TWI804211B - Signal extender and signal transmission method - Google Patents

Abstract

A signal extender, which can solve the problem of traditional signal voltage offset. The signal extender can be used to connect a first device and a second device to transmit messages, including at least a first endpoint, a second endpoint, a channel switcher and a driving unit. The first endpoint can be connected to the first device, and the second endpoint can be connected to the second device. The channel switcher is connected with the first endpoint, and one of the first channel or the second channel can be selected to connect with the first endpoint and the second endpoint according to all switching signals. The driving unit is connected to the second channel, and can generate a second electronic signal transmitted on the second channel according to a first electronic signal provided by the second device when the second channel is selected to be connected with the first endpoint and the second endpoint. The second channel will transmit the second electronic signal to the first device, and the baseline voltage of the second electronic signal does not exceed a preset value.

Description

Signal Extender and Signal Transmission Method

This application relates to a signal extender, in particular to a signal transmission method capable of correcting the signal level in the signal extender.

In a general computer control center, the screen and the computer room are often separated by two places. When the screen is connected to the host computer, signal extension products such as extenders are required to strengthen signal transmission. Among the transmission signals, there is a pair of display data channel (Display Data Channel; DDC) signals that are responsible for transmitting the best resolution information (EDID) and image encryption information (HDCP) that can be used by the screen to ensure that users get the best images quality.

FIG. 1 is a schematic diagram of a conventional connection between a first device 110 and a second device 120 via a Display Data Channel (DDC). The first device 110 has a first interface P1, and the second device 120 has a second interface P2. The first interface P1 and the second interface P2 can be connected by a data line to establish a DDC channel. In order to transmit data signals, a set of transceivers are included in the first device 110 and the second device 120 , namely, the first receiver 112 , the first transmitter 114 , the second receiver 122 and the second transmitter 124 . Generally speaking, electronic signals are transmitted by means of a current or voltage change. When the second transmitter 124 in the second device 120 is about to transmit data to the first device 110, the second transmitter 124 turns on the transistor Q2 in the second device 120 according to the logic values of 1 and 0 in the data. Or close, so that a current _IL flowing from the first interface P1 to the second interface P2 is generated on the DDC connection, and finally pulled down to the ground by the transistor Q2. In this way, the first receiver 112 in the first device 110 can read the voltage level on the first interface P1, and judge that the data value transmitted by the second device 120 is 0 or 1.

In contrast, when the first transmitter 114 in the first device 110 also transmits data to the second receiver 122 in the second device 120 through the transistor Q1 . The detailed principle will not be repeated.

In other words, the DDC channel is to transfer data between systems through the open drain circuit (Open Drain) of the chip-level bus (I2C Bus). However, the open-drain circuit has the problems of being unable to extend the transmission distance and cascading, which may easily cause the equivalent internal resistance of the circuit to be too high and cause the reference voltage of the I2C low level to be too high, that is, it is used to represent the logic low voltage ratio of bit 0. The critical value is still high. As a result, the interpretation will fail and the screen cannot be displayed.

For example, there is a line internal resistance _RL on the DDC channel between the first interface P1 and the second interface P2. The line internal resistance _RL is a concept of equivalent resistance, which summarizes various line losses occurring on the DDC, the internal resistance of the analog switching circuit, the oxidation attenuation of the printed circuit board, or the internal load impedance of the integrated circuit, and the internal resistance R of the second device. _B etc. Therefore, when the second transmitter 124 of the second device 120 pulls down the voltage on the DDC channel, for the first receiver 112, the read voltage value on the first interface P1 is roughly converted into:

V=R _L /(R _L +R _A )

where R _A is the internal resistance of the first device. When the length of the DDC channel is very long, or when an extender is connected in series, it is easy to cause the value of the line internal resistance _RL to increase. According to the above formula, when the ratio of the internal resistance _RL of the line is too large, the logic low voltage used to represent the bit 0 will be higher than the interpretable critical value, which will affect the connection function of the DDC channel.

In view of this, an improved signal extender and signal transmission method are to be developed.

