CN1988745A - Led illumination unit, projection display device using the same, and method of operating led illumination unit - Google Patents
Led illumination unit, projection display device using the same, and method of operating led illumination unit Download PDFInfo
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- CN1988745A CN1988745A CNA2006101687153A CN200610168715A CN1988745A CN 1988745 A CN1988745 A CN 1988745A CN A2006101687153 A CNA2006101687153 A CN A2006101687153A CN 200610168715 A CN200610168715 A CN 200610168715A CN 1988745 A CN1988745 A CN 1988745A
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- led
- fluorescent lifetime
- luminescence unit
- lifetime section
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
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- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
- Circuit Arrangement For Electric Light Sources In General (AREA)
Abstract
An LED illumination unit, a projection display device using the LED illumination unit, and a method of operating the LED illumination unit are provided. The LED illumination unit includes a light source with a plurality of LEDs, and a lighting control unit which sequentially turns on the LEDs for lighting time sections which are assigned for each LED in a cyclic time period. The lighting control unit includes a driving signal modulator which generates a modulation signal for turning on at least one of the LEDs with a lighting duty that is shorter than the lighting time section for the at least one of the LEDs. The method includes sequentially turning on a plurality of LEDs of the LED illumination unit for lighting time sections which are assigned for each LED in a cyclic time period. At least one of the LEDs is turned on with a lighting duty that is shorter than its lighting time section.
Description
The application requires the 2005-366324 Japanese patent application submitted in Japanese Department of Intellectual Property on December 20th, 2005 and the priority of the 10-2006-089156 korean patent application submitted in Korea S Department of Intellectual Property on September 14th, 2006, and the open of these two applications all is contained in this by reference.
Technical field
The method that equipment consistent with the present invention and method relate to light-emitting diode (LED) luminescence unit, use the projection display equipment of this LED luminescence unit and operate this LED luminescence unit, more particularly, relate to that display image comes up by light shining display medium (as reflective viewing screen or transmissive viewing screen).
Background technology
In the projection display equipment (as projecting apparatus and rear-projection TV set) of prior art, use LED as light source, and by pulsed illumination method operation LED.
For example, when utilizing the LED projection full-colour image of emission primaries (as red, green and blue), launch redness, green and blue light in turn by time-sharing procedure, and utilize the picture signal corresponding to come red, the green and blue light of ground, space modulation with the light of each color.
In 2005-149132 Japanese Patent Application Publication (Fig. 2 and Fig. 4), the electronic building brick erection unit that is used to pick up and handle the image processing apparatus of image and has this image processing apparatus is disclosed.This image processing apparatus comprises: light source has a plurality of LED; Led drive circuit utilizes the pulse-width modulation method to regulate from the brightness of the light of LED emission.
In addition, in 2005-5112 Japan Patent open (Fig. 1, Fig. 2 and Fig. 3) a kind of led drive circuit is disclosed.Disclosed led drive circuit produces the triangular current signal with skew, and by utilizing current detector and on-off controller to come change frequency to be higher than the current signal of the photoresponse frequency of human eye, operates LED for approximate with constant-current mode.
Yet the method for the visible light led light source of prior art, the projection display equipment that utilizes led light source and operation led light source has following shortcoming.
When LED is luminous, produce heat simultaneously, the light output of LED that this heat drop is low.Therefore, when LED work provided high brightness luminescent for a long time, the luminous efficiency of LED was along with the time reduces, and the life-span of LED also reduces.
For example, in redness, green and the light source of blue led assembling, because versicolor LED produces thermal impact each other, so the reduction of easier generation brightness with the generation white light.In addition, redness, green and blue led have different hot propertys according to their color.Therefore, red, green has different brightness and life-span with blue led.Therefore, for steady operation, be difficult to regulate brightness and the driving time of LED.
In order to address these problems, can regulate the brightness of LED according to the 2005-149132 Japanese Patent Application Publication.Yet disclosed pulse-width modulation method is designed for and utilizes the light source captured image in this is open.In disclosed pulse-width modulation method, the brightness of measurement target utilizes the result who measures to produce pulse-width signal, to obtain the exposure energy of expectation.
