JP2007312030A - Headphone detecting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a headphone detecting curcuit capable of reducing power consumption by placing an amplifier for a headphone in a mute state when the headphone is not used. <P>SOLUTION: A mute control unit CB places an amplifier IC1 for a speaker in a mute state and the amplifier IC2 for the headphone in a non-mute state based upon a detection signal when the plug of the headphone is inserted into a headphone jack HJ1, and places the amplifier IC1 for the speaker in a non-mute state and the amplifier IC2 for the headphone in a mute state based upon the detection signal when the plug of the headphone is not inserted into the headphone jack HJ1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a headphone detection circuit that is provided in an apparatus that includes an amplifier that drives a speaker and headphones, and that detects this when the headphones are in use and silences the speaker sound.

  FIG. 1 is a circuit diagram of a conventionally proposed headphone detection circuit. In the headphone detection circuit of FIG. 1, a headphone jack with a plug detection terminal is used as the headphone jack HJ0. In addition to the ground terminal 4 and the output terminal 5 for outputting an audio signal and driving the headphone, the headphone jack HJ0 has a first plug for obtaining a detection signal as to whether or not a headphone plug is inserted. A detection terminal (contact) 6 and a second plug detection terminal (contact) 7 are provided. The first plug detection terminal 6 and the second plug detection terminal 7 are extended from an internal mechanical switch and turned on / off by plugging / unplugging.

  The audio signal input terminal a is connected to the input of the speaker amplifier IC1 via the resistor R3, and is further connected to the ground via the transistor Tr constituting the mute circuit MUTE. The audio signal input terminal a is also connected to the input of the headphone amplifier IC2 through the resistor R4. The output of the headphone amplifier IC2 is connected to the output terminal 5 of the headphone jack HJ0 via a DC cut capacitor C1.

  The second plug detection terminal 7 of the headphone jack HJ0 is connected to the pull-up resistor R2 and the input terminal IN of the control block CB0. The output OUT of the control block CB0 is connected to the base terminal of the transistor Tr constituting the mute circuit MUTE. The control block CB0 is composed of a buffer.

  Next, the operation will be described. When no plug is inserted into the headphone jack HJ0, the second plug detection terminal 7 is connected to the ground via the first plug detection terminal 6, so that the input terminal IN of the control block CB0 has a LOW level. Is supplied. At this time, the control block CB0 is configured to output a LOW level voltage to the output terminal OUT. As a result, the transistor Tr of the mute circuit MUTE is turned off, an audio signal is output from the speaker amplifier IC1, and the speaker SP is driven.

  On the other hand, when a plug is inserted into the headphone jack HJ0, the second plug detection terminal 7 of the headphone jack HJ0 is separated from the first plug detection terminal 6 and opened inside. Since the pull-up resistor R2 is connected to the second plug detection terminal 7, a HI level voltage is supplied to the input terminal IN of the control block CB0. At this time, the control block CB0 is configured to output a HI level voltage to the output terminal OUT. As a result, the transistor Tr of the mute circuit MUTE is turned on, and no audio signal is output from the speaker amplifier IC1, so that the speaker SP is not driven (see, for example, Patent Document 1).

JP 2001-8283 A

  However, in the headphone detection circuit described in Patent Document 1 described above, the headphone amplifier IC2 is not muted when the headphones are not used. Therefore, not only the power consumption increases, but also the DC cut capacitor C1 may be deteriorated, so that improvement has been demanded.

  The present invention has been made to solve the above-described problems. By switching the headphone amplifier to the mute state when the headphones are not used, the power consumption is reduced and the deterioration of the DC cut capacitor is suppressed. An object of the present invention is to obtain a headphone detection circuit.

  In order to solve the above-described problem, in the headphone detection circuit according to the present invention, the mute control unit is configured to mute the speaker amplifier based on the detection signal when the headphone plug is inserted into the headphone jack. When the headphone amplifier is not muted and the headphone plug is not inserted in the headphone jack, the speaker amplifier is unmuted and the headphone amplifier is muted based on the detection signal. It is characterized by.

