KR910007424Y1 - On-screen display circuit - Google Patents

Abstract

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Description

Color TV's on-screen display circuit

1 is a conventional circuit diagram.

2 is a circuit diagram of the present invention.

3 is an operating waveform of each part of FIG.

4 illustrates one embodiment of an on-screen display.

* Explanation of symbols for main parts of the drawings

10: dedicated screen for R1-R15: resistance

C1: Capacitor Q1-Q8: Transistor

The present invention relates to an on-screen display circuit of a color television. In particular, when an on-screen blanking signal is generated, the present invention cuts off the luminance signal of the television and generates an on-screen blanking signal in which the width of the blanking signal is adjusted with a simple circuit. The present invention relates to a circuit capable of directly driving a color signal switching element of a CRT with the generated color signal current.

In general, an on-screen display in color television performs an ON screen display as shown in (402) in FIG. 3 in an arbitrary region of a cathod-ray-tube (CRT) such as (401) in FIG. However, for the on-screen display as shown in 402 of FIG. 3, a blanking area is provided around the display letter 404 as shown in 403.

In order to perform the on-screen display as described above, a circuit constructed as shown in FIG. 1 has been conventionally used by using the on-screen exclusive circuit 100 which is an integrated circuit. Referring to the conventional on-screen display process according to the above configuration, when the blank signal (V _BLK ) of the on-screen dedicated circuit 100 is a "high" signal, the signal is a "low" signal through the Nazgate G1. It is inverted and applied to the base of the transistor Q21. At this time, the transistor Q21 is turned off and outputs the second inverted "high" signal to the collector stage. Since the diode D22 is turned on to the second power supply VCC of the collector of the transistor Q21 to apply a "high" signal to the base of the PNP type transistor Q22, the transistor Q22 is also turned off. D23 is turned on. Therefore, the potential of the node point A becomes "high" to cut off the path of the luminance signal (-Y) of the television, turn off the PNP-type transistor Q23, and display on-screen to the emitter end of the transistor Q23. Outputs an on-screen blanking signal Y in a " high " state.

In addition, the potential of the node point (b) (d) (d) when the blank signal V _BLK of the on-screen dedicated circuit 100 is the "high" signal is "high" and this potential is the NAND gate G2-. It is applied to one side end of G4). In this case, when applied to the rest of the one end of the on-screen-only circuit 100 color signals (V _B, V _G, V _R) of the "high" optionally NAND gates (G2-G4) above a color signal of the state of the color signals The NAND gates G2-G4 to be input are negatively multiplied by the blank signal V _BLK and the received color signal, respectively, and applied to the emitter terminals of the drive transistors Q24 to Q26 on the CRT side.

That is, when an arbitrary color signal VB, VG, or VR is output from the on-screen blanking circuit 100 during the on-screen blanking time, the emitter potential of the corresponding driving transistors Q24-Q26 of the CRT becomes low. The driving transistors Q24-Q26 are turned on, and thus, the collector terminal of the driving transistors Q24-Q26 applies the color signal to the on-screen display signal.

The capacitors C27-C29 are used for noise reduction, the resistors R32-R34 are for current limiting, and the diodes D4-D6 are for protecting the transistors Q24-Q26.

At this time, when the blank signal V _BLK signal of the on-screen dedicated circuit 100 is set to "low", the transistor is inverted to the "high" signal of the first power supply, which is a signal of 5 T of the TTL level by the NAND gate G1. Turn on (Q21). Here, the first power source means a power source having a TTL level. At this time, when the transistor Q21 is turned on, since the second power supply VCC is bypassed through the transistor Q21, the potential of the collector is “low”, and thus the diode D22 is also turned off. Transistor Q22 is also turned on. Therefore, since the diode D23 is also turned off, the potential of the node point A becomes "low", and the luminance signal (-Y) of the television is applied to the transistor Q23 to release the on-screen blanking signal and Output the luminance signal.

