JPH08237035A - Method for supplying power to amplifier - Google Patents

Abstract

PURPOSE: To make the size of a sounding equipment small by interrupting a power switch at a high speed with a control signal of a high frequency pulse to charge up a voltage controlled capacitor connected in parallel with an amplifier thereby raising a power supply voltage in a state almost constant at all times. CONSTITUTION: When a switching transistor(TR) 21 being a power switch is conductive by outputting a control signal A from a control circuit 11 in a sounding equipment 13 to apply a power supply voltage to an amplifier 31, at first a control signal is outputted interruptingly for 50-100msec, a continuous control signal is outputted to make the switching TR 21 conductive to apply power supply voltage to the amplifier 31. Then an output time t1 of the control signal is selected nearly to 1/6-1/10 of an output interrupt time in the interrupting application time to limit the conduction time of the switching TR 21, then a charging voltage of a voltage control capacitor 25, that is, an applied voltage V to the amplifier 31 is gradually increased. Moreover, the interrupting frequency is selected to be a frequency more than an audible frequency or a high frequency more than a reproduction frequency of a speaker 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power-on method for an amplifier which powers on in response to the operation of a melody IC or the like.

[0002]

2. Description of the Related Art Today, a control clock using a microcomputer has come to be widely used as a time signal clock or the like which sounds a music by operating a sounding device at a predetermined time. As shown in FIG. 3, such a sounding device receives a voice signal or a music signal from the melody IC41 or the like which starts its operation in response to an operation signal from the control circuit 11, and is turned on by a control signal from the control circuit 11. The power is applied to the amplifier 31 via the switching transistor 21, and the audio signal or the like output from the melody IC 41 or the like is amplified by the amplifier 31 and is output from the speaker 35.

In such a sounding device 13, when a predetermined power supply voltage is applied at a dash when the amplifier 31 is started up, a pop sound of "bugs" is generated when the power is turned on, which is offensive to the ears, so that the control circuit 11 outputs. Input control signal to the switching transistor 21 via the limiting circuit 16 including the limiting resistor 16 and the limiting capacitor 17, and the amplifier 31
4 is grounded via the voltage control capacitor 25, and when the power supply voltage is applied to the amplifier 31, the charging voltage of the voltage control capacitor 25 in parallel with the amplifier 31 is applied to the amplifier 31, as shown in FIG. In addition, the rise of the power supply voltage V applied to the amplifier 31 is limited to prevent the pop sound from being generated.

[0004]

As described above, the method of using the limiting resistor and the limiting capacitor in the limiting circuit and also using the voltage control capacitor in parallel with the amplifier makes the voltage applied to the amplifier smooth. Although it can be increased, it has a drawback that it is difficult to downsize the sounding device and the manufacturing cost is increased because a large-capacity capacitor is used as the limiting capacitor and the voltage control capacitor.

Further, since the limit value of the limiter circuit changes depending on the temperature, the time until the voltage applied to the amplifier reaches a predetermined power supply voltage is not constant depending on the temperature, and the time until the amplifier reaches stable operation. There was a drawback that there was variation in.

[0006]

According to the present invention, when a power supply voltage is applied to an amplifier, a control signal which is a pulse having a frequency higher than a reproduction frequency of a speaker or higher than a human audible frequency is added to a switching transistor using a power switch. ,
It is assumed that the power supply voltage is interrupted to charge the voltage control capacitor in parallel with the amplifier, and then a predetermined power supply voltage is applied to the amplifier and the voltage control capacitor.

[0007]

According to the present invention, since the switching transistor is intermittently charged by the control signal in the form of a high frequency pulse to charge the voltage control capacitor, the voltage applied to the amplifier can be gradually increased, and the control signal with the intermittent frequency is obtained. Since the frequency is set to a high frequency equal to or higher than the reproduction frequency of the speaker or equal to or higher than the human audible frequency, it is possible to prevent the audible frequency noise from being emitted from the speaker due to the power supply voltage fluctuation of the amplifier.

[0008]

EXAMPLE A sounding device 13 for carrying out the method according to the present invention is
As shown in FIG. 1, the output terminal of a control circuit 11 using a microcomputer is connected to the base of a PNP type switching transistor 21 via a limiting resistor 16, and the emitter of the switching transistor 21 used as a power switch is a power source. In addition, the collector of the switching transistor 21 is connected to the power supply terminal of the amplifier 31 and the voltage control capacitor 25 in parallel with this amplifier 31, and the audio signal input from the audio signal input terminal 37 is amplified by the amplifier 31. The speaker 35 is used to make a sound.

In the sounding device 13, when the power supply voltage is applied to the amplifier 31 by outputting the control signal A from the control circuit 11 to make the switching transistor 21 used as a power switch conductive, as shown in FIG. It is assumed that the control signal is intermittently output for 50 milliseconds to 100 milliseconds and then the continuous control signal is output to make the switching transistor 21 conductive and apply the power supply voltage to the amplifier 31.