The embodiment of the present application provides a signal extender, which can solve the problem of the traditional signal voltage level shift. The signal extender can be used to connect a first device and a second device to transmit information, and at least includes a first terminal, a second terminal, a channel switcher, and a driving unit. The first terminal can be connected to the first device, and the second terminal can be connected to the second device. The channel switcher is connected to the first terminal, and can select one of a first channel or a second channel to connect with the first terminal and the second terminal according to a switching signal. The drive unit is connected to the second channel, and when the second channel is selected to be connected to the first terminal and the second terminal, a first electronic signal provided by the second device can be generated on the second channel. A second electronic signal sent on the second channel. The second channel transmits the second electronic signal to the first device, and the reference voltage of the second electronic signal does not exceed a preset value.

In a further embodiment, when the switching signal causes the channel switch to switch to the second channel, the driving unit pulls the current to the ground line, and makes the reference voltage of the second electronic signal not high at this default value.

In a further embodiment, the signal extender further includes a direction judging unit, connected between the first terminal and the channel switch, for judging the direction of a current on the first terminal to generate the Toggle signal. When the direction of the current is from the first device to the first terminal, the switch signal makes the channel switcher switch to the second channel.

In a further embodiment, the channel switcher is connected to the first endpoint. The channel switcher connects the first terminal with the first channel or the second channel according to the switching signal to form a signal transmission channel between the first device and the second device. Specifically, the direction judging unit includes a comparator connected to different positions on the signal transmission channel to detect a potential difference. The direction judging unit can output the switching signal according to the potential difference, so that the channel switcher decides to use the first channel or the second channel.

In a further embodiment, the direction judging unit further includes a logic gate, electrically coupled to the output terminal of the comparator and the first terminal, for judging the direction of the current, when the direction of the current is from When the first device flows into the first terminal, the direction judging unit makes the switching signal a high potential signal, otherwise makes the switching signal a low potential signal.

In a further embodiment, the driving unit may include a first transistor and a second transistor. The first transistor includes a first drain connected to the second channel and a voltage source, a first source grounded, and a first gate. The second transistor includes a second drain connected to the first gate and the voltage source, a second source connected to ground, and a second gate connected to the second terminal. When the channel switch switches to use the second channel, the second gate receives the first electronic signal from the second device, so that the first transistor correspondingly transfers the current from the first device to the The first source is pulled down to ground, and the first transistor generates a second electronic signal with a lower level for reading by the first device.

In a further embodiment, the signal extender may be a DDC channel extender, and the first electronic signal and the second electronic signal may be serial data link signals. The first device is a computer host, and the second device is a monitor.

Another embodiment of the present application is based on a signal transmission method realized by the above-mentioned signal extender, which can transmit information between a first device and a second device. Firstly, according to a switching signal, one of a first channel or a second channel is selected, and the first device and the second device are connected in series. When the second channel is selected to be connected to the first terminal and the second terminal in the signal extender, a second electronic signal is generated according to a first electronic signal provided by the second device, and the second The channel transmits the second electronic signal to the first device; wherein the reference voltage of the second electronic signal does not exceed a preset value.

In a further embodiment, the switching signal is determined according to the direction of a current on the first terminal. When the direction of the current is from the first device to the first terminal, the switch signal makes the channel switcher switch to the second channel.

In a further embodiment, when the switching signal selects to use the second channel, a driving unit is used to pull the current to the ground line, and make the reference voltage of the second electronic signal not higher than the preset value .

To sum up, the signal extender provided by the embodiment of the present application can solve the problem of the traditional signal voltage level shift. A direction judging unit is used to judge the direction of the current, and a driving unit is used to generate a second electronic signal with a correct reference voltage according to the first electronic signal, so that the first device can correctly receive the message to be transmitted by the second device.

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of this application.

FIG. 2 is a structure diagram of a signal extender 200 connected in series with the first device 110 and the second device 120 according to the embodiment of the present application. This application proposes a signal extender 200, which is serially connected between the first device 110 and the second device 120, so as to improve the signal quality of the DDC channel and solve the problems caused by the traditional technology. Two ends of the signal extender 200 each include a first terminal Pa and a second terminal Pb. The first terminal Pa can be connected to the first interface P1 of the first device 110 . And the second terminal Pb can be connected to the second interface P2 of the second device 120 . Generally speaking, the first device 110 may be, but not limited to be a computer host, and the second device 120 may be, but not limited to be a monitor. The embodiments of the present application may also be applicable to other occasions where a cable extender is used to transmit digital data.

