Switch Terminal Voltage Sensing With Ringing Noise Damping
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Solution Overview
Problem
Existing switch overcurrent measuring apparatuses suffer from decreased accuracy due to ringing noise caused by voltage resonance between inductors and capacitors, leading to incorrect overcurrent detection.
Innovation Solution
Incorporating a damping device with specific impedance properties in the electrical path to suppress ringing noise, allowing for accurate overcurrent measurement by comparing voltage across switch terminals immediately after state change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If voltage measurement is performed immediately after switch turns on for quick overcurrent detection, then detection speed is improved, but measurement accuracy deteriorates due to ringing noise
Solution Approach 1:
The patent introduces a damping device as an intermediary element in the voltage measurement circuit. This damping device selectively attenuates the ringing frequency components while allowing the fundamental voltage signal to pass through, thereby enabling accurate overcurrent detection immediately after switch turn-on without waiting for ringing to converge.
Solution Approach 2:
The patent changes the impedance parameter of the measurement circuit by introducing a damping device with frequency-dependent impedance characteristics. The damping device presents high impedance at ringing frequencies to suppress noise while maintaining low impedance at fundamental frequencies for accurate voltage measurement, thus resolving the contradiction between speed and accuracy.
2Measurement precision
If damping device with high impedance at ringing frequency is added to suppress noise, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent employs a damping device whose impedance parameter varies with frequency - high impedance at ringing frequencies to suppress noise and low impedance at fundamental frequencies to minimize circuit impact. This parameter change approach achieves noise suppression without significantly increasing device complexity.
Solution Approach 2:
The damping device can be implemented using simple, inexpensive components such as resistors or ferrite beads that are readily available and easy to integrate into existing circuits. These components provide effective damping without adding substantial complexity or cost to the overall system.
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
Enables quick and accurate detection of overcurrent without waiting for ringing to converge, reducing the risk of measurement errors and enabling smaller, less costly switch components.
Implementation Method 1
A damping device is arranged in the electrical path. The damping device has a property that an impedance thereof at a given frequency band is higher than that in a frequency band outside the given frequency band. The given frequency band includes a ringing frequency band (Rngf) of voltage which appears between the major terminals of the target-driven switch
Data Source
AI summary
A switch overcurrent measuring apparatus includes an electrical path with a first end connecting with a high potential terminal of a pair of major terminals of a target-driven switch, a diode arranged in the electrical path to have a cathode facing the high potential terminal, and an overcurrent measuring device which connects with a second end of the electrical path. After a command for the switch is changed to an ON-command, the device measures voltage developed between the terminals. When the voltage is higher than an overcurrent threshold, the device determines that an overcurrent is flowing. A damping device arranged in the electrical path has a property that an impedance thereof at a given frequency band is higher than that in a frequency band outside. The given frequency band includes a ringing frequency band of voltage which appears between the terminals and arises from switching between operating states.