CN101577998A - Method and device for controlling light-emitting diode luminance feedback - Google Patents
Method and device for controlling light-emitting diode luminance feedback Download PDFInfo
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- CN101577998A CN101577998A CNA2008100913917A CN200810091391A CN101577998A CN 101577998 A CN101577998 A CN 101577998A CN A2008100913917 A CNA2008100913917 A CN A2008100913917A CN 200810091391 A CN200810091391 A CN 200810091391A CN 101577998 A CN101577998 A CN 101577998A
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Abstract
The invention discloses a method and a device for controlling light-emitting diode luminance feedback. The junction temperature of a light-emitting diode is detected by reverse saturation current generated when the light-emitting diode is reversely biased; and then, luminance is compensated to the light-emitting diode according to a relation between the junction temperature and the luminance of the light-emitting diode. Therefore, the invention has the advantages of low cost, high reaction speed, dynamic adjustment, and the like and is greatly beneficial to the mass production of the application of the light-emitting diode.
Description
Technical field
The present invention relates to a kind of led technology, relate in particular to a kind of light-emitting diode luminance feedback and device thereof as backlight sources of display device.
Background technology
Flourish along with scientific and technological industry, the application of light-emitting diode changes the illumination functions that can be used as the lamp source into from simple indication purposes.And because brightness and the efficient of LED effectively promote, the replacement rate that makes LED be applied to Backlight For Liquid Crystal Display Panels also significantly promotes.
Yet LED is under the environment of high temperature, or temperature can significantly improve after using a period of time for a long time, and can influence the characteristic of high-brightness LED this moment, causes the shortcoming of the brightness decline, luminous efficiency reduction, luminescent lifetime shortening etc. of LED.In addition, because of the RGB luminance delay amount difference in the LCD, under the situation of brightness decline friction speed, can cause LCD that uneven phenomenon is arranged in the performance of color, even influence presenting of whole color.
At the problems referred to above, there are several schemes can improve LED at present in problem that backlight suffered from.A kind of is to utilize the colourama sensing element to be arranged on around the panel, utilizes the colourama sensing element to detect the retardation of light, produces the magnitude of current that feedback signal is controlled LED more in view of the above, and then reaches the effect of control LED brightness; Yet the cost of this kind mode is higher, and the retardation that detects light is the retardation of integral display, in case when display is multizone control, this Photosensing Units position arrangement optically is set is very difficult.Another kind of mode then is to utilize the variation of the feedback voltage of LED (Vf), infers the knot surface temperature of LED, and then is converted into the retardation of light, produces feedback signal control LED brightness again; So because of electric current can make also drift thereupon of feedback voltage with the temperature drift, rather unstable, and situation about changing for LED grouping (bin) control because of Vf also can change if only use very little grouping, is a burden greatly to the cost of whole LED backlight module.Another kind of mode then is to utilize the ambient temperature of thermal sensing element testing LED, calculates the light delay amount again, and then produces feedback signal control LED brightness; But this mode is than inaccuracy, and feedback still need wait until the time that heat is transmitted, and is a big shortcoming on reaction speed.
In view of this, the present invention proposes a kind of light-emitting diode luminance feedback and device thereof, to improve this above-mentioned shortcoming.
Summary of the invention
Main purpose of the present invention provides a kind of light-emitting diode luminance feedback and device thereof, it utilizes reverse current to decide the knot surface temperature, with the brightness of compensation adjustment LED in view of the above, so can solve the problem of existing cost problem, LED grouping control problem and reaction time length etc.
Another object of the present invention provides a kind of light-emitting diode luminance feedback and device thereof, and it need not utilize any sensing element, so can effectively reduce cost; And the fast advantage of reaction speed simultaneously is very helpful for the production of the various application of LED.
Another object of the present invention provides a kind of light-emitting diode luminance feedback and device thereof, and it can dynamically adjust the blanking time of detecting reverse current according to LED-backlit module user mode or temperature, with the brightness of dynamic compensation LED.
