USB Port Controller Power Mode Switching for Low Energy
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Solution Overview
Problem
USB port controllers in battery-powered devices face high power consumption due to the need to maintain serial interface circuitry in a powered condition, leading to inefficiencies in low-power operating modes, especially in systems with multiple idle ports where unnecessary interruptions occur.
Innovation Solution
The USB port controller switches between normal and low-power modes based on commands from a port manager circuit, automatically returning to low-power mode unless a communication transaction is detected, thereby reducing power consumption and minimizing interruptions from messaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the port controller maintains serial interface circuitry in a powered condition to react quickly to read or write transactions, then the response speed is improved, but the power consumption increases
Solution Approach 1:
The patent implements dynamic power mode switching where the port controller transitions between normal power mode and low-power idle mode based on operational state. The controller can quickly exit idle mode upon detecting I2C bus activity (rising or falling edges on SDA or SCL lines), ensuring rapid response while minimizing power consumption during idle periods.
Solution Approach 2:
The port controller periodically monitors the I2C bus for activity while in idle mode by detecting signal edges on the SDA or SCL lines. This periodic monitoring allows the controller to remain in low-power state until actual communication is needed, at which point it transitions to normal operation mode.
2Use of energy by moving object
If the port manager sends commands to place idle port controllers back into idle mode after communications transactions, then the power consumption is reduced, but the system complexity and interruption overhead increase
Solution Approach 1:
The port controller autonomously manages its own power state transitions by monitoring I2C bus activity independently. When the controller detects bus activity, it automatically exits idle mode and begins processing transactions without requiring port manager intervention. After completing transactions, it automatically returns to idle mode, eliminating the need for port manager commands and reducing system complexity.
Solution Approach 2:
The port controller continuously monitors the I2C bus for activity signals and uses this feedback to dynamically adjust its power state. The detection of rising or falling edges on SDA or SCL lines provides feedback that triggers automatic mode transitions, creating a self-regulating system that reduces power consumption without requiring external control commands.
3Reliability
If all idle port controllers respond to communications transactions even when not addressed, then the system reliability is improved, but the power consumption and interruption overhead increase significantly
Solution Approach 1:
The port controller performs preliminary monitoring of the I2C bus while in idle mode to detect activity before full communication engagement. By detecting signal edges in advance, the controller can prepare for upcoming transactions and only fully activate when necessary, avoiding unnecessary responses to transactions not intended for it while maintaining system reliability.
Data Source
AI summary
Described examples include USB port controllers with a control circuit configured to switch from a normal first power mode to a second power mode for reduced power consumption in response a command from a port manager circuit, and to switch from the second power mode to the first power mode in response to detected activity on a communications connection, or a detected connection of a USB device to a USB port connector. After switching back to the first power mode in response to detected communications activity, the control circuit automatically switches operation of the USB port controller back to the second power mode unless a communications transaction addressed to the USB port controller is received within a non-zero certain time after switching from the second power mode to the first power mode.