JPH0125447B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a station searching device for a television receiver.

First, a conventional station searching device will be explained with reference to FIG.
In the figure, 11 is an electronic tuner, 12 is a video intermediate frequency filter, 13 is a video intermediate frequency amplification circuit,
14 is a video detection circuit, 15 is an AFT detection circuit, 1
6 is a synchronization separation circuit, 17 is a TV signal discrimination detection circuit, 18 is an AFT-UP, DOWN signal generation circuit,
19 is an AFT control circuit, 20 is a preset control circuit, 21 is a tuning clock generator circuit, 22 is an information counter, 23 is an address input control circuit, 24 is a tuning voltage storage circuit, and 25 is a D/A ( 26 is a tuned voltage integration circuit. Also, a is the video intermediate frequency signal, b is the AFT detection output, c is the video detection output, and d
is AFT-UP signal, e is AFT-DOWN signal, f
is the synchronization signal, g is the flyback signal of the receiver, h
is a television signal discrimination signal, h' is an AFT signal, k is an address signal, l is a tuner tuning voltage signal, m is a tuner tuning voltage, i is a search trigger signal, j is a search station, normal mode switching signal, and 27 is a search signal. The station trigger switch 28 is a station search/normal mode changeover switch.

Now, the changeover switch 28 is set to the search mode (j=+
At the time of B), a TV signal in the VHF-LOW band that the electronic tuner 11 can receive at the lowest tuning voltage is input from the antenna, and at the same time, the address signal k is applied to the address input control circuit 23 to tune a certain address. When the search trigger switch 27 is pressed in this state, a trigger pulse of i=+B is applied to the preset control circuit 20, and the tuning clock generator circuit 2
1 clock is started, and the output l of the D/A converter circuit 25 is increased. This output l is integrated by the tuning voltage integration circuit 26 and is then integrated into the electronic tuner 1.
1, and when the tuner tuning voltage m becomes the tuning voltage of the television signal, a video intermediate frequency signal a is obtained.
This signal a passes through a video intermediate frequency filter 12 and is amplified by a video intermediate frequency amplification circuit 13;
Input to AFT detection circuit 15 and AFT detection output b
The other is input to the video detection circuit 14 to output the video detection output c, and the synchronous separation circuit 1
6, it becomes a synchronizing signal f, which is input to a television signal discrimination and detection circuit 17, where it is AND gated with a flyback signal g, and outputs a television signal discrimination signal h.
In addition, the AFT detection output b is a voltage V _H , which is set in advance by the AFT-UP, DOWN signal generation circuit 18.
When compared with V _L , when b≧V _H , AFT-UP signal d
= LOW (hereinafter abbreviated as L), AFT-DOWN signal e
=High (hereinafter abbreviated as H) is output, and when b≦V _L ,
Output d=H, e=L. Outputs d, e, and h are input to the AFT control circuit 19, and when the tuning voltage m is increased to capture a television signal, the AFT detection output b is generally V _L <b<V _H →b>V _H →
It changes in the order of V _L < b < V _H → b < V _L → V _L < b < V _H. Along with this, the AFT-UP signal d changes from H to L.
→H→H, AFT-DOWN signal e is H→
Changes from H→L→H, and h changes from L→H→H→L
The AFT control circuit 19 outputs d.
and h, e and h are AND gated and input to the preset control circuit 20, where the tuning voltage signal l when the signal d changes from L to H and the tuning voltage signal l when the signal e changes from H to L The optimum tuning voltage is calculated from the voltage signal l, the rising operation of the tuning clock generator circuit 21 is stopped, the optimum tuning point is set, and the signal l is finally integrated to tune the electronic tuner 1.
In addition to 1, a video intermediate frequency signal a at the optimum tuning point is obtained.

In this way, the search operation stops every time a TV signal is captured, so when starting the search operation next time, turn on the search trigger switch 27, set i=+B, and then adjust the tuning voltage m until the TV signal is captured. raise. The operation when a TV signal is captured is as described above, and the search trigger switch 27 is activated each time.
When you turn on and apply a trigger input that sets i=+B, the tuning voltage m rises to the maximum voltage in the UHF band and then stops.As a result, the station searching operation stops and the tuning voltage signal l
Set the preset control circuit 20 to the minimum voltage for the lowest channel of the VHF-LOW band.
starts to move from station searching operation to fine tuning operation. In other words, the AFT control circuit 19 and preset control circuit 20 operate in two ways: station searching operation and fine tuning operation.
When station searching is in progress, d=L, e=H→d
= H, e = L, the AFT information changes, and if h = H during this change period, the circuits 19 and 20 validate the AFT information d and e and stop the station searching operation, and the fine inch user Move on to the cleaning operation. If the relationship between the signals d, e, and h is other than this, the AFT information d and e are invalidated and the station searching operation is continued, resulting in an increase in the signal l. In addition, in the case of fine inch euning operation other than station searching operation, h=H, d=H,
The combination e=L (set as combination A), h=H,
The AFT information of outputs d and e is valid only in the combination of d=L and e=H (combination B), and in the case of combination A, the tuning clock generator circuit 21 is used to lower the signal l. This is an operation that works in the opposite direction and works in the opposite direction for combination B, making combinations other than A and B invalid.

