JPH03165634A - Signal transmission system - Google Patents

Abstract

PURPOSE:To prevent deterioration in the quality of an analog signal by sending a digital signal while isolating a digital signal transmission line between a digital circuit being one hybrid circuit and a digital circuit being other hybrid circuit electrically. CONSTITUTION:An analog signal outputted from an analog circuit 4 of one hybrid circuit 2 is sent through an analog signal transmission line 22 to an analog circuit 14 of other hybrid circuit 12 to make the ground level of the hybrid circuits 2, 12 to a same level. A digital signal outputted from a digital circuit of one hybrid circuit 2 is sent through a digital signal transmission line 32 to a digital circuit of other hybrid circuit 12. An isolation transmission means 8 isolates the digital signal transmission line 32 between the digital circuit of the hybrid circuit 2 and the digital circuit of the other hybrid circuit 12 electrically and sends the digital signal. Thus, the signal transmission system not deteriorating the quality of the analog signal is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal transmission system used in AV equipment and the like.

[Prior Art] FIG. 4 shows audio equipment (for example, a CD player and
This figure shows a conventional signal transmission system used in audio amplifiers. The mixing circuit 202 includes an analog circuit 204 and
A microcomputer 206 as a digital circuit,
An input/output interface 207 is provided. This mixed circuit 202 is used, for example, in a CD player. The analog circuit 204 is capable of outputting an analog signal. Analog circuit 204, microcomputer 206, and human output interface 207 are commonly grounded via ground line 208. microcomputer 20
6 is capable of inputting and outputting digital signals. The digital signal output from the microcomputer 206 is output via the input/output interface 207. A digital signal input to the input/output interface 207 is input to the microcomputer 206 .

The mixing circuit 212 includes an analog circuit 214, a microcomputer 216 as a digital circuit, and an input/output interface 217. This mixed circuit 212 is
For example, it is used in audio amplifiers. analog circuit 2
14 is capable of inputting an analog signal. The analog circuit 214, microcomputer 216, and input/output interface 217 are connected to each other via a ground line 218.
Commonly grounded. The microcomputer 216 is capable of inputting and outputting digital signals. The digital signal output from the microcomputer 216 is output via the input/output interface 217. The digital signal input to the input/output interface 217 is
It is input to the microcomputer 216.

The audio cable 222 is connected to the hot side signal line 224
and a ground side signal line 226. The digital transmission cable 232 includes a hot side signal line 234 and a shielded line 236.

The signal line 226 of the audio cable 222 is connected to the ground line 208 of the mixed circuit 202 and the ground line 218 of the mixed circuit 212, respectively. As a result, the ground potentials of mixed circuit 202 and mixed circuit 212 are brought to the same level. One end of the signal line 224 is connected to the output of the analog circuit 204. The other end of the signal line 224 is
Connected to the input of analog circuit 214. Mixed circuit 20
The analog signal output from the analog circuit 204 of No. 2 is transmitted to the analog circuit 214 of the mixed circuit 212 via the signal line 224. The return current of the analog signal transmitted to analog circuit 214 returns to analog circuit 204 via signal line 226 .

Shield wire 236 of digital signal cable 230 is not connected to at least one of ground lines 208, 218 to avoid forming an electrical loop with ground line 208, signal wire 224, ground line 218, and shield wire 236. One end of the signal line 236 is connected to the mixing circuit 2
It is connected to the input/output of the input/output interface 207 of 02. The other end of the signal line 236 is connected to the human output of the input/output interface 217 of the mixing circuit 212. The digital signal output from the microcomputer 206 of the mixed circuit 202 is transmitted to the microcomputer 216 of the mixed circuit 212 via the human output interface 207, the signal line 234, and the input/output interface 217. The return current of the digital signal transmitted to the microcomputer 216 returns to the microcomputer 206 via the ground line 218, the signal line 226, and the ground line 208.

Further, the digital signal output from the microcomputer 216 of the mixed circuit 212 is transmitted to the human output interface 217, the signal line 134, and the input/output interface 2.
07 to the microcomputer 206 of the mixed circuit 202. The return current of the digital signal transmitted to the microcomputer 206 is connected to the ground line 2.
08, via the signal line 226 and the ground line 218,
Return to microcomputer 216.

The signal lines 224 and 226 of the conventional audio cable 222 constitute an analog signal transmission path, and the signal line 234 of the digital cable 232 and the audio cable 22 constitute an analog signal transmission path.
Two signal lines 226 constitute a digital signal transmission path.

