Buck-Boost Charger Current Limit Loop for Sense Resistor Failure
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Solution Overview
Problem
Conventional battery charging circuits with damaged or short-circuited current sense resistors lack output current limiting, leading to potential damage to internal and external components due to unchecked current surges.
Innovation Solution
Incorporating a second current sense resistor to sense battery discharge current, allowing the system to determine and apply an output current limit, thereby protecting components from excessive current in case of a malfunction or short circuit at the primary current sense resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single current sense resistor is used to monitor output current, then the circuit structure is simple, but the reliability is poor because the circuit cannot protect itself when the resistor fails or shorts
Solution Approach 1:
The current monitoring function is segmented into two independent paths: one through the first current sense resistor (RS1) for normal operation, and another through the second current sense resistor (RS2) for backup protection. This segmentation ensures that if one path fails, the other can take over to maintain system reliability.
Solution Approach 2:
The system implements beforehand cushioning by pre-configuring the second current sense resistor (RS2) and its associated current limit loop as a backup protection mechanism. This backup is established in advance and automatically activates when the primary current sense resistor (RS1) fails, preventing catastrophic damage without requiring real-time detection of the failure.
2Object-affected harmful factors
If no current limit protection is implemented, then the device complexity is reduced, but harmful factors increase due to potential damage from unchecked current surges
Solution Approach 1:
The second current sense resistor (RS2) acts as an intermediary protection mechanism. It provides a backup current sensing path that mediates between the potential harmful current surge and the system components, enabling the current limit loop to regulate and protect the system when the primary sensing path fails.
3Reliability
If a backup current sense resistor is added for protection, then the reliability improves, but the device complexity increases due to additional components and control logic
Solution Approach 1:
The system implements self-service through automatic failover. The current limit loop continuously monitors both current sense resistors and automatically switches to using the backup resistor (RS2) when the primary resistor (RS1) fails, without requiring external intervention or complex control logic. The system protects itself autonomously.
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
Effectively limits short circuit current using battery discharge current, preventing damage to internal and external circuitry even when the primary current sense resistor is damaged or short-circuited, ensuring safe operation and component protection.
Implementation Method 1
a first current sense resistor positioned in a battery charging circuit, wherein the first current sensor resistor is configured to sense a first current value at a first port
Implementation Method 2
a second current sensor resistor configured to sense a battery discharge current value output from a battery
Data Source
AI summary
A method, apparatus and non-transitory computer-readable medium of regulating current within a battery charging circuit. The apparatus including a first current sense resistor configured to sense a first current value at a first port, a second current sensor resistor configured to sense a battery discharge current value output from a battery, and a processor configured to, in response to a short circuit or malfunction at the first current sense resistor, use the battery discharge current value to determine an output current limit and to limit the current at the first port according to the output current limit.