CN101107887A - Backlight control apparatus and display apparatus - Google Patents
Backlight control apparatus and display apparatus Download PDFInfo
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- CN101107887A CN101107887A CNA200680002922XA CN200680002922A CN101107887A CN 101107887 A CN101107887 A CN 101107887A CN A200680002922X A CNA200680002922X A CN A200680002922XA CN 200680002922 A CN200680002922 A CN 200680002922A CN 101107887 A CN101107887 A CN 101107887A
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Abstract
A PWM generating circuit is adapted to generate a PWM pulse signal the frequency of which is an odd multiple of the vertical synchronizing frequency. A frequency divider circuit frequency divides the PWM pulse signal generated by the PWM generating circuit. An AND gate provides a logical product related to the PWM pulse signal generated by the PWM generating circuit and to the frequency division pulse signal outputted from the frequency divider circuit. An OR gate provides a logical sum related to the PWM pulse signal generated by the PWM generating circuit and to the frequency division pulse signal outputted from the frequency divider circuit. A selector outputs, as a light modulation pulse signal, the output signal of the OR gate when an established duty ratio is equal to or greater than 50 percents, while it outputs, as a light modulation pulse signal, the output signal of the AND gate when the established duty ratio is smaller than 50 percents. In this way, the frequency of the light modulation pulse signal is 5/2 times the frequency of the vertical synchronizing signal.
Description
Technical field
The present invention relates to control back-lighting brightness backlight control apparatus and have the display unit of this device.
Background technology
LCD TV or liquid crystal indicator use in the video equipment of liquid crystal like that, the back-lighting that the general using cold-cathode tube is formed luminous, display image.Inverter is used to produce control and drives the drive signal that back-lighting is used.
In order to control back-lighting brightness, curtage dimming mode and PWM light modulation (pulse train light modulation) mode is generally arranged, the former makes the input direct voltage or the input dc power rheologyization of inverter, thereby the electric current of cold-cathode tube circulation is changed, luminous on The latter PWM (pulse-width modulation) the control frequency of oscillation and stop luminous.
The curtage dimming mode has the little and stable advantage of noise (heard sound) that inverter produces, but has the little shortcoming of dimming scope.
On the other hand, the PWM dimming mode has the big advantage of dimming scope, and function of carrying out the back-lighting adjustment with the user etc. is used.
The vertical synchronizing frequency of the pwm pulse signal of driving inverter and the vision signal of input is generally asynchronous.Yet, when pwm pulse signal and vertical synchronizing frequency are asynchronous, produce interference stripes appear in noise on phenomenon movable on the picture or picture phenomenon.
Therefore, propose to make pwm pulse signal and the synchronous scheme (for example referring to Patent Document 1) of vertical synchronizing frequency.
Yet, when the frequency setting of pwm pulse signal is the integral multiple of vertical synchronizing frequency,, produce flicker (referring to Patent Document 2) because the time of liquid crystal light transmission changes.In order to prevent to produce flicker, in the liquid crystal indicator that has the back-lighting controlled function of patent documentation 2, (n for more than or equal to 2 integer) makes the PWM light modulation drive circuit of fluorescent lamp flash of light m time (m is greater than n and be the integer of the multiple of non-n) during being arranged on the n picture and showing.
Patent documentation 1: the spy opens flat 11-126696 communique
Patent documentation 2: the spy opens flat 7-325286 communique
Recently, LCD TV and liquid crystal indicator have in the display unit of LCD panel like that, and video signal processing system is made of LSI (large scale integrated circuit).Be implemented in the system of the required scanning of LCD panel display image, contour correction, gamma correction etc. with 1 LSI.
This LSI is in order to bring into play the advantage on the cost, built-in various peripheral circuits, the PWM generation circuit of the pwm pulse signal of also built-in generation driving inverter.
In order to prevent LCD panel flicker, the frequency setting that hope will drive the pwm pulse signal of inverter is odd number/2 times of vertical synchronizing frequency.
Yet the PWM generation circuit that is made of LSI can only be the integral multiple of vertical synchronizing frequency with the frequency setting of pwm pulse signal.
On the other hand, in the liquid crystal indicator that has the back-lighting controlled function of patent documentation 2 records, can utilize PWM light modulation drive circuit portion to make the frequency flash of light of fluorescent tube with m/n.
Yet, the circuit structure complexity of PWM light modulation drive circuit portion, and can not utilize the existing PWM that constitutes by LSI that circuit takes place.Therefore, component costs and manufacturing cost height.
And the transition period of circuit when switching the pwm pulse signal duty ratio takes place in existing PWM, and the pwm pulse signal duty ratio is touched, and pwm pulse signal produces instantaneous short period pulse sometimes.Thereby the brightness variation that back-lighting takes place is discontinuous, or picture either overt or covert phenomenon of moment takes place.
The object of the present invention is to provide a kind ofly can prevent flicker again, again can miniaturization and the backlight control apparatus of cost degradation and have the display unit of this device.
Another object of the present invention is to provide a kind of and can prevent flicker, the discontinuous variation of brightness again and moment brightness changes, again can miniaturization and the backlight control apparatus of cost degradation.
