CN104902610A - Dimming control method and correlative backlight controller - Google Patents
Dimming control method and correlative backlight controller Download PDFInfo
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- CN104902610A CN104902610A CN201410076766.8A CN201410076766A CN104902610A CN 104902610 A CN104902610 A CN 104902610A CN 201410076766 A CN201410076766 A CN 201410076766A CN 104902610 A CN104902610 A CN 104902610A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
Provided are a dimming control method and a correlative backlight controller. The embodiment provides the dimming control method comprising: providing a dimming state signal which indicates that a light-emitting element should be driven to emit light if being equal to a first logical value or indicates that the light-emitting element should not emit light if being equal to a second logical value; when the dimming state signal is equal to the first logical value, providing a closed loop, enabling a power converter to supply power to the light-emitting element in order to provide electrical power required by light emission of the light-emitting element, and enabling a signal of the closed loop to be approximately a preset value; and when the dimming state signal is equal to the second logical value and the light-emitting time of the dimming state signal being equal to the first logical value is not more than a preset shortest power supply time, continuously enabling the power converter to supply power to the light-emitting element in order that the power supply time of the power converter is not shorter than the shortest power supply time.
Description
Technical field
The present invention is broadly directed to dimming controlling method and relevant backlight controller, particularly relates to the dimming controlling method and backlight controller that can avoid glimmering.
Background technology
Good luminous efficiency, the component size of simplifying and permanent component life, make light-emitting diode (LED) extensively be thrown light on or backlight industry adopted.For example, the backlight module in computer or video screen, great majority, from traditional cold-cathode tube (Cold Cathode Fluorescent Lamp, CCFL) module, convert LED module to.
General LED module, during as backlight module, its control circuit all contains two blocks haply.One is power supply changeover device, and its possibility one switch type power supplying device, in order to provide the driving voltage required for LED; Another is Given current controller device, and control flow check is through the size of current of LED module.
LED module often needs the function of adjustment screen intensity, and therefore, control circuit just has the demand of light modulation.General industry has two kinds of dimming modes: PWM light modulation (PWM dimming) and simulation light modulation (analog dimming).PWM light modulation also has and is called as digital dimming.PWM light modulation adopts a digital signal to determine LED module and is in the ratio of fluorescent lifetime to whole circulation timei, namely the work period (duty cycle); And when fluorescent lifetime, the luminosity of LED module is a fixed value; Not fluorescent lifetime outside fluorescent lifetime, LED module is roughly not luminous.Relative, adopt the LED module of simulation light modulation (also have and be called resistance-type light modulation), its luminescence is uninterrupted, but its brightness is then controlled by an analog signal.
Power supply changeover device often has a loop, carrys out the driving voltage of stable LED module.This loop has certain frequency range and certain reaction time.If the fluorescent lifetime under PWM light modulation is shorter than the reaction time of power supply changeover device, that power supply changeover device is reacting under the situation had little time, probably cannot in time provide enough electric energy, maintain the driving voltage needed for LED module, thus cause human eye to experience and the generation of unwelcome flicker (flickering) problem.
Summary of the invention
One embodiment of the invention provide a kind of dimming controlling method, include: a dimming state signal is provided, when it is first logical value, represent that at least one light-emitting component should be driven to emit light, when it is second logical value, represent that this light-emitting component should not be luminous; When this dimming state signal is this first logical value, provide a loop, and a power supply changeover device is powered to these light-emitting components, to provide the electric energy needed for this light-emitting component luminescence, and make a signal of this loop be approximately a preset value; And, when this dimming state signal transition is this second logical value, and the fluorescent lifetime that this dimming state signal is positioned at this first logical value be no more than one preset the shortest power-on time time, continue this power supply changeover device is powered to this light-emitting component, be not shorter than this shortest power-on time to make a power-on time of this power supply changeover device.
One embodiment of the invention provide a kind of backlight controller, include a current control unit and a converter control unit.This current control unit produces a dimming state signal according to a PWM dim signal, and controls a drive current of at least one light-emitting component.When this dimming state signal is first logical value, represent that this drive current should not be 0; When this dimming state signal is second logical value, represent that this drive current should be 0.This converter control unit can control a power supply changeover device, makes it power to this light-emitting component.When this dimming state signal is this first logical value, this converter control unit provides a loop, and this power supply changeover device is powered to these light-emitting components, to provide the electric energy needed for this light-emitting component luminescence.When this dimming state signal transition is this second logical value, and the fluorescent lifetime that this dimming state signal is positioned at this first logical value be no more than one preset the shortest power-on time time, this converter control unit continues this power supply changeover device is powered to this light-emitting component, is not shorter than this shortest power-on time to make a power-on time of this power supply changeover device.
Accompanying drawing explanation
Fig. 1 shows a traditional backlight module (backlight module) 10, wherein for example there are four LED module LED
1~ LED
4.
