CN110706669A - A voltage compensation circuit - Google Patents

Abstract

A voltage compensation circuit for compensating a VCOM voltage of a liquid crystal panel includes: one end of the input capacitor is used for being connected with the CFVCOM _ FB terminal; the first compensation unit is provided with a first connecting end used for connecting the other end of the input capacitor and a second connecting end connected with a VCOM end and used for controlling the compensation depth of the voltage at the CFVCOM _ FB end; the second compensation unit is provided with a first input end connected with the first connecting end of the first compensation unit and a second input end connected with the VCOM end and is used for compensating the voltage of the CF _ VCOM end; and the input end of the filtering output unit is connected with the output end of the second compensation unit, and the output end of the filtering output unit is connected with the CF _ VCOM end and used for filtering and outputting the compensated voltage. The invention realizes the isolation effect on the direct current voltage through the input capacitor. The first compensation unit controls the compensation depth of the voltage at the CFVCOM _ FB terminal, and the second compensation unit controls the voltage compensation. In addition, the stability of the output voltage is further improved by the filtering output unit.

Description

A voltage compensation circuit

technical field

The invention belongs to the field of displays, in particular to a voltage compensation circuit.

Background technique

With the development of the liquid crystal display technology, the display effect of the liquid crystal display panel is getting higher and higher. In order to achieve a better display effect, the display effect of the panel is generally adjusted by adjusting the reference voltage (VCOM) compensation multiple of the deflection of the liquid crystal molecules. However, the liquid crystal molecules must be driven with an AC signal and maintain a certain polarity for a long time, and the liquid crystal molecules may be damaged. Therefore, the VCOM pole is used as the common pole of the positive and negative inversion reference of the liquid crystal molecule, and the voltage is required to be very accurate. It needs to be set at the middle value of the positive and negative inversion voltage. If the set value is not uniform, it will cause the screen to flicker.

At present, TFT circuit design generally includes aluminum process and copper process. The line loss of the aluminum process is relatively large, and the line loss of the copper process is relatively small. On the aluminum process or large-size copper process screen, the difference between the VCOM at the near end and the far end is large, causing flickering in different areas of the screen.

Terminology: The VCOM terminal is the VCOM voltage connection port generated by the GAMMA chip; the CF_VCOM terminal is the near-end connection port where the VCOM voltage is connected to the display line; the CFVCOM_FB terminal is the VCOM voltage is connected to the display line. The remote connection port.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a voltage compensation circuit, which has a simple structure and eliminates the problem of flickering in different areas of the screen.

A voltage compensation circuit according to an embodiment of the present invention includes: an input capacitor, one end of which is used to connect to the CFVCOM_FB end; a first compensation unit, which has a first connection end used to connect the other end of the input capacitor and a second connection to the VCOM end terminal for compensating the CF_VCOM terminal voltage; a second compensation unit, which has a first input terminal connected to the first connection terminal of the first compensation unit and a second input terminal connected to the VCOM terminal for compensation The CF_VCOM terminal voltage; a filter output unit, the input terminal of which is connected to the output terminal of the second compensation unit, and the output terminal is connected to the CF_VCOM terminal for outputting the compensated voltage.

The voltage compensation circuit according to the embodiment of the present invention has at least the following technical effects: the isolation of the DC voltage is achieved through the input capacitor. The CFVCOM_FB terminal voltage is clamped by the first compensation unit, thereby realizing the control of the compensation depth of the CFVCOM_FB terminal voltage, and then the voltage compensation is realized by the second compensation unit. Compared with the traditional compensation method, the compensation effect is more stable. In addition, the compensation voltage is further filtered by the filtering output unit to further improve the stability of the output voltage.

According to some embodiments of the present invention, the first compensation unit includes: a first diode, the anode is connected to the other end of the input capacitor, and the cathode is connected to the VCOM terminal; a second diode, the anode is connected is connected to the cathode of the first diode, and the cathode is connected to the anode of the first diode.

According to some embodiments of the present invention, the second compensation unit includes: a first resistor, one end of which is connected to the other end of the input capacitor; a second resistor, one end of which is connected to the other end of the first resistor , the other end is connected to the input end of the filter output unit; the negative input pin of the operational amplifier unit is connected to the other end of the first resistor, the positive input pin is connected to the VCOM end, and the output pin is connected to the The input end of the filter output unit is connected, the ground pin is connected with the ground wire, and the working power pin is used to connect the external power supply.

According to some embodiments of the present invention, the second compensation unit further includes: a first capacitor connected between the seventh pin of the operational amplifier unit and the ground line; and a second capacitor connected in parallel with the first capacitor.

According to some embodiments of the present invention, the filtering output unit includes: a third resistor, one end of which is connected to the output end of the second compensation unit; and a third capacitor, which is connected to the other end of the third resistor and ground between the lines.