Summary of the invention
(1) in order to solve above-mentioned problem, defer to the backlight control apparatus of one aspect of the invention, the brightness of control back-lighting wherein has: the light modulation pulse signal that control brightness is used responds, and drives the inverter of described back-lighting; The instruction unit of the duty ratio of indication light modulation pulse signal; According to the duty ratio and the vertical synchronizing signal of instruction unit indication, produce the frequency of odd-multiple and be subjected to the pulse generator of the 1st pulse signal of pulse-width modulation with vertical synchronizing frequency; The 1st pulse signal that the paired pulses generator produces carries out frequency division, and exports the frequency divider of the 2nd pulse signal of 1/2nd frequencies with the 1st pulse signal; Carry out the 1st logic element of the 1st logical operation of the 1st pulse signal of relevant pulse generator generation and the 2nd pulse signal that frequency divider is exported; Carry out the 2nd logic element of the 2nd logical operation of the 1st pulse signal of relevant pulse generator generation and the 2nd pulse signal that frequency divider is exported; And selector, this selector is in the duty ratio of instruction unit indication during more than or equal to setting, the output signal of selecting the 1st logic element is as the 3rd pulse signal, in the duty ratio of instruction unit indication during less than setting, the output signal of selecting the 2nd logic element is as the 3rd pulse signal, and the 3rd pulse signal of frequency of odd number/2 times that has vertical synchronizing frequency by such output is as the light modulation pulse signal.
In this backlight control apparatus, during the duty ratio of instruction unit indication light modulation pulse signal, pulse generator produces the 1st pulse signal according to the duty ratio and the vertical synchronizing signal of indication.This 1st pulse signal has the frequency of the odd-multiple of vertical synchronizing frequency, and is subjected to pulse-width modulation.By frequency divider with the 1st pulse signal frequency division after, export the 2nd pulse signal from frequency divider.This 2nd pulse signal has 1/2nd frequency of the 1st pulse signal.
The 1st logic element carries out the 1st logical operation about the 1st pulse signal and the 2nd pulse signal.The 2nd logic element carries out the 2nd logical operation about the 1st pulse signal and the 2nd pulse signal.
The duty ratio of instruction unit indication is during more than or equal to setting, and selector selects the output signal of the 1st logic element as the 3rd pulse signal; The duty ratio of instruction unit indication is during less than setting, and selector selects the output signal of the 2nd logic element as the 3rd pulse signal.Thus, output has the 3rd pulse signal of frequency of odd number/2 times of vertical synchronizing frequency as the light modulation pulse signal.Inverter is exchanged light pulse signal and is responded, and drives back-lighting.
Like this, provide the light modulation pulse signal of the frequency of odd number/2 times, so prevent to use the picture of the display unit of backlight control apparatus to produce flicker with vertical synchronizing frequency to inverter.
At this moment, backlight control apparatus also comprises frequency divider, the 1st and the 2nd logic element and selector except that comprising inverter, pulse generator and instruction unit.Therefore, can utilize the output of simple structure to have the light modulation pulse signal of frequency of odd number/2 times of vertical synchronizing frequency.Its result, backlight control apparatus can miniaturization and cost degradation.
(2) setting can be 50%.In the case, the duty ratio of instruction unit indication was more than or equal to 50% o'clock, and selector selects the output signal of the 1st logic element as the 3rd pulse signal; The duty ratio of instruction unit indication is during less than setting, and selector selects the output signal of the 2nd logic element as the 3rd pulse signal.Thus, inverter output had the 3rd pulse signal of frequency of odd number/2 times of vertical synchronizing frequency as the light modulation pulse signal.
(3) can make pulse generator at the duty ratio D of instruction unit indication more than or equal to 50% o'clock, the duty ratio of the 1st pulse signal is set at 2 (D-50) %, less than 50% o'clock, the duty ratio of the 1st pulse signal is set at 2D% at the duty ratio D of instruction unit indication.
Thus, the duty ratio D of instruction unit indication is more than or equal to 50% o'clock, to inverter output have vertical synchronizing frequency odd number/2 times frequency and also have light modulation pulse signal more than or equal to 50% duty ratio of appointment.Again, the duty ratio D of instruction unit indication is less than 50% o'clock, to inverter output have vertical synchronizing frequency odd number/2 times frequency and also have light modulation pulse signal less than 50% duty ratio of appointment.
(4) selector is being used when switching the duty ratio of instruction unit indication more than or equal to the value of setting with less than the value of setting, the pulse signal of duty ratio that has regulation during output is certain is as the light modulation pulse signal.
In the case, using when switching the duty ratio of instruction unit indication the light modulation pulse signal that output has the regulation duty ratio to inverter more than or equal to the value of setting with less than the value of setting.Thus, when above-mentioned switching duty cycle, the light modulation pulse signal is stably changed.Like this, the duty ratio that can prevent the light modulation pulse signal is touched.Therefore, can prevent that the brightness that produces back-lighting from changing discontinuous and generation brightness either overt or covert phenomenon of moment.
(5) selector is being used when switching the duty ratio of described instruction unit indication more than or equal to the value of setting with less than the value of setting, the 2nd pulse signal of frequency divider output was as the light modulation pulse signal during output was certain.
In the case, using when switching the duty ratio of described instruction unit indication the light modulation pulse signal that output has 50% duty ratio to inverter more than or equal to the value of setting with less than the value of setting.Thus, when above-mentioned switching duty cycle, the light modulation pulse signal is stably changed.Like this, the duty ratio that can prevent the light modulation pulse signal is touched.Therefore, can prevent that the brightness that produces back-lighting from changing discontinuous and generation brightness either overt or covert phenomenon of moment.
(6) pulse expansion that can also have the 1st pulse signal that pulse generator is produced arrives certain width, and exports the pulse stretcher of the 4th pulse signal of the pulse with expansion, and the 4th pulse signal of frequency divider paired pulses expander output carries out frequency division.
In the case, with the pulse expansion of the 1st pulse signal, the 4th pulse signal with the pulse after the expansion is carried out frequency division.Thus, when preventing the change in duty cycle of instruction unit indication, produce the unsuitable cycle in the light modulation pulse signal.Therefore, can prevent that the brightness that produces back-lighting from changing discontinuous and generation brightness either overt or covert phenomenon of moment.
