Battery Charger Overcurrent Protection via Sense Resistor Feedback
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Solution Overview
Problem
Battery chargers often experience excessive current flow due to defects in components like FETs or inductors, which can damage other components in the system, and existing solutions fail to effectively prevent such overcurrent conditions.
Innovation Solution
A battery charger system that monitors current flow across a sense resistor and uses a switching regulator with PWM logic and comparators to detect overcurrent conditions, turning off the adapter switch or disabling current paths to prevent damage, and includes a monitor and control circuit with filters to enhance sensitivity and noise suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing overcurrent protection solutions are used, then some current protection is provided, but they fail to effectively prevent overcurrent conditions caused by component defects
Solution Approach 1:
The patent implements preliminary protective actions by monitoring current flow before excessive current can cause damage. The system continuously monitors the voltage drop across a sense resistor and compares it against reference voltages representing safe current thresholds. When an overcurrent condition is detected, the system proactively disables the adapter switch or PWM logic to prevent damage to FETs, inductors, and other components, rather than waiting for failure to occur.
2Measurement precision
If current monitoring and protection circuits are added, then overcurrent detection capability is improved, but device complexity increases
Solution Approach 1:
The patent introduces a sense resistor as an intermediary element to enable current monitoring without directly measuring current. By measuring the voltage drop across this small resistor, the system can accurately determine current flow levels. This intermediary approach allows precise current detection while keeping the monitoring circuit relatively simple, as it only requires voltage comparison circuitry rather than complex current measurement systems.
Solution Approach 2:
The system implements feedback control by continuously monitoring the voltage drop across the sense resistor and comparing it against reference voltages. The monitor and control circuit uses this feedback information to determine when overcurrent conditions exist and automatically adjusts the PWM duty cycle or disables the adapter switch to correct the condition, creating a closed-loop protection system that maintains reliability without requiring overly complex open-loop circuitry.
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 prevents excessive current from damaging components by detecting overcurrent conditions and adjusting the current flow, thereby protecting the charger and connected components from damage.
Implementation Method 1
sensing a voltage drop that is related to the electrical current passing between the switching regulator and the battery port
Implementation Method 2
comparing the sensed voltage drop against at least one reference voltage
Data Source
AI summary
Systems and methods are provided for overcurrent protection in a battery charger. In certain embodiments, a method includes turning on an adapter switch to receive electrical power from an adapter connected to the battery charger; controlling a switching regulator to direct electrical current between the switching regulator and a battery port. Further, the method includes sensing a voltage drop that is related to the electrical current passing between the switching regulator and the battery port; comparing the sensed voltage drop against at least one reference voltage; and, when the sensed voltage exceeds the reference voltage, changing operation of the adapter switch to protect the battery charger from an overcurrent state.