WO2004061830A2

WO2004061830A2 - Improved optical storage device

Info

Publication number: WO2004061830A2
Application number: PCT/GB2003/005712
Authority: WO
Inventors: David Lockwood; Christopher Perrott
Original assignee: Infinite Data Storage Ltd
Current assignee: Infinite Data Storage Ltd
Priority date: 2003-01-04
Filing date: 2003-12-24
Publication date: 2004-07-22
Anticipated expiration: 2005-07-04
Also published as: GB2420906B; GB2420906A; GB2412229B; AU2003298450A8; GB2412229A8; GB0601777D0; WO2004061830A3; GB0513095D0; GB2412229A; GB0300173D0; AU2003298450A1; GB2420906A8

Abstract

An optical data storage device and method for operating such a device. The device has means for drawing current from an internal power source and an external power source and is also provided with switching means that switches the device between a first mode, where the internal power source is electrically connected to power driving means, and a second mode where an external power source is electrically connected to power driving means. The device has power driving means which receives power at a lower voltage rating from the internal power source than when attached to the external power source. This feature improves the electrical efficiency of the device.

Description

Improved Optical Storage Device

This invention relates to an optical data storage device that has an improved efficiency power supply. In particular it relates to a portable optical data storage device that exhibits improved power efficiency consumption.

Reference in the following description to an optical data storage device includes reference to Compact Disc Recordable devices (CD-R) , Compact Disc Rewritable devices (CD-RW) , Digital Versatile Disc Recordable devices (DVD-R and DVR+R) and Digital Versatile Disc Rewritable devices (DVD-R, DVD+RW and DVD-RAM) , amongst others.

In recent times, recordable optical data storage devices have been developed as independent external units for use with both desktop and laptop Personal Computers. These external units provide an alternative to the traditional internal unit designs normally incorporated within Personal Computers. Further development has seen the production of recordable optical data storage ' devices that operate under battery power and/or under power provided from an external source e.g. a mains supply. However, such units have only a limited battery life that significantly restricts their operating lifetime.

External optical data storage devices described in the Prior Art all rely on components traditionally used within internal data storage device solutions. The main reason for this is due to the economies of scale relating to the production of these components. However, the power consumption of the components used within these internal storage devices is typically not optimised, as the power supply is derived directly from the computer's primary power source.

A typical Prior Art optical data storage device 1 is shown in Figure 1. The optical data storage device 1 comprises a power supply 2, a 5V voltage regulator 3, a Computer Processing Unit (CPU) 4, a Digital Signal Processor (DSP) 5 and a power driver IC 6. In this example the outputs of the power driver IC 6 are shown for focus 7, tracking 8, spindle 9 and sled control 10 as is known to those skilled in the art. Alternative outputs are also employed in the art, for example for tray ejection (not shown) .

As can be seen the operation of the optical data storage device 1 relies on a voltage regulator 3. Voltage regulation ensures that any battery supply provides a steady voltage supply rail as is required due to varying CMOS (Complementary Metal-Oxide Semiconductor) geometry. Typical voltage supply rail values are 5v, 3v3 and 2v5. The power driver IC 6 used to drive the spindle motor is supplied from the 5v rail in order to achieve maximum spindle speed. However, this is not the most efficient system, as it requires the employment of further step-up/down regulators in order to cope with the range of possible battery voltages. The efficiency level of such 5V rail systems is typically around 75%. In contrast, the efficiency level of systems that employ 3v3 step-up/down regulators is typically around 90%. Therefore, when the optical data storage device is being operated under battery power, it is desirable to use a 3v3 supply for the power driver IC 6 so as to optimise efficiency and thus extend the battery life. However, the use of such a 3v3 supply has the effect of limiting the top speed at which the spindle motor can operate.

Figure 2 presents a schematic representation of the effect of a focus servo 11 during a seek operation, as typically employed by the optical data storage device 1. The focus servo 11 is designed to maintain a lens 12 at a constant distance from a disc surface 13 such that the disc surface 13 remains within the focal plane of the lens 12 thus maintaining an incident light beam 14 as a focused spot 15 on the disc surface 13.

