CN102708804B - Backlight dimming method and backlight driving circuit - Google Patents
Backlight dimming method and backlight driving circuit Download PDFInfo
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- CN102708804B CN102708804B CN201110324741.1A CN201110324741A CN102708804B CN 102708804 B CN102708804 B CN 102708804B CN 201110324741 A CN201110324741 A CN 201110324741A CN 102708804 B CN102708804 B CN 102708804B
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Abstract
The invention discloses a backlight dimming method, which comprises the following steps that: a determination module of a main control unit acquires a pulse signal duty ratio according to a gray scale value of a picture to be displayed and compares the duty ratio with a set duty ratio threshold value; when the duty ratio acquired by the determination module is greater than the duty ratio threshold value, a pulse width modulation (PWM) signal generation module of the main control unit generates a PWM signal and outputs the signal to a light dimming controller; when the duty ratio acquired by the determination module is smaller than the duty ratio threshold value, a pulse frequency modulation (PFM) signal generation module of the main control unit generates a PFM signal and outputs the signal to the light dimming controller; and the light dimming controller performs light dimming according to the input PWM signal or the input PFM signal. The invention also discloses a corresponding backlight driving circuit. When required output backlight current is relatively low, the working efficiency of the system can be effectively improved; the power consumption is reduced, the electromagnetic interference (EMI) is reduced, and the color temperature consistency of a light emitting diode (LED) backlight source during working at low current is improved; and when the backlight dimming method is applied to 1D dimming and 2D dimming, an effect is relatively good.
Description
Technical field
The present invention relates to lcd technology, particularly relate to a kind of light-dimming method and backlight drive circuit of backlight.
Background technology
Current, light emitting diode (LED, Light Emitting Diode) more and more extensive in the application of backlight of LCD field, utilize the LCD TV product of LED backlight and concept of environmental protection frivolous with it to conquer a lot of user, LED lamp tube becomes the main application product of backlight gradually.
At present, LED backlight driving circuit adopts following two kinds of modes usually when regulating the LED lamp tube brightness as backlight: simulation light modulation and pulse-length modulation (PWM, Pulse Width Modulation), wherein, simulation dimming mode adopts constant-current drive circuit, the brightness of LED backlight is changed by the back facet current size changing LED backlight, in the program range of adjustment of back facet current be limited in a maximal value to this maximal value about (i.e. 10: 1 dimming scopes) between 10%, and the chromatogram of LED and current related, the colour temperature that LED shows when changing back facet current size is all different with chromaticity coordinates, display effect can be affected, PWM is the make-and-break time ratio by controlling back facet current, thus change the effective value of back facet current, reach the object changing LED lamp tube brightness, i.e. back facet current or be in maximal value, be turned off, when the dutycycle of pwm signal regulates in 100%-10%, the linearity is fine, can raise the efficiency relative to simulation dimming mode, and can avoid, when curent change, colour cast occurs, when the dutycycle of pwm signal regulates within 10%-1%, back facet current is very little, the rise time (Rising time) of pwm signal and fall time (Falling time) are fixed, the linearity of light modulation (Dimming) can be poor, and the efficiency of backlight drive can sharply decline simultaneously, and very little in the dutycycle of PWM and make backlight drive circuit ON time very in short-term, the maximal value that backlight drive circuit exports back facet current can change with the change of PWM dutycycle, affects the colour temperature consistance of LED backlight, thus affects display effect.
Summary of the invention
In view of this, fundamental purpose of the present invention is the light-dimming method and the backlight drive circuit that provide a kind of backlight, causes backlight drive efficiency low and affect the conforming problem of LED backlight colour temperature to solve the existing dimming mode being applied to backlight.
For achieving the above object, technical scheme of the present invention is achieved in that
The invention provides a kind of light-dimming method of backlight, described method comprises:
The determination module of main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle and this dutyfactor value and a duty cycle threshold set is compared;
When the dutycycle that determination module obtains is higher than described duty cycle threshold, the pwm signal generation module of described main control unit produces pwm signal and exports to described light adjusting controller;
When the dutycycle that described determination module obtains is lower than described duty cycle threshold, the PFM signal generator module of described main control unit produces PFM signal and exports to light adjusting controller;
Light adjusting controller by input pwm signal or PFM signal carry out light modulation.
