JPS5818337Y2 - Automatic volume adjustment device for audio equipment - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an automatic volume adjustment device for automobile audio equipment, etc.

In conventional car tape recorders, external noise,
For example, engine noise during high-speed driving, noise in tunnels, etc.
It was necessary to adjust the volume by operating the volume knob each time the external noise changed.

The present invention attempts to detect external noise inside a car and adjust the volume according to its output.The present invention will be explained below with reference to the drawings.

In the figure, number 1 is an external noise collector (microphone), number 2 is an amplifier,
3 is a volume, 4 is a noise rectifier circuit, 5 is an output terminal of the sound collector output circuit 18, 6 is a reproduction magnetic head which is an audio signal source, 7 is an amplifier for output amplification of the audio signal source, 8 is a branch point, l″!Volume adjustment circuit, 10 is an audio amplification amplifier, 11
12 is a speaker, 12 is an amplifier, 13 is a volume adjustment circuit cancel switch, 14 is a junction, 15 is a power switch for the amplifier 2, and 16.17 is an input/output terminal of the volume adjustment circuit 9.

The sound collected by the sound collector 1 is amplified by the amplifier 2, controlled by the volume 3, and then converted to DC by the rectifier circuit 4, and a DC output appears at the output terminal 5 of the sound collector output circuit 18.

This DC output increases or decreases depending on external noise, and the volume adjustment circuit 9 is appropriately controlled.

The operating point of the circuit is set according to the magnitude of the output voltage of the 9+2 output terminal 5, that is, the magnitude of external noise, so that the circuit can be activated at any time, and the sound collector 1 is installed inside the vehicle.

Next, the output signal of the head 6 is amplified by an amplifier 7, passes through 8 and i, is amplified by an amplifier 10, and is amplified by a speaker 11.
to drive.

On the other hand, the signal amplified by the amplifier 7 and branched from the amplifier 8 passes through the amplifier 12 and is applied to the input terminal 14 of the amplifier 2 at a position opposite to the input signal from the sound collector 1; It acts to cancel the input signal from the

13 is a volume adjustment circuit 1p cancel switch;
This is linked to the Orh off of the power switch 15 of the amplifier 2.

Next, the volume adjustment circuit 9 will be explained.

This circuit uses diode switching and turns on diodes D2 to D5 depending on the magnitude of the voltage at the output terminal 5.

The volume is adjusted by turning it off.

That is, when the sum of the voltage at the output terminal 5 and the peak voltage of the AC input signal from the amplifier 7 exceeds the biased voltage, the diodes D2 to D5, which are appropriately biased, are turned on and the input signal is turned on. passes.

By connecting multiple sets of such diode switching circuits in parallel and setting the switching bias of the diodes to various values, each diode performs 0nXoff operation as the voltage at the output terminal 5 changes. .

Furthermore, by providing a resistance difference between R8 to R1□, the output increases or decreases as the number of parallel circuits in which the diodes are in the on state increases or decreases.

For example, as the external noise increases and the voltage at the output terminal 5 increases, the number of parallel circuits in which diodes are turned on is increased, and the impedance of 9 is decreased to increase the volume.

The output of the output terminal 5 is controlled by the volume adjustment circuit 1, and is set by the time constants of C3 and R4 so that it changes slowly in response to changes in external noise. In contrast, the circuit 90 is not operated, and the output signal of the circuit 9 is gradually increased or decreased as external noise changes.

The constants of each circuit element in the drawings are as follows.

R1-R2* R3sR5t R6e R8? R20
is 10KJ7R4, R□2 is 50KQz R7tRts
is 500, Q.

R8 is 20KQ, RIO is 40KQXR□□ is 80KQ
.

R□3 'R14tR15*R17tR19 is 100, 2XR16 is 200Ω, C1, C2, C4, C6,
C7, C8, C9 are 3.2 l? , C3 is 4μFXC5
is 0.1μFXC1o is lOμF0 Furthermore, in this embodiment, an example in which a playback head is used as an audio signal source has been described, but the present invention is not limited to such an embodiment, and may be applied to a tuner of a radio receiver. Needless to say.

As shown below, this invention automatically adjusts the volume according to the magnitude of external noise, so there is no need to adjust the volume every time the external noise changes, and it is especially suitable for use in automotive audio equipment. Extremely effective.

Also, power & ON to the amplifier that constitutes the sound collector output circuit.
We have provided a power switch for FF control and a volume adjustment circuit cancel switch that works in conjunction with this power switch and shorts between the input and output terminals of the volume adjustment circuit when the power switch is turned off, so when a beat occurs, etc. By operating these switches, it is possible to prevent the occurrence of beats, etc.

Further, since the volume adjustment circuit is composed of a plurality of sets of diodes and bias circuits for each of the diodes, it has various advantages such as easy integration into an IC, easy to miniaturize the circuit, and low power consumption.

[Brief explanation of drawings]

The drawing is a circuit diagram of a main part of an automatic volume adjustment device for audio equipment according to the present invention. 1...external noise collector, 5...output terminal, 6...playback head, I...audio signal source output amplification amplifier,''! ...Volume adjustment circuit, 1
0... Amplifier for audio amplification, 12... Amplifier for phase inversion, 18... Sound collector output circuit.

Claims (1)

[Scope of utility model registration request] an external noise collector, a sound collector output circuit that amplifies and rectifies the output of the sound collector and provides a time constant, an audio signal source output amplification circuit that amplifies the output of the audio signal source, and the audio signal source output. a circuit for inverting the phase of the output of the amplifier circuit and combining it with the output of the sound collector; a volume adjustment circuit comprising a plurality of sets of switching diodes and bias circuits for each of the diodes; and amplifying the output of the volume adjustment circuit. an audio amplification circuit;
Turn on the power to the amplifier that constitutes the sound collector output circuit,
The sound collector output circuit is equipped with a power switch for OFF control, and a volume adjustment circuit cancel switch that operates in conjunction with the power switch and shorts between the input and output terminals of the volume adjustment circuit when the power switch is turned OFF. An automatic volume adjustment device for audio equipment, wherein an output and an output of the audio signal source output amplification circuit are respectively applied to the volume adjustment circuit.