JPS584490B2 - switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching device that can be used for purposes such as controlling the transmission of audio signals, and provides a device that protects the transistors used.

First, an outline of voice multiplex reception fatigue that can be used with the switching device of the present invention will be explained with reference to FIG.

Here, 1 is an input terminal to which a multiplexed audio signal demodulated by the audio demodulation circuit of the television receiver is supplied; 2 is a multiplex demodulation circuit that demodulates main and sub audio signals from the input signal; 3
4 is a broadcast mode detection circuit that identifies the presence or absence of a control signal from the input signal and detects the +7 transmission mode; 4 is a reception mode switching circuit that selects the desired reception mode using a switch or the like;
These circuits are similar to those of ordinary receiving devices.

The multiplex demodulation circuit 2 connects the broadcast mode detection circuit 3 to terminals 5 and 6.
demodulates the input signal according to the stereo detection signal and the different type detection signal output to the receiver, switches the output based on the instruction from the reception mode switching circuit 4, and outputs main and sub audio signals to the output terminals 7 and 8. do.

In the case of stereo broadcast reception, an L signal is output to the output terminal 7 and an R signal is output to the output terminal 8.

In the case of receiving a different type of broadcast, either the main audio signal is output to both output terminals 7 and 8 (main audio reception), or the output terminals 7,
8 (sub-audio reception), or the main audio signal is output to the output terminal 7 and the sub-audio signal is output to the output terminal 8 (main-sub simultaneous reception).

When receiving monaural broadcasting, the same audio signal is output to both output terminals 7 and 8.

Numerals 9 and 10 are output circuits that amplify and output the respective audio signals, and 11 and 12 are a pair of left and right speakers that produce audio.

The speakers 11 and 12 may be built into the television receiver.

Reference numeral 13 denotes a circuit for adding indirect sound, and this indirect sound adding circuit 13 includes an indirect sound signal that switches the indirect sound signal to be added at the time of stereo reception and at other times by the stereo detection output of the broadcast mode detection circuit 3. A sound switching circuit 14, a delay circuit 15 that delays the indirect sound signal by a predetermined time, a defeat circuit 16 that switches whether or not to add the indirect sound signal depending on the reception mode, and an inversion circuit that inverts the indirect sound signal. 17, and synthesis circuits 18 and 19 that add forward and reverse indirect sound signals to the two original audio signals, respectively.

During stereo reception, the output terminal 7 of the multiplex demodulation circuit 2 is connected to L.
The audio signal is outputted to the output terminal 8, and the R signal is outputted to the output terminal 8, respectively, and a stereo detection output is generated to the output terminal 5 of the broadcast mode detection circuit 3.

Therefore, at this time, the indirect sound switching circuit 14 switches to stereo based on its detection output, and creates the (LR)' signal as an indirect sound signal.

This (LR)' signal is then added to delay circuit 15 and delayed.

The optimum delay time during stereo reception is about 0.15 msec.

The delayed indirect sound signal (L-R)' signal is taken out via the defeat circuit 16, added to the L audio signal in the synthesis circuit 18 to form an L+(L-R)' signal, and is emitted from the speaker 11.

Further, the inverting circuit 17 inverts the polarity to create a (R-L)' signal, and the synthesizing circuit 19 adds it to the R audio signal and adds it to the R+(R-
L)' signal, which is generated from the speaker 12.

In this way, it is possible to cancel out the evening losstalk components from the speakers on the opposite side that reach the left and right ears of the listener from the two speakers IL12, and the two speakers 11 and 12 are connected to the television receiver. Even if they are provided at narrow intervals as in a cabinet, it is possible to improve the separation between L and R sounds at the position of the listener's ears, and it is possible to significantly expand the sound field of stereo sound.

Next, when only one of the main audio or sub audio is received during heterogeneous reception (during heterogeneous selective reception) and during non-multiplex reception, both the output terminals 7 and 8 of the multiplex demodulation circuit 2 output the same signal. An output signal (M signal) is generated, which is either a main audio signal, a secondary audio signal or a non-multiplexed single signal.

Therefore, in either case, a monaural reception state is achieved.

In this case, since there is no low-level stereo detection output from the output terminal 5 of the broadcast mode detection circuit 3, the M signal is directly output as the M' signal as an indirect sound signal.

On the other hand, the optimum delay time of the M' signal for expanding the sound field during monaural reception is approximately 4 mSec, which is longer than that during stereo reception.

The M' signal of the delayed indirect sound signal is taken out via the defeat circuit 16, and synthesized with the M signal in the synthesis circuit 18.
The signal is emitted from the speaker 11 as a +M'' signal.