FIG. 3 is a schematic structural diagram of a signal extender 200 according to an embodiment of the present application. The signal extender 200 mainly includes three circuit units: a direction determining unit 210 , a channel switcher 220 and a driving unit 230 .

The first terminal Pa can be connected to the first device 110 , and the second terminal Pb can be connected to the second device 120 . The channel switcher 220 is connected to the first terminal Pa, and can select one of a first channel L1 or a second channel L2 to connect to the second terminal Pb according to a switching signal #S. More precisely, the first path L1 is defined as the line segment extending from the first switching point SW1 to the second terminal Pb, and the second path L2 is defined as connecting from the second switching point SW2 to the third terminal Pc, then passes through the driving unit 230 and extends to the line segment of the second end point Pb. The channel switcher 220 can select to connect the first terminal Pa to the first switching contact SW1 or the second switching contact SW2 according to the switching signal #S, thereby changing the data transmission between the first device 110 and the second device 120 path.

The driving unit 230 is connected to the second channel L2. When the second channel L2 is selected to be connected to the first terminal Pa and the second terminal Pb, the driving unit 230 generates a second electronic signal ES1 transmitted on the second channel L2 according to a first electronic signal ES1 provided by the second device 120. Electronic signal ES2. The second channel L2 transmits the second electronic signal ES2 to the first device 110 . In this embodiment, the information transmitted by the second device 120 using the first electronic signal ES1 will be copied into the second electronic signal ES2 and then correctly delivered to the first device 110 . The signal quality of the second electronic signal ES2 is improved, that is, the reference voltage therein will not exceed a preset value. For example, the bit values 0 and 1 in digital data are usually represented by logic high and logic low levels of electronic signals. The criteria for judging the logic high potential and the logic low potential respectively have preset ranges according to different applications. When the potential of the electronic signal is lower than a preset value representing a logic low level, it can be judged as a bit value of 0. The reference voltage of an electronic signal represents the lowest voltage that can be displayed during transmission. The first electronic signal ES1 output by the second device 120 often has a problem of too high reference voltage due to the internal resistance _RL of the circuit, so it is a signal of poor quality. The drive unit 230 designed in this embodiment has better sensitivity, can read correct information from the first electronic signal ES1 with poor signal quality, and convert it into a second electronic signal ES2 with better signal quality and then transmit it to the second electronic signal ES2. The first device 110 ensures correctness of data transmission.

In one embodiment, when the second device 120 intends to transmit data to the first device 110 , the first electronic signal ES1 carrying the information is transmitted to the driving unit 230 by the second device 120 in the form of a voltage change. The driving unit 230 obtains the information to be transmitted in the first electronic signal ES1 according to the voltage variation on the second terminal Pb. At the same time, the driving unit 230 can correspondingly generate a second electronic signal ES2 carrying the same information according to the first electronic signal ES1 and send it to the first device 110 . In this embodiment, since the current of the second electronic signal ES2 is independent from the transmission path of the first electronic signal ES1, the signal quality is not affected by the internal resistance _RL of the circuit.

When the switching signal #S causes the channel switcher 220 to switch and connect to the second channel L2 , the driving unit 230 can transmit the second electronic signal ES2 to the first device 110 . For example, when transmitting the second electronic signal ES2, the driving unit 230 can pull down the current Ic from the first device 110 to the ground line, and make the reference voltage representing bit 0 in the second electronic signal ES2 not higher than a predetermined value. set value. The first device 110 can read the information to be transmitted in the second electronic signal ES2 according to the voltage condition on the first interface P1. Although in the embodiment of FIG. 3 , the driving unit 230 pulls down the current Ic to the ground. However, in implementing the design, the current may also be pulled down to other circuits.

