JPS5842650B2 - Denshi Kirikae Cairo - Google Patents

Description

Detailed Description of the Invention The present application relates to a switching circuit that electronically switches output, and in particular detects voltage induced in the human body, operates a switch circuit, and controls the channel selection voltage with the switch circuit to select a channel. This invention relates to an electronic channel selection device.

FIG. 1 shows an example of a conventional electronic channel selection device.

In other words, the human body contact terminal a corresponding to the selectable channel
1 to an amplify the human body induced voltage to a predetermined level with corresponding n amplifiers b1 to bn, and store which one of the human body contact terminals a1 to an is designated (contacted) in the memory circuit 1. The designated channel is stored even if the human body is removed from the human body contact terminals a1 to an.

The voltage distribution circuit 2 is controlled by the contents stored in the memory circuit 1, and its output voltage is applied to the electronic tuner 3 to receive a designated channel.

Now, if a human body comes into contact with the human body contact terminals a1 to an, the voltage induced in the human body, that is, the commercial frequency of 50 Hz or 6
A voltage of 0 Hz is applied to any of the amplifiers b1 to bn,
Considering a semiconductor integrated circuit (IC) in which the amplifiers b1 to bn and part of the voltage distribution circuit 2 are integrated into the same pellet, these amplifiers b1 to bn and the voltage distribution circuit 2 are Often formed by a common ground line and taken out from one external ground lead.

Therefore, the input signals amplified by the amplifiers b1 to bn are outputted as a weight on the output of the voltage distribution circuit, which should originally output a constant DC voltage, due to the resistance component of the ground line of the semiconductor integrated circuit element.

The output capacitance of the variable capacitance element in the electronic tuner 3, which is determined by the output voltage of this voltage distribution circuit, fluctuates at a frequency of 50 Hz or 60 Hz included in the human input signal, and the effect thereof may be clearly visible on the received image.

In addition, if the device has a function that temporarily interrupts the AFT circuit while selecting a channel, if you continue to touch the human body contact terminal, the AF
There are cases where the T circuit continues to be interrupted, which is inconvenient.

The present application provides a switch circuit that improves these points, and the amplifier operates only at the moment when the human body induced voltage is applied to one of the amplifiers, and the memory circuit determines which human body contact terminal the human body contacts. After memorizing the information, the amplifier stops operating.

Therefore, after the channel is switched by contacting the human body contact terminal, the input signal is not amplified by the amplifier, so even if there is a resistance component in the ground line, the input signal component applied to the voltage distribution circuit is extremely small.

Therefore, the commercial frequency component contained in the input signal generated at the output of the voltage distribution circuit is extremely small, and the output capacitance of the variable capacitance element in the electronic tuner is kept constant, so that no fluctuation appears in the received image.

Also, since the AFT circuit is only momentarily cut off, the AF
The non-operating period of the T circuit is extremely short.

As described above, according to the present invention, all the conventional inconveniences can be solved.

FIG. 2 shows the configuration of the present application.

FIG. 2 is drawn focusing on one channel.

The human body induced voltage applied to the human body contact terminal a is amplified by the amplifier and sets the memory circuit (or holding circuit).

In the electronic channel selection device, if a human body induced voltage is applied to another human body contact terminal a, this memory content will be erased and replaced with the memory content corresponding to that terminal a, or the holding circuit 1 will be This is set so that one channel always performs the storage operation.

The voltage distribution circuit 2 is controlled according to the contents stored in the memory circuit 1, and a predetermined tuning voltage is applied to the electronic tuner 3.

On the other hand, the output signal of the memory circuit 1 operates the switch 4 which grounds the input circuit of the amplifier, thereby preventing the input signal from being applied to the amplifier at the same time as the memory circuit completes its predetermined operation.

Therefore, according to the present application, the above-mentioned inconvenience does not occur.

Note that the above-mentioned switch does not necessarily need to be provided at the input of the amplifier; for example, it may be used to cut off the power supply circuit of a given amplifier, or it may be provided before the output stage in the amplifier circuit to achieve the same effect. can be expected.

FIG. 3 shows an embodiment of the present application.

