KR20000003539A - Method for tuning calibration through calibration of vco oscillating frequency of television - Google Patents

Abstract

PURPOSE: A method for calibrating a tuning through a calibration of the VCO oscillating frequency of a television is provided to always maintain a stable tuning state and to simplify a circuit. CONSTITUTION: A method for compensating a deviation of a VCO oscillating frequency comprises: turning on a television for tuning a tuner IF frequency and an image halfway frequency of a main chroma IC; correcting in case of a deviation of a matching relation of the tuner IF frequency and the image halfway frequency of the main chroma IC; and making a matching standard frequency.

Description

Tuning Correction Method by Correcting the Baco Oscillation Frequency of Television

The present invention relates to a method for correcting a tuning misalignment by correcting a television's own VCO oscillation frequency. In particular, the present invention relates to a VCO automatic compensation method (VCO frequency for television) for preventing a tuning misalignment caused when a television is switched by an external change such as high temperature or low temperature.

When the oscillation frequency changes due to temperature or power voltage fluctuation during the tuning, the receiving image may be blurred or unreceivable. Therefore, AFT voltage is applied to the variable capacitance diode to keep the oscillation frequency constant. . For example, in a television set with an intermediate image frequency (IF) of 38.9 MHz, the AFT region has a margin of about 0.5 MHZ up and down at 38.9 MHz, and a method of maintaining a constant oscillation frequency changed by the influence of high temperature is used. have.

However, when the variation of the oscillation frequency is out of the AFT range because the coil characteristic of the VCO is greatly changed due to the external environment, the tuning misalignment cannot be prevented. Therefore, a temperature compensation capacitor is conventionally used to prevent this. Hardware methods and AFT ranges have been widened in advance and stored in the microcomputer to respond.

However, in the conventional method of preventing the misalignment caused by the temperature change or the change of the tuning voltage, when the temperature compensation capacitor is used, the circuit becomes complicated, the product cost becomes expensive, and the AFT range is applied in a wide range in advance. The method can cope only within a range of a predetermined AFT region, and there is a problem in that a tuning distortion cannot be prevented when it is out of a predetermined AFT range.

The present invention has been invented to solve the above problems of the prior art, and an object of the present invention is to provide a method that can be prevented by software by comparing the VCO oscillation frequency with a set value through AFT adjustment.

According to the technical concept of the present invention, when the television is turned on, the VCO adjusting step of adjusting the VCO oscillation frequency such that the tuner IF frequency and the main chroma IC maintains a tuning relationship, and when the tuner IF frequency and the main chroma IC are out of sync An automatic VCO setting step of resetting the VCO oscillation frequency, a crystal oscillation step of oscillating a matching reference oscillation frequency for measuring the VCO, a step of comparing and discriminating the current VCO oscillation frequency and a set value, and an AFT operation according to the determination result A method is provided which includes a mode indicating step and an automatic AFT operation step of feeding back to the VCO adjusting step through AFT adjustment.

1 is a schematic diagram illustrating a voltage synthesizer electronic tuning method.

2 is a schematic system diagram of an AFT circuit.

3 is a configuration diagram of an oscillation circuit.

Figure 4 is a flow chart of the AFT range automatic reset method of the present invention.

<Description of the symbols for the main parts of the drawings>

100: channel button unit 110: preset adjustment unit

120: Tunneling IC 121: Tunneling control unit

122: mode control unit 123: memory control unit

124: data register 125: comparator

126: AFT 127,230: oscillation circuit

128: divider 130: memory control IC

140: memory IC 141: control unit

142: address register 143: data register

144: memory 150: integrating circuit

200: tuner circuit 210: RF amplifier

220: mixer circuit portion 300: AFT circuit portion

310: frequency amplifier 320: phase discrimination transformer

330: phase detector 340: DC amplifier

350: variable capacitance diode 400: video intermediate frequency amplifier

Hereinafter, with reference to the accompanying drawings for the configuration and operation of the present invention will be described in detail.

FIG. 1 is a schematic block diagram illustrating a voltage synthesis method (hereinafter, referred to as a VS method) applied to the present invention among electronic tuning methods.

