JP2006067025A - Pop noise prevention circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pop noise prevention circuit capable of surely and efficiently preventing production of pop noise. <P>SOLUTION: In the pop noise prevention circuit 100 wherein an amplifier 10 amplifies a received audio signal and a speaker 20 outputs sound on the basis of the amplified audio signal, a voltage detection means (e.g., microcomputer 50) detects a voltage of an amplifier voltage source for applying a voltage to the amplifier 10, and when the detected voltage exceeds a prescribed voltage at which the amplifier 10 generates pop noise, a connection switching control means (e.g., microphone 50) closes a relay 30 interposed between the amplifier 10 and the speaker 20 to connect the amplifier 10 to the speaker 20 thereby allowing the speaker 20 to output sound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pop noise prevention circuit, and more particularly to a pop noise prevention circuit for preventing a pop noise generated by a speaker such as an audio device.

  In an audio device, an impact noise called pop sound may be generated from a speaker during a transition from when power is turned on to when an amplifier rises and stabilizes.

  Since this pop sound is harsh and uncomfortable, a technique for preventing the pop sound from being generated has been proposed.

  For example, in order to prevent a pop sound that occurs when the mute is released when the power is turned on, a technique is known in which the mute state is gradually released in a plurality of stages without being released in one stage (for example, , See Patent Document 1).

  In addition, a technique is known in which the amount of current flowing to the speaker when the power is turned on is adjusted by a transistor so that current does not flow suddenly to the speaker, thereby preventing pop noise (see, for example, Patent Document 2). .)

There is also known a technique for performing mute control for forcibly stopping the signal transmission operation of the amplifier for a predetermined time when the audio device is turned on so that no pop sound is output from the speaker.
JP 2000-341047 A JP 2001-284969 A

  However, in the case of the above-mentioned Patent Document 1, although it is smaller than the pop sound when the mute state is released all at once, a slight pop sound may occur at each stage where the mute state is released in a plurality of stages. Could not be completely prevented.

  Further, in the case of Patent Document 2, since the speaker is connected to an amplifier (amplifier) or a power source, a pop sound may occur depending on the amount of current flowing through the speaker.

  In addition, in the case of technology that performs mute control to forcibly stop the signal transmission operation of the amplifier for a predetermined time so that the pop sound is not output from the speaker, in order to prevent the pop sound from being generated, Since it is necessary to stop the signal transmission operation of the amplifier without fail until it reaches a stable state that does not occur, the stop time is set so as to maintain an extra muffled state even after the stable state is reached. Had the problem of being wasted.

  An object of the present invention is to provide a pop sound prevention circuit that can reliably and efficiently prevent the occurrence of pop sounds.

In order to solve the above problems, the invention described in claim 1 is a pop sound prevention circuit, which outputs an audio based on an amplifier to which an audio signal is input and an amplified audio signal output from the amplifier. A speaker, a relay interposed between the amplifier and the speaker, a transistor connected to a relay voltage source for applying a voltage to the relay via a coil portion of the relay, and a voltage to the amplifier Voltage detecting means for detecting a voltage value of the voltage source for the amplifier to be applied; and when the voltage value detected by the voltage detecting means exceeds a predetermined voltage value at which the amplifier generates a pop sound, the transistor is turned on. Connection switching control means for switching on / off, and the connection switching control means switches the on / off of the transistor to the coil portion of the relay. The voltage from the voltage source relay to be pressurized is controlled by the contacts of the relay are closed, characterized in that the amplifier and the speaker are connected.

  The invention according to claim 2 is a pop sound prevention circuit, an amplifier to which an audio signal is input, a speaker that outputs audio based on an amplified audio signal output from the amplifier, the amplifier, and the speaker And a voltage detecting means for detecting a voltage value of an amplifier voltage source for applying a voltage to the amplifier, and a voltage value detected by the voltage detecting means causes the amplifier to generate a pop sound. And a connection switching control means for closing the switch and connecting the amplifier and the speaker when a predetermined voltage value is exceeded.