The function of the direction judging unit 210 is to judge the signal transmission direction or the current direction between the first device and the second device, so as to determine the channel to be switched. The specific implementation manner can be extended to several kinds. For example, the direction judging unit 210 can be a microcontroller (MCU) of the signal extender 200, an application-specific chip (ASIC), or a programmable logic gate array (FPGA), which has simple control, calculation, and judgment functions. , which can execute code to achieve specific functions. Under this structure design, the direction judging unit 210 can directly take the voltage or current on the first terminal Pa as an input signal, and generate the corresponding switching signal #S after the internal pre-designed program operation and judgment. A flash memory (not shown) can be implemented in the signal extender 200 to store firmware or a control program, so that the direction determining unit 210 can execute accordingly. In another situation, the control program can also be directly made into a logic circuit and integrated into the direction judging unit 210 . Since there are many mature solutions for realizing the control purpose based on microprocessors and programs, this embodiment will not describe in detail.

On the other hand, the direction determination unit 210 can be implemented with a specific circuit architecture. FIG. 4 is a specific circuit diagram of the direction judging unit 210 of the embodiment of the present application. The direction judging unit 210 is connected between the first terminal Pa and the channel switcher 220, and can judge the direction of the current Ic on the first terminal Pa to generate the switching signal #S. The output switching signal #S can be used to make the channel switcher 220 decide to use the first channel L1 or the second channel L2 to form a physical signal transmission channel extending from the first interface P1 to the second interface P2.

More specifically, the direction determining unit 210 may include a comparator 212 . The comparator 212 has two input terminals, respectively connected to different positions on the signal transmission channel, such as between the first interface P1 and the first terminal Pa, to detect a potential difference #V. To further illustrate, between different positions on the signal transmission channel connected to the comparator, a line resistance may be included to make the passing current generate a potential difference, for example, a resistance may be arranged between the first interface P1 and the first terminal Pa R _P , when any current flows through it, a potential difference #V is created. The comparator 212 of the direction determination unit 210 can correspondingly determine the switching signal #S according to the potential difference #V. For example, when the direction of the current Ic is from the first device 110 to the first terminal Pa, the switching signal #S causes the channel switcher 220 to switch to the second channel L2.

In this embodiment, the comparator 212 can be a commercially available amplifier chip driven by the voltage source V _DD . The two input terminals of the comparator 212 are respectively matched with corresponding resistors R1 , R2 , R3 and R4 to adjust the level of the input voltage. Considering the high-speed transmission frequency required by the DDC channel, the comparator 212 can select a specification that matches the high-speed frequency. These specification values can be appropriately adjusted depending on the actual design of the product, and therefore are not limited in the embodiments of the present application.

In a further embodiment, the DDC channel may be in a specific state, such as a non-signaling state. In this embodiment, the direction judging unit 210 is designed to judge whether the state of the DDC channel meets a specific condition, and when the specific condition is met, the DDC channel is switched to a preset state through the switching signal #S. For example, the direction determining unit 210 further includes a logic gate 214 electrically coupled to the output terminal of the comparator 212 and the first terminal Pa. The logic gate 214 executes an "and (AND)" logic operation, the purpose of which is to judge the direction of the current Ic, that is, to further limit the switching signal #S to select the second channel L2 when the actual signal transmission is confirmed, otherwise The default state of the signal extender 200 is to use the first channel L1. Therefore, when the second channel L2 is selected, the direction of the current Ic flows from the first device to the first terminal Pa, and the direction determination unit 210 makes the switching signal #S a logic high potential signal. When the first channel L1 is selected, the switch signal #S is a logic low potential signal.

In a further embodiment, the direction judging unit includes a first inverter and a second inverter. A first inverter is connected to the first terminal Pa and the input terminal of the logic gate 214 , and can transmit the inverse logic potential of the voltage of the first terminal Pa to the logic gate 214 . The second inverter is connected to the output terminal of the logic gate 214 and can receive the switching signal and generate an inverted switching signal #S.

