Signal transmission circuit, signal output circuit and electronic module

Abstract

The invention provides a signal transmission circuit, a signal output circuit and an electronic module, the signal transmission circuit comprises a first voltage-controlled current source, a cable, a first resistor and a terminating circuit, the terminating circuit and the first resistor are respectively used as terminating parts to be connected to a sending end and a receiving end of the cable to perform impedance matching, and meanwhile, the terminating parts are connected to the transmitting end and the receiving end of the cable to perform impedance matching. The first voltage-controlled current source outputs a current signal, loads an analog video signal and transmits the analog video signal to a receiving end of the signal transmission circuit, the terminating circuit is provided with a voltage node and an impedance circuit, the voltage node provides voltage with the same size as that of a transmitting end, and the terminating circuit does not shunt the current signal output by the transmitting end when a reflected signal is not considered; moreover, when the impedance value deviation between the cable and the receiving end is large and signal reflection occurs, the reflected signal reflected back to the transmitting end is terminated and eliminated by the impedance circuit, and the reflected signal is not reflected back to the receiving end again, so that the ghosting of the video picture of the receiving end is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of analog video signals, and in particular relates to a signal transmission circuit, a signal output circuit and an electronic module. Background Art

[0002] The current-type drive circuit currently used for analog video transmission is usually terminated in the form of a two-terminal parallel resistor, such as Figure 1 As shown, this termination method can achieve impedance matching better and reduce signal reflection, but it brings an obvious problem, that is, there is a driving current shunting at the transmitting end, and the shunting ratio will be affected by ground noise, which will cause the voltage across the resistor at the receiving end to be affected by ground noise. Then, it is meaningless to introduce current signals to transmit analog video signals.

[0003] There is also a type of current-type driving circuit that chooses not to terminate at the transmitting end in order to maintain the ability to suppress ground noise. This requires that the impedance of the cable and the receiving end are well matched. However, when the impedance value deviation between the cable and the receiving end is large, signal reflection will occur at the receiving end. When the reflected signal reaches the transmitting end, it will be reflected again because there is no termination. When this signal is transmitted to the receiving end, ghosting will be seen on the video screen. Summary of the invention

[0004] The object of the present invention is to provide a signal transmission circuit, aiming to solve the problem of shunting or ghosting in traditional termination methods.

[0005] A first aspect of an embodiment of the present invention provides a signal transmission circuit for transmitting an analog video signal, the signal transmission circuit comprising:

[0006] A first voltage-controlled current source connected to a transmitting end of the signal transmission circuit;

[0007] A cable, a first end of which is connected to the transmitting end;

[0008] a first resistor, wherein a first end of the first resistor is connected to a second end of the cable to form a receiving end of the signal transmission circuit, and a second end of the first resistor is grounded;

[0009] A termination circuit connected to the transmitting end, wherein the termination circuit is provided with a voltage node and an impedance circuit connected between the voltage node and the transmitting end;

[0010] The voltage of the voltage node is equal to the voltage of the transmitting end of the signal transmission circuit;

[0011] The impedance circuit is used to terminate the reflected signal reflected back from the receiving end.

[0012] Optionally, the termination circuit further includes:

[0013] A second voltage-controlled current source connected to the voltage node;

[0014] The adjustable resistance circuit is connected to the voltage node and is triggered by the resistance adjustment signal to adjust the output resistance and output an impedance equal to that of the cable.

[0015] Optionally, the impedance circuit includes a second resistor, which is connected in series between the voltage node and the transmitting end.

[0016] Optionally, the resistance value of the second resistor is equal to the resistance value of the first resistor;

[0017] The impedance of the adjustable resistance circuit is equal to the characteristic impedance of the cable.

[0018] Optionally, the impedance circuit further includes a voltage follower connected in series between the voltage node and the second resistor.

[0019] Optionally, the adjustable resistance circuit includes a programmable resistor.

[0020] Optionally, the adjustable resistance circuit includes a plurality of resistance units connected in parallel, and each resistance unit includes a controllable switch and a third resistor connected in series.

[0021] Optionally, parameters of the first voltage-controlled current source and the second voltage-controlled current source are the same.

[0022] A second aspect of an embodiment of the present invention provides a signal output circuit, comprising a signal source circuit and the signal transmission circuit as described above, wherein the signal source circuit is connected to a transmitting end of the signal transmission circuit, and the signal source circuit is used to output the analog video signal.

