KR100226477B1 - Sound signal control circuit in tv - Google Patents

Abstract

The present invention relates to a TV audio signal control circuit, and in particular, even when the input pilot signal is weak and the control signal for controlling the audio signal output path is unstable, the control signal of a constant level is output, thereby outputting the audio signal by the unstable control signal. It relates to a circuit that can suppress noise caused by frequent changes of paths.

Inputted to the comparator through a phase locked loop circuit and a low pass filter for converting the pilot signal detected by the FM demodulation circuit to a DC signal of a predetermined level, the output signal of the comparator is input to the register in series and stored, and then the predetermined input signal Is stored in parallel by the synchronization signal transmitted from the clock generator and input to the AND gate, and when the AND signal of the AND operation is performed at the AND gate is input to the decoder and the microcomputer, the microcomputer and the decoder input the stereo control signal or Switching control of the audio signal output path of the audio matrix circuit 48 using the audio multiplex control signal allows output of an appropriate voice signal.

Description

TV voice signal control circuit

1 is a block diagram of a conventional TV audio signal control circuit.

2 is a block diagram of a TV audio signal control circuit of the present invention.

3 is a control signal waveform diagram of a TV audio signal control circuit of the present invention.

Explanation of symbols for main parts of the drawings

11, 13: limiter 12, 14: FM demodulation circuit

15 band pass filter 16 AM demodulation circuit

17, 19: phase locked loop circuit 18, 20: low pass filter

22: decoder 23: audio matrix circuit

24: micom 21, 41, 44: comparator

42, 45: Register 47: Clock Generator

43, 46: AND gate

The present invention relates to a TV audio signal control circuit, and in particular, even when the input pilot signal is weak and the control signal for controlling the audio signal output path is unstable, the control signal of a constant level is output, thereby outputting the audio signal by the unstable control signal. It relates to a circuit that can suppress noise caused by frequent changes of paths.

In general, the sound intermediate frequency of a TV is a mixture of a 4.5 MHz main carrier signal and a 4,724 MHz subcarrier signal, and a stereo / audio multiple pilot for a signal in a frequency band about 55.069 kHz away from 4,724 MHz. A signal is inserted, and such a voice intermediate frequency signal is divided into a main carrier signal and a subcarrier signal through a band pass filter and input to a voice signal output terminal.

1 is a block diagram showing the configuration of a conventional TV audio signal output circuit.

The main carrier signal SIF1 is input to the first limiter circuit 11, and the main carrier signal SIF1 output by removing noise through the first limiter circuit 11 is input to the first FM demodulation circuit 12. The output signal of the first FM demodulation circuit 12 is input to the audio matrix circuit 23.

The sub-carrier signal SIF2 is input to the second limiter circuit 13, and the sub-carrier signal SIF2 output by removing noise through the second limiter circuit 13 is input to the second FM demodulation circuit 14. And a voice signal included in the subcarrier signal SIF2 is detected through the second FM demodulation circuit 14 and input to the audio matrix circuit 23, and also from an output signal of the second FM demodulation circuit 14. Stereo / voice multiple pilot signals are detected through the band pass filter 15 and the AM demodulation circuit 16.

When the pilot signal detected through the second FM demodulation circuit 14 is a stereo pilot signal, it is passed to the comparator 21 as a stereo control signal via the first phase locked loop circuit 17 and the first low pass filter 18. Input to the comparator 21 as a voice multiple control signal via the second phase locked loop circuit 19 and the second low pass filter 20 in the case of the voice multiple pilot signal, and the output of the comparator 21 is The audio signal output mode data of the microcomputer 24 is input to the decoder 22 and the microcomputer 24, respectively, and the control signal of the decoder 22 is input to the audio matrix circuit 23.

The operation of the conventional TV audio signal output circuit configured as described above is performed by the first FM demodulation circuit 12 to which the main carrier signal SIF1 is inputted, and a sum signal of a mono audio signal or a stereo left signal and a right signal ( L + R is output to the audio matrix circuit 23, and the second FM demodulation circuit 14 to which the subcarrier signal SIF2 is input is used for the stereo / audio multiple pilot signal and the stereo left and right signals. Difference signals LR or two-channel audio multiplexed signals are output so that stereo or audio multiplexed signals are input to the audio matrix circuit 23 and the stereo / audio multiplexed pilot signals are subcarrier signals SIF2 through the band pass filter 15. ), And then the AM demodulation circuit 16 performs AM detection of a 150 Hz stereo pilot signal or a 276 Hz voice multiple pilot signal that is AM modulated in the 55 kHz band.

