VCOM drive circuit for LCD screen

Abstract

The utility model provides a VCOM drive circuit for an LCD screen, which is used for adjusting VCOM voltage required by the LCD screen and comprises a voltage input circuit, a voltage division circuit, a separation circuit, a load circuit and a voltage output circuit. The voltage division circuit is used for dividing the voltage of the voltage input circuit and transmitting the divided voltage of the voltage input circuit to the separation circuit; the first end of the separation circuit is connected with the voltage division circuit, the second end of the separation circuit is connected with the voltage output circuit, the second end of the separation circuit is connected with the voltage output circuit, the first end of the separation circuit is used for receiving the voltage of the voltage input circuit after voltage division, and the second end of the separation circuit is used for receiving the voltage of the voltage output circuit after voltage division. The second end of the separation circuit is used for outputting the voltage input to the separation circuit to the voltage output circuit, and the separation circuit is used for isolating the voltage division circuit and the load circuit to prevent product failure caused by the fact that the VCOM voltage cannot be adjusted to the optimum.

Description

Technical Field

[0001] The utility model belongs to the technical field of LCD display screens, and in particular relates to a VCOM driving circuit for an LCD screen. Background Art

[0002] LCD screens usually require driving voltages AVDD, VGH, VGL, and VCOM. However, the VCOM voltage refers to the intermediate voltage used to control the liquid crystal molecules in the liquid crystal display. It is used to balance the positive and negative polarities of the liquid crystal molecules to keep them in a vertical or horizontal orientation. The VCOM voltage required by the LCD screens of the same model is inconsistent. In order to ensure the quality and stability of the displayed image, the jitter value is measured on the flicker screen during verification, and the VCOM voltage is adjusted for each LCD screen to ensure that the DB value of the flicker screen is in the best state and is judged as a good product within the specification.

[0003] Conventional designs use AVDD to obtain the VCOM voltage through resistor voltage division, such as Figure 1 As shown, there is no resistor R3 in the actual circuit. This resistor R3 is an equivalent load diagram of the LCD. By using resistor voltage division, the theoretical voltage VCOM = (R2) / (R1+VR1+R2)*AVDD when the LCD screen is not connected. However, when the LCD screen is actually connected, the equivalent resistance R3 of the LCD is connected in parallel with R2, and the resistance value of the lower section of VCOM in the circuit will decrease, so that the voltage of VCOM will drop. Because the resistance between the VCOM point and GND of each LCD is inconsistent, it will be impossible to calculate the theoretical value of VCOM in the early stage of development, resulting in product failure. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides a VCOM driving circuit for an LCD screen, which is used to solve the problems mentioned in the above background technology.

[0005] The utility model provides the following technical solution: a VCOM driving circuit for an LCD screen, used to adjust the required VCOM voltage of the LCD screen, including a voltage input circuit, a voltage dividing circuit, a separation circuit, a load circuit, and a voltage output circuit;

[0006] The input end of the voltage divider circuit is connected to the voltage input circuit, and the voltage divider circuit is used to divide the voltage of the voltage input circuit and transmit the divided voltage of the voltage input circuit to the separation circuit;

[0007] The first end of the separation circuit is connected to the voltage divider circuit, the second end of the separation circuit is connected to the voltage output circuit, the second end is connected to the voltage output circuit, the first end of the separation circuit is used to receive the voltage of the voltage input circuit after voltage division, the second end of the separation circuit is used to output the voltage input to the separation circuit to the voltage output circuit, and the separation circuit is used to isolate the voltage divider circuit from the load circuit;

[0008] The load circuit is connected between the second end of the separation circuit and the voltage output circuit, and the load circuit is an equivalent load of the LCD screen.

[0009] Compared with the prior art, the utility model has the following beneficial effects: the voltage divider circuit is isolated from the load circuit by a separation circuit, so that the voltage output by the voltage divider circuit is isolated from the load circuit, and the load circuit and the voltage divider circuit are prevented from forming a parallel circuit, so that the two are not affected by each other, so that the resistance value of the lower section of VCOM in the VCOM driving circuit will not be affected, and thus the voltage of VCOM will not be affected, thereby improving the manufacturing feasibility of the product and preventing product failure due to the VCOM voltage not being adjusted to the optimum.

[0010] Furthermore, the voltage input circuit is an analog circuit power supply.

[0011] Furthermore, the voltage divider circuit includes an adjustable resistor, a first resistor, and a second resistor. The adjustable resistor is connected in series with the first resistor. The first resistor is connected in series with one end of the second resistor, and the other end of the second resistor is grounded.

[0012] Furthermore, the voltage input circuit, the adjustable resistor, the first resistor, the second resistor and the second resistor are connected in sequence to form an electrical loop, and the current range of the electrical loop is 1mA to 6mA.

