JP2785559B2 - Muting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muting device for use in a vehicle-mounted audio device in which a cassette deck and a radio receiver are integrated.

2. Description of the Related Art Conventionally, an audio device or the like is provided with a muting circuit, and muting is applied for a short time at the time of mode switching or the like, thereby preventing generation of annoying noise sound. Further, conventionally, there has been proposed a device for gradually releasing the muting when the power is turned on to gradually increase the volume, thereby preventing a sudden increase in the volume when the power is turned on.

However, in the above-mentioned conventional example, separate muting circuits are required to perform muting for a short time at the time of mode switching and gradually release muting at the time of power-on. There is a problem that the circuit configuration becomes complicated and the cost increases. The present invention solves the above conventional problems
Power switch with a simple circuit configuration.
Muting quickly in a short time when key-on other than
As well as muting gradually when the power is turned on
An excellent muting device that can cancel
It is intended to provide.

In order to achieve the above object, the present invention provides a key determining means for determining a key input operated from a plurality of key input means, and a key determining means.
When the first muting is determined by the
Key control means, and the key determination means
When the key-on other than is determined, the second muting system
Control signal generating means for generating a control signal;
Direct from the power supply according to the signal level of the
A first method for making the supplied DC voltage conductive or nonconductive
Driving means and a signal of the second muting control signal
Makes the DC voltage conductive or non-conductive according to the level
The second drive means having a large time constant and the first drive means.
The above DC voltage is charged when the driving means is conducting and discharged when it is not conducting.
Charging / discharging means for performing
All of which have a small time constant when the second driving means is conducting.
A second charge / discharge for charging the DC voltage and discharging when the DC voltage is turned off
Means, and the charge and discharge voltage of the first and second charge and discharge means are
Muted to signal transmission line directly applied to base
And a common muting transistor
When the power switch is turned on, the muting state is gradually reduced.
At the time of key-on except for the power switch.
It is characterized in that it is applied to the shooting .

According to the present invention, there is provided a driving system in which different muting control signals are generated according to a key input operated from a plurality of key input means, and the muting control signal is applied. The charging and discharging of the charging / discharging means is controlled through the means, and the muting is performed with the response characteristic corresponding to the key input in the same muting circuit by the charging / discharging voltage of the charging / discharging means. Is controlled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. This embodiment is a muting device used in a vehicle-mounted audio device in which a cassette deck and a radio receiver are integrated. In FIG. 1, reference numeral 1 denotes a left signal transmission line through which a left channel audio signal is transmitted;
Are the right signal transmission lines for transmitting the right channel signal, 3
Is a transistor whose emitter and collector are connected to the left signal transmission line 1 and the ground, respectively, and 4 is a transistor whose emitter and collector are connected to the right signal transmission line 2 and the ground, respectively.
The muting of the audio signal transmitted through the left signal transmission line 1 and the right signal transmission line 2 is performed by controlling the base voltage. Reference numeral 5 denotes a key matrix circuit provided in the in-vehicle audio device. The key matrix circuit 5 includes various keys. 6
Reference numeral denotes a power switch of the vehicle-mounted audio device. A power supply voltage is supplied to each circuit such as a microcomputer and an amplifier circuit via the power switch 6. Reference numeral 7 denotes a control circuit composed of a microcomputer or the like. The control circuit 7 includes a key determination means 8 for determining whether the keys of the key matrix circuit 5 and the power switch 6 are on or off, The muting control signal generator 9 generates a different muting control signal according to the determination result. The control circuit 7 includes a PLL circuit for FM and AM radios, a deck control signal generating means for outputting various control signals to the cassette deck, and the like. The microcomputer is supplied with power directly from the power supply without passing through the power switch 6. Reference numerals 10 and 11 are output terminals from which muting control signals are output. Reference numeral 12 denotes a muting signal generation circuit that generates a muting signal in accordance with a signal output from the muting control signal generation means 9. The muting signal output from the muting signal generation circuit 12 includes resistors 13 and 14. Is applied to the bases of the transistors 3 and 4 constituting the muting circuit. Next, the muting signal generation circuit 12
Will be described. Reference numerals 15 and 16 denote output terminals 10 and 11 of the muting control signal generating means 9 as bases.
And the transistor 1
A predetermined DC voltage (5 V) is applied to the emitters 5 and 16. The collectors of the transistors 15 and 16 are connected to the anodes of diodes 19 and 20 via resistors 17 and 18, respectively. 21 and 22 are capacitors connected between the anodes of the diodes 19 and 20 and the ground;
Reference numeral 4 denotes a resistor connected between the anodes of the diodes 19 and 20 and the ground. The capacitor 21 and the resistor 23 and the capacitor 22 and the resistor 24 form charge / discharge circuits 25 and 26, respectively. The time constant of one charge / discharge circuit 25 is larger than the time constant of the other charge / discharge circuit 26. Transistors 15 and 16 have a low level signal (L) at the base.
Becomes conductive when is applied. Therefore, the transistor 15,
The current flows through the capacitor 2 through the 16 emitters and collectors.
The capacitors 21 and 22 are supplied to the capacitors 21 and 22 and charged. When a high level signal (H) is applied to the bases of the transistors 15 and 16, the transistors 15 and 16 become non-conductive, so that the charges charged in the capacitors 21 and 22 are transferred to the resistors 23 and 24.
Is discharged through. The charging voltage of the capacitors 21 and 22 is applied to the transistors 3 and 3 via the diodes 19 and 20.
The muting control is applied to the base of No. 4 to perform muting control. Next, the operation of the above embodiment will be described with reference to FIGS. In this embodiment, the muting is gradually released when the power switch 6 of the on-vehicle audio device is turned on, and the muting is instantaneously performed when the mode is switched, for example, when the band is switched from FM broadcasting to AM broadcasting. Is what you do. FIG. 2A shows the on / off state of the power switch 6. When the power switch 6 is turned on at time t1, the power switch is determined to be on by the key determination means 8, and the muting control signal generating circuit 9 outputs the time t2 after a predetermined time T has elapsed from time t1, as shown in FIG. Is output. This muting control signal is output terminal 1
0 is applied to the base of the transistor 15, and the transistor 15 is turned off at time t2. When the transistor 15 is on, a direct current is supplied to the capacitor 21 through the transistor 15 and the capacitor 2
1 is charged. Since the charging voltage of the capacitor 21 is applied to the bases of the transistors 3 and 4 via the diode 19, the transistors 3 and 4 are turned on, and the signal transmission lines 1 and 2 are set to the ground potential, so that they are muted. Has become. Here, at time t2, a high-level signal (H) is applied to the base of the transistor 15, so that the transistor 15 is turned off. When the transistor 15 becomes non-conductive, the electric charge charged in the capacitor 21 is discharged through the resistor 23, so that the voltage applied to the bases of the transistors 3 and 4 becomes the time t2 as shown in FIG. Then, the muting state is gradually released. Therefore, at time t1, the power switch 6
The sound volume gradually increases after a predetermined time T has elapsed after the power is turned on, and is prevented from suddenly increasing when the power switch is turned on. On the other hand, when a predetermined key of the key matrix circuit 5, for example, a key for switching a band is operated in a state where the in-vehicle audio device is operating, the operation of the band switching key is determined by the key determination means 8, and the muting control is performed. The muting control signal shown in FIG. 3A is output from the signal generating means 9 from the output terminal 11 and applied to the base of the transistor 16. When the muting control signal shown in FIG. 3A is applied to the base of the transistor 16, the transistor 16 becomes conductive at time t3 and charges the capacitor 22, and becomes nonconductive at time t4 to discharge the charge of the capacitor 22. I do. FIG. 3 (B) shows a voltage waveform applied to the bases of the transistors 3 and 4, and when the base voltage of the transistors 3 and 4 exceeds a predetermined value, the transistors 3 and 4
Are turned on and muting is applied for a predetermined period. When the band switching key or the like is operated in this manner, the charge / discharge circuit 26 having a small time constant is used.
A rapid muting operation can be performed. As described above, in the above embodiment, when the power switch is turned on, the muting state can be gradually released, and the volume can be gradually increased. In addition, when a bunt switching key or the like is operated, a short-time muting operation can be performed quickly to obtain an operation feeling with a quick response.