[Problem to be Solved by the Invention] In such a conventional signal transmission system, at least one of the shield wires of the digital transmission cable is separated from the ground of the mixed circuit.
signal line 234 - impedance of microcomputer 206 and human output interface 207 -> ground line 208 -> signal line 226 of audio cable 222
An electrical loop is formed in the order of -> ground line 208 -> impedance of microcomputer 216 and input/output interface 217 -> signal line of data transmission cable 232, which rotates in the forward or reverse direction.

Therefore, in conventional signal transmission systems, magnetic flux interlinks within this electrical loop, causing induced noise in the electrical loop. Therefore, induced noise is superimposed on the analog signal, degrading the quality of the analog signal.

Furthermore, since the digital signal flows through an electrical loop, the digital signal is superimposed on the analog signal, degrading the quality of the analog signal.

An object of the present invention is to solve the above-mentioned technical problems and provide a signal transmission system in which the quality of analog signals does not deteriorate.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention has the following configuration.

That is, the signal transmission system according to the present invention includes a plurality of mixed circuits each including an analog circuit to input or output an analog signal and a digital circuit to input or output a digital signal, and in which the analog circuit and the digital circuit are commonly grounded. and an analog signal transmission line that transmits the analog signal output from the analog circuit of one mixed circuit to the analog circuit of the other mixed circuit, and that makes the ground potential of each mixed circuit the same level, and A digital signal transmission path that transmits the digital signal output from a digital circuit to the digital circuit of the other mixed circuit, and a digital signal transmission path between the digital circuit of one mixed circuit and the digital circuit of the other mixed circuit are electrically connected. or an insulated transmission means for transmitting a digital signal while electrically insulating between the digital signal transmission path and at least one of the digital circuits.

[Operation] Each of the plurality of mixed circuits includes an analog circuit that inputs or outputs an analog signal and a digital circuit that inputs or outputs a digital signal. The analog and digital circuits of each mixing circuit are commonly grounded.

The analog signal transmission path transmits the analog signal output from the analog circuit of one mixed circuit to the analog circuit of the other mixed circuit, and sets the ground potential of each mixed circuit to the same level.

The digital signal transmission path transmits the digital signal output from the digital circuit of one mixed circuit to the digital circuit of the other mixed circuit.

The insulating transmission means electrically isolates the digital signal transmission path between the digital circuit of one mixed circuit and the digital circuit of the other mixed circuit, or connects the digital signal transmission path and at least one of the digital circuits. Transmits digital signals while being electrically isolated.

In this invention, since electrical insulation is provided by the insulated transmission means, no electrical loop is formed. Therefore, even if there is a magnetic flux, the induced noise does not flow into the electrical loop, so the induced noise is not superimposed on the analog signal, and the quality of the analog (N''r) does not deteriorate.

Furthermore, since the digital signal does not flow through an electrical loop, the digital signal is not superimposed on the analog signal, and the quality of the analog signal does not deteriorate.

[Example] Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is a simplified circuit diagram of one embodiment of the invention.

The mixing circuit 2 includes an analog circuit 4, a microcomputer 6 as a digital circuit, an input/output interface 7, and a transformer 8 as an isolated transmission means. This mixing circuit 2 is used, for example, in a CD player. The analog circuit 4 is capable of outputting analog signals. The microcomputer 6 is capable of manually inputting and outputting digital signals. The digital signal output from the microcomputer 6 is output via the input/output interface 7. The digital signal input to the input/output interface 7 is input to the microcomputer 6.

One ends of the analog circuit 4, microcomputer 6, input/output interface 7, and transformer 80 winding 8a are commonly grounded via a ground line IO. Winding 8
The other end of a is connected to the input/output terminal of the microcomputer 6.

The mixing circuit 12 includes an analog circuit 14, a microcomputer 16 as a digital circuit, an input/output/interface 17, and a transformer 18 as an insulation transmission means. The analog circuit 14 is capable of inputting analog signals.The microcomputer circuit 16 is capable of inputting and outputting digital signals.The digital signals output from the microcomputer 16 are The digital signal inputted to the input/output interface 17 is outputted via the output interface 17. The digital signal inputted to the input/output interface 17 is inputted to the microcomputer 16. One end of the winding 18a is commonly grounded via a ground line 20.(Ii
The other end is connected to the output end 1 of the input/output interface 17 .

