JP4287037B2 - Servo control device and servo control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo control device that performs embedded servo control by providing a servo area in a track direction of a data surface in a recording medium such as a magnetic disk.
[0002]
In recent years, some recording / reproducing apparatuses using a magnetic disk or the like as a recording medium perform embedded servo control in order to improve data reading accuracy. In such a recording / reproducing apparatus, further increase in recording capacity is a problem. In order to improve the recording capacity of the recording medium, there is a configuration in which the data area is increased by reducing the servo area while reliably performing servo control. In order to reduce the servo area, it is necessary to increase the operation speed of the automatic gain control circuit (AGC circuit) of the data reading circuit.
[0003]
[Prior art]
FIG. 16 shows a data reading device for performing a data reading operation from a recording medium such as a magnetic disk.
[0004]
Data read from the recording medium via a read head (not shown) is input to the AGC circuit 1 as an input signal in. The AGC circuit 1 has its gain set based on the AGC control voltage SG1 output from the D / A converter 2, amplifies the input signal in based on the gain, and outputs the output signal SG2 to the filter circuit 3 To do.
[0005]
The filter circuit 3 is composed of a low-pass filter, and outputs an output signal SG3 obtained by removing unnecessary high-frequency components from the output voltage SG2 of the AGC circuit 1 to the A / D converter 4.
[0006]
The A / D converter 4 converts the analog output signal SG3 output from the filter circuit 3 into a digital output signal SG4 and outputs the digital output signal SG4 to the servo processing circuit 5.
The servo processing circuit 5 performs a processing operation for performing servo control of the reading position by the reading head based on the digital output signal SG4 of the A / D converter 4, and outputs read data to the next stage.
[0007]
The output signal SG4 of the A / D converter 4 is also input to the AGC control circuit 6. The AGC control circuit 6 is inputted with a target value PA stored in advance in a register or the like. The target value PA is a value that allows the output signal SG3 of the filter circuit 3 to be substantially in the full range with respect to the input level of the A / D converter 4.
[0008]
The AGC control circuit 6 compares the output signal SG4 of the A / D converter 4 with the target value PA, and outputs a digital output signal SG5 obtained by integrating the error component to the D / A converter 2. .
[0009]
The D / A converter 2 converts the digital output signal SG5 of the AGC control circuit 6 into an analog signal and outputs the analog signal to the AGC circuit 1 as an AGC control voltage SG1.
[0010]
The A / D converter 4, the servo processing circuit 5, the AGC control circuit 6 and the like operate based on a clock signal CLK generated by a PLL circuit or the like.
FIG. 17 shows servo areas in which a large number are recorded partially on each track of a recording medium such as a magnetic disk. That is, the servo area includes an R / W recovery area 7, a servo mark area 8, an AGC area 9, and a phase detection area 10.
[0011]
FIG. 18 shows an input signal in when the recorded contents of such a servo area are read. The input signal in shown in the figure is actually a Lorentz waveform but is displayed as a sin waveform for the sake of simplicity.
[0012]
Then, when reading the servo area, as shown in the figure, first, the R / W recovery area 7 is read at a predetermined amplitude and frequency at the first read time t1, and then the servo mark area 8 is second. Is read as a continuous level of 0 at the read time t2.
[0013]
Next, the AGC region 9 is read as a signal having a lower frequency and a larger amplitude than the R / W recovery region 7 at a read time t3, and then the phase detection region 10 is read at a read time t4 with the same frequency and the same amplitude as the AGC region 9. Read out.
[0014]
The AGC control voltage SG1 when reading such a servo area will be described with reference to FIG.
When the read operation of the R / W recovery area 7 is started by the read head, the output signal SG4 of the A / D converter 4 based on the input signal in read from the R / W recovery area 7 and the target value PA The error is calculated by the AGC control circuit 6, and the AGC control voltage SG1 is output from the D / A converter 2 based on the output signal SG5 of the AGC control circuit 6.
[0015]
At this time, the amplitude of the input signal in based on the read operation of the R / W recovery region 7 is small, and the error between the output signal SG4 of the A / D converter 4 and the target value PA input to the AGC control circuit 6 is large. As a result, the voltage level of the AGC control voltage SG1 rises.
[0016]
By such an operation, the output signal SG4 of the A / D converter 4 converges so as to coincide with the target value PA.
Next, during the read operation of the servo mark area 8, the output signal SG4 of the A / D converter 4 becomes 0 level continuous based on the input signal in that becomes 0 level continuous.
[0017]
Then, the output signal SG5 of the AGC control circuit 6 is fixed, and the AGC control voltage SG1 is also fixed.
Next, the read operation of the AGC area 9 is started, and an error between the output signal SG4 of the A / D converter 4 and the target value PA based on the input signal in read from the AGC area 9 is calculated again by the AGC control circuit 6. Based on the output signal SG5 of the AGC control circuit 6, the AGC control voltage SG1 is output from the D / A converter 2.
[0018]
That is, when the read operation is switched from the servo mark region 8 to the AGC region 9, the amplitude of the input signal in based on the read operation of the AGC region 9 is greater than the amplitude of the input signal in based on the read operation of the R / W recovery region 7. growing. For this reason, the output signal SG3 of the filter circuit 3 has an amplitude exceeding the target value.
[0019]
Then, due to the operation of the AGC control circuit 6, the AGC control voltage SG1 gradually decreases, and the output signal SG4 of the A / D converter 4 eventually converges to the target value PA.
