CN203573622U - Voltage comparison circuit and liquid crystal display comprising same - Google Patents

Abstract

A voltage comparison circuit and a liquid crystal display including the voltage comparison circuit. The voltage comparison circuit includes: a voltage dividing unit that divides the input voltage by a first voltage dividing ratio and a second voltage dividing ratio to generate a first voltage and a second voltage; and outputs a first signal based on the first voltage and the reference voltage and a comparison unit that outputs a second signal based on the second voltage and the reference voltage; a logic gate that outputs a result signal of whether the input voltage is within a predetermined voltage range based on the first signal and the second signal.

Description

Voltage comparison circuit and liquid crystal display including the voltage comparison circuit

technical field

The utility model relates to a voltage comparison circuit and a liquid crystal display including the voltage comparison circuit, in particular to a voltage comparison circuit for determining whether the voltage is within a predetermined range, that is, a liquid crystal display including the voltage comparison circuit.

Background technique

Thin-film transistor liquid crystal display (TFT-LCD) is a commonly used liquid crystal display at present. In TFT-LCD, each pixel is equipped with a semiconductor switch (that is, a transistor), and each pixel can be directly controlled by point pulses, so each node is relatively independent and can be continuously controlled, which not only improves the display The response speed is fast, and the display color scale can be precisely controlled at the same time.

In TFT-LCD, the control of the light point display duration is to rely on the pixel signal to charge the capacitor through a semiconductor switch (ie, TFT), and then rely on the electric field formed by the capacitor voltage to control the twisting of the liquid crystal molecules. In each field period, the TFT is turned on once so as to charge and discharge the capacitor once, and the voltage for turning on the TFT is VGH (that is, the gate conduction voltage), and the voltage for turning off the TFT is VGL. When implementing a TFT based on an N-channel MOS transistor, VGH is generally a positive voltage of about 10-20V to be fully turned on, and VGL is generally a negative voltage of about -5V to be fully turned off.

Whether the VGH of the TFT is in the predetermined voltage range will directly affect the display effect of the TFT-LCD, and the VGH of the TFT is easily offset by electrostatic discharge (ESD), so a method that can detect whether the VGH of the TFT is in its predetermined voltage range is needed circuit to determine whether VGH has deviated from its predetermined range due to the effects of ESD.

Utility model content

In view of the above problems in the prior art, the utility model provides a voltage comparison circuit capable of determining whether the gate conduction voltage of a TFT-LCD is within a predetermined voltage range and a liquid crystal display including the voltage comparison circuit.

According to an aspect of the present invention, there is provided a voltage comparison circuit for determining whether an input voltage is within a predetermined voltage range, including: performing voltage division on the input voltage according to a first voltage division ratio and a second voltage division ratio to generate a second A voltage division unit for the first voltage and the second voltage; a comparison unit for outputting the first signal based on the first voltage and the reference voltage and outputting the second signal based on the second voltage and the reference voltage; outputting whether the input voltage is based on the first signal and the second signal A logic gate that results in a signal within a predetermined voltage range.

Preferably, the comparing unit is configured to output the first signal and the second signal having different levels when the reference voltage is smaller than the first voltage and larger than the second voltage.

Preferably, the logic gates are XOR logic gates.

Preferably, the comparing unit is a dual comparator chip, and has a first input terminal receiving the first voltage, a second input terminal receiving the second voltage, a reference voltage input terminal receiving the reference voltage, and a terminal outputting the first voltage and the reference voltage. A first output terminal of the first signal of the comparison result and a second output terminal of the second signal of the comparison result of the second voltage and the reference voltage.

Preferably, the comparing unit includes: a first comparator configured to compare the first voltage with a reference voltage and output a first signal; and a second comparator configured to compare the second voltage with the reference voltage and output a second signal. Comparators.

Preferably, the comparison unit includes a first transistor and a second transistor, wherein the first transistor has a gate receiving the first voltage, a source connected to ground, and a drain receiving a predetermined voltage, and the second transistor has a drain receiving the second voltage. The gate, the source connected to ground, and the drain receiving a predetermined voltage, wherein the logic gate is connected to the drains of the first transistor and the second transistor to receive the first signal and the second signal.