(7) pulse stretcher can comprise one-shot multivibrator.In the case, the 1st pulse signal is responded, output has the 4th pulse signal of pulse with the certain width after its expansion, and the 4th pulse signal of pulse with expansion is carried out frequency division.Thus, when preventing the change in duty cycle of instruction unit indication, produce the unsuitable cycle in the light modulation pulse signal.Therefore, can prevent that the brightness that produces back-lighting from changing discontinuous and generation brightness either overt or covert phenomenon of moment with simple structure.
(8) can make the 1st logical operation be logic and, the 2nd logical operation is a logic product.
In the case, the 1st logic element calculate about the logic of the 1st pulse signal and the 2nd pulse signal and.The 2nd logic element is calculated the logic product about the 1st pulse signal and the 2nd pulse signal.Thus, selector output has the 3rd pulse signal of frequency of odd number/2 times of vertical synchronizing frequency as the light modulation pulse signal.
(9) can make the 1st logic element comprise OR-gate, the 2nd logical operation comprises AND gate.
In the case, OR-gate calculate about the logic of the 1st pulse signal and the 2nd pulse signal and.AND gate is calculated the logic product about the 1st pulse signal and the 2nd pulse signal.Thus, selector output has the 3rd pulse signal of frequency of odd number/2 times of vertical synchronizing frequency as the light modulation pulse signal.
(10) defer to the present invention's display unit on the other hand, have: the video signal conversion of input is become the form of regulation and tell the signal processing circuit of vertical synchronizing signal simultaneously; To be shown as the display panel of image from the vision signal that signal processing circuit obtains; Be arranged on the back-lighting of displaying plate face; And the backlight control apparatus of the brightness of control back-lighting, wherein backlight control apparatus comprises the inverter that the light modulation pulse signal that control brightness is used responds and drives back-lighting; The instruction unit of the duty ratio of indication light modulation pulse signal; According to the duty ratio and the vertical synchronizing signal of instruction unit indication, produce the frequency of odd-multiple and be subjected to the pulse generator of the 1st pulse signal of pulse-width modulation with vertical synchronizing frequency; The 1st pulse signal that the paired pulses generator produces carries out frequency division, and exports the frequency divider of the 2nd pulse signal of 1/2nd frequencies with the 1st pulse signal; Carry out the 1st logic element of the 1st logical operation of the 1st pulse signal of relevant pulse generator generation and the 2nd pulse signal that frequency divider is exported; Carry out the 2nd logic element of the 2nd logical operation of the 1st pulse signal of relevant pulse generator generation and the 2nd pulse signal that frequency divider is exported; And selector, this selector is in the duty ratio of instruction unit indication during more than or equal to setting, the output signal of selecting the 1st logic element is as the 3rd pulse signal, in the duty ratio of instruction unit indication during less than setting, the output signal of selecting the 2nd logic element is as the 3rd pulse signal, and the 3rd pulse signal of frequency of odd number/2 times that has vertical synchronizing frequency by such output is as the light modulation pulse signal.
In this display unit, will be changed to prescribed form and tell vertical synchronizing signal simultaneously by the vision signal of signal processing circuit input.One side by back-lighting from the back side to the display panel irradiates light, one side shows image based on vision signal by display panel.Adjust the brightness of back-lighting by backlight control apparatus.
In this backlight control apparatus, during the duty ratio of instruction unit indication light modulation pulse signal, pulse generator produces the 1st pulse signal according to the duty ratio and the vertical synchronizing signal of indication.This 1st pulse signal has the frequency of the odd-multiple of vertical synchronizing frequency, and is subjected to pulse-width modulation.By frequency divider with the 1st pulse signal frequency division after, export the 2nd pulse signal from frequency divider.This 2nd pulse signal has 1/2nd frequency of the 1st pulse signal.
The 1st logic element carries out the 1st logical operation about the 1st pulse signal and the 2nd pulse signal.The 2nd logic element carries out the 2nd logical operation about the 1st pulse signal and the 2nd pulse signal.
The duty ratio of instruction unit indication is during more than or equal to setting, and selector selects the output signal of the 1st logic element as the 3rd pulse signal; The duty ratio of instruction unit indication is during less than setting, and selector selects the output signal of the 2nd logic element as the 3rd pulse signal.Thus, output has the 3rd pulse signal of frequency of odd number/2 times of vertical synchronizing frequency as the light modulation pulse signal.Inverter is exchanged light pulse signal and is responded, and drives back-lighting.
Like this, owing to provide the light modulation pulse signal of the frequency of odd number/2 times, therefore prevent to use the picture of the display unit of backlight control apparatus to produce flicker with vertical synchronizing frequency to inverter.
At this moment, backlight control apparatus also comprises frequency divider, the 1st and the 2nd logic element and selector except that comprising inverter, pulse generator and instruction unit.Therefore, can utilize the output of simple structure to have the light modulation pulse signal of frequency of odd number/2 times of vertical synchronizing frequency.Its result, backlight control apparatus can miniaturization and cost degradation.
(11) can constitute signal processing circuit and described pulse generator by large scale integrated circuit.Thus, can make signal processing circuit and pulse generator miniaturization.In the case, the light modulation pulse signal of the frequency by adding frequency divider, the 1st and the 2nd logic element and selector at large scale integrated circuit and inverter, can export odd number/2 times with vertical synchronizing frequency.Its result, backlight control apparatus can miniaturization and cost degradation.
(12) display panel can comprise LCD panel.In the case, one side by back-lighting from the back side to the display panel irradiates light, one side shows image based on vision signal by display panel.Adjust the brightness of back-lighting by backlight control apparatus.