Tuning IC 120 coupled with channel button unit 100 and preset adjustment unit 110, memory IC 140, memory control IC 130 for controlling memory IC 140, and tuning station IC And an integrating circuit 150 for processing the tuning voltage output from the 120.

The channel selection IC 120 receives the adjustment signal input from the preset adjustment unit 110 to control the mode and mode control unit 122, and receives the control signal input from the channel button unit 100 to process The oscillation circuit section 127, the divider 128, and the channel information stored in the memory IC 140 and the channel information output from the divider of the tuning circuit are configured. A memory controller 123 and a data register 124 for processing data for comparison by the comparator 125 and an AFT 126 for adjusting the change in the oscillation voltage.

The VS method converts the tuning voltage and band switching voltage of 0-33V into digital signals and stores them in the memory IC for each channel button. When the desired channel is set for each channel button and the channel button is pressed afterward, the digital signal corresponding to the channel button is taken out according to the operation of the channel IC 120, and converted into a tuning voltage and a band switching voltage (D / A conversion). ) Is applied to the electronic tuner.

2 is a schematic system diagram of an AFT circuit for AFT adjustment in the above VS method. A variable signal is applied to the RF amplifier 210 for amplifying the input RF signal, the mixed circuit 220 mixed with the output frequency of the RF high frequency amplifier and the local oscillation frequency of the oscillator circuit 230, and the oscillator circuit 230. A tuner circuit portion 200 including a variable capacitance diode 240 to be supplied, an image intermediate frequency amplifier 400 for converting and amplifying the tune signal of the tuner circuit portion 200 into an intermediate frequency IF and the image A frequency amplifier 310 for frequency amplifying the image signal output from the intermediate frequency amplifier 400, a phase discriminating transformer 320 for determining a phase in the output signal of the frequency amplifier 310, and a phase detector ( 330, an AFT circuit unit 300 including a DC amplifier 340 for amplifying the output DC component signal of the phase detector 330.

Here, if the local oscillation frequency of the oscillator circuit 230 is out of the higher direction, the image intermediate frequency is lower than 38.9MHz so that a negative voltage appears at the output of the phase detector 330. When the negative voltage is applied to the variable capacitance diode 240 of the oscillation circuit unit 230, the capacitance is increased to lower the oscillation frequency to the correct frequency.

In the automatic resetting method of the AFT range according to the change of the coin voltage of the present invention, the AFT range is adjusted to have a range of ± 0.5 MHz while the image intermediate frequency is set to 38.9 MHz. When the tuning voltage is VHF, a unique tuning voltage VT for each channel is set in the range of 0 to 33V and stored in the memory IC 140.

When the local oscillation frequency is changed due to the change of intrinsic tuning voltage of each channel due to the change of the internal and external environment such as the temperature change in the stable adjustment state of the television, the range of the variation is 38,9MHz ± 0.5MHz In the range, the compensation is made by the AFT circuit, but if the local oscillation frequency is out of the AFT range (± 0.5 MHz), the reception is poor or not received.

3 is a circuit diagram illustrating the oscillation circuit of FIGS. 1 and 2.

In the VCO, when a part of the amplification circuit is provided with a resonant circuit and the part of the output signal energy is returned in phase to the input side, a high frequency signal with a constant period is generated in the amplifier itself.

In Fig. 3, the capacitor of the LC resonant circuit is divided into two and the signal is positively fed back to the input side. The oscillation frequency f is determined by the LC size of the resonance circuit, and is obtained by the following equation.

4 is a flowchart illustrating a method for correcting the VCO oscillation frequency of the present invention.

A VCO adjusting step (S100) for turning on the television to tune the tuner IF frequency and the image intermediate frequency of the main chroma IC;

Automatic VCO setting step (S200) for correcting when the matching relationship between the tuner IF frequency matched in the VCO adjustment step and the image intermediate frequency of the main chroma IC is different, and

A crystal oscillation step (S300) performed to create a matching reference frequency;

A VCO comparison discrimination step (S400) for comparing and determining whether the ACO-adjusted VCO oscillation frequency and the matching reference frequency generated in the crystal oscillation step (S300) are the same in the automatic VCO setting step (S200);

A normal operation step (S500) of performing a normal television display when the determination result in the VCO comparison and discrimination step (S400) is the same as the adjusted VCO oscillation frequency and the matching reference frequency generated in the crystal oscillation step;

AFT operation mode for converting the operation mode to perform AFT adjustment when the determination result in the VCO comparison determination step (S400) is that the adjusted VCO oscillation frequency and the matching reference frequency generated in the crystal oscillation step are not the same. Conversion step (S600),

According to the AFT operation mode conversion step (S600), the AFT adjustment operation is automatically performed, and the automatic AFT operation step (S700) of supplying the adjustment signal to the VCO adjustment step is performed.

