Magnetic disk device

Abstract

The invention provides a magnetic disk device with high write performance. A controller of a magnetic disk device calculates a first amount of power, which is the amount of power required for an unloading operation of a magnetic head, on the basis of the state of a VCM when the VCM is operating. The controller calculates a first setting value based on the first power amount. In response to an amount of second data, which is first data that is stored in the volatile memory and has not been written to the disk, exceeding a first set value, the controller executes a first write operation that writes a part or all of the second data to the disk. When the supply of power from the outside is interrupted, the controller executes an unloading operation and a transfer of the second data to the non-volatile memory using power generated on the basis of the back electromotive force of the second motor.

Description

[0001] This application claims the priority of Japanese Patent Application No. 2023-158709 (filing date: September 22, 2023) as a basic application. The present application incorporates the entire contents of the basic application by reference. Technical Field

[0002] This embodiment relates to a magnetic disk device. Background Art

[0003] Conventionally, in a magnetic disk device, user data received from a host is temporarily stored in a volatile memory, and then the user data stored in the volatile memory is written to a magnetic disk.

[0004] In addition, a magnetic disk device that can perform a power loss protection (PLP) action is known. In the PLP action, when a power failure occurs, user data in the volatile memory that has not yet been written to the magnetic disk is transferred (saved) to the non-volatile memory by using the backup power. This prevents the user data in the volatile memory that has not yet been written to the magnetic disk from being lost from the magnetic disk device. Summary of the invention

[0005] An embodiment of the present invention provides a magnetic disk device having high writing performance.

[0006] The magnetic disk device involved in this embodiment includes a magnetic disk, a magnetic head, a first motor, a second motor, a non-volatile memory, a volatile memory and a controller. The magnetic head performs writing and reading on the magnetic disk. The first motor causes the magnetic head to move relative to the magnetic disk in the radial direction. The second motor causes the magnetic disk to rotate. The volatile memory stores the first data received from the host device at least until it is written to the magnetic disk. The controller calculates the first amount of electric power as the amount of electric power required for the unloading action of the magnetic head based on the first state of the first motor when the first motor is in operation. The controller calculates the first setting value based on the first amount of electric power. In response to the amount of the second data as the first data stored in the volatile memory and not yet written to the magnetic disk exceeding the first setting value, the controller performs the first writing action of writing part or all of the second data to the magnetic disk. When the power supply from the outside is interrupted, the controller uses the power generated based on the back electromotive force of the second motor to perform the unloading action and the transfer of the second data to the non-volatile memory. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing an example of the configuration of the disk device according to the first embodiment.

[0008] Figure 2 This is a diagram showing an example of the structure of the magnetic disk according to the first embodiment.

[0009] Figure 3 This is a diagram showing an example of a plurality of areas formed on the recording surface of the magnetic disk according to the embodiment.

[0010] Figure 4 This is a diagram for explaining an example of transition of the amount of write data stored in the write buffer according to the first embodiment.

[0011] Figure 5 This is a diagram showing an example of a more detailed configuration of the cache management unit according to the first embodiment.

[0012] Figure 6 This is a flowchart showing an example of the operation of the cache management unit according to the first embodiment.

[0013] Figure 7 This is a flowchart showing an example of an operation corresponding to a write command according to the first embodiment.

[0014] Figure 8 This is a flowchart showing an example of control of the second writing operation according to the first embodiment.

[0015] Fig. 9 This is a flowchart showing an example of the operation when a power outage occurs according to the first embodiment.

[0016] Fig.10 This is a diagram showing an example of the configuration of a magnetic disk device according to the second embodiment.

[0017] Description of symbols

[0018] 1 disk; 2 SPM; 3 VCM; 4 axis; 5 power supply circuit; 6 hard disk control circuit; 7 RAM; 8 FROM; 9 servo control circuit; 10 head control circuit; 11 read / write channel; 15 servo area; 16 data area; 17 track; 51 power failure detection unit; 52 power switch; 61 access control unit; 62, 62a buffer management unit; 63, 63a VCM resistance estimation unit; 64, 64a SPM resistance estimation unit; 65 first electric power estimation unit; 66 second electric power estimation unit; 67 PLP set value calculation unit; 71 write buffer; 72 read buffer; 81 PLP transfer area; 91 SPM control unit; 92 VCM control unit; 93 SPM power generation control unit; 94 SPM voltage / current monitoring unit; 95 VCM voltage / current monitoring unit; 100, 100a magnetic disk device; 110 recording surface; 120 LBA area; 130 medium cache area; 151 VCM temperature sensor; 152 SPM temperature sensor; 200 host device; 300 power supply; MH head. DETAILED DESCRIPTION

[0019] Hereinafter, the magnetic disk device according to the embodiment will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.

[0020] (First embodiment)

[0021] Figure 1 1 is a block diagram showing an example of the configuration of a disk device according to the first embodiment. The disk device 100 can be connected to a host device 200. The disk device 100 functions as an external storage device of the host device 200. The disk device 100 is connected to an external power supply 300. The disk device 100 operates using power supplied from the power supply 300.

[0022] The magnetic disk device 100 comprises a magnetic disk 1, a spindle motor (SPM) 2, a magnetic head MH, an actuator arm AA, a voice coil motor (VCM) 3, a power supply circuit 5, a hard disk control circuit 6, a RAM (Random Access Memory) 7, a FROM (Flash read only Memory) 8, a servo control circuit 9, a head control circuit 10 and a read / write channel 11.

[0023] The magnetic disk device 100 receives an access command from the host device 200. The magnetic disk device 100 writes data to the magnetic disk 1 or reads data from the magnetic disk 1 according to the received access command.

[0024] The access command includes a logical address. The disk device 100 provides a logical address space to the host device 200. The logical address indicates a position in the address space. The host device 200 specifies a position to write data or a position to read data by using the logical address. In addition, the logical address is expressed as LBA (Logical Block Address).

[0025] A magnetic layer capable of recording various information is provided on the surface of the magnetic disk 1. The magnetic disk device 100 may include a single magnetic disk 1 or a plurality of magnetic disks 1 coaxially arranged. Figure 1 In order to simplify the description, only one disk 1 is shown.

[0026] Figure 2 This is a diagram showing an example of the structure of the magnetic disk 1 according to the first embodiment. Servo data for positioning the magnetic head MH is written to the magnetic layer formed on the surface of the magnetic disk 1 by, for example, a servo writer or self servo writing (SSW).

