Transmission circuit for ethernet device

A transmission circuit including four transmission component sets for an Ethernet device is provided. Each transmission component set are coupled between an Ethernet connector and an Ethernet chip. Each transmission component set includes a transformer, two capacitors, and four transmission lines (TLs). The transformer includes four terminals and two center taps. Two diagonal terminals of the four terminals are coupled to a ground. The other two diagonal terminals of the four terminals are coupled to the Ethernet connector and, through one of the two capacitors, to the Ethernet chip via two of the four TLs, respectively. The two center taps are coupled to the Ethernet connector and, through the other one of the two capacitors, to the Ethernet chip via the other two of the four TLs, respectively.

CROSS REFERENCE TO RELATED APPLICATION

The present invention claims priority under 35 U.S.C. § 119 to Taiwanese Application No. 105209444 filed on Jun. 23, 2016, including the specification, claims, drawings, and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a transmission circuit for an Ethernet device. More particularly, the transmission circuit of the present invention can replace a transmission circuit used in a traditional Ethernet device to provide signal coupling and direct-current (DC) isolation characteristics necessary for Ethernet transmission and to provide the burst protection function.

Descriptions of the Related Art

With the rapid development of the network science and technologies, Ethernet-related products can be found everywhere in people's daily life. Transmission circuits in Ethernet devices currently available on the market include a number of components such as an LAN transformer, a plurality of resistors and a plurality of capacitors. Among such components, the LAN transformer at least includes a common-mode inductor and a transformer (e.g., the 1000 BASE-T MAGNETICS MODULES manufactured by Bothhand Enterprise Inc.). Therefore, the production cost of the transmission circuit used in the traditional Ethernet device is relatively high.

Accordingly, an urgent need exists in the art to provide a transmission circuit using a fewer number of components and providing the burst protection function to replace transmission circuits used in traditional Ethernet devices.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a transmission circuit using a fewer number of components and providing the burst protection function to replace transmission circuits used in traditional Ethernet devices.

To achieve the aforesaid objective, the present invention discloses a transmission circuit for an Ethernet device. The transmission circuit comprises four transmission component sets. Each of the transmission component sets is coupled between an Ethernet connector and an Ethernet chip. Each of the transmission component sets comprises a transformer, two capacitors, and four transmission lines. The transformer of each of the transmission component sets comprises four terminals and two center taps. Two diagonal terminals of the four terminals are coupled to a ground. The other two diagonal terminals of the four terminals are coupled to the Ethernet connector and, through one of the two capacitors, to the Ethernet chip via two of the four transmission lines, respectively. The two center taps are coupled to the Ethernet connector and, through the other one of the two capacitors, the Ethernet chip via the other two of the four transmission lines, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments described below are intended to illustrate technical contents of the present invention but not to limit the scope of the present invention. It shall be appreciated that, in the following embodiments and the attached drawings, elements not related to the present invention are omitted from depiction, and dimensional relationships among individual elements in the drawings are only provided for ease of understanding but not to limit the actual scale.

A first embodiment of the present invention is shown inFIG. 1, which is a schematic view of an Ethernet application circuit1of the present invention. The Ethernet application circuit1is a part of an Ethernet device (not shown) and comprises an Ethernet connector11, a transmission circuit13and an Ethernet chip15.

The Ethernet connector11may be an Ethernet connector having an RJ-45 interface, and comprises a Tx0+ pin, a Tx0− pin, a Tx1+ pin, a Tx1− pin, a Tx2+ pin, a Tx2− pin, a Tx3+ pin and a Tx3− pin. The Ethernet chip15may be a chip from one of various manufacturers, e.g., an RTL8201 chip from Realtek Semiconductor Co., which comprises an MD0+ pin, an MD0− pin, an MD1+ pin, an MD1− pin, an MD2+ pin, an MD2− pin, an MD3+ pin and an MD3− pin. Because the primary technical content of the present invention focuses on the transmission circuit13and how the transmission circuit13of the present invention is coupled between the Ethernet connector11and the Ethernet chip15in place of a transmission circuit used in a traditional Ethernet application circuits can be readily appreciated by those of ordinary skill in the art according to the following description, the Ethernet connector11and the Ethernet chip15will not be further described herein.

