Magneto-Resistive Current Sensor for Low-Loss DC and AC Detection
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Solution Overview
Problem
Current sensors in power supplies face challenges such as high loss, cost, accuracy issues, and noise in existing technologies like resistor-based, Hall effect, magneto resistive, and current transformer methods, which are not suitable for both DC and AC applications and have limitations in signal detection and integration.
Innovation Solution
A current sensor using a coupled inductor configuration with on-chip electronics, where a coil is placed in close proximity to a current-carrying wire to induce a VSENSE signal with low loss and low cost, incorporating a reset circuit and integrator for accurate current sensing, and employing programmable gain amplifiers for calibration and temperature compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor is used to sense current, then the current can be detected, but the circuit experiences high loss
Solution Approach 1:
The patent replaces the traditional resistive sensing mechanism with a magnetic field-based sensing mechanism using a magneto-resistive element. Instead of measuring current through voltage drop across a resistor (Ohm's law), the invention detects the magnetic field generated by the current-carrying conductor and translates it into a resistance change signal. This substitution eliminates the need for power-dissipating resistors while maintaining current measurement capability.
2Loss of energy
If the resistor value is reduced to mitigate loss, then the circuit loss decreases, but the detectable signal becomes smaller
Solution Approach 1:
The patent introduces a magneto-resistive element as an intermediary between the current-carrying conductor and the measurement circuit. This element acts as a transducer that converts the magnetic field (proportional to current) into an electrical signal through resistance modulation. The intermediary amplifies the measurement signal without requiring a large voltage drop, thereby maintaining both low loss and high signal detectability.
3Loss of energy
If a Hall effect device is used to detect current, then the loss is relatively low, but the cost increases and accuracy and noise issues worsen
Solution Approach 1:
The patent employs a magneto-resistive element, which is a more cost-effective and integrated solution compared to Hall effect devices. The magneto-resistive technology can be fabricated using standard semiconductor processing techniques, making it cheaper and more suitable for integration. The element provides sufficient measurement precision without the high cost and noise susceptibility associated with Hall effect sensors.
4Measurement precision
If a current transformer is used to detect current, then the current can be sensed, but the device becomes large and only works with AC circuits
Solution Approach 1:
The patent creates a universal current sensing solution that works for both DC and AC applications. The magneto-resistive element responds to the magnetic field generated by current flow regardless of whether the current is direct or alternating. This eliminates the limitation of current transformers that only work with AC, providing a single sensor type that can measure both DC and AC currents with the same circuit topology.
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 solution provides a low-loss, cost-effective, and accurate current sensing method suitable for both DC and AC applications, with improved signal detection and reduced noise, enabling efficient current monitoring in power supplies.
Implementation Method 1
a coil is placed in close proximity to a current-carrying wire to induce a VSENSE signal
Data Source
AI summary
A current sensor includes a sensing circuit for sensing current and supplying indications thereof. The current sensor also includes two or more output terminals coupled to the sensing circuit that alternately supply respective indications of the sensed current according to control signals supplied to the current sensor.