Fig. 2 A is some signal waveforms in Fig. 1.
Fig. 2 B shows as fluorescent lifetime T
dIM-ONvery in short-term, some signal waveforms in Fig. 1.
Fig. 3 shows the backlight module 100 implemented according to the present invention.
Fig. 4 shows the backlight controller 104 in Fig. 3.
Fig. 5 A shows as fluorescent lifetime T
dIM-ONthan the shortest power-on time T
mIN-ONin short-term, some signal waveforms in Fig. 4.
Fig. 5 B shows as fluorescent lifetime T
dIM-ONthan the shortest power-on time T
mIN-ONtime long, some signal waveforms in Fig. 4.
Fig. 6 display is used for producing power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELmethod flow diagram 800.
Fig. 7 display is used for producing power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELother method flow chart 900.
[symbol description]
10 backlight modules
12 stepup transformers
14 backlight controllers
16 current control units
18 converter control unit
23 building-out capacitors
28 power switchs
100 backlight modules
101,103 divider resistances
104 backlight controllers
106 current control units
108 converter control unit
122 minimum selectors
130 operational amplifiers
132 multiplexers
140 pulse-width modulators
142 operation transconductance amplifiers
160 status units
800 method flow diagrams
802,804,806,808,810,812,814,816,818,820 steps
900 method flow diagrams
902,904 steps
CD
1~ CD
4current controller
CS
1~ CS
4pin
COM pin
D delay cell
DIM pin
DIM
1~ DIM
4dim signal
DIM
oNdimming state signal
DIM
pWMpWM dim signal
DRV pin
FB
1~ FB
4pin
GAT
1~ GAT
4pin
ILED
1~ ILED
4drive current
LED
1~ LED
4lED module
OVP pin
R record
RS
1detect resistance
S
dRVcontrol signal
S
hOLDinhibit signal
S
pOWERpower supply signal
S
sELselect signal
T
0time point
T
dIM-OFFnot fluorescent lifetime
T
dIM-ONfluorescent lifetime
T
lOOPloop time
T
mIN-ONthe shortest power-on time
T
pOWER-ONpower-on time
T
pUMPthe constrained feed time
T
sTARTUPinitial time
V
cOMbucking voltage
VFB
mINminimum feedback voltage
V
iNinput voltage
V
oUTdriving voltage
V
sETthe voltage preset
Embodiment
In this manual, have the symbol that some are identical, it represents to have the element of identical or similar structure, function, principle, and can know by inference according to the instruction of this specification for those skilled in the art.For the succinct degree of specification is considered, the element of identical symbol will no longer repeat.
In order to solve the too short and flicker problem caused of fluorescent lifetime under PWM light modulation, therefore, in one embodiment of this invention, provide the shortest power-on time.Even if fluorescent lifetime compared with the shortest power-on time come short, power supply changeover device after at least continued power has the shortest power-on time, is just stopped power supply.In one embodiment, after the fluorescent lifetime of LED module terminates, power supply changeover device regulates the loop of (regulate) driving voltage to interrupt by being used for, and continued power, until the shortest power-on time terminates.
So, although very short of the fluorescent lifetime under PWM light modulation, the electric energy that power supply changeover device can supply volume gives LED module, guarantees that LED module is at fluorescent lifetime afterwards, has enough driving voltages, can be correctly luminous.
Do not have the continued power under loop, the event that driving voltage may be caused too high occurs.In one embodiment of this invention, once too high voltages event occurs, power supply changeover device is just stopped power supply, but PWM light modulation still can be carried out and unaffected.
In one embodiment of this invention, power supply changeover device not necessarily continued power until the shortest power-on time terminates.Once in fluorescent lifetime, the driving voltage of LED module may have situation on the low side, that power supply changeover device with regard to continued power until the shortest power-on time terminates.Contrary, if in fluorescent lifetime, the driving voltage of LED module may be enough, and the power supply of that power supply changeover device just terminates along with fluorescent lifetime and stops.
Fig. 1 shows a traditional backlight module (backlight module) 10, wherein for example there are four LED module LED
1~ LED
4.Stepup transformer (booster) 12 as the example of a power supply changeover device, by input voltage V
iNconvert driving voltage V to
oUT, be used for power supply driving LED module LED
1~ LED
4.Four current controller CD
1~ CD
4control flow check is through LED module LED respectively
1~ LED
4drive current ILED
1~ ILED
4.
Converter control unit 18 and current control unit 16 is had in backlight controller 14.Converter control unit 18 controls stepup transformer 12, and current control unit 16 controls current controller CD
1~ CD
4.According to PWM dim signal DIM
pWM, converter control unit 18 determines whether stepup transformer 12 powers, and current control unit 16 determines drive current ILED
1~ ILED
4value.With LED module LED
1for example, when backlight controller 14 will make it luminous, drive current ILED
1for certain value; When backlight controller 14 will make it not luminous, drive current ILED
1be approximately 0.Current control unit 16 is by pin FB
1~ FB
4a minimum feedback voltage VFB corresponding to minimum value wherein
mIN, give converter control unit 18.
