KR100215200B1 - Capstan servo circuit of digital vcr - Google Patents

Abstract

The present invention relates to a digital VSR capstan servo circuit. The digital V-Cal's capstan servo circuit includes: a band pass filter unit for extracting the front and rear parts of the track from the output signal of the playhead; and amplifying a difference signal between two signals from the band pass filter to generate an error signal. A differential amplifying unit; and a signal processing unit configured to output an error signal generated by the differential amplifying unit by performing sample holding and amplification processing; And a capstan control unit for controlling the processing operation of the signal processing unit and the capstan driving signal generation operation of the capstan driving unit so as to accurately trace the reproduction head with respect to the tape track.

Description

Digital VCA's Capstan Servo Circuit

1 is a configuration diagram of a capstan servo circuit of a conventional analog VR.

2 is a block diagram of a capillary servo circuit of a digital BC in accordance with a preferred embodiment of the present invention.

3 is a timing diagram according to a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

210: head 211: band-pass filter

214: differential amplifier 220: capstan controller

221: microcomputer 240: capstan drive unit

250: capstan motor

Detailed description of the invention

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to digital VRCs, and more particularly, to a digital VCE capstan servo circuit that performs tape travel control so that a video track can be traced by a video head during playback.

In the general home video system (KlS), V-RA is used for recording and reproducing the video signal by the rotating head method; In order to obtain a clear screen, it is necessary to precisely control the rotation speed and rotation phase of the video head, and the driving speed of the tape, and the servo circuit is used for this purpose.

The capstan servo circuit performs the tape travel control so that the running speed of the tape is kept constant during recording and the video track is accurately traced by the video head during playback.

1 shows a typical analog VSR capstan servo circuit.

The analog VSR capstan servo circuit includes a control head 110. In general, the analog track forms a control track on the lower edge of the tape in the longitudinal direction of the tape during recording. At the time of reproduction, this control track is scanned by the control head 11, and the reproduction of the pilot (pi1ot) signal is performed by this scanning.

The analog VSR capstan servo circuit also includes a comparator 120. This comparator 120 is connected to the output of the control head 110. Therefore, the blood ilutsin reproduced by the control head 110 during the regeneration is input to the comparator 120. The comparator 120 generates an error signal by comparing the pilot signal of the loader to the control head 110 with a predetermined reference signal Vref.

The analog VSR capstan servo circuit also includes a microcomputer 130. The microcomputer 130 is connected to the output side of the comparator 120, and generates and outputs a pulse width modulated signal PW according to an error signal input from the comparator 130.

The analog VSR capstan servo circuit also includes a low pass filter 140. The low pass filter 140 is connected to the output side of the micro point computer 130, and extracts only the low pass component of the pulse width modulation signal PW input from the microcomputer 130 and outputs it as a capstan driving signal. The capstan driving signal output from the low pass filter 140 is provided to the capstan motor 150, and the tape running control is performed by the provision so that the video track is accurately traced by the video head (not shown).

However, in the conventional analog VSR capstan servo circuit of such a configuration, since the running speed of the tape is judged based on a weak signal read from the center portion of the track, the accuracy of the determination of the driving speed of the tape itself is inferior. Therefore, the table driving control becomes unstable, so that the video track is not accurately traced by the video head, and accordingly, there is a problem that a clean image is not obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a digital VSR capstan servo circuit which performs tape running control so that a non-t1 track is accurately traced by a playhead.

The capstan servo circuit of the present invention includes a band pass filter, a differential amplifier, a signal processor, a capstan driver, and a capstan controller. This bandpass filter unit extracts the front and rear signals of the track from the output signal of the playhead.

The differential amplifier amplifies the difference signal between the two signals input from the band pass filter to generate an error signal.

The signal processor outputs the error signal generated by the differential amplifier by performing sample holding and amplification.

The capstan driver supplies the capstan motor with the capstan driving signal obtained by inverting or non-inverting the error signal output from the synth processor.

The capstan control unit controls the processing operation of the signal processing unit and the capstan driving signal generation operation of the capstan driving unit so as to accurately trace the playhead with respect to the video track of the tape.

According to the present invention having such a configuration, since the video track of the dape is accurately traced by the playhead, a clear image is obtained.

There may be a plurality of embodiments of the present invention, the following describes the preferred embodiment in detail. This preferred embodiment enables a better understanding of the objects, features and advantages of the present invention.

2 shows a capstan servo circuit of a digital VC according to a preferred embodiment of the present invention.

