JPS6115671Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a monaural, stereo signal that is played back as a stereo signal when listening on the headphone jack by attaching a plug to the headphone jack, and as a monaural signal when listening on the speaker. Regarding automatic switching circuits.

Recently, even small tape recorders are becoming stereo. In order to make such a small stereo tape recorder convenient to carry, it is important to make it compact and lightweight. It is being regenerated.

However, stereo playback is not always necessary and monaural playback may be sufficient. In such cases, it is convenient to listen to the playback through speakers.

In view of the above points, the present invention is an automatic monaural stereo switching system that allows stereo playback on the headphone when the plug is inserted into the headphone jack, and monaural playback on the speakers when the plug is removed from the headphone jack. Regarding circuits.

The present invention will be explained below with reference to the drawings. In Figure 1, 1 and 2 are first and second amplifier circuits, 3 is a headphone jack, and output terminals 6 and 7 are connected to resistors 4 and 5, which can be opened and closed by attaching and removing plugs (not shown). It has jack switches 8 and 9.
Reference numeral 10 denotes a speaker whose both ends are connected to the first amplifier circuit 1 and the second amplifier circuit 2 via the jack switch 8, and 11 is a transistor controlled by the jack switch 9.

Next, the operation of the monaural stereo automatic switching circuit of the present invention will be explained.

(1) First, a case will be explained in which a plug is inserted into the headphone jack 3 and stereo playback is performed using the headphone.

When a plug (not shown) is inserted into the headphone jack 3, the contact pieces 8a, 8b of the jack switch 8 and the contact piece 9 of the jack switch 9 are inserted.
a, 9c are closed. Therefore, the L signal from the terminal A is amplified by the first amplifier circuit 1 and then applied to the left side of the headphone via the resistor 4.
Also, the R signal from terminal B passes through the contacts 9a and 9c of the jack switch 9, enters the second amplifier circuit 2, is amplified, and is supplied to the right side of the headphone via the resistor 5, so that stereo reproduction is performed at the headphone. It can be done. At this time, a reverse bias voltage from the resistor 12 is applied to the base of the transistor 11 via the contacts 8a and 8b of the jack switch 8, turning off the transistor 11 so that it has no effect.

(2) Next, a case will be explained in which the plug is disconnected from the headphone jack 3 and monaural reproduction is performed from the speaker 10.

In this case, the contact piece 8a of the jack switch 8,
8c and jack switch 9 contact pieces 9a, 9b
is closed.

In this state, the L signal from terminal A is applied to the first amplifier circuit 1, while the R signal from terminal B is also applied to the input side of the first amplifier circuit 1 through contacts 9a and 9b of the jack switch 9. , said L
It is mixed with the signal and amplified by the input amplifier circuit 1.

The amplified LR mixed signal is applied to one end of the speaker 10 via contacts 8a and 8b of the jack switch 3. The amplified LR mixed signal is also applied to the negative terminal of the second amplifier circuit 2 through the resistor 13. At this time, since no reverse bias voltage is applied to the transistor 11, it is turned on, so that the second amplifier circuit 2 obtains a signal on its output side with the same amplitude and opposite phase as the output of the first amplifier circuit 1, so that the so-called BTL perform an action. Therefore, this is equivalent to adding an LR mixed signal with twice the amplitude to the speaker 10, and drives the speaker 10 with a sufficiently large signal.

FIG. 2 is a circuit diagram showing another embodiment of the monaural stereo automatic switching circuit of the present invention, which is the same as the above except that a phase inverting transistor 14 is provided on the input side and the circuit connection is partially changed. .

The operation shown in FIG. 2 will be explained below separately for stereo playback and monaural playback.

(1) Stereo playback.