By the way, the changeover switch 28 is now connected to the search mode, and the signal l is at its minimum and the band is VHF-
When the circuits 19 and 20 are set to LOW and the circuits 19 and 20 enter the fine tune operation, the signal l is at its minimum and the electronic tuner 11 can receive the television signal, so immediately after this, the signals h, d, and e are The combination is either A or B. In the case of combination B, the signal l increases, but in the case of combination A, the signal l increases.
works in the direction of lowering the voltage below the minimum voltage, resulting in the maximum voltage, and the band changes from VHF-LOW to UHF.
Changes to Therefore, even if the trigger switch 27 is turned on next time in the search mode and the circuit 20 is triggered by the trigger of i=+B, the search operation will stop because the signal l is at its maximum and the band is UHF. → Band = VHF-LOW, l = minimum → Electronic tuner 11 catches a certain channel of VHF-LOW → d, e, h combination becomes A → l = maximum, band = UHF, and in the end, how many times is the search trigger The drawback was that even if a signal was added, it was not possible to search from UHF to VHF-LOW.

Therefore, the purpose of this invention is to set the automatic station searching operation to the lowest tuning voltage after the tuning voltage reaches the maximum in the UHF band, the station searching operation stops, the band changes to the VHF-LOW band, and the tuning voltage is set to the lowest level. Automatic station search and operation
In the VHF-LOW band, the VHF-LOW band can receive television signals at the lowest tuning voltage in a station search device equipped with an electronic tuner and an intermediate frequency signal processing circuit that can receive TV signals in the VHF-LOW band at a tuning voltage near the lowest. When the TV station is broadcasting, after the automatic station search operation reaches the maximum tuning voltage of the UHF band, the band will definitely change to VHF-LOW and the tuning voltage can be set to the lowest value.The next time you start the automatic station search operation. To provide a station searching device for a television receiver that can automatically search from the lowest tuning voltage of the VHF-LOW band.

The station searching device for a television receiver of this invention includes:
As the tuning voltage changes, tune in from the lowest channel of the VHF-LOW band to the highest channel of the UHF band, and when the highest channel of the UHF band is reached, tune to the lowest channel of the VHF-LOW band, and then tune to the lowest channel of the VHF-LOW band. In a television receiver's search device that selects the highest channel of the UHF band after reaching the lowest channel of the LOW band, there is an electronic tuner to which the tuning voltage is supplied to control the channel selection, and this electronic tuner. an intermediate frequency amplification processing circuit that processes the output voltage of the intermediate frequency amplification processing circuit; an AFT detection circuit that detects the difference between the frequency of the intermediate frequency output signal of the intermediate frequency amplification processing circuit and a predetermined intermediate frequency; and a detection output of the intermediate frequency amplification processing circuit. A television signal detection circuit that determines that the signal is a television signal, and automatic station searching by sequentially changing the tuning voltage from the minimum voltage for the lowest channel of the VHF-LOW band to the maximum voltage for the highest channel of the UHF band. Depending on the output of the AFT detection circuit and the output of the TV signal detection circuit, the station search is stopped when a TV signal is received, and when the maximum voltage for the highest channel of the UHF band is reached, the station search operation is stopped and the VHF-LOW An automatic station searching processing circuit that completes automatic station searching by setting the minimum voltage for the lowest channel of the band, and then performs normal tuning controlled by the output of the AFT detection circuit, and a user operation. a search trigger switch that supplies a search start signal to the automatic station search processing circuit to start the automatic station search operation; and a search trigger switch that starts the automatic station search operation by supplying a search start signal to the automatic station search processing circuit; and a changeover switch that switches between normal station selection operation, and the changeover switch is switched to the automatic station search operation side and the automatic station search is ended and VHF-LOW is selected.
and a regulation circuit that prohibits the output of the AFT detection circuit from being supplied to the automatic station search processing circuit when the voltage is set to the minimum voltage for the lowest channel of the band. be.