For achieving the above object, one embodiment of the present invention proposes a kind of light-emitting diode luminance feedback, it controls at least one light-emitting diode, and the method provides the reverse biased of moment to light-emitting diode earlier, and detects the reverse saturation current of this light-emitting diode when reverse biased; Calculate the knot surface temperature of light-emitting diode again according to this reverse saturation current; Utilize the relation of setting up in advance of knot surface temperature and light-emitting diode luminance at last, light-emitting diode is carried out luminance compensation.
On the other hand, the present invention also provides a kind of light-emitting diode luminance feed back control system, mainly be to utilize power-supply unit to provide working bias voltage or reverse biased, and utilize diverter switch to select to switch this working bias voltage or reverse biased and give light-emitting diode to light-emitting diode; When power-supply unit was supplied the reverse biased of moment, current detecting unit detected light-emitting diode and puts the reverse saturation current that produces at this moment; Other has control unit to control the action of all elements, and control unit calculates the knot surface temperature of light-emitting diode earlier according to reverse saturation current, according to the relation between this knot surface temperature and the light-emitting diode luminance, directly light-emitting diode is carried out luminance compensation again.
Beneath by specific embodiment and explanation in detail in conjunction with the accompanying drawings, when the effect that is easier to understand purpose of the present invention, technology contents, characteristics and is reached.
Description of drawings
Fig. 1 is the current/voltage operating characteristic of general PN diode;
Fig. 2 is a device circuit schematic diagram of the present invention;
Fig. 3 is the schematic flow sheet of method of the present invention;
Fig. 4 is the schematic diagram that concerns of knot surface temperature of the present invention and brightness.
Embodiment
The present invention utilizes the reverse saturation current of PN junction face to calculate light-emitting diodes duct ligation surface temperature, and then produces a kind of technology of feedback.
With regard to general PN diode, the different light-emitting diodes that same wafer or same process are made, its forward current can be because of different voltage or currents combination difference to some extent, but the performance of its reverse saturation current then has consistency, and its reason can be explained from the ideal diode equation formula shown in following:
Saturation current density
Wherein, D
pRepresent hole diffusion coefficient; D
nRepresent electron diffusion coefficient; P
NoRepresent the density of minority carrier hole when heat balance; N
PoRepresent the density of minority carrier electronics when heat balance; L
pBe represented as hole-diffusion length; And L
nRepresent electron diffusion length.
By aforesaid equation as can be known, curtage changes, and still can not change reverse saturation current, but the voltage-current characteristic of diode can change in time, and as shown in Figure 1, knot surface temperature Ta is less than Tb, and its voltage-current characteristic as shown in the figure; With regard to reverse saturation current, knot surface temperature Tb reverse saturation current down will be that the pass of its simplification is greatly than the reverse saturation current Ta under: tie the every rising 10 of surface temperature spend reverse saturation current then will become original two times greatly.Also because such characteristic of semiconductor is arranged, add that the luminosity of LED and knot surface temperature have confidential relation, so the present invention can utilize this characteristic to come that brightness compensates to LED.
Fig. 2 is a device circuit schematic diagram of the present invention, and as shown in the figure, light-emitting diode luminance feed back control system 10 comprises at least one or a plurality of light-emitting diode 12, and it is to send light source with as Backlight For Liquid Crystal Display Panels; Power-supply unit 14 is used to provide can be for the working bias voltage of element operate as normal or the reverse biased of moment, and having diverter switch 16 to connect each this light-emitting diode 12 and power-supply unit 14, working bias voltage that is provided with Switching power feeding unit 14 or reverse biased are to light-emitting diode; Switch to moment during reverse biased in diverter switch 16, current detecting unit 18 detects the reverse saturation current that light-emitting diodes 12 produce when reverse biased; Other has control unit 20 to be electrically connected with light-emitting diode 12, power-supply unit 14, diverter switch 16 and current detecting unit 18 formation, be used to control the action of above-mentioned each element and carry out various computings, wherein, this control unit 20 calculates the knot surface temperature of light-emitting diode 12 earlier according to the variable quantity of reverse saturation current, according to the relation of the brightness of tying surface temperature and light-emitting diode 12, light-emitting diode 12 is carried out luminance compensation again.
