JPH0452852Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> This invention relates to a noise removal device for digital audio equipment.

<Prior Art> With the recent development of digital electronic technology, the digitalization of consumer electronics is progressing rapidly.

In audio playback equipment as well, we are seeing the emergence of digital audio disks in which the control section and other signal processing are digitalized.

FIG. 2 is a diagram showing an example of the configuration of a digital audio disk player, in which 10 is an optical deck mechanism, 20 is an optical deck control circuit, 30 is a preamplifier, 40 is a digital signal circuit, 50 is an analog signal circuit, and 60 is a preamplifier. A system control section 70 is a power supply circuit that replaces the commercial AC power supply with DC power and supplies power to each of the above units via a power supply line 71.

The optical deck mechanism 10 is a disk motor 1
1, an optical pickup 12, and a feed motor for the optical pickup, each of which is controlled by an optical deck control circuit 20.

The RF signal from the optical pickup 12 is shaped by a preamplifier 30 and sent to a digital signal circuit 4.
Sent to 0.

The digital signal circuit 40 includes a synchronization detection circuit 41
, a digital signal processing circuit 42 , and a crystal oscillator 43 serving as a clock pulse generation source, and the output converted into a digital signal is sent to an analog signal circuit 50 via a digital signal line 51 .

The analog signal circuit 50 consists of a digital/analog converter 53, a deglitch circuit 54, and low-pass filters 55, 55, in which a digital signal is converted into an analog signal, and then separated into left and right analog signals, which are passed through the low-pass filter 55,
55 and is output to output terminals 56 and 56.

Note that a deglitch signal line 52 is connected to the deglitch circuit 54 from the digital signal circuit 40.

The system control unit 60 includes operation keys 62 and a display 6.
3 and a system control circuit 61.

Each of these units is densely packaged in one cabinet to constitute a digital audio disc player.

Incidentally, the clock pulse signal generated by the crystal oscillator 43 mentioned above and the current changes caused by the operation of the logic elements constituting the system control circuit 61 and the digital signal processing circuit 42 are noise sources in themselves.

These internal noises are directly or indirectly coupled and transmitted to the analog signal circuit 50 through electrostatic and electromagnetic coupling between each unit that is densely mounted, and the quality of the analog signal output is degraded. There was a problem with being exposed.

In order to cope with this problem, conventional methods have been used to remove the noise by shielding the noise generating portion and the analog signal circuit 50, or by inserting a filter.

As a result, these measures were effective in suppressing the noise component in the analog signal output to a practical level.

However, with such conventional methods, it is not possible to sufficiently eliminate the noise directly radiated and induced in the digital signal line 51 and the influence of noise transmission due to a type of coupling caused by the common impedance of the power supply circuit, and it is difficult to achieve high-fidelity reproduction. However, it has not been possible to obtain a satisfactory high-quality analog audio signal output when performing.

<Purpose of the invention> In consideration of the above points, this invention provides a noise prevention device for digital audio equipment that can suppress the transmission of noise generated within the digital audio equipment and obtain a high-quality audio signal output. The purpose is to

<Structure of the invention> a Summary The gist of the structure of this invention is that in a digital audio device that converts a digital signal into an analog signal, the rectifying element and the smoothing capacitor of the power supply circuit are connected to the analog signal circuit 5.
0 and other circuit parts, and includes a means for converting the output of the digital signal circuit 40 into an optical signal, a means for transmitting the optical signal, and a means for receiving the optical signal and converting it into an electrical signal. This is a noise removal device for digital audio equipment, which is equipped with converting means and transmits the electrical signal to a digital/analog converter 53.

b. Example Hereinafter, an example of this invention will be described based on the drawings.

FIG. 1 is a block diagram showing an embodiment of this invention, and parts common to those in FIG. 2 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 1, the output signal of the digital signal circuit 40 is guided to a light emitting element 80, the optical output of the light emitting element 80 is guided to a light receiving element 82 via a light transmission member 81, and the electrical output of the light receiving element 82 is transferred to a logic level shifter. 57 to the digital/analog converter 53.