For example, the first inverter can be a transistor Q3, and the second inverter can be a transistor Q4. A transistor Q3 is connected to the first terminal Pa and the input terminal of the logic gate 214 , and can transmit the inverse logic potential of the voltage of the first terminal Pa to the logic gate 214 . The signal generated by the output terminal of the logic gate 214 is the switching signal #S, which is connected to the second switching node SW2 in the channel switcher 220 . At the same time, the transistor Q4 is connected to the output terminal of the logic gate 214 to invert the switching signal #S and transmit it to the first switching contact SW1. In this embodiment, a Metal Oxygen Semiconductor Field Effect Transistor (MOSFET) can be used to realize the phase inversion function of the transistor Q3 and the transistor Q4. Each inverter is connected to the voltage source V _DD , and is matched with corresponding resistors R5 and R6 to adjust the output signal level. The values of these resistors can be appropriately adjusted according to product specifications, and therefore are not limited in the embodiments of the present application.

To sum up, one of the possible operation modes of the direction judging unit 210 in FIG. 4 is to judge the current direction according to the voltage difference between the first interface P1 and the first terminal Pa to generate a switching signal #S for the channel switcher 220 to perform. next steps.

FIG. 5 is a specific circuit diagram of the channel switcher 220 according to the embodiment of the present application. In the channel switcher 220, there are two sets of switch circuits, the first switch circuit 223 and the second switch circuit 227, wherein the first switch circuit 223 is arranged between the first channel L1 and the first terminal Pa, and the second switch circuit 227 It is arranged between the second channel L2 and the first end point Pa. The first switch circuit 223 receives the inverted switching signal #S, and the second switch circuit 227 receives the switching signal #S. When the switching signal #S is a high potential signal, the first switch circuit 223 forms an open circuit, and the second switch circuit 227 forms a circuit, so that the second channel L2 is connected to the first terminal Pa. When the switching signal #S is a low potential signal, the second switch circuit 227 is turned off, and the first switch circuit 223 is turned on, so that the first channel L1 is connected to the first terminal Pa.

Further, the first switch circuit 223 is composed of a transistor 222 and a transistor 224, and is used to determine the conduction state from the first terminal Pa to the second terminal Pb according to the voltage value on the first switching contact SW1. The second switch circuit 227 is composed of a transistor 226 and a transistor 228, and is used for determining the conduction state from the first terminal Pa to the third terminal Pc according to the voltage value on the second switching contact SW2. The third terminal Pc is connected to the driving unit 230 shown in FIG. 3 . However, according to the design of the direction judging unit 210 in FIG. 4 , the voltage values of the first switching point SW1 and the second switching point SW2 are logically inverted. In other words, only one set of the first switch circuit 223 and the second switch circuit 227 is turned on each time, while the other set is turned off. Therefore, the channel switcher 220 realizes the function of selecting the first channel L1 or the second channel L2 to conduct signals according to the switching signal #S.

The function of the channel switcher 220 can be summarized as, according to the switching signal #S, the first terminal Pa is connected to the first channel L1 or the second channel L2 to form a signal transmission channel between the first device 110 and the second device 120 . The first switch circuit 223 is connected between the first channel L1 and the first terminal Pa. The second switch circuit 227 is connected between the second channel L2 and the first terminal Pa. More specifically, the first switch circuit 223 receives the inversion of the switching signal #S from the first switching point SW1, and the second switching circuit 227 receives the switching signal #S from the second switching point SW2. When the switching signal #S is a high potential signal, the first switch circuit 223 forms an open circuit, and the second switch circuit 227 forms a circuit, so that the second channel L2 is connected to the first terminal Pa. In contrast, when the switching signal #S is a low potential signal, the second switch circuit 227 is turned off, and the first switch circuit 223 is turned on, so that the first channel L1 is connected to the first terminal Pa.

In this embodiment, the first switch circuit 223 is composed of a transistor 222 and a source S of the transistor 224 connected in series. Meanwhile, the gate G of the transistor 222 and the gate G of the transistor 224 are commonly connected to the first switching point SW1. Likewise, the second switch circuit 227 is composed of a transistor 226 and a transistor 228 connected in series with the source S. The gate G of the transistor 226 and the gate G of the transistor 228 are commonly connected to the second switching point SW2. In FIG. 5, the drain D of the transistor 222 and the drain D of the transistor 226 are connected to the first terminal Pa, and the drain D of the transistor 224 and the drain D of the transistor 228 are connected to the second terminal respectively. point Pb and the third terminal point Pc. In actual design, the first switch circuit 223 and the second switch circuit 227 are not limited to the double transistor series connection method shown in FIG. 5 , and a single or multiple transistors may be used to realize the switch circuit. On the other hand, it will be appreciated that although the source and drain connections are specified in transistors 222, 224, 226, and 228 above, in many types of transistors, the source and drain are functionally It has the same property, that is, the coupling mode of the source and the drain can be reversed.

