Ultrahigh Voltage Solid Electrolytic Capacitor Surge Current Handling
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Solution Overview
Problem
Conventional solid electrolytic capacitors face issues with delamination and dielectric failure, particularly in high voltage applications due to the inherent weakness of conductive polymer electrolytes and the formation of 'hot spots' during surge currents, leading to degradation and breakdown.
Innovation Solution
The method involves anodically oxidizing a sintered porous anode body at higher forming voltages and lower temperatures to improve dielectric quality, combined with applying a dispersion of conductive polymer particles, such as substituted polythiophene, to form a solid electrolyte, which enhances the capacitor's ability to withstand high voltages and surge currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive polymer electrolytes are used, then low ESR and non-burning failure mode are achieved, but delamination occurs during formation or operation
Solution Approach 1:
The patent applies composite materials by combining conductive polymer particles with a binder material to form a composite solid electrolyte. This composite structure provides both the electrical conductivity of the polymer particles and the mechanical strength and adhesion of the binder, preventing delamination while maintaining low ESR and non-burning failure mode characteristics.
2Quantity of substance
If thinner dielectric areas are present to increase capacitance, then higher capacitance density is achieved, but hot spots develop during surge current leading to dielectric breakdown
Solution Approach 1:
The patent changes the electrical parameters of the solid electrolyte by incorporating conductive polymer particles with specific conductivity characteristics. This modifies the current distribution within the capacitor, reducing the formation of hot spots in thinner dielectric areas during surge current events, thereby preventing dielectric breakdown while maintaining high capacitance density.
3Power
If high voltage is applied to increase power density, then higher power output is achieved, but surge current causes dielectric degradation and breakdown
Solution Approach 1:
The conductive polymer particles act as an intermediary material between the electrodes and the dielectric layer. They provide a controlled electrical interface that manages surge current distribution, preventing direct high-stress contact between surge currents and the dielectric, thus protecting against degradation while enabling high voltage operation for increased power density.
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 resulting ultrahigh voltage solid electrolytic capacitor exhibits improved breakdown voltage and surge current handling capabilities, with specific charge ranging from 3,000 to 40,000 μF*V/g and peak surge current up to 800 Amps, while maintaining uniformity and consistency of the dielectric surface coverage.
Implementation Method 1
anodically oxidizing a sintered porous anode body at a forming voltage of about 300 volts or more to form an anode that contains a dielectric coating on the anode body
Implementation Method 2
applying a dispersion of conductive polymer particles to the anode to form a solid electrolyte
Data Source
AI summary
A capacitor for use in ultrahigh voltage environments is provided. During formation of the capacitor, the forming voltage employed during anodization is generally about 300 volts or more and at temperatures ranging from about 10° C. to about 70° C. Such conditions can substantially improve the quality and thickness of the dielectric without adversely impacting the uniformity and consistency of its surface coverage. In addition, the solid electrolyte is also formed from a dispersion of preformed conductive polymer particles. In this manner, the electrolyte may remain generally free of high energy radicals (e.g., Fe2+ or Fe3+ ions) that can lead to dielectric degradation, particularly at the ultrahigh voltages noted above.