Shielded Capacitor Assembly for Low ESR at High Frequency
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Solution Overview
Problem
Conventional capacitor assemblies face challenges in maintaining low equivalent series resistance (ESR) and smooth impedance behavior above their self-resonant frequency, particularly in high-frequency applications such as electric vehicle charging stations.
Innovation Solution
A capacitor assembly comprising multiple capacitor elements arranged in stacked pairs with bus bars connected to their terminals, and conductive shields covering the side surfaces of the capacitor elements to enhance heat dissipation and reduce ESR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If capacitor elements are connected with wide tabs enclosing minimal area to reduce series inductance, then high frequency performance is improved, but ESR reduction is limited and heating issues persist above self-resonant frequency
Solution Approach 1:
The patent transitions from two-dimensional tab connections to three-dimensional conductive shields that wrap around the capacitor elements. This dimensional change allows the shields to provide multiple connection paths and larger surface area for heat dissipation, simultaneously reducing ESR and improving high-frequency performance without the trade-off present in conventional tab designs
Solution Approach 2:
The conductive shields act as intermediary elements between the capacitor elements and the bus bars. These shields provide an intermediate connection structure that reduces the overall series inductance and ESR of the capacitor assembly, while also serving as heat dissipation pathways, thus mediating between the electrical connection requirements and thermal management needs
2Adaptability or versatility
If low-capacitance elements are arranged nearest the terminals and high-capacitance elements further away to present sequential impedance range, then impedance matching is improved, but ESR remains high and heating occurs above self-resonant frequency
Solution Approach 1:
The patent merges the functions of impedance matching and ESR reduction by integrating conductive shields with all capacitor elements regardless of their position in the stack. This combination allows the assembly to maintain sequential impedance characteristics while simultaneously providing low ESR pathways through the shields, eliminating the need to choose between impedance matching and low ESR designs
3Power
If capacitor assembly is designed to handle high frequency ripple currents at significant amperage levels, then power handling capability is improved, but supernumerary resonances cause excessive heating
Solution Approach 1:
The patent converts the potentially harmful effect of self-resonance and supernumerary resonances into beneficial heat dissipation pathways. The conductive shields are designed to provide controlled resonance paths that dissipate energy as heat through their surface area, transforming what would be harmful concentrated heating into beneficial distributed heat dissipation that actually helps manage temperature during high-power operation
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 proposed design achieves low ESR and smooth impedance curves across a wide frequency spectrum, minimizing heating and ensuring efficient performance even above the self-resonant frequency.
Implementation Method 1
conductive shields covering the side surfaces of the capacitor elements to enhance heat dissipation and reduce ESR
Implementation Method 2
A first polarity bus bar and a second polarity bus bar are electrically connected to the plurality of capacitor elements
Data Source
AI summary
A capacitor assembly comprises a plurality of capacitor elements (e.g., four or more capacitor elements) each having a first end surface and a second end surface defining a first polarity terminal and a second polarity terminal, respectively. The plurality of capacitor elements are arranged in at least one stacked pair with a first polarity terminal of a first capacitor element in each stacked pair being opposed to a first polarity terminal of a second capacitor element in such stacked pair. The plurality of capacitor elements in this aspect are contained in a housing. A first polarity bus bar and a second polarity bus bar are electrically connected to the plurality of capacitor elements. The plurality of capacitor elements may be connected in parallel.