In the stereo / audio multiple pilot signal obtained as described above, in the case of a stereo signal, a 150 Hz pilot signal is inputted to the first phase locked loop circuit 17 to activate the first phase locked loop circuit 17 so that the stereo signal has the same frequency as that of the input signal. Outputs a pulse signal, and the output pulse signal of the first phase locked loop circuit 17 is filtered by the first low pass filter 18 to output a DC signal having a predetermined level, and 276 Hz in the case of an audio multiple signal. The pilot signal of is inputted to the second phase locked loop circuit 19 to activate the second phase locked loop circuit 19 to output a pulse signal having the same frequency as that of the input signal. The output pulse signal is filtered by the second low pass filter 20 to output a DC signal having a predetermined level.

The DC signal of a predetermined level output through the first low pass filter 18 or the second low pass filter 20 is input to the comparator 21 and then compared with the reference voltage set in the comparator 21. A control signal having a binary logic value is generated through the control signal, and the generated control signal is input to the decoder 22 and the microcomputer 24, and the microcomputer 24 and the decoder 22 are input from the comparator 21. Then, by switching the audio signal output path of the audio matrix circuit 23 using the stereo / audio multiple control signal, an appropriate audio signal is output.

In the conventional TV audio signal output circuit, when a weak pilot signal is input due to radio interference, the level of the control signal input to the decoder is not constant. Therefore, the audio signal output path of the audio matrix circuit changes irregularly. There is a problem that noise occurs in the voice signal.

Accordingly, the present invention outputs a control signal of a constant level even when the input pilot signal is weak and the control signal for controlling the audio signal output path is unstable, resulting in frequent changes of the voice signal output path due to the unstable control signal. The purpose is to be able to suppress noise.

According to the present invention for this purpose, when a stereo pilot signal is converted into a DC signal and inputted, first comparison means for comparing the voltage of the input DC signal with a reference voltage and an output signal of the first comparison means are inputted. A first storage element for storing a predetermined signal and storing the stored signal collectively when the storage of the predetermined signal is completed; a first logic gate for receiving a signal outputted collectively from the first storage element as an input and performing a predetermined logical operation; When the voice multiple pilot signal is converted into a DC signal and inputted, second comparison means for comparing the voltage of the input DC signal with a reference voltage, and an output signal of the second comparison means are input and stored, Inputs a second memory element for collectively outputting the stored signals when the storage is completed, and a signal collectively output from the second memory element A second logic gate for receiving a predetermined logic operation, a clock generator for generating signal input / output synchronization signals of the first memory element and the second memory element, and a user through a control means provided in the TV receiver. When the audio signal mode of the audio signal mode is set, a microcomputer for transmitting the user's setting contents to the decoder, a decoder for controlling the audio signal output path of the audio matrix circuit according to the audio signal output mode data transmitted from the microcomputer, and the audio signal detection And an audio matrix circuit for receiving a voice signal output from the means as an input and outputting an appropriate voice signal according to the voice signal output path set through the decoder.

In addition, the comparing means comprises a comparator in which the first comparing means and the second comparing means compare the input signal with the reference signal, the storage element is composed of a serial-to-parallel register, and the logic gate is an AND operation of the input signal. And a logic element for outputting a binary logic signal.

Referring to the preferred embodiment of the present invention as follows.

Through the band pass filter and the AM demodulation circuit, the stereo / audio multiple pilot signal included in the output signal of the FM demodulation circuit is detected. When the detected pilot signal is a stereo pilot signal, the stereo pilot signal is converted into a DC signal of a predetermined level. Input to the first comparator 41 via a phase-locked loop circuit for converting and a low pass filter, and the output signal of the first comparator 41 is serially input and stored in a first register 42 which is a register, and then a predetermined input When the signal is stored, the batch signal is output in parallel by the synchronization signal transmitted from the clock generator 47 and input to the first AND gate 43. The control signal of which the AND operation is performed at the first AND gate 43 is performed with the decoder. It is entered into the microcomputer.

When the pilot signal detected through the FM demodulation circuit is a voice multiple pilot signal, the second comparator 44 passes through a phase locked loop circuit for converting the voice multiple pilot signal into a DC signal having a predetermined level and a low pass filter. Input, the output signal of the second comparator 22 is serially input and stored in the second register 45, and then a predetermined input signal is stored and collectively output in parallel by the synchronization signal transmitted from the clock generator 47. The control signal input to the second AND gate 46 and the AND operation performed on the second AND gate 26 is input to the decoder and the microcomputer.

