KR20000010947U - Digital audio interface - Google Patents

Abstract

The present invention relates to a digital audio interface for transmitting a digital audio signal to an external device. When the digital audio signal is input, the present invention generates a first pulse wave having a predetermined voltage level and outputs the first pulse wave on a first line L1. A low voltage differential signal transmitter for generating a second pulse wave in which the pulse wave is inverted and outputting the second pulse wave on the second line L2; A transformer for transforming the voltage levels on the first line L1 and the second line L2 to output to the third line L3 and the fourth line L4; A noise removing circuit for removing noise components of the transformed first and second pulse waves on the third and fourth lines; And a low voltage differential signal receiver for generating the digital audio signal based on a voltage difference component of the first pulse wave and the second pulse wave from which the noise component is removed.

Description

Digital audio interface

The present invention relates to a digital audio interface, and more particularly, to a digital audio interface for removing common mode noise of an interface using a low voltage differential device.

Generally, digitalized audio signals are transmitted to achieve high sound quality, such as Compact Discs (CDs) and / or Digital Audio Tape Players (DATPs). When an audio signal is represented in digital form, a significant amount of data is generated. However, because the available bandwidth allocated for audio signals is limited, a 16-bit pulse code modulation (PCM) audio signal sampled at a significant amount, for example 48 KHz, is compressed and transmitted to transmit at about 128 KHz, a limited audio band. On the decoder side, the compressed and decoded audio data is decompressed to perform signal processing.

In order to realize high sound quality, such digital audio system adopts Dolby AC-3 or MPEG audio for multi-channel as well as linear PCM of up to 24 bits and sampling frequency of up to 64KHz. Two-channel playback is performed with a basic function, and playback by multiple channels is handled by an external decoder.

In this case, audio data transmission to an external decoder uses a nonlinear data transmission digital audio interface, and the above-described digital audio interface is related to the present invention.

1 illustrates a prior art digital audio interface.

Referring to FIG. 1, the prior art digital audio interface includes a low voltage differential signal transmitter 100, a transformer 110, a termination resistor R1, and a low voltage differential signal receiver 120.

In FIG. 1, the low voltage differential signal transmitter 100 receives a TTL (Transistor Transistor Logic) level audio signal, that is, a pulse wave as shown in FIG. 2A.

The low voltage differential signal transmitter 100 generates a low voltage differential signal when an audio signal having a TTL level is input. In FIG. Shows the voltage on the other output line L2 of the full voltage differential signal transmitter 100.

As shown in FIG. 2B, the voltage on one output line L1 of the low voltage differential signal transmitter 100 has a pulse wave having a peak to peak of 400 mV, a minimum voltage of 1.0 V, and a maximum voltage of 1.4 V. to be.

In addition, the voltage on the other output line L1 of the low voltage differential signal transmitter 100 has a peak to peak of 400 mV, a minimum voltage of 1.0 V, and a maximum voltage of 1.4 V as shown in FIG. 2C. The piezo has a 180 ° phase difference with the voltage on one side output line L1 of low voltage differential signal transmitter 10.

One output line L1 voltage and the other output line L2 voltage of the low voltage differential signal transmitter 100 are provided to the transformer 110. The transformer 110 boosts the voltage on one output line L1 and the voltage on the other output line L2 of the low voltage differential signal transmitter 100 to a predetermined voltage level, and outputs them on the lines L3 and L4, respectively.

The voltage level on the lines L3 and L4 is adjusted to a predetermined level due to the termination resistor R1, as shown in Figs. 2D and 2E.

The voltage on the line L3 is a pulse wave having a peak to peak of 400 mV, a minimum voltage of 2.0 V, and a maximum voltage of 2.4 V, as shown in FIG. 2D. In addition, the voltage on the line L4 is a pulse wave having a 180 ° phase difference with the voltage on the line L3, as shown in FIG. 2E.

The voltage on line L3 is provided to one input terminal of the low voltage differential signal receiver 120, and the voltage on line L4 is provided to the other input terminal of the low voltage differential signal receiver 120.

The low voltage differential signal receiver 120 generates a TTL level audio signal by using a difference between the voltage on the line L3 and the voltage on the line L4 and provides the same to a decoder not shown.

As such, the digital audio interface functions as an interface to the DVD and / or digital audio signal + between the digital TV system and an external device. However, in the conventional digital audio interface, if noise is generated on the lines L3 and L4 as shown in FIG. 2F due to external factors, false audio signals may be generated at the output of the low voltage differential signal receiver 120. There is concern.