According to the present invention, owing to provide the light modulation pulse signal of the frequency of odd number/2 times, therefore prevent to use the picture of the display unit of backlight control apparatus to produce flicker with vertical synchronizing frequency to inverter.
At this moment, backlight control apparatus also comprises frequency divider, the 1st and the 2nd logic element and selector except that comprising inverter, pulse generator and instruction unit.Therefore, can utilize the output of simple structure to have the light modulation pulse signal of frequency of odd number/2 times of vertical synchronizing frequency.Its result, backlight control apparatus can miniaturization and cost degradation.
Description of drawings
Fig. 1 is the block diagram of composition that the display unit of the back-light device with embodiment of the present invention 1 is shown.
Fig. 2 is the sequential chart of the signal of each one in the backlight control apparatus of Fig. 1.
Fig. 3 is the block diagram of composition that the display unit of the back-light device with embodiment of the present invention 2 is shown.
Fig. 4 is the sequential chart that the work usefulness of the backlight control apparatus when setting duty ratio is switched in explanation.
Fig. 5 is the block diagram of composition that the display unit of the back-light device with embodiment of the present invention 3 is shown.
Fig. 6 is the sequential chart that the work usefulness of the backlight control apparatus when setting duty ratio is switched in explanation.
Embodiment
(1) execution mode 1
(1-1) composition of backlight control apparatus
Fig. 1 is the block diagram of composition that the display unit of the back-light device with embodiment of the present invention 1 is shown.
Among Fig. 1, display unit has: control device 10, interpolation circuit 20, inverter circuit 30, MPU (microprocessor unit) 40, liquid crystal board module 50 and remote controller 60.Control device 10, interpolation circuit 20, inverter circuit 30, MPU (microprocessor unit) 40 and remote controller 60 constitute backlight control apparatus.
Add circuit 20 and comprise frequency dividing circuit 21, AND gate 22, OR-gate 23 and selector 24.Liquid crystal board module 50 comprises LCD panel 51 and back-lighting 52.Back-lighting 52 is made up of for example cold-cathode tube, and it is configured in the back side of LCD panel 51.
To signal processing circuit 11 incoming video signal VD.Signal processing circuit 11 is transformed into the rgb signal CS that is fit to LCD panel 51 with vision signal VD, also tells vertical synchronizing signal VS and horizontal-drive signal (not shown) from vision signal VD simultaneously.To supply with LCD panel 51 by the rgb signal CS that signal processing circuit 11 obtains.Thus, according to rgb signal CS, display image on LCD panel 51.
The vertical synchronizing signal VS that utilizes signal processing circuit 11 to tell is supplied with PWM circuit 12 takes place.Circuit 12 takes place and produces and synchronous PWM (pulse-width modulation) the pulse signal P1 of vertical synchronizing signal VS in PWM.The pwm pulse signal P1 that circuit 12 can produce the integral multiple with vertical synchronizing frequency (vertical scanning frequency) takes place in this PWM.
In the present embodiment, the pwm pulse signal P1 that circuit 12 is set the frequency that produces the odd-multiple with vertical synchronizing frequency for is taken place in PWM.
The pwm pulse signal P1 that circuit 12 generations take place 21 couples of PWM of frequency dividing circuit carries out frequency division, and output frequency division pulse signal P2.The frequency of divided pulse signal P2 be pwm pulse signal P1 frequency 1/2nd.
AND gate 22 is calculated the logic product that the pwm pulse signal P1 and the divided pulse signal P2 that frequency dividing circuit 21 is exported of circuit 12 generations take place relevant PWM.OR-gate 23 calculate relevant PWM take place pwm pulse signal P1 that circuit 12 produces and frequency dividing circuit 21 outputs divided pulse signal P2 logic and.
24 couples of duty cycle control signal DC of selector respond, and export the output signal of AND gate 22 or the output signal of OR-gate 23 selectively, as pwm pulse signal P3.Pwm pulse signal P3 is supplied with inverter circuit 30, as the light modulation pulse signal.
The pwm pulse signal P3 that inverter circuit 30 is supplied with according to selector 24 supplies with back-lighting 52 with drive signal DR.Thus, drive back-lighting 52.Adjust the brightness of back-lighting 52 by the duty ratio of control pwm pulse signal P3.
Here, set the duty ratio of supplying with the pwm pulse signal P3 of inverter circuit 30 as the light modulation pulse signal according to vision signal VD or from the instruction of remote controller 60.Below, the duty ratio of the pwm pulse signal P3 that will set according to vision signal VD or from the instruction of remote controller 60 is called the setting duty ratio.
(1-2) work of backlight control apparatus
Below, with reference to the concrete work of the backlight control apparatus of Fig. 2 key diagram 1.Fig. 2 is the sequential chart of the signal of each one in the backlight control apparatus of Fig. 1.
Fig. 2 (a) illustrates and sets duty ratio more than or equal to 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3.Fig. 2 (b) illustrates and sets duty ratio less than 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3.The transverse axis of Fig. 2 is the time.
Vision signal VD is made up of for example composite video signal, or is made up of luminance signal and color difference signal.As indicated above, vision signal VD is transformed into the rgb signal CS that is fit to LCD panel 51 by signal processing circuit 11.At this moment, 11 couples of vision signal VD of signal processing circuit carry out for example scan process.In the scan process, the pixel count of the viewing area of vision signal VD is transformed into the exploring degree that is fit to LCD panel 51.And, vision signal VD is carried out contour correction, gamma correction, white balanced adjust etc., so that the characteristic by correcting liquid crystal display panel 51, the picture quality of vision signal VD is transformed into meets user preferences.
