Battery Charging Circuit Current Ratio Stabilization
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Solution Overview
Problem
Existing battery charging circuits in constant current mode experience inaccuracies due to non-ideal characteristics of electronic components, leading to fluctuations in charging current as time increases, which affects the stability of the charging process.
Innovation Solution
A battery charging circuit design that includes a charging transistor, a first transistor, a second transistor, and sensors to adjust the voltage proportional relationship between the threshold voltages of these transistors, using a voltage regulator to maintain a constant current ratio between the charging current and the sensing current, thereby stabilizing the charging current over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional battery charging circuit uses a charging transistor and sensing transistor with fixed sizes, then the circuit structure is simple, but the charging current becomes inaccurate over time due to non-ideal transistor characteristics
Solution Approach 1:
The patent applies dynamics by making the transistor sizes adjustable rather than fixed. The charging transistor and sensing transistor sizes are dynamically adjusted based on the ratio of reference currents to maintain accurate charging current over time, resolving the issue of component degradation while managing circuit complexity.
Solution Approach 2:
The patent changes physical parameters (transistor sizes W/L ratios) to compensate for non-ideal characteristics. By adjusting the width and length parameters of the charging and sensing transistors based on measured current ratios, the system maintains accuracy despite component variations and aging.
2Productivity
If the charging transistor size is increased to provide higher charging current, then the charging speed improves, but the current ratio between charging current and sensing current becomes less accurate
Solution Approach 1:
The patent implements feedback by continuously monitoring the ratio between charging current and sensing current, then adjusting the transistor sizes to maintain the desired current ratio. This closed-loop control ensures both high charging current and accurate measurement, resolving the contradiction between productivity and measurement precision.
Solution Approach 2:
The system dynamically adjusts transistor sizes based on operating conditions. When high charging current is needed, the charging transistor is enlarged, and the sensing transistor is proportionally adjusted to maintain accurate current ratio measurement, enabling both high speed and precision.
3Stability of the object's composition
If multiple transistors with different sizes are used to maintain current ratio accuracy, then the charging current stability improves, but the device complexity increases
Solution Approach 1:
The patent segments the charging circuit into multiple transistor components with different functions: charging transistors for current delivery and sensing transistors for measurement. By dividing the circuit into specialized segments, the system achieves stable current ratio control while managing overall complexity through functional separation.
Solution Approach 2:
The patent uses multiple sensing transistors that are scaled versions of each other, creating a proportional relationship between their sizes and the currents they measure. This copying approach with scaling allows accurate current ratio measurement without requiring completely different circuit topologies, managing complexity through repetition with variation.
Data Source
AI summary
A battery charging circuit adjusts a voltage proportional relationship between a turned-on voltage of a charging transistor and a turned-on voltage of a first transistor according to a first voltage corresponding to a charging current and a second voltage corresponding to the charging current, so that a ratio between the charging current and a first current sensing the charging current is a constant value or close to a constant value.