FIG. 6 is a specific circuit diagram of the driving unit 230 of the embodiment of the present application. In addition to the ground and the voltage source V _DD , the driving unit 230 is also connected to the third terminal Pc and the second terminal Pb. The driving unit 230 may include a first transistor 232 and a second transistor 234 . The first transistor 232 includes a first drain D1 coupled to the second channel L2 and a voltage source V _DD through the third terminal Pc, a first source S1 grounded, and a first gate G1 . A resistor R7 may be included between the first drain D1 and the voltage source V _DD for adjusting the voltage and current. The second transistor 234 includes a second drain D2 connected to the first gate G1. The second drain D2 is also connected to the voltage source V _DD through a resistor R8 . The second source S2 is grounded, and the second gate G2 is connected to the second terminal Pb. When the channel switcher 220 switches to use the second channel L2, the second gate G2 receives the first electronic signal ES1 of the second device 120 through the second terminal Pb, so that the first transistor 232 correspondingly transfers the signal from the first device 110 The incoming current Ic is pulled down to ground the first source S1 , and the driving unit 230 generates a second electronic signal ES2 for the first device 110 to read. More precisely, when the second device 120 transmits data through the first electronic signal ES1 with poor signal quality, the second transistor 234 of the driving unit 230 is turned on or off according to the voltage change on the second terminal Pb, Then the first gate G1 of the first transistor is turned on or off by the voltage change of the second drain D2 of the second transistor 234, and then the first drain D1 of the first transistor 232 generates second electrons Signal ES2. The driving unit 230 is designed so that the first device 110 will not be affected by the internal resistance _RL of the circuit when reading the second electronic signal ES2. Since the first transistor 232 and the second transistor 234 in the driving unit 230 must be responsible for correctly obtaining data from the first electronic signal ES1 with poor signal quality, the configuration parameters of the first transistor 232 and the second transistor 234 can be Specially optimized to achieve better implementation results.

It can be understood that the first electronic signal ES1 received by the driving unit 230 from the second terminal Pb, and the second electronic signal ES2 output from the third terminal Pc are actually composed of continuous voltage or current waveforms changes to represent the data passed. Therefore, the form of expression in the process of signal transmission is not limited to voltage or current, but can also be a series of transformation combinations of voltage and current. In this embodiment, the first transistor 232 and the second transistor 234 can also be implemented by commercially available transistors, such as MOSFETs. Considering the demand for high-speed transmission, the model specification can be changed according to the demand, which is not limited in this application.

FIG. 7 is a flowchart of a signal transmission method according to an embodiment of the present application. The signal transmission method run in the signal extender 200 proposed in this application can be summarized as the following steps, to transmit information between a first device 110 and a second device 120 . First, in step 701, the signal extender 200 is activated. In step 703, under no signal or non-transmitting state, the first channel L1 is turned on by default to transmit electronic signals. In this application, the electronic signal may be a serial data line signal (SDA) conforming to the DDC specification. In step 705 , the direction determination unit 210 in the signal extender 200 detects the direction of the current on the transmission line. In step 707 , it is determined whether the current flows from the first device 110 to the second device 120 . If not, continue to maintain the state of step 703, and use the first channel L1 to connect the first device 110 and the second device 120 together in series.

In contrast, if it is determined that the current flows from the first device 110 to the second device 120 , then proceed to step 709 , switch to the second channel L2 , and enable the driving unit 230 to transmit electronic signals to the first device 110 . More precisely, when the second channel L2 is selected to be connected to the first terminal Pa and the second terminal Pb in the signal extender, a second electron is generated according to a first electronic signal ES1 provided by the second device 120 and send the second electronic signal ES2 to the first device 110 through the second channel L2. In this embodiment, the content of the data transmitted by the second electronic signal ES2 is substantially the same as that of the first electronic signal ES1, but since the current paths are isolated from each other, the internal resistance _RL in the original channel will not affect the reading of the first device 110. The second electronic signal ES2.