Preferably, the first transistor and the second transistor are both P-channel transistors or N-channel transistors.

Preferably, the voltage dividing unit includes: a first voltage dividing circuit that divides the input voltage according to a first voltage dividing ratio to generate the first voltage; performs voltage dividing on the input voltage according to a second voltage dividing ratio to generate the second voltage. Second voltage divider circuit.

Preferably, the first voltage dividing circuit includes a first resistor and a second resistor connected in series, and the second voltage dividing circuit includes a third resistor and a fourth resistor connected in series.

According to another aspect of the present invention, a voltage comparison circuit of a liquid crystal display is provided, the voltage comparison circuit is the above-mentioned voltage comparison circuit, and is used for detecting the turn-on voltage of a thin film transistor of a liquid crystal display.

According to another aspect of the present invention, a liquid crystal display is provided, which has the above-mentioned voltage comparator circuit, which is used to detect whether the turn-on voltage of the thin film transistor of the liquid crystal display is within a predetermined range as an input voltage.

Preferably, the liquid crystal display further includes: a controller for controlling a refresh operation of a screen of the liquid crystal display based on a resultant signal output by the voltage comparison circuit.

According to the voltage comparison circuit of the present invention, it can be determined whether the input voltage is within its predetermined voltage range by comparing the input voltage such as the gate-on voltage of the TFT-LCD with a reference voltage. Moreover, since the voltage comparator circuit can be formed by simple electronic components such as resistors, its cost is relatively low.

Description of drawings

These and/or other aspects and advantages of the present utility model will become clear and easier to understand through the following description of the embodiments in conjunction with the accompanying drawings, wherein:

Fig. 1 shows the block diagram of the voltage comparator circuit according to the embodiment of the present utility model;

2 to 5 show simplified circuits of voltage comparison circuits according to the first to fourth embodiments of the present invention.

Detailed ways

Embodiments of the invention will now be described in detail, examples of which are shown in the accompanying drawings, wherein like reference numerals refer to like parts throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

FIG. 1 is a block diagram of a voltage comparison circuit according to an embodiment of the present invention. As shown in FIG. 1 , the voltage comparison circuit according to the embodiment of the present invention may include a voltage dividing unit 100 , a comparison unit 200 , and a logic gate 300 .

The voltage dividing unit 100 divides an input voltage VIN (for example, a gate-on voltage VGH of a TFT-LCD) according to a first voltage dividing ratio and a second voltage dividing ratio to generate a first voltage VOUT1 and a second voltage VOUT2 . Here, for convenience of description, it is assumed that the first voltage VOUT1 is greater than the second voltage VOUT2 , that is, the first voltage division ratio is smaller than the second voltage division ratio.

Meanwhile, for the convenience of description, it is also assumed that the predetermined voltage range of the input voltage (for example, the gate turn-on voltage of the TFT-LCD) is VTH1 to VTH2, wherein VTH1 is smaller than VTH2. That is, under normal circumstances, the input voltage VIN should satisfy the following mathematical formula (1):

VTH1<VIN<VTH2 (1)

In addition, the first voltage division ratio and the second voltage division ratio of the voltage division unit 100 are respectively set as shown in the following mathematical formulas (2) and (3):

r1=VREF/VTH1 (2)

r2=VREF/VTH2 (3)

Wherein, r1 and r2 are respectively the first voltage dividing ratio and the second voltage dividing ratio of the voltage dividing unit 100 . And VREF is a reference voltage of the comparison unit 200 which will be described below.

Therefore, the first voltage VOUT1 and the second voltage VOUT2 output from the voltage dividing unit 100 may satisfy the following mathematical expressions (4) and (5):

VOUT1=VIN×r1=VIN×VREF/VTH1 (4)

VOUT2=VIN×r2=VIN×VREF/VTH2 (5)

For this, the voltage dividing unit 100 may include a first voltage divider 110 and a second voltage divider 120 . The first voltage divider can divide the input voltage VIN according to the first voltage division ratio, and output the first voltage VOUT1. The second voltage divider 120 may divide the input voltage VIN according to a second voltage dividing ratio, and output a second voltage VOUT2.