For going up the LED luminescence unit that forms image by ruddiness, green glow and blue light sequentially being shone display medium (as reflective viewing screen or transmissive viewing screen), transmit required exposure energy by pulse-width modulation, the time cycle of sequential illumination ruddiness, green glow and blue light comprises time-out interval.Because time-out interval, the frequency that light color changes reduces, and causes the problem relevant with image quality, increases as flicker.
In addition, even relate to the relevant 2005-5112 Japanese Patent Application Publication suggestion of led drive circuit with the luminescent device that is used for automobile or traffic lights when driving current signal is square wave, the frequency that is higher than the photoresponse frequency of human eye by utilization is modulated driving current signal and also can be similar to constant current-mode and come driving LED.Yet the disclosure does not have openly or is proposed to be used in the led drive circuit and the method for the reduction of the brightness that reduces LED.
Summary of the invention
Exemplary embodiment of the present invention has overcome above shortcoming and above other shortcoming of not describing.In addition, the present invention does not need to overcome above-mentioned shortcoming, and exemplary embodiment of the present invention can overcome above-mentioned any problem.
The invention provides a kind of LED luminescence unit, when LED is opened in proper order light shining when being used on display medium display image on the display medium, the brightness by the visible light LED that reduces to be caused by the thermal conductance that LED produces reduces the LED luminescence unit that can be operated reliably.The present invention also provides a kind of method of using the projection display equipment of this LED luminescence unit and operating this LED luminescence unit.
According to an aspect of the present invention, provide a kind of LED luminescence unit, described LED luminescence unit comprises: light source comprises a plurality of LED; Luminous controling unit, for in cycle circulation timei to the fluorescent lifetime section of each LED appointment, sequentially open LED, wherein, described luminous controling unit comprises the drive signal modulator, and the drive signal modulator produces with at least one the luminous duty of fluorescent lifetime section that is shorter than LED and opens described at least one modulation signal among the described LED.
According to a further aspect in the invention, provide a kind of projection display equipment that uses described LED luminescence unit.
According to a further aspect in the invention, a kind of method of the LED of operation luminescence unit is provided, described method comprise in cycle circulation timei to the fluorescent lifetime section of each LED appointment, sequentially open a plurality of LED of described LED luminescence unit, wherein, with the luminous duty that is shorter than described fluorescent lifetime section open described LED described at least one.
According to the present invention, at least one among the visible light LED is opened with the luminous duty of width less than the fluorescent lifetime section.Therefore, compare with other LED that opens with 100% duty ratio in the fluorescent lifetime section, it is hot less that this LED produces.In addition, when LED closes, in the time-out interval of fluorescent lifetime section, can discharge heat from LED easily.Therefore, can reduce the temperature of light source.
The term duty ratio is illustrated in the interior fluorescent lifetime of fluorescent lifetime section of appointment and the ratio of whole fluorescent lifetime section.The waveform of modulation signal is not limited to rectangular wave.
In this case,, can regulate LED although close LED for the time-out interval in the fluorescent lifetime section, thus brightness and width at intermittence by changing the LED in the fluorescent lifetime section of appointment, and human eye can't be perceived LED and close.In persistence of vision, stimulating end back light stimulus to keep.Therefore, the people perceives LED and is opened with display image continuously.
For example, open in the LED luminescence unit of LED with the projection display equipment of demonstration full-colour image in order, at the appointed time sequential transmission ruddiness, green glow and blue light in Duan the fluorescent lifetime section.The setting-up time cycle, thus in this time cycle, human eye is perceived redness, green and blue blend color.Therefore, when the intensity level of suitable setting LED, human eye can not be perceived the intermittent time section less than the fluorescent lifetime section.
In addition, increased difference between the intensity level of the physics integrated value of brightness of LED and the LED that human eye is perceived in the enough little gap between intermittence.Compare with the physics integrated value of the brightness of LED, it is brighter that LED seems.
