Sound control circuit

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a voice control circuit that prevents pop noise from being generated when the power switch is turned off in a circuit configuration provided with means for blocking the voice signal of the voice output IC.

【0002】

[Conventional technology]

In a color television receiver, control has been conventionally performed by using the output of a reset IC as a circuit for suppressing a pop noise sound (hereinafter referred to as a pop sound) when the power switch is turned off. FIG. 2 is a diagram showing the configuration of the conventional circuit that suppresses the popping sound. The mute operation when the power is turned on and off will be described below with reference to FIG.

【0003】

First, the operation when the power is turned on will be described. 1 is the terminal to which the voice signal is input, and 2 is input to the voice switching output IC. The voice switching IC2 is controlled by the IIC BUS of the microcomputer 9 and selects the desired input signal. The audio signal selected by the audio switching IC 2 is input to the audio output IC of 3, and this output is sent to the speaker of 4 to reproduce the sound. In addition, the audio output IC3 has a built-in audio mute circuit 16 so that the audio output is cut off by muting when the terminal voltage is LOW.

【0004】

16 is an audio mute circuit, and 13 transistors operate as switches to control the audio mute of the audio output IC of 3. Voltages from 11 power sources are applied to the base of 13 transistors. The 12 resistors are current limiting resistors. Since the power supply of 11 rises quickly, it rises quickly when the power switch is turned on, and the transistor of 13 is turned on, so the mute circuit operates and cuts off the audio output. With such a configuration, the popping sound is suppressed because the power is turned on.

【0005】

If the 13 transistors that were turned on when the power was turned on remain on, the sound from the speaker remains blocked, so it is necessary to cancel the sound mute. Since the power switch of 6 is on, the voltage from the power supply of 5 is stabilized and supplied to the reset IC of 8 by the regulator of 7. The voltage of the regulator (REG) of 7 is also supplied to the reset IC of 8. When the voltage supplied to the reset IC of 8 reaches the reference voltage, the output of the reset IC 8 changes from LOW to HIGH. This output is supplied to 14 transistors and 9 microcomputers. Current flows through the 14 transistors through the current limiting resistor 15, turning on the 14 transistors.

【0006】

Next, since the 13 transistors are turned off, the audio mute is canceled and the audio is output from the audio output IC.

【0007】

On the other hand, since the HIGH signal is also supplied to the 9 microcomputers, the microcomputers are reset, and then the IIC data is sent to the 2 voice switching ICs, so that the desired input signal is selected. In addition, 9 microcomputers port control 10 TV power supply control circuits and decide to turn the circuits on and off.

【0008】

Next, the operation when the power is turned off will be described. When the power switch of 6 is turned off, the power supply to the regulator of 7 is stopped, so the output voltage drops. When the voltage supplied to the reset IC of 8 becomes less than the reference voltage, the output of the reset IC changes from HIGH to LOW and resets the microcomputer of 9, so the IIC data supplied to the audio switching IC of 2 and the TV power supply of 10 Port control to the control circuit is stopped. At this time, the voice switching IC of 2 is not controlled and voice signal switching noise is generated. Since this is output as a popping sound, it is necessary to operate 16 audio mute circuits in order to suppress the popping sound.

【0009】

According to this configuration, the power supply voltage of the reset IC of 8 drops when the power switch of 6 is turned off, so that the output of the reset IC of 8 becomes LOW. This voltage is detected and 14 transistors are turned off. Next, since the 13 transistors are turned on, the sound is muted, the sound output is cut off, and the popping sound can be suppressed.

【0010】

[Problems to be Solved by the Invention]

This delay time occurs because the reset IC of 8 sets the output to LOW when it drops to the reference voltage. The delay time at this time is shown in Fig. 3. (A) of FIG. 3 shows the output voltage waveform of the reset IC of 8, and (B) shows the output voltage waveform of the regulator of 7. From this figure, the delay time from when the main power switch of 6 is turned off until the input voltage of the reset IC of 8 reaches the reference voltage can be seen.

【0011】

Moreover, since the 14 transistors operate as switches, if the base current is increased, the accumulated charge increases and the delay time when the power is turned off becomes longer. If the delay time becomes longer, the timing of the audio mute will be further delayed. When the power switch of 6 is turned off, the IIC control of the audio switching IC of 2 will stop first, so the switching sound will become a popping sound and the audio of 3 will be output. Output from the IC.

【0012】

Therefore, if the base current of the 14 transistors is reduced in order to shorten the delay time, the current becomes insufficient this time, the transistor 14 does not turn on, and a phenomenon occurs in which no sound is produced even when the power is turned on.

【0013】

In this way, it was necessary to consider the variation constraints of the transistor base current and hFE, and it was difficult to set the circuit constants. Further, since the hFE decreases at a low temperature due to the temperature characteristics of the transistor, the level of the popping sound tends to deteriorate.

【0014】

[Means for solving problems]

In order to solve the above-mentioned problems, the voice control circuit of the present invention is characterized in that the mute circuit is operated without a delay time by using an inverting switch linked with a power switch instead of a reset pulse of a microcomputer to control the mute circuit. It is the one.

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

In the sound control circuit of the present invention, the sound output IC is provided with a sound mute function, a transistor for controlling the mute terminal thereof is provided, and another transistor for controlling the transistor is provided for the control. In order to control the transistor of, by providing an inversion switch linked with the power switch and shutting it off, the voice mute is applied without delay time when the power switch is turned off, and pop noise from the speaker is prevented from being generated. It is a feature. Hereinafter, an embodiment of the present invention will be described with reference to FIG.

【0016】

(Embodiment 1) An embodiment of the present invention will be described with reference to FIG. The same reference numerals are used for the same configurations as those of the above-mentioned conventional examples, and the description thereof will be omitted. In the conventional example, 14 transistors are controlled from 8 reset ICs, but in the present invention, it is changed to be controlled by 6 switches.

【0017】

17 resistors are inserted to turn on 14 transistors when 10 TV power control circuits are on. The power switch of 6 consists of A switch and B switch and is linked. When the A switch is turned on, the B switch is turned off, and when the A switch is turned off, the B switch is turned on.

【0018】

According to this configuration, when the power switch of 6 is turned off, the switch of A is turned off and the switch of B is turned on at the same time, so that the base voltage of the 14 transistors is grounded without delay time. In other words, the delay time at the reset IC of 8 is eliminated, and the mute operation is accelerated by the delay time, which facilitates circuit design. Furthermore, it is possible to suppress deterioration of the popping sound level due to the temperature characteristics of the transistor.

【0019】

[Effect of the invention]

As described above, since the mute circuit can be directly controlled by the inverting switch linked with the power switch in the present invention, the pop noise sound from the speaker when the power switch is turned off can be suppressed.

[Simple explanation of drawings]

[Figure 1]

Circuit diagram of audio output circuit in one embodiment of the present invention [Figure 2]

Circuit diagram of the audio output circuit in the conventional example [Fig. 3]

The figure which shows the waveform of the reset IC of the audio output circuit [Explanation of symbols]

1 Voice signal 2 Voice switching IC 3 Audio output IC 4 speakers 5 Power supply 6 Power switch 7 regulator 8 Reset IC 9 Microcomputer 10 TV power control circuit 11 Power supply 12 resistance 13 transistor 14 transistor 15 resistance 16 Audio mute circuit 17 resistance