Independently Driven Write Coils for HDD Magnetic Field Tuning
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Solution Overview
Problem
Conventional hard disc drives (HDDs) lack the capability to individually tune the write current for each write coil, limiting the fine-tuning of magnetic flux density and affecting data writing precision.
Innovation Solution
The implementation of separate preamplifiers to independently drive at least two write coils within a writer assembly, allowing for independent control of the current applied to each coil to fine-tune the cumulative magnetic write field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If write coils are connected in series within each writer assembly, then the device complexity is reduced, but the capability to tune the write current individually to each write coil is lost
Solution Approach 1:
The patent divides the writer assembly into multiple independently controllable write coils (first write coil, second write coil, etc.), each connected to its own preamplifier. This segmentation allows individual current tuning for each coil while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The patent implements dynamic control of write current by allowing independent adjustment of current magnitude and phase for each write coil through separate preamplifiers. This enables real-time optimization of magnetic flux density distribution across different track regions.
2Measurement precision
If separate preamplifiers are used to independently drive write coils, then the write current tuning precision is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by providing each write coil with its own dedicated preamplifier, enabling localized current optimization for specific track regions. This allows precise control of magnetic field characteristics at different radial positions without affecting other coils.
Solution Approach 2:
The patent utilizes parameter changes by independently adjusting current magnitude, phase, and timing for each write coil through separate preamplifiers. This enables optimization of write performance across varying track densities and radial positions by modifying electrical parameters without changing the physical coil structure.
3Manufacturing precision
If write coils are driven independently, then the magnetic flux density fine-tuning capability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent employs universal preamplifier designs that can drive multiple write coils with identical or similar characteristics. This multi-functionality allows the same preamplifier circuitry to be reused across different coil configurations, simplifying manufacturing while maintaining independent control capability.
Solution Approach 2:
The patent implements preliminary calibration and characterization of write coils during manufacturing, storing optimization parameters in lookup tables. This preliminary action enables precise magnetic flux density control during operation without requiring complex real-time adjustments, simplifying both manufacturing and operation.
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 precise control over the magnetic write field, improving data writing precision by allowing adjustment of magnetic field angle, magnitude, gradient, overshoot amplitude, and phase, leading to enhanced HDD performance.
Implementation Method 1
the write coils within each writer assembly function to transform the electrical current into a magnetic field and direct the resulting magnetic flux density through a write pole to write data to the platters
Data Source
AI summary
A writer assembly having two separately driven write coils allows a combined write field generated by the writer assembly to be fine turned and optimized for a particular application. Two preamplifiers may be incorporated into a printed circuit board in order to separately drive the write coils. In other implementations, there may be more than two write coils and corresponding preamplifiers.