The transmission circuit13comprises four transmission component sets13a.Each of the transmission component sets13ais coupled between the Ethernet connector11and the Ethernet chip15. Each of the transmission component sets13acomprises two capacitors C1, C2, a transformer TR and four transmission lines T1, T2, T3, T4.

The transformer TR comprises four terminals e1, e2, e3, e4and two center taps t1, t2. In this embodiment, two diagonal terminals e2, e3of the four terminals e1, e2, e3, e4are coupled to a ground G. The other two diagonal terminals e1, e4of the four terminals e1, e2, e3, e4are coupled to the Ethernet connector11and, through the capacitor C2, to the Ethernet chip15via the transmission lines T1, T4respectively. As shown inFIG. 1, the terminal e1is coupled to the Ethernet connector11via the transmission line T1, and the terminal e4is coupled to the Ethernet chip15through the capacitor C2and via the transmission line T4.

The two center taps t1, t2are coupled to the Ethernet connector11and, through the capacitor C1, to the Ethernet chip15via the transmission lines T2and T3respectively. As shown inFIG. 1, the center tap t2is coupled to the Ethernet connector11via the transmission line T3, and the center tap t1is coupled to the Ethernet chip15through the capacitor C1and via the transmission line T2.

The capacitors C1, C2on the transmission lines T2, T4can provide signal coupling and DC isolation effects. The capacitors C1, C2may be non-polar capacitors having capacitance values of 33 nanofarad (nF) to 0.33 microfarad (μF). The transformer TR may have an inductance value of 150 microhenry (μH) to 400 μH, and provide impedance matching, lightning protection, common-mode filtering or the like functions within a specific frequency range (e.g., 1 MHz˜125 MHz). Accordingly, by replacing a transmission circuit used in a traditional Ethernet device with the transmission circuit13shown inFIG. 1, the present invention can use a minimized number of components to provide signal coupling and DC isolation characteristics necessary for Ethernet transmission and provide the burst protection function.

A second embodiment of the present invention is shown inFIG. 2, which is a schematic view of an Ethernet application circuit2according to the present invention. The transmission circuit13in the Ethernet application circuit2is a circuit equivalent to the transmission circuit13in the Ethernet application circuit1.

Unlike the first embodiment, in the transmission circuit13of the present invention, two diagonal terminals e1, e4 of the four terminals e1, e2, e3, e4are coupled to the ground G. The other two diagonal terminals e3, e2of the four terminals e1, e2, e3, e4are coupled to the Ethernet connector11and, through the capacitor C1, to the Ethernet chip15via the transmission lines T3, T2respectively. As shown inFIG. 2, the terminal e3is coupled to the Ethernet connector11via the transmission line T3, and the terminal e2is coupled to the Ethernet chip15via the capacitor C1and through the transmission line T2.

The two center taps t1, t2are coupled to the Ethernet connector11and, through the capacitor C2, to the Ethernet chip15via the transmission lines T1and T4respectively. As shown inFIG. 2, the center tap t1is coupled to the Ethernet connector11via the transmission line T1, and the center tap t2is coupled to the Ethernet chip15through the capacitor C2and via the transmission line T4.

Similarly, the capacitors C1, C2on the transmission lines T2, T4can provide signal coupling and DC isolation effects. The transformer TR can provide impedance matching, lightning protection, common-mode filtering or the like functions within a specific frequency range. Accordingly, by replacing a transmission circuit used in a traditional Ethernet device with the transmission circuit13shown inFIG. 2, the present invention can use a minimized number of components to provide signal coupling and DC isolation characteristics necessary for Ethernet transmission and provide the burst protection function.

A third embodiment of the present invention is shown inFIGS. 3A and 3B, which are schematic views of Ethernet application circuits3a,3baccording to the present invention respectively. In this embodiment, each transmission component set13further comprises an inductor L, and one of the two diagonal terminals coupled to the ground G is coupled to the ground G via the inductor L. The inductor L may have an inductance value of 1 μH to 100 μH.

The transmission circuit13inFIG. 3Ais an extension of the transmission circuit13inFIG. 1. InFIG. 3A, the transmission component set13aof the transmission circuit13further comprises an inductor L, and the terminal e3is coupled to the ground G further via the inductor L. Similarly, the transmission circuit13inFIG. 3Bis an extension of the transmission circuit13inFIG. 2. InFIG. 3B, the transmission component set13aof the transmission circuit13further comprises an inductor L, and the terminal e1is coupled to the ground G further via the inductor L.

