USB Data Pin Impedance Detection for Charger Safety
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Solution Overview
Problem
Existing power supply systems fail to detect improper loading conditions, such as shorted pins, which can lead to unnecessary power consumption and damage to both the charger and the portable electronic device, especially when data signal pins are damaged or shorted, causing the charger to continue supplying power without notification.
Innovation Solution
A device that determines the impedance at a data pin of a communication interface by injecting a test current and sensing both the voltage with and without the test current, using a sensing circuit to compare the voltages and determine if the pin has a short condition, thereby identifying improper loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the charger relies on notifications from the loading device to detect improper loading conditions, then the device complexity is reduced, but the reliability of detecting shorted pins deteriorates because the loading device may be unable to notify the charger when data signal pins are damaged or shorted
Solution Approach 1:
The charger performs self-detection of improper loading conditions by actively measuring impedance at its own data pins using a test current source and sensing circuit, rather than relying on notifications from the loading device. This allows the charger to independently detect shorted pins and terminate power supply accordingly, resolving the contradiction by making the charger self-sufficient in detection while maintaining simple structure.
2Ease of operation
If the charger continuously supplies power to the loading device without detection, then the ease of operation is improved, but the harmful factors increase due to unnecessary power consumption and potential damage to the charger and loading device
Solution Approach 1:
The charger performs impedance detection before continuously supplying power to the loading device. By injecting a test current and measuring the voltage response at the data pin, the charger identifies improper loading conditions in advance and terminates power supply accordingly, preventing unnecessary power consumption and potential damage while maintaining simple charging operation.
3Measurement precision
If impedance detection is performed using a current source and sensing circuit, then the measurement precision of detecting shorted pins is improved, but the device complexity increases due to additional components
Solution Approach 1:
The sensing circuit serves multiple functions: it senses the voltage response to the injected test current for impedance calculation, and can also function as part of the normal data communication path during USB operation. This multi-functionality allows precise impedance detection while minimizing additional circuit complexity, as the same circuit infrastructure supports both detection and communication roles.
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
Enables the device to detect improper loading conditions without relying on notifications from the electronic device, preventing damage by terminating the power supply or discontinuing the connection when an improper condition is detected, thus ensuring safe and efficient charging.
Implementation Method 1
a current source configured to selectively inject a test current to the data pin
Implementation Method 2
a sensing circuit for sensing a first test voltage corresponding to a voltage at the data pin without the test current injected, and a second test voltage corresponding to another voltage at the data pin with the test current injected. The sensing circuit determines the impedance at the data pin based on the first test voltage and the second test voltage.
Data Source
AI summary
A device for determining impedance at a data pin of a communication interface. In one embodiment, the device includes a current source configured to selectively inject a test current to the data pin. The device also includes a sensing circuit for sensing a first test voltage corresponding to a voltage at the data pin without the test current injected, and a second test voltage corresponding to another voltage at the data pin with the test current injected. The sensing circuit determines the impedance at the data pin based on the first test voltage and the second test voltage.