is designed as a self-oscillating system that automatically generates the required high-frequency alternating voltage without external control signals. The positive feedback through the resonant circuit enables the circuit to self-regulate and self-oscillate at the desired frequency, reducing the need for complex external control systems and power management circuits
2Reliability
If high frequencies above 100 kHz are used to avoid neuromuscular stimulations, then patient safety is improved, but switching losses and efficiency decrease
Solution Approach 1:
The patent employs periodic switching action through self-oscillating cascode circuits that operate in alternating phases. The resonant circuit naturally oscillates at the desired high frequency, causing the cascode transistors to switch periodically in a push-pull manner. This periodic operation allows the circuit to achieve high frequencies above 100 kHz for patient safety while minimizing switching losses through optimized switching timing and resonant energy transfer
Solution Approach 2:
The circuit parameters including switching frequency, resonant frequency, and operating voltage are optimized to work together at high frequencies. The resonant circuit is designed with specific L and C values to oscillate at the target frequency range, and the cascode transistor parameters are selected to minimize switching losses at these high frequencies, thereby maintaining both patient safety and energy efficiency
3Stability of the object's composition
If self-oscillating operation with resonant circuit is implemented, then frequency stability and spectral purity are improved, but circuit complexity increases
Solution Approach 1:
The patent implements positive feedback through the resonant circuit connected to the cascode circuits. The resonant circuit feeds a portion of the output signal back to the input, reinforcing the oscillation at the desired frequency. This feedback mechanism ensures frequency stability and spectral purity by continuously reinforcing the fundamental frequency while suppressing harmonics, achieving stable self-oscillation without requiring complex external frequency control circuits
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 proposed generator achieves high efficiency and frequency stability, particularly at frequencies above 100 kHz, with reduced switching losses and simplified configuration, making it suitable for electrosurgical applications.
Implementation Method 1
A self-oscillating generator circuit with a resonant circuit between the outputs of two cascode circuits, which operate in push-pull mode with positive feedback
Implementation Method 2
The cascode circuits are connected with one another in feedback (positive feedback) manner and thus form together with the resonant circuit a self-oscillating generator
Data Source
AI summary
A power generator (22) according to the invention is configured in a self-oscillating manner. It comprises two cascode circuits (31, 32), the outputs (A1, A2) of which are connected with a parallel resonant circuit (23) in order to excite it in push-pull manner. The input transistors (33, 35) of cascode circuits (31, 32) are cross-coupled, whereas the control electrodes of the output transistors (34, 36) are connected with non-varying potential. The power oscillator (22) is self-controlled such that the transistors (33-36) comprise lowest switching losses.