Current Control Device Temperature Compensation
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Solution Overview
Problem
Current current control devices for electric loads face challenges in maintaining accurate current control due to changes in resistance value of current detection resistors with temperature fluctuations, leading to decreased accuracy and increased costs, as they require precise resistors that do not change with temperature.
Innovation Solution
A current control device with a microprocessor, nonvolatile program memory, and temperature detection circuit that uses temperature characteristic data to calculate a corrected target current, allowing for accurate current control even with self-heating and temperature differences, using a current detection resistor that does not require precise temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current detection resistor with high temperature stability is used, then current control accuracy is maintained, but product cost increases
Solution Approach 1:
The patent applies parameter changes by introducing temperature compensation parameters (correction values) that are stored in the microprocessor. These correction values adjust the detected current reading based on temperature-dependent resistance variations, allowing the system to maintain accuracy without requiring expensive temperature-stable resistors. The microprocessor dynamically modifies the measurement parameter (current reading) based on temperature conditions.
Solution Approach 2:
The patent creates a virtual model of the resistance temperature characteristic through correction values stored in memory. Instead of physically compensating for temperature effects, the system copies the expected resistance behavior at different temperatures and uses this model to correct the actual measurements, achieving accuracy through information processing rather than physical precision components.
2Measurement precision
If temperature compensation is implemented, then current control accuracy is maintained across temperature variations, but device complexity increases
Solution Approach 1:
The patent implements feedback by continuously monitoring temperature and using this information to adjust the current detection readings. The system feeds back the temperature condition to the microprocessor, which then applies appropriate correction values to the detected current, creating a closed-loop compensation mechanism that maintains accuracy across temperature variations.
Solution Approach 2:
The patent replaces physical/chemical temperature compensation mechanisms (such as temperature-stable resistor materials or complex compensation circuits) with electronic software-based correction. The microprocessor uses stored correction values to digitally adjust the measurement, substituting mechanical/physical complexity with computational simplicity.
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 accurate current control across varying temperatures without the need for expensive, temperature-stable resistors, reducing product costs while maintaining control precision.
Implementation Method 1
a temperature detection circuit which includes a temperature sensor and generates measured voltages Sa and Sb corresponding to a normal-temperature ambient temperature Ta and an actual operation ambient temperature Tb
Implementation Method 2
an amplifier circuit part for current detection which amplifies a voltage across the current detection resistor, and generates a monitored voltage Ef which is based mainly on a current proportional component proportional to the load current Im
Data Source
AI summary
Initial calibration is performed only under normal-temperature environment, and accurate current control is performed under practical use temperature environment. A temperature sensor 171 is arranged close to a current detection resistor 126 having predetermined temperature characteristics. Resistance values are estimated in a calibration environment and a practical use environment, an actually measured load current in the calibration environment corresponding to a target load current is stored as control characteristic data, a corrected target current corresponding to the target load current is calculated, and a converted target current based on a change ratio of current detection resistance is controlled as a target current for current control. A resistance change amount by heat generation of the current detection resistor 126 which cannot be entirely detected by the temperature sensor 171 is corrected in control characteristic data, such that linearity of control characteristics is improved.