Bidirectional Current Sensor Circuit for Thermoelectric Control
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Solution Overview
Problem
Current sensor circuits face challenges in accurately measuring bi-directional current signals while minimizing power consumption, particularly in applications involving thermoelectric cooling or heating devices, where efficient thermal control is crucial.
Innovation Solution
A bidirectional current sensor circuit utilizing complementary output stages with first and second transistors of different types, along with mirror transistors and a buffer circuit, to provide a load current signal indicative of magnitude and polarity, allowing for accurate operation mode determination of thermoelectric devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resistor is used for current-to-voltage conversion, then the current sensor can be inexpensive and accurate, but it consumes significant power and introduces unwanted resistance in the circuit path
Solution Approach 1:
The patent replaces the resistor-based current-to-voltage conversion mechanism with a transistor-based sensing mechanism. The sense transistor operates in a high-impedance state during measurement, eliminating the need for a physical resistor in the current path. This substitution dramatically reduces power consumption while maintaining measurement accuracy through voltage sensing at the transistor gate.
Solution Approach 2:
The patent introduces a sense transistor as an intermediary element between the current source and the measurement circuit. The transistor's gate voltage, which is proportional to the current, is sensed without requiring current to flow through a resistive element. This intermediary approach allows accurate current measurement without the power loss and resistance issues of direct resistive conversion.
2Measurement precision
If a current sensor circuit is designed to accurately measure bi-directional current signals, then the operating mode of thermoelectric devices can be determined, but the power consumption of the sensor circuit increases
Solution Approach 1:
The patent employs periodic sampling of the transistor gate voltage to determine both magnitude and polarity of bi-directional current. Rather than continuously powering active sensing components, the circuit periodically measures the voltage state, reducing average power consumption while maintaining the ability to detect current direction and magnitude changes over time.
Solution Approach 2:
The patent uses the inherent high-impedance state of the transistor gate to create an equipotential sensing point that reflects current magnitude without drawing significant current itself. By measuring voltage at this equipotential point rather than forcing current through a sensing element, the circuit achieves bi-directional measurement capability with minimal power consumption.
3Measurement precision
If a resistor is placed in the circuit path for current measurement, then the current can be converted to voltage, but unwanted resistance is introduced affecting circuit performance
Solution Approach 1:
The patent substitutes the physical resistor with a field-effect transistor used in a voltage sensing configuration. The transistor's gate terminal provides a high-impedance voltage sensing point that does not introduce significant resistance into the current path. This replacement eliminates the harmful resistive effects while preserving the current-to-voltage conversion function through electronic field effects rather than physical resistance.
Solution Approach 2:
The transistor gate serves as an intermediary sensing point that couples to the current-carrying circuit without significantly loading it. The gate's high input impedance allows voltage proportional to current to be sensed without introducing the unwanted resistance that would occur with a direct resistive connection in the current path.
Data Source
AI summary
A bidirectional current sensor circuit can be configured to generate a scaled version of a load current using a first transistor from a power regulator output stage and a second transistor that can be a mirror or scaled version of the first transistor. A trim circuit can be provided to correct gain errors under current sinking or current sourcing conditions. In an example, the bidirectional current sensor circuit can be configured to detect a polarity or a magnitude of a current signal that is used to operate a thermoelectric device.