During a seek operation such a process results in a large peak in the power consumption of the optical data storage device 1 at the start and end of the operation. This is a result of the fact that as the lens 12 begins to move from land to groove to land, crossing tracks on the disc surface 13, the focus servo 11 sees a large step error on the transitions. The focus servo 11 then reacts by refocusing the incident light beam 14 onto the new area of the disc surface 13, be it an area of land or groove. The high gain of the focus servo 11, and the relatively large step inputs in focus error due to the land to groove crossings, causes an associated focus actuator (not shown) to be driven with a high current in order to reposition the lens 12. However, once the sled 10 has accelerated to a velocity sufficient that the track crossing frequency is outside the bandwidth of the focus servo 11 (the bandwidth typically being approximately 2-4 kHz, ) the focus servo 11 no longer responds significantly to the track crossings. At this stage the current drawn by the focus servo 11 is much smaller than during the acceleration phase.

During the end of the deceleration phase, the track crossing frequency again reduces to a frequency inside the bandwidth of the focus servo 11. Again the current drawn by the focus servo 11 increases to a high level as the focus servo 11 attempts to refocus the lens between the areas of land and groove.

For internal optical data storage devices 1, these periods of higher current demand do not pose a significant problem, as the current supply is not drawn from a battery source. However, for portable battery operated systems, these increased current drawing periods act to significantly reduce the efficiency of the system and hence the lifetime of the battery.

It is an object of the present invention to provide an optical storage device that exhibits improved power efficiency consumption thus resulting in an increase in the lifetime of any battery employed to power the device. According to a first aspect of the present invention there is provided an optical data storage device for drawing current from an internal power source and an external power source comprising a switching means, voltage regulation means and a power driving means, wherein the switching means switches the device between a first mode, where the internal power source is electrically connected to the power driving means, and a second mode where the external power source is electrically connected to the power driving means such that when the device operates in the first mode the power driving means receives power at a lower voltage rating than when operating in the second mode, thus improving the electrical efficiency of the device when operating within the first mode.

Preferably the optical data storage device further comprises a spindle motor wherein the power driving means supplies a driving voltage to the spindle motor.

Preferably the switching means comprises a detection means such that the power source can be automatically detected and the switching means switched as appropriate.

Most preferably the internal power source is electrically connected to the power driving means by voltage regulation means.

Preferably when operating in the first mode the internal power supply provides an internal voltage output to the voltage regulation means.

Preferably, the voltage regulation means comprises a first voltage regulator. Optionally the internal voltage output comprises a voltage of around 3V.

Preferably when operating in the second mode the switching means provides a first external voltage output to the power driving means and a second external voltage output to the voltage regulation means.^'

Optionally the first and second external voltage outputs comprise voltages of around 5V.

Preferably, the voltage regulation means further comprises a second voltage regulator.

Most preferably the internal power source comprises a battery.

Preferably the first and second voltage regulators comprise a plurality of regulator voltage outputs suitable for use by other electrical components of the device.

According to a second aspect of the present invention there is provided a method of increasing the efficiency of an optical data storage device suitable for drawing current from an internal power source and an external power source comprising the steps of: Detecting the source of power; and Setting the device to operate on a first or second mode of operation dependent on whether the source of power is the internal or external power source.

Preferably the mode of operation of the device is set by a switch. Most preferably the switch automatically detects the source of power and sets the mode of operation as appropriate.

Optionally, setting the mode of operation further comprises loading a set of servo parameters appropriate to the mode of operation using a computer memory means.

Preferably in the first mode of operation the switch provides an internal voltage output to a voltage regulation means.

Preferably the voltage regulation means provides a first regulated voltage for use by electrical components of the device.

Preferably, in the second mode of operation the switch provides a first external voltage output to a power driving means and a second external voltage output to a second voltage regulator.

Preferably the power driving means operates a spindle motor of the device.

Preferably the second voltage regulator provides a second regulated voltage for use by electrical components of the device.

According to a third aspect of the present invention there is provided a method of increasing the efficiency of an optical data storage device comprising the steps of: Detecting a period of acceleration of a seek operation of the device; and Reducing the response time of a focus servo system from a normal operational value during the period of acceleration.

Optionally wherein positive or negative acceleration is detectable.

Preferably reducing the response time of a focus servo system comprises altering the operating bandwidth of the focus servo. Alternatively, reducing the response time of a focus servo system comprises switching a hardware circuit into focus servo system.

