Cov Lus Nug Piv Txwv Sib Tham Txog Cov Teeb Ci (LEDs)
Lub teeb ci ntsa iab (LED) yog ib lub khoom siv semiconductor uas tso tawm lub teeb thaum muaj hluav taws xob ntws los ntawm nws. Qhov tshwm sim tom qab LEDs hu ua electroluminescence, qhov twg cov khoom siv semiconductor tso tawm lub teeb thaum raug hluav taws xob cuam tshuam. LEDs tau dhau los ua nrov heev hauv ntau yam kev siv vim lawv cov kev ua haujlwm zoo thiab lub neej ntev piv rau cov teeb pom kev ib txwm muaj xws li cov teeb incandescent.
Hauv tsab xov xwm no, peb yuav tham txog qee qhov teeb meem piv txwv ntsig txog LEDs thiab piav qhia lawv cov kev daws teeb meem thiab kev sib tham kom ntxaws kom pab nkag siab lub tswv yim tom qab qhov xwm txheej no.
Piv txwv lus nug 1: Cov khoom yooj yim ntawm LEDs
Lus Nug: Ib lub LED muaj peev xwm tso tawm lub teeb nrog lub wavelength ntawm 650 nm (nanometers). Xam lub zog ntawm cov photons uas tso tawm los ntawm lub LED no hauv electron-volts (eV).
Kev Sib Tham:
Lub zog photon tuaj yeem suav los ntawm kev siv Planck's equation:
\[ E = \frac{hc}{\lambda} \]
Qhov twg:
- \( E \) yog lub zog photon,
- \( h \) yog Planck tus nqi tas mus li (\(6.626 \times 10^{-34} \text{ Js}\)),
- \( c \) yog qhov ceev ntawm lub teeb (\(3 \times 10^8 \text{ m/s}\)),
- \( \lambda \) yog qhov wavelength ntawm lub teeb (650 nm lossis \(650 \times 10^{-9} \text{ m}\)).
Hloov cov nqi no rau hauv qhov sib npaug ua rau:
\[
E = \frac{6.626 \times 10^{-34} \times 3 \times 10^8}{650 \times 10^{-9}}
= \frac{1.9878 \times 10^{-25}}{650 \times 10^{-9}}
= 3.05 \times 10^{-19} \text{ J}
\]
Tom ntej no, peb hloov Joules mus rau electron-volts siv qhov kev hloov pauv \(1 \text{ eV} = 1.602 \times 10^{-19} \text{ J}\):
\[
E = \frac{3.05 \times 10^{-19}}{1.602 \times 10^{-19}}
≈ 1.90 \text{ eV}
\]
Yog li, lub zog photon uas tawm los ntawm LED nrog lub wavelength ntawm 650 nm yog li 1.90 eV.
Piv txwv 2: LED Forward Voltage
Lo lus nug: Lub LED liab muaj lub zog pem hauv ntej ntawm 2V thiab xav tau tam sim no ntawm 20 mA kom ua haujlwm tau zoo. Xam lub zog uas lub LED siv.
Kev Sib Tham:
Yuav kom xam lub zog uas LED nqus tau, peb siv cov qauv yooj yim rau lub zog, uas yog:
\[ P = V \times I \]
Qhov twg:
- \( P \) yog lub zog hauv Watts (W),
- \( V \) yog qhov voltage hauv Volts (V),
- \(I \) yog tam sim no hauv Amperes (A).
Hloov cov nqi no rau hauv qhov sib npaug:
\[
P = 2 V = 20 mA
= 2 \text{ V} \times 0.02 \text{ A}
= 0.04 W
\]
Yog li, lub zog uas lub LED liab nqus tau ua haujlwm ntawm qhov voltage pem hauv ntej ntawm 2V thiab tam sim no ntawm 20 mA yog 0.04 Watts.
Piv txwv 3: Kev Ua Haujlwm Zoo ntawm LED
Lo lus nug: Lub teeb xiav LED muaj qhov ua tau zoo ntawm 30%. Yog tias lub teeb LED siv 0.1 W ntawm lub zog hluav taws xob, muaj pes tsawg lub zog raug tso tawm ua lub teeb?
