MOSFET Switch Short-Circuit Detection With Noise-Filtered Voltage Sensing
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Solution Overview
Problem
Existing short-circuit protection circuits for MOSFET switches face a trade-off between noise resistance and protection speed, as they are vulnerable to noise during switching operations, which can lead to false short-circuit detection and potential breakdown of the switch.
Innovation Solution
A short-circuit protection device comprising a voltage measurement unit, a filter unit to attenuate high-frequency noise, and an amplifying unit to adjust the voltage margin, allowing for rapid detection of short circuits and improved noise resistance by filtering and amplifying the drain voltage within specific bandwidths and gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitor size is increased to reduce noise influence, then noise resistance is improved, but the short-circuit protection speed slows down
Solution Approach 1:
The voltage measurement function is segmented into two parallel paths: one path measures the drain voltage directly through a capacitor for fast short-circuit detection, while the other path measures the source voltage through a resistor for noise-resistant operation. This segmentation allows each path to be optimized for its specific function without compromising the other.
Solution Approach 2:
A voltage conversion unit acts as an intermediary to convert between drain voltage and source voltage measurements. When drain voltage measurement is too sensitive to noise, the system switches to source voltage measurement through this intermediary, maintaining measurement accuracy while reducing noise influence.
2Measurement precision
If the reference voltage is set to a small value to detect short circuits with small drain voltage, then detection sensitivity is improved, but the margin against noise is reduced
Solution Approach 1:
The reference voltage is made dynamic rather than fixed. The voltage conversion unit adjusts the reference voltage level based on the measured source voltage, maintaining an appropriate margin between the reference voltage and measured voltage even when operating with small voltage values. This dynamic adjustment preserves both detection sensitivity and noise margin.
Solution Approach 2:
The system changes the measurement parameter from drain voltage to source voltage when noise becomes problematic. By measuring source voltage instead of drain voltage and appropriately adjusting the reference voltage, the system maintains detection capability while improving noise immunity.
3Measurement precision
If the measured voltage depends on drain voltage, then short-circuit detection capability is improved, but vulnerability to switching noise increases
Solution Approach 1:
Instead of measuring drain voltage directly (which is vulnerable to noise), the system inverts the approach by measuring source voltage through a resistor. This inverted measurement method provides the same short-circuit detection capability while being inherently more resistant to drain voltage switching noise.
Solution Approach 2:
A resistor is introduced as an intermediary element to measure source voltage instead of directly measuring drain voltage. This intermediary measurement approach converts the noisy drain voltage signal into a cleaner source voltage signal for comparison, reducing noise vulnerability while maintaining detection accuracy.
Data Source
AI summary
Disclosed is a short-circuit protection device for a switch. The short-circuit protection device according to a first embodiment of the present invention may include: a voltage measurement unit configured to measure an output voltage of the switch and output the output voltage as a measured voltage; a filter unit configured to filter the measured voltage to a specified bandwidth and output a first voltage; and a comparison unit configured to compare a specified reference voltage with the first voltage.