[0013] Furthermore, the separation circuit is an operational amplifier, which includes a first pin, a second pin, a third pin, a fourth pin, and a fifth pin. The first pin is connected in parallel to the branch where the voltage output circuit is located, the second pin is grounded, the third pin is connected in parallel to the branch where the second resistor is located, the fourth pin is connected in series to the branch where the voltage output circuit is located, and the fifth pin is connected in parallel to the branch where the voltage input circuit is located.

[0014] Furthermore, the voltage at the fifth pin is greater than the voltage at the fourth pin.

[0015] Furthermore, the voltage output circuit is a VCOM voltage.

[0016] Furthermore, the load circuit is a third resistor, one end of the third resistor is connected in parallel to the branch where the voltage output circuit is located, and the other end of the third resistor is grounded. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is shown as a circuit diagram of the prior art.

[0018] Figure 2 It is a schematic diagram showing the structure of a VCOM driving circuit for an LCD screen in an embodiment of the utility model;

[0019] Figure 3 It is a circuit diagram of a VCOM driving circuit for an LCD screen in an embodiment of the utility model.

[0020] Explanation of main component symbols: 1. Voltage input circuit; 2. Voltage divider circuit; 21. Adjustable resistor; 22. First resistor; 23. Second resistor; 3. Separation circuit; 4. Load circuit; 5. Voltage output circuit.

[0021] The following specific implementation manner will further illustrate the present utility model in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the utility model, the utility model will be described more fully below with reference to the relevant drawings. Several embodiments of the utility model are shown in the drawings. However, the utility model can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the utility model more thorough and comprehensive.

[0023] It should be noted that when an element is said to be "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is said to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] See also Figures 2 to 3As shown, a VCOM driving circuit for an LCD screen in an embodiment of the utility model is used to adjust the required VCOM voltage of the LCD screen. The VCOM driving circuit includes a voltage input circuit 1, a voltage dividing circuit 2, a separation circuit 3, a load circuit 4, and a voltage output circuit 5;

[0026] The input end of the voltage divider circuit 2 is connected to the voltage input circuit 1, and the voltage divider circuit 2 is used to divide the voltage of the voltage input circuit 1 and transmit the divided voltage of the voltage input circuit 1 to the separation circuit 3;

[0027] The first end of the separation circuit 3 is connected to the voltage divider circuit 2, the second end of the separation circuit 3 is connected to the voltage output circuit 5, the second end is connected to the voltage output circuit 5, the first end of the separation circuit 3 is used to receive the voltage of the voltage input circuit 1 after voltage division, the second end of the separation circuit 3 is used to output the voltage input to the separation circuit 3 to the voltage output circuit 5, and the separation circuit 3 is used to isolate the voltage divider circuit 2 from the load circuit 4;

[0028] The load circuit 4 is connected between the second end of the separation circuit 3 and the voltage output circuit 5 , and the load circuit 4 is an equivalent load of the LCD screen.

[0029] It is worth noting that the voltage divider circuit 2 is isolated from the load circuit 4 by the separation circuit 3, so that the voltage output by the voltage divider circuit 2 is isolated from the load circuit 4, and the load circuit 4 is prevented from forming a parallel circuit with the voltage divider circuit 2, so that the two are not affected by each other, so that the resistance value of the lower section of VCOM in the VCOM driving circuit will not be affected, and the voltage of VCOM will not be affected, thereby improving the manufacturing feasibility of the product and preventing product failure due to the VCOM voltage not being adjusted to the optimal level.

[0030] Specifically, the voltage input circuit 1 is an analog circuit power supply. In this embodiment, the analog circuit power supply is an AVDD voltage.

[0031] Specifically, the voltage divider circuit 2 includes an adjustable resistor 21, a first resistor 22, and a second resistor 23. The adjustable resistor 21 is connected in series with the first resistor 22, the first resistor 22 is connected in series with one end of the second resistor 23, and the other end of the second resistor 23 is grounded. The expression of the theoretical voltage output by the VCOM driving circuit is VCOM=(R2) / (R1+VR1+R2)*AVDD. The output VCOM voltage is adjusted by the VR1 adjustable resistor to ensure the best state of each LCD screen. In the expression, VCOM is the voltage of the voltage output circuit 5, R1 is the first resistor 22, R2 is the second resistor 23, VR1 is the adjustable resistor 21, and AVDD is the voltage of the voltage input circuit 1.

[0032] More specifically, the voltage input circuit 1, the adjustable resistor 21, the first resistor 22, the second resistor 23 and the second resistor 23 connected in sequence are grounded to form an electric loop, and the current range of the electric loop is 1mA to 6mA. It is worth noting that the resistance range of the resistor R1 / R2 and the adjustable resistor VR1 need to be selected according to the voltage range of VCOM in the LCD specification, and the maximum and minimum values ​​of the LCD VCOM voltage are determined by the maximum and minimum values ​​of the adjustable resistor VR1. The current I=AVDD / (VR1+R1+R2) in the loop from AVDD to VR1 / R1 / R2 to GND is controlled within 6mA to avoid the influence of the excessive current here on the AVDD front stage.

