JP2898459B2 - Volume control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a voltage controlled amplifier and a digital / analog (hereinafter sometimes abbreviated as "D / A") converter to fade-in and fade-out the volume of a volume device. The present invention relates to a volume control circuit for controlling.

[0002]

2. Description of the Related Art When a sound volume device is turned on after a lapse of a set time using a timer or turned off after a lapse of a set time in a sleep mode, it is necessary to gradually change the volume over time. . Conventionally, in order to perform fade-in and fade-out according to such an operation mode, input data of a D / A converter is 1 dB to 1 dB.
It is necessary to continuously send a large amount of data that changes in small steps of 2 dB until the final target level is reached.

[0003]

In order to keep sending such a large amount of input data, the load on the controller increases. For this reason, for example, a memory device having a large capacity is required, and the device cost is increased. On the other hand, when the amount of input data is reduced, the level difference of the data between each step becomes large and changes stepwise.
There is a problem that cannot be changed smoothly and is hard to hear.

SUMMARY OF THE INVENTION It is an object of the present invention to make it possible to fade in or fade out a volume by giving a large change in one step without changing an input control signal which is volume control data into a large amount of control data in fine steps. It is another object of the present invention to provide a sound volume control circuit having a simple circuit configuration and capable of reducing costs.

[0005]

SUMMARY OF THE INVENTION The present invention provides a digital / analog converter which converts digital volume control data into a DC voltage and outputs the DC voltage, and integrates an output voltage from the digital / analog converter to form a limiting resistor R and Charging capacitor C4
Are connected in series, an integration circuit from which the output voltage is derived from both ends of the charging capacitor C4, and the charging capacitor C4.
A plurality of charging capacitors C1, each having a capacity larger than 4
2, C3 and the plurality of charging capacitors C1, C2, C
3 and a selection circuit for selecting whether to connect in parallel to the charging capacitor C4 of the integration circuit or to leave the connection unconnected, and the plurality of charging capacitors C1 and C2. , C3 and the capacitor C4 of the integrating circuit, respectively, a charging / discharging resistor r sufficiently larger than the limiting resistor R of the resistance integrating circuit, and a voltage whose gain is controlled by the output voltage from the integrating circuit. A volume control circuit including a control amplifier.

[0006]

According to the present invention, the output of the digital / analog converter which generates a DC voltage corresponding to the input digital volume control data is integrated by a series connection of a limiting resistor R and a charging capacitor C4. , And is input as a control voltage to a voltage-controlled amplifier whose gain can be controlled.

At this time, if the time constant of the integrating circuit is small, the output of the voltage controlled amplifier can be changed at a high response speed in accordance with the input to the digital / analog converter, and conversely, if the time constant is large, it is slow. It is possible to gradually change the response speed.

One of a plurality of large-capacity charging capacitors C1, C2 and C3 can be selectively connected to the charging capacitor C4 of the integrating circuit, and the time constant of the integrating circuit is set according to the operation mode. By properly setting the digital / analog converter, if only the digital volume control data corresponding to the desired final level is input,
It is possible to control fade-in and fade-out in which the volume changes smoothly with the set time constant. A plurality of charging / discharging resistors r are connected in series to the plurality of charging capacitors C1, C2, and C3, respectively. Since r >> R, a reliable fade-out operation can be performed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing the technology underlying the present invention. Voltage control amplifier 1 from the input side in the signal amplification circuit
And an amplifier 4 such as a power amplifier are interposed in series.
The voltage control amplifier 1 is provided with a gain control input terminal, and is composed of a variable gain amplifier whose gain increases and decreases according to the level of a control voltage input to this input terminal. When the voltage control amplifier 1 receives the input signal S 1, the voltage control amplifier 1 amplifies the gain with a gain determined by the applied control voltage value, outputs a voltage, and supplies the voltage to the power amplifier 4. The power amplifier 4 power-amplifies this input and outputs it to the subsequent stage, for example, a loudspeaker, so that the speaker emits sound.

