JPH03145311A - Peak holding circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] A peak hold circuit that has a peak hold means that holds the peak value of a servo signal whose amplitude changes due to changes in the position of a controlled object, and which maintains an accurate peak even if the signal is distorted. In the peak hold circuit as described above, full wave rectification means for full wave rectification of one servo signal and another servo signal is provided before the peak hold means. It consists of:

[Industrial application field]

The present invention relates to a peak hold circuit, and more particularly, to a peak hold circuit having a peak hold means for holding the peak value of a servo signal whose amplitude changes due to changes in the position of a controlled object.

[Conventional technology]

Generally, there are the following types of peak hold circuits. This is provided, for example, in a servo control device for a magnetic head of a magnetic disk device, and is included in a demodulation circuit 12 that demodulates a servo signal from a disk enclosure (DE) 11, as shown in FIG. . The servo signal demodulated by this demodulation circuit 12 is sent to an AD converter 13.
The digitized signal is processed by a processor 14, converted into an analog signal by a DA converter 15, and is input to a drive circuit 16 for a voice coil motor that moves a magnetic head based on this signal.

In this servo control, as shown in Figures 6 and 9, the servo heads read the servo information recorded on two adjacent servo tracks, and peak the maximum value of these values (voltage). The hold circuit holds the signals, and the comparison circuit compares the maximum positive voltage values of both signals.The point where the voltage values of both signals are equal is the position where the other read/write head is correctly on track (on-track). It is determined that In this example, four types of servo signals, ie, N, N, Q, and O signals, are written on each servo surface as shown in FIG. 6, and as shown in FIG. When the head is at the position, the N signal that has signals written on both tracks read by this head is large regardless of the movement of the head, and the N signal that has no servo signals written on both tracks is at the position of the head. It will be 0 regardless. Then, Q is not written on track 1 but only on track 2, and conversely, Q is written only on track 1 and not on track 2, so the head is in the center of both tracks (6th In the on-track state located at A) in the figure, the waveforms of Q and the mouth are equal, and the peak values held by the peak hold circuit are equal.

Here, when the head is shifted in the middle direction (upward direction) in Figure 6, the portion of the entire head gap that spans track 1 increases, the amplitude of the rotation becomes larger than Q, and the peak hold circuit The voltage held is also higher in times than in Q. On the other hand, when the head is shifted in the J direction (downward) in Figure 6, the portion of the total head gap length that spans track 2 increases, and the amplitude of Q becomes larger than before, which is held by the peak hold circuit. The voltage applied is also higher in Q than in Q. Therefore, by comparing these peak values with a comparator, the position of the servo head (that is, the read/write head that is interlocked with the servo head) can be controlled.

Here, there are four types of signals N, N, Q, ? ) is used to perform position control because the four adjacent tracks can be recognized by writing different patterns of signals for each of the four adjacent tracks. The head positions at this time are shown as head B, head C, and head D in FIG. 6, and the read waveforms at these positions are shown at the corresponding positions.

By the way, there is a conventional peak hold circuit used in such a device as shown in FIG. This is included in the demodulation circuit that demodulates the servo signal from the disk enclosure (DE), and converts the signal input to the differential amplifier 21 into an AGC (auto gain controller).
The signal is amplified under control from 22, and is inputted via the pulse area detector 23 and through the window shown in FIG. 9. Output A.

From B, C, D, respectively, N, N, as shown in FIG.
A signal in which the peaks of Q and W are held is generated. And these signals are each A.

The signals are input to operational amplifiers 25 and 26 corresponding to B, C, and D, and the difference thereof is output. As described above, this output is digitized by the A-D converter, processed by the processor, and then converted to analog by the DA converter, and then passed through the voice motor drive circuit to drive the voice coil motor that drives the head.

Specifically, this sample and hold circuit is provided for each signal, and as shown in FIG. 8, the voltage is finally held by a capacitor 31 and this value is output. Further, this sample and hold circuit receives a signal corresponding to the window from the gate 32, and the gate voltage is set to O.
When the voltage becomes V, the transistor Tri is turned on, a bias is applied to the transistor Tr2, the input waveform is amplified, and the capacitor 31 is charged with this voltage value. When charging is completed, the battery is discharged according to a time constant determined by the resistor 32, and charging is started at the next timing.

