# US 7,610,164 B1 · System and method of constant power biasing circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,610,164 B1 - Document ID: US7610164B1 - Status: Granted - Kind: B1 - Application number: 11/875,506 - Filed: 2007-10-19 - Granted: 2009-10-27 - Earliest claimed: 2006-10-31 - Assignees: Marvell International Ltd. - Inventors: Kan Li - Web page: https://patentgrep.com/patent/US7610164B1 ## CPC - G11B 5/6064: {using air pressure} - G11B 5/6005: {Specially adapted for spacing from a rotating disc using a fluid cushion} - G11B 5/607: {using thermal means} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A system is provided to adjust a separation distance between a read/write sensing head and a data storage medium surface in a hard disk. The thermal expansion of the sensing head based on heat generated by power dissipated through the sensing head is precisely controlled. When electrical resistance is not accurately known, a calibration is performed in which a specific input value is matched to a predetermined reference electrical power. The matching is done through a reference voltage source, that remains at a fixed value, and a calibration factor is successively adjusted through a feedback loop until an optimum value of the calibration factor is obtained. At the conclusion of the calibration process, the feedback loop is disabled and the optimally attained value of the calibration constant is frozen. The electronic circuit to implement the proposed system is based on cost effective CMOS technology. ## Claims ### Claim 1 A method for controlling a thermal expansion of a power dissipating device based on heat generated by power dissipation, comprising: during a calibration step: receiving a first data input value representing a known amount of a reference electrical power to be dissipated by the power dissipating device prior to device operation; executing an algorithm to convert the first data input value into a component of the reference electrical power in order to establish a mathematical relationship between the first data input value and an amount of electrical power dissipated by the power dissipating device; adjusting the amount of electrical power dissipated by the power dissipating device to determine a calibration factor that modifies the component of the reference electrical power to establish an operating calibration factor for the power dissipating device; during a power control step: receiving a second data input value that represents a determined electrical power to be dissipated by the power dissipating device in operation; executing an algorithm to convert the second data input value into a component of the determined electrical power to be dissipated by the power dissipating device in operation; adjusting the component of the determined electrical power by the established operating calibration factor; and setting the operating electrical power of the device according to the adjusted component of the determined electrical power. ### Claim 2 (depends on 1) The method of claim 1, wherein the calibration step is performed only once during a power-up cycle. ### Claim 3 (depends on 1) The method of claim 1, wherein the setting is performed a plurality of times for different values of the second data input value. ### Claim 4 (depends on 1) The method of claim 1, the step of adjusting during the calibration step comprising: obtaining an initial value of the calibration factor; modifying the component of the reference electrical power by the initial value of the calibration factor; applying the modified component of the reference electrical power to the power dissipating device; measuring an amount of electrical power dissipated by the power dissipating device; comparing the amount of electrical power dissipated by the power dissipating device with the reference electrical power; and adjusting the calibration factor to establish the operating calibration factor for the power dissipating device based on the comparison. ### Claim 5 (depends on 4) The method of claim 4, wherein the adjusting is undertaken when the comparison fails to satisfy a pre-defined criterion. ### Claim 6 (depends on 5) The method of claim 5, wherein the adjusting occurs successively through a feedback loop until the comparison satisfies the pre-defined criterion. ### Claim 7 (depends on 6) The method of claim 6, wherein the adjusting further comprises: evaluating whether the comparison fails to satisfy the pre-defined criterion; determining a sign of a change in the calibration factor to reduce a difference in the comparison; and adjusting the initial value of the calibration factor by applying a predetermined incremental value with the determined sign to establish an interim value of the calibration factor, wherein the component of the electrical power is modified based on the interim value of the calibration factor. ### Claim 8 (depends on 7) The method of claim 7, further comprising repeating the modifying, measuring, comparing and adjusting until the comparing satisfies the pre-defined criterion, a last value interim value of the calibration factor being set as the established value of the calibration factor for the power dissipating device in operation. ### Claim 9 (depends on 8) The method of claim 8, wherein, when the established value of the calibration factor is set, the feedback loop is disabled completing the calibrating. ### Claim 10 (depends on 4) The method of claim 4, wherein the measuring the amount of electrical power dissipated by the power dissipating device comprises sensing a component of the electrical power being dissipated by the power dissipating device, and the comparing compares the sensed component of electrical power being dissipated by the power dissipating device with a reference value for that component of power. ### Claim 11 (depends on 1) The method of claim 1, further comprising storing the established operating calibration factor in a storage device, wherein, on a next power-up cycle, the stored established operating calibration factor is obtained as an initial value of the calibration factor. ### Claim 12 (depends on 1) The method of claim 1, wherein the power dissipated by the power dissipating