When the plug is inserted into the headphone jack 3 as described above, the jack switches 8 and 9 are switched to the state shown, and stereo reproduction is performed. That is, the L signal from the terminal A is taken out from the emitter of the transistor 14 in the same phase, is amplified by the first amplifier circuit 1, and then passes through the resistor 4 and enters the left side of the headphone. The R signal from terminal B passes through contacts 8a and 8b of jack switch 8, enters second amplifier circuit 2, is amplified, and is applied to the right side of the headphone via resistor 5, so that stereo reproduction is performed at the headphone. At this time, the reverse bias voltage of the resistor 15 is applied to the base of the transistor 11 via the contacts 9a and 9c of the jack switch 9, so the transistor 11 is turned off.
The signal from the collector of transistor 14 is the second
This prevents it from being applied to the amplifier circuit 2. Furthermore, since one end of the speaker 10 is not grounded, no signal is applied to the speaker 10 at this time.

(2) Monaural playback.

Next, a case will be described in which the plug is pulled out from the headphone jack and monaural reproduction is performed through the speaker 10.

At this time, the jack switches 8 and 9 are switched to the opposite side to that shown in the figure, and since no reverse bias is applied to the base of the transistor 11, the transistor 11 is turned on. Also, the R signal from the terminal B passes through the contacts 8a and 8c of the jack switch 8 and is mixed with the L signal from the terminal A and applied to the base of the transistor 14. Then, signals of the same amplitude but opposite phase are obtained from the emitter and collector of the transistor 14.

The signal extracted from the emitter is amplified by a first amplifier circuit 1 and then supplied to one end of a speaker 10. On the other hand, the signal extracted from the collector is applied to the second amplifier circuit 2 via the transistor 11, and the amplified signal is applied to the jack switch 9.
It is supplied to the other end of the speaker 10 through the contact pieces 9a and 9b.

Since signals with the same amplitude and opposite phase are obtained on the output sides of the first and second amplifier circuits 1 and 2 and BTL operation is performed, twice the voltage is applied to both ends of the speaker 10. Even if the outputs of the second amplifier circuits 1 and 2 are small, the speaker 10 can be sufficiently driven.

As described above, the monaural stereo automatic switching circuit of the present invention selectively connects speakers to the output side of each amplifier circuit using a jack switch that is opened and closed by connecting and disconnecting a headphone jack and a plug. Since the transistor connected to the input side of the headphone jack is controlled, when a plug is inserted into the headphone jack, the L and R signals are amplified by each amplifier circuit, driving the left and right headphones, and stereo reproduction is possible. Also, when the plug is removed from the headphone jack, the L and R mixed signals are applied to the inputs of each amplifier circuit with the same amplitude and opposite phase.
Since amplified signals with the same amplitude and opposite phase are obtained on the output side, twice the signal voltage is applied to the speaker whose both ends are connected to the output of the amplification circuit. Therefore, even if the amplification degree of each amplifier circuit is small, the speaker can be sufficiently driven.

[Brief explanation of the drawing]

1 and 2 are monaural and stereo automatic switching circuit diagrams of the present invention. 1...First amplifier circuit, 2...Second amplifier circuit, 3
...headphone jack, 8,9...jack switch, 10...speaker, 11...transistor.

Claims (1)

[Scope of utility model registration request] first and second amplification circuits for amplifying the signal;
a jack switch that is opened and closed by connecting and disconnecting the headphone jack and the plug;
It consists of a speaker connected to an amplifier circuit via the jack switch, and a transistor controlled by the jack switch, and when the headphone jack and the plug are coupled, the L signal and the R signal are transmitted to the first and second channels, respectively. The L and R signals amplified by the second amplifier circuit and the first and second amplifier circuits are applied to the headphone, and when the plug is removed from the headphone jack, the L and R signals are amplified by the jack switch. The mixed L signal and R signal are divided into two, one of the signals is directly applied to the first amplifier circuit, and the other divided signal is phase-inverted and applied to the second amplifier circuit via the transistor. , the first amplifier circuit and the second
Extract output signals with the same amplitude and opposite phase from the amplifier circuit,
A monaural stereo automatic switching circuit characterized in that these output signals are applied to both ends of a speaker.