With such an operation, the read operation of the phase detection region 10 is started in a state where the output signal SG3 of the filter circuit 3 is substantially in the full range with respect to the input level of the A / D converter 4.
[0020]
Since the frequency and amplitude of the input signal “in” by the read operation of the phase detection region 10 are equal to those of the AGC region 9, the read operation of the phase detection region 10 is performed first when the output signal SG 3 of the filter circuit 3 is sent to the A / D converter 4 Will be performed in a state where the input level is almost full range.
[0021]
Accordingly, it is possible to promptly perform servo control for reliably reading the phase information stored in the phase detection area 10 and correcting the reading position.
[0022]
[Problems to be solved by the invention]
In the read operation of the servo area as described above, the AGC control voltage SG1 is switched every time the read area is switched so that the output signal SG3 of the filter circuit 3 becomes an input level of the full range to the A / D converter 4. Done.
[0023]
Therefore, every time the area is switched, it takes time until the output signal SG3 of the filter circuit 3 converges to an almost full range input level for the A / D converter 4, and it is difficult to compress the servo area.
[0024]
In particular, when the read operation of the phase detection region 10 is started, the output signal SG3 of the filter circuit 3 is sufficient for the AGC region 9 so that the input signal SG3 has an almost full range input level from the beginning. A sample data amount and a data storage area are required.
[0025]
An object of the present invention is to provide a servo control device capable of increasing the recording capacity of a recording medium by compressing the servo area while reliably reading the information stored in the servo area.
[0026]
[Means for Solving the Problems]
As shown in FIG. 1, the AGC circuit 1 has different amplitudes read from an R / W recovery area, a servo mark area, an AGC area, and a phase detection area that constitute a servo area recorded on a recording medium. Is amplified so as to have a predetermined amplitude based on the AGC control voltage SG1. The filter circuit 3 removes unnecessary frequency components from the output signal SG2 of the AGC circuit 1. The A / D converter 4 performs A / D conversion on the output signal SG3 of the filter circuit 3. The AGC control circuit 11 generates an AGC signal SG8 for controlling the gain of the AGC circuit 1 based on the output signal SG4 of the A / D converter 4. The D / A converter 2 converts the AGC signal SG8 into an analog signal and outputs the analog signal to the AGC circuit 1 as an AGC control voltage SG1. Based on the amplitude ratio between the first input signal read from the R / W recovery region and the second input signal read from the AGC region or phase detection region, the read operation of the AGC region or phase detection region is performed. Prior to this, the AGC control circuit 11 includes a preceding control unit that outputs a control signal for generating the AGC signal corresponding to the AGC region or the phase detection region.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a first embodiment of a servo control apparatus embodying the present invention. This embodiment has the same configuration as the conventional example except for the AGC control circuit 11, and the same components are denoted by the same reference numerals, and detailed description thereof is omitted.
[0028]
The AGC control circuit 11 includes an error calculator 12, a multiplier 13, and an integrator 14, as shown in FIG.
The error calculator 12 is similarly provided in the AGC control circuit 6 of the conventional example, and receives the output signal SG4 of the A / D converter 4, the clock signal CLK, and the target value PA.
[0029]
Then, the error calculator 12 sequentially calculates an error between the digital signal sequentially input from the A / D converter 4 and the target value PA based on the clock signal CLK, and successively calculated two errors before and after. Are sequentially output to the multiplier 13 as an output signal SG6 based on the clock signal CLK.
[0030]
A specific configuration of the multiplier 13 will be described with reference to FIG. The multiplier 13 includes a multiplier 15 and a selector 16, and the multiplier 15 receives the output signal SG 6 of the error calculator 12 and the coefficient μ from the selector 16.
[0031]
The selector 16 is supplied with coefficient values C and D and an AGC high-speed pull-in signal W stored in advance in a register of the data reader. The coefficient values C and D are set so that C> D.
[0032]
As shown in FIG. 5, the high-speed pull-in signal W is an H-level pulse signal input from the CPU of the data reading device during the read operation of the R / W recovery area 7.
[0033]
The selector 16 outputs the coefficient value C as a coefficient μ to the multiplier 15 when the high-speed pull-in signal W is at the H level, and when the high-speed pull-in signal W is L level, the selector 16 sets the coefficient value D as the coefficient μ. Output to the multiplier 15.
[0034]
Accordingly, the multiplier 13 outputs an output signal SG7 obtained by multiplying the output signal SG6 of the error calculator 12 by the coefficient μ.
A specific configuration of the integrator 14 will be described with reference to FIG. The integrator 14 includes an adder 17, a flip-flop circuit 18, a multiplier 19, and a selector 20.
[0035]
The output signal SG7 of the multiplier 13 is input to the adder unit 17, and the output signal of the multiplier unit 19 is input to the adder unit 17.
The output signal of the adder 17 is input to the flip-flop circuit 18, and the flip-flop circuit 18 outputs the output signal of the adder 17 to the multiplier 19 based on the clock signal CLK.
[0036]
The multiplier 19 receives a coefficient NNN from the selector 20. The selector 20 is supplied with a servo mark detection signal V and coefficient values N and 1 stored in advance in a register.
[0037]
When the servo mark detection signal V is at the H level, the selector 20 outputs the coefficient value N to the multiplier 19 as the coefficient NNN. When the servo mark detection signal V is at the L level, the selector 20 sets the coefficient value 1 to the coefficient NNN. To the multiplication unit 19.
