LED knowledge
LED lighting parameters
14-01-22
LED is a photoelectric device manipulation of compound material PN junction. It has a PN node electrical nature of junction devices: I-V, C-V nature nature and nature: optical spectral response nature, luminous intensity to nature, nature and the thermal nature of time.
1, LED electrical nature
Follow the primary parameters of preparing 1.1I-V nature characterization of LED chip PN node system. LED I-V nature is nonlinear, rectifying nature: single guide electric, namely low contact resistance with positive bias that, contrary to the high contact resistance.
(1) positive dead: (Figure OA or OA 'section) a against V0 off voltage, when V
(2) the positive quest: current IF and applied voltage exponential does
IF=IS (eqVF/KT – 1) -------------------------IS for the reverse saturation current.
V>0, V>VF positive task area IF with VF index rose IF=ISeqVF/KT
(3): V<0 PN junction reverse deadband and reverse bias
V=-VR, reverse leakage current IR (V=-5V), GaP 0V, GaN 10uA.
(4) V<-VR reverse breakdown, VR called reverse breakdown voltage; voltage corresponding to the IR VR to reverse leakage current. When the reverse bias is constantly increase to V<-VR, then IR thrown suddenly increase and a breakdown phenomenon. Because of the compound material don't gap, a variety of LED reverse breakdown voltage VR gap.
1.2C-V nature
In view of the LED chip are 9 × 9MIL (250 × 250um), 10 × 10mil, 11 × 11mil (280 × 280um), 12 × 12mil (300 × 300um), the PN node size is differ, the junction capacitance (zero bias) C ≈ n+pf dominance.
C-V nature is two function does (Figure 2). The 1MHZ AC signal with C-V nature test instrument.
1.3 the maximum allowable power dissipation of PFm
Current flowing through the LED IF, when the pressure drop for UF power loss is P=UF * IF
The LED task, the bias, bias may not make carrier composite sub light, there are one one parts into heat, so the junction temperature rise. If the junction temperature of Tj, the external conditions of temperature is Ta, when the Tj>Ta, by means of heat transfer in heat pipe to heat, leisurely (power), can be expressed as P=KT (Tj - Ta).
1.4 response time
Response schedule sign a demonstrator tracking external dynamic change speed. Several existing LCD (liquid crystal display) about 10-3~10-5S, CRT, PDP, LED to 10-6~10-7S (US).
The response time from the perspective of use, is the LED lighting and combustion delay time, namely graph TR, tf. Figure t0 value is very small, can be neglected.
Junction capacitance and impedance of the response time depends on the carrier lifetime, device.
The lighting time LED -- rise time tr refers to the power supply is connected to achieve the 10% began to glow brightness deformity, non-stop to shiny luminosity to deformity value of 90% time.
LED combustion time -- fall time TF is Kuang deformity luminous weakened to a copy of the 10% time.
Gap materials prepared LED response time are not the same; such as GaAs, GaAsP, GaAlAs and the response time of <10-9S, GaP for 10-7S. In their available in 10~100MHZ high frequency system.
2, LED optical nature
Light emitting diode with infrared (not visible) and visible light two series, the former is available radiation, the latter available photometry to measure the optical nature.
2.1 luminescence intensity and its angular distribution I
2.1.1 luminous intensity (normal intensity) is critical to comply with characterization of emitting light intensity. LED application is cylindrical, spherical package, because the convex lens effect, so they have very strong point: located in the normal direction of maximum intensity, and the degree of its surface is 90 ° angle. When the deviation angle θ executed to gap, the intensity will change. The luminous intensity as the gap package form and strength to the angular direction.
The 2.1.2 angular distribution of luminous intensity I theta is characterizations of LED luminous intensity distribution in each direction. It mainly depends on the encapsulation process (include a bracket, die head, epoxy resin grain growth scattering agent and no)
First in order to obtain high pointing angle distribution (Figure 1)
The LED tube core die grain head farther;
The use of conical (bullet). The grain head;
Epoxy resin to package don't add scattering agent.
By adopting the measures can make LED2 θ 1/2=6 ° control, greatly improve the directivity.
The scattering current several commonly used packaging angle (2 θ 1/2 angle LED:5 °) round, 10 °, 30 °, 45 °
2.2 emission peak wavelength and spectral distribution
The LED luminous intensity or power input with the wavelength change and the gap, as a distribution curve -- spectral distribution curve. When the curve will be past, device independent dominant wavelength, purity and other stakeholders also and chromatic parameters.
The LED spectrum distribution and the preparation of the compound semiconductor category, essence and PN node layout (epitaxial layer thickness, mixed impurities) and irrelevant, but not many forms, and the device package.
The LED spectral distribution curve
1 blue InGaN/GaN2 and green GaP:N3 red GaP:Zn-O
4 infrared GaAs5Si photosensitive photoelectric tube 6 tungsten filament lamp
The blue InGaN/GaN light-emitting diodes, light emitting peak λ p=460 ~ 465nm
The green GaP:N LED, λ p=550nm luminescence peaks
The red GaP:Zn-O LED, λ p=680 ~ 700nm luminescence spectra
The infrared LED using GaAs materials, luminescence peak λ p=910nm
The Si photodiode, generally as photoelectric receiving.
