JPH06178143A - Horizontal blanking signal generation circuit - Google Patents

Abstract

PURPOSE:To improve the performance as a monitor by preventing the occurrence of a horizontal loop back bright line which is easy to appear at a raster end by generating a blanking signal which coincides with a true horizontal fly-back line period in a phase and in a pulse width. CONSTITUTION:A horizontal drive signal voltage A from a horizontal drive transformer 4 is impressed on the base of a transistor TR 1. By this signal, pulse voltage B is generated in the collector of the TR 1. The time T1 of this voltage B becomes a horizontal fly-back line period and coincides with the fly-back line period of horizontal deflection current E. At the inversion input terminal of an arithmetic amplifier 1, the voltage A is inputted, the reference voltage of voltage Vc is grounded and impressed by a negative polarity at a non-inversion input terminal. The output voltage C of the amplifier 1 is inputted in an FF(flip flop) 3 and the type of the FF 3 inverting the output every the rise part of the input signal is used. By this operation, the FF 3 outputs a rectangular blanking signal D. This signal D becomes the signal which coincides with a period T1 in a phase and in a pulse width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal blanking signal generation circuit having improved horizontal blanking performance in a display monitor, a television receiver or the like.

[0002]

2. Description of the Related Art FIG. 3A is a circuit diagram of a main part showing an example of a conventional horizontal blanking signal generation circuit, FIG. 3B is a voltage waveform diagram of a portion with a reference numeral of FIG. 3A and 3B are diagrams showing a waveform diagram and a phase relationship between these waveforms. Hereinafter, the conventional generation of the horizontal blanking signal will be described with reference to FIG. A horizontal AFC (automatic frequency control) pulse generated in the horizontal deflection circuit is also used as the input signal (a) of the blanking signal generation circuit shown in FIG. This AFC pulse is cut by direct current with a capacitor C31, speeded up with a capacitor C32, divided into a predetermined amplitude by R31 and R32, and a negative value is added to the average value level by a diode D31 in order to remove an unnecessary component near the zero potential. Cut the directional component (V1). This cut signal becomes the base voltage of the transistor TR31.

On the other hand, as shown in the figure, TR31 has an emitter resistance of zero, and a collector load resistor R33 is selected to saturate the collector and the emitter when the base input voltage exceeds a predetermined voltage.
Make the collector output rectangular wave. This rectangular wave collector voltage output is subjected to phase inversion and a predetermined amplitude by the inverting circuit 31 to obtain a horizontal blanking signal (b). The horizontal blanking signal (b) is superimposed on the video signal applied to the cathode of the cathode ray tube, and the superimposed signal is shown in FIG.
It should be noted that FIG. 6D is a waveform diagram example of the horizontal deflection current (sawtooth wave) flowing in the horizontal deflection yoke (coil). In the waveform diagrams (a) and (b), the rising portion of the horizontal blanking signal (b) is delayed by the time Td from the rising point T1 of the pulse (a). The reason why this Td occurs is that the cut by the diode D31 is the main cause as described above, and there is the response delay time of the other TR31 and the like.

This Td naturally affects the waveform (c), and blanking does not start simultaneously at the start point of the blanking period of the horizontal deflection current (d) (to the right in the screen state), but after Td. Will be. This means that the blanking of the scanning beam is not sufficient during Td, and that part,
It appears as a vertical bright line that looks like the screen is folded.
In color TV receivers, etc., in general, the horizontal amplitude is often set slightly larger (overscan) than the size in principle, and in such a case, even if the above-mentioned folded bright line occurs on the circuit, It does not actually appear on the screen. However, in the display monitor, the so-called underscan may be performed in which the entire raster portion is displayed on the cathode ray tube, in contrast to the above-described overscan in view of its application and performance. In such a case, the folded bright line appears on the screen, which deteriorates the quality of the display monitor.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of the horizontal blanking process of the above-mentioned folded bright line, and to provide a horizontal blanking signal generation circuit for solving the problem. To aim.

