JPH0584710B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] In addition to the reception of ordinary television broadcasts, the present invention is applicable to the reception of video signals with different horizontal frequencies from a conversion device that doubles the number of scanning lines. The present invention relates to a multi-scan television receiver capable of performing a multi-scan television receiver.

[Conventional technology]

For example, in an NTSC television signal, an image is formed with a vertical frequency of approximately 60 Hz and a horizontal frequency of approximately 15.75 KHz. In response, a conversion device has been proposed that doubles the number of scanning lines through arithmetic processing or the like to improve the quality of the received image. When using this device, the signal that will be output will have a vertical frequency of approximately 60Hz and a horizontal frequency of approximately 31.5KHz.
It's getting old.

In addition, some output signals from computers for so-called high-resolution display have a horizontal frequency of about 24 KHz. Furthermore, in so-called high-definition television, the horizontal frequency is expected to be approximately 33.75KHz.

Currently, a multi-scan television receiver has been proposed which allows a single device to receive various signals having different horizontal frequencies.

First, a multi-scan television receiver proposed by the applicant will be explained with reference to FIGS. 3 to 5.

Figure 3 shows the overall block diagram. In this figure, when receiving a normal video signal from a normal television broadcast tuner, video tape recorder, video disc player, satellite broadcast tuner, some personal computers, etc., the video signal is supplied to input terminal 1. is supplied to the RGB processing circuit 3 through the video processing circuit 2 to form three primary color signals. Further, the video/RGB switching signal supplied to the input terminal 4 is supplied to the RGB processing circuit 3, whereby the three primary color signals from the selected video signal are supplied to the cathode ray tube 6 through the output circuit 5.

Further, the video signal from the input terminal 1 is supplied to a synchronization separation circuit 7, and vertical and horizontal synchronization signals are separated. Furthermore, the switching signal from the input terminal 4 is supplied to the sync separation circuit 7, whereby the vertical sync signal from the selected video signal is supplied to the vertical deflection circuit 8, and the vertical deflection signal thus formed is transmitted to the cathode ray tube 6.
vertical deflection yoke 9. Further, the horizontal synchronization signal from the video signal selected by the synchronization separation circuit 7 is supplied to the AFC circuit 10 and the mode detection circuit 11, and the signal from this AFC circuit 10 is supplied to the horizontal oscillation circuit 12, and the mode detection circuit The normal control signal from 11 is sent to the horizontal oscillation circuit 12.
is supplied to The signal from the horizontal oscillation circuit 12 is then supplied to the horizontal deflection circuit 13, and the horizontal deflection signal thus formed is transmitted to the horizontal deflection yoke 1 of the cathode ray tube 6.
4. Furthermore, the signal from the horizontal deflection circuit 13 is transmitted to the high voltage generating circuit 1 such as a flyback transformer.
5 and the generated high voltage is supplied to the high voltage terminal 16 of the cathode ray tube 6, and part of the signal is
The signal is supplied to the AFC circuit 10.

Further, commercial power from the power supply input 17 is supplied to the power supply circuit 18, and a normal voltage according to the signal from the mode detection circuit 11 is supplied to the horizontal deflection circuit 13. Also, commercial power from the power input 17 is supplied to another power supply circuit 19, and the voltage formed is supplied to other circuits.

This allows normal video signal reception. On the other hand, digital or analog R, G, and B primary color signals (hereinafter referred to as
It's called an RGB signal. ), digital RGB signals supplied to input terminals 20R, 20G, 20B and input terminals 21R, 21G, 21B
The analog RGB signals supplied to the input terminal 4 are selected by the changeover switch 22 and supplied to the RGB processing circuit 3, and are selected by the changeover signal from the input terminal 4 and supplied to the output circuit 5.

Further, a digital synchronization signal from the input terminal 20S and an analog synchronization signal from the input terminal 21S are selected by the changeover switch 23 and supplied to the synchronization separation circuit 7, and selected by the changeover signal from the input terminal 4 to perform vertical deflection. It is supplied to the circuit 8 and the AFC circuit 10. Furthermore, the signal from the synchronization separation circuit 7 is supplied to the mode detection circuit 11, and a control signal corresponding to the frequency of the horizontal synchronization signal is formed, and the horizontal oscillation circuit 12,
It is supplied to the horizontal deflection circuit 13 and the power supply circuit 18.

