JPH0431471B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an oscillation frequency control voltage generation circuit in a horizontal deflection oscillation circuit, and in particular, to an oscillation frequency control voltage generation circuit in a horizontal deflection oscillation circuit. An oscillation frequency control voltage generation circuit in a horizontal deflection oscillator circuit suitable for use in required equipment, for example, a display equipment that is required to project an image on the image plane of a cathode ray tube using video signals that comply with multiple scanning standards. Regarding.

(Prior Art) Examples of image reproducing devices that reproduce images using cathode tube rays include television receivers and display devices used in various information devices. However, as is well known, in order to reproduce an image on a cathode ray tube in such an image reproduction device, it is necessary to deflect the electron beam of the cathode ray tube in the vertical and horizontal directions according to a predetermined scanning standard. Ru.

By the way, the scanning standards that should be applied when reproducing images often differ depending on the standard format of the television system that is being received, for example in the case of television receivers, and there are also various scanning standards that should be applied when reproducing images. When it comes to display devices in information equipment, the scanning standards are often so different that each manufacturer of the equipment sets their own scanning standards.

As mentioned above, when the scanning standards differ, the configuration of the deflection circuit will naturally differ, but if an image reproducing device with a different configuration is configured for each different scanning standard, it will not be possible to produce a wide variety of products in small quantities. Since the production is disadvantageous 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 many proposals have been made to meet this demand. It is well known that

Figure 4 shows an example of a conventional horizontal deflection oscillation circuit used in equipment configured to reproduce video signals that comply with multiple scanning standards. Equipped with an oscillation frequency control voltage generation circuit that can generate a DC voltage according to the repetition frequency of the synchronization signal,
By controlling the oscillation frequency of the voltage controlled oscillator using the DC voltage generated by the oscillation frequency control voltage generation circuit, the horizontal deflection oscillation frequency is made variable over a wide frequency range. 1 is a block diagram of an example of a conventional horizontal deflection oscillation circuit.

In FIG. 4, In is an input terminal for a horizontal synchronizing signal, and this input terminal In 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 In is connected to the frequency-voltage conversion circuit FVC.
and the phase comparator circuit PDET, and the frequency-voltage conversion circuit FVC generates a DC voltage Ef corresponding to the repetition frequency fh of the horizontal synchronization signal Ph, which is applied as a frequency control voltage to the voltage-controlled oscillator VCO, and the voltage A rectangular wave output signal R having a repetition frequency corresponding to the frequency control voltage Ef is supplied from the controlled oscillator VCO to the horizontal deflection output circuit DEFC. As a result, the horizontal deflection output circuit DEFC causes a sawtooth wave horizontal deflection current S to flow through the horizontal deflection coil Ch, and the electron beam of the cathode ray tube (not shown) is deflected in the horizontal direction.

In addition, the horizontal retrace pulse Pc generated by the horizontal deflection output circuit DEFC described above is transmitted to the phase comparator circuit PDET.
As a result, the phase comparison circuit PDET outputs a DC voltage Ep corresponding to the phase difference between the horizontal synchronizing signal Ph and the horizontal retrace pulse Pc, and supplies it to the voltage controlled oscillator VCO described above.

In the circuit arrangement shown in FIG. 4 having the above-described configuration, the free-running oscillation frequency fo of the voltage controlled oscillator VCO is
The characteristics of the frequency conversion circuit FVC and the voltage control are set so that the change pattern approximately matches the frequency change pattern within the required frequency change range of the repetition frequency fh of the horizontal synchronization signal Ph supplied to the input terminal In. The characteristics of the oscillator VCO are set, and
A DC voltage corresponding to the phase difference between the horizontal synchronizing signal Ph and the retrace pulse Pc in the phase comparison circuit PDET causes the voltage controlled oscillator VCO to move in the direction in which the phase difference between the horizontal synchronizing signal Ph and the retrace pulse Pc is made zero. When controlled, the horizontal deflection current S is at the input terminal In
The frequency and phase are set to match the frequency and phase of the horizontal synchronizing signal supplied to the horizontal synchronizing signal.

