JPS58111529U

JPS58111529U - automatic frequency control circuit

Info

Publication number: JPS58111529U
Application number: JP754282U
Authority: JP
Inventors: 神津　光宏
Original assignee: 株式会社東芝
Priority date: 1982-01-25
Filing date: 1982-01-25
Publication date: 1983-07-29

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図は従来のチューナ回路、映像中間興竺回路、自動
周波数制御（以下ＡＦＴ）回路のブロック図、第２図は
チューナ回路内のＡＦＴ回路に印加されるＡＦＴ制御電
圧特性（８字特性）を示す特硅図、第３図はＡＦＴ制御
電圧発生回路の構成を示す回路図、第４図は電源電圧の
変動に対するＡＦＴ特性の変化を示す特性図、第５図は
同調調整時の電源電圧変動に対するＡＦＴ引込範囲の変
化を示す特性図、第６図は本考案の実施例に係るＡＦＴ
制御回路を示す回路図、第７図は第６図の回路において
可変抵抗を変化させバ場合の８字特性の変化を示す特性
図、第８図は同特性のＡＦＴ引込範囲を示す特性図、第
９図番ｊ本考案の他の実゛施例に係るＡＦＴ制御電圧処
理回路を示す回路図である。　”− ，１・・・・・・アンテナ端子、２・・・・・・チュー
ナ回路、３１・・・・・・ＰＩＦ／ＡＦＴ回路、４・・
・・・・ＡＦＴ制御電圧処理回路、５・・・・・・ＡＦ
Ｔ動作動作子・・・・・・ＡＦＴディフィートスイッチ
、８・・・・・・定電圧電源回路、９・・・・・・電圧
安定化回路。Figure 1 is a block diagram of a conventional tuner circuit, video intermediate circuit, and automatic frequency control (AFT) circuit, and Figure 2 is the AFT control voltage characteristic (character 8 characteristic) applied to the AFT circuit in the tuner circuit. Figure 3 is a circuit diagram showing the configuration of the AFT control voltage generation circuit, Figure 4 is a characteristic diagram showing changes in AFT characteristics due to fluctuations in power supply voltage, and Figure 5 is power supply voltage during tuning adjustment. A characteristic diagram showing changes in AFT pull-in range with respect to fluctuations, FIG. 6 is an AFT according to an embodiment of the present invention.
A circuit diagram showing the control circuit, FIG. 7 is a characteristic diagram showing the change in the figure 8 characteristic when changing the variable resistance in the circuit of FIG. 6, and FIG. 8 is a characteristic diagram showing the AFT pull-in range of the same characteristic. FIG. 9 is a circuit diagram showing an AFT control voltage processing circuit according to another embodiment of the present invention. "-, 1... Antenna terminal, 2... Tuner circuit, 31... PIF/AFT circuit, 4...
...AFT control voltage processing circuit, 5...AF
T operation element: AFT defeat switch, 8: Constant voltage power supply circuit, 9: Voltage stabilization circuit.

Claims

[Scope of utility model registration request]

The voltage that detects the out-of-tuning of the tuner circuit is amplified and taken out by a differential amplifier, the respective differential outputs are combined to form an AFT control voltage, and the voltage is applied to a local vibration circuit to detect the out-of-tuning. In order to correct the AFT operation and temporarily release the AFT operation during channel selection, the AFT defeat switch short-circuits each operation output to obtain the AFT reference voltage, and based on this voltage, the voltage above the tuning point and In the automatic frequency control circuit in which the lower pull-in range is determined, a fixed voltage circuit is provided to supply one end of the AFT defeat switch, and a variable synthesis ratio is provided to the other end of the front nine AFT differential switches. An automatic frequency control circuit characterized in that the automatic frequency control circuit is configured to be able to apply an AFT control voltage, and when the AFT is canceled during the channel selection, the voltage of the fixed voltage circuit is supplied to the local oscillation circuit.