  According to a third aspect of the present invention, in the pop noise prevention circuit according to the second aspect, the switch is a relay including a coil portion and a contact point, and a relay voltage source for applying a voltage to the relay; A transistor connected to the relay voltage source via the coil portion of the relay, and the connection switching control means applies to the coil portion of the relay based on switching on / off of the transistor The amplifier and the speaker are connected by controlling the voltage from the relay voltage source and closing the contact of the relay.

  According to the first aspect of the present invention, in the pop sound prevention circuit in which the amplifier amplifies the input sound signal and the speaker outputs sound based on the amplified sound signal, the amplifier applies a voltage to the amplifier. When the voltage detection means detects the voltage value of the voltage source and the voltage value detected by the voltage detection means exceeds a predetermined voltage value at which the amplifier generates a pop noise, the connection switching control means applies a voltage to the relay. Based on switching on / off of the transistor connected via the relay coil source and the relay coil unit, the application of the voltage from the relay voltage source to the relay coil unit is controlled. By closing the contact, the amplifier and the speaker are connected. For example, the connection switching control means switches off the transistor, cuts off the application of voltage from the relay voltage source to the coil portion of the relay, and closes the contact of the relay to connect the amplifier and the speaker. To do.

  That is, in the pop noise prevention circuit, the transistor is switched on / off when the voltage value applied to the amplifier from the amplifier voltage source exceeds a predetermined voltage value at which the amplifier generates a pop noise. Thus, the contact of the relay is closed, the amplifier and the speaker are connected, and the sound can be output from the speaker, so that no pop sound is output from the speaker.

  Therefore, the pop sound prevention circuit can reliably and efficiently prevent the pop sound from being generated.

  According to the second aspect of the present invention, in the pop sound prevention circuit in which the amplifier amplifies the input sound signal and the speaker outputs sound based on the amplified sound signal, the amplifier applies a voltage to the amplifier. The voltage detection means detects the voltage value of the voltage source, and when the voltage value detected by the voltage detection means exceeds a predetermined voltage value at which the amplifier generates a pop sound, the connection switching control means The switch interposed between the two is closed to connect the amplifier and the speaker.

  That is, in the pop noise prevention circuit, after the voltage value applied to the amplifier from the amplifier voltage source exceeds a predetermined voltage value at which the amplifier generates a pop noise, the amplifier and the speaker are connected, and the speaker Since the sound can be output from the speaker, the pop sound is not output from the speaker.

  Therefore, the pop sound prevention circuit can reliably and efficiently prevent the pop sound from being generated.

  According to the invention described in claim 3, it is of course possible to obtain the same effect as that of the invention described in claim 2. In particular, the switch is a relay composed of a coil portion and a contact, and connection switching control is achieved. The means is configured to switch on / off of a transistor connected via the coil portion of the relay to a relay voltage source that applies a voltage to the relay, and to supply the voltage from the relay voltage source to the relay coil portion. By controlling the application and closing the contact of the relay, the amplifier and the speaker are connected. For example, the connection switching control means switches off the transistor, cuts off the application of voltage from the relay voltage source to the coil portion of the relay, and closes the contact of the relay to connect the amplifier and the speaker. To do.

  That is, in the pop noise prevention circuit, the transistor is switched on / off when the voltage value applied to the amplifier from the amplifier voltage source exceeds a predetermined voltage value at which the amplifier generates a pop noise. As a result, the contact of the relay is closed and the amplifier and the speaker are connected, so that the connection between the amplifier and the speaker can be switched so that the pop sound is not more preferably output from the speaker.

  Hereinafter, a pop noise prevention circuit according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram showing the overall configuration of a pop sound prevention circuit according to an embodiment of the present invention.

  As shown in FIG. 1, the pop sound prevention circuit 100 includes an amplifier 10 to which an audio signal is input, a speaker 20 that outputs sound based on the amplified audio signal output from the amplifier 10, and the amplifier 10 and the speaker 20. A relay 30 interposed therebetween, a transistor 40 for switching supply of current to the relay 30, a microcomputer 50 (hereinafter referred to as a microcomputer 50) as a control unit of the pop noise prevention circuit 100, and the like. .

  The amplifier 10 operates based on a voltage applied from a main power supply terminal 10b as an amplifier voltage source (Vcc).