The above points will be explained with reference to FIG. 5 as follows. In Figure 5, the horizontal axis is voltage,
The vertical axis is the frequency, and the straight line FVC in the figure represents the change characteristic of the output voltage Ef of the frequency-voltage conversion circuit FVC with respect to the change in the repetition frequency fh of the horizontal synchronization signal Ph.
The straight line VCO is the change characteristic of the free-running oscillation frequency fo of the voltage controlled oscillator VCO with respect to the change in the input DC voltage Ef.

In the horizontal deflection oscillator circuit shown in Fig. 4, the frequency difference △f in Fig. 5 between the repetition frequency fh of the horizontal synchronizing signal Ph for the same DC voltage Ef and the free-running oscillation frequency fo of the voltage controlled oscillator VCO is Voltage controlled oscillator in the frequency change range Zf
VCO → horizontal deflection output circuit DEFC → phase comparison circuit
If the frequency and phase of the horizontal deflection current S and the input terminal
Since the frequency and phase of the horizontal synchronizing signal Ph supplied to In match within the predetermined frequency change range Zf, in the horizontal deflection oscillator circuit shown in Figure 4,
Images based on video signals conforming to various horizontal scanning standards within the predetermined frequency change range Zf can be correctly displayed on the display screen of the cathode ray tube.

(Problems to be Solved by the Invention) The horizontal deflection oscillator circuit shown in FIG. This can be done normally, but if the horizontal synchronizing signal Ph supplied to the input terminal In is missing, the output voltage Ef of the frequency-voltage conversion circuit FVC becomes zero, so in that case, the characteristic diagram shown in Figure 5 As can be easily seen from the figure, the oscillation frequency of the voltage controlled oscillator VCO is extremely reduced.

In the frequency-voltage conversion circuit FVC, which is used as an oscillation frequency control voltage generation circuit in a conventional horizontal deflection oscillator circuit, when the horizontal synchronization signal Ph supplied to its input terminal In is absent, the output voltage Ef changes. The point that the voltage becomes zero will be explained as follows with reference to FIGS. 6 and 7, which show an example configuration of a conventional frequency-voltage conversion circuit FVC.

That is, in FIG. 6, which shows an example of the configuration of a conventional frequency-voltage conversion circuit FVC, it is composed of coupling capacitors C1, C2, NAND circuits N1, N2, resistors R1, R2, etc., and is surrounded by a dotted line frame. The part is a well-known monostable multivibrator MM, and the resistor R3 whose one end is connected to the output side of the NAND circuit N1 is a smoothing resistor, which performs a smoothing operation together with the smoothing capacitor C3. .

FIGS. 7a to 7c show the NAND circuit N in the frequency-voltage conversion circuit FVC of the conventional configuration shown in FIG.
7 is a waveform diagram of signals at one input point a of the NAND circuit N1, the Q output terminal of the NAND circuit N1, and the Q bar output terminal of the NAND circuit N2; The horizontal synchronizing signal Ph is supplied to one input point a of the NAND circuit N1 via the coupling capacitor C1 in MM, and b in FIG.
is the output pulse Ro appearing at the Q output terminal of
Further, c in FIG. 7 is a pulse appearing at the Q bar output terminal of the NAND circuit N2, and c in FIG.
The pulse shown in is of opposite polarity to the output pulse Ro shown in FIG. 7b.

The output pulse shown in FIG. 7b above
Ro is a rectangular wave having a pulse width Tw (however, the pulse width Tw is shorter than the horizontal scanning period Th) from the time of the horizontal synchronizing signal Ph given as one input of the NAND circuit N1.