This allows digital or analog RGB
Signal reception is performed. Furthermore, when performing so-called superimposed image reception in which an RGB signal is displayed superimposed on the above-mentioned normal video signal, the switching signal supplied to the input terminal 4 is set to RGB mode, and the switching signal is supplied to the input terminal 24. The Y _s signal indicating the position of the superimposed signal and the Y _n signal indicating the superimposed range are
These Y _S ,
Switching between the video signal and the RGB signal is performed during the Y _n signal.

Various signals are received in the manner described above. Further, in the above-described apparatus, the horizontal deflection system is specifically configured as follows. In FIG. 4, the horizontal synchronization signal from the synchronization separation circuit 7 is transmitted to the mode detection circuit 11 via the horizontal synchronization signal input terminal 7H.
Frequency-voltage conversion circuit (FVC) 31 that constitutes
is supplied to form a voltage according to the horizontal frequency. The output voltage of this FVC31 is the changeover switch 3
The other fixed contact 32c of this changeover switch 32 is grounded via a reference voltage source 33. In this case, the voltage value of the reference voltage source 33 is set equal to the voltage value obtained when a horizontal synchronizing signal of, for example, the NTSC system with a horizontal frequency of about 15.75 KHz is supplied to the input side of the FVC 31. Further, this changeover switch 32 is supplied with a video/RGB changeover signal from the input terminal 4 via the video RGB changeover signal input terminal 4a to its control terminal, and when this video/RGB changeover signal indicates video signal input, the changeover switch is activated. 32 movable contacts 32a are connected to the other fixed contact 32c, and when the video/RGB switching signal indicates RGB signal input, the movable contact 32a of the changeover switch 32 is connected to one fixed contact 32b. The voltage obtained at the movable contact 32a of the changeover switch 32 is supplied through a buffer amplifier 34 to a voltage controlled oscillator (VCO) 35 constituting the horizontal oscillation circuit 12. The oscillation output of this VCO 35 is the drive circuit 36
The signal is supplied to a switching transistor 37 constituting the horizontal deflection circuit 13 through the signal.

Further, the voltage obtained at the movable contact 32a of the changeover switch 32 is supplied through a gain control amplifier 38 to a parametric power supply circuit 39 of, for example, YZ type, which constitutes the power supply circuit 18. The output voltage of this power supply circuit 39 is fed back to the gain control amplifier 38 through the voltage dividing circuit 40, and the output voltage is stabilized. This output voltage is supplied to the flyback transformer 41.

A switching transistor 37 is connected in series to this flyback transformer 41. Further, a damper diode 42, a resonant capacitor 43, and a series circuit of a horizontal deflection yoke 14 and an S-shaped correction capacitor 44 are connected in parallel to the switching transistor 37.

Further, the horizontal synchronizing signal is supplied to the detection circuit 45 that constitutes the AFC circuit 10, and the voltage dividing circuit 4 provided in series with the switching transistor 37.
The signal from 6 is supplied to the detection circuit 45, and the AFC
A signal is formed. This signal is supplied to the control terminal of the VCO 35 through a low pass filter (LPF) 47.

Furthermore, capacitors 49 and 50 are connected in parallel to the resonant capacitor 43 through a switch circuit 48. Further, capacitors 52 and 53 are connected in parallel to the S-shaped correction capacitor 44 through a switch circuit 51. In addition, the voltage from the FVC 31 is supplied to a comparator circuit 54 for binary comparison corresponding to voltages of 20KHz and 30KHz of the input horizontal frequency, for example, and the voltage is 20KHz.
Thereafter, a three-value comparison output corresponding to each range of 20 to 30KHz and 30KHz or more is formed, and depending on this comparison output, the two switches built in each of the switch circuits 48 and 51 are turned off or both are turned off. Control is performed so that it is turned on.

As a result, in this horizontal deflection system,
15 to 15 in synchronization with the input horizontal synchronization signal at VCO35
An oscillation signal that changes to 34KHz is formed to perform horizontal deflection, and at the same time, a voltage that changes from 58 to 123 volts depending on the horizontal frequency is generated in the power supply circuit 39, so that the amplitude of the horizontal deflection is constant. Control is performed to ensure that In addition, in parallel with the resonance capacitor 43 and the S-shaped correction capacitor 44, capacitors 49, 50, and 52 are installed depending on the horizontal frequency range.
53 are connected, and the characteristics of each are corrected.

