JPH01208079A - Horizontal deflecting circuit - Google Patents

Abstract

PURPOSE:To hold a stable synchronizing condition even when the frequency range of an input horizontal synchronizing signal is widely changed by switching plural self-travelling oscillation frequency adjusting circuits with the output electric power of a frequency voltage converting circuit. CONSTITUTION:A direct current voltage in accordance with the repeated frequency of an input horizontal synchronizing signal is generated by a frequency voltage conversion 2 and supplied to a VCO 4. Two adjusting circuits of the free-running oscillation frequency of the VCO 4 are provided, and these are switched and adjusted by a switch SW. A frequency range is divided into A and B, the input horizontal synchronizing signal of an approximately intermediate 24kHz is inputted to a terminal 1 at the range of A, while a phase comparison 3 is not executed, a variable resistance R3 is adjusted, and the free-running oscillation frequency of the VCO 4 is matched to 24kHz. In the range of B, an approximately intermediate 52kHz is inputted to a terminal 1, a variable resistance R5 is adjusted, and the free-running of the VCO 4 is matched to 52kHz. As the result, the picture due to the video signal in accordance with the horizontal scanning standard between 15.75-70kHz is correctly displayed on the CRT.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to horizontal deflection circuits, particularly devices that are required to emit oscillation waves of horizontal deflection frequencies of various different frequency values. 3 (Prior Art) Concerning a horizontal deflection circuit suitable for use in a display device requiring, for example, to project an image based on video signals complying with a plurality of scanning standards onto the image plane of a cathode ray tube. Examples of image reproducing devices that are designed to reproduce images include preview receivers and display devices used in various types of information devices. In order to reproduce an image on a cathode ray tube in a 9 reproduction device, it is necessary, as is well known, to deflect the electron beam of the cathode ray tube horizontally and vertically according to a predetermined scanning standard.

By the way, the scanning standards to be applied when reproducing images often differ depending on the standard format of the previsicon system used for image reception, for example in the case of previsicon receivers, and various types of information are When it comes to display devices in electronic devices, the scanning standards are often so different that it can be said that each device manufacturer sets its own scanning standards.

As mentioned above, when the scanning standards are different, the configuration of the deflection circuit will naturally be different, but if an image reproducing device with a different configuration is configured each time the scanning standard is different, it is impossible to use a wide variety of Since production is done in small quantities, which has various disadvantages in terms of production management and cost, there has been a desire for a deflection circuit that can be used for multiple scanning standards, and there have been many proposals to meet this demand. What has been done is well known.

FIG. 3 shows an example of a conventional horizontal deflection circuit used in equipment configured to reproduce video signals that comply with multiple scanning standards. An oscillation frequency control voltage generation circuit capable of generating a DC voltage according to the repetition frequency of the signal is provided, and the oscillation frequency of the voltage control oscillator is controlled by the DC voltage generated by the oscillation frequency control 711 pressure generation circuit. FIG. 2 is a block diagram of an example of a conventional horizontal deflection circuit in which the horizontal deflection oscillation frequency is made variable over a wide frequency range.

In FIG. 3, the input terminal 1 is supplied with a horizontal synchronizing signal Ph from a pre-stage circuit (not shown) or an external input terminal. The horizontal synchronizing signal ph supplied to the input terminal 1 is input to a frequency-voltage converter circuit 2 and a phase comparator circuit 3, and the frequency-voltage converter circuit 2 converts the horizontal synchronizing signal Ph into a DC voltage according to the repetition frequency rh of the horizontal synchronizing signal Ph. [Generate r. The voltage controlled oscillator 4 uses it as a frequency control voltage.
The voltage control excavator 4 supplies a square wave output signal with a repetition frequency corresponding to the frequency control voltage Ef described above to the horizontal deflection output circuit 5. As a result, the horizontal deflection output circuit 5 causes a sawtooth wave horizontal deflection current S to flow through the horizontal deflection coil [h, and the electron beam of the cathode ray tube (not shown) is directed in the horizontal direction (-).

Further, by supplying the horizontal retrace pulse Pc generated by the horizontal deflection output circuit 5 to the phase comparator circuit 3, the phase comparator circuit 3 responds to the phase difference between the horizontal synchronizing signal Pf and the horizontal retrace pulse Pc. Output the DC type B-Ep,
It is applied to the voltage controlled oscillator 4 described above.

Further, the circuit constituted by resistor R1, capacitor G+, and C2 is a well-known two-wheel time constant circuit, and smoothes the output signal of phase comparator circuit 3 and supplies it to voltage controlled oscillator 4. Moreover, the resistor R2 and the variable resistor R3 are connected to the voltage controlled oscillator 4.
This is a circuit for adjusting the free-running starting wave number f. Vcc is a power supply voltage.

It should be noted that the frequency-voltage conversion circuit is well known, and its structure and operation are specifically shown in, for example, Japanese Patent Application No. 157649/1983, so a description thereof will be omitted here.