In such scheme, described duty cycle threshold is 10%.
In such scheme, the described gray-scale value according to needing display frame, obtains pulse signal dutycycle, for: from the mapping table between stored picture grey values and pulse signal dutycycle, inquire the dutycycle that correspondence needs display frame gray-scale value.
In such scheme, described generation PFM signal, also comprise: the determination module of described main control unit is according to the gray-scale value needing display frame, obtain the time interval of PFM signal, the time interval of the pulse signal dutycycle that the PFM signal generator module of described main control unit obtains according to described determination module and PFM signal produces PFM signal.
In such scheme, the determination module of described main control unit is according to the gray-scale value needing display frame, obtain the time interval of PFM signal, for: the determination module of described main control unit, from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
Present invention also offers a kind of light-dimming method of backlight, described method comprises:
The determination module of main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and exports described pulse signal to the pwm signal generation module of light adjusting controller and PFM signal generator module;
According to inputted pulse signal, the pwm signal generation module of light adjusting controller produces pwm signal, or the PFM signal generator module of light adjusting controller produces PFM signal;
The pwm signal that the light-adjusting module of light adjusting controller is produced by described pwm signal generation module or the PFM signal that described PFM signal generator module produces carry out light modulation.
In such scheme, the PFM signal generator module of described light adjusting controller produces PFM signal, for:
The PFM signal generator module of described light adjusting controller, according to the pulse signal of input, obtains the back facet current desired value need exporting to backlight; Detecting the current back facet current exporting to backlight, when described back facet current being detected lower than described back facet current desired value, producing PFM signal.
In such scheme, the PFM signal generator module of described light adjusting controller produces PFM signal, comprising:
Produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, in real time the time interval of the described PFM signal of adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value;
Or, produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
Present invention also offers a kind of backlight drive circuit, described backlight drive circuit comprises main control unit and light adjusting controller; Wherein, main control unit comprises: determination module, pwm signal generation module and PFM signal generator module, determination module is used for according to the gray-scale value needing display frame, obtains pulse signal dutycycle and this dutyfactor value and a duty cycle threshold set is compared; Pwm signal generation module is used for, when the dutycycle that described determination module obtains is higher than the duty cycle threshold preset, produces pwm signal and exporting to described light adjusting controller; PFM signal generator module is used for, when the dutycycle that described determination module obtains is lower than the duty cycle threshold preset, produces PFM signal and exporting to light adjusting controller;
Light adjusting controller, carries out light modulation for the pwm signal by inputting or PFM signal.
In such scheme, described determination module, also for according to the gray-scale value needing display frame, obtains the time interval of PFM signal; Described PFM signal generator module, the time interval also for the pulse signal dutycycle that obtains according to described determination module and PFM signal produces PFM signal, and exports described PFM signal to described light adjusting controller.
In such scheme, described determination module, also for from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
Present invention also offers a kind of backlight drive circuit, described backlight drive circuit comprises main control unit and light adjusting controller, and main control unit comprises determination module, and light adjusting controller comprises pwm signal generation module, PFM signal generator module and light-adjusting module; Wherein,
Determination module, for according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and exports described pulse signal to the pwm signal generation module of light adjusting controller and PFM signal generator module;
Pwm signal generation module is used for according to inputted pulse signal, produces pwm signal;
PFM signal generator module is used for according to inputted pulse signal, produces PFM signal;
Light-adjusting module, carries out light modulation for the PFM signal produced by pwm signal or the described PFM signal generator module of described pwm signal generation module generation.
In such scheme, described PFM signal generator module, also for the pulse signal according to input, obtains the back facet current desired value need exporting to backlight; Detect the current back facet current exporting to backlight, when the current back facet current exporting to backlight is lower than described back facet current desired value, produce PFM signal.
