KR100417414B1 - Automatic frequency control method for tuning of video equipment - Google Patents

Abstract

The present invention relates to an automatic frequency control method at the time of tuning of a video apparatus, and an automatic frequency control (AFC) operation is performed only until a step (STEP) determined by a microcomputer, even if a synchronization signal detection period (interval between h and i) Because of the difference in tuning characteristics of the applied tuner, the automatic tuning drift (DRIFT) at the time of operation causes the initial automatic frequency control point If it is placed at this specific point, the screen state is unstable. Accordingly, the present invention extends the AFC operation range in a specific channel partly due to the tuning characteristic, and improves the unstable operation in a specific state, so that it can be viewed on a clear screen.

Description

Automatic frequency control method for tuning of video equipment

The present invention is intended to compensate for the lack of automatic frequency control at the time of tuning of video equipment such as a VCR or a TV and an unreasonable operation. Especially, in order to control the AFC operation at the time of tuning by using a microcomputer When turning on the channel up / down, power off, switching from the other mode to the tuner input, when the tuning frequency range is out of the specified AFC on state, the microcomputer uses the sync signal and automatic frequency control signal To an automatic frequency control method at the time of tuning of a video apparatus that extends the AFC operation range in a specific channel and improves the screen instability in a specific state.

As shown in FIG. 1, the circuit configuration of a conventional automatic frequency tuning device of a video apparatus is such that a signal to be tuned is output as a pulse width modulation signal PWM and an automatic frequency control signal (AFC) and a horizontal synchronization signal (H-SYNC); A power supply 30 for supplying a tuning voltage; A mixer 40 for mixing the tuning voltage of the power supply 30 with the pulse width modulation signal PWM of the microcomputer 20; A low pass filter 50 for filtering the mixed signal through the mixer 40 to remove unnecessary frequency parts; A tuner 10 for tuning a high frequency (RF) broadcast signal according to an output voltage of the low-pass filter 50 and converting it to an intermediate frequency (IF) and outputting the tuned signal; An intermediate frequency demodulator 60 for converting a high frequency (RF) broadcast signal tuned through the intermediate frequency IF of the tuner 10 into an intermediate frequency IF; And a horizontal synchronization separator 70 for separating the horizontal synchronization signal H-SYNC from the signal demodulated by the intermediate frequency demodulator 60 and outputting the separated horizontal synchronization signal H-SYNC to the microcomputer 20.

As shown in FIG. 3, the automatic frequency control method for tuning a video apparatus includes a first step of checking the presence or absence of a synchronization signal; A second step in which the automatic frequency control (AFC) voltage is shifted in steps of h and d or the number of steps of STEP 2 in the rising direction within the interval e and i when the synchronizing signal is present in the first step; If the presence or absence of the synchronizing signal is not checked again after the movement in the second step, stopping the step movement and moving the tuned voltage by the number of steps determined in STEP2 in the descending direction; A fourth step of checking whether the AFC signal has entered the d and e sections if there is a sync signal in the third step; If the tuning voltage moves to STEP 1 in the ascending direction and then enters the interval b and c, the fifth step of maintaining and checking the tuning state; If it is not possible to enter in the fourth step, the tuning voltage is shifted in the descending direction by the number of steps determined in STEP2 at the beginning of the interval h and d or e and i; If there is no synchronization signal in the first step, the tuning voltage is unconditionally moved in the upward direction by the number of steps determined in STEP3 when j or k section is present; An eighth step of checking whether the synchronizing signal and the AFC signal after moving in the seventh step enter d and c sections; And if it is not entered in the eighth step, the unconditional tuning voltage is shifted in the descending direction by the number of steps determined by STEP3 at the beginning of the j or k section; Checking whether the synchronizing signal and the AFC signal have entered the d and e sections in the ninth step; An eleventh step of proceeding to the fifth step when entering the section in the third, sixth, eighth, and tenth steps; And if it fails to enter the interval in the third, sixth and tenth steps, it maintains the initial state and then ends the twelfth step.

The conventional technology thus constructed will be described in detail as follows.

When the microcomputer 20 outputs a signal for selecting a desired channel to the mixer 40 as a pulse width modulation signal PWM, the mixer 40 outputs a tuning voltage signal supplied from the power supply unit 30 And outputs it to the low-pass filter 50.

The low-pass filter 50 low-pass-filters the unnecessary signal generated during mixing and transmits the low-pass filtered signal to the tuner 10 so that the tuner 10 can adjust the voltage to be input to the low- Frequency signal corresponding to the channel, converts it to an intermediate frequency (IF), and transmits it to the intermediate frequency demodulation unit (60).

The intermediate frequency demodulator 60 outputs a video signal obtained by demodulating the input intermediate frequency IF to the horizontal sync separator 70 and outputs an automatic frequency control (AFC) signal to the microcomputer 20 .