[0027] exist Figure 2In the figure, as an example of the configuration of the servo area in which the servo data is written, the servo area 15 arranged in a radial shape is shown. In the circumferential direction, a data area 16 in which data can be written is set between two servo areas 15. A plurality of concentric tracks 17 are set in the radial direction of the magnetic disk 1. On the tracks 17, a plurality of sectors in which data of a predetermined size is written are set in the data area 16. The predetermined size is the sector size.

[0028] The servo data includes a servo mark, a Gray code, a burst pattern, and a post code. When writing data to or reading data from the disk 1, the positioning of the head MH, that is, the seek control and the tracking control, is performed based on the servo data read by the head MH from the servo area 15.

[0029] The recording surface of the magnetic disk 1 is divided into at least two areas having different uses. One of the at least two areas is an LBA area, and the other of the at least two areas is a medium cache area.

[0030] Figure 3 This is a diagram showing an example of a plurality of areas formed on the recording surface of the magnetic disk 1 according to the embodiment.

[0031] exist Figure 3 In the illustrated example, in the recording surface 110 of the magnetic disk 1, an LBA area 120 is provided on the inner diameter side, and a media cache area 130 is provided on the outer diameter side.

[0032] The LBA is mapped to the LBA area 120. The host device 200 can specify the location of the write destination or the location of the read destination in the LBA area 120 by using the LBA. The LBA area 120 is the final storage destination of the user data received from the host device 200. In addition, the user data received from the host device 200, that is, the user data requested to be written by the write command is expressed as write data.

[0033] The media cache area 130 is used as a temporary storage location for write data.

[0034] The number and position of the media cache area 130 provided on the recording surface 110 are not limited to Figure 3 In addition, the number and position of the LBA area 120 provided on the recording surface 110 are not limited to Figure 3 In the recording surface 110, in addition to the LBA area 120 and the media cache area 130, an area for any purpose may be provided.

[0035] return Figure 1 Provide explanation.

[0036] The writing and reading of data to and from the magnetic disk 1 are performed via the magnetic head MH. The magnetic head MH is provided at one end of the actuator arm AA and performs the writing and reading of data to and from the magnetic disk 1. The magnetic head MH includes a write head WH for writing data to the magnetic disk 1 and a read head RH for reading data from the magnetic disk 1. The magnetic head MH is supported on the slider SL.

[0037] The SPM 2 rotates the magnetic disk 1. The magnetic head MH moves relative to the surface of the magnetic disk 1 in the circumferential direction while maintaining a state of being slightly lifted from the surface of the magnetic disk 1 by utilizing the lift force generated by the rotation of the magnetic disk 1.

[0038] The VCM 3 is provided at the end of the actuator arm AA opposite to the end where the magnetic head MH is provided. The VCM 3 drives the actuator arm AA to rotate about the shaft 4. Thus, the VCM 3 moves the magnetic head MH relative to the magnetic disk 1 in the radial direction.

[0039] When the magnetic disk 1 stops rotating, the VCM 3 moves the magnetic head MH to a ramp mechanism (not shown). The ramp mechanism is provided at a position away from the magnetic disk 1 and is configured to hold the magnetic head MH. The operation of moving the magnetic head MH from the magnetic disk 1 to the ramp mechanism is referred to as an unloading operation.

[0040] The head control circuit 10 writes data to the magnetic disk 1 by sending a write signal corresponding to data input from the read / write channel 11 to the write head WH. The head control circuit 10 also amplifies a read signal output from the read head RH and supplies it to the read / write channel 11.

[0041] The read / write channel 11 modulates the write data stored in the write buffer 71 and outputs the modulated write data to the head control circuit 10. In addition, the read / write channel 11 demodulates the data transmitted from the head control circuit 10 and outputs the demodulated data to the read buffer 72.

[0042] The RAM 7 is a volatile memory capable of high-speed operation. A write buffer 71 and a read buffer 72 are allocated to the RAM 7 .

[0043] The write buffer 71 is an area that stores write data received from the host device 200 at least until the write data is written to the magnetic disk 1 . The write data received from the host device 200 is temporarily stored in the write buffer 71 and then written from the write buffer 71 to the magnetic disk 1 .

[0044] The read buffer 72 is an area for temporarily storing user data read from the disk 1 in response to a read command. The data read from the disk 1 is stored in the read buffer 72 and then transferred from the read buffer 72 to the host device 200 .

[0045] The RAM 7 may include, in addition to the write buffer 71 and the read buffer 72 , an area for loading various data or programs used by the hard disk control circuit 6 and the like.

[0046] The FROM 8 is a nonvolatile memory storing various data and programs used by the hard disk control circuit 6, etc. A PLP dump area 81 is also allocated to the FROM 8. In the PLP dump area 81, write data in the write buffer 71 is dumped by the PLP operation.

[0047] The PLP action is an action to transfer the write data stored in the write buffer 71 that has not been stored in the disk 1 to the nonvolatile memory when a power failure occurs. The PLP action prevents the write data that has not been stored in the disk 1 from being lost from the disk device 100. Thus, the write data received in the write buffer 71 is protected from being lost from the disk device 100.

[0048] In addition, the power outage is an improper interruption of the supply of power from the power source 300. The power outage may also include interrupting the supply of power from the power source 300 in a normal sequence.

[0049] The servo control circuit 9 includes an SPM control unit 91 , a VCM control unit 92 , an SPM power generation control unit 93 , an SPM voltage / current monitoring unit 94 , and a VCM voltage / current monitoring unit 95 .

[0050] The SPM control unit 91 controls the rotation of the SPM 2. The SPM voltage / current monitoring unit 94 monitors the voltage value and the current value of the power supplied to the SPM 2. The SPM voltage / current monitoring unit 94 has a circuit for measuring the voltage value and the current value of the power supplied to the SPM 2, and the voltage value and the current value are repeatedly measured by the circuit. The SPM control unit 91 can use the voltage value and the current value obtained by the SPM voltage / current monitoring unit 94 to control the rotation of the SPM 2.

[0051] The VCM control unit 92 controls the rotation of the VCM 3. The VCM voltage / current monitoring unit 95 monitors the voltage value and the current value of the power supplied to the VCM 3. The VCM voltage / current monitoring unit 95 includes a circuit for measuring the voltage value and the current value of the power supplied to the VCM 3, and the voltage value and the current value are repeatedly measured by the circuit. The VCM control unit 92 can use the voltage value and the current value obtained by the VCM voltage / current monitoring unit 95 to control the rotation of the VCM 3.

