Circuit for testing LVDS signal and ground short circuit

Abstract

The present application relates to a circuit for testing a short circuit between an LVDS signal and a ground. The circuit for testing a short circuit between an LVDS signal and a ground comprises: an acquisition module, a calculation module and a prompt module. The acquisition module comprises a first test unit, a second test unit and a voltage divider unit. The first test unit and the second test unit are electrically connected to the voltage divider unit respectively; the calculation module is electrically connected to the first test unit; and the prompt module is electrically connected to the calculation module. The solution provided by the present application can accurately test whether there is a foreign object between the LVDS routing and the ground wire that causes a short circuit, thereby quickly screening out defective products.

Description

Technical Field

[0001] The utility model relates to the technical field of display screens, in particular to a circuit for testing an LVDS signal and a ground short circuit. Background Art

[0002] LVDS is a low voltage differential signal technology used for high-speed data transmission. Its principle is to form a signal loop through a terminal resistor, so that the current output by the constant current source driver flows through the terminal resistor, and the high and low logic levels are generated by the current direction of the resistor.

[0003] In the related art, the LVDS interface used in LCD display screens is usually integrated on the FPC board, and usually uses 5 pairs of LVDS differential pairs. Crosstalk will occur between adjacent differential pairs, causing signal distortion, so a ground wire is needed to separate adjacent differential pairs so that they do not interfere with each other. However, during the production process of LCD display screens, it is inevitable that foreign objects such as copper scraps will fall between the LVDS wiring and the ground wire, causing a short circuit between the LVDS wiring and the ground wire. Utility Model Content

[0004] The purpose of the utility model is to overcome the deficiencies in the prior art and provide a circuit for testing the short circuit between LVDS signals and ground, which can accurately test whether there is a foreign object between the LVDS wiring and the ground wire causing the short circuit, thereby quickly screening out defective products.

[0005] The purpose of this utility model is achieved through the following technical solutions:

[0006] The first aspect of the present application provides a circuit for testing LVDS signals and ground short circuits, including: an acquisition module, including a first test unit, a second test unit and a voltage divider unit, the first test unit and the second test unit are electrically connected to the voltage divider unit respectively; an operation module, electrically connected to the first test unit; and a prompt module, electrically connected to the operation module.

[0007] The voltage dividing unit includes a resistor R1 , a resistor R4 , a resistor R2 , and a resistor R5 . The resistor R1 , the resistor R4 , the resistor R2 , and the resistor R5 are electrically connected to the first testing unit, respectively.

[0008] The voltage dividing unit further includes a resistor R3 and a resistor R6, and the resistor R3 and the resistor R6 are electrically connected to the second testing unit respectively.

[0009] The first test unit includes a first detection point and a second detection point. The first detection point is electrically connected to the resistor R1 and the resistor R2 respectively, and the second detection point is electrically connected to the resistor R4 and the resistor R5 respectively.

[0010] The second test unit includes a third detection point and a fourth detection point. The third detection point is electrically connected to the resistor R2 and the resistor R3 respectively. The fourth detection point is electrically connected to the resistor R5 and the resistor R6 respectively.

[0011] The operation module includes an operational amplifier U1 and an operational amplifier U2, the first end of the operational amplifier U1 is electrically connected to the first detection point, the second end of the operational amplifier U1 is electrically connected to the first end of the operational amplifier U2, and the second end of the operational amplifier U2 is electrically connected to the second detection point.

[0012] The operation module further includes a chip U3 , and the chip U3 is electrically connected to the second end of the operational amplifier U1 and the first end of the operational amplifier U2 , respectively.

[0013] The prompt module includes an LED lamp, a first end of the LED lamp is electrically connected to the third end of the operational amplifier U1 and the third end of the operational amplifier U2 respectively, and a second end of the LED lamp is grounded.

[0014] It also includes a first connecting terminal, wherein the first connecting terminal is electrically connected to the third detection point.

