IGBT Current Detection Circuit for Overcurrent Protection
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Solution Overview
Problem
Conventional semiconductor devices with overcurrent protection functions for lateral IGBTs face challenges in achieving a sufficient sense ratio between currents passing through a sense resistor and the principal switching element, leading to variations in the current value at which the overcurrent protection function is exhibited, due to limitations in the resistance value of the sense resistor and the size of the current detecting IGBT.
Innovation Solution
The semiconductor device includes a principal IGBT and a current detecting IGBT formed on the same substrate, with the base region of the current detecting IGBT electrically connected to the emitter region of the principal IGBT, allowing for a higher sense ratio by doubling the current passing through the detecting resistor, thereby increasing the resistance value and size of the detecting IGBT, reducing variations in the current value at which the overcurrent protection function is exhibited.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resistance value of the sense resistor is increased to improve current detection sensitivity, then the voltage generated across the sense resistor increases, but the emitter region potential increases making it difficult for current to pass through the current detecting IGBT
Solution Approach 1:
The patent divides the current detection function into two separate paths: one through the sense resistor for voltage comparison, and another through the current detecting IGBT for protection triggering. This segmentation allows the sense resistor to have higher resistance for better detection sensitivity without affecting the current detecting IGBT's operation, as each component operates in its own optimized circuit path.
Solution Approach 2:
The patent introduces an auxiliary N-type semiconductor region as an intermediary element that provides an additional current path. This intermediary structure allows current to bypass the potential barrier at the emitter region by flowing through the auxiliary region, thereby enabling the sense resistor to operate at higher resistance values without preventing current flow through the detection system.
2Use of energy by moving object
If the size of the current detecting IGBT is reduced to lower its power consumption, then the current passing through the detecting resistor decreases, but the sense ratio becomes insufficient leading to variations in the overcurrent protection threshold
Solution Approach 1:
The patent creates a simplified copy of the main IGBT structure (the current detecting IGBT) that mirrors the essential current flow characteristics but operates at lower power. This copying approach allows the detection function to be performed by a smaller, lower-power device while maintaining accurate current sensing through the auxiliary semiconductor region that compensates for the reduced size.
Solution Approach 2:
The patent changes the electrical parameters of the detection circuit by introducing the auxiliary N-type region, which modifies the current distribution and voltage characteristics. This parameter change enables the current detecting IGBT to operate at lower power consumption while maintaining sufficient sense ratio through the enhanced current path provided by the auxiliary region.
3Productivity
If the resistance value of the sense resistor is made small to allow sufficient current flow, then the voltage generated across it is insufficient for accurate detection, but increasing it improves detection accuracy
Solution Approach 1:
The patent segments the detection function into two independent measurement paths: one through the sense resistor that can operate at higher resistance for better voltage signal generation, and another through the current detecting IGBT that ensures sufficient current flow for protection triggering. This segmentation resolves the contradiction by allowing each component to operate in its optimal resistance range.
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 increases the sense ratio by twice or more compared to conventional devices, allowing for a larger resistance value and IGBT size, thereby reducing variations in the current value at which the overcurrent protection function is exhibited, enhancing the reliability of the overcurrent protection circuit.
Implementation Method 1
a voltage generated between both ends of the sense resistor 54 and a voltage generated by the reference voltage circuit 55 are compared with each other by the voltage comparator 56
Data Source
AI summary
A semiconductor device includes a principal IGBT controllable in accordance with a gate voltage applied to a gate electrode thereof, a current detecting IGBT connected to the principal IGBT in parallel and a current detecting part including a detecting resistor capable of detecting a current passing through the current detecting IGBT. The base region of the current detecting IGBT and the emitter region of the principal IGBT are electrically connected to each other, and the emitter region of the current detecting IGBT and the emitter region of the principal IGBT are electrically connected to each other through the detecting resistor.