JPH07111427A - Electronic volume - Google Patents

Abstract

PURPOSE:To control the adjustment of an accurate and stable output level and to reduce the cost of an applied equipment by varying a duty ratio of a pulse train so as to adjust an output level of an analog demodulation signal. CONSTITUTION:The control from a computer 3 is implemented by using a bit string outputted circulatingly from one port and a DC variable voltage obtained from a smoothing circuit 5. The voltage is adjusted by a ratio of logical 1 of a bit string outputted from the port to a logical 0, that is, the control of a duty ratio. On the other hand, a pulse width signal inputted from a pulse width modulation circuit 1 to a switching circuit 2 is received from the circuit 5 as a pull-up voltage to control an output pulse amplitude. That is, when a port output bit string is logical 1, the pulse level is controlled maximum, when the port output bit string is logical 0, the pulse level is controlled minimum, and when the port output bit string is between the logical 1 and 0, the ratio of the logical 1 with respect to logical 0 is controlled, that is, the pulse level proportional to the duty ratio is controlled and an output level from the circuit 2 is adjusted between the maximum and the minimum level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic volume for electronically adjusting the level of an analog output signal in various audio equipments, communication equipments and the like.

[0002]

2. Description of the Related Art A conventional electronic volume of this kind is constructed by combining an attenuator having different attenuation and an analog switch, and a method of adjusting the divided amount of the input voltage by switching the switch is generally used. Is.
This method complicates the switch configuration and, for example, when adjusting the level by remote control using a computer, a large number of analog switches are turned on independently.
There is a problem in that a plurality of ports are required to turn on / off and a relatively complicated circuit is required to interface with a computer.

As other electronic volume,
Using VCA (Voltage Controlled Amplifier), LED-CD
Some parts such as S photo couplers and FETs are used, but the electronic volume composed of these is difficult to calculate the amount of attenuation, and it is a relatively advanced analog circuit to pursue accuracy. It is necessary to make full use of technology. Also,
There is a problem that variations easily occur and it is easily affected by temperature changes, and there is a drawback that inexpensive and stable performance cannot be obtained.

[0004]

As described above, in the conventional electronic volume, in order to perform an accurate and stable operation when remotely operated by a computer, a complicated and advanced technique is applied in hardware or software. There is a problem in that it needs to be used and the cost becomes high.

The present invention has been made in order to solve the above problems, and an accurate and stable operation can be performed even by remote control by a computer connected through a single port with a simple combination of hardware and software. It is intended to provide electronic volume.

[0006]

An electronic volume according to the present invention modulates an analog amplitude waveform into a pulse signal whose pulse width is modulated according to the amplitude and inputs the pulse signal to the base of a switching circuit, and opens the switching circuit. The collector is configured to input a variable voltage obtained by smoothing a pulse train which is controlled by varying the duty ratio of the pulse train repeatedly output from one port in a predetermined cycle according to the volume setting amount.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention processes an analog signal by modulating it into a pulse signal. That is, the analog amplitude signal is replaced with the pulse width modulation signal, the output level is adjusted by adjusting the pulse amplitude (height), and the pulse signal is demodulated again into the analog signal. That is, as shown in FIG. 1, the amplitude waveform of the analog signal (a) can be replaced with the pulse width modulation signal (b), and its output level is as shown in (MAX) to (MIN). The output level is adjusted by adjusting the height (voltage value).

Specific examples of the present invention will be described below. FIG. 2 is a block diagram showing an embodiment of the present invention, in which 1 is a pulse width modulation circuit, 2 is a switching circuit, 3 is a computer, 4 is a table storing bit strings in the computer 3, and 5 is a table. The smoothing circuit 6 is an LPF. The analog signal a shown in FIG. 1A is input to the pulse width modulation circuit 1, and the analog signal a shown in FIG.
The pulse width modulation signal shown in (b) is output to the switching circuit 2. On the other hand, in the computer 3, the bit string data (shown in FIG. 3) stored in the rable 4 provided on the RAM by software is repeatedly read and output from the port. This becomes a voltage value according to the volume setting in the next smoothing circuit 5, and is given as a pull-up voltage of the open collector of the switching circuit 2.