By PWM circuit 12 taking place synchronously produces pwm pulse signal P1 with vertical synchronizing signal VS.At this moment, the frequency setting that PWM is taken place the pwm pulse signal P1 that circuit 12 produces is the frequency of the multiple of desired frequency.For example in order to obtain 5/2 times pwm pulse signal P3 of vertical synchronizing frequency, the frequency setting that the pwm pulse signal P1 that circuit 12 produces taken place PWM is 5 times of vertical synchronizing frequency.In the example of Fig. 2, the frequency of pwm pulse signal P1 is 5 times of frequency of vertical synchronizing signal VS.
Utilize duty ratio specification signal DI, control the duty ratio of pwm pulse signal P1 according to setting duty ratio with the method for setting forth later.In the example of Fig. 2, the duty ratio of pwm pulse signal P1 is 50%.
Pwm pulse signal P1 is by frequency dividing circuit 21 frequency divisions.As shown in Figure 2, the frequency of divided pulse signal P2 be pwm pulse signal P1 frequency 1/2.
AND gate 22 is calculated the logic product of pwm pulse signal P1 and divided pulse signal P2.OR-gate 23 calculate pwm pulse signal P1 and divided pulse signal P2 logic and.
Set duty ratio more than or equal to 50% o'clock, shown in Fig. 2 (a), the output signal of selector 24 output OR-gates 23 is as pwm pulse signal P3.Thus, making the frequency of pwm pulse signal P3 is 5/2 times of vertical synchronizing signal VS.
At this moment, the duty ratio of pwm pulse signal P3 is set at by deducting 2 times of 50% value that obtains from setting duty ratio.In the example of Fig. 2 (a), setting duty ratio is 75%.Therefore, pwm pulse signal P1 is set at 50%.Thus, the duty ratio of pwm pulse signal P3 is 75%.
Set duty ratio less than 50% o'clock, shown in Fig. 2 (b), the output signal of selector 24 output AND gates 22 is as pwm pulse signal P3.Thus, making the frequency of pwm pulse signal P3 is 5/2 times of vertical synchronizing signal VS.
At this moment, the duty ratio with pwm pulse signal P3 is set at 2 times that set duty ratio.In the example of Fig. 2 (b), setting duty ratio is 25%.Therefore, pwm pulse signal P1 is set at 50%.Thus, the duty ratio of pwm pulse signal P3 is 25%.
(1-3) effect of execution mode 1
In the present embodiment, by setting duty ratio more than or equal to the output signal of selecting OR-gate 23 at 50% o'clock, set duty ratio less than the output signal of selecting AND gate 22 at 50% o'clock, can have the pwm pulse signal P3 of frequency of odd number/2 times of vertical synchronizing signal VS inverter circuit 30 outputs.Thus, the picture that prevents LCD panel 51 glimmers.
In the case, adding circuit 20 by newly establishing, only is the pwm pulse signal P3 that the control device 10 of pwm pulse signal P1 of integral multiple of vertical synchronizing frequency can produce the frequency of odd number/2 times with vertical synchronizing frequency with producing.As a result, backlight control apparatus can miniaturization and cost degradation, can also make the display unit thinning simultaneously, gently change and cost degradation.
(2) execution mode 2
(2-1) composition of backlight control apparatus
Fig. 3 is the block diagram of composition that the display unit of the backlight control apparatus with embodiment of the present invention 2 is shown.
The difference of the backlight control apparatus of Fig. 3 and the backlight control apparatus of Fig. 1 is: add circuit 20 and also comprise selector 25.
MPU40 is according to vision signal VD or to PWM circuit 12 takes place from the instruction of remote controller 60 duty ratio oscillator signal DI is provided, and duty cycle control signal DC is provided for selector 24, returns selector 25 fixed duty cycle switching signal SD is provided.The selection operation of fixed duty cycle switching signal SD control selector 25.
25 pairs of regulation duty ratios of selector switching signal SD responds, and the divided pulse signal P2 of the pwm pulse signal P3 of outlet selector 24 output or frequency dividing circuit 21 outputs selectively is as pwm pulse signal P4.Pwm pulse signal P4 is used as the light modulation pulse signal supplies with inverter circuit 30.
The pwm pulse signal P4 that inverter circuit 30 is supplied with according to selector 23 supplies with back-lighting 52 with drive signal DR.Thus, drive back-lighting 52.By the duty ratio of control pwm signal P4, adjust the brightness of back-lighting 52.
The composition of the other parts of the backlight control apparatus of Fig. 3 is identical with the composition of the appropriate section of the backlight control apparatus of Fig. 1.
(2-2) work of backlight control apparatus
In the backlight control apparatus of Fig. 3, it is identical with the sequential chart of Fig. 2 (a) more than or equal to the sequential chart of 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3 to set duty ratio, and it is identical with the sequential chart of Fig. 2 (b) less than the sequential chart of 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3 to set duty ratio.
Fig. 4 is the sequential chart that the work usefulness of the backlight control apparatus when setting duty ratio is switched in explanation.
Fig. 4 illustrates and sets duty ratio, duty cycle control signal DC, fixed duty cycle switching signal SD and pwm pulse signal P4.The transverse axis of Fig. 4 is the time.
Among Fig. 4, when duty cycle control signal DC is low level, the output signal of selector 24 output AND gates 22 is as pwm pulse signal P3, and duty cycle control signal DC is when being high level, and the output signal of selector 24 output OR-gates 23 is as pwm pulse signal P3.
