Write Current Driver Circuit for Inductive Head Ringing Reduction
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Solution Overview
Problem
Existing write current drivers for inductive heads in mass storage drives face issues with ringing in the write current, which affects transition placement and size, leading to reduced storage capacity and reliability, due to the dissipation of write current by matching resistors and premature switching of polarity.
Innovation Solution
A system comprising a writer circuit with a metal-oxide semiconductor transistor boost circuit and a matching circuit that provides a boost current to the inductive write head for a specified time, decoupling the matching resistors during switching to prevent current dissipation and enhance transition speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If matching resistors are used to reduce ringing in write current, then ringing is reduced and transition placement is improved, but write current is dissipated and transition time is extended
Solution Approach 1:
The circuit performs preliminary action by proactively detecting the ringing condition and preemptively adjusting the write current waveform before the transition completes. The controller monitors the write current and modifies subsequent transitions to compensate for ringing effects, preventing placement errors before they occur rather than relying on passive resistors that dissipate current.
Solution Approach 2:
The controller dynamically changes parameters of the write current waveform based on detected ringing conditions. When ringing is detected, the controller adjusts transition parameters such as duration, amplitude, or shape to compensate for the ringing effect, thereby maintaining accurate placement without dissipating current through resistors.
2Speed
If write current polarity is switched before steady state is reached to maintain fast transition, then transition speed is improved and storage capacity increases, but placement accuracy decreases and reliability reduces
Solution Approach 1:
The controller implements feedback by continuously monitoring the write current waveform for ringing conditions. Based on this feedback, the controller dynamically adjusts the timing and parameters of polarity switching, allowing fast transitions when conditions permit while maintaining placement accuracy when ringing is detected. This closed-loop control resolves the contradiction between speed and reliability.
3Reliability
If matching resistors are used to reduce impedance mismatch, then ringing is reduced, but write current is dissipated and storage capacity decreases
Solution Approach 1:
The patent replaces the passive mechanical/electrical approach of using resistors to reduce ringing with an active control system. The controller electronically adjusts write current parameters to compensate for ringing, substituting the resistor-based damping approach with a software/control-based solution that does not dissipate current and preserves storage capacity.
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 solution shortens the magnetic flux transition time, increases storage capacity, and maintains accurate transition placement without dissipating write current, thereby improving the reliability and efficiency of data storage.
Implementation Method 1
A fast magnetic flux transition will require a small amount of space, while a slow magnetic flux transition will require a large amount of space. Since the amount of space on a magnetic platter is fixed, a faster rate of transition in the magnetic flux can mean that more information can be stored in the disk drive.
Implementation Method 2
The magnetic flux on the magnetic platter can be affected by an inductive write head. The transitions in the magnetic flux can be created by switching the polarity of a write current on the inductive write head.
Data Source
AI summary
System and method for write current drivers for inductive heads used in mass storage drives. A preferred embodiment comprises a write current circuit coupled to an inductive write head, a MOS transistor boost circuit and a matching circuit, both coupled to the write current circuit. The write current circuit provides a first current to the inductive write head, while the MOS transistor boost circuit provides a second current for a specified duration to the inductive write head when the MOS transistor boost circuit receives a control signal. The matching circuit selectively decouples a resistive element from the inductive write head when it receives the control signal. The MOS transistor boost circuit can accelerate the transition in a switching of the polarity of the write current and the matching circuit helps to reduce ringing without negatively affecting the speed of the polarity switching by decoupling when the second current is provided.