The horizontal sync separator 70 separates the horizontal sync signal from the input video signal and outputs the separated horizontal sync signal to the microcomputer 20.

Accordingly, the microcomputer 20 receives the synchronization signal SYNC input from the horizontal synchronization demultiplexing unit 70 as in (A) of FIG. 2 and the synchronization signal SYNC as shown in (B) of the second diagram from the intermediate frequency demodulator 60, The tuning control is performed using an AFC signal as shown in FIG.

The microcomputer 20 first checks whether there is a sync signal SYNC input from the horizontal sync separator 70.

As a result of checking, if the synchronization signal SYNC exists and the automatic frequency control (AFC) signal is within the interval h and d or between the interval e and i, the tuning voltage is shifted by the number of steps (nSTEP) determined in STEP2 in the UP direction The tuning voltage is shifted to the STEP1 in the up direction (UP) or the down direction (DOWN) when it enters the interval d and e.

Thereafter, when the AFC signal enters the interval b and c, the interval is in the ON range of the automatic frequency control signal (AFC), and thus the AFC ON state is maintained and continuously checked.

This operation is repeated continuously.

If the AFC signal does not enter within the interval d and e, the tuning voltage is shifted in the downward direction by the number of steps (nSTEP) determined in STEP2 at the beginning of the interval h or d or between the interval e and i, And e, the tuning voltage moves to STEP1 in the rising direction or the falling direction. When the AFC signal enters the b and c sections, the AFC ON state is maintained and continuously checked.

Also, if the AFC signal can not enter within the interval d and e, the initial state is maintained.

If there is no synchronizing signal (SYNC) after the AFC signal has the synchronizing signal and the AFC signal has shifted by the number of steps determined by STEP2 in the rising direction within the interval of h and d and the interval of e and i, (NSTEP) determined in STEP2 in the descending direction, and if the AFC signal enters the interval d and e later, the next operation is the same as that described above, and if the AFC signal is not entered, the initial state is maintained and completed.

If there is no synchronizing signal (SYNC) for the first time, then the tuning voltage is up unconditionally when it is in the i or k section. NSTEP to STEP3 If the synchronizing signal and the AFC signal enter the d and e sections during the movement, do.

In the above, STEP1, STEP2, and STEP3 have the following conditions.

STEP1 <STEP2 <STEP3

If the sync signal and the AFC signal do not enter within the interval d and e, if the sync signal and the AFC signal enter the interval d and e during the nSTEP movement in STEP 3 in the direction that the unconditional tuning voltage is down at the first point of the j or k section, As mentioned above, it is performed in the same manner, and if not entered, it is maintained in the initial state and the screen is not found.

Through the above-described method, the channel is automatically tuned.

However, in the conventional technique as described above, since the automatic frequency control (AFC) is operated only until the step (STEP) determined by the microcomputer, even if the synchronization signal sensing period (interval between h and i) Due to the difference in tuning characteristics, the automatic frequency control operation range is narrow even within the synchronization detection interval, so that the screen can not be properly tuned.

If the initial automatic frequency control point is located at a specific point (interval between e and i) due to tuning drift (DRIFT) during operation, the unstable state on the screen, that is, Which is not natural.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a tuner- , The microcomputer uses the synchronous signal and the automatic frequency control signal to extend the AFC operation range in a specific channel and improve the unstable picture in a specific state when the AFC on state is out of the predetermined range And to provide an automatic frequency control method when tuning the device.

According to an aspect of the present invention, there is provided an automatic frequency control method for tuning a video apparatus, comprising: a first step of checking whether a synchronization signal exists or not, as shown in FIG. 4; A second step of comparing the automatic frequency control signal level with a reference level and checking whether the automatic frequency control signal level exists in a high or a level interval when the synchronization signal is present in the first step; If the automatic frequency control signal is present in the high level interval in the second step, the tuning voltage is moved to the STEP2 in the upward direction. If the automatic frequency control signal enters the d and e intervals, the tuning voltage is moved to the STEP1 in the upward direction again so as to enter the b and c intervals A third step; If the automatic frequency control signal exists in the low level interval in the second step, the tuning voltage is moved to STEP2 in the descending direction, and if the automatic frequency control signal enters the d and e intervals, the tuning voltage is moved to STEP1 in the descending direction again so as to enter the interval b and c A fourth step; A fifth step of maintaining an automatic frequency control (AFC) on state and continuously checking if the automatic frequency control signal enters the b and c sections in the third and fourth steps; If there is no synchronization signal in the first step, unconditionally unconditionally moving the tuning voltage in the down direction by the number of steps determined in STEP3; A seventh step of checking whether there is a synchronization signal while moving the tuning voltage in the j or k section in the upward direction by the number of steps determined in STEP3 if the synchronization signal appears in the step 6, ; If the synchronization signal is present in the seventh step, the process proceeds to the second step. If the synchronization signal does not continue, the j step is performed in the initial state of the j or k section.

