JPH08279740A - Audio system - Google Patents

Abstract

PURPOSE: To improve the quality of an audio system by controlling the length of muting time to be short corresponding to the state of a power source by judging the length of a period of power failure and switching the muting time. CONSTITUTION: When a voltage of 12V of a set power source 7 is decreased lower than 5V of a standby power source 8, a TrTR2 is turned on as well, a capacitor C1 is discharged through a resistor R4 , and the potential at a point A is turned to 0V. When the power source is turned on again, a reset voltage is generated, this reset voltage is canceled and an operating state is recovered; a microcomputer(MP) is programmed so as to check the voltage at the point A. Then, the point A is checked at a time t1 and when the voltage is found to be 0V at such a time, long-time power failure is judged. Then, muting for about one second is generated until the operation of a circuit is stabilized. Even when instantaneous power failure is quickly repeated, the time of power failure can be monitored. Next, when the period of power failure is extremely short, though the voltage 12V of the set power source 7 is slowly dropped, since the power source is restored again before the standby power source 8 reaches the voltage 5V, the MP 5 immediately cancels the muting operation of a circuit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device configured to control muting of audio output using a microcomputer.

[0002]

2. Description of the Related Art In a device which outputs an audio signal, for example, in order to prevent noise generated from a speaker when the power is turned on in the case of an audio device and when the receiving band is switched or the receiving frequency is switched in the case of a receiver. , Generally has a muting function. As a means for controlling this muting, a microcomputer is generally used, but when the power is turned on, a reset signal is applied to the microcomputer, so that in the case of a receiver, reception band switching and reception frequency For switching, the microcomputer detects a key operation and generates a muting signal. The muting signal is configured to generate a muting signal for a predetermined time each time the operation of switching the reception band or the reception frequency is performed when the reset signal is input.

[0003]

Therefore, even when the power supply is interrupted, a constant muting signal is always output when the reset signal is input to the microcomputer, which is equivalent to the time when the power is turned on for a long time. The sound was cut off for a long time, and the device was of poor quality.

[0004]

According to the present invention, there is provided means for determining the length of a power failure to control the muting time. The output of the determination circuit is configured to maintain a constant level voltage and become 0 V when the driving power source is lowered. When a reset signal is input to the microcomputer when the power is turned on, the voltage of this judgment circuit is checked. If the voltage is at a predetermined level, muting is immediately turned off. If it is 0 V, the muting signal is detected. Is configured to output.

[0005]

[Function] Since the length of power failure is checked when the power is turned on,
If the power is turned on after a short power failure, the muting can be released immediately and the audio signal can be output.

[0006]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an FM receiver having a microcomputer. The received signal is amplified by the front end 1, converted into an intermediate frequency, and input to the FM detection circuit 2. The detected signal is input to the MPX demodulation circuit 3, and L
It is separated into a channel signal and an R channel signal, and a stereo signal is output from the receiver through the muting circuit 4. The muting circuit 4 is controlled by the microcomputer 5.

On the other hand, as the power source of the receiver, the power switch 12 is turned on from the commercial power source through the power cord 13 and rectified to obtain a predetermined DC voltage.
2V is applied to the front end 1, the FM detection circuit 2, and the MPX demodulation circuit 3. The standby power source 8 applies 5V as an operating power source for the microcomputer 5 and can also be used for holding the memory of the microcomputer when the power source is turned off for a long time. It is configured. The 5V power supply 9 is used as a power supply other than the microcomputer 5. The reset circuit 10 is for supplying a reset voltage to the microcomputer 5 when the power is turned on.
The power failure determination circuit 11 is a circuit newly provided for monitoring the power source, and is controlled by 12 V of the set power source 7, the standby power source 8, and the microcomputer 5.

This operation will be described with reference to FIG. Figure 2 shows the power switch 1 of the receiver after a relatively long power outage
FIG. 3 is a timing chart when the power is turned on after the power is turned off for a long time according to 2. When 12V of the set power supply 7 becomes lower than 5V of the standby power supply 8, the transistor TR1 is turned on, the transistor TR2 is also turned on, the capacitor C1 is discharged through the resistor R4, and the voltage at the point A is 0V.
Becomes

It is assumed that the microcomputer is programmed to check the voltage at the point A when the power is turned on again to generate the reset voltage, the reset voltage is released, and the operating state is restored. Then, at time t1, point A is checked, and at this time the voltage is 0 V, so it is determined that there is a long-term power failure, and muting for about 1 second occurs until the circuit operation stabilizes. Further, after checking the point A at t1, the transistors TR3 and TR4 are turned on by the microcomputer 5 and the capacitor C1 is charged to enable the next power failure monitoring. Transistor TR by microcomputer 5
Since the time to turn ON 3 is only required to charge the capacitor C1, it can be set to a very short time. Therefore, it is possible to monitor the power failure time even if there are rapid repeated power failures.

Next, a case where the power failure is extremely short will be described with reference to FIG. At the time of a power failure, the voltage 12V of the set power supply 7 gradually drops, but since the power is restored again before the voltage 5V of the standby power supply 8 is reached, the transistor TR1 remains in the cutoff state, and therefore the potential at the point A also. It remains unchanged at 5V. At time t1 after the power is turned on, the microcomputer 5 checks the potential at the point A, but since it is 5 V, it is determined that there is an instantaneous power failure, and the muting operation of the muting circuit 4 can be immediately released.

[0011]

According to the present invention, it is possible to judge the length of a power failure,
Since the muting time is switched, a long interruption of sound does not occur at the momentary power failure, and the quality of the audio device is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an audio device according to the present invention.

FIG. 2 is a diagram showing a control timing of an embodiment of an audio device according to the present invention.

FIG. 3 is a diagram showing a control timing of an embodiment of an audio device according to the present invention.

[Explanation of symbols]

 1 Front End 2 FM Detection Circuit 3 MPX Demodulation Circuit 4 Muting Circuit 5 Microcomputer 6 PLL Circuit 7 Set Power Supply 8 Standby Power Supply 9 5V Power Supply 10 Reset Circuit 11 Power Failure Judgment Circuit 12 Power Switch 13 Power Cord

Claims (1)

[Claims] 1. An audio device in which muting of audio output is controlled by using a microcomputer, a power supply detecting means for detecting a power failure time length, and a power source based on the length of time detected by the power failure detecting means. An audio device comprising means for controlling the time from turning on to releasing the muting.