JPH05161090A - Audio amplifier circuit for television receiver - Google Patents

Abstract

PURPOSE:To obtain an easy to see pattern by eliminating rattling noise sound due to vibration of a cabinet or a cathode ray tube and of vibration of a shadow mask caused by an audio output even when the audio output is very large. CONSTITUTION:The circuit is provided with diodes 25, 26 used to detect a DC voltage proportional to the sound output level and the voltage is divided to provide a base current to a negative feedback transistor(TR) 30 and a collector current in response to a current amplification factor of the TR 30 is negatively fed back to a bus control terminal 10 of a sound volume sound quality control circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio amplifier circuit of a television receiver, and more specifically, to fluctuations in the shadow mask of a cathode-ray tube and a change in screen size due to an unnecessarily large low-frequency audio output, and to a cabinet. The present invention relates to an audio amplifier circuit designed to reduce chattering noise.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of an audio amplifier circuit of a conventional television receiver. In FIG. 2, 1 is an audio R signal input terminal and 2 is an audio L signal input terminal. The audio signal input from is controlled by the volume / sound quality control circuit 3 based on the control functions respectively input from the volume control terminal 8, the balance control terminal 9, the bus control terminal 10, and the treble control terminal 11, and the control signal is It is output to the voice R output terminal 4 and the voice L output terminals 4 and 5, respectively. Each of the terminals 8, 9, 10, 1
Reference numeral 1 is control by a commonly used DC voltage. 6 is a power supply terminal, and 7 is a ground terminal.

A voice output circuit 12 has a voice R output terminal 1
The audio R output is output to 5 to drive the speaker 17, while the audio L output is output to the audio L output terminal 16 to drive the speaker 18. Reference numeral 13 is a power supply terminal, and 14 is a ground terminal. A power supply circuit 19 supplies the deflection output circuit 22 in addition to the audio output circuit 12. 20 is a ground terminal, 21 is a deflection output circuit 22
The power supply terminal 23, the ground terminal 23, and the deflection yoke 24 are driven by the deflection output circuit 22.

Next, the operation of the above configuration will be described. The sound R signal and the sound L signal inputted from the input terminals 1 and 2 are amplified in the sound output circuit 12 in the sound volume / sound quality control circuit 3, and the sound output signal is amplified in the sound output circuit 12 according to the preference. The speakers 17 and 18 are driven by the audio R output and the audio L output that are output from the terminals 15 and 16 of 12.

[0005]

The audio amplification circuit of the conventional television receiver is configured as described above, and when outputting a normally heard sound volume, an audio signal is output without any problem, but the maximum sound volume is obtained. If the input is very large in the vicinity and depending on the broadcast content, the vibration caused by the audio output will vibrate the TV cabinet or CRT, causing chattering and shaking of the shadow mask of the CRT. Stripes may appear. This effect also appears in the power supply terminal of the audio output circuit,
When power is also supplied to the audio output circuit from the power supply circuit that supplies power to the horizontal deflection circuit and high voltage generation circuit, there is a problem that visually unpleasant symptoms such as screen size change appear. It was

The present invention has been made in order to solve the above problems, and an audio amplifier circuit of a television receiver capable of reducing the above-mentioned symptoms even when the audio output is very large. The purpose is to provide.

[0007]

An audio amplifier circuit of a television receiver according to the present invention comprises means for detecting an audio output from an audio output circuit, and a bus for a volume / sound quality control circuit according to the detected audio output. And a means for controlling the maximum volume in the low frequency range by applying negative feedback to the control terminal.

[0008]

According to the present invention, the voice output is detected, and the negative feedback is applied to the bass control terminal of the volume / sound quality control circuit according to the size of the voice output to control the maximum volume in the low frequency range. The fluctuation of the shadow mask of the cathode ray tube, the change in screen size, and the chattering noise of the cabinet are reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an audio amplifier circuit of a television receiver according to the present invention. In FIG.
Reference numeral 26 is a voice output detection diode, 27 and 28 are resistors for adjusting the negative feedback amount, 29 is a smoothing capacitor, 30 is a negative feedback transistor, and 31 is a negative feedback amount adjusting resistor. Since other configurations are the same as those of the conventional example shown in FIG. 2, the corresponding parts are denoted by the same reference numerals and detailed description thereof will be omitted.

The operation from 1 to 24 in FIG. 1 is the same as the conventional example. During such operation, the audio output terminal 1
Audio outputs appear at 5 and 16 and the diode 25,
A DC voltage proportional to the volume of the sound is generated across the capacitor 29 by the capacitor 26 and the capacitor 29. This voltage is divided by the resistance ratio of the negative feedback amount adjusting resistors 27 and 28 to give a base current to the negative feedback transistor 30 according to the current amplification factor of the transistor 30, and is limited by the negative feedback amount adjusting resistor 31. The collected collector power is drawn from the bus control terminal 10 to operate to lower the bus control voltage. The respective control voltages of the volume / sound quality control circuit 3 have such a polarity that the output rises when the voltage is raised, and when the voice output is increased, the volume of the low range is automatically reduced. Therefore, when the audio output is very large, only the low-range volume that is proportional to the volume is reduced, and the mid-range and high-range volumes that do not matter are output without being reduced. Symptoms such as shaking of the shadow mask when the output is high, changes in the screen size, and rattling cabinet noise are reduced.

Although an NPN transistor is used as the negative feedback transistor 30 in the above embodiment, a PNP transistor is used when the control voltage of the bus control terminal 10 has a polarity opposite to that of the above embodiment. Even if it does, the same effect as the above-mentioned example is produced.

When the voltage across the smoothing capacitor 29 is negatively fed back to the bus control terminal 10 and the current capacity required for control is sufficient, the use of the negative feedback transistor 30 is unnecessary. It is possible to

[0013]

As described above, according to the present invention, the audio output is detected and the negative feedback is applied to the bus control terminal, so that the audio in the midrange or high range is not damaged. It is possible to reduce the fluctuation of the shadow mask of the cathode ray tube and the change in the screen size that occur when the output is very large, and also the chattering noise of the cabinet, and it is possible to obtain a screen that is easy to see visually. Play.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an audio amplifier circuit of a television receiver according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a sound amplification circuit of a conventional television receiver.

[Explanation of symbols]

 1 audio R signal input terminal 2 audio L signal input terminal 3 volume / sound quality control circuit 4,15 audio R output terminal 5,16 audio L output terminal 10 bus control terminal 12 audio output circuit 17,18 speaker 25,26 audio output detection Diode 27, 28 Negative feedback amount adjusting resistor 30 Negative feedback transistor

Claims (1)

[Claims] 1. A means for detecting a voice output from a voice output circuit, and a means for controlling a maximum volume in a low frequency range by applying negative feedback to a bus control terminal of a volume / sound quality control circuit according to the detected voice output. An audio amplifier circuit for a television receiver, characterized by being provided with.