JPH09102751A - Voice muting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To immediately perform the voice mute output via a mute output pin of a microcomputer when a main power switch is turned off. SOLUTION: When a main power switch 6 is turned off, the switch 6 is set at its OFF side. Thus the potential of a microcomputer switch detection point A is connected to a reference potential point GND via a resistor R2 and dropped down to 0V from 5V of an ordinary level. Then the base potential of a transistor TR Q1 is dropped via a resistor R1 and the TR Q1 is turned on. Then the charged electric charge of a capacitor C1 is outputted to a microcomputer mute output point B as a voice muting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device having a main power switch and an audio mute circuit at power on / off,
Particularly, the present invention relates to an audio mute circuit capable of preventing an abnormal sound generated before the mute of the microcomputer when the main power switch is turned off.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional audio mute circuit. In the audio mute circuit in FIG.
The power plug 4 for inputting the AC power 3 is connected to the input side of the power circuit 2 and one end of the relay switch 5, and the other end of the relay switch 5 is connected to the input side of the power circuit 12. The output side of the power supply circuit 2 is the microcomputer power supply 1
Of the main power supply switch 6 and the SW2 side terminal a2 of the main power supply switch 6
Is connected to the terminal a1 on the SW1 side and the power supply pin 7 of the microcomputer 10. The SW1-side terminal c1 of the main power switch 6 is connected to the switch detection pin 8 of the microcomputer 10, and the SW2-side terminal c2 of the main power switch 6 and the power pin 9 of the microcomputer 10 are for driving the relay switch 5 (not shown). It is connected to the coil.

Also, the mute output pin 1 of the microcomputer 10
1 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the collector of the transistor Q1 and the mute signal output terminal 13 which form the circuit (mute circuit) 20. The output side of the power supply circuit 12 is a capacitor C2 forming a circuit (mute circuit) 20.
Is connected to the anode of the diode D3 and one end of the resistor R1, and the other end of the resistor R1 is connected to the base of the transistor Q1. Further, the emitter of the transistor Q1 is connected to the reference potential point GND via the capacitor C1 and the cathode of the diode D1, and the anode of the diode D1 and the cathode of the diode D3 are both connected to the power supply pin 7 of the microcomputer 10. Has been done.

Next, the operation of the above circuit will be described. FIG. 4 is a diagram showing a procedure of audio mute when the main power supply is turned off in the conventional audio mute circuit. FIG. 5 is a timing chart of the conventional audio mute circuit.

When the power is turned on / off by the remote controller, the power relay switch 5 is on / off controlled by a control signal from the power pin 9 of the microcomputer 10.

On the other hand, in the case of turning on / off the main power supply switch 6, as shown in step 1 of FIG. 4, when the main power supply switch 6 is turned off (the terminals c1 and b1 of SW1 are connected and the terminal of SW2 is connected). When c2 and b2 are connected), FIG.
As shown in (a), the switch detection pin 8 of the microcomputer 10
The electric potential at the point C drops from 5V to 0V at the position (A) in the figure. As a result, the microcomputer 10 detects that the main power switch 6 is turned off, controls the relay switch 5 by the control signal from the power pin 9 of the microcomputer 10, and supplies the AC power 3 to the power circuit 12. Stop. At this time, SW2 of the main power switch 6 is used in consideration of the malfunction of the microcomputer 10, and the mechanical switch is also used for control. The switch detection pin 8 of the microcomputer 10 is a port for processing the data of the microcomputer 10 in the off mode when the main power switch 6 is off, and the mute output pin 11 of the microcomputer 10 is also in the off mode.

In this way, when the main power switch 6 is turned off, the voltage at the point C of the switch detection pin 8 of the microcomputer 10 drops, and the microcomputer 10 judges that the switch is off,
A mute signal is output from the mute output pin 11 of the microcomputer 10. By the way, as shown in FIG. 5B, it takes time for chattering prevention until the microcomputer 10 outputs mute from the mute output pin 11, and there is a delay due to the timing of data reading by the microcomputer 10 itself. , A delay time (between (a) to (d) in FIG. 5) 31 of 50 to 100 ms after switch detection is generated. During this period, when the audio power supply circuit falls at the timing shown in (c) of FIG. 5C, the offset causes
At this falling timing (c), an abnormal sound 32 is generated as shown in FIG. 5 (d).

