KR20000003537A - Tuner image intermediate frequency correction method through tuning voltage control of television - Google Patents

Abstract

PURPOSE: A tuner image intermediate frequency correction method is provided to always maintain the IF frequency within the AFT range by correcting the tuning voltage according to the IF frequency change of the television. CONSTITUTION: The tuner image intermediate frequency compensation method comprises: checking the current tuner IF frequency as turning on a television in a high or a low temperature; memorizing by checking the current tuning voltage(VT) if the IF frequency is higher or lower than the AFT range; and compensating the voltage by using the memorized tuning voltage of the current channel as a standard.

Description

Tuner Image Intermediate Frequency Correction by Adjusting Tuning Voltage of Television

The present invention relates to a method for automatically correcting a tuner image intermediate frequency (hereinafter referred to as "IF frequency") by adjusting the tuning voltage (VT) of a television. In particular, the present invention relates to a method for automatically compensating for distortion of an IF frequency generated when a television is switched by an external change such as high temperature or low temperature.

In case of TV mode or channel phone, if the IF frequency changes due to high or low temperature or fluctuations in power voltage, the received image may be blurred or unreceivable. Therefore, the IF frequency is always set to AFT (Automatic Frequency Tuning). You need to keep it within range.

The conventional method for correcting the IF frequency of a television has been to allow a change in the IF frequency only within a preset AFT range using an AFT circuit. For example, in a television set with an IF frequency of 38.9 MHz, the AFT region has a margin of about 0.5 MHz above and below 38.9 MHz, and compensates when the IF frequency changes within that region.

As a method of improving the IF frequency by developing a little from the above method, a method in which the AFT range is further widened in advance and stored in the microcomputer to make the allowable change range of the IF frequency larger.

However, the method of applying the AFT range, which is a conventional method for preventing the IF frequency from changing due to the temperature change or the power supply voltage, to be applied in a wide range in advance, can cope only within the range of the defined AFT range. Since the IF frequency cannot be corrected, there is a problem that cannot prevent the screen distortion.

The present invention has been invented to solve the above problems of the prior art, an object of the present invention is to provide a method for compensating the tuning voltage in accordance with the change of the IF frequency of the television to always maintain the IF frequency within the AFT range. have.

According to the technical concept of the present invention, when the television is turned on in a high or low temperature environment, the current tuner IF frequency is checked, and the present tuning is performed when the IF frequency is larger or smaller than the AFT range (38.9 MHz ± 0.5 MHz). A method of checking and memorying the voltage VT and repeatedly compensating the voltage based on the synchronized voltage of the memorized current channel is always performed to maintain the tuner IF frequency properly.

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 flowchart illustrating a tuner image intermediate frequency correction method by adjusting the tuning voltage 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") to which an IF frequency correction method of the present invention is applied.

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 correcting distortion of an IF frequency 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 IF frequency is lower than 38.9MHz so that a negative voltage is output to the output of the phase detector 330. When the negative voltage is applied to the variable capacitance diode 240 of the oscillation circuit 230, the capacitance is increased to adjust the oscillation frequency to correct the IF frequency so as to lower the correct frequency.

IF Frequency Correction According to Variation of Tuning Voltage VT In the present invention, the AFT range is adjusted with a range of ± 0.5 MHz while the IF frequency is set to 38.9 MHz. When the tuning voltage is VHF, intrinsic tuning voltage (VT) is set for each channel in the range of 0 to 33V and stored in the memory IC 140.

If the IF frequency is changed due to the change of the internal and external environment such as temperature change in the stable adjustment state of the television as described above, the variation range is compensated by the AFT circuit in the IF frequency range of 38,9MHz ± 0.5MHz. If the IF frequency is out of the AFT range (± 0.5MHz) above the local oscillation frequency, the reception is poor or not received.

3 is a flowchart illustrating an IF frequency correction method by correcting the tuning voltage VT of the present invention.

A television on step (S100) of turning on a television with a remote control unit,

An RF input step (S200) through which the RF high frequency amplified by the tuner circuit unit is input;

A tuner IF output step (S300) of outputting an RF medium frequency input to the tuner circuit unit as an image intermediate frequency;

An IF frequency determination step (S400) for determining whether the IF frequency output in the tuner IF output step (S300) is 38.9 MHz, which is a set value, and

When the IF frequency is determined to be 38.9MHz in the IF frequency determination step (S400) and the normal operation step (S500) that performs a normal operation,

In the IF frequency discriminating step (S400), if it is determined that the IF frequency is not 38.9 MHz, the frequency-size discrimination step (S600) for determining whether the IF frequency is larger or smaller than 38.9 MHz,

A first VT voltage checking step S700 for checking a current tuning voltage when it is determined that the IF frequency is greater than 38.9 MHz in the frequency band discrimination step (S600);

A first voltage adjustment step S800 of supplying a variable amount to the tuner IF output step S300 by adding a variable amount based on the tuning voltage VT checked in the first VT voltage checking step S700;

A second VT voltage checking step (S900) of checking a current tuning voltage when it is determined that the IF frequency is smaller than 38.9 MHz in the frequency-case discrimination step (S600);

A second voltage adjusting step (S1000) is applied to the tuner IF output step (S300) by reducing the variable amount based on the VT voltage checked in the second VT voltage checking step (S900).

