Battery Charger Input Sensing to Prevent Reverse-Boosting
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Solution Overview
Problem
Switch-mode battery chargers often fail to detect the removal of an input power supply, leading to unintended reverse-boosting operations due to difficulties in accurately determining when the inductor current reaches zero and the inherent limitations of high-side NFET topology, which can cause the charger to incorrectly operate in reverse-boost mode.
Innovation Solution
Implementing a system with a first and second sensing device to detect input current and voltage levels, respectively, and disabling the charger when both are below threshold values, thereby distinguishing between reverse-boosting and a weak input power supply without requiring software interaction or stopping normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the battery charger uses switch-mode architecture to provide buck conversion, then charging efficiency is improved, but the charger cannot accurately detect removal of input power supply leading to reverse-boosting operation
Solution Approach 1:
The patent introduces an intermediary detection mechanism that senses the voltage at the input node to determine whether the input power supply has been removed. This intermediary sensor allows the system to distinguish between a weak input power supply and complete removal, preventing reverse-boosting operation while maintaining the efficient switch-mode architecture.
Solution Approach 2:
The patent implements a feedback control mechanism where the controller continuously monitors the input node voltage and adjusts the switching operation accordingly. When the voltage indicates input power supply removal, the controller provides feedback to disable the charger, preventing unintended reverse-boosting while maintaining normal operation during genuine charging conditions.
2Stability of the object's composition
If the battery charger operates at high duty-cycle to prevent reverse-boosting, then stability is improved, but the charger cannot reach 100% duty-cycle limiting its ability to fully prevent reverse-boosting
Solution Approach 1:
The patent applies preliminary action by detecting the removal of the input power supply before reverse-boosting can occur. The detection mechanism identifies the condition early, allowing the controller to disable the charger proactively rather than attempting to counteract reverse-boosting after it has started, thus achieving complete prevention without duty-cycle limitations.
3Measurement precision
If the battery charger continuously monitors input current and voltage to detect reverse-boosting, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the monitoring system multi-functional by using the same voltage sensing mechanism for both detecting input power supply removal and detecting reverse-boosting conditions. This universal approach allows accurate detection of both states without requiring separate complex monitoring circuits, thus maintaining detection accuracy while minimizing added complexity.
Data Source
AI summary
Exemplary embodiments are related to detecting a reverse-boosting operation of a battery charger. A device may include a plurality of switches for receiving an input voltage at an input port and conveying an output voltage. The device may also include a first sensing device coupled to the input port configured to detect if an input current is less than a threshold current. Further, the device may include a second sensing device selectively coupled to the input port to detect if the input voltage is less than a threshold voltage.