JPS58704B2 - tv jiyeonji yuzouki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television receiver, and an object of the present invention is to improve image quality by modulating the scanning speed of an electron beam on a phosphor screen.

Conventionally, a pulse signal corresponding to a change in the level of a video signal is used as a drive signal, and this signal is used to apply a voltage to an electrostatic deflection plate installed in a cathode ray tube, modulating the scanning speed of the electron beam on the phosphor screen, and improving the image quality. There are known methods that attempt to improve this, but this method requires a higher applied voltage and the use of a cathode ray tube with a new electrostatic deflection plate installed inside.

The present invention drives two switching elements with pulses corresponding to the rise and fall level changes of a video signal, generates a resonant current, and adjusts the scanning speed of the electron beam on the phosphor screen to the vicinity of the electron gun of the cathode ray tube. The image quality is improved by modulating the speed using a deflection yoke for speed modulation installed in the yoke.

If we consider the black and white pattern of the video signal shown in Figure 1 I, if the video signal corresponds to the pattern I, which originally has a steep rise and fall, as shown in Figure 1, the image quality will be poor. However, in reality, due to the frequency characteristics of the receiver, the video signal has slow rises and falls as shown in (2).

Therefore, currently, television receivers differentiate the video signal twice and superimpose the signal shown in (■) on the original signal to obtain the video signal shown in (■).The image quality is improved by emphasizing the rising and falling edges. ing.

In this case, the luminance at the rising and falling white levels increases more clearly than in case (2).

In other words, when a large electron beam current flows, the beam and spot become large, resulting in too much emphasis on white.

The present invention aims to eliminate the above problems, and one embodiment thereof will be described below with reference to the drawings.

FIG. 2 shows the circuit configuration of the main parts of the preview receiver according to the present invention, and FIG. 3 shows the current or voltage waveforms of each part obtained by this circuit.

In Fig. 2, A is a video signal input terminal, 1 is a video amplifier, 2 is a buffer amplifier, 3 is a differentiator circuit consisting of a capacitor 31 and a resistor 32, 4 is a pulse amplifier, 5 is a delay circuit, and 6 is a speed modulator. This is an output circuit to obtain the resonant current for use.

This output circuit 6 consists of four NPN and PNP transistors Tr1. Tr2 is used, and the collector of Tr is a resistor R.
It is connected to the power source B through Tr2, and also connected to a resonance capacitor C7 and auxiliary deflection yokes D and Y, and R2, C2, D, and Y are similarly connected to Tr2.

The emitters of Trl and Tr2 are connected in common, and resistors R5 and R4 and capacitors C5 and C4 are connected to the base as shown in the figure.

Dl and D2 are capacitors C1 and C2 and auxiliary deflection yoke D
, Y is a variable capacitance diode connected between Y and Y.

7 is a separation circuit that separates the positive and negative pulse signals delayed by the delay circuit 5; 8 and 9 are clip circuits that clip the positive and negative pulse signals to predetermined levels; this clip signal is connected to the resistor R5; ,R.

respectively via variable capacitance diodes D1. Applied to D2.

Now, the video signal (■) in Figure 3 is amplified by the video amplification circuit 1, passes through the buffer amplifier 2, and the differentiator circuit 3 converts it into a pulse signal (■) in the same figure corresponding to the rising - L and falling times of the video signal (■). Become.

This pulse signal is amplified by an amplifier 4, further delayed by a delay circuit 5, and transistors Tr1. Applied to Tr2.

This pulse signal is applied to the capacitor 31. As a result obtained from the differentiating circuit including the resistor 32, the rising edge of the video signal becomes a positive pulse and the falling edge becomes a negative pulse.

Then, switching transistors Tr1. A speed modulation coil D that drives Tr2 and is installed near the electron gun of the cathode ray tube.
, Y inductance and resonance capacitance C110
It works as a switch for each resonant circuit consisting of 2.

At this time, the pulse signal of ■ is as clear from the figure.
The signal corresponds to the width of the rising and falling parts of the video signal.

That is, there is no signal pulse and the transistor Tr1. Tr
2 is cut off, the capacitance of the capacitor C1 and the variable capacitance diode D1 is connected to the power supply B, and the capacitance of C2 and Dl is connected to the damping resistor R from the power supply B.
1, R2, and when Trl and Tr2 reach saturation or active regions, respectively, capacitors C1 and C2 and diodes D1. Due to the charge charged in D2 and the inductance of the auxiliary deflection yokes D and Y, one cycle of resonant current can be obtained during the rising and falling period as shown in FIG. 3 (3).

The portions corresponding to the rise and fall of this resonant current have shapes with a 180° phase difference.

The positive and negative pulse signals separated by the separation circuit 7 are extracted by the clip circuit 8.9 as a signal having the same constant amplitude and corresponding to the pulse width of the differential pulse signal, and the voltage of this signal is The variable capacitance diode D
1°D2, and the variable capacitance diodes D1.D2 are driven according to the pulse width of the signal pulse. Control the capacitance of D2.

In this way, the variable capacitance diode D1. D2, the resonance period determined by the capacitance of capacitors C1 and C2 and the inductance of the deflection yokes D and Y can be made to match the pulse width shown in Fig. 3 (■), and exactly one cycle of the resonant current shown in Fig. 3 (■) can be obtained during this period. can.