  Embodiments of a headphone detection circuit according to the present invention will be described in detail below. Note that the present invention is not limited to the embodiments. In the following, the outline and features of the headphone detection circuit of the present invention will be described as an embodiment, and then an example relating to the headphone detection circuit will be described.

[Embodiment]
The headphone detection circuit of the present embodiment includes a speaker amplifier that receives an audio signal and drives a speaker, a headphone amplifier that receives an audio signal and drives a headphone, and a headphone jack that is connected to the output of the headphone amplifier. A headphone plug insertion detection unit for detecting that a headphone plug is inserted into the headphone jack; and a mute control unit for controlling a mute state of the speaker amplifier and the headphone amplifier based on a detection signal of the headphone plug insertion detection unit And.

  When the headphone plug is inserted into the headphone jack, the mute control unit mutes the speaker amplifier and sets the headphone amplifier to the non-muted state based on the detection signal, and plugs the headphone into the headphone jack. When is not inserted, the speaker amplifier is set in a non-mute state and the headphone amplifier is set in a mute state based on the detection signal.

  According to the headphone detection circuit of the present embodiment, power consumption can be reduced by setting the headphone amplifier to the mute state when the headphones are not used.

  In the headphone detection circuit of the present embodiment, an audio signal changeover switch provided in the headphone jack is used as the headphone insertion detection unit. Thereby, a headphone jack can be made into a thing with few internal circuits and terminals, and size reduction can be achieved.

  Further, in the headphone detection circuit of the present embodiment, the mute control unit turns on and off the transistors provided between the input of the speaker amplifier and the headphone amplifier and the ground, and thereby the speaker amplifier and the headphone. Each amplifier is muted / unmuted. That is, since the mute circuit can be realized by a transistor, the circuit can be reduced in size.

Example 1.
FIG. 2 is a circuit diagram of the headphone detection circuit according to the first embodiment of the present invention. In the headphone detection circuit of this embodiment shown in FIG. 2, a headphone jack with an audio signal changeover switch is used as the headphone jack HJ1. The headphone jack HJ1 is provided with a ground terminal 1, an output terminal 2 for outputting an audio signal to the headphones, and an audio signal changeover switch terminal 3 that is connected to and separated from the output terminal 2 by plugging / unplugging operation. Yes.

  The headphone detection circuit also receives an audio signal input from the input terminal a, amplifies the audio signal, and a speaker amplifier IC1 that drives the speaker SP. Similarly, the headphone detection circuit receives an audio signal input from the input terminal a. A headphone amplifier IC2 for amplifying the input audio signal and driving the headphone inserted in the headphone jack HJ1 is provided.

  Further, the headphone detection circuit includes a pull-down resistor R1 connected to the output terminal terminal 2 of the headphone jack HJ1 and a pull-up resistor connected to the audio signal switching switch terminal (hereinafter simply referred to as switch terminal) 3 of the headphone jack HJ1. R2, a first mute circuit MUTE1 for muting the speaker output, a second mute circuit MUTE2 for muting the headphone output, and a control block CB composed of a microcomputer or the like for controlling them. In the present embodiment, the control block CB has a configuration or function in which two inverters (NANDs) are connected in series, and derives the first and second outputs OUT1 and OUT2.

  Further details will be described with reference to FIG. The audio signal input terminal a is connected to the input of the speaker amplifier IC1 via the resistor R3, and is further connected to the ground via the transistor Tr1 constituting the first mute circuit MUTE1. The transistor Tr1 is connected between the input of the speaker amplifier IC1 (the speaker amplifier IC1 side from the resistor R3) and the ground.

  The audio signal input terminal a branches after the resistor R3 before being connected to the input of the headphone amplifier IC2 via the resistor R4, and further via the transistor Tr2 constituting the second mute circuit MUTE2. Connected to ground. The transistor Tr1 is connected between the input of the headphone amplifier IC2 (the headphone amplifier IC2 side from the resistor R4) and the ground.