In such scheme, described PFM signal generator module, also for: produce dutycycle higher than the PFM signal of described duty cycle threshold, according to the current back facet current exporting to backlight, in the time interval of the described PFM signal of real-time adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value; Or, produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
The present invention is by PWM and pulse frequency modulation (PFM, Pulse Frequency Modulation) the mixing dimming mode that combines, when dutycycle is lower than certain value, produce PFM signal and carry out light modulation based on this PFM signal, when the back facet current requiring to export is lower, can effectively improve system works efficiency, reduce power consumption, reduce EMI, improve the colour temperature consistance of LED backlight when low current works, when being applied to 1D Dimming and 2D Dimming, effect can be better.
Accompanying drawing explanation
Fig. 1 is the realization flow figure of the light-dimming method of a kind of backlight of the present invention;
Fig. 2 is the realization flow figure of the light-dimming method of the another kind of backlight of the present invention;
Fig. 3 is the oscillogram of PFM signal;
Fig. 4 is the corresponding relation schematic diagram of the back facet current value of dutycycle value and output under PWM mode;
Fig. 5 is the backlight power consumption contrast schematic diagram showing different picture under 1D-Dimming;
When Fig. 6 is display the same painting face, integrally adjusting light (Global Dimming) contrasts schematic diagram with the power consumption of 1D-Dimming;
Fig. 7 is the one composition structural representation of backlight drive circuit instantiation of the present invention.
Embodiment
Basic thought of the present invention is: the dimming mode combined by PFM and PWM, namely the light levels of display frame is needed for different loading conditions, select different dimming modes, backlight when realizing liquid crystal display regulates, the efficiency of backlight drive in liquid crystal display process can not only be improved, reduce power consumption, reduce electromagnetic interference (EMI) (EMI, Electro Magnetic Interference), also be conducive to improving the colour temperature consistance of LED backlight when low current simultaneously, when being applied to one dimension light modulation (1D-Dimming) and two-dimentional light modulation (2D-Dimming), effect is better.
The specific implementation process of said method can comprise the following two kinds mode:
The first, main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle, according to obtained pulse signal dutycycle, produces pwm signal or PFM signal and exports to light adjusting controller; Described light adjusting controller by input pwm signal or PFM signal carry out light modulation.
Here, described main control unit can according to the gray-scale value needing display frame, obtain the time interval of PFM signal, produce PFM signal according to the time interval of obtained pulse signal dutycycle and PFM signal, and export described PFM signal to described light adjusting controller.Particularly, described main control unit, from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
The second, main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and exports described pulse signal to light adjusting controller; Described light adjusting controller, according to inputted pulse signal, produces pwm signal or PFM signal, and passes through produced pwm signal or PFM signal carries out light modulation.
Here, described light adjusting controller, according to the pulse signal of input, obtains the back facet current desired value need exporting to backlight; Detect the current back facet current exporting to backlight, when described back facet current being detected lower than described back facet current desired value, producing PFM signal and exporting.
Particularly, described light adjusting controller produces the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, time interval of the described PFM signal of real-time adjustment also exports, and the back facet current exporting to backlight until current reaches described back facet current desired value; Or, described light adjusting controller produces the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, the time interval of the described PFM signal of real-time adjustment and dutycycle also export, and the back facet current exporting to backlight until current reaches described back facet current desired value.
Wherein, the PFM signal dutyfactor that described light adjusting controller exports is higher than the duty cycle threshold preset, and such as, when described duty cycle threshold is 10%, the dutycycle of the PFM signal that light adjusting controller produces can in 20%-30%.As shown in Figure 3, wherein, under activating (Active) state, PFM signal is pulse signal to the waveform of PFM signal; Under inactive (Inactive) state, the PFM signal of output is low level signal.In practical application, PFM signal is when Active state, and light adjusting controller controls power switch work, and PFM signal is when Inactive state, and light adjusting controller controls power switch and quits work.
Wherein, in the specific implementation process of above-mentioned two kinds of modes, the generation of pwm signal is identical with existing PWM mode, does not repeat them here.