The first voltage divider 110 and the second voltage divider 120 may be implemented by voltage dividing resistors, but the implementation of the voltage dividing unit 100 is not limited thereto.

The comparison unit 200 outputs a first comparison signal COM1 based on the first voltage VOUT1 and the reference voltage VREF and a second comparison signal COM2 based on the second voltage VOUT2 and the reference voltage VREF. For example, the comparing unit 200 can compare the first voltage VOUT1 with the reference voltage VREF to output the first comparison signal COM1 , and compare the second voltage VOUT2 with the reference voltage VREF to output the second comparison signal COM2 .

When the first voltage VOUT1 is greater than VREF, the comparison unit 200 outputs the first comparison signal COM1 of the first level, and when the first voltage VOUT1 is smaller than VREF, the comparison unit 200 outputs the first comparison signal COM1 of the second level. At the same time, when the second voltage VOUT2 is greater than VREF, the comparison unit 200 outputs the second comparison signal COM2 of the first level, and when the second voltage VOUT2 is smaller than VREF, the comparison unit 200 outputs the second comparison signal COM2 of the second level. .

When the reference voltage VREF is between the first voltage VOUT1 and the second voltage VOUT2, the comparison unit 200 outputs the first comparison signal COM1 and the second comparison signal COM2 with different levels from each other, and when the reference voltage VREF is greater than the first voltage VOUT1 and the second comparison signal COM2 When both the second voltage VOUT2 is lower than both the first voltage VOUT1 and the second voltage VOUT2 , the comparison unit 200 outputs the first comparison signal COM1 and the second comparison signal COM2 with the same level. However, the level forms of the first comparison signal COM1 and the second comparison signal COM2 output by the comparison unit 200 are not limited thereto.

Here, the comparison unit 200 may be realized by a dedicated comparator chip, and may also be realized by elements such as transistors.

To this end, the comparing unit 200 may include a first comparator 210 and a second comparator 220 .

The first comparator 210 compares the first voltage VOUT1 with the reference voltage VREF and outputs a first comparison signal COM1 as a result of the comparison. That is, when the first voltage VOUT1 is greater than VREF, the first comparator 210 outputs the first comparison signal COM1 of the first level, and when the first voltage VOUT1 is less than VREF, the first comparator 210 outputs the first comparison signal COM1 of the second level. A comparison signal COM1.

The second comparator 220 compares the second voltage VOUT2 with the reference voltage VREF and outputs a second comparison signal COM2 as a comparison result. That is, when the second voltage VOUT2 is greater than VREF, the second comparator 220 outputs the second comparison signal COM2 of the first level, and when the second voltage VOUT2 is less than VREF, the second comparator 220 outputs the second comparison signal COM2 of the second level. Two compare signal COM2.

When the first comparator 210 and the second comparator 220 are implemented by transistors, the reference voltage VREF may be a source voltage. That is, the first comparator 210 can be turned on or off according to the source voltage to provide signals of different levels.

The first comparator 210 and the second comparator 220 may be implemented by transistors.

The logic gate 300 may determine whether the input voltage is within a predetermined voltage range based on the levels of the first comparison signal COM1 and the second comparison signal COM2. That is, the logic gate may output a result signal RES indicating whether the input voltage is within a predetermined voltage range based on the first comparison signal COM1 and the second comparison signal COM2 .

For example, when the comparison unit 200 is realized as described above to output the first comparison signal COM1 and the second comparison signal COM2 whose levels are different from each other when the reference voltage VREF is between the first voltage VOUT1 and the second voltage VOUT2, the logic The gate 300 may determine whether the input voltage is within a predetermined voltage range based on whether the levels of the first comparison signal COM1 and the second comparison signal COM2 are the same. At this time, the logic gate 300 may preferably be an exclusive OR logic gate.

However, implementing the logic gate 300 as an XOR logic gate is only an exemplary embodiment, and the logic gate 300 may be implemented by other types of logic gates according to the output form of the comparison unit 200 .