In addition, when the blank signal V _BLK is generated as a low signal, the potential of the node point (b, d, d) is also in a low state, and thus the output of the NAND gates G2-G4 is the color signal V _B, Regardless of the output of V _{G and} V _R , it becomes a "high" signal and is applied to the emitters of the respective driving transistors Q24-Q26, so that the driving transistors Q24-Q26 maintain the turn-off state. Therefore, the path of the color signals V _B, V _G, V _R for the on-screen display is blocked.

The conventional on-screen display circuit as described above has to use two power sources by level shifting to the second power supply of the supply power supply (VCC) using the first power supply of the TTL level, and generates an on-screen blanking signal. In order to perform three inversion transition operations (output of the on-screen dedicated circuit 100 → NAND gate G1 → transistor Q21-Q22), the capacitor C21-C23 is used for speed up. , Diodes (D21-D23), Schottky transistors, etc. should be used, and since the imager driving method is used for the driving transistors Q24-Q26, sufficient drive current for each emitter of the driving transistors Q24-Q26 Since the NAND gate (G2-G4) was used to satisfy), the configuration was complicated by many components and the cost was increased.

Accordingly, an object of the present invention is to provide a circuit capable of generating an on-screen blanking signal by level shifting a power by directly using a signal of an on-screen dedicated circuit in an on-screen display circuit.

Another object of the present invention is to provide a circuit capable of driving an on-screen color signal by using a drive transistor of a CRT as a base drive method.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a detailed circuit diagram of an embodiment of the present invention and includes an on-screen dedicated circuit 10, a resistor R1-R6, a capacitor C1, and a transistor Q1-Q3. A level converting unit which is directly switched by the blank signal V _BLK of 10) to form a path of the blanking signal and determines a blanking width to generate an on-screen blanking signal level-shifted to a predetermined power supply by the leveling signal ( A luminance signal switch unit composed of resistors R7-R9 and transistors Q4-Q5 and switched by the blanking signal to block the luminance signal (-Y) of the television and output an on-screen blanking signal ( 30, and resistors R10-R15 and transistors Q6-Q8, which are directly driven by the color signal (B, G, R) currents of the on-screen dedicated circuit 10 to switch the path of the on-screen color signal. It consists of a color signal switch 40.

FIG. 3 is an operational waveform diagram of each part of FIG. 2, (3A) is a waveform diagram of a blank signal V _BLK , (3B) is a waveform diagram of a luminance signal (-Y), and (3C) is a luminance signal. waveform and, (3D) of (Y) is also God V _R wave, (3E) is a waveform of the signal V _G, (3F) is a waveform of the V _B.

In addition, the on-screen display area displayed on the CRT is the same as in FIG. 4, and the reference numerals are the same.

Based on the above-described configuration, the present invention will be described in detail with reference to FIGS.

First, the generation process of the on-screen blanking signal will be described.

When the blank signal V _BLK is output as a "high" signal in the on-screen dedicated circuit 10 as in (3A), the PNP transistor Q1 is turned off. When the transistor Q1 is turned off, the emitter side is in a "high" state and the transistor Q2 is also in a turn-off state. Therefore, a "high" state signal is output to the collector terminal of the transistor Q2 and the transistor Q3. Turn on).

At this time, when the transistor Q3 is turned on, the power of the TTL level is shifted level to the second power supply Vcc, whereby the potential of the node point a occurs in the "high" state of the second power supply Vcc level. do. That is, when the on-screen dedicated circuit 10 outputs a "high" signal of the TTL level 5V, which is the first power source, the level converter 20 converts the level to 12V of the second power source Vcc. .

When the state of the node point a becomes a "high" level state, the second power supply level Vcc is applied to the emitter terminal of the transistor Q4 so that the transistor Q4 is turned off, thereby The PNP transistor Q5 is also turned off (3B) to prevent the application of the luminance signal (-Y) of the television generated as shown in 3B.

Accordingly, the second power supply VCC is generated at the emitter terminal of the transistor Q5 (3c) and outputs a "high" signal, which is a blanking signal for on-screen display as shown in 3c. At this time, the output state of the node point a is the same as the output state of the luminance signal Y as shown in (3C).

