JPS5846775A - Sound discriminating output processing circuit for television receiver - Google Patents

Abstract

PURPOSE:To prevent the occurrence of buzz, by extracting a differential discrimination output from a frequency discriminating circuit which uses the separate carrier type SIF signal to an input and then separating an AFT circuit from an audio signal extracting circuit. CONSTITUTION:The SIF signal is fed to a frequency discriminating circuit 3 from a terminal P1. The circuit 3 is provided with a buffer stage 3a, a differential discriminating stage 3b, and a 180 deg.-phase shifter constituting a coil L1 and capacitors C1, C2. The discriminating output given from the stage 3b is led to an AFT voltage extracting circuit 4. The circuit 4 contains current mirror circuits 4a, 4b and 4c, and the DC voltage corresponding to the current difference between transistors T13 and T17 is delivered to a terminal P4 in the form of the AFT voltage. Then a DC level is obtained from the collector of a transistor T19 of a differential amplifying stage 5b of a sound amplifying circuit 5, and a certain audio signal emerges at a terminal P8. As a result, a mutual effect can be eliminated between an AFT circuit and an audio signal extracting circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound discrimination output processing circuit for a television receiver.

In base-hole television receivers, the local output of the tuner is
The AνT′ pressure for wave number control is vXy (Eirin intermediate station wave number)
The voice signal is reproduced from the 8IF (8IF) signal.
Generally, this is carried out by obtaining an intercarrier signal based on beat C2 of the audio intermediate frequency signal and the above-mentioned image carrier signal. However, in this method, AP
T voltage voltage generation frequency discrimination circuit and audio recovery! M detection circuits are required for each, but the disadvantage of the intercarry 1 method is 18×1.
Become.

Therefore, the applicant of the present invention proposed the following method in Japanese Patent Application No. 55-54470. That is, the 81F signal of the Separate Chara 1 type derived from the duna was guided into a single frequency discrimination (7M detection) circuit to perform frequency discrimination, and the audio signal and human YT solder pressure were obtained from the discrimination output. That is what it is.

Figure 1 shows a schematic configuration of the main parts of a television receiver that adopts this method. However, the following points should be noted here.In other words, in the same figure, the #I4 wave number discrimination circuit (C1) is configured to obtain AFTl [pressure and audio signals from the output of 31, so the above discrimination 4-1 When giving the output of circuit T31 to the human FT@pressure extraction circuit (4) and the audio amplification circuit (T5), it is necessary to ensure that both circuits are not affected by the two circuits. Ah cloudy.

However, the present invention has been made for the purpose of solving such problems, and hereinafter, one embodiment 4 of the present invention shown in Fig. 2 will be described.
I'll explain about the second one.

2nd t! ! Q shows an embodiment in which a portion including the processing circuit of the present invention surrounded by a broken line in FIG. 1 is converted into IO,
Portions-2 corresponding to the blocks in FIG. 1 are given the same figure numbers. In this circuit C2 of FIG. 2, 8 IF[4't
(Center 1 wave ff154.2 sMH!r is the terminal (Pl)
This sxy signal is used for frequency discrimination (FMQ wave)
Circuit (30 leads.

Nkili! 1 wave number discrimination circuit (J is a transistor (〒1)
(Buffer amplification stage (5a) consisting of T, etc.), differential discrimination stage C5 consisting of fungistors ('I'm) to (Ts)°, etc.
b External 4t coil (Ll) and conductor? (09)(
Ox) The peak differential stage (5b) is equipped with a 180° phase shifter and has a peak differential V-type double configuration, and its discrimination output is from the TI and T4 valley collectors of the differential discrimination stage (5b) to the base WR pond-type v ('1' 4) ('l'th) Next step AFT 4 pressure extraction cycle 11 (4) t:
It sings as if guided. What are the characteristics of this frequency discrimination circuit (4)? It's 6 Ni like J5 cause.

! The TIE pressure extraction circuit (4) is connected to the first. Second
゜3rd current Mifu circuit II (41 (4m)) (40) G, external resistor (n) connected to IF element (P4)
a) (Rb) and a capacitor (button 1).

Each input side transistor (TI) (Tll) of the first and second current Mihu circuit (41 (411) and the output side transistor (TIO) of the 42 current Miff circuit (4b) is connected to the input side transistor (Tli) of the ms current Miff circuit (4a).
j:, connected. Therefore, the resistances (R11) (R14) and (R1A) to (R1A) of each current mirror circuit are
If all values of 11) are equal, it is equal to the collector current of one (T4) of the output side transistor (Tll → differential discrimination stage (5'l)) of the 5J2 surge i2-circuit (4b). Current flows, and the output side transistor ('1y) c of the 6th channel flow Mihu circuit (40) is connected to the other ('1y) c of the upper gaM differential stage.
TI)'s collector current C2 equal *m flows. As a result, 711. T17 current! ! I: A corresponding DC voltage will be generated at the terminal (P4).