After device 10 frameworks of the present invention have been described, continue simultaneously and the whole feedback that light-emitting diode luminance feed back control system 10 carries out to be described in conjunction with Fig. 2 and flow chart shown in Figure 3, as shown in the figure, method of the present invention includes the following step in regular turn: at first, shown in step S10, the current switching that utilizes diverter switch 16 that power-supply unit 14 is supplied is the reverse biased pattern; Then shown in step S12, the reverse biased that moment is provided by power-supply unit 14 is to light-emitting diode 12; Shown in step S14, current detecting unit 18 detects the reverse saturation current that each light-emitting diode 12 is produced on the time point of this reverse biased afterwards; Reverse saturation current will become original two times because the every rising 10 of knot surface temperature is spent then, thus can be shown in step S16, and control unit 20 can calculate the knot surface temperature of light-emitting diode 12 according to the variable quantity of reverse saturation current; As at last shown in step S18, control unit 20 according to the relation of the brightness of tying surface temperature and light-emitting diode 12, carries out luminance compensation to light-emitting diode 12 again.
Wherein, control unit 20 can establish the relation function formula of knot surface temperature and light-emitting diode 12 brightness in advance or concern the table of comparisons, and therefore its relation can get the light-emitting diode luminance that knot surface temperature is at this moment corresponded to reference to shown in Figure 4, compensates again.In addition, control unit 20 also can be set the time of this reverse saturation current of change detection of diverter switch 16, if light-emitting diode 12 uses frequent and cause temperature to raise, then the time interval can be shortened, and makes its number of times that can increase luminance compensation, and vice versa.
For general light-emitting diode, under the situation of reverse biased Vr=5V, its reverse saturation current Ir is about about 50 μ A that (but this numerical value may change because the LED production method is different, but the order of magnitude is about 50 μ A haply), after the long-time use of light-emitting diode, when the present invention measures reverse saturation current I ' after the temperature change, can calculate present knot surface temperature Δ T by following formula:
Wherein, every rising 10 degree of knot surface temperature, reverse saturation current will double.
The present invention utilizes reverse current to decide the knot surface temperature, with the brightness of compensation adjustment LED in view of the above, no matter which kind of distribution the voltage (Vf) of light-emitting diode is grouped in, reverse saturation current all can not change with the characteristic that the knot surface temperature changes, and therefore can solve existing Vf and be grouped in the difficulty of being brought in the method for Vf variation prediction knot surface temperature; The specific heat sensing element is quite a lot of soon again on the reaction speed, utilize the LED self character, need not utilize any sensing element, cost is cheap again, so can solve long etc. problem of existing cost problem, LED grouping control problem and reaction time, be very helpful for the production of the various application of LED.In addition, the present invention also can with the brightness of dynamic compensation LED, have more elasticity according to using LED dynamically to adjust the blanking time of detecting reverse saturation current as the user mode or the ambient temperature of backlight module in the use.
Above-described embodiment only is for technological thought of the present invention and characteristics are described, its purpose makes those skilled in the art can understand content of the present invention and is implementing according to this, when can not with qualification interest field of the present invention, promptly all equalizations of doing according to spirit disclosed in this invention change or modify, and must be encompassed in the interest field of the present invention.
Claims (13)
1, a kind of light-emitting diode luminance feedback is used to control at least one light-emitting diode, comprises the following steps:
The reverse biased of moment is provided;
Detect the reverse saturation current of described light-emitting diode when described reverse biased;
Calculate the knot surface temperature of described light-emitting diode according to described reverse saturation current; And
According to the brightness relationship of described knot surface temperature and described light-emitting diode, described light-emitting diode is carried out luminance compensation.
2, light-emitting diode luminance feedback as claimed in claim 1, wherein said reverse saturation current utilizes the current detecting unit detection to obtain.
