Planar Transformer Stray Capacitance Reduction
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Solution Overview
Problem
Electrosurgical devices face significant challenges due to stray capacitance in their output transformers, leading to HF current leakage, which existing transformer designs have not adequately addressed.
Innovation Solution
A planar push-pull output transformer with a split transformer configuration using inductively coupled planar ferrite cores to minimize stray capacitance, enhance inductance leakage, and improve waveform filtering, while allowing easy attachment of cooling heat-sinks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional transformer design is used, then the transformer can provide power transformation, but stray capacitance is high causing HF current leakage
Solution Approach 1:
The transformer is divided into two separate planar cores (first planar core and second planar core) with windings distributed across both cores. This segmentation reduces the overall stray capacitance by distributing the magnetic flux and electrical fields across separate physical structures, thereby minimizing HF current leakage while maintaining power transformation functionality.
2Volume of moving object
If transformer size is reduced for compactness, then device footprint is minimized, but stray capacitance increases causing more HF leakage
Solution Approach 1:
The invention transitions from traditional three-dimensional wound transformers to a planar two-dimensional configuration. The windings are arranged in planar layers on flat cores, reducing the vertical height and overall volume while distributing capacitance across a larger surface area, thereby minimizing stray capacitance effects despite compact dimensions.
3Manufacturing precision
If traditional winding structures are used, then power transformation is achieved, but waveform filtering is insufficient producing non-sinusoidal output
Solution Approach 1:
The transformer structure is segmented into two independent planar core assemblies, each contributing to the overall magnetic circuit. This segmentation enables better control of magnetic flux distribution and reduces harmonics, producing a cleaner sinusoidal waveform while maintaining a relatively simple planar construction that is easier to manufacture than complex traditional windings.
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 stray capacitance to about 5 pF, enhances waveform filtering to produce a sinusoidal output, increases isolation breakdown voltage to 10 kV, and facilitates efficient cooling, thereby minimizing HF current leakage and improving operational stability.
Implementation Method 1
A first planar ferrite core and a second planar ferrite core inductively coupled to one another and disposed in a common magnetic circuit
Implementation Method 2
A planar push-pull output transformer with a split transformer configuration using inductively coupled planar ferrite cores to minimize stray capacitance
Implementation Method 3
The use of planar ferrite cores allows cooling heat-sinks to be attached easily to the flat surface of the planar core
Data Source
AI summary
A planar transformer power supply for an electrosurgical device to minimize stray capacitance comprising a step down/step-up isolation transformer and circuitry to limit the effects of a short circuit in the output of the planar transformer power supply on the input to the planar transformer power supply to enhance power capacity at a low load impedance as low as from about 5 ohms to about 10 ohms and to operate at resonance at the output of the planar transformer power supply.