[0038]
The coefficient value N is a ratio between the amplitude of the input signal in when the R / W recovery region 7 is read and the amplitude of the input signal in when the AGC region 9 is read.
That is, the ratio between the amplitude of the input signal in when the R / W recovery region 7 is read and the amplitude of the input signal in when the AGC region 9 is read is constant and can be measured in advance.
[0039]
For example, if the amplitude of the input signal in when the AGC region 9 is read is n times the amplitude of the input signal in when the R / W recovery region 7 is read, the coefficient value N is set to 1 / n. Is done.
[0040]
The multiplier 19 multiplies the output signal of the flip-flop circuit 18 by a coefficient NNN and outputs an output signal SG8. The adder 17 adds the output signal SG7 of the multiplier 13 and the output signal SG8 of the multiplier 19 and outputs the result to the flip-flop circuit 18.
[0041]
With this configuration, the integrator 14 integrates the digital output signal SG8 obtained by integrating the digital output signal SG7 of the multiplier 13 or the digital output signal SG7 obtained by integrating the digital output signal SG7 of the multiplier 13 and N times the digital output signal SG8. / A output to the A converter 2 as an AGC signal.
[0042]
Next, the operation of the servo control apparatus configured as described above will be described with reference to FIG.
When a read operation of a servo area starting with a read operation of the R / W recovery area 7 is started during a read operation of a magnetic disk or the like, an H level servo area signal SAS is sent from the CPU controlling the data reading apparatus to the servo process. Input to the circuit 5.
[0043]
Along with the rise of the servo area signal SAS, an AGC high-speed pull-in signal W that is an H level pulse signal is input to the selector 16 of the multiplier 13.
When the input signal in is input with the amplitude and frequency corresponding to the R / W recovery region 7 at the first read time t1 shown in FIG. 18 by the start of the read operation of the R / W recovery region 7, the input The signal in is input to the A / D converter 4 via the AGC circuit 1 and the filter circuit 3.
[0044]
The A / D converter 4 outputs an output signal SG4 obtained by converting the output signal SG3 of the filter circuit 3 into a digital signal to the servo processing circuit 5 and the AGC control circuit 11.
[0045]
In the AGC control circuit 11, the error calculator 12 calculates an average value of errors between the digital output signal SG4 sequentially output from the A / D converter 4 and the target value PA, and the average value is used as the output signal SG6 as a multiplier. 13 are sequentially output.
[0046]
In the multiplier 13, when the AGC pull-in signal W at the H level is input to the selector 16, the coefficient μ input from the selector 16 to the multiplier 15 becomes a large coefficient value C, and the coefficient μ is input to the input signal SG6. Multiplication is performed and output as an output signal SG7.
[0047]
In the integrator 14, since the servo mark detection signal V is still at the L level, the integration operation of the input signal SG7 is performed with the coefficient NNN = 1, and the output signal SG8 is output to the D / A converter 2.
[0048]
The D / A converter 2 converts the digital input signal SG8 into an analog signal and outputs an AGC control voltage SG1 to the AGC circuit 1.
By such an operation, as shown in FIG. 5, when the read operation of the R / W recovery region 7 is started, the AGC control voltage SG1 changes abruptly based on the rising edge of the AGC high-speed pull-in signal W.
[0049]
Then, the output signal SG3 of the filter circuit 3 is converged so as to be almost full range with respect to the input level of the A / D converter 4, and the output signal SG4 of the A / D converter 4 is converged to the target value PA.
[0050]
Next, the read operation of the servo mark area 8 is started, and when the 0 level signal is continuously input to the AGC control circuit 11 h times, the output signal SG6 of the error calculator 12 is changed by the operation of the error calculator 12. 0.
[0051]
Then, the output signal SG8 of the AGC control circuit 11 becomes a constant level, and the AGC control voltage SG1 output from the D / A converter 2 becomes a constant level.
Next, when the servo mark detection signal V of H level is input from the servo processing circuit 5 to the selector 20 of the integrator 14 along with the read operation of the servo mark area 8, the coefficient NNN output from the selector 20 to the multiplier 19 is obtained. N is selected and output.
[0052]
Then, the output signal SG8 of the integrator 14 instantaneously decreases based on a preset ratio, and the AGC control voltage SG1 also instantaneously decreases to a constant level.
Next, when the read operation of the AGC region 9 is started and an input signal in having a large amplitude is input, the error calculator 12 detects an error between the output signal SG4 of the A / D converter 4 and the target value PA. Is done.
[0053]
However, the maximum value of the output signal SG4 of the A / D converter 4 is already close to the target value PA by the AGC control voltage SG1 set during the read operation of the AGC region 9.
[0054]
Then, the output signal SG3 of the filter circuit 3 has an amplitude close to the full range of the input level of the A / D converter 4.
Then, after the read operation of the AGC region 9 is completed, the read operation of the phase detection region 10 is started, and the data stored in the phase detection region 10 is converted into a digital signal with high accuracy by the A / D converter 4. It is output to the servo processing circuit 5.
[0055]
By such an operation, the integrator 14 constitutes a preceding control unit that outputs the output signal SG8 corresponding to the AGC region 9 in advance when the servo mark region 8 is read.
[0056]
With the servo control device configured as described above, the following operational effects can be obtained.
