Magnetic Disk Device Power Supply Control for Data Protection
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Solution Overview
Problem
Conventional magnetic disk devices face issues with power loss protection (PLP) when external power sources are cut off, leading to unstable power supply and potential data loss due to reliance on counter electromotive force, which can cause voltage drops and increase failure risks.
Innovation Solution
The magnetic disk device employs a dual power source system where one power source continues to supply power to unnecessary circuits until they are fully powered down, then switches to counter electromotive force for PLP operations, ensuring stable power and preventing voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system switches to PLP function using counter electromotive force when external power is cut off, then data protection is achieved, but voltage drops occur and reliability decreases
Solution Approach 1:
The system performs preliminary power down processing of unnecessary circuits before switching to PLP mode. The control device identifies and powers down circuits not needed for PLP operations (such as servo control, signal processing) before the external power is completely cut off, ensuring that only essential PLP circuits remain active and can operate stably on counter electromotive force
Solution Approach 2:
The system extracts and separates essential PLP circuits from non-essential circuits. By identifying and isolating only the circuits necessary for PLP operations (power management, data transfer to/from cache) from the full system, the patent ensures that PLP circuits receive stable power while non-essential circuits are powered down, preventing voltage drops on PLP circuits
2Reliability
If all circuits are powered down immediately when external power is cut off, then power loss protection is activated, but essential circuits may not have stable power for data protection
Solution Approach 1:
The system performs preliminary power down processing of unnecessary circuits before the external power is completely cut off. The control device proactively identifies and powers down non-essential circuits while external power is still available, creating a buffer period where PLP essential circuits can be prepared and stabilized before the transition to counter electromotive force power
Solution Approach 2:
The system provides beforehand cushioning by maintaining power to essential PLP circuits through the other stable power source during the transition period. This cushioning power supply ensures that PLP circuits have sufficient time to complete their operations without experiencing voltage drops or power instability
3Adaptability or versatility
If counter electromotive force is used for PLP power source, then data protection function is enabled, but voltage instability increases failure risks
Solution Approach 1:
The system segments the power supply into two independent stable power sources (e.g., 5V and 12V rails) and uses one power source to power down processing while the other provides stable power to PLP circuits. This segmentation ensures that PLP circuits have a dedicated stable power source independent of the external power being cut off
Solution Approach 2:
The system uses an intermediary power source (the other stable power source) to bridge the transition period. Instead of directly switching PLP circuits to counter electromotive force power, the intermediary power source maintains stable voltage during the transition, allowing PLP operations to complete reliably before the intermediary power is also cut off
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
This approach enhances the reliability of the magnetic disk device by stabilizing power supply during power outages, preventing PLP power source drops, and reducing the risk of data loss, while also simplifying the processing procedure and shortening startup times.
Implementation Method 1
The PLP function is a function to write data that has been stored in a DRAM to a FROM by using a counter electromotive force (PLP power source) generated by a disk motor for driving a disk, when the disk is stopped.
Data Source
AI summary
A magnetic disk device according to an embodiment operates by receiving power supply from a first power source and a second power source. The first power source supplies power with a first voltage. The second power source supplies power with a second voltage higher than the first voltage. The magnetic disk device includes a first control device and a second control device. The first control device detects whether or not power cutoff has occurred in either one of the first power source and the second power source. When the first control device detects the power cutoff having occurred in either one of the first/second power sources, the second control device causes the other one of the first/second power sources to supply power to an unnecessary circuit until power down processing is completed in the unnecessary circuit. The unnecessary circuit is a circuit whose power supply is to be stopped.