The audio cable 22 includes a hot side signal line 24 and a ground side signal line 26 for analog signal transmission. The digital transmission cable 32 includes a hot side signal line 34 and a signal line 36 as digital signal transmission paths. One end of the signal line 24 of the audio cable 22 is connected to the output of the analog circuit 4 of the mixing circuit 2. The other end of the signal line 24 is connected to the analog circuit 14 of the mixing circuit 12.
connected to the input of The signal line 26 of the audio cable 22 is connected to the ground line 10 of the mixing circuit 2 and the mixing circuit 1.
2 ground lines 20, respectively. As a result, the ground potentials of mixing circuit 2 and mixing circuit 12 are brought to the same level. Signal line 34 of digital transmission cable 32
are connected to one ends of windings 8b and 18b of transformers 8 and 18, respectively. The signal line 36 functions as a shield and is connected to the other ends of the windings 8b and 18b of the transformer 8.18, respectively.

The analog signal output from the analog circuit 4 of the mixing circuit 2 is transmitted to the analog circuit 14 of the mixing circuit 12 via the signal line 24. The return current of the analog signal transmitted to the analog circuit 14 returns to the analog circuit 4 via the signal line 26.

The digital signal output from the microcomputer 6 of the mixing circuit 2 is sent to the turnout interface 7 and the transformer 8.
windings 8a, 8b, signal wires 34, 36, windings 18b, 18a of transformer 18, and input/output interface 17
The signal is transmitted to the microcomputer 16 of the mixing circuit 12 via. Here, since the return current of the digital signal transmitted to the transformer 8 is insulated by the transformer 8, it returns via at48a. Since the return current of the digital signal output from the transformer 8 is insulated by the transformer 8 and the transformer 18, it returns to the winding 8b of the transformer 8 via the signal line 34, 36 and the winding 18b of the transformer 18. Since the return current of the digital signal output from the transformer 18 is insulated by the transformer 18, it returns from the microcomputer 16 to the winding 18a.

The digital signal output from the microcomputer 16 of the mixing circuit 12 is transmitted via the input/output interface 17, the windings 18a, 18b of the transformer 18, the signal lines 34, 36, the windings 8a, 8b of the transformer 8, and the input/output interface 7. , is transmitted to the microcomputer 6 of the mixing circuit 2. The return current of the digital signal transmitted to the transformer 18 returns via the winding 18a since the transformer 18 is insulated.

Since the transformer 18 and the transformer 8 are insulated, the return current of the digital signal output from the transformer 18 returns to the winding 18b of the transformer 18 via the signal line 34, 36 and the winding 8b of the transformer 8.

Since the transformer 8 is insulated, the return current of the digital signal output from the transformer 8 returns from the microcomputer 6 to the winding 8a.

In this way, from my 20 computer 6 to the microcomputer 16, and from the microcomputer 16
A digital signal is transmitted from the microcomputer 6 to the microcomputer 6. Furthermore, the signal lines 34 and 36 and the microcomputer 6 are electrically insulated by the transformer 8. Furthermore, the signal lines 34 and 36 are electrically insulated from the microcomputer 16 by a transformer 18.

Therefore, microcomputer 6→ground line 10
An electrical loop that rotates in the order of →signal line 26→ground line 20→microcomputer 16→microcomputer 6 in the forward or reverse direction is not formed. Therefore, even if there is magnetic flux, the induced noise does not flow into the electrical loop, so the induced noise is not superimposed on the analog signal, and the quality of the analog signal does not deteriorate.

Furthermore, since the digital signal does not flow through an electrical loop, the digital signal is not superimposed on the analog signal, and the quality of the analog signal does not deteriorate.

Note that if a transformer is provided in the microcomputer of each mixing circuit, it is possible to interface with the mixing circuit without considering electrical loops, and moreover, no electrical loops are formed.

In the above-described embodiment, a transformer is provided in each of the mixing circuit 2 and the mixing circuit 12, but in another embodiment of the present invention, a transformer may be provided only in either the mixing circuit 2 or the mixing circuit 12. You can also do this.

Also, as shown in FIG. 2, the transformer is connected to the signal lines 34, 3
It may be provided in the middle of 6.

FIG. 3 is a detailed circuit diagram of the vicinity of the microcomputer 6 of the mixing circuit 2 according to another embodiment of the present invention, and parts corresponding to those in the embodiment of FIG. 1 are given the same reference numerals.

What should be noted in this embodiment is that photocoupler 42, 44 is used as an insulated transmission means instead of a transformer.