(1) The ratio of the amplitude of the input signal read from the R / W recovery area 7 and the amplitude of the input signal read from the AGC area 9 during the read operation of the servo mark area 8 prior to the read operation of the AGC area 9 Therefore, the AGC control voltage SG1 can be switched in advance, so that when the read operation of the AGC region 9 is started, the maximum value of the output signal SG4 of the A / D converter 4 is set to a value that approximates the target value PA. be able to.
(2) When the read operation of the AGC area 9 is started, the maximum value of the output signal SG4 of the A / D converter 4 can be set to a value that approximates the target value PA. In addition, the phase detection region 10 can be read with high accuracy. Further, even if the phase detection area 10 is provided subsequent to the servo mark area 8 without providing the AGC area 9, the phase detection data recorded in the phase detection area 10 can be read with high accuracy.
(3) Since the AGC area 9 can be reduced or omitted, the amount of data in the servo area can be reduced and the recording capacity of the data area can be increased, so that the recording capacity of the recording medium can be increased. it can.
(4) During the read operation of the R / W recovery region 7, the AGC control voltage SG1 is changed abruptly based on the input of the high-speed pull-in signal W to the multiplier 13, and the output signal SG4 of the A / D converter 4 Can be quickly brought close to the target value PA.
(Second embodiment)
FIG. 6 shows a second embodiment. In this embodiment, two types of target values PA1 and PA2 can be set in the error calculator 12 of the first embodiment, and the coefficient NNN inputted to the multiplier 19 of the integrator 14 is fixed to 1. The other configuration is the same as that of the first embodiment.
[0057]
That is, two types of target values PA1 and PA2 preset in a register or the like are input to the selector 21, and the servo mark detection signal V is input to the selector 21.
[0058]
If the servo mark detection signal V is L level, the selector 21 outputs the target value PA1 to the error calculator 12, and if the servo mark detection signal V is H level, the selector 21 calculates the error of the target value PA2. To the device 12.
[0059]
The target values PA1 and PA2 are set based on the ratio between the amplitude of the input signal in based on the read operation of the R / W recovery region 7 and the amplitude of the input signal in based on the read operation of the AGC region 9.
[0060]
The target value PA1 is set so that the output signal SG3 of the filter circuit 3 becomes the full range of the input level of the A / D converter 4 during the read operation of the R / W recovery region 7, for example, the R / W recovery region. 7 and the ratio of the amplitude of the input signal in from the AGC region 9 is 1: 2, the ratio between the target values PA1 and PA2 is set to 1: 2.
[0061]
The operation of the servo control apparatus configured as described above will be described with reference to FIG.
When the read operation of the R / W recovery area 7 is started, the servo mark detection signal V is at the L level, so that the selector 21 selects the target value PA1 and outputs it to the error calculator 12.
[0062]
Then, the AGC control voltage SG1 is changed by the operation of the AGC control circuit 11 based on the target value PA1, the average value of the output signal SG4 of the A / D converter 4 converges to the target value PA1, and the output of the filter circuit 3 The signal SG3 has a substantially full range with respect to the input level of the A / D converter 4. This operation is the same as in the first embodiment.
[0063]
Next, when the read operation of the servo mark area 8 is started, the output signal SG6 of the error calculator 12 is fixed to 0, and the AGC control voltage SG1 becomes a constant level. Next, when the servo mark detection signal V becomes H level, the target value input to the error calculator 12 is switched from PA1 to PA2.
[0064]
In this state, when the read operation of the AGC region 9 is started, the amplitude of the input signal in changes. However, since the target value has been previously switched to PA2, the output signal SG6 of the error calculator 12 is close to 0. The level of the AGC control voltage SG1 hardly changes.
[0065]
Then, after the read operation of the AGC region 9 is completed, the read operation of the phase detection region 10 is started in a state where the output signal SG3 of the filter circuit 3 is maintained at a substantially full range with respect to the input level of the A / D converter 4. Then, the data stored in the phase detection area 10 is converted into a digital signal with high accuracy by the A / D converter 4 and output to the servo processing circuit 5.
[0066]
By such an operation, the error calculator 12 constitutes a preceding control unit that outputs the output signal SG6 corresponding to the AGC region 9 in advance when the servo mark region 8 is read.
[0067]
In the servo control device of this embodiment, the following operational effects can be obtained, and among the operational effects obtained in the first embodiment, the operational effects obtained in (3) and (4). The same effect can be obtained.
(1) Based on the ratio of the amplitude of the input signal read from the R / W recovery area 7 and the amplitude of the input signal read from the AGC area 9 during the read operation of the servo mark area 8 prior to the read operation of the AGC area 9 Since the target value of the average value of the output signal SG4 of the A / D converter 4 can be switched from PA1 to PA2 in advance, when the read operation of the AGC area 9 is started, the output signal of the A / D converter 4 The average value of SG4 can be a value that approximates the target value.
(2) When the read operation of the AGC region 9 is started, the average value of the output signal SG4 of the A / D converter 4 can be set to a value approximating the target value PA1, so the AGC region 9 is reduced In addition, the phase detection region 10 can be read with high accuracy. Further, even if the phase detection area 10 is provided subsequent to the servo mark area 8 without providing the AGC area 9, the phase detection data recorded in the phase detection area 10 can be read with high accuracy.
