ESD Filter with Balanced Parasitic Capacitance for Common Mode Noise
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Solution Overview
Problem
Existing common mode filters with integrated ESD protection devices face challenges in maintaining predetermined filter characteristics while ensuring effective ESD protection, as the parasitic inductance and capacitance introduced by the ESD protection device affect the original filter characteristics, leading to deteriorated performance.
Innovation Solution
A filter design incorporating a differential transmission line, a common mode choke coil, and an ESD protection circuit with strategically placed series resonant circuits and diodes, where the parasitic capacitances of the ESD protection devices are balanced to form trap filters for common mode noise, reducing parasitic components and improving ESD protection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ESD protection device is integrated into a common mode filter, then ESD protection capability is improved, but parasitic inductance and capacitance affect the filter characteristics causing performance deterioration
Solution Approach 1:
The ESD protection function is separated from the common mode filter into an independent ESD protection circuit. This segmentation allows each component to be optimized independently - the filter maintains its original characteristics while the ESD circuit provides protection without introducing harmful parasitics into the filter path.
Solution Approach 2:
A dedicated ESD protection circuit acts as an intermediary between the differential transmission line and ground, providing ESD protection through a separate current path. This intermediary structure prevents ESD currents from flowing through the filter components, avoiding degradation of filter characteristics.
2Manufacturing precision
If the size of the ESD protection device is reduced to decrease parasitic capacitance, then filter characteristic is improved, but ESD protection characteristic deteriorates
Solution Approach 1:
By segmenting the ESD protection function into a separate circuit with dedicated components, the ESD device can be optimized for protection performance without size constraints imposed by filter requirements. The separate ESD circuit can use larger capacitance values for better protection while the filter maintains its own optimized component values.
Solution Approach 2:
The ESD protection circuit uses parameter optimization specific to ESD protection - including larger capacitance values and carefully selected inductance values - without being constrained by filter performance requirements. This allows the ESD circuit to achieve superior protection characteristics independent of the filter's parameter constraints.
3Adaptability or versatility
If wiring sections connect the common mode filter and ESD protection device, then ESD protection function is added, but inductive component (parasitic inductance) increases affecting filter performance
Solution Approach 1:
The ESD protection circuit serves as an intermediary with dedicated low-inductance connection paths to ground. This separate intermediary structure provides ESD protection through a parallel path that does not introduce parasitic inductance into the filter's signal path, maintaining filter performance while adding protection functionality.
Solution Approach 2:
The ESD protection is implemented in a separate dimensional space - a parallel current path to ground - rather than series connections that would affect the filter's signal path. This dimensional separation allows ESD protection functionality to be added without impacting the filter's electrical characteristics.
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 filter design maintains predetermined filter characteristics while enhancing ESD protection performance by widening the elimination band for common mode noise and reducing unnecessary coupling and induction, thereby improving overall filter performance.
Implementation Method 1
a common mode choke coil including a first inductor inserted in the first signal line, and a second inductor inserted in the second signal line and magnetically coupled to the first inductor
Implementation Method 2
a first series resonant circuit is formed by a parasitic capacitance of the first ESD protection device, a parasitic capacitance of the third ESD protection device, and the third inductor, and a second series resonant circuit is formed by a parasitic capacitance of the second ESD protection device, the parasitic capacitance of the third ESD protection device, and the third inductor
Data Source
AI summary
A filter that includes a series circuit of a first Zener diode and a second Zener diode, a third Zener diode connected between a node and ground, and a third inductor. A first series resonant circuit is formed by a parasitic capacitance of the first Zener diode, a parasitic capacitance of the third Zener diode, and the third inductor, and a second series resonant circuit is formed by a parasitic capacitance of the second Zener diode, the parasitic capacitance of the third Zener diode, and the third inductor. Moreover, the parasitic capacitances of the first Zener diode and the second Zener diode are substantially equal, and the parasitic capacitance of the third Zener diode is larger than the parasitic capacitance of each of the first Zener diode and the second Zener diode.