FIG. 8 is a schematic diagram of signal levels in an embodiment of the present application. In a traditional signal extender, due to the existence of the internal resistance _RL of the circuit, the reference voltage of the transmitted first electronic signal ES1, that is, the voltage SL1 used to represent the bit value 0, is often higher than the preset logic low level The judgment level VL makes it impossible for the receiver to read a value of 0. The method proposed in this application can correctly read the first electronic signal ES1 and generate the second electronic signal ES2 with correct logic potential accordingly. The logic potential is correct, which means that the voltage SH representing the bit value 1 is higher than the preset judgment level VH of the logic high potential, and the voltage SL2 representing the bit value 0 will not exceed the preset judgment level VL of the logic low potential . The advantage of this embodiment is that the second electronic signal ES2 with improved quality is used to replace the first electronic signal ES1 and sent to the first device 110 , so that the data can be smoothly transmitted and interpreted by the first device 110 . The above-mentioned high-potential judgment level VH and low-potential judgment level VL are common preset values in digital circuits, so the actual range is not within the limits of the embodiments of the present application. For example, the default judgment level VH of logic high level may be 1.0V, and the default judgment level VL of logic low level may be 0.6V.

The embodiment of the present application takes a DDC channel extender as an example, and the first electronic signal ES1 and the second electronic signal ES2 may be the sequence data link signal SDA. However, the same design can also be applied to signal transmission extenders of other specifications, such as high-definition multimedia interface HDMI or display port DP.

To sum up, the signal extender provided by the embodiment of the present application can solve the problem of the traditional signal voltage level shift. A direction judging unit 210 is used to judge the direction of the current, and a driving unit 230 is used to generate a second electronic signal ES2 with a correct reference voltage according to the first electronic signal ES1, so that the first device 110 can correctly receive the message to be transmitted by the second device 120 . The signal extender of this application can be implemented in a simple and pure hardware manner without firmware intervention. It can be applied in any DDC channel with no compatibility problem.

It should be noted that, in this document, the term "comprising", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, It also includes other elements not expressly listed, or elements inherent in the process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising that element.

The embodiments of the present application have been described above in conjunction with the drawings, but the present application is not limited to the above-mentioned specific implementations. The above-mentioned specific implementations are only illustrative and not restrictive. Those of ordinary skill in the art will Under the inspiration of this application, many forms can be made without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

110: first device 120: second device I _L : current R _L : line internal resistance R _A : first device internal resistance R _B : second device internal resistance R _P : resistors R1~R8: resistors V _DD : voltage source 112: first receiver 114: first transmitter 122: second receiver 124: second transmitter P1: first interface P2: second interface Pa: first endpoint Pb: second endpoint Pc: third Terminal 200: Signal Extender 210: Direction Judgment Unit 212: Comparator 214: Logic Gate 220: Channel Switcher 222, 224, 226, 228: Transistor 230: Drive Unit Q1~Q4: Transistor ES1: First Electronics Signal ES2: second electronic signal 223: first switch circuit 227: second switch circuit 232: first transistor 234: second transistor L1: first channel L2: second channel SW1: first switching contact SW2: Second switching contact S1: first source G1: first gate D1: first drain S2: second source G2: second gate D2: second drain #V: potential difference _IC : current # S: switching signal SH, SL1, SL2: voltage VH, VL: preset judgment level G: gate D: drain S: source 701-709: steps

The drawings described here are used to provide a further understanding of the application and constitute a part of the application. The schematic embodiments and descriptions of the application are used to explain the application and do not constitute an improper limitation to the application. In the schema:

FIG. 1 is a schematic diagram of a conventional connection between a first device 110 and a second device 120 through a display data channel DDC.

FIG. 2 is a structure diagram of a signal extender 200 connected in series with the first device 110 and the second device 120 according to the embodiment of the present application.

FIG. 3 is a schematic structural diagram of a signal extender 200 according to an embodiment of the present application.