Here, to PWM the duty ratio specification signal DI that circuit 12 provides Fig. 3 taking place with I2C (Inter integrated circuit: between integrated circuit) bus, duty cycle control signal DC is provided for selector 24 with the port of MPU40.Therefore, make set duty ratio from less than 50% value transform to more than or equal to 50% value the time, or make set duty ratio from more than or equal to 50% value transform to less than 50% value the time, strict, the timing that duty ratio specification signal DI changes is inconsistent sometimes with the timing that duty cycle control signal DC changes.Thereby when setting change in duty cycle, duty ratio moment of pwm pulse signal P3 is departed from the setting duty ratio before and after changing sometimes.
In the example of Fig. 4, set duty ratio and switch to 55% timing from 45% and stagger from the timing that low level rises to high level with duty cycle control signal DC.
Therefore, duty cycle control signal DC rises to the timing of high level and duty ratio from low level and switches between 55% the timing from 45%, the duty ratio instability of the pwm pulse signal P3 of selector 24 outputs, thus the brightness that back-lighting 52 takes place changes the whole image either overt or covert phenomenon of moment that produces discontinuous or LCD panel 51.
So, in the present embodiment, set duty ratio from less than 50% value transform to more than or equal to 50% value the time and set duty ratio from more than or equal to 50% value transform to less than 50% value the time, allow fixed duty cycle switching signal SD produce the pulse of constant width.The timing that this pulse shifts to an earlier date when changing than duty cycle control signal DC rises to high level, and the timing that lags than the setting change in duty cycle time drops to low level.
When selector 25 is low level at fixed duty cycle switching signal SD, the pwm pulse signal P3 of outlet selector 25 outputs is as pwm pulse signal P4, when fixed duty cycle switching signal SD was high level, the divided pulse signal P2 of output frequency division circuit 21 outputs was as pwm pulse signal P4.The duty ratio of divided pulse signal P2 is 50%.
Thus, set duty ratio from less than 50% value transform to more than or equal to the transition period of 50% value and set duty ratio from more than or equal to 50% value transform to transition period less than 50% value, the duty ratio of pwm pulse signal P4 is 50%.
In the example of Fig. 4, set duty ratio and transformed to 55% o'clock from 45%, pwm pulse signal P4 changes to 45%, 50% and 55% successively.
Like this, stably change for the duty ratio of the pwm pulse signal P4 that inverter circuit 30 provides.
(2-3) effect of execution mode 2
Like this, by setting duty ratio more than or equal to the output signal of selecting OR-gate 23 at 50% o'clock, set duty ratio less than the output signal of selecting AND gate 22 at 50% o'clock, can have the pwm pulse signal P3 of frequency of odd number/2 times of vertical synchronizing signal VS inverter circuit 30 outputs.Thus, the picture that prevents LCD panel 51 glimmers.
In the case, adding circuit 20 by newly establishing, only is the pwm pulse signal P3 that the control device 10 of pwm pulse signal P1 of integral multiple of vertical synchronizing frequency can produce the frequency of odd number/2 times with vertical synchronizing frequency with producing.As a result, backlight control apparatus can miniaturization and cost degradation, can also make the display unit thinning simultaneously, gently change and cost degradation.
And, by using fixed duty cycle switching signal SD, set duty ratio from less than 50% value transform to more than or equal to 50% value the time and set duty ratio from more than or equal to 50% value transform to less than 50% value the time, pwm pulse signal is stably changed.Utilize this point, prevent that the duty ratio of pwm pulse signal P4 from touching.Therefore, the brightness that prevents back-lighting 52 change to produce the whole image either overt or covert phenomenon of moment of discontinuous or LCD panel 51.
The duty ratio of pwm pulse signal P1 is when 0% or 100% changes to other value, because the difference of control device 10, pwm pulse signal P1 departs from suitable value sometimes.Even in this case, also can the duty ratio of pwm pulse signal P4 stably be changed with fixed duty cycle switching signal SD.
(3) execution mode 3
(3-1) composition of backlight control apparatus
Fig. 5 is the block diagram of composition that the display unit of the backlight control apparatus with embodiment of the present invention 3 is shown.
The difference of the backlight control apparatus of Fig. 5 and the backlight control apparatus of Fig. 1 is: add circuit 20 and also comprise one-shot multivibrator 26.
Provide PWM that the pwm pulse signal P1 that circuit 12 produces takes place for one-shot multivibrator 26.26 couples of pwm pulse signal P1 of one-shot multivibrator respond, and output has the expansion pulse signal P5 of the pulse of Rack.Particularly, expansion pulse signal P5 have form behind the rising edge of pwm pulse signal P1 certain during the pulse of high level.
The expansion pulse signal P5 that 21 pairs of one-shot multivibrators of frequency dividing circuit 26 produce carries out frequency division, and output frequency division pulse signal P2.The frequency of divided pulse signal P2 is 1/2nd of pwm pulse signal P1 and a frequency of expanding pulse signal P5.
AND gate 22 is calculated the logic product that the pwm pulse signal P1 and the divided pulse signal P2 that frequency dividing circuit 21 is exported of circuit 12 generations take place relevant PWM.OR-gate 23 calculate relevant PWM take place pwm pulse signal P1 that circuit 12 produces and frequency dividing circuit 21 outputs divided pulse signal P2 logic and.
24 couples of duty cycle control signal DC of selector respond, and export the output signal of AND gate 22 or the output signal of OR-gate 23 selectively, as pwm pulse signal P3.Pwm pulse signal P3 is supplied with inverter circuit 30, as the light modulation pulse signal.
The pwm pulse signal P3 that inverter circuit 30 is supplied with according to selector 24 supplies with back-lighting 52 with drive signal DR.Thus, drive back-lighting 52.Adjust the brightness of back-lighting 52 by the duty ratio of control pwm pulse signal P3.
