CN101383129B - Liquid crystal display power switch control method and device - Google Patents

Abstract

The invention relates to a method for controlling a power switch of a liquid crystal display, comprising step 1, detecting an operating voltage; step 2, judging whether the voltage value of the operating voltage is less than a preset threshold voltage value, and if yes, performing step 3, otherwise performing step 1; 3. Cut off the connection between the voltage input terminal and the voltage output terminal, and perform step 1. The present invention also proposes a liquid crystal display power switch device, which includes a switch module connected between the voltage input terminal and the voltage output terminal, and the switch module is connected with a control module that controls the switch module to be turned on or off. The control module is connected to the voltage input terminal and is used for detecting the working voltage output by the voltage input terminal. The invention controls the voltage value of the output voltage by comparing the voltage value of the working voltage with the preset threshold voltage value, thereby automatically turning on and off the power supply of the liquid crystal display, avoiding the cumbersome procedures of manually controlling the power on or off.

Description

Liquid crystal display power switch control method and device

technical field

The invention relates to a power switch control method and its device, in particular to a liquid crystal display power switch control method and its device.

Background technique

The liquid crystal display needs to input a stable rated voltage to output the display screen normally. When the input voltage is unstable, especially when the input voltage is significantly lower than the rated voltage of the LCD, it will seriously affect the output picture quality of the LCD. This phenomenon is usually called "abnormal lighting phenomenon". For example, when the liquid crystal display normally displays the picture, the required input voltage is 5V, but the power supply voltage will drop due to factors such as excessive circuit load or unstable voltage stabilization system. When the input voltage is less than 3.8V, the output picture of the liquid crystal display will The quality is seriously affected, making the user unable to distinguish the currently displayed screen, and "abnormal lighting phenomenon" appears. In this case, the user needs to manually turn off the power to avoid the display outputting bad pictures. The factors are uncertain, and the user cannot judge when the power supply voltage will return to stability. Therefore, after the user turns off the display, he cannot know when the display will resume normal operation, which affects the use of the user to a certain extent.

Contents of the invention

The invention provides a liquid crystal display power switch control method and its device to overcome the technical defect that the liquid crystal display cannot automatically cut off the power when the working voltage is lower than the working voltage in the prior art.

In order to achieve the above object, the present invention provides a liquid crystal display power switch control method, comprising:

Step 1. Detect the working voltage;

Step 2. Determine whether the voltage value of the working voltage is less than the preset threshold voltage value, if so, perform step 3, otherwise, the voltage input terminal and the voltage output terminal are automatically turned on, and perform step 1;

Step 3. Cutting off the connection between the voltage input terminal and the voltage output terminal, and performing step 1; the step 1 specifically includes: detecting the working voltage according to a preset time interval.

In the above technical solution, the voltage value of the output voltage is controlled by comparing the voltage value of the working voltage with the preset threshold voltage value, so as to realize automatic power-off when the working voltage is lower than the preset threshold voltage value, and when the working voltage recovers It is automatically turned on when it is higher than the preset threshold voltage, avoiding the cumbersome procedures of manually controlling the power on or off.

In order to achieve the above object, the present invention also provides a liquid crystal display power switch device, including a switch module connected between the voltage input terminal and the voltage output terminal, and the switch module is connected to the switch module that controls the switch module to be turned on or off. connected to a control module, the control module is connected to the voltage input end, and is used to detect the operating voltage output by the voltage input end; the control module includes a receiving unit for receiving the operating voltage, and the receiving unit A comparison unit connected to compare the voltage value of the operating voltage with a preset threshold voltage value, and a control unit connected to the comparison unit, the control unit is used to output a control signal to the switch module; the control The unit includes a timing subunit for setting a time interval and responding to the trigger signal output by the comparison unit according to the time interval.

