Piezoelectric Transformer Power Supply for MRI EMI Reduction
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Solution Overview
Problem
Conventional voltage converter devices generate high transient currents that produce significant Electromagnetic Interference (EMI), making them unsuitable for applications like MRI and low noise signal switching due to adverse effects on imaging quality and signal integrity, and they often have electrical isolation and leakage current issues that raise patient safety concerns.
Innovation Solution
A power supply utilizing a piezoelectric transformer and an oscillator circuit to generate a sinusoidal voltage waveform, which is used in a self-oscillating linear DC to DC step-converter configuration with a feedback circuit and micro-electromechanical system (MEMS) switch to achieve reduced EMI and efficient voltage step-up conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional voltage converter devices (switching circuits, charge-pumps, flyback inductors) are used, then voltage conversion function is achieved, but high transient currents generate significant EMI that affects imaging quality and signal integrity
Solution Approach 1:
The patent replaces conventional electronic switching circuits, charge-pumps, and flyback inductors with a piezoelectric transformer that operates on piezoelectric principles rather than electromagnetic switching. This mechanical/vibrational approach eliminates the high transient currents that generate EMI, while still achieving voltage conversion through resonant frequency operation of the piezoelectric material
Solution Approach 2:
The invention changes the operating parameters from high-current switching modes to low-current resonant vibration modes. By operating the piezoelectric transformer at its resonant frequency with sinusoidal drive signals, the system achieves voltage conversion with dramatically reduced current transients and EMI emissions compared to conventional switching converters
2Object-generated harmful factors
If shielding and filtering are used to reduce EMI, then EMI levels are lowered, but magnetic and RF field homogeneity is distorted
Solution Approach 1:
Instead of using shielding and filtering to suppress EMI after it is generated, the invention inverts the approach by eliminating the EMI generation mechanism itself. The piezoelectric transformer inherently operates without the high-current switching that creates EMI, making shielding and filtering unnecessary and preserving field homogeneity
3Object-generated harmful factors
If air core transformer techniques are used, then EMI is reduced compared to magnetic transformers, but efficiency is low and large currents still generate EMI
Solution Approach 1:
The patent replaces electromagnetic transformer operation with piezoelectric vibration-based operation. The piezoelectric transformer uses mechanical vibrations at resonant frequency to transfer energy between input and output electrodes through the piezoelectric material, eliminating the need for large currents and achieving both high efficiency and low EMI
4Power
If high voltage interfaces are used to provide power outside noise sensitive areas, then power delivery is achieved, but electrical isolation and leakage current issues arise that concern patient safety
Solution Approach 1:
The invention extracts and eliminates the high voltage interface component that creates isolation and leakage current problems. By using a piezoelectric transformer that can operate with low-voltage sinusoidal inputs and generate high-voltage outputs internally through voltage multiplication, the system removes the need for external high voltage interfaces while maintaining electrical isolation and patient safety
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 minimizes EMI emissions, allowing operation in magnetic environments like MRI systems and provides low noise power conversion with reduced adverse effects on signal quality and patient safety, while maintaining efficient voltage amplification.
Implementation Method 1
Power supply with a piezoelectric transformer and method for power conversion
Implementation Method 2
The oscillator circuit controls a sinusoidal voltage waveform at an input of the piezoelectric transformer
Data Source
AI summary
A power supply with a piezoelectric transformer is provided. A method for power conversion is also provided. The power supply includes a piezoelectric transformer and an oscillator circuit connected to the piezoelectric transformer. The oscillator circuit controls a sinusoidal voltage waveform at an input of the piezoelectric transformer to drive the piezoelectric transformer.