KR940008572Y1 - Tracking preset automatic regulating circuit for vtr - Google Patents

Abstract

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Description

VTR tracking preset automatic adjustment circuit

1 is a circuit diagram of the present invention.

2 is a waveform diagram of a circuit according to the present invention.

3 is an internal circuit diagram of the envelope detector 10 in FIG.

4 is an internal circuit diagram of the integrator 20 of FIG.

5 is a waveform diagram output from the microcomputer 40 of FIG.

6 is a flowchart of a circuit according to the present invention.

* Explanation of symbols for main parts of the drawings

10: envelope detector 20: integrator

30: A / D converter 40: Microcomputer

50: variable delay unit 60: EEPROM

The present invention relates to a VTR (Video Tape Recorder), and more particularly, to a tracking reset automatic adjustment circuit.

In the conventional VTR, the capstan motor and the drum motor use constant speed and phase control circuits to control the tape running. The distance from the video head of the drum to the control head must be managed accurately. In order to maintain this accuracy, a tape nut is attached to the side of the audio control head assembly and adjusted in the manufacturing process. However, the adjustment point is incorrect due to the expansion and contraction of the tape nut. The action of the tape nut is related to the retardation phase of the control pulse during reproduction and to the recording phase of the control pulse during recording. In other words, if the ACE (Audio Control Erazer) head is moved away from the drum by turning the tape nut, if the playback is in progress, the pick-up of the control signal must be managed accurately from the video head to the control head. If the distance is different for each VTR, the screen noise will occur. Thus, the ACE head was positioned so that the reproduction FM signal of the VTR regeneration circuit was maximized by reproducing the standard tape for adjustment in the VTR where the reset adjustment was completed, but there was a problem of mechanical manual adjustment in the manufacturing process.

Accordingly, an object of the present invention is to provide a tracking preset automatic adjustment circuit of a VTR capable of automatically resetting a tracking signal by judging an envelope signal of a reproduction FM signal.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram of the present invention, and includes an envelope detector 10 for converting a reproduction FM signal into an envelope signal, and an integrator 20 for integrating the output signal of the envelope detector 10 and outputting it by the integral control signal 1. ), An A / D converter 30 for converting the output signal of the integrator 20 to digital, a micom 40 for reset by the output signal of the A / D converter 30, and the micom A variable delay unit 50 which gives a delay time by serially outputting the maximum preset data memorized at 40 and an EEPROM (Electrically Erasable Programmable Read Only Memory) storing data applied to the variable delay unit 50. And a preset start switch (SW) connected to the microcomputer (40) preset start input terminal (PR) to start detecting preset data.

2 is a waveform diagram of a circuit according to the present invention, FIG. 3 is an internal circuit diagram of the envelope detector 10 in FIG. 1, FIG. 4 is an internal circuit diagram of the integrator 20 in FIG. 1, and FIG. 5 is in FIG. This is a waveform diagram output from the microcomputer 40.

6 is a flow chart of a circuit according to the present invention, the first process of outputting a preset initial value to low the integral control signal and storing the reset data and the integral peak value, and the sampling data after the first process is the maximum value If it is not the maximum value by checking the authorization is a second step of increasing the preset time, and if the maximum value is a third step of outputting the preset data by calculating the preset output value.

Based on the above configuration, the present invention will be described in detail with reference to FIGS. 1-7.

First, the function of the preset actual microcomputer 40 is a serial communication output such as the waveform of FIG. 2 (b) and first inputs the minimum value of the preset time Tp to the variable delay unit 50 for capstan phase control. The minimum input is integrated with the envelope signal after confirming whether the delay is sufficient by performing a sufficient delay. Therefore, the integrator is applied to the rising edge time of the head switch (HSW) signal such as the second-degree waveform after the delay time TC of one or more cycles of the head switch (HSW) signal considering the capstan phase control response speed. In 20, the integration of the envelope signal Vi applied from the envelope detector 10 is started. The integrated signal Vo is digitally converted by the A / D converter 30 to read the digitally integrated integral value at the pulling edge of the head switch signal HSW, and the integral value is read. Set, the integral control signal 1 applied from the integral control terminal C goes from low to high.

At this time, the preset time (TP) and the envelope integral peak value are stored in the RAM in the microcomputer 40 as shown in the second degree (g) waveform, the preset time (TP) data is increased by Tp, and the increase of Tp is 16.67 ms or more. Repeat the above process until. By repeating the above process, N preset times (TP) and N integrals are stored as shown in FIG. 2 (g). The operation waveform of FIG. 1 is shown in FIG. 2, and the reproduction FM signal such as the waveform of FIG. 2 (c) is driven by the envelope detector 10 composed of a full-wave rectifier and a low pass filter (LPF) as shown in FIG. d) Like a waveform, it becomes an envelope signal. The envelope signal is integrated through the integrator 20 configured as shown in FIG. 4 to form a waveform of FIG. 2 (f), and the integral control signal of the integrator 20 applied from the integral control terminal C of the microcomputer 40. (1) becomes the waveform of FIG. 2 (e). In FIG. 4, the output signal Vi of the envelope detector 10 is input to the non-inverting input terminal of the operational amplifier OP and grounded by connecting a resistor R to the inverting input terminal. Connect to the op amp output terminal.

The operation-amplified signal through the operational amplifier (OP) outputs a resistor (R). When the integral control signal (1) goes from high to low, this low signal is transmitted through the resistor (R). Output only when Q) is turned off. The quantity of data is related to the degree of reset adjustment. In the conventional method, the error of preset adjustment is limited to ± 0.5, so ΔTp is 0.5ms and the variable range is 0-16.67ms (1/2 cycle of SW pulse). It is necessary to do Therefore, the number of data is 34 (= 16.67 / 0.5 + 1), and the memory requirement is 34 x 2 x bytes = 68 bytes. Preset data having the largest envelope integrated peak value among the data stored as waveforms shown in FIG. 2 (g) and (h) is input to the variable delay unit 50 through the serial communication outputs CLk, Csp and Datap as shown in FIG. Let's do it.

If the envelope peak value data is even, the median value of the center two preset data is outputted, and if it is odd, the center preset data is outputted.

The preset data detection process is connected to the preset start input terminal PR of the microcomputer 40 and is started when the preset start switch SW is input.

First, the preset initial value is output in step 1A, and the integration control signal 1 is output from high to low in step 2A, and then step 3A is performed.

In step (3A), the preset data and the integral peak value are memorized, and in step (4A), it is checked whether the number of sampling data (N) is the maximum value, and if it is not the maximum value, step (5A) is performed. do.

In step 5A, the preset time TP is increased to perform step 1A again. In step (6A), the preset output value is calculated, and in step (7A), the preset data is output and finished.

As described above, the tracking signal is automatically determined by judging the envelope signal of the reproduction FM signal of the VTR, and there is an advantage of a simple circuit configuration by adjustment by a software input method.

Claims (1)

In the tracking reset adjustment circuit of the VTR, an envelope detector 10 for converting a reproduction FM signal into an envelope signal, an integrator 20 for integrating an output signal of the envelope detector 10 and outputting the integral signal by an integral control signal; In addition, the AD converter 30 for converting the output signal of the integrator 20 into digital, the micom 40 wave to be reset by the output signal of the A / D converter 30, in the micom 40 A variable delay unit 50 which gives a delay time by serially outputting the maximum memorized preset data, an EEPROM 60 which stores data applied to the variable delay unit 50, and the microcomputer 40 free of charge. A tracking preset automatic adjustment circuit for a VTR, comprising: a preset start switch (SW) connected to a set start input terminal and starting detection of preset data by switching.