JPS58166136U

JPS58166136U - automatic frequency control circuit

Info

Publication number: JPS58166136U
Application number: JP6195082U
Authority: JP
Inventors: 神津　光宏
Original assignee: 株式会社東芝
Priority date: 1982-04-30
Filing date: 1982-04-30
Publication date: 1983-11-05

Abstract

(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Brief explanation of drawings]

□　　第１図は従来の自動周波数制御機能を備えたテレ
ビジョン受像機のブロック図、第２図Ａは８字特性と感
度特性とを関連させて示す特性図、第２図Ｂは引込電圧
の′特性を示す特性図、第２図Ｃは局部発振周波数の誤
差特性を示す特性図、第３図は本考案にかかる自動周波
数制御回路の第１実施例を示す回路図、第４図はＦＥＴ
のＩＤ　　ｖｃｓ特性を７示す特性図、第５図Ａは本考
案によって選局時にＡＦＴがかかり誤差周波数が変化す
るときの誤差特性を示す特性図、第５図Ｂは第５図Ａの
特性に対応する引込電圧の特性図、第６図は本考案の第
２実施例を示す回路図である。２１・・・・・・チューナ（２１３・・・・・・局部発
振回路）、２３・・・・・・周波数弁別回路、２４・・
・・・・ＡＦＴ信号発生回路、２５・・・・・・引込範
囲抑制回路、２５１・・・・・・スイッチ、２５２・・
・・・・可変抵抗器、２７・・・・・・直流バイアス回
路、Ｑｂ　Ｑ２・・・用トランジスタ、Ｑ３・・・　　
。・・・ＦＥＴ１Ｒ１〜Ｒ６・・・・・・抵抗。□ Figure 1 is a block diagram of a television receiver equipped with a conventional automatic frequency control function, Figure 2A is a characteristic diagram showing the figure 8 characteristic and sensitivity characteristic in relation to each other, and Figure 2B is a diagram showing the relationship between the figure 8 characteristic and the sensitivity characteristic. Figure 2C is a characteristic diagram showing the error characteristics of the local oscillation frequency, Figure 3 is a circuit diagram showing the first embodiment of the automatic frequency control circuit according to the present invention, and Figure 4 is a characteristic diagram showing the error characteristics of the local oscillation frequency.
Figure 5A is a characteristic diagram showing the error characteristics when AFT is applied during channel selection according to the present invention and the error frequency changes. Figure 5B is a characteristic diagram showing the characteristics of Figure 5A. The corresponding drawing voltage characteristic diagram and FIG. 6 are circuit diagrams showing a second embodiment of the present invention. 21... Tuner (213... Local oscillation circuit), 23... Frequency discrimination circuit, 24...
... AFT signal generation circuit, 25 ... Pull-in range suppression circuit, 251 ... Switch, 252 ...
...Variable resistor, 27...DC bias circuit, transistor for Qb Q2..., Q3...
. ...FET1R1-R6...Resistance.

Claims

[Scope of utility model registration request]

A tuner whose oscillation frequency of a local oscillation circuit is adjusted by a tuning operation to receive a desired channel, and a tuner whose oscillation frequency is set above or below the normal frequency for receiving the desired channel based on the output of this tuner. The oscillation frequency of the local oscillation circuit is comprised of a frequency discrimination circuit that discriminates how much the error frequency has deviated, and a frequency control signal generation circuit that generates a pull-in signal according to the discrimination result and outputs it to the local oscillation circuit. a frequency pull-in means for constantly pulling in the regular frequency according to the pull-in signal;
An automatic frequency control circuit comprising: a pull-in range suppressing circuit configured to perform the pull-in operation when a pull-in signal generated according to the error frequency reaches a predetermined control value during a channel selection operation.