Secondary Battery Protection Circuit Temperature Drift Compensation
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Solution Overview
Problem
Existing secondary battery protection circuits face variations in temperature characteristics of reference voltage due to manufacturing variations, leading to inconsistent overcharge detection voltages.
Innovation Solution
A secondary battery protection circuit is designed with a reference voltage circuit using a depletion-type and enhancement-type transistor in series, featuring an adjustment circuit that adjusts the size ratio of these transistors and a voltage divider to minimize temperature characteristic variations, ensuring a stable reference voltage and overcharge detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reference voltage circuit uses a depletion-type transistor and enhancement-type transistor connected in series, then the reference voltage can be generated, but variation in temperature characteristic occurs due to manufacturing variation
Solution Approach 1:
The patent adjusts the size ratio (width-to-length ratio) of the depletion-type transistor and enhancement-type transistor to optimize the reference voltage's temperature characteristic. By changing the physical dimensions of the transistors, the circuit compensates for manufacturing variations and reduces temperature-dependent voltage drift, thereby improving reliability without requiring higher manufacturing precision
Solution Approach 2:
The patent introduces an adjustment circuit that dynamically modifies the size ratio of transistors based on detected temperature characteristics. This dynamic adjustment allows the reference voltage circuit to adapt to manufacturing variations and maintain stable performance across different operating conditions, resolving the contradiction between reliability and manufacturing precision
2Reliability
If the size ratio of transistors is adjusted to reduce temperature characteristic variation, then reference voltage stability improves, but the device complexity increases
Solution Approach 1:
The patent employs a self-adjustment mechanism where the adjustment circuit automatically detects temperature characteristic variations and modifies the transistor size ratio accordingly. This self-service approach eliminates the need for external calibration or complex control systems, improving reference voltage stability while minimizing the increase in device complexity
Solution Approach 2:
The patent implements a feedback loop that monitors the reference voltage's temperature characteristic and adjusts the transistor size ratio in response. This feedback mechanism enables automatic compensation for temperature variations, achieving improved reliability through a relatively simple additional circuit rather than complex structural modifications
Data Source
AI summary
A secondary battery protection circuit for a secondary battery includes: a reference voltage circuit configured to generate a reference voltage by using a depletion-type transistor and a transistor unit of enhancement type connected in series with the depletion-type transistor; a voltage divider configured to output a detection voltage obtained by dividing a power source voltage of the secondary battery; a detection circuit configured to detect an abnormal state of the secondary battery based on the reference voltage and the detection voltage; a first adjustment circuit configured to adjust a size ratio of the depletion-type transistor to the transistor unit based on threshold voltages of the depletion-type transistor and the transistor unit; and a second adjustment circuit configured to adjust the detection voltage based on the reference voltage after adjusting the size ratio.