This voltage is collected as the AvT voltage.

Here, when creating the APT voltage (2. The exchange, that is, the audio signal component during the discrimination output from the differential discrimination stage (51m) a) is smoothed. , f@child(P4)l2 The obtained AP'l'@pressure is,
The DC component of the upper ε discrimination output, that is, 8I? This means that the signal C2 changes depending on the wave number of the signal.

In addition, upper εAIF? The slope of the linear variation region (W゛) of the voltage characteristic (fourth factor) is much more than that of the linear detection region (Z) of the characteristic ′ (Fig. 5) of the frequency valve individual circuit (3).
62 is selected to have a steep slope, is this AF? The purpose is to achieve the same sensitivity as above, but since such a point is outside the gist of the present invention, a detailed explanation will be omitted. ) Another output side transistor (T1)
The base 6; receives a current equal to the collector current of the TM of the differential discrimination stage (3m) [the emitter consisting of the fungistor ('l'l@) and the transistor (T%!) acting as its load] Tahoe a stage (51) and its emitter follower output have the same resistance value CR14)C
R25) A differential amplification stage (5b) consisting of transistors (T19) (T211) and their constant current transistor (T21), etc., which are applied to each base via a differential pair transistor ('[1 ) is connected to the base of the external device for attenuating sound wave frequency components and is composed of a condenser f(04) or the like. Therefore, the first current Mihu times W
The discrimination output taken out by T7C of
3tl)(: When guided (;, the DC component of the discrimination output is T9ζ'I'2(
Each base C2 of l is applied, but the AC component, that is, the audio signal component, is C'r 1 ?
As a result, the differential amplification stage (5b) performs amplification only on the AC component C of the discrimination output. When the tuner is detuned, the operating point of the four-wave number discrimination circuit (3) moves from point A in FIG. 3 to point B or point 0 (two points), and the DC level of the discrimination output changes.

71 of the differential amplifier stage (5b)? , T2O, an audio signal whose DC level is maintained at a constant potential is obtained.The audio signal is then guided to the audio output circuit through an f amount control circuit (not shown), etc.

As explained above, the speech discrimination output processing circuit of the present invention has the following features:
Separate carrier type 81 derived from tuner
A differential type discrimination output is extracted from a frequency discrimination circuit that takes the 11F signal as input. 6; The differential discrimination output χ'4-flow Mihu circuit [two leads.

With this current mirror circuit, the output for creating the AFTi voltage and the output for taking out the voice signal are taken out separately, so the circuit for creating the %AFT voltage and the circuit for taking out the audio signal are 6 seconds apart from each other. It is not affected by the other party's influence, so it is possible to obtain accurate AFT pressure and audio signals.

In addition, the APT voltage is created using both of the differential discrimination outputs, and the audio signal is filtered so as to be obtained from one of the differential discrimination outputs, so it is possible to obtain a large AF'l' voltage ( AFT control sensitivity is increased by 52 inventive circuit yxc
In this case, the number of external parts and the number of external terminals are reduced, which is preferable.

In the embodiment shown in Fig. 2, a beak differential detector was used as the T frequency discrimination circuit for extracting the discrimination output of the Hiro differential type, but the degree of AM suppression in the w4 wave number discrimination operation C2 may be slightly reduced. If there are two sacrificial ships, it is possible to use quadrateia type detectors.

[Brief explanation of drawings]

Figure 1 is a block diagram schematically showing the main parts of a universally used television receiver** according to the present invention.
A circuit diagram showing an example of an AI circuit. 13 and 4 are characteristic diagrams for explaining the operation. (3): lie wave number discrimination circuit, (4): AνT voltage extraction circuit, (5): audio amplification circuit, (3m): 31
Kinbetsudan. (4B) (4b) (40): '1lEfi Mihu circuit.

Claims (1)

[Claims] (1) A separate carrier-type system-intermediate frequency signal derived from a tuner is passed through a single pigeon frequency discriminator.
．． The differential type discrimination output is taken out from the 1121ii1 wave number discrimination circuit, and the differential discrimination output [electric power, -circuit I] is derived respectively, and this current microcircuit is used to create APT@pressure. Separate the output and the output for audio signal extraction. Audio discrimination output processing circuit for the receiver. Claim 1, characterized in that the output for extracting the voice signal is extracted only from the first current circuit in which one of the differential discrimination outputs is manually powered. Speech discrimination output processing circuit in item -. (The sound discrimination output processing circuit according to claim 1, wherein the wave number discrimination circuit is constituted by a peak differential type detector.