It shall be appreciated that, by additionally disposing the inductor L to compensate for the possibly generated phase difference so that phases from each pair of signal lines to the ground G match each other as far as possible, the transmission circuit13of this embodiment further reduces the phase difference possibly caused by non-uniformity of paths from each pair of transmission lines to the ground G. The inductance value of the inductor L is determined based on a half of the single-side turn number of the transformer TR.

A fourth embodiment of the present invention is shown inFIGS. 4A and 4B, which are schematic views of Ethernet application circuits4a,4bof the present invention respectively. The transmission circuit13inFIGS. 4A and 4Bare extensions of the transmission circuits13inFIGS. 3A and 3B. In this embodiment, each transmission component set13afurther comprises a matching component set MCS, which is coupled between two transmission lines T2, T4that are arranged between the capacitors C1, C2and the Ethernet chip15. The matching component set MCS is used to adjust the impedance matching between the transmission circuit13and different network chips.

The matching component set MCS, which may be as shown inFIGS. 5A to 5E, provides the impedance circuit matching effect in the circuit by virtue of the capacitive character of components and provides a burst protection function by virtue of breakdown characteristics of the diode component. InFIGS. 5A to 5E, a contact P1is coupled to the transmission line T2, a contact P2is coupled to the transmission line T4, and a contact P3is coupled to the ground G or a system ground (not shown). It shall be appreciated that, the ground G refers to a ground terminal of the device enclosure (i.e., an external ground terminal); however, the system ground refers to a common ground terminal (i.e., an internal ground terminal) which is usually at 0 volt.

InFIG. 5A, the matching component set is a bidirectional transient voltage suppressor (TVS) diode BTVS. The bidirectional TVS diode BTVS may have a capacitance value of 0.35 picofarad (pF) to 6 pF. InFIG. 5B, the matching component set MCS comprises a combination of a first bidirectional TVS diode BTVS1and a second bidirectional TVS diode BTVS2. The first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2are coupled to each other in series and between the transmission lines T2and T4, and a contact Q between the first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2is coupled to the ground G or the system ground. The first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2may have capacitance values of 1 pF to 10 pF.

InFIG. 5C, the matching component set MCS comprises a first high-speed diode set, a second high-speed diode set and a unidirectional TVS diode. The unidirectional TVS diode may have a capacitance value of 1 pF to 10 pF. The matching component set MCS may be a single semiconductor packaged component, and consists of four low-capacitance diodes and one unidirectional TVS diode. Specifically, the first high-speed diode set comprises two high-speed diodes D1, which are coupled to each other in forward series and have a contact Q1therebetween coupled to the second transmission line T2.

The second high-speed diode set comprises two high-speed diodes D2, which are coupled to each other in forward series and have a contact Q2therebetween coupled to the fourth transmission lines T4. The unidirectional TVS diode TVS is coupled with the first high-speed diode set and the second high-speed diode set in forward parallel and has a contact Q3coupled to the ground G or the system ground.

InFIG. 5D, the matching component set MCS comprises a first bidirectional TVS diode BTVS1, a second bidirectional TVS diode BTVS2and a first inductor L1. The first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2are coupled to each other in series and between the two transmission lines T2and T4. A contact Q between the first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2is coupled to the ground G or the system ground through the first inductor L1.

It shall be appreciated that, the matching component set MCS ofFIG. 5Dis an extension of the matching component set MCS ofFIG. 5B, in which the first inductor L1is additionally disposed to provide a common-mode filtering effect for handling common-mode noises of specific frequencies. The first bidirectional TVS diode BTVS1and the second bidirectional TVS diode BTVS2may have capacitance values of 1 pF to 10 pF. The first inductor L1may have an inductance value of 10 μH to 50 μH.

InFIG. 5E, the matching component set MCS comprises a first inductor L1, a first high-speed diode set, a second high-speed diode set and a unidirectional TVS diode TVS. The first high-speed diode set comprises two high-speed diodes D1, which are coupled to each other in forward series and have a contact Q1therebetween coupled to the second transmission line T2. The second high-speed diode set comprises two high-speed diodes D2, which are coupled to each other in forward series and have a contact Q2therebetween coupled to the fourth transmission line T4.

