Monolithic RC Snubber Integration in Power Transistors
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Solution Overview
Problem
Existing RC snubber designs in switching circuits are ineffective in damping output ringing due to parasitic impedances, leading to excessive voltage overshoot and EMI noise, particularly in compact form factor circuits like DrMOS, where external snubbers are only moderately effective and can reduce circuit efficiency.
Innovation Solution
Monolithic integration of an RC snubber within a power transistor in a single die, where the snubber capacitor and resistor are designed to dampen output ringing by directly coupling across the output capacitance, bypassing parasitic package inductance and eliminating the need for discrete components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If external RC snubber is added on PCB to control output ringing, then voltage overshoot and EMI are reduced, but device complexity and manufacturing cost increase due to additional discrete components
Solution Approach 1:
The patent merges the RC snubber circuit with the power transistor by integrating the snubber capacitor between the drain and source regions, and the snubber resistor in series with the source region, allowing both the power switching function and the ringing suppression function to be performed by a single monolithic device structure, thereby eliminating the need for external discrete RC components
2Object-affected harmful factors
If external RC snubber is added to dampen ringing, then EMI is reduced, but manufacturing cost increases due to additional discrete components and assembly steps
Solution Approach 1:
The snubber circuit is merged into the monolithic power transistor structure, where the capacitor is formed between doped regions and the resistor is formed as a doped region or diffused layer, enabling fabrication through standard semiconductor processing steps without requiring additional discrete components or assembly operations
3Stress or pressure
If RC snubber is added to control ringing, then voltage stress is reduced, but the solution becomes less effective due to parasitic impedances in external connections
Solution Approach 1:
The snubber circuit is merged directly into the semiconductor device structure, placing the capacitor between the drain and source regions and the resistor in series with the source, which eliminates external connection parasitics and ensures effective damping of voltage ringing and reduction of voltage stress during switching transitions
4Object-affected harmful factors
If external RC snubber is used to dampen ringing, then high-frequency noise is reduced, but circuit efficiency decreases due to energy dissipation
Solution Approach 1:
The snubber resistor is localized in series with the source region rather than being an external component, allowing precise control of the damping effect only where needed to suppress high-frequency noise and ringing, while minimizing overall energy dissipation and maintaining circuit efficiency
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 monolithic integration significantly reduces output ringing, effectively suppressing high-frequency noise and EMI, while maintaining circuit efficiency by directly addressing the parasitic impedances and eliminating the need for external components.
Implementation Method 1
The snubber capacitor and the snubber resistor are configured to substantially dampen output ringing when the power transistor switches states
Data Source
AI summary
In one general aspect, a semiconductor structure can include a power transistor including a body region extending in a silicon region, a gate electrode insulated from the body region by a gate dielectric, a source region extending in the body region where the source region is of opposite conductivity type from the body region, a source interconnect contacting the source region, and a backside drain. The semiconductor structure can include an RC snubber monolithically integrated with the power transistor in a die. The RC snubber can include a snubber electrode insulated from the silicon region by a snubber dielectric such that the snubber electrode and the silicon region form a snubber capacitor.