Accordingly, an object of the present invention is to provide a digital audio interface that suppresses generation of false data by adding a noise removing circuit to an input terminal of a low voltage differential signal receiver.

The present invention for achieving the above object is a digital audio interface for transmitting a digital audio signal to an external device: when the digital audio signal is input, generates a first pulse wave of a predetermined voltage level on the first line L1 A low voltage differential signal transmitter configured to output a second pulse wave in which the first pulse wave is inverted and to output the second pulse wave on a second line L2; A transformer for transforming the voltage levels on the first line L1 and the second line L2 to output to the third line L3 and the fourth line L4; A noise removing circuit for removing noise components of the transformed first and second pulse waves on the third and fourth lines; And a low voltage differential signal receiver for generating the digital audio signal based on the voltage difference component of the first pulse wave and the second pulse wave from which the noise component is removed.

1 is a detailed circuit diagram showing a digital audio interface of the prior art;

2A is a waveform diagram of a TTL signal input to a digital audio interface;

2B, 2C, 2D, and 2E are sub-waveform diagrams inside the digital audio interface,

Figure 2f is a waveform diagram for explaining the problem of the prior art,

3 is a detailed circuit diagram of a digital audio interface according to an embodiment of the present invention.

<Description of the code | symbol about the principal part of drawing>

100: low voltage differential signal transmitter 110: transformer

120: low voltage differential signal receiver 300: noise cancellation circuit

R2, R3, R4: Resistor C: Condenser

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 shows a digital audio interface according to an embodiment of the present invention.

As can be seen with reference to Figure 3, the digital audio interface according to an embodiment of the present invention is almost the same as the digital audio interface of the prior art shown in Figure 1, the most distinctive difference in the process of interfacing the audio signal The noise elimination circuit 300 may be further provided.

Therefore, in FIG. 3, the same reference numerals are used to designate identical members that perform the same functions as those of FIG. 1, and will be described below with reference to the newly added noise removing circuit 300.

Referring to FIG. 3, one end of the first resistor R2 is connected to the line L3, one end of the second resistor R3 is connected to the line L4, and the other end of the first resistor R2 is the second resistor. It is connected to the other end of R3. Also, the noise removing circuit 300 is connected to the other end of the first resistor R2 and the other end of the second resistor R4.

Here, the noise removing circuit 300 is composed of a third resistor R4 and a capacitor C. One end of the third resistor R4 is connected to the other end of the first resistor R2 and the other end of the second resistor R4. In addition, one end of the capacitor C is connected to the other end of the third resistor R4, and the other end thereof is grounded.

Referring to Figure 3, the operation of the digital audio interface according to an embodiment of the present invention will be described.

First, when the voltage on the line L3 output from the transformer 110 and the voltage on the line L4 are the same as in Fig. 2f, the voltage level on the line L3 is readjusted by the first resistor R2, and the noise component on the line L3 is zero. It is removed by the filtering action by the three resistors R4 and the capacitor C, and is input to the low voltage differential signal receiver 120 at one input terminal.

In addition, the voltage level on the line L4 is readjusted by the second resistor R3, and the noise component on the line L4 is removed by the filtering action by the third resistor R4 and the capacitor C, so that the low voltage differential signal receiver 120 Is input to the other input terminal.

Therefore, since the signal input to the low voltage differential signal receiver 120 is noise-free, false data does not occur at the output of the low voltage differential signal receiver 120.

As described above, the present invention suppresses the generation of false data by adding a noise prevention circuit to the input terminal of the low voltage differential signal receiver, thereby providing an effect of performing a more accurate interface function.

Claims (1)

In a digital audio interface for transmitting a digital audio signal to an external device: When the digital audio signal is input, a first pulse wave having a predetermined voltage level is generated and output on the first line L1, and a second pulse wave in which the first pulse wave is inverted is generated and output on the second line L2. Low voltage differential signal transmitter; A transformer for transforming the voltage levels on the first line L1 and the second line L2 to output to the third line L3 and the fourth line L4; A noise removing circuit for removing noise components of the transformed first and second pulse waves on the third and fourth lines; And a low voltage differential signal receiver for generating the digital audio signal based on the voltage difference component of the first pulse wave and the second pulse wave from which the noise component is removed.