JPS6322509B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal polarity switching circuit, and more particularly to a video signal polarity switching circuit that switches the polarities of television video signals having different polarities so that they become the same polarity.

For example, in a television receiver that receives broadcast waves, the polarity of a video signal as a received signal is fixed and not arbitrary. However, in recent television games, display monitors, and the like, the polarity of the video signal is not fixed, and a video signal with a polarity suitable for each device is created. Therefore, in order to use a video signal from a display monitor in another device, for example, since the polarity is not determined, it is necessary to provide a conversion circuit to obtain the required polarity. However, if such a conversion circuit is attached to each device, it lacks versatility, increases the number of models, and increases costs.

Therefore, the main object of the present invention is to provide a video signal polarity switching circuit that can derive a video signal of the same polarity regardless of the polarity of the input video signal.

In summary, the present invention provides a video signal including a blanking signal to a blanking signal voltage generating means, and if the blanking signal has the first polarity when the synchronization signal has the first polarity, the blanking signal is blanked. A voltage corresponding to the polarity of the signal is generated to derive a video signal whose polarity is not inverted from the video signal switching means, and if the blanking signal has the second polarity, the polarity is inverted based on the voltage corresponding to the polarity. The system is designed to derive the video signal that is displayed.

The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

FIG. 1 is an electric circuit diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. 1. FIG. 3 is an electrical circuit diagram of the synchronous signal switching circuit included in FIG. 1, and FIG. 4 is a waveform diagram for explaining the operation of FIG. 3.

The video signal polarity switching circuit shown in FIG. 1 includes a video amplification circuit 2 that amplifies a video signal applied to an input terminal 1, and a video signal of the same polarity and an inverted polarity based on the output of the video amplification circuit 2. A video signal polarity inversion circuit 5 for deriving a video signal, a synchronization signal switching circuit 4 for deriving a synchronization signal of the same polarity regardless of the polarity of the synchronization signal applied to the input terminal 3, and an output of the synchronization signal switching circuit 4. a blanking signal voltage generation circuit 8 that generates a voltage according to the polarity of a blanking signal included in the video signal based on the blanking signal voltage generation circuit 8; and a video signal applied to the input terminal 1 based on the voltage from the blanking signal voltage generation circuit 8. and a video signal switching circuit 6 that derives a positive polarity video signal regardless of the polarity of the video signal.

Here, the aforementioned synchronizing signal switching circuit 4 will be explained with reference to FIGS. 3 and 4. The synchronization signal switching circuit 4 includes a waveform shaping circuit 41 that shapes the waveform of the synchronization signal applied to the input terminal 3, and a waveform shaping circuit 4.
1, a sync signal polarity inversion circuit 42 that inverts the polarity of the sync signal shaped in step 1; a sync signal voltage generation circuit 43 that generates a voltage according to the polarity of the output of the waveform shaping circuit 41; It includes a synchronization signal switching circuit 44 that derives a negative polarity synchronization signal regardless of the polarity of the synchronization signal.

First, when a positive polarity synchronization signal is applied to the input terminal 3, this synchronization signal is applied to the resistor 411 and the capacitor 4.
16 to the base of transistor 415. A power supply voltage +Vc is divided by resistors 413 and 412 and applied to the base of the transistor 415 as a bias voltage. When the transistor 415 receives the positive synchronization signal, it generates a negative synchronization signal across the resistor 414 connected to its collector. This synchronization signal inverted to negative polarity is given to a polarity inversion circuit 42 and passed through a low resistor 421 and a capacitor 423 to a transistor 424.
given on the basis of. Therefore, a synchronization signal whose polarity is inverted to the original positive polarity is derived from the collector of the transistor 424. This positive synchronization signal is applied to the transistor 4 included in the pulse switching circuit 44.
Given to the base of 53.

On the other hand, the negative polarity synchronization signal whose waveform has been shaped and whose polarity has been inverted by the waveform shaping circuit 41 is provided to the synchronization signal voltage generation circuit 43. Then, this negative polarity synchronization signal is passed through a resistor 431 to a capacitor 433.
Charge 3. This negative polarity synchronization signal is shown in Figure 4a.
As shown in FIG. 2, since the high level period is long, the voltage generated across the capacitor 433 becomes the high level voltage V1. This voltage V1 is applied to the base of the transistor 449 via a resistor 441 and a backflow prevention diode 445 included in the pulse switching circuit 44, and is applied to the base of the transistor 449 via a resistor 442 and a backflow prevention diode 446.
Given on a base of 0. Therefore, transistors 449 and 450 are conductive and their respective collectors are at a low level. transistor 449
Since the collector of is connected to the base of transistor 453, this transistor 453 becomes non-conductive.