(Third embodiment)
FIG. 8 shows a third embodiment. In this embodiment, the filter circuit 3 is switched during the read operation of the R / W recovery region 7 and during the read operation of the AGC region 9 by switching the cut-off frequency fc of the filter circuit 3 of the first embodiment. The output signal SG3 is set to almost the full range of the input level of the A / D converter 4.
[0068]
This utilizes the fact that the amplitude of the output signal SG3 of the filter circuit 3 changes when the cut-off frequency fc of the filter circuit 3 is switched.
That is, during the read operation of the R / W recovery region 7, the filter circuit 3 is operated at the first cut-off frequency fc1, and the amplitude of the output signal SG3 of the filter circuit 3 is the input level of the A / D converter 4. To be almost full range.
[0069]
Further, during the read operation of the AGC region 9 and the phase detection region 10, the filter circuit 3 is operated at the second cut-off frequency fc2, and the amplitude of the output signal SG3 of the filter circuit 3 is determined by the A / D converter 4. Make the input level almost full range.
[0070]
Further, switching between the first cutoff frequency fc1 and the second cutoff frequency fc2 is performed by the servo mark detection signal V as in the first and second embodiments.
[0071]
Further, the switching means for the cut-off frequencies fc1 and fc2 of the filter circuit 3 can be easily performed by switching the circuit constants in the same manner as in a normal filter circuit.
In the servo control circuit of this embodiment, the following operational effects can be obtained, and among the operational effects obtained in the first embodiment, the operational effects obtained in (3) are the same. An effect can be obtained.
(1) Based on the ratio of the amplitude of the input signal read from the R / W recovery area 7 and the amplitude of the input signal read from the AGC area 9 during the read operation of the servo mark area 8 prior to the read operation of the AGC area 9 Since the cutoff frequency of the filter circuit 3 can be switched in advance, when the read operation of the AGC region 9 is started, the output signal SG3 of the filter circuit 3 becomes almost the full range of the input level of the A / D converter 4. Can be set as follows.
(2) When the read operation of the AGC region 9 is started, the output signal SG3 of the filter circuit 3 can be set to almost the full range of the input level of the A / D converter 4, so that even if the AGC region 9 is reduced, The phase detection region 10 can be read with high accuracy. Further, even if the phase detection area 10 is provided subsequent to the servo mark area 8 without providing the AGC area 9, the phase detection data recorded in the phase detection area 10 can be read with high accuracy.
(Fourth embodiment)
FIG. 9 shows the operation of the servo control circuit of the fourth embodiment. In this embodiment, the read operation of each of the servo regions 7, 8, 9, 10 is performed with the coefficient value input to the multiplier 19 of the integrator 14 of the first embodiment being 1. Do.
[0072]
Then, in the R / W recovery area 7 and the AGC area 9, the output signal SG 8 of the AGC control circuit 11 is fetched by the CPU and latched by the latch signal LA output at the timing when the AGC control voltage converges to a constant level.
[0073]
Then, the output voltage SG8 of the AGC control circuit 11 when the output signal SG4 of the A / D converter 4 converges to the target value PA in each of the regions 7 and 9 can be latched. Then, the target value output to the error calculator 12 is switched by firmware preset in the CPU based on the latch data so that the ACG control voltage SG1 is switched at high speed when the servo area is switched.
[0074]
By adopting such a configuration, the servo area can be reduced as in the above-described embodiment.
(Fifth embodiment)
10 to 12 show a fifth embodiment. In this embodiment, the frequency of the output signal SG8 of the integrator 14 of the AGC control circuit 11 when the operation speed of the D / A converter 2 of each of the embodiments cannot catch up with the operation speed of the AGC control circuit 11 is described. Is adapted to the operating frequency of the D / A converter 2.
[0075]
As shown in FIG. 10, the output signal SG8 of the integrator 14 is input to the flip-flop circuit 22. The clock signal CLK input to the integrator 14 is divided by two by the frequency divider 23 and input to the flip-flop circuit 22 as the clock signal CK.
[0076]
Each time the clock signal CK is input, the flip-flop circuit 22 takes in the output signal SG8 of the integrator 14 and outputs it as an output signal SG9 to the D / A converter 2.
[0077]
With such a configuration, the output signal SG8 of the integrator 14 shown in FIG. 11 is output from the flip-flop circuit 22 as the output signal SG9 shown in FIG. Then, the output signal SG9 of the flip-flop circuit 22 is converted into an AGC control voltage SG1 of an analog signal by the D / A converter 2 and output to the AGC circuit 1.
[0078]
By such an operation, even when the operation speed of the D / A converter 2 is slower than the operation speed of the AGC control circuit 11, the output signal SG8 of the AGC control circuit 11 is halved by the flip-flop circuit 22. Can be converted to an AGC control voltage SG 1 by the D / A converter 2 and output to the AGC circuit 1.
[0079]
Further, although the conversion accuracy for converting the output signal SG8 of the AGC control circuit 11 into the AGC control voltage SG1 is lowered, there is substantially no problem if the operation speed of the AGC circuit 1 is taken into consideration.
(Sixth embodiment)
FIG. 13 shows a sixth embodiment. This embodiment shows a circuit for calculating the coefficient N input to the selector 20 of the integrator 14 in the first embodiment.
The input signal in is input to the absolute value calculation unit 24. The absolute value calculation unit 24 generates an absolute value of the amplitude of the input signal “in” input as an analog value, and outputs the absolute value to the first and second average value calculation units 25 and 26.