[0052] The SPM power generation control unit 93 generates power using the back electromotive force generated in the SPM2 when the power is off. When the power is off, the hard disk control circuit 6 starts the PLP operation. In the PLP operation, since the power from the power supply 300 cannot be used, the back electromotive force generated by the continued rotation of the SPM2 due to inertia is used. The SPM power generation control unit 93 supplies the back electromotive force generated in the SPM2 to each circuit of the magnetic disk device 100 via the power switch 52 provided in the power supply circuit 5.

[0053] The power supply circuit 5 supplies power to each circuit of the magnetic disk device 100. The power supply circuit 5 includes a power failure detection unit 51 and a power switch 52.

[0054] The power failure detection unit 51 detects a power failure. For example, the power failure detection unit 51 monitors the voltage of the power supply line for receiving power supply from the power supply 300. When the value of the voltage of the power supply line is greater than a predetermined threshold value, it is determined that no power failure has occurred. When the value of the voltage of the power supply line becomes smaller than the threshold value, the power failure detection unit 51 determines that a power failure has occurred. A value slightly smaller than the value of the voltage required for the magnetic disk device 100 to operate normally is used as the threshold value. In addition, the detection method of the power failure based on the power failure detection unit 51 is not limited to this.

[0055] The power switch 52 switches the supply source of the power for driving each circuit of the magnetic disk device 100. During a period when the power failure detection unit 51 has not detected the power failure, the power switch 52 supplies the power supplied from the power supply 300 to each circuit of the magnetic disk device 100. In response to the detection of the power failure by the power failure detection unit 51, the power switch 52 supplies the power generated by the SPM power generation control unit 93 based on the back electromotive force of the SPM2 to each circuit of the magnetic disk device 100.

[0056] The hard disk control circuit 6 includes an access control unit 61 and a buffer management unit 62. The hard disk control circuit 6 is an example of a controller.

[0057] The access control unit 61 interprets the access command received from the host device 200. In addition, the access control unit 61 controls data transfer between the disk 1 and each buffer 71, 72 and data transfer between each buffer 71, 72 and the host device 200 based on the access command.

[0058] When receiving a write command from the host device 200, the access control unit 61 saves the write data requested to be written by the write command in the write buffer 71. When the write data is saved in the write buffer 71, the access control unit 61 notifies the host device 200 of the completion of the execution of the write command. The completion of the execution of the write command can be notified before the write data is saved in the LBA area 120. As a result, the transfer rate of the write data from the host device 200 to the magnetic disk device 100, that is, the write performance, is improved.

[0059] In the first embodiment, in order to increase the write performance as much as possible, the capacity of the write buffer 71 is set large.

[0060] The access control unit 61 performs command reordering when writing the write data in the write buffer 71 to the disk 1. Command reordering is an action of determining the order of writing the multiple write data in the write buffer 71 to the disk 1 so that the writing of the multiple write data can be completed as early as possible when writing the multiple write data to the disk 1. Thus, the order of writing the multiple write data to the disk 1 may be different from the order of receiving the corresponding multiple write commands.

[0061] By setting the capacity of the write buffer 71 to be larger, the efficiency of command reordering is improved.

[0062] Compared with setting the capacity of the write buffer 71 to be large in this way, the amount of data that can be transferred to the PLP transfer area 81 through the PLP action is subject to various restrictions. As mentioned above, the PLP action is performed by using the back electromotive force generated in the SPM2. Since the power generation based on the back electromotive force can only be maintained during the period when the SPM2 rotates due to inertia, the upper limit of the amount of data that can be transferred from the write buffer 71 to the PLP transfer area 81 depends on the amount of power generated based on the back electromotive force, etc. Therefore, it is impossible to transfer all the write data stored in the write buffer 71 to the PLP transfer area 81 without omission.

[0063] Therefore, the access control unit 61 copies the write data stored in the write buffer 71 to the medium cache area 130 as appropriate. When a power outage occurs, the original write data stored in the write buffer 71, whose copy is written to the medium cache area 130, is lost from the write buffer 71. After the power supply from the power supply 300 is resumed, the write data identical to the original write data is restored in the write buffer 71 based on the copy stored in the medium cache area 130.

[0064] All the write data stored in the write buffer 71 that has not been copied to the media cache area 130 is transferred to the PLP transfer area 81 in response to the power failure. Therefore, the amount of the write data stored in the write buffer 71 that has not been copied to the media cache area 130 is controlled to be as small as possible not to exceed the PLP setting value. The PLP setting value corresponds to the upper limit of the data transferred to the PLP transfer area 81, and it is guaranteed that the user data up to the amount of the PLP setting value can be transferred to the PLP transfer area 81 without omission.

[0065] Hereinafter, write data received from the host device 200 but not yet written to the LBA area 120 is referred to as temporarily stored data. The temporarily stored data includes write data stored in the write buffer 71, a copy of the write data stored in the media cache area 130, and write data transferred to the PLP transfer area 81.

[0066] Furthermore, among the write data in the write buffer 71 , the write data whose copy has not yet been written to the media cache area 130 is expressed as unprotected temporary storage data.

[0067] Furthermore, a copy of the write data written to each media cache area 130 is expressed as duplicate data.

[0068] The operation of copying the write data stored in the write buffer 71 to the media cache area 130 is described as a first write operation. The operation of writing the write data stored in the write buffer 71 to the LBA area 120 is described as a second write operation.

[0069] Figure 4 This is a diagram for explaining an example of the change in the amount of write data stored in the write buffer 71 involved in the first embodiment. In this figure, the timing of receiving the write command, the timing of executing the first write action, the change in the amount of unprotected temporarily stored data over time, the change in the amount of write data in the write buffer 71 over time, and the change in the amount of data transferred to the LBA area 120 based on the second write action over time are depicted.

[0070] The amount of write data in the write buffer 71 is represented by numerical information of percentage with the capacity of the write buffer 71 set to 100%. Also, the amount of unprotected temporary storage data is represented by numerical information of percentage with the PLP setting value set to 100%.