Can set the fluorescent lifetime section, thereby duty ratio is the integrated value of 100% modulation signal less than duty ratio less than the integrated value of 100% modulation signal.In this case, because be that 100% situation is compared with duty ratio, the heat that LED produces reduces, and reduces so can more effectively prevent the brightness of LED.
Description of drawings
In conjunction with the drawings exemplary embodiment of the present invention is described in detail, above-mentioned and other aspects of the present invention will become apparent, wherein:
Fig. 1 illustrates the schematic diagram that has used according to the projection display equipment of the LED luminescence unit of exemplary embodiment of the present invention;
Fig. 2 is the functional block diagram that is illustrated in the structure of the luminescence unit of describing among Fig. 1 of LED according to an exemplary embodiment of the present invention;
Fig. 3 is the curve chart that the modulation signal of a plurality of LED that are used for the luminescence unit of LED according to an exemplary embodiment of the present invention described at Fig. 1 is shown;
Fig. 4 is the curve chart that is illustrated in the detailed waveform patterns of the modulation signal of describing among Fig. 3, and described modulation signal is by the drive signal modulator generation of LED luminescence unit according to an exemplary embodiment of the present invention;
Fig. 5 is the curve chart that illustrates as the response of the human eye photic stimuli of the function of time;
Fig. 6 is the curve chart that the reduction of LED brightness is shown;
Fig. 7 shows the curve chart of the waveform patterns of the modulation signal that the drive signal modulator by LED luminescence unit according to an exemplary embodiment of the present invention produces;
Fig. 8 is the curve chart that the waveform patterns of the modulation signal that the drive signal modulator by LED luminescence unit according to an exemplary embodiment of the present invention produces is shown.
Embodiment
Describe the present invention more completely now with reference to accompanying drawing, exemplary embodiment of the present invention illustrates in the accompanying drawings.Label identical in the accompanying drawing is represented components identical, therefore will omit description of them.
LED and the projection display equipment that uses this LED according to an exemplary embodiment of the present invention will be described now.
Fig. 1 illustrates to have used the schematic diagram of the projection display equipment 1 of LED luminescence unit 2 according to an exemplary embodiment of the present invention.Fig. 2 illustrates the functional block diagram of LED luminescence unit 2 according to an exemplary embodiment of the present invention.Fig. 3 shows and is used for the curve chart of the modulation signal of a plurality of LED of LED luminescence unit 2 according to an exemplary embodiment of the present invention.Fig. 4 is the curve chart that is illustrated in the detailed waveform patterns of the modulation signal of describing among Fig. 3, and this modulation signal is by the drive signal modulator generation of LED luminescence unit 2 according to an exemplary embodiment of the present invention.
Input utilizes LED luminescence unit 2 that full-colour image is projected on the reflective viewing screen 6 to projection display equipment 1 according to picture signal.
Projection display equipment 1 comprises LED luminescence unit 2, collector lens 3, spatial modulator 4, projecting lens 5 and controller 10, whole operations of controller 10 control projection display equipments 1.
In order to show full-colour image, LED luminescence unit 2 sequentially produces corresponding to the light of the different wave length of three primary colors (as red, green and blue) at least by time-sharing procedure.
To describe the structure of LED luminescence unit 2 now in detail.
See figures.1.and.2, LED luminescence unit 2 comprises light source 22, led drive circuit 21, current detector 23, drive signal modulator 24 and power circuit 20, and 20 pairs of light sources 22 of power circuit provide power.
Led drive circuit 21, current detector 23 and drive signal modulator 24 are used to the Luminous clock signal according to controller 10, and LED 22R, 22G and 22B are sequentially opened their fluorescent lifetimes separately in each cycle circulation timei.Led drive circuit 21, current detector 23 and drive signal modulator 24 are formed luminous controling unit 70.
The Luminous clock signal is the signal that obtains the LED luminous sequential that order is opened in each cycle circulation timei.Luminous signal can have frequency range same as the prior art, as 180Hz to 360Hz.In current exemplary embodiment, luminous fundamental frequency f
0Be 240Hz.
For driving LED 22R, 22G and 22B individually, led drive circuit 21 is according to from the modulation signal transitions of drive signal modulator 24 electric current from power circuit 21.
