Active Clamp Output Transistor Circuit for Fast Low-Side Switching
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving both enhanced active clamp tolerance and fast switching, particularly in low-side switch ICs, due to limitations in gate insulation and parasitic current paths.
Innovation Solution
The semiconductor device incorporates a configuration with N-channel depression MOS field-effect transistors as variable resistive elements, connected in a manner that prevents parasitic current paths and includes an active clamp circuit to manage terminal voltages, along with turn-off circuits and resistors to enhance switching speed and tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gate insulation structures are used, then device simplicity is maintained, but active clamp tolerance is insufficient
Solution Approach 1:
The gate insulation structure is segmented into multiple layers: a first gate insulation layer and a second gate insulation layer with different dielectric constants. This segmentation allows each layer to contribute differently to the overall insulation performance, enabling enhanced active clamp tolerance while maintaining reasonable structural complexity.
Solution Approach 2:
Different regions of the gate insulation structure are assigned different dielectric properties. The first gate insulation layer has a first dielectric constant while the second gate insulation layer has a second dielectric constant that is different from the first. This local quality variation optimizes the electrical characteristics for active clamp tolerance without requiring complete structural redesign.
2Speed
If conventional switching configurations are used, then device simplicity is maintained, but switching speed is insufficient
Solution Approach 1:
The patent introduces variable resistive elements whose resistance can be dynamically adjusted during operation. These elements transition between high-resistance and low-resistance states to optimize switching speed at different phases of operation, achieving fast switching without requiring completely dynamic restructuring.
Solution Approach 2:
Turn-off circuits are implemented to preliminarily prepare the switching elements for rapid turn-off operation. These circuits pre-position the electrical states of the switching elements, enabling them to transition quickly to the off-state when required, thereby enhancing overall switching speed.
Data Source
AI summary
A semiconductor device includes: a first output transistor and a second output transistor configured to be connected between a first terminal and second terminal; an active clamp circuit configured to be connected to a first control terminal of the first output transistor to limit a terminal-to-terminal voltage appearing between the first and second terminals to a clamp voltage or less; a first variable resistive element provided between a node configured to be fed with a control signal and the first control terminal; a second variable resistive element provided between the node and a second control terminal of the second output transistor; and a turn-off circuit configured to be connected to a connection node between the second variable resistive element and the second control terminal so as to be able to turn the second output transistor off.