Further, in the above-described apparatus, the vertical deflection system is specifically configured as follows. In FIG. 5, the vertical synchronization signal from the synchronization separation circuit 7 is supplied to the sawtooth wave oscillator 61 constituting the vertical deflection circuit 8 via the vertical synchronization signal input terminal 7V. A sawtooth wave is formed by charging and discharging. This sawtooth wave is supplied to a comparison circuit 64 to form a three-value comparison output indicating a predetermined voltage range and lower or higher voltage ranges, and this comparison output is supplied to a control terminal of an up-down counter (UDC) 65. . A vertical synchronizing signal is supplied to the counting terminal of this UDC 65. The count value of this UDC 65 is supplied to a DA conversion circuit (DAC) 66, and a current source 63 is controlled by the converted analog value.

Therefore, a sawtooth wave whose peak value (amplitude) is controlled within a predetermined voltage range is extracted from the sawtooth wave oscillator 61 regardless of the frequency of the vertical synchronization signal. This sawtooth wave passes through the output circuit 67 to the vertical deflection yoke 9.
is supplied to Furthermore, a series circuit of a capacitor 68 and a resistor 69 is connected in series to this deflection yoke 9, and a voltage dividing circuit 70 is connected in parallel to this resistor 69. The divided voltage output of this voltage dividing circuit 70 is supplied to the output circuit 67.

This ensures that vertical deflection always has a constant amplitude even if the vertical frequency changes. Furthermore, the voltage dividing circuit 70
By making one of the resistors variable, the amplitude of the vertical deflection can be arbitrarily controlled.

Furthermore, another set of sawtooth wave oscillator 61 to DAC66 circuits (oscillator 71 to DAC76) is provided.
The output value of the DAC 76 of this circuit is supplied to a pin distortion correction signal forming circuit 77, and a parabolic signal with a vertical period from the midpoint of the connection between the deflection yoke 9 and the capacitor 68, for example, is supplied to the pin distortion correction signal forming circuit 77. A distortion correction signal is formed. This signal is supplied to the pin distortion correction circuit.

In this manner, in the above-described apparatus, the necessary horizontal and vertical deflections are performed in accordance with various different horizontal and vertical frequencies, and various signals are received.

[Problem that the invention seeks to solve]

Conventionally, the flyback transformer 4 has been used as a power source for the voltage applied to the screen grid of the cathode ray tube 6.
It is obtained by rectifying the flyback pulse of 1.

On the other hand, the beam current of the cathode ray tube 6 is inversely proportional to the cathode voltage as shown in FIG. 6, and as the screen grid voltage increases from EG2 to EG2', the cathode cutoff voltage increases. In the above-mentioned multi-scan television receiver, the horizontal frequency of the input signal varies considerably, for example from 15 KHz to 33 KHz, so the voltage applied to the screen grid also varies. For this reason, in a video signal having a relatively high horizontal frequency, there was an inconvenience in that black areas on the screen appeared gray.

In view of these points, the present invention aims to propose a device in which the black part of the screen does not shine even if the horizontal frequency of the input signal changes.

[Means for solving problems]

The multi-scanning television receiver of the present invention detects the horizontal frequency of an input signal, converts it into a voltage, applies this voltage to a horizontal deflection circuit, and switches the horizontal deflection frequency of this horizontal deflection circuit to receive input signals of different horizontal frequencies. In a multi-scan television receiver that receives images, the horizontal frequency of the input signal is detected,
This detection output is used to control the DC potential of the video signal that drives the cathode ray tube in accordance with the horizontal frequency.

[Effect]

According to such a configuration, the DC potential of the video signal that drives the cathode ray tube is controlled according to changes in the horizontal frequency of the input signal, so that even if the horizontal frequency of the input signal changes, the black part of the screen will not illuminate. There is no.

