DATA / RELIABILITY LEP STA 41 01 ™ Reliability Pack October 9, 2014 3542 Basset Street tel: +1-408-734-1096 Santa Clara, CA 95054 USA email: info@luxim�com www�luxim�com Contents LEP System Glossary ���������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������3 How LEP Technology Works ������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������4 Bulb Thermodynamics and Lifetime Considerations���������������������������������������������������������������������������������������������������������������������������������������5 Environmental Condition������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������6 DVT/HALT Summary ���������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������7 Lumens/CCT Versus Orientation������������������������������������������������������������������������������������������������������������������������������������������������������������������������������9 Lumens/CCT Versus Power ������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������ 10 Lumens/CCT Versus Temperature������������������������������������������������������������������������������������������������������������������������������������������������������������������������ 11 Electrical Profile Ignition and Warm-Up ������������������������������������������������������������������������������������������������������������������������������������������������������������ 12 Start Time Versus Temperature������������������������������������������������������������������������������������������������������������������������������������������������������������������������������ 13 MTBF Summary ��������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 14 MTBF Study Details��������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 15 Accelerated Testing��������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 16 Notes on Lumens Maintenance and CCT Change������������������������������������������������������������������������������������������������������������������������������������������ 17 Lumen Maintenance������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������ 18 CCT Change ���������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 19 Field Trial Data������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������ 20 UV and IR Performance ������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������� 21 Compliance & Performance Testing��������������������������������������������������������������������������������������������������������������������������������������������������������������������� 22 LEP System Glossary Ceramic Resonator Lamp Emitter Assembly Mechanical assembly containing a ceramic resonator and a quartz lamp. Ceramic resonator channels the RF (radio-frequency) energy into the lamp resulting in a powerful light emitting plasma. The lamp contains halides needed to generate the plasma. RF Driver Power amplifier (PA) assembly that uses an LDMOS device to convert electrical energy into RF power. The PA is designed for ruggedness and efficiency. The RF driver also contains controls circuit for digital and Emitter Assembly analog lighting controls. LEP System RF Driver System consisting of an emitter assembly and RF driver connected by an RF cable. Power Supply Component that converts AC power into DC power. LEP system requires a 28 volt DC input. Fixture The end lighting system that contains the LEP system, light shaping components, power supply, and heat sinks. Power Supply APPLICATION / BRIEF How LEP Technology Works LEP light sources create a light-emitting plasma by coupling RF (radio-frequency) energy into an electrode-less quartz lamp. The RF energy is created and amplified by an RF circuit that is driven by a Solid-State Power Amplifier. The following three steps outline the process of light generation in all LEP systems: Lamp Resonant Cavity or “Puck” Step 1: Input An RF circuit is established by connecting an RF power Probe amplifier to a ceramic resonant cavity known as the “puck”. In the center of the puck is a sealed quartz lamp that contains materials consistent with metal-halide lamps. Feedback Probe Power Amplifier Step 2: The puck, driven by the power amplifier, creates a standing wave confined within its walls. The electric field is strongest at the center of the lamp which ionizes the gasses inside the lamp (purple glow). Step 3: The ionized gas in turn heats up and evaporates the metal-halide materials