Frequency-voltage conversion circuit shown in Figure 6
In FVC, monostable multivibrator MM
A horizontal synchronizing signal having a repetition frequency fh that is supplied to one input point a of the NAND circuit N1 in
Let the period of Ph be Th, and also the frequency voltage conversion circuit
If the supply voltage to FVC is Eo, the above-mentioned square wave output pulse Ro is connected to resistor R3 and capacitor C3.
The voltage value of the DC voltage Ef obtained by smoothing with the smoothing circuit configured by is expressed as Ef=(Tw/Th)Eo=Tw・Eo・fh, and the frequency voltage The DC output voltage Ef from the conversion circuit FVC is proportional to the repetition frequency fh of the horizontal synchronizing signal Ph.

The frequency-voltage conversion circuit FVC shown in FIG. 6 described above
Horizontal synchronizing signal Ph supplied to point a at
disappears after the time indicated by ta in Fig. 7, after the time of the pulse width Tw of the rectangular wave Ro has elapsed from the time position of the horizontal synchronization signal Ph that appeared last. The voltage at the Q output terminal of the NAND circuit N1 becomes zero.

Now, the horizontal deflection output circuit driven by the output signal from the voltage controlled oscillator VCO mentioned above.
The DEFC is configured so that it can operate normally within a predetermined frequency range regardless of the frequency, but as mentioned above, the oscillation frequency of the voltage controlled oscillator VCO is extremely low. In such a case, the frequency of the input signal supplied to the horizontal deflection output circuit DEFC is
Since the frequency is outside the predetermined frequency range of DEFC, the current, voltage, and loss in the horizontal deflection output circuit DEFC increase dramatically, and finally the horizontal deflection output circuit
Things can also happen that can damage the DEFC.

There is also a need for equipment that requires oscillation of oscillation waves with horizontal deflection frequencies of various different frequency values, for example, to project images on the image plane of a cathode ray tube using video signals that comply with multiple scanning standards. In horizontal deflection oscillator circuits used in display devices that use In addition to causing undesirable phenomena such as screen abnormalities and abnormal noises in the horizontal deflection output circuit DEFC due to a temporary drop in power, there are also problems such as the risk of circuit damage as mentioned above. It was hot.

(Means for Solving the Problems) The present invention provides a voltage controlled oscillator using a DC voltage generated by an oscillation frequency control voltage generation circuit that can generate a DC voltage according to the repetition frequency of a supplied horizontal synchronizing signal. An oscillation frequency control voltage generation circuit provided in a horizontal deflection oscillation circuit configured to control the oscillation frequency, which is a monostable multivibrator configured by two NAND circuits and a time constant circuit. Each input terminal of an individual low-pass filter constituted by a resistor and a capacitor is connected to the Q output terminal and the Q bar output terminal, and one end is connected to the Q output terminal of the monostable multivibrator. The other end of the above-mentioned one low-pass filter is connected to the output terminal of the oscillation frequency control voltage generation circuit, and one end of the above-mentioned one low-pass filter is connected to the Q-bar output terminal of the above-mentioned monostable multivibrator. The present invention provides an oscillation frequency control voltage generation circuit in a horizontal deflection oscillation circuit, which is connected to the cathode of a Zener diode whose anode is connected to the output terminal side of the oscillation frequency control voltage generation circuit at the other end.

(Example) Hereinafter, specific contents of the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention will be explained in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention. In FIG. 1, the frequency-voltage conversion described with reference to FIG. The same drawing numerals as those used in FIG. 6 are used for each component corresponding to each component in the circuit FVC.

In the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention shown in FIG.
4 is a resistor, R5 is a resistor connected as necessary,
ZD is a Zener diode, the circuit configuration shown in the dotted frame MM in the figure is a monostable multivibrator MM configured using NAND circuits N1 and N2, and Q is a Q output terminal. ,Q
Bar is the Q bar output terminal.

Q output terminal of NAND circuit N1 in monostable multivibrator MM and frequency-voltage conversion circuit
A low-pass filter composed of a resistor R3 and a capacitor C3 is connected between the output terminal OUT of the FVC, and the signal appearing at the Q output terminal of the NAND circuit N1 is passed through the low-pass filter. The output Ef of the frequency-voltage converter circuit FVC is output from point b.
Sent to the FVC output terminal OUT.