Fig. 2 A is some signal waveforms in Fig. 1, from top to bottom, includes PWM dim signal DIM
pWM, minimum feedback voltage VFB
mIN, bucking voltage V on building-out capacitor 23
cOM, and control the control signal S of the power switch (power switch) 28 in stepup transformer 12
dRV.As PWM dim signal DIM
pWMfor in logic 1 time, be fluorescent lifetime T
dIM-ON, LED module LED
1~ LED
4luminous; Contrary, as PWM dim signal DIM
pWMfor in logic 0 time, be not fluorescent lifetime T
dIM-OFF, LED module LED
1~ LED
4not luminous.In this description, fluorescent lifetime T
dIM-ONrefer to the time that a LED module at least should be had to be driven to emit light, and not fluorescent lifetime T
dIM-OFFrefer to the time be driven to emit light without any a LED module.
Shown in Fig. 2 A, at not fluorescent lifetime T
dIM-OFFin, control signal S
dRVbe fixed as 0 in logic, power switch 28 is closed, so stepup transformer 12 is not to LED module LED
1~ LED
4power supply.At not fluorescent lifetime T
dIM-OFFin, because drive current ILED
1~ ILED
4all be approximately 0, so minimum feedback voltage VFB
mINdriving voltage V will be approximated greatly
oUT.At not fluorescent lifetime T
dIM-OFFin, bucking voltage V
cOMapproximately remain unchanged.
Shown in Fig. 2 A, at fluorescent lifetime T
dIM-ONin, control signal S
dRVperiodically provide pulse, in order to switch power switch 28, make stepup transformer 12 couples of LED module LED
1~ LED
4power supply.Because have a LED module luminescence at least, so at fluorescent lifetime T
dIM-ONin, minimum feedback voltage VFB
mINcan decline.For example, at fluorescent lifetime T
dIM-ONin, feedback voltage V FB
mINbe used for adjusting bucking voltage V with the difference of 0.4V
cOM, it determines control signal S instantly
dRVpulse duration.So, feedback voltage V FB
mIN, bucking voltage V
cOM, control signal S
dRV, driving voltage V
oUTthen provides a loop (close loop).In fig. 2, stepup transformer 12 according to this loop, modulator control signal S
dRVin pulse duration, to make minimum feedback voltage VFB
mINapproximately maintain 0.4V.
Fig. 2 B shows as fluorescent lifetime T
dIM-ONvery in short-term, some signal waveforms in Fig. 1.As shown in Fig. 2 B, once fluorescent lifetime T
dIM-ONvery in short-term, bucking voltage V
cOMalso come suddenly not get back to its due steady state voltage (steady state voltage), fluorescent lifetime T
dIM-ONjust finish.Therefore, bucking voltage V
cOM-at fluorescent lifetime T
dIM-ONat the end of, will fluorescent lifetime T be followed
dIM-ONdifference to some extent before beginning.As Fig. 2 B left side shown in, experienced by a fluorescent lifetime T
dIM-ONafter, bucking voltage V
cOMhave dropped some a little.Such difference will along with PWM dim signal DIM
pWMlight modulation dimming cycle (dimming cycle) number increase and accumulate.If bucking voltage V
cOMthe decline continued, means the electric energy that stepup transformer 12 is supplied, may be not enough to driving LED module LED
1~ LED
4, make it at fluorescent lifetime T
dIM-ONcannot be luminous.As Fig. 2 B right-hand part shown in, minimum feedback voltage VFB
mINbe starkly lower than 0.4V, meaning may have LED module this is bright and do not work.
Fig. 3 shows the backlight module 100 implemented according to the present invention.In one embodiment, backlight controller 104 is integrated circuits, has pin DRV, COM, DIM, FB
1~ FB
4, CS
1~ CS
4, GAT
1~ GAT
4and OVP, be connected to stepup transformer 12, building-out capacitor 23, LED module LED
1~ LED
4, current controller CD
1~ CD
4, and divider resistance 101 and 103.
Fig. 4 shows the backlight controller 104 in Fig. 3, and it has converter control unit 108 and current control unit 106.
As shown in Figure 4, in current control unit 106, there is several delay cell D, be used for PWM dim signal DIM
pWMpostpone, and produce dim signal DIM
2~ DIM
4.Dim signal DIM
1~ DIM
4then control drive circuit CC respectively
1~ CC
4.Drive circuit CC
1~ CC
4internal circuit roughly the same.Below will illustrate drive circuit CC
1, and drive circuit CC
2~ CC
4can analogize and learn, be not repeated.Drive circuit CC
1there is operational amplifier 130 and multiplexer (multiplexer) 132.Operational amplifier 130 and the current controller CD in Fig. 3
1together, drive current ILED can be controlled
1value.As dim signal DIM
1for in logic 1 time, drive current ILED
1with detection resistance RS
1product approximate greatly one preset voltage V
sET, so LED module LED
1luminous; As dim signal DIM
1for in logic 0 time, drive current ILED
1equal 0, LED module LED
1not luminous.Briefly, dim signal DIM
1determine LED module LED
1whether driven, with fixing Intensity LEDs.