[0023] A third aspect of an embodiment of the present invention provides an electronic module, comprising the signal output circuit as described above.

[0024] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned signal transmission circuit includes a first voltage-controlled current source, a cable, a first resistor and a termination circuit, the termination circuit and the first resistor are respectively connected as termination parts to the transmitting end and the receiving end of the cable for impedance matching, and at the same time, the first voltage-controlled current source outputs a current signal and loads an analog video signal to transmit to the receiving end of the signal transmission circuit, the termination circuit is provided with a voltage node and an impedance circuit, the voltage node provides a voltage of the same magnitude as the transmitting end, when the reflected signal is not considered, the termination circuit will not shunt the current signal output by the transmitting end, and when the impedance value deviation between the cable and the receiving end is large and a signal reflection occurs, the reflected signal reflected back to the transmitting end is terminated and eliminated by the impedance circuit, and the reflected signal will not be reflected back to the receiving end again, thereby reducing the ghosting of the video screen at the receiving end. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 It is a schematic diagram of the structure of a traditional current-type driving circuit;

[0027] Figure 2 A schematic diagram of a first structure of a signal transmission circuit provided by an embodiment of the present invention;

[0028] Figure 3 A second structural schematic diagram of a signal transmission circuit provided by an embodiment of the present invention;

[0029] Figure 4 A third structural schematic diagram of a signal transmission circuit provided by an embodiment of the present invention;

[0030] Figure 5 A fourth structural schematic diagram of a signal transmission circuit provided by an embodiment of the present invention;

[0031] Figure 6 A fifth structural schematic diagram of a signal transmission circuit provided by an embodiment of the present invention;

[0032] Figure 7 A sixth structural schematic diagram of a signal transmission circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] A first aspect of an embodiment of the present invention proposes a signal transmission circuit for transmitting an analog video signal. The signal transmission circuit is a current-type driving circuit. The signal transmission circuit outputs a current signal to the corresponding cable L1. At the same time, an analog video signal is loaded on the current signal. The analog video signal follows the current signal and is sent to a receiving module at the back end through the cable L1. The receiving module is used to receive the analog video signal, parse the analog video signal, and display the corresponding video screen.

[0036] Among them, Figure 2 As shown, the signal transmission circuit includes:

[0037] A first voltage-controlled current source I1 is connected to a transmitting end in of a signal transmission circuit;

[0038] A cable L1, a first end of the cable L1 is connected to a transmitting end in;

[0039] A first resistor R1, wherein a first end of the first resistor R1 is connected to a second end of the cable L1 to form a receiving end out of the signal transmission circuit, and a second end of the first resistor R1 is grounded;

[0040] The termination circuit 100 is connected to the transmitting terminal in, and a voltage node Vc and an impedance circuit 10 connected between the voltage node Vc and the transmitting terminal in are provided in the termination circuit 100;

[0041] The voltage of the voltage node Vc is equal to the voltage of the transmitting end in of the signal transmission circuit;

[0042] The impedance circuit 10 is used to terminate the reflected signal reflected back from the receiving end out.

[0043] In this embodiment, the first voltage-controlled current source I1 can be triggered to output a current signal of corresponding magnitude according to the received voltage signal, wherein the magnitude of the output current signal can be set accordingly according to parameters such as the length and characteristic impedance of the cable L1.

[0044] The termination circuit 100 and the first resistor R1 are connected in parallel to the transmitting end in and the receiving end out of the cable L1 as termination resistors to achieve impedance matching. By setting the termination circuit 100 and the first resistor R1, the impedance of the link of the entire signal transmission circuit is consistent, reducing signal reflection, distortion and other problems, and improving the transmission quality of the analog video signal.

[0045] Among them, one end of the termination circuit 100 is connected to the transmitting end in, and the other end of the termination circuit 100 is connected to the ground or a power supply end of a preset size. The impedance of the termination circuit 100 is equal to the characteristic impedance of the cable L1, thereby achieving impedance matching of the transmitting end in.

[0046] When transmitting an analog video signal, the analog video signal is first sent to the transmitting end in, and is loaded and output together with the current signal output by the first voltage-controlled current source I1. The analog video signal is transmitted to the receiving end out and the receiving module connected to the receiving end out through the cable L1. The receiving module is used to receive the analog video signal, parse the analog video signal, and display the corresponding video screen.

