JPH04123663U - receiving device - Google Patents

Abstract

(57) [Summary] In a receiving device that extracts a synchronization signal of a received video carrier wave from a synchronization detection circuit (5) and performs automatic frequency control by connecting an AFC circuit (6) to a tuner (2), The synchronization detection circuit (5) is connected to the AFC circuit (6), and the synchronization detection signal of the synchronization detection circuit (5) causes A
It is configured to control the synchronization control signal output of the FC circuit (6), and the AFC no-signal voltage from the intermediate frequency amplification circuit (3) input to the AFC circuit (6) is output from the synchronization detection circuit (5). By turning off the AFC voltage input to the tuner (2) using the synchronization detection signal of the tuner (2), it is possible to prevent the AFC voltage from changing due to noise input even when no video carrier wave is input, and the tuner (2) can be prevented from changing due to noise input. The reception operation of 2) can be started by the AFC voltage at the optimal tuning point, and for example, the tuner (2) can be started by using a microcomputer chip that was unable to receive reception when the TV broadcast was restarted after the TV broadcast was interrupted. It is possible to easily improve reception functions and reduce manufacturing costs.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention is a receiving device installed in, for example, a television or a video tape recorder. Regarding the location.

0002

[Conventional technology]

Conventionally, the feedback signal from the intermediate frequency amplifier circuit (IF) was transmitted from the timer circuit. A that performs automatic frequency control of the tuner by controlling with the AFC control signal of An FC circuit was installed.

0003

[Problem that the idea aims to solve]

The above-mentioned conventional technology is capable of interrupting broadcasting when a video carrier wave is not being input. The AFC no-signal voltage is determined by the characteristics of the intermediate frequency amplification circuit, but Noise input to the circuit will cause the AFC voltage to change and remain fixed at a maximum or minimum value. The tuner is controlled by the AFC voltage applied, causing functional problems such as making reception impossible. There was a problem.

0004

[Means to solve the problem]

However, in the present invention, the synchronization signal of the received video carrier wave is output from the synchronization detection circuit. Receiving device that performs automatic frequency control by connecting the AFC circuit to the tuner. At the same time, the synchronization detection circuit is connected to the AFC circuit, and the synchronization detection circuit of the synchronization detection circuit is connected to the AFC circuit. The configuration is such that the tuning control signal output of the AFC circuit is controlled by the output signal. The AFC wireless signal from the intermediate frequency amplification circuit that is input to the AFC circuit is The signal voltage is turned off by the synchronization detection signal from the synchronization detection circuit and input to the tuner. By setting the AFC voltage to the optimum tuning point, the video carrier wave will not be input. It can prevent the AFC voltage from changing due to noise input even if the tuner's receiving operation is The operation can be started by the AFC voltage at the optimum tuning point, for example from the time of interruption of the television broadcast. Microcomputer chip that was unable to receive reception when broadcasting started again A tuner can be configured using This is something that can be easily achieved.

[0005]

【Example】

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Figure 1 shows television or This is a receiving circuit for a video tape recorder, and the video carrier wave is transmitted from the television antenna (1) to the video tape recorder. A tuner (2) that inputs (radio frequency signal) and receives it by preset tuning. An intermediate frequency amplification circuit (3) that selects a frequency, and video transmission from the amplification circuit (3) A detection circuit (4) that separates the wave into an audio signal and a video signal, and a horizontal and vertical a synchronization detection circuit (5) for extracting a synchronization signal from the detection circuit (4); and the tuner. (2) AFC circuit (6) that performs automatic frequency control; AFC detection signal (tuned frequency signal) from circuit (3) and from timer circuit (7) Input the AFC control signal (AFC-DEFT signal) to the AFC circuit (6) and the AFC signal (AFC voltage) which is the tuning control signal output of the AFC circuit (6). The audio signal is applied to the tuner (2) and also from the detection circuit (4). output to a speaker or audio magnetic head through the output terminal (8), or The video signal from the detection circuit (4) is sent to the cathode ray tube or the like through the output terminal (9). or a video magnetic head.

[0006] In addition, an AFC controller incorporating the timer circuit (7) and the OR circuit (10) is also provided. The roll circuit (11) is configured with a microcomputer, and the AF of the timer circuit (7) An OR circuit ( 10), and the synchronization detection circuit (5) is connected to the AFC circuit (6). is connected to the AFC control circuit (11), and the synchronization detection circuit (5) is connected to the AFC control circuit (11). The period detection signal (SD signal) is input to the AFC circuit (6) via the OR circuit (10). The AFC circuit (6) is activated by the synchronization detection signal (SD signal) of the synchronization detection circuit (5). This controls the AFC signal (AFC voltage) output of the When the input of the video carrier wave disappears, the AFC no-signal voltage is output from the intermediate frequency amplification circuit (3). pressure is input to the AFC circuit (6), but there is no AFC signal from the amplifier circuit (3). The voltage is turned off by the synchronization detection signal (SD signal) from the synchronization detection circuit (5). Then, set the AFC signal (AFC voltage) input to the tuner (2) at the optimum tuning point (for example, 4.5 volts).