That is, in the present invention, control from the computer 3 side is obtained by avoiding the method of using many ports and by bit stream cyclically output from one port and its RC smoothing as shown in FIG. It is controlled by the voltage value of the DC variable voltage. This voltage value is adjusted by controlling the ratio of the logic "1" of the bit string output from one port, that is, the duty ratio. In addition,
Since this port output is used after being smoothed, a slow bit string output generated by low-speed interrupt processing is sufficient.

On the other hand, in the pulse width modulation signal input from the pulse width modulation circuit 1 to the base of the switching circuit 2, the switching circuit 2 is composed of an open collector, and the voltage from the smoothing circuit 5 is used as a pull-up voltage. Is input, and the amplitude (height) of the output pulse is controlled within the range of (MAX) to (MIN) in FIG. 1, for example.
That is, the bit string of the port output is (max) in FIG.
If all "1" as shown in Fig. 3, the maximum (volume), if all "0" as shown in (min) of Fig. 3, the minimum (silence), during that (mid) ratio of "1" of the bit string That is, it becomes possible to control the pulse height in proportion to the duty ratio. That is, the output level of the output from the switching circuit 2 can be adjusted, for example, between (MAX) to (MIN) in FIG.

This adjustment can be easily realized by, for example, reducing the number of logic "1" of the port output by half in the case of lowering the current output by 6 decibels (halving the amplitude of the analog voice output). In general, when it is desired to lower the decibel by X decibels from the current state, the software may be changed from the current bit string (when the number of pulses is N) to a bit string that retains N · 10 ^{X / 20} logic “1”.

That is, the port output on the side of the computer 3 circulates and outputs a pulse train of, for example, 10-bit pulse (this number of bits corresponds to the resolution of the electronic volume). Then, at the maximum volume, all logic "1" is output as shown in (max), and when there is no sound, all logic "0" is output as shown in (min). Also, in the case of attenuating X decibels from the maximum volume level, the ratio of all "1" to "1" should be reduced to 10 ^{X / 20} times by changing the software. For smooth operation, the "1" s are not concentrated at one place, but are thinned out in a dispersed manner as shown in (mid) of FIG.

The pulse width modulation circuit 1 is well known, but it may have a circuit structure in which an analog signal is superimposed on a trigger reference voltage for determining the relaxation time of the multivibrator. Further, although demodulation to an analog signal is performed by a low-pass filter (LFP) 6, it is often designed to cut off an unnecessarily high frequency in a circuit or receiver that originally handles an analog signal. With such a circuit configuration, the low pass filter 6 can be omitted.

[0014]

As described above, the electronic volume of the present invention is capable of remotely controlling a relatively accurate and stable output level adjustment via a single port with a simple combination of hardware and software, and various communication devices. The cost of audio equipment, electronic musical instruments, home appliances, etc. can be reduced. Further, there is an effect that the envelope control of the tone signal can be realized by a simple circuit.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation principle of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a diagram for explaining a port output for adjusting a duty ratio with a volume setting amount according to the present invention.

[Explanation of symbols]

 1 pulse width modulation circuit 2 switching circuit 3 computer 4 RAM table 5 smoothing circuit 6 LPF

Claims (2)

[Claims] 1. An electronic volume adjuster for adjusting an output level of an analog signal waveform, means for modulating an analog amplitude waveform into a pulse signal having a pulse width modulated according to the amplitude, and inputting the pulse signal into a base of a switching circuit, one port The duty ratio of the pulse train that is repeatedly output from the control circuit is varied and controlled according to the volume setting amount, and smoothed to obtain a voltage that varies according to the volume setting amount. And a means for demodulating a pulse width modulated signal having an amplitude corresponding to the voltage output from the open collector into an analog signal waveform, by varying the duty ratio of the pulse train, the output level of the analog demodulated signal An electronic volume that is characterized by adjusting. 2. The variable duty ratio is such that, when it is desired to lower the X decibel volume, if the number of logic "1" s in the pulse train is N, the number of logic "1" s is N.10.
The electronic volume according to claim 1, wherein the electronic volume is calculated by using an equation that has ^{X / 20} pulses.