A have four inputs or door, according to dim signal DIM
1~ DIM
4, produce dimming state signal DIM
oN.In other words, LED module LED
1~ LED
4in any one should the luminescence by driving, dimming state signal DIM
oNit can be 1 in logic; If LED module LED
1~ LED
4be not driven to emit light, that dimming state signal DIM
oNit can be 0 in logic.
Minimum selector 122 is according to pin FB
1~ FB
4on voltage in minimum value, produce minimum feedback voltage VFB
mIN.From the viewpoint of certain, minimum feedback voltage VFB
mINrepresent pin FB
1~ FB
4on voltage in one of them.Pin FB
1on voltage, for example, namely LED module LED
1a terminal voltage.
In converter control unit 108, as power supply signal S
pOWERfor in logic 1 time, pulse-width modulator 140 is just according to bucking voltage V
cOMperiodically produce pulse, pin DRV provides control signal S
dRV, stepup transformer 12 will to LED module LED
1~ LED
4power supply; As power supply signal S
pOWERfor in logic 0 time, pin DRV will be clamped to 0V, so stepup transformer 12 will be stopped power supply.Briefly, power supply signal S
pOWERcan represent that whether stepup transformer 12 is to LED module LED
1~ LED
4power supply.
Converter control unit 108 separately has an operation transconductance amplifier (operational trans conductance amplifier, OTA) 142.Between operation transconductance amplifier 142 and pin COM, there is a switch, be controlled by inhibit signal S
hOLD.Inhibit signal S
hOLDfor in logic 0 time, operation transconductance amplifier 142 can to building-out capacitor 23 discharge and recharge, changes bucking voltage V
cOM.As inhibit signal S
hOLDfor in logic 1 time, for open a way between operation transconductance amplifier 142 and building-out capacitor 23, building-out capacitor 23 is not charged or discharged, so bucking voltage V
cOMroughly remain unchanged.
Multiplexer 132 is according to selection signal S
sELdecide to provide minimum feedback voltage VFB
mINor 0.2V gives an input of operation transconductance amplifier 142.
As selection signal S
sEL, inhibit signal S
hOLD, power supply signal S
pOWERwhen being respectively 0,0,1, connect feedback voltage V FB
mIN, bucking voltage V
cOM, control signal S
dRV, driving voltage V
oUTsignal path just constitute a loop (close loop), and converter control unit 108 makes stepup transformer 12 couples of LED module LED
1~ LED
4power supply, target is the minimum feedback voltage VFB allowed in loop
mINapproximate 0.4V greatly.This loop, can by for 1 selection signal S
sEL, be 0 inhibit signal S
hOLD, or be 0 power supply signal S
pOWERinterrupted, become open circuit loop (open loop).
Status unit 160 is according to dimming state signal DIM
oN, decide to select signal S
sEL, inhibit signal S
hOLD, power supply signal S
pOWERlogical value.From in a certain respect, whether status unit 160 also determines provides this loop.
Fig. 5 A shows as fluorescent lifetime T
dIM-ONthan the shortest power-on time T
mIN-ONin short-term, some signal waveforms in Fig. 4.From top to bottom, the waveform in Fig. 5 A sequentially represents PWM dim signal DIM
pWM, dim signal DIM
1~ DIM
4, dimming state signal DIM
oN, power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sEL, and control signal S
dRV.
Please with reference to Fig. 4 and Fig. 5 A.Dim signal DIM
1~ DIM
4approximately equivalent PWM dim signal DIM
pWMbut, have different time delays.Dimming state signal DIM
oNbe one or door or door to dim signal DIM
1~ DIM
4operation result, shown in Fig. 5 A.Fluorescent lifetime T
dIM-ONrepresent dimming state signal DIM
oNfor in logic 1 time.As previously described, at fluorescent lifetime T
dIM-ONin, have at least a LED module should be luminous by driving.Contrary, not fluorescent lifetime T
dIM-OFFrepresent dimming state signal DIM
oNfor the time of 0 (being namely driven to emit light without any a LED module) in logic.PWM dim signal DIM
pWMroughly determine dimming state signal DIM
oNwaveform.
Shown in Fig. 5 A, PWM dim signal DIM at the beginning
pWM, dim signal DIM
1~ DIM
4, dimming state signal DIM
oN, power supply signal S
pOWER, select signal S
sEL, control signal S
dRVbe all 0, only have inhibit signal S
hOLDbe 1.Now, be driven to emit light without any a LED module, bucking voltage V
cOMroughly remain unchanged, stepup transformer 12 is not powered to LED module LED
1~ LED
4.
