JPH0652869B2 - Digital / analog converter - Google Patents

Description

The present invention relates to improvements in digital / analog converters (hereinafter referred to as D / A converters), and relates to D / A converters suitable for D / A conversion of audio data. It is a thing.

[Problems to be Solved by Prior Art and Invention]

Conventionally, a D / A converter is used when converting digital data such as an audio signal into an analog signal. In such a D / A converter, the most adverse effect on the error during D / A conversion is the MSB error. Ie MSB
Corresponds to the polarity bit of the output analog signal, which causes a zero-crossing distortion (shown in FIG. 4) at the zero-crossing point, which has a great influence on the auditory sense, especially when the output level is small. The present invention aims to reduce such a zero-cross distortion generated at the time of polarity reversal in terms of hearing.

[Means for Solving the Problems]

The present invention has means for producing two data by adding and subtracting bias data to and from input data, and means for making the bias data zero in a range where the result exceeds a predetermined level by addition or subtraction, and synthesizes both data. This is a D / A converter characterized by obtaining one analog output.

[Action]

According to the present invention, when the two data are D / A converted by the above configuration, the two data are MBS near the original zero-cross point.
The reversal of does not occur. That is, the distortion based on the D / A conversion error of the MSB is generated in the above two data at the position corresponding to the level other than the zero cross point of the original data. Therefore, the zero-cross distortion is generated at a high level other than near the zero level, which is hard to hear.

〔Example〕

The present invention will be described with reference to an embodiment used in the D / A converter of a CD player.

FIG. 1 is a block diagram of the present invention, and FIG. 2 is a diagram showing input / output. A 16-bit digital signal from the optical pickup is passed through a signal processing system and a digital filter and then input to the serial-parallel converter 1 as 16-bit + α-bit serial data input to be converted into parallel data A. In the subsequent stage, an overflow detector 2 and an underflow detector 3 are provided for comparing with the data preset in advance by presets 5 and 6 to detect whether the result exceeds a predetermined level by addition or subtraction. In this case, the control input C of the adder 8 and the subtractor 9 for adding or subtracting the value preset by the preset 7 to the parallel voltage A, for example, the 7-bit data B set to 7 bits, via the OR circuit 4 The adder 8 or the subtracter 9 outputs the data A as it is without adding or subtracting the preset value of the preset 7 by notifying the operation prohibition. Even if the presets 5 and 6 are set to 7 bits and a 7-bit digital value is added, overflow does not occur within a predetermined level. The adder 8 and the subtracter 9 always add / subtract the 7-bit digital value of the preset 7 preset value. Adder 8,
The output data D ₁ and D ₂ of the subtractor 9 are parallel
Parallel / serial conversion is performed by the serial converters 10 and 11 (not required if the D / A converter is a parallel input type) and input to the D / A converters 12 and 13. D
Analog data E ₁ and E _{2 obtained} by D / A converting the biased data D ₁ and D ₂ by the A converters 12 and 13 respectively by the adder 14 are combined F =
E ₁ + E ₂ is obtained and becomes one analog output F. The adder 14 inverts one side of the digital data D ₁ and D ₂ to D
After the A / A conversion, a differential amplification configuration may be used. Therefore, it is possible to provide a digital-analog converter in which zero-cross distortion does not occur when the input signal is equal to or less than the bias value.

〔The invention's effect〕

According to the present invention, the change point of the MSB can be changed from 0 by adding and subtracting the bias to the input data,
In particular, since the MSB does not change at a low level equal to or lower than the bias value, it is possible to eliminate the zero cross distortion due to the inversion of the MSB. Further, even if the level is equal to or higher than the bias value, the amount of zero cross distortion is different between the addition side and the subtraction side, so that the amount of distortion when combined can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining input-output, FIG. 3 is a diagram for explaining waveforms, (A) is addition (B) Subtraction (C) shows the composite waveform and zero cross distortion. FIG. 4 is a waveform diagram showing the zero-cross distortion of the conventional example. 1 ... Serial-parallel converter 2 ... Overflow detector 3 ... Underflow detector 4 ... OR circuit 5,6,7 ... Preset circuit 8 ... Adder 9 ... Subtractor 10,11 ... Parallel -Serial converter 12, 13 ... D / A converter 14 ... Adder.

Claims (1)

[Claims] 1. An adding circuit and a subtracting circuit for adding and subtracting predetermined bias data to and from input digital data,
A digital-to-analog converter that digital-to-analog converts the digital data added by the adder circuit and the digital data subtracted by the subtractor circuit, and an overflow of the digital-analog converter that occurs when the predetermined bias data is added and subtracted. A detection circuit that detects underflow from the input digital data in advance and prohibits addition and subtraction by the addition circuit and the subtraction circuit, and an addition circuit that adds both data converted into analog data by the digital-analog converter. A digital-to-analog converter, which is provided, improves zero cross distortion by adding and subtracting predetermined bias data, and prevents overflow and underflow from occurring.