[0033] Specifically, the separation circuit 3 is an operational amplifier, and the operational amplifier includes a first pin, a second pin, a third pin, a fourth pin, and a fifth pin. The first pin is connected in parallel to the branch where the voltage output circuit 5 is located, the second pin is grounded, the third pin is connected in parallel to the branch where the second resistor 23 is located, the fourth pin is connected in series to the branch where the voltage output circuit 5 is located, and the fifth pin is connected in parallel to the branch where the voltage input circuit 1 is located. It is worth noting that the voltage obtained after being divided by the voltage divider circuit 2 enters the operational amplifier through the third pin of the component U1, and then outputs to the voltage output circuit 5 (VCOM). At this time, the voltage of the third pin is consistent with the voltage of the output fourth pin, but the third pin and the fourth pin are in an isolated state, and the equivalent load (third resistor) of the LCD and the second resistor 23 will not form a parallel circuit, and will not affect each other.

[0034] Specifically, the voltage at the fifth pin is greater than the voltage at the fourth pin. In this embodiment, the fifth pin of the operational amplifier (U1) in the VCOM driving circuit is connected to the power supply (VDD) within the range of the device and the voltage is greater than the voltage of the fourth pin, otherwise the operational amplifier will fail.

[0035] In this embodiment, the voltage output circuit 5 is a VCOM voltage.

[0036] In this embodiment, the load circuit 4 is a third resistor, one end of the third resistor is connected in parallel to the branch where the voltage output circuit 5 is located, and the other end of the third resistor is grounded.

[0037] In summary, the VCOM driving circuit for an LCD screen in the above-mentioned embodiment of the utility model isolates the voltage divider circuit 2 from the load circuit 4 through the separation circuit 3, so that the voltage output by the voltage divider circuit 2 is isolated from the load circuit 4, and the load circuit 4 is prevented from forming a parallel circuit with the voltage divider circuit 2, so that the two are not affected by each other, so that the resistance value of the lower section of VCOM in the VCOM driving circuit will not be affected, and the voltage of VCOM will not be affected, thereby improving the manufacturing feasibility of the product and preventing product failure due to the VCOM voltage not being adjusted to the optimal level.

[0038] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0039] The above-mentioned embodiments only express several implementation methods of the utility model, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the utility model. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A VCOM driving circuit for an LCD screen, used to adjust the required VCOM voltage of the LCD screen, characterized in that: It includes a voltage input circuit, a voltage dividing circuit, a separation circuit, a load circuit, and a voltage output circuit; The input end of the voltage divider circuit is connected to the voltage input circuit, and the voltage divider circuit is used to divide the voltage of the voltage input circuit and transmit the divided voltage of the voltage input circuit to the separation circuit; The first end of the separation circuit is connected to the voltage divider circuit, the second end of the separation circuit is connected to the voltage output circuit, the second end is connected to the voltage output circuit, the first end of the separation circuit is used to receive the voltage of the voltage input circuit after voltage division, the second end of the separation circuit is used to output the voltage input to the separation circuit to the voltage output circuit, and the separation circuit is used to isolate the voltage divider circuit from the load circuit; The load circuit is connected between the second end of the separation circuit and the voltage output circuit, and the load circuit is an equivalent load of the LCD screen.

2. The VCOM driving circuit for an LCD screen according to claim 1, characterized in that: The voltage input circuit is an analog circuit power supply.

3. The VCOM driving circuit for an LCD screen according to claim 1, characterized in that: The voltage divider circuit includes an adjustable resistor, a first resistor, and a second resistor. The adjustable resistor is connected in series with the first resistor. The first resistor is connected in series with one end of the second resistor. The other end of the second resistor is grounded.

4. The VCOM driving circuit for an LCD screen according to claim 3, characterized in that: The voltage input circuit, the adjustable resistor, the first resistor, the second resistor and the second resistor are connected in sequence to form an electric loop, and the current range of the electric loop is 1mA to 6mA.

5. The VCOM driving circuit for an LCD screen according to claim 3, characterized in that: The separation circuit is an operational amplifier, which includes a first pin, a second pin, a third pin, a fourth pin, and a fifth pin. The first pin is connected in parallel to the branch where the voltage output circuit is located, the second pin is grounded, the third pin is connected in parallel to the branch where the second resistor is located, the fourth pin is connected in series to the branch where the voltage output circuit is located, and the fifth pin is connected in parallel to the branch where the voltage input circuit is located.

6. The VCOM driving circuit for an LCD screen according to claim 5, characterized in that: The voltage at the fifth pin is greater than the voltage at the fourth pin.

7. The VCOM driving circuit for an LCD screen according to claim 1, characterized in that: The voltage output circuit is VCOM voltage.

8. The VCOM driving circuit for an LCD screen according to claim 1, characterized in that: The load circuit is a third resistor, one end of the third resistor is connected in parallel to the branch where the voltage output circuit is located, and the other end of the third resistor is grounded.

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