CN101614592A - A detection method of chip junction temperature in LED lighting fixtures - Google Patents

Abstract

Translated fromChinese

本发明公开了一种检测LED照明灯具中芯片结温的方法。本发明是根据LED材料禁带宽度随温度的变化规律来确定LED灯具中LED芯片结温，包括三个步骤：①通很低占空比的脉冲电压，直接获得LED芯片在此温度下的发光峰位；②正常工作条件下，测量LED灯具发光峰位，对比从中得出发光峰位的漂移量即两者之差，利用波长的漂移量定出两者的温度差异；③由于①是在很低脉冲电压下测量，温度就等于室温，室温加上两者的温度差异判断在此条件下LED灯具中LED芯片的温度。本发明可在±0.6度的误差范围内表征在不同条件下LED照明灯具中LED芯片的实际温度，有利于LED灯具的性能表征和优化研究。

The invention discloses a method for detecting the chip junction temperature in an LED lighting fixture. The present invention determines the junction temperature of the LED chip in the LED lamp according to the change law of the band gap of the LED material with temperature, including three steps: ① Passing a pulse voltage with a very low duty ratio to directly obtain the luminescence of the LED chip at this temperature Peak position; ②Under normal working conditions, measure the luminous peak position of LED lamps, compare the drift amount of the luminous peak position, that is, the difference between the two, and use the wavelength drift to determine the temperature difference between the two; ③Because ① is in Measured under very low pulse voltage, the temperature is equal to the room temperature, and the room temperature plus the temperature difference between the two can determine the temperature of the LED chip in the LED lamp under this condition. The invention can characterize the actual temperature of the LED chip in the LED lighting fixture under different conditions within the error range of ±0.6 degrees, and is beneficial to the performance characterization and optimization research of the LED lighting fixture.

Description

A kind of detection method of LED lighting chips junction temperature

Technical field

The present invention relates to the detection technique of semiconductor light-emitting-diode (LED), be meant a kind of detection method of LED lighting chips junction temperature especially.

Background technology

The electricity-saving lamp group is an international trend, and China is taking its place in the front ranks of the world with LED electricity-saving lamp application facet, is exactly concentrated reflection on Beijing Olympic, and can further be able to further development on Shanghai World's Fair.In the field of this high speed development, effective detection technique for the led chip junction temperature in the important technology parameter-LED light fixture of decision LED electricity-saving lamp group reliability has not caught up with far away, but this technology is again the necessary guarantee that the LED electricity-saving lamp obtains quick application development.

LED utilizes the solid semiconductor chip as luminescent material, and when two ends add forward voltage, the charge carrier in the semiconductor takes place compound and causes that photo emissions produces visible light.Use the semiconductor pn light principle of binding up one's hair and make LED and come out, successfully developed white light LEDs by Japanese Nichia company (day inferior) in 1996 in early 1960s.LED is with its intrinsic characteristics, and characteristics such as, cold light source fast as power saving, life-span length, vibration resistance, response speed are widely used in fields such as pilot lamp, signal lamp, display screen, Landscape Lighting; In our daily life also everywhere as seen, as household electrical appliance, telephone set, Dashboard illumination, automobile anti-fog lamp, traffic lights etc.In recent years, along with people's deepening continuously to semiconductive luminescent materials research, the development and application of the continuous progress of LED manufacturing process and new material (element nitride crystal and fluorescent powder), versicolor ultra-high brightness LED has been obtained breakthrough, and its luminescence efficiency has improved nearly 1000 times.Yet to make really that such LED illumination can widespread use, its reliability is extremely important, the key that determines its reliability is the junction temperature of pn knot, particularly forms the gordian technique place that becomes the integrity problem that must solve in the LED illumination application project that obtains of junction temperature state after the LED lighting lamp group.