Furthermore, the deglitch control signal of the digital signal circuit 40 is guided to the light emitting element 83, the optical output of the light emitting element 83 is guided to the light receiving element 85 via the light transmission member 84, and the electrical output of the light receiving element 85 is guided to the light receiving element 85 via the logic level shifter 58. It is arranged to lead to a deglitch circuit 54.

The light transmitting members 81 and 84 described above are formed of optical fiber or transparent synthetic resin with good light transmittance, and the light emitting elements 80 and 83 and the light receiving element 8
2 and 85 may be made to face each other using air as a medium, or a lens may be disposed between them to achieve the same effect.

On the other hand, the power supply circuit includes a power transformer 76 having two secondary windings, and two sets of rectifier circuits A72 and B each having a rectifying element and a smoothing capacitor.
It consists of 74. One secondary winding of a power transformer 76 is connected to the rectifier circuit A72, and its output is connected to the analog signal circuit 50 via a power supply line 73. Also rectifier circuit B
The other secondary winding of a power transformer 76 is connected to 74, and its output is connected to the optical deck mechanism 10, the optical deck control circuit 20, the preamplifier 30, and the digital signal circuit 4 via a power supply line 75.
0, connected to the system control unit 60. Note that the above-mentioned power transformer 76 may be constituted by two separate power transformers.

Although the configuration described above is composed of a light emitting element, a light transmitting member, and a light receiving element, the same effects as described above can be achieved even if the light transmitting means is configured by a photocoupler. Furthermore, this invention is not limited to the digital audio disc player of the above embodiment, but is applicable to audio circuits of digital audio tape equipment and video disc players that aim to output high-quality audio signals, etc. Similar effects can be achieved when applied to audio circuits of devices that convert signals into analog signals.

<Operation of the invention> This invention is constructed as described above, and the above-mentioned clock pulse noise and operation noise of the logic element are superimposed as noise components on the digital signal output and the deglitch signal output of the digital signal circuit 40. There is. These signal outputs are input to light emitting elements 80 and 83, respectively, and converted into optical signals. This optical signal is transmitted to light receiving elements 82 and 85 via optical transmission members 81 and 84, and photoelectric conversion is performed.

Due to light transmission between the light emitting elements 80, 83 and the light receiving elements 82, 85, the electrical output of the light receiving elements 82, 85 becomes a digital signal from which the common impedance of the signal transmission system is completely separated and noise components are removed. and is further outputted as a logic level shifter 57,
58 performs waveform shaping of the digital signal and removes residual noise components.

On the other hand, two independent rectifier circuits A72 and B74
Therefore, the analog signal circuit 50 and other circuit parts are supplied with power separately, and coupling via the common impedance of the power supply circuit and the power supply line is prevented.

<Effect of the invention> As described above, in the noise removal device for digital audio equipment according to this invention, the analog signal circuit and the digital signal circuit each have separate and independent rectifier circuits, and the digital signal circuit and the analog signal circuit Since the signal transmission between the device and the device is carried out via optical signals, it suppresses the transmission of noise components generated within the device, which could not be sufficiently removed using conventional methods, and outputs a high-quality analog signal. This has the effect of realizing clear high frequency reproduction.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of this invention.
FIG. 2 is a block diagram of a conventional digital audio disc player. 40... Digital signal circuit, 50... Analog signal circuit, 53... Digital/analog converter, 72... Rectifier circuit A, 74... Rectifier circuit B,
80... Light emitting element, 81... Light transmission member, 82...
…Light receiving element.

Claims (1)

[Scope of utility model registration request] For digital audio equipment that converts digital signals into analog signals,
A rectifying element and a smoothing capacitor of the power supply circuit are formed separately and independently in the analog signal circuit and other circuit parts, and a means for converting the output of the digital signal circuit into an optical signal and transmitting the optical signal. and a means for receiving the optical signal and converting it into an electrical signal, and converting the electrical signal into a digital/digital signal.
A noise removal device for digital audio equipment, characterized in that the noise is removed by transmitting the noise to an analog converter.