[0047] Among them, a voltage node Vc is provided in the termination circuit 100, and the voltage of the voltage node Vc is equal to the voltage of the transmitting terminal in. There is a corresponding impedance between the voltage node Vc and the ground terminal. Under the condition of no transmitting signal, since the voltage of the voltage node Vc is equal to the voltage of the transmitting terminal in, no voltage difference is generated, and no current flows between the voltage node Vc and the transmitting terminal in. The current signal output by the first voltage-controlled current source I1 of the transmitting terminal in will not be shunted, so that it will not be affected by the ground noise Vg, and the first resistor R1 of the receiving terminal out is protected from the influence of the ground noise Vg, thereby ensuring the transmission efficiency and reliability of the analog video signal.

[0048] At the same time, when the impedance between the cable L1 and the impedance of the first resistor R1 at the receiving end out is not completely matched and the impedance value has a large deviation, signal reflection occurs after the analog video signal is sent to the receiving end out, and the reflected signal is transmitted back to the transmitting end in through the cable L1. At this time, since an impedance circuit 10 is set at the voltage node Vc and the transmitting end in, the impedance circuit 10 is connected to the voltage node Vc, and its terminal voltage is equal to the voltage of the transmitting end in, so termination is achieved. The impedance circuit 10 terminates the reflected signal, thereby eliminating the repeated reflection of the reflected signal at the transmitting end in and the receiving end out, reducing the ghosting of the video screen at the receiving end out, and improving the display effect of the video screen of the back-end receiving module.

[0049] The termination circuit 100 may use a corresponding current source, an impedance circuit 10, etc. In an optional embodiment, as Figure 3 As shown, the termination circuit 100 further includes:

[0050] A second voltage-controlled current source I2 connected to the voltage node Vc;

[0051] The adjustable resistance circuit 20 is connected to the voltage node Vc, and is triggered by the resistance adjustment signal to adjust the output resistance and output an impedance equal to that of the cable L1.

[0052] In this embodiment, the second voltage-controlled current source I2 and the adjustable resistance circuit 20 constitute a voltage source, and the connection node between the second voltage-controlled current source I2 and the adjustable resistance circuit 20 is a voltage node Vc. By adjusting the parameters of the second voltage-controlled current source I2 and / or the resistance value of the adjustable resistance circuit 20, the voltage of the voltage node Vc is equal to the voltage at the output end of the first voltage-controlled current source I1.

[0053] There is an adjustable resistance circuit 20 between the voltage node Vc and the ground. When there is no transmitting signal, since the voltage of the voltage node Vc is equal to the voltage of the transmitting end in, no voltage difference is generated, and no current flows between the voltage node Vc and the transmitting end in. The adjustable resistance circuit 20 and the impedance circuit 10 will not shunt the current signal output by the first voltage-controlled current source I1 of the transmitting end in, so that it will not be affected by the ground noise Vg, thereby preventing the first resistor R1 of the receiving end out from being affected by the ground noise Vg, thereby ensuring the transmission efficiency and reliability of the analog video signal.

[0054] At the same time, when the impedance between the cable L1 and the impedance of the first resistor R1 at the receiving end out is not completely matched and the impedance value has a large deviation, signal reflection occurs after the analog video signal is sent to the receiving end out, and the reflected signal is transmitted back to the transmitting end in through the cable L1. At this time, since an impedance circuit 10 is set at the voltage node Vc and the transmitting end in, the impedance circuit 10 is connected to the voltage node Vc, and its terminal voltage is equal to the voltage of the transmitting end in, so termination is achieved. The impedance circuit 10 terminates the reflected signal, thereby eliminating the repeated reflection of the reflected signal at the transmitting end in and the receiving end out, reducing the ghosting of the video screen at the receiving end out, and improving the display effect of the video screen of the back-end receiving module.

[0055] The impedance circuit 10 may use a resistor with a corresponding resistance value. In an optional embodiment, Figure 4 As shown, the impedance circuit 10 includes a second resistor R2, which is connected in series between the voltage node Vc and the transmitting end in, and the first end of the second resistor R2 is connected to the connection node between the second voltage-controlled current source I2 and the adjustable resistance circuit 20, and is terminated to a voltage equal to that of the first voltage-controlled current source I1. When the impedance between the cable L1 and the impedance of the first resistor R1 at the receiving end out is not completely matched, and a large deviation occurs in the impedance value, a signal reflection occurs after the analog video signal is sent to the receiving end out, and the reflected signal is transmitted back to the transmitting end in through the cable L1. At this time, since the second resistor R2 is set at the voltage node Vc and the transmitting end in, the second resistor R2 is terminated, and the second resistor R2 eliminates the termination of the reflected signal, thereby eliminating the repeated reflection of the reflected signal at the transmitting end in and the receiving end out, reducing the ghosting of the video screen at the receiving end out, and improving the display effect of the video screen of the back-end receiving module.

