Trench MOSFET with Isolated Coupled Element for Noise Reduction
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Solution Overview
Problem
DC-DC converters in portable electronic devices face challenges in reducing power loss and noise generation, particularly due to high switching frequencies and stray capacitances in conventional trench MOSFETs, which affect compactness and efficiency.
Innovation Solution
A trench MOSFET design with an additional conductive element isolated from the gate and drain, which reduces resistive and capacitive effects, and a trench element control circuit dynamically adjusts voltages to minimize power losses and noise, employing a snubber circuit to suppress voltage transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional trench MOSFET designs are used, then device compactness is achieved, but power loss and noise generation increase due to high switching frequencies and stray capacitances
Solution Approach 1:
The trench structure is segmented into multiple regions with different conductive elements. The gate electrode is divided into first and second gate electrodes positioned at different depths, and conductive elements are strategically placed at specific locations within the trench to reduce stray capacitances while maintaining compactness.
Solution Approach 2:
An independent conductive element is introduced as an intermediary component within the trench structure. This conductive element is electrically isolated from the gate and drain, serving as a mediator to reduce the drain-to-gate capacitance (Cgd) by providing an alternative electrical path that shields the gate from the drain.
2Productivity
If switching frequency is increased to improve converter efficiency, then power conversion efficiency improves, but noise generation and stray capacitance effects worsen
Solution Approach 1:
The patent converts the harmful effect of high switching frequency (which increases noise and stray capacitance effects) into a benefit by introducing the independent conductive element that specifically targets and reduces the drain-to-gate capacitance. This allows high-frequency operation with reduced noise generation, as the conductive element shields the gate from drain voltage transitions.
3Object-generated harmful factors
If gate-to-drain capacitance (Cgd) is reduced to minimize noise, then noise generation decreases, but device structure complexity increases
Solution Approach 1:
The independent conductive element is nested within the existing trench structure, utilizing the same vertical space as the gate and drain electrodes. This nested configuration reduces Cgd without requiring additional lateral space or fundamentally changing the trench architecture, thereby minimizing the increase in device complexity.
Data Source
AI summary
A trench MOSFET is disclosed that includes a semiconductor substrate having a vertically oriented trench containing a gate. The trench MOSFET further includes a source, a drain, and a conductive element. The conductive element, like the gate is contained in the trench, and extends between the gate and a bottom of the trench. The conductive element is electrically isolated from the source, the gate, and the drain. When employed in a device such as a DC-DC converter, the trench MOSFET may reduce power losses and electrical and electromagnetic noise.