JPH01320672A - Error signal detecting circuit for reference values of rotational speed and phase of disk - Google Patents

Abstract

PURPOSE:To widen an effective phase detecting period up to one horizontal cycle period and to facilitate a phase locking by comparing a sample-hole output with a reference voltage and replacing it with the period of a slanting line on a trapezoidal wave with the output. CONSTITUTION:When the input of a switch 11 is connected to a comparator 12, a sampling point is moved to A-F and the trapezoidal wave slanting line outside is sampled (SP) like a E point, one preceding SP point C is larger than OV, and therefore, the sample-hold output is also larger than the OV. Consequently, since the output port of a comparator becomes H, the trapezoidal wave of the position of the D point becomes the H and the output becomes the H. Since a preceding F point is smaller than the OV in the G point, the output port of the comparator becomes the L, and the output to sample the slanting line part outside G becomes the L. Thus, a phase locking is facilitated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an error signal detection circuit for reference values of disc rotational speed and phase, which is suitable for use in a time base correction circuit of a video disc player. .

[Prior art] Conventionally, as a disk speed and phase control method,
There is a technique disclosed in Japanese Patent No. 2-188057. Next, the contents will be explained. FIG. 3 is a block diagram showing a conventional method. 1 is a current source, 2 is a capacitor, 3
is a switch for resetting the trapezoidal wave; 4 is the first reference signal for resetting and starting the trapezoidal wave; 5 is a switch for replacing the output of the phase/speed difference detector 9 through the buffer 10 with the trapezoidal wave. The switch 6 is a second reference signal that controls the switch 5, and the reference numeral 7 is a sample and hold circuit that samples and holds the trapezoidal wave using the synchronization signal 8.

FIG. 4 is an operational waveform diagram showing waveforms for explaining the circuit operation of FIG. 3. In FIG. 4, (a) shows the first reference signal 4, and (b) shows the second reference signal 6. (
The shaded portion of the trapezoidal wave in c) is a waveform obtained by the current flowing into the capacitor 2 from the current source 1. During the period of the second reference signal (b) or H', the output of the phase/velocity difference detector 9 is input to the sample hold circuit 7. The phase difference detector 9 is an edge trigger type digital phase difference detector, and has a function of detecting a frequency difference as well.

Therefore, since the average value of the trapezoidal wave changes in accordance with the speed deviation, it is a sample-and-hold type phase detector having a speed detection function. When the phase is locked, the sampling pulse (d) samples on the diagonal line of the trapezoidal wave (c). That is, although it is a sampling type phase difference detector that is resistant to loss of the sampling pulse (d), which is a synchronization signal, it has the feature that it is capable of detecting a speed difference even when the speed deviates. However, in order to output speed information, the second reference signal (b) H'
During this period, a duty of around 50% is required. As a result, the period of the shaded portion, which is the effective phase detection period of the trapezoidal wave (C), becomes short. There is no problem when the system is stable and sampling is performed at the center of the shaded area, but during the pull-in process, the sampling pulse moves on a trapezoidal wave, so the longer the shaded area, which is the effective phase detection period, the more advantageous it becomes. be.

This will be explained using FIG. In FIG. 5, (a) is the second reference signal, which corresponds to (b) in FIG. (B) shows a trapezoidal waveform, which corresponds to (C) in FIG. FIG. 5 shows the state immediately before one phase lock is achieved when the speed difference is approximately O. Since the speed difference is O, the speed difference output is 0, and the area outside the shaded area of the trapezoidal wave is Ov. In Figure 5 (b),
S indicates the position of the sampling pulse 6 Until the phase is locked, the sampling pulse S moves on the diagonal line of the trapezoidal wave. In Figure 5 (b), sampling pulse S
Assuming that the is moving from left to right, the edge of the shaded area (
When shifting further to the right from A), the sampling output suddenly becomes Ov. Also, even if it shifts to the left, if it shifts to the left from the left end (B).

Similarly, the sampling output suddenly changes to Ov. Because the output changes suddenly just before phase lock, it may not be possible to pull in smoothly.

From this, it can be said that the length between the hatched sections (A) and (B) is more advantageous.

However, as mentioned above, the period (fifth
The period lHj in (a) in the figure is also necessary and is naturally limited. The period of one horizontal opening signal is 63 μsec (
(In the case of NTSC system), the shaded area (A) -
(B) is limited to around 30,1As19c.

[Problems to be Solved by the Invention] The above-mentioned conventional technology has a problem in that the effective phase detection period is short and phase lock cannot be performed smoothly.

SUMMARY OF THE INVENTION An object of the present invention is to provide an error signal detection circuit for reference values of the rotational speed and phase of a disk, which can extend the effective phase detection period to 63 μsec and smoothly lock the phase.

[Means for Solving the Problems] Immediately before phase locking, there is almost no speed difference, and the sampling pulse moves slowly on the diagonal line. Therefore, the above objective is achieved by comparing the sample and hold output with a reference voltage and using that output to replace the shaded period on the trapezoidal wave.

