Integrated Snubber in Single Poly MOSFET for Ringing Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
MOSFET devices face a trade-off between efficiency and ringing due to high parasitic capacitance (Coss), making it difficult to achieve optimal balance and reduce voltage peaks in DC-DC applications, especially with shielded gate trench MOSFETs which have fixed Coss values.
Innovation Solution
Integration of a snubber circuit within the MOSFET die using dummy device structures in parallel with active MOSFETs, allowing for adjustable Coss values and reduced PCB area without additional mask layers, enabling flexible design to minimize ringing while maintaining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If SGT MOSFET devices are used to achieve high Coss values, then device efficiency is improved, but ringing increases due to fixed Coss values
Solution Approach 1:
The patent applies dynamics by making the Coss value adjustable rather than fixed. Dummy device structures are integrated into the MOSFET die, allowing the designer to dynamically adjust the total Coss value by connecting different numbers of dummy devices in parallel, thereby optimizing the balance between efficiency and ringing for specific application requirements
Solution Approach 2:
The patent changes the parameter Coss from a fixed value to an adjustable value range. By integrating dummy device structures that can be selectively connected, the total Coss becomes a variable parameter that can be tuned to achieve optimal performance, resolving the contradiction between efficiency improvement and ringing control
2Object-generated harmful factors
If external snubber circuits are added to reduce ringing, then voltage peaks are reduced, but device complexity and PCB area increase
Solution Approach 1:
The patent merges the snubber circuit functionality directly into the MOSFET die by integrating dummy device structures. This combination eliminates the need for separate external snubber components, reducing PCB area and overall device complexity while maintaining the ability to reduce voltage peaks and control ringing
Solution Approach 2:
The dummy device structures serve multiple functions: they can act as additional capacitance to reduce ringing, they provide adjustable Coss values for optimization, and they eliminate the need for external snubber circuits. This multi-functionality reduces overall system complexity while achieving voltage peak control
3Object-generated harmful factors
If Coss is increased to reduce ringing, then voltage peaks are reduced, but device efficiency decreases
Solution Approach 1:
The patent makes Coss a dynamic, adjustable parameter rather than a fixed value. By selectively connecting dummy device structures, the total Coss can be precisely tuned to achieve the minimum necessary capacitance for ringing control, avoiding excessive Coss values that would unnecessarily reduce efficiency
Solution Approach 2:
The patent transforms Coss from a fixed parameter to an adjustable parameter with a specific range. This allows optimization of the Coss value for each application, finding the precise balance point where ringing is adequately controlled while efficiency is maximized, rather than using overly conservative high Coss values
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 approach allows for independent adjustment of Coss values, reducing voltage peaks and maximizing efficiency without external snubbers, thus achieving a better balance between efficiency and ringing while minimizing fabrication costs.
Implementation Method 1
The MOSFET's switching behavior is affected by the parasitic capacitances between the device's three terminals, that is, gate-to-source (CGS), gate-to-drain (CGD) and drain-to-source (CDS) capacitances.
Implementation Method 2
a snubber capacitor supplements the value of CDS of the MOSFET. Since CDS is a component of Coss, an increase in CDS will increase the value of Coss.
Data Source
AI summary
A MOSFET device includes one or more active device structures and one or more dummy structures formed from semiconductor drift region and body regions. The dummy structures are electrically connected in parallel to the active device structures. Each dummy structure includes an electrically insulated snubber electrode formed proximate the body region and the drift region, an insulator portion formed over the snubber electrode and a top surface of the body region, and one or more electrical connections between the snubber electrode and portions of the body region and a source electrode. It is emphasized that this abstract is provided to comply with rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.