Chirped Degaussing Waveform for Magnetic Storage Write Head
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Solution Overview
Problem
Magnetic storage devices, such as hard disk drives, face issues with erase-after-write (EAW) failure modes due to residual magnetization from write heads, which can degrade prewritten data, and conventional degaussing current waveforms are not always effective in achieving a net-zero magnetization state.
Innovation Solution
A degaussing circuit generates a current waveform that oscillates between opposite polarities with both changing amplitude and frequency over time, specifically using a down-chirped waveform formed by circuitry comprising a voltage-controlled oscillator and voltage ramp generators, to effectively degauss write heads and prevent EAW.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional degaussing current waveform with fixed frequency is used, then the write head magnetization can be switched between opposite polarities, but the write head may not achieve a net-zero magnetization state and EAW incidents persist
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed-frequency degaussing waveform to a chirped waveform where the frequency dynamically changes over time. The frequency starts high and decreases linearly throughout the degaussing pulse duration, allowing the system to adapt to different magnetization states and achieve more effective degaussing. This dynamic adjustment resolves the contradiction by improving reliability through better magnetization cancellation while maintaining reasonable circuit complexity through systematic frequency modulation.
Solution Approach 2:
The patent changes the frequency parameter of the degaussing current waveform dynamically during the pulse. By implementing a linear frequency decrease from an initial frequency to a final frequency over the pulse duration, the system optimizes its ability to cancel residual magnetization. This parameter change approach allows the degaussing waveform to effectively target different magnetization states, improving the reliability of achieving net-zero magnetization without requiring overly complex circuitry.
2Reliability
If the write current is switched off immediately after writing, then the write head relaxes back to net-zero magnetization state, but residual magnetization erases or degrades prewritten data
Solution Approach 1:
The patent applies preliminary action by implementing a degaussing current waveform that is applied immediately after the write current is switched off, before the write head can accidentally erase prewritten data. The chirped waveform is designed to start as soon as the write pulse ends, proactively canceling residual magnetization before it can cause harm. This timing-critical preliminary action resolves the contradiction by protecting data integrity while minimizing the time loss through efficient, immediate degaussing.
Solution Approach 2:
The patent converts the harmful residual magnetization that would normally cause EAW into a beneficial effect by using it as the target for the degaussing waveform. The chirped waveform is specifically designed to counteract the residual magnetization state, turning the problematic remaining magnetization into an opportunity to demonstrate the effectiveness of the degaussing technique. This approach protects data integrity by actively neutralizing the harmful residual fields rather than simply waiting for natural relaxation.
3Reliability
If a degaussing current waveform with decreasing amplitude is applied, then the write head magnetization oscillations are gradually reduced, but the degaussing process takes longer than necessary
Solution Approach 1:
The patent applies dynamics by implementing a chirped waveform where the frequency changes over time rather than using a fixed frequency. The frequency starts high and linearly decreases throughout the pulse duration, which allows for more efficient magnetization cancellation. This dynamic frequency adjustment enables the system to achieve net-zero magnetization faster while maintaining reliability, resolving the contradiction between achieving complete degaussing and minimizing the duration of the degaussing process.
Solution Approach 2:
The patent changes the frequency parameter dynamically during the degaussing pulse, implementing a linear frequency decrease from an initial frequency to a final frequency. This parameter change allows the waveform to adapt to the changing magnetization state of the write head, achieving more effective and faster degaussing. By optimizing the frequency trajectory, the system reduces the overall duration needed to achieve net-zero magnetization while maintaining high reliability in the degaussing process.
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 results in shorter degaussing times and is more effective in degaussing write heads that were previously difficult to degauss, reducing data degradation and maintaining data integrity.
Implementation Method 1
a voltage-controlled oscillator and voltage ramp generators
Implementation Method 2
The inductive write head 100 includes two ferrite cores 120. One of the ferrite cores 120 is partially surrounded by a coil 130 to produce an electromagnet. Applying current to the coil 130 generates a strong magnetic field
Implementation Method 3
Writing logical data on the magnetic disk 110 involves reversing the polarity of the current through the coil 130... to create a pattern of two oppositely-oriented remanent states on the magnetic disk 110
Implementation Method 4
The degaussing current is characterized by a current waveform that oscillates between opposite polarities with both an amplitude and a frequency that change over time
Data Source
AI summary
A circuit for use with a memory storage device including a magnetic storage medium and a write head operative to subject the magnetic storage medium to a magnetic field in response to an application of current to the write head, includes a write circuit operative to generate a write current supplied to the write head. The write current is characterized by a current waveform that reverses polarity in accordance with data to be stored on the magnetic medium. The circuit for use with the memory storage device further includes a degauss circuit operative to generate a degaussing current supplied to the write head. The degaussing current is characterized by a current waveform that oscillates between opposite polarities with an amplitude and a frequency that change over time.