Then, in the intermittent input time T0 of 50 to 100 milliseconds, the conduction time of the switching transistor 21 is set by setting the output time t1 of the control signal to about 1/6 to 1/10 of the output interruption time t2. By limiting the voltage, the charging voltage of the voltage control capacitor 25, that is, the voltage V applied to the amplifier 31 is gradually increased.

Further, the intermittent frequency of the control signal at the intermittent turn-on time T0 is higher than the audible frequency or the speaker 35.
The reproduction frequency is higher than the reproduction frequency. In this embodiment, the control signal output from the control circuit 11 is a high-frequency pulse in this way, and the power switch for supplying the power supply voltage to the amplifier 31 is interrupted at high speed, and the voltage control capacitor 25 in parallel with the amplifier 31 is provided. The power supply voltage V applied to the amplifier 31 is quickly raised in a short time so that the amplifier 31 is charged in a short time such as about 0.1 seconds, and this interruption is a high-frequency intermittent signal exceeding the audible frequency or the reproduction frequency of the speaker 35. Therefore,
The rise of the power supply voltage V applied to the amplifier 31 gradually rises due to the interruption of hundreds to thousands or more times within about tens of milliseconds to hundreds of milliseconds, and the voltage is smoothly raised to generate the pop sound. It can be turned on to prevent it.

Further, due to the interruption of the power supply voltage, the amplifier 31
Even if a fluctuating output occurs in the output of, if the fluctuating frequency exceeds the reproduction frequency of the speaker 35, it will not be output as a sound from the speaker 35, and if it is higher than the audible frequency, a sound will be output from the speaker 35. Since the person cannot hear the output even if it is output, it is possible to reliably prevent the generation of noise due to the intermittent power supply.

The duty ratio (t1: t1 + t2) of the control signal output from the control circuit 11 is determined by the voltage control capacitor 2
Depending on the capacity of 5 and the state of the power supply circuit, several tens of milliseconds to 100
It is set so that the power supply terminal voltage of the amplifier 31 reaches a predetermined voltage in about milliseconds, and the output time t1 is about 1/6 to 1/10 of the interruption time t2.
The duty ratio is about one-half.

As described above, in this embodiment, the power switch is switched on and off at high speed by the control signal which is a pulse signal, and
The voltage control capacitor 25 in parallel with 31 is charged to
This is a method to prevent the pop sound from being generated by quickly and smoothly increasing the voltage applied to 31. Therefore, by adjusting and setting the control circuit 11, the control signal of a predetermined duty ratio is output at the start of the control signal output. As a result, the power supply voltage to be applied to the amplifier 31 can be always raised in a substantially constant state, and the limiting capacitor 17 can be omitted as compared with the conventional case, so that the sounding device 13 can be provided. It becomes easy to miniaturize, and the sounding device 13 having the built-in amplifier 31 incorporated in a timepiece such as a timepiece clock that generates electronic sound or a toy that generates electronic sound using a voice IC or a melody IC41 is inexpensive. It will be possible to manufacture and miniaturize, and to easily incorporate the sounding device 13.

In this way, when outputting the control signal, the method of turning on / off the switching transistor 21 which is the power switch by first outputting the control signal in the form of a high frequency pulse for a short time is a melody IC.
When a microcomputer is already used for the control circuit 11 for controlling the sound generating device 41, the sounding device 13, etc., it can be implemented very easily by setting the frequency and the duty ratio in the control circuit 11.

Although the control signal shown in FIG. 4 is a control signal having an L level signal, the control circuit 11 may output an H level signal as a control signal in accordance with the switching transistor 21.

[0017]

According to the present invention, the voltage applied to the amplifier is charged by charging the voltage control capacitor in parallel with the amplifier by switching the power switch on and off at a high speed by the control signal of the high frequency pulse of the reproduction frequency of the speaker or the audible frequency or more. This is a method to quickly and smoothly raise the pop-up noise to prevent the pop noise from being generated, so the power supply voltage can always be raised in a substantially constant state, and the limiting capacitor is omitted compared to the conventional method. Therefore, there is an advantage that the sounding device can be miniaturized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a sounding device for implementing the method according to the present invention.

FIG. 2 shows a signal which has been subjected to the method according to the invention.

FIG. 3 is a circuit diagram showing a conventional sounding device.

FIG. 4 is a diagram showing a power supply voltage in a conventional sounding device.

[Explanation of symbols]

11 Control Circuit 13 Sounding Device 15 Limiting Circuit 16 Limiting Resistor 17 Limiting Capacitor 21 Switching Transistor 25 Voltage Controlling Capacitor 31 Amplifier 35 Speaker 37 Input Terminal 41 Melody IC

Claims (1)

[Claims] 1. When a voltage is applied to an amplifier, a control signal having a frequency higher than a reproduction frequency of a speaker or higher than an audible frequency of a person is applied to a power switch of the amplifier,
A method for powering on an amplifier, characterized by applying a predetermined power supply voltage to the amplifier and the voltage control capacitor after charging a voltage control capacitor in parallel with the amplifier by intermittently supplying a power supply voltage.