Temperature Measurement Circuit Using Iterative Comparator Merging
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Solution Overview
Problem
Existing temperature measurement methods for battery charging, particularly for lithium-ion batteries, face challenges due to large resistance differences within critical temperature limits (0° C. to 50° C.) and offset errors in voltage comparators, making precise temperature measurement difficult.
Innovation Solution
A circuit arrangement using a single comparator with a sequential logic unit and digitally controllable switching elements for iterative comparison and superposition of temperature-dependent measurement signals, reducing the influence of offset errors and allowing high voltage usage, which includes a digitally controllable current source and analog-to-digital conversion for precise temperature determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple voltage comparators are used for temperature measurement, then measurement precision is improved, but device complexity increases and offset errors are introduced
Solution Approach 1:
The patent merges multiple comparator functions into a single comparator by implementing an iterative measurement process. The single comparator repeatedly compares different voltage divisions against the reference voltage, with the sequentially controlled switching element directing different measurement signals to the comparator input over time. This consolidation eliminates the need for multiple parallel comparators while maintaining measurement capability across the full temperature range.
Solution Approach 2:
The patent employs periodic action through iterative comparison cycles. The measurement process repeats multiple times, with each iteration comparing a specific voltage division against the reference voltage. The sequential logic unit controls the timing and progression of these iterative comparisons, allowing the system to gather temperature information across different voltage thresholds through repeated measurement cycles rather than simultaneous parallel comparisons.
2Measurement precision
If multiple voltage comparators are used for temperature measurement, then measurement precision is improved, but offset errors increase
Solution Approach 1:
By consolidating multiple comparator functions into a single comparator, the patent eliminates the cumulative offset errors that would arise from using multiple independent comparators. The single comparator introduces only one set of offset characteristics, which can be more easily calibrated and compensated. The iterative measurement process maintains precision by comparing against the same stable reference voltage throughout all measurement iterations.
3Device complexity
If simple constant current circuits are used, then device complexity is reduced, but measurement precision deteriorates due to large resistance differences
Solution Approach 1:
The patent segments the temperature measurement range into multiple intervals, each associated with a specific voltage division ratio. The sequentially controlled switching element selects which voltage division to compare against the reference voltage based on the current measurement iteration. This segmentation allows the system to handle the large resistance differences (up to 10 kΩ) by breaking them into manageable comparison steps, maintaining precision without requiring complex analog circuitry.
Solution Approach 2:
The patent introduces dynamic control through the sequentially operated switching element and logic unit. Rather than using fixed constant current circuits, the system dynamically adjusts which voltage division is presented to the comparator in each iteration. This dynamic approach allows the measurement system to adapt to different resistance values and temperature ranges, maintaining precision across the full operating range while keeping the analog circuitry relatively simple.
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 solution enables precise temperature measurement by iteratively comparing and superimposing signals, reducing offset errors and allowing high voltage usage, thus improving the accuracy of temperature determination within the critical temperature range for battery charging.
Implementation Method 1
Thermistors, especially NTC resistors, i.e., thermistors with negative temperature coefficients, are generally used and make it possible to measure the temperature as a function of a variable resistance.
Data Source
AI summary
A circuit arrangement for temperature measurement comprises an input for connecting a temperature-sensitive element, a that is connected to a first input of a comparator. A reference voltage is connected to a second input of the comparator. Furthermore, the arrangement comprises a sequential logic, that is coupled to the output of the comparator that comprises a first output and a second output. A digitally controllable switch element for providing a superposition signal is connected to the output of the sequential logic and the first input of the comparator.