At time point t
0, PWM dim signal DIM
pWMwhen becoming 1 by 0 transition, dimming state signal DIM
oNalso and then 1 is become by 0 transition, declaration fluorescent lifetime T
dIM-ONbeginning.Shown in Fig. 5 A, status unit 160 internal preset has from fluorescent lifetime T
dIM-ONa period of time after beginning is initial time T
sTARTUP, from fluorescent lifetime T
dIM-ONanother a period of time after beginning is the shortest power-on time T
mIN-ON.The shortest power-on time T
mIN-ONthan initial time T
sTARTUPlong.
At initial time T
sTARTUPin, power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe respectively 1,1,0.This means bucking voltage V
cOMroughly remain unchanged, and stepup transformer 12 is according to bucking voltage V
cOMthe control signal S determined
dRVand power supply is to LED module LED
1~ LED
4, and be used for regulation and control (regulate) minimum feedback voltage VFB
mINloop do not formed (or being provided).Introduce initial time T
sTARTUPthere is a special benefit: reduce fluorescent lifetime T
dIM-ONminimum feedback voltage VFB at the beginning
mINthe unstable impact caused.As fluorescent lifetime T
dIM-ONtime at the beginning, minimum feedback voltage VFB
mINunderstand from a very high value decline suddenly (shown in illustrating as Fig. 2 A and Fig. 2 B).Now, first bucking voltage V
cOMmaintain, minimum feedback voltage VFB can be avoided
mINerror message in decline process is to bucking voltage V
cOMthe impact made the mistake.
In Fig. 5 A, initial time T
sTARTUPto fluorescent lifetime T after terminating
dIM-ONthe time terminated is called loop time T
lOOP.At loop time T
lOOPin, power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe respectively 1,0,0.Therefore, feedback voltage V FB is connected
mIN, bucking voltage V
cOM, control signal S
dRV, driving voltage V
oUTsignal path just constitute a loop, converter control unit 108 makes stepup transformer 12 couples of LED module LED
1~ LED
4power supply, target is the minimum feedback voltage VFB allowed in loop
mINapproximate 0.4V greatly.
In fig. 5, fluorescent lifetime T
dIM-ONto the shortest power-on time T after terminating
mIN-ONtime between end, be called constrained feed time T
pUMP.At constrained feed time T
pUMPin, power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe respectively 1,0,1.Owing to selecting signal S
sELthe multiplexer 132 in Fig. 4 is made to provide 0.2V to operation transconductance amplifier 142, so previously at loop time T
lOOPmiddle formed loop has been interrupted.Now, because inhibit signal S
hOLDbe 0, and two inputs of trsanscondutance amplifier 142 have fixing voltage difference (=0.4V-0.2V), so trsanscondutance amplifier 142 will charge to building-out capacitor 23 with certain electric current, bucking voltage V
cOMcan be raised.Note that at constrained feed time T
pUMPin, although without any a LED module luminescence, stepup transformer 12 still can according to by the bucking voltage V drawn high
cOM, come LED module LED
1~ LED
4power supply.
In fig. 5, the shortest power-on time T
mIN-ONafter end, power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe turned into 0,1,0 respectively, get back to fluorescent lifetime T
dIM-ONstate before beginning.Power supply signal S
pOWERbe 1 timing definition be power-on time T
pOWER-ON.Shown in Fig. 5 A, as fluorescent lifetime T
dIM-ONthan the shortest power-on time T
mIN-ONin short-term, power-on time T
pOWER-ONapproximate the shortest power-on time T greatly
mIN-ON.
Fig. 5 B shows as fluorescent lifetime T
dIM-ONthan the shortest power-on time T
mIN-ONtime long, some signal waveforms in Fig. 4.Fig. 5 B and Fig. 5 A something in common, can analogize and learn, be not repeated.Different from Fig. 5 A, fluorescent lifetime T in figure 5b
dIM-ONthan the shortest power-on time T
mIN-ONlong.Therefore, Fig. 5 B does not have the constrained feed time T in Fig. 5 A
pUMP(it starts from fluorescent lifetime T
dIM-ONend and end at the shortest power-on time T
mIN-ONend).In figure 5b, power-on time T
pOWER-ONapproximate greatly fluorescent lifetime T
dIM-ON.
Fig. 6 display is used for producing power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELmethod flow diagram 800, go for the status unit 160 in Fig. 4.
In step 802, dimming state signal DIM
oNwhen being 0, just maintain power supply signal S always
pOWERbe 0 and inhibit signal S
hOLDbe 1, do not power to make stepup transformer 12 and maintain bucking voltage V
cOM.As status signal DIM
oNwhen becoming 1, enter step 804 and 806.
