CN102854446B - Method for detecting service life of LED (light emitting diode) device, detection circuit and application thereof - Google Patents
Method for detecting service life of LED (light emitting diode) device, detection circuit and application thereof Download PDFInfo
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Abstract
The invention provides a method for detecting service life of an LED (light emitting diode) device. The method comprises the following steps of: establishing a curve diagram of a luminous flux change trend of the LED device under normal work current and a curve diagram of a voltage change trend of the LED device under test current, and obtaining a linear relationship between the two curve diagrams; providing aging current for the tested LED device, and switching to the test current when the time is aging time; detecting and recording voltage values at two ends of the tested LED device; switching the test current to the aging current again, and repeatedly detecting in different time points; providing multiple current to repeatedly detect; drawing the curve diagram of the voltage change trend of the LED device according to the detected voltage values; and deducing the curve diagram of the luminous flux change trend of the tested LED device, and evaluating the service life of the tested LED device. According to the invention, the detection period is short, the labor cost is saved; the affect of human factors on the aging detection result in the detection process is reduced, and the detection accuracy is improved.
Description
Technical field
The present invention relates to LED technology field, a kind ofly specifically adopt the method in electric parameters testing LED component life-span and the application of testing circuit and this testing circuit.
Background technology
LED (Light Emitting Diode) is a kind of solid-state semiconductor device, can convert electrical energy into luminous energy.Have that power consumption is little, spotlight effect good, reaction velocity is fast, controllability is strong, can bear the advantages such as high impact forces, long service life, environmental protection.LED just progressively substitutes conventional light source, becomes forth generation light source.
The production of LED component and research and development, the assessment in its serviceable life is one inevitable operation in actual production process.At present, the LED life test carried out in industry, with time m-luminous flux be changed to Primary Reference index.Namely, in specific environmental test chamber, lasting or interval passes into aging current (i.e. LED product running current to LED product, be generally 20mA ~ 1000mA), along with passage of time, the luminous flux of LED product can decline gradually, when the luminous flux of LED product drop to initial value 70% corresponding to time, be defined as the life-span of LED product.Because the theoretical life-span of LED product is very long, complete real-time measurement cannot be applied aborning; Therefore, also work out the scheme of some accelerating lifetime testing in industry, if North America illumination association is for the method for testing standard of LED product: LM80 and TM-21, infer LED product serviceable life by the LED product light flux variations of 3000 ~ 6000 hours.Detection time is longer, and up to the present, the testing scheme in all LED product life-spans is all can only to detect the optical parametric such as luminous flux or brightness as Appreciation gist.
Summary of the invention
In view of the problem and blemish of prior art, a wherein object of the present invention is to provide a kind of LED component life detecting method.
Another order of the present invention is to provide a kind of LED component life tests circuit
An also order of the present invention is the application providing a kind of LED component life tests circuit.
In order to achieve the above object, present invention employs following technical scheme:
A kind of LED component life detecting method, comprises the following steps:
A, set up the light flux variations trend of LED component under running current and the LED component curve map in the change in voltage trend of measuring current, draw the light flux variations trend of LED component under running current and the LED component linear relationship in the change in voltage trend of measuring current according to this curve map;
B, provide an aging current to tested LED component, make tested LED component continue to light aging; When digestion time arrives, aging current is switched to measuring current; Now, detect and record the magnitude of voltage at tested LED component two ends, completing once aging-test period; Then, measuring current is switched to aging current again, repeat above-mentioned detection action at different time points;
C, provide the measuring current of multiple different current value to repeat above-mentioned b step, corresponding detection also records the magnitude of voltage at tested LED component two ends;
The magnitude of voltage that d, basis detect draws the curve map of tested LED component in the change in voltage trend of measuring current;
E, derive the curve map of the light flux variations trend of tested LED component in the linear relationship of the change in voltage trend of measuring current according to the light flux variations trend of LED component under running current and LED component, the suite line chart mated the most with change in voltage trend and light flux variations trend is for foundation, by the luminous flux of corresponding time point compared with the initial luminous flux of tested LED component, evaluate the life-span of tested LED component.
As the preferred technical solution of the present invention: the light flux variations trend of described LED component under running current and LED component are expressed as in the linear relationship of the change in voltage trend of measuring current: Φ=k
2ln (t)+b, V=k
1ln (t)+a; Wherein, k
2=k
1.
As the preferred technical solution of the present invention: described measuring current is current density≤31A/m
2corresponding current value.
A kind of LED component life tests circuit, comprises LED component burn in test circuit, and described LED component aging current input end is also in parallel is provided with measuring current input end, is provided with switching between this aging current input end and this measuring current input end.