[0015] It also includes a second connecting terminal, wherein the second connecting terminal is electrically connected to the fourth detection point.

[0016] Compared with the prior art, the utility model has at least the following advantages:

[0017] The second test unit of the acquisition module is used to electrically connect to the LVDS line, divide the collected voltage through the voltage divider unit, and then calculate the voltage value through the first test unit and the operation module to see whether the voltage value can light up the prompt module. If so, the LVDS line and the ground line are not short-circuited, otherwise, they are short-circuited. In this way, the above method is simple to operate and can accurately test whether there is a foreign object between the LVDS line and the ground line that causes a short circuit, thereby quickly screening out defective products. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings required for use in the embodiments are briefly introduced below.

[0019] Figure 1 It is a structural schematic diagram of a circuit for testing a short circuit between an LVDS signal and a ground in one embodiment of the utility model;

[0020] Figure 2 A circuit diagram of a circuit for testing a short circuit between an LVDS signal and a ground in one embodiment of the utility model;

[0021] Figure 3It is a circuit diagram of another implementation of a circuit for testing the short circuit between an LVDS signal and a ground in an embodiment of the utility model. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0023] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0024] Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, or a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] In the related art, the LVDS interface used in LCD display screens is usually integrated on the FPC board, and usually uses 5 pairs of LVDS differential pairs. Crosstalk will occur between adjacent differential pairs, causing signal distortion, so a ground wire is needed to separate adjacent differential pairs so that they do not interfere with each other. However, during the production process of LCD display screens, it is inevitable that foreign objects such as copper scraps will fall between the LVDS wiring and the ground wire, causing a short circuit between the LVDS wiring and the ground wire.

[0026] In response to the above problems, an embodiment of the present application provides a circuit for testing the short circuit between LVDS signals and ground, which can accurately test whether there is a foreign object between the LVDS trace and the ground line causing a short circuit, thereby quickly screening out defective products.

[0027] The technical solution of the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0028] See also Figure 1 and Figure 2 A circuit for testing a short circuit between an LVDS signal and a ground includes: an acquisition module 100, an operation module 200 and a prompt module 300, wherein the acquisition module 100 includes a first test unit, a second test unit and a voltage divider unit, wherein the first test unit and the second test unit are electrically connected to the voltage divider unit respectively; the operation module 200 is electrically connected to the first test unit; and the prompt module 300 is electrically connected to the operation module.

[0029] It should be noted that the acquisition module 100 is used to acquire the voltage of the LVDS circuit, the calculation module 200 is used to calculate the voltage, and the prompt module 300 is used to prompt the staff to facilitate the judgment of whether the LVDS line is short-circuited with the ground line. In this way, the above method is simple to operate and can accurately test whether there is a foreign object between the LVDS line and the ground line to cause a short circuit, thereby quickly screening out defective products.

[0030] It is also necessary to note that, please refer to Figure 3 , the LVDS wiring is integrated on the FPC board, and a PPC terminal matching resistor RL is set between the third detection point and the fourth detection point, with a resistance of 100 ohm. The resistor RL here is used to simulate the LVDS wiring.

[0031] See also Figure 1 Specifically, the voltage dividing unit includes a resistor R1, a resistor R4, a resistor R2 and a resistor R5, and the resistor R1, the resistor R4, the resistor R2 and the resistor R5 are electrically connected to the first test unit respectively.

[0032] Specifically, the voltage dividing unit further includes a resistor R3 and a resistor R6, and the resistor R3 and the resistor R6 are electrically connected to the second test unit respectively.

[0033] It should be noted that the resistors R1, R4, R2, R5, R3 and R6 are all voltage divider resistors, wherein the resistance of the resistors R1 and R4 is 45kohm, the resistance of the resistors R2 and R5 is 5kohm, and the resistance of the resistors R3 and R6 is 50kohm.

