JPH0712118B2 - How to prevent the generation of noise in electronic circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is not concerned with noise mixed from the outside,
The present invention relates to a method for removing the cause of the noise that is generated at various points inside the electronic circuit. Further, the present invention relates to a method for preventing the generation of noise generated in an electronic circuit in which a plurality of loads are electrically connected between a positive output and a negative output of a DC power supply, and a television and a radio. It can be used for various electronic circuits such as receivers, receivers and measuring instruments.

[Conventional technology]

Conventionally, there have been provided various electronic circuits in which a plurality of loads are electrically connected between a positive electrode output and a negative electrode output of a direct-current power supply. A plurality of metal bodies are electrically connected to the one-polarity output of the DC power supply. The term "metal body" as used herein refers to a metal such as a shield of a shielded wire, a chassis, a metal casing, and a metal portion covering the surface of a component.

The electronic circuit (1) has been conventionally constructed as shown in the first drawing.

That is, in FIG. 1, (2) is a DC power supply, and (4)
Is a plurality of loads electrically connected between the positive output and the negative output of the DC power supply (2), respectively, and these electronic circuits (1) are configured by these loads. The loads (4) are specifically transistors, ICs, Ls, Cs, Rs.
Etc. In addition, in FIG.
(5), (7) and (8) are metal bodies existing around the electronic circuit (1), and are electrically connected to the one-polarity output of the DC power supply (2). In the drawing,
(5) is the shield of the shielded wire, (7) is the chassis,
(8) shows other metal bodies, and for convenience of explanation,
Each is shown separately.

In the above conventional electronic circuit (1), an electrical connection between the output of one polarity of the DC power supply (2) and a portion of each load (4) to be electrically connected to this output, and a metal body The electrical connection between (5), (7), (8) and the one-polarity output of the DC power supply (2) has been performed as follows.
That is, as shown in FIG. 1, one end of the one-polarity output of the DC power supply (2) is used as a base point (3), and basically different on one electric conductor connected to this base point (3). Each load (4) can be directly connected to several points (see the two loads (4) on the left side in FIG. 1), or the shield (5) of the shield wire connected to the base point (3) Yashiashi (7)
Or the like, each load (4) is connected, and the base point (3) and each load (4) are indirectly connected via the shield (5), chassis (7), etc. (in FIG. 1). , Two loads on the right (see 4)). Also, each metal body (8)
Is generally a chassis (7) connected to a base (3)
(See the metal body (8) at the center in FIG. 1) or at an appropriate place on the one electric conductor (metal bodies (8) on both sides in FIG. 1) Had been). In addition, in FIG. 1, (6) shows the part which electrically connects the base point and each load (4), and (9) shows the base point (3) and each metal body (5), (7). , (8) are electrically connected to each other.

[Problems to be Solved by the Invention]

In the conventional electronic circuit (1) as shown in the above-mentioned first illustration, noise remains even if nozzles mixed by external radio waves or the like are removed by a magnetic shield or the like, and noise is generated at various places inside the electronic circuit (1). Was confirmed to occur. Then, as this noise, in addition to ordinary pulse noise, a phenomenon in which the 0 level of the output of an electronic circuit such as a measuring instrument circuit changes was confirmed.

The inventors of the present invention have found that the cause of the noise generated in the electronic circuit (1) is considered as follows.

That is, in the conventional electronic circuit (1) shown in FIG.
An electrical connection between the one-polarity output of the DC power supply (2) and a portion of each load (4) to be electrically connected to this output,
Also, since the electrical connection between the metal bodies (5), (7) and (8) and one polarity of the DC power supply (2) was made as described above, it is assumed that no potential difference originally occurs during circuit design. Each of the considered loads (4) has a relatively large level of AC component and DC component with respect to the base point (3) at the lower side portion (the portion electrically connected to the base point (3)) in the figure. It is considered that a potential difference is generated, and the signal level and the potential on the ground side of the transistor / IC are affected by the potential difference, and noise is generated. It is considered that the AC component of the potential difference is a main cause of normal pulse noise, and the change of the DC component of the potential difference is a cause of the 0 level change of the electronic circuit output.

