USB Device Power Configuration Switching
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Solution Overview
Problem
USB hosts, particularly those running Microsoft Windows, often fail to correctly enumerate multiple USB device power configurations, leading to unusable devices when the USB port cannot support the reported power requirements, resulting in voltage sags and erratic operation.
Innovation Solution
A method for USB devices to independently determine the capabilities of an upstream USB port by enabling and disabling connections, reporting different power configurations, and using voltage sag detection to manage power draw, allowing flexible power configuration switching between low and high power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If USB device reports high-power configuration to USB host, then device can operate at higher power levels, but USB host may fail to enumerate the device if the port cannot support the power requirements
Solution Approach 1:
The USB device dynamically switches between high-power and low-power configurations based on enumeration success. The device initially reports high-power configuration, and if enumeration fails, it automatically switches to low-power configuration and re-enumerates, allowing adaptation to different host port capabilities.
Solution Approach 2:
The device changes the power configuration parameter based on host response. By monitoring whether the host sends a setup stage timeout or recognition, the device determines whether to maintain high-power configuration or switch to low-power configuration, effectively adapting to host port power capabilities.
2Power
If USB device draws more current than reported in configuration descriptors, then device can achieve higher performance, but device will not pass USB certification testing
Solution Approach 1:
The device performs preliminary testing by initially reporting high-power configuration and attempting enumeration. This allows the device to test whether the host port can actually support the higher current draw before committing to that configuration, ensuring both performance optimization and certification compliance.
Solution Approach 2:
The device uses feedback from the host's enumeration response to determine appropriate power configuration. By monitoring whether enumeration succeeds or fails, the device adjusts its current draw to match host capabilities, ensuring both optimal performance and compliance with USB certification requirements.
3Productivity
If USB host does not enumerate multiple device configurations, then enumeration process is simpler and faster, but device becomes unusable when port cannot support reported power requirements
Solution Approach 1:
The USB device performs self-testing and self-configuration by monitoring host enumeration responses. The device autonomously determines whether the host supports high-power configuration by detecting enumeration success or failure, and automatically switches configurations accordingly, eliminating the need for the host to explicitly enumerate multiple configurations.
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 USB devices to correctly determine and manage power usage based on the USB port's capabilities, preventing voltage sags and ensuring reliable operation, while allowing for intelligent power management and optimal function prioritization.
Implementation Method 1
determining a capability of an upstream universal serial bus (USB) port to supply power to the USB device by detecting voltage sag on a VBUS conductor
Data Source
AI summary
A system for a universal serial bus (USB) device to perform power configuration to operate with a USB host. A connection to the USB host is enabled. Then a high-power configuration is reported to the USB host and successful enumeration by the USB host is monitored for. If such enumeration is not forthcoming within a preset time, the connection to the USB host is disabled and re-enabled, and a low-power configuration is then reported to the USB host. Optionally, the system can further ramp up power usage until a preset high-power configuration is reached, or until there is voltage sag on the VBUS and then either ramp power usage back down or measure the sag and set to a calculated power usage.