In the exemplary embodiment shown in Fig. 3, by luminous fundamental frequency f
0The period T of determining
0, as T
0=1/f
0=t
4-t
1, produce modulation signal 30R, 30G and 30B by the order time-sharing procedure, with driving LED 22R, 22G and 22B.For example, at fluorescent lifetime section T
R(t
1-t
2), T
G(t
2-t
3) and T
B(t
3-t
4), wherein, t
1＜t
2＜t
3＜t
4, launch the light of red wavelength, the light of green wavelength and the light of blue wavelength respectively.
Thermal characteristics according to LED 22R, 22G and 22B can be determined fluorescent lifetime section T individually
R, T
GAnd T
BWidth.In this exemplary embodiment, because LED 22G and 22B have essentially identical thermal characteristics, and LED 22R has the thermal characteristics of relative mistake, so with fluorescent lifetime section T
R, T
GAnd T
BBe set as follows: T
R/ T
0=0.2 (20%), T
G/ T
0=0.4 (40%), T
B/ T
0=0.4 (40%).
In the luminescent method of prior art, LED 22R, 22G and 22B are at fluorescent lifetime section T
R, T
G, and T
BDuty ratio with 100% is opened.In the luminous pulse-width modulation method that is used for of prior art because in the fluorescent lifetime section of appointment, carry out with 100% duty ratio luminous, so be respectively T with the duty ratio of LED 22R, 22G and 22B
R/ T
0, T
G/ T
0And T
B/ T
0Mode with respect to fundamental frequency f
0Determine fluorescent lifetime section T
R, T
GAnd T
BIn addition, determine to be applied to the drive current that is used for modulation signal 30R, 30G and 30B of LED 22R, 22G and 22B, on reflective viewing screen 6, to obtain the optical energy density of expectation according to duty ratio.
Yet in the exemplary embodiment shown in Fig. 3 and Fig. 4, modulation signal 30R, 30G or 30B are in period of time T
0Appointment fluorescent lifetime section T
R, T
GOr T
BInterior burst frequency f
bBe higher than luminous fundamental frequency f
0Pulse-width signal.In Fig. 4, t
SAnd t
EThe fluorescent lifetime section T of expression appointment
R, T
GOr T
BStarting point and end point.
Can according in order to obtain because the frequency f that happens suddenly is suitably selected in the experiment that the relation between the intrinsic brilliance that LED brightness reduction that heat causes and human eye discover that produces is carried out
bAnd duty ratio.Specifically, can from high frequency, select the burst frequency f
bThereby, at the fluorescent lifetime section T of appointment
R, T
GOr T
BIn can produce at least two pulses.
For example, pulse-width modulation can be set at as follows: f
b=20 * f
0, T
b(pulse period)=1/f
b, duty ratio=50%.
In this case, be that 100% situation is compared with using duty ratio, be used for the required power of driving LED 22R, 22G and 22B and reduce half.
In addition, modulation signal 30R, 30G or 30B can have the peak value identical with the pulse-width signal of prior art.For example, (30G, peak drive current 30B) can be 1.5A to be used for modulation signal 30R.
Now the function of LED luminescence unit 2 will be described with respect to the operation of projection display equipment 1.
Fig. 5 is the curve chart that illustrates as the response of the human eye photic stimuli of the function of time.Fig. 6 is the curve chart of reduction that the brightness of LED is shown.
When the controller 10 of projection display equipment 1 received the redness, green of color separated and blue image signal, controller 10 sent to LED luminescence unit 2 with clock signal.
The drive signal modulator 24 of LED luminescence unit 2 produces modulation signal 30R, 30G and 30B then, and they are sent to led drive circuit 21.The drive current corresponding with modulation signal 30R, 30G and 30B can be supplied to LED 22R, 22G and the 22B of light source 22 subsequently.Therefore, according to the waveform patterns of modulation signal 30R, 30G and 30B, can operate LED 22R, 22G and 22B individually.