The operation of the TV audio signal output circuit of the present invention configured as described above will be described below with reference to FIG.

A, A 'and C in Fig. 3 are the output waveforms of the stereo signals, B, B' and D are the output waveforms of the audio multiple control signals, and ① and ④ are DC signals of irregular waveforms caused by the weak pilot signals. And (2) are mono cases where no pilot signal exists, (3) is a case where the stereo control signal is at a high level, and (5) is a waveform when the audio multiple control signal is at a high level.

The binary logic signal is generated by comparing the DC signal input to the first comparator 41 with the reference voltage set in the first comparator 41, and the binary logic signal generated in this manner is the first register 42. When the storage of the predetermined signal is completed, the stored signals are output in parallel to the first AND gate 43 in accordance with the synchronization signal transmitted from the clock generator 47, and the first AND The gate 43 performs an AND operation on the input signal and outputs an operation result having a constant level to the decoder.

In addition, a binary logic signal is generated by comparing the DC signal input to the second comparator 44 with the reference voltage set in the second comparator 44, and the generated binary logic signal is converted into a second register ( 45 is input and stored in series, and when the storage of the predetermined signal is completed, the stored signals are output in parallel to the second AND gate 46 according to the synchronization signal transmitted from the clock generator 47, and the second signal is outputted in parallel. The AND gate 46 performs an AND operation on the input signal and outputs an operation result having a constant level to the decoder.

When the stereo control signal or the multiplex audio control signal having a constant level is continuously input to the decoder, the microcomputer and the decoder switch the audio signal output path of the audio matrix circuit by using the input stereo control signal or the multiplex audio control signal. It will output an appropriate voice signal.

At this time, when the pilot signal detected through the FM demodulation circuit is weak and a DC control signal having a constant level is not input and an irregular waveform signal is input to the comparators 41 and 44, an irregular waveform control signal is inputted to the comparator 41 or 44. A predetermined signal is stored by storing in the registers 42 and 45 connected to the comparators 41 and 44, and the stored signals are stored in the AND gates 43 and (connected to the respective registers 42 and 45). 46 is outputted collectively to perform an AND operation, so as to output a control signal having a constant level of high level or low level.

Therefore, the present invention outputs a control signal of a constant level even when the input pilot signal is weak and the control signal for controlling the audio signal output path is unstable, so that the noise generated due to the frequent change of the voice signal output path due to the unstable control signal. The effect of suppressing this is provided.

Claims (4)

By detecting the audio signal and the pilot signal from the input carrier signal, and controlling the audio signal output path of the audio matrix circuit by obtaining the stereo or voice multiple control signal through the conversion of the detected pilot signal, A television sound signal control circuit, comprising: first comparing means for receiving a stereo control signal as an input and comparing the same with a reference voltage; A first memory element for inputting and storing the output signal of the first comparing means, and outputting the stored signals collectively when the storage of the predetermined signal is completed; A first logic gate configured to receive a signal output from the first memory element and perform a predetermined logic operation; Second comparing means for receiving an audio multiple control signal as an input and comparing the same with a reference voltage; A second memory element for inputting and storing the output signal of the second comparing means, and outputting the stored signals collectively when the storage of the predetermined signal is completed; A second logic gate which receives a signal output from the second memory element as an input and performs a predetermined logic operation; A clock generator for generating signal input / output synchronization signals of the first and second memory elements; A microcomputer for transmitting the user's setting contents to the decoder when the user sets the predetermined voice signal mode through the control means provided in the TV receiver; A decoder for controlling a voice signal output path of an audio matrix circuit according to the voice signal output mode data transmitted from the microcomputer; And an audio matrix circuit for receiving a voice signal output from said voice signal detecting means as an input and outputting an appropriate voice signal according to a voice signal output path set through a decoder. The TV audio signal control circuit according to claim 1, wherein the comparing means is a comparator in which the first comparing means and the second comparing means compare the input signal with the reference signal. The TV audio signal control circuit according to claim 1, wherein the storage element is a SERIAL-TO-PARALLEL register. The TV audio signal control circuit according to claim 1, wherein the logic gate is constituted by a logic element which performs an AND operation on an input signal and outputs a calculation result.