JPH024500Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a muting device that prevents abnormal noise from occurring when power is turned on. (b) Prior Art A muting device for preventing abnormal noises from occurring when the power is turned on is described in, for example, Japanese Utility Model Publication No. 53-23067. The muting device shown in the above-mentioned Japanese Utility Model Publication No. 53-23067 has a collector connected to a signal transmission line through which an audio signal flows, and a base of an NPN-type muting transistor whose emitter is grounded. The positive power supply voltage is directly applied. Therefore, the muting transistor is quickly turned on when the power is turned on, the signal transmission line is grounded, the muting operation is not delayed, and there is an advantage that no abnormal sound is generated from the speaker. However, since the voltage applied to the muting transistor is not regulated, when the mutating transistor operates in the active region when the muting is canceled, the ripple component superimposed on the power supply voltage may cause the signal transmission line to This has the disadvantage that it adversely affects the flowing audio signal, and the speaker emits sound containing ripple components. However, if a constant voltage is applied to the base of the muting transistor, another drawback arises: the rise of muting is delayed. (c) Purpose of the invention The present invention has been made in view of the above-mentioned points, and aims to provide a muting device in which the start of the muting operation is sufficiently early and no ripple component is generated at the end of the muting operation. (d) Structure of the invention The muting device according to the invention includes a first voltage generation circuit that generates a first DC voltage, and a voltage generating circuit that rises later than the first DC voltage generated by the first voltage generation circuit and has a constant voltage. a second voltage generation circuit that generates a second DC voltage; a first signal generation circuit connected to the output terminal of the first voltage generation circuit; and a first signal generation circuit connected to the output terminal of the second voltage generation circuit. a second signal generation circuit that generates an output signal that falls later than an output signal generated by the first signal generation circuit; and a switching circuit that operates in accordance with the output signals of the first and second signal generation circuits. It consists of (E) Embodiment FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a power supply circuit, 2 is a first signal generation circuit that generates a signal using the output voltage of the power supply circuit 1;
3 is a constant voltage circuit that makes the output voltage of the power supply circuit 1 constant; 4 is a second signal generating circuit that generates a signal using the output voltage of the constant voltage circuit 3; 5 is the first and second signal generating circuit; An OR circuit 6 takes the OR of the respective output signals of the signal generation circuits 2 and 4, and a signal transmission line 7 6 corresponds to the output signal of the OR circuit 5.
This is a switching circuit that drops the audio signal flowing through the circuit to ground. When power is applied to the above circuit, a power supply voltage containing a ripple component as shown in FIG. 2A is generated at the output terminal of the power supply circuit 1. When the power supply voltage is applied to the first signal generating circuit 2, a voltage including a ripple component as shown in FIG. 2B is generated from the first signal generating circuit 2 for a predetermined period of time. The output voltage of the first signal generating circuit 2 is applied to the switching circuit 6 via the OR circuit 5.
is turned on, the signal transmission line 7 is grounded, and muting is performed. On the other hand, the power supply voltage is also applied to a constant voltage circuit 3, and after being made constant by the constant voltage circuit 3 as shown in FIG.
Then, the second signal generating circuit 4 generates a voltage as shown in FIG. Therefore, as _shown in FIG. Since the output voltage of the signal generation circuit 4 is applied, the muting operation continues from the start of generation of the output voltage of the first signal generation circuit 2 until the end of generation of the output voltage of the second signal generation circuit 4. and,
Assuming that the voltage applied to the switching circuit 6 reaches a saturation state when the voltage applied to the switching circuit 6 is at a level higher than _V1 in _{FIG .} ,
The fall is smooth. Therefore, no ripple sound is generated when muting ends. 3 is a circuit diagram showing a specific example of the embodiment shown in FIG. 1, in which 8 is a power supply circuit, 9 is a constant voltage circuit that constantizes the power supply voltage generated from the power supply circuit 8 , and 10 is the power supply circuit 8. 11 is a second signal generating circuit connected to the output terminal of the constant voltage circuit 9 ; 12 is a base connected to the first and second signal generating circuits 10 and 11 ; This is a muting transistor which is connected to a common connection point of each output end of the transistors, has a collector connected to the signal transmission line 13, and has an emitter grounded. When a positive voltage is applied to the input terminal of the first signal generating circuit 10 , the capacitor 15 connected to the emitter of the transistor 14 is quickly charged via the diode 16, and the capacitor 17 connected to the base is charged. Since the transistor 14 is gradually charged according to the charging time constant determined by the time constant circuit of the resistor 18 and the resistor 18, the transistor 14 is turned on from the time when a positive voltage is applied to the input terminal until the charging of the capacitor 17 is completed. , the transistor 14
A positive voltage is generated from the collector of the Further, the second signal generation circuit 11 has the same configuration as the first signal generation circuit 10 , and the transistor 1
The capacitor 20 connected to the base of the second signal generating circuit 11 is connected to the base of the second signal generating circuit 11 .
