Piezoelectric Transformer Electrode Design for Ohmic Input
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Solution Overview
Problem
Conventional piezoelectric transformers experience inefficiencies due to capacitive input impedance, leading to reactive power components and increased losses, which cannot be fully mitigated by existing compensation methods without heat generation or operating outside optimal efficiency ranges.
Innovation Solution
The piezoelectric transformer design features inner electrodes with differently dimensioned sub-sections in multiple layers, ensuring the input capacitance is less than or equal to the output capacitance multiplied by the transformation ratio, resulting in a purely ohmic input impedance and minimized reactive power components, even under varying loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional series inductance is used to compensate capacitive input impedance, then reactive power component is reduced, but electrical losses increase due to transfer losses between input capacitance and series inductance
Solution Approach 1:
The invention extracts and eliminates the series inductance component from the control circuit by redesigning the electrode structure. The different dimensioning of inner electrodes in multiple layers directly compensates for capacitive input behavior without requiring external compensation components, thereby removing the source of transfer losses while maintaining circuit simplicity.
Solution Approach 2:
The invention applies local quality by creating non-uniform electrode dimensions at specific locations within the piezoelectric element. The inner electrodes in different layers have different lengths, with some extending further than others, creating localized capacitive effects that collectively compensate for the overall capacitive input impedance without affecting the entire structure uniformly.
2Ease of operation
If piezoelectric transformer is operated outside maximum efficiency range to achieve purely ohmic input impedance, then reactive power component is eliminated, but efficiency decreases due to increased losses in piezoelectric element
Solution Approach 1:
The invention performs preliminary action by pre-configuring the electrode dimensions during manufacturing to achieve the desired capacitive compensation effect. The inner electrodes are designed with specific different lengths before operation, so that the transformer inherently exhibits purely ohmic input impedance at maximum efficiency without requiring operational adjustments or compromises.
Solution Approach 2:
The invention changes the geometric parameters of the inner electrodes, specifically the length of electrodes in different layers. By adjusting these dimensions to satisfy the condition L1 < L2, the electrical characteristics of the transformer are modified to achieve purely ohmic input impedance while maintaining operation at maximum efficiency point.
3Temperature
If finite electrode conductance is increased to reduce heat-up, then electrical losses decrease, but device complexity increases due to additional compensation requirements
Solution Approach 1:
The invention enables the piezoelectric transformer to self-compensate for its capacitive input behavior through its own electrode structure. The different dimensioning of inner electrodes creates internal capacitive effects that automatically compensate for losses without requiring external compensation circuits or additional control mechanisms, thereby reducing heat-up without increasing device complexity.
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
This design achieves maximum efficiency with a purely ohmic input impedance, eliminating reactive power components and reducing electrical losses, allowing for simpler control and increased overall efficiency without the need for additional components like series inductance.
Implementation Method 1
a piezoelectric element with a predetermined longitudinal dimension of length L, along which at least one input side and at least one output side of the transformer are defined
Implementation Method 2
The efficiency maximum of such a piezoelectric transformer is reached at a specific resonance frequency
Data Source
AI summary
The invention relates to a piezoelectric transformer having a piezoelectric element (1) of the length L, wherein an input voltage Uin can be applied on an input side (2) for being transformed into an output voltage Uout on the output side (3) according to a transformation ratio Uout/Uin=Ku. The piezoelectric element (1) comprises multiple plies (4a, 4b, 4c) of inner electrodes, which are arranged in multiple different layers (S1, S2, S3). Each ply (4a, 4b, 4c) of inner electrodes extends along at least one predetermined sub-section of a predetermined length, wherein sub-sections of plies (4a, 4c) of a first group of layers (S1, S3) and sub-sections of plies (4b) of a second group of layers (S2) have different dimensions, so that the piezoelectric transformer satisfies the following condition: Cin≤N2Cout, wherein Cin indicates the input capacitance, Cout indicates the output capacitance, and N indicates the transformation ratio of the ideal transformer.