JPH087694Y2 - Muting control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application This invention relates to a muting control circuit, and more particularly to a muting control circuit for an audio device equipped with a microcomputer.

(B) Conventional Technology Conventionally, as shown in FIG. 2, it has a plurality of output terminals,
For example, a muting control circuit has been provided which performs a desired muting operation by selectively using output terminals according to a program of a microcomputer according to detection of a decrease in power supply voltage or a plurality of other states.

The conventional muting control circuit shown in FIG. 2 will be described below.

The terminal 12 of the microcomputer 11 is an input port, to which a voltage detection circuit for detecting a decrease in the power supply voltage VCC of the analog power supply is connected. The cathode side of the Zener diode D11 is connected to the power supply voltage VCC, the anode side is connected to the base of the transistor Q11 via the resistor R11, and the resistor R12 is connected between the base of the transistor Q11 and the ground. The emitter of the transistor Q11 is grounded, and the collector on the output side is directly connected to the base of the transistor Q12. The collector of the transistor Q12 is the output of the voltage detection circuit and is connected to the input port 12 of the microcomputer.

The terminals 13 and 14 of the microcomputer 11 are output ports for signals input to the muting control circuit to operate the muting control circuit (“muting control signal”), and are connected to the input terminals of the muting control circuit, respectively. There is. That is, the output port 13 is connected to the base of the transistor Q13 of the switch circuit via the resistor R14, and the output port 14 is connected to the base of the transistor Q14 of the switch circuit like the transistor Q13 via the resistor R15.

The VDD power supply is applied to the bases of both transistors Q13 and Q14 of the switch circuit by resistors R16 and R17 and is in a pull-up state, and the emitter sides of both transistors Q13 and Q14 are connected to the VDD power supply.

The collector of the transistor Q14 is the first output terminal MO11 of the muting control circuit, and the collector of the transistor Q13 is the second output terminal MO of the muting control circuit.
Twelve.

The operation of the muting control circuit of FIG. 2 configured as above will be described below.

When the VCC voltage, which is the input of the voltage detection circuit, is higher than the specified value, transistor Q11 turns on and transistor Q12 also turns on.
VDD power supply level is output. That is, the output of the voltage detection circuit becomes "H". When the output of the voltage detection circuit becomes "H", the output is input to the input port 12 of the microcomputer 11 and the program outputs "H" level as a muting control signal to the output port 14, for example. In this case, the transistor Q14 is turned off, so that the first output terminal MO11 of the muting control circuit becomes "L" level and is output from the output terminal of the muting control circuit to perform muting of the audio signal or the like. No signal (“muting signal”) is output.

Conversely, when the VCC voltage that is the input of the voltage detection circuit is equal to or lower than the specified value, the transistor Q11 is turned off and the transistor Q12 is also turned off, so that the ground level is output to the collector of the transistor Q12. That is, the output of the voltage detection circuit becomes "L". When the output of the voltage detection circuit becomes “L”, the output is input to the input port of the microcomputer 11.
12 input and by the program, for example output port
"L" level is output to 14 as a muting control signal. In this case, the transistor Q14 is turned on and the first output terminal MO11 of the muting control circuit becomes "H" level to output the muting signal.

Further, the microcomputer 11 is programmed so as to determine the state in which the muting operation should be performed by another means not shown and output a muting control signal. When the muting operation is performed by such a program, for example, by setting the output port 13 to the "L" level, the second output terminal MO12 of the muting control circuit is set to the "H" level and the muting signal is output. . In addition, "H" or "L" is applied to the output port 13.
The operation when is output is the same as that of the output port 14.

Muting of the audio device is performed by the muting signal output from the output terminal MO11 or MO12 of the above two muting control circuits. The output of the output port 14 may depend on the voltage detection circuit depending on the setting of the microcomputer program. The signal and the detection signal by other means not shown are ORed to form a control signal for the muting signal output of MO11, and not only the control by voltage detection but also the detection by other means not shown
It is also possible to perform muting by the output from the output terminal MO11 of.

(C) Problems to be solved by the invention However, in any of the above-described conventional muting control circuits, control is performed through the program operation of the microcomputer in any case. The number of I / O ports required for muting control increases, and there is a delay that cannot be ignored until the muting control signal is issued after detection, and effective muting operation cannot be performed. However, there is a drawback in that muting cannot be carried out immediately when the value decreases.

This invention was made in view of the above points,
The purpose is to eliminate the drawbacks of the conventional example, and to perform muting directly due to the power supply voltage drop without going through the microcomputer, and the input / output port of the microcomputer required for muting control. It is an object of the present invention to provide a muting control circuit configured to reduce the number and perform a muting operation immediately when the power supply voltage drops.

(D) Means for Solving the Problem A muting control circuit according to the present invention is a muting control circuit having an input terminal and an output terminal for issuing a muting signal in response to an input signal. The input terminal of is connected to the output port of the microcomputer that arbitrarily outputs the muting control signal, and the other input terminal is used as the output terminal of the voltage detection circuit that detects the decrease of the power supply voltage and outputs the muting control signal. The output port of the microcomputer and the output terminal of the voltage detection circuit are connected via a diode to form a wired OR circuit.