[0056] In order to improve the termination effect, in an optional embodiment, the resistance value of the second resistor R2 is equal to the resistance value of the first resistor R1, and the impedance of the adjustable resistance circuit 20 is equal to the characteristic impedance of the cable L1.

[0057] The sizes of the first resistor R1 and the second resistor R2 can be set accordingly according to requirements, such as 50Ω, 75Ω, etc.

[0058] The termination circuit 100 has the same structure as the first voltage-controlled current source I1, the cable L1 and the first resistor R1. The adjustable resistor circuit 20 acts as a load and is adjusted to an impedance value equal to that of the cable L1 according to a resistance adjustment signal. Without considering the reflected signal, the output voltages of the two voltage-controlled current sources are equal. At this time, the voltage node Vc is connected to the transmitting end in through the second resistor R2, and no shunting of the output current signal occurs.

[0059] Correspondingly, in order to make the voltages at both ends of the second resistor R2 equal, in an optional embodiment, the parameters of the first voltage-controlled current source I1 and the second voltage-controlled current source I2 are the same, and the link results between the termination circuit 100 and the transmitting end in and the receiving end out are exactly the same. By adjusting the impedance of the adjustable resistance circuit 20, its resistance value is equal to the resistance value of the cable L1, and since the impedances of the first resistor R1 and the second resistor R2 are equal, the voltages at both ends of the second resistor R2 are equal. In the absence of a transmitting signal, since the voltage node Vc is equal to the voltage of the transmitting end in, no voltage difference is generated, and no current flows between the voltage node Vc and the transmitting end in. The second resistor R2 and the adjustable resistance circuit 20 will not shunt the current signal output by the first voltage-controlled current source I1 of the transmitting end in, so that it will not be affected by the ground noise Vg, thereby protecting the first resistor R1 of the receiving end out from the influence of the ground noise Vg, thereby ensuring the transmission efficiency and reliability of the analog video signal.

[0060] At the same time, when the impedance between the cable L1 and the impedance of the first resistor R1 at the receiving end out is not completely matched and the impedance value has a large deviation, signal reflection occurs after the analog video signal is sent to the receiving end out, and the reflected signal is transmitted back to the transmitting end in through the cable L1. At this time, since the second resistor R2 is set at the voltage node Vc and the transmitting end in, the second resistor R2 is connected to the voltage node Vc, and its terminal voltage is equal to the voltage of the transmitting end in, so termination is achieved. The second resistor R2 eliminates the termination of the reflected signal, thereby eliminating the repeated reflection of the reflected signal at the transmitting end in and the receiving end out, reducing the ghosting of the video screen at the receiving end out, and improving the display effect of the video screen of the back-end receiving module.

[0061] In order to achieve signal isolation and realize high impedance input, such as Figure 5 As shown, in an optional embodiment, the impedance circuit 10 also includes a voltage follower 11 connected in series between the voltage node Vc and the second resistor R2. The input end of the voltage follower 11 is high impedance, which can reduce the load impact on the adjustable resistance circuit 20, while maintaining the stability of the adjustable resistance circuit 20 and reducing the signal interference of the transmitting end in.

[0062] The adjustable resistance circuit 20 may be an integrated circuit or a discrete component. In an optional embodiment, Figure 6As shown, the adjustable resistance circuit 20 includes a programmable resistor 21. The programmable resistor 21 adjusts resistance according to a received resistance adjustment signal, outputs an impedance equal to that of the cable L1, and provides a voltage equal to that of the transmitting end in.

[0063] In another alternative embodiment, if Figure 7 As shown, the adjustable resistance circuit 20 includes a plurality of resistance units 22 connected in parallel, and each resistance unit 22 includes a controllable switch K1 and a third resistor R3 connected in series.

[0064] In this embodiment, multiple controllable switches K1 receive decoding signals respectively, and a preset number of controllable switches K1 are selected according to the decoding signals, thereby realizing parallel output of multiple third resistors R3, outputting impedance equal to that of cable L1, and providing a voltage equal to that of the transmitting end in.

