Resonant Current Sensor Circuit for Noise-Resistant DC Detection
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Solution Overview
Problem
Current sensors face challenges in accurately detecting direct current due to noise interference, particularly when using Hall elements.
Innovation Solution
A current sensor circuit is designed with a detection coil, resonant capacitor, phase adjusting circuit, switching circuit, and signal converting circuit to detect direct current with high accuracy by adjusting the pulse period of the drive signal to match the resonant frequency of the series resonant circuit, thereby suppressing noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall element is used to detect direct current, then the current can be detected non-contact, but the detection accuracy deteriorates when noise is superimposed on the detection signal
Solution Approach 1:
The patent applies resonance vibration to the detection coil by driving it at its resonant frequency. This mechanical vibration approach allows the system to operate in a high-Q resonant state, which naturally filters out noise frequencies and enhances the signal-to-noise ratio, thereby improving current detection accuracy in noisy environments
Solution Approach 2:
The patent changes the operating parameters by utilizing the resonant frequency of the detection coil as the driving frequency. By adjusting the drive signal frequency to match the coil's resonant frequency, the system maximizes the coil's sensitivity and Q-factor, which improves detection precision while suppressing noise through resonant amplification of the desired signal
2Measurement precision
If the pulse period of the drive signal is adjusted to follow the resonant frequency of the series resonant circuit, then the detection accuracy is improved, but the device complexity increases due to the phase adjusting circuit
Solution Approach 1:
The patent implements a feedback mechanism where the phase adjusting circuit continuously monitors the resonant frequency of the series resonant circuit and adjusts the pulse period of the drive signal accordingly. This feedback loop ensures that the drive frequency tracks the resonant frequency, maintaining optimal detection accuracy while automating the frequency adjustment process
Solution Approach 2:
The phase adjusting circuit serves multiple functions: it generates the drive signal, adjusts the pulse period to match resonant frequency, and maintains synchronization with the resonant circuit. By consolidating these functions into a single circuit block, the patent reduces overall system complexity despite the added sophistication required for frequency tracking
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
The circuit effectively detects direct current with high accuracy while minimizing noise interference, utilizing a magnetic field bias to ensure inductance changes occur in a linear region, enhancing detection precision.
Implementation Method 1
a detection coil configured such that an inductance changes with the direct current
Implementation Method 2
a resonant capacitor that constitutes a series resonant circuit together with the detection coil
Implementation Method 3
a magnetic field bias unit that applies a magnetic field bias to the magnetic core
Data Source
AI summary
A current sensor circuit includes a detection coil configured such that an inductance changes with a direct current, a resonant capacitor, a phase adjusting circuit that receives a feedback signal from the resonant capacitor and outputs a drive signal, a switching circuit that includes a plurality of switching elements forming a half-bridge circuit or a full-bridge circuit and supplies an alternating current signal to the detection coil and the resonant capacitor by causing the plurality of switching elements to perform a switching operation in accordance with a pulse period of the drive signal, a signal converting circuit that converts the drive signal output from the phase adjusting circuit into a detection signal indicating a change in the direct current, and a detection terminal that outputs the detection signal to the outside.