Electronic system with current conservation mechanism and method of operation thereof

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/878,963 filed Sep. 17, 2013, and the subject matter thereof is incorporated herein by reference thereto.

TECHNICAL FIELD

An embodiment relates generally to an electronic system, and more particularly to a system for reducing peak current load of the electronic system.

BACKGROUND

Modern consumer and industrial electronic devices require storage of information, such as digital photographs, videos, electronic mail, calendar, or contacts. These devices can be electronic systems, such as notebook computers, desktop computers, servers, televisions, and digital video recorders, and are providing increasing levels of functionality to support modern life. Research and development in the existing technologies can take a myriad of different directions.

As the volume of data stored in these electronic devices increases, hard disk drives (HDD) must have more data tracks and higher data frequencies must be accommodated. The increase in data capacity, more tracks, and faster interface protocols have driven a constant increase in peak current load. In order to meet the demand of extended battery life in notebook computers, extraordinary measures must be taken to limit the current drawn by the hard disk drive.

The demands of high capacity storage in battery operated environments can impose conflicting requirements on the electronic devices. The demand for higher performance, extended battery life, lower cost, and shrinking size can spawn complex product decisions that attempt to provide a balanced compromise. When the parameters of size, interface type, and capacity are fixed at a design point, there are few compromises that can reduce current demand and maintain device performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C shows an operational diagram of an electronic system according to an embodiment.

FIG. 2 is a line graph of the power supply current of a prior art disk drive in a head repositioning operation.

FIG. 3 is a line graph of the power supply current of the electronic system according to one embodiment in a head repositioning operation.

FIG. 4 is a plot of the primary current loads of the electronic system according to an embodiment.

FIG. 5 is a flow chart of a method of operating an embodiment of the electronic system in a current harvesting mode of operation.

DETAILED DESCRIPTION

A need still remains for an electronic system with current conservation mechanism for improving utilization of supply current while maintaining data performance. The improved utilization of supply current can be provided by a reduction in peak current amplitude without compromising system performance. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is increasingly critical that answers be found to these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.

Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.

Certain embodiments have other steps or elements in addition to or in place of those mentioned above. The steps or elements will become apparent to those skilled in the art from a reading of the following detailed description when taken with reference to the accompanying drawings.

The following embodiments are described in sufficient detail to enable those skilled in the art to make and use the embodiments. It is to be understood that other embodiments would be evident based on the present disclosure, and that system, process, or mechanical changes may be made without departing from the scope of an embodiment.

In the following description, numerous specific details are given to provide a thorough understanding of the embodiments. However, it will be apparent that the embodiments can be practiced without these specific details. In order to avoid obscuring an embodiment, some well-known circuits, system configurations, and process steps are not disclosed in detail.

The drawings showing embodiments of the system are semi-diagrammatic, and not to scale and, particularly, some of the dimensions are for the clarity of presentation and are shown exaggerated in the drawing figures. Similarly, although the views in the drawings for ease of description generally show similar orientations, this depiction in the figures is arbitrary for the most part. Generally, an embodiment can be operated in any orientation. The embodiments have been numbered first embodiment, second embodiment, etc. as a matter of descriptive convenience and are not intended to have any other significance or provide limitations for an embodiment. For reference purposes the data surface of the media is defined as being “horizontal” though it is understood that the electronic system can operate at any angle. Position of the head over the media is referred to as a “vertical” displacement or flying height.

Referring now to FIGS. 1A, 1B, and 1C, therein are shown an operational diagram of an electronic system 100 according to an embodiment. The electronic system 100 can represent an apparatus for one of the embodiments. An embodiment depicted in FIGS. 1A-1C are shown as a hard disk drive, as an example, although it is understood that the electronic system 100 as the embodiment can be a tape drive, a solid-state hybrid disk drive, or other magnetic media-based storage device. Further for example, the electronic system 100 can represent a desktop computer, a notebook computer, a server, a tablet, a television, a household appliance, or other electronic systems utilizing magnetic media storage.

The electronic system 100 including a head 102 actuated over a media 104. The head 102 can be mounted to a flex arm 118. The head 102 (FIG. 1B) can optionally include a laser 106 for heating the media 104 during part of a write process (e.g., the head is part of an Energy-Assisted Magnetic Recording (EAMR) drive). The flying height 108 can be adjusted (e.g., by use of a heater element in the head not shown in FIG. 1B) while writing data to the media 104 or as an error recovery process during reading from the media 104. Also in an embodiment of FIG. 1B, the head 102 comprises a write element 110 (e.g., an inductive coil) and a read element 112 (e.g., a magnetoresistive read element).