(E) Function Since the output port of the microcomputer and the output terminal of the voltage detection circuit are connected via the diode, a wired OR circuit is formed. Therefore, one of the output terminals of the muting control circuit can respond to the muting instruction from the microcomputer and can respond to the output of the voltage detection circuit at high speed.

(F) Embodiment An embodiment of the muting control circuit according to the present invention will be described with reference to FIG.

In FIG. 1, Q1 to Q4 are transistors, D1 is a zener diode, D2 is a diode, and R1 to R7 are resistors.

The circuit consisting of Q1, Q2, D1, R1, R2, and R3 is a voltage detection circuit that detects a drop in the power supply voltage of the analog power supply. In this circuit, the cathode side of Zener diode D1 is connected to the power supply voltage VCC of the analog power supply, the anode side is connected to the base of transistor Q1 via resistor R1, and
R2 is connected between the base of transistor Q1 and ground.

The emitter of the transistor Q1 is grounded, the collector side is connected to the VDD power source of the digital power source via the resistor R3, and the collector side is connected to the base of the transistor Q2 in the next stage.

The transistor Q2 is a grounded-emitter type switching circuit, and the collector is the output terminal of the voltage detection circuit. This output terminal is a terminal which issues a muting control signal and is connected to the input terminal of the muting control circuit. That is, it is connected to the base of the transistor Q4 via the resistor R4.

The base of the transistor Q4 is pulled up to the VDD power supply via the resistor R7, and an open collector switching circuit whose emitter side is connected to the VDD power supply is configured. The collector of the transistor Q4 is the first output terminal MO.
It is 1, so that the muting signal is output.

On the other hand, the terminal 13 of the microcomputer 11 is an output port of the muting control signal and is connected to the input terminal of the muting control circuit. That is, it is connected to the base of the transistor Q3 via the resistor R5.

The base of the transistor Q3 is pulled up to the VDD power source via the resistor R6, and an open collector switching circuit similar to the transistor Q4 in which the emitter side is connected to the VDD power source is configured. The collector of the transistor Q3 is the second output terminal MO2.

Further, the output port 13 forms a wired OR circuit with the output terminal of the voltage detection circuit, that is, the collector of the transistor Q2 via the diode D2.

The output port 13 arbitrarily outputs a muting control signal according to the program of the microcomputer.

The operation of the muting control circuit of FIG. 1 configured as above will be described below.

When the voltage level of the VCC power supply falls below the level set by the Zener diode D1 and the resistors R1 and R2,
Transistor Q1 is cut off and transistor Q2
Becomes conductive and the collector potential of the transistor Q2 becomes the ground level, the base potential of the transistor Q4 drops and becomes conductive, the VDD power supply level, that is, "H" level is output to the collector and the muting signal due to the power supply voltage drop. Is output from the first output terminal MO1.

On the other hand, from the output port 13 of the microcomputer to the output port 13 by the program in the microcomputer.
When the muting control signal output from the transistor becomes "L" level, the resistor R5 lowers the base potential of the transistor Q3 and the transistor Q3 becomes conductive, so that the VDD power supply level to the collector, that is, the "H" level muting signal Output from the output terminal MO2 of.

Further, when the muting control signal from the output port 13 of the microcomputer 11 becomes the “L” level, the diode D2 and the collector of the transistor Q2 have a wired OR circuit configuration, so that the diode D2 becomes conductive and the transistor Q2 Even when is off, the base potential of the transistor Q4 is lowered to make the transistor Q4 conductive similarly to the above, and the muting signal is output from the first output terminal MO1.

The output port 13 of the microcomputer 11 as described above
Not only the muting signal can be output from the first output terminal MO1 by the wired OR circuit by the muting control signal output from the, but also the power supply voltage drop is detected for the muting signal from the first output terminal MO1. If it does, it can respond and output at high speed.

(G) Effect of the Invention According to the muting control circuit of the present invention, the muting control signal is directly input to the microcomputer without inputting the output signal of the voltage detection circuit, and the muting is performed by the program in the microcomputer. By connecting the output port that outputs the control signal and the output terminal of the voltage detection circuit by the wired OR circuit, the muting signal can be controlled by the muting control signal from any one of the output terminals. In addition, the number of input / output ports of the microcomputer can be reduced, and further, the muting operation due to the detection of the power supply voltage drop can respond at high speed and the timing delay can be reduced.

Moreover, it has excellent features such as a simple structure and easy implementation because it can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a muting control circuit according to the present invention. FIG. 2 is a circuit diagram showing a conventional example. Description of main symbols Q1 to Q4: Transistor D1: Zener diode D2: Diode R1 to R7: Resistor

Claims (1)

[Scope of utility model registration request] 1. A muting control circuit having an input terminal and an output terminal for issuing a muting signal in response to an input signal, wherein one input terminal of the control circuit outputs a muting control signal arbitrarily. Connected to the output port of the computer, the other input terminal is connected to the output terminal of the voltage detection circuit that detects the decrease of the power supply voltage and outputs the muting control signal, and the output port of the microcomputer and the output of the voltage detection circuit A muting control circuit for audio equipment, characterized in that it is connected to a terminal via a diode to form a wired OR circuit.