JPH0631993B2 - Sounding circuit - Google Patents

Description

The present invention relates to a sounding circuit.

[Prior Art] Usually, an alarm sound of a clock is created by synthesizing rectangular waves of different frequencies. However, if the sound signal is composed of only rectangular waves, the sound quality becomes hard. Therefore,
Of the synthesized rectangular waves having different frequencies, a low frequency rectangular wave may be enveloped and a high frequency rectangular wave may be amplitude-modulated to soften the sound quality. Charge and discharge of the capacitor are used for amplitude modulation.

By the way, since there is a preference for sound quality, there is a switch that allows selection between hard sound quality and soft sound quality. When realizing such a function using an integrated circuit,
A switch for selecting sound quality and a capacitor for amplitude modulation are provided outside the integrated circuit, and a terminal for connecting the switch and a terminal for connecting the capacitor are provided in the integrated circuit.

[Problems to be Solved] In the above-described conventional sounding circuit, since the switch for selecting the sound quality and the capacitor for amplitude modulation are connected to different terminals of the integrated circuit, the number of terminals of the integrated circuit increases. There was a problem.

It is an object of the present invention to obtain a sounding circuit with a reduced number of integrated circuit terminals.

[Means for Solving the Problems] An open / close switch that can be opened / closed is connected in series to a capacitor that amplitude-modulates an acoustic signal, and the open / close switch is opened by a detection circuit connected to a contact point between the open / close switch and the capacitor. When it is determined to be in the state, the control circuit controls charge / discharge of the capacitor. The capacitor and the open / close switch are formed outside the integrated circuit and are connected to the same terminal of the integrated circuit.

[Embodiment] FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

In the figure, the portion within the broken line is formed in the integrated circuit.

SS is an acoustic signal generation circuit, which generates a rectangular wave acoustic signal of, for example, several kilohertz.

CC is a capacitor and provides an envelope for amplitude-modulating the acoustic signal generated by the acoustic signal generation circuit.

MD is a modulation circuit, which generates a modulation signal by amplitude-modulating the acoustic signal generated by the acoustic signal generation circuit SS.

SP is a sounding means, for example, a speaker is used.

DR is a drive circuit which drives the sounding means SP based on the modulation signal.

SW1 is an open / close switch that can be opened and closed, and a capacitor C
It is connected in series with C and selects soft or hard sound quality. .

DT is a detection circuit, which detects the open / closed state of the open / close switch SW1 at the moment when the switch SW2 described later is closed, and holds the detection output until the switch SW2 is closed next.

PT1 is a first pattern generation circuit, which generates a digital pattern for charging and discharging the capacitor CC based on a signal from the detection circuit. The generated pattern corresponds to a sounding pattern, and for example, a continuous sounding pattern is generated.

TR is a switching circuit, which is turned on / off in response to the output signal of the first pattern generation circuit PT1.
The switching circuit TR is formed of a transistor or the like.

RL is a discharge resistor, which discharges the electric charge of the capacitor CC when the switching circuit TR is in the off state. The resistance value of the discharge resistance RL is on the order of mega ohms.

RS is a charging resistor, which charges the capacitor CC when the switching circuit TR is in the ON state. The resistance value of the charging resistor RS is much smaller than the resistance value of the discharging resistor RL.

The switching circuit TR, the discharging resistor RL and the charging resistor RS constitute a control circuit CR.

PT2 is a second pattern generation circuit, and generates a sounding pattern different from the sounding pattern generated by the first pattern generating circuit, for example, an intermittent sounding pattern.
This tone generation pattern is a digital pattern, like the first pattern generation circuit.

SW2 is a sound generation switch, which switches the circuit to the sound generation state when closed.

TM1, TM2 and TM3 are terminals of the integrated circuit.

Next, the operation of the present embodiment will be described with reference to the waveform diagram shown in FIG.

The waveforms a to d in FIG. 2 show the waveforms at points a to d in FIG.

When the sound generation switch SW2 is closed, the detection circuit DT, the first pattern generation circuit PT1 and the second pattern generation circuit PT2 are in the operable state. The detection circuit DT detects the voltage of the terminal TM1 at the moment when the tone generation switch SW2 is closed and holds the detection output. That is, when the open / close switch SW1 is open, the voltage of the terminal TM1 becomes "0". At this time, the output of the detection circuit DT is held at "1" and the first pattern generation circuit PT1 is selected. When the open / close switch SW1 is closed, the voltage of the terminal TM1 becomes "1". At this time, the output of the detection circuit DT is held at "0", and the second pattern generation circuit PT2 is selected.