Furthermore, since the low level signal at the collector of transistor 450 is applied to the base of transistor 451, transistor 451 is not conductive and its collector becomes high level. This transistor 4
The collector of 51 is connected to the base of transistor 452. Further, a negative polarity synchronization signal is applied to the base of the transistor 452 from the waveform shaping circuit 41 via a resistor 454 . When the collector of the transistor 451 becomes high level, the transistor 452 becomes conductive, and a negative synchronization signal is output to its emitter. This negative polarity synchronizing signal is led out from the output terminal 3' via a backflow prevention diode 447. in this way,
When a positive polarity synchronization signal is applied to the input terminal 3, a negative polarity synchronization signal is obtained from the output terminal 3'.

Next, when a negative polarity synchronization signal is applied to the input terminal 3, the waveform shaping circuit 41 derives a positive polarity synchronization signal. This positive polarity synchronization signal is inverted to the original negative polarity synchronization signal by the synchronization signal polarity inversion circuit 42, and charges the capacitor 433 of the synchronization signal voltage generation circuit 43. At this time, since the positive polarity synchronization signal has a long low level period as shown in FIG. 4b, the terminal voltage of the capacitor 433 becomes the low level voltage V2. Since the terminal voltage of capacitor 433 is at low level, transistor 4
49,450 is not conductive. transistor 450
Since the transistor 451 is not conductive, the transistor 451 is rendered conductive by a high level signal applied from the power supply +Vc through the resistor 443 to its base. As transistor 451 becomes conductive, its collector becomes low level, and transistor 452 becomes non-conductive.

On the other hand, as the transistor 449 becomes non-conductive, its collector becomes high level.
Transistor 453 becomes conductive. Therefore, the transistor 453 transmits the negative polarity synchronization signal whose polarity has been inverted by the synchronization signal polarity inversion circuit 42 from the emitter through the backflow prevention diode 448 to the output terminal 3'.
It is derived as follows. In this way, even if a negative polarity synchronization signal is applied to the input terminal 3, the same negative polarity synchronization signal can be obtained from the output terminal 3'.

Referring again to FIG. 1, as mentioned above, the input terminal 3
Even if a positive or negative polarity synchronization signal is applied to the synchronization signal, the synchronization signal switching circuit 4 always derives a negative polarity synchronization signal. This negative polarity synchronization signal is applied to the base of the transistor 82 via a backflow prevention diode 81 included in the blanking signal voltage generation circuit 8. Then, this transistor 82 becomes conductive based on the negative polarity synchronization signal.

When a positive polarity video signal is applied to the input terminal 1, the video amplification circuit 2 amplifies the video signal and provides it to the video signal polarity inversion circuit 5. Video signal polarity inversion circuit 5 includes a differential amplifier constituted by transistors 51 and 52, and includes resistors 53 to 58 and a capacitor 59 as peripheral circuits. Then, a negative-polarity video signal whose polarity is inverted is derived from the collector of the transistor 51, and a positive-polarity video signal whose polarity is not reversed is derived from the collector of the transistor 52. The positive polarity video signal is applied to the base of a transistor 69 as a first switching means included in the video signal switching circuit 6, and is also applied to the base of a transistor 69 as a first switching means included in the video signal switching circuit 6, and is also applied to the above-mentioned signal via a resistor 89 and a capacitor 91 included in the blanking signal voltage generation circuit 8. Applied to the emitter of transistor 82. Further, a video signal of negative polarity whose polarity has been inverted is applied to the base of a transistor 68 serving as a second switching means. The positive video signal applied to the emitter of the transistor 82 charges the capacitor 92 from its emitter via the collector and resistor 87 when the transistor 82 becomes conductive based on the negative synchronization signal.
At this time, the positive-polarity video signal includes a negative-polarity blanking signal, as shown in FIG. 2a, and the synchronization signal has a pulse width narrower than the pulse width of this blanking signal. Therefore, the capacitor 92 is charged with a low level voltage according to the polarity of the blanking signal only while switching is being performed based on the synchronization signal. This low level voltage is applied to the base of transistor 65 via resistor 70 and diode 61 for preventing backflow, and is also applied to the base of transistor 67 via resistor 71 and diode 62 for preventing backflow. Therefore, transistors 65 and 67 each become non-conductive.
The collector of the transistor 67 is connected to the base of the transistor 68, and the collector of the transistor 67 is connected to the base of the transistor 68.
As transistor 7 becomes non-conductive, transistor 68 becomes conductive. When the transistor 68 becomes conductive, the negative video signal applied to its base is led out from the output terminal 9 via the backflow prevention diode 63.

