JPS6123473A - Dc reproducing circuit - Google Patents

Abstract

PURPOSE:To obtain stable display quality by adding an emitter follower circuit to an output of a DC reproducing circuit to make the output of a video circuit constant so as to prevent ringing and uneven luminance. CONSTITUTION:The DC reproducing circuit 10 has a structure that an emitter follower circuit 11 is added to an output of the DC reproducing circuit 5 and an integration capacitor C2 is not directly connected to a video output circuit 2 and the charging to the integration capacitor C2 when a video signal is turned off is avoided by a transistor 12. As a result, the discharge from the integration capacitor C2 when a video signal is turned off is avoided by a transistor 12. As a result, the discharge from the integration capacitor C2 to a coupling capacitor C1 is lost and after display such as solid all over the pattern is applied for several sec and even when the display is changed or repeated, no ringing is generated.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention allows the output of video circuits such as televisions, display devices, etc. to be controlled regardless of the pulse width of the video signal.
This invention relates to a DC regeneration circuit that can maintain a constant level.

In the information processing field, display devices such as televisions and displays are used as output devices.Display devices temporarily display characters, symbols, and graphics on a cathode ray tube, but the display data is sent as a video signal. It will be done.

The sent video signal is amplified by a video circuit to a voltage that drives a cathode ray tube, and is outputted to be displayed on the screen. At this time, the DC level of the video output from the video circuit varies depending on the pulse width of the input video signal, so it is necessary to provide a DC regeneration circuit in the video circuit to maintain a constant DC level output from the video circuit. be.

[Conventional technology]

FIG. 2 shows a video circuit with a conventional DC regeneration circuit. In the figure, a video signal input to a video input circuit 1 is input to a video output circuit 2 via a coupling capacitor C1, and is amplified in the video output circuit 2 to a voltage that drives a cathode ray tube (CRT). Output.

Note that 3 represents a transistor, 4 represents a power supply, and r represents a resistance.

A DC reproduction circuit 5 for holding the output of the video output circuit 2 constant is composed of an amplifier 6, a transistor, a diode 8, and a He capacitor Ct.

vslH5, which is not shown in FIG.
The transistor 7 receives the signal and operates.

While the transistor 7 is OFF, the output of the amplifier 6 passes through the diode 8 and is accumulated in the capacitor C2.

By feeding back this acid soil to the video output circuit 2, the third
As shown in the figure, the pulse width of the video signal is large or small.
To suppress the fluctuation of the dark level of the video output as shown in A, and keep it constant as shown in B.

[Problems that the invention attempts to solve]

However, when performing special functions such as changing the display after a few seconds of displaying an all-screen solid image using the video signal shown in FIG. When, linking 9 as shown
occurs, and the dark level momentarily changes to the bright level, causing the problem that the raster is displayed.

[Means for solving problems]

The above problems are solved by the DC regeneration circuit of the present invention, which includes an emitter follower circuit added to the output 1 of the DC regeneration circuit for making the output of the video circuit constant.

[For production]

That is, by adding an emitter follower circuit to the output of the DC regeneration circuit and avoiding direct connection between the human power of the video output circuit and the integrating capacitor of the DC regeneration circuit, it is possible to
By eliminating the charging of the integrating capacitor C1 at F, it is possible to prevent the raster from being displayed at the time of switching.

Furthermore, changes in the T)C level of the video output circuit due to changes in the pulse width of the video signal can be prevented, and stable display quality without uneven brightness can be obtained.

[Real room example]

The gist of the present invention will be specifically explained below with reference to the drawings.

FIG. 1 &l is a block diagram illustrating an embodiment of the present invention;
The first color is a detailed diagram of the DC regeneration circuit shown in FIG. 1(a), and the same symbols indicate the same objects throughout the diagrams.

In the figure, the DC regeneration circuit 10 has a structure in which an emitter follower circuit 11 is added to the output of the ladder DC regeneration circuit 5 shown in FIG. 2 so that the integrating capacitor C2 is not directly connected to the video output circuit 2.

The emitter follower circuit 11 is made up of a transistor 12 and a resistor r, as shown in FIG. The rest is the same as in FIG. 2, and the explanation will be omitted.

The transformer S raster 12 eliminates charging of the integrating capacitor C2 when the video signal is OFF. the result,
Integral capacitor C! As a result, the coupling capacitor C1 is no longer discharged, and even if the display is changed or repeated after the above-mentioned full-screen solid display is performed for several seconds, the erratic linking 9 shown in FIG. 4 does not occur.

Therefore, no raster is displayed, and stable display can be achieved by preventing brightness unevenness due to changes in the video signal pulse width.

〔Effect of the invention〕

As explained above, according to the present invention, an emitter follower circuit is added to the output of a conventional DC regeneration circuit, and linking is prevented by avoiding direct connection between the human power of the video output circuit and the integrating capacitor of the DC regeneration circuit. This prevents brightness unevenness caused by changes in the pulse width of the video signal and provides stable display quality.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram explaining one embodiment of the present invention, FIG. 1(b) is a detailed diagram of the DC regeneration circuit of FIG. 1(a),
FIG. 2 is a diagram of a video circuit equipped with a conventional DC reproduction circuit, FIG. 3 is a diagram illustrating video output that is affected by changes in video signal pulse width, and FIG. 4 is a diagram illustrating linking. In the figure, l is a video input circuit, 2 is a video output circuit, 3 is a transistor, 4 is a power supply, 6 is an amplifier, 7 is a transistor, etc.
8 is a diode, IO is a DC regeneration circuit, 11 is an eminter follower circuit, and 12 is a transistor.

Claims (1)

[Claims] detecting a change in the dark level of the video output of the video circuit, and feeding back a DC component to the video circuit to compensate for the change;
1. A DC regeneration circuit for making the output of the video circuit constant, characterized in that an emitter follower circuit is added to the output of the DC regeneration circuit.