The potential difference having the relatively large level AC component and DC component is considered to occur for the following two reasons. Firstly, in the conventional electronic circuit (1) shown in the first drawing, each load (4) is connected to several different points on one electric conductor connected to the base point (3) as described above. Therefore, the current flowing through each load (4), the transient current flowing through the distributed capacitance existing in each portion of the circuit, and the like are combined and flow in the electric conductor. Therefore, the current flowing in the electric conductor has a relatively high level of the alternating current component and the level of the direct current component, and a voltage drop occurs in the electric conductor in response to this current, with respect to the base point (3). It is considered that a potential difference having a relatively large level of AC component and DC component is generated in the lower portion of each load (4) in the figure. Note that the voltage level applied to the distributed capacitance in each part of the circuit changes due to the change in the potential difference due to the AC component,
It is considered that a transient current for charging or discharging flows in the distributed capacitance, and this transient current again causes the alternating-current component of the potential difference and repeats this. As described above, the current flowing through the electric conductor is also a combination of the currents flowing through the loads. Therefore, if the DC component of the current flowing through each load (4) changes according to changes in temperature, humidity, etc., It is considered that the change in the DC component of the current flowing in the electric conductor is relatively large, and thus the change in the DC component of the potential difference is large. Secondly, in the conventional electronic circuit (1) shown in FIG. 1, each load (4) is applied to the shield (5) and the chassis (7) of the shield wire connected to the base point (3) as described above. Since each metal body (8) is connected to the chassis (7) or an appropriate place on the one electric conductor, each metal body (5),
It is considered that when the potentials of (7) and (8) fluctuate, the fluctuation causes a potential difference directly to the lower part of each load (4) in the figure with respect to the base point (3).

The present invention has been made by paying attention to the cause of the above-mentioned noise generation, and it is possible to prevent the generation of the noise generated at various places inside the conventional electronic circuit (1) as shown in the first diagram. It seeks to provide a way to do it.

[Means for Solving the Problems] Therefore, in the present invention, an electronic circuit in which a plurality of loads are electrically connected between the positive electrode output and the negative electrode output of the DC power supply, respectively, is present in the vicinity thereof. In the case where a plurality of metal bodies are electrically connected to the one-polarity output of the DC power supply, the one-polarity output end of the DC power supply is used as a base point, and the one-polarity output is electrically connected to the one-polarity output. Wiring is individually performed between each load portion and the base point, and wiring is independently performed between each metal body and the base point.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to FIG.

FIG. 2 shows an example of an electronic circuit (1) using the present invention, which corresponds to the electronic circuit (2) shown in FIG. 1, and the same components as those in FIG. Is attached and the description thereof is omitted.

In the electronic circuit (1) shown in FIG. 2 using the present invention, the output terminal of one polarity of the DC power supply (2) is used as the base point (3) as in the electronic circuit (1) shown in FIG. However, unlike the above-mentioned conventional electronic circuit (1) shown in FIG. 1, the load (4) and the base point (3) of each load (4) to be electrically connected to the one-polarity output of the DC power supply (2) The spaces are individually wired. That is, the portion of each load (4) and the base point (3) are individually connected using an electric conductor insulated from the others, and the portion of each load (4) is other than the base point (3). Is not connected to the other. In the electronic circuit (1) shown in FIG. 2, unlike the electronic circuit (1) shown in FIG. 1, the metal bodies (5), (7), (8) and the base point (3) are isolated from each other. Is wired in. That is, the metal bodies (5), (7), (8) and the base point (3) are individually connected using an electric conductor insulated from the other, and the metal bodies (5), ( 7) and (8) are not connected to others except the base point (3).

The second illustrated electronic circuit (1) using the present invention as described above
According to the above, firstly, between the site (lower site in the figure) and the base point (3) of each load (4) to be electrically connected to the one-polarity output of the DC power supply (2), respectively. Since they are wired independently, the current flowing through the corresponding load (4) and the current flowing through the distributed capacitance in the vicinity of the load (4) individually flow through each wiring (electric conductor). Therefore, the current flowing through each of the wirings has a sufficiently low level of the AC component and the level of the DC component as compared with the conventional electronic circuit (1) shown in FIG. 1, and the load (4) with respect to the base point (3) The potential difference in the lower part of the figure in () is substantially the same in both the AC component level and the DC component level. In this way, the level of the AC component of the potential difference becomes small, so that the fluctuation of the voltage level applied to the distributed capacitance existing in each part of the circuit becomes smaller than the conventional one, and the transient current flowing in the distributed capacitance becomes sufficiently small. Also from this point, the level of the AC component of the above potential difference becomes sufficiently small.

Further, as described above, the currents flowing through the corresponding loads (4) individually flow through the respective wirings. Therefore, even if the temperature, humidity, etc. change, the change in the DC component of the currents flowing through the respective wirings is conventionally changed. Therefore, the change in the DC component of the potential difference is sufficiently small.

In addition, the electronic circuit (1) shown in the second figure using the present invention.
Secondly, according to the second method, the metal bodies (5), (7), (8) and the base point (3) are individually wired. ), (8) changes, just change the potential of the base point (3) of the DC power supply (2), the change is lower than the base point (3) of each load (4) in the figure. No potential difference is generated in the side part.

From the two points described above, in the second illustrated electronic circuit (1) using the present invention, the potential difference of the lower part of each load (4) in the figure with respect to the base point (3) is the level of the AC component as well as the DC The level of the component is also sufficiently small and becomes almost the same potential, and the change in the DC component of the potential difference is also sufficiently small. Therefore, the electronic circuit (1) shown in FIG.
Pulse-like noise that has been generated inside and 0 of electronic circuit output
Generation of noise such as level fluctuation is effectively prevented.