〔Example〕

Hereinafter, an embodiment of the multi-scan television receiver of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIGS. 3 to 5 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, 80R, 80G and 80B indicate input terminals to which R, G and B signals from the RGB process circuit 3 are supplied, respectively.
0R, 80G and 80B are connected to resistors 81R and 8, respectively.
NPN type first, second and third transistors 82R, 82G and 8 are connected via 1G and 81B, respectively.
2B, and the emitters of the first, second and third transistors 82R, 82G and 82B are connected to resistors 83R, 83G and 83B, respectively.
The collectors of the first, second and third transistors 82R, 82G and 82B are connected to the first, second and third transistors of the cathode ray tube 6 through resistors 84R, 84G and 84B, respectively. This first, along with connecting to the cathodes KR, KG and KB of
The collectors of the second and third transistors 82R, 82G and 82B are commonly connected through a series circuit consisting of resistors 85R, 85G and 85B and coils 86R, 86G and 86B, respectively. 87R,
87G and 87B are variable resistors for white balance adjustment, and one ends of the variable resistors 87R, 87G, and 87B are connected to power terminals 88R, 88G, and 88B, respectively, to which power +B is supplied, and The other ends of 87R, 87G and 87B are grounded, and the variable resistors 87R, 87G and 87
The sliders of B are connected to resistors 89R, 89G and 89, respectively.
B to the connection points between the emitters of the first, second and third transistors 82R, 82G and 82B and resistors 83R, 83G and 83B, respectively. Further, 90G and 90B are variable resistors for white peak adjustment, and one end of the variable resistors 90G and 90B is connected to the emitters of the second and third transistors 82G and 82B and resistors 83G and 83B, respectively. This variable resistor 90
The other end of G is a power terminal 91G to which power +B is supplied.
resistors 92G and 9 connected in series between
2G connection point, and the other end of variable resistor 90B is connected to the connection point of resistors 92B and 93B connected in series between power supply terminal 91B to which power supply +B is supplied and ground.

On the other hand, 41S indicates a secondary coil of the flyback transformer 41, the first intermediate voltage tap of this secondary coil 41S is connected to the anode of a diode 94, and the cathode of this diode 94 is connected to a resistor 9.
5 and a capacitor 96, and the connection point of this resistor 95 and capacitor 96 is connected to the base of a PNP type transistor 97,
The collector of this transistor 97 is connected to the common connection point of coils 86R, 86G, and 86B, and the collector of this transistor 97 is grounded through a parallel circuit consisting of a resistor 98 and a capacitor 99. 83R,
Connect to the common connection point of 83G and 83B.

On the other hand, the second intermediate voltage tap of the secondary coil 41S of the flyback transformer 41 is connected to the diode 10.
1, and the cathode of this diode 101 is grounded through a series circuit consisting of a resistor 102 and a capacitor 103.
2 and the capacitor 103 are connected to the anode of the diode 106 via the variable resistor 104 and the resistor 105 connected in series, and the cathode of the diode 106 is connected to the base of the transistor 97. The slider is connected to the screen grid G2 of the cathode ray tube 6, and the connection point between the variable resistor 104 and the resistor 105 is connected to the emitter of the transistor 97 via the resistor 107. Other components such as a horizontal deflection system and a vertical deflection system are constructed in the same manner as in the multi-scan television receiver shown in FIGS. 3 to 5 described above.

According to this configuration, the horizontal frequency is about 33.75KHz
When a video signal of
and 80B, and these three primary color signals are supplied to first, second and third transistors 82R and 82G, respectively.
and the cathode KR of the cathode ray tube 6 via 82B,
It is supplied to KG and KB respectively, and the horizontal frequency is approximately 15.75KHz by the flyback transformer 41.
The potential of the screen grid G2 of the cathode ray tube 6 increases compared to the case of . At this time, the cathode ray tube 6
The voltage fluctuation of the screen grid G2 is detected by the transistor 97, the resistors 105, 107, and the diode 106, and the detection output from the transistor 97 via the buffer amplifier 100 causes the first, second, and third transistors 82R, 82G to be detected.
and cathode KR, KG of cathode ray tube 6 from 82B
and the DC potential of the video signal supplied to the KB is increased. Therefore, due to the rise in the potential of the screen grid G2, the cathodes KR, KG of the cathode ray tube 6,
Even if the cut-off voltage of KB increases, the cathode
By increasing the DC potential of the video signal supplied to KR, KG, and KB, the horizontal frequency is approximately
Even when a video signal of about 33.75KHz, which is relatively higher than 15.75KHz, is received, the black part on the screen can be prevented from turning gray.

Furthermore, when a video signal with a horizontal frequency of about 15.75 KHz is input, a predetermined image can be obtained as in the conventional case.