A is a human body contact terminal connected to the base of transistor 110, and this transistor and transistors 12 and 13 are connected to each other.
, 14 and a resistor 15 constitute an amplifier. Also, in the memory circuit 1, transistors 16, 18, 20, resistors 17, 19, 23 and a Zener diode 26 constitute a holding circuit. The holding circuit A operation □ state is detected by a comparison amplifier consisting of a transistor 27 and a resistor 21, and its output is taken out by a transistor 34.

When human body induced voltage is applied to all terminals a, the output amplified by the amplifier is applied to the base of the transistor 160 that constitutes the input circuit of the holding circuit, so that the base voltage becomes higher than the voltage of the Zener diode 26. , all the holding circuits of the n circuits shown in FIG.
Even if the input is removed, the set state is maintained by the action of transistors 18 and 20.

At this time, the emitter voltage of the transistor 27 becomes higher than the reference voltage 28, the transistor 27 becomes conductive, and the current defined by the emitter resistor 21 flows through the transistors 34 and 2.
5 are simultaneously driven to control a voltage distribution circuit (omitted) with the collector of the transistor 34, and with the transistor 25,
Input terminal a is grounded to prevent input from being applied to the amplifier.

Therefore, the operation of the holding circuit is such that the transistor 27 is inserted as one threshold circuit, and the transistors 18, 20
If the bias conditions are set so that the transistor 27 operates when the holding circuit exceeds the limit that allows holding operation, the operation of the holding circuit will surely shift to the holding state at the moment an input is applied. Once completed, the amplifying circuit and holding circuit 1 will no longer be affected by the input.

On the other hand, all other holding circuits 1 are in the reset state, so
The transistor 25 is in a cut-off state, and is in a state where it can shift to a holding operation in response to an input signal applied thereafter.

As described above, according to the present invention, all the drawbacks of the prior art described above can be eliminated with a simple configuration, and the effect is very large.

Further, the present application can be applied to improve the noise resistance of electronic switch circuits.

FIG. 4a shows another embodiment of the present invention, in which the transistor 2
5, 27, and the resistor 21 are different from those in Fig. 3.
When the memory circuit 1 is activated, the power to the amplifier circuit is cut off, the transistors 40 and 51 are in saturated operation, and the base bias of the transistor 51 is connected to the power supply line by the resistors 45 and 46. The transistor 44 is obtained from the connection point of the resistors 49 and 50 connected in series between the emitter connection point of the resistor '3'9 and the 'F' transistor 51 and the ground line. The operation is the same as in the case described above, although there is a configuration upper limit in that it is driven by a signal given by the input signal.

Figure 4 is a diagram in which the switch circuit part of the transistor 51 in a is replaced with a switch circuit composed of a transistor 62, and the common parts with a are omitted, and in order to clarify the correspondence, the common parts are are given the same symbol.

In this case, the operating state of the transistor 62 is opposite to that in case a, so the connection of the transistor 35 is different, and when the transistors 38 and 40 are in the holding operation, the transistor 6
2 is cut off, transistor 35 is also cut off, and the operation of transistors 31 and 330 is stopped.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional electronic channel selection device. FIG. 2 is a block diagram showing the principle of the present application. FIG. 3 and FIGS. 4a and 4b are circuit diagrams illustrating an embodiment of the present application. 11.12,13,14,16,1B, 20°25.2
7, 31, 32, 33, 34, 35° 36.3B, 40
, 44, 47, 51, 62...--transistor,
15,17,19,21.22゜23.37,39,4
1,42,43,45°46.4B,49,50,6L
63...Resistor, 26...Zener diode, 28, 64...Bias voltage source.

Claims (1)

[Claims] 1. An input terminal to which an input signal is applied by human body contact, an amplifier that amplifies the input signal applied to the input terminal, a memory circuit that is maintained in a predetermined state by supplying the amplified output of the amplifier, and the memory circuit. An electronic switching circuit comprising: a circuit for detecting that the amplifier is maintained in the predetermined state; and a switch means for preventing the input signal from being input to the amplifier by the output of the circuit.