Particularly, the light-dimming method of a kind of backlight provided by the invention, realizes the brightness regulation of LED backlight during liquid crystal display, with reference to shown in Fig. 1, mainly can comprise the following steps:
Step 101: the determination module of main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle and this dutyfactor value and a duty cycle threshold set compared;
Particularly, the determination module of main control unit from the mapping table between stored picture grey values and pulse signal dutycycle, can inquire the dutycycle that correspondence needs display frame gray-scale value.
Step 102: when the dutycycle that determination module obtains is higher than described duty cycle threshold, the pwm signal generation module of described main control unit produces pwm signal and exports to described light adjusting controller; When the dutycycle that described determination module obtains is lower than described duty cycle threshold, the PFM signal generator module of described main control unit produces PFM signal and exports to light adjusting controller;
Here, produce PFM signal can comprise: the determination module of described main control unit is according to the gray-scale value needing display frame, obtain the time interval of PFM signal, the time interval of the pulse signal dutycycle that the PFM signal generator module of described main control unit obtains according to described determination module and PFM signal produces PFM signal.
Step 103: light adjusting controller by input pwm signal or PFM signal carry out light modulation.
In practical application, due to PWM mode dutycycle lower than 10% time, the linearity of light modulation (Dimming) can be poor, the efficiency of backlight drive can sharply decline simultaneously, and the colour temperature consistance of LED backlight can be affected, to such an extent as to affect display effect, therefore, described duty cycle threshold can be preferably 10%.
Particularly, the light-dimming method of another kind of backlight provided by the invention, realizes the brightness regulation of LED backlight during liquid crystal display, as shown in Figure 2, mainly can comprise the following steps:
Step 201: the determination module of main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and export described pulse signal to the pwm signal generation module of light adjusting controller and PFM signal generator module;
Step 202: according to inputted pulse signal, the pwm signal generation module of light adjusting controller produces pwm signal, or the PFM signal generator module of light adjusting controller produces PFM signal;
Step 203: the pwm signal that the light-adjusting module of light adjusting controller is produced by described pwm signal generation module or the PFM signal that described PFM signal generator module produces carry out light modulation.
Here, the PFM signal generator module of described light adjusting controller produces PFM signal, for: the PFM signal generator module of described light adjusting controller, according to the pulse signal of input, obtains the back facet current desired value need exporting to backlight; Detecting the current back facet current exporting to backlight, when described back facet current being detected lower than described back facet current desired value, producing PFM signal.
Particularly, the PFM signal generator module of described light adjusting controller produces PFM signal, comprise: produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, in the time interval of the described PFM signal of real-time adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value; Or, produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
Table 1 be based on TI DDA009IC design a LED drive circuit (Driver) Dimming when dutycycle is 10%-100% dutyfactor value and export to LED backlight back facet current value between mapping table, Fig. 4 is the corresponding relation schematic diagram of back facet current and the dutycycle obtained based on table 1, wherein, the representative value of LED current (Current) is 60mA.
Table 1
As seen from Figure 4, adopt PWM mode when dutycycle is between 10%-100%, the linearity is better, and as calculated, efficiency is at about 70%-92%, and regulating effect is good, and efficiency is also higher, can avoid the difference of colour temperature and chromaticity coordinates simultaneously.
If Fig. 5 is the comparison showing different picture backlight power consumption under 1D-Dimming, full white mode maximum power dissipation is 4.07W, as Fig. 6 be display the same painting face Global Dimming and 1D-Dimming power dissipation ratio comparatively.Can obtain from Fig. 5 and Fig. 6, in 1D-Dimming or 2D-Dimming, in the Dimming of dutycycle between 10%-100%, can better backlight power consumption be saved, raise the efficiency.
But under light-load state, PWM dimming effect is then not ideal enough.When the back facet current that need export is very little, namely dutycycle lower than 10% time, by the impact of Rising time and Falling time, the linearity of Dimming is very poor, and very sharp current waveform can be produced, not only easily produce noise like this, increase EMI, the efficiency of whole backlight also can be very poor simultaneously.Now, PFM pattern is selected to carry out light modulation, by the PFM signal of output duty cycle higher than duty cycle threshold, skip pulse when needed, pwm signal is avoided to cause when dutycycle is lower the efficiency of backlight drive to decline and affect the conforming problem of colour temperature of LED backlight, thus raising backlight drive efficiency improve the colour temperature consistance of LED backlight.