Junction temperature is the key element of reliability measurement during LED device engineering is used as the important parameter of weighing a LED device performance quality, also is the major product in the LED testing product.Can be used for the research in LED light fixture reliability and serviceable life to the measurement of junction temperature, therefore, the junction temperature of accurately measuring semiconductor light-emitting-diode has important and practical meanings.Up till now for this reason, the product of all kinds of detection junction temperatures both domestic and external is to utilize electrical properties, thermal property, luminosity and colorimetry character to measure junction temperature mostly.At present, the method for measuring the LED junction temperature has following several usually: 1, and forward voltage method: utilize the temperature effect of LED electronic transport, under the condition of steady current, obtain the linear relationship of forward voltage and junction temperature; 2, pin method: be the pin temperature of utilizing LED, try to achieve junction temperature by dissipated power and thermal resistivity; 3, blue Bai Bifa: being a kind of non-contacting measuring method, is to utilize in the white light LEDs electroluminescent spectrum power ratio of blue light and white light to measure junction temperature; 4, the infrared photography method: be the method that the measurement junction temperature used always distributes, but its cost height, speed is slow, and device is the state that does not encapsulate or break a seal.Yet these methods all are the measurements that is confined to single tube LED device, for detections tens of and even hundreds of the series-parallel LED lamp of single tube groups, because the complicacy of crosstalking mutually and bringing that forms on the electricity makes that all electrical methods are difficult to use; And infrared method is because after the encapsulation, the led chip in the light fixture is exposed no longer simply outside, and the packed material of the infrared ray that gives off on the chip stops for this reason, makes infrared non-contact measurement method lose efficacy; The blue Bai Bifa of spectroscopy is best suited for the light fixture measurement, but the best result that its precision is reported on document only is ± 2 degree, and need the priori of product, the mobile meeting of blue light emitting wavelength causes the very big of measured value to be moved, the calibration problem in the measuring method of giving has been brought very big difficulty, is difficult to practical application for this reason.We vary with temperature the junction temperature that rule is determined led chip in the LED light fixture with LED material energy gap, present this method only can arrive junction temperature the precision of error greater than 10 degree surely, mainly be to be hampered by from luminescent spectrum to determine that interface material energy gap error is bigger, also do not have effective method to be accurate to the precision that the junction temperature of chip in the LED lighting is measured in 1 degree so far.Use under the increasing situation in LED lighting engineering, in order to investigate the light fixture reliability, more and more needing can high-precision measurement LED lighting chips junction temperature.

Summary of the invention

Purpose of the present invention is exactly to propose a kind of detection method that can reach high-precision LED lighting chips junction temperature.

The present invention judges the junction temperature of chip in the LED light fixture under the normal operating conditions according to moving of its luminous peak position.

Concrete technical scheme of the present invention is as follows:

1, at first for accurately the determining of the glow peak peak position of energy gap, mainly be to get rid of from the influence of the fluorescence of fluorescent powder to glow peak.Need to select suitable glow peak wavelength band to determine peak position for this reason.The method of Cai Yonging is for this reason: A, the light fixture spectrum that the junction temperature of light fixture is stabilized in some temperature takes multiple measurements (as more than 10 times), obtains 10 above spectroscopic datas.B is a central point with the peak position value on the data, constantly expands to both sides, investigates the peak position dispersion of coming out according to the data segment match after expanding, and the expanding data of getting the dispersion minimum is measured the spectrum segment of usefulness for the junction temperature of this light fixture.C, the definite of last spectrum peak position obtained with the linear fitting that mixes of Gaussian lineshape by Lorentzian lineshape, makes definite precision of peak position reach the highest in data extract.As shown in Figure 1: be the spectrogram of light fixture when 45 spend, circle is an experimental point, and solid line is for fitting curve, can see fitting curve and experimental point coincide good.