[0071] like Figure 4As shown, as the write command is received, the write data is stored in the write buffer 71, thereby increasing the amount of write data in the write buffer 71. In addition, the amount of unprotected temporarily stored data increases as the write command is received. And, after the amount of unprotected temporarily stored data reaches the PLP setting value (timing t1), the first write operation is started.

[0072] In a period P1 before the timing t1 which is the timing of the first writing operation, the magnetic disk device 100 continuously executes the second writing operation. In a period after the timing t1, the first writing operation is executed every time the amount of unprotected temporarily saved data reaches the PLP setting value. During the period when the first writing operation is not executed, that is, Figure 4 The second write operation is performed in the period P1 and each period P2. Thus, the amount of write data in the write buffer 71 gradually decreases except for each timing when the write data is stored in the write buffer 71 according to the write command.

[0073] The amount of data transferred to the LBA area 120 by the second write operation is Figure 4 It takes the maximum value in the period P1 and each period P2, and becomes zero at each timing when the first writing operation is performed.

[0074] The amount of data transferred to the LBA area 120 based on the second write operation can be regarded as the transfer rate of the write data to the disk 1. Therefore, in the period after timing t1, the line L1 obtained by averaging the amount of data transferred to the LBA area 120 based on the second write operation is equivalent to the transfer rate of the write data to the disk 1. It is clear from the line L1 that in the period after timing t1, the transfer rate of the write data to the disk 1 deteriorates because the first write operation is often performed.

[0075] When the transfer rate of write data to the magnetic disk 1 deteriorates, the transfer rate of write data from the host device 200 to the magnetic disk device 100 (referred to as write performance in this specification) may also deteriorate.

[0076] In the embodiment, in order to suppress the deterioration of the transfer rate to the magnetic disk 1 caused by the execution of the first write operation as much as possible, the execution frequency of the first write operation is reduced as much as possible. Specifically, the hard disk control circuit 6 reduces the execution frequency of the first write operation as much as possible by increasing the PLP setting value as much as possible. By reducing the execution frequency of the first write operation, the write performance is improved.

[0077] Here, the technology compared with the first embodiment is described. The technology compared with the embodiment is described as a comparative example. According to the comparative example, the PLP setting value is set to a fixed value. In the manufacturing process, a fixed value common to multiple disk devices is set as the PLP setting value in each disk device. The worst value of the amount of data that can be transferred based on the PLP action is estimated, and the PLP setting value is determined based on the worst value. And, the PLP setting value is set in multiple disk devices.

[0078] The amount of power that can be used in the PLP action may vary depending on the conditions when the disk device is in operation (e.g., the motor temperature of the SPM or VCM). Thus, the amount of data that can be transferred by the PLP action may vary depending on the conditions. However, according to the comparative example, the PLP setting value is set based on the worst value of the amount of data that can be transferred by the PLP action. Thus, there is room for increasing the amount of data that can be transferred by the PLP action.

[0079] In contrast, according to the first embodiment, a buffer management unit 62 capable of dynamically changing the PLP setting value is provided. The buffer management unit 62 obtains the state of each motor 2, 3 while the magnetic disk device 100 is performing normal operation, and estimates the amount of power that can be used in the PLP operation based on the obtained state. Furthermore, the buffer management unit 62 sets the PLP setting value based on the estimated amount of power. Thus, compared with the comparative example, the PLP setting value can be increased, and the execution frequency of the first write operation can be suppressed.

[0080] The following describes how to determine the PLP setting value.

[0081] In order to prevent the magnetic head MH from being attracted to the magnetic disk 1 during power-off, an unloading operation is performed before the PLP operation starts. Thus, the following equation (1) holds true.

[0082] P gSPM ≧P UL +P PLP ··(1)

[0083] P gSPM The amount of power generated by the back electromotive force generated in SPM2 is referred to as the SPM power generation amount. UL It is the amount of power consumed in the unloading operation, more precisely, the amount of power consumed in the VCM3 during the unloading operation. The amount of power consumed in the unloading operation is expressed as the unloading power consumption. PLP The amount of power used for data transfer based on the PLP operation is expressed as the PLP power amount.

[0084] By transforming the formula (1), the following formula (2) is obtained.

[0085] P PLP ≦P gSPM -P UL …(2)

[0086] As is clear from equation (2), the maximum amount of power P generated by SPM that can be used in data transfer based on PLP operation is gSPM Subtract the power consumption of unloading P UL The amount of electricity obtained.

[0087] PLP setting value C PLP According to PLP power quantity P PLP Therefore, the PLP setting value C PLP It can be derived by the following formula (3).

[0088] C PLP ≦C ref *(P PLP / P PLPref )··(3)

[0089] C ref It is the reference value of PLP setting value. PLPref is the reference value of PLP power, and is C ref The amount of PLP power required to transfer the amount of write data.

[0090] Unloading power consumption P UL Depends on the coil temperature of VCM3. For example, in a situation where seeks occur continuously, the coil resistance of VCM3 increases due to the heating of the coil of VCM3. As a result, the power consumption of VCM3 during the unloading operation, i.e., the unloading power consumption P UL Increase.

[0091] Power consumption P UL It can be expressed by the following formula (4). In formula (4), R VCM is the coil resistance of VCM3. VCM is the current flowing in VCM3.

[0092] P UL =∫(R VCM *I VCM 2 )dt…(4)

[0093] As is clear from equation (4), the power consumption UL and the coil resistance R of VCM3 are VCM Therefore, the hard disk control circuit 6 calculates the power consumption P based on the following formula (5): UL Make an inference.

[0094] P ULest =P ULref *(R VCMest / R VCMref )··(5)

[0095] P ULest is the estimated value of the unloading power consumption. VCMref It is the reference value of the coil resistance of VCM3. ULref is the reference value of the unloading power consumption, more specifically, the coil resistance value of VCM3 is R VCMref The amount of power consumed by unloading during operation. VCMest It is the estimated value of the coil resistance of VCM3.

[0096] SPM power generation amount P gSPM It is obtained by the following formula (6).

[0097]

[0098] I SPM This is the induction current that flows due to the back electromotive force voltage of SPM2. V EMF is the back EMF voltage generated in SPM2. R SPM is the coil resistance of SPM2. LOAD This is the resistance of the load that consumes the back electromotive force of SPM2.

[0099] When the coil temperature of SPM2 rises, the coil resistance R SPM When the coil resistance R of SPM2 SPM When the SPM power generation amount P increases gSPM Therefore, the hard disk control circuit 6 calculates the power generation amount P of SPM2 based on the following equation (7). gSPM Make an inference.

