JPH04178944A - Remote control circuit for stereophonic headphone - Google Patents

Abstract

PURPOSE:To switch an arbitrary mode by operating a changeover switch provided in a remote controller, varying a remote resistance value, and outputting a mode switching signal in desired combination from a plurality of comparators provided at a stereophonic body side. CONSTITUTION:One side of a remote controller 12 is connected directly to a reference voltage output line of an audio signal line, and used as a reference voltage of a remote control circuit. On the other hand, a plurality of comparators 44, 45 are provided at a stereophonic body to compare remote terminal outputs with different remote reference voltages. The output of both the comparators 44, 45 are supplied to a mode selector 36, which outputs a desired mode output. Here, a comparator output responsive to the combination of the switches can be obtained by turning ON, OFF of changeover switches 41, 42. Thus, many modes can be selected by less switches.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a remote control circuit for a headphone stereo, and in particular, a remote control circuit for a headphone stereo, in particular, a remote control circuit that allows mode switching of the stereo main body to be performed with a simple circuit configuration using a plurality of changeover switches provided on the remote controller. Concerning an improved remote control circuit that can be used.

[Prior Art] In a portable cassette stereo or a headphone stereo with a built-in CD or VTR device, it is preferable to switch the modes of the stereo main body using a remote controller connected to a headphone jack separately from the main body. be.

For such mode switching, modes such as on/off switching, rewinding, etc. of the cassette tape are selected, and a user wearing headphones can easily perform mode switching operations using a remote controller at hand.

Generally, a remote controller is inserted between a phone jack and headphones, and some of the audio signal lines and control lines are shared. FIG. 4 shows a typical headphone stereo in which a remote controller 12 and headphones 13 are connected to a stereo main body 10 made of a cassette tape via a headphone jack 11.

FIG. 5 shows a conventional remote control circuit, and only the output stage of the stereo main body side is shown, including a common power amplifier 20, a right power amplifier 21, and a left power amplifier 22.

The common power amplifier 20 provides a virtual reference voltage for the audio signal, has a non-inverting input terminal supplied with a bias voltage from a bias power supply 23, and has an inverting input terminal and an output terminal connected through a feedback resistor 24. Further, a constant current source 25 is connected to the inverting input terminal.

On the other hand, a constant current source 26 is connected to the inverting input terminal of the right power amplifier 21, a feedback resistor 27 is connected between the inverting input terminal and the output terminal, and the bias voltage is supplied via a resistor 28. ing.

The right audio signal R1n is supplied to the non-inverting input terminal of the right power amplifier 2.

Similarly, the left power amplifier 22 has a similar configuration, and includes a constant current source 29, a feedback resistor 30, a bias resistor 31,
A left audio signal Lin is supplied.

Therefore, according to such a power output stage, the output of the common power amplifier 20 can be used as a virtual reference voltage on the headphone side, and audio playback signals according to the input voltages RIn and LIn can be supplied to the headphones 13R and 143L. .

Since such a power output stage does not require a capacitor on the output side, it has the advantage that the device can be miniaturized and the circuit configuration can be simplified in small portable equipment.

The outputs of the power amplifiers 20, 21, and 22 are respectively connected to terminals C and R of the headphone jack 11.

When the headphone jack is inserted, a predetermined audio signal is supplied to the right headphone 13R and the left headphone 13L.

In the above manner, from the stereo main body 10 to the headphones 13
In order to supply a desired mode switching signal to the stereo main body 10 by the remote controller 12 described above, conventionally, a changeover switch 3 provided on the remote controller 12 is used.
2 is used.

That is, one end of the changeover switch 32 is connected to the terminal C of the headphone jack 11, and the other end is connected to the ground terminal GND of the headphone jack 11.

Therefore, according to this conventional device, the remote control signal can be superimposed on the common signal line and the mode switching signal can be supplied to the stereo main body 10.

The stereo main body side has a comparator 33 for receiving a switching signal, and the switching signal of the changeover switch 32 is supplied to a non-inverting input terminal of the comparator 33.

A power supply voltage is further supplied to the non-inverting input terminal of the comparator 33 via a resistor 35.

When the selector switch 32 in FIG. 5 is in the OFF state,
The non-inverting input terminal of the comparator 33 is supplied with substantially the power supply voltage, and as a result, the comparator 33 outputs the rHJ signal. When the selector switch 32 is turned on, the comparator 33
The non-inverting input terminal of the comparator 33 becomes the ground potential, and as a result, the output of the comparator 33 is inverted to rLJ.

Therefore, if the output of the comparator 33 is determined by the mode selector 36 and a predetermined mode signal is output, the user can manually control the stereo main body 10 by operating the changeover switch 32 provided on the remote controller 12. Mode switching can be performed.

[Problems to be Solved by the Invention] However, although such conventional devices have the advantage of being able to share the signal line and the control line as described above, on the other hand, the connection between the audio signal and the control signal is It is necessary to ensure separation.