In the above technical solution, by comparing and judging the voltage value of the operating voltage input to the liquid crystal display and the preset voltage value, the automatic opening and closing of the liquid crystal display is controlled, avoiding the need for the user to manually open the liquid crystal display when the input voltage is low And the cumbersome procedure of turning off the power supply of the liquid crystal display, when the input voltage returns to high voltage, the liquid crystal display in the off state will automatically display, which is also conducive to reminding the user in time, so that the user can continue to use the liquid crystal display.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Fig. 1 is a schematic flow chart of the implementation of the control method of the present invention;

Fig. 2 is a schematic structural diagram of the first embodiment of the switch device of the present invention;

3 is a schematic structural diagram of a second embodiment of the switch device of the present invention;

Fig. 4 is a schematic structural diagram of a third embodiment of the switch device of the present invention;

Fig. 5 is a schematic structural diagram of a fourth embodiment of the switch device of the present invention;

Fig. 6 is a schematic structural diagram of a fifth embodiment of the switching device of the present invention;

Fig. 7 is a schematic structural diagram of a sixth embodiment of the switch device of the present invention;

FIG. 8 is a schematic timing diagram of a sixth embodiment of the switching device of the present invention.

Detailed ways

Fig. 1 is a schematic diagram of the implementation flow of the control method of the present invention. As shown in Figure 1, the liquid crystal display power switch control method of the present invention comprises:

Step 1, detecting the voltage value of the working voltage;

Step 2, judging whether the voltage value of the working voltage is less than the preset threshold voltage value, if yes, execute step 3, otherwise execute step 1;

Step 3. Cut off the connection between the voltage input terminal and the voltage output terminal, and perform step 1.

Among them, the time interval for detecting the voltage value of the operating voltage in step 1 will have a certain impact on the quality of the display screen, such as: the detection time interval is too short, so that the detection is too frequent and the response time of the liquid crystal display increases to affect the quality of the display screen, the detection time interval If it is too long, it is not conducive to cut off the power supply in time to avoid abnormal lighting phenomenon. Therefore, those skilled in the art can preset a reasonable time interval according to actual needs, and detect the working voltage according to the preset time interval.

Since the working voltage of the normal display screen of the LCD is usually 5V, when the input voltage is 3.8V, but different LCD monitors start to have different starting voltages for displaying poor images, so the threshold voltage can be preset to 3.3V ~3.8V.

In addition, in step 3, the voltage input terminal can be selected to output a reset signal with a voltage value of 0 to the voltage output terminal to cut off the connection between the voltage input terminal and the voltage output terminal. The technician can also choose to cut off the voltage input terminal and the voltage output terminal according to actual conditions. Other means of breaking the connection between the voltage output terminals.

In the above technical solution, the voltage value of the output voltage is controlled by comparing the voltage value of the working voltage with the preset threshold voltage value, so as to realize automatic power-off when the working voltage is lower than the preset threshold voltage value, and when the working voltage recovers It is automatically turned on when it is higher than the preset threshold voltage, avoiding the cumbersome procedures of manually controlling the power on or off.

The invention also provides a liquid crystal display power switch device.

Fig. 2 is a schematic structural diagram of the first embodiment of the switch device of the present invention. As shown in FIG. 2 , the liquid crystal display power switch device includes a switch module 10 connected between the voltage input terminal Vin and the voltage output terminal Vout, and the switch module 10 is connected with a control module 20 that controls the switch module 10 to be turned on or off. The control module 20 is connected to the voltage input terminal Vin for detecting the working voltage output from the voltage input terminal Vin.

Fig. 3 is a schematic structural diagram of the second embodiment of the switch device of the present invention. As shown in FIG. 3 , the control module 20 may include a receiving unit 201 for receiving an operating voltage, a comparing unit 202 connected to the receiving unit 201 for comparing the voltage value of the operating voltage with a preset threshold voltage value, and comparing with The control unit 203 connected to the unit 202 is configured to output control signals to the switch module 10 .

Fig. 4 is a schematic structural diagram of a third embodiment of the switch device of the present invention. As shown in Figure 4, the comparison unit 202 in the control module 20 also includes a setting subunit 2021 for setting the threshold voltage value, and an operation subunit 2022 connected to the setting subunit 2021 and the receiving unit 201 for comparing the operating voltage voltage value and a preset threshold voltage value, and output a trigger signal to the control unit 203 according to the comparison result.

Fig. 5 is a schematic structural diagram of a fourth embodiment of the switching device of the present invention. As shown in Figure 5, the control unit 203 in the control module 20 specifically includes a reset signal subunit 2031, which is used to provide a reset signal with a voltage value of 0 in response to the trigger signal output by the comparison unit, and an output subunit connected to the reset signal subunit 2031 The unit 2032 is configured to output the control signal to the switch module 10 . When the voltage value of the working voltage is greater than or equal to the preset threshold voltage value, the reset signal subunit 2031 responds to the trigger signal and provides a reset signal with a voltage value of 0. When the reset signal subunit 2031 outputs the reset signal, the output subunit 2032 is turned on, and a control signal with an output voltage value of 0 is sent to the switch module 10; when the voltage value of the operating voltage is less than the preset threshold voltage value, the reset signal subunit 2031 responds to the shutdown trigger signal, does not output the reset signal, and the output subunit 2032 A control signal for maintaining the operating voltage constant is provided to the switch module 10 .

Fig. 6 is a schematic structural diagram of a fifth embodiment of the switching device of the present invention. As shown in Figure 6, the control unit 203 in the control module 20 further includes a timing subunit 2033, which is connected with the comparison unit 202 for setting the time interval, and provides the trigger signal output by the comparison unit 202 to reset according to the time interval set. Signal subunit 2031.

Fig. 7 is a schematic structural diagram of a sixth embodiment of the switching device of the present invention. As shown in Figure 7, the switch module includes a voltage divider resistor R, one end of the voltage divider resistor R is connected to the source S1 of the P-channel enhancement type field effect transistor and the connection point of the voltage input terminal Vin, and the voltage divider resistor R is another One end is connected to the connection point of the drain D2 of the N-channel enhanced field effect transistor and the gate G1 of the P-channel enhanced field effect transistor, the source S2 of the N-channel enhanced field effect transistor is grounded, and the N-channel enhanced field effect transistor The gate G2 of the FET is connected to the control module, and the drain D1 of the P-channel enhanced FET is connected to the voltage output terminal Vout.

An example of the working process of the liquid crystal display power switch device is as follows:

Assuming that the working voltage of the normal output picture of the liquid crystal display is 5V, when the working voltage drops to 3.8V, the output picture of the liquid crystal display will display poorly; the preset threshold voltage value Vth is set to 3.8V in the control module; N-channel enhanced type The turn-on voltages V _GS2(th) and V _GS1(th) of the field effect transistor and the P-channel enhancement type field effect transistor are both 2V; the voltage dividing value Vr of the voltage dividing resistor is 1V; the total current of the circuit is about 1A.

FIG. 8 is a schematic timing diagram of a sixth embodiment of the switching device of the present invention. Referring to Figure 7 and Figure 8, A and B are selected as reference points, VA and VB represent the voltage values of points A and B respectively, and one end of the control module is grounded. The control module compares the operating voltage Vin with the preset threshold voltage value Vth, and when the voltage value of the operating voltage Vin=5V is greater than the preset threshold voltage value Vth=3.8V, the control module provides a voltage value that maintains the operating voltage. The control signal is given to the switch module. At this moment, the voltage value VA=Vin(5V) of the reference point A; the gate voltage V _G2 =Vin=5V of the N-channel enhancement type field effect transistor, because the N-channel enhancement type field effect transistor The source S2 is grounded, its source voltage V _S2 =0, the gate-source voltage V _GS2 =V _G1 -V _S1 =5V of the N-channel enhancement type field effect transistor, and the opening of the N-channel enhancement type field effect transistor Voltage V _GS2 (th)=2V, so the N-channel enhancement type field effect transistor is turned on, and the N-channel enhancement type field effect transistor drain voltage V _D2 =0; the voltage value VB of reference point B=0; the P-channel The source of the enhanced field effect transistor is connected to the voltage input terminal Vin, and the source voltage and gate voltage of the P-channel enhanced field effect transistor are respectively V _S1 =Vin=5V, V _G1 =V _D2 =0, so P The gate-source voltage V _GS1 of the channel enhanced field effect transistor = V _G1 -V _S1 = -5V, and the turn-on voltage V _GS1 (th) of the P channel enhanced field effect transistor is -2V, so the P channel enhanced The type field effect transistor is turned on, and the output voltage of the voltage output terminal maintains the working voltage, Vout=Vin;

When the operating voltage decreases, for example, when the operating voltage Vin=3V, the control module compares the input voltage Vin with the preset threshold voltage value Vth, and the operating voltage Vin=3V is less than the preset threshold voltage value Vth=3.8V, and the control module provides The control signal whose output voltage value is 0 is given to the switch module. At _this time, the voltage value VA of the reference point A=0V; The source of the tube is grounded, V _S2 = 0, V _GS2 = V _G2 -V _S2 = 0V, and V _GS1 (th) = 2V, so the N-channel enhancement type field effect transistor is turned off; the voltage value VB of the reference point B = 2V; the source of the P-channel enhanced field effect transistor is connected to the voltage input terminal, V _S1 = Vin = 3V, V _GS2 = -Vr = -1V, and V _GS2 (th) = -2V, so the P-channel enhancement The type field effect tube is turned off, the voltage output terminal output voltage value Vout=0, and the liquid crystal display is automatically turned off;

The control module detects the operating voltage next time, and when the voltage value Vin of the operating voltage is higher than the preset threshold voltage value Vth=3.8V, the liquid crystal display will be automatically turned on again.

In addition, the switch module can also use MOS transistors (such as: P-channel junction field effect transistors and N-channel junction field effect transistors), which specifically include voltage dividing resistors, one end and the source of the P-channel junction field effect transistors. It is connected to the connection point of the voltage input point, and the other end of the voltage dividing resistor is connected to the connection point of the drain of the N-channel JFET and the gate of the P-channel JFET, and the N-channel JFET The source of the tube is grounded, the gate of the N-channel JFET is connected to the control module, and the drain of the P-channel JFET is connected to the voltage output terminal;

When the operating voltage is greater than or equal to 3.8V (the display screen is abnormal below 3.8V), the N-channel junction field effect transistor is turned on; the P-channel junction field effect transistor is turned on, and the output voltage of the voltage output terminal is equal to the operating voltage, and the liquid crystal display Normal display; when the operating voltage is less than 3.8V, the N-channel junction field effect transistor is turned off; the P-channel junction field effect transistor is turned off, the voltage value of the output voltage at the voltage output terminal is equal to 0, and the LCD is automatically turned off.

The switch module can also be a pole-type transistor (such as: NPN transistor and PNP transistor), specifically including a voltage divider resistor, one end of the voltage divider resistor is connected to the emitter of the NPN transistor and the connection point of the voltage input end, and the other end of the voltage divider resistor is connected to the NPN transistor. The base of the PNP transistor is connected to the junction point of the collector of the PNP transistor, the emitter of the PNP transistor is grounded, the base of the PNP transistor is connected to the control module, and the collector of the NPN transistor is connected to the voltage output terminal;

When the working voltage is greater than or equal to 3.8V (the display screen is abnormal below 3.8V), the PNP transistor is turned on; the NPN transistor is turned on, the output voltage of the voltage output terminal is equal to the working voltage, and the LCD displays normally; when the working voltage is less than 3.8V, the PNP The transistor is turned off; the NPN transistor is turned off, the voltage value of the output voltage at the voltage output terminal is equal to 0, and the liquid crystal display is automatically turned off.

The liquid crystal display power switch device of the present invention realizes the automatic opening and closing of the control liquid crystal display by comparing and judging the working voltage input to the liquid crystal display, and avoids the tediousness of manually opening and closing the liquid crystal display power supply when a low voltage is input. Program, when the input voltage returns to a high voltage, the liquid crystal display in the off state will automatically display, which is also conducive to reminding the user in time, so that the user can continue to use the liquid crystal display.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. a power supply switch controlling method for LCD is characterized in that, comprising:

Step 1, testing voltage;

Whether the magnitude of voltage of step 2, judgment task voltage less than default threshold voltage, is execution in step 3 then, otherwise the automatic conducting of voltage input end and voltage output end, and execution in step 1;

Connection between step 3, cut-out voltage input end and the voltage output end, execution in step 1;

Described step 1 is specially: detect described operating voltage according to the default time interval.

2. power supply switch controlling method for LCD according to claim 1, it is characterized in that, described step 3 is specially: is that 0 reset signal is cut off the connection between voltage input end and the voltage output end, execution in step 1 by voltage input end to the voltage output end output voltage values.

3. LCD power switch device of implementing claim 1 or 2 described power supply switch controlling method for LCD, it is characterized in that, comprise the switch module that is connected between voltage input end and the voltage output end, described switch module is connected with the control module of described switch module conducting of control or disconnection, described control module is connected with described voltage input end, is used to detect the operating voltage of described voltage input end output; Described control module comprises the receiving element that is used to receive described operating voltage, the comparing unit of the magnitude of voltage that is used for more described operating voltage that is connected with described receiving element and default threshold voltage, and the control module that is connected with described comparing unit, described control module is used to export control signal and gives switch module;

Described control module comprises regularly subelement; Be used to set interval, and respond the trigger pip of described comparing unit output according to the described time interval.

4. according to the described LCD power switch device of claim 3, it is characterized in that described comparing unit comprises the operator unit that is connected with control module with described receiving element, be used to export trigger pip and give control module; And be connected with described operator unit subelement is set, be used to be provided with threshold voltage.

5. according to the described LCD power switch device of claim 4, it is characterized in that, described control module comprises the reset signal subelement that is connected with described comparing unit, being used to provide magnitude of voltage is 0 reset signal, and the output subelement that is connected with described reset signal subelement, be used to export control signal and give switch module.

6. according to the described LCD power switch device of claim 3, it is characterized in that, described switch module comprises divider resistance, one end of described divider resistance is connected with the tie point of the source electrode of P-channel enhancement type field effect transistor and described voltage input end, the described divider resistance other end is connected with the drain electrode of N channel enhancement field effect transistor and the tie point of the grid of P-channel enhancement type field effect transistor, described N channel enhancement field effect transistor source ground, the grid of described N channel enhancement field effect transistor is connected with described control module, and the drain electrode of described P-channel enhancement type field effect transistor is connected with described voltage output end.

7. according to the described LCD power switch device of claim 3, it is characterized in that, described switch module comprises divider resistance, one end of described divider resistance is connected with the source electrode of P channel junction field-effect pipe and the tie point of described voltage input end, the described divider resistance other end is connected with the drain electrode of N channel junction field-effect pipe and the tie point of the grid of P channel junction field-effect pipe, described N channel junction field-effect pipe source ground, the grid of described N channel junction field-effect pipe is connected with described control device, and the drain electrode of described P channel junction field-effect pipe is connected with described voltage output end.

8. according to the described LCD power switch device of claim 3, it is characterized in that, described switch module comprises divider resistance, described divider resistance one end is connected with the emitter of NPN transistor and the tie point of described voltage input end, the described divider resistance other end is connected with the base stage of NPN transistor and the tie point of the transistorized collector of PNP, described PNP emitter ground connection, the transistorized base stage of described PNP is connected with described control device, and the collector of described NPN transistor is connected with described voltage output end.

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