Therefore, conventionally, an audio mute circuit 20 composed of Q1 is used for a power supply circuit 12 (for example, 12V) having a quick off response when the power is turned off, and as shown in the procedure 2 of FIG. The mute signal output prevents the abnormal sound 32 generated because the audio system power supply is not in time for the power supply to fall. That is, in FIG. 3, when the main power switch 6 is turned off, the relay switch 5 is turned off and each power source of the power circuit 12 (12V) is turned off. Power 12
When the V line falls, the potential at point E drops and the base potential of the transistor Q1 drops. On the other hand, the power supply circuit 1
2 (12V) uses a power supply circuit with a quick off response, the potential at the point E is as shown in FIG. 5 (e), as shown in FIG. 5 (a). The potential reduction starts at the timing (a) when the potential at the point C decreases.

When the potential at the point E decreases and the base potential of the transistor Q1 decreases, the base potential of the transistor Q1 is 5 because the capacitor C1 is charged through the diode D1.
When VV _f (D1) -V _BE (Q1) or less, the transistor Q1 is turned on, and as shown in FIG. 5 (f), the charge of the capacitor C1 is output from the collector of Q1 as a mute signal at the timing of (a). (Q1 mute output). Incidentally, the diode D1
Is the 5V load isolation, and the diode D2 is the microcomputer 10
This is for preventing backflow to the mute output pin 11.

However, with this method, it is necessary to search for or design a power supply device with a quick power-off response every time the power supply circuit configuration is changed, and there is a problem that the design margin is small.

[0011]

As described above, the mute output pin 1 of the microcomputer 10 when the main power switch 6 is off.
In order to prevent the abnormal sound generated before the output of the mute signal output from No. 1, the mute signal output from the mute circuit 20 must be obtained by using the power supply device having a quick power off response. In order to obtain a fast mute signal output, a power supply with a quick power-off response is required, and therefore there is a problem (defect) that it is necessary to select or design a power supply with a fast power-off response for each chassis.

In order to solve such a problem, the present invention provides an audio mute circuit capable of obtaining an audio mute output from the mute output pin 11 of the microcomputer 10 at the same time when the main power switch 6 is turned off. The purpose is.

[0013]

An audio mute circuit according to the present invention operates in conjunction with a main power switch for turning on and off a power supply path from a DC power supply,
In the ON state, one input terminal is connected to the DC power supply,
In the off state, the other input end is connected to the reference potential point via the first resistor, and the second switch whose potential at the output end is switched according to the on / off state of the main power switch and the anode are A diode connected to the output terminal of the power switch, a storage means connected between the cathode side of the diode and the reference potential point, and holding the voltage when the second switch is turned on, and an emitter Is connected to the cathode of the diode and the base is connected to the second
And a transistor which is connected to the output terminal of the second switch via the resistor and which is turned on when the main power switch is turned off and outputs the voltage of the storage means to the collector.

An audio mute circuit according to a second aspect of the present invention is the audio mute circuit according to the first aspect,
It is characterized in that the storage means discharges at the same time when the transistor is turned on and outputs a mute signal from the collector of the transistor.

According to the first or second aspect of the present invention, the audio mute circuit is configured by detecting the main power switch of the microcomputer (transition to the off state). Since the audio mute signal output is obtained at the same time when the main power switch is turned off, it is possible to prevent the generation of an abnormal sound when the main power switch is turned off.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of an audio mute circuit of the present invention.

FIG. 2 is a timing chart of the audio mute circuit of the present invention.

In the audio mute circuit shown in FIG.
The power plug 4 for inputting the AC power 3 is connected to the input side of the power circuit 2 and one end of the relay switch 5, and the other end of the relay switch 5 is connected to the input side of the power circuit 15. The output side of the power supply circuit 2 is the microcomputer power supply 1
Of the main power supply switch 6 and the SW2 side terminal a2 of the main power supply switch 6
Is connected to the terminal a1 on the SW1 side and the power supply pin 7 of the microcomputer 10. The SW1-side terminal c1 of the main power switch 6 is connected to the switch detection pin 8 of the microcomputer 10, and the SW2-side terminal c2 of the main power switch 6 and the power pin 9 of the microcomputer 10 are for driving the relay switch 5 (not shown). It is connected to the coil. Further, the SW1-side terminal b1 of the main power switch 6 is connected to the reference potential point GND via the resistor R2.

Further, the mute output pin 1 of the microcomputer 10
1 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the collector of the transistor Q1 that constitutes the circuit (mute circuit) 21 and the mute signal output terminal 13. And the transistor Q1
Is connected to the reference potential point GND via the capacitor C1.
Is connected to the cathode of the diode D1, and the anode of the diode D1 is connected to the base of the transistor Q1 via the resistor R1 and to the switch detection pin 8 of the microcomputer 10.