The media 104 is a structure for storing information. For example, the media 104 can be made of an aluminum alloy, ceramic/glass, or a similar non-magnetic material. The top and bottom surfaces of the media 104 can be covered with magnetic material deposited on one or both sides of the media 104 to form a coating layer capable of magnetization.

Any suitable version of the laser 106 can be employed in the embodiments, such as a laser diode. In addition, embodiments can employ any suitable techniques for focusing the laser on the media 104, such as a suitable waveguide, magnifying lens, or other suitable optics. The laser 106 is increased to a write power in order to heat the disk, thereby decreasing the coercivity of the media 104 so that the data is written more reliably.

A media motor 114 can rotate the media 104, about a center of the media 104, at constant or varying media speed 107. For illustrative purposes, the media motor 114 is described as a motor for a rotation, although it is understood that the media motor 114 can be other media transport motors for a tape drive, as an example.

The media motor 114 can be controlled by a motor driver current 116, such as a three phase driver current, sourced from a motor driver 120. The motor driver 120 can sequence the motor driver current 116 based on a commutation logic 121. The commutation logic 121 can monitor an unused phase of the motor driver current 116 in order to source current to the media motor 114 or harvest current from the rotating mass of the media motor 114, while coasting with one or more of the media 104 attached.

The commutation logic 121 can control the timing of the application of the motor driver current 116 while controlling the media speed 107 of the media 104. The switching of the commutation logic 121 can place a cyclical demand for power from the power supply current 124 sourced from the host power supply (not shown). A head actuation motor 130 can be used to position the head 102 over the media 104. The head actuation motor 130 generally requires a significant portion of the power supply current 124 when changing the position of the head 102.

As examples, the head actuation motor 130 can be a voice coil motor assembly, a stepper motor assembly, or a combination thereof. The head actuation motor 130 can generate a torque for positioning the head 102 relative to the media 104 by applying a current demand from the power supply current 124.

A tapered end of the flex arm 118 can include the head 102. The flex arm 118 can be mounted to the head actuation motor 130, which is pivoted around a bearing assembly 126 by the torque generated by the head actuation motor 130. The head 102 can include a single instance of the write element 110 and a single instance of the read element 112 that is narrower than the write element 110. The head 102 can fly over the media 104 at a dynamically adjustable span of the flying height 108, which represents a vertical displacement between the head 102 and the media 104. The head 102 can be positioned by the flex arm 118 and the head actuation motor 130 and can have the flying height 108 adjusted by control circuitry 138.

The head 102 can be positioned over the media 104 along an arc shaped path between an inner diameter of the media 104 and outer diameter of the media 104. For illustrative purposes, the head actuation motor 130 is configured for rotary movement of the head 102. The head actuation motor 130 can be configured to have a different movement. For example, the head actuation motor 130 could be configured to have a linear movement resulting in the head 102 traveling along a radius of the media 104 in a first direction 134 or opposite the first direction 134.

The head 102 can be positioned over the media 104 to create magnetic transitions or detect magnetic transitions from the coating layer that can be used to representing written data or read data, respectively. The position of the head 102 and the media speed 107 of the media 104 can be controlled by the control circuitry 138. Examples of the control circuitry 138 can include a processor, an application specific integrated circuit (ASIC) an embedded processor, a microprocessor, a hardware control logic, a hardware finite state machine (FSM), a digital signal processor (DSP), digital circuitry, analog circuitry, optical circuitry, or a combination thereof. The control circuitry 138 can also include memory devices, such as a volatile memory, a nonvolatile memory, or a combination thereof. For example, the nonvolatile storage can be nonvolatile random access memory (NVRAM) or Flash memory and a volatile storage can be static random access memory (SRAM) or dynamic random access memory (DRAM).

The control circuitry 138 can be configured to control the media motor 114 for adjusting the media speed 107 of the media 104. A plurality of servo sectors 122 dispersed around the media 104 to form radial spokes. The control circuitry 138 can monitor the frequency of occurrence of the servo sectors 122, in order to determine the rotation rate of the media 104, to calculate the media speed 107. The combination of the demand for current from the media motor 114 and the head actuation motor 130 can cause a peak current that exceeds the specification for the power supply current 124.

