JP2865572B2 - Digital-to-analog converter with analog multiplication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital / analog converter of an analog multiplication system, and more particularly to a digital / analog converter of an analog multiplication system which has a simple structure and effectively suppresses the generation of pop noise by a non-variable DC value. It relates to an analog converter.

[0002]

2. Description of the Related Art In FIG.
The two waveforms are synthesized by multiplying the tone waveform shown in FIG. 2A by the envelope waveform also shown in FIG. 2B. The sound waveform is (c) or (d) in the figure.
It was as shown in the figure. The following two methods have been used as such speech synthesis results.

Digital speech synthesis: Digital data of a tone (tone) waveform and an envelope waveform are multiplied by a multiplier prior to input to a digital / analog converter, and the product is input to the digital / analog converter. And synthesizes the voice. However,
Disadvantages include the need for multipliers and relatively high system operating frequencies.

Analog voice synthesis: digital /
Since the analog converter itself does not have an offset adjustment function and an appropriate positive / negative signal processing function, for example, as shown in FIG.
Value. Therefore, in practical use, pop noise (p
In order to suppress the noise, it is usually necessary to add a pair-coupled capacitor to remove the DC component, which is disadvantageous in cost.

[0005]

The problem to be solved by the present invention is that the digital-to-analog converter according to the prior art has a problem in that a separate multiplier is provided or a pair coupling is performed to remove pop noise. And the need to add a capacitor, the structure becomes complicated, and as a result, it is difficult to reduce the manufacturing cost.

[0006]

According to the present invention, there is provided a digital / analog converter which multiplies a first digital signal by a second digital signal and outputs an analog signal from a speaker. , A first digital signal is input, the first digital signal is converted into a conversion code signal, the most significant bit of the first digital signal is made the most significant bit representing the positive / negative value of the conversion code signal, and the first Code conversion means for setting an absolute value of a deviation of the first digital signal from an intermediate value of the digital signal as an absolute value of the conversion code signal; a conversion code signal and a second digital signal connected to the code conversion means and inputted; And a multiplying means for generating a multiplied signal by multiplying the multiplied signal by the multiplying means. Together, it outputs a drive signal, to provide a digital / analog converter of the analog multiplier system having a driving means for outputting an analog signal by driving the speaker.

[0007]

According to the present invention, first, a first digital signal is code-converted into a conversion code signal by code conversion means, and the most significant bit of the first digital signal is set as the most significant bit representing the positive / negative value of the conversion code signal. The absolute value of the deviation of the first digital signal from the intermediate value of the first digital signal is used as the absolute value of the conversion code signal, and is then multiplied by the second digital signal. The object of effectively suppressing and removing pop noise is achieved by a simple circuit configuration without impairing the speech synthesis effect.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described below with reference to the drawings. 1 to 3 (a) to 3 (c), an analog multiplication type digital / analog converter according to the present invention multiplies a first digital signal T4 'to T0' and a second digital signal E4 to E0. Analog signal (for example, sound wave) from speaker 500 as a multiplication signal
Is output. Here, the first digital signals T4 'to T0' are specifically data signals such as tones, voices, and speeches, and are illustrated and described by limiting them to 5 bits for convenience of description. The second digital signals E4 to E0 are specifically data signals such as envelopes and volumes, which are also limited to 5 bits for convenience of explanation.

As shown in FIG. 1, a digital / analog converter of the analog multiplication type according to the present invention comprises:
Code conversion circuit 100 as code conversion means, multiplication circuit 200 as multiplication means, and drive circuit as drive means
300.

FIG. 2 shows an example of the circuit configuration of the code conversion circuit 100. The first digital signals T4'-T
0 'is input and the first digital signal T
4 'to T0' are converted into conversion code signals T4 to T0.
The most significant bit T4 'of the first digital signals T4' to T0 'is used as the most significant bit T4 representing the positive / negative value of the conversion code signals T4 to T0, and at the same time, the intermediate value of the first digital signals T4' to T0 '( The absolute value of the deviation of the first digital signals T4 'to T0' with respect to 16) is taken as the absolute value of the numerical value part T3 to T0 of the converted code signal. That is, the most significant bit T4 'of the first digital signals T4' to T0 '
If = 0, T4 = 0, so the converted code signal has a negative value. If T4 '= 1, T4 = 1, so the converted code signal has a positive value. In this case, as shown in the following Table 1, the first digital signals T4 'to T0' are obtained with a deviation with respect to the intermediate value (16), and the absolute value of the deviation is determined by the numerical value T3 to T0 of the conversion code signal. It is an absolute value.