2, detection system as shown in Figure 3: the LED light fixture is connected to the program control stabilized voltage supply of EDM Generator of Adjustable Duty Ratio, and voltage source is regulated its dutycycle by serial ports by computer control and made the LED lamp luminescence; The another side of computing machine is controlled spectrometer by USB interface, and the light that the LED light fixture is sent out introduces spectrometer through the optical fiber coupling.This system can detect the luminous of LED light fixture more conveniently like this.

3, during measurement, at first (recurrence interval is more than the 10ms under the pulse power effect of low-repetition-frequency and low duty ratio, the energising dutycycle is less than 5%), the peak value of pulse current size during with the light fixture operate as normal DC current values identical, the time of the rising edge of pulse will be controlled in the pulse width 5%, uses above-mentioned the 1st point methods and draw luminous peak position λ accurately from the luminous spectrum of LED light fixture₁

4, change power supply it is operated under the dc state, record the LED lamp luminescence spectrum of this moment after stablizing, use above-mentioned the 1st point methods and make luminous peak position λ accurately₂

5, by λ₂With λ₁Difference Δ λ, make the junction temperature discrepancy delta T under pulse and direct supply drive.Determine that the concrete formula that junction temperature T is adopted is:

(T-T₀)＝cΔλ+dΔλ²

c＝27.8±0.2，d＝-1.22±0.08

The light fixture junction temperature is exactly room temperature T because above-mentioned the 3rd the middle pulse power drives down₀Thereby the junction temperature T that can draw under the light fixture duty is T₀+ Δ T.

The present invention has following advantage:

1, this method has overcome conventional electrical method and infrared photography method and has determined deficiency in the junction temperature, interconnective circuit is irrelevant between each single tube of this method and light fixture, also irrelevant to the encapsulation state of LED single tube with light fixture, be suitable for the light fixture product that different types of light fixture product and different manufacturers are originated for this reason.

2, this method has overcome the demarcation difficulty that blue light emitting wave length shift that the blue white ratio method of optics causes for quantum structure difference in the led chip brings, the quantum structure parameter is how to get irrelevant among this method and the LED, because each tame producer can constantly optimize various parameters in the LED quantum structure in order to optimize the LED performance, can form influence for the white ratio method of existing indigo plant like this.But this method is not influenced by this.

3, this method has overcome the big deficiency of conventional definite LED glow peak bit error, can be more accurately fixed the peak position of spectrum, make definite precision improvement to 1 degree of junction temperature, and satisfy light fixture and carry out reliability and detect desired junction temperature measurement precision.

Description of drawings

Fig. 1: 45 degree junction temperature spectrograms, solid line is for fitting curve, and circle is an experimental point.

Fig. 2: 45 degree peak position partial enlarged drawings, and the peak position partial enlarged drawing under other four junction temperature temperature spots are followed successively by 45 degree, 60 degree, 75 degree, 90 degree and 105 degree from left to right.Can clearly see along with junction temperature rises the continuous red shift of curve (long wavelength's direction).

Fig. 3: detection system synoptic diagram.

Fig. 4: the measured value after light fixture is stable, illustration is the spectrum of LED light fixture, the trigonometric sum round spot is respectively the junction temperature that same light fixture is measured under two kinds of thermal environments.

Embodiment

The present invention is described in further detail below by embodiment and accompanying drawing.

1, tested LED light fixture energized is luminous, 100 watts of LED light fixture rated power, 32 ~ 34 volts of rated voltages adopt the power supply of 33V voltage of voltage regulation source in this example, and the voltage source dutycycle is 1% and two kinds of patterns of direct current.By optical fiber the light fixture issued light is directly guided to spectrometer inside.The application of spectral instrument can obtain the spectrum of LED light fixture shown in Fig. 4 illustration, very close with 1% with the spectrum that obtains of two kinds of direct currents power supply power modes, yet the spectrum peak in about 450 nanometers has very little moving, this amount of movement is owing to junction temperature difference under two kinds of powering modes causes that the present invention will determine this amount of movement accurately.