[0034] See also Figure 1 Specifically, the first test unit includes a first detection point and a second detection point, the first detection point is electrically connected to the resistor R1 and the resistor R2 respectively, and the second detection point is electrically connected to the resistor R4 and the resistor R5 respectively.

[0035] It should be noted that the first detection point is C and the second detection point is D.

[0036] See also Figure 2Specifically, the second test unit includes a third detection point and a fourth detection point, the third detection point is electrically connected to the resistor R2 and the resistor R3 respectively, and the fourth detection point is electrically connected to the resistor R5 and the resistor R6 respectively.

[0037] It should be noted that the third detection point is A and the fourth detection point is B.

[0038] See also Figure 2 Specifically, the operation module 200 includes an operational amplifier U1 and an operational amplifier U2, the first end of the operational amplifier U1 is electrically connected to the first detection point, the second end of the operational amplifier U1 is electrically connected to the first end of the operational amplifier U2, and the second end of the operational amplifier U2 is electrically connected to the second detection point. Specifically, the operation module 200 also includes a chip U3, which is electrically connected to the second end of the operational amplifier U1 and the first end of the operational amplifier U2.

[0039] It should be noted that the input voltages of the operational amplifier are IN1 and IN2, the power supply is VCC and GND, the pull-up resistor is 1K, the pull-up voltage is VCC, when the input voltage IN1>IN2, that is, the voltage of the positive input terminal is higher, the output is high level; when the input voltage IN2>IN1, that is, the voltage of the negative input terminal is higher, the output is low level. Among them, the models of operational amplifiers U1 and U2 can be LM741, the model of chip U3 can be BL1117-CX, and the output voltage of the operational amplifier of this application is 1.25V.

[0040] See also Figure 2 In one embodiment, the prompt module 300 includes an LED lamp, a first end of the LED lamp is electrically connected to the third end of the operational amplifier U1 and the third end of the operational amplifier U2, and a second end of the LED lamp is grounded.

[0041] It should be noted that the prompt module 300 is an LED lamp, but is not limited to an LED lamp, and can also be an electronic component such as a buzzer that can prompt the staff.

[0042] See also Figure 2 In one embodiment, the first connection terminal is further included, and the first connection terminal is electrically connected to the third detection point. Specifically, the second connection terminal is further included, and the second connection terminal is electrically connected to the fourth detection point.

[0043] It should be noted that the circuit is integrated on the PCB board, and the third detection point and the fourth detection point are plugged into the FPC board through the first connection terminal and the second connection terminal to be electrically connected to the LVDS wiring.

[0044] The following explains the test principle of this circuit. For better explanation, Figure 3 The middle resistor RL is the FPC terminal matching resistor, and the resistance value of RL is 100ohm.

[0045] Normal test results:

[0046] The voltage value of the first detection point C is:

[0047] Vc=VCC*(R2+R3) / (R1+R2+R3)=3.3V*(5kohm+50kohm) / (45kohm+5kohm+50kohm)=1.875V

[0048] The voltage value of the second detection point D is:

[0049] Vd=VCC*(R5+R6) / (R4+R5+R6)=3.3V*(5kohm+50kohm) / (45kohm+5kohm+50kohm)=1.875V

[0050] Therefore, the voltage values ​​at the first detection point C and the second detection point D are both 1.875V, which is greater than the output voltage of chip U3 1.25V. Therefore, the output results of operational amplifiers U1 and U2 are both 3.3V, and the LED light is turned on. The staff can determine that there is no short circuit between the LVDS wiring and the ground wire.

[0051] Detect abnormal normal state:

[0052] When the LVDS line and the ground line are short-circuited, the resistor R3 is connected in parallel with the external FPC board and then in series with the resistors R1 and R2. Therefore, the voltage value of the first detection point C is:

[0053] Vc=VCC*(R2+R3||RL) / (R1+R2+R3||RL)

[0054] =3.3V*(5Kohm+(50kohm||100ohm)) / (45kohm+5kohm+(50kohm||100ohm))

[0055] =0.335V

[0056] Among them, || means that two resistors are connected in parallel, and the calculation method is the sum of the two resistors divided by the product of the two resistors.

