JPS5838682Y2 - television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television receiver, and particularly to a blanking device therefor, and is intended to effectively perform the blanking operation.

FIG. 1 shows a conventional example.

In the figure, 1 and 2 are the first and second video amplifier circuits, 3 is the blanking pulse input terminal, 4 is the coupling capacitor, 5 is the discharge resistor, 6 is the reverse current blocking diode, and 7 is the bias resistor. , and one end of this resistor 7 is connected to the above-mentioned first. It is connected to the connection point of the second video amplification circuits 1 and 2 to form a blanking circuit.

Further, FIG. 2 shows the blanking pulse at this time.

Here, A indicates the absolute level of the pulse, B indicates the ringing level, and C indicates the absolute level of the effective ringing pulse.

In the above configuration, the blanking pulse shown in FIG. 2 applied to the input terminal 3 passes through the coupling capacitor 4, the discharge resistor 5, the reverse current blocking diode 6, and the resistor 7. It is added to the connection point between the second video amplification circuits 1 and 2 to perform a blanking operation.

However, in the conventional configuration described above, when the absolute level A of the blanking pulse is small and when the absolute level B of ringing is large, the absolute level C of the effective ringing pulse is
has the disadvantage that it becomes small and effective blanking cannot be performed.

The present invention eliminates the above-mentioned drawbacks of the conventional method, and effectively performs blanking by shaping the differential waveform of the blanking pulse and applying a DC bias by superimposing a DC voltage on the differential waveform voltage. It is.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

In FIG. 3, 1 and 2 are the first . a second video amplification circuit;
3 is a blanking pulse input terminal, 8 is a coupling capacitor,
9 and 10 are bias resistors, 11 is a reverse current blocking diode, and 12 is a resistor, one end of which is connected to the connection point of the first and second video amplifier circuits 1 and 2.

Further, one end of the bias resistor 6 is connected to a 10B power source 13.

Figures 4A and 4C are waveform diagrams of blanking pulses for explaining the effects of the present invention.

FIG. 4A shows a waveform when the blanking pulse is not differentiated (it can be considered as the waveform at point a in FIG. 1).

), Figure 4 shows the waveform when the blanking pulse is differentiated,
In other words, the waveform at point b in Fig. 3 when the bias resistor 9 is not present, and the waveform at point b in Fig. 4 when the blanking pulse is differentiated and a DC voltage is applied from the DC power supply 13 through the bias resistor 9. It is.

In Fig. 4 A, 2 and C, D and D' are the blanking levels, and E and E' are the levels from the blanking levels D and D' to the peak H of the ringing in the scanning period G (hereinafter, This is called the ringing open level.

), F, F'. F// indicates the blanking contribution pulse width, respectively.

To explain the operation of FIG. 3, when a blanking pulse is applied to the input terminal 3, the pulse is applied to the coupling capacitor 8.
and is differentiated and waveform-shaped by bias resistors 9 and 10, and the fourth
A blanking pulse as shown in Figure C appears at point b, and a period of blanking contribution pulse width F// of this blanking pulse,
The reverse current blocking diode 11 is opened and a blanking operation is performed.

Here, in the blanking pulse shown in FIG. 4C, the peaks H of the ringing peaks during the scanning period are brought to the same level by the coupling capacitor 8 and bias resistors 9 and 10.

The level of this peak H is when DC bias ■ is applied.
It is fixed at a level slightly lower than the blanking level D'.

Therefore, sufficient blanking can be performed by the wide blanking contribution pulse width F// of the blanking pulse.

On the other hand, the effect of differentiation will be explained with reference to FIG.

For the blanking pulse before differentiation shown in Figure 4A, the fourth
Assuming that the blanking levels D and D' of the differentiated blanking pulse shown in the figure are the same level, the relationship between the blanking contribution pulse widths F and F' is phase-wise after the differentiation. Although the blanking pulse width (blanking contribution pulse width F' in FIG. 4 is advanced), the blanking pulse widths can be made almost equal.

However, regarding the ringing open levels E and E', by making the levels of the peak H of the ringing during the scanning period G equal, the ringing open level E' after differentiation becomes larger than the open level E before differentiation.

Therefore, according to the configuration shown in FIG. 3, in combination with the magnitude of the blanking contributing pulse width F//, a stable and sufficient blanking operation can be performed.

As explained above, according to the present invention, by shaping the differential waveform of the blanking pulse and applying a DC bias by superimposing a DC voltage on the differential waveform voltage, the influence of ringing, etc. on the blanking pulse in the scanning period is reduced. The width of the blanking contribution pulse can be effectively utilized, and a stable blanking operation can be performed.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional television receiver, Fig. 2 is a waveform diagram of a conventional blanking pulse, Fig. 3 is a circuit diagram of a television receiver according to an embodiment of the present invention, and Fig. 4 i9
Figures 1 and 2 are waveform diagrams of blanking pulses for explaining the effects of the present invention. 1.2...Video amplification circuit, 3...Blanking pulse input terminal, 8...Coupling capacitor, 9, 10...Bias resistor, 13・・・・・・
・DC power supply.

Claims (1)

[Scope of utility model registration request] It is characterized by providing means for differentially shaping the blanking pulse, means for superimposing a DC voltage on the differentially shaped waveform, and applying the blanking pulse after superimposing the DC voltage to a video amplification circuit to perform blanking. television receiver.