According to the present invention, as is apparent from the above embodiment, different muting control signals are generated in accordance with a key input operated from a plurality of key input means. The charging / discharging of the charging / discharging means is controlled through the applied driving means.
Muting is controlled by the same muting circuit with the response characteristic according to the key input by the charging / discharging voltage.When the power is turned on, muting is gradually released, and the volume can be gradually increased, Muting can be performed quickly when the reception band is switched.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a muting device according to an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is a diagram illustrating the operation of the embodiment.

[Explanation of symbols]

 1, 2 signal transmission line 3, 4 transistor 5 key matrix circuit 6 power switch 7 control circuit 8 key determination means 9 muting control signal generation means 10, 11 output terminal 12 muting signal generation circuit 13, 14 resistor 15, 16 transistor 17, 18 Resistance 19, 20 Diode 21, 22 Capacitor 23, 24 Resistance 25, 26 Charge / discharge circuit

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03F 1/00-3/00 H03G 1/00-5/00

Claims (1)

(57) [Claims] A key determining means for determining a key input operated from a plurality of key input means;
When the first muting is determined by the
Key control means, and the key determination means
When the key-on other than is determined, the second muting system
Control signal generating means for generating a control signal;
Direct from the power supply according to the signal level of the
A first method for making the supplied DC voltage conductive or nonconductive
Driving means and a signal of the second muting control signal
Makes the DC voltage conductive or non-conductive according to the level
The second drive means having a large time constant and the first drive means.
The above DC voltage is charged when the driving means is conducting and discharged when it is not conducting.
Charging / discharging means for performing
All of which have a small time constant when the second driving means is conducting.
A second charge / discharge for charging the DC voltage and discharging when the DC voltage is turned off
Means, and the charge and discharge voltage of the first and second charge and discharge means are
Muted to signal transmission line directly applied to base
And a common muting transistor
When the power switch is turned on, the muting state is gradually reduced.
At the time of key-on except for the power switch.
Muting device characterized by applying muting.