Step 804 makes power supply signal S
pOWERwith inhibit signal S
hOLDbe all 1, make power-on time T
pOWER-ONstart, and maintain bucking voltage V
cOM.And step 806 is maintained power supply signal S instantly
pOWER, inhibit signal S
hOLD, select signal S
sELlogical value, make three at initial time T
sTARTUPinside all can not change.
Step 808 subsequent steps 806, checks power-on time T
pOWER-ONwhether than the shortest power-on time T
mIN-ONlong.If power-on time T
pOWER-ONalso do not exceed power-on time T
mIN-ON, step 810 then checks dimming state signal DIM
oNwhether be 1.T while power is being supplied
pOWER-ONdo not exceed power-on time T
mIN-ON, and dimming state signal DIM
oNwhen being 1, representing and instantly should be positioned at loop time T
lOOPin, so step 812 subsequent steps 810, by power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe set to 1,0,0 respectively.If power-on time T
pOWER-ONdo not exceed power-on time T
mIN-ON, and dimming state signal DIM
oNbut become 0, represent and instantly should be positioned at constrained feed time T
pUMPin, so step 814 subsequent steps 810, by power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe set to 1,0,1 respectively.After step 812 or 814 completes, step 808 continues inspection power-on time T
pOWER-ONwhether than the shortest power-on time T
mIN-ONlong.
Once power-on time T
pOWER-ONthan the shortest power-on time T
mIN-ONlong, step 818 subsequent steps 808, checks dimming state signal DIM
oNwhether be 1.Now, dimming state signal DIM
oNif be still 1, representing at present is still be positioned at loop time T
lOOPin, so step 816 continues, with the same ground of step 812, by power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELbe set to 1,0,0 respectively.T while power is being supplied
pOWER-ONexceed the shortest power-on time T
mIN-ONafter, as long as dimming state signal DIM
oNbe 0, just represent and can get back to fluorescent lifetime T
dIM-ONstate before beginning, so step 820 makes power supply signal S
pOWERbe 0 and inhibit signal S
hOLDbe 1, and enter step 802.
From the instruction of Fig. 6, initial time T
sTARTUPinterior action is reached set by step 804 and 806.Constrained feed time T
pUMPinterior action is reached set by step 814.And loop time T
lOOPinterior action is reached set by step 812 and 816.
Also can learn from the result of Fig. 5 A and Fig. 5 B, the backlight controller 104 in Fig. 3, its power-on time T
pOWER-ONat least the shortest power-on time T
mIN-ON.If fluorescent lifetime T
dIM-ONtoo short, that is except loop time T
lOOPwith initial time T
sTARTUPoutside, backlight controller 104 will add constrained feed time T voluntarily
pUMP, make power-on time T
pOWER-ONequal the shortest power-on time T
mIN-ON, shown in Fig. 5 A.Once fluorescent lifetime T
dIM-ONenough long, make power-on time T
pOWER-ONexceed the shortest power-on time T
mIN-ON, constrained feed time T
pUMPwill disappear and not exist, shown in Fig. 5 B.
Constrained feed time T
pUMPexistence, fluorescent lifetime T can be avoided
dIM-ONtoo short caused flicker problem.Constrained feed time T
pUMPstepup transformer 12 can be forced there is no minimum feedback voltage VFB
mINfeedback information condition under, additionally power blindly.And the electric energy of these Extra Supplies will be accumulated in the output of stepup transformer 12, the fluorescent lifetime T after guaranteeing
dIM-ONin, LED module LED
1~ LED
4there are enough electric energy luminous.
The stepup transformer 12 that allows blindly continues to export electric energy, may make driving voltage V
oUTcontinuous raising.In one embodiment of this invention, the converter control unit 108 in Fig. 3 detects driving voltage V by pin OVP and divider resistance 101 and 103
oUT.Once driving voltage V
oUTtoo high (the protection magnitude of voltage default more than), converter control unit 108 will make control signal S
dRVfor 0 in logic, stop LED module LED
1~ LED
4power supply, to prevent too high driving voltage V
oUTdamage is caused to some electronic components.Now, current control unit 106 is still according to PWM dim signal DIM
pWMcontrol drive current ILED
1~ ILED
4.In other words, in one embodiment, once driving voltage V
oUTtoo high, constrained feed time T
pUMPto not allow to occur; And as driving voltage V
oUTafter dropping to a safety value, constrained feed time T
pUMPcan occur once again, to avoid the problem of glimmering.
In the diagram, as inhibit signal S
hOLDwhen being 1, because for open a way between operation transconductance amplifier 142 and building-out capacitor 23, so select signal S
sELcan be arbitrary value, all can not to bucking voltage V
cOMhave an impact.For example, the initial time T in Fig. 5 A and Fig. 5 B
sTARTUPin, select signal S
sELbeing not limited to 0 in logic, also can be 1 in logic.