3, light-emitting diode luminance feedback as claimed in claim 1, every rising 10 degree of wherein said knot surface temperature, then described reverse saturation current will become original two times.
4, light-emitting diode luminance feedback as claimed in claim 1, the pass of the brightness of wherein said knot surface temperature and described light-emitting diode are the relation function formula of setting up in advance or concern the table of comparisons.
5, light-emitting diode luminance feedback as claimed in claim 1 wherein before the step of the reverse biased that described moment is provided, comprises that also Switching power is the step of reverse biased.
6, light-emitting diode luminance feedback as claimed in claim 1, wherein said light-emitting diode are two when above, and it carries out above steps separately.
7, light-emitting diode luminance feedback as claimed in claim 1, wherein said light-emitting diode is as Backlight For Liquid Crystal Display Panels.
8, a kind of light-emitting diode luminance feed back control system is used to control at least one light-emitting diode, and described light-emitting diode luminance feed back control system comprises:
Power-supply unit, it provides working bias voltage or reverse biased;
Diverter switch connects described light-emitting diode and described power-supply unit, provides described working bias voltage or described reverse biased to described light-emitting diode to switch described power-supply unit;
Current detecting unit, it detects the reverse saturation current of described light-emitting diode when described reverse biased; And
Control unit, control above-mentioned each element action, described control unit calculates the knot surface temperature of described light-emitting diode earlier according to described reverse saturation current, according to the brightness relationship of described knot surface temperature and described light-emitting diode, described light-emitting diode is carried out luminance compensation again.
9, light-emitting diode luminance feed back control system as claimed in claim 8, every rising 10 degree of wherein said knot surface temperature, then described reverse saturation current will become original two times.
10, light-emitting diode luminance feed back control system as claimed in claim 8, the pass of the brightness of wherein said knot surface temperature and described light-emitting diode are the relation function formula of setting up in advance or concern the table of comparisons.
11, light-emitting diode luminance feed back control system as claimed in claim 8, wherein said light-emitting diode is two when above, and described control unit is controlled each described light-emitting diode respectively and carried out described reverse saturation current separately and detect and described luminance compensation.
12, light-emitting diode luminance feed back control system as claimed in claim 8, wherein said control unit also can be set the time of the described reverse saturation current of change detection of described diverter switch.
13, light-emitting diode luminance feed back control system as claimed in claim 8, wherein said light-emitting diode is a Backlight For Liquid Crystal Display Panels.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008100913917A CN101577998A (en) | 2008-05-08 | 2008-05-08 | Method and device for controlling light-emitting diode luminance feedback |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2008100913917A CN101577998A (en) | 2008-05-08 | 2008-05-08 | Method and device for controlling light-emitting diode luminance feedback |
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| CN101577998A true CN101577998A (en) | 2009-11-11 |
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| CNA2008100913917A Pending CN101577998A (en) | 2008-05-08 | 2008-05-08 | Method and device for controlling light-emitting diode luminance feedback |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103139993A (en) * | 2013-02-26 | 2013-06-05 | 广东工业大学 | Light emitting diode (LED) luminance regulating device and regulating method based on LED self-sensing detection |
| CN103970961A (en) * | 2014-05-23 | 2014-08-06 | 重庆大学 | Temperature sensor-free LED junction temperature predicting and controlling method |
-
2008
- 2008-05-08 CN CNA2008100913917A patent/CN101577998A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103139993A (en) * | 2013-02-26 | 2013-06-05 | 广东工业大学 | Light emitting diode (LED) luminance regulating device and regulating method based on LED self-sensing detection |
| CN103139993B (en) * | 2013-02-26 | 2017-02-08 | 广东工业大学 | Light emitting diode (LED) luminance regulating device and regulating method based on LED self-sensing detection |
| CN103970961A (en) * | 2014-05-23 | 2014-08-06 | 重庆大学 | Temperature sensor-free LED junction temperature predicting and controlling method |
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