In the circuit arrangement shown in the third diagram having the above-described configuration, the free-running oscillation frequency f of the voltage-controlled oscillator 4 is within the necessary frequency change range of the repetition frequency fh of the horizontal dome signal ph supplied to the input terminal 1. The characteristics of the frequency @ voltage conversion circuit 2 and the characteristics of the voltage control 211 oscillator 4 are set, and the horizontal Synchronization signal Ph
By the DC voltage according to the phase difference between the retrace pulse Pc and the retrace pulse Pc,
When the voltage controlled oscillator 4 is controlled in a direction in which the phase difference with the horizontal synchronization signal 4i@Ph and the retrace pulse PC is zero, the horizontal deflection current S is equal to the frequency and phase of the horizontal synchronization signal supplied to the input terminal 1. It is made to the frequency and phase that are defeated.

The above points will be explained with reference to FIG. 4 as follows. In FIG. 4, the horizontal axis is frequency, the vertical axis is voltage, and the straight line "V" in the figure is the change characteristic of the output voltage Lf of the frequency-voltage conversion circuit 2 with respect to the change in the repetition frequency rh of the horizontal synchronizing signal ph, and the straight line vCO is a change characteristic of the free-running oscillation frequency fo of the voltage controlled oscillator 4 with respect to a change in the input DC voltage Ef.

The conventional horizontal deflection circuit uses the standard television frequency 15 as the horizontal synchronizing signal ph supplied from the input terminal 1.
．． 75Hz to approximately twice the frequency of 31.5 to 33kHz
It would have been better if it could support up to 15.75 to 33 KIIz.

To adjust the free-running oscillation frequency of the voltage controlled oscillator, first input the horizontal synchronizing signal ph of H7 from the output terminal 1 at a frequency of about 24, which is approximately the middle of the frequency range, and supply the horizontal retrace pulse Pc, for example. The phase comparator circuit 3 is made inoperable by means such as stopping the phase comparator circuit 3. Then, the free-running oscillation frequency f of the voltage controlled oscillator 4 is set to about 24
The variable resistor R3 is adjusted to match the frequency of Hz.

In the horizontal deflection oscillation circuit shown in FIG. 3, the repetition frequency fh of the horizontal synchronizing signal ph for the same DC voltage [f,
Free-running oscillation frequency f of the voltage controlled oscillator 4.

The frequency difference Δr1 in FIG. 4 between If it is small enough to fall within the pull-in range, the frequency and phase of the horizontal (-) current S and the frequency and phase of the horizontal current S supplied to input terminal 1 are equal to the planned frequency. Therefore, the horizontal deflection circuit shown in FIG. It is possible to display it correctly.

(Problem to be Solved by the Invention) In recent years, with the advancement of information equipment, etc., it has become necessary for the horizontal synchronizing signal ph supplied from the input terminal 1 to be able to support a wide range of frequencies from 15.75 K11z to approximately 70 KHz. It became so.

Therefore, even if the frequency difference Δ'1 in FIG. 4 becomes large as Δf2, and even if the free-running oscillation frequency is adjusted at a frequency approximately at the center of the frequency range, the frequency m range is narrow, so the frequency difference Δr becomes iyJ There has been a problem in that synchronization is lost beyond the pull-in range of the control system, or even within the pull-in range, there is not enough margin, and synchronization is quickly lost due to noise or the like.

The present invention aims to solve the above problems, and provides a horizontal deflection circuit that can maintain a stable horizontal synchronizing state even if the frequency range of an input horizontal synchronizing signal changes widely. It is something.

(Means for solving the problem) In order to achieve the above object, a frequency-voltage conversion circuit that generates a DC voltage according to the repetition frequency of an input horizontal synchronizing signal, and a frequency-voltage conversion circuit that generates a DC voltage according to the repetition frequency of the input horizontal synchronization signal, and A voltage controlled oscillator that obtains an oscillation output of a frequency, and controlling the voltage controlled oscillator with an output signal obtained by comparing the phases of the input horizontal synchronization signal and a signal corresponding to the output signal of the voltage controlled oscillator, A phase comparator circuit operates to synchronize the phase of the output signal of the human horizontal synchronizer No. 13 and the output signal of the voltage controlled oscillator. a plurality of free-running oscillation frequency adjustment circuits that variably adjust the oscillation frequency at a plurality of specific frequencies among the repetition frequencies of the input horizontal synchronization signal to match the specific frequency; and a plurality of free-running excavation frequency adjustments. The present invention provides a horizontal deflection circuit characterized in that the circuit includes a switching circuit that switches according to the output voltage of the frequency-voltage conversion circuit.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the horizontal circuit of the present invention. FIG. 2 is a diagram showing the characteristics of FIG. 1. Parts that are the same as those shown in the figure are indicated with the same number.