On the other hand, the polarity is inverted in the inverting circuit 17, and then combined with the M signal in the combining circuit 19, and the signal is generated from the speaker 12 as the M-M'' signal.

In this way, the sound field is expanded even though it is monaural by synthesizing the M'' voice and -M'' voice, which are delayed and have opposite polarities to the M voice emitted from the speakers 11 and 12 during monaural reception. Can play pseudo-stereo audio.

Now, during stereo reception, heterogeneous selective reception, and non-multiplex reception as described above, in each case, the effective effect of sound field expansion is achieved by creating and synthesizing indirect sound signals. However, in the case of simultaneous main and sub-reception in which both the main audio and sub-audio are received during heterogeneous reception, for example, when the main audio is generated by speaker 11 and the sub-audio is generated by speaker 12. (Actually, one of them often uses earphones)
If indirect sounds are synthesized as described above, unnecessary crosstalk will occur between the main sound and the sub-sound, which are completely different.

Therefore, in such a case, the default circuit 16 is switched to block the indirect sound so as not to extract it.

Conventionally, a switching circuit as shown in FIG. 2 has been used for this circuit.

That is, a low-level foreign detection output is applied from the output terminal of the broadcast mode detection circuit 3 to the base of one transistor 20 of the transistors 20 and 21 connected in parallel via the diode 22, and the other transistor 2
When a low level instruction output indicating that simultaneous main and sub reception is being applied from the reception mode switching circuit 4 via the diode 23 to the base of 1, a high level output is output from the resistor 24 of the collector. is taken out, added to the base of the transistor 26 via the constant voltage diode 25, and made conductive, thereby grounding the transmission path of the indirect sound signal and cutting off its transmission.

In this way, crosstalk between the main audio and the sub audio can be eliminated during simultaneous main and sub audio reception, and each can be reproduced separately with good separation.

A switch 27 is connected to the emitters of the transistors 20 and 21.
A display light emitting diode 28 is connected through the resistor 29, and a resistor 29 is provided to apply a driving voltage thereto.

However, in such a conventional circuit, when the switch 27 is open, a high-level switching input is applied to the base of one transistor 20, making it conductive, and the base of the other transistor 21 becomes conductive. When a low-level switching input is applied and the input is cut off, the voltage generated in the emitter resistor 29 is applied as a reverse voltage between the base and emitter of the transistor 21 that is cut off. , there was a risk that the transistor 21, which was cut off, would be damaged.

Furthermore, if the resistor 24 is increased to prevent this, a sufficient voltage cannot be applied to the constant voltage diode 25, and if the resistor 29 is decreased, a sufficient voltage for driving the light emitting diode 28 cannot be obtained.

Therefore, the present invention provides a switching device that eliminates such drawbacks, and as shown in FIG.
1, the collector is connected to the power supply via two series-connected resistors 30 and 31, and the connection point of the series resistors 30 and 31 is connected to the base of the control transistor 26 via the constant voltage diode 25. A control voltage is applied.

In this way, even when only one of the transistors 20 and 21 is conductive and the other is cut off, the current will flow through the series resistors 30 and 31, and this resistor 30 will be Same as the conventional resistor 24, resistor 3
By newly adding 1, it is possible to reduce the current value and reduce the voltage generated across the emitter resistor 29, thereby preventing damage to the transistor that is shutting off.

Furthermore, since current can be passed through the constant voltage diode 25 only through the resistor 30, a sufficient voltage can be applied.

Although the above description has been made regarding the case of an audio multiplex receiver, it goes without saying that the present invention can be used as a switching means for various other circuits.

As detailed above, the present invention is useful in that it is possible to obtain sufficient output through the constant voltage diode connected to the collector side of two or more transistors connected to a common collector and common emitter without damaging them. It is possible to obtain a suitable device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an audio multiplex receiver that can use the switching device of the present invention, FIG. 2 is a circuit diagram of a conventional switching device, and FIG. 3 is a circuit diagram of a switching device according to an embodiment of the present invention. It is a diagram. 20, 21, 26...transistor, 25...
... Constant voltage diode, 29, 30, 31...
··resistance.

Claims (1)

[Claims] 1 Connect multiple transistors with switching inputs to their bases, connect the common collector and common emitter, ground the common emitter through a resistor, and connect the common collector to the power supply through two resistors connected in series. A switching device characterized in that a control voltage is applied to the base of a transistor for controlling signal transmission through a constant voltage diode from the midpoint of a series resistor connected to the transistor.