The composition of the other parts of the backlight control apparatus of Fig. 5 is identical with the composition of the appropriate section of the backlight control apparatus of Fig. 1.
(3-2) work of backlight control apparatus
In the backlight control apparatus of Fig. 5, it is identical with the sequential chart of Fig. 2 (a) more than or equal to the sequential chart of 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3 to set duty ratio, and it is identical with the sequential chart of Fig. 2 (b) less than the sequential chart of 50% o'clock vertical synchronizing signal VS, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3 to set duty ratio.
Fig. 6 is the sequential chart that the work usefulness of the backlight control apparatus when setting duty ratio is switched in explanation.Setting duty ratio when Fig. 6 (a) illustrates without one-shot multivibrator 26, duty cycle control signal DC, pwm pulse signal P1, divided pulse signal P2 and pwm pulse signal P3.Setting duty ratio when Fig. 6 (b) illustrates with one-shot multivibrator 26, duty cycle control signal DC, pwm pulse signal P1, expansion pulse signal P5, divided pulse signal P2 and pwm pulse signal P3.
Among Fig. 6, when duty cycle control signal DC is low level, the output signal of selector 24 output AND gates 22 is as pwm pulse signal P3, and duty cycle control signal DC is when being high level, and the output signal of selector 24 output OR-gates 23 is as pwm pulse signal P3.
Here, shown in Fig. 6 (a), under the situation without one-shot multivibrator 26, when setting change in duty cycle, pwm pulse signal P3 produces the unsuitable cycle.In this example, when setting change in duty cycle, instantaneous shortening of the cycle of pwm pulse signal P3.Thereby it is discontinuous that the brightness of back-lighting 52 changes generation, and the picture either overt or covert phenomenon of moment of LCD panel 51 takes place.
Therefore.In the present embodiment, one-shot multivibrator 26 is set, shown in Fig. 6 (b), in pwm pulse signal P3, produces the unsuitable cycle when preventing to set change in duty cycle by prime at frequency dividing circuit 21.Thus, the brightness that prevents back-lighting 52 change to produce discontinuous and the picture either overt or covert phenomenon of moment of LCD panel 51 takes place.
(3-3) effect of execution mode 3
In the present embodiment, by setting duty ratio more than or equal to the output signal of selecting OR-gate 23 at 50% o'clock, set duty ratio less than the output signal of selecting AND gate 22 at 50% o'clock, can have the pwm pulse signal P3 of frequency of odd number/2 times of vertical synchronizing signal VS inverter circuit 30 outputs.Thus, the picture that prevents LCD panel 51 glimmers.
In the case, adding circuit 20 by newly establishing, only is the pwm pulse signal P3 that the control device 10 of pwm pulse signal P1 of integral multiple of vertical synchronizing frequency can produce the frequency of odd number/2 times with vertical synchronizing frequency with producing.As a result, backlight control apparatus can miniaturization and cost degradation, can also make the display unit thinning simultaneously, gently change and cost degradation.
By using one-shot multivibrator, in pwm pulse signal P3, produce the unsuitable cycle when preventing to set change in duty cycle again.Thus, the brightness that prevents back-lighting 52 change to produce discontinuous and the picture either overt or covert phenomenon of moment of LCD panel 51 takes place.
Moreover degree is touched in the brightness of visually allowing in degree that the cycle of the pwm pulse signal P3 when considering to switch the setting duty ratio is touched and the back-lighting 52, the pulse duration of the expansion pulse signal P5 that decision one-shot multivibrator 26 produces.
(4) corresponding relation of each component units of claims and each one of execution mode
Below, the example of the corresponding relation of each component units of claims and each one of execution mode is described, but the example that the invention is not restricted to set forth below.
In the above-mentioned execution mode, inverter circuit 30 is equivalent to inverter, MPU40 or remote controller 60 are equivalent to instruction unit, circuit 12 takes place and is equivalent to pulse generator in PWM, frequency dividing circuit 21 is equivalent to frequency divider, selector 24 or selector 24,25 are equivalent to selector, and one-shot multivibrator 26 is equivalent to pulse stretcher, and LCD panel 51 is equivalent to display panel.Pwm pulse signal P3 or pwm pulse signal P4 are equivalent to the light modulation pulse signal, pwm pulse signal P2 is equivalent to the 1st pulse signal, OR-gate 23 is equivalent to the 1st logic element, AND gate 22 is equivalent to the 2nd logic element, logic and be equivalent to the 1st logical operation, logic product is equivalent to the 2nd logical operation.
(5) other execution mode
In the above-mentioned execution mode 1～3, OR-gate 23 as the 1st logic element, is used as the 2nd logic element with AND gate 22, but is not limited thereto, for example also can NOT-AND gate be used as the 2nd logic element with NOR gate as the 1st logic element.
In the above-mentioned execution mode 3, one-shot multivibrator 26 is used as pulse stretcher, but is not limited thereto also available other waveform shaping circuit.
Also can in the backlight control apparatus of execution mode 2, the one-shot multivibrator of the backlight control apparatus of above-mentioned execution mode 3 be set.
Industrial practicality
Backlight control apparatus of the present invention is to the back of the body of the display unit such as LCD TV, liquid crystal indicator The light modulation of back lighting is useful, and especially the control of paired pulses string light modulation is useful.