According to some embodiments of the present invention, the voltage compensation circuit further includes: a fourth resistor connected between the CF_VCOM terminal and the ground wire.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of an embodiment of the present invention.

Reference number:

The first compensation unit 100 , the second compensation unit 200 , and the filter output unit 300 .

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In the description of the present invention, if there is a description of the first, second, third, fourth, etc., only for the purpose of distinguishing technical features, and should not be understood as indicating or implying relative importance or implicitly indicating the indicated The number of technical features or implicitly indicates the order of the indicated technical features.

In the description of the present invention, unless otherwise clearly defined, words such as setting and connection should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meaning of the above words in the present invention in combination with the specific content of the technical solution.

A voltage compensation circuit according to an embodiment of the present invention is described below with reference to FIG. 1 .

The voltage compensation circuit according to the embodiment of the present invention includes: an input capacitor C1 , a first compensation unit 100 , a second compensation unit 200 , and a filter output unit 300 .

The input capacitor C1 has one end connected to the CFVCOM_FB end; the first compensation unit 100 has a first connection end connected to the other end of the input capacitor C1 and a second connection end connected to the VCOM end, used to control the compensation depth of the voltage at the CFVCOM_FB end the second compensation unit 200, which has a first input end connected with the first connection end of the first compensation unit 100, and a second input end connected with the VCOM end for compensating the CF_VCOM end voltage; the filter output unit 300, which The input terminal is connected to the output terminal of the second compensation unit 200 , and the output terminal is connected to the CF_VCOM terminal for filtering and outputting the compensated voltage.

Referring to FIG. 1 , the input capacitor C1 is connected between the CFVCOM_FB terminal and the first compensation unit 100 to isolate the DC voltage component that may exist in the voltage of the CFVCOM_FB terminal. The first compensation unit 100 is connected after the input capacitor C1, and can play a role in controlling the voltage compensation depth of the CFVCOM_FB terminal, so as to ensure that the input voltage fluctuation will not be too large. The second compensation unit 200 plays the role of a compensation voltage by means of feedback, and outputs the processed voltage by taking the voltage compensated by the first compensation unit 100 and the voltage of the VCOM terminal together as an input mode. The filtering output unit 300 performs further filtering processing on the voltage output by the second compensation unit 200 before outputting.

According to the voltage compensation circuit of the embodiment of the present invention, the isolation effect on the DC voltage is realized through the input capacitor C1. The voltage compensation is realized by the first compensation unit 100 and the second compensation unit 200, and the compensation effect is more stable compared with the traditional compensation method. In addition, by further filtering by the filtering output unit 300, the stability of the output voltage is further improved.

In some embodiments of the present invention, referring to FIG. 1 , the first compensation unit 100 includes: a first diode D1 and a second diode D2. The first diode D1, the anode is connected to the other end of the input capacitor C1, and the cathode is connected to the VCOM terminal; the second diode D2, the anode is connected to the cathode of the first diode D1, and the cathode is connected to the first diode D1 the anode connection. The CFVCOM_FB terminal voltage input is processed by the input capacitor C1 and then connected to the first compensation unit 100. When the CFVCOM_FB terminal voltage is higher than the VCOM terminal voltage by one turn-on voltage of the first diode D1, the first diode D1 will be turned on , the effect of making the voltage of the first input terminal of the second compensation unit 200 not higher than the voltage of the VCOM terminal plus a diode turn-on voltage will finally be achieved. Similarly, when the voltage of the VCOM terminal is higher than the voltage of the CFVCOM_FB terminal by the turn-on voltage of the second diode D2, the second diode D2 will be turned on, and finally the voltage of the first input terminal of the second compensation unit 200 will be reached. It will not be lower than the VCOM terminal voltage minus the effect of a diode conduction voltage. Finally, the voltage of the first input terminal of the second compensation unit 200 is maintained within the range of the voltage of the VCOM terminal plus and minus a diode conduction voltage, which can effectively prevent the abnormal voltage output of the CF_VCOM terminal when the voltage fluctuation of the CFVCOM_FB terminal is too large. question.