Next, the operation of the above circuit will be described. The difference between the audio mute circuit of the present invention and the conventional audio mute circuit is that the microcomputer 10 has an audio mute generation circuit 21 composed of a transistor Q1 at a switch output point A for detecting the state of the main power switch 6. Connect the resistor R to the SW1 terminal b1 of the main power switch 6.
2 is added to determine the off response of the switch detection pin of the microcomputer 10 and the base current of Q1.

First, when the normal remote controller power is turned on / off, an audio mute signal is output from the mute output pin 11 of the microcomputer 10 to the mute signal output terminal 13 via the diode D2 regardless of the detection of the main power switch.

Next, when the main power switch 6 is turned off, the main power switch 6 in FIG. 1 is turned off.
Then, the potential of the microcomputer switch detection point A shown in FIG. 2A is connected to the reference potential point GND via the resistor R2, and drops from the normal 5V to 0V. As a result, when the base potential of the transistor Q1 decreases via the resistor R1, the transistor Q1 is turned on, and the charge charged in the capacitor C1 is output as an audio mute signal to the microcomputer mute output point B shown in FIG. 2B. ,
It is output to the mute signal output terminal 13.

At this time, since the mute signal is not output from the mute output pin 11 of the microcomputer 10, that is, since the potential is 0 V, the diode D2 from the output of the mute circuit 21 to the mute output pin 11 of the microcomputer, It acts as a backflow prevention element (diode). Therefore, at the same time when the main power switch 6 is turned off, the audio mute signal is output from the Q1 to the mute signal output terminal 13.

By the way, the abnormal sound 32 is generated at the timing (ki) when the power supply of the audio system is turned off as shown in FIG. 2C, but the power supply of the audio system is turned off. As is apparent from FIG. 2, the main power switch 6 is turned off at the timing of FIG. 2C, the power relay switch 5 is turned off, and the power supply circuit 15 is turned off.
As a result, at the timing when the power supply for the audio system falls (ki), the audio mute signal is output to the microcomputer mute output point B as shown in FIG. As is apparent from the speaker output signal (voltage) shown, the abnormal sound 32 does not occur (can be prevented). The resistor R2 used between the terminal b1 of SW1 of the main power switch 6 and the reference potential point GND has the same switch SW1 of the main power switch 6 when the discharge time constant of the switch detection line is long. , To instantly set the base potential of the transistor Q1 to a low level to turn on the transistor Q1.

[0025]

As described above, according to the present invention, the microcomputer uses the switch output terminal for detecting the state of the main power switch and the audio mute circuit composed of the transistor Q1. As described above, by changing the timing of the abnormal sound with the power load,
It is not necessary to create a power supply with a quick power-off response for the mute circuit, and it is possible to provide an audio mute circuit that effectively and reliably prevents abnormal sound when the main power supply is off.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of an embodiment of an audio mute circuit of the present invention.

FIG. 2 is a timing chart of the audio mute circuit of the present invention.

FIG. 3 is a circuit diagram showing a conventional audio mute circuit.

FIG. 4 is a diagram showing a procedure of audio mute when a main power supply is turned off in a conventional audio mute circuit.

FIG. 5 is a timing chart of a conventional audio mute circuit.

[Explanation of symbols]

 1 ... Microcomputer power supply 2 ... Power supply circuit 3 ... AC power supply 4 ... Power supply plug 5 ... Relay switch 6 ... Main power supply switch 7 ... Vcc 8 ... Switch detection pin 9 ... Power pin 10 ... Microcomputer 11 ... Mute output pin 13 ... Mute signal output Terminal 15 ... Power supply circuit 21 ... Mute circuit Q1 ... Transistor D1, D2 ... Diode R1, R2 ... Resistor

Claims (2)

[Claims] 1. A direct current power supply, and a switch for turning on / off power supply from the direct current power supply, wherein a reference is provided via a first input terminal connected to the direct current power supply and a first resistor. Second connected to potential point
A power switch that has an input end and an output end, and that connects the output end to the first input end in an on state and connects the output end to the second input end in an off state, A diode having one end connected to the output end of the power switch and a capacitor connected between the other end of the diode and the reference potential point are included, and the capacitor is charged via the diode when the power switch is turned on. Power storage means, an emitter / collector path and a base, the emitter is connected to the other end of the diode, and the base is connected to the output terminal of the power switch via a second resistor, And a transistor configured to use the charging voltage of the storage means to conduct the emitter-collector path to obtain an audio mute signal at the collector. Audio muting circuit, characterized by comprising. 2. The audio mute circuit according to claim 1, wherein the storage means discharges rapidly at the same time when the transistor is turned on and outputs a mute signal from the collector of the transistor.