[0080]
The first average value calculation unit 25 calculates an average value of the input signal in based on the read operation of the R / W recovery region 7, and includes an addition unit 27a, a flip-flop circuit 28a, a counter 29a, and a division unit 30a. It consists of.
[0081]
The input signal in is input to the adder 27a, and the output signal of the adder 27a is input to the flip-flop circuit 28a. The flip-flop circuit 28a receives the clock signal CLK, and latches and outputs the output signal of the adder 27a based on the clock signal CLK.
[0082]
The output signal of the flip-flop circuit 28a is input to the dividing unit 30a and to the adding unit 27a. Accordingly, the adder 27a and the flip-flop circuit 28a perform an integration operation similar to that of the adder 17 and the flip-flop circuit 18 of the integrator 14.
[0083]
The clock signal CLK is input to the counter circuit 29a. The counter 29a counts the clock signal CLK and outputs the count value to the division unit 30a.
[0084]
A reset signal RS1 is input to the counter circuit 29a. As shown in FIG. 14, the reset signal RS1 is input when the servo mark detection signal V becomes H level, and is canceled when the reading operation of the phase detection region 10 is completed.
[0085]
The division unit 30a calculates and outputs an average value A of the input signal in by dividing the integral value output from the flip-flop circuit 28a by the count value counted by the counter 29a.
[0086]
With such a configuration, the first average value calculation unit 25 calculates and outputs the average value A of the amplitude of the input signal in based on the read operation of the R / W recovery region 7.
The second average value calculator 26 has the same configuration as the first average value calculator 25 except that the reset signal RS2 is input to the counter 29b.
[0087]
As shown in FIG. 14, the reset signal RS2 is input based on the end of the reading operation of the phase detection region 10, and is released after a predetermined time after the servo mark detection signal V becomes H level.
[0088]
With such a configuration, the second average value calculation unit 26 calculates and outputs the average value B of the amplitude of the input signal in based on the reading operation of the AGC region 9 and the phase comparison region 10.
[0089]
The first recording signal RA shown in FIG. 14 is a signal for taking the average value A calculated by the first average value calculation unit 25 into a register or the like, and the second recording signal RB is a second average signal. This is a signal for taking the average value B calculated by the value calculation unit 26 into a register or the like.
[0090]
The signals RA and RB can be generated by a counter that counts the number of samples since the length (number of samples) of each region in which the reading operation is performed is known in advance.
[0091]
Next, the amplitude ratio between the R / W recovery region 7 and the phase detection region 10 can be calculated based on the average values A and B thus calculated, and the amplitude ratio is stored in the register as the coefficient N. do it.
[0092]
With the configuration and operation as described above, the coefficient N can be calculated and stored in a register.
In FIG. 14, the first and second average value calculation units 25 and 26 can be shared if there is no period in which both the reset signals RS1 and RS2 are at the H level.
(Seventh embodiment)
FIG. 15 shows a seventh embodiment. In this embodiment, the servo mark detection signal V is generated by the sample number counter 31, and the other configuration is the same as that of the first embodiment.
[0093]
That is, in the servo mark area 8, the length of the area (number of samples) is known in advance, and usually there are about 30 to 40 samples.
Then, the number of samples is counted by the sample number counter 31 during the read operation of the servo mark area 8, and when the predetermined number of samples is counted, the servo number detection signal V is output from the sample number counter 31 to the AGC control circuit 11. To do. With such a configuration, the servo mark detection signal V can be generated.
[0094]
Further, since the output timing of the servo mark detection signal V is not required to be so strict, the clock signal CLK for operating the sample number counter 31 is a clock signal CLK obtained by dividing a normal sample clock by n, for example, by 8. Also good.
[0095]
With such a configuration, a counter with a low operating speed can be used, and the number of bits of the counter can be reduced, so that the circuit area can be reduced.
