Current Detection Circuit With Mediated Leakage Isolation
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Solution Overview
Problem
Current semiconductor devices with normally-on-type switching elements face challenges in accurately detecting output currents due to manufacturing variations in on-resistance, which affects the reliability of current detection.
Innovation Solution
A current detection circuit is designed with a normally-on-type switching element and a pair of normally-off-type switching elements, where the gate voltage of one normally-off-type element is connected to the gate of another, and a division circuit processes the drain voltages of both to accurately detect output currents, mitigating the influence of manufacturing variations by using a common semiconductor substrate and specific dimension ratios for the switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a normally-on-type switching element is used to achieve high voltage resistance and low loss, then the device performance is improved, but accurate output current detection becomes impossible due to leakage current
Solution Approach 1:
A normally-off-type switching element is introduced as an intermediary between the normally-on-type switching element and the current detection circuit. This intermediary element can be completely turned off to block leakage current, enabling accurate current detection while the normally-on-type element continues to provide low loss operation.
2Productivity
If manufacturing processes are used to produce switching elements, then production is achieved, but manufacturing variations cause characteristic variations such as on-resistance that reduce detection reliability
Solution Approach 1:
The invention changes the operational parameters of the switching elements by using different gate voltage levels for the normally-on-type and normally-off-type elements. This allows the system to operate in different states (on/off combinations) that compensate for manufacturing variations and enable reliable current detection despite parameter spreads.
3Use of energy by moving object
If a normally-on-type switching element is used to reduce power loss, then energy efficiency is improved, but leakage current prevents accurate current detection
Solution Approach 1:
The system dynamically switches between different switching element states depending on the operational phase. During normal operation, the normally-on-type element provides low loss. During detection phases, the normally-off-type element is used in specific on/off states to enable accurate measurement without continuous power loss.
Data Source
AI summary
A current detection circuit includes normally-on-type and a first normally-off-type switching elements with main current paths that are connected in series, and a second normally-off-type switching element that has a source and a gate that are connected to a source and a gate of the first normally-off-type switching element and a drain that is connected to a constant current source, and executes a division process by using drain voltages of the two normally-off-type switching elements.