[0065] The resistance values ​​of the third resistors R3 may be equal or different, and the specific values ​​are not limited. The controllable switch K1 may be a switch device with controlled on and off, such as a MOS tube, a triode, etc.

[0066] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned signal transmission circuit includes a first voltage-controlled current source I1, a cable L1, a first resistor R1 and a termination circuit 100, the termination circuit 100 and the first resistor R1 are respectively connected to the transmitting end in and the receiving end out of the cable L1 as termination parts for impedance matching, and at the same time, the first voltage-controlled current source I1 outputs a current signal and loads an analog video signal to transmit to the receiving end out of the signal transmission circuit, the termination circuit 100 is provided with a voltage node Vc and an impedance circuit 10, the voltage node Vc provides a voltage of the same magnitude as that of the transmitting end in, when the reflected signal is not considered, the termination circuit 100 will not shunt the current signal output by the transmitting end in, and when the impedance value deviation between the cable L1 and the receiving end out is large and a signal reflection occurs, the reflected signal reflected back to the transmitting end in is terminated and eliminated by the impedance circuit 10, and the reflected signal will not be reflected back to the receiving end out again, thereby reducing the ghosting of the video screen at the receiving end out.

[0067] The present invention also proposes a signal output circuit, which includes a signal source circuit and a signal transmission circuit. The specific structure of the signal transmission circuit refers to the above embodiment. Since the signal output circuit adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. Among them, the signal source circuit is connected to the sending end in of the signal transmission circuit, and the signal source circuit is used to output an analog video signal.

[0068] The signal source circuit can be a signal generator or a display module, and the specific type is not limited. The signal source circuit outputs an analog video signal to the transmitting end in of the signal output circuit, and is output together with the current signal of the signal output circuit to the receiving end out of the signal transmission circuit and the receiving module at the back end. The receiving module is used to receive the analog video signal, analyze the analog video signal, and display the corresponding video screen.

[0069] The present invention also proposes an electronic module, which includes a signal output circuit. The specific structure of the signal output circuit refers to the above-mentioned embodiment. Since the electronic module adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0070] The electronic module may be a display device, a signal transmission device, etc. The electronic module may also include a back-end receiving module, and the specific structure is not limited.

[0071] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A signal transmission circuit for transmitting analog video signals, characterized in that: The signal transmission circuit comprises: A first voltage-controlled current source connected to a transmitting end of the signal transmission circuit; A cable, a first end of which is connected to the transmitting end; a first resistor, wherein a first end of the first resistor is connected to a second end of the cable to form a receiving end of the signal transmission circuit, and a second end of the first resistor is grounded; A termination circuit connected to the transmitting end, wherein the termination circuit is provided with a voltage node and an impedance circuit connected between the voltage node and the transmitting end; The voltage of the voltage node is equal to the voltage of the transmitting end of the signal transmission circuit; The impedance circuit is used to terminate the reflected signal reflected back from the receiving end.

2. The signal transmission circuit according to claim 1, characterized in that: The termination circuit further comprises: A second voltage-controlled current source connected to the voltage node; The adjustable resistance circuit is connected to the voltage node and is triggered by the resistance adjustment signal to adjust the output resistance and output an impedance equal to that of the cable.

3. The signal transmission circuit according to claim 1, characterized in that: The impedance circuit includes a second resistor, which is connected in series between the voltage node and the transmitting end.

4. The signal transmission circuit according to claim 3, characterized in that: The resistance value of the second resistor is equal to the resistance value of the first resistor; The impedance of the adjustable resistance circuit is equal to the characteristic impedance of the cable.

5. The signal transmission circuit according to claim 3, characterized in that: The impedance circuit further includes a voltage follower connected in series between the voltage node and the second resistor.

6. The signal transmission circuit according to claim 2, characterized in that: The adjustable resistance circuit includes a programmable resistor.

7. The signal transmission circuit according to claim 2, characterized in that: The adjustable resistance circuit includes a plurality of resistance units connected in parallel, and each resistance unit includes a controllable switch and a third resistor connected in series.

8. The signal transmission circuit according to claim 2, characterized in that: The parameters of the first voltage-controlled current source and the second voltage-controlled current source are the same.

9. A signal output circuit, characterized in that: It comprises a signal source circuit and the signal transmission circuit according to any one of claims 1 to 8, wherein the signal source circuit is connected to a transmitting end of the signal transmission circuit, and the signal source circuit is used to output the analog video signal.

10. An electronic module, characterized in that: Comprising the signal output circuit as claimed in claim 9.

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