When the first pattern generation circuit PT1 is selected,
The following operations are performed.

The first pattern generation circuit PT1 outputs a rectangular wave sounding pattern as shown in FIG. 2a. The frequency of this signal is about several to several tens of hertz. When the output signal a is "1", the switching circuit TR is turned on. The capacitor CC is charged through the charging resistor RS, but since the resistance value of the charging resistor RS is very small, the charging is completed instantly. The input signal b of the modulation circuit MD becomes "1". When the output signal a is "0", the switching circuit TR is turned off. The electric charge stored in the capacitor CC is discharged through the discharge resistance RL, but the discharge resistance RL has a very large resistance value, and therefore the discharge is performed slowly. The input signal b of the modulation circuit MD gradually decreases according to the time constant determined by the resistance value of the discharge resistor RL and the capacitance value of the capacitor CC. In the modulation circuit MD, the acoustic signal generation circuit SS is added to the input signal b of the modulation circuit MD.
The signal d from is superimposed and a signal as shown in FIG. 2d is output. That is, the output signal d from the modulation circuit MD
Is a modulation circuit MD for the signal c from the acoustic signal generation circuit SS.
The amplitude is modulated by the input signal b. The frequency of the signal c from the acoustic signal generation circuit SS is about several kilohertz. As described above, according to the tone generation pattern a from the first pattern generation circuit PT1, the terminal TM3 is connected to the terminal shown in FIG.
A signal as shown in is output. The drive circuit DR receives the signal d and drives the sounding means SP. Since the drive signal has a gentle envelope as shown in FIG. 2D, a sound of soft tone quality is generated from the sounding means SP.

When the detection circuit DT selects the second pattern generation circuit PT2, the following operation is performed.

The second pattern generation circuit PT2 generates a tone generation pattern different from the tone generation pattern generated by the first pattern generation circuit. In the modulation circuit MD, the signal from the acoustic signal generation circuit SS is superimposed on the digital output signal from the second pattern generation circuit PT2. The drive circuit DR receives the output signal from the modulation circuit MD and receives the sounding means S.
Drive P. Since the drive signal is a combination of digital signals of different frequencies, the sound generating means SP
Produces a hard sound quality.

In the embodiment described above, the first pattern generation circuit PT1
And the second pattern generation circuit PT2 are provided to generate different sounding patterns, but one sounding pattern may be used. For example, in the above embodiment, only the first pattern generation circuit PT1 may be provided and the output of the first pattern generation circuit PT1 may be distributed based on the signal from the detection circuit DT. At this time, one output of the first pattern generation circuit PT1 is input to the switching circuit TR so as to generate a sound with a soft sound quality, and the other output is input to the modulation circuit MD to generate a sound with a hard sound quality. You can do it like this.

[Effect] In the sounding circuit of the present invention, the open / close switch for selecting the sound quality and the capacitor for amplitude modulation are connected to the same terminal of the integrated circuit, and the detection of the open / closed state of the open / close switch and the charging / discharging of the capacitor have the same terminal. Therefore, the number of terminals of the integrated circuit can be reduced. Therefore, the cost of the integrated circuit is reduced.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining the operation of FIG. SS ... Acoustic signal generation circuit CC ... Capacitor SW1 ... Open / close switch DT ... Detection circuit CR ... Control circuit

Claims (1)

[Claims] 1. An acoustic signal generation circuit that generates an acoustic signal, a capacitor that applies amplitude modulation to the acoustic signal generated by the acoustic signal generation circuit, and an openable / closable open / close switch connected in series to the capacitor. A detection circuit connected to the contact between the open / close switch and the capacitor to detect the open / closed state of the open / close switch; and when the open / close switch is determined to be open by the detection circuit, the charge / discharge of the capacitor is controlled. And a control circuit for controlling the sound signal generation circuit, the detection circuit and the control circuit are formed in an integrated circuit, and the capacitor and the open / close switch are formed outside the integrated circuit.