[0006]

According to the present invention, a pulse having a predetermined width in the negative direction at the start and end of a horizontal blanking period and a constant negative reference voltage are input, and the pulse is supplied to the reference voltage. A horizontal blanking signal generation circuit including a differential amplifier circuit that further inverts the negative portion and outputs the inverted signal, and a flip-flop circuit that inverts the output at each rising portion of the signal from the differential amplifier circuit. It is provided.

[0007]

The differential amplifier circuit phase-inverts and outputs a portion in which the input pulse having a predetermined width in the negative direction at the start and end of the horizontal blanking period becomes more negative than the constant reference voltage. The flip-flop to which the phase-inverted pulse is input inverts the output at each rising portion of the pulse. As a result, a blanking signal is generated which rises at the start of the horizontal blanking period and falls at the end thereof.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A horizontal blanking signal generating circuit according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an essential part showing an embodiment of a horizontal blanking signal generation circuit according to the present invention, and FIG. 2 is a voltage waveform diagram of the same reference numerals (a to d) and a horizontal deflection yoke (coil) in FIG. It is a horizontal deflection current waveform (e). In FIG. 1, 1 is an operational amplifier as a differential amplifier circuit, 2 is a power supply as a reference voltage, and 3 is a flip-flop. As an existing one, 4
Is a horizontal drive transformer, TR1 is a horizontal output transistor, and D1 is a damper diode.

Next, the operation of the present invention will be described. A horizontal drive signal voltage having the waveform shown in FIG. 2A is applied from the horizontal drive transformer 4 to the base of the horizontal output transistor TR1. Due to this signal (a), a pulse voltage having the waveform shown in FIG.
The time T1 of this collector pulse (b) becomes the horizontal blanking period, which coincides with the horizontal blanking current blanking period shown in FIG. The horizontal drive signal (a) is input to the inverting input terminal (-terminal) of the operational amplifier 1, and the non-inverting input terminal (+ terminal) is input.
, A reference voltage of the voltage Vc is applied with a negative polarity with respect to the ground as shown. As a result, the operational amplifier 1, which functions as a differential amplifier, phase-inverts and outputs the horizontal drive signal (a) of (-Vc) or less, as shown in FIG. This output voltage is shown in FIG.

The output voltage (c) is the flip-flop 3
The flip-flop 3 has a type which inverts its output at every rising portion of the input signal (for example,
T-type flip-flop) is used. By this operation,
The flip-flop 3 outputs a rectangular-wave blanking signal shown in FIG. The blanking signal (d) becomes a signal which matches the horizontal blanking period T1 both in terms of phase and pulse width. The horizontal blanking signal (d) thus obtained is superimposed on the video signal in the same manner as described with reference to FIG.
Although it is used for predetermined horizontal blanking, since "Td" as in the case of FIG. 3 does not exist, the blanking operation is normally performed.

[0011]

As described above, according to the present invention, since a blanking signal which is matched in phase and in pulse width is generated in a true horizontal blanking period, so-called underscan is required. It is possible to prevent the generation of horizontal folded bright lines that are likely to appear on the edge of the raster on the display monitor, and improve the performance of the monitor.

[Brief description of drawings]

FIG. 1 is a circuit diagram of essential parts showing an embodiment of a horizontal blanking signal generation circuit according to the present invention.

FIG. 2 is a signal waveform diagram for explaining FIG.

3A is a circuit diagram of a main part of a conventional horizontal blanking signal generation circuit, and FIG. 3B is a signal waveform diagram for explaining FIG.

[Explanation of symbols]

 1 operational amplifier 2 reference power supply 3 flip-flop TR1 horizontal output transistor 31 inverting circuit

Claims (1)

[Claims] 1. When generating a horizontal blanking signal for a display monitor or the like, a pulse having a predetermined width in the negative direction at the start and end of a horizontal blanking period and a constant negative reference voltage are input, and the pulse is supplied. A differential amplifier circuit for inverting the phase of a portion more negative than the reference voltage for output, and a flip-flop circuit for inverting the output at each rising edge of the signal from the differential amplifier circuit. Horizontal blanking signal generator circuit.