The VCO adjusting step (S100) is a process of tuning the tuner IF frequency of 38.9 MHz and the 38.9 MHz image intermediate frequency of the main chroma IC, and fixing the IF frequency to 38.9 MHz to maintain a matching relationship between them.

The automatic VCO adjustment step (S200) is a step performed to re-adjust it when the IF frequency matched by the action in the VCO adjustment step (S100) is changed due to the use environment, to maintain the matching relationship again. .

The crystal oscillation step (S300) is a step for generating a frequency of 38.9MHz as a reference to be compared with the VCO oscillation frequency readjusted in the automatic VCO step (S200).

The VCO comparison determination step (S400) is the adjusted current VCO oscillation frequency in the automatic VCO setting step (S200) of adjusting the matching relationship by AFT adjustment and the matching reference frequency in the crystal oscillation step (S300) 38.9. This step is to compare the MHz and determine it.

The automatic AFT operation step (S700) is determined in that the frequency does not match in the VCO comparison determination step (S400) receives an instruction in the AFT operation mode conversion step (S600) to convert the operation of the system to the AFT adjustment mode This step performs AFT adjustment. The AFT adjustment at this time is to correct the wrong VCO oscillation frequency. The difference from the AFT adjustment performed in the automatic VCO setting step (S200) is that the AFT adjustment in the automatic VCO setting step is a process in which the oscillation frequency is adjusted within the limit of the AFT adjustment area (38.9 MHz ± 0.5 MHz). In the automatic AFT operation step S700, when the oscillation frequency is out of the AFT range, the VCO oscillation frequency is corrected according to the procedure of the present invention.

As described above, by repeatedly correcting the VCO oscillation frequency which is changed according to the change in the use environment of the television, it is possible to always receive a television screen in a good state.

As described above, in the present invention, when using a television in a high or low temperature environment, a separate automatic AFT operation is performed to check the current VCO oscillation frequency and correct the VCO oscillation frequency outside the AFT range through a basic AFT adjustment process. By compensating through the steps, it is possible to keep the tuning in a stable state even when the internal and external environment of the television is changed by preventing the misalignment of the tuning. Also, by simplifying the tuning circuit by implementing a separate automatic AFT operation by the programmatically. The effect can be intended.

Claims (2)

In the method of correcting the VCO oscillation frequency is distorted due to the characteristic change of the VCO coil when using the television in a high temperature or low temperature environment, Adjusting the VCO to turn on the television to tune the tuner IF frequency and the image intermediate frequency of the main chroma IC; An automatic VCO setting step for correcting when the matching relationship between the tuner IF frequency matched in the VCO adjusting step and the image intermediate frequency of the main chroma IC is different; A crystal oscillation step performed to create a matching reference frequency, A VCO comparison and discrimination step of comparing and comparing the ACO-adjusted VCO oscillation frequency with the matching reference frequency generated in the crystal oscillation step in the automatic VCO setting step, and A normal operation step of performing normal television display when the determination result in the VCO comparison and discrimination step is the same as the adjusted VCO oscillation frequency and the matching reference frequency generated in the crystal oscillation step; An AFT operation mode conversion step of converting an operation mode to perform AFT adjustment when the determination result in the VCO comparison determination step is that the adjusted VCO oscillation frequency and the matching reference frequency generated in the crystal oscillation step are not the same; , The automatic AFT operation step of supplying the adjustment signal to the VCO adjustment step by automatically performing the AFT adjustment operation according to the instructions of the AFT operation mode conversion step through the correction of the VCO oscillation frequency of the television Tuning correction method. The method of claim 1, wherein the automatic VCO setting step resets the wrong VCO oscillation frequency through adjustment in an AFT adjustment area.