Electrosurgical Generator H-Bridge Leakage Reduction
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Solution Overview
Problem
Radiofrequency amplifiers using phase-shifted full bridge resonant inverters face issues with common mode currents and high frequency leakage due to the presence of a series capacitor in the tank, which can lead to charge imbalances and potential harm to patients or users.
Innovation Solution
An electrosurgical generator with a tank topology and an H-bridge configuration, where a capacitor is placed at the center tap of the transformer's secondary winding, along with a charge drain mechanism using a switching member to control charge imbalance, reduces common mode currents and high frequency leakage by mitigating current imbalances between terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a capacitor is placed in series with the secondary of the transformer to prevent DC current flow, then patient safety is improved, but common mode currents and high frequency leakage increase
Solution Approach 1:
A common mode choke is introduced as an intermediary component in series with the capacitor CS2. The choke acts as a mediator that blocks common mode currents and high frequency leakage while allowing the capacitor to continue preventing DC current flow to the patient. This resolves the contradiction by adding a component that specifically targets the harmful high frequency effects without interfering with the DC blocking function.
Solution Approach 2:
The solution applies different filtering characteristics to different frequency ranges by combining a capacitor (which blocks DC) with a common mode choke (which targets high frequency common mode currents). Each component addresses a specific quality of the harmful factors - the capacitor handles DC prevention while the choke handles high frequency suppression, creating localized quality improvement for each type of harmful current.
2Object-affected harmful factors
If capacitor CS2 is added to the tank circuit to block DC current, then safety is improved, but charge imbalance and high frequency output distortion occur
Solution Approach 1:
The common mode choke serves as an intermediary that compensates for the distorting effects of capacitor CS2 on high frequency output. By placing the choke in series with the capacitor, it filters out the high frequency distortions and charge imbalances introduced by the capacitor while maintaining the DC blocking function, thus preserving output quality.
Solution Approach 2:
The invention converts the harmful high frequency distortion and charge imbalance caused by capacitor CS2 into a manageable issue by using the common mode choke to filter these specific artifacts. The choke transforms the problematic high frequency content into a filtered signal, turning the harmful side effect into a controlled parameter that can be managed within the circuit design.
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 effectively reduces common mode currents and high frequency leakage, ensuring safer operation by preventing DC current flow into the output and allowing for precise control of RF energy delivery during electrosurgical procedures.
Implementation Method 1
a capacitor (CS2) placed in series with the secondary of the transformer T1 to prevent DC current from flowing into the output of the active terminal 110
Implementation Method 2
electrosurgical generator that uses a phase-shifted full bridge resonant inverter
Data Source
Figure 1
Figure 2
Figure 3A~5
AI summary
The present disclosure is directed to an electrosurgical generator an H-bridge and a tank driven by the H-bridge. The tank includes a transformer having a primary winding and a secondary winding. The secondary winding includes a first coil and a second coil. In the electrosurgical generator, a capacitor is connected in series between the first coil and the second coil.