which form a bright plasma column within the lamp (blue to bright white light). This plasma column is centered within the quartz envelope and radiates light very efficiently. In the back side of the lamp, a highly reflective powder is used to reflect nearly all of this light in the forward direction. Bulb Thermodynamics and Lifetime Considerations The LEP emitter design aims to maintain an optimal thermodynamic power balance that enables the highest plasma output while keeping the lamp wall under a safe operating temperature. The total RF power into the emitter, P in, is balanced with the radiated optical power, P radiated, and conducted heat by the puck, P conducted. The lamp chemistry or fill and the geometry are the main parameters used to optimize luminous flux while keeping the lamp wall temperature below 1100 Kelvin or 827 Celsius. A halide pool gathers at the coldest spot of the lamp replenishing the plasma through a reversible phase change process during its entire lifetime. At the designed vapor pressures and quartz temperatures, devitrification and wall whitening processes are rare resulting in a long-lasting lamp. A properly designed lamp operating at its specified environment eliminates catastrophic lamp failures. It should be noted that the LEP lamp does not contain metal electrodes as a typical HID lamp. Electrodes are the primary cause of failure in such systems where electrode wear-out, wall darkening from sputtered electrodes, and cracking of quartz-metal seal are common. LEP emitters do not display any of these failure modes. It is also worth noting that a significant amount of energy (>20%) in HID lamps are wasted in heating electrodes where this energy is used to create light in a LEP system. Therefore, the LEP emitter is inherently much more robust and efficient compared to traditional HID lamp systems. P radiated <1100 Kelvin 6000 K P conducted P in Halide pool (cold spot) At steady state, the gases (Ar, Hg, metal halides) are in local thermodynamic equilibrium. Environmental Condition The lamp performance is stated for the following environmental conditions: MIN MAX UNITS Operating Temperature -40 45 Celsius Storage Temperature -40 100 Celsius Humidity 5% to 95% RH, Non Condensing Operating Altitude 12,000 Feet Transportation Altitude 36,000 Feet • At ambient temperatures higher than 45 C, the driver temperature can exceed its recommended limits which will impact its long term reliability. In order to operate for long periods of time at elevated ambient temperatures, the LEP driver must be heat sunk more thoroughly and its base temperature validated at the elevated temperatures. The RF cable is rated for up to 105 C temperature surrounding and therefore should not exceed this limit if operating in higher ambient temperatures. • At ambient temperatures lower than -40 C, start time becomes longer and can exceed the specification for the system. Though there is no specific impact on lifetime or reliability at cold temperatures, the lamp may experience difficulty in igniting or warming up to full brightness in the allotted time. See page 13 for the impact of ambient temperature on start up times. • The bare LEP system outside of a light fixture is not IP rated. The fixture should be designed such that water and moisture are kept out of the lamp area as much as possible. Standard sealing principles for outdoor fixtures apply to LEP fixtures. Please refer to the LEP Fixture Design Guide for further information. DVT/HALT Summary The following Design Verification Test (DVT) of LEP STA-40 lamps was performed in accordance with mil and ETSI (telecommunications) standards for outdoor products to simulate extreme environmental and mechanical conditions. The tests, unless otherwise stated, were done to the bare lamp system and not in a light fixture. Some of the indicated testing were performed in a mock up fixture that prevents direct moisture from forming on the lamp. The lamps also were subjected to Highly Accelerated Life Testing (HALT) by increasing stress levels to induce failures in order to identify the weak points in the design. The lamp systems were subjected to increasing temperature, vibration, and power stresses while operating. The reported values are the limits where the lamp operated without any damage. Non-Operational TEST CONDITIONS CYCLES RESULTS Temperature Cycling -40º C to +70º C 30 min. intervals – x10 No Failures Constant Temperature* w/ Humidity +70º