JPS6324676Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jack switching circuit that does not generate noise when a plug is inserted into or removed from a jack.

2. Description of the Related Art Portable radio receivers and the like are used to play music through headphones by inserting a plug into a jack when walking, while at home, music is played through speakers. However, noise is generated while the plug is being attached to and removed from the jack. This is because the plug opens and closes several contacts on the jack switch before it is fully seated in the jack.

The present invention relates to a jack switching circuit which prevents the generation of harsh sounds by muting the signal path from the beginning of inserting the plug into the jack until it is completely attached.

The present invention will be explained below with reference to the drawings. 1 is an audio signal circuit such as a tuner, from which an L signal and an R signal are obtained. Reference numerals 2 and 3 are amplifier circuits for amplifying the L signal and R signal, and the output of the amplifier circuit 2 is selectively applied to the input side of the amplifier circuit 3 through a supply circuit 4 with opposite polarity. Reference numeral 5 indicates contact pieces 7, 8, 9, 10, which are turned on and off by attaching and detaching the plug 6.
11, a jack switch 12 between the output terminals of the amplifier circuits 2 and 3;
a jack switch having 8, 9, 10, 11;
12 is a speaker connected between the output terminals of the amplifier circuits 2 and 3 via the jack switch 5 ;
16 are first to fourth switching transistors that are turned on and off by the jack switch 5 , 17
18 and 19 are muting transistors that are controlled by the fourth switching transistor 16 and mute the input sides of the amplifier circuits 2 and 3.

Next, the operation of the present invention will be explained. A case in which playback is performed through the speaker 12 without first inserting the plug 6 into the jack will be described. At this time, only the L signal is obtained from the audio signal circuit 1. This obtained L signal is amplified by the amplifier circuit 2, and then the jack switch 5 , which is turned on at this time, is
is applied to one end of the speaker 12 through the contact piece 7 . A part of the amplified signal is applied to the input side of the amplifier circuit 3 through the supply circuit 4 with opposite polarity, and a part of the amplified signal is applied to the output side of the amplifier circuit 3 with a magnitude equal to and opposite to the output of the amplifier circuit 2. A polar signal is obtained. Since that signal is applied to the other end of the speaker 12, the speaker 12 is driven with a signal that is twice as large.

Next, the case of stereo playback using headphones will be explained. When inserting the plug 6 into the jack, each part of the plug 6 opens and closes each contact on the jack, which may cause noise. transistor 18,
19 is turned on and the input sides of the amplifier circuits 2 and 3 are muted, so that no noise is generated.

That is, when you start inserting the plug 6 into the jack,
First, part A of the plug 6 short-circuits the contact pieces 9 and 10 and contacts the contact piece 11. Then, R of amplifier circuit 3
The signal is grounded through the resistor 20 and capacitor 21, and the magnitude of the signal applied to the speaker 12 changes rapidly. However, the second switching transistor 14 is turned on because it is biased through the contact 11 which remains on until the plug is fully inserted into the jack. Also, at this time, the contact pieces 9, 1
0,11 through the first switching transistor 1
3 is also biased and the first switching transistor 13 is also turned on, so the fourth switching transistor 16 is turned off and the muting transistors 18 and 19 are turned on, which prevents noise from being generated from the speaker 12. do not have.

When the plug is further inserted, the A part of the plug 6 contacts the contact piece 9, and the B part contacts the contact piece 10, so the R signal from the amplifier circuit 3 flows through the headphone coils 22 and 23, and the phase is reversed, resulting in a monaural state. becomes. At this time, contact piece 9, headphone coil 2
2, 23, a bias is applied to the first switching transistor 13 through the contact piece 10, keeping the first switching transistor 13 on and the muting transistors 18, 19 on. As plug 6 is inserted, next is A of plug 6.
contacts the contact pieces 8 and 9, short-circuiting each output side of the amplifier circuits 2 and 3, but at this time, the discharge current of the capacitor 21 causes the first switching transistor 13 to
Turn on and continue the muting state.

As the plug 6 is inserted into the jack, the A part of the plug 6 comes into contact with the contact piece 8 and the C part with the contact piece 10, and only the L signal of the amplifier circuit 2 is applied to the headphone coil 22. At this time, the output of the speaker 12 is also directly applied to the headphone coil 22, which may be harsh to the ears. However, a bias is applied to the first switching transistor 13 by the contact pieces 8, 10 and the headphone coil 22, and the muting transistors 18, 19 are kept turned on.

Finally, the A part of the plug 6 contacts the contact piece 8, the B part contacts the contact piece 9, and the C part contacts the contact piece 10, thereby establishing a normal connection. Therefore, the L signal of the amplifier circuit 2 is applied to the headphone coil 22, and the R signal of the amplifier circuit 3 is applied to the headphone coil 23, thereby achieving stereo reproduction. At this time, the contact pieces 7 and 11 are turned off,
The speaker 12 is deactivated and the second and third switching transistors 14 and 15 are turned off. When the second switching transistor 14 is turned off, the fourth switching transistor 16 is turned on, and the muting transistors 18 and 19 are turned off, thereby canceling the muting operation. Then, an L signal and an R signal are generated from the audio signal circuit 1,
They are added to amplifier circuits 2 and 3, respectively.

At this time, the third switching transistor 15
is turned off, the operational transistor 17 is turned on and the supply circuit 4 is deactivated, so the outputs of the amplifier circuits 2 and 3 are directly connected to the headphone coil 2.
Added to 2 and 23.

As mentioned above, the jack switching circuit of the present invention mutes the amplifier circuit from the time the plug begins to be inserted into the jack until it is completely inserted, which eliminates the discomfort that conventionally occurs when inserting a plug into a jack. can completely eliminate the sound.

[Brief explanation of the drawing]

The figure is a jack switching circuit diagram of the present invention. 1...Audio signal circuit, 2, 3...Amplification circuit, 4
... Supply circuit, 5 ... Jack switch, 6...
...Plug, 7-11... Contact piece, 13-16... First to fourth switching transistor, 18, 19
...Miuteng transistor.

Claims (1)

[Scope of utility model registration request] An amplification circuit that amplifies left and right signals, a plug that has parts A and B to which one end of the left and right headphone coils are connected, and a part C that is grounded, and a plurality of contact pieces that open and close when the plug is attached and detached. a switching transistor for muting that is turned on and off by the jack switch; a switching transistor for switching operations; and a muting transistor that is controlled by the switching transistor for muting and mutating the audio signal of the amplifier circuit. ,
It is controlled by a switching transistor for operation switching, and consists of an operation transistor that controls a supply circuit that inverts and supplies the output side signal of one amplifier circuit to the input side of the other amplifier circuit, so that no plug is inserted into the jack switch. At the same time, the switching transistor for operation switching is turned on, the operating transistor is turned off, and the output side signal of one amplifier circuit is supplied to one end of the speaker, and is inverted and applied to the input side of the other amplifier circuit via the supply circuit. , the output side signal of the other amplifier circuit is supplied to the other end of the speaker, and muting is performed via the contact piece of the jack switch with which the above-mentioned parts A, B, and C of the plug come into contact while inserting or removing the plug from the jack switch. Controls the transistor, turns on the muting transistor, mutes the input side of the amplifier circuit, turns off the switching transistor for operation switching when the plug is completely attached to the jack switch, turns on the operating transistor, and disables the supply circuit. A jack switching circuit characterized in that left and right audio signals obtained from an audio signal circuit are amplified by respective amplifier circuits and supplied to left and right headphone coils via a jack switch.