No matter what material made of LED, there is a relative light intensity was the strongest at the (light input maximum), and the corresponding to a wavelength, the wavelength is called peak wavelength, represented by lambda P. Only monochromatic light is wavelength λ P
The spectral line width: at the peak of bilateral + delta lambda LED spectral line
1, LED electrical nature
Follow the primary parameters of preparing 1.1I-V nature characterization of LED chip PN node system. LED I-V nature is nonlinear, rectifying nature: single guide electric, namely low contact resistance with positive bias that, contrary to the high contact resistance.
(1) positive dead: (Figure OA or OA 'section) a against V0 off voltage, when V
(2) the positive quest: current IF and applied voltage exponential does
IF=IS (eqVF/KT – 1) -------------------------IS for the reverse saturation current.
V>0, V>VF positive task area IF with VF index rose IF=ISeqVF/KT
(3): V<0 PN junction reverse deadband and reverse bias
V=-VR, reverse leakage current IR (V=-5V), GaP 0V, GaN 10uA.
(4) V<-VR reverse breakdown, VR called reverse breakdown voltage; voltage corresponding to the IR VR to reverse leakage current. When the reverse bias is constantly increase to V<-VR, then IR thrown suddenly increase and a breakdown phenomenon. Because of the compound material don't gap, a variety of LED reverse breakdown voltage VR gap.
1.2C-V nature
In view of the LED chip are 9 × 9MIL (250 × 250um), 10 × 10mil, 11 × 11mil (280 × 280um), 12 × 12mil (300 × 300um), the PN node size is differ, the junction capacitance (zero bias) C ≈ n+pf dominance.
C-V nature is two function does (Figure 2). The 1MHZ AC signal with C-V nature test instrument.
1.3 the maximum allowable power dissipation of PFm
Current flowing through the LED IF, when the pressure drop for UF power loss is P=UF * IF
The LED task, the bias, bias may not make carrier composite sub light, there are one one parts into heat, so the junction temperature rise. If the junction temperature of Tj, the external conditions of temperature is Ta, when the Tj>Ta, by means of heat transfer in heat pipe to heat, leisurely (power), can be expressed as P=KT (Tj - Ta).
1.4 response time
Response schedule sign a demonstrator tracking external dynamic change speed. Several existing LCD (liquid crystal display) about 10-3~10-5S, CRT, PDP, LED to 10-6~10-7S (US).
The response time from the perspective of use, is the LED lighting and combustion delay time, namely graph TR, tf. Figure t0 value is very small, can be neglected.
Junction capacitance and impedance of the response time depends on the carrier lifetime, device.
The lighting time LED -- rise time tr refers to the power supply is connected to achieve the 10% began to glow brightness deformity, non-stop to shiny luminosity to deformity value of 90% time.
LED combustion time -- fall time TF is Kuang deformity luminous weakened to a copy of the 10% time.
Gap materials prepared LED response time are not the same; such as GaAs, GaAsP, GaAlAs and the response time of <10-9S, GaP for 10-7S. In their available in 10~100MHZ high frequency system.
2, LED optical nature
Light emitting diode with infrared (not visible) and visible light two series, the former is available radiation, the latter available photometry to measure the optical nature.
2.1 luminescence intensity and its angular distribution I
2.1.1 luminous intensity (normal intensity) is critical to comply with characterization of emitting light intensity. LED application is cylindrical, spherical package, because the convex lens effect, so they have very strong point: located in the normal direction of maximum intensity, and the degree of its surface is 90 ° angle. When the deviation angle θ executed to gap, the intensity will change. The luminous intensity as the gap package form and strength to the angular direction.
The 2.1.2 angular distribution of luminous intensity I theta is characterizations of LED luminous intensity distribution in each direction. It mainly depends on the encapsulation process (include a bracket, die head, epoxy resin grain growth scattering agent and no)
First in order to obtain high pointing angle distribution (Figure 1)
The LED tube core die grain head farther;
The use of conical (bullet). The grain head;
Epoxy resin to package don't add scattering agent.
By adopting the measures can make LED2 θ 1/2=6 ° control, greatly improve the directivity.
The scattering current several commonly used packaging angle (2 θ 1/2 angle LED:5 °) round, 10 °, 30 °, 45 °
2.2 emission peak wavelength and spectral distribution
The LED luminous intensity or power input with the wavelength change and the gap, as a distribution curve -- spectral distribution curve. When the curve will be past, device independent dominant wavelength, purity and other stakeholders also and chromatic parameters.
The LED spectrum distribution and the preparation of the compound semiconductor category, essence and PN node layout (epitaxial layer thickness, mixed impurities) and irrelevant, but not many forms, and the device package.
The LED spectral distribution curve
1 blue InGaN/GaN2 and green GaP:N3 red GaP:Zn-O
4 infrared GaAs5Si photosensitive photoelectric tube 6 tungsten filament lamp
The blue InGaN/GaN light-emitting diodes, light emitting peak λ p=460 ~ 465nm
The green GaP:N LED, λ p=550nm luminescence peaks
The red GaP:Zn-O LED, λ p=680 ~ 700nm luminescence spectra
The infrared LED using GaAs materials, luminescence peak λ p=910nm
The Si photodiode, generally as photoelectric receiving.
No matter what material made of LED, there is a relative light intensity was the strongest at the (light input maximum), and the corresponding to a wavelength, the wavelength is called peak wavelength, represented by lambda P. Only monochromatic light is wavelength λ P
The spectral line width: at the peak of bilateral + delta lambda LED spectral line
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