Transformer Guard Ring Layout for Higher Isolation Withstand Voltage
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Solution Overview
Problem
The existing semiconductor devices with transformers configured as high-side and low-side transformers in DC-DC converters face insufficient withstand voltage between these transformers.
Innovation Solution
The semiconductor device incorporates a configuration with a semiconductor substrate, insulating films, coils, and guard rings, where the coils are electrically connected in series, and the guard rings surround the coils to stabilize potential differences, thereby securing the withstand voltage between the transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transformers are configured as high-side and low-side transformers in DC-DC converters, then power conversion function is achieved, but withstand voltage between transformers is insufficient
Solution Approach 1:
A guard ring is introduced as an intermediary element between the high-side transformer and low-side transformer. The guard ring is electrically connected to a guard ring potential that is different from both the high-side transformer potential and low-side transformer potential, thereby mediating the voltage difference and preventing direct high-voltage stress between the transformers. This intermediary structure effectively increases the withstand voltage capability without requiring complex insulation designs.
2Reliability
If transformer insulation is increased to improve withstand voltage, then voltage integrity is improved, but semiconductor chip size increases
Solution Approach 1:
Instead of increasing insulation thickness in the vertical dimension (which would increase chip area), the solution introduces a guard ring structure that operates in the electrical potential dimension. By creating a third potential level (guard ring potential) between the high-side and low-side transformer potentials, the design achieves voltage isolation without requiring additional physical space, thus maintaining compact chip area while improving withstand voltage capability.
3Reliability
If guard ring is added to secure withstand voltage, then voltage integrity is improved, but device complexity increases
Solution Approach 1:
The guard ring is merged with the existing transformer structure by positioning it adjacent to the coils and integrating it into the same planar layout. The guard ring shares the same structural platform and fabrication process as the coils, combining multiple functions (transformer operation and voltage protection) into a unified structure. This merging approach minimizes additional complexity while achieving the desired withstand voltage improvement.
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 configuration ensures a secure withstand voltage between the transformers, allowing for the downsizing of semiconductor chips while maintaining the desired voltage integrity and improving common mode transient immunity (CMTI).
Implementation Method 1
The first guard ring and the second guard ring are adjacent to each other while being spaced apart from each other in plan view... a withstand voltage between a transformer made of a first coil and a third coil and a transformer made of a second coil and a fourth coil can be secured
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, an insulating film, a first coil, a second coil, a third coil, a fourth coil, a first guard ring and a second guard ring. The first coil and the second coil are formed on the semiconductor substrate. The third coil faces the first coil through the insulating film. The fourth coil faces the second coil through the insulating film. The first guard ring is formed to surround the third coil in plan view. The second guard ring is formed to surround the fourth coil in plan view. The first guard ring and the second guard ring are adjacent to each other while being spaced apart from each other in plan view.