2, (recurrence interval is 10ms under the pulse power effect of low-repetition-frequency and low duty ratio, energising dutycycle 1%), the peak value of pulse current size during with the light fixture operate as normal DC current values be all 2.7 amperes mutually, the time 0.5ms of the rising edge of pulse, the 1st point methods of application technology scheme, under this pulse power duty, after having measured 10 spectrum, selected by calculating that about 20 nano spectral scopes are to determine the best band of peak position around the peak position, from the luminous spectrum of LED light fixture, drawn luminous peak position λ for this reason accurately₁, and write down temperature T this moment₀

3, changing power supply is operated under the dc state (100% dutycycle) it, record the LED lamp luminescence spectrum of this moment after stable, the 1st point methods of application technology scheme, under this direct supply duty, after having measured 10 spectrum, selected by calculating that about 20 nano spectral scopes are to determine the best band of peak position around the peak position, made luminous peak position λ for this reason accurately₂

4, by λ₂With λ₁Difference Δ λ, application of formula:

(T-T₀)＝cΔλ+dΔλ²

c＝27.8±0.2，d＝-1.22±0.08

Make the junction temperature discrepancy delta T under pulse and direct supply driving.The light fixture junction temperature is exactly room temperature T and the pulse power drives down₀Thereby, can draw the junction temperature T under the light fixture duty₀+ Δ T.

5, after working 20 minutes under normal direct supply drives for light fixture the size of junction temperature shown in Fig. 4 intermediate cam point and round dot, their distinguish correspondence with background room temperature T₀The junction temperature discrepancy delta T=14.8K of=300K and Δ T=12.7K, their junction temperature is respectively T like this₀+ Δ T=314.8K and T₀+ Δ T=312.7K, the difference of the two is because light fixture is in the different heat dissipation environments.Their error can see from its fluctuation in time, and its fluctuation has reached the purpose that high precision is determined junction temperature in the light fixture in ± 0.6 degree.

Aforesaid embodiment is only in order to illustrate technological thought of the present invention and characteristics; its purpose is to make those of ordinary skill in the art can understand content of the present invention and implements according to this; the scope of this patent also not only is confined to above-mentioned specific embodiment; be all equal variation or modifications of doing according to disclosed spirit, still be encompassed in protection scope of the present invention.

Claims (2)

1. method of measuring led chip junction temperature in the LED light fixture is characterized in that concrete steps are as follows:

A. make LED luminous tested LED light fixture energized, the light fixture issued light is directly guided to spectrometer inside by optical fiber;

B. at first under the pulse power effect of low-repetition-frequency and low duty ratio, the peak value of pulse current size during with the light fixture operate as normal DC current values identical, the time of the rising edge of pulse will be controlled in the pulse width 5%, determines luminous peak position λ₁

C. change power supply it is operated under the dc state, record the LED lamp luminescence spectrum of this moment after stablizing, determine luminous peak position λ₂

D. by λ₂With λ₁Difference Δ λ, make the junction temperature discrepancy delta T under pulse and direct supply drive.The light fixture junction temperature is exactly operating ambient temperature T and the pulse power drives down₀, room temperature normally, thus can draw junction temperature T under the light fixture duty₀+ Δ T.

2. a kind of method of measuring led chip junction temperature in the LED light fixture according to claim 1 is characterized in that: determine luminous peak position λ among described step B and the C₁, λ₂Method may further comprise the steps:

(1) the light fixture spectrum that the junction temperature of light fixture is stabilized in some temperature takes multiple measurements (as more than 10 times), obtains 10 above spectroscopic datas;

(2) be central point with the peak position value on the data, constantly expand to both sides, investigate the peak position dispersion of coming out according to the data segment match after expanding, the expanding data of getting the dispersion minimum is measured the spectrum segment of usefulness for the junction temperature of this light fixture;

(3) the definite of last spectrum peak position obtained with the linear fitting that mixes of Gaussian lineshape by Lorentzian lineshape, makes definite precision of peak position reach the highest in data extract.

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