This photocoupler 42.44 has a signal line 34.36,
It is provided between the microcomputer 6 and the microcomputer 6. Signal line 3
A mini plug 46 is connected to one end of 4.36.

An input/output interface 52 is provided between the connector 48.50 to which the mini-plug 46 is connected and the photocoupler 42.44. An input/output interface 54 is provided between the microcomputer 6 and the photocoupler 42,44. The mini-plug 46 is connected to a connector 48, for example.

AC power output from the secondary winding 58 of the power transformer 56 is converted into DC power by a power supply circuit 60.

This DC power is supplied between the power supply line 62 and the ground line 10 to energize the microcomputer 6, input/output interface 54, and the like. AC power output from the secondary winding 66 of the power transformer 56 dedicated to the input/output interface 52 is converted into DC power by a power supply circuit 68. This DC power is connected to a power line 70 and a ground line 7.
2 and energizes the human output interface 52. Ground line 72 connects to high impedance circuit 74
are lifted from the ground and connected to the ground side terminals 48a and 50a of the connectors 48 and 50, respectively.

In the input/output interface 52, the connector 48,
50 hot side terminals 48b, 50b and ground line 7
A resistor 76 and a Zener diode 78 are connected in series between the two. Power line 70 and ground line 72
A transistor 80, a diode 82, and a resistor 84 are connected in series between them. Resistor 84 is connected in parallel to Zener diode 78. A resistor 86 is connected between the base of the transistor 80 and the power supply line 70. The base of transistor 80 is connected to the collector of phototransistor 90 of photocoupler 42 via resistor 88 . The emitter of phototransistor 90 is connected to ground line 72 .

The cathode of diode 82 is connected to the input of inverter 94 via resistor 92 . Inverter 94 is powered with DC power between power line 70 and ground line 72 . The output of the inverter 94 is the photocoupler 4
It is connected to the cathode of the light emitting diode 96 of No. 4. The anode of the light emitting diode 96 is connected to the power supply line 70 via a resistor 98.

At the human output interface 54, the power line 62
A transistor 102 and a resistor 104 are connected in series between the transistor 102 and the ground 94710. transistor 102
The collector of is connected to the input port of the microcomputer 6. A resistor 106 is connected between the emitter and base of the transistor 102.

The base of transistor 102 is connected to the collector of phototransistor 110 of photocoupler 44 via resistor 108 . The emitter of phototransistor 110 is connected to ground line 10. The transistor 112 and the light emitting diode 114 of the photocoupler 42 are connected in series between the power supply line 62 and the ground 94710. The base of the transistor 112 is connected to the power supply line 62 via a resistor 116 and to the output port of the microcomputer 6 via a resistor 118.

Note that the vicinity of the microcomputer 16 of the mixing circuit 12 is similarly configured.

Mutual transmission of digital signals between the microcomputer 6 of the mixing circuit 2 and the microcomputer 16 of the mixing circuit 12 is performed when the signal line 34 of the digital transmission cable 32 is active high. When outputting a digital signal from the microcomputer 16 of the mixing circuit 12 to the microcomputer 6 of the mixing circuit 2, the digital signal is output from the microcomputer 16 of the mixing circuit 12 via the signal lines 34 and 36, and Hot side terminal 50
When is set to a high level, the output of the inverter 94 becomes a low level, and the light emitting diode 96 of the photocoupler 44
lights up.

At this time, the return current returns to the mixing circuit 12 side via the ground line 72 and the signal line 36. When the light emitting diode 96 lights up, a photocurrent flows through the phototransistor 11O, and the transistor! 02 is conductive.

As a result, a high level signal is given to the human power port of the microcomputer 6.

Signal line 3 from microcomputer I6 of mixing circuit 12
A digital signal is output through 4.36 and connected to connector 5.
When the hot side terminal 50 of 0 is set to low level, or when no digital signal is output from the microcomputer 16 of the mixing circuit 12, the inverter 94
The output becomes high level, and the light emitting diode 96 of the photocoupler 44 turns off. When the light emitting diode 96 is turned off, no photocurrent flows through the phototransistor 11O, so the transistor 102 is cut off. As a result, a low level signal is given to the human power port of the microcomputer 6.

From the microcomputer 6 of the mixing circuit 2 to the mixing circuit 12
When outputting a digital signal to the microcomputer 16, when the output port of the microcomputer 6 is set to low level, the transistor 112 becomes conductive.
The light emitting diode 114 of the photocoupler 42 lights up.

