JPS6139692A - System switching circuit - Google Patents

Abstract

PURPOSE:To permit automatic reception of various television system signals with a single television receiver by discriminating the various television system signals with discriminating means such as PAL/NTSC, 50Hz/60Hz. CONSTITUTION:A color carrier signal CW and a burst signal BU are fed to a PAL/NTSC detection circuit 11. When an NTSC signal inputs, an output of the detection circuit 11 is a zero level. When a PAL signal inputs, however a signal, which becomes high for each one horizontal scanning line is outputted to the detection circuit 11. With this difference, the PAL and NTSC systems are discriminated from each other. A field frequency detection circuit 12 further outputs a discrimination output A2 representing either 50Hz or 60Hz as the field frequency. Further, a detection circuit 15 discriminates a voice carrier signal. The individual discrimination outputs are fed to a mode switching circuit 16, which can produce switching signals S1 to S4 according to the detected television system.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a system suitable for automatically identifying a number of different television systems and switching the signal processing system of a television receiver. Regarding switching circuits.

[Technical background of the invention and its problems]

If we classify the television systems currently used in the world, there are 11 types, as shown below. In Table 1,
VTR means video teso recorder, and vDP means video disc layerer.

Table 1 When there are various television systems as described above, there are areas or users in which a television receiver that can handle only a single system is inconvenient.

[Purpose of the invention]

This invention was made to deal with the above circumstances,
In order to automatically receive various television systems on one television receiver, PAL/NTS
It is an object of the present invention to provide a system switching circuit which has a discrimination means such as C, 50Hz, 760Hz, etc., and can obtain discrimination signals for various television systems.

[Summary of the invention]

This invention utilizes PAL and NTSC as shown in FIG.
PAL, 4TSC detection circuit 11 that discriminates television signals based on the phase relationship between burst signals and color carrier signals.
, a field frequency detection circuit 12 that discriminates between 50 Hz and 60 Hz of the field frequency, and 4. of the audio carrier signal.
5 MHz and other frequencies 5.5 MHz, 6
, OMHz, 6.5 MHz discrimination means 13゜14
．． 15, and by matrixing the status of each discrimination output, PAL (NTSC) color killer voltage, and SECAM color killer voltage in a mode switching circuit 16, various television systems can be automatically discriminated. It's something.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a portion 10 surrounded by a broken line is an integrated circuit. The PAL/NTSC detection circuit 11 includes:
A color carrier signal y and a burst signal BU are input. This PAL/NTSC detection circuit 11 is a circuit that performs phase detection between the color carrier signal and the burst signal BU. Assuming that an NTSC television signal is currently being received, the output A1 of this detection circuit 11 is at zero level.

This is because, as shown in FIG. 2, the phase difference between the color carrier signal y of the NTSC system and the burst signal BU is 90° for each horizontal scanning line, and always maintains a constant relationship. Next, assuming that a PAL television signal is being received, the output A1 of the detection circuit 11 becomes high level for each horizontal line. This is because, as shown in FIG. 2, the phase relationship between the color carrier signal and the burst signal BU is such that it swings every horizontal line. As a result, the PAL/NTSC detection circuit 1
It is possible to obtain a discrimination output between the PAL system and the NTSC system.

Next, 12 is a field frequency detection circuit, into which a vertical synchronizing signal and a horizontal blanking signal 4' are input.

The field frequency is 50Hz! There are two types: 60Hz. Therefore, if the vertical frequency is 50Hz, 1
The number of horizontal synchronizing signals for one field is 625/2, and if the vertical frequency is 60 Hz, the number of horizontal synchronizing signals for one field is 525/2. Utilizing this fact, if the relationship between the vertical synchronization signal and the horizontal synchronization signal (or horizontal Planck's pulse) is counted and determined by a counter, the determination output A2 as to whether the field frequency is 50Hz or 60Hz can be obtained. can be obtained.

