Voice Coil Motor Retract Control via Programmable Resistor
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Solution Overview
Problem
Conventional disk drive systems lack flexibility in controlling the voltage across the voice coil motor during actuator retraction, relying on hard-wired external resistors which limits system design and user customization.
Innovation Solution
A voice coil motor control circuit with an on-chip variable resistor that regulates the current to maintain a constant voltage across the voice coil motor, allowing programmable control without external passive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hard-wired external resistors are used for voice coil motor retraction control, then the circuit implementation is simple, but the programmability and precision of voltage control are limited
Solution Approach 1:
The patent combines the resistor function with the integrated circuit by incorporating a programmable resistor array and control logic within the same chip. This merging eliminates the need for external hard-wired resistors while providing programmable resistance values, thus improving adaptability without proportionally increasing overall system complexity.
Solution Approach 2:
The patent introduces a dynamic, programmable resistance control mechanism that allows the resistance value to be changed via software control. This transforms the static hard-wired resistor into a dynamic component whose value can be adjusted programmably, enabling precise voltage control during retraction operations while maintaining circuit integration.
2Measurement precision
If external resistors are used for retraction control, then the implementation is straightforward, but precision in maintaining constant voltage is insufficient
Solution Approach 1:
The patent implements a feedback control mechanism where the voice coil motor current is sensed and used to regulate the programmable resistor value. This closed-loop feedback system maintains precise constant voltage control during retraction by continuously adjusting the resistance based on actual current conditions, achieving high measurement precision through active control.
Solution Approach 2:
The patent utilizes programmable resistance parameter changes to precisely control the voltage across the voice coil motor during retraction. By dynamically adjusting the resistance value through software control based on detected current levels, the system achieves precise voltage regulation without requiring complex external circuitry.
3Adaptability or versatility
If programmable control is implemented, then flexibility and precision are improved, but the system complexity and cost increase
Solution Approach 1:
The patent merges the programmable resistance control functionality directly into the integrated circuit chip, combining what would traditionally be separate external components (resistors, control logic) into a single integrated unit. This integration provides programmable control flexibility while minimizing the increase in overall system complexity and component count.
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 and programmable control of the retract operation, reducing the risk of actuator rebound and ensuring successful parking, while eliminating the need for external resistors, thus reducing system cost and complexity.
Implementation Method 1
a voice coil motor moves an actuator arm on which the read/write heads are mounted
Implementation Method 2
Incorporating an on-chip variable resistor in parallel with the voice coil motor, coupled with a low-side amplifier to regulate current and maintain a constant voltage across the motor
Data Source
AI summary
A disk drive system including retract logic for control of the voice coil motor in a retract operation, in which the voice coil motor positions the read/write head actuator arm in a safe place in a loss-of-power event, is disclosed. The retract logic includes circuitry for controlling the application of power to the voice coil motor from an external capacitor, so that a constant voltage is maintained across the voice coil motor. Current from the capacitor is directed to an internal variable resistor that conducts a selected current, in parallel with the current applied to the voice coil motor. The voltage developed across the variable resistor is applied to one input of a control amplifier, which receives the voltage across the voice coil motor at another input; the control amplifier in turn controls the gate of a low side transistor. The transistor passes current to the extent that the voltage across the voice coil motor corresponds to that developed across the variable resistor.