WBG Semiconductor Device With Monolithic Current Limiting
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Solution Overview
Problem
Power semiconductor devices using wide band gap (WBG) semiconductors like SiC and GaN face challenges in maintaining low ON resistance while ensuring high load short circuit withstand capability, as the increased mobility and reduced ON resistance lead to rapid temperature rises and breakdown during short circuits, limiting their application in inverters.
Innovation Solution
Incorporating a monolithically formed current limiting circuit within the same chip as the main transistor, with a trench or planar MOSFET structure, and adjusting the p-well concentration profile to separate the thresholds of the main and shunt MOSFETs, allowing for accurate current limitation and enhanced thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If WBG semiconductor material (SiC or GaN) is used to reduce ON resistance, then the ON resistance decreases significantly, but the element temperature rises rapidly during load short circuit causing breakdown
Solution Approach 1:
The patent applies preliminary anti-action by incorporating a current limiting circuit that activates before thermal breakdown occurs. The circuit monitors current flow and automatically limits it when abnormal conditions are detected, preventing the temperature rise that would lead to breakdown during load short circuit events
Solution Approach 2:
The current limiting circuit acts as an intermediary between the power source and the WBG semiconductor device. It mediates the current flow, allowing normal operation while preventing harmful current levels during short circuits, thus protecting the device from thermal damage
2Loss of energy
If the ON resistance is reduced to improve efficiency, then power loss decreases, but the load short circuit current increases causing faster temperature rise
Solution Approach 1:
The current limiting circuit implements feedback control by continuously monitoring the current flowing through the WBG semiconductor device and automatically adjusting the current level when abnormal conditions are detected. This feedback mechanism allows the system to maintain low ON resistance for efficiency while preventing harmful current levels during short circuits
3Reliability
If external current limiting circuits are used to prevent breakdown, then reliability improves, but device complexity and cost increase
Solution Approach 1:
The patent merges the current limiting circuit with the WBG semiconductor device by forming both on the same semiconductor substrate. This integration combines multiple functions into a single device structure, reducing overall system complexity while maintaining reliability through built-in current limiting protection
Data Source
AI summary
A semiconductor device having high reliability and high load short circuit withstand capability while maintaining a low ON resistance is provided, by using a WBG semiconductor as a switching element of an inverter circuit. In the semiconductor device for application to a switching element of an inverter circuit, a band gap of a semiconductor material is wider than that of silicon, a circuit that limits a current when a main transistor is short circuited is provided, and the main transistor that mainly serves to pass a current, a sensing transistor that is connected in parallel to the main transistor and detects a microcurrent proportional to a current flowing in the main transistor, and a lateral MOSFET that controls a gate of the main transistor on the basis of an output of the sensing transistor are formed on the same semiconductor.