Can be focused on the spatial modulator 4 by coalescence by collector lens 3 from ruddiness, green glow and the blue light of 2 emissions of LED luminescence unit.In order to show the image of redness, green and blue color separated, spatial modulator 4 spatial modulation ruddiness, green glow and blue light.Being projected lens 5 at the image of the color separated that shows on the spatial modulator 4 amplifies and is projected on the reflective viewing screen 6.Because the image of color separated is merged in people's eyes, so people can see full-colour image from the light of the color of the order of reflective viewing screen 6 reflections.
In pulse-width modulation of the present invention, in the fluorescent lifetime section identical, with less than 100% duty ratio modulation pulsewidth with fluorescent lifetime section in the pulse-width modulation of prior art.Yet, although the duty ratio in the fluorescent lifetime section less than 100%, can be used LED luminescence unit 2, and the problem that does not reduce about brightness.For the reason of this point, will make an explanation now.
In this exemplary embodiment, because duty ratio is 50%, so from the amount of the light of light source 22 emissions amount less than the light of when duty ratio is 100%, launching.Therefore, when using light source 22 as the light source of printer (in this printer, light source is used to scan the photoconductor with specific light sensitivity), scanning can reduce along with the reduction of duty ratio.
Yet, for by LED luminescence unit with radiation of visible light display image on the display medium (as reflective viewing screen or transmissive viewing screen), when operating the LED luminescence unit in a predetermined manner, people's eyes can not be perceived the lowering of luminance of the image that the reduction by the optical output power of LED luminescence unit causes.
When people's eyes received light stimulus, after light stimulus finished, the people perceived light stimulus and continues for some time.This just is called persistence of vision.With reference to Fig. 5, see having intensity I when eyes
iLight pulse the time, the consciousness intensity I of light pulse
vAlong with the time weakens.Consciousness intensity curve 100 little by little reduces subsequently more sharp.
Because this persistence of vision, ruddiness, green glow and the blue light that can perceive the order radiation are as white light.The frequency compounding that the light of different colours can use with projecting apparatus in such a way.Yet, too not big different of the consciousness intensity of light and actual luminous intensity.From when changing red, green and blue fluorescent lifetime section, destroyed the situation of white balance, or the situation for the emit white light ruddiness of radiation simultaneously, green glow and blue light is appreciated that to increase the consciousness intensity of image behind order radiation ruddiness, green glow and blue light.
With reference to Fig. 4, when the burst frequency f
b(1/T
b) increase to fundamental frequency f
0(1/T
0) when above, because persistence of vision, at fluorescent lifetime section T
R, T
GOr T
BIn, human eye more is difficult to perceive discrete light pulse.As a result, compare with the amount of the light of launching from light source 22, image can be shown brightlyer. Produce modulation signal 30R, 30G and 30B based on this fact.
In addition, according to exemplary embodiment of the present invention, owing to can reduce from the amount of the light of light source 22 emission, thus can reduce the heat that produces by light source 22, thus can reduce about because the problem that the brightness of the light source 22 that the thermal conductance that produces causes reduces.This will carry out more detailed description in the back.
Fig. 6 shows owing to produce thermal conductance and causes the curve chart that LED brightness reduces.In Fig. 6, trunnion axis is represented fluorescent lifetime (t), and vertical axis is represented brightness (P).
When LED launched light continuously and receives constant drive current simultaneously, owing to produce heat, the temperature of LED raise.Therefore, LED-based temperature characterisitic, the brightness P of LED is from original brightness P
iReduce, shown in the brightness curve among Fig. 6 101.Then, when the temperature of LED reached poised state, the brightness P of LED was near steady state value.
For example, be opened from 0 to t as LED
10Interval when long, the brightness P of LED reduces Δ P
10When LED is opened from z to t
20Interval when long, wherein, t
10＜t
20, the brightness P of LED reduces Δ P
20In addition, owing to the heat that produces along with fluorescent lifetime increases, so be opened from 0 to t as LED
10Short time at interval ratio be opened from 0 to t
20The long heat that produces at interval the time few.Therefore, when total fluorescent lifetime equated, the brightness of LED reduced still less under the situation of high-frequency pulsed width modulation.Therefore, by using high-frequency pulsed width modulation can carry out luminous effectively.