[Function] When the sampling pulse is moving slowly on the diagonal line of the trapezoidal wave, the output of the sample/hold circuit provides information on whether the sampling pulse is moving to the right or to the left on the diagonal line of the trapezoidal wave. It represents. therefore,
By comparing the sample-and-hold output with a reference voltage and replacing the output with the period outside the hatched area of the trapezoidal wave, the period outside the hatched area appears to be longer, and can be extended to the period of the reference signal. Therefore, the phase lock range is widened and smooth phase locking is possible.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. 1st
In the figure, 1 to 4 and 6 to 9 are the same as the same symbols in FIG. Reference numeral 13 denotes a switch which switches the input to the trapezoidal wave side or the output side of a switch 11, which will be described later, in response to the reference signal 6, and its output is connected to the sample and hold circuit 7. 15 is a frequency detector which inputs the reference signal and the reproduced horizontal synchronizing signal and outputs a signal indicating whether the reproduced horizontal synchronizing signal is within or outside a set frequency range.

The signal is input to the switch 11 as an input switching signal for the switch 11. Reference numeral 11 denotes a switch that inputs the output of the 1-phase/velocity difference detector 9 or the output of a comparator 12, which will be described later, and outputs either input to the switch 13. 12 is
This is a comparator that compares the output of the sample and hold circuit 7 with a reference voltage.

Next, the operation will be explained using FIG. 2. (a) is the second reference signal 6. (b) represents the input waveform of the sample and hold circuit 7, (c) represents the output of the sample and hold circuit 7, and (d) represents the output of the comparator 12. Further, (A) to (G) in (B) in FIG. 2 indicate the position of the reproduction synchronization signal, that is, the sampling point. When the input of the switch 11 is connected to the comparator 12, as shown in this figure, when the sampling points move from (A) to (F), as at point (D), When sampling outside the diagonal line of the trapezoidal wave, the previous sampling point (C) is larger than Ov, so the sample hold output is also larger than Ov.

Therefore, since the output of the converter is also 'H', the trapezoidal wave at the position of point (D) is H.
Its output will be 'H level. Also,
At point (G), the previous point (F) is smaller than 0 (■), so the output of the converter is L, and the output sampled outside the shaded area (G) is 'L'. .

As mentioned above, when the sampling point moves from the left to the right of the diagonal line of the trapezoidal wave and further moves outside the diagonal line, j H
Sample j. Furthermore, when it moves from right to left and reaches outside the shaded area, it outputs L level. In this way, when the sampling point moves just before locking one phase, the sampling output is LH(1
Even if the detection output moves over a horizontal period (horizontal cycle period), the detection output does not output false phase information, so one phase lock is easily achieved. The switch 11 is connected to the comparator port when the frequency error is small and the phase is about to be locked, and is connected to the phase/velocity detector 9 side when the frequency error is large. Therefore, the settings of the frequency error detector 15 should be set according to the response performance of the system. This is because the switch 11 is switched by the output of the frequency error detector 15.

[Effects of the Invention] According to the present invention, the effective phase detection period can be extended to IH (one horizontal cycle period), so phase locking can be easily achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a waveform diagram explaining the operation of the embodiment of the present invention, FIG. 3 is a block diagram showing the conventional method, FIG. 4 is an operation waveform diagram explaining the conventional method, and FIG. , is a waveform diagram illustrating the problems of the conventional method. 1... constant current source, 2... capacitor, 3... first
switch, 4... first reference signal, 5... second switch, 6... second reference signal, 7... sample and hold circuit, 8... reproduced horizontal synchronizing signal, 9...
Phase, speed detector, 10...Buffer, 11...Switch 2.12...Frequency detector, 13...Switch 1゜7・'

Claims (1)

[Scope of Claims] 1. An error signal detection circuit that compares the rotational speed and rotational phase of a disc in a video disc player with a reference value, and detects and outputs each error signal, comprising trapezoidal wave generating means; a reset signal that receives a first reference signal as a reference value and resets and starts the trapezoidal wave generated by the trapezoidal wave generating means;
a start means; a first switch into which the trapezoidal wave is input to a first input terminal of the first and second input terminals; a synchronization signal periodically generated in synchronization with the rotation of the disk; A phase difference and speed difference detection circuit detects a phase difference and a speed difference between the first reference signal and the output from the first switch, which samples and holds the synchronization signal as the error signal. a sample-and-hold circuit that outputs an output, a comparison circuit that receives the output of the sample-and-hold circuit and a reference voltage, compares the levels between the two, and outputs the result; and a comparison circuit that receives the first reference signal and that is constant with the reference voltage. a second reference signal generating means for outputting a second reference signal having a phase difference of and causing the first switch to perform a switching operation between the first input terminal and the second input terminal; A frequency difference detection circuit receives a first or second reference signal and the synchronization signal and detects and outputs a frequency difference between the two, and a first input terminal receives the output of the phase difference/speed difference detection circuit. a second switch that receives the output of the comparator circuit at a second input terminal, switches between the two based on a frequency difference output from the frequency detection circuit, and outputs the result to a second input terminal of the first switch; An error signal detection circuit for a reference value of rotational speed and phase of a disk, comprising: