Laser Controller for Heat-Assisted Magnetic Recording
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Solution Overview
Problem
In heat-assist recording schemes for magnetic disk devices, existing technologies face challenges in maintaining data reliability and extending the lifespan of light sources and near-field transducers due to constant power usage, which leads to degradation and increased power consumption, while intermittent power control can compromise data reliability and signal quality.
Innovation Solution
A magnetic disk device that switches between two control modes based on the pulse width of data to be written, with the first control maintaining constant light source output and the second control intermittently changing the output between two values, thereby optimizing power usage and reducing degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant power is supplied to the light source, then data reliability is maintained, but power consumption increases and component lifespan decreases
Solution Approach 1:
The patent applies periodic action by switching the light source between ON and OFF states based on the pulse width of incoming data signals. When the pulse width exceeds a threshold, the light source is turned ON to ensure adequate heating for reliable data recording; when the pulse width is below the threshold, the light source is turned OFF to reduce power consumption. This periodic control strategy resolves the contradiction by dynamically adjusting power supply based on actual recording needs.
2Reliability
If constant power is supplied to the light source, then data reliability is maintained, but component lifespan decreases
Solution Approach 1:
The patent implements periodic action by controlling the light source to operate only when necessary (when pulse width exceeds threshold), rather than continuously. This reduces thermal accumulation and mechanical stress on the light source components, thereby extending its operational lifespan while maintaining data reliability during active recording periods.
3Use of energy by moving object
If intermittent power control is used, then power consumption is reduced, but data reliability may be compromised
Solution Approach 1:
The patent employs feedback by continuously monitoring the pulse width of incoming data signals and using this information to control the light source state. The controller compares the pulse width against a predetermined threshold and adjusts the light source accordingly, ensuring that power is supplied only when the signal characteristics indicate reliable recording conditions, thus maintaining data reliability while reducing overall power consumption.
4Use of energy by moving object
If intermittent power control is used, then power consumption is reduced, but signal quality may deteriorate
Solution Approach 1:
The patent uses feedback control by monitoring pulse width parameters and adjusting light source operation accordingly. This ensures that signal quality is maintained during recording periods when adequate pulse width is detected, while power is saved during periods when the signal characteristics indicate that full power is not required, thus balancing signal quality with power consumption.
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 improves data reliability, extends the lifespan of light sources and near-field transducers, and reduces power consumption while maintaining signal quality across the entire frequency band.
Implementation Method 1
laser light generated by a light source (laser diode) is converted by a near field transducer into near-field light
Implementation Method 2
converted by a near field transducer into near-field light to be irradiated onto part of the surface of a magnetic disk
Implementation Method 3
by applying a magnetic field to the temperature-raised part of the magnetic disk by a magnetic field generating element, data is recorded magnetically
Data Source
AI summary
According to one embodiment, there is provided a magnetic disk device including a light source, a light irradiation element, and a controller. The light irradiation element is configured to receive light from the light source to irradiate light onto a magnetic disk. The controller is configured to switch between a first control and a second control according to a pulse width of data to be written onto the magnetic disk. The first control keeps an output of the light source at a first value. The second control makes the output of the light source change periodically between the first value and a second value lower than the first value.