Integrated Overcurrent Protection Circuit for Semiconductor Devices
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Solution Overview
Problem
Conventional overcurrent protection circuits for semiconductor devices require an externally connected sense resistor, increasing substrate area and cost.
Innovation Solution
An integrated overcurrent protection circuit that generates a sense voltage corresponding to the on-current of the output transistor, allowing for appropriate overcurrent protection operations without the need for an externally connected sense resistor, using a pulse-by-pulse method and a timer latch method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an externally connected sense resistor is used for overcurrent protection, then overcurrent detection accuracy is improved, but substrate area and cost increase
Solution Approach 1:
The patent merges the sense resistor function with the semiconductor device substrate by forming a sense electrode that extends from the bottom surface through the substrate to the output transistor. This integration eliminates the need for external sense resistors while maintaining overcurrent detection capability, thereby reducing substrate area and component count.
Solution Approach 2:
The patent introduces an intermediary sense electrode structure that acts as both a substrate connection element and a current sensing element. This sense electrode serves as a mediator between the output transistor and the control circuit, enabling overcurrent detection without requiring external components.
2Measurement precision
If an externally connected sense resistor is used for overcurrent protection, then overcurrent detection accuracy is improved, but device cost increases
Solution Approach 1:
The patent merges the sense resistor function with the semiconductor device substrate by forming a sense electrode that extends from the bottom surface through the substrate to the output transistor. This integration eliminates the need for external sense resistors while maintaining overcurrent detection capability, thereby reducing substrate area and component count.
Solution Approach 2:
The semiconductor device performs its own current sensing function through the integrated sense electrode, eliminating the need for separate external sense resistors. This self-service approach reduces component count, assembly complexity, and overall device cost while maintaining detection accuracy.
3Stability of the object's composition
If pulse-by-pulse overcurrent protection method is used, then switching operation stability is improved, but response time to sustained overcurrent increases
Solution Approach 1:
The control circuit continuously monitors the sense voltage through feedback and compares it against threshold values. When overcurrent is detected, the control circuit adjusts the output transistor switching accordingly. This feedback mechanism enables both stable pulse-by-pulse protection and timely response to sustained overcurrent conditions.
Solution Approach 2:
The patent employs periodic sampling of the sense voltage at each switching cycle to detect overcurrent conditions. This periodic action provides stable pulse-by-pulse protection while the accumulation of detected overcurrent events over multiple periods enables timely detection of sustained overcurrent conditions.
Data Source
AI summary
A semiconductor device includes an integration of a first external terminal to which a DC input voltage is input, a second external terminal to which a rectifying and smoothing circuit is externally connected, an output transistor connected between the first external terminal and the second external terminal, a control circuit arranged to turn on and off the output transistor so that a desired DC output voltage can be obtained from the rectifying and smoothing circuit, a current detection circuit arranged to generate a sense voltage corresponding to an on-current of the output transistor, and an overcurrent protection circuit arranged to monitor the sense voltage so as to perform an overcurrent protection operation. The overcurrent protection circuit performs a first overcurrent protection operation of a pulse-by-pulse method when detecting that the sense voltage exceeds a first threshold value voltage, and performs a second overcurrent protection operation of a timer latch method when detecting that the sense voltage continues to increase though the first overcurrent protection operation is being performed.