FIG. 4 is a specific circuit diagram of the direction judging unit 210 of the embodiment of the present application.

FIG. 5 is a specific circuit diagram of the channel switcher 220 according to the embodiment of the present application.

FIG. 6 is a specific circuit diagram of the driving unit 230 of the embodiment of the present application.

FIG. 7 is a flowchart of a signal transmission method according to an embodiment of the present application.

FIG. 8 is a schematic diagram of signal levels in an embodiment of the present application.

110: First device

120: Second device

Ic: current

R _L : Internal resistance of the line

P1: the first interface

P2: the second interface

Pa: first endpoint

Pb: second endpoint

Pc: the third endpoint

200: signal extender

210: direction judgment unit

220: Channel switcher

230: drive unit

L1: first channel

L2: second channel

SW1: The first switching contact

SW2: Second switching contact

#V: potential difference

#S: switch signal

ES1: First Electronic Signal

ES2: Second Electronic Signal

Claims (8)

A signal extender, used to connect a first device and a second device to transmit information, comprising: a first terminal, used to connect the first device; a second terminal, used to connect the second device ; A channel switcher, connected to the first terminal, according to a switching signal, select one of a first channel or a second channel to connect to the second terminal; a direction judgment unit, connected to the second terminal Between a terminal and the channel switcher, it is used to determine the direction of a current on the first terminal to generate the switching signal, wherein when the direction of the current is flowing from the first device into the first terminal , the switching signal causes the channel switcher to select and connect to the second channel; and a drive unit, connected to the second channel, for being connected to the first terminal and the second terminal when the second channel is selected When the point is connected, a second electronic signal is generated according to a first electronic signal provided by the second device, wherein the second channel transmits the second electronic signal to the first device, and the reference voltage of the second electronic signal not exceed a preset value. The signal extender as described in claim 1, wherein when the switching signal causes the channel switcher to select and connect to the second channel, the driving unit pulls down a current from the first device to the ground line, and the driving unit Make the reference voltage of the second electronic signal not exceed the preset value. The signal extender as described in claim 1, wherein the channel switcher connects the first terminal to the first channel or the second channel according to the switching signal to form a signal transmission channel; the direction judgment unit includes a a comparator connected to the signal transmission channel to detect a potential difference; and The direction judging unit outputs the switching signal according to the potential difference, so that the channel switcher is connected to the first channel or the second channel. The signal extender as described in claim 3, wherein: the direction judging unit further includes a logic gate electrically coupled to the output terminal of the comparator and the first terminal for judging the direction of the current; and When the direction of the current is from the first device to the first terminal, the direction judging unit makes the switching signal a high potential signal, otherwise makes the switching signal a low potential signal. The signal extender as described in claim 1, wherein the drive unit includes: a first transistor, including a first drain connected to the second channel and a voltage source, a first source grounded, and a first a gate; and a second transistor, including a second drain connected to the first gate and the voltage source, a second source connected to ground, and a second gate connected to the second terminal; wherein: when When the channel switcher is connected to the second channel, the second gate receives the first electronic signal from the second device, so that the first transistor correspondingly sends a current from the first device to the second device. A source is pulled down to ground, and makes the first transistor generate the second electronic signal for the first device to read. The signal extender as described in Claim 1, wherein: the signal extender is a DDC channel extender; the first electronic signal and the second electronic signal are serial data link signals; the first device is a computer host; and The second device is a display. A signal transmission method for transmitting information between a first device and a second device, comprising: According to a switching signal, make a channel switch select one of a first channel or a second channel, and pass the first device and the second device through the selected first channel or the second channel string connected together; when the second channel is selected, generate a second electronic signal according to a first electronic signal provided by the second device; judge the direction of a current between the first device and the second device to generating the switching signal; wherein when the direction of the current flow is from the first device, the switching signal causes the channel switcher to select and connect to the second channel; and transmit the second electronic signal to the In the first device, the reference voltage of the second electronic signal does not exceed a preset value. The signal transmission method as described in claim item 7, wherein when the switching signal selects the second channel, the current is pulled down to the ground line by a driving unit, and the reference voltage of the second electronic signal is not higher than the preset set value.

Images