JPS61283278A - Pulse generator - Google Patents

Abstract

PURPOSE:To prevent a horizontal center from moving by slicing a place neighboring of about half of the amplitude of a horizontal output pulse from a horizontal output circuit and inputting it to a horizontal AFC circuit. CONSTITUTION:DC voltage V1 is set so that it becomes voltage at the neighbor ing of about half of the amplitude of the horizontal output pulse impressed on the base of a PNP transistor 6. With this setting, at the collector of the transistor 9 which is the output of the first comparator, a pulse having the width and the phase of about half of the amplitude of the horizontal output pulse is outputted and the output of the first comparator is inputted to a horizon tal AFC circuit B31. Thereby, it is possible to prevent at imperfect control on a horizontal pulse output circuit 27 and the moving of a picture in the right and left direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pulse generator for horizontal AFC used in television sets.

(Prior Art) In recent years, AFC circuits with double loops have been increasingly used in the synchronization section of horizontal deflection circuits of televisions.

The above-mentioned conventional example will be explained below with reference to the drawings. FIG. 4 shows the configuration of a conventional horizontal AFC circuit and a horizontal blanking pulse generation circuit. In FIG. 4, 23 is a synchronization separation circuit for extracting a synchronization signal from the composite video signal.

24 is a horizontal AFC circuit A that performs phase detection on the horizontal synchronization signal obtained by the synchronization separation circuit 23 and the output of the horizontal oscillator 25, and controls the horizontal oscillator 25. 25 is the horizontal AF
This is a horizontal oscillator controlled by C circuit A.

26 is the horizontal oscillator 25 from the output of the horizontal oscillator 25.
This is a horizontal AFC pulse generation circuit that generates a pulse that determines the AFC center for applying AFC between the output of the horizontal output circuit 29 and the output of the horizontal output circuit 29.

27 is a horizontal pulse output circuit for generating a horizontal pulse output from the horizontal oscillator 25; 28 is a horizontal drive circuit, and 29 is a horizontal output circuit. 33, 35.37
34 and 36 are resistors, and NPN transistors 34 and 36 are pulse generating circuits that generate horizontal AFC pulses and horizontal blanking pulses from the output of the horizontal output circuit 29. A horizontal AF 31 detects the 0 phase of the output of the horizontal oscillator 25 and the output of the horizontal output circuit 29 and controls the horizontal pulse output circuit 27.
This is C circuit B.

The operation of the horizontal AFC circuit and horizontal blanking pulse generation circuit configured as above will be explained below. FIG. 5 shows a timing chart of the conventional operation and will also be described.

First, the composite video signal shown in FIG. 5 (■) is input to the synchronization separation circuit 23, and only the synchronization signal is extracted as shown in FIG. 5 (■). The synchronization signal is input to the horizontal AFC circuit A24. The horizontal oscillator 25 is an oscillator that oscillates at twice the horizontal frequency as shown in FIG. Output and phase detected, horizontal AFC
The horizontal oscillator 25 is controlled by the output of the circuit A24, and the synchronization signal and the oscillator are synchronized.

Next, one of the outputs of the horizontal oscillator 25 is led to the horizontal AFC pulse generation circuit 26, which first detects the part where the level of the oscillator output in FIG. First, using this pulse of ■-1, generate a sawtooth wave as shown in Figure 5 ■-2 using the C-R circuit, and the sawtooth wave exceeds level (b). Use parts.

A horizontal AFC pulse as shown in Fig. 5-3 is generated.

The other output of the horizontal oscillator 25 is led to a horizontal pulse output circuit 27, which receives the control of the horizontal AFC circuit B31 and outputs a horizontal pulse as shown in FIG. The output of this horizontal pulse output circuit 27 is output from the horizontal drive circuit 28. The deflection coil is driven through the horizontal output circuit 29. Also, one output of the horizontal output circuit is resistor 33, 35.3
7. As shown in FIG. 5 (2), both the pulse used in the horizontal AFC circuit B31 and the horizontal blanking pulse are simultaneously obtained from the pulse generating circuit constituted by the transistors 34 and 36.

The horizontal AFC circuit B31 performs AFC detection during the period when the output pulse of the transistor 36 (Fig. 5-3) is at H level. That is, after the output pulse of the transistor 36 rises and becomes H level, until the output of the horizontal AF pulse generation circuit 26 ((■) in FIG. 5) becomes H level,
The horizontal AFC circuit B flows a negative current as shown in Figure 5 (■), and the period from the time when the output of the horizontal AFC pulse generation circuit 26 becomes H level until the pulse for horizontal AFC circuit B becomes L level is shown in Figure 5. A positive current is passed as shown in (2), and the output pulse phase of the horizontal pulse output circuit 27 is controlled by the output of the horizontal AFC circuit B31 so that the negative current and the positive current are always equal. For example, when the phase of the output of the horizontal output circuit 29 (Fig. 5 ■) advances due to a change in screen brightness, the current in the horizontal AFC circuit B becomes negative, as is clear from Fig. 5 ■. Become. When this is filtered, it is detected that the DC potential of the filter decreases,
The output phase of the horizontal pulse output circuit 27 is delayed and controlled so that the position of the image on one screen does not move.

