JPH0556365A - On-screen display circuit - Google Patents

Abstract

PURPOSE:To easily see an on-screen display by adding an inverter circuit to a contrast control signal so that a detection output signal and the on-screen signal may not change at the same time at the time of the change of contrast. CONSTITUTION:An inverter 6 is connected with a contrast control signal 4, a clamp circuit 7 is made not to be applied with the voltage higher than the set voltage and the gain of an amplifier 8 for amplifying an on-screen signal 3 is controlled by a signal from the clamp circuit 7. when contrast is lowered, the contrast control signal 4 is inverted by an inverter 6 and is added to an amplifier 8, the on-screen signal 3 is amplified 8 and is outputted by being mixed with a detection output 2 in a mixing circuit 1. At this time, as the on-screen signal 3 is amplified 8, the on-screen information is easily seen on a TV screen even if the contrast is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-screen display circuit for displaying an on-screen without a feeling of strangeness when the contrast of a television receiver changes.

[0002]

2. Description of the Related Art FIG. 2 is a schematic block diagram of a conventional on-screen display circuit. In the figure, 1 is a circuit for mixing the detection output signal of the television signal and the on-screen signal. 2 is the detection output signal line of the television number, 3 is the Ekascreen signal line,
Reference numeral 4 is a contrast control signal line. 5
Is the output line of the mixed signal.

The operation of the on-screen display circuit configured as described above will be described below.

The detection output signal 2 and the on-screen signal 3 are mixed by the mixing circuit 1, controlled by the contrast control signal 4, and output on the output line 5.

[0005]

However, as can be seen from the configuration of the conventional example in the operation when the contrast changes, the contrast of the mixed signal changes when the contrast changes, and the contrast of both the detection output signal and the on-screen signal changes. And the on-screen information becomes difficult to see on the screen when the contrast is lowered.

In view of the above problems, the present invention provides an on-screen display circuit that makes it easier to see the information on the on-screen display screen when the contrast changes.

[0007]

In order to achieve this object, the on-screen display circuit of the present invention includes an amplifier for inverting the contrast control signal and controlling the level of the on-screen signal, as well as the detection output signal and the on-signal. It is characterized in that the contrast of the screen signal is not changed at the same time.

[0008]

With the above structure, the contrast of the detection output signal and the contrast of the on-screen signal do not change at the same time when the contrast changes, and the level of the on-screen signal rises when the contrast is lowered, so that the on-screen information can be easily seen on the TV screen. Will be displayed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic block diagram of an on-screen display circuit according to an embodiment of the present invention.

In the figure, 1 is a mix circuit, 2 is a detection signal output line, 3 is an on-screen signal line, 4 is a contrast control signal line, 5 is a mixed signal output line, and the above is the configuration of FIG. It is similar.

Reference numeral 6 denotes an inverter, which is connected to the contrast control. 7 is a clamp circuit, which is designed so that the voltage does not exceed the set value. 8 is an amplifier for amplifying the on-screen signal, and the gain of the amplifier is 7
It is controlled by the signal from the clamp circuit.

The operation of the on-screen display circuit configured as described above will be described below.

The operation when the contrast is not changed is similar to that of the conventional example, and the operation when the contrast is changed relating to the on-screen display circuit of the present invention will be described here. When the contrast is lowered, the contrast control signal is inverted by the 6 inverter,
In addition to the amplifier of 8, the on-screen signal of 2 is amplified and mixed with the detection output of 3 by the mixing circuit of 1 to be output. At this time, since the on-screen signal is amplified, the on-screen information does not become difficult to see on the television screen even when the contrast is lowered.

As described above, according to the present embodiment, the on-screen information can be displayed on the television screen without making it difficult to see when the contrast changes.

[0015]

As described above, according to the present invention, it is possible to make the on-screen display at the time of contrast change easy to see by simply adding a simple circuit at low cost, and the practical effect thereof is great. is there.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an on-screen display circuit according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram showing a conventional on-screen display circuit.

[Description of symbols] 1 mix circuit 2 detection output signal 3 on-screen signal 4 contrast control signal 5 output signal 6 inverter 7 clamp circuit 8 amplifier

Claims (1)

[Claims] 1. A circuit for mixing a detection output signal of a television signal and an on-screen signal is provided, and an inverter circuit is added to the contrast control signal so that the detection output signal and the on-screen signal do not change simultaneously when the contrast changes. An on-screen display circuit, which is configured to control the gain of the on-screen signal and further includes a clamp circuit to change the contrast of the on-screen signal within a certain range.