In another embodiment, the shortest power-on time T is positioned at when the time
mIN-ONtime interior, the anode of the operation transconductance amplifier 142 in Fig. 4 is not meet 0.4V, but meets 0.8V.Therefore, loop time T
lOOPbe positioned at the shortest power-on time T
mIN-ONinterior part, loop will make minimum feedback voltage VFB
mINapproach toward 0.8V; Loop time T
lOOPbe positioned at the shortest power-on time T
mIN-ONouter part, loop will make minimum feedback voltage VFB
mINapproach toward 0.4V.
In some embodiments of the invention, each power-on time T
pOWER-ONnot the shortest power-on time T must be more than or equal to
mIN-ON.For example, in some embodiments of the present invention, even if fluorescent lifetime T
dIM-ONalso do not arrive the shortest power-on time T
mIN-ON, constrained feed time T
pUMPnot necessarily can add, but can some conditions of additional reference.
Fig. 7 display is used for producing power supply signal S
pOWER, inhibit signal S
hOLD, select signal S
sELother method flow chart 900, also go for the status unit 160 in Fig. 4.Step 902 and 904 is adds additional compared to the method flow diagram 900 in Fig. 6, Fig. 7.Step 902 is connected in step 812, and both are all executed in loop time T
lOOPtime.Step 902 checks minimum feedback voltage VFB
mINwhether be less than 0.4V, and determine record R according to this.If the result that step 902 checks, minimum feedback voltage VFB
mINbe less than 0.4V, this has meaned driving voltage V instantly
oUTdriving LED module LED may be not enough to
1~ LED
4; Otherwise, driving voltage V instantly
oUTalso enough carry out driving LED module LED
1~ LED
4.
Step 904 is connected in step 810, in order to determine whether perform constrained feed time T
pUMPthe step 814 of action.If in step 904, record R points out previous loop time T
lOOPin minimum feedback voltage VFB
mINbe less than 0.4V, step 814 just can perform, and starts constrained feed time T
pUMP, make power-on time T
pOWER-ONextend to the shortest power-on time T
mIN-ON.So, driving voltage V can be eliminated
oUTnot enough problem.Contrary, if in step 904, record R points out previous loop time T
lOOPin minimum feedback voltage VFB
mINbe not less than 0.4V, step 820 continues, and 814 can not perform, power-on time T
pOWER-ONterminate at once.Now, power-on time T
pOWER-ONwill than the shortest power-on time T
mIN-ONshort.
Method flow diagram 900 in Fig. 7 can according to loop time T
lOOPin testing result, decide constrained feed time T
pUMPwhether add.Compared to the method flow 800 in Fig. 6, method flow 900 may obtain the conversion efficiency that higher electric energy turns luminous energy, also may avoid driving voltage V
oUTtoo high event occurs.
Except minimum feedback voltage VFB
mINoutside, also have other signals can be used for identification driving voltage V
oUTwhether enough carry out driving LED module LED
1~ LED
4.For example, at loop time T
lOOPin, if the pin GAT in Fig. 3
1~ GAT
4among have any one, its overtension (more than a preset security value), also can represent driving voltage V instantly
oUTenough do not drive all LED module LED
1~ LED
4.Pin GAT
1~ GAT
4on voltage, namely current controller CD
1~ CD
4the gate terminal control voltage of interior NMOS, NMOS herein can be considered a current controling element.
The foregoing is only the preferred embodiments of the present invention, all equalizations done according to claims of the present invention change and modify, and all should belong to covering scope of the present invention.
Claims (17)
1. a dimming controlling method, includes:
One dimming state signal is provided, when it is first logical value, represents that at least one light-emitting component should be driven to emit light, when it is second logical value, represent that this light-emitting component should not be luminous;
When this dimming state signal is this first logical value, provide a loop, and a power supply changeover device is powered to described light-emitting component, to provide the electric energy needed for this light-emitting component luminescence, and make a signal of this loop be approximately a preset value; And
When this dimming state signal transition is this second logical value, and the fluorescent lifetime that this dimming state signal is positioned at this first logical value be no more than one preset the shortest power-on time time, continue this power supply changeover device is powered to this light-emitting component, be not shorter than this shortest power-on time to make a power-on time of this power supply changeover device.
2. dimming controlling method as claimed in claim 1, wherein, continues this step that this power supply changeover device is powered to this light-emitting component, includes:
This loop is opened a way;
There is provided certain electric current to a building-out capacitor discharge and recharge, to change a bucking voltage of this building-out capacitor; And
According to this bucking voltage, this power supply changeover device is powered to this light-emitting component.
3. dimming controlling method as claimed in claim 1, also includes:
When this dimming state signal transition is this second logical value, and this power-on time exceed this shortest power-on time time, this loop is opened a way, and stops this power supply changeover device to power to this light-emitting component.