The control circuitry 138 can be configured to cause the head 102 to move relative to the media 104, or vice versa. The control circuitry 138 can also be configured to manage the instantaneous demand for power from the system power supply 124. In an embodiment of the invention, the control circuitry 138 can switch off the current to the motor driver 120. The mass of the media 104 spinning will allow the media motor 114 to coast substantially at or near the media speed 107 for a period of time. The coasting of the media motor 114 is due to the inertia of the media 104 spinning freely when the media motor 114 is not driven with full power by the motor controller 120. The control circuitry 138 can take advantage of the coasting of the media motor 114 to reduce a peak demand on the power supply current 124 by providing the media motor 114 less than full power, for example half power, one quarter power, or no power. Some embodiments can harvest current from the coasting of the media motor 114 in order to further reduce the peak demand on the power supply current 124.

In one embodiment, the electronic system 100 further comprises control circuitry 138 configured to execute the flow diagram of FIG. 1C of a method 500 of operation of an electronic system 100 in an embodiment. The method 500 includes: controlling a media motor having a media attached in a block 140; positioning a head over a media in a block 142; adjusting a media speed for the media in a block 144; and disengaging a motor driver for coasting the media, and activating a head actuation motor, with the media coasting, for accelerating the head in a first direction including repositioning the head over the media in a block 146. Additional details related to the flow diagram will be provided below in conjunction with FIGS. 2-5.

Referring now to FIG. 2, therein is shown a line graph 201 of the power supply current of a prior art disk drive in a head repositioning operation. The line graph of the power supply current depicts a horizontal time scale 202 measured in milliseconds and a vertical amperage scale 204 measured in amperes. The composite of the current represented by the vertical amperage scale 204 can have a specification current limit 206. The specification current limit 206 can represent the maximum amount of current that has been allocated by the system power supply 124 of FIG. 1A for operation of the prior art disk drive (not shown). By way of an example the specification current limit 206 can be 1.8 amperes.

A spindle at speed current 208 can represent the motor drive current 116 of FIG. 1A from the media motor 114 of FIG. 1A. By way of an example, the average of the spindle at speed current 208 can be 0.5 amperes. A voice coil motor (VCM) seek current 210 can present a rapid increase in current demand, above the spindle at speed current 208, that can reach or exceed the specification current limit 206. This condition can lead to long term system reliability problems and performance degradation.

By way of an example, the profile of the VCM seek current 210 is shown having a peak demand of 1.3 amperes above the spindle at speed current 210. It is understood that different amounts of current demand can be required for the VCM seek current 210. An acceleration curve represented by the time between X and X+2 on the horizontal time scale 202. The VCM seek current in this time segment can represent accelerating the head 102 of FIG. 1A for performing a seek to a different one of the data tracks on the media 104.

Also by way of an example, the VCM seek current 210 between the times X+5 and X+7 can represent the deceleration of the head 102 for stopping over a target data track on the media 104. It is understood that the deceleration of the head can consume a different amount of the current than the acceleration portion of the seek. During these movements of the head 102, the spindle at speed current will remain relatively constant with, for example, the average at 0.5 amperes. It is understood that the shape and peak of the acceleration curve can be different based on the length of the seek and the speed of the movement. In all cases the current demand of the VCM seek current 210 and the spindle at speed current 208 are additive and can exceed the specification current limit 206.

Referring now to FIG. 3, therein is shown a line graph 301 of the power supply current 124 of FIG. 1A of the electronic system 100, according to one embodiment, in a repositioning operation of the head 102 of FIG. 1A. The line graph 301 depicts a horizontal time scale 302 measured in milliseconds and a vertical amperage scale 304 measured in amperes. The composite of the current represented by the vertical amperage scale 304 can have a specification current limit 306. The specification current limit 306 can represent the maximum amount of current that has been allocated by the system power supply 124 of FIG. 1A for operation of the electronic system 100 of FIG. 1A. By way of an example the specification current limit 306 can be 1.8 amperes.

A media at speed current 308 can represent the motor drive current 116 of FIG. 1A from the media motor 114 of FIG. 1A when the media 104 of FIG. 1A is at a constant velocity. By way of an example, the average of the motor drive current 116 can be 0.5 amperes. A head actuation motor (HAM) seek current 310 can present a rapid increase in current demand, above the media at speed current 308, that can reach an operational maximum current 312 that remains well below the specification current limit 306. The media speed current 308 differs from the spindle at speed current 208 of FIG. 2 in that the media speed current 308 can be substantially reduced or switched off during repositioning activities of the head 102 in the electronic system 100, while the spindle at speed current 208, of the prior art system, maintains a constant average current through all operations. Likewise, the HAM seek current 310 differs, from the VCM seek current 210, by being coordinated by the control logic 138 of FIG. 1A to only be asserted when the media at speed current 308 has been reduced or switched off.