The tuner IF output step (S300) is a step of outputting the changed IF frequency affected by environmental changes such as high temperature or low temperature.

The IF frequency determination step (S400) is a step of determining whether the IF frequency output from the tuner IF output step (S300) is 38.9MHz, which is a rated set value. If the IF frequency determined in this step is within 30.5MHZ, for example, within ± 0.5MHz, the frequency is adjusted without any further action. Therefore, the display proceeds to the normal display step (S500). However, if the IF frequency in the above example in the above IF frequency determination step (S400) outside the 38.9MHz ± 0.5MHz frequency adjustment is not possible in the AFT circuit should be performed in the frequency adjustment step of the present invention.

If the frequency discrimination step (S600) is determined that the frequency determined in the IF frequency determination step is out of 38.9MHz ± 0.5MHz, the IF frequency is smaller than the AFT negative adjustment range (-0.5) at the rated value or AFT It is a step of determining whether it is larger than the positive adjustment area (+0.5).

The first voltage adjusting step S700 is a value W reduced by the width of the pulse width modulation PWM based on the current tuning voltage VT checked in the first voltage checking step S500. The IF frequency is corrected by adding the variable amount x out of the AFT adjustment area and supplying the value W = W + x to the tuner IF output step S300.

The second voltage adjusting step (S900) checks the current tuning voltage (VT) by checking the current tuning voltage (VT) when the IF frequency is determined to be less than 39.9 MHz ± 0.5 MHz in the frequency-to-small and large discriminating step (S600). By correcting the incorrect IF frequency by supplying a value (W = Wx) obtained by subtracting the variable amount (x) to the tuner IF output step (S300) on the basis of

As described above, in the present invention, when the television is used in a high or low temperature environment, in order to correct the tuner IF frequency that is changed due to the change of the environment, the IF frequency deviates from the AFT control region by plus and minus is determined. In this case, the process of checking the current tuning voltage and adding or subtracting a variable amount based on the tuning voltage and supplying it to the tuner IF output stage is repeated all the time, thereby affecting changes in the television usage environment such as high or low temperature. As it can maintain an appropriate IF frequency at all times without receiving, there is an effect that can receive the screen in good condition,

In addition, since the method of the present invention can be performed using a microcomputer without adding a separate hardware device for the IF frequency correction, it is possible to simplify the product simplification and high-end.

Claims (4)

In the method for correcting the IF frequency distortion caused by the change in the use environment of the television due to high or low temperature, A tuner IF output stage for receiving an RF input and outputting an IF frequency; IF frequency discrimination step of determining whether the currently output tuner IF frequency is equal to the set value, A frequency case discrimination step of determining whether the discriminator value is larger or smaller than the set value when the tuner IF frequency does not match the set value in the frequency discriminating step; A first VT voltage checking step of checking a current tuning voltage when it is determined that the IF frequency is larger than a set value in the frequency-sizing discrimination step; A first voltage adjusting step of supplying the tuner IF output step by adding a variable amount based on the tuning voltage VT checked in the first VT voltage checking step; A second VT voltage checking step of checking a current tuning voltage when it is determined that the IF frequency is smaller than a set value in the frequency-case discrimination step; Tuner video intermediate frequency by adjusting the tuning voltage of the television, including a second voltage adjusting step of supplying the tuner IF output step by subtracting a variable amount based on the VT voltage checked in the second VT voltage checking step. Calibration method. The tuner image intermediate frequency correction method according to claim 1, wherein the set value determined in the IF frequency discrimination step is 38.9 MHz ± 0.5. The method according to claim 2, wherein the frequency band discrimination step, when it is determined that the frequency determined in the IF frequency determination step is out of 38.9MHz ± 0.5MHz (nominal value), IF frequency is AFT negative adjustment range (-0.5MHz) at the rated value And determining whether it is smaller than or greater than the AFT plus adjustment region (+0.5 MHz). The method of claim 1, wherein the first voltage adjusting step is performed by subtracting the value W by the width of the pulse width modulation PWM based on the current tuning voltage VT checked in the first voltage checking step. Adds the variable amount x out of the AFT adjustment area of the signal and supplies the value (W = W + x) to the tuner IF output step, In the second voltage adjusting step, when it is determined that the IF frequency is smaller than a predetermined value in the frequency-sizing discrimination step, the present variable voltage is checked based on the checked tuning voltage VT. A method of adjusting the tuner image intermediate frequency by adjusting the tuning voltage of a television, characterized by supplying a value (W = Wx) obtained by subtracting (x) to the tuner IF output step.