[0057] Furthermore, since the fourth detection point B is grounded, the voltage value of the second detection point D is:

[0058] Vd=VCC*R5 / (R4+R5)=3.3V*5Kohm / (45Kohm+5Kohm)=0.33V

[0059] Therefore, the third detection point C and the fourth detection point D are both lower than the output voltage 1.25V of chip U3, so the output results of operational amplifiers U1 and U2 are 0V, i.e., low level. At this time, the LED light is not turned on, and the staff can judge that there is an abnormality in the LVDS routing.

[0060] The scheme of the present application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of the various embodiments have their own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the specification are not necessarily required for the present application. In addition, it can be understood that the steps in the method of the embodiment of the present application can be adjusted in order, merged and deleted according to actual needs, and the modules in the device of the embodiment of the present application can be merged, divided and deleted according to actual needs.

[0061] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A circuit for testing short circuit between LVDS signal and ground, characterized in that: include: The acquisition module comprises a first test unit, a second test unit and a voltage divider unit, wherein the first test unit and the second test unit are electrically connected to the voltage divider unit respectively; A computing module, electrically connected to the first testing unit; The prompt module is electrically connected to the computing module.

2. The circuit for testing the short circuit between LVDS signal and ground according to claim 1, characterized in that: The voltage dividing unit includes a resistor R1 , a resistor R4 , a resistor R2 , and a resistor R5 . The resistor R1 , the resistor R4 , the resistor R2 , and the resistor R5 are electrically connected to the first testing unit, respectively.

3. The circuit for testing the short circuit between LVDS signal and ground according to claim 2, characterized in that: The voltage dividing unit further includes a resistor R3 and a resistor R6, and the resistor R3 and the resistor R6 are electrically connected to the second testing unit respectively.

4. The circuit for testing the short circuit between LVDS signal and ground according to claim 3, characterized in that: The first test unit includes a first detection point and a second detection point. The first detection point is electrically connected to the resistor R1 and the resistor R2 respectively, and the second detection point is electrically connected to the resistor R4 and the resistor R5 respectively.

5. The circuit for testing the short circuit between LVDS signal and ground according to claim 4, characterized in that: The second test unit includes a third detection point and a fourth detection point. The third detection point is electrically connected to the resistor R2 and the resistor R3 respectively. The fourth detection point is electrically connected to the resistor R5 and the resistor R6 respectively.

6. The circuit for testing the short circuit between LVDS signal and ground according to claim 5, characterized in that: The operation module includes an operational amplifier U1 and an operational amplifier U2, the first end of the operational amplifier U1 is electrically connected to the first detection point, the second end of the operational amplifier U1 is electrically connected to the first end of the operational amplifier U2, and the second end of the operational amplifier U2 is electrically connected to the second detection point.

7. The circuit for testing the short circuit between LVDS signal and ground according to claim 6, characterized in that: The operation module further includes a chip U3 , and the chip U3 is electrically connected to the second end of the operational amplifier U1 and the first end of the operational amplifier U2 , respectively.

8. The circuit for testing the short circuit between LVDS signal and ground according to claim 6, characterized in that: The prompt module includes an LED lamp, a first end of the LED lamp is electrically connected to the third end of the operational amplifier U1 and the third end of the operational amplifier U2 respectively, and a second end of the LED lamp is grounded.

9. The circuit for testing the short circuit between LVDS signal and ground according to claim 5, characterized in that: It also includes a first connecting terminal, wherein the first connecting terminal is electrically connected to the third detection point.

10. The circuit for testing the short circuit between LVDS signal and ground according to claim 5, characterized in that: It also includes a second connecting terminal, wherein the second connecting terminal is electrically connected to the fourth detection point.

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