By way of an example, the profile of the HAM seek current 310 is shown having a peak demand of 1.3 amperes. It is understood that different amounts of current demand can be required for the HAM seek current 310. An acceleration curve can be represented by the time between X and X+2 on the horizontal time scale 302. The HAM seek current 310 in this time segment can represent accelerating the head 102 of FIG. 1A for performing a seek to a different one of the data tracks on the media 104. The acceleration curve represented by the time between X and X+2 is an example and the actual time for the acceleration curve can be different.

The operational maximum current 312 can be achieved by reducing or eliminating the media at speed current 308 during the application of the HAM seek current 310. The media 104 can maintain sufficient inertia to stay within the operational speed range required by the control circuitry 138 of FIG. 1A to read position information from the servo sectors 122 of FIG. 1A. By reducing or eliminating the media at speed current 308 during the time between X and X+2 on the horizontal time scale 302, the full current demand of the HAM seek current 310 sets the operational maximum current 312, which provides additional operating margin.

It is understood that the HAM seek current 310 can be reduced to substantially zero when the head 102 is at a constant velocity and the HAM seek current 310 represents the acceleration and deceleration of the head 102. The media at speed current 308, representing the motor drive current 116 for the media motor 114, can be reduced between the X and X+2, and the X+5 and X+7 on the horizontal time scale 302. It is understood that the actual seek time can be different than shown and the X+2 and X+7 are examples only.

The coordination of the switching of the media at speed current 308 and the HAM seek current 310 can be performed by the control circuitry 138 of FIG. 1A. The control circuitry 138 can utilize the commutation logic 121 in the motor driver 120 to monitor the media speed 107 of FIG. 1A during the coasting of the media 104. The duration of the acceleration and deceleration of the head actuation motor 130 of FIG. 1A can be sufficiently short that the inertia of the media 104 can maintain the media speed 107 with no additional application of the motor drive current 116. If a significantly long acceleration of the head 102 is required, a reduced amount of the motor drive current 116 can be applied to the media motor 114 in order to keep the media speed 107 within operational limits for writing or reading the media 104. The determination of the media speed 107 and the application of a reduced amount or none of the motor drive current 116 is coordinated by the control circuitry 138.

The control circuitry 138 manage the media speed 107, through the control of the motor drive current 116, in order to provide the correct rotation rate of the media 104 for read or write operations that can follow the repositioning operation of the head 102. By way of an example, the media 104 will be maintained at a nominal value of the media speed 107 beyond the X+7 time mark, which indicates the end of the repositioning operation of the head 102.

It has been discovered that some embodiments can significantly reduce the operational maximum current 312 by coordinating the reduction of the media at speed current 308 and the HAM seek current 310. The reduction of the operational maximum current 312 can provide significant margin between the operational maximum current 312 and the specification current limit 306. The reduced current demand presented by the electronic system 100 can allow extended operational battery life in portable systems, reduced thermal and electrical requirements for fixed systems, and increased reliability due to a stable reduced demand on the power supply current 124 of FIG. 1A.

Referring now to FIG. 4, therein is shown a plot 401 of the primary current loads of the electronic system 100 according to an embodiment. The plot 401 of the primary current loads of the electronic system depicts a HAM seek current 310 and the motor driver current 116. The HAM seek current 310 displays a characteristic current profile for the acceleration and deceleration of the head actuation motor 130 of FIG. 1A.

In a track following region 402, the head 102 of FIG. 1A can be in a track following mode and requires no acceleration. The control circuitry 138 of FIG. 1A can receive a command to relocate the head 102 to another location on the media 104 of FIG. 1A. The control circuitry 138 can coordinate the reduction of the motor drive current 116 in a head acceleration region 404, while asserting a rapid increase in the head actuation motor 130. The increase in the amplitude of the HAM seek current 310 is counteracted by the reduction in the motor drive current 116, resulting in the host power supply 124 providing the operational maximum current 312 that is much less that the specification current limit 306.

An embodiment can provide a motor pitch region 406, such as a region of increased speed of the media motor 114. The motor pitch region 406 can provide an increased speed of the media motor 114 in preparation for reducing the motor drive current 116 during a current harvesting region 410 or a harvesting recovery region 412. The motor pitch region 406 can increase the speed of the media motor 114 by a fixed percentage that allows the control circuitry 138 to maintain the reading of the servo sectors 122 of FIG. 1A throughout the coasting of the media motor 114.

