JP2718163B2 - Tuning device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel selection device having an AD converter used for a television receiver, an AM / FM radio receiver, and the like.

2. Description of the Related Art In recent years, a tuning device that controls an electronic tuner using a varactor diode performs not only control of tuning but also many other functions such as turning on / off a television receiver and adjusting a volume. I have come to have. In addition, efforts have been made to use more ICs in one type in terms of mass productivity and cost, which play a central role in this IC.

 Hereinafter, a conventional example will be described with reference to the drawings.

FIG. 3 shows a block diagram of a conventional tuning device. Reference numeral 1 denotes an AFT circuit of the television receiver. The AFT voltage generated here is input to the AD converter 3 in the channel selection IC 13 and is converted into a digital signal, and further input to the central processing unit 5.
Output port 7 by the control software based on ROM6
More output is output, and the reception frequency of the electronic tuner 9 is correctly corrected.

On the other hand, the power supply voltage E ₀ is divided by the dividing resistors 11 (R ₁₁ ) and 12 (R ₁₂ ). When R ₁₁ = R _12, the voltage of E _0/2 is AD
It is provided as an input to the converter 4. Now, the voltage of the input port 14 key 15 of the television video input switching signal is pushed falls to 0V than E _0. Since the control software of the ROM 6 is programmed as shown in FIG. 4, it detects that there is an input to the input port 14 and then performs an input from the AD converter 4. The AD converter 4 is applied is E _0/2 as described above. Therefore, when the output port 8 has one video input,
The signal controls the television / video input switching circuit 10. In this way, this tuning device has no video terminal by combining the values of resistors 11 and 12.
One video terminal, two video terminals, and three types of television receivers can be shared.

Problems to be Solved by the Invention However, in the conventional means, it is necessary to have one extra AD converter in the channel selection IC, and the IC becomes large-scale and causes a cost increase. In addition, there is a single AD converter, and there is also a multiplex technology for apparently realizing a plurality of AD converters. However, even in this case, it was impossible to reduce the number of IC pins.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an IC having no video, one video terminal, and two video terminals without increasing the number of AD converters of the channel selection IC and without increasing the number of pins of the IC. It is an object of the present invention to provide a tuning device that can be shared by various types of television receivers.

Means for Solving the Problems In order to achieve this object, the tuning apparatus of the present invention is provided with a switch circuit for switching the input of the AD converter by turning on and off the power of the television receiver. It is configured so that the second information, that is, the number of video terminals, can be input when the power is turned off, and the channel selection IC that receives the input signal also receives the AFT signal when the power is turned on and the second information when the power is turned off. This purpose is achieved by distinguishing the processing as follows.

Operation Therefore, according to the tuning device of the present invention, only one AD converter is required for the tuning IC, and the number of pins as the IC can be reduced, so that the tuning IC can be reduced in size. , Cost can be reduced.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a channel selection device in one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an AFT circuit of a television receiver, the output of which is input to a central processing unit 5 via an AD converter 3. The central processing unit 5 is connected to a control software ROM 6, and the control software stored therein is configured so that this system centering on the central processing unit 5 operates. Reference numeral 20 denotes a power ON / OFF key of the television receiver, and reference numeral 21 denotes a television / video input switching key, which are connected to the central processing unit 5 through input ports 23 and 22, respectively. A control output signal from the central processing unit 5 is supplied to an electronic tuner 9 via an output port 7, supplied to a television / video input switching circuit 10 via an output port 8, and provided with an output port 11 and a resistor 13. Is supplied to a transistor 16 which drives a power supply relay 17 via the power supply. Further, the output signal of the output port 11 is supplied via a resistor 12 to a transistor 15 for switching the input of the AD converter 3.

The operation of the tuning device configured as described above will be described below. Now, if the power is turned off, output port 1
The output of 1 is “L”, and the base current of the transistor 15 flows through the resistor 12 to make the transistor 15 conductive. At that time, the power supply of the AFT circuit 1 is in the OFF state, and if the impedance viewed from the output terminal is Z ₀ , the AD converter 3 Will be input. Here, R ₁₄ indicates the resistance value of the resistor 14. Now, the input voltage to the Z ₀ = R ₁₄ becomes E _0/2. As shown in the flow chart of FIG. 2, the central processing unit 5 performs an input from the AD converter 3 when the power is off and stores it in the internal RAM 24.

Next, when the power ON / OFF key 20 is pressed and the power is turned on,
The level of the input port 23 temporarily changes from “H” to “L”, and the central processing unit 5 switches the power from the OFF state to the ON state. At the same time, the output of output port 11 changes from “L” to “H”.
Switch to. As a result, the power relay 17 is a transistor
16 is turned on by conduction, and the power of the television receiver is turned on. At the same time, the base of transistor 15
Since the signal becomes “H” via the line 12, the transistor 15 is turned off, and the output signal from the AFT circuit 1 is used as it is in the AD converter 3.
Will be entered. Therefore, as shown at the time of power-on in the second flowchart, the central processing unit 5
AFT processing is performed by using the input of AFT as an AFT voltage, and as a result, the reception frequency of the electronic tuner 9 is correctly corrected.

In this state, when the television / video input switching key 21 is pressed, the input port 22 temporarily changes from "H" to "L", and the central processing unit 5 detects that there is an input, and turns off the power. Sometimes the voltage value stored in RAM 24 is read, and the Of the output port 8 according to the respective voltage values, one of “no change”, “output a change output in binary”, and “output a change output in ternary” Execute Now, since the read voltage value is E _0/2 , the output port 8 outputs an output that changes in binary. That is, the output of "L" becomes "H", and the output is input to the television / video switching circuit 10, and as a result, the state of "television" is switched to the state of "video input".

Also, when using this in a TV receiver without a video terminal, More, when the R ₁₄ to choose greater than 2Z _0, used for two with a television receiver video terminals This can be achieved by selecting R ₁₄ smaller than Z _0/2 .

Effects of the Invention As described above, according to the present invention, in a channel selection device including an AD converter, a voltage indicating a reception state and second information such as the number of video terminals for TV / video input switching are sent to the AD converter. When inputting, a switch circuit that switches the input according to the power ON / OFF of the TV receiver is provided, so that it is possible to input the voltage indicating the reception state when the power is ON, and to input the second information when the power is OFF. is there. Therefore, only one AD converter is required, and IC conversion can be easily performed.

In this example, information on the AFT voltage and the number of terminals for TV / video input switching is taken up, but other voltages indicating the reception state include the AGC voltage and the broadcast mode of audio multiplex broadcasting, and the second information includes audio information. It is conceivable whether multiplex broadcasting is supported, whether satellite broadcasting is supported, and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram of a channel selection device according to an embodiment of the present invention, FIG. 2 is a flowchart of control software showing the operation of the central processing unit of FIG. 1, and FIG. 3 is a block diagram of a conventional channel selection device. FIGS. 4, 5 and 6 are flowcharts of control software showing the operation of the central processing unit in the conventional tuning device. 1 ... AFT circuit, 2 ... Tuning IC, 3 ... AD converter, 5 ...
... Central processing unit, 9 ... Electronic tuner, 10 ... TV / video input switching circuit.

Claims (1)

(57) [Claims] The present invention has an AD converter, which has two types of voltage as an input of the AD converter, the voltage indicating a reception state of a television receiver, and second voltage information independent of this voltage. A tuning circuit comprising a switch circuit for switching the input of the AD converter when the power is turned on and off, and when the power is turned on, the voltage indicating the reception state is input, and when the power is turned off, the second information is input. .