Shunt Resistor Error Voltage Cancellation
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Solution Overview
Problem
Large shunt resistors used for high current monitoring face challenges in surface-mounting on voltage detection circuit boards due to size constraints, making it difficult to apply existing wiring structures that cancel error voltages caused by self-inductance.
Innovation Solution
A voltage detection circuit design featuring a shunt resistor with main electrodes, detection terminals, and wirings where the detection terminals are directed outward with a constant distance, and a low-pass filter comprising resistance and capacitance is used to cancel error voltages by forming a relationship between effective inductance, self-inductance, and mutual-inductance, ensuring only the resistance-based voltage is output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is used for high current monitoring, then the current detection capability is improved, but the device size increases making it difficult to surface-mount on voltage detection circuit boards
Solution Approach 1:
The shunt resistor device is segmented into distinct functional components: a resistance body for current monitoring, main electrodes for current flow, detection terminals for voltage measurement, and connection portions for circuit integration. This segmentation allows each component to be optimized independently, enabling high current detection capability while maintaining a compact form factor suitable for surface-mounting.
2Area of stationary object
If a surface-mount type resistor is used, then the device size is reduced for easy mounting, but the self-inductance error voltage cannot be effectively cancelled
Solution Approach 1:
A low-pass filter circuit is introduced as an intermediary element between the shunt resistor and the measurement system. This filter acts as a mediator that removes high-frequency noise and error voltages caused by self-inductance, allowing the compact surface-mount resistor to achieve measurement precision comparable to larger through-hole resistors.
3Length of stationary object
If the detection terminals are positioned close to the resistance body, then the wiring length is reduced, but the mutual-inductance effect is insufficient to cancel self-inductance error
Solution Approach 1:
The detection terminals are positioned at an optimized distance from the resistance body, and the low-pass filter parameters (resistance and capacitance values) are carefully selected to achieve the desired cutoff frequency. This parameter optimization ensures that the mutual-inductance effect is sufficient to cancel self-inductance error while maintaining minimal wiring length.
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 design effectively removes error voltages caused by self-inductance, allowing accurate current monitoring by isolating the voltage output from the resistance body, improving detection accuracy and reducing external magnetic flux influence.
Implementation Method 1
error voltage caused by tiny self-inductance of current detection resistor
Implementation Method 2
voltage basing on mutual-inductance formed at voltage detection wiring
Implementation Method 3
a low-pass filter consisting of a resistance (r) and a capacitance (C) is coupled with the pair of wirings
Implementation Method 4
a magnetic flux Φ formed by a current I flowing through the resistance body pass through the pair of the wirings to cause a mutual-inductance M
Implementation Method 5
a magnetic flux Φ formed by a current I flowing through the resistance body pass through the pair of the wirings to cause a mutual-inductance M
Implementation Method 6
the voltage caused at both ends of the shunt resistor by the current is detected, and the current is detected from already-known resistance value
Data Source
AI summary
Provided is a voltage detection circuit, which can remove influence of error voltage caused by tiny amount of self-inductance existing in a shunt resistor, though in the resistor for large current usage, which is impossible to surface-mount on a voltage detection circuit board. The shunt resistor device comprises: a resistance body (11); a pair of main electrode (12) for flowing current to be monitored through the resistance body; a pair of detection terminal (13a) for detecting voltage caused in the resistance body; and a pair of wiring (23) each electrically connected to the detection terminal. And, a pair of voltage detection wiring consisting of the detection terminal (13a) and the wiring (23) is brought closer, at prescribed location, than distance between each of connection position of the pair of the detection terminal (13a) on the main electrode (12). A low-pass filter having resistance value (r) and capacitance (C) is provided at next stage after the pair of the wiring, and said low-pass filter having a relationship Le/R=C·r, when Le (=L−M) is the effective inductance, and R is the resistance value of the resistance body.