The unidirectional TVS diode TVS is coupled with the first high-speed diode set and the second high-speed diode set in forward parallel, and has a contact Q3coupled to the ground G or the system ground through the first inductor L1. Similarly, the matching component set MCS ofFIG. 5Eis an extension of the matching component set MCS ofFIG. 5C, in which the first inductor L1is additionally disposed to provide a common-mode filtering effect for handling common-mode noises of specific frequencies. The unidirectional TVS diode TVS may have a capacitance value of 1 pF to 10 pF. The first inductor L1may have an inductance value of 10 μH to 50 μH.

The matching component sets MCS shown inFIGS. 5A to 5Eadopt appropriate capacitive components to achieve the matching effect, and adopt components having breakdown, clamping or switching characteristics to provide the network chip15with the additional burst protection function. It shall be appreciated that, as will be readily understood by those of ordinary skill in the art from the above descriptions, any components having the same functions as the matching component set MCS of the present invention can be applied to the transmission circuit13of the present invention, so any transmission circuit13obtained by simply replacing or modifying the matching component set MCS shall fall within the scope of the present invention.

On the other hand, the matching component set MCS of the present invention may also adopt a simple inactive component to achieve the matching effect, but not additionally provide the burst protection function, as shown inFIGS. 6A to 6F. InFIGS. 6A to 6F, the contact P1is coupled to the second transmission line T2, the contact P2is coupled to the fourth transmission line T4, and the contact P3is coupled to the ground G or the system ground.

InFIG. 6A, the matching component set MCS comprises a first resistor R1and a second resistor R2. The first resistor R1and the second resistor R2may have resistances of 1 kilo-ohm (kΩ) to 10 kΩ. A contact Q between the first resistor R1and the second resistor R2is coupled to the ground G or the system ground. InFIG. 6B, the matching component set MCS comprises a first capacitor C3and a second capacitor C4. A contact Q between the first capacitor C3and the second capacitor C4is coupled to the ground G or the system ground. The first capacitor C3and the second capacitor C4may have capacitance values of 1 pF to 10 pF.

InFIG. 6C, the matching component set MCS is a resistor R coupled between the second transmission line T2and the fourth transmission line T4. The resistor R may have a resistance value of 1 kΩ to 20 kΩ. InFIG. 6D, the matching component set MCS is a capacitor C coupled between the second transmission line T2and the fourth transmission line T4. The capacitor C may have a capacitance value of 1 pF to 8 pF.

InFIG. 6E, the matching component set MCS comprises a first capacitor C3, a second capacitor C4and a first inductor L1. The first capacitor C3and the second capacitor C4may have capacitance values of 1 pF to 10 pF. The first inductor L1may have an inductance value of 10 μH to 50 μH. The first capacitor C3and the second capacitor C4are coupled to each other in series and between the second transmission line T2and the fourth transmission line T4. A contact Q between the first capacitor C3and the second capacitor C4is coupled to the ground G or the system ground through the first inductor L1.

InFIG. 6F, the matching component set MCS comprises a first capacitor C3, a second capacitor C4, a first inductor L1and a second inductor L2that are connected in series. The first capacitor C3is coupled to the second transmission line T2, and the second capacitor C4is coupled to the fourth transmission line T4. The first inductor L1and the second inductor L2are coupled to each other in series and between the first capacitor C3and the second capacitor C4. A contact Q between the first inductor L1and the second inductor L2is coupled to the ground G or the system ground. The first capacitor C3and the second capacitor C4may have capacitance values of 1 pF to 20 pF. The first inductor L1and the second inductor L2may have inductance values of 10 μH to 50 μH.

It shall be appreciated that, the inductor L in the third embodiment and the matching component set MCS in the fourth embodiment are components additionally provided in but not essential to the transmission circuit13of the present invention. In other words, inFIGS. 4A and 4B, the transmission circuit13of the present invention may also not comprise the inductor L for compensating for possibly generated phase differences.

According to the above descriptions, as compared with transmission circuits of traditional Ethernet devices, the transmission circuit of the present invention not only uses a smaller number of components, but can also provide signal coupling and DC isolation, impedance matching and common-mode noise filtering functions necessary for Ethernet transmission to improve the signal transmission performances and also provide the burst protection function. Thereby, the cost needed for producing the transmission circuit of the present invention is significantly lower than that of the transmission circuit of the traditional Ethernet device.