Charging Current Limit Circuit Hardware Safety Validation
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Solution Overview
Problem
Rechargeable batteries, particularly lithium-ion batteries, can become volatile when charged with excessive current, posing risks of damage or injury due to overheating, fire, or explosion, often caused by incorrect programming or malicious modifications, which existing technologies fail to adequately mitigate.
Innovation Solution
A charge current limiting circuit that implements a hardware-based limit using a current-limiting resistor (Rmax) to control the charging current, ensuring it does not exceed a safe maximum (Imax), while allowing programmable charging profiles to support various charging scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a programmable charging current is used to support various charging scenarios, then adaptability is improved, but the risk of excessive current causing battery volatility increases
Solution Approach 1:
The circuit performs preliminary action by pre-determining a safe maximum charging current value during manufacturing and hardcoding it into the circuit. This preliminary safety parameter is stored in a secure location and used to validate any programmable charging current settings before actual charging occurs, preventing excessive current from being applied to the battery.
Solution Approach 2:
The circuit introduces an intermediary safety mechanism that acts as a mediator between the programmable charging current and the battery. This intermediary layer validates the programmed current against the pre-determined safe maximum and intervenes to prevent dangerous charging conditions, thus protecting the battery while allowing programmable flexibility.
2Reliability
If a hardware-based current limit is implemented to prevent excessive current, then battery safety is improved, but device complexity increases
Solution Approach 1:
The circuit implements self-service by incorporating an on-chip analog-to-digital converter that automatically compares the programmable charging current against the pre-determined safe maximum. The circuit self-validates the safety of charging parameters without requiring external validation hardware, thus improving battery safety while minimizing additional circuit complexity.
Solution Approach 2:
The circuit merges multiple functions into a single integrated solution by combining the safe maximum current determination, storage, and validation logic within the same charging circuit IC. This consolidation achieves hardware-based safety validation without proportionally increasing overall device complexity, as the safety features are integrated rather than added as separate external components.
3Reliability
If the safe maximum charging current is pre-determined and stored in the circuit, then protection against malicious modifications is improved, but manufacturing complexity increases
Solution Approach 1:
The circuit uses a cost-effective approach by implementing the safe maximum current storage in a simple, non-volatile memory location within the IC that is programmed during manufacturing. This disposable-like approach means the safety parameter is set once during production and cannot be easily modified, providing robust protection against malicious changes while avoiding the need for complex secure element hardware or encryption mechanisms.
Solution Approach 2:
The circuit replaces potential mechanical or external validation systems with an integrated electronic validation mechanism. The safe maximum current is stored digitally within the IC and validated through electronic comparison circuits, eliminating the need for external hardware validation devices or complex mechanical safety mechanisms, thus simplifying manufacturing while maintaining strong protection against modification.
Data Source
AI summary
Aspects of the present disclosure provide for circuit. In at least some examples, the circuit includes a controller, a current source, a switch, and a digital-to-analog converter (DAC). The controller includes an analog-to-digital converter (ADC) having an input and an output, a first register, and a second register coupled to the output of the ADC. The switch is coupled between an output of the current source and a first node and has a control terminal coupled to the controller. The first node is coupled to the input of the ADC and is configured to couple to a resistor. The DAC has an input coupled to the controller and an output configured to couple to a battery.