The charging time constant of the battery is increased. Therefore, the second
The time during which a positive voltage is generated from the collector of the transistor 19 of the signal generating circuit 11 is longer than the time during which a positive voltage is generated from the collector of the transistor 14 of the first signal generating circuit 10. Now, if the power switch 21 is turned on,
Since a positive power supply voltage is generated at the output terminal of the power supply circuit 8 , the first signal generation circuit 10 immediately generates a positive voltage from the output terminal. Therefore, since the positive voltage is applied to the base of the muting transistor 12, the mutating transistor 1
2 turns on. On the other hand, the positive power supply voltage generated at the output terminal of the power supply circuit 8 is made into a constant voltage by a constant voltage circuit 9 and applied to the second signal generation circuit 11 .
Since the capacitor 22 is charged via the resistor 23, the second signal generating circuit 11 generates the output voltage only after a predetermined time period after the first signal generating circuit 10 generates the output voltage. Further, the first and second signal generation circuits 10 and 11
are PNP type transistors 14 and 1, respectively.
The output voltage is obtained from the collectors of the first and second signal generating circuits 10 and 11 because the collectors are connected to each other. An output voltage is generated from the collector-to-collector connection point A. Therefore, muting starts with the generation of the output voltage of the first signal generation circuit 10 , and the muting starts with the generation of the output voltage of the first signal generation circuit 10.
It ends when the output voltage of 1 ends. FIG. 4 is a circuit diagram showing another embodiment of the present invention,
The first signal generating circuit 10 is connected to the output terminal of the constant voltage circuit 9 , and the integrated circuit 24 provided with the same second signal generating circuit as the second signal generating circuit 11 in FIG. Resistor 25 connected to the output end
and the decoupling capacitor 26. In FIG. 4, circuits that are the same as those in FIG. 3 are given the same number. In the above circuit, when a voltage is generated at the output terminal of the constant voltage circuit 9, the first signal generating circuit 10 immediately generates an output voltage. On the other hand, the second signal generation circuit provided in the integrated circuit 24 outputs an output from the terminal 27 of the integrated circuit 24, which is the output end of the second signal generation circuit, after the decoupling capacitor 24 is charged via the resistor 25. Generates voltage. As a result, even in the above-mentioned circuit, muting is applied from the time when the first signal generating circuit 10 starts generating the output voltage until the second signal generating circuit provided in the integrated circuit 24 finishes generating the output voltage. become. Furthermore, since the output voltage of the first signal generating circuit 10 quickly rises at the same time as the power supply voltage applied to the input terminal of the first signal generating circuit 10 , it can be used as an inhibit signal for an integrated circuit. In FIG. 4, when the output voltage of the first signal generating circuit 10 is generated, the transistors 28 and 29 are turned on, the inhibit terminal 31 of the integrated circuit 30 becomes "L", and each part in the integrated circuit 30 is turned on. is kept in a prohibited state. Note that the emitter of the transistor 28 is open, and its base is connected to the collector of the transistor 14 of the first signal generating circuit 10 , and the collector is connected to the base of the transistor 29. By using the transistor 28, when a large negative signal is generated on the signal transmission line 13, the resistors 32 and 33, the diode 34, and the resistor 3 are connected to the ground.
5 and the path between the base and collector of the muting transistor 12, which can prevent current from flowing and causing distortion. In that case, similar distortion can be prevented by using a diode, but
Since a diode has a large reverse current and is not suitable for a low distortion muting device, the transistor 28 is more preferable. (f) Effects of the invention As described above, according to the invention, since the start of muting is controlled by the output signal of the first signal generation circuit, it has the advantage of providing a muting device with a quick start-up operation. In addition, since the end of the mutating is controlled by the output signal of the second signal generation circuit, which applies a constant voltage to the input terminal, the ripple component is modulated into an audio signal and output when the mutating ends. It has the advantage that there is no problem. Further, since the start of mutating can be adjusted by the first signal generating circuit, and the time of ending mutating can be adjusted by the second signal generating circuit, there is an advantage that design is easy.
Since the output signal of the first signal generating circuit can be used as an inhibit signal, it has the advantage that the cost can be reduced compared to providing the muting device and the circuit for generating the inhibit signal independently of each other.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
Figure 2 A to E are characteristic diagrams for the purpose of explanation.
FIG. 3 is a circuit diagram showing a specific example of FIG.
The figure is a circuit diagram showing another specific example. Explanation of main symbols, 1...Power supply circuit, 2...1st
Signal generation circuit, 3... Constant voltage circuit, 4... Second signal generation circuit, 6... Switching circuit.

Claims (1)

[Scope of utility model registration request] a first voltage generation circuit that generates a first DC voltage; and a second voltage generation circuit that generates a second DC voltage that rises later than the first DC voltage generated by the first voltage generation circuit and is regulated. a voltage generation circuit, a first signal generation circuit connected to the output terminal of the first voltage generation circuit, and an output signal connected to the output terminal of the second voltage generation circuit, which is generated by the first signal generation circuit. a second signal generating circuit that generates an output signal that falls slowly, and a switching circuit that operates according to the output signals of the first and second signal generating circuits, A muting device that drives the switching circuit with a signal to perform muting.