In this way, the resonant period T of the resonant circuit consisting of the inductance and capacitance C1, C2, D1°D2 of the auxiliary deflection yokes D and Y matches the width of the differential signal pulse, and the period T of the resonant current coincides with the rise and rise of the video signal. This will coincide with the time of descent.

Furthermore, the above-mentioned resonant current depends on the magnitude of the input signal pulse applied to transistors Tr1 and Tr2. Tr2
The output impedance of the resonant circuit differs, and the amplitude of the resonant current of the resonant circuit changes.

As a result of the above, when a signal pulse is obtained at the rising and falling portions of the video signal (2), the switching transistor Tr1. Tr2 becomes a saturation region or an active region, and during this pulse signal period, it is possible to obtain the horizontal scanning speed vH shown in FIG.

Figure 3 (■) is a horizontal scanning velocity v on an electron beam raster that is attached to a cathode ray tube (described later) and is modulated by velocity modulation deflection yokes D and Y to which resonance current (■) is applied.
This indicates H.

In other words, when the resonant current is large, horizontal scanning is accelerated;
When it's small, slow down.

In other words, the horizontal scanning speed (■H) on the lameter is as shown in (■) in FIG.

When a video signal rises, the first half cycle is fast and the next half cycle is slow.

Also, in the falling portion, the speed is slow in the first half cycle and fast in the next half cycle.

Generally, the brightness that appears on the screen is determined by the product of the horizontal scanning speed and the video signal level.

Therefore, if we look at Figure 3 ■ which shows the video signal level and ■ which shows the horizontal scanning speed, as shown in Figure 3 ■, the black level and white level in the rising and falling periods of the video signal are emphasized, and the black level The change from the white level to the white level or vice versa becomes steep as shown in FIG. 3V, and the sharpness of the image is improved.

Incidentally, the damping resistors R1 and R2 are used for damping to prevent resonance from continuing as shown by the broken line in FIG. 3 when the signal pulse disappears.

Further, a resistor R' indicated by a broken line is a damping resistor for preventing parallel resonance caused by the inductance of the deflection yokes D and Y and their distributed capacitance.

Figures 4 and 5 show the main parts of a cathode ray tube equipped with the aforementioned auxiliary velocity deflection yokes D and Y, and Figure 6 shows the deflection yokes D and Y.
This shows the coil core of Y.

4 and 5, 51 is a deflection coil core for speed modulation;
52 is a beauty magnet, 53 is a pole piece,
54 is a cathode ray tube glass, 55 is a focus electrode, 56
57 is the second grid, 57 is the first grid, 58 is the cathode, and 59 is the deflection coil core for speed modulation. Two cores 59 are mounted outside the focus electrode 56 of the cathode ray tube.

This core 59 has a deflection coil 60 for speed modulation.
is wound into a toroidal shape to form a deflection yoke for speed modulation.

As described above, the television receiver of the present invention uses two transistors, operates the transistors separately according to the rising and falling pulse signals of the video signal, and further converts the above pulse signals into positive and negative pulse signals. It is separated by a separation circuit, stopped by a clip circuit, and drives a variable capacitance diode with a signal with the same negative signal level, changing the capacitance according to the pulse width of the pulse signal, and using the inductance of the deflection coil for speed modulation. Switching pulse period (rise,
This method performs speed modulation by obtaining a one-cycle resonant current with a period of (falling period), and the beam spot is improved by emphasizing the white level, as in the case of adding a double differentiated image signal to the conventional video signal. A clear image can be obtained without an increase in the image quality and an accompanying decrease in image clarity.

Furthermore, since the correction resonance current is used in accordance with the rising and falling periods, it is possible to make the fine parts of the image clear.

[Brief explanation of drawings]

Figs. 1 - 2 are explanatory diagrams of a conventional method for correcting brightness signals, Fig. 2 is a circuit diagram of the main part of an embodiment of the television receiver of the present invention, and Figs. A signal waveform diagram obtained from the circuit shown in the figure, FIG. 4 is a structural cross-sectional view of the main part of the cathode ray tube in the same television receiver, and FIG.
A line sectional view, FIG. 6 1 is a front view of the speed modulation core, and ■ is a side view of the same. 3...Differential circuit, 6...Output circuit, Tr. Tr2...transistor, C1, C2...resonance capacitor, D1+D2...variable capacitance diode, D, Y...
Deflection yoke for speed modulation, R1, R2...damping resistance.

Claims (1)

[Claims] 1 An auxiliary deflection yoke installed at the neck of the cathode ray tube, two transistors of different polarity driven by a pulse signal obtained in response to a predetermined level change of the video signal, and an output terminal of each of these transistors. a resonant circuit constituted by a connected variable capacitor and an inductance of the auxiliary deflection yoke; the two transistors control the resonant circuit to obtain a resonant current; A preview characterized in that the period of the resonant current is changed by changing the bias voltage applied to the variable capacitor, and the resonant current is caused to flow through the auxiliary deflection yoke to modulate the scanning speed of the electron beam on the phosphor screen. receiver.