WO2003075456A1

WO2003075456A1 - Mute circuit for preventing pop noise, and speaker drive circuit

Info

Publication number: WO2003075456A1
Application number: PCT/JP2003/002458
Authority: WO
Inventors: Osatoshi Tokawa; Kazuhiko Fujimori
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2002-03-04
Filing date: 2003-03-04
Publication date: 2003-09-12
Also published as: JP2003258559A; AU2003211528A1

Abstract

A speaker drive circuit and a mute circuit for preventing pop noise from occurring upon activating/stopping of a drive amplifier. The present circuit comprising a drive amplifier (101), a coupling capacitor (103) and a switch (108) connected between the coupling capacitor (103) and a speaker (104), wherein the switch (108) selectively connects the coupling capacitor (103) to a ground potential or the speaker (104). This interrupts the signal-conveying path to the speaker (104) and provides a rapid charging/discharging of the coupling capacitor (103) to prevent pop noise, and further shortens the time in which to charge/discharge the coupling capacitor (103).

Description

Description Mute circuit for pop noise prevention Speaker drive circuit Technical field

The present invention relates to a mute circuit and a speed driving circuit for preventing pop noise generated when a driving amplifier starts and stops. Background art

An example of a conventional unbalanced speaker drive circuit (conventional example 1) is configured as shown in FIG.

In FIG. 1, reference numeral 11 denotes a drive amplifier, 12 denotes a drive amplifier start / stop signal, 13 denotes a coupling capacitor, 14 denotes a speaker, 15 denotes a voice input signal, 16 denotes a drive amplifier output signal, 17 is a speaker input signal.

FIG. 2A is a timing chart showing the timing of the drive pump start Z stop signal 12, FIG. 2B is a timing chart showing the drive amplifier output signal 16 and FIG. 2C is a timing chart showing the speaker input signal 17, respectively.

Another example (conventional example 2) of the conventional balanced speaker drive circuit is configured as shown in FIG.

In FIG. 3, reference numerals 21 and 22 denote drive amplifiers, reference numeral 23 denotes a drive amplifier start / stop signal, reference numeral 24 denotes a speaker, reference numeral 25 denotes an audio input signal, reference numeral 26 denotes a positive-phase side drive amplifier output signal, and reference numeral 27 Is an output signal of the opposite-phase drive amplifier.

4A shows the timing of the drive amplifier start / stop signal 23, FIG. 4B shows the positive-phase drive amplifier output signal 26, and FIG. 4C shows the negative-phase drive amplifier output signal 27, respectively. It is a timing chart.

Further, the mute circuit disclosed in Japanese Utility Model Registration No. 799963Q (conventional example 3) has a configuration shown in FIG. In FIG. 5, reference numeral 31 denotes a mute switch, 32 denotes a resistor having a higher impedance than a speaker, 33 denotes a drive amplifier, 34 denotes a drive amplifier start-up Z stop signal, 35 denotes a coupling capacitor, and 36 denotes a drive capacitor. Speaker. This mute circuit activates the drive amplifier 33 with the mute switch 31 turned off. When the driving amplifier 33 starts, the coupling capacitor 35 is charged via the resistor 32. By turning on the mute switch 31 after charging is completed, noise at the time of starting the drive amplifier is removed.

However, in the structure of the conventional example 1 shown in FIG. 1, FIG. 2 A to Figure 2 C Timing As shown in ring chart, drive amplifier 1 1 startup and coupling capacitors stops (time t _{1 0,} t of When 13 is rapidly charged and discharged, a differentiated waveform is output, which may drive the speaker 14 to generate pop noise.

In addition, in the configuration of Conventional Example 2 shown in FIG. 3, as shown in the timing charts of FIGS. 4A and 4B, a potential difference occurs in the output signals of the drive amplifiers 21 and 22. In some cases, the speed force 24 is driven to generate noise.

In addition, in the configuration of Conventional Example 3 shown in FIG. 5, since the coupling capacitor 35 is charged via the resistor 32, there is a disadvantage that the charging time becomes longer in accordance with the impedance of the resistor 32. Was. In addition, when the mute switch 31 is turned on to perform the normal sounding operation, the reactive current flows through the resistor 32, so that the power consumption increases. Disclosure of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pop noise preventing mute circuit and a speed driving circuit which can completely prevent pop noise by solving all problems of the conventional example.

In the present invention, the driving amplifier is kept while maintaining the propagation path to the speaker as in the related art. When starting and stopping the drive amplifier, instead of starting the amplifier, connect the switch to the ground potential and cut off the signal transmission path to the speaker to prevent pop noise from being output from the speaker. here _c that way, the "startup drive amplifier", in addition to the case where the power supply of the speaker driving circuit including a driving amplifier is turned (power is turned on), the power supply is turned on force This includes the case where the output of the drive amplifier is prohibited (for example, the drive amplifier is in a high impedance state) and the drive amplifier can output signals. Even in the latter case, bias fluctuations occur, which may cause pop noise.Therefore, according to the present invention, even in such a case, the switch is switched to the ground side in advance to reduce the pop noise. To prevent.

Similarly, “when the drive amplifier is stopped” means that the power of the speaker drive circuit including the drive amplifier is turned off, and that the power is turned on but the signal output of the drive amplifier is allowed. This also includes when signal output is disabled.

Further, according to the present invention, when starting and stopping the drive amplifier, the power coupling capacitor is charged and discharged only through the switch, so that high-speed charging and discharging can be performed. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a circuit diagram showing an example of a configuration of a conventional circuit.

FIG. 2A is a timing chart showing the timing of the drive amplifier start / stop signal in the circuit of FIG. 1,

FIG. 2B is a timing chart showing a drive amplifier output signal in the circuit of FIG.

FIG. 2C is a timing chart showing the speaker input signal in the circuit of FIG. 4 Figure 3 is a circuit diagram showing the configuration of another example of a conventional circuit.

FIG. 4A is a timing chart showing the timing of the drive amplifier start / stop signal in the circuit of FIG. 3,

FIG. 4B is a timing chart showing the output signal of the positive-phase drive amplifier in the circuit of FIG. 3,

FIG. 4C is a timing chart showing the output signal of the negative-phase drive amplifier in the circuit of FIG. 3,

FIG. 5 is a circuit diagram showing the configuration of another example of the conventional circuit,

FIG. 6 is a circuit diagram showing a configuration of a speaker drive circuit (including a pop sound prevention mute circuit) according to Embodiment 1 of the present invention.

FIG. 7A is a timing chart showing the timing of the drive amplifier start / stop signal in the circuit of FIG. 6,

FIG. 7B is a timing chart showing a drive amplifier output signal in the circuit of FIG. 6,

FIG. 7C is a timing chart showing an output signal of the control circuit in the circuit of FIG. 6,

FIG. 7D is a timing chart showing a speaker input signal in the circuit of FIG. 6,

FIG. 8 is a circuit diagram showing a configuration of a speed driving circuit according to Embodiment 2 of the present invention,

FIG. 9A is a timing chart showing the timing of the drive amplifier start Z stop signal in the circuit of FIG. 8,

FIG. 9B is a timing chart showing the output signal of the positive-phase drive amplifier in the circuit of FIG. 8,

FIG. 9C is a timing chart showing the output signal of the negative-phase drive amplifier in the circuit of FIG. 8,

Figure 9D is a timing diagram showing the output signal of the control circuit in the circuit of Figure 8. ,

FIG. 9E is a timing chart showing the in-phase speaker input signal in the circuit of FIG.

FIG. 9F is a timing chart showing the negative-phase speaker input signal in the circuit of FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. (Embodiment 1)

FIG. 6 is a block diagram showing a configuration of a speaker drive circuit (including a pop sound preventing mute circuit) according to Embodiment 1 of the present invention. FIG. 7 is a timing chart showing the operation of the circuit of FIG.

In FIG. 1, reference numeral 101 denotes an unbalanced drive amplifier, 1◦2 denotes a drive amplifier start-up Z stop signal, 103 denotes a coupling capacitor, 104 denotes a speaker, 105 denotes a voice input terminal, 106 is a drive amplifier output signal, 107 is a speaker input signal, 108 is a switch for switching the connection destination of the coupling capacitor 103, and 109 is a control for switching the switch 108. Circuit (switch switching control circuit).

FIG. 7A shows the timing of the drive amplifier start / stop signal 102 (that is, the timing of switching the switch 108 when the drive amplifier 101 starts and stops, and FIG. 7B shows the drive amplifier output signal 1). 06 and FIG. 7C are output signals (switch switching control signals) of the control circuit 109, and FIG. 7D is a timing chart showing the speaker input signal 107, respectively.