According to a fourth aspect of the present invention there is provided a method of increasing the efficiency of an optical data storage device in accordance with the first aspect of the present invention comprising the steps of: Setting the mode of operation of the device in accordance with the second aspect of the present invention; and Reducing the response time of a focus servo system of the device in accordance with the third aspect of the present invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 presents a schematic representation of an optical data storage device as described in the Prior Art; Figure 2 presents a schematic representation of the operation of a focus servo of the portable optical data storage device of Figure 1; Figure 3 presents a block diagram of components of a portable optical data storage device, operating from an internal battery power supply, in accordance with an aspect of the present invention; and Figure 4 presents a block diagram of components of the portable optical data storage device of Figure 3, operating from an external power supply.

Figures 3 and 4 present a block diagrams of a portable optical data storage device 16 in accordance with aspects of the present invention. The portable optical data storage device 16 can be seen to comprise a switch 17, a voltage regulator 18 or 19, a power driver IC 20 and a plurality of voltage input means 21 for use by other components of the device 16. The portable optical data storage device 16 further comprises a CPU, a DSP, a spindle etc. (not shown) as is known to those skilled in the art. Power can be supplied to the portable optical data storage device 16 from either a battery power supply 22 or from an external power supply 23, as shown.

The switch 17 permits the optical data storage device 16 to change between a battery operating mode 24, as shown in Figure 3, or an external power operating mode 25 as shown in Figure 4. When operating in the battery operating mode 24 the switch 17 is employed to provide a 3v3 supply to a voltage regulator 18 that then provides a 3v3 regulated supply to the power driver IC 20 and the voltage input means 21. The greater efficiency of the 3v3 voltage regulators provides for greater efficiency of the portable optical data storage device 16 and hence extends the lifetime of the battery power supply 22.

When operating in the external power operating mode 25 the switch 17 is employed to supply a voltage of 5V as required by the power driver IC 20 so as to obtain a maximum spindle speed. In the external power operating mode 25 this power supply 23 is connected directly to the power driver IC without passing through the voltage regulator 19. On passing through the voltage regulator 19 the external power supply provides a 5V supply to the voltage input means 21

Employing such a configuration acts to increase the efficiency, as well as reducing the production cost, of the portable optical data storage device 16 as the voltage regulator 19 used for the 5v supply of the voltage input means 21 can be selected with a lower overall current limit.

It should be noted that when the portable optical data storage device 16 is operating on the battery operating mode it exhibits a spindle speed that is slower than when the device 16 is drawing a current from the external power supply 23.

A further improvement to the efficiency of the portable optical data storage device 16 can be achieved by employing the Computer Processing Unit to detect which mode the portable optical data storage device 16 is operating on. The CPU then loads the relevant set of servo parameters into the Digital Signal Processor, thus reducing further the current consumption on the battery whilst optimising the performance for the given supply. An example of such an operation would be the creation of two sets of seek coefficients, one for use within the battery operating mode 24 the other for use within the external power operating mode 25.

The portable optical storage device 16 is also capable of reducing the current demand and the peak currents required by the Prior Art optical data storage devices, as described above. The portable optical data device 16 performs this function, by dynamically reducing the response time of the focus servo system during the lower speed acceleration portion of the seek operation. The focus servo system is then retained in this mode until it approaches the target track at the end of the seek operation. At this time the normal focus servo operation is resumed.

Effectively, during the acceleration and deceleration phases of the seek operation, the bandwidth of the focus servo is altered. This can be achieved either directly by the Digital Signal Processor, or by switching in a hardware circuit, with the effective bandwidth reduction again controlled by either the DSP or CPU at both the start and end of the seek operation.

The portable optical data storage device described above has a number of inherent advantages over those described in the Prior Art that act to improve the efficiency of this device and so allows the lifetime of any associated battery to be extended. The incorporation of the switch allows the portable optical data storage device to move between two operating modes thus improving the power efficiency of the device when operating from a battery power supply. In addition when the portable optical data storage device operates from an external power supply the power and cost efficiency of the associated 5v voltage regulator can be improved by directly powering the spindle power driver IC without the required current initially passing through the 5v voltage regulator.