(Problem to be Solved by the Invention) However, in the configuration method described above, as explained in the operation of the prior art example, the pulses used in the horizontal AFC circuit B31, like the horizontal blanking pulses, are used in the horizontal output circuit. Since the output pulse is obtained by slicing the base of the output pulse of No. 29, the brightness of the screen changes and the anode current changes.

When the phase of the horizontal output pulse fluctuated, the phase of the horizontal pulse output circuit 27 could not be controlled sufficiently using the output of the horizontal AFC circuit B31. In other words, when the screen is made brighter, the output pulse phase of the horizontal output circuit 29 advances, and unless high voltage fluctuations are taken into account, the screen shifts to the right. The horizontal pulse output circuit 27 is controlled so that this phase change is corrected by the output of the horizontal AFC circuit B31, but as mentioned earlier, the root of the output pulse of the horizontal output circuit 29 is also connected to the horizontal AFC circuit B31. When sliced and used, the correction was not sufficient and when the screen was made brighter, the problem occurred that the screen shifted to the right.

In view of the above problems, the present invention provides a pulse generator for horizontal AFC that can prevent the screen position from moving even if the brightness of the television screen changes.

(Means for Solving the Problems) In order to achieve this object, the horizontal AFC pulse generator of the present invention differs from the conventional method in which the vicinity of the root of the horizontal output pulse is sliced and used as the horizontal AFC pulse. In the present invention, a comparator is provided, a horizontal output pulse is input to one end of the comparator, and a DC voltage is applied to the other end of the comparator so that a portion around half the amplitude of the horizontal output pulse can be sliced. is applied, and the comparator generates a pulse having a width and phase approximately half of the horizontal output pulse, which is used as a horizontal AFC pulse.

(Function) Conventionally, horizontal AFC was applied based on phase information near the root of the horizontal output pulse, and therefore correction was not applied sufficiently, resulting in under-correction. FIG. 6 shows a horizontal output waveform when the screen is brightened, and phase information will be explained using each slice level. First, when the screen is brightened, the horizontal output phase moves forward, and as shown by the broken line in Figure 6, the upper side of the horizontal output tends to move forward in phase. As shown in Figure (1), there is little information that the phase of the horizontal output has advanced, and if this pulse is used for AFC, the horizontal AFC output cannot sufficiently correct the output phase of the horizontal pulse output circuit. On the other hand, if you set the slice level to (C), you will receive information that the horizontal output phase has advanced too much, as shown in Figure 6 (3).
If this pulse is used for horizontal AFC, the output phase of the horizontal pulse output circuit will be overcorrected in the horizontal AFC output, and the phase of the horizontal output will be delayed. From the above, since the slice level (a) is under-correction and the slice level (C) is over-correction, there will always be a location between (a) and (c) where appropriate correction can be obtained. Therefore (a)
When slicing the point (b) of the horizontal output, which is between
) is obtained, and this pulse is used for horizontal AF.
By using it in C, the horizontal AFC output can properly correct the phase of the horizontal pulse output circuit, making it possible to prevent the position of the image on one screen from moving even if the screen brightness changes. can.

(Example) An example of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a horizontal AFC pulse generator according to an embodiment of the present invention. In FIG. 1, 1 and 2 are resistors that divide the horizontal output pulse input from the horizontal output circuit, 3 is a coupling capacitor, 4 and 5 are bias resistors, and 6 is a PNP transistor forming an emitter follower.

7 is an emitter resistance of the emitter follower. Also 8,
9 is a PNP transistor constituting the first comparator;
10 is an emitter resistance of the first comparator, 11 is a collector resistance of the first comparator, 12 is a PNP transistor forming an emitter follower, and 13 is an emitter resistance of the emitter follower. 14.15 is a PNP transistor forming the second comparator, 16 is an emitter resistance of the second comparator, 17 is a collector resistance of the second comparator, 18 is a PNP transistor forming an emitter follower, and 19 is an emitter resistance of the emitter follower. It is. 20 is a bias resistor R1, 21 is a bias resistor R2, and 22 is a bias resistor R3.

The operation of the horizontal AFC pulse generator configured as described above will be explained below with reference to FIGS. 1, 2, and 3. Although the entire horizontal AFC circuit is shown in FIG. 3, the same components as in FIG. 4 described in the prior art section are given the same numbers as in FIG. 4, and their explanation will be omitted.