  The output of the speaker amplifier IC2 is connected to the speaker SP. The output of the headphone amplifier IC2 is connected to the output terminal 2 of the headphone jack HJ1 via the DC cut capacitor C1 and to the pull-down resistor (1 kΩ) R1. The pull-down resistor R1 is connected between the connection point between the capacitor C1 and the output terminal 2 and the ground.

  The switch terminal 3 of the headphone jack HJ1 is connected to the pull-up resistor (100 kΩ) R2 and the input terminal IN of the control block CB. The pull-up resistor R2 is connected between the connection point between the switch terminal 3 and the input terminal IN and the + B terminal. The first output (positive logic) OUT1 of the control block CB is connected to the base terminal of the transistor Tr1 constituting the first mute circuit MUTE1. The second output (negative logic) OUT2 of the control block CB is connected to the base terminal of the transistor Tr2 constituting the second mute circuit MUTE2.

  Next, the operation will be described. When the headphone plug is not inserted into the headphone jack HJ1, the switch terminal 3 of the headphone jack HJ1 is internally short-circuited with the output terminal 2. Since the pull-down resistor R1 is connected to the output terminal 2, a voltage of LOW level is supplied to the input terminal IN of the control block CB by voltage dividing operation with the pull-up resistor R2. At this time, the LOW level voltage returned to the positive logic by the two inverters is output to the first output terminal OUT1 of the control block CB, and the logically inverted HI level voltage is output to the second output terminal OUT2. It is controlled so that

  Since the first output terminal OUT1 of the control block CB is at the LOW level, the first mute circuit MUTE1 is turned off (the transistor Tr1 is turned off), the audio signal is output from the speaker amplifier IC1, and the speaker SP is driven. On the other hand, since the second output terminal OUT2 of the control block CB is at the HI level, the second mute circuit MUTE2 is turned on (the transistor Tr2 is turned on), and no audio signal is output from the headphone amplifier IC2, so that the voltage applied to the resistor R1 Does not fluctuate.

  On the other hand, when a headphone plug is inserted into the headphone jack HJ1, the switch terminal 3 of the headphone jack HJ1 is opened away from the output terminal 2 inside. Since the pull-up resistor R2 is connected to the switch terminal 3, the HI level voltage is supplied to the input terminal IN of the control block CB. At this time, the first output terminal OUT1 of the control block CB is controlled so that the HI level voltage returned to the positive logic is output, and the logically inverted LOW level voltage is output to the second output terminal OUT2. .

  Since the first output terminal OUT1 of the control block CB is at the HI level, the first mute circuit MUTE1 is turned on, no audio signal is output from the speaker amplifier IC1, and the speaker SP is not driven. On the other hand, since the second output terminal OUT2 of the control block CB is at the LOW level, the second mute circuit MUTE2 is turned off, the audio signal is output from the headphone amplifier IC2, and the audio signal is supplied to the output terminal of the headphone jack HJ1. Sound is output from the headphones.

  As will be understood from the above description of the operation, the switch terminal 3 of the headphone jack HJ1 constitutes a headphone insertion detection unit that detects whether or not a headphone plug is inserted into the headphone jack HJ1. The control block CB constitutes a mute controller that controls the mute state of the speaker amplifier IC1 and the headphone amplifier IC2 based on the detection signal of the headphone insertion detector (switch terminal 3).

  Thus, in the headphone detection circuit of the present embodiment, the control block CB (mute control unit) controls the speaker amplifier IC1 based on the detection signal when the headphone plug is inserted into the headphone jack HJ1. When the headphone amplifier IC2 is set to the mute state and the headphone amplifier IC2 is set to the non-mute state, and the headphone plug is not inserted into the headphone jack HJ1, the speaker amplifier IC1 is set to the non-mute state based on the detection signal and the headphone amplifier is set. IC2 is muted. In this way, by setting the headphone amplifier IC2 in the mute state when the headphones are not used, it is possible to reduce power consumption and suppress deterioration of the DC cut capacitor C1.