[0100] P gSPMest =P gSPMref *(R SPMest / R SPMref )··(7)

[0101] P gSPMest is the estimated value of the SPM generated power. SPMest is the estimated value of the coil resistance of SPM2. SPMref This is the reference value of the coil resistance of SPM2. gSPMref is the reference value of the SPM power generation, more precisely, the coil resistance of SPM2 is R SPMref The amount of SPM power generated at that time.

[0102] Figure 1The buffer management unit 62 shown in FIG. 6 sets the PLP setting value C based on the relationship between the above-mentioned values. PLP .

[0103] Figure 5 1 is a diagram showing an example of a more detailed configuration of the buffer management unit 62 according to the first embodiment. In the example shown in this figure, the buffer management unit 62 includes a VCM resistance estimation unit 63, an SPM resistance estimation unit 64, a first power estimation unit 65, a second power estimation unit 66, and a PLP setting value calculation unit 67.

[0104] The VCM resistance estimation unit 63 obtains the current value and voltage value of the power supplied to the VCM 3 measured by the VCM voltage / current monitoring unit 95. The VCM resistance estimation unit 63 calculates the estimated value R of the coil resistance of the VCM 3 based on the current value and voltage value of the power supplied to the VCM 3. VCMest For example, the VCM resistance estimation unit 63 obtains the estimated value R of the coil resistance of the VCM 3 by dividing the obtained voltage value by the obtained current value. VCMest .

[0105] The first power amount estimating unit 65 calculates the estimated value R of the coil resistance obtained by the VCM resistance estimating unit 63. VCMest The estimated value P of the unloading power consumption is calculated by using formula (5): ULest In addition, the reference value P ULref , R VCMref The reference values ​​PULref and RVCMref may be set to values ​​common to a plurality of magnetic disk devices 100 or may be set to different values ​​for each magnetic disk device 100 .

[0106] The SPM resistance estimation unit 64 obtains the current value and voltage value of the power supplied to the SPM 2 measured by the SPM voltage / current monitoring unit 94. The SPM resistance estimation unit 64 calculates the estimated value R of the coil resistance of the SPM 2 based on the current value and voltage value of the power supplied to the SPM 2. SPMest For example, the VCM resistance estimation unit 63 obtains the estimated value R of the coil resistance of SPM2 by dividing the obtained voltage value by the obtained current value. SPMest .

[0107] The second electric energy estimating unit 66 calculates the estimated value R of the coil resistance obtained by the SPM resistance estimating unit 64. SPMest The estimated value P of the SPM generated power is calculated by using equation (7): gSPMest In addition, the reference value R SPMref , P gSPMref The reference value R is set by the designer in advance. SPMref , P gSPMrefA common value may be set in each of the plurality of magnetic disk devices 100 , or a different value may be set for each magnetic disk device 100 .

[0108] The PLP setting value calculation unit 67 calculates the PLP setting value C PLP .

[0109] Specifically, the PLP setting value calculation unit 67 calculates the estimated value P of the unloading power consumption based on the estimated value P ULest , Estimated value of SPM power generation PgSPMest And formula (2), calculate the maximum value P of the power that can be used in PLP operation PLPmax The PLP setting value calculation unit 67 calculates the value of the maximum value P PLPmax The PLP setting value C is calculated by using formula (3) PLP The maximum value that can be set is C PLPmax In addition, the reference value P PLPref , C ref The reference value P is set by the designer in advance. PLPref , C ref The PLP setting value calculation unit 67 may set a common value in each of the plurality of magnetic disk devices 100, or may set a different value for each magnetic disk device 100. PLPmax To determine the PLP setting value C PLP The PLP setting value calculation unit 67 can calculate the maximum value C PLPmax Determine the PLP setting value C PLP , or by the maximum value C PLPmax Subtract the predetermined margin to obtain the PLP setting value C PLP .

[0110] Next, the operation of the magnetic disk device 100 according to the first embodiment will be described.

[0111] Figure 6 This is a flowchart showing an example of the operation of the buffer management unit 62 according to the first embodiment.

[0112] The buffer management unit 62 determines whether the update timing of the PLP setting value has arrived (S101). The method for determining the update timing of the PLP setting value can be set by the designer. For example, it can be set so that the update timing of the PLP setting value arrives at a predetermined time period. In another example, it can also be set so that the update timing of the PLP setting value arrives at a predetermined time period after the disk device 100 is started.

[0113] In addition, before the initial update timing, a predetermined initial value can be used as the PLP setting value. The initial value can be set by the same method as the aforementioned comparative example. Alternatively, the PLP setting value used before the last action was stopped can also be used as the initial value.

[0114] The update timing of the PLP setting value is set to arrive multiple times at different timings after startup. In addition, the update timing of the PLP setting value may be set to arrive only once after startup.

[0115] When the update timing of the PLP setting value has not arrived ( S101 : NO (No)), the process of S101 is executed again.

[0116] When the update timing of the PLP setting value arrives ( S101 : Yes), the VCM resistance estimation unit 63 obtains the current value and the voltage value of the power supplied to the VCM 3 from the VCM voltage / current monitoring unit 95 ( S102 ).

[0117] The VCM resistance estimating unit 63 obtains the current value and the voltage value from the VCM voltage / current monitoring unit 95 while power is being supplied to the VCM 3, that is, while the VCM 3 is operating. Specifically, the VCM resistance estimating unit 63 obtains the current value and the voltage value from the VCM voltage / current monitoring unit 95 during a seek accompanied by access to the LBA area 120 or the medium cache area 130. Alternatively, the VCM resistance estimating unit 63 may forcibly start a seek that is not accompanied by access to the LBA area 120 or the medium cache area 130 in order to obtain the current value and the voltage value, and obtain the current value and the voltage value from the VCM voltage / current monitoring unit 95 during the forcibly started seek.

[0118] The VCM resistance estimation unit 63 calculates the coil resistance value (more precisely, the estimated value R) of the VCM 3 based on the current value and the voltage value of the power supplied to the VCM 3. VCMest )(S103).

[0119] The first power estimating unit 65 calculates the unloading power consumption (more precisely, the estimated value P of the unloading power consumption) based on the coil resistance value obtained by the VCM resistance estimating unit 63 and the equation (5). ULest )(S104).