First, in FIG. 3, the output of the horizontal output circuit 29 is input to the first comparator 3Q, and its output is input to the horizontal AFC circuit B.
31. Similarly, the output of the horizontal output circuit 29 is input to the second comparator 32, and its output is output as a horizontal blanking output.

Here, the first comparator and the second comparator shown in FIG. 3 will be explained in detail using FIG. 1.

First, the horizontal output pulse is divided by resistors 1 and 2, then via a coupling capacitor 3, biased by resistors 4 and 5, input to the base of a PNP transistor 6 forming an emitter follower, and output to the emitter of the PNP transistor 6. and the base of the PNP transistor 8 constituting the first comparator and the PN constituting the second comparator.
P applied to the base of transistor 14.

On the other hand, the base of the PNP transistor 12 constituting the emitter follower is connected to the resistor 2Q, Zl, and
ccX(R2+R3)/(R1+R2+R3) DC
Since the voltage is applied, the emitter of the emitter follower has a D of V□+Vat (base-emitter voltage).
C voltage is generated and the PNP forming the first comparator
Applied to the base of transistor 9. Here, the DC
If the voltage v1 is set to a voltage around half the amplitude of the horizontal output pulse applied to the base of the PNP transistor 6, the voltage of the PNP transistor 9, which is the output of the first comparator, The collector has a second
As shown in Figure ■, approximately half the amplitude of the horizontal output pulse.
A pulse with a similar width and phase is output.

The output pulse of this first comparator is
By inputting the signal to the C circuit B31, it is possible to prevent the conventional case where the horizontal pulse output circuit 27 could not be sufficiently controlled when the brightness of the screen changed, causing the screen to move left and right.

Furthermore, the base of the PNP transistor 18 constituting the emitter follower is connected to vi=Vcc by resistors 21 and 22.
A DC voltage of XR3/(R1+R2+R3) is applied. Similarly to the above, if the DC voltage v2 is set near the root of the amplitude of the horizontal output pulse applied to the base of the PNP transistor 6.

PNP transistor 1 which is the output of the second comparator
A pulse having a width and phase near the root of the horizontal output pulse is output to the collector 5, as shown in FIG. If the output of this second comparator is used as a horizontal blanking pulse for video blanking, regular blanking can be performed.

(Effects of the Invention) As described above, in the present invention, the brightness of the screen can be adjusted by slicing a portion around half the amplitude of the horizontal output pulse from the horizontal output circuit and inputting a large amount to the horizontal AFC circuit Bhe. Even when the phase of the horizontal output pulse from the horizontal output circuit changes due to a change in the phase, the horizontal pulse output circuit 27 can be controlled to cancel out the phase change, and the screen will shift to the left or right in any case. This will prevent the horizontal center from moving.

Furthermore, by generating pulses for horizontal AFC and pulses for horizontal blanking separately, the screen does not shift to the left or right due to changes in screen brightness, and horizontal blanking can be performed with the necessary phase and width. This makes it possible to create an optimal design for both, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a horizontal AFC pulse generator according to an embodiment of the present invention. FIG. 2 is a diagram showing waveforms of various parts in the embodiment of FIG. 1. FIG. 3 is a block diagram showing the entire horizontal AFC circuit using the pulse generator of the present invention. FIG. 4 is a diagram showing an entire block diagram of a conventional horizontal AFC circuit. FIG. 5 is a diagram showing waveforms of various parts in the circuit of FIG. 4. FIG. 6 is a diagram showing the relationship between the horizontal output waveform when the brightness changes and the phase information when it is sliced at various levels. 8, 9, 14, 15... PNP transistors forming the comparator, 10, 11, 16, 17, 20
, 21.22...Resistor, 29...Horizontal output circuit, 3
0...First comparator, 31...Horizontal AFC circuit B. 32...Second comparator. Patent applicant: Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] (1) By applying the horizontal output pulse of the television set to one end and applying a DC voltage that can slice a portion around 1/2 of the amplitude of the horizontal output pulse to the other end, and comparing these, 1. A pulse generator comprising a comparator that generates a pulse used for horizontal AFC having a width and phase approximately half the amplitude of a horizontal output pulse. (2) a first comparator that applies a horizontal output pulse of a television set to one end and applies a DC voltage capable of slicing a portion around half the amplitude of the horizontal output pulse to the other end; D where the output pulse is applied to one end and the vicinity of the wide root of the horizontal output pulse can be sliced.
a second comparator applying the C voltage to the other end;
The first comparator generates a pulse used for horizontal AFC having a width and phase that is approximately half the amplitude of the horizontal output pulse, and the second comparator generates a pulse at the root of the horizontal output pulse. A pulse generator characterized in that it generates a pulse having a similar width and phase for horizontal blanking of a video signal output.