  The amplifier 10 amplifies the audio signal input from the input terminal 10 a and outputs the amplified audio signal from the output terminal to the speaker 20.

  The amplifier 10 is a pop-on generator that generates noise that causes abnormal noise called pop noise when the voltage applied from the main power supply terminal 10b exceeds a predetermined voltage value (for example, 5 volts). It becomes.

  The speaker 20 outputs sound by vibrating the vibrating body based on the amplified sound signal input from the amplifier 10.

  The relay 30 includes a coil part 31 and a contact 32.

  The coil part 31 is an electromagnet having an iron core inside the coil, and generates a magnetic force when a current flows through the coil part 31, and moves the contact 32 with the magnetic force to switch between opening and closing of the contact 32. Yes. That is, by switching the opening and closing of the contact 32, the relay 30 as a switch is switched on and off.

  The relay 30 in the present embodiment is a normally closed contact (normally closed, NC). When no current flows through the relay 30 (coil unit 31), the contact 32 is closed, and the relay 30 (coil unit 31) has a current. When the current flows, the contact 32 is opened.

  The speaker 20, the contact 32 of the relay 30, and the amplifier 10 are connected in series. When the contact 32 is closed, the speaker 20 and the amplifier 10 are connected, so that the contact 32 is closed. In addition, the relay 30 as a switch is turned on, the audio signal output from the amplifier 10 is input to the speaker 20, and the audio is output from the speaker 20.

  Further, a power supply terminal 30 a as a relay voltage source for applying a voltage to the relay 30 and causing a current to flow is connected to the transistor 40 via a coil portion 31 of the relay 30. A voltage of (ALL + 12V), for example, is applied to the pop noise prevention circuit 100 (relay 30) from the power supply terminal 30a as a relay voltage source.

  The power supply terminal 30 a, the coil portion 31 of the relay 30, and the transistor 40 are connected in series, and the coil portion 31 is connected to the collector of the transistor 40.

  The emitter of the transistor 40 is grounded, and the base of the transistor 40 is connected to the microcomputer 50.

  When the base current is supplied to the transistor 40, the transistor 40 is turned on, and the collector current flows. The current from the power supply terminal 30a as the relay voltage source flows to the coil portion 31, and the contact 32 is connected. It is supposed to open.

  On the other hand, when the base current is not supplied to the transistor 40, the transistor 40 is turned off, the collector current does not flow, the current from the power supply terminal 30a as the relay voltage source is not supplied to the coil unit 31, and the contact 32 is closed. It is like that.

  A diode 60 is connected in parallel with the coil portion 31 of the relay 30, and the anode of the diode 60 is connected to the transistor 40 side and the cathode thereof is connected to the power supply terminal 30 a side.

  The diode 60 is a surge absorbing diode.

  The coil part 31 of the relay 30 has a large inductance, and when the current supply from the power supply terminal 30a stops, the current flowing through the coil part 31 decreases rapidly. Such a sudden change in current generates a large electromotive force called a surge. Since this surge may destroy the transistor 40, the current caused by the surge is bypassed to the diode 60 so that the transistor 40 is not subjected to a surge load.

  The microcomputer 50 detects the voltage applied to the amplifier 10 and the pop noise prevention circuit 100, and switches the transistor 40 on and off based on the voltage value detected by the detection port 51. A control port 52 for switching supply of current is provided.

  A power supply terminal 50a as a microcomputer voltage source for applying a voltage to the microcomputer 50 and causing a current to flow is connected to the detection port 51 side of the microcomputer 50. A voltage of (ALL + 5V), for example, is applied to the pop noise prevention circuit 100 (microcomputer 50) from the power supply terminal 50a as a voltage source for the microcomputer. Note that the voltage of “+5 V” from the power supply terminal 50a corresponds to a predetermined voltage value at which the amplifier 10 generates noise that causes pop noise.

  Further, a diode 70 is connected between the detection port 51 side of the microcomputer 50 and the main power supply terminal 10b, with the anode of the diode 70 facing the microcomputer 50 and the cathode facing the main power supply terminal 10b. It is connected. A power supply terminal 50 a as a microcomputer voltage source is positioned between the detection port 51 side of the microcomputer 50 and the anode side of the diode 70.

