USB Port Current Source Detection Circuit
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Solution Overview
Problem
Existing methods for verifying if a USB port has sufficient power to charge a rechargeable battery are complex and unreliable, potentially damaging the USB port circuitry.
Innovation Solution
A controller is coupled to the USB port and rechargeable battery, ramping the source current to a predetermined peak and monitoring the output voltage, disconnecting the current if the voltage drops below a minimum threshold, and repeating the process after a delay to ensure the USB port can sustain the charging current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the USB controller uses a complex data evaluation process to identify USB type, then the power verification may be more thorough, but the device complexity and operation complexity increase significantly
Solution Approach 1:
The patent changes the verification approach from complex data evaluation to monitoring physical parameter changes (voltage drop) during current ramping. The controller ramps up current and observes voltage response, using simple threshold comparison instead of complex data processing to determine USB port capability
Solution Approach 2:
The patent replaces the software-based complex data evaluation process with a hardware-based electrical measurement approach. By using voltage monitoring circuitry to detect voltage drops during controlled current application, the system substitutes computational complexity with direct physical measurement
2Productivity
If the USB port is used to charge a rechargeable battery without verification, then the charging process can start immediately, but the USB port circuitry may be damaged due to insufficient power
Solution Approach 1:
The patent implements preliminary verification before charging by ramping up current in steps and monitoring voltage drops. This preliminary action identifies USB port power capability and suspended states before full charging begins, preventing damage while enabling quick startup once verification is complete
Solution Approach 2:
The patent introduces an intermediary verification process between the USB port and battery charging. The controller acts as an intermediary that mediates the connection by performing safety checks through controlled current application and voltage monitoring before allowing direct charging to proceed
3Reliability
If the source current is disconnected when voltage drops below threshold, then the USB port is protected from damage, but the charging process is interrupted and must be restarted after a delay
Solution Approach 1:
The patent uses periodic verification during the charging process by continuously monitoring voltage during current ramping. When voltage drops indicate a suspended state, the system periodically retries after delay intervals, transforming a potentially permanent failure into a recoverable condition through repeated verification attempts
Data Source
AI summary
A system and method for determining if a USB port can source sufficient current to charge a rechargeable battery at a predetermined peak current level. Detection circuitry is disposed between the USB port and the battery. The detection circuitry includes a current source that is controlled to provide to the battery an increasing current that is sourced by the USB port. As the source current is increased from an initial value to a predetermined peak current source value, the output voltage of the USB port is monitored. If the USB port output voltage drops below a specified threshold voltage before the current source has ramped to the peak current source value, the load current is removed from the battery and an indication is provided that the USB port cannot provide the specified current. The detection process is then repeated after a specified delay interval. If the current source ramps up to the peak source current value and the USB port voltage has not decreased below the specified threshold voltage, charging of the rechargeable battery from the USB port continues at the peak source current.