[0007] As shown in Figure 2, when the power is turned on and preset tuning is performed, the channel When switching the AFC control signal (AFC-DEFT signal) of the timer circuit (7), No.) is used as the AFC signal (AFC voltage) of the AFC circuit (6) for approximately 600 milliseconds. As shown in Figure 2 (A), the AFC control Approximately 300 milliseconds have passed since the signal (AFC-DEFT signal) became an L level output. By this time, the synchronization detection signal (SD signal) has become an L level output, and the synchronization detection circuit (5) When the synchronization detection signal is detected, the AFC control signal (AFC-DEFT signal No.) maintains the L level output even after 300 milliseconds, and as shown in Figure 2 (B), The AFC control signal (AFC-DEFT signal) becomes L level output and about 3 Even after 00 milliseconds have passed, the synchronization detection signal (SD signal) continues to output H level, and synchronization is completed. If the synchronization detection signal (SD signal) of the detection circuit (5) is not detected, the AFC control The roll signal (AFC-DEFT signal) is outputted at H level again after 300 milliseconds. At the same time, as shown in FIG. 2(C), the AFC control signal ( After the AFC-DEFT signal) becomes H level output again, the synchronization detection signal (SD signal) signal) becomes an L level output and a synchronization detection signal (SD signal) is detected, the AF This outputs the C control signal (AFC-DEFT signal) at L level. No AFC output from the intermediate frequency amplification circuit (3) when no image carrier wave is input. Instead of the signal voltage, use the AFC signal (AFC voltage) at the optimum tuning point (for example, 4.5 volts). voltage) is applied to the tuner (2), and the AFC signal (AFC voltage) is set to the higher one (approximately 9. 0 volts) or lower (approximately 0.5 volts) and tuner (2) reception. This prevents the operation from stopping.

[0008] Furthermore, as shown in FIG. 3, the microcomputer shown in the above embodiment is used. In place of the AFC control circuit (11), a timer circuit (7) and an OR circuit (1 0) can be easily separated and configured as an independent circuit, and the above implementation Similar to the example, the tuner (2) is stuck at an incorrect tuning point of the AFC signal (AFC voltage). The synchronization detection signal of the synchronization detection circuit (5) (SD signal) to return the AFC signal (AFC voltage) to the optimum tuning point and receive it again. It is structured in such a way that it can be trusted.

[0009]

[Effect of the idea]

As is clear from the above embodiments, the present invention provides a synchronized signal of the received video carrier wave. The signal is taken out from the synchronization detection circuit (5), and the AFC circuit (6) is connected to the tuner (2). In the receiving device that performs automatic frequency control by connecting the synchronization detection circuit (5) is connected to the AFC circuit (6), and A is detected by the synchronization detection signal of the synchronization detection circuit (5). It is configured to control the tuning control signal output of the FC circuit (6). The AFC no-signal voltage from the intermediate frequency amplifier circuit (3) input to the circuit (6) is synchronously detected. It is turned off by the synchronization detection signal from the output circuit (5) and input to the tuner (2). By setting the AFC voltage to the optimum tuning point, it is possible to prevent the image carrier wave from being input. can also prevent the AFC voltage from changing due to noise input, and The signal operation can be initiated by the AFC voltage at the optimum tuning point, e.g. Microcontrollers that were unable to receive data when broadcasting resumed after it was interrupted The tuner (2) can be configured using a computer chip, improving reception function and manufacturing. This makes it possible to easily reduce costs.

[Brief explanation of drawings]

FIG. 1 is a receiving circuit diagram.

FIG. 2 is an output diagram.

FIG. 3 is a receiving circuit diagram showing a modified example.

[Explanation of symbols]

(2) Tuner (5) Synchronization detection circuit (6) AFC circuit

Claims (1)

[Scope of utility model registration request] 1. A receiving device that extracts a synchronization signal of a received video carrier wave from a synchronization detection circuit and performs automatic frequency control by connecting an AFC circuit to a tuner.
A receiving device characterized in that the synchronization detection circuit is connected to an AFC circuit, and the synchronization detection signal of the synchronization detection circuit controls the tuning control signal output of the AFC circuit.