  In the headphone detection circuit of the present embodiment, the audio signal changeover switch terminal 3 provided in the headphone jack HJ1 is used as the headphone insertion detection unit. As a result, the headphone jack HJ1 can have a smaller internal circuit and number of terminals, and can be miniaturized.

  Although the mute circuit of this embodiment is connected to the input side of the amplifier, it may be connected to the output side of the amplifier. When connecting to the input side of the amplifier as in the present embodiment, it can be constituted by a transistor, but when connecting to the output side of the amplifier, for example, a relay having a mechanical contact is used.

Example 2
FIG. 3 is a circuit diagram of a headphone detection circuit according to Embodiment 2 of the present invention. In the headphone detection circuit of FIG. 3, a headphone jack with a plug detection terminal similar to that of FIG. 1 is used as the headphone jack HJ2. In addition to the ground terminal 4 and the output terminal 5 for driving the headphone by outputting an audio signal to the headphone jack HJ2, a headphone jack HJ2 is used to obtain a detection signal for detecting whether or not a headphone plug is inserted. One plug detection terminal 6 and a second plug detection terminal 7 are provided (headphone plug insertion detection unit). The first plug detection terminal 6 and the second plug detection terminal 7 are extended from an internal mechanical switch and turned on / off by plugging / unplugging.

  The output of the headphone amplifier IC2 is connected to the output terminal 5 of the headphone jack HJ2 via a DC cut capacitor C1. The second plug detection terminal 7 of the headphone jack HJ2 is connected to the pull-up resistor R2 and the input terminal IN of the control block CB0. Other configurations are the same as those of the first embodiment.

  In the headphone detection circuit of the present embodiment, the effect of reducing the size of the headphone jack cannot be incorporated, but the same effects as those of the first embodiment can be obtained. In addition, since signals from the first plug detection terminal 6 and the second plug detection terminal 7 are used as detection signals for inserting headphones, the circuit design is easy and the operation is stable.

  The headphone detection circuit according to the present invention can be applied to a device that includes a speaker and an amplifier that drives the headphone.

It is a circuit diagram of the headphone detection circuit proposed conventionally. 1 is a circuit diagram of a headphone detection circuit according to Embodiment 1 of the present invention. It is a circuit diagram of the headphone detection circuit of Example 2 of this invention.

Explanation of symbols

1, 4 Ground terminal 2, 5 Output terminal 3 Audio signal changeover switch terminal (Headphone insertion detection part)
6 1st plug detection terminal (headphone insertion detection part)
7 Second plug detection terminal (headphone insertion detection unit)
IC1 Speaker amplifier IC2 Headphone amplifier CB Control block (mute controller)
HJ1, HJ2 Headphone jack

Claims (3)

An amplifier for a speaker that receives an audio signal and drives the speaker;
An amplifier for headphones that receives headphones and drives audio signals;
A headphone jack connected to the output of the headphone amplifier;
A headphone plug insertion detection unit for detecting that a headphone plug is inserted into the headphone jack;
A mute control unit for controlling the mute state of the speaker amplifier and the headphone amplifier based on a detection signal of the headphone plug insertion detection unit;
The mute controller
When a headphone plug is inserted into the headphone jack, the speaker amplifier is muted based on the detection signal and the headphone amplifier is unmuted.
When the headphone plug is not inserted into the headphone jack, the headphone amplifier is put into a non-mute state and the headphone amplifier is put into a mute state based on the detection signal. . The headphone detection circuit according to claim 1, wherein an audio signal changeover switch provided in the headphone jack is used as the headphone insertion detection unit. The mute control unit mutes the speaker amplifier and the headphone amplifier by turning on / off a transistor provided between the input of the speaker amplifier and the headphone amplifier and the ground, respectively. The headphone detection circuit according to claim 1, wherein the headphone detection circuit is in a state / non-mute state.

Images