[0096]
(Supplementary note 1) An AGC circuit that amplifies input signals having different amplitudes read from a plurality of areas in a servo area recorded on a recording medium so as to have predetermined amplitudes based on an AGC control voltage;
A filter circuit for removing unnecessary frequency components from the output signal of the AGC circuit;
An A / D converter for A / D converting the output signal of the filter circuit;
An AGC control circuit that generates an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter;
A D / A converter for converting the AGC signal into an analog signal and outputting the analog signal as an AGC control voltage;
A servo control device comprising:
Based on the amplitude ratio of the input signal read from each area in the servo area, a prior control unit is provided that outputs a control signal for generating the AGC signal corresponding to the area prior to the read operation of each area. Servo control device characterized by that. (1)
(Supplementary note 2) An AGC control voltage is used to input input signals of different amplitudes read from the R / W recovery area, the servo mark area, the AGC area, and the phase detection area constituting the servo area recorded on the recording medium. An AGC circuit that amplifies to a predetermined amplitude based on
A filter circuit for removing unnecessary frequency components from the output signal of the AGC circuit;
An A / D converter for A / D converting the output signal of the filter circuit;
An AGC control circuit that generates an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter;
A D / A converter for converting the AGC signal into an analog signal and outputting the analog signal as an AGC control voltage;
A servo control device comprising:
Based on the amplitude ratio between the first input signal read from the R / W recovery region and the second input signal read from the AGC region or phase detection region, the read operation of the AGC region or phase detection region is performed. A servo control device comprising a preceding control unit that outputs a control signal for generating the AGC signal corresponding to the AGC region or the phase detection region in advance. (2)
(Supplementary note 3) The servo according to supplementary note 2, wherein the preceding control unit is provided with a switching unit in the AGC control circuit for switching the AGC signal based on the amplitude ratio during a read operation of the servo mark area. Control device. (3)
(Supplementary Note 4) The AGC control circuit includes:
An error calculator for calculating an error between the output signal of the A / D converter and a target value set in advance so that the output signal of the filter circuit is in a full range with respect to the input level of the A / D converter; ,
A multiplier for multiplying an output signal of the error calculator by a first coefficient set in advance;
An integrator that integrates the output signal of the multiplier to generate the AGC signal;
The switching unit is configured by the integrator that performs an integration operation by multiplying the second coefficient based on an input of the second coefficient based on the amplitude ratio during a read operation of the servo mark area. The servo control device according to appendix 3. (4)
(Supplementary Note 5) The second coefficient is a ratio of the average value of the amplitude of the input signal based on the read operation of the R / W recovery region and the average value of the amplitude of the input signal based on the read operation of the AGC region. The servo control device according to appendix 4, wherein the servo control device is calculated by a calculation circuit. (5)
(Supplementary Note 6) The AGC control circuit includes:
An error calculator for calculating an error between the output signal of the A / D converter and a target value set in advance so that the output signal of the filter circuit is in a full range with respect to the input level of the A / D converter; ,
A multiplier for multiplying the output signal of the error calculator by a preset coefficient;
An integrator that integrates the output signal of the multiplier to generate the AGC signal;
4. The servo control apparatus according to claim 3, wherein the switching unit includes an error calculator that switches the target value based on the amplitude ratio during a read operation of the servo mark area. (6)
(Supplementary Note 7) A counter that outputs a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided, and the AGC signal is output by the switching unit based on the servo mark detection signal. 4. The servo control device according to appendix 3, wherein switching is performed.
[0097]
(Supplementary Note 8) A counter that outputs a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided, and a second output is generated by the integrator based on the servo mark detection signal. 5. The servo control device according to appendix 4, wherein an integral operation multiplied by a coefficient is performed.
[0098]
(Supplementary Note 9) A counter that outputs a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided, and the target value is switched based on the servo mark detection signal. The servo control device according to appendix 6, which is characterized.
[0099]
(Supplementary note 10) The preceding control unit is configured by a filter constant switching device that switches a cutoff frequency of the filter circuit based on the amplitude ratio during a read operation of the servo mark area. Servo control device. (7)
(Supplementary Note 11) A counter that outputs a servo mark detection signal when a predetermined number of samples are counted during the read operation of the servo mark area is provided, and based on the servo mark detection signal, a cutoff frequency of the filter circuit is provided. 11. The servo control device according to appendix 10, wherein the servo control device is switched.
[0100]
(Supplementary note 12) The servo control device according to any one of supplementary notes 4 to 6, wherein the multiplier selects a large value as the first coefficient based on an AGC high-speed pull-in signal. (8)
(Supplementary Note 13) A frequency conversion circuit for adapting the frequency of the output signal of the AGC control circuit to the operating frequency of the D / A converter is provided between the AGC control circuit and the D / A converter. The servo control device according to any one of appendices 1 to 12, characterized in that: (10)
(Supplementary note 14) Input signals of different amplitudes read from the R / W recovery area, the servo mark area, the AGC area, and the phase detection area that constitute the servo area recorded on the recording medium are converted into AGC control voltages. Is amplified by the AGC circuit so as to have a predetermined amplitude, the unnecessary frequency component is removed by the filter circuit from the output signal of the AGC circuit, and then the output signal of the filter circuit is A / D converted by the A / D converter. Based on the output signal of the A / D converter, an AGC signal for controlling the gain of the AGC circuit is generated by the AGC control circuit, and the AGC signal is converted into an analog signal by the D / A converter, A servo control method for outputting an AGC control voltage to the AGC circuit,
Based on the amplitude ratio between the first input signal read from the R / W recovery region and the second input signal read from the AGC region or phase detection region, the read operation of the AGC region or phase detection region is performed. A servo control method characterized by generating the AGC signal corresponding to the AGC region or the phase detection region in advance. (9)
(Supplementary Note 15) The AGC signal at the time of the read operation of the R / W recovery area and the AGC signal at the time of the read operation of the AGC area are captured and stored in advance, and the AGC signal is generated by firmware based on the storage result 15. The servo control method according to appendix 14, characterized by:
[0101]
【The invention's effect】
As described in detail above, the present invention can provide a servo control apparatus that can compress the servo area and increase the recording capacity of the recording medium while reliably reading the information stored in the servo area. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment.
FIG. 2 is a block diagram showing an AGC control circuit.
FIG. 3 is a block diagram illustrating a multiplier.
FIG. 4 is a block diagram showing an integrator.
FIG. 5 is a timing waveform chart showing the operation of the first embodiment.
FIG. 6 is a block diagram showing a second embodiment.
FIG. 7 is a timing waveform chart showing the operation of the second embodiment.
FIG. 8 is a timing waveform chart showing the operation of the third embodiment.
FIG. 9 is a timing waveform chart showing the operation of the fourth embodiment.
FIG. 10 is a block diagram showing a fifth embodiment.