In some embodiments of the present invention, referring to FIG. 1 , the second compensation unit 200 includes: a first resistor R1 , a second resistor R2 , and an operational amplifier unit U1 . One end of the first resistor R1 is connected to the other end of the input capacitor C1; one end of the second resistor R2 is connected to the other end of the first resistor R1, and the other end is connected to the input end of the filter output unit 300; the operational amplifier unit, its The negative input pin is connected to the other end of the first resistor, the positive input pin is connected to the VCOM end, the output pin is connected to the input end of the filter output unit 300, the ground pin is connected to the ground wire, and the working power pin Used to connect external power supply AVDD. The first resistor R1, the second resistor R2 and the operational amplifier form a differential subtractor with negative feedback. Let the voltage of the VCOM terminal be Ui2, the input voltage of the negative input pin of the operational amplifier unit U1 is Ui1, and the operational amplifier unit U1 The output voltage of the output pin is Uo, then Uo=Ui2+(Ui2-Ui1)(R2/R1); the ratio of R2 and R1 can be adjusted, and the specific ratio needs to be debugged according to the actual test screen. When it is large, adjust the ratio so that the screen does not flicker. After the adjustment of the second compensation unit 200 is completed and the actual working state is entered, the output voltage is adjusted according to the voltage input from the negative input pin of the op amp unit U1 and the VCOM terminal voltage of the positive input pin through a differential subtractor with negative feedback. In addition, the first resistor R1 and the input capacitor C1 form a differential circuit, which can better isolate the DC voltage.

In some embodiments of the present invention, referring to FIG. 1 , the second compensation unit 200 further includes: a first capacitor C2 and a second capacitor C3. The first capacitor C2 is connected between the working power pin of the operational amplifier unit U1 and the ground wire; the second capacitor C3 is connected in parallel with the first capacitor C2. The first capacitor C2 and the second capacitor C3 are mainly used for filtering, and are used to ensure the stability of the operation of the operational amplifier unit U1.

In some embodiments of the present invention, referring to FIG. 1 , the filter output unit 300 includes a third resistor R3 and a third capacitor C4. One end of the third resistor R3 is connected to the output end of the second compensation unit 200 ; the third capacitor C4 is connected between the other end of the third resistor R3 and the ground wire. The third resistor R3 and the third capacitor C4 form a filter circuit, which can play a good filtering role, further ensure the stability of the output voltage, and play an auxiliary role in reducing screen flicker.

In some embodiments of the present invention, referring to FIG. 1 , a fourth resistor connected between the CF_VCOM terminal and the ground line is further included. The fourth resistor acts as a discharge resistor, which can discharge the screen end when the power is turned off.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples", etc., is meant to incorporate the embodiments A particular feature, structure, material, or characteristic described by an example or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the above-mentioned embodiments of the present invention have been described in detail in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned embodiments, and those of ordinary skill in the art can understand that these embodiments can be carried out without departing from the principle and purpose of the present invention. For various changes, modifications, substitutions and alterations, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. A voltage compensation circuit for compensating a VCOM voltage of a liquid crystal panel, comprising:

one end of the input capacitor is used for being connected with the CFVCOM _ FB terminal;

the first compensation unit (100) is provided with a first connecting end used for connecting the other end of the input capacitor and a second connecting end connected with a VCOM end and used for controlling the compensation depth of the voltage at the CFVCOM _ FB end;

a second compensation unit (200) having a first input terminal connected to the first connection terminal of the first compensation unit (100), a second input terminal connected to the VCOM terminal, for compensating a CF _ VCOM terminal voltage;

and the input end of the filtering output unit (300) is connected with the output end of the second compensation unit (200), and the output end of the filtering output unit is connected with the CF _ VCOM end, and the filtering output unit is used for filtering and outputting the compensated voltage.

2. A voltage compensation circuit according to claim 1, wherein the first compensation unit (100) comprises:

a first diode having an anode connected to the other end of the input capacitor and a cathode connected to the VCOM terminal;

and the anode of the second diode is connected with the cathode of the first diode, and the cathode of the second diode is connected with the anode of the first diode.

3. A voltage compensation circuit according to claim 1, wherein the second compensation unit (200) comprises:

a first resistor having one end connected to the other end of the input capacitor;

one end of the second resistor is connected with the other end of the first resistor, and the other end of the second resistor is connected with the input end of the filtering output unit (300);

and a negative input pin of the operational amplifier unit is connected with the other end of the first resistor, a positive input pin of the operational amplifier unit is connected with the VCOM end, an output pin of the operational amplifier unit is connected with the input end of the filtering output unit (300), a ground pin of the operational amplifier unit is connected with a ground wire, and a working power supply pin of the operational amplifier unit is used for being connected with an external power supply.

4. A voltage compensation circuit according to claim 3, wherein the second compensation unit (200) further comprises:

the first capacitor is connected between the seventh pin of the operational amplifier unit and the ground wire;

and the second capacitor is connected with the first capacitor in parallel.

5. A voltage compensation circuit according to claim 1, wherein the filter output unit (300) comprises;

a third resistor, one end of which is connected with the output end of the second compensation unit (200);

and the third capacitor is connected between the other end of the third resistor and the ground wire.

6. The voltage compensation circuit of claim 1, further comprising: a fourth resistor connected between the CF _ VCOM terminal and a ground line.