# US 10,374,528 B2 · Efficient energy recovery in disk drive during power loss > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,528 B2 - Document ID: US10374528B2 - Status: Granted - Kind: B2 - Application number: 15/714,151 - Filed: 2017-09-25 - Published: 2018-03-15 - Granted: 2019-08-06 - Earliest claimed: 2013-09-27 - Assignees: Seagate Technology LLC - Applicants: Seagate Technology LLC - Inventors: Binh Kim Lieu; Mark Lowell Elliott; Raye A. Sosseh - Web page: https://patentgrep.com/patent/US10374528B2 ## CPC - H02P 3/18: for stopping or slowing an AC motor - G06F 1/263: {Arrangements for using multiple switchable power supplies, e.g. battery and AC (G06F1/30 takes precedence)} - H02J 9/06: with automatic change-over {, e.g. UPS systems} - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY ## Abstract A back electromotive force of a rotating motor is converted into a voltage for a load by driving, in accordance with a duty cycle, at least one switching circuit that couples the back electromotive force to a load through a rectifying circuit. An error signal is generated that is a difference between the load voltage and a reference voltage. The duty cycle is controlled as a function of the error signal to cause the load voltage to approach the reference voltage. ## Claims ### Claim 1 A method, comprising: detecting power loss to a rotating motor of a storage device; in response to detecting the power loss, performing a shut-down procedure comprising: coupling a back electromotive force of the rotating motor to a load using a switching circuit, the load comprising components of the storage device; driving the switching circuit according to a duty cycle generating an error signal that is a difference between the back electromotive force and a reference voltage; and controlling the duty cycle as a function of the error signal to cause the back electromotive force to approach the reference voltage. ### Claim 2 (depends on 1) The method claim 1, wherein: back electromotive force comprises three back electromotive forces that are 120 degrees out of phase with each other. ### Claim 3 (depends on 1) The method of claim 1, wherein controlling the duty cycle as a function of the error signal comprises controlling the duty cycle in proportion with the error signal. ### Claim 4 (depends on 1) The method of claim 1, wherein controlling the duty cycle as a function of the error signal comprises controlling the duty cycle in proportion with the error signal and using a damping constant multiplied by a derivative of the error signal. ### Claim 5 (depends on 1) The method of claim 1, wherein controlling the duty cycle as a function of the error signal comprises controlling the duty cycle in proportion with the error signal and using an integral gain parameter multiplied an integral of the error signal over time. ### Claim 6 (depends on 1) The method of claim 1, wherein controlling the duty cycle as a function of the error signal comprises controlling the duty cycle in proportion with the error signal, using a damping constant multiplied by a derivative of the error signal, and using an integral gain parameter multiplied an integral of the error signal over time. ### Claim 7 (depends on 1) The method of claim 1, wherein the rotating motor is a spindle motor of a hard disk drive. ### Claim 8 (depends on 1) The method of claim 1, wherein: the components include at least a data channel controller and non-volatile cache; and performing the shut-down procedure comprises storing data from the data controller into the non-volatile cache. ### Claim 9 (depends on 1) The method of claim 1, wherein the components include at least a memory controller and non-volatile cache; and performing the shut-down procedure comprises storing information that describes a state of a memory system controlled by the memory controller into the non-volatile cache. ### Claim 10 (depends on 1) The method of claim 1, wherein: the components include at least a voice coil motor coupled to an armature that bears a read/write head of the hard disk drive; and performing the shut-down procedure comprises actuating the voice coil motor to move the read/write head to a safety area. ### Claim 11 A power back-up system for a storage device, comprising: circuitry configured to implement a shut-down process in response to loss of power, the shut-down process including one or more shut-down tasks; at least one rectifier; at least one switching circuit, the at least one switching circuit configured to couple a back electromotive force from a rotating motor to at least one component of the storage device through the at least one rectifier; a pulse width modulator configured to drive the switching circuit according to a duty cycle; and a control system comprising: error circuitry configured to determine a difference between the back electromotive force and a reference voltage; and a feedback controller configured to regulate the duty cycle as a function of the error signal to cause the back electromotive force to approach the reference voltage. ### Claim 12 (depends on 11) The system of claim 11, further comprising a capacitor configured to reduce ripple of the load voltage. ### Claim 13 (depends on 11) The system of claim 11, wherein the feedback controller provides a feedback control signal to the pulse width modulator in response to the error signal. ### Claim 14 (depends on 13) The system of claim 13, wherein the control system includes a synchronizer configured to multiply the control signal by each of three sine waves that correspond to the motor speed and phase for three phases of motor rotation. ### Claim 15 (depends on 11) The system of claim 11, wherein the regulated back electromotive force is coupled to deliver power to a voice coil motor to move an armature carrying a read/write head to a safe location relative to a magnetic disk. ### Claim 16 (depends on 11) The system of claim 11, wherein the feedback controller is configured to implement one or more of proportional feedback control, proportional integral feedback control, proportional integral derivative feedback control, linear, quadratic regulator control, and adaptive control. ### Claim 17 A memory system, comprising: a disk drive comprising a motor; a non-volatile cache; a power back-up system, comprising: circuitry configured to implement a shut-down process in response to loss of power, the shut-down process including one or more shut-down tasks; at least one rectifier; at least one switching circuit, the at least one switching circuit configured to couple a back electromotive force from a rotating motor to at least one component of the memory system through the at least one rectifier; a pulse width modulator configured to drive the switching circuit according to a duty cycle; and a control system comprising: error circuitry configured to determine a difference between the back electromotive force and a reference voltage; and a feedback controller configured to regulate the duty cycle as a function of the error signal to cause the back electromotive force to approach the reference voltage. ### Claim 18 (depends on 17) The memory system of claim 17, wherein the shut-down tasks comprise moving an armature carrying a read/write head to a predetermined location in response to detection of external power loss. ### Claim 19 (depends on 17) The memory system of claim 17, wherein the shut-down tasks comprise storing data to the non-volatile cache. ### Claim 20 (depends on 17) The memory system of claim 17, wherein the shut-down tasks comprise storing values of state parameters of the memory system to the nonvolatile cache.