FIG. 11 is a waveform diagram showing the operation of the fifth embodiment.
FIG. 12 is a waveform diagram showing the operation of the fifth embodiment.
FIG. 13 is a block diagram showing a sixth embodiment.
FIG. 14 is a timing waveform chart showing a sixth embodiment.
FIG. 15 is a block diagram showing a seventh embodiment.
FIG. 16 is a block diagram showing a conventional example.
FIG. 17 is an explanatory diagram showing a servo area.
FIG. 18 is a waveform diagram showing an input signal.
FIG. 19 is a timing waveform diagram showing an operation of a conventional example.
[Explanation of symbols]
1 AGC circuit
2 D / A converter
3 Filter circuit
4 A / D converter
11 AGC control circuit

Claims (10)

An AGC circuit that amplifies input signals having different amplitudes read from a plurality of areas in a servo area recorded on a recording medium so as to have a predetermined amplitude based on an AGC control voltage;
A filter circuit for removing unnecessary frequency components from the output signal of the AGC circuit;
An A / D converter for A / D converting the output signal of the filter circuit;
An AGC control circuit that generates an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter;
A servo control device including a D / A converter that converts the AGC signal into an analog signal and outputs the analog signal to the AGC circuit as an AGC control voltage;
Based on the relationship that the amplitude ratio of input signals read from a plurality of areas in the servo area is constant, a control signal for generating the AGC signal corresponding to the area is output prior to the read operation of each area. A servo control device comprising a preceding control unit. Input signals having different amplitudes read from the R / W recovery area, the servo mark area, the AGC area, and the phase detection area constituting the servo area recorded on the recording medium are determined based on the AGC control voltage. An AGC circuit that amplifies the amplitude to
A filter circuit for removing unnecessary frequency components from the output signal of the AGC circuit;
An A / D converter for A / D converting the output signal of the filter circuit;
An AGC control circuit that generates an AGC signal for controlling a gain of the AGC circuit based on an output signal of the A / D converter;
A servo control device including a D / A converter that converts the AGC signal into an analog signal and outputs the analog signal to the AGC circuit as an AGC control voltage;
Based on the amplitude ratio between the first input signal read from the R / W recovery region and the second input signal read from the AGC region or phase detection region, the read operation of the AGC region or phase detection region is performed. A servo control device comprising a preceding control unit that outputs a control signal for generating the AGC signal corresponding to the AGC region or the phase detection region in advance. 3. The servo control apparatus according to claim 2, wherein the preceding control unit is provided with a switching unit that switches the AGC signal based on the amplitude ratio during a read operation of the servo mark area in the AGC control circuit. The AGC control circuit includes:
An error calculator for calculating an error between the output signal of the A / D converter and a target value set in advance so that the output signal of the filter circuit is in a full range with respect to the input level of the A / D converter; ,
A multiplier for multiplying an output signal of the error calculator by a first coefficient set in advance;
An integrator that integrates the output signal of the multiplier to generate the AGC signal;
The switching unit is configured by the integrator that performs an integration operation by multiplying the second coefficient based on an input of the second coefficient based on the amplitude ratio during a read operation of the servo mark area. The servo control device according to claim 3. The second coefficient is calculated by a coefficient calculation circuit that calculates a ratio between the average value of the input signal amplitude based on the read operation in the R / W recovery region and the average value of the input signal amplitude based on the read operation in the AGC region. 5. The servo control device according to claim 4, wherein The AGC control circuit includes:
An error calculator for calculating an error between the output signal of the A / D converter and a target value set in advance so that the output signal of the filter circuit is in a full range with respect to the input level of the A / D converter; ,
A multiplier for multiplying the output signal of the error calculator by a preset coefficient;
An integrator that integrates the output signal of the multiplier to generate the AGC signal;
4. The servo control apparatus according to claim 3, wherein the switching unit includes an error calculator that switches the target value based on the amplitude ratio during a read operation of the servo mark area. 3. The servo control device according to claim 2, wherein the preceding control unit is configured by a filter constant switching device that switches a cutoff frequency of the filter circuit based on the amplitude ratio during a read operation of the servo mark area. . 7. The servo control device according to claim 4, wherein the multiplier selects the coefficient having a large value based on an AGC high-speed pull-in signal. Input signals having different amplitudes read from the R / W recovery area, the servo mark area, the AGC area, and the phase detection area constituting the servo area recorded on the recording medium are determined based on the AGC control voltage. The AGC circuit amplifies the signal so that the amplitude becomes the same as that of the AGC circuit. The filter circuit removes unnecessary frequency components from the AGC circuit output signal, and the A / D converter converts the output signal of the filter circuit to Based on the output signal of the converter, an AGC signal for controlling the gain of the AGC circuit is generated by the AGC control circuit, the AGC signal is converted into an analog signal by the D / A converter, and the AGC circuit A servo control method for outputting as an AGC control voltage,
Based on the amplitude ratio between the first input signal read from the R / W recovery region and the second input signal read from the AGC region or phase detection region, the read operation of the AGC region or phase detection region is performed. A servo control method characterized by generating the AGC signal corresponding to the AGC region or the phase detection region in advance. A frequency conversion circuit is provided between the AGC control circuit and the D / A converter to adapt the frequency of the output signal of the AGC control circuit to the operating frequency of the D / A converter. The servo control device according to any one of claims 1 to 8.

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