CN210722412U

CN210722412U - Voltage compensation circuit

Info

Publication number: CN210722412U
Application number: CN201921557782.3U
Authority: CN
Inventors: 李戡; 李铭
Original assignee: Guangdong Changhong Electronics Co Ltd
Current assignee: Guangdong Changhong Electronics Co Ltd
Priority date: 2019-09-19
Filing date: 2019-09-19
Publication date: 2020-06-09
Anticipated expiration: 2029-09-19

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 utility model discloses an input capacitance has realized the isolation to direct voltage. 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

Voltage compensation circuit

Technical Field

The utility model belongs to the display field, concretely relates to voltage compensation circuit.

Background

With the development of liquid crystal display technology, people have higher and higher display effect on liquid crystal display panels. In order to achieve better display effect, the display effect of the panel is generally adjusted by adjusting the compensation factor of the reference Voltage (VCOM) for the liquid crystal molecule deflection. However, the liquid crystal molecules must be driven by an ac signal and maintain a certain polarity for a long time, and the liquid crystal molecules may be broken. Therefore, the VCOM electrode is used as the common electrode for the positive and negative inversion reference of the liquid crystal molecules, the voltage requirement is very accurate, and needs to be set at the middle value of the positive and negative inversion voltage, and if the set value is not uniform, the screen flicker can be caused.

Currently, the TFT circuit design generally includes an aluminum process and a copper process. The line loss of the aluminum process is large, the line loss of the copper process is small, and the difference of VCOM at the near end and the far end is large on an aluminum process or a large-size copper process screen, so that different areas of the screen flicker.

The terms: VCOM end is VCOM voltage connection port produced by GAMMA chip; the CF _ VCOM terminal is a near-end connection port for connecting VCOM voltage to a display screen line; the CFVCOM _ FB terminal is the far end connection port where the VCOM voltage is connected to the display screen lines.

SUMMERY OF THE UTILITY MODEL

The utility model discloses aim at solving one of the technical problem that exists among the prior art at least. Therefore, the utility model provides a voltage compensation circuit, voltage compensation circuit simple structure has eliminated the problem of the different regional scintillation of screen.

According to the utility model discloses voltage compensation circuit, include: 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 compensating the voltage of the CF-VCOM end; a second compensation unit having a first input terminal connected to the first connection terminal of the first compensation unit, a second input terminal connected to the VCOM terminal, for compensating the CF _ VCOM terminal voltage; 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 outputting the compensated voltage.

According to the utility model discloses voltage compensation circuit has following technological effect at least: the isolation of the direct voltage is achieved by the input capacitance. The first compensation unit clamps the voltage of the CFVCOM-FB terminal, so that the control of the compensation depth of the voltage of the CFVCOM-FB terminal is realized, and then the second compensation unit realizes the compensation of the voltage. In addition, the compensation voltage is further filtered through the filtering output unit, and the stability of the output voltage is further improved.

According to some embodiments of the invention, the first compensation unit 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.

According to some embodiments of the invention, the second compensation unit 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; 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, 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.

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

According to some embodiments of the invention, the filter output unit comprises; one end of the third resistor is connected with the output end of the second compensation unit; and the third capacitor is connected between the other end of the third resistor and the ground wire.

According to some embodiments of the invention, the voltage compensation circuit further comprises: a fourth resistor connected between the CF _ VCOM terminal and a ground line.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

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

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

Reference numerals:

a first compensation unit 100, a second compensation unit 200, and a filtering output unit 300.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present invention, and should not be construed as limiting the present invention.

In the description of the present invention, if there are first, second, third, fourth, etc. described, it is only for the purpose of distinguishing technical features, and it is not understood that relative importance is indicated or implied or that the number of indicated technical features is implicitly indicated or that the precedence of the indicated technical features is implicitly indicated.

In the description of the present invention, unless there is an explicit limitation, the 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 by combining the specific contents of the technical solution.

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

According to the utility model discloses voltage compensation circuit, include: input capacitor C1, first compensation unit 100, second compensation unit 200, and filtering output unit 300.

An input capacitor C1, one end of which is connected to the CFVCOM _ FB terminal; a first compensation unit 100 having a first connection terminal for connecting the other end of the input capacitor C1, a second connection terminal for connecting the VCOM terminal, and a compensation depth for controlling the CFVCOM _ FB terminal voltage; 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 the CF _ VCOM terminal voltage; and a filter output unit 300, an input end of which is connected to the output end of the second compensation unit 200, and an output end of which is connected to the CF _ VCOM end, 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, and serves to isolate a dc voltage component that may exist in the CFVCOM _ FB terminal. The first compensation unit 100 is connected after the input capacitor C1, and can control the compensation depth of the CFVCOM _ FB voltage to ensure that the input voltage fluctuation is not too large. The second compensation unit 200 functions as a compensation voltage by means of feedback, and outputs a processed voltage by using the voltage compensated by the first compensation unit 100 and the voltage at the VCOM terminal as input modes. The filter output unit 300 further filters the voltage output from the second compensation unit 200 and outputs the filtered voltage.