An embodiment of this invention is shown in FIG. In the figure, 31 is an intermediate frequency amplification processing circuit including the circuits 12 to 14 and 16 in FIG. 1, and 32 is the circuit 19 to 25.
This is an automatic station search processing circuit that includes Also circuit 1
1, 15, 17, 18, 26 and switch 2
7 and 28 are the same as in FIG. Also, 41,4
4 is a switching transistor, 42, 43, 4
Reference numeral 5 designates their base bias resistors, and the signal i is connected to the input/output terminal of the circuit 32 and is H during the station searching operation and L otherwise. transistor 4
The regulation circuit Q including 1 and 44 operates when i=L and j=H (i.e., when station search mode is not in operation)
This is an AND gate that only switches (turns on) the transistor 41. Further, r is a signal for turning off the AFT detection circuit 15. In this case, if r=L due to the regulation circuit Q, then
The AFT detection output b is set to the set voltages V _L and V _H of the AFT-UP and DOWN signal generation circuit 18 such that V _L < b < V _H . Next, the circuit operation will be explained. The conditions explained in the conventional example, that is, VHF at the antenna input.
- The selector switch 28 is turned on when a receivable TV signal is input with the lowest tuning voltage m in the LOW band, and when j = +B, the trigger switch 27 is turned on instantaneously and i = +B. The automatic station search processing circuit 32 is instantly triggered to the station search state. As a result, the signal l and the tuning voltage m rise, catch the TV signal, and then stop, but each time i=
Adding a +B pulse will result in station searching operation. The terminal to which the signal i of the circuit 32 is applied is an input/output terminal, and during station searching, i=H, and since j=H, the transistor 41 is off, so r=H.
Therefore, the AFT detection circuit 15 detects the signal a for the signal a.
Outputs AFT detection signal b. Tuning voltage m is UHF
When the maximum is reached, the search operation stops as explained earlier, l, m = minimum, band = VHF
It is set to LOW, which changes i=L.
At this time, the inputs j and i of the regulation circuit Q are j=H, i=
Since it becomes L, the transistor 41 turns on, and r
=L, so V _L < b < V _H. Therefore, even if the television signal (11) is received at the minimum tuning voltage m of the VHF-LOW band, h=H in the circuit 32, but the AFT information d, e becomes H and is not transmitted. Therefore, l and m are minimum → maximum, and the band is
There is no change from VHF-LOW to UHF. In other words, if a search trigger is applied next time, the VHF-LOW band tuning voltage m will be searched from the lowest value.

As described above, the station searching device for a television receiver of the present invention includes an electronic tuner that can receive various broadcast waves by changing the tuning voltage, an AFT detection circuit that detects the difference between an intermediate frequency and a set frequency, A TV signal detection circuit that determines that it is a TV signal based on the video signal output from the intermediate detection amplifier circuit and the video detection circuit and the flyback pulse signal of the receiver, and a search start signal that is triggered by the user. The voltage rises and falls smoothly, and the output voltage
It is used as the tuning voltage of the electronic tuner, and by raising and lowering its output, when the broadcast radio waves are searched and a TV signal is captured, the search stop signal output from the TV signal detection circuit and the output of the AFT detection circuit are generated. A circuit that generates an output voltage that obtains the optimal tuning voltage depending on the voltage, makes the output voltage constant, and ultimately maintains the condition of receiving broadcast radio waves, and an automatic station search processing circuit that stores the output voltage. In the station searching device for a television receiver, the electronic tuner is capable of receiving the broadcast signal of the lowest channel of the VHF LOW channel in the VHF LOW band and near the lowest tuning voltage, and the station searching operation is performed in the UHF LOW band. If the function is such that the search operation stops at the maximum tuning voltage, when the search start signal is applied when the tuning voltage is maximum and the band is UHF, the tuning voltage will change from the maximum to the minimum when the band becomes VHF LOW. In order to do this, we have installed a circuit that turns off the AFT information of the AFT detection circuit when not searching in station search mode, so automatic station searching can be performed reliably from the VHF-LOW band with the lowest tuning voltage by the search start operation. effective.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional example, and FIG. 2 is a circuit diagram of an embodiment of the present invention. 11...Electronic tuner, 15...AFT detection circuit,
17... Television signal detection circuit, 27... Search trigger switch, 31... Intermediate frequency amplification processing circuit, 32... Automatic search processing circuit, Q... Regulation circuit.

Claims (1)

[Claims] 1 As the tuning voltage changes, tune in from the lowest channel of the VHF-LOW band to the highest channel of the UHF band, and when the highest channel of the UHF band is reached, select the lowest channel of the VHF-LOW band, and then tune to the lowest channel of the VHF-LOW band. - In a television receiver's search device that selects the highest channel of the UHF band after reaching the lowest channel of the LOW band, the electronic tuner to which the tuning voltage is supplied to control the channel selection, and this electronic An intermediate frequency amplification processing circuit that processes the output voltage of the tuner, and detecting the difference between the frequency of the intermediate frequency output signal of this intermediate frequency amplification processing circuit and a predetermined intermediate frequency.
an AFT detection circuit; a television signal detection circuit that determines that the detected output signal of the intermediate frequency amplification processing circuit is a television signal;
From the minimum voltage for the lowest channel of the LOW band
Automatically searches for stations by sequentially changing the voltage up to the maximum voltage for the highest channel of the UHF band, and stops searching when a TV signal is received according to the output of the AFT detection circuit and the output of the TV signal detection circuit.
When the maximum voltage for the highest channel of the UHF band is reached, the station search operation is stopped and the automatic station search is terminated by setting the voltage to the minimum voltage for the lowest channel of the VHF-LOW band. An automatic station search processing circuit that performs normal station selection under inch-unning control, and a station search trigger that supplies a search start signal to this automatic station search processing circuit and starts automatic station search operation according to the user's operation. a switch, a changeover switch for switching the operation of the station search processing circuit between an automatic station search operation and a normal station selection operation according to a user's operation; Finish the search
and a regulation circuit that prohibits the output of the AFT detection circuit from being supplied to the automatic station search processing circuit when the voltage is set to the minimum voltage for the lowest channel of the VHF-LOW band. A station searching device for television receivers.