This advantage is particularly important for the projection display equipment (as projecting apparatus and projection TV) of the very bright illumination light of needs.
As mentioned above, according to exemplary embodiment of the present invention, the pulse-width modulation modulation signal, therefore in given fluorescent lifetime section, modulation signal has the duty ratio less than 100%, and the burst frequency f
bBe higher than basic glow frequency f significantly
0Therefore,, reduce from the amount of the light of light source 22 emission although when comparing with the pulse duration modulation method of prior art because the after image effect, the amount of the light that can discover keep and the pulse-width modulation of prior art basic identical.In addition, can reduce the reduction of heat that produces by light source 22 and the brightness of the light source 22 that causes in large quantities.Therefore, can stably use LED 22R, 22G and the 22B of light source 22.
According to exemplary embodiment of the present invention, in LED luminescence unit 2, by above-mentioned pulse duration modulation method, drive signal modulator 24 produces at least one the modulation signal that is used for LED 22R, 22G and 22B, thereby can operate LED in given fluorescent lifetime section according to pulse-width signal.
In addition, can be simply the width of light pulse by regulating the modulation signal that changes duty ratio prevent or reduce the reduction of the brightness of LED.
Now exemplary embodiment according to the present invention is described by the LED luminescence unit.
Fig. 7 is the curve chart that the waveform patterns of the modulation signal that the drive signal modulator 240 by LED luminescence unit 200 according to an exemplary embodiment of the present invention produces is shown.
Except LED luminescence unit 200 comprised drive signal modulator 240, the LED luminescence unit 200 of present embodiment had and LED luminescence unit 2 identical construction shown in Fig. 2.
The drive signal modulator 240 of LED luminescence unit 200 produces modulation signal 40R, 40G or 40B, and described modulation signal 40R, 40G or 40B are different with above-mentioned modulation signal 30R, 30G or 30B.
Fluorescent lifetime section T in the time cycle
R, T
GOr T
BIn produce modulation signal 40R, 40G or 40B in the identical mode shown in the embodiment of Fig. 3.
With reference to Fig. 7, waveform patterns is the power modulation waveform patterns, and this pattern has signal level from I
p(from t
1To t
2) change to I
0(t
2To t
3) stairstepping.Fluorescent lifetime section T
R, T
GOr T
B=t
4-t
1, wherein, t
1＜t
2＜t
3＜t
4, and I
p＞I
0
The experimental result of the relation between can changing based on the consciousness brightness that brightness reduction and human eye are shown is set peak I
pWith luminous duty t
2-t
1And t
3-t
2In order to prevent to reduce the life-span of LED 22R, 22G and 22B, come peak limiting I with the amplitude and the boundary of duration of the drive current of LED 22R, 22G and 22B
p
Suppose I
p=2I
0, (t
2-t
1)=(1/3) (t
4-t
1) and (t
3-t
1)=(2/3) (t
4-t
1), the function of modulation signal 40R, 40G or 40B will be described now.
With reference to Fig. 7, in the fluorescent lifetime section of appointment, by the step pulse 100 of above-mentioned setting appointment can make the heat that produces by LED 22R, 22G and 22B with have signal level I
0The heat that produces with the modulation square pulse 41 of 100% duty ratio is identical.
Because modulation signal 40R, the 40G of present embodiment or 40B have peak I p when beginning, so from t
1To t
2The time interval in, brightness curve 104 is reduced to point (b) with the form of the curve shown in Fig. 6 101 from maximum point (a).Then, from t
2To t
3Next time interval in, it approximately is peak I that the level of modulation signal 40R, 40G or 40B drops to
pHalf value I
0Therefore, the heat that LED produces reduces by half, from t
2To t
3Time interval brightness curve 104 change to point (c) not from t from point (b)
1To t
2To change ground steep the time interval.At point (c), brightness is P
1From t
3To t
4The time interval in, LED closes.Yet human eye can not be perceived LED and close.Therefore, brightness P
1Keep a little while.
