JPH0614311Y2 - Drum servo device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drum servo device of a video tape recorder.

<Outline of the Invention> The present invention relates to the phase control for aligning the phase of the head switching pulse of the drum motor during recording with the reference signal (vertical synchronization signal) in the drum servo device of the video tape recorder. It is a drum servo device having means for detecting and correcting a specific deviation.

<Prior Art> FIG. 2 shows a block diagram of a drum servo device at the time of recording in a conventional video tape recorder.

The FG signal output from the drum motor 1 is sent to the FG amplifier 2
Is input to the speed detector 3 through the, the cycle of the FG signal is detected by the speed detector 3, and a speed error signal whose center value is a preset cycle is output.

On the other hand, the PG signal output from the drum motor 1 is input to the head switching pulse generation circuit 5 via the PG amplifier 4. The head switching pulse generation circuit 5 creates a head switching pulse for switching heads, and inputs this to a phase comparator 6 in the next stage, where it performs phase comparison with a reference signal (vertical synchronizing signal of video signal). A phase shift for a predetermined phase interval is output as a phase error signal. The phase error signal and the speed error signal described above are mixed and input to the servo amplifier 7, where the output is increased and the level is shifted, and the output is output to the motor drive circuit 8.
To control the drum motor 1.

<Problems to be solved by the invention> According to the conventional method, the operating point of the phase control system fluctuates due to the mixing method of the phase error signal and the speed error signal, the operating point of the DC level of the servo amplifier and the level shift variation. However, the phase interval between the head switching pulse and the vertical synchronizing signal may be out of phase with the preset interval. In such a case, the specifications on the recording tape pattern may not be met.

<Means for solving the problems> As a means for solving such problems, the phase error signal is averaged several times to detect the steady deviation of the phase, and the steady phase deviation signal (servo error signal) is generated. And a differential amplifier having the output of the adder for adding the speed error signal and the phase error signal as a non-inverting input and the steady phase deviation signal as an inverting input. The drum motor is controlled by the output from.

<Embodiment> FIG. 1 shows a block diagram of a drum servo device of the present invention.

Normal speed control and phase control are performed in the same manner as in the past.

According to the present invention, the phase error signal output from the phase comparator 6 is averaged several times by the phase error averaging circuit 9, and the averaged signal is output as the phase error averaging signal. This phase error averaged signal is compared with the phase error signal level (referred to as a reference level) output when there is no phase error by the level comparator 10, and the difference including the polarities of these two levels is taken. The level of this difference corresponds to the deviation of the rotation phase of the drum motor 1 (this signal is called a deviation signal). This difference signal and the difference signal of the deviation signal previously stored in the memory (including the interface) 11 are subtracted including the polarity, and this difference signal is newly replaced in the memory 11 and simultaneously written The signal of the level corresponding to is input to the differential amplifier 12 as a servo error signal. A signal obtained by mixing the servo error signal, the phase error signal and the speed error signal is input to the differential amplifier 12 and the output signal is input to the motor drive circuit 8 through the servo amplifier 7 and the drum motor 1 To control.

By performing the above process in the averaging circuit 9 every time the averaging is completed, it is possible to always apply the drum servo having no phase deviation.

<Effect of device> As described above, according to the drum servo device of the present invention, the phase error signal is averaged several times to detect the steady-state deviation amount of the phase, and the signal obtained by adding the speed error signal and the phase error signal is detected. However, since the steady phase deviation is corrected, it is possible to always perform reliable drum servo without phase deviation.

[Brief description of drawings]

FIG. 1 is a block diagram of the drum servo device of the present invention, and FIG.
The figure is a block diagram of a conventional drum servo device. 1 ... Drum motor, 2 ... FG amplifier, 3 ... Speed detector, 4 ... PG amplifier, 5 ... Head switching pulse generation circuit, 6 ... Phase comparator, 7 ... Servo amplifier, 8 ... Motor drive circuit, 9 ... Averaging circuit, 1
0 ... Level comparator, 11 ... Memory, 12 ... Differential amplifier.

Claims (1)

[Scope of utility model registration request] 1. A speed detector for generating a speed error signal based on an FG signal output from a drum motor, and a head switching pulse generation circuit for generating a head switching pulse based on a PG signal output from a drum motor. A drum provided with a phase comparator for performing a phase comparison between the head switching pulse and a reference signal such as a vertical synchronization signal to generate a phase error signal, and an adder for adding the speed error signal and the phase error signal In the servo device, the phase error signal is averaged several times to detect the stationary phase deviation amount, and the stationary phase deviation signal generating means for generating the stationary phase deviation signal is added, and the speed error signal and the phase error signal are added. A non-inverting input of the adder output and a differential amplifier of which the steady phase deviation signal is the inverting input. Drum servo system and controls the drum motor by.