Sense IGBT Feedback Capacitance for Accurate Current Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor devices with parallel-connected insulated gate bipolar transistors (IGBTs), the sense current at switching time differs from the main IGBT current due to the ratio of sense IGBT and main IGBT, leading to false overcurrent sensing and potential unnecessary shutdowns, especially when the rise time of the sense IGBT is short.
Innovation Solution
A semiconductor device configuration where the sense element has a higher threshold voltage and larger feedback capacitance than the main element, with the sense element connected in parallel via a sense resistor, allowing for accurate current sensing by suppressing sense current variation at switching times through appropriate correction factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sense IGBT has the same structure as the main IGBT, then the sense current can be measured through the sense resistor, but the sense current at switching time differs from the main IGBT current due to different rise times, causing false overcurrent sensing
Solution Approach 1:
The patent applies local quality by giving the sense IGBT different structural parameters compared to the main IGBT. Specifically, the sense IGBT is designed with a larger base region width (Wb) and different doping concentrations to achieve a longer rise time. This localized structural modification ensures that the sense current waveform matches the main IGBT current waveform during switching, enabling accurate measurement without false overcurrent detection.
Solution Approach 2:
The patent employs parameter changes by adjusting key structural parameters of the sense IGBT, including base region width (Wb), emitter region doping concentration (Ne), and base doping concentration (Nb). These parameter modifications are specifically designed to extend the rise time of the sense IGBT, making it comparable to the main IGBT's switching characteristics, thereby resolving the measurement accuracy issue during switching transitions.
2Speed
If the sense IGBT has a short rise time, then the switching response is fast, but the sense current varies significantly at switching time, leading to overestimation and unnecessary shutdowns
Solution Approach 1:
The patent uses parameter changes to optimize the sense IGBT's rise time. By increasing the base region width (Wb) from typical values and adjusting doping concentrations, the rise time is extended to match the main IGBT's switching characteristics. This ensures that the sense current accurately reflects the main IGBT current during switching, preventing overestimation while maintaining adequate switching speed for protective functionality.
3Measurement precision
If the sense IGBT structure is modified to match switching characteristics, then accurate current sensing is achieved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by modifying only the sense IGBT's structural parameters while keeping the main IGBT design unchanged. The sense IGBT uses specific parameter sets (larger Wb, adjusted doping concentrations) that are optimized for current sensing, whereas the main IGBT maintains its original design for power switching. This localized differentiation achieves accurate sensing without complicating the overall device architecture.
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 effectively reduces the variation in sense current during switching times, enabling accurate main current sensing without overestimation, thus preventing unnecessary shutdowns and ensuring reliable operation.
Implementation Method 1
the sense element has an insulated gate bipolar transistor structure with a feedback capacitance larger than a feedback capacitance of the main element
Data Source
AI summary
According to one embodiment, a semiconductor device includes a main element and a sense element. The main element is connected between a collector terminal and an emitter terminal. The main element has an insulated gate bipolar transistor structure. The sense element is connected in parallel with the main element via a sense resistor between the collector terminal and the emitter terminal. The sense element has an insulated gate bipolar transistor structure with a feedback capacitance larger than a feedback capacitance of the main element.