As a result, the peak voltage of each signal is maintained at a constant time constant as shown in FIG.

As a result, the values of N, N, Q, and u are compared, and the movement of the servo head is controlled.

(Problems to be Solved by the Invention) As described above, in the conventional peak hold circuit, the peak values of the signals N, N, and Q are held at the maximum positive value.

However, if the signal is distorted due to disturbance etc., the peak value may drop, and in such cases it is not possible to perform accurate peak hold, and furthermore, the peak value cannot be accurately controlled. The problem is that you can't control your body.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a peak hold circuit that can perform accurate peak hold even if a signal is distorted.

[Means to solve the problem]

In the present invention, means for solving the above problems are as follows:
As shown in FIG. 1, in a peak hold circuit having a peak hold means 1 for holding the peak value of a servo signal whose amplitude changes due to a change in the position of a controlled object, all servo signals are input to the stage before the peak hold means 1. 2. Full-wave rectifying means 2 for rectifying waves is provided.

[Effect]

According to the present invention, since the input signal is full-wave rectified by the full-wave rectification means provided before the peak hold means, even if the input signal is distorted due to disturbance, the input signal will be on the positive side and the positive side after being inverted. Since either higher peak value on the negative side is held in the peak hold means, an accurate peak value can be held.

〔Example〕

Embodiments of the peak hold circuit according to the present invention will be described below with reference to the drawings.

2 to 4 show embodiments of the peak hold circuit according to the present invention. In this embodiment, the configuration is the same as that of a conventional peak hold device except that a full wave rectifier 40 is provided before the peak hold means 41, so the same means are given the same reference numerals and a detailed explanation thereof will be given. is omitted.

In this embodiment, the full-wave rectifier means uses a full-wave rectifier circuit in which four diodes 41, 42, 43, and 44 are combined in a bridge, as shown in FIG. 3, for example. According to this full-wave rectifier circuit, an AC signal applied to a terminal is full-wave rectified and appears as a positive signal. This signal is input to the peak hold circuit shown in the conventional example.

FIG. 4 shows the servo signal and window signal that have passed through this full-wave rectifier circuit. The servo signal input in this way has two peaks for one signal,
The peak hold circuit holds the higher peak value of these two peaks. That is, in a peak hold circuit, the means that actually holds the peak value is a capacitor, and generally such a capacitor holds its highest voltage when it is charged multiple times.

Therefore, according to this embodiment, even if distortion occurs in the servo signal due to disturbance etc., if the effect of the distortion only affects the waveform on one side of the servo signal, the peak value to be held is is the higher of the two peaks, and its peak value is maintained normally.

In the above embodiment, a magnetic disk device was used as an example of the disk device, but it goes without saying that the present invention can also be applied to other disk devices such as an optical disk device.

〔Effect of the invention〕

As explained above, according to the present invention, a full-wave rectifier circuit for full-wave rectifying the servo signal is provided before the peak-hold means of the peak-hold circuit, so that even if distortion occurs in the servo signal due to disturbance etc., the full-wave rectifier circuit is provided. When the distortion effect only affects the waveform on one side of the servo signal, the peak value held will be the higher of the two signals, and the peak value will be held normally and accurately. This has the effect that it is possible to perform accurate servo control.

3... Comparator

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of the present invention, FIG. 2 is a block diagram showing an embodiment of the peak hold circuit according to the present invention, and FIG.
Figure 4 is a timing chart showing the operation of the peak hold circuit example shown in Figure 2, and Figure 5 is a magnetic disk drive circuit. A block diagram showing the servo circuit of the device, FIG. 6 is a diagram showing the state of the servo surface of the magnetic disk device and read signals, FIG. 7 is a diagram showing a conventional peak hold circuit, and FIG. 8 is a diagram showing a conventional peak hold circuit. FIG. 9 is a timing chart showing the operation of a conventional peak hold circuit. l...Peak hold means 2...Full wave rectifier circuit Principle of the present invention No. 11! 13
The 51st episode of Mf Zuichijiru Zeta Rode! I End of the story / 1 company attached / Go No. 71! 1

Claims (1)

[Claims] In a peak hold circuit having a peak hold means (1) for holding the peak value of a servo signal whose amplitude changes due to a change in the position of a controlled object, A peak hold circuit characterized by being provided with full-wave rectification means (2) for full-wave rectification of a servo signal and other servo signals.