Four-Terminal Electronic Load Resistor for Solder Resistance Error Reduction
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Solution Overview
Problem
The resistance value of solder in electronic load apparatuses changes with temperature, causing errors in measuring voltage and current values during environmental tests, as it can be similar to the resistance value of the load element, leading to inaccurate determination of output voltage or current from power supply apparatuses.
Innovation Solution
An electronic load apparatus is designed with a measurement resistor having four contacts, a reference circuit, a transistor, and a feedback circuit, where the measurement resistor's resistance value is determined based on voltage and current values across it, minimizing the impact of solder resistance changes by using a configuration that ensures the current through the measurement resistor is smaller than the load current, thus reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional two-contact measurement resistor is used, then the device complexity is low, but the measurement precision deteriorates due to solder resistance changes affecting voltage and current measurements
Solution Approach 1:
The measurement resistor is divided into two separate resistors: a first measurement resistor connected in series with the load, and a second measurement resistor connected in parallel with the load. This segmentation allows independent optimization of each resistor's function and connection method, reducing the impact of solder resistance changes on measurement accuracy while maintaining manageable device complexity through modular architecture
Solution Approach 2:
A current detection circuit is introduced as an intermediary component to detect the current flowing through the first measurement resistor. This intermediary circuit enables indirect measurement of current through voltage conversion across the first measurement resistor, eliminating the need for direct current measurement and reducing sensitivity to solder resistance variations
2Measurement precision
If the measurement resistor is placed in series with the load, then the current through the measurement resistor is smaller reducing solder resistance impact, but the voltage drop across the measurement resistor increases affecting measurement accuracy
Solution Approach 1:
The measurement function is segmented into two independent paths: a series connection path with the first measurement resistor for current sensing, and a parallel connection path with the second measurement resistor for voltage sensing. This segmentation allows each resistor to be optimized for its specific function without compromising the other, balancing measurement precision with power loss considerations
Solution Approach 2:
The traditional single-resistor measurement approach is replaced with a dual-resistor system where one resistor operates in series for current measurement and another operates in parallel for voltage measurement. This substitution of measurement methodology allows independent optimization of each resistor's position and value, reducing the trade-off between measurement accuracy and power loss
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 configuration effectively reduces errors caused by solder resistance changes, providing accurate measurements of voltage and current values by ensuring the measurement resistor's resistance value is known and controlled, thereby improving the accuracy of power supply testing.
Implementation Method 1
A load current value passing through a second contact of a measurement resistor is determined based on a voltage value across the measurement resistor and a resistance value of the measurement resistor
Data Source
AI summary
The present disclosure relates to an electronic load apparatus. An embodiment of the present disclosure includes an electronic load apparatus including: a measurement resistor, a reference circuit, a transistor, and a feedback circuit. The measurement resistor includes a first contact, a second contact, a third contact, and a fourth contact. The first contact and the second contact are located at a first end of the measurement resistor. The third contact and the fourth contact are located at a second end of the measurement resistor. A reference power (or a reference voltage) electrically connects to the reference circuit. The reference circuit and the first contact of the measurement resistor are electrically connected. The transistor includes a drain, a gate, and a source. The reference circuit and the gate of the transistor are electrically connected. One of the source and the drain of the transistor electrically connects to the second contact of the measurement resistor. The other one of the drain and the source of the transistor electrically connects to an output terminal of a unit under test. The feedback circuit and the fourth contact of the measurement resistor are electrically connected. The feedback circuit and the reference circuit are electrically connected.