According to the utility model discloses voltage compensation circuit has realized the isolation effect to direct voltage through input capacitance C1. The voltage compensation is realized through the first compensation unit 100 and the second compensation unit 200, and compared with the conventional compensation mode, the compensation effect is more stable. In addition, the stability of the output voltage is further improved by further filtering by the filtering output unit 300.

In some embodiments of the present invention, referring to fig. 1, the first compensation unit 100 includes: a first diode D1, a second diode D2. The anode of the first diode D1 is connected with the other end of the input capacitor C1, and the cathode of the first diode D1 is connected with the VCOM end; the anode of the second diode D2 is connected to the cathode of the first diode D1, and the cathode is connected to the anode of the first diode D1. The CFVCOM _ FB terminal voltage input is processed by the input capacitor C1 and then connected to the first compensation unit 100, and when the CFVCOM _ FB terminal voltage is higher than the VCOM terminal voltage by a conducting voltage of the first diode D1, the first diode D1 is turned on, so that the effect of preventing the first input terminal voltage of the second compensation unit 200 from being higher than the VCOM terminal voltage plus a diode conducting voltage is finally achieved. Similarly, when the voltage at the VCOM terminal is higher than the voltage at the CFVCOM _ FB terminal by a turn-on voltage of the second diode D2, the second diode D2 is turned on, and the effect of preventing the voltage at the first input terminal of the second compensation unit 200 from being lower than the voltage at the VCOM terminal by a diode turn-on voltage is finally achieved. Finally, the first input end voltage of the second compensation unit 200 is kept in the range of the positive and negative diode conducting voltages of the VCOM end voltage, so that the problem of abnormal CF _ VCOM end voltage output caused by overlarge CFVCOM _ FB voltage fluctuation can be effectively prevented.

In some embodiments of the present invention, referring to fig. 1, the second compensation unit 200 includes: the circuit comprises a first resistor R1, a second resistor R2 and an operational amplifier unit U1. A first resistor R1, one end of which is connected to the other end of the input capacitor C1; a second resistor R2, one end of which is connected to the other end of the first resistor R1, and the other end of which is connected to the input end of the filter 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 AVDD. The first resistor R1, the second resistor R2 and the operational amplifier form a differential subtractor with negative feedback, the VCOM terminal voltage is set as Ui2, the negative input pin input voltage of the operational amplifier unit U1 is Ui1, the output pin output voltage of the operational amplifier unit U1 is Uo, and then Uo is Ui2+ (Ui2-Ui1) (R2/R1); the ratio of R2 to R1 can be adjusted, the specific ratio needs to be debugged according to an actual test picture, and the main mode is as follows: when the screen load changes greatly, the ratio is adjusted to enable the screen to achieve the effect of no flicker. When the second compensation unit 200 finishes the adjustment and enters the actual working state, the output voltage is adjusted by a differential subtracter with negative feedback according to the voltage input by the negative input pin of the operational amplifier unit U1 and the VCOM terminal voltage of the positive input pin. In addition, the first resistor R1 and the input capacitor C1 form a differential circuit, which plays a better role in blocking 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 supply pin of the operational amplifier unit U1 and the ground wire; and the second capacitor C3 is connected with the first capacitor C2 in parallel. The first capacitor C2 and the second capacitor C3 are mainly used for filtering, and are used for ensuring the stability of the operation of the operational amplifier unit U1.

In some embodiments of the present invention, referring to fig. 1, the filtering output unit 300 includes; a third resistor R3 and a third capacitor C4. A third resistor R3 having one end connected to the output end of the second compensation unit 200; and a third capacitor C4 connected between the other end of the third resistor R3 and ground. The third resistor R3 and the third capacitor C4 form a filter circuit, so that a good filtering effect can be achieved, the stability of output voltage is further guaranteed, and the auxiliary screen flash lightening effect is achieved.

In some embodiments of the present invention, referring to fig. 1, further comprising a fourth resistor connected between the CF _ VCOM terminal and the ground line. The fourth resistor is used as a discharge resistor and can play a role in discharging the screen end when the power is off.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above 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 embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to the above embodiments, and those skilled in the art can understand that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

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.