For this reason, as is clear from FIG. 5, in the conventional circuit, the output terminal of the common power amplifier 2o and the comparator 33
Similarly, on the headphone side of the headphone jack 11, the selector switch 32 and the headphone 13 are connected to each other.
A capacitor 38 for cutting DC components is provided between the two.

Therefore, the conventional device has the advantage of being able to transmit audio signals and control signals using the shared signal line, while limiting the number of terminals of the headphone jack 11 to four. Although the output stage of the stereo main body was made into an output capacitor-less circuit, there was a drawback in that capacitors 37 and 38 had to be provided as shown in FIG.

In particular, as each conventional capacitor 37.38,
When the load impedance of headphones is 16 to 32 Ω, a capacitor with a relatively large capacity of 200 to 500 μF must be used, which causes the problem of increasing the size of the device and further increasing the cost of small portable devices. Ta.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide an improved remote control circuit that does not require an increase in the number of terminals of a headphone jack compared to the conventional one, and does not require a large capacitance capacitor.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a remote resistor connected to a remote controller between a reference voltage output terminal of a common power amplifier and a remote terminal of a headphone jack; The stereo main body is equipped with a plurality of comparators, which are connected to a plurality of selector switches that change the remote resistance value by switching combinations of remote resistances, and the first input terminal of each comparator is connected to the bias of the common power amplifier. Different remote reference voltages are supplied from a power supply through a voltage dividing resistor, the bias power supply is connected to a remote terminal of a headphone jack through a remote bias resistor, and a second input terminal of each comparator is connected to a remote terminal of the headphone jack. are commonly connected, the remote resistance value is changed by operating the changeover switch, and the comparator output is switched by changing the remote terminal voltage.

[Operation] Therefore, according to the present invention, by simply changing the remote resistance value by operating the changeover switch provided on the remote controller, a desired combination of modes can be selected from the plurality of comparators provided on the stereo main body. It becomes possible to output a switching signal.

According to the present invention, each comparator is supplied with a different remote reference voltage, and with respect to this base T$ main voltage,
The remote terminal voltage determined by the remote resistance value set by operating the changeover switch is compared, and arbitrary mode switching becomes possible.

According to the present invention, by arbitrarily setting the number of comparators and changeover switches, it is possible to switch a desired number of modes.

According to the present invention, since the remote control circuit shares the reference voltage output line of the audio signal line only as a voltage reference, it is characterized in that there is no need for a capacitor for cutting off DC components as in the prior art.

Further, since the reference voltage and the remote reference voltage are supplied from a common bias power supply, there is an advantage that the comparison action is not adversely affected even if the bias power supply voltage fluctuates.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a preferred embodiment of the remote control circuit according to the present invention, and the same members as in FIG.

In this embodiment as well, an output capacitor-less circuit is used in the output stage of the stereo main body, and the device is miniaturized by eliminating the capacitor.

The remote controller 12 of this embodiment includes two changeover switches 41.42, and these two switches 41.4
2 allows three types of mode switching, ie, power off, playback, and rewind operations, to be performed on the hand side.

The remote controller 12 has a common power amplifier 2.
0 reference voltage output terminal C and a remote terminal RE provided in the headphone jack 11 in this embodiment, the remote resistor 43 includes a remote resistor 43 whose both ends are connected to a changeover switch. Connected to 41.42.

In the embodiment, one remote resistor 43 is provided, but
In the present invention, it is preferable to arrange a plurality of remote resistors in series, and furthermore, by connecting each resistor to the reference voltage output terminal C via a plurality of changeover switches, it is possible to switch any number of modes. do.

As is clear from FIG. 1, according to the present invention, the resistance value between the reference voltage output terminal C and the remote terminal RE can be changed by controlling the plurality of changeover switches 41 and 42 on and off. .

In the embodiment, when a plurality of such remote resistors 43 are provided, the resistance connection may be in series, parallel, or a series-parallel combination, and in addition, the connection of each changeover switch is not limited to the parallel connection as in the embodiment. Any connection relationship can be used.

In any case, according to the present invention, one lead wire of the remote controller 12 is directly connected to the reference voltage output line of the audio signal line and used as the reference voltage of the remote control circuit, which is not necessary in the conventional circuit. The existing DC voltage cutoff capacitor can be removed.

On the other hand, the stereo main body is provided with a plurality of comparators, 44.45 in the embodiment, and these comparators 44.45
A remote terminal RE is connected to the inverting input terminal of.

Further, different remote reference voltages are supplied to the non-inverting input terminals of each comparator 44, 45 from the bias power supply 23 of the common power amplifier 20 via voltage dividing resistors.

Therefore, each comparator 44,45 will compare the remote terminal output at a different remote reference voltage.

Further, the bias power supply 23 is connected to a remote bias resistor 4.
A desired remote terminal voltage can be applied to the common inverting input terminal of both comparators 44, 45 by switching on/off the selector switch 41, 42.

The outputs of both comparators 44, 45 are fed to a mode selector 36, which can output a desired mode output, ie, a power off, playback or rewind control signal.