As described above, according to this example, the horizontal frequency of the input signal is detected and converted into a voltage, this voltage is applied to the horizontal deflection circuit 13, and the horizontal deflection frequency of the horizontal deflection circuit 13 is switched to produce a different horizontal frequency. In a multi-scan television receiver that receives an input signal, the horizontal frequency of the input signal is
Since the DC potential of the video signal that drives the cathode ray tube 6 is controlled by the detection output from the potential change of the screen grid G2, even if the horizontal frequency of the input signal changes, the black part of the screen remains unchanged. There is a benefit in preventing the occurrence of flashing.

FIG. 2 shows another embodiment of the multi-scan television receiver of the present invention. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this example, the horizontal synchronizing signal obtained from the horizontal synchronizing signal input terminal 7H shown in FIG. 31b, and the smoothed output of this LPF 31b is passed through a buffer amplifier 108 to resistors 83R, 83G, and 83G.
3B common connection point.

Also, the secondary coil 4 of the flyback transformer 41
The second intermediate voltage tap of 1S is connected to the diode 101.
The cathode of this diode 101 is grounded through a series circuit consisting of a resistor 102 and a capacitor 103.
and the connection point of the capacitor 103 to the variable resistor 10
4 to ground, and the slider of this variable resistor 104 is connected to the screen grid G2 of the cathode ray tube 6. Other components such as a horizontal deflection system, a vertical deflection system, and a signal processing system are constructed in the same manner as in the multi-scan television receiver shown in FIG.

According to this configuration, a voltage corresponding to the horizontal frequency of the input signal is output from the monostable multivibrator 31a and the LPF 31b, and this output voltage causes the first, second, and third transistors 82R, 8
2G and 82B to cathode ray tube 6 cathode KR,
The DC potential of the video signal supplied to KG and KB is controlled, and as in the embodiment shown in FIG.
Even when a 33.75KHz video signal is received, the black areas on the screen can be prevented from appearing gray.

As described above, the horizontal frequency of the input signal is detected and converted into a voltage, this voltage is applied to the horizontal deflection circuit 13, and the horizontal deflection frequency of the horizontal deflection circuit 13 is switched to receive input signals of different horizontal frequencies. In the scanning type television receiver, the horizontal frequency of the input signal is detected, and the detected output is used to control the DC potential of the video signal that drives the cathode ray tube 6 in accordance with the horizontal frequency. It is easy to understand that the same effects as those of the embodiment shown in FIG. 1 described above can be obtained.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations may be adopted without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, the DC potential of the video signal that drives the cathode ray tube 6 is controlled according to changes in the horizontal frequency of the input signal, so that even if the horizontal frequency of the input signal changes, the black part of the screen will not illuminate. There is a benefit in preventing this.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the essential parts of the multi-scan television receiver of the present invention, and FIG.
FIG. 3 is a block diagram showing an example of a multi-scan television receiver;
Fig. 4 is a block diagram showing the horizontal deflection system extracted from Fig. 3, Fig. 5 is a block diagram showing the vertical deflection system extracted from Fig. 3, and Fig. 6 is a diagram used to explain Fig. 3. be. 6 is a cathode ray tube, 31 is an FVC, 31a is a monostable multivibrator, 31b is an LPF, 41 is a flyback transformer, 41S is a secondary coil of the flyback transformer, 80R, 80G, and 80B
are input terminals, 82R, 82G and 82B are first, second and third transistors, respectively; 94,
101 and 106 are diodes, 95 and 9, respectively.
8, 102, 105 and 107 are resistors, respectively; 9
6, 99 and 103 are capacitors, 97 is a transistor, 100 and 108 are buffer amplifiers, KR, KG and KB are cathodes, and G2 is a screen grid.

Claims (1)

[Claims] 1. A detection unit that detects the horizontal frequency of an input signal, and a horizontal deflection unit that determines a mode according to this detection output, switches the horizontal scanning frequency according to this mode, and performs horizontal deflection. in a multi-scan television receiver that receives input signals of different horizontal frequencies, the detection output of the detection section controlling the DC potential of the video signal that drives the cathode ray tube according to the horizontal frequency. A multi-scan television receiver characterized by comprising a control section. 2. A second detection unit is provided for detecting the horizontal frequency of the input signal by a change in the potential of the screen grid of the cathode ray tube, and the control unit controls the DC potential of the video signal based on the detection output of the detection unit. A multi-scan television receiver according to claim 1, characterized in that the television receiver is configured to: