Variable Duty Cycle Back-EMF Rectification for Head Parking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing systems fail to maintain the power supply voltage for a voice coil motor above a minimum threshold during sudden power loss, leading to inadequate energy transfer from a spindle motor, which can result in incomplete parking of the reading/writing head and potential disk damage.
Innovation Solution
A management apparatus with a first and second switching circuit coupled with the spindle motor and voice coil motor, respectively, and a controller that adjusts duty cycles to convert back electromotive force voltage into a power supply voltage, ensuring the voltage remains above the threshold by optimizing the duty cycle ratio based on resistances and inductances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If synchronous rectification technology is used to decrease dissipation of body diodes, then the voltage for driving the VCM is increased, but the duration the voltage remains above the minimum threshold is still insufficient to complete the parking operation
Solution Approach 1:
The patent applies dynamics by making the duty cycle variable rather than fixed. The controller dynamically adjusts the duty cycle of the switching circuit based on real-time conditions to optimize energy transfer. This allows the system to adapt the rectification efficiency and voltage output duration to match the varying energy requirements of the VCM during the parking operation, thereby extending the duration the voltage remains above the minimum threshold.
Solution Approach 2:
The patent changes the parameter of duty cycle from a fixed value to a variable parameter that can be adjusted by the controller. By modifying the duty cycle parameter, the system optimizes the energy transfer from the spindle motor to the VCM, ensuring that the voltage remains above the minimum threshold for the complete duration of the parking operation. This parameter adjustment directly addresses the insufficient duration problem.
2Use of energy by moving object
If the spindle motor converts kinetic energy to electric energy during sudden power loss, then energy is provided to the VCM, but the energy dissipated by mechanical frictions and MOS transistor resistances reduces the available energy for head parking
Solution Approach 1:
The patent converts the harmful effect of energy dissipation into a beneficial control parameter. By introducing a variable duty cycle, the system optimizes the energy transfer efficiency to compensate for the inevitable losses due to friction and resistance. The duty cycle adjustment ensures that the maximum possible energy is transferred to the VCM, turning the energy loss situation into a controllable parameter that can be optimized for complete head parking.
Solution Approach 2:
The patent implements feedback control where the controller monitors the energy transfer process and adjusts the duty cycle accordingly. This feedback mechanism ensures that the energy dissipated by mechanical frictions and MOS transistor resistances is compensated by optimizing the switching parameters, thereby maximizing the net energy available for head parking operations during sudden power loss.
3Reliability
If the reading/writing head is not parked in the specific area during sudden power loss, then the head may fall on the disk and damage it, but the existing control systems cannot ensure complete parking under power loss conditions
Solution Approach 1:
The patent prepares the system in advance for power loss conditions by implementing a variable duty cycle control mechanism that is specifically designed to extend the voltage duration. This preliminary preparation ensures that when sudden power loss occurs, the system can immediately utilize the optimized energy transfer to complete the head parking operation within the available energy window, thereby preventing head-disk contact and damage.
Solution Approach 2:
The patent uses feedback control to monitor the parking operation progress and adjusts the duty cycle in real-time to ensure completion. This feedback mechanism guarantees that the head parking operation is completed reliably even under sudden power loss conditions, preventing the harmful outcome of head falling on the disk by continuously optimizing the energy transfer until parking is achieved.
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
The apparatus effectively prolongs the duration the power supply voltage remains above the minimum threshold, enhancing the energy transfer and ensuring the voice coil motor receives sufficient power for head parking, thereby preventing disk damage during power loss.
Implementation Method 1
The energy provided by the spindle motor is due to the back-electromotive force (BEMF) which, once rectified, provides energy to the VCM motor which acts as an electric load
Implementation Method 2
synchronous rectification technology is currently used. This technology provides switching, under the conditions of turn-on and turn-off, the MOS transistors of the control device in an appropriate sequence; thereby the rectification process is provided with less energy dissipation
Data Source
AI summary
A management apparatus is described of a rotating motor and a load during power loss; the apparatus comprises a first switching circuit coupled with the rotating motor and a controller of said first switching circuit. The controller is configured to drive the first switching circuit so as to convert a back-electromotive force voltage developed in the rotating motor into a power supply voltage for the load. The first switching circuit is driven in accordance with a first duty cycle. The apparatus comprises a second switching circuit coupled with the load and driven in accordance with a second duty cycle. The controller is configured to vary said first and said second duty cycles to keep the power supply voltage for the load above or equal to a threshold voltage.