The difference in FIG. 1 from the conventional example shown in FIG. 3 is that two free-running 'Q-synchronized frequency adjustment circuits for the voltage controlled oscillator 4 are provided. That is, there are two circuits: a circuit composed of resistors 1 and 2 and a variable resistor R3, and a circuit composed of a resistor R4 and a variable resistor Rh. These two circuits are configured to be switched and adjusted by a changeover switch SW.

As shown in Figure 2, the frequency range is 15.75~33
Divide into 2 into K117 and 33-7QKtlz, 15.75
~33K11z input horizontal synchronizing signal 8 of 24Ktlz, which is a roughly intermediate frequency, is input to input terminal 1, and as described above, variable resistor R3 is varied without phase comparison operation being performed. Adjust the free-running oscillation frequency of the voltage controlled oscillator to match 24 tlz.

In addition, in the range of 33 to 70 KHz, an input horizontal synchronizing signal of 52 KIIz, which is an intermediate frequency, is input to input terminal 1, and as described above, the variable resistor R5 is changed to Adjust to match the free running oscillation frequency of the voltage controlled oscillator to 52 KHz.

As a result, the change characteristic of the free-running oscillation frequency fo of the voltage control excavator 4 with respect to the change in the input DC voltage f becomes two discontinuous straight lines VCO1 as shown in FIG.

It becomes VCO2 and switches at a point of 33KHz.

Frequency difference Δf1 in FIG. It can be seen that Δf3 is significantly smaller than Δf2 of the conventional example shown in FIG.

Therefore, the planned frequency change range is 15.75 to 70
Images based on video signals conforming to various horizontal scanning standards in K11z can be correctly displayed on the display surface of the cathode ray tube.

Note that the DC voltage Ef that is the output of the frequency-voltage conversion circuit 2
Since corresponds to the frequency of the incoming horn synchronization signal, the changeover switch SW is operated so that the frequency is switched to 33 Hz by this DC voltage Ef.

In addition, in the embodiment not shown in FIGS. 1 and 2, the frequency range of the input synchronizing signal was 15.75 to 70 KHz, so the frequency range was divided into two and the free-running (Tatsu frequency) Although you have made variable adjustments, if you want to roughly keep Δf small, or if the frequency range of the input synchronization signal is further expanded, increase the number of divisions to 3 or 4 to perform variable adjustment of the free-running oscillation frequency. Of course, it is a good thing to do.

(Effects of the Invention) Since the horizontal deflection circuit of the present invention is configured as described above, even if the frequency range of the input synchronization signal changes widely, the synchronization does not deviate and is always in a stable synchronization state. can be held, and has an extremely excellent practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the horizontal deflection circuit of the present invention, FIG. 2 is a diagram showing the characteristics of FIG. 1, FIG. 3 is a block diagram showing a conventional horizontal deflection circuit, and FIG. is a diagram showing the characteristics of FIG. 3; 1... Input terminal, 2... Frequency @ voltage conversion circuit, 3...
...Phase comparison circuit, 4...Voltage controlled oscillator, 5 river water type deflection output circuit, C+, C2... Capacitor, D...
- Output signal, [f, [:I)19. DC voltage, FV・
・Characteristics of frequency voltage conversion circuit, Lh...Horizontal deflection coil, Pc...Retrace pulse, ph...Horizontal synchronization signal, R+, R2, Ra...Resistance, R3, R5...Variable Resistance, S...Horizontal deflection current, S14...Selector switch, Vcc-'rii source voltage, VC(h, VC
O2...Characteristics of the free-running oscillation frequency of the voltage-controlled excavator, Δ
f. Δf1 to Δf3...Frequency difference. 1F21 Side wave & fh , f, (mn□ ′? 2 mouths

Claims (1)

[Scope of Claims] A frequency-voltage conversion circuit that generates a DC voltage according to the repetition frequency of an input horizontal synchronization signal; a voltage-controlled oscillator that obtains an oscillation output with a frequency that corresponds to the output voltage of the frequency-voltage conversion circuit; By controlling the voltage controlled oscillator with an output signal obtained by comparing the phases of the input horizontal synchronization signal and a signal corresponding to the output signal of the voltage controlled oscillator, the input horizontal periodic signal and the output of the voltage controlled oscillator are controlled. a phase comparison circuit that operates to synchronize the phases of signals; and a phase comparison circuit that, when the phase comparison operation is not performed, sets the free-running oscillation frequency of the voltage controlled oscillator to one of a plurality of specific frequencies among the repetition frequencies of the input horizontal synchronization signal. , comprising a plurality of free-running oscillation frequency adjustment circuits that variably adjust the frequency to match the specific frequency, and a switching circuit that switches the plurality of free-running oscillation frequency adjustment circuits according to the output voltage of the frequency-voltage conversion circuit. A horizontal deflection circuit characterized in that it is configured by: