JPH10313496A - Active speaker circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of a noise output from a power amplifier circuit by nullifying a power control signal when the floating state of an input side pre-grounding terminal is detected. SOLUTION: When an input connection code 3 is not connected while a connecting code 7 connects a set body side 1 and an active speaker circuit 21, the input side of an amplifier 6a of the circuit 21 and a pre-grounding terminal 21b will be in a floating state. Since the terminal 21b is connected to a Vcc side of a power source circuit 8 through a bias circuit 33, and the Vcc voltage is applied, the terminal 21b becomes will be in the same potential as Vcc and turns on a transistor 34. As a result, because an input terminal of a standby switch 6 is grounded through the transistor 34, a control signal that is supplied from the body 1 to a control input terminal 21c is nullified, the switch 6b is not operated and power is not fed to the amplifier 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active speaker circuit for preventing generation of noise output when an amplifier power supply is turned on in a state where input wiring cords are not properly connected.

[0002]

2. Description of the Related Art A conventional active speaker circuit is shown in FIG.
As shown in the figure, the input connection cord 3 and the power amplifier circuit 6
Set body 1 and active speaker circuit 4 using connection cord 7 for supplying power and control signals
By connecting the terminals, a speaker output signal is supplied from the output amplifier 2 of the set body 1 to the active speaker circuit 4 and amplified by the amplifier 6a of the power amplifier circuit 6 to drive the speaker 5. As a result, it is possible to enjoy high-quality sound by adding the active speaker circuit 4 or the like to a television or a car radio that does not already have sufficient audio output. This active speaker circuit 4
A power amplifier circuit 6 including an amplifier 6a and a standby switch 6b, a power supply circuit 8, and the like are provided. The speaker signal output from the set body 1 is input to the amplifier 6 a of the power amplifier circuit 6 via the input connection cord 3. The ground of the set body 1 is connected to the pre-ground of the power amplifier circuit 6 of the active speaker circuit 4 via the input connection cord 3, and the power of the power supply circuit 8 of the active speaker circuit 4 via the connection cord 7. Also connected to ground. In the power amplifier circuit 6 of the active speaker circuit 4, the pre-ground and the power ground of the power supply circuit 8 are not connected.

[0003]

Since the conventional active speaker circuit is configured as described above, when the input connection cord 3 is not connected, the amplifier input side of the power amplifier circuit 6 is in a floating state. Yes,
When the power of the amplifier 6a of the power amplifier circuit 6 is turned on in this state, the transient state at the time of turning on the power is amplified, so-called pop noise is generated, and a relatively loud noise is output from the speaker. was there.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an active speaker circuit capable of preventing the occurrence of noise output when the power of the amplifier of the power amplifier circuit is turned on when the amplifier input side of the power amplifier circuit is in a floating state. It is in.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a set body for transmitting an audio signal and a control signal for power control, and an input connection cord and a signal connection cord connected to the set body. A power amplifier that is separably connected and amplifies an audio signal supplied through the input connection cord, a speaker driven by an output signal of the power amplifier, a driving power supply of the speaker and the power amplifier, and a signal from the set body. An active speaker circuit including an active speaker having a standby switch for turning on power operated by a control signal for power control via a connection cord, wherein the input main body and the active speaker are not connected by the input connection cord. The resulting input-side preground terminal of the power amplifier Wherein said providing the control signal controlling means for disabling the control signal for power control that is supplied to the standby switch when detecting a floating state.

In the active speaker circuit of the present invention, when the set main body and the active speaker are connected by the input connection cord, the active speaker circuit is turned off to supply a control signal for power control to the standby switch. When the set body is not connected to the active speaker, the power supply control signal to the standby switch is cut off by turning on the switch. Therefore, it is possible to prevent generation of noise output when the power of the amplifier of the power amplifier circuit is turned on when the amplifier input side of the power amplifier circuit is in a floating state.

[0007]

Next, an embodiment of an active speaker circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an example of an active speaker circuit according to the present invention. In FIG. 1, the same elements as those in the circuit diagram shown in FIG. 2 are denoted by the same reference numerals. In this active speaker circuit, the audio signal output terminal 1a of the set body 1 and the audio signal input terminal 21a of the active speaker circuit 21 and the ground terminal 1b of the set body 1
And the pre-ground terminal 2 on the active speaker circuit 21 side
1b are connected by input connection cords 3 respectively. Also, a control signal output terminal 1c of the set body 1 and a control input terminal 2c of the active speaker circuit 21 side.
1c, the Vcc connection terminal 1d of the set body 1 and the Vcc connection terminal 21d of the active speaker circuit 21, and the ground connection terminal 1e of the set body 1 and the ground connection terminal 21e of the active speaker circuit 21 are connected by the connection cord 7. Each is connected. The ground terminal 1b is connected to the ground connection terminal 1 inside the set body 1.
e. The set main body 1 is not provided with a power supply circuit for supplying power.

The audio signal output terminal 1a and the ground terminal 1b
After that, the audio signal is supplied to the audio signal input terminal 21a and the pre-ground terminal 21b of the active speaker circuit 21 via the input connection cord 3. Further, a control signal for controlling on / off of the amplifier 6a is output from the control signal output terminal 1c to the control input terminal 21c of the active speaker circuit 21 via the connection cord 7. Also, the Vcc connection terminal 1d of the set body 1 and the Vcc connection terminal 21d of the active speaker circuit 21, the ground connection terminal 1e of the set body 1 and the ground connection terminal 21e of the active speaker circuit 21 via the connection cord 7. Are connected, the ground of the set body 1 and the ground of the active speaker circuit 21 are connected in common, and the Vc of the set body 1
The c line and the Vcc line on the active speaker circuit 21 side are commonly connected.

The active speaker circuit 21 includes a power amplifier circuit 6, a power supply circuit 8, and a speaker 5. The power amplifier circuit 6 includes an amplifier 6a and a standby switch 6b for controlling on / off of the amplifier 6a based on the control signal. The control signal input terminal of the standby switch 6b is connected to the control input terminal 21c via the resistance element 31. The power amplifier circuit 6 is provided with a Vcc terminal, a power ground terminal, and a pre-ground terminal (not shown).
The power ground terminal is connected to the (−) terminal of the power supply circuit 8, which is the ground of the active speaker circuit 21. The pre-ground terminal is separated from the power ground terminal in the power amplifier circuit 6 and is not commonly connected, but is connected to the pre-ground terminal 21b. The speaker 5 is an output terminal of the amplifier 6a and the power supply circuit 8 which is a power ground of the active speaker circuit 21.
, The speaker 5 and the active speaker circuit 21 are integrally assembled.
Alternatively, the speaker 5 may be connected to the active speaker circuit 21 separately.

The active speaker circuit 21 further includes a bias circuit 33 for applying the Vcc voltage of the power supply circuit 8 to the pre-ground terminal of the power amplifier circuit 6 via a resistor 32. A collector / emitter of a switching transistor 34 is connected between the standby switch side of the resistance element 31 and the ground of the active speaker circuit 21 which is a (-) terminal of the power supply circuit 8, and the base of the transistor 34 is a resistance element. It is connected to the pre-ground terminal 21b of the power amplifier circuit 6 via 35. In this embodiment, the transistor 34 and the resistance elements 32 and 35 constitute control signal control means for invalidating and validating the power control signal supplied to the standby switch 6.

Next, the operation will be described. When the set body 1 and the active speaker circuit 21 are connected by the connection cord 7 and the input connection cord 3, the base of the transistor 34 is connected to the base of the set body 1 via the resistor 35 and the input connection cord 3. The transistor 34 is kept off because the pre-ground terminal 21b is connected to the ground and the pre-ground terminal 21b is at the ground potential. As a result, the control signal supplied from the set body 1 to the control input terminal 21c is supplied to the standby switch 6b via the resistance element 31, and the standby switch 6b is connected to the amplifier 6a.
Turn on the power. The amplifier 6a amplifies the speaker signal supplied from the speaker signal input terminal 21a and drives the speaker 5.

On the other hand, if the input connection cord 3 is not connected while the set body 1 and the active speaker circuit 21 are connected by the connection cord 7, the input side of the amplifier 6a of the active speaker circuit 21 The pre-ground terminal 21b enters a floating state. When the pre-ground terminal 21b is in a floating state, the pre-ground terminal 21b is connected to the Vcc side of the power supply circuit 8 via the bias circuit 33, and this Vcc voltage is applied.
The potential is turned on, and the transistor 34 is turned on. As a result, the input terminal of the standby switch 6 is connected to the transistor 3
4, the control signal supplied from the set body 1 to the control input terminal 21c is not supplied to the standby switch 6b.

Therefore, even if the control signal is supplied from the set body 1 to the active speaker circuit 21 in a state where the input connection cord 3 is not connected between the set body 1 and the active speaker circuit 21, the control signal Becomes invalid, the standby switch 6b is not operated, and the power is not turned on to the amplifier 6a. Therefore, even when the input side of the amplifier 6a of the power amplifier circuit 6 is in a floating state, there is an effect that generation of noise when power is turned on can be prevented.

In the embodiment described above, the transistor 34 is connected between the standby switch side of the resistance element 31 and the ground of the active speaker circuit 21 which is the (-) terminal of the power supply circuit 8, and the transistor 34 By connecting the base to the pre-ground terminal of the power amplifier circuit 6 via the resistance element 35, the input connection cord 3
Has been described in which the transistor 34 is turned on in a state where is not connected, and the control signal supplied from the set body 1 to the active speaker circuit 21 is invalidated. A switch circuit is inserted in series between the switch circuit 31 and the standby switch 6b to turn on / off the switch circuit.
The turning off may be controlled by the potential of the pre-ground terminal of the power amplifier circuit 6, and a pull-down resistor may be connected between the control terminal side of the standby switch 6b and the ground of the active speaker circuit 21.

In such a configuration, the switch circuit is controlled to be turned off when the potential of the pre-ground terminal of the power amplifier circuit 6 is at the Vcc level. The control signal supplied to the switch 6b is cut off and invalidated. When the switch circuit is turned off, the control terminal side of the standby switch 6b is fixed to the reference potential of the power supply circuit 8, which is the ground of the active speaker circuit 21, by the pull-down resistor. Therefore, the same effect as in the above embodiment can be expected.

[0016]

As described above, according to the present invention, a set main body for transmitting an audio signal and a control signal for power control is detachably connected to the set main body via an input connection cord and a signal connection cord. A power amplifier for amplifying an audio signal supplied through the input connection cord, a speaker driven by the output of the power amplifier, a driving power supply for the speaker and the power amplifier, and a signal connection cord from the set body. An active speaker circuit comprising an active speaker having a power-on standby switch operated by a power control signal, wherein the power amplifier generated when the set main body and the active speaker are not connected by the input connection cord. Input side pre-ground terminal floating It was constructed in which a control signal controlling means for disabling the power control control signal supplied to the standby switch when detecting.
Therefore, it is possible to prevent generation of noise output when the power of the amplifier of the power amplifier circuit is turned on when the amplifier input side of the power amplifier circuit is in a floating state.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of an active speaker circuit of the present invention.

FIG. 2 is a circuit diagram showing a conventional active speaker circuit.

[Explanation of symbols]

1 set body side, 6 power amplifier circuit, 6a
... Amplifier, 6b ... Standby switch (control circuit),
8 power supply circuit, 21 active speaker circuit, 2
1a: Audio signal input terminal, 21b: PreGND,
21c ... control terminal, 21d ... Vcc connection terminal (power supply terminal), 21e ... ground connection terminal (power supply terminal), 3
3. Bias circuit (resistance circuit).

Claims (3)

[Claims] 1. A set body for transmitting an audio signal and a control signal for power control, and is detachably connected to the set body via an input connection cord and a signal connection cord, and supplied through the input connection cord. A power amplifier for amplifying an audio signal, a speaker driven by an output signal of the power amplifier, a driving power source for the speaker and the power amplifier, and a power control signal from the set body via a signal connection cord. An active speaker circuit including an active speaker having a power-on standby switch, wherein the input connection cord causes a floating state of an input-side preground terminal of the power amplifier to be generated when the set main body and the active speaker are not connected. When it is detected, Provided control signal controlling means for disabling the power control control signal supplied to the switch, the active speaker circuit, characterized in that. 2. The control signal control means turns off when the set main body and the active speaker are connected by the input connection cord and supplies a control signal for power control to the standby switch. 2. The active speaker circuit according to claim 1, further comprising a switching element that is turned on when the set main body and the active speaker are not connected to each other and cuts off a power control control signal to the standby switch. 3. The active speaker circuit according to claim 1, wherein the switching element is turned on by the power supply voltage when the set main body and the active speaker are not connected by the input connection cord.