Power Semiconductor Current Sense with Inactive Outer Cells
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Solution Overview
Problem
Conventional current sense features in power semiconductor devices, such as power MOSFETs, inaccurately report current in the linear region due to increased resistance and misalignment of outer cells, leading to limited current gain compared to the saturation region.
Innovation Solution
Incorporating inactive cells at the outer boundaries of the current sense feature in power semiconductor devices, with a dual gate structure where inactive cells are shorted to the power electrode and have a different conductivity than active cells, to stabilize current measurement across both saturation and linear regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sense features are used in power semiconductor devices, then current measurement is accurate in the saturation region, but current measurement accuracy deteriorates in the linear region due to increased resistance and misalignment of outer cells
Solution Approach 1:
The patent applies local quality by making the outer cells of the current sense feature have different properties from the inner cells. Specifically, the outer cells are designed with adjusted doping concentrations or geometric dimensions to compensate for their inherently higher resistance and misalignment issues. This localized modification ensures that all cells, including outer ones, contribute uniformly to current sensing across both saturation and linear regions, resolving the measurement accuracy deterioration in the linear region.
2Device complexity
If outer cells of current sense feature are used without compensation, then device structure is simple, but current gain is limited in the linear region due to different resistive behavior
Solution Approach 1:
The patent employs parameter changes by modifying key parameters of the outer cells, such as doping concentration, cell width, or length, to adjust their resistive behavior. By changing these parameters, the outer cells' resistance is brought into alignment with the inner cells, ensuring consistent current gain across both saturation and linear regions. This approach maintains structural simplicity while significantly improving current sensing reliability.
3Measurement precision
If inactive cells are added at outer boundaries to compensate for resistive behavior discrepancies, then current measurement accuracy improves across all regions, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the current sense feature into distinct inner cells and outer cells, each with optimized characteristics. The outer cells are further segmented into active and inactive portions, where inactive cells serve as compensation elements. This segmentation allows precise control over current distribution and resistance matching, improving measurement accuracy while keeping the added complexity localized and manageable.
Data Source
AI summary
A power semiconductor device includes a power device and a current sense device formed in a common semiconductor region.