Accordingly, present invention also offers a kind of backlight drive circuit, described backlight drive circuit comprises main control unit and light adjusting controller; Wherein, main control unit comprises: determination module, pwm signal generation module and PFM signal generator module, determination module is used for according to the gray-scale value needing display frame, obtains pulse signal dutycycle and this dutyfactor value and a duty cycle threshold set is compared; Pwm signal generation module is used for, when the dutycycle that described determination module obtains is higher than the duty cycle threshold preset, produces pwm signal and exporting to described light adjusting controller; PFM signal generator module is used for, when the dutycycle that described determination module obtains is lower than the duty cycle threshold preset, produces PFM signal and exporting to light adjusting controller; Light adjusting controller, carries out light modulation for the pwm signal by inputting or PFM signal.
Wherein, described determination module, also for according to the gray-scale value needing display frame, obtains the time interval of PFM signal; Described PFM signal generator module, the time interval also for the pulse signal dutycycle that obtains according to described determination module and PFM signal produces PFM signal, and exports described PFM signal to described light adjusting controller.
Here, described determination module, also for from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
Present invention also offers another kind of backlight drive circuit, described backlight drive circuit comprises main control unit and light adjusting controller, and main control unit comprises determination module, and light adjusting controller comprises pwm signal generation module, PFM signal generator module and light-adjusting module; Wherein, determination module, for according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and exports described pulse signal to the pwm signal generation module of light adjusting controller and PFM signal generator module; Pwm signal generation module is used for according to inputted pulse signal, produces pwm signal; PFM signal generator module is used for according to inputted pulse signal, produces PFM signal; Light-adjusting module, carries out light modulation for the PFM signal produced by pwm signal or the described PFM signal generator module of described pwm signal generation module generation.
Wherein, described PFM signal generator module, also for the pulse signal according to input, obtains the back facet current desired value need exporting to backlight; Detect the current back facet current exporting to backlight, when the current back facet current exporting to backlight is lower than described back facet current desired value, produce PFM signal.
Here, described PFM signal generator module, also for: produce dutycycle higher than the PFM signal of described duty cycle threshold, according to the current back facet current exporting to backlight, in the time interval of the described PFM signal of real-time adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value; Or, produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
In practical application, above-mentioned pwm signal generation module and PFM signal generator module all can be realized by a square-wave generator, and detailed process is prior art, does not repeat them here.Described light-adjusting module is the module possessing dimming function, can be the light adjusting controller in Fig. 7.
In practical application, the structure of backlight drive circuit as shown in Figure 7, specifically can comprise: input filter, power switch, inductance or transformer, output rectification or wave filter, light adjusting controller and main control unit, wherein, input end Vin connects power supply, output end vo ut output back facet current and backlight voltage are to LED backlight, and output end vo ut is connected with light adjusting controller, also the back facet current of output is fed back to light adjusting controller.In practical application, described LED backlight can be LED lamp bar (Bar).Wherein, main control module specifically can comprise above-mentioned determination module, pwm signal generation module and PFM signal generator module.
Particularly, when the picture that need show is darker, require that dutycycle is lower than 10%, now, above-mentioned backlight drive circuit can carry out light modulation by the following two kinds mode and export back facet current:
First, main control unit is according to the light levels needing display frame, produce PFM signal and also export light adjusting controller to, light adjusting controller is operated in discontinuous mode according to PFM signal, and the back facet current that backlight drive circuit exports to LED backlight maintains the level of requirement;
In this case, PFM signal is that the picture gray scale shown as required produces, and its dutycycle and Inactive time span are determined, directly this PFM signal are exported to light adjusting controller and carry out light modulation.
Particularly, when needing the picture gray scale of display higher, during the picture namely needing display brightness higher, PFM signal is in Active state, light adjusting controller is in running order, control power switch works, power switch control inputs power supply, input filter, inductance or transformer and export rectification or overall filter and export backlight voltage to LED backlight, now, the back facet current of LED backlight can be larger, the brightness of LED backlight will be comparatively large, over the display just can the higher picture of display brightness.
