Battery Charge Indicator Circuit Using NTC Sensor Locking Switch
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Solution Overview
Problem
Existing rechargeable battery state of charge displays often require a microprocessor to accurately differentiate operating states, leading to incorrect values when this component is not used, resulting in inability to distinguish between charging and discharging states.
Innovation Solution
A state of charge circuit with an NTC sensor and a locking switch coupled to an evaluation unit, allowing for accurate display of charge status without a microprocessor, using voltage levels to determine if the battery is being charged or discharged, and preventing display during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microprocessor is used to accurately differentiate operating states, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the state of charge display circuit into distinct functional parts: a display unit with multiple LEDs showing charge levels, and a separate control unit with the NTC sensor and locking switch. This segmentation allows the display function to be simple while the control logic handles the complexity of differentiating operating states through voltage level detection.
Solution Approach 2:
The patent introduces an NTC (negative temperature coefficient) sensor as an intermediary element that provides temperature-dependent resistance information to the evaluation unit. This intermediary allows the system to indirectly determine operating states (charging vs. discharging) through voltage level changes caused by temperature variations, avoiding the need for direct complex microprocessor control.
2Device complexity
If a microprocessor is not used to reduce cost, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The state of charge display circuit serves itself by using the inherent temperature-dependent electrical characteristics of the NTC sensor to automatically differentiate between charging and discharging states. The evaluation unit monitors voltage levels at the NTC contacts and autonomously controls the locking switch and display without requiring external microprocessor intervention, achieving both simplicity and accuracy.
Solution Approach 2:
The patent exploits parameter changes in the NTC sensor's electrical characteristics (resistance and voltage level) that occur with temperature variations during charging and discharging. By monitoring these parameter changes at the NTC contacts, the system can accurately determine operating states using simple voltage comparison logic instead of complex microprocessor algorithms.
3Reliability
If the state of charge display is blocked during operation, then reliability is improved, but loss of information increases
Solution Approach 1:
The patent implements a dynamic locking mechanism controlled by the locking switch that adaptively enables or disables the state of charge display based on detected operating states. The evaluation unit continuously monitors NTC voltage levels and dynamically adjusts display visibility - blocking it during charging/discharging when readings would be inaccurate, and enabling it during idle states when accurate information can be provided. This dynamic approach maintains reliability while minimizing information 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
Enables cost-effective, accurate display of battery state of charge without a microprocessor, protecting the battery from over-discharge by activating the locking switch when voltage falls below a minimum threshold.
Implementation Method 1
a Z sensor designed as an NTC is provided in the state of charge circuit, which is coupled to the evaluation unit
Data Source
AI summary
Storage batteries having a rechargeable battery (12) for operating electric tools often have a state of charge indicator. A state of charge circuit (10), which has a sensor (20) which is coupled to the evaluation unit (14), is provided in order to identify the operating state of the storage battery. A locking switch (22) for preventing indication of the state of the charge is coupled to the evaluation unit (14). If charging or discharging of the rechargeable battery (12) is identified using the sensor (20), the locking switch (22) is used to prevent indication of the current state of charge.