A D / A converter 2 is connected to a gain control input terminal of the voltage control amplifier 1 via a time constant selection circuit 3. The D / A converter 2 receives digital volume control data D corresponding to the final level at the time of fade-in or fade-out, converts the data into a DC voltage having a value corresponding to the level, and outputs the DC voltage. On the other hand, the time constant selection circuit 3 includes a CR integration circuit having a predetermined time constant including a limiting resistor R and a charging capacitor C4, and a selection switch 5
And a plurality of charging capacitors C1, C2, and C3 selectively connected in parallel to the charging capacitor C4 through the capacitor C4, and any one of a plurality of different time constants determined by the capacitances of the capacitors C1 to C4. One, select switch 5
Has a function that can be selected by the operation of

In the above configuration, when the D / A converter 2 outputs a DC voltage corresponding to the level of the digital volume control data, the DC voltage is supplied to the voltage control amplifier 1 through the limiting resistor R as a control voltage. At this time, the value of the capacitor C4 is sufficiently small as compared with the other capacitors C1 to C3, there is no selection signal input to the selection terminals T1 to T3, the selection switch 5 is off, and the capacitors C1 to C3 are If not selected, the time constant selection circuit 3
Since the shortest time constant is selected, the voltage controlled amplifier 1 generates an output that changes with a fast response in accordance with the input of the D / A converter 2.

When a selection signal corresponding to the operation mode is input to any of the selection terminals T1 to T3, one of the capacitors C1 to C3 is selected and connected to the capacitor C4 in parallel. As a result, the time constant can be made much longer than the initial time constant determined by the capacitor C4. For example, a sleep mode or the like is selected as an operation mode so that the volume is smooth and the listener does not feel uncomfortable. , The time constant determined by the resistor R and the capacitors C4 + C1 to C3 is selected, so that only the data of the desired final level needs to be input to the D / A converter 2. A smooth volume change is obtained. For example, when the device is turned on by a timer, the input data D to the D / A converter 2 receives the final data, selects one of the capacitors C1 to C3 according to the selection signal, and selects the capacitor C4.
, A smooth volume change fade-in is possible based on the time constant determined by the time constant selection circuit 3.

FIG. 2 is a circuit diagram of one embodiment of the present invention.
Based on the configuration of FIG. 1, it is a device that is particularly suitable for use in fading out. In the time-constant selection circuit 3, each of the capacitors C1 to C3 to be selectively connected is connected in series with a charging / discharging resistor r. In this case, the charge / discharge resistance r is set to r >> R. When fading out when turning off after a lapse of a set time such as a sleep mode from a normal listening use state, a desired one of the capacitors C1 to C3 is selected by a selection signal and a desired time constant is set.

Even if the output of the D / A converter 2, that is, the final data is set to 0, the control voltage for the voltage control amplifier 1 is smoothly reduced by discharging with the time constant set by R and C4 + selection capacitors C1 to C3. Therefore, a reliable fade-out operation can be performed.

When fading in, the capacitor C
1 to C3 may be deselected so that the amplifier 4 can output an output that smoothly changes with a time constant determined by R and C4.

[0016]

As described above, according to the present invention, the output voltage from the digital / analog converter is changed so as to gradually increase or decrease according to the time constant selected according to the operation mode in the time constant circuit. Thereafter, by applying the control voltage to the voltage control amplifier whose gain can be changed, a smooth volume change can be performed even if the amount of digital / analog control data, that is, the number of steps is reduced.

As a result, the load (work load) on a controller such as a microcomputer for generating the volume control data is reduced, and the memory can be saved. Excellent effect of avoiding and smoothly fading in and out is achieved. In particular, fade-out can be reliably performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a technique on which the present invention is based.

FIG. 2 is a circuit diagram of one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Voltage control amplifier 2 D / A converter 3 Time constant selection circuit 4 Amplifier 5 Selection switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H03G 3/02 H04N 5/60 H04R 3/00 310

Claims (1)

(57) [Claims] 1. A digital / analog converter which converts digital volume control data into a DC voltage and outputs the DC voltage, and integrates an output voltage from the digital / analog converter to connect a limiting resistor R and a charging capacitor C4 in series. And an integration circuit from which the output voltage is derived from both ends of the charging capacitor C4; a plurality of charging capacitors C1, C2 having a larger capacity than the charging capacitor C4; and a plurality of charging capacitors C1, C2. , C3, and the charging capacitor C4 of the integration circuit.
And a selection circuit for selecting whether to be connected in parallel or to be left unconnected, and respectively inserted between the plurality of charging capacitors C1, C2, C3 and the capacitor C4 of the integrating circuit, A volume control circuit, comprising: a charge / discharge resistance r sufficiently larger than a limiting resistance R of the circuit; and a voltage control amplifier whose gain is controlled by an output voltage from an integration circuit.