When needing the picture gray scale of display lower, during the picture namely needing display brightness higher, PFM signal is in Inactive state, and light adjusting controller can be in out-of-work state, controls power switch and closes, now, can only rely on the backlight voltage in inductance or transformer discharge maintenance LED backlight, now, the back facet current in LED backlight can be less, the brightness of LED backlight will be dark, over the display just can the lower picture of display brightness.
Under this working method, light adjusting controller only needs the signal according to receiving to carry out work, Real-time Collection back facet current under all right duty of light adjusting controller, judge back facet current value whether in the scope of setting value, and dynamic adjustments is carried out to back facet current, this process is this area common technology, does not repeat them here.
The second, main control unit, according to the light levels needing display frame, produces pulse signal and exports to light adjusting controller, and wherein, the pulse signal dutycycle that main control unit produces is lower than 10%; Light adjusting controller produce dutycycle higher than 10% PFM signal, and according to the pulse signal that main control unit exports, obtain exporting back facet current desired value, the back facet current fed back according to output end vo ut again and the back facet current desired value that need export, adjustment produce time interval of PFM signal, or adjustment institute produces the time interval and the dutycycle (during adjustment, the dutycycle of PFM signal is all the time on 10%) of PFM signal, until the back facet current of output reaches described need export described back facet current desired value.
Particularly, light adjusting controller receives the pwm signal of dutycycle below 10% that main control chip sends, light adjusting controller changes into PFM regulative mode, produce certain dutycycle and (be greater than 10%, such as 50% etc.) PFM signal, simultaneously, light adjusting controller receives the back facet current of LED backlight feedback, judge whether back facet current reaches back facet current desired value, if back facet current is less than back facet current desired value, produce the PFM signal of Active state, if back facet current is greater than back facet current desired value, produce the PFM signal of Inactive state.
When PFM signal is Active state, light adjusting controller produces the control signal of certain dutycycle to power switch, power switch works, the voltage of power switch control input end Vin, input filter, inductance or transformer and export rectification or wave filter work, by output end vo ut output voltage to LED backlight, the back facet current controlled in LED backlight raises, until back facet current is elevated to back facet current desired value;
When PFM signal is Inactive state, light adjusting controller stops producing described control signal to power switch, power switch quits work, now, backlight voltage in LED backlight only supplies by the electric discharge of the energy-storage travelling wave tube such as electric capacity or inductance, thus the back facet current in control LED backlight declines, until back facet current drops to back facet current desired value.
Wherein, according to the size automatically switching duty cycle coefficient that need export back facet current, light adjusting controller can be made to reduce dynamic power consumption under light load conditions, and improves conversion efficiency.Particularly, closed-loop dynamic is controlled, now conventional mode is proportional-integral-differential (PID, Proportion Integration Differentiation) control, dynamically carry out regulable control by the difference of Real-time Collection control objectives and target setting, also other existing control algolithm can realize this function by some.
The above, be only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.
Claims (10)
1. a light-dimming method for backlight, is characterized in that, described method comprises:
The determination module of main control unit, according to the gray-scale value needing display frame, obtains the time interval of pulse signal dutycycle, PFM signal, and this dutycycle and a duty cycle threshold set is compared;
When the dutycycle that determination module obtains is higher than described duty cycle threshold, the pwm signal generation module of described main control unit produces pwm signal and exports to light adjusting controller;
When the dutycycle that described determination module obtains is lower than described duty cycle threshold, the time interval of the pulse signal dutycycle that the PFM signal generator module of described main control unit obtains according to described determination module and PFM signal produces PFM signal and exports to light adjusting controller;
Light adjusting controller by input pwm signal or PFM signal carry out light modulation.
2. the light-dimming method of backlight according to claim 1, it is characterized in that, described duty cycle threshold is 10%.
