Integrated EMI Filter TVS Circuit with Stable Capacitance
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Solution Overview
Problem
Conventional EMI filters with integrated transient voltage suppressors (TVS) face unreliable filtering performance due to capacitance variations induced by bias voltage and environmental factors like light and noise, affecting audio signal reception quality.
Innovation Solution
A TVS circuit integrated with an EMI filter featuring Zener diodes and MOS capacitors, where the capacitors are connected in parallel between input and ground terminals, maintaining constant total capacitance across different bias voltages, and utilizing a semiconductor substrate with doped regions and trenches filled with dielectric material to ensure symmetric capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Zener diode junction capacitance is used for EMI filter capacitance, then the filter can be integrated with TVS on a monolithic device, but the capacitance varies with bias voltage and environmental conditions leading to unreliable filtering performance
Solution Approach 1:
The patent segments the capacitance function by introducing separate MOS capacitors distinct from the Zener diode structure. The Zener diode handles voltage suppression while dedicated MOS capacitors provide filtering capacitance, eliminating the coupling between TVS and filter capacitance functions that caused reliability issues.
Solution Approach 2:
The MOS capacitors serve dual purposes: they provide the necessary capacitance for EMI filtering while also being part of the integrated circuit structure. The same capacitor structures contribute to both signal filtering and can be configured to support the TVS operation, achieving multi-functionality without compromising reliability.
2Adaptability or versatility
If Zener diode is configured with floating junction to achieve symmetrical blocking structure, then bi-directional voltage suppression is enabled, but capacitance becomes very sensitive to environmental conditions such as light and noise
Solution Approach 1:
The patent extracts the capacitance function from the Zener diode's floating junction by introducing separate MOS capacitors. This removes the harmful environmental sensitivity associated with the floating junction capacitance while preserving the bi-directional voltage suppression capability of the Zener diode structure.
Solution Approach 2:
The MOS capacitors act as intermediaries between the Zener diode's voltage suppression function and the EMI filter's capacitance requirement. By introducing this intermediary element, the patent decouples the environmental sensitivity of the Zener junction from the filter capacitance, allowing bi-directional suppression without environmental vulnerability.
3Reliability
If high capacitance tolerance value is used to maintain reliable filtering performance under environmental variations, then filtering reliability improves, but the device requires larger capacitance tolerance specifications increasing design complexity
Solution Approach 1:
The patent changes the physical parameters of the capacitors by using MOS capacitor structures with gates connected to fixed potential nodes. This parameter change stabilizes the capacitance value against environmental variations, achieving reliable filtering performance without requiring excessive capacitance tolerance margins.
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 provides a stable and controllable capacitance, enhancing filtering performance by maintaining constant capacitance values regardless of bias voltage changes, thus ensuring reliable signal reception and reduced sensitivity to environmental conditions.
Implementation Method 1
a TVS circuit integrated with an EMI filter featuring Zener diodes and MOS capacitors, where the capacitors are connected in parallel between input and ground terminals, maintaining constant total capacitance across different bias voltages
Implementation Method 2
This invention relates to an improved circuit configuration and method of manufacturing a symmetrical bi-directional blocking transient voltage suppressor (TVS) implemented with zener diodes and zener diode triggered bipolar transistors
Implementation Method 3
utilizing a semiconductor substrate with doped regions and trenches filled with dielectric material to ensure symmetric capacitance
Implementation Method 4
trenches filled with dielectric material to ensure symmetric capacitance
Data Source
AI summary
A transient voltage suppressing (TVS) circuit with uni-directional blocking and symmetric bi-directional blocking capabilities integrated with an electromagnetic interference (EMI) filter supported on a semiconductor substrate of a first conductivity type. The TVS circuit integrated with the EMI filter further includes a ground terminal disposed on the surface for the symmetric bi-directional blocking structure and at the bottom of the semiconductor substrate for the uni-directional blocking structure and an input and an output terminal disposed on a top surface with at least a Zener diode and a plurality of capacitors disposed in the semiconductor substrate to couple the ground terminal to the input and output terminals with a direct capacitive coupling without an intermediate floating body region.