device in operation is set to control a thermal expansion of the power dissipating device based on heat generated by the power dissipation. ### Claim 13 (depends on 1) The method of claim 1, wherein the power dissipating device is a read/write sensing head and the power dissipated by the power dissipating device in operation is set to control a separation distance between the read/write sensing head and a data storage medium with which the read/write sensing head cooperates. ### Claim 14 (depends on 1) The method of claim 1, wherein the method is executed by a fly high controller in a read/write system. ### Claim 15 A system for controlling a thermal expansion of a power dissipating device based on heat generated by the power dissipation, comprising: the power dissipating device; a data inputting device for inputting a data input value representing a known amount of a reference electrical power to be dissipated by the power dissipating device; a calibration device that determines a calibration factor to adjust a component of power; a data converter that converts the data input value into the component of power and that modifies the component of power by the calibration factor before the component of power is applied to the power dissipating device; a sensor unit that senses a component of power dissipated by the power dissipating device; a power measurement unit that measure the power dissipated by the power dissipating device according to the sensed component; a comparison unit that compares the measured power dissipated by the power dissipating device with a reference power value to determine whether a difference satisfies a pre-defined criterion; and a parameter adjustment unit that adjusts the calibration factor based on the comparison to further modify the component of power until the comparison of the measured power dissipated by the power dissipating device and the reference power value satisfies the pre-defined criterion to establish a value of the calibration factor for operation of the power dissipating device. ### Claim 16 (depends on 15) The system of claim 15, wherein a Complementary Metal Oxide Semiconductor (CMOS) circuit implements at least one of the data converter, the sensor unit, the power measurement unit, comparison unit or the parameter adjustment unit. ### Claim 17 (depends on 15) The system of claim 15, wherein the data converter converts the data input value into a component of power, the component of power being at least one of an electrical current through the power dissipating device or an electrical voltage across the power dissipating device, by executing a power converting algorithm. ### Claim 18 (depends on 17) The system of claim 17, wherein, when the component of power is an electrical current through the power dissipating device, the data converter further comprises a semiconductor current mirror. ### Claim 19 (depends on 17) The system of claim 17, wherein, when the component of power is an electrical voltage across the power dissipating device, the data converter unit further comprises a voltage gain amplifier. ### Claim 20 (depends on 15) The system of claim 15, wherein the parameter adjustment unit adjusts the calibration factor by determining a sign of a change in the calibration factor to reduce a difference in the comparison between the measured power dissipated by the power dissipating device and the reference power value, and applying a predetermined incremental value with the determined sign to a current value of the calibration factor to establish a next value of the calibration factor to be applied by the data converter. ### Claim 21 (depends on 15) The system of claim 15, wherein the comparison unit compares the sensed component of power with a reference value for that sensed component. ### Claim 22 (depends on 15) The system of claim 15, wherein the error signal generating unit computes an error between the sensed component of power and the corresponding reference value. ### Claim 23 (depends on 15) The system of claim 15, wherein the power dissipating device in operation is subject to thermal expansion based on heat generated by the power dissipation, and the established value of the calibration factor for operation of the power dissipating device is applied to a component of power based on a data input value to control the thermal expansion of the power dissipating device. ### Claim 24 (depends on 15) The system of claim 15, wherein the power dissipating device is a read/write sensing head and the power dissipated by the power dissipating device in operation is set to control a separation distance between the read/write sensing head and a data storage medium with which the read/write sensing head cooperates. ### Claim 25 A fly high controller in a read/write system including a circuit component that is configured to adjust electrical power dissipated by a power dissipating device of the fly high controller, the circuit component comprising: a data inputting device for inputting a data input value representing a known amount of a reference electrical power to be dissipated by the power dissipating device; a calibration device that determines a calibration factor to adjust a component of power; a data converter that converts the data input value into the component of power and that modifies the component of power by the calibration factor before the component of power is applied to the power dissipating device; a sensor unit that senses a component of power dissipated by the power dissipating device; a power measurement unit that measure the power dissipated by the power dissipating device according to the sensed component; a comparison unit that compares the measured power dissipated by the power dissipating device with a reference power value to determine whether a difference satisfies a pre-defined criterion; and a parameter adjustment unit that adjusts the calibration factor based on the comparison to further modify the component of power until the comparison of the measured power dissipated by the power dissipating device and the reference power value satisfies the pre-defined criterion to establish a value of the calibration factor for operation of the power dissipating device.