USB to SATA Bridge Power Limiting via Command Delay
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Solution Overview
Problem
Peripheral subsystems connected to a computer via USB, such as disk drives, face limitations in power supply due to USB's maximum current constraints, necessitating additional power supply circuitry that increases cost, complexity, and weight.
Innovation Solution
Implementing a USB to SATA bridge with software-controlled power limiting, which estimates power consumption based on command data and parameters, delaying acknowledgments to manage power usage within USB's maximum allowable limits, thereby reducing peak power draw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external power supply circuitry is added to meet USB power requirements, then power supply reliability is improved, but device complexity and cost increase
Solution Approach 1:
The USB host device automatically determines the power requirements of the peripheral subsystem and configures power delivery accordingly, eliminating the need for separate external power supply circuitry in the peripheral device. The host controller service performs power requirement determination and configuration automatically.
Solution Approach 2:
The peripheral subsystem communicates its power requirements to the USB host through the USB interface, enabling the host to adjust power delivery dynamically. This feedback mechanism allows the host to allocate power resources efficiently without requiring complex external power circuits in the peripheral device.
2Reliability
If external power supply circuitry is added to meet USB power requirements, then power supply reliability is improved, but weight increases
Solution Approach 1:
The USB host device provides power determination and configuration services automatically, eliminating the need for heavy external power supply circuitry in the peripheral subsystem. The host controller handles all power management functions centrally.
3Power
If maximum current is drawn from USB connection, then power availability is improved, but USB specification compliance deteriorates
Solution Approach 1:
The USB host dynamically adjusts power delivery based on the peripheral subsystem's actual requirements and USB specification limits. The host controller service continuously monitors and configures power allocation to match demand while staying within specification constraints.
Solution Approach 2:
The system changes power delivery parameters dynamically based on determined requirements, adjusting current allocation to match actual needs rather than continuously drawing maximum current. This ensures compliance while providing sufficient power.
4Reliability
If power consumption is reduced to meet USB limits, then USB specification compliance is improved, but performance deteriorates
Solution Approach 1:
The USB host dynamically configures power delivery to match the peripheral subsystem's actual operational requirements, providing maximum power when needed and reducing it during idle periods. This dynamic adjustment maintains performance while ensuring specification compliance.
Solution Approach 2:
The system adjusts power consumption parameters based on determined requirements, changing power allocation dynamically rather than using fixed limits. This allows the system to achieve USB compliance while maintaining optimal performance when required.
Data Source
AI summary
A Universal Serial Bus (USB) to Serial ATA (SATA) bridge device and method for operating same in a USB connected mass storage subsystem supports software management of power consumption. The USB to SATA bridge estimates power consumption based on known power consumption characteristics of SATA disk drives when performing commands involved in accessing SATA drive, or takes measurements of power consumption during execution of commands to determine when responses to a USB host device are to be delayed. By selectively delaying responses to the USB host device issuing the commands, the USB to SATA bridge manages the rate at which the host issues commands to the USB mass storage subsystem and is thereby able to automatically limit power consumption of the USB mass storage subsystem to that that available over the USB link.