[0120] The SPM resistance estimating unit 64 obtains the current value and voltage value of the power supplied to the SPM 2 from the SPM voltage / current monitoring unit 94 (S105). The SPM resistance estimating unit 64 obtains the current value and voltage value from the SPM voltage / current monitoring unit 94 while power is being supplied to the SPM 2, that is, while the SPM 2 is operating.

[0121] The SPM resistance estimation unit 64 calculates the coil resistance value (more precisely, the estimated value R) of the SPM 2 based on the current value and the voltage value of the power supplied to the SPM 2. SPMest )(S106).

[0122] The second power estimation unit 66 calculates the SPM generated power (more precisely, the estimated value P of the SPM generated power) based on the coil resistance value obtained by the SPM resistance estimation unit 64 and equation (7). gSPMest )(S107).

[0123] The PLP setting value calculation unit 67 calculates a new PLP setting value based on the unloading power consumption, the SPM power generation, equations (2) and (3) (S108). The new PLP setting value calculated in the process of S108 is used for the control of the first writing operation until the process of S108 is executed next time.

[0124] Figure 7 This is a flowchart showing an example of an operation corresponding to a write command according to the first embodiment.

[0125] When the access control unit 61 receives the write command and write data (S201), the access control unit 61 stores the write data in the write buffer 71 (S202). Then, the access control unit 61 notifies the host device 200 of the completion of the execution of the write command based on the completion of storing the write data in the write buffer 71 (S203).

[0126] The access control unit 61 determines whether the amount of unprotected temporary storage data in the write buffer 71 exceeds the PLP setting value ( S204 ).

[0127] When the amount of unprotected temporary storage data in the write buffer 71 exceeds the PLP setting value (S204: Yes), the access control unit 61 copies the unprotected temporary storage data to the media cache area 130 (S205). The process of S205 corresponds to the first write operation.

[0128] In the process of S205 , the access control unit 61 may copy the unprotected temporary storage data exceeding the PLP setting value to the media cache area 130 . Alternatively, the access control unit 61 may copy all the unprotected temporary storage data to the media cache area 130 .

[0129] After the processing of S205, or when the amount of unprotected temporary storage data in the write buffer 71 does not exceed the PLP setting value (S204: No), the operation corresponding to the write command ends.

[0130] Figure 8This is a flowchart showing an example of control of the second writing operation according to the first embodiment.

[0131] The access control unit 61 determines whether the magnetic disk device 100 is in an idle state (S301). The idle state is, for example, a state in which no access command is received from the host device 200 for a period exceeding a predetermined time.

[0132] When the magnetic disk device 100 is not in the idle state ( S301 : No), the access control unit 61 executes the process of S301 again.

[0133] When the magnetic disk device 100 is in the idle state (S301: Yes), the access control unit 61 selects a write data related to a write command from the temporarily stored data in the write buffer 71 (S302). The access control unit 61 selects the write data based on the command reordering.

[0134] The access control unit 61 writes the selected write data to the LBA area 120 (S303). The process of S303 corresponds to the second write operation.

[0135] Following the process of S303, the access control unit 61 invalidates the write data in the write buffer 71 that has been written to the LBA area 120 and the copy data of the write data in the media cache area 130 (S304). Then, the access control unit 61 executes the process of S301 again.

[0136] Invalidation of written data means making the area storing the written data usable. Invalidation of written data may also be erasure of the written data.

[0137] In addition, Figure 8 In the example shown, the second write operation is executed when the magnetic disk device 100 is in the idle state, but the trigger of the second write operation is not limited thereto. The second write operation may be executed based on any trigger as long as the second write operation is executed during a period when the first write operation is not executed.

[0138] Fig. 9 This is a flowchart showing an example of the operation when a power outage occurs according to the first embodiment.

[0139] When the power failure detection unit 51 detects the occurrence of a power failure ( S401 ), the power switch 52 switches the source of power supply to each circuit from the power supply 300 to the SPM power generation control unit 93 ( S402 ).

[0140] In response to detecting the occurrence of power failure, the hard disk control circuit 6 executes an unload operation (S403). In addition, the access control unit 61 transfers the unprotected temporary storage data in the write buffer 71 to the PLP transfer area 81 (S404).

[0141] Furthermore, the processes of S403 and S404 are executed using the electric power generated based on the back electromotive force of SPM2.

[0142] When the process of S404 is completed, the magnetic disk device 100 stops operating (S405).

[0143] Then, when the power supply from the power supply 300 to the magnetic disk device 100 is restarted (S406), the access control unit 61 transfers the temporarily saved data in the PLP dump area 81 and the copied data in the medium cache area 130 to the write buffer 71 (S407). Thus, the temporarily saved data saved in the write buffer 71 immediately before the power is turned off is restored in the write buffer 71. Then, the operation when the power is turned off is completed.

[0144] In the description of the first embodiment described above, the hard disk control circuit 6 writes part or all of the temporarily saved data that has not been protected in the first write operation to the media cache area 130 .

[0145] However, it is also possible to configure the medium cache area 130 to be discarded from the disk 1, and the hard disk control circuit 6 to write part or all of the temporarily saved data that was not protected in the first write operation to the LBA area 120. In such a configuration, the hard disk control circuit 6 also writes the temporary saved data to the LBA area 120. Figure 6 In the PLP operation, the hard disk control circuit 6 transfers the unprotected temporary saved data to the PLP transfer area 81. When the power supply is restarted, the hard disk control circuit 6 transfers the write data transferred to the PLP transfer area 81 to the write buffer 71.

[0146] Furthermore, the hard disk control circuit 6 estimates the SPM generated power amount and the load shedding consumed power amount, and calculates the PLP set value based on the estimated amounts.

[0147] However, one of the SPM generated power and the load shedding power consumption may be given as a setting value by a designer. The hard disk control circuit 6 may be configured to estimate the other of the SPM generated power and the load shedding power consumption.