On the other hand, the collector of transistor 65 is connected to the base of transistor 66, and the collector of transistor 66 is connected to the base of transistor 69. Therefore, since the transistor 65 becomes non-conductive, the transistor 66 becomes conductive in response to a high level signal applied via the resistor 72 from the power supply +Vc. As this transistor 66 becomes conductive, the transistor 6
9 becomes non-conductive. Since the transistor 69 is non-conductive, the positive video signal applied to its base is not output.

As described above, when a positive polarity video signal is applied to the input terminal 1, a reverse polarity video signal is also derived from the output terminal 9.

Next, when a negative-polarity video signal is applied to the input terminal 1, a positive-polarity video signal is derived from the collector of the transistor 51, and a negative-polarity video signal is derived from the collector of the transistor 52. This negative polarity video signal is sent to a capacitor 92 via a transistor 82 that switches based on a synchronization signal.
to charge. At this time, as shown in Figure 2b,
Since the video component has a negative polarity and the blanking signal is at a high level, the charging voltage of the capacitor 92 is at a high level. Since the charging voltage of capacitor 92 is at a high level, transistors 65 and 67 become conductive. As transistor 67 becomes conductive, transistor 68 becomes non-conductive.

On the other hand, as transistor 65 becomes conductive, transistor 66 becomes non-conductive. As transistor 66 becomes non-conductive, transistor 69 becomes conductive. And transistor 69
A video signal of negative polarity applied to the base of is led out from the output terminal 9 via the backflow prevention diode 64.

In the above description, a video signal of negative polarity is derived based on a video signal of positive polarity or negative polarity, but it may be configured to generate a video signal of positive polarity conversely. Furthermore, although the case has been described in which the synchronizing signal for switching the transistor 82 included in the blanking signal voltage generating circuit 8 is also of negative polarity, it may also be configured to switch with positive polarity.

As described above, according to the present invention, the polarity of the blanking signal included in the video signal is determined based on the synchronization signal, and if the video signal has the required polarity, it is directly derived without reversing the polarity. If the blanking signal has the opposite polarity, a video signal with the polarity inverted is derived, so a video signal with the same polarity can be obtained regardless of the polarity of the input video signal.

[Brief explanation of the drawing]

FIG. 1 is a specific electrical circuit diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. 1. FIG. 3 is a specific electrical circuit diagram of the synchronizing signal switching circuit included in FIG. 1, and FIG. 4 is a waveform diagram for explaining the operation of FIG. 3. In the figure, 4 is a synchronous signal switching circuit, 41 is a waveform shaping circuit, 42 is a synchronous signal polarity inversion circuit, and 43 is a synchronous signal switching circuit.
44 is a sync signal voltage generation circuit, 44 is a sync signal polarity switching circuit, 5 is a video signal polarity inversion circuit, 6 is a video signal switching circuit, 69 is a first switching means, 6
Reference numeral 8 indicates a second switching means, and reference numeral 8 indicates a blanking signal voltage generation circuit.

Claims (1)

[Scope of Claims] 1. A video signal polarity switching circuit that derives a video signal that includes a blanking signal of a first or second polarity and has a polarity opposite to the blanking signal as a video signal of the same polarity. synchronous signal generating means for generating a synchronous signal; video signal polarity inverting means for inverting the polarity of the video signal; blanking signal voltage generating means for generating voltage;
and Deriving a video signal to be applied to the input of the video signal polarity reversing means based on the fact that a voltage according to the first polarity is applied from the blanking signal voltage generating means, and according to the second polarity. A video signal polarity switching circuit comprising video signal switching means for deriving a video signal whose polarity is inverted based on the voltage applied to the video signal polarity inversion means. 2. The synchronizing signal generating means is the first or second synchronizing signal generating means.
synchronous signal polarity switching means for deriving a synchronous signal having a polarity as a synchronous signal of the same polarity, the synchronous signal polarity switching means for reversing the polarity of the synchronous signal; synchronizing signal voltage generating means for generating a voltage according to the polarity; and a voltage according to the first polarity being applied from the synchronizing signal voltage generating means to the input of the synchronizing signal polarity reversing means. The method according to the present invention includes a synchronization signal switching means for deriving a synchronization signal and deriving a synchronization signal whose polarity is inverted based on the application of a voltage according to the second polarity. The video signal polarity switching circuit according to scope 1. 3. The video signal switching means performs switching based on the fact that a voltage corresponding to the first polarity is applied from the blanking signal voltage generation means, and switches the video signal applied to the input of the video signal polarity inversion means. and a first switching means for deriving a polarity-inverted image of the output of the video signal polarity reversing means, which performs switching based on a voltage corresponding to the second polarity being applied from the blanking signal voltage generation means. The video signal polarity switching circuit according to claim 1, comprising second switching means for deriving the signal.