In addition, when it is necessary to ground the equipment using the electronic circuit (1) as shown in FIG. 2 in which the present invention is used to the ground or to set the potential of the place where this equipment is installed,
It is directly connected to the base point (3). In that case, the ground terminal on the device side for connecting to the ground or the like is previously insulated from the chassis or the like, and the ground terminal and the base point (3) are directly connected using an electric conductor insulated from the other.

In the present invention, the one-polarity output end of the DC power supply (2) is used as the base point (3), but noise can be similarly prevented regardless of whether the output polarity is positive or negative.

Next, effects obtained when the present invention is actually used in various electronic circuits will be described.

(1) When applied to a television circuit White is beautiful on the screen, and especially in a scene where direct sunlight hits a snow scene, the stages from the feeling of eye pain to the white part of the shadow are clearly expressed, Intermediate colors such as skin are also expressed as if they were natural colors. Further, the scanning lines on the screen are almost invisible, the image is stable, the general TV screen likeness is reduced, and it is close to that of a film, so that there is little eye fatigue even when viewed for a long time.

The voice became clearer than before, and especially the high-pitched parts of musical instruments became easier to hear, making it easier to hear even at distant positions. Before the implementation, the volume of the voice was distorted when it was turned more than half, but after the implementation, even if the volume was raised, it was not distorted. And these effects are the phenomena which appeared because the noise was not generated in the electronic circuit.

(2) When implemented in a portable radio circuit The same effect as in the case of TV sound in (1) was obtained.

(3) When implemented in a transformerless receiver circuit Even if this changes from the era of vacuum tubes to the era of transistors and ICs, the cause of noise should not have changed. The machine was subjected to the method of the present invention. In this transformerless method, when the power switch is turned on, a large hum sounds and the hum becomes smaller with the passage of time, and when the sound gets smaller to some extent, the broadcast sound starts to come in and the sound gradually increases and stabilizes, but a small hum sounds. Remain. This hum has the characteristic that the size changes when the polarity of the plug of the AC power supply is reversed, and it is used with the smaller polarity of this hum.

The result of carrying out the method of the present invention is that the hum sound disappears completely,
Then, the same effect as in the case of the television sound of (1) was obtained.

(4) When applied to the circuits of measuring instruments When the method of the present invention is applied to measuring instruments, recorders, etc.,
Since there is no need for a filter to remove noise generated inside measuring instruments and recorders, the frequency is the same as the noise until now, or it was discarded as data because it was close to now, and it is unusable. Data will be obtained. Further, the 0 level fluctuation of the output signal, which is a kind of noise, coming out from each measuring device or the like does not occur.
This means that, when converting these analog data recorded on tape with a data recorder to digital data when processing these measurement data with a computer, if the 0 level fluctuates, the converted digital data will be Since it becomes inaccurate, there are problems in this processing, but there is an effect that these problems can be solved.

This is an example in which it is not possible to measure because the noise of about 10 milliamperes on average enters into the measured current of about 1 to 10 microamperes in the current measurement. Some data have been obtained by continuously measuring this minute current over a long period of time by preventing the occurrence of.

In addition to the above effects, there is also the possibility of downsizing in terms of space by omitting some filters etc. in terms of manufacturing equipment,
In addition, the production cost can be reduced by omitting a relatively expensive filter.

And, the present invention is a method that is particularly effective for a dangerous accident that occurs suddenly in a control device using a robot or an electronic circuit among many electronic devices suffering from noise, and has no reproducibility. However, since this method can be easily implemented at the manufacturing stage of electronic devices and the like, its effect is very large.

〔The invention's effect〕

According to the present invention, it is possible to effectively prevent the generation of noise that occurs at various locations inside an electronic circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional electronic circuit, and FIG. 2 is a circuit diagram showing an example of an electronic circuit using the method of the present invention. (1) …… Electronic circuit, (2) …… DC power supply, (3) ……
Base point, (4) …… load, (5) …… shield (metal body), (6) …… portion connecting the base point and load, (7) ...
… Chassis (metal body), (8) …… Metal body, (9) ……
The part where the base point and the metal body are connected.

Claims (1)

[Claims] 1. An electronic circuit in which a plurality of loads are electrically connected between a positive electrode output and a negative electrode output of a DC power supply, respectively, wherein a plurality of metal bodies around the load are one polarity of the DC power supply. Which is electrically connected to the output of the DC power supply, the output terminal of one polarity of the DC power supply is used as a base point, and the portion of each load to be electrically connected to the output of the one polarity is connected to the base point. A method for preventing generation of noise generated in an electronic circuit, characterized in that wiring is performed independently, and wiring is independently performed between each of the metal bodies and the base point.