The current harvesting region 410 can provide a current source for driving the head actuation motor 130 in an initial braking of the head actuation motor 130. The control circuitry 138 can utilize the current harvesting region 410 to coast the media motor 114 while applying the braking current to the head actuation motor 130. The control circuitry 138 can utilize the inertia of the media motor 114 to provide a current source for driving the head actuation motor 130 through the initial portion of the deceleration process in order to further reduce the operational maximum current 312 and reduce the overall current demand of the electronic system 100 of FIG. 1A. The inertia of the media motor 114 can provide a free-wheel current 116 back through the motor driver 120 of FIG. 1A, which can be harvested by the control circuitry 138 for driving the head actuation motor 130 in order to reduce the operational maximum current 312. The control circuitry 138 can utilize the commutation logic 121 of FIG. 1A for timing the harvesting of the free-wheel current 116 and monitoring the speed of the media motor 114 in the current harvesting region 410.

The control circuitry 138 can utilize the motor pitch region 406 to increase the inertia of the media 104 by increasing the media speed 107 in anticipation of the deceleration of the media motor 114 caused by the harvesting of the free-wheel current 116. Immediately after the harvesting recovery region 412, the media speed 107 can be within the operational limits of the electronic system 100 for performing writes or reads of the media 104. During the head acceleration region 404, the motor pitch region 406, the current harvesting region 410, and the harvesting recovery region 412, the control circuitry 138 can monitor the position of the head 102 and the approximate rotation rate of the media 104 through the monitoring of the servo sectors 122.

The control circuitry 138 can initiate the harvesting recovery region 412 as a function of the media speed 107, the distance to the destination track, a current threshold indicator, or a combination thereof. The control circuitry 138 can reengage the motor drive current 116 within the harvesting recovery region 412 in order to restore the nominal value of the media speed 107. Beyond the harvesting recovery region 412, the media speed 107 can be at the nominal value for immediate initiation of a write or read operation of the media 104. It is understood that additional rotational latency can be required in order to reach the starting location of the write or read operation on the destination track of the media 104. The rotational latency is not extended by the harvesting of the free-wheel current 116 by the control circuitry 138.

It is understood that the current harvesting region 410 is shown only on the deceleration portion of the HAM seek current 310 as an example and the current harvesting region 410 can be utilized during other operations as well. It is further understood that the control circuitry 138 can coordinate the timing of the reduction of the motor drive current 116 in the head acceleration region 404, increase the media speed 107 of FIG. 1A in the motor pitch region 406, and coordinate the harvesting of the free-wheel current 116 in the current harvesting region 410.

It has been discovered that the electronic system 100 can provide a dynamic power management process for reducing the operational maximum current 312 to be substantially less that the specification current limit 306. The reduction in the demand on the current from the host power supply 124 of FIG. 1A can translate to less expensive system power supplies, reduced heat generation, and a balance of current demand and seek performance. By reducing the motor drive current 116 prior to activating the HAM seek current 310, the control circuitry 138 can maintain the performance of the electronic system 100 while providing the operational maximum current substantially below the specification current limit 306.

It is understood that the media speed 107 can be at a nominal value after the harvesting recovery region 412. The nominal value of the media speed 107 can be sufficient for immediately reading the media 104 but insufficient for writing the media 104 or the nominal value of the media speed 107 can be sufficient for immediately reading or writing the media 104.

Referring now to FIG. 5, therein is shown a flow chart of a method 550 of operating an embodiment of the electronic system 100 in a current harvesting mode of operation. The flow chart of the method 550 depicts: controlling a media coupled to a media motor in a block 552; positioning a head over the media in a block 554; adjusting a media speed for the media in a block 556; disengaging a motor driver for coasting the media in a block 558; harvesting a free-wheel current from the media motor in a block 560; and activating a head actuation motor, using the free-wheel current, for accelerating the head in a first direction including repositioning the head over the media in a block 562.

The resulting method, process, apparatus, device, product, and/or system is straightforward, cost-effective, uncomplicated, highly versatile, accurate, sensitive, and effective, and can be implemented by adapting known components for ready, efficient, and economical manufacturing, application, and utilization. Another important aspect of an embodiment is that it valuably supports and services the historical trend of reducing costs, simplifying systems, and increasing performance.

These and other valuable aspects of an embodiment consequently further the state of the technology to at least the next level.

While the embodiments have been described in conjunction with a specific detailed description, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the aforegoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the included claims. All matters set forth herein or shown in the accompanying drawings are to be interpreted in an illustrative and non-limiting sense.