Programmable Battery Protection System with Fuse-Based Threshold Generation
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Solution Overview
Problem
Conventional battery protection systems face challenges in accurately detecting overcurrent and short-circuit conditions due to variations in the on-resistance of charging and discharging FETs, leading to potential damage or safety risks, especially in lithium-ion batteries.
Innovation Solution
A programmable battery protection system utilizing an array of fuses, latches, and MOSFETs to generate a threshold voltage for comparators, which is calculated based on the actual on-resistance of FETs during testing, allowing for accurate detection of overcharge, overdischarge, and short-circuit conditions, and featuring an automatic fuse refresh mechanism to maintain accurate threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fixed threshold battery protection systems are used, then the device complexity is low, but the measurement precision of overcurrent and short-circuit detection deteriorates due to FET on-resistance variations
Solution Approach 1:
The system performs preliminary characterization of FET on-resistance values during manufacturing testing. The measured resistance values are stored in non-volatile memory (e.g., EEPROM) before the product leaves the factory. This preliminary action enables the system to use accurate, device-specific resistance values for threshold calculations during actual operation, significantly improving detection precision without requiring complex real-time measurement circuitry.
Solution Approach 2:
The system creates a digital copy of the FET on-resistance characteristics by storing the measured resistance values in non-volatile memory. This digital replica allows the microcontroller to accurately calculate protection thresholds based on actual device parameters rather than using generic worst-case values, thereby improving measurement precision while keeping the hardware relatively simple.
2Reliability
If FET on-resistance variations are not compensated, then the device complexity remains low, but the reliability of battery protection deteriorates due to inaccurate threshold detection
Solution Approach 1:
The system performs preliminary measurement and storage of FET on-resistance values during manufacturing. This advance characterization ensures that reliable, device-specific protection thresholds can be calculated during operation, improving protection reliability without requiring complex real-time compensation circuits.
Solution Approach 2:
The system uses the stored FET resistance values to dynamically calculate and adjust protection thresholds based on actual device characteristics. This feedback mechanism ensures that the protection system adapts to the specific electrical properties of each device, significantly improving reliability by preventing both false alarms and missed protection events.
3Measurement precision
If non-volatile memory is added to store FET resistance values, then the measurement precision improves, but the manufacturing cost increases
Solution Approach 1:
The system uses a single non-volatile memory component to serve multiple functions: storing FET resistance characterization data, storing protection threshold values, and potentially storing device identification information. This multi-functional use of the memory component maximizes the value derived from the additional manufacturing cost while improving measurement precision.
Solution Approach 2:
The system changes the approach from using fixed, conservative threshold values to using dynamically calculated thresholds based on measured electrical parameters (FET on-resistance). This parameter change enables more accurate detection while the cost of storing these parameters in non-volatile memory is offset by the elimination of expensive worst-case design margins.
4Reliability
If accurate FET resistance measurement and storage is implemented, then the reliability of battery protection improves, but the manufacturing process complexity increases
Solution Approach 1:
The system performs FET resistance measurement and threshold calculation as a preliminary step during the manufacturing testing process. By completing this characterization before final assembly, the system ensures reliable protection thresholds are established without requiring complex real-time measurement capabilities in the final product, thus improving reliability while keeping manufacturing process complexity manageable.
Data Source
AI summary
A programmable battery protection system. Implementations may include: a battery, only two field effect transistors (FETs), and a battery protection integrated circuit (IC). The battery protection IC may include an array of fuses, first plurality of latches, second plurality of latches, and a comparator. The array of fuses, first plurality of latches, and second plurality of latches may be coupled with a fuse refresh circuit coupled with an analog trigger circuit and a logic trigger circuit. The fuse refresh circuit may be configured to refresh the states of the latches using states of the array of fuses in response to receiving an operating trigger signal generated by the analog trigger circuit or a logic trigger signal generated by the logic trigger circuit. The first plurality of latches may be used to generate a threshold voltage that is provided to the comparator.