An additional advantage of an aspect of the present invention results from the employment of different servo parameters for both of the operating modes. This acts to reduce the current consumption on any associated battery whilst optimising the performance for any power supply.

A yet further advantage of an aspect of the present invention results from the ability to vary the response time of the focus servo system. During periods of acceleration and deceleration of a seek operation the response time of the focus servo system is reduced so reducing the current demands placed on the power supply.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention herein intended.

Claims

1. An optical data storage device for drawing current from an internal power source and an external power source comprising a switching means, voltage regulation means and a power driving means, wherein the switching means switches the device between a first mode, where the internal power source is electrically connected to the power driving means, and a second mode where the external power source is electrically connected to the power driving means such that when the device operates in the first mode the power driving means receives power at a lower voltage rating than when operating in the second mode to improve the electrical efficiency of the device when operating within the first mode.

2. An optical data storage device as claimed in claim 1 wherein the optical data storage device further comprises a spindle motor wherein the power driving means supplies a driving voltage to the spindle motor.

3. An optical data storage device as claimed in claim 1 or claim 2 wherein, the switching means comprises a detection means such that the power source can be automatically detected and the switching means switched as appropriate.

4. An optical data storage device as claimed in any of claims 1 to 3 wherein, the internal power source is electrically connected to the power driving means by the voltage regulation means.

5. An optical data storage device as claimed in any preceding claim wherein, when operating in the first mode the internal power supply provides an internal voltage output to the voltage regulation means .

6. An optical data storage device as claimed in any preceding claim wherein the voltage regulation means comprises a first voltage regulator.

7. An optical data storage device as claimed in claim 5 or claim 6 wherein, the internal voltage output comprises a voltage of around 3v3.

8. An optical data storage device as claimed in any preceding claim wherein, when operating in the second mode the switching means provides a first external voltage output to the power driving means and a second external voltage output to the voltage regulation means .

9. An optical data storage device as claimed in claim 8 wherein, the first and second external voltage outputs comprise voltages of around 5N.

10. An optical data storage device as claimed in any preceding claim wherein, the voltage regulation means further comprises a second voltage regulator.

11. An optical data storage device as claimed in any preceding claim wherein, the internal power source comprises a battery.

12. An apparatus as claimed in claim 6 and claim 10 wherein, the first and second voltage regulators comprise a plurality of regulator voltage outputs suitable for use by other electrical components of the device.

13. A method of increasing the efficiency of an optical data storage device suitable for drawing current from an internal power source and an external power source comprising the steps of: Detecting the source of power; and Setting the device to operate on a first or second mode of operation dependent on whether the source of power is the internal or external power source.

14. A method as claimed in Claim 13 wherein, the mode of operation is set by a switch.

15. A method as claimed in claim 14 wherein the switch automatically detects the source of power and sets the mode of operation as appropriate.

16. A method as claimed in any of claims 13 to 15 wherein, setting the mode of operation further comprises loading a set of servo parameters appropriate to the mode of operation using a computer memory means .

17. A method as claimed in any of claims 13 to 16 wherein, the first mode of operation the switch provides an internal voltage output to a voltage regulation means .

18. A method as claimed in claim 17 wherein the voltage regulation means provides a first regulated voltage for use by electrical components of the device.

19. A method as claimed in any of claims 13 to 18 wherein, in the second mode of operation the switch provides a first external voltage output to a power driving means and a second external voltage output to a second voltage regulator.

20. A method as claimed in claim 19 wherein, the power driving means operates a spindle motor of the device.

21. A method as claimed in claim 19 or claim 20 wherein, the second voltage regulator provides a second regulated voltage for use by electrical components of the device.

22. A method of increasing the ef iciency of an optical data storage device comprising the steps of: Detecting a period of acceleration of a seek operation of the device; and Reducing the response time of a focus servo system from a normal operational value during the period of acceleration.

23. A method as claimed in claim 22 wherein, positive or negative acceleration is detectable.

24. A method as claimed in claim 22 and 23 wherein, reducing the response time of a focus servo system comprises altering the operating bandwidth of the focus servo.

25. A method as claimed in any of claims 22 and 23 wherein, reducing the response time of a focus servo system comprises switching a hardware circuit into focus servo system.