[0011]

[Table 1]

FIG. 3 shows an example of a circuit configuration of the multiplying circuit 200.
As shown in (a) to (c), it is mainly composed of a pair of current mirrors, and the conversion code signals T4 to T0 and the second
By storing the digital signal signals E4 to E0 in the register RI1 of FIG. 3B and the register RI2 of FIG. 3C, respectively, clock signals CKT and CKT having relatively large frequencies are stored.
The input of the conversion code signals T4 to T0 and the second digital signals E4 to E0 can be controlled by the KE, and the multi-channel synthesis by the time division method becomes possible. In FIG. 3B, the temporary storage of the conversion code signals T4 to T0 is controlled by the clock signal CKT, and in FIG.
The clock signal CKE controls temporary storage of the second digital signals E4 to E0. The electric resistance R shown in FIG. 3A can be adjusted by adjusting the current Ib1 to obtain the second digital signal E44.
E00 are used to control the magnitude of the current Ib2 via a switching element (for example, a MOS transistor). The conversion code signals T33 to T00 in FIG. 3B are used to control the magnitude of the output current I via a switch element (for example, a MOS transistor).
Is directly proportional to the product (multiplied signal) obtained by multiplying the conversion code signals T33 to T00 and the second digital signals E44 to E00. Then, the conversion code signal T44, that is, / SIGN
(/ SIGN represents an inverted signal of the signal SIGN for convenience). SIGN controls only an output path of a drive circuit 300 described later to output a positive / negative signal. The conversion code signals T33 to T00 and the second digital signals E44 to E44
As can be seen from FIG. 4 showing another example of the configuration of the multiplication circuit according to the present invention, the value of “00” can be interchanged and adjusted.

The drive circuit 300 can be a bridge output circuit as shown in FIG. 1, and is based on the magnitude of the current I and the signals / SIGN and SIGN (determining the path of the current I). The speaker 500 is driven to output an analog signal (audio wave).

Although the technical concept of the present invention has been described with reference to the preferred embodiments, the present invention is not intended to limit the present invention, but to the extent that it does not depart from the technical scope of the present invention. The present invention can be appropriately modified or changed based on the disclosed matter.

[0015]

As described above, the digital-to-analog converter of the analog multiplication system according to the present invention first converts the first digital signal into a converted code signal by the code converting means, and converts the first digital signal into a converted code signal. The most significant bit is the most significant bit representing the positive / negative value of the conversion code signal, and the first bit relative to the intermediate value of the first digital signal is
Since the absolute value of the deviation of the digital signal is used as the absolute value of the conversion code signal and then multiplied by the second digital signal, pop noise can be effectively suppressed without generating a variable DC value. it can. In addition, by temporarily storing the conversion code signal and the second digital signal in a register and performing register control at a relatively large clock frequency, time-division multi-channel synthesis can be realized. It is extremely valuable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing components of a digital / analog converter of an analog multiplication system according to the present invention.

FIG. 2 is a code conversion circuit diagram showing a circuit configuration example of the code conversion circuit in FIG. 1;

3 (a), 3 (b) and 3 (c) are multiplier circuit diagrams showing circuit configuration examples of the multiplier circuit in FIG.

FIG. 4 is a multiplication circuit diagram showing another example of a circuit configuration of the multiplication circuit in FIG. 1;

FIG. 5 is an explanatory diagram showing a conventional speech synthesis technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Code conversion means (code conversion circuit) 200 Multiplication means (multiplication circuit) 300 Driving means (drive circuit) 500 Speaker T4 'First digital signal T3' First digital signal T2 'First digital signal T1' First digital signal T0 '1st digital signal T4 conversion code signal T3 conversion code signal T2 conversion code signal T1 conversion code signal T0 conversion code signal E4 second digital signal E3 second digital signal E2 second digital signal E1 second digital signal E0 second digital signal RI1 register RI2 register CKT clock signal CKE clock signal

Claims (4)

(57) [Claims] 1. A digital / analog converter for multiplying a first digital signal by a second digital signal and outputting an analog signal from a speaker, wherein the first digital signal is input and the first digital signal is A conversion code signal is converted, the most significant bit of the first digital signal is set as the most significant bit representing the positive / negative value of the conversion code signal, and the absolute value of the deviation of the first digital signal with respect to the intermediate value of the first digital signal is converted. Code conversion means for setting a value as an absolute value of the conversion code signal; multiplication means connected to the code conversion means for multiplying the input conversion code signal and the second digital signal to generate a multiplication signal; The multiplication means is connected to the multiplication means, the multiplication signal is input from the multiplication means, a driving signal is output, and the speaker is A digital-to-analog converter of an analog multiplication method, comprising: a driving unit for driving to output an analog signal. 2. The digital / analog converter according to claim 1, wherein said multiplying means comprises a current mirror circuit. 3. The digital / analog conversion according to claim 2, wherein the conversion code signal and the second digital signal are respectively connected to the current mirror circuit via a register. vessel. 4. The digital / analog converter according to claim 1, wherein said driving means is a bridge output circuit.