Resonant Inverter Dead-Time Optimization via Sensor Feedback
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Solution Overview
Problem
Phase-shifted full bridge resonant inverters in electrosurgical generators face efficiency drops due to suboptimal dead-times in field effect transistors (FET) transitions, leading to partial zero-voltage and hard-switching, which affects the dynamic range and efficiency of radiofrequency amplifiers.
Innovation Solution
An electrosurgical generator with a sensor array and PWM controller that measures input and output properties to calculate efficiency and load measurements, adjusting dead-times based on these measurements and a look-up table to optimize FET transitions, ensuring optimal phase-shift and load conditions for improved efficiency and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed dead-time is provided between FET pulses to avoid short circuit, then the reliability of the resonant inverter is improved, but the efficiency drops dramatically due to partial hard-switching
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed dead-time to a dynamic, adjustable dead-time that adapts to varying operating conditions. The controller modifies the dead-time duration based on real-time measurements of tank voltage, phase-shift, and load conditions, allowing the system to optimize between reliability (avoiding short circuits) and efficiency (minimizing hard-switching losses) across different operating points.
Solution Approach 2:
The patent implements parameter changes by adjusting the dead-time parameter based on measured operating conditions. The controller uses look-up tables and real-time measurements to modify the dead-time duration, transforming it from a static parameter to a dynamically optimized parameter that responds to changing tank voltage, phase-shift, and load conditions.
2Ease of operation
If the dead-times are too large or too short, then the FET transition operates in partial zero-voltage and partial hard-switching, but the efficiency of the resonant inverter drops dramatically
Solution Approach 1:
The patent applies feedback by continuously measuring tank voltage, phase-shift, and load conditions, then using this information to adjust the dead-time. The controller implements a closed-loop system where efficiency measurements and operating conditions feed back to optimize the dead-time parameter, ensuring FET transitions operate in zero-voltage switching mode rather than hard-switching mode.
Solution Approach 2:
The patent uses preliminary action by pre-calculating optimal dead-times for various operating conditions and storing them in look-up tables. Before actual operation at a given power level, the system has already determined the appropriate dead-time based on anticipated tank voltage and phase-shift conditions, allowing immediate optimization without trial-and-error adjustments.
3Loss of energy
If optimal dead-times are adjusted based on tank voltage and phase-shift measurements, then the efficiency and dynamic range are improved, but the device complexity increases due to sensor array and controller requirements
Solution Approach 1:
The patent applies universality by designing the sensor array and controller to perform multiple functions: measuring tank voltage, determining phase-shift, calculating load conditions, selecting optimal dead-times from look-up tables, and adjusting FET gating signals. This multi-functional approach consolidates what could be separate complex subsystems into an integrated control architecture.
Solution Approach 2:
The system implements self-service by using its own operational measurements (tank voltage, phase-shift, current) to automatically adjust its own timing parameters. The controller monitors the resonant inverter's performance and autonomously optimizes the dead-time without requiring external intervention or complex manual calibration procedures.
Data Source
AI summary
The present disclosure is directed to an electrosurgical generator including a resonant inverter having an H-bridge and a tank. A sensor array measures at least one property of the tank. A pulse width modulation (PWM) controller outputs a first PWM timing signal and a second PWM timing signal to the H-bridge. The PWM controller controls a dead-time between the first PWM timing signal and the second PWM timing signal based on the at least one property measured by the sensor array.