[0148] As described above, according to the first embodiment, the hard disk control circuit 6 calculates the coil resistance value of the VCM 3 based on the current value and voltage value of the power supplied to the VCM 3 measured by the VCM voltage / current monitoring unit 95 (for example, refer to Figure 6The hard disk control circuit 6 calculates the unloading power consumption based on the coil resistance value of VCM3 (for example, referring to Figure 6 The hard disk control circuit 6 calculates the PLP setting value based on the unloading power consumption (for example, referring to Figure 6 In response to the amount of unprotected temporarily saved data exceeding the PLP setting value, the hard disk control circuit 6 executes a first write operation (for example, referring to S108) of writing a part or all of the unprotected temporarily saved data to the disk 1. Figure 7 When the power supply from the outside is interrupted, the hard disk control circuit 6 uses the power generated based on the back electromotive force of SPM2 to perform the unloading operation and transfer the unprotected temporary storage data to the PLP transfer area 81 (for example, refer to Fig. 9 S402~S404).

[0149] This reduces the frequency of the first write operation, and as a result, the write performance improves.

[0150] According to the embodiment, the hard disk control circuit 6 calculates the PLP power amount, which is the amount of power available for data transfer based on the PLP operation, from the unloading power consumption amount. The hard disk control circuit 6 calculates the PLP setting value based on the PLP power amount.

[0151] Thus, compared with the comparative example, the PLP setting value can be increased and the frequency of the first writing operation can be reduced.

[0152] According to the embodiment, the hard disk control circuit 6 calculates the coil resistance value of SPM2 based on the current value and voltage value of the power being supplied to SPM2 measured by the SPM voltage / current monitoring unit 94 (for example, refer to Figure 6 The hard disk control circuit 6 calculates the SPM generated electric power based on the coil resistance value of the SPM 2.

[0153] Thus, compared with the comparative example, the PLP setting value can be increased and the frequency of the first writing operation can be reduced.

[0154] Furthermore, according to the embodiment, in the first write operation, the hard disk control circuit 6 copies part or all of the unprotected temporarily saved data to the medium cache area 130. The hard disk control circuit 6 executes a second write operation of writing the write data saved in the write buffer 71 to the LBA area 120 at least during the period when the first write operation is not executed.

[0155] According to the embodiment, when the power supply from the power source 300 is restarted (for example, see Fig. 9The hard disk control circuit 6 transfers the copy written to the medium cache area 130 and the write data transferred to the PLP transfer area 81 to the write buffer 71 (for example, refer to Fig. 9 S407).

[0156] This can prevent write data that has not yet been written to the magnetic disk 1 from being lost from the magnetic disk device 100 due to power failure, and can increase the capacity of the write buffer 71. As a result, the write performance is improved.

[0157] According to the embodiment, the hard disk control circuit 6 calculates the coil resistance value of SPM2 based on the current value and voltage value of the power being supplied to SPM2 measured by the SPM voltage / current monitoring unit 94 (for example, refer to Figure 6 The hard disk control circuit 6 calculates the SPM generated power based on the coil resistance value of the SPM 2 (for example, referring to Figure 6 The hard disk control circuit 6 calculates the PLP setting value based on the SPM generated power (for example, referring to Figure 6 In response to the amount of unprotected temporarily saved data exceeding the PLP setting value, the hard disk control circuit 6 executes a first write operation (for example, referring to S108) of writing a part or all of the unprotected temporarily saved data to the disk 1. Figure 7 When the power supply from the outside is interrupted, the hard disk control circuit 6 uses the power generated by the back electromotive force of SPM2 to transfer the unprotected temporary storage data to the PLP transfer area 81 (for example, refer to Fig. 9 (S402, S404).

[0158] This reduces the frequency of the first write operation, and as a result, the write performance improves.

[0159] According to the embodiment, the PLP power amount, which is the amount of power available for storing data based on the PLP operation, is calculated among the SPM generated power amount, and the PLP setting value is calculated based on the PLP power amount.

[0160] Thus, compared with the comparative example, the PLP setting value can be increased and the frequency of the first writing operation can be reduced.

[0161] (Second embodiment)

[0162] According to the first embodiment, the buffer management unit 62 calculates the coil resistance value of each motor 2, 3 based on the current value and the voltage value of the power supplied to each motor 2, 3. The method of obtaining the coil resistance value of each motor 2, 3 is not limited to this.

[0163] In the second embodiment, another example of a method for obtaining the coil resistance value of each motor 2, 3 is described. In addition, matters different from the first embodiment are described below. Matters similar to the first embodiment are omitted or briefly described.

[0164] Fig.10 This is a diagram showing an example of the configuration of a magnetic disk device 100a according to the second embodiment. In this diagram, the same configuration as that of the first embodiment is omitted from illustration.

[0165] The magnetic disk device 100 a includes a VCM temperature sensor 151 and an SPM temperature sensor 152 .

[0166] The VCM temperature sensor 151 is provided at a predetermined position inside the VCM 3 or in the vicinity of the VCM 3. The VCM temperature sensor 151 measures the coil temperature of the VCM 3.

[0167] The SPM temperature sensor 152 is provided at a predetermined position inside the SPM 2 or in the vicinity of the SPM 2. The SPM temperature sensor 152 measures the coil temperature of the SPM 2.

[0168] The hard disk control circuit 6 includes a buffer management unit 62a instead of the buffer management unit 62 of the first embodiment. The buffer management unit 62a includes a VCM resistance estimation unit 63a, an SPM resistance estimation unit 64a, a first power estimation unit 65, a second power estimation unit 66, and a PLP setting value calculation unit 67.

[0169] The VCM resistance estimation unit 63a calculates an estimated value R of the coil resistance of the VCM 3 based on the coil temperature of the VCM 3 measured by the VCM temperature sensor 151. VCMest .

[0170] The coil resistance of VCM3 depends on the coil temperature of VCM3. The correspondence between the coil temperature of VCM3 and the coil resistance of VCM3 is set in advance for the magnetic disk device 100, and the VCM resistance estimation unit 63a calculates the estimated value R of the coil resistance of VCM3 based on the correspondence. VCMest The VCM resistance estimation unit 63a may further add a margin to a value determined based on the correspondence between the coil temperature of the VCM3 and the coil resistance of the VCM3 as the estimated value R of the coil resistance of the VCM3. VCMest .

[0171] The SPM resistance estimating unit 64a calculates an estimated value R of the coil resistance of the SPM2 based on the coil temperature of the SPM2 measured by the SPM temperature sensor 152. SPMest .

[0172] The coil resistance of SPM2 depends on the coil temperature of SPM2. The correspondence between the coil temperature of SPM2 and the coil resistance of SPM2 is set in advance for the magnetic disk device 100, and the SPM resistance estimation unit 64a calculates the estimated value R of the coil resistance of SPM2 based on the correspondence. SPMest .