The operation and effect of the present invention will be described in detail with reference to the block diagram shown in FIG.

The microcomputer 20 checks whether an automatic frequency control (AFC) signal exists in a high level section, that is, a section of h and d, whether or not there is a sync signal SYNC input from the horizontal sync separator 70 do.

As a result of the check, if the AFC signal is present in the high level interval, the microcomputer 20 moves to STEP2 in the direction of increasing the tuning voltage, and moves to STEP1 in the upward direction when it enters the interval d and e.

As described above, when the AFC signal enters the section between b and c while moving to STEP1 as described above, the AFC keeps on the on state because it is on-range of the AFC.

If the AFC signal is present in the low level section, that is, in the low level section, that is, in the section between e and i while the synchronization signal SYNC exists, the AFC signal is shifted to STEP2 in the descending direction, When entering the section, the tuning voltage continues to go down to STEP1 and enter the section between b and c.

If it moves to STEP 1 and enters the section between b and c, the AFC ON state is maintained and checked continuously as described above.

Here, the division into STEP1 <STEP2 <STEP3 is required because the speed control of the AFC operation and the detailed operation for error prevention are required.

If there is no synchronization signal SYNC in the above, the microcomputer 3 goes to step 3 in the direction of the j or k section (when the AFC signal is at the high level and the synchronization signal is not present at one point of the entire interval) (Step 20). If there is a sync signal SYNC, it is checked whether the AFC signal is present in the high level interval or in the low level interval, and then the operation is performed as described above.

If there is no synchronization signal SYNC as a result of checking the existence of the synchronization signal SYNC while moving by the number of steps determined in STEP3, the number of steps (nSTEP) determined in STEP3 in the direction of increasing the tuning voltage in the original j or k section, And if there is a synchronization signal, it performs the same operation as the operation in the previous synchronization section. If there is no synchronization signal, it refers to all operations that are completed and held in the original state in the j or k section.

In this case, when the j or k section is kept in the original state, it means that the occurrence of tuning drift is large and the video signal does not appear on the screen when the AFC is out of the AFC operation range set by the microcomputer 20 and the AFC is not turned on.

As described above in detail, the present invention has the effect of extending the AFC operation range in a specific channel partly due to the tuning characteristic, and improving the unstable operation in a specific state, so that it can be viewed on a clean screen.

FIG. 1 is a circuit diagram of an automatic frequency tuning device of a conventional video equipment; FIG.

Fig. 2 is a signal waveform diagram of each part in Fig. 1; Fig.

FIG. 3 is a flowchart of an automatic frequency control method in tuning of a conventional video apparatus.

FIG. 4 is a flowchart illustrating an automatic frequency control method for tuning a video apparatus according to the present invention.

FIG. 5 is a waveform diagram of a synchronization signal and an automatic frequency control signal required in the normal tuning in FIG.

Description of Reference Numerals to Main Parts of the Drawings *****

10: tuner 20: microcomputer

30: Power supply unit 40: Mixer

50: low pass filter 60: intermediate frequency demodulator

70: Horizontal sync separator

Claims (4)

A first step of checking presence or absence of a synchronization signal; A second step of comparing the automatic frequency control signal level with a first reference level and checking whether the automatic frequency control signal level exists in a high or low level interval if the synchronization signal is present in the first step; If the automatic frequency control signal exists in the high level interval in the second step, move the tuning voltage in the up direction to enter the first target interval; If the automatic frequency control signal exists in the low level interval in the second step, move the tuning voltage in the falling direction to enter the first target interval; If the automatic frequency control signal enters the first target section in the third and fourth steps, moves the tuning voltage in the up or down direction to enter the second target section; And a sixth step of maintaining an automatic frequency control (AFC) on state when the automatic frequency control signal enters the second target section in the fifth step. The automatic frequency control method according to claim 1, wherein the first target interval is a period d and an interval e. The automatic frequency control method according to claim 1, wherein the second target interval is a period between b and c. The method of claim 1, further comprising: a seventh step of checking whether a sync signal is present while the unconditioned tuning voltage is shifted by a predetermined number of steps in a descending direction when the sync signal is present in the j or k section in the first step; If the synchronization signal is present, proceeding to the second step, and if not, continuing the tuning voltage in the j or k section to the STEP 3 in the rising direction and checking whether there is a synchronization signal; If the synchronizing signal is present in the eighth step, proceeding to the second step and continuing to the j-th or k-th period in the initial state of the j or k section, Control method.