At this time, the color signals V _R, V _{G, and} V _{B of} the on-screen dedicated circuit 10 are outputted as 3D, 3E, and 3F, respectively, and the transistors Q6 through the resistors R10-R12. And a color signal for on-screen display in the blank signal (V _BLK ) period. That is, the transistors Q6-Q8 form a passage for driving a color signal of a character to be displayed on the on-screen display area 402 on the CRT 401. The transistor Q6 is formed of blue (BLUE: B). Transistor Q7 drives green (G) and transistor Q8 drives red (Read: R). The CRT 401 then mixes the color signals V _R, V _G, V _B to determine the color of the on-screen display characters.

In the process of generating the on-screen blanking signal described above, the transistors Q1-Q2 are directly " off " switched (first switching) by the blank signal V _BLK of the on-screen dedicated circuit 10 and the resistor R5-. Biased by R6) to adjust the width of the blanking signal, whereby transistor Q3 is " on " switched (second switch) to generate a blanking signal level shifted to the second power supply VCC. . Therefore, when the blank signal V _BLK is generated, it is possible to drastically reduce the parts necessary for speed-up by directly switching and inverting the signal and level shifting step by the signal V _BLK . The fourth and fifth switching elements transistors Q4 to Q5 are " off " switched by the blanking signal to block the luminance signal (-Y) of the television and generate an on-screen blanking signal by the second power supply VCC. .

Second, we look at how to turn off the on-screen display.

When the blank signal V _BLK of the on-screen dedicated circuit 10 transitions to a "low" signal such as (3A), the transistor Q1, which is a PNP type, is turned on. Turned on by the signal divided at -R4). Then, the transistor Q2 outputs a "low" signal to the collector stage, so that the transistor Q3 is turned off, so that the potential of the node point a becomes a "low" level (3B). The transistor Q4 is switched in accordance with the state of the easy signal -Y. In this case, the transistor Q5 is switched by the television luminance signal -Y, which is a state in which the on-screen blanking signal is released and the level of the luminance signal Y of the television is output as shown in 3C.

In this case, since the on-screen dedicated circuit 10 does not output the color signals V _R, V _{G, and} V _B like (3D), 3E, and 3F, the CRT driving transistors Q6-Q8 turn off. Keep it.

As described above, when a blank signal is generated in the on-screen display circuit, it is possible to switch directly by this signal and then level shift to the input power supply, thereby reducing all the parts that speed up and adjusting the width of the blank signal. A blanking signal of width can be obtained.

Claims (2)

In the color television on-screen display circuit having the on-screen dedicated circuit 10 for generating a blank signal (V _BLK ) and color signals (V _R, V _G, V _B ) for on-screen display, the on-screen display a receives the blank signal (V _BLK) circuit 10, and the blank signal (V _BLK), the blank signal (V _BLK) of the first power level are switched upon receipt of a second power source (Vcc) level of the CRT drive levels Receives the shifted level converter 20 and the output of the level converter 20, and is switched when receiving the level shifted blank signal to block the supply path of the television luminance signal (-Y) and turn on the CRT Receives a luminance signal switch unit 30 for outputting the blank signal for setting the screen display area to the CRT, and the color signals (V _R, V _G, V _B ) of the on-screen dedicated circuit 10, and The on-screen area is directly switched by respective color signals V _R, V _{G and} V _B On-screen display circuit of a color television, characterized in that consisting of a switch unit 40 for outputting a color signal for display on the CRT. The first transistor Q1 of claim 1, wherein the level shift unit 20 is switched off by a blank signal V _BLK having a TTL level for outputting the on-screen dedicated circuit 10, and the first transistor Q1. A second transistor Q2 for switching in conjunction with the off switching of the first transistor Q1 and a blank signal which is switched by the off switching of the second transistor Q2 to be level-shifted to the power supply VCC level. An on-screen display circuit connected to an output terminal of a third transistor (Q3), wherein the level shifted blank signal width comprises a resistor (R6).