As described above, according to the present invention, the reference voltages of the plurality of comparators provided on the stereo main body are obtained by the combination of the bias power supply 23 and the voltage dividing resistors 46, 47° 48, and the remote terminal RE A desired switching signal can be supplied to the mode selector 36 according to the signal level input from the mode selector 36.

The mode switching action of this embodiment will be explained below.

FIG. 1 shows a power off mode in which both switches 41, 42 are in the off state. In this embodiment, the bias voltage of the bias power supply 23 is assumed to be 0.75V, taking as an example a stereo cassette tape recorder with a 1°5Vffi battery specification. By this bias power supply 23, the common power amplifier 20
A virtual reference voltage of, for example, 0.65V is output to terminal C from.

In the present invention, the remote terminal voltage selected by the changeover switch is compared with the remote reference voltage using the bias voltage on the stereo main body side and the virtual reference voltage on the headphone side. Therefore, since the audio signal line is used as a reference voltage line for the control circuit both on the stereo main body and on the headphone side, it is possible to eliminate large capacitance capacitors.

Due to the voltage dividing resistors 46, 47, and 48, in the state shown in FIG.
2V and 0.67V.

In FIG. 1, the voltage at the remote terminal RE is set to 0.75 volts, which is the same as the voltage at the bias power supply 23, since both cut-off switches 41 and 42 are in the off state.

Therefore, this remote terminal voltage is applied to either comparator 44.
45, and the outputs of both comparators 44 and 45 are both rLJ.

As a result, the mode selector 36 can instruct the power off mode in response to this input signal.

Next, FIG. 2 shows a reproduction mode, at which time the changeover switch 41 is turned on.

Therefore, at this time, from the remote terminal RE to the switch 41
The circuit is closed through the reference voltage terminal C, so that the voltage at the remote terminal RE drops to 0.65V.

At this time, since the reference voltages of the comparators 44 and 45 remain unchanged, the outputs of both the comparators 44 and 45 are both inverted to rHJ, as is clear from the figure.

Therefore, the mode selector 36 can issue a reproduction instruction at this time.

On the other hand, FIG. 3 shows a fast return mode in which the selector switch 42 is turned on.

At this time, the remote terminal RE is connected to the reference voltage output terminal C via the remote resistor 43 and switch 42.

Therefore, in this state, due to the presence of the remote resistor 43, the remote terminal voltage increases by the amount of the remote resistor 43 compared to the state shown in FIG. 2, and in this embodiment becomes 0.7 .

As a result, the comparator 44 is "H" and the comparator 45 is r
By outputting the LJ signal, the mode selector 36 can command the fast rewind mode.

As described above, according to the present invention, it is possible to obtain a comparator output according to the combination of these switches by turning on/off the changeover switches, and it is possible to select a large number of modes with a small number of switches.

Further, according to the present invention, since the common line for the audio signal and the control signal is a virtual reference voltage line, there is an advantage that the large capacitance capacitor that is conventionally required is completely unnecessary.

Further, according to the present invention, the virtual reference voltage corresponds to the bias power supply, and even if there is a fluctuation in the bias power supply, the remote reference voltage of the comparator in the present invention and the virtual reference voltage are linked. This has the advantage of not being affected by voltage fluctuations.

[Effects of the Invention] As explained above, according to the present invention, a remote control circuit can be provided which uses an audio signal line and a control line in common without increasing the number of headphone jack terminals, and which eliminates the need for a large capacitor. It becomes possible to provide

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a preferred embodiment of a headphone stereo remote control circuit according to the present invention; Figs. 2 and 3 are circuit explanatory diagrams showing a play mode and a fast rewind mode of the above embodiment, respectively; Fig. 4; 1 is an overall configuration diagram of a headphone stereo using a cassette tape recorder, and FIG. 5 is a circuit diagram showing an example of a conventional remote control circuit. 10...Stereo main unit 11...Headphone jack 12...Remote controller 13...Headphones 20...Common power amplifier 21...Right power amplifier 22...Left power amplifier 23...Bias power supply 41.42... Changeover switch 43...
Remote resistance 44.45... Comparator 46.47.48... Voltage dividing resistor 49...
remote bias resistor

Claims (1)

[Claims] A headphone stereo remote control circuit in which an audio signal is supplied from a headphone jack to headphones through a common power amplifier, a right power amplifier, and a left power amplifier, and a remote controller is provided between the headphone jack and the headphones. In this case, the remote controller includes a remote resistor connected between the reference voltage output terminal of the common power amplifier and the remote terminal of the headphone jack, and a plurality of changeover switches that change the remote resistance value by intermittent the remote resistor. The stereo main body is provided with a plurality of comparators, and a first input terminal of each comparator is supplied with a different remote reference voltage from a bias power supply of a common power amplifier via a voltage dividing resistor, and the bias A power supply is connected to a remote terminal of the headphone jack via a remote bias resistor, the remote terminal is commonly connected to the second input terminal of each of the comparators, and the remote resistance value is changed by operating the changeover switch, A headphone stereo remote control circuit characterized by switching comparator output according to changes in remote terminal voltage.