[0173] The first electric energy estimating unit 65 , the second electric energy estimating unit 66 , and the PLP setting value calculating unit 67 execute the same processing as that of the first embodiment.

[0174] In this way, the hard disk control circuit 6 may calculate the coil resistance value of the VCM 3 based on the coil temperature of the VCM 3 measured by the VCM temperature sensor 151 , and calculate the unloading power consumption based on the coil resistance value of the VCM 3 .

[0175] Furthermore, the hard disk control circuit 6 may calculate the coil resistance value of SPM2 based on the coil temperature of SPM2 measured by the SPM temperature sensor 152 , and calculate the SPM generated electric power based on the coil resistance value of SPM2 .

[0176] As described in the first embodiment and the second embodiment, the hard disk control circuit 6 may also calculate the unloading power consumption based on the current value and voltage value of the power being supplied to the VCM3, and calculate the unloading power consumption based on the coil temperature of the VCM3. That is, the hard disk control circuit 6 calculates the unloading power consumption based on the state of the VCM3 when the VCM3 is operating. The state of the VCM3 when the VCM3 is operating is the current value and voltage value of the power being supplied to the VCM3, or the coil temperature of the VCM3.

[0177] In addition, as described in the first embodiment and the second embodiment, the hard disk control circuit 6 may also calculate the SPM generated power based on the current value and voltage value of the power being supplied to SPM2, and may also calculate the SPM generated power based on the coil temperature of SPM2. That is, the hard disk control circuit 6 calculates the SPM generated power based on the state of SPM2 when SPM2 is operating. The state of SPM2 when SPM2 is operating is the current value and voltage value of the power being supplied to SPM2, or the coil temperature of SPM2.

[0178] Several embodiments of the present invention are described above, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are included in the invention described in the claims and the scope of their equivalents.

Claims

1. A magnetic disk device comprising: disk; a magnetic head for performing writing and reading on the magnetic disk; a first motor for moving the magnetic head relative to the magnetic disk in a radial direction; a second motor for rotating the magnetic disk; Non-volatile memory; a volatile memory that stores first data received from the host device at least until the data is written to the magnetic disk; as well as Controller, the controller, calculating a first amount of electric power as an amount of electric power required for an unloading operation of the magnetic head based on a first state of the first motor when the first motor is operating, calculating a first set value based on the first amount of electric power, In response to the amount of the second data as the first data stored in the volatile memory and not yet written to the magnetic disk exceeding the first set value, executing a first writing operation of writing a part or all of the second data to the magnetic disk, When the power supply from the outside is interrupted, the unloading operation and the transfer of the second data to the nonvolatile memory are performed using the power generated based on the back electromotive force of the second motor.

2. The magnetic disk device according to claim 1, further comprising a first measuring circuit for measuring a current value and a voltage value related to the electric power being supplied to the first motor, The first state is the current value and the voltage value measured by the first measuring circuit, respectively. The controller calculates a first resistance value as a coil resistance value of the first motor based on the first state, and calculates the first electric energy based on the first resistance value.

3. The magnetic disk device according to claim 1, further comprising a first temperature sensor for measuring a coil temperature of the first motor, The first state is the coil temperature of the first motor measured by the first temperature sensor. The controller calculates a first resistance value as a coil resistance value of the first motor based on the first state, and calculates the first electric energy based on the first resistance value.

4. The magnetic disk device according to claim 1, The controller obtains a second amount of electric power as a generated electric power based on a back electromotive force of the second motor, calculates a third amount of electric power as an amount of electric power in the second amount of electric power that can be used in the transfer based on the first amount of electric power, and calculates the first set value based on the third amount of electric power.

5. The magnetic disk device according to claim 4, The controller calculates the second electric energy based on a second state of the second motor when the second motor is operating.

6. The magnetic disk device according to claim 5, further comprising a second measuring circuit for measuring a current value and a voltage value related to the electric power being supplied to the second motor, The second state is the current value and the voltage value measured by the second measuring circuit, respectively. The controller calculates a second resistance value as a coil resistance value of the second motor based on the second state, and calculates the second electric energy based on the second resistance value.

7. The magnetic disk device according to claim 5, further comprising a second temperature sensor for measuring a coil temperature of the second motor, The second state is the coil temperature of the second motor measured by the second temperature sensor. The controller calculates a second resistance value as a coil resistance value of the second motor based on the second state, and calculates the second electric energy based on the second resistance value.

8. The magnetic disk device according to any one of claims 1 to 7, The disk is allocated with a first area and a second area to which a logical address usable by the host device is mapped. The first write operation is an operation of copying a part or all of the second data to the second area. The controller executes a second write operation of writing third data, which is the first data stored in the volatile memory, into the first region at least while the first write operation is not executed.

9. The magnetic disk device according to claim 8, When the power supply from the outside is resumed, the controller transfers the second data written in the second area and the second data transferred to the nonvolatile memory to the volatile memory.

10. A magnetic disk device comprising: disk; a magnetic head for performing writing and reading on the magnetic disk; a motor to rotate the disk; Non-volatile memory; a volatile memory that stores first data received from the host device at least until the data is written to the magnetic disk; as well as Controller, the controller, calculating a first resistance value as a coil resistance value of the motor based on a state of the motor when the motor is operating, calculating a first electric power amount as a generated electric power amount based on a back electromotive force of the motor based on the first resistance value, calculating a first set value based on the first amount of electric power, In response to the amount of the second data as the first data stored in the volatile memory and not yet written to the magnetic disk exceeding the first set value, executing a first writing operation of writing a part or all of the second data to the magnetic disk, When the power supply from the outside is interrupted, the second data is transferred to the nonvolatile memory using the power generated based on the back electromotive force of the motor.

11. The magnetic disk device according to claim 10, further comprising a measuring circuit for measuring a current value and a voltage value related to the electric power being supplied to the motor, The states are the current value and the voltage value measured by the measurement circuit, respectively.

12. The magnetic disk device according to claim 10, A temperature sensor is further provided, the temperature sensor measuring the coil temperature of the motor, The state is the coil temperature measured by the temperature sensor.

13. The magnetic disk device according to claim 11, The controller calculates a second amount of electric power, which is an amount of electric power that can be used for the transfer, out of the first amount of electric power, and calculates the first set value based on the second amount of electric power.

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