Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B3/00—Line transmission systems
  • H04B3/02—Details
  • H04B3/28—Reducing interference caused by currents induced in cable sheathing or armouring
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
  • H04B5/20—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by the transmission technique; characterised by the transmission medium
  • H04B5/24—Inductive coupling
  • H04B5/26—Inductive coupling using coils
  • H04B5/266—One coil at each side, e.g. with primary and secondary coils
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/0264—Arrangements for coupling to transmission lines
  • H04L25/0266—Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/0264—Arrangements for coupling to transmission lines
  • H04L25/0272—Arrangements for coupling to multiple lines, e.g. for differential transmission
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
  • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
  • H03K17/60—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors
  • H03K17/605—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors with galvanic isolation between the control circuit and the output circuit
  • H03K17/61—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being bipolar transistors with galvanic isolation between the control circuit and the output circuit using transformer coupling
• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
  • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
  • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
  • H03K17/689—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors with galvanic isolation between the control circuit and the output circuit
  • H03K17/691—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors with galvanic isolation between the control circuit and the output circuit using transformer coupling
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
  • H04B5/20—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by the transmission technique; characterised by the transmission medium
  • H04B5/22—Capacitive coupling

Definitions

• the invention relates to a coupling circuit for a bus subscriber to a bus line of a field bus with DC-free and differential, EIA-485 / EIA-422 compliant signal transmission according to a TTP protocol, in which the two inputs / outputs a send / receive component of the bus station with a first winding of a signal transformer and the two poles of the bus line are connected to a second winding of the signal transformer.
• Inductive bus couplers use a signal transformer for galvanic isolation, which acts as a galvanic isolation between the data bus and the bus participant.
• a signal transformer for galvanic isolation acts as a galvanic isolation between the data bus and the bus participant.
• potential differences between the bus participants and the bus participants and the bus line are allowed.
• Taking into account the properties of real signal transformers in contrast to theoretically ideal transformers occurs due to the capacitive coupling between the transformer windings for coupling at least a portion of occurring dynamic disturbances.
• Such over-coupling interference can lead to transmission errors or cause permanent damage to the connected components. Therefore, if necessary, a corresponding protective circuit must adequately suppress these disturbances.
• Common-mode interference caused by indirect lightning strike can occur between reference potentials of the bus users and are often referred to as "ground offset" or they can occur through coupling into the differential bus line.
• An object of the invention is to suppress such interference on the part of the bus subscribers to a safe level, without affecting the signal quality.
• the first winding has a center tap, which is connected to the local reference potential of the bus subscriber via a capacitor whose capacity is at least 100 times the parasitic capacitance of the transformer.
• crosstalk disturbances on the part of the bus subscriber are suppressed.
• the suppression is carried out in a manner that, although common-mode interference can be suppressed, the push-pull useful signal, however, no attenuation dampened.
• the capacitive connection of the center tap to a local reference potential is expedient if connected components superimpose a dc voltage on the useful load signal.
• the parasitic coupling capacitance of the transformer Since the capacitor is located on the isolated side for interference suppression, in addition to the low internal resistance of the interference source, the parasitic coupling capacitance of the transformer also acts. Only then is it possible on the one hand to substantially reduce the interference voltage, and on the other hand there is only a small current flow, since the parasitic coupling capacitance in the pF range Hegt and thus limits current to values that no longer lead to the destruction of components.
• the capacitance of the capacitor is 5 to 500 nF.
• the signal transmitter is arranged near the transmitting / receiving component of the bus subscriber.
• the local reference potential corresponds to the common ground, but it can also be provided that the local reference potential corresponds to one pole of a supply voltage, since the poles of the supply voltage also have a fixed capacitive coupling to ground.
• a bus subscriber 101 is coupled by means of a signal transmitter 103 to a bus line 102.
• the bus subscriber 101 has a transmitting / receiving component 104, of which for simplicity only the receiving component is shown, and a local reference potential 106, in this example ground.
• the terminals 108, 109 namely the input terminals of the transmitting / receiving component 104 of the bus subscriber 101 are connected to a first winding of a signal transformer 103 and the two poles of a bus line 102 are connected to a second winding of this signal transformer.
• the first winding of the transformer 103 has a center tap 107, which is connected via a capacitor 105 to the reference potential 106.
• a direct coupling of the center tap 107 to the local reference potential 106 is for typical ElA-485 or EIA-422 compliant transmit / receive components 104 is not possible because the terminals 108 and 109 a DC voltage is superimposed.
• the signal transformer 103 is constructed with the bus driver 101 in a common housing or on a common printed circuit board, since it is advisable to arrange the transformer as close as possible to the transmitting / receiving component 104 in order to achieve as low a connection to the reference potential 106 as possible.
• the coupling circuit counteracts dynamic common-mode interference in the form of a potential difference between the bus subscriber 101 and the bus line 102 and the transmit / receive component 104 is protected against over-voltage at the terminals 108 and 109 against the local reference potential 106.
• the interference currents through the signal transformer winding run in opposite directions, whereby no magnetic field builds up.
• the transformer winding mainly the ohmic conductor resistances and only a small inductive resistance component by stray inductances or asymmetries in winding or current flow act.
• the measure of the achievable interference suppression is approximately calculated by the dividing ratio of the parasitic capacitance 110 of the transformer 103 and that of the capacitor 105 as follows: u Stör c
• Ustör interference voltage between bus subscriber 101 and bus line 102.
• C K parasitic capacitance 110.
• the parasitic capacitance of signal transducers is typically in the range of 10 pF to 50 pF. With a capacitance of the capacitor of e.g. 47nF calculated according to the above formula, a noise suppression of about 1000 to 5000. Practice has shown that the capacity should usefully at least 100 times the parasitic capacitance 110 of the transformer 103 should be. Conventional values of the capacitance of the capacitor 105 are between 5 to 500 nF.
• the DC-free, differentially transmitted useful signal is not subject to any additional Dämpf ung by the bypass capacitor 105, since no current flows through the capacitor 105 for differential signals.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Power Engineering (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
• Logic Circuits (AREA)
• Dc Digital Transmission (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=44065549

Family Applications (1)

Country Status (6)

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Family Cites Families (5)

• 2010
  • 2010-02-17 AT ATA239/2010A patent/AT509840B1/de not_active IP Right Cessation
• 2011
  • 2011-02-17 CN CN2011800101774A patent/CN102934367A/zh active Pending
  • 2011-02-17 WO PCT/AT2011/000082 patent/WO2011100775A1/de active Application Filing
  • 2011-02-17 EP EP11709311A patent/EP2537258A1/de not_active Withdrawn
  • 2011-02-17 JP JP2012553144A patent/JP2013520111A/ja not_active Withdrawn
  • 2011-02-17 US US13/579,503 patent/US20130049853A1/en not_active Abandoned

Non-Patent Citations (1)

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