3. the light-dimming method of backlight according to claim 1, it is characterized in that, the described gray-scale value according to needing display frame, obtain pulse signal dutycycle, for: from the mapping table between stored picture grey values and pulse signal dutycycle, inquire the dutycycle that correspondence needs display frame gray-scale value.
4. the light-dimming method of backlight according to claim 1, it is characterized in that, the determination module of described main control unit is according to the gray-scale value needing display frame, obtain the time interval of PFM signal, for: the determination module of described main control unit, from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
5. a light-dimming method for backlight, is characterized in that, described method comprises:
The determination module of main control unit, according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and output pulse signal is to the pwm signal generation module of light adjusting controller and PFM signal generator module;
According to inputted pulse signal, the pwm signal generation module of light adjusting controller produces pwm signal, or the PFM signal generator module of light adjusting controller produces PFM signal;
The pwm signal that the light-adjusting module of light adjusting controller is produced by described pwm signal generation module or the PFM signal that described PFM signal generator module produces carry out light modulation;
Wherein, the PFM signal generator module of described light adjusting controller, according to the pulse signal of input, obtains the back facet current desired value need exporting to backlight; Detecting the current back facet current exporting to backlight, when described back facet current being detected lower than described back facet current desired value, producing PFM signal.
6. the light-dimming method of backlight according to claim 5, is characterized in that, the PFM signal generator module of described light adjusting controller produces PFM signal, comprising:
Produce the PFM signal of dutycycle higher than duty cycle threshold, according to the current back facet current exporting to backlight, in real time the time interval of the described PFM signal of adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value;
Or, produce the PFM signal of dutycycle higher than duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
7. a backlight drive circuit, is characterized in that, described backlight drive circuit comprises main control unit and light adjusting controller; Wherein, main control unit comprises: determination module, pwm signal generation module and PFM signal generator module, determination module is used for according to the gray-scale value needing display frame, obtains the time interval of pulse signal dutycycle, PFM signal, and this dutycycle and a duty cycle threshold set is compared; Pwm signal generation module is used for, when the dutycycle that described determination module obtains is higher than the duty cycle threshold preset, produces pwm signal and exporting to light adjusting controller; PFM signal generator module is used for when the dutycycle that described determination module obtains is lower than the duty cycle threshold preset, and the time interval of the pulse signal dutycycle obtained according to described determination module and PFM signal produces PFM signal and produces PFM signal and export to light adjusting controller;
Light adjusting controller, carries out light modulation for the pwm signal by inputting or PFM signal.
8. backlight drive circuit according to claim 7, it is characterized in that, described determination module, also for from the mapping table between stored picture grey values and pulse signal interval, inquires the PFM signal interval that correspondence needs display frame gray-scale value.
9. a backlight drive circuit, is characterized in that, described backlight drive circuit comprises main control unit and light adjusting controller, and main control unit comprises determination module, and light adjusting controller comprises pwm signal generation module, PFM signal generator module and light-adjusting module; Wherein,
Determination module, for according to the gray-scale value needing display frame, obtains pulse signal dutycycle, and output pulse signal is to the pwm signal generation module of light adjusting controller and PFM signal generator module;
Pwm signal generation module is used for according to inputted pulse signal, produces pwm signal;
PFM signal generator module is used for according to inputted pulse signal, obtains the back facet current desired value need exporting to backlight; Detect the current back facet current exporting to backlight, when the current back facet current exporting to backlight is lower than described back facet current desired value, produce PFM signal;
Light-adjusting module, carries out light modulation for the PFM signal produced by pwm signal or the described PFM signal generator module of described pwm signal generation module generation.
10. backlight drive circuit according to claim 9, it is characterized in that, described PFM signal generator module, also for: produce dutycycle higher than the PFM signal of duty cycle threshold, according to the current back facet current exporting to backlight, in the time interval of the described PFM signal of real-time adjustment, the back facet current exporting to backlight until current reaches described back facet current desired value; Or, produce the PFM signal of dutycycle higher than described duty cycle threshold, according to the current back facet current exporting to backlight, adjust the time interval and the dutycycle of described PFM signal in real time, the back facet current exporting to backlight until current reaches described back facet current desired value.
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