First, before the drive amplifier 101 is started (before time), the switch 108 is switched to the B terminal side by a control signal from the control circuit 109 and connected to the ground potential. The audio input terminal 105 is a silent input. Next, at time, the drive amplifier start-up Z stop signal 102 turns on and drives When the driving amplifier 101 is started, the output of the driving amplifier 101 becomes a signal having a DC voltage through a transient response and is stabilized.

At this time, the coupling capacitor 103 is rapidly charged. The charging completion After the completion, at time t _2, the switch 1 0 8 is switched more terminal A to the output signal of the control circuit 1 0 9, is thereby coupling capacitor 1 0 3 of the destination, the speaker 1 0 4

Here, the timing of switching the switch 108 from the B terminal to the A terminal may be determined after the stability of the signal output via the input coupling capacitor 103 is detected by a detector (not shown) or at a predetermined timing. After the period has elapsed.

Then, an audio signal (regular audio signal) is input from the audio input terminal 105, and the speaker 104 sounds.

When stopping the drive amplifier 104 (when the power is turned off, etc.), stop the input of the audio signal to the audio input terminal 105 and then start the drive amplifier. Z Turn off the stop signal 102 (time t ₄₎ (i.e. time t ₃ before), Ru switches the connection destination to the ground potential of Suitsuchi 1 0 8 by the output signal of the control circuit 1 0 9.

Then, at time t _4, by turning off the driving amplifier start / stop signal 1 0 2 stops driving § pump 1 0 1.

(Embodiment 2)

FIG. 8 is a block diagram showing a configuration of a speaker drive circuit (sound reproduction circuit) according to Embodiment 2 of the present invention. FIG. 9 is a timing chart showing the operation of the circuit of FIG.

In FIG. 8, reference numerals 201 and 202 denote balanced drive amplifiers, 203 denotes a drive amplifier start / stop signal, 204 and 205 denote coupling capacitors, 206 denotes speed, 207 is an audio input terminal, 209 is a positive-phase drive amplifier output signal, 209 is a negative-phase drive amplifier output signal, 210 is a positive-phase speed input signal, and 211 is reverse. Phase speaker side input signals, 2 1 2 and 2 1 3 A switch for switching the connection destinations of the coupling capacitors 204 and 205, and a control circuit 214 for controlling the switching of the switches 2 12 and 2 13 is provided. Figure 9A shows the timing of the drive amplifier start-up Z stop signal 203 (that is, the timing of switching the switches 2 1 2 and 2 1 3 when the drive amplifiers 201 and 202 start up and Z stops). B is the output signal of the positive-phase drive amplifier 208, Figure 9C is the output signal of the negative-phase drive amplifier 209, and Figure 9D is the output signal (switch switching control signal) of the control circuit 214. E is a timing chart showing the positive-phase input signal and FIG. 9F is a timing chart showing the negative-phase input signal.

First, the switches 2 12 and 2 13 are connected to the ground potential before time t i by the output signal of the control circuit 2 14. The audio input terminal 207 is a silent input.

At time t, the drive amplifier activation Z stop signal 203 turns on, and the drive amplifiers 201 and 202 are activated. The output of the drive amplifiers 201 and 202 becomes a signal having a DC voltage through a transient response and is stabilized.

At this time, the coupling capacitors 204 and 205 are rapidly charged. After completion of charging this, at time t _2, the switch 2 1 2 and Suitsuchi 2 1 3, the control circuit 2 1 4 output signal by switching to the A terminal side and C terminal side, respectively Erare, thereby, the coupling capacitor The connection destination of 204 and 205 is the speed force 206.

Here, the timing of switching the switch 2 12 from the B terminal to the A terminal and the timing of switching the switch 2 13 from the D terminal to the C terminal are output via the power coupling capacitors 204 and 205, respectively. After the detected signal is detected by a detector (not shown) or after a predetermined period has elapsed.

Then, an audio signal is input from the audio input terminal 207, and the speech force 206 is sounded.

Next, when the drive amplifiers 201 and 202 are stopped, after the input of the audio signal to the audio input terminal 207 is stopped, the drive amplifier is activated and before the Z stop signal 203 is turned off. (Time t _3), switches the switch 20 1, 20 2 to connect to the ground potential by the output signal of the control circuit 2 14.

