JPS6110389Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a television receiver, and more specifically, it relates to an improvement of a device that can automatically switch between two arbitrary channels of received broadcast programs. It is something.

Conventionally, there were television receivers that displayed images of two types of programs on the same screen at the same time, allowing you to watch the program on the main channel while monitoring the content of the program on the secondary channel, but the audio output was only from the main channel. Sub-channel programs have to be read only from the image, which tends to make them unclear, and if the main channel program and sub-channel program are displayed on the same screen at the same time, it becomes difficult to watch. It was seen.

Therefore, as shown in Japanese Patent Laid-Open No. 53-83529, for example, it is possible to receive two or more desired channels in a time-sharing manner, and when a preset time has elapsed while watching a program on the main channel, There are also televisions that can automatically switch to a sub-channel program for a predetermined period of time and temporarily monitor the sub-channel program.

However, in this method, the control pulse that switches between the main and sub channels has a constant period (T ₁ + T ₂ ), and the time ratio between T ₁ and T ₂ can be changed arbitrarily within that period. , the period T cannot be changed, and the time division of both the main and sub channels is restricted in this respect. Furthermore, the conventional method requires a separate control pulse generator independent of the normal image receiving circuit to generate control pulses, and has the disadvantage of requiring a separate and complicated circuit such as a multivibrator or flip-flop circuit.

Therefore, in this invention, we focused on obtaining a control synchronization signal by shaping the waveform of the existing vertical synchronization signal, and selected several types of synchronization pulses with expanded synchronization using a multi-stage frequency divider. It is designed to be able to be used as a control pulse in a timely manner, and the period itself can be selectively switched, providing a more practical type for television receivers where both the main and sub channels can be viewed in a time-sharing manner. It is something that

FIG. 1 is a block diagram showing an embodiment of the television receiver according to this invention. In the figure, 1 is an input terminal for a synchronization signal supplied from a synchronization separation circuit (not shown), and 2 is an input terminal for input terminal 1. This vertical deflection circuit receives the supplied synchronization signal as an input and generates a sawtooth wave to be supplied to the vertical deflection coil 3 and the waveform shaping circuit 4. 5 is a waveform shaping circuit 4
A frequency divider that divides the pulse waveform by
6 is a differentiating circuit for differentiating the pulse waveform taken out from the frequency divider; 7 is a timer circuit that is activated by negative pulses of the differentiated waveform taken out from the differentiating circuit 6 and generates a pulse for a certain fixed time; 8 is a switching circuit that performs a channel switching operation based on the output pulse from the timer circuit 7; 9 is an antenna for receiving television radio waves; 10 is a tuner;
1 is a tuner output terminal.

First, the sawtooth wave taken out from the vertical deflection circuit 2 is supplied to the vertical deflection coil 3, and
The signal is supplied to the waveform shaping circuit 4 and becomes a shaped synchronization pulse, which is then supplied to the multiple stage frequency divider 5. This shaped synchronization pulse becomes a frequency-divided output waveform whose period is expanded by the frequency divider 5 according to the number of stages. _S1 is a switching cycle selection switch for taking out a divided output of a desired cycle time. The selected frequency-divided output is supplied to the differentiating circuit 6, which drives the timer circuit 7 with the negative pulse of the differentiating output to obtain an output pulse with a constant time width, which is used for switching to select the main channel and the sub-channel. By supplying the signal to the circuit 8 through the main/sub channel selection switch _S2 , the sub channel is automatically switched to the sub channel for a certain period of time, and then automatically returned to the main channel again. The switching period from the main channel to the sub-channel can be arbitrarily selected by providing multiple output terminals of the frequency divider circuit and switching using the selection switch _S1 . If a volume 17 for adjusting the time width of the output pulse is provided, it becomes possible to easily change the time width of the output pulse.

A more detailed explanation will be given below with reference to the specific circuit configuration example shown in FIG. 2 and the waveform example shown in FIG.

In FIG. 2, numerals 1 to 11 are the same as in FIG.

The sawtooth wave (FIG. 3a) taken out from the vertical deflection circuit 2 is supplied to the input of the waveform shaping circuit 4 and is applied to a kind of clip circuit consisting of resistors R ₁ , R ₂ and a diode d ₁ . Only the pulse wave above the part shown by the dotted line in a is extracted, resulting in the waveform shown in b, and the switching transistor
Added to TR ₁ 's base input. The switching transistor _TR1 is turned on between the collector and emitter where the base input pulse is input, and turned off when the input pulse disappears, repeating this operation to obtain an output waveform as shown in c.

Switching transistor of waveform shaping circuit 4
Output voltage waveform c extracted from the collector of TR ₁
is supplied to the input of the frequency divider 5, and phase inversion is performed by the NOT circuit _N1 , resulting in a waveform indicated by d.

Here, the main/sub channel selection switch _S2 is a switch for selecting only the main channel A, automatic switching of the main/sub channels B, or only the sub channel C by its switching operation together with the interlocked reset switch _S3 . However, FIG. 2 shows a state in which only the main channel is selected. In this state, the power supply voltage Vcc ₁ passes through the reset switch S ₃ and is applied to the NOT circuit N ₂ of the frequency divider 5, so that the first to fifth flip-flop circuits 12, 13, 14, 15, 1
The reset terminal R of 6 is in a state of zero voltage, and each flip-flop circuit is in an inoperative state. Next, if switches S ₂ and S ₃ are placed on the B side,
The NOT circuit _N2 input becomes zero, and voltage is applied to the reset terminal R from the moment the switch is turned to the B side as shown in Figure 3e.
2, 13, 14, 15, and 16 start operation.