For modulation square pulse 41, because the level of pulse 41 keeps constant value I
0, this is worth I
0It is peak I
pHalf, so brightness curve 105 is in point (e) beginning of half height of the height with point (a), at time interval t
1To t
4In, dropping to brightness with the form of the curve shown in Fig. 6 101 is P
2(P
2＜P
1) point (f).
Although for the step pulse 100 and the square pulse 41 of this exemplary embodiment, the total heat that LED produces is identical, and than square pulse 41, it is much smaller that the brightness of LED reduces ground for step pulse 100.In addition, because persistence of vision, when replacing square pulses 41 driving LED with step pulse 100, human eye is perceived much bright from the LED emission.
Although for step pulse 100 and square pulse 41, the heat that LED produces is identical, and trapezoidal pulse 100 can reduce the heat that LED produces, as the peak I by regulating impulse 100
pWith time point t
2And t
3
As mentioned above, in this exemplary embodiment, among LED 22R, 22G and the 22B at least one, the drive signal modulator 240 of LED luminescence unit 200 is at fluorescent lifetime section T
R, T
GOr T
BInitial part produce and to have peak I
pPower modulation signal 40R, 40G or 40B.
When the heat of gathering is low, at time period T
R, T
GOr T
BInitial part, the light that LED emission has high-high brightness, thus improve the luminous efficiency of LED.Therefore, can high brightness operation LED.
In addition, in this exemplary embodiment, the level of power modulation signal 40R, 40G or 40B has peak value when beginning, and reduces along with the time is dull then.
In this case, the heat that LED produces is dull to be reduced, thereby the brightness that can reduce LED effectively reduces.
Here, the term dullness is used to represent that sensu lato dullness reduces, and comprises that staged reduces.
Another exemplary embodiment of the present invention will be described now.
Fig. 8 is the curve chart that the waveform patterns of the modulation signal that is produced by the drive signal modulator according to the LED luminescence unit of another exemplary embodiment of the present invention is shown.
The drive signal modulator produces modulation signal 50R, 50G or 50B, rather than modulation signal 40R, 40G or 40B.
The experimental result of the relation between can changing according to the consciousness brightness that brightness reduction and human eye are shown is set I
q, I
rWith time interval t
1To t
5In order to prevent to reduce the life-span of LED 22R, 22G and 22B, come peak limiting I with the amplitude and the boundary of duration of the drive current of LED 22R, 22G and 22B
q
Heat that produces according to LED 22R, 22G and 22B and the interference between LED 22R, 22G and the 22B, the modulation signal that can use this exemplary embodiment for all LED or at least one LED of LED 22R, 22G and 22B.In the fluorescent lifetime section of appointment, can recently operate a LED or some LED that produces a spot of heat among LED 22R, 22G and the 22B and reduce the reduction of brightness with 100% duty.
In addition, although the LED of three visible emitting is arranged in the above-described embodiments, the quantity of LED also can be 2, four or more a plurality of.For example, can use two red LED, two green LED and two blue leds.In addition, a plurality of LED can be set separately, rather than be assembled into single light source.
In addition, although at fixed time the section T
0, LED is sequentially opened, but at the appointed time the section T
0, two or more LED can be opened simultaneously.For example, can open red LED, green LED and blue led simultaneously, to improve apparent brightness.
And projection display equipment can utilize transmissive viewing screen rather than reflective viewing screen to come display image.For example, projection display equipment can be to use the rear-projection TV set of transmissive viewing screen.
In addition, although used the LED luminescence unit in projection display equipment, the LED luminescence unit also can be used for other with the device of light radiation to the display medium (for example, reflective viewing screen or transmissive viewing screen), as light-emitting device or projecting apparatus.
Within the scope of the invention, the assembly of projection display equipment and LED luminescence unit can be used for different structures.
As mentioned above, for the method for LED luminescence unit, the projection display equipment that uses the LED luminescence unit and operation LED luminescence unit, at least one LED in the LED luminescence unit recently operates with the duty less than 100% in its fluorescent lifetime section.Therefore, reduced the fever time of LED.In addition, in idle time period, LED can discharge the heat of generation.Therefore, can reduce because the brightness that the thermal conductance that LED produces causes reduces, thus the reliability of raising LED luminescence unit.