Next, the circuit structure of the voltage comparison circuit according to the embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5 . In the following description, in order to avoid confusing the technical solution of the present invention, the description of common knowledge will be omitted.

FIG. 2 shows a simplified circuit of the voltage comparison circuit according to the first embodiment of the present invention. As shown in FIG. 2 , the voltage comparison circuit according to the embodiment of the present invention may include a first voltage divider 110 , a second voltage divider 120 , a comparison unit 200 , and a logic gate 300 .

The first voltage divider 110 includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2 having a resistance value satisfying the formula (2), while the second voltage divider 120 includes a resistance value satisfying the formula (3). The resistance value of the third voltage dividing resistor R3 and the fourth voltage dividing resistor R4.

The first voltage divider 110 composed of the first resistor R1 and the second resistor R2 divides the gate-on voltage VGH (ie, the input voltage) to output the first voltage VOUT1 to the comparison unit 200 . Meanwhile, the second voltage divider 120 composed of the third resistor R3 and the fourth resistor R4 divides the gate-on voltage VGH to output the second voltage VOUT2 to the comparison unit 200 .

The comparison unit 200 compares the first voltage VOU1 and the second voltage VOUT2 with the reference voltage VREF, respectively, and outputs the first comparison signal COM1 and the second comparison signal COM2 as the comparison result.

The logic gate 300 outputs a signal LCD_ESD_DET as a result signal based on the first comparison signal COM1 and the second comparison signal COM2 received from the comparison unit 200 to inform whether the gate turn-on voltage is within a predetermined power supply range.

Since the operation principle of the voltage comparison circuit according to the embodiment of the present invention has been described above with reference to FIG. 1 , its detailed description is omitted here.

FIG. 3 shows a simplified circuit of a voltage comparison circuit according to a second embodiment of the present invention. As shown in FIG. 3 , the voltage comparison circuit according to the embodiment of the present invention may include a first voltage divider 110 , a second voltage divider 120 , a first comparator 210 , a second comparator 220 and a logic gate 300 .

The structure of the voltage comparison circuit of FIG. 3 is basically similar to that of the voltage comparison circuit of FIG. 2, the only difference being that the voltage comparison circuit of FIG. VREF and the second voltage VOUT2 are compared with the reference voltage VREF.

Since the operation principle of the voltage comparison circuit according to the embodiment of the present invention has been described above with reference to FIGS. 1 and 2 , a detailed description thereof is omitted here.

FIG. 4 shows a simplified circuit of a voltage comparison circuit according to a third embodiment of the present invention. As shown in FIG. 4 , the voltage comparison circuit according to the embodiment of the present invention may include a first voltage divider 110 , a second voltage divider 120 , a first comparator 210 , a second comparator 220 and a logic gate 300 .

Here, the first comparator 210 and the second comparator 220 are formed of N-channel transistors.

Here, the reference voltages of the first comparator 210 and the second comparator 220 may be their turn-on voltages, so the first comparator 210 and the second comparator 220 may receive the first voltage VOUT1 and the second voltage VOUT2 and Whether the source voltage difference is greater than the conduction voltage to output a high-level or low-level signal to the logic gate. That is, since the source voltage is equal to zero, the first comparator 210 and the second comparator 220 can output a high level or a low level to the logic gate according to whether the first voltage VOUT1 and the second voltage VOUT2 received by them are greater than the conduction voltage. flat signal.

For this, the gate of the first comparator 210 may receive the first voltage VOUT1, the source of the first comparator 210 is grounded, and the drain of the first comparator 210 is connected to a voltage of 3V via a resistor. The gate of the second comparator 220 may receive the second voltage VOUT2, the source of the second comparator 220 is grounded, and the drain of the second comparator 220 is connected to a voltage of 3V through a resistor.

Since the operation principle of the voltage comparison circuit according to the embodiment of the present invention has been described above with reference to FIGS. 1 to 3 , its description is omitted here.

FIG. 5 shows a simplified circuit of a voltage comparison circuit according to a fourth embodiment of the present invention. As shown in FIG. 5 , the voltage comparison circuit according to the embodiment of the present invention may include a first voltage divider 110 , a second voltage divider 120 , a comparison unit 200 and a logic gate 300 .

The comparison unit 200 of FIG. 5 is a comparator including two N-channel transistors.

Since the operation principle of the voltage comparison circuit according to the embodiment of the present invention has been described above with reference to FIGS. 1 and 4 , its description is omitted here.

According to the voltage comparison circuit of the present invention, it can be determined whether the input voltage is within its predetermined voltage range by comparing the input voltage such as the gate-on voltage of the TFT-LCD with a reference voltage. Moreover, since the voltage comparator circuit can be formed by simple electronic components such as resistors, its cost is relatively low.

Although embodiments of the invention have been shown and described with reference to exemplary embodiments thereof to illustrate the principles of the invention, the invention is not limited to the shown and described embodiments. It should be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, it should be understood that such changes, modifications and equivalents are all included within the scope of the present invention.

Claims (12)

1. for determining that input voltage, whether at a voltage comparator circuit for predetermined voltage range, is characterized in that comprising:

By the first partial pressure ratio and the second partial pressure ratio, input voltage execution dividing potential drop is generated the partial pressure unit of the first voltage and second voltage;

Based on the first voltage and reference voltage output first signal and the comparing unit based on second voltage and reference voltage output secondary signal;

Based on first signal and secondary signal output-input voltage whether in the logic gate of the consequential signal of predetermined voltage range.

2. voltage comparator circuit according to claim 1, wherein, comparing unit is constructed to be less than the first voltage and be greater than second voltage time output has first signal and the secondary signal of varying level when reference voltage.

3. voltage comparator circuit according to claim 1, wherein, logic gate is exclusive or logic gate.

4. voltage comparator circuit according to claim 2, wherein, comparing unit is dual comparator chip, and has first output terminal of first signal of comparative result of the reference voltage input end, output the first voltage and the reference voltage that receive the first input end of the first voltage, the second input end that receives second voltage, reception reference voltage and the second output terminal of the secondary signal of the comparative result of output second voltage and reference voltage.

5. voltage comparator circuit according to claim 2, wherein, comparing unit comprises:

The first comparer, is constructed to the first voltage and reference voltage to compare, and output first signal;

The second comparer, is constructed to second voltage and reference voltage to compare, and output secondary signal.

6. voltage comparator circuit according to claim 1, wherein, comparing unit comprises the first transistor and transistor seconds,

Wherein, the first transistor has the drain electrode of the grid of reception the first voltage, the source electrode that is connected to ground and reception predetermined voltage, and transistor seconds has the drain electrode that receives the grid of second voltage, the source electrode that is connected to ground and reception predetermined voltage,

Wherein, the drain electrode that logic gate is connected to the first transistor and transistor seconds is to receive first signal and secondary signal.

7. voltage comparator circuit according to claim 6, wherein, the first transistor and transistor seconds are p channel transistor or N channel transistor simultaneously.

8. voltage comparator circuit according to claim 1, wherein, partial pressure unit comprises:

By the first partial pressure ratio, input voltage execution dividing potential drop is generated the first bleeder circuit of the first voltage;

By the second partial pressure ratio, input voltage execution dividing potential drop is generated the second bleeder circuit of second voltage.

9. voltage comparator circuit according to claim 8, wherein, the first bleeder circuit comprises the first resistor and the second resistor that are connected in series, and the second bleeder circuit comprises the 3rd resistor and the 4th resistor that are connected in series.

10. a voltage comparator circuit for liquid crystal display, is characterized in that this voltage comparator circuit is the voltage comparator circuit as described in any one claim in claim 1-9, in order to the forward voltage of the thin film transistor (TFT) of detection LCD monitor.

11. 1 kinds of liquid crystal display, it is characterized in that, there is the voltage comparator circuit as described in any one claim in claim 1-9, in order to detect it using the forward voltage of the thin film transistor (TFT) of liquid crystal display as input voltage whether within preset range.

12. liquid crystal display according to claim 11, also comprise: the consequential signal based on voltage comparator circuit output and control the controller of the refresh operation of the screen of liquid crystal display.

Images