Kev Sib Tham:
Quantum efficiency (η) yog qhov sib piv ntawm lub zog tso tawm hauv daim ntawv ntawm lub teeb (P_luminous) rau lub zog hluav taws xob nkag (P_input):
\[ η = \frac{P_{\text{luminous}}}{P_{\text{input}}} \]
Yuav nrhiav tau \( P_{\text{luminous}} \), siv cov kab zauv hauv qab no nrog tus nqi ua haujlwm ntawm 30% lossis 0.30:
\[
0.30 = \frac{P_{\text{luminous}}}{0.1 \text{ W}}
\]
Yog li ntawd:
\[
P_{\text{luminous}} = 0.30 \times 0.1 \text{ W}
= 0.03 W
\]
Yog li, lub zog tso tawm los ntawm LED hauv daim ntawv ntawm lub teeb yog 0.03 Watt.
Piv txwv teeb meem 4: Series LED Circuit
Lo lus nug: Koj muaj peb lub LEDs nrog lub zog hluav taws xob pem hauv ntej ntawm 2V txhua qhov uas yuav tsum tau txuas nrog ua ke. Yog tias qhov hluav taws xob qhov chaw yog 9V, txiav txim siab tus nqi ntawm lub resistor xav tau los txwv qhov tam sim no rau 20 mA.
Kev Sib Tham:
Thaum cov LEDs txuas nrog ua ke, tag nrho cov hluav taws xob xav tau yog qhov sib npaug ntawm cov hluav taws xob pem hauv ntej ntawm txhua lub LED:
\[
V_{total} = V_f1 + V_f2 + V_f3
= 2V + 2V + 2V
= 6 V
\]
Qhov residual voltage uas yuav tsum tau dissipated los ntawm lub resistor yog:
\[
V_{R} = V_{qhov chaw} – V_{tag nrho}
= 9V – 6V
= 3 V
\]
Nrog rau qhov xav tau tam sim no ntawm 20 mA, tus nqi resistor yog xam los ntawm kev siv Ohm's Law:
\[
R = \frac{V_{R}}{I}
= \frac{3V}{20 mA}}
= \frac{3V}{0.02A}
= 150 \Omega
\]
Yog li, tus nqi resistor xav tau yog 150 ohms.
Piv txwv 5: Lub voj voog txwv tam sim no LED sib luag
Lo lus nug: Hauv ib lub voj voog, muaj ob lub LEDs sib luag, txhua tus muaj lub zog hluav taws xob pem hauv ntej ntawm 2V thiab tam sim no ntawm 20 mA. Tag nrho tam sim no xav tau los ntawm 5V qhov hluav taws xob yog tias siv lub resistor rau txhua lub LED yog dab tsi?
Kev Sib Tham:
Rau cov LEDs uas teeb tsa ua ke, txhua lub LED yuav muaj tib lub zog hluav taws xob, uas yog lawv lub zog hluav taws xob pem hauv ntej, thiab txij li thaum lawv xav tau 20 mA ntawm tam sim no ib lub LED tag nrho tam sim no yog:
\[
Kuv_{tag nrho} = Kuv_1 + Kuv_2
= 20 \text{mA} + 20 \text{mA}
= 40 mA
\]
Yuav xam tus nqi resistor rau txhua LED:
\[
V_{R} = V_{qhov chaw} – V_f
= 5V – 2V
= 3 V
\]
Tus nqi resistor los txwv qhov tam sim no hauv txhua LED yog:
\[
R = \frac{V_{R}}{I}
= \frac{3V}{20 mA}}
= \frac{3V}{0.02A}
= 150 \Omega
\]
Yog li, txhua lub LED xav tau 150 ohm resistor. Tag nrho cov tam sim no xav tau los ntawm 5V fais fab mov yog 40 mA.
Xaus
Cov LEDs yog cov khoom tseem ceeb hauv cov khoom siv hluav taws xob niaj hnub no vim lawv muaj peev xwm muab teeb pom kev zoo nrog lub neej ntev. Kev nkag siab txog cov ntsiab lus yooj yim xws li voltage pem hauv ntej, tam sim no, lub zog, quantum efficiency, thiab yuav ua li cas teeb tsa lawv hauv lub voj voog yuav muab lub hauv paus ruaj khov rau kev siv ua haujlwm. Cov piv txwv saum toj no yog thawj kauj ruam rau kev paub txog ntau yam kev siv thiab kev xam zauv ntsig txog kev siv LEDs hauv cov voj voog hluav taws xob.