As the preferred technical solution of the present invention: the measuring current of described measuring current input end input is current density≤31A/m
2corresponding current value
As the preferred technical solution of the present invention: described switch is the electronic switch that can automatically switch.
Above-mentioned testing circuit is applied to LED illumination lamp, the current input terminal parallel connection of this LED illumination lamp be provided with measuring current input end, be provided with switching between the current input terminal of LED illumination lamp and this measuring current input end.
Compared with prior art, sense cycle of the present invention is short, saves labour turnover, and reduces the impact of human factor on aging test result in testing process, increases the degree of accuracy of LED component life tests.
Accompanying drawing explanation
Fig. 1 is the light flux variations trend of LED component under running current set up and the LED component curve map in the change in voltage trend of measuring current.
Fig. 2 is the test philosophy figure of LED sample in the embodiment of the present invention.
Fig. 3 is the change in voltage trend curve figure that in the embodiment of the present invention, LED sample is set up under the measuring current of 0.002mA and the light flux variations trend curve figure derived.
Fig. 4 is the change in voltage trend curve figure that in the embodiment of the present invention, LED sample is set up under the measuring current of 0.0008mA and the light flux variations trend curve figure derived.
Fig. 5 is the change in voltage trend curve figure that in the embodiment of the present invention, LED sample is set up under the measuring current of 0.0002mA and the light flux variations trend curve figure derived.
Fig. 6 is applied to the schematic diagram of LED illumination lamp for test circuit in the present invention.
Embodiment
Refer to Fig. 1, for the light flux variations trend of LED component under running current set up and LED component are at the curve map of the change in voltage trend of measuring current.
Described " light flux variations trend " is that LED component is under running current, the optical parameter of different time points test, the running current of middle low power LED component is generally 10 ~ 150mA, and the running current of high power LED device is generally 300 ~ 1500mA.
Described measuring current is " minimum electric current ", and under " minimum electric current " refers to chip size, current density is less than 31A/m
2corresponding current value, the ratio of current density and LED electrical current and LED chip size.Be of a size of 27milx11mil(1mil=25.4um with length and width) chip calculate, the electric current that described " minimum electric current " is current value≤6 μ A.
According to LED component under running current, the optical parameter of different time points and LED component are under " minimum electric current ", and the voltage data of different time points, sets up the curve map as Fig. 1; In diagram, LED component has identical variation tendency at the voltage change curve of " minimum electric current " and the luminous flax curve of LED component under running current, and under time logarithmic coordinate, both linear relationship is approximate to be respectively expressed as: V=k
1ln (t)+a, Φ=k
2ln (t)+b; Wherein, V is LED component when passing into " minimum electric current ", and the magnitude of voltage at its two ends, Φ is the luminous flux of LED component under running current, k
1for representing slope, the k of the straight line (being positioned at the straight line of below in diagram) of voltage linear
2for representing the slope of the straight line (being positioned at the straight line of top in diagram) that luminous flux is linear, a, b are respectively coordinate and indulge intercept, and ln (t) is logarithmic time (corresponding testing time).In diagram, the straight line gradient that the straight line of expression voltage linear is linear with representing luminous flux is approximate consistent, therefore, and k
1with k
2approximately equal.
LED component, after passing into " minimum electric current ", obtains corresponding k according to the change of logarithmic time (or testing time), magnitude of voltage
1value; Due to k
1be approximately equal to k
2, substitute into Φ=k
2ln (t)+b, namely the luminous flux of corresponding time point can be estimated, by the luminous flux of corresponding time point compared with the initial luminous flux of LED component, just can evaluate the life-span (luminous flux of LED product drops to the time corresponding to 70% of initial value, is defined as the life-span of LED product) of LED component.
Referring to Fig. 2, is the test philosophy figure of tested LED sample.
In burn in test circuit, the parallel connection of LED component aging current input end a measuring current input end is set, and between aging current input end and measuring current input end, add the electronic switch K that can automatically change, first electronic switch K connects aging circuit, there is provided Iburn in(aging current, i.e. the running current of LED component) make LED continue to light aging; When digestion time arrives, electronic switch K will automatically switch to test circuit, and provide Itest(measuring current, i.e. minimum electric current) to LED; Wherein, Itest≤6 μ A; Now, detect and record the magnitude of voltage at LED two ends.So far once aging-test period terminates.Then, measuring current is switched to aging current again, repeat above-mentioned detection action at different time points.
Above-mentioned test action need adopt the measuring current repeated test of multiple different current value, to set up the change in voltage trend curve figure of LED sample under each measuring current, derive the curve map of light flux variations trend, thus find out the suite line chart that change in voltage trend mates the most with light flux variations trend.