C @ 90% RH 3 days No Failures Random Vibration 10 Hz @ 0.015 g2 /Hz 60 min./axis No Failures 40 Hz @ 0.015 g2 /Hz 500 Hz @ 0.00015 g2 /Hz Overall: 1.04 g (rms) Moisture Intrusion* (Temperature Humidity) +30º C & +60º C Transverse & Vertical Axis 12 hr. intervals – x6 No Failures Operational TEST CONDITIONS CYCLES RESULTS Temperature Cycling -45° C to +60° C 11 hr. intervals – x2 No Failures Constant Temperature* w/ Humidity +40° C @90% RH 4 days No Failures Sine Sweep Vibration 5 Hz – 62 Hz @ 5 mm/s 60 min./Axis No Failures 62 Hz – 200 Hz @ 2 m2/s3 Symmetric (round) Emitter, thus, X = Y Axis Total: 2 m2/s3 Random Vibration 5 Hz – 10 Hz @ +12 dB 30 min./Axis 10 Hz – 50 Hz @ 0.02 m2/ s3 Symmetric (round) Emitter, thus, X = Y Axis 50 Hz – 100 Hz @ -12 dB Overall: 1.063 m/s2 (rms) Shock (Bump) X & Z Axis Half Sine Wave: 25 g No Failures X & Z Axis 6 ms intervals – x1000/Axis No Failures Symmetric (round) Emitter, thus, X = Y Axis +X – x1000, -X – x1000 +Z – x1000, -Z – x1000 Salt Fog* +98° F in a Salt Fog of 5% NaCl (specific gravity: 1.035 & pH of 7.0) 4 days total exposure No Failures 2 days with one unit cycling 1 hr. on, then 30 min. off Other 2 days, unit off Highly Accelerated Life Testing TEST CONDITIONS CYCLES RESULTS Temperature Extremes w/ Varying DC Voltages -75° C to +55° C 4 hr. interval total No Failures Temperature Extremes* Cycling -40° C to +60° C 108 min. intervals – x8 (15° C/min. gradients) No Failures Random Vibration* 0.5 g (rms) to 7.0 g (rms) 0.5 g (rms) – 15 min. 5 Hz – 500 Hz/g step 1.0 g (rms) – 30 min. No Mechanical Failures 23V DC to 32V DC @ -75° C, -20° C & +45° C 1.5 g (rms) – 15 min. 2.0 g (rms) – 15 min. 3.0 g (rms) – 15 min. 5.0 g (rms) – 15 min. 7.0 g (rms) – 5 min. Temperature Extremes* Cycling w/ Vibration Cycling -40° C to +60° C 2.0 g (rms) to 6.0 g (rms) 5 Hz – 500 Hz/g step *Testing done in simulated fixture. 13 min. + 20 sec. intervals – x5 (15° C/min. gradients) No Failures Lumens/CCT Versus Orientation STA-41 lamps are designed for vertical down operation and up to 30° Tilt as illustrated in the following diagram� In the vertical up orientation from -30° (or +330°) to +30°, the plasma output fluctuates due to the thermodynamics inside the lamp� Operating in the pointing up configuration is prohibited where the lamp could exhibit flicker� UP Down 30° Max 30°° Max 30° Max Yes No Lumens/CCT Versus Power The following curves depict the power consumption and color temperature (CCT) of the STA-41 light source as it dims from 100% to 20%. STA-41 source can be electronically dimmed via digital controls or by 1-10V analog control. Light Output (%) Lumens/CCT Versus Temperature The following data depicts the variation in light output and CCT change over the entire ambient operating temperature range from -40° to +45° C. There is a maximum of -3% lumens penalty at hot temperatures and a +100 kelvin color shift at cold temperatures. The lumens decrease is a result of RF amplifier inefficiency at hot and the color shift is due to decreased 120% 170 100% 140 80% 110 Light Output Change (%) 60% 80 CCT Change (Delta Kelvins) 40% 50 20% 20 0% -10 -60 -40 -20 0 Environment Temperature (Degrees Celcius) 20 40 60 Delta Kelvins % Lumens Change lamp cold spot temperature. Electrical Profile Ignition and Warm-Up The following data shows the current profile that the RF driver draws during its warm up process. It is typical for the RF amplifier to draw as much as 14 amperes from the DC power source. Therefore, the DC power source must be chosen such that it does not have a cut off below 14 amperes. Start Current Profile (V=28 volts) Start Current Profile (V=28 Volts) 16 16 14 14 Current (Amperes) 12 12 10 10 8 6 4 (Amperes) Current Min Range Max Range 2 0 00 120 120 240 240 360480 480600 360 720 600 (Seconds) TimeTime (seconds) 840 960 840 1080 960 720 1080 Start Time Versus Temperature The following data shows the lamp start time as a function of temperatures. The lamp start time takes up to 10 seconds longer at cold temperatures of -40º C compared with room temperature. 25C Start Time Moments Target 20 25 30 Mean28.7 35 40 45 Std Dev 4.4 Std Err Mean 0.8 Upper 95% Mean 30.3 Lower 95% Mean 27.1 50 -40C Start Time Moments Target 20 25 30 Mean32.1 35 40 45 Std Dev 7.0 Std Err Mean 1.2 Upper 95% Mean 34.7 Lower 95% Mean 29.6 50 +55C Start Time Moments Target 20 25 30 Mean27.6 35 40 45 50 Std Dev 3.9 Std Err Mean 0.7 Upper 95% Mean 29.0 Lower 95% Mean 26.2 MTBF Summary MