Summary of the invention
The invention provides a kind of power supply switch controlling method for LCD and device thereof, to overcome the technological deficiency that to cut off the power supply automatically when the LCD operating voltage is lower than operating voltage in the prior art.
To achieve these goals, the invention provides a kind of power supply switch controlling method for LCD, 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.
In the technique scheme, come the magnitude of voltage size of control output voltage by magnitude of voltage that compares operating voltage and the threshold voltage of presetting, thereby realize when operating voltage is lower than default threshold voltage, cutting off the power supply automatically, the complicated procedures of manual control energized or disconnection has been avoided in automatic conducting when operating voltage recovers to be higher than default threshold voltage.
To achieve these goals, the present invention also provides a kind of LCD power switch device, 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.
In technique scheme, by the magnitude of voltage of operating voltage of input LCD and predeterminated voltage value being compared and judging, realized opening and closing automatically of control LCD, avoided when the input low-voltage, the user needs manually opened and closes the complicated procedures of LCD power supply, and when input voltage reverted to high voltage, the LCD that is in closed condition showed automatically, help again in time reminding the user, make things convenient for user's use LCD that continues.
Below by drawings and Examples, technical scheme of the present invention is described in further detail.
Embodiment
Fig. 1 is a control method implementing procedure synoptic diagram of the present invention.As shown in Figure 1, power supply switch controlling method for LCD of the present invention comprises:
The magnitude of voltage of 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 execution in step 1;
Connection between step 3, cut-out voltage input end and the voltage output end, execution in step 1.
Wherein, the time interval of the magnitude of voltage of testing voltage can produce certain influence to the display frame quality in the step 1, as: detection time is too short at interval, feasible detection is too frequent and the LCD response time increases and influence the display frame quality, detection time is long at interval, be unfavorable for again in time cutting off the electricity supply to avoid occurring lighting a lamp unusually phenomenon, therefore, those skilled in the art can preset a rational time interval according to actual needs, and according to default time interval testing voltage.
Because the operating voltage of the normal display frame of LCD is generally 5V, when input voltage is 3.8V, but different LCD begins to occur the starting potential difference of the bad phenomenon of display frame, therefore, threshold voltage can be preset as 3.3V~3.8V.
In addition, in the step 3, can select voltage input end is that 0 reset signal is cut off the connection between voltage input end and the voltage output end to the voltage output end output voltage values, and the technician also can select to cut off other cut-out modes that connect between voltage input end and the voltage output end according to actual conditions.
In the technique scheme, come the magnitude of voltage size of control output voltage by magnitude of voltage that compares operating voltage and the threshold voltage of presetting, thereby realize when operating voltage is lower than default threshold voltage, cutting off the power supply automatically, the complicated procedures of manual control energized or disconnection has been avoided in automatic conducting when operating voltage recovers to be higher than default threshold voltage.
The present invention also provides a kind of LCD power switch device.
Fig. 2 is the structural representation of switchgear first embodiment of the present invention.As shown in Figure 2, the LCD power switch device comprises the switch module 10 that is connected between voltage input end Vin and the voltage output end Vout, switch module 10 is connected with the control module 20 of these switch module 10 conductings of control or disconnection, control module 20 is connected with voltage input end Vin, is used to detect the operating voltage of voltage input end Vin output.
Fig. 3 is the structural representation of switchgear second embodiment of the present invention.As shown in Figure 3, control module 20 can comprise the receiving element 201 that is used to receive operating voltage, the comparing unit 202 of the magnitude of voltage that is used for the comparison operating voltage that is connected with receiving element 201 and default threshold voltage, and the control module 203 that is connected with comparing unit 202, be used to export control signal and give switch module 10.
Fig. 4 is the structural representation of switchgear the 3rd embodiment of the present invention.As shown in Figure 4, comparing unit 202 also comprises subelement 2021 is set in the control module 20, be used to be provided with threshold voltage, and with the operator unit 2022 that subelement 2021 is connected with receiving element 201 is set, be used for the magnitude of voltage and default threshold voltage of comparison operating voltage, and export trigger pip according to comparative result and give control module 203.
Fig. 5 is the structural representation of switchgear the 4th embodiment of the present invention.As shown in Figure 5, control module 203 specifically comprises reset signal subelement 2031 in the control module 20, it is 0 reset signal that the trigger pip that is used to respond comparing unit output provides magnitude of voltage, and the output subelement 2032 that is connected with reset signal subelement 2031, be used to export control signal and give switch module 10.When the magnitude of voltage of operating voltage during more than or equal to default threshold voltage, trigger pip is opened in 2031 responses of reset signal subelement, it is 0 reset signal that magnitude of voltage is provided, when reset signal subelement 2031 output reset signals, output subelement 2032 is opened, and output voltage values is that 0 control signal is given switch module 10; When the magnitude of voltage of operating voltage during less than default threshold voltage, trigger pip is closed in 2031 responses of reset signal subelement, does not export reset signal, and output subelement 2032 provides keeps the constant control signal of operating voltage magnitude of voltage to switch module 10.
Fig. 6 is the structural representation of switchgear the 5th embodiment of the present invention.As shown in Figure 6, control module 203 also further comprises regularly subelement 2033 in the control module 20, be connected with comparing unit 202, be used to set interval, and the trigger pip of comparing unit 202 being exported according to the time interval that is provided with offers reset signal subelement 2031.
Fig. 7 is the structural representation of switchgear the 6th embodiment of the present invention.As shown in Figure 7, switch module comprises a divider resistance R, the end of this divider resistance R is connected with the tie point of the source S 1 of P-channel enhancement type field effect transistor and voltage input end Vin, the tie point of the drain D 2 of the divider resistance R other end and N channel enhancement field effect transistor and the grid G 1 of P-channel enhancement type field effect transistor is connected, N channel enhancement field effect transistor source S 2 ground connection, the grid G 2 of N channel enhancement field effect transistor is connected with control module, and the drain D 1 of P-channel enhancement type field effect transistor is connected with voltage output end Vout.
The course of work of LCD power switch device is exemplified below:
Suppose that it is 5V that LCD is normally exported the operating voltage of picture, when operating voltage dropped to 3.8V, the output picture of LCD can show bad; It is 3.8V that default threshold voltage Vth is set in the control module; The cut-in voltage V of N channel enhancement field effect transistor and P-channel enhancement type field effect transistor
GS2 (th)And V
GS1 (th)Size is 2V; Divider resistance partial pressure value Vr is 1V; The circuit total current is about 1A.
Fig. 8 is the sequential synoptic diagram of switchgear the 6th embodiment of the present invention.With reference to Fig. 7 and Fig. 8, choose A and B as the reference point, VA and VB represent the magnitude of voltage that A point and B are ordered respectively, control module one end ground connection.Control module compares operating voltage Vin and the threshold voltage Vth that presets, when the magnitude of voltage Vin=5V of operating voltage greater than default threshold voltage Vth=3.8V, control module provides the constant control signal of the magnitude of voltage of keeping operating voltage to switch module, at this moment, the magnitude of voltage VA=Vin (5V) of reference point A; The grid voltage V of N channel enhancement field effect transistor
G2=Vin=5V, since source S 2 ground connection of N channel enhancement field effect transistor, its source voltage V
S2=0, the gate-source voltage V of N channel enhancement field effect transistor
GS2=V
G1-V
S1=5V, and the cut-in voltage V of N channel enhancement field effect transistor
GS2(th)=and 2V, thus the unlatching of N channel enhancement field effect transistor, and N channel enhancement field effect transistor drain voltage V
D2=0; The magnitude of voltage VB=0 of reference point B; The source electrode of P-channel enhancement type field effect transistor is connected with voltage input end Vin, and the source voltage and the grid voltage of P-channel enhancement type field effect transistor are respectively V
S1=Vin=5V, V
G1=V
D2=0, so the gate source voltage V of P-channel enhancement type field effect transistor
GS1=V
G1-V
S1=-5V, and the cut-in voltage V of P-channel enhancement type field effect transistor
GS1(th) be-2V that so the P-channel enhancement type field effect transistor is opened, it is constant that the voltage output end output voltage is kept operating voltage, Vout=Vin;
When operating voltage reduces, for example during operating voltage Vin=3V, control module compares input voltage vin with the threshold voltage Vth that presets, operating voltage Vin=3V is less than default threshold voltage Vth=3.8V, it is that 0 control signal is to switch module that control module provides output voltage values, at this moment, the magnitude of voltage VA=0V of reference point A; The grid voltage V of N channel enhancement field effect transistor
G2=0, since the source ground of N channel enhancement field effect transistor, V
S2=0, V
GS2=V
G2-V
S2=0V, and V
GS1(th)=2V, so N channel enhancement field effect transistor is closed; The magnitude of voltage VB=2V of reference point B; The source electrode of P-channel enhancement type field effect transistor is connected with voltage input end, V
S1=Vin=3V, V
GS2=-Vr=-1V, and V
GS2(th)=-2V, so the P-channel enhancement type field effect transistor is closed, voltage output end output voltage values Vout=0 closes LCD automatically;
Control module detects operating voltage next time, and when the magnitude of voltage Vin of operating voltage was higher than default threshold voltage Vth=3.8V, LCD can be opened again automatically.
In addition, switch module can also be selected metal-oxide-semiconductor (as: P channel junction field-effect pipe and N channel junction field-effect pipe) for use, specifically comprise divider resistance, one end is connected with the source electrode of P channel junction field-effect pipe and the tie point of voltage input point, the 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, N channel junction field-effect pipe source ground, the grid of N channel junction field-effect pipe is connected with control module, and the drain electrode of P channel junction field-effect pipe is connected with described voltage output end;
When operating voltage during more than or equal to 3.8V (the following display frame of 3.8V occurs unusual), N channel junction field-effect pipe is opened; P channel junction field-effect pipe is opened, and the voltage output end output voltage equals operating voltage, and LCD normally shows; When operating voltage during less than 3.8V, N channel junction field-effect pipe is closed; P channel junction field-effect pipe is closed, and the magnitude of voltage of voltage output end output voltage equals 0, and LCD is closed automatically.
The all right bipolar transistor (as: NPN transistor and PNP transistor) of switch module, specifically comprise divider resistance, divider resistance one end is connected with the emitter of NPN transistor and the tie point of voltage input end, the other end of divider resistance is connected with the tie point of the base stage of NPN transistor with the transistorized collector of PNP, PNP emitter ground connection, the transistorized base stage of PNP is connected with control module, and the collector of NPN transistor is connected with voltage output end;
When operating voltage during more than or equal to 3.8V (the following display frame of 3.8V occurs unusual), the PNP transistor is opened; NPN transistor is opened, and the voltage output end output voltage equals operating voltage, and LCD normally shows; When operating voltage during less than 3.8V, the PNP transistor is closed; NPN transistor is closed, and the magnitude of voltage of voltage output end output voltage equals 0, and LCD is closed automatically.
LCD power switch device of the present invention passes through comparison and the judgement to the operating voltage of input LCD, realized opening and closing automatically of control LCD, avoided when the input low-voltage, the user needs manually opened and closes the complicated procedures of LCD power supply, when input voltage reverts to high voltage, the LCD that is in closed condition shows automatically, helps in time reminding the user again, makes things convenient for user's use LCD that continues.
It should be noted that at last: above embodiment only in order to technical scheme of the present invention to be described, is not intended to limit; Although with reference to previous embodiment the present invention is had been described in detail, those of ordinary skill in the art is to be understood that: it still can be made amendment to the technical scheme that previous embodiment is put down in writing, and perhaps part technical characterictic wherein is equal to replacement; And these modifications or replacement do not make the essence of appropriate technical solution break away from the spirit and scope of embodiment of the invention technical scheme.