Next, the means for determining the audio carrier signal will be explained.

The audio carrier signal is 4.5 M as seen in Table 1
T(z, 5.5 MHz, 6.0111f'H
There are 6.5MHz and 6.5MHz types. Among these four types of signals, 5, 5 MHz, 6.0 MHz, 6.
Focusing on the three signals of 5 MHz, these are 6 M
The relationship is ±500Hz with Hz as the center. Therefore,
By mixing the 500 kHz oscillation output with this audio carrier, it can be converted into a single 6 MHz signal.

The system that obtains this operation uses a 500kHz oscillator 13.
and a mixing circuit 14. Therefore, when the output B1 obtained from the mixing circuit 14 is 6 MHz, the audio carriers at this time are 5.5 MHz and 6.0 MHz.
.

6.5 MHz. Next, the output of the mixing circuit 14 is set to 4.5 MHz15. OMH
Input to the z detection circuit 15. This detection circuit 15 includes 4
, a 5 MHz audio carrier signal (separated by a filter) and a 6 MHz output from the mixing circuit 14, determines which signal is present, and outputs the determination output A3. can be obtained. The detection circuit 15 may be either a filter or a multiplication circuit.

Next, a method for determining whether the television system is PAL or NTSC or 5ECA or M will be explained. This means that when receiving the PAL or NTSC system, the PAL (NTSC) color killer voltage KVI is at a high level, and the SECAM color killer voltage KV2 is at a low level. The killer voltage 'v1 is at low level and the SECAM color killer voltage KV2 is at high level.

The state of the killer voltages KVI, KV2 is determined by whether the color carrier is 3.58 MHz (PAL, NTSC) or 4.43 MHz (SECAM). Further, when receiving a black and white broadcast, the killer voltages KVI and KV2 are at a low level regardless of the system. When the killer voltages KVI and KV2 are at low level, the mode switching circuit 16 switches between 3 and 5 for the color carrier oscillator.
It is set so that the switching output S1 of 8 MHz and 4.53 MHz is not changed at an appropriate period. next,
When a color broadcast is received, the color carrier oscillator is set to be phase-locked to the color burst, so
Killer voltage KVI depends on the television system at this time.
, KV2 signal is high level on one side and low level on the other side. When such a relationship occurs, 3.58 M
The switching output S1 of 4.53 MHz and 4.53 MHz is set to be maintained at the current state.

The mode switching circuit 16 has the above-mentioned discrimination outputs kl, 12.
．． 13 and killer voltages KVI and KV2 as inputs,
A matrix calculation is performed using each input to determine the television system currently being processed. This generates a switching signal 81. for switching the signal processing circuit of the television system. S2,83. Obtain S4.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a system switching circuit that can automatically identify various television systems having different systems and obtain a switching signal for a television signal processing system.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a configuration showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of signal vectors of NTSC and PAL systems. 11... PAL/NTSC detection circuit, 12... Field frequency detection circuit, 13... Oscillator, 14...
Mixing circuit, 15-4.5 Ml(z/6.0■(2 detection circuit, 16...mode switching circuit. Applicant's attorney, patent attorney, Takehiko Suzue, Figure 2 BLJ ic- 1 U-- Δ1

Claims (1)

[Claims] Means for discriminating between PAL and NTSC television systems by phase detection of a color carrier signal and a burst signal, and obtaining a first discrimination output; 5.5 MHz, 6.0 MHz, and 6. means for determining based on the relationship with the synchronization signal and obtaining a second determination output;
Convert any of 5Hz to 6MHz, and convert this converted 6MHz
z and 4.5 MHz of the audio carrier signal to obtain a third discriminating power;
A first color killer voltage obtained during C-scheme television signal processing and a second color-killer voltage obtained during SECAM-scheme television signal processing are input,
A system switching circuit characterized by comprising mode switching means for matrixing the states of each of these inputs and obtaining outputs for discriminating various television systems.