JP2552306Y2 - PAL / SECAM switching modulator IC - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an IC for a PAL / SECAM switching modulator.
The present invention relates to a VTR (video deck) modulator that is applied to a television system of an AL system or a SECAM system.

[Conventional technology]

FIG. 2 shows a block diagram of an example of the conventional art. In the figure, 1
Is a PAL-dedicated IC, which includes a clamp circuit 2, a clip circuit 3, an amplifier 4 (above, a video signal system), an amplifier 5, and an FM modulation oscillation circuit 6.
(Above, an audio signal system). The video signal input to the terminal 8 is mixed with the following audio signal via the clamp circuit 2, the clip circuit 3, and the amplifier 4. When applied to the PAL system, connects the switch SW ₁ to SW ₄ to each terminal P side. The audio signal coming into terminal 10 is sent to emphasis circuit 11
Through the FM modulation oscillation circuit 6
5, is mixed with the video signal via the switch SW _3, SW _4, oscillator
Negative balanced modulation is applied by a balanced modulator 9 using the output of 14 as a carrier wave, taken out from an output terminal 12 and supplied to a television receiver. At the time of FM modulation, the FM modulation oscillating circuit 6 tunes and oscillates at the output of the tuning circuit 13, and uses this oscillation frequency signal as a carrier wave to perform FM modulation with an audio signal.

On the other hand, when applied to the SECAM system, the switch SW ₁ to SW ₄
Are connected to the terminal S side. Audio signal AM modulator 15 which is incoming to the terminal 10, the ceramic filter 16, is mixed with the video signal via the switch SW _4, multiplied by the positive balanced modulation by balanced modulator 9, it is discharged from the output terminal 12 . Upon AM modulation, FM modulation oscillator 6 oscillates taken tuning at the output of the tuning circuit 18, the oscillation frequency signal, the amplifier 5, is supplied to the AM modulator 15 as a carrier wave through a switch SW ₃ .

[Problems to be solved by the invention]

In the conventional modulator, IC1 is dedicated to PAL,
The SECAM type AM modulator 15 is provided outside the IC 1,
The switch SW ₁ to SW ₄ tuned circuits 13 and 18 and the like in addition to this is provided on the outside of the IC1. AM modulator 15 outside IC1
The length of the pattern becomes longer due to the provision of the filter, and the noise is easily mixed. Therefore, a ceramic filter 16 for suppressing the high frequency of the sound is required to prevent this. As described above, the conventional modulator has a problem that the number of external parts provided outside the IC is increased, and it is difficult to reduce the size of the device and the cost is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a PAL / SECAM switching modulator IC that can reduce the number of external components of the IC and reduce the size and cost of the modulator.

[Means for solving the problem]

The present invention is an IC for a PAL / SECAM switching modulator that selectively modulates with a PAL or SECAM modulation method according to a switching signal by a PAL or SECAM input audio signal, wherein the PAL input audio signal is A PAL tuning circuit for modulating is externally connected, and an oscillation signal of a frequency set by the PAL tuning circuit is input to the FAL by the PAL input audio signal.
A PAL input audio signal FM modulation oscillation circuit for M-modulation, and a SECAM tuning circuit for modulating the SECAM input audio signal are externally connected to oscillate a frequency for modulating the SECAM input audio signal. A SECAM oscillation circuit for outputting a signal, and an oscillation signal oscillated from the SECAM oscillation circuit to the SCAM.
An AM modulator for performing AM modulation with an input audio signal for ECAM is built in.

[Action]

In the present invention, in particular, since the AM modulator is provided in the IC, the pattern length can be shortened as compared with the conventional example in which the AM modulator is an external component of the IC. Such a ceramic filter can be configured without having to be provided as an external component of the IC. In addition, since the tuning circuits can be separately connected to the IC, a switch for switching the tuning circuits is not required, and external components can be reduced. Therefore, the number of IC external parts can be reduced as a whole, and the modulator can be downsized.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, the same components as those in FIG. In FIG. 1, reference numeral 20 denotes a PAL / SECAM IC, which includes a clamp circuit 2, a cup circuit 3, an amplifier 4 (above, a video signal system), an AM modulator 21, an FM modulation oscillation circuit 6, an oscillation circuit 22, an amplifier 24, It is composed of a switch circuit 25 (above, an audio signal system) and forms a main part of the present invention. Switch SW _1-emphasis circuit 11 to the outside of the IC 20, such as a tuning circuit 13 and 18 are provided.

When applied to the PAL system, the connecting switches SW ₁ to the terminal P side, and supplies the oscillation operation switching control signal for FM modulation terminal 26. The audio signal input to the terminal 10 is subjected to FM modulation by the FM modulation oscillation circuit 6 through the emphasis circuit 11,
The signal is supplied to the balanced modulator 9 via the amplifier 24. At the time of FM modulation, the FM modulation oscillation circuit 6 is activated by the FM modulation oscillation operation switching control signal switched and output from the switch circuit 25, and is tuned by the output of the tuning circuit 13 to oscillate.

On the other hand, when applied to the SECAM system, the connecting switches SW ₁ to the terminal S side, it supplies the AM modulation oscillator operation switching換切switching control signal to the terminal 26. The audio signal coming into terminal 10
The signal is subjected to AM modulation by the AM modulator 21 and supplied to the balanced modulator 9 via the amplifier 24. At the time of AM modulation, the oscillation circuit 22 is activated by the AM modulation oscillation operation switching control signal switched and output from the switch circuit 25, and is tuned by the output of the tuning circuit 18 to oscillate.

In the present invention, the AM modulator 21 and the PA
Since the FM modulation oscillation circuit 6, oscillation circuit 22, switch circuit 25, and the like for the L system are provided in the IC 20, the number of IC external parts can be reduced and the modulator can be downsized. In this case, in particular, since the AM modulator 21 is provided in the IC 20, the pattern length can be shortened as compared with the conventional example in which the AM modulator is configured as an external component of the IC. There is no need to provide a ceramic filter 16 for suppressing high-frequency sound as an external component of the IC, and it is not necessary to provide switches SW ₃ and SW ₄ as in the conventional example.

[Effect of the invention]

As described above, according to the present invention, in particular, since the AM modulator is provided in the IC, the number of external components of the IC can be reduced, and the tuning circuits can be separately connected to the IC. There is no need for a switch to change over, and external components can be reduced, so that the modulator can be downsized.
Inexpensive configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an example of the related art. 6 FM modulation oscillator circuit, 10 audio signal input terminal, 11 emphasis circuit, 12 output terminal, 13, 18 tuning circuit, 20 P
AL / SECAM dual-purpose IC, 21: AM modulator, 22: oscillation circuit, 25: switch circuit, 26: oscillation operation switching control signal input terminal, SW ₁
…switch.

Claims (1)

(57) [Scope of request for utility model registration] 1. A PAL / SECAM switching modulator IC for selectively modulating a PAL or SECAM modulation method according to a switching signal by a PAL or SECAM input audio signal, wherein the PAL input audio signal is A PAL tuning circuit for modulating the signal is externally connected, and the PAL input audio signal
A PAL input audio signal FM modulation oscillation circuit for FM-modulating an oscillation signal of a frequency set by the AL tuning circuit, and a SECAM tuning circuit for modulating the SECAM input audio signal are externally connected, and An SECAM oscillation circuit that outputs an oscillation signal having a frequency for modulating a SECAM input audio signal; and an SEC signal that oscillates from the SECAM oscillation circuit.
A PAL / SECAM switching modulator IC with a built-in configuration that incorporates an AM modulator that performs AM modulation with an AM input audio signal.