Current Transformer Sensing Circuit for Load-Dependent Offset Control
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Solution Overview
Problem
Current sensing devices in DC/DC converters face challenges in accurately measuring high currents due to offset currents that fluctuate with load conditions, making it difficult to achieve precise measurements across various load scenarios.
Innovation Solution
A current sensing device comprising a current transformer, a voltage limiting circuit, and a current direction limiting circuit that generates sensing voltages based on the output current and voltage, allowing for distinct voltage application and current direction control, thereby stabilizing the sensing current despite changes in load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a current transformer is used for indirect measurement of high current, then the measurement range is extended, but offset currents are generated that fluctuate with load conditions, degrading measurement precision
Solution Approach 1:
The patent introduces a compensation current as an intermediary element to counteract the offset current. The compensation current is generated in opposition to the offset current, effectively canceling it out. This mediator approach allows the system to maintain both the extended measurement range of the current transformer and the precision needed for accurate current sensing.
Solution Approach 2:
The patent dynamically adjusts the compensation current parameter based on the detected offset current characteristics. By changing the magnitude and direction of the compensation current in response to varying load conditions, the system maintains measurement precision across different operating ranges while preserving the extended measurement capability.
2Measurement precision
If Hall-type sensors are used on the output side for high current sensing, then current measurement capability is improved, but cost and device size increase
Solution Approach 1:
The patent creates an electrical copy of the offset current through the compensation current mechanism. Instead of using expensive Hall sensors to directly measure the high current, the system uses a simplified current transformer setup and compensates for errors by generating a corresponding compensation signal. This copying approach achieves accurate current sensing without the cost and size penalties of Hall sensors.
Solution Approach 2:
The patent replaces the mechanical/electromagnetic Hall sensor system with an electrical compensation system based on current transformer principles. This substitution eliminates the need for complex mechanical or electromagnetic sensor structures, reducing both cost and device size while maintaining measurement capability through the compensation mechanism.
3Measurement precision
If offset current compensation is implemented, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the offset detection and compensation functions into an integrated circuit system. The compensation current generation is combined with the existing current transformer circuitry, and the control logic is integrated to work seamlessly with the transformer and sensing elements. This merging reduces overall device complexity compared to having separate, standalone compensation components.
Solution Approach 2:
The compensation system is designed to automatically detect and correct offset currents without requiring external intervention or complex control mechanisms. The circuit self-regulates by continuously monitoring the output and generating the appropriate compensation current, eliminating the need for additional complex control hardware or software management.
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
Enables high-accuracy current measurement in DC/DC converters even under varying load conditions by compensating for energy differences and maintaining consistent sensing current offsets, improving the overall precision of current sensing.
Implementation Method 1
a current transformer that includes a primary side constituting at least a part of a path through which a sensing target current flows in a sensing target circuit, and is configured to generate, to a secondary side, an output current according to characteristics of the sensing target current
Data Source
AI summary
A current sensing device for sensing an alternating current includes a current transformer that includes a primary side constituting at least a part of a path through which a sensing target current flows in a sensing target circuit, and is configured to generate, to a secondary side, an output current according to characteristics of the sensing target current, a voltage limiting circuit that is connected to both ends of the secondary side and is configured to provide a path through which at least a part of the output current flows, and to limit a voltage applied to both ends of the secondary side in a distinguishable manner according to a direction of the output current, a sensing voltage generation circuit configured to generate a sensing voltage based in part on at least one of the output current and a voltage of the voltage limiting circuit, and a current direction limiting circuit that electrically connects both ends of the secondary side to the sensing voltage generation circuit, and is configured to limit a direction of a current transferred from both ends of the secondary side to the sensing voltage generation circuit.