Input pulses applied to the clock pulse input CP of the first flip-flop circuit 12 (FIG. 3d)
starts dividing the frequency from the moment the above-mentioned switches S ₂ and S ₃ are turned on to the B side, and the output terminal Q ₁ operates as shown in Fig. 3 f.
The frequency-divided waveform is shown in . The output waveform of the first flip-flop circuit 12 is further supplied to the input of the second flip-flop circuit 13 for further frequency division, and at its output terminal _Q2 , the waveform shown in FIG.
The frequency-divided waveform is shown in . Similarly, the frequency dividing operation is performed in the third, fourth, and fifth flip-flop circuits Q ₃ , Q ₄ , and Q ₅ in order.
The period of the output waveform is as shown in FIG. 3h and i, and is 2 ⁿ (n: the number of stages of the flip-flop circuit).

2nd to 5th flip-flop circuits 1
The respective outputs of channels 3, 14, 15, and 16 are supplied to the differentiating circuit 6 by selecting the period of the automatic switching time of an arbitrary main/sub channel by the switching period switch _S1 . The differential output waveform of the frequency-divided output waveform g is indicated by j, and the differential output waveform of the frequency-divided output waveform h is indicated by k. l is the differential output waveform j, m is the differential output waveform k
This is the output waveform of the timer circuit 7 that supplies and inputs
_T1 , and by selecting it, the switching period of the main and sub channels can be selected.

Now, assuming that the waveform supplied to the differentiating circuit 6 is the output waveform of the second flip-flop circuit 13 shown in FIG. 3g, the differentiated waveform is shown in FIG. Timer circuit 7
is composed of a monostable multivibrator, and its output waveform becomes a pulse waveform as shown in Figure 3, and is automatically switched to the sub-channel side for a time T ₂ , and automatically returns to the main channel again when the time T ₂ ends. The signal is supplied to a switching circuit 8 which performs such a switching operation. The time T ₂ is varied by Δt by the sub-channel operating time adjusting volume 17 in the timer circuit 7. When the input pulse shown in FIG. 3 is supplied to the switching circuit 8, it passes through the diodes d ₃ and d ₅ and the transistor
Voltage is supplied to the bases of TR ₃ and TR ₅ , transistors TR ₃ and TR ₅ are turned on, and the tuner ₁₀ is turned on through the sub-channel band switch S5.
A band selection control voltage is supplied to the channel selection voltage terminal 20 of the tuner 10, and a voltage taken out from the channel selection voltage terminal 20 of the tuner ₁₀ is supplied to the diode d6 and the sub-channel selection volume 18. In this case, a sub-channel band switch _S5 and a sub-channel selection volume are provided so that the band and channel can be set in advance to select an arbitrary sub-channel.

On the other hand, when _the input pulse shown in _FIG .
The transistors TR ₂ and TR ₄ are turned ON through d ₂ and d ₄ , and the band selection control voltage is supplied to the tuner 10 through the main channel band switch S _4-1 , and the control voltage is applied to the channel selection voltage terminal 20 of the tuner 10. is supplied by diode _d7 and main channel selection volume 19. In this case, the main channel band switch S _4-1 selects the main channel band, and the switches S _4-2 and S _4-3 linked thereto select the upper and lower limits of the frequency range in each main channel band. Determined by the resistors r ₁ , r ₂ , r ₃ , r ₄ , r ₅ , r ₆ connected to each switch,
The main channel selection volume 19 is provided for main channel selection.

Further, by switching the main/sub channel selection switch _S2 to the C side, a voltage is applied to the switching circuit, and the transistors _TR3 and _TR5 are turned on and held on the sub channel side.

As mentioned above, this idea expands the period of the stable synchronization pulse obtained by waveform shaping the vertical synchronization signal using a frequency divider circuit, and inputs the differential output of this frequency-divided output pulse to a timer circuit to generate an output pulse. Since the switching circuit for switching both the main and sub channels is driven by the switching circuit, the switching circuit for switching both the main and sub channels can be automatically switched in a time-division manner for viewing. This makes it possible to provide a more practical television receiver of this type that does not require a control pulse generator and can obtain a desired time division state by selectively switching the period itself.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main structure of a television receiver according to the invention, FIG. 2 is a wiring diagram showing a specific example of the same circuit, and FIG. 3 is a waveform diagram illustrating the operating state. 2... Vertical deflection circuit, 4... Waveform shaping circuit, 5
... Frequency divider, 6 ... Differentiation circuit, 7 ... Timer circuit, 8 ... Switching circuit, 10 ... Tuner, 17 ... Volume, S ₁ ... Switching period selection switch, S ₂ ... Main/sub Channel selection switch.

Claims (1)

[Claims for Utility Model Registration] (1) A waveform shaping circuit that shapes the waveform of a vertical synchronizing signal to obtain a synchronizing pulse; a frequency dividing circuit that expands the period of this synchronizing pulse by a multi-stage frequency divider; A switching period selection switch that takes out the frequency division output of a desired stage; A timer circuit that receives the differential output of the selected frequency division output as input and obtains an output pulse of a constant time width; A television receiver consisting of a switching circuit that switches between both sub channels. (2) The television receiver according to claim 1, wherein the timer circuit is provided with a volume for adjusting the time width of the output pulse.