Furthermore, between the Q-bar output terminal of the NAND circuit N2 and the output terminal OUT of the frequency-voltage conversion circuit FVC, there is a series connection circuit consisting of a low-pass filter constituted by a resistor R4 and a capacitor C4, and a Zener diode ZD. The anode side of the Zener diode is connected to the frequency-voltage conversion circuit.
It is connected to the output terminal OUT of the FVC, and the signal appearing at the Q-bar output terminal of the NAND circuit N2 is smoothed by the aforementioned low-pass filter and appears at point c.

Now, if we consider a circuit in which the Zener diode ZD is omitted from the circuit layout shown in Figure 1,
In that case, as the frequency of the horizontal synchronizing signal input to the circuit changes, the DC voltage Eb that appears at point b in the circuit and the DC voltage Ec that appears at point c in the circuit follow the straight line in Figure 2. As shown in FIG. Connect a Zener diode ZD between the above-mentioned points b and c in the circuit,
The output voltage from the frequency-voltage conversion circuit FVC is limited when the frequency of the horizontal synchronization signal input to the frequency-voltage conversion circuit FVC becomes an abnormal value.

Figure 3a shows points b and c in the circuit layout shown in Figure 1.
The Zener diode ZD connected between the
DC voltage Eb that appears at point b in the circuit and DC voltage that appears at point c in the circuit when the repetition frequency of the horizontal synchronizing signal input to the circuit is the lower limit frequency f1 of the predetermined repetition frequency. The repetition frequency of the input horizontal synchronizing signal and the frequency-voltage conversion circuit when the resistor R3 and the resistor R4 have the same resistance value.
FIG. 3 is a diagram showing the relationship between FVC and output voltage Ef.

The characteristics of the frequency-voltage conversion circuit FVC shown in FIG. 3a above are as follows:
Ef is limited by the Zener voltage Vz of the Zener diode ZD, and the output voltage Ef at the upper limit frequency f2 of the repetition frequency of the input horizontal synchronizing signal is the forward voltage of the Zener diode ZD (indicating diode characteristics). Therefore, the output voltage Ef at frequencies other than the predetermined frequency range f1 to f2 in the horizontal synchronizing signal remains unchanged.

Next, b in Fig. 3 is b in the circuit layout shown in Fig. 1.
Zener diode connected between point and point c
ZD is the DC voltage Eb that appears at point b in the circuit and the point c in the circuit when the repetition frequency of the horizontal synchronizing signal input to the circuit is the lower limit frequency f1 of the predetermined repetition frequency. Zener voltage Vz equal to the difference voltage with the appearing DC voltage Ec
In addition, this is a diagram showing the relationship between the repetition frequency of the input horizontal synchronizing signal and the output voltage Ef of the frequency-voltage conversion circuit FVC when a resistor R3 with a larger resistance value than the resistor R4 is used. be.

In the circuit layout shown in the first diagram showing an embodiment of the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention, the lower limit frequency f1, the upper limit frequency f2, the Zener voltage of the Zener diode ZD, etc. are simply In relation to the pulse width Tw of the output pulse from the stable multivibrator MM,
Needless to say, this can be set freely as a design matter.

Furthermore, if a resistor R5 shown by a dotted line is connected between point b and ground in Figure 1, the relationship between the repetition frequency of the input horizontal synchronizing signal and the output voltage Ef will be as shown in Figure 3. (c), which increases the degree of freedom in design.

Furthermore, it can be easily inferred from the above that if the connection polarity of the Zener diode Vz in the circuit arrangement shown in Figure 1 is reversed, the output characteristics of the circuit will be as shown in Figure 3 d. would be able to do so.