Then, the microcomputer 50 controls this circuit according to a control program for controlling the pop sound prevention circuit 100.

  For example, the microcomputer 50 performs control for detecting a voltage value of an amplifier power supply (Vcc) that supplies power to the amplifier 10 as voltage detection means.

  Further, the microcomputer 50 serves as connection switching control means when the voltage value detected by the voltage detection means exceeds a predetermined voltage value (for example, 5 volts) that causes the amplifier 10 to generate noise that causes popping noise. The transistor 40 is controlled to be turned off.

  Specifically, when the voltage value of the amplifier power supply (Vcc) input to the detection port 51 of the microcomputer 50 is lower than a predetermined voltage value, the potential of the detection port 51 becomes Low, and the control port 52 becomes High. . Then, the control port 52 supplies a current (base current) to the transistor 40 and switches the transistor 40 on.

  When the voltage value of the power supply for amplifier (Vcc) input to the detection port 51 of the microcomputer 50 is higher than a predetermined voltage value, the potential of the detection port 51 becomes High and the control port 52 becomes Low. The control port 52 cuts off the supply of current (base current) to the transistor 40 and switches the transistor 40 off.

  Next, the operation of the pop noise prevention circuit 100 according to the present invention will be described based on the flowchart shown in FIG.

  First, the main power supply of the amplifier 10 in the audio device including the pop sound prevention circuit 100 is turned on, and a voltage is applied to the amplifier 10 and the circuit from the main power supply terminal 10b (step S101).

  Next, the microcomputer 50 detects the voltage value at the detection port 51 (step S102).

  When the microcomputer 50 determines that the voltage value at the detection port 51 does not exceed 5 (V) and the detection port 51 is Low (step S102; No), the process proceeds to step S103.

  That is, when the voltage value of the voltage applied to the main power supply terminal 10b is less than 5 (V), the voltage of ALL + 5 (V) is applied to the circuit from the power supply terminal 50a as the microcomputer voltage source. The potential at the point A of the circuit in FIG. 1 is drawn to the point B side through the diode 70. Accordingly, since the potential of the detection port 51 becomes Low, it can be determined that the voltage value at the detection port 51 is less than 5 (V). As the potential of the detection port 51 becomes Low, the control port 52 becomes High, and the process proceeds to Step S103.

  In step S <b> 103, the microcomputer 50 supplies a base current to the transistor 40 based on the fact that the control port 52 is High. Then, the transistor 40 is turned on (step S103).

  Next, a current is supplied to the coil portion 31 of the relay 30, the contact 32 of the relay 30 is opened and turned off, and the speaker 20 is disconnected from the amplifier 10 (step S104). That is, even if an audio signal is input to the amplifier 10, no sound is output from the speaker.

  Then, the process returns to step S102.

  On the other hand, when the microcomputer 50 determines that the voltage value at the detection port 51 exceeds 5 (V) and the detection port 51 is High (step S102; Yes), the process proceeds to step S105.

That is, the voltage of ALL + 5 (V) is applied to the circuit from the power supply terminal 50a as the voltage source for the microcomputer, but when the voltage value at the main power supply terminal 10b is 5 (V) or more, the circuit of FIG. Since the potential at the point A is lower than the potential at the point B, the movement of current through the diode 70 is eliminated. Accordingly, since the potential of the detection port 51 becomes High, it can be determined that the voltage value at the detection port 51 is 5 (V) or more. Then, as the potential of the detection port 51 becomes High, the control port 52 becomes Low, and the process proceeds to Step S105.

  In step S105, based on the fact that the control port 52 is low, the microcomputer 50 cuts off the supply of the base current to the transistor 40. Then, the transistor 40 is turned off (step S105).

  Next, the current is not supplied to the coil portion 31 of the relay 30, the contact 32 of the relay 30 is closed, and the speaker 20 is connected to the amplifier 10 (step S106). That is, when an audio signal is input to the amplifier 10, audio is output from the speaker.