Current flows from the power supply line 62 through the resistors 116 and 118 and the output port of the microcomputer 6 to the ground line IO, and from the power supply line 62 through the transistor 112 and the light emitting diode 114 to the ground line 10.

When the light emitting diode 114 is turned on, a photocurrent flows through the phototransistor 90, causing the transistor 80 to conduct and the connector 48. 50 hot side connectors 48b, 50b
becomes high level. This high level signal is applied to the mixing circuit 12 via the signal line 34. Mixing circuit 1
Return current from side 2 returns to ground line 72 via signal line 36 and ground side connectors 48a, 50a of connectors 48.50. As a result, a high level signal is transmitted from the microcomputer 6 of the mixing circuit 2 to the mixing circuit 12 side.

From the microcomputer 6 of the mixing circuit 2 to the mixing circuit 12
When outputting a digital signal to the microcomputer 16 or when not outputting a digital signal,
When the output port of the microcomputer 6 is set to high level, the transistor 112 is cut off and the photocoupler 4 is turned off.
The second light emitting diode 114 is turned off. When the light emitting diode 114 is turned off, no photocurrent flows through the phototransistor 90, so the transistor 80 is cut off and the hot side connectors 48b, 50b of the connectors 48, 50 become low level. This low level signal is transmitted to the mixing circuit 12 side via the signal line 34.

In this way, digital signals are transmitted without being electrically coupled by the photocoupler 42, 44, so no electrical loop is formed.

In addition to the connector 48, a connector 50 is provided to which another mixing circuit (for example, used in a cassette tape deck) can be connected via the mini plug 46.

That is, by sequentially connecting three or more mixing circuits, communication can be performed without forming an electrical loop between the mixing circuits.

In addition, as another embodiment of the present invention, a photo coupler is used in place of the transformer shown in FIG. 2, and the photo coupler is connected to the signal line 34.
．． It may be provided in the middle of 36.

In addition, in the above embodiment, a transformer and a photocoupler were used as insulation transmission means, but electricity-heat-electricity,
It may also be implemented using other insulated transmission means that performs electricity-acoustic-electricity conversion.

Further, in the above-described embodiment, the digital signals are transmitted serially, but the present invention may also be applied to parallel transmission.

Furthermore, although the analog signal is transmitted in one direction and the digital signal is transmitted in both directions, it may also be applied when transmitting an analog signal in both directions or when transmitting a digital signal in one direction. .

[Effects of the Invention] As described above, the present invention can electrically isolate the digital signal transmission path between the digital circuit of one mixed/night circuit and the digital circuit of the other mixed circuit, or The present invention includes an insulating transmission means for transmitting digital signals while electrically insulating between the circuit and at least one digital circuit.

Therefore, since the insulating transmission means is electrically insulated, no electrical loop is formed. Therefore, even if there is magnetic flux, the induced noise does not flow into the electrical loop, so the induced noise is not superimposed on the analog signal, and the quality of the analog signal does not deteriorate.

Furthermore, since the digital signal does not flow through an electrical loop, the digital signal is not superimposed on the analog signal, and the quality of the analog signal does not deteriorate.

[Brief explanation of the drawing]

FIG. 1 is a simplified circuit diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of a signal line 34, 36 in another embodiment of the present invention, and FIG. 3 is a simplified circuit diagram of another embodiment of the present invention. A detailed circuit diagram around the microcomputer 6 in the example, FIG. 4 is a conventional circuit diagram. 2.12...Mixing circuit 4.14...Analog circuit 6.16...Microcomputer 8.18...Transformer 22...Audio cable 24, 26.34.36...Signal line 32 ...Digital transmission cables 42, 44...Photo coupler

Claims (1)

[Claims] A plurality of mixed circuits each comprising an analog circuit that inputs or outputs an analog signal and a digital circuit that inputs or outputs a digital signal, the analog circuits and the digital circuits being commonly grounded, and a mixture of one or the other. An analog signal transmission path that transmits the analog signal output from the analog circuit of one circuit to the analog circuit of the other mixed circuit and makes the ground potential of each mixed circuit the same level, and the analog signal output from the digital circuit of one mixed circuit. While electrically insulating the digital signal transmission path that transmits the digital signal from the mixed circuit to the digital circuit of the other mixed circuit, and the digital signal transmission path between the digital circuit of one mixed circuit and the digital circuit of the other mixed circuit, Alternatively, a signal transmission system comprising: insulation transmission means for transmitting a digital signal while electrically insulating between the digital signal transmission path and at least one digital circuit.