JPS59821Y2 - Electronic channel selection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic tuning device that performs tuning by stepping pulses for a varactor tuner using a variable capacitance diode as a tuning element in a television receiver.

Conventionally, this type of electronic tuning device that uses a sequential tuning method has a memory function, and has a stepwise tuning circuit that supplies a tuning voltage to a varactor diode, and a stepwise tuning circuit for incrementing the channel. The pulse generation circuit, which receives the pulses, is composed of a counter drive circuit that outputs a counter pulse to the step selection circuit, a switch for driving the pulse generation circuit, etc., and the channel advances at a constant speed. In order to obtain channel increments of one step faster than the constant speed of It had some drawbacks.

The present invention improves this and provides a circuit that can perform automatic stepping of two functional channels at fixed time intervals and step stepping that can be stepped even faster than this by distinguishing between one switch operation. The present invention will be explained with reference to an embodiment shown in the figure below. 1 is a pulse generation circuit;
Resistance a connected to the power source consisting of DC voltage source element B, resistance a
A capacitor b is connected between the capacitor b and the ground, a resistor C1 is connected to its connection point j, a PNP transistor d is connected to the emitter side of the resistor C, an NPN transistor e is connected inversely between the collector and base of the same transistor, A so-called complementary type astable multivibrator is constituted by a voltage dividing resistor f9g provided between the power supply and ground on the output side, and the output side is connected to a counter drive circuit.

In the above configuration, a switching switch 2 is provided between the emitter of the NPN transistor e and the ground, and a resistor is connected between the emitter of the transistor e and the power source with a connection point k, and a resistor is connected between the emitter of the transistor e and the power source at the connection point k. The anode side of the diode i is connected to k, and the cathode side is connected to the connection point j.

The operation of the above-mentioned configuration will be explained below.As shown in Figure 2, the output pulse of the above-mentioned astable multivibrator has a pulse width of several m5ec, and the time until the next pulse is output is several hundred m5ec. It is assumed that the system is operating at .

Now, if you operate and keep switch 2 in the closed state, the free running time of the Astable multivibrator (for example, about several hundred m5ec, which is enough to instantly check the switching screen one after another) will cause the channel walkway to move. will be carried out.

In this state, capacitor b is charged with the time constant of resistor a.

When the switch 2 is opened, the capacitor b is charged through the diode i due to the resistance.

Now, if the value of the above-mentioned resistance is made smaller than the value of the resistor a, as shown in Fig. 3, compared to the time T1 when the switch 2 is closed, the resistance will be low during the period T2 when the switch 2 is opened. A constant voltage V due to the action of diode i and diode i.

The time relationship is that T2 can be shortened by the period of T3 from T1, and the capacitor b has a voltage of ■.

When the battery is charged to the point where switch 2 is closed, a pulse is generated.

Therefore, when the operation of switch 2 is repeated faster than the free running time of the astable multivibrator, by making T2 smaller than the period during which switch 2 is open, a pulse synchronized with the repetition of switch 2 is output. .

As explained above, in this application, charging of the normal capacitor B is performed through the resistor A by simply pressing and holding the switch, and this allows the channel selection to advance to the extent that it can be instantly confirmed on the screen when selecting a channel. In particular, in connection with the switch 2 connected between the emitter of the transistor e of the complementary transistors d and e and the ground, the diode i quickly charges the capacitor b, so that the desired station can be turned on and off without checking the screen when selecting a station. Even though high-speed channel selection is possible by repeatedly operating the same switch 2, the circuit can be configured extremely simply.

That is, by keeping the switch 2 closed, the channels are automatically advanced using the free running time of the rear stable multivibrator, and the repeated operation of the switch 2 is performed faster than the free running time of the rear stable multivibrator. Even if this occurs, channel increments can be performed in sufficient synchronization with the follow-up.

In this way, a circuit can be easily constructed using a DC voltage source that allows compatible operation of a constant speed and a channel step faster than the constant speed depending on the usage situation of one switch.

Furthermore, when selecting a channel by repeatedly operating a switch, the function of the diode allows one channel to be incremented quickly with one operation, so even if the switch operation is quickly repeated until the desired channel is reached, the channel increments quickly and reliably. As a result, operability can be further improved.

Note that the switch 2 may be a mechanical switch or an electronic switch.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of essential parts of an electronic channel selection device showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the same, and FIG. 3 is an operation curve diagram. In the figure, 1 is a pulse generation circuit, 2 is a switch, and a. C, f, g, and h are resistors, i is a diode, b is a capacitor, and d and e are transistors.

Claims (1)

[Scope of utility model registration request] A PNP type transistor and an NPN type transistor are
The base of the NP transistor and the collector of the NPN transistor are connected, and the collector of the PNP transistor and the base of the NPN transistor are connected to form a complementary circuit connection, and the emitter of the PNP transistor in the same circuit and the power supply terminal are connected. B, a first resistor and a second resistor are connected in series, a capacitor is connected between the connection point of the two resistors and the ground, and a fourth resistor is connected between the power supply and the ground. Connect the fifth resistor in series, and
The connecting point of the two voltage dividing resistors is connected to the base of the PNP transistor and the collector of the NPN transistor to form a stepping pulse output terminal, and a switch is provided between the emitter of the NPN transistor and ground. A third resistor having a smaller resistance value than the first resistor is connected between the emitter and the power source, and the anode side of a diode is connected to the emitter side, and the cathode side of the diode is connected to the second resistor. An electronic channel selection device comprising a pulse generating circuit connected to the emitter side of the PNP transistor through a pulse generating circuit.