Although illustrate and described the present invention particularly with reference to exemplary embodiment of the present invention, but will be understood by those skilled in the art that, under the situation that does not break away from the spirit and scope of the present invention that limit by claim and legal equivalents thereof, can make various modifications in form and details.
Claims (12)
1, a kind of LED luminescence unit comprises:
Light source comprises a plurality of LED;
Luminous controling unit, in cycle circulation timei to the fluorescent lifetime section of each LED appointment, sequentially open LED,
Wherein, described luminous controling unit comprises the drive signal modulator, and described drive signal modulator produces with at least one the luminous duty of fluorescent lifetime section that is shorter than LED and opens described at least one modulation signal among the described LED.
2, LED luminescence unit according to claim 1, wherein, described drive signal modulator produces described at least one the described modulation signal be used for opening described LED in described fluorescent lifetime section by pulse-width modulation.
3, LED luminescence unit according to claim 2, wherein, the predetermined frequency of described drive signal modulator utilization is carried out described pulse-width modulation, thereby produces at least two pulses in described fluorescent lifetime section.
4, LED luminescence unit according to claim 1, wherein, at the first half sections of described fluorescent lifetime section, described modulation signal has peak value, described drive signal modulator by power modulation in described fluorescent lifetime section, open described LED described at least one.
5, LED luminescence unit according to claim 4, wherein, described modulation signal has described peak value at the starting point place of described fluorescent lifetime section.
6, LED luminescence unit according to claim 5, wherein, described modulation signal has the dull in time waveform patterns that reduces.
7, LED luminescence unit according to claim 5, wherein, described modulation signal has the waveform patterns that the mode with ladder reduces in time.
It is 8, a kind of that described projection display equipment comprises the LED luminescence unit by light shining the projection display equipment that comes display image on the screen with the size of amplifying,
Wherein, described LED luminescence unit comprises:
Light source comprises a plurality of LED;
Luminous controling unit, in cycle circulation timei to the fluorescent lifetime section of each LED appointment, sequentially open LED,
Wherein, described luminous controling unit comprises the drive signal modulator, and described drive signal modulator produces with at least one the luminous duty of fluorescent lifetime section that is shorter than LED and opens described at least one modulation signal among the described LED.
9, projection display equipment according to claim 8, wherein, described drive signal modulator produces described at least one the described modulation signal be used for opening described LED in described fluorescent lifetime section by pulse-width modulation.
10, projection display equipment according to claim 8, wherein, at the first half sections of described fluorescent lifetime section, described modulation signal has peak value, described drive signal modulator by power modulation in described fluorescent lifetime section, open described LED described at least one.
11, projection display equipment according to claim 10, wherein, described modulation signal has described peak value and the dull in time waveform patterns that reduces at the starting point place of described fluorescent lifetime section.
12, a kind of method of operating the LED luminescence unit, described method comprise in cycle circulation timei to the fluorescent lifetime section of each LED appointment, sequentially open a plurality of LED of described LED luminescence unit,
Wherein, with at least one the luminous duty of fluorescent lifetime section that is shorter than described LED open described LED described at least one.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2005366324A JP2007171364A (en) | 2005-12-20 | 2005-12-20 | Visible light led light source apparatus, image projection system using the same, and method of driving visible light led |
| JP2005366324 | 2005-12-20 | ||
| KR1020060089156 | 2006-09-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1988745A true CN1988745A (en) | 2007-06-27 |
Family
ID=38185334
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2006101687153A Pending CN1988745A (en) | 2005-12-20 | 2006-12-19 | Led illumination unit, projection display device using the same, and method of operating led illumination unit |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP2007171364A (en) |
| KR (1) | KR100788700B1 (en) |
| CN (1) | CN1988745A (en) |
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Also Published As
| Publication number | Publication date |
|---|---|
| KR20070065777A (en) | 2007-06-25 |
| JP2007171364A (en) | 2007-07-05 |
| KR100788700B1 (en) | 2007-12-26 |
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