Referring to following list, is the corresponding different I test(measuring current of this LED sample (length and width are of a size of 27milx11mil)), the VF(forward voltage of different test duration) value:
The curve map of tested LED component in the change in voltage trend of measuring current is drawn according to the magnitude of voltage detected.
Then, according to the light flux variations trend of LED component under running current and the LED component linear relationship (V=k in the change in voltage trend of measuring current
1ln (t)+a, Φ=k
2ln (t)+b; k
1=k
2) derive the curve map of the light flux variations trend of tested LED component, the suite line chart mated the most with change in voltage trend and light flux variations trend is for foundation, by the luminous flux of corresponding time point compared with the initial luminous flux of tested LED component, evaluate the life-span of tested LED component.
Wherein, when measuring current is more than 0.006mA, the curve map of change in voltage trend mates not obvious with the curve map of light flux variations trend.
Refer to Fig. 3 to Fig. 5, be respectively the change in voltage trend curve figure that test sample is set up under the measuring current of 0.002mA, 0.0008mA, 0.0002mA and the light flux variations trend curve figure derived.Point in Fig. 3 to Fig. 5 in ellipse is not match point, and when measuring current is 0.0008mA, the curve map of change in voltage trend only has with the curve map of light flux variations trend and does not mate, and other point all meets light flux variations trend under running current of LED component that Fig. 1 expresses and the LED component linear relationship in the change in voltage trend of measuring current.
The luminous flux parameter testing list of sample:
Above-mentioned data are luminous flux data that test sample adopts classic method test, and compared with the luminous flux data in Fig. 5, both conform at the luminous flux data of test.
Refer to Fig. 6, it is very important that LED illumination lamp maintains stable light output, at the current input terminal of a LED illumination lamp measuring current input end in parallel, switched between current input terminal and this measuring current input end by Automatic Electronic Switch K; When LED illumination lamp works, timing adds Itest(measuring current, wherein Itest≤6 μ A) test out magnitude of voltage corresponding to different time points, draw change in voltage trend curve, again by the relation of voltage and luminous flux, infer optical attenuation degree, then regulate Iop(point light current), make luminous flux maintain a definite value, thus make the light output of LED illumination lamp relatively stable.
The foregoing is only preferred embodiment of the present invention, be not used for limiting practical range of the present invention; Every equivalence change of doing according to the present invention and amendment, all cover by the scope of claims of the present invention.
Claims (3)
1. a LED component life detecting method, is characterized in that, comprises the following steps:
A, set up the light flux variations trend of LED component under running current and the LED component curve map in the change in voltage trend of measuring current, draw the light flux variations trend of LED component under running current and the LED component linear relationship in the change in voltage trend of measuring current according to this curve map;
B, provide an aging current to tested LED component, make tested LED component continue to light aging; When digestion time arrives, aging current is switched to measuring current; Now, detect and record the magnitude of voltage at tested LED component two ends, completing once aging-test period; Then, measuring current is switched to aging current again, repeat above-mentioned detection action at different time points;
C, provide the measuring current of multiple different current value to repeat above-mentioned b step, corresponding detection also records the magnitude of voltage at tested LED component two ends;
The magnitude of voltage that d, basis detect draws the curve map of tested LED component in the change in voltage trend of measuring current;
E, derive the curve map of the light flux variations trend of tested LED component in the linear relationship of the change in voltage trend of measuring current according to the light flux variations trend of LED component under running current and LED component, the suite line chart mated the most with change in voltage trend and light flux variations trend is for foundation, by the luminous flux of corresponding time point compared with the initial luminous flux of tested LED component, evaluate the life-span of tested LED component.
2. LED component life detecting method according to claim 1, is characterized in that: the light flux variations trend of described LED component under running current and LED component are expressed as in the linear relationship of the change in voltage trend of measuring current: Φ=k
2ln (t)+b, V=k
1ln (t)+a; Wherein, k
1for the straight slope of voltage linear, k
2for the straight slope that luminous flux is linear, k
2=k
1, a, b are respectively coordinate and indulge intercept.
3. LED component life detecting method according to claim 1, is characterized in that: described measuring current is current density≤31A/m
2corresponding current value.
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| CN104391237A (en) * | 2014-11-26 | 2015-03-04 | 电子科技大学中山学院 | LED (light-emitting diode) chip life quick estimation method |
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| DE102015105914B3 (en) * | 2015-04-17 | 2016-08-11 | Siteco Beleuchtungstechnik Gmbh | Method and device for determining a life expectancy information of an LED module |
| CN105004981B (en) * | 2015-07-30 | 2018-08-17 | 电子科技大学中山学院 | L ED chip life acceleration estimation method |
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| CN109946581A (en) * | 2019-04-14 | 2019-06-28 | 苏州科技大学 | A kind of LED test automatic control system |
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