Thereafter, by turning off the driving amplifier activation stop signal 20 3 to time t ₄ to stop driving amplifiers 20 1, 202.

As described above, the speaker drive circuit of the present embodiment has a differential output force S. In the present embodiment, unlike the conventional example of FIG. 3, the speaker 206 is connected via the coupling capacitors 204 and 205. Drive. As described above, in the conventional circuit of FIG. 3, when a potential difference occurs between the output signals of the two drive amplifiers 21 and 22, the potential difference causes pop noise. However, in the present embodiment, even if there is a potential difference between the output signals of the two drive amplifiers 201 and 202, no problem occurs, and no potential difference occurs at the input of the speaker 206.

Also, in each embodiment, when the drive amplifiers 101, 201, and 202 are turned off (turning on / off the power of the speaker and the drive circuit), the speakers 104 and 206 are cut off from the signal path. Therefore, pop noise from the speakers 104 and 206 caused by the transient response waveform output from the coupling capacitors 103, 204, and 205 is reliably prevented.

In addition, since the resistor 32 as shown in FIG. 5 is not connected to the switches 108, 212, and 213, the coupling capacitors are not connected when the drive amplifiers 101, 201, and 202 are turned on / off. 103, 204, and 205 are rapidly charged and discharged only through switches 108, 212, and 213 (with very small time constants). Therefore, the charging and discharging time of the coupling capacitors 103, 204, and 205 is reduced. As a result, the intervals at which the switches 108, 212, and 213 are switched are reduced, and efficient operation is possible.

In addition, since there is no ground resistance as in the conventional example of FIG. 5, there is no fear that a reactive current flows.

Further, the configuration of the present invention is extremely simple and easy to realize.

As described above, in the present invention, the signal transmission path to the speaker is held. Instead of starting the drive amplifier as it is, connect the switch to the ground potential and cut off the transmission path to the speaker when the drive amplifier starts and stops, so that pop noise generated when the drive amplifier starts and stops can be assured. Can be prevented.

Further, since the coupling capacitor is charged and discharged only through the switch, the charging and discharging of the coupling capacitor can be accelerated.

This description is based on Japanese Patent Application No. 2002-057901 filed on Mar. 4, 2002. All this content is included here. Industrial applicability

The present invention can be applied to a speaker drive circuit.

Claims

The scope of the claims

1. A pop noise preventing mute circuit in a circuit for driving a speed through a coupling capacitor by a speaker driving amplifier, wherein the power coupling is connected between the coupling capacitor and the speaker. A switch for switching a connection destination of the capacitor to one of the above-mentioned speed force or ground potential;

A control circuit for controlling switching of the switch,

The control circuit includes:

When the speaker drive amplifier is activated, the switch is controlled to switch the connection destination of the coupling capacitor to a ground potential, thereby cutting off the signal path to the speaker and only connecting the switch. Charging the coupling capacitor via the power supply, and after completion of the charging, switching the switch to return the connection destination of the power coupling capacitor to the speed.

Mute circuit for pop noise prevention.

2. The control circuit comprises:

Before the speaker drive amplifier is stopped, the switch is switched to switch a connection destination of the coupling capacitor to a ground potential.

A muting circuit for preventing pop noise according to claim 1.

3. A drive amplifier for driving the speaker;

A coupling capacitor having one terminal connected to the output terminal of the drive amplifier; an input terminal connected to the other terminal of the power coupling capacitor; and a first output terminal of two output terminals having the speed The second output terminal is grounded without a resistor, and the input terminal is connected to one of the first and second output terminals. A switch provided by a switch control signal, A control circuit that generates the switching control signal and supplies the switching control signal to the switch.

The control circuit includes:

The switch is switched to the second output terminal before the drive amplifier is started, and the switch is switched to the first output terminal before a normal speaker drive signal is output from the drive amplifier. And a switch for switching the switch to the second output end before the drive amplifier is stopped.

4. The control circuit includes:

At the time of starting the drive amplifier, after detecting the stability of the output of the drive amplifier, or after a lapse of a predetermined period from the start timing of the drive amplifier, the switch is switched from the second output terminal side to the first switch. 4. The speaker drive circuit according to claim 3, wherein the speaker drive circuit returns to an output end side of the speaker.