4. dimming controlling method as claimed in claim 1, also includes:
Receive a digital dimming signal;
According to this digital dimming signal, produce several passage enable signal, to control several light-emitting component respectively; And
According to described passage enable signal, produce this dimming state signal.
5. dimming controlling method as claimed in claim 1, also includes:
By this digital dimming signal delay, with produce described passage enable signal one of them.
6. dimming controlling method as claimed in claim 1, also includes:
When in the initial time after this dimming state signal transition is this first logical value, this loop is opened a way, and this power supply changeover device is powered to this light-emitting component;
Wherein, this shortest power-on time is shorter than this off-period.
7. dimming controlling method as claimed in claim 6, in this initial time, a bucking voltage of a building-out capacitor roughly remains unchanged.
8. dimming controlling method as claimed in claim 1, also includes:
When this dimming state signal is this first logical value, detects the drive singal driving this light-emitting component, a record is provided according to this;
When this dimming state signal transition is this second logical value, this fluorescent lifetime is no more than this shortest power-on time preset, and when this is recorded as first value, continues this power supply changeover device is powered to this light-emitting component; And
When this dimming state signal transition is this second logical value, this fluorescent lifetime is no more than this shortest power-on time preset, and when this is recorded as second value, stops this power supply changeover device to power to this light-emitting component.
9. dimming controlling method as claimed in claim 8, wherein, this drive singal is represented as a terminal voltage of this light-emitting component.
10. dimming controlling method as claimed in claim 8, wherein, this drive singal is a control voltage of a current controling element.
11. dimming controlling methods as claimed in claim 1, also include:
Detect the driving voltage that this power supply changeover device exports; And
When this driving voltage is more than a preset value, this power supply changeover device is stopped to power to this light-emitting component.
12. dimming controlling methods as claimed in claim 1, wherein, this light-emitting component includes a LED element.
13. dimming controlling methods as claimed in claim 1, wherein, provide this step of this loop, operate in the primary Ioops time; Continue this step that this power supply changeover device is powered to this light-emitting component, operate in the constrained feed time; This constrained feed is pressed for time and is connected to this loop time.
14. 1 kinds of backlight controllers, include:
One current control unit, a dimming state signal is produced according to a PWM dim signal, and control a drive current of at least one light-emitting component, wherein, when this dimming state signal is first logical value, represent that this drive current should not be 0, when this dimming state signal is second logical value, represent that this drive current should be 0; And
One converter control unit, can control a power supply changeover device, makes it power to this light-emitting component;
Wherein, when this dimming state signal is this first logical value, this converter control unit provides a loop, and this power supply changeover device is powered to described light-emitting component, to provide the electric energy needed for this light-emitting component luminescence; And
When this dimming state signal transition is this second logical value, and the fluorescent lifetime that this dimming state signal is positioned at this first logical value be no more than one preset the shortest power-on time time, this converter control unit continues this power supply changeover device is powered to this light-emitting component, is not shorter than this shortest power-on time to make a power-on time of this power supply changeover device.
15. as the backlight controller of claim 14, and wherein, this converter control unit provides this loop, and this backlight controller operates in the primary Ioops time; When this converter control unit continues to make this power supply changeover device power to this light-emitting component, this backlight controller operates in the constrained feed time; This constrained feed is pressed for time and is connected to this loop time.
16. as the backlight controller of claim 15, wherein, in this constrained feed time, this converter control unit provides certain electric current to a building-out capacitor discharge and recharge, to change a bucking voltage of this building-out capacitor, to make this power supply changeover device, this light-emitting component output power is increased.
17. as the backlight controller of claim 15, wherein,
When operating in this loop time, according to the drive singal driving this light-emitting component, this converter control unit provides a record;
When this dimming state signal transition is this second logical value, this fluorescent lifetime is no more than this shortest power-on time preset, and when this is recorded as first value, this converter control unit makes this backlight controller operate in this constrained feed time; And
When this dimming state signal transition is this second logical value, this fluorescent lifetime is no more than this shortest power-on time preset, and when this is recorded as second value, this converter control unit stops this power supply changeover device to power to this light-emitting component.
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|---|---|---|---|
| CN201410076766.8A CN104902610B (en) | 2014-03-04 | 2014-03-04 | Dimming controlling method and related backlight controller |
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|---|---|---|---|
| CN201410076766.8A CN104902610B (en) | 2014-03-04 | 2014-03-04 | Dimming controlling method and related backlight controller |
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| CN102573192B (en) * | 2010-12-16 | 2014-05-21 | 联咏科技股份有限公司 | Protection device of driving voltage of light-emitting diode and driving device |
| CN103068093B (en) * | 2011-10-19 | 2014-12-03 | 通嘉科技股份有限公司 | Control method of light-emitting diode bunch |
| IN2012DE00931A (en) * | 2011-12-28 | 2015-09-04 | 02 Micro Inc |
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