  As described above, in the pop sound prevention circuit 100 according to the present invention, the voltage value applied from the main power supply terminal 10b is a predetermined voltage value (for example, 5V) that causes the amplifier 10 to generate noise that causes pop sound. ), The sound is not output from the speaker 20 by turning off the contact 32 of the relay 30. Then, when the voltage value applied from the main power supply terminal 10b exceeds a predetermined voltage value (for example, 5 V), the speaker 20 is connected to the amplifier 10 by turning on the contact 32 of the relay 30. You can switch to a connected state.

  That is, in the pop sound prevention circuit 100, after the voltage value applied from the main power supply terminal 10b exceeds a predetermined voltage value that causes the amplifier 10 to generate noise that causes pop sound, the sound is output from the speaker 20. As a result, the pop sound is not output from the speaker 20.

  Therefore, the pop sound prevention circuit 100 can reliably prevent the pop sound from being generated.

  In particular, the pop noise prevention circuit 100 detects a voltage value applied from the main power supply terminal 10b, and thus when the amplifier 10 is applied with a predetermined voltage value that generates noise that causes a pop noise. Since the speaker 20 cannot output sound and the pop sound is not output from the speaker 20, the circuit is kept in a mute state until a stable state where no pop sound is generated as in the prior art. Compared with this, it is possible to prevent the pop sound from occurring more efficiently.

  Further, since the detected voltage value exceeds a predetermined voltage value that is the pop sound generation timing, the sound is immediately switched to a state in which sound is output from the speaker 20, so that the sound of the speaker 20 with respect to the change of the voltage value. Good tracking of output switching.

  In the above embodiment, an example in which the normally closed contact (NC) relay 30 or the NPN transistor 40 is used to switch the opening and closing (on / off) of the contact 32 of the relay 30 has been described. The present invention is not limited to this, and may be configured to switch opening / closing (ON / OFF) of the relay contacts using a normally open contact (NO) relay or a PNP transistor.

  Further, the application of the present invention is not limited to the above-described embodiment, and it is needless to say that the application can be appropriately changed without departing from the spirit of the present invention.

It is a circuit diagram which shows the pop sound prevention circuit which concerns on this invention. 3 is a flowchart showing the operation of the pop sound prevention circuit according to the present invention.

Explanation of symbols

10 amplifier 10a input terminal 10b main power supply terminal (voltage source for amplifier)
20 Speaker 30 Relay (switch)
30a Power supply terminal (Relay voltage source)
31 Coil part 32 Contact 40 Transistor 50 Microcomputer (voltage detection means, connection switching control means)
50a Power supply terminal 51 Detection port 52 Control port 60 Diode 70 Diode 100 Pop noise prevention circuit

Claims (3)

An amplifier to which an audio signal is input;
A speaker that outputs audio based on the amplified audio signal output from the amplifier;
A relay interposed between the amplifier and the speaker;
A transistor connected to a relay voltage source for applying a voltage to the relay via a coil portion of the relay;
Voltage detecting means for detecting a voltage value of an amplifier voltage source for applying a voltage to the amplifier;
Connection switching control means for switching on / off the transistor when the voltage value detected by the voltage detection means exceeds a predetermined voltage value at which the amplifier generates a pop sound; and
When the connection switching control means switches on / off of the transistor, the voltage from the relay voltage source applied to the coil portion of the relay is controlled, and the contact of the relay is closed. The pop sound prevention circuit, wherein the amplifier and the speaker are connected. An amplifier to which an audio signal is input;
A speaker that outputs audio based on the amplified audio signal output from the amplifier;
A switch interposed between the amplifier and the speaker;
Voltage detecting means for detecting a voltage value of an amplifier voltage source for applying a voltage to the amplifier;
When the voltage value detected by the voltage detection means exceeds a predetermined voltage value at which the amplifier generates a pop sound, connection switching control means for closing the switch and connecting the amplifier and the speaker;
A pop sound prevention circuit comprising: The switch is a relay composed of a coil portion and a contact point,
A relay voltage source for applying a voltage to the relay;
A transistor connected to the relay voltage source via a coil portion of the relay;
The connection switching control means controls the voltage from a relay voltage source applied to the coil portion of the relay based on switching on / off of the transistor, and closes the contact of the relay, thereby the amplifier. The pop sound prevention circuit according to claim 2, wherein the speaker is connected to the pop sound.

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