The oscillation frequency control voltage generation circuit in the horizontal deflection oscillator circuit of the present invention is capable of handling screen abnormalities caused by a decrease in the oscillation frequency of the horizontal deflection oscillation circuit that occurs when the supply of the horizontal synchronizing signal Ph is interrupted, and the horizontal deflection output circuit
It is possible to effectively solve problems such as the occurrence of abnormal sounds in the DEFC and damage to the horizontal deflection output circuit, etc. In addition, in the circuit of the present invention, the repetition frequency of the horizontal synchronization signal is set to a predetermined upper limit frequency. f2
Even in the above case, it is clear from the characteristics shown in FIG. 3 that the same effect can be achieved.

(Effects) As is clear from the above detailed explanation, the present invention provides a DC voltage generated by an oscillation frequency control voltage generation circuit that can generate a DC voltage according to the repetition frequency of a supplied horizontal synchronizing signal. An oscillation frequency control voltage generation circuit provided in a horizontal deflection oscillation circuit in which the oscillation frequency of a voltage controlled oscillator is controlled by The Q output terminal and the Q bar output terminal of the monostable multivibrator described above are connected to respective input terminals of individual low-pass filters each composed of a resistor and a capacitor. The other end of one of the low-pass filters described above, one end of which is connected to the Q output terminal, is connected to the output terminal of the oscillation frequency control voltage generation circuit, and one end is connected to the Q bar output terminal of the monostable multivibrator. An oscillation frequency control voltage generation circuit in a horizontal deflection oscillation circuit in which the cathode of a Zener diode whose anode is connected to the output terminal side of the oscillation frequency control voltage generation circuit is connected to the other end of the other low-pass filter described above. Therefore, in the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention,
A Zener diode is connected between the output terminals of each low-pass filter connected to the Q output terminal and Q bar output terminal of the monostable multivibrator, respectively, and the frequency of the horizontal synchronization signal input to the frequency-voltage conversion circuit FVC is determined. The present invention limits the output voltage from the frequency-voltage conversion circuit FVC when the input horizontal synchronization signal becomes an abnormal value. Even if the repetition frequency of the synchronization signal is abnormally low or high, it can effectively solve problems such as screen abnormalities, abnormal sounds in the horizontal deflection output circuit DEFC, and damage to the horizontal deflection output circuit, etc. The present invention satisfactorily solves all the problems encountered in conventional circuits.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the oscillation frequency control voltage generation circuit in the horizontal deflection oscillation circuit of the present invention;
2, 3, and 5 are characteristic diagrams; FIG. 5 is an explanatory waveform diagram; FIG. 4 is a block diagram showing an example configuration of a horizontal deflection oscillation circuit; and FIG. 6 is a conventional oscillation frequency control voltage generation circuit. An example circuit diagram, and FIG. 7 is an explanatory waveform diagram. FVC...Frequency voltage conversion circuit, VCO...Voltage controlled oscillator, PDET...Phase comparison circuit, DEFC...
...Horizontal deflection output circuit, N1, N2... NAND circuit, C1-C4... Capacitor, R1-R4...
Resistor, ZD...Zena diode.

Claims (1)

[Claims] 1. The oscillation frequency of the voltage controlled oscillator is controlled by the DC voltage generated by an oscillation frequency control voltage generation circuit that can generate a DC voltage according to the repetition frequency of the supplied horizontal synchronization signal. The oscillation frequency control voltage generation circuit provided in the horizontal deflection oscillation circuit is a monostable multivibrator configured by two NAND circuits and a time constant circuit. The input terminals of individual low-pass filters constituted by resistors and capacitors are connected, and one end of the above-mentioned low-pass filter is connected to the Q output terminal of the above-mentioned monostable multivibrator, and the other end of the above-mentioned low-pass filter is connected to the other end of the above-mentioned low-pass filter. The output terminal of the oscillation frequency control voltage generation circuit is connected to the other end of the other low-pass filter, which has one end connected to the Q-bar output terminal of the monostable multivibrator. This is an oscillation frequency control voltage generation circuit in a horizontal deflection oscillator circuit, which is constructed by connecting the cathode of a Zener diode whose anode is connected to the output terminal side of the horizontal deflection circuit.