The capstan servo circuit of the digital VC according to the present exemplary embodiment includes a band pass filter unit 211. The band pass filter 211 includes a first band pass filter 212 and a second band pass filter 213 connected to the output side of the head 210, respectively. 212 and the second band pass filter 213 extract the front and rear parts of the track from the output signal of the head 21. The first band pass filter 212 and the second band pass filter 213 are extracted. Has a cutoff frequency for this extraction.

The digital VCS capstan servo circuit according to the present preferred embodiment also includes a differential amplifier 214. The differential amplifier 214 is connected to the output side of the first and second band pass filters 212 and 213. The differential amplifier 214 amplifies the difference between two signals inputted from the first and second band pass filters 212 and 213. It generates a signal.

The digital VCS capstan servo circuit of the present invention also includes a signal processing section including first and second sample holding sections 231 and 232 and differential amplifier 233 and third sample holding section 234. The first sample holding part 231 includes a first switch SW1 and a first capacitor C1, and the second sample holding part 232 includes a second switch SW2 and a second capacitor C2. The third sample holder 234 is configured of a third switch SW3 and a third capacitor C3. The differential amplifier 233 is provided between the first and second sample holding portions 231 and 232 and the third sample holding portion 234.

The digital VCS capstan servo circuit according to the present preferred embodiment also includes a capstan control unit 220 composed of a switching switch SW0, a fourth capacitor C4 and a microcomputer 221. The capstan control unit 220 having such a configuration controls the processing operation of the signal processing unit and the driving signal generation operation of the capstan driving unit 210 described later according to the tape traveling speed, which will be described with reference to FIG. 3.

3 is a timing diagram according to the present preferred embodiment. When the running speed of the tape is correct, the microcomputer 221 uses the first and second sample holding portions as shown in (b) and (c) based on the head switching signal (HSW) shown in (a) of FIG. 231, 232). That is, a control is made to turn on the first sample holding part 231 at the rising edge of one pulse and the falling edge of the next pulse of the head switching signal HSW, and at the same time, the head switching signal HSW. The second sample holding unit 232 is turned on at the falling edge of one pulse and the rising edge of the next one. According to this control, the first and second sample holders 231 and 232 sample and hold the error signals input from the differential amplifier 214 and provide them to the differential amplifier 233.

The differential amplifier 233 amplifies the difference between the two signals from the first and second sample holders 231 and 232 and outputs the crab three sample holder 234. At this time, the third switch SW3 of the third sample holder 234 is turned on at the falling edge of each pulse of (d) of FIG. 3 and the trapped head switching signal HSW. Under control.

The capstan servo circuit of the present invention digital VR also includes a capstan driving unit 240. The capstan driver 240 includes inverters R, R, A3 and a fourth switch SW4. The signal output from the third sample holder 234 is input to the capstan driver 240. The capstan driving unit 240 has two routes, one of which is a route for directly transferring the output of the third sample head portion 234 to the capstan motor 250, and the other of the third sample holding portion 234. Route to reverse the output. Selection of one of these two routes is performed by switching the fourth switch SW4 under the control of the microcomputer 221. The inverters R, R and A3 are provided for the inversion; the inverter consists of two resistors R and R having the same resistance value and an operational amplifier A3.

When the running speed of the tape is high, the microcomputer 221 controls the capstan driving unit 240, more specifically, the fourth switch SW4, as shown in FIG. 3 (e). Through switching of the fourth switch SW4; The capstan driving signal for causing the video track to be traced by the playhead is generated and provided to the capstan motor 250.

On the other hand, when the running speed of the tape is slow, the microcomputer 221 holds the first and second sample holders, unlike when the air cooling speed of the trapped dape is fast as shown in Figs. By changing and controlling the sections 231 and 232, the video track is accurately traced by the playhead.

As described in detail above, in the present invention, since the video track is traced accurately by the video head, a clear image is obtained.

Although a preferred embodiment of the present invention has been described so far, it is obvious to those skilled in the art that the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the appended claims. .

Claims (1)

A band pass filter unit for extracting the front and rear parts of the track from the output signal of the playhead; A differential amplifier for amplifying a difference signal between two signals from the band pass filter and generating an error signal; A signal processor for outputting an error signal generated by the differential amplifier by performing sample holding and amplification; A capstan driving unit which provides a capstan driving signal to the capstan motor obtained by inverting or non-inverting an error signal output from the signal processing unit; And a capstan control section for controlling the processing operation of the signal processing section and the capstan driving signal generation operation of the capstan driving section so as to accurately trace a playhead to a tape track.