Current Measurement Device Common-Mode Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As measured currents increase, shunt resistors must be made smaller to reduce losses, leading to weaker detection voltage signals that are prone to noise, especially common-mode noise, making high-accuracy current detection difficult, especially when common-mode noise is significant.
Innovation Solution
A current measurement device is configured with an additional terminal connected to the power supply line of an amplifier circuit, which includes a shunt resistor and a pair of voltage signal lines connected to the amplifier circuit, with a third signal line connected to a common line to reduce the influence of common-mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the shunt resistance value is lowered to reduce loss, then energy loss is reduced, but the detection voltage signal becomes weaker and more susceptible to common-mode noise
Solution Approach 1:
The patent introduces a common-mode noise countermeasure terminal as an intermediary component. This terminal provides a dedicated path for common-mode noise to be shunted to ground, acting as a mediator that separates the noise pathway from the signal pathway. By providing this intermediate noise discharge path, the system can use low-value shunt resistors for energy efficiency while the intermediary terminal handles the noise rejection function.
Solution Approach 2:
The patent segments the functionality by separating signal transmission from noise discharge. The shunt resistor handles current measurement while the common-mode noise countermeasure terminal handles noise rejection. This segmentation allows each component to be optimized independently - the shunt resistor can have very low resistance for minimal power loss, while the noise countermeasure terminal provides the necessary noise filtering capability.
2Measurement precision
If a high-sensitivity amplifier is used to amplify the weak detection voltage signal, then signal detection capability is improved, but common-mode noise is also amplified making high-accuracy current detection impossible
Solution Approach 1:
The patent converts the harmful common-mode noise into a beneficial effect by providing a dedicated discharge path. The common-mode noise that would normally be amplified by the high-sensitivity amplifier is instead directed through the common-mode noise countermeasure terminal to ground. This transforms the noise from a harmful factor into a controlled current path, allowing the amplifier to focus on amplifying only the differential signal.
Solution Approach 2:
The common-mode noise countermeasure terminal serves as an intermediary that protects the amplifier from common-mode noise. By providing this intermediate noise discharge path before the amplifier, the terminal prevents the noise from reaching and being amplified by the sensitive amplifier circuitry.
3Loss of energy
If the shunt resistor resistance value is reduced to not more than 0.1 mΩ to minimize loss, then energy efficiency is improved, but the influence of noise on the detection signal increases
Solution Approach 1:
The patent segments the functions of power loss reduction and noise rejection into separate components. The shunt resistor is optimized for minimal power loss with resistance values of 0.1 mΩ or less, while the common-mode noise countermeasure terminal is specifically designed to handle noise rejection. This functional segmentation allows each component to be optimized for its primary purpose without compromise.
Solution Approach 2:
The common-mode noise countermeasure terminal acts as an intermediary that protects the detection system from noise. This intermediate component provides a dedicated noise discharge path that is separate from the signal path, allowing the shunt resistor to operate at extremely low resistance values while the intermediary terminal handles the noise mitigation function.
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 suppresses common-mode noise during current detection, enabling high-accuracy current measurement even with low-resistance shunt resistors.
Implementation Method 1
an amplifier circuit with which the current measurement circuit is provided to amplify a voltage signal
Implementation Method 2
The third signal line may reduce an influence of a common-mode noise of the common line on the pair of first and second voltage signal lines
Data Source
AI summary
A current measurement device comprising: a shunt resistor; a pair of first and second voltage signal lines connected to the shunt resistor; and a current measurement circuit for measuring a current using a signal by the pair of first and second voltage signal lines. The pair of first and second voltage signal lines are connected to an amplifier circuit with which the current measurement circuit is provided to amplify a voltage signal. A third signal line which is a signal line different from the pair of first and second voltage signal lines and drawn from the shunt resistor is connected to a common line of the current measurement circuit.