Claims (12)
1. a backlight control apparatus is controlled the brightness of back-lighting, it is characterized in that having:
The light modulation pulse signal that control brightness is used responds, and drives the inverter of described back-lighting;
Indicate the instruction unit of the duty ratio of described light modulation pulse signal;
According to the duty ratio and the vertical synchronizing signal of described instruction unit indication, produce the frequency of odd-multiple and be subjected to the pulse generator of the 1st pulse signal of pulse-width modulation with vertical synchronizing frequency;
The 1st pulse signal that described pulse generator is produced carries out frequency division, and output device has the frequency divider of the 2nd pulse signal of 1/2nd frequencies of described the 1st pulse signal;
Carry out the 1st logic element of the 1st logical operation of the 2nd pulse signal of the 1st pulse signal that produces about described pulse generator and the output of described frequency divider;
Carry out the 2nd logic element of the 2nd logical operation of the 2nd pulse signal of the 1st pulse signal that produces about described pulse generator and the output of described frequency divider; And
Selector, this selector is in the duty ratio of described instruction unit indication during more than or equal to setting, the output signal of selecting described the 1st logic element is as the 3rd pulse signal, in the duty ratio of described instruction unit indication during less than setting, the output signal of selecting described the 2nd logic element is as the 3rd pulse signal, and the 3rd pulse signal of (odd number/2) frequency doubly that has vertical synchronizing frequency by such output is as described light modulation pulse signal.
2. the backlight control apparatus described in claim 1 is characterized in that,
Described setting is 50%.
3. the backlight control apparatus described in claim 2 is characterized in that,
Described pulse generator at the duty ratio D of described instruction unit indication more than or equal to 50% o'clock, the duty ratio of the 1st pulse signal is set at 2 (D-50) %, less than 50% o'clock, the duty ratio of the 1st pulse signal is set at 2D% at the duty ratio D of described instruction unit indication.
4. the backlight control apparatus described in claim 1 is characterized in that,
Described selector is being used when switching the duty ratio of described instruction unit indication more than or equal to the value of described setting with less than the value of described setting, and the pulse signal of duty ratio that has regulation during output is certain is as described light modulation pulse signal.
5. the backlight control apparatus described in claim 4 is characterized in that,
Described selector is being used when switching the duty ratio of described instruction unit indication more than or equal to the value of described setting with less than the value of described setting, and the 2nd pulse signal of described frequency divider output was as described light modulation pulse signal during output was certain.
6. the backlight control apparatus described in claim 1 is characterized in that,
The pulse expansion that also has the 1st pulse signal that described pulse generator is produced is to certain width, and output has the pulse stretcher of the 4th pulse signal of the pulse after the expansion,
Described frequency divider carries out frequency division to the 4th pulse signal of described pulse stretcher output.
7. the backlight control apparatus described in claim 6 is characterized in that,
Described pulse stretcher comprises one-shot multivibrator.
8. the backlight control apparatus described in claim 1 is characterized in that,
Described the 1st logical operation be logic and, described the 2nd logical operation is a logic product.
9. the backlight control apparatus described in claim 7 is characterized in that,
Described the 1st logic element comprises OR-gate, and described the 2nd logical operation comprises AND gate.
10. display unit is characterized in that having:
The video signal conversion of input become the form of regulation and isolate the signal processing circuit of vertical synchronizing signal simultaneously;
To be shown as the display panel of image from the vision signal that described signal processing circuit obtains;
Be arranged on the back-lighting at the back side of described display panel; And
Control the backlight control apparatus of the brightness of described back-lighting,
Described backlight control apparatus comprises
The light modulation pulse signal that control brightness is used responds, and drives the inverter of described back-lighting;
Indicate the instruction unit of the duty ratio of described light modulation pulse signal;
According to the duty ratio and the isolated vertical synchronizing signal of described signal processing circuit of described instruction unit indication, produce the frequency of odd-multiple and be subjected to the pulse generator of the 1st pulse signal of pulse-width modulation with vertical synchronizing frequency;
The 1st pulse signal that described pulse generator is produced carries out frequency division, and output device has the frequency divider of the 2nd pulse signal of 1/2nd frequencies of described the 1st pulse signal;
Carry out the 1st logic element of the 1st logical operation of the 2nd pulse signal of the 1st pulse signal that produces about described pulse generator and the output of described frequency divider;
Carry out the 2nd logic element of the 2nd logical operation of the 2nd pulse signal of the 1st pulse signal that produces about described pulse generator and the output of described frequency divider; And
Selector, this selector is in the duty ratio of described instruction unit indication during more than or equal to setting, the output signal of selecting described the 1st logic element is as the 3rd pulse signal, in the duty ratio of described instruction unit indication during less than setting, the output signal of selecting described the 2nd logic element is as the 3rd pulse signal, and the 3rd pulse signal of (odd number/2) frequency doubly that has vertical synchronizing frequency by such output is as described light modulation pulse signal.
11. the display unit described in claim 10 is characterized in that,
Constitute described signal processing circuit and described pulse generator by large scale integrated circuit.
12. the display unit described in claim 10 is characterized in that,
Described display panel comprises LCD panel.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2005016455 | 2005-01-25 | ||
| JP016455/2005 | 2005-01-25 | ||
| JP030065/2005 | 2005-02-07 | ||
| JP037144/2005 | 2005-02-15 |
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| Publication Number | Publication Date |
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| CN101107887A true CN101107887A (en) | 2008-01-16 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNA200680002922XA Pending CN101107887A (en) | 2005-01-25 | 2006-01-18 | Backlight control apparatus and display apparatus |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111327301A (en) * | 2020-04-14 | 2020-06-23 | 京东方科技集团股份有限公司 | Pulse width modulation circuit, modulation method and electronic equipment |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111327301A (en) * | 2020-04-14 | 2020-06-23 | 京东方科技集团股份有限公司 | Pulse width modulation circuit, modulation method and electronic equipment |
| US11949422B2 (en) | 2020-04-14 | 2024-04-02 | Beijing Boe Technology Development Co., Ltd. | Pulse width modulation circuit, method for pulse width modulation, and electronic device |
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