Charging Circuit Adapter Disconnection Detection
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Solution Overview
Problem
Battery charging circuits with switch-mode architecture often get stuck in an undesirable boost-back state after the input power supply is removed, causing the battery to discharge, which violates industry specifications and cannot be completely prevented due to accuracy limitations of zero-crossing detection circuits.
Innovation Solution
A charging circuit with a switchable load and a comparator that periodically disables power delivery from the adapter and activates the switchable load for a fixed duration to determine if the power adapter is disconnected, preventing boost-back operation by sensing voltage collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero-crossing detection circuits are used to detect adapter disconnection, then the detection capability is provided, but the accuracy limitations cause incomplete prevention of boost-back behavior
Solution Approach 1:
The patent introduces a switchable load as an intermediary component between the adapter input and the rest of the charging circuit. This load acts as a mediator that, when activated, creates a deliberate voltage collapse condition that reliably indicates adapter disconnection, overcoming the insufficient detection accuracy of conventional zero-crossing circuits.
Solution Approach 2:
The system performs preliminary action by periodically activating the switchable load before the boost-back condition can occur. This proactive measurement cycle detects adapter presence/absence in advance, allowing the control circuit to prevent boost-back behavior before it happens, rather than reacting after detection failure.
2Reliability
If the switchable load is activated periodically to detect adapter disconnection, then boost-back prevention is improved, but additional power consumption and circuit complexity are introduced
Solution Approach 1:
The switchable load serves multiple functions: it acts as a measurement device for detecting adapter disconnection, a control element for creating voltage collapse conditions, and part of the overall power management system. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in circuit complexity while achieving reliable boost-back prevention.
3Measurement precision
If the switchable load activates for fixed duration periods, then accurate detection of adapter removal is achieved, but power is consumed during measurement cycles
Solution Approach 1:
The system uses periodic action by activating the switchable load for fixed duration periods rather than continuously. This periodic measurement approach achieves accurate detection of adapter removal while minimizing power consumption compared to continuous monitoring, as the load is only activated when measurement is required.
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
Prevents battery discharge by accurately determining when the power adapter is removed, ensuring compliance with industry specifications and minimizing the risk of boost-back behavior.
Implementation Method 1
A comparator may sense the voltage at the input terminal
Data Source
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AI summary
A charging circuit using a switch mode power supply to charge a battery from a connected external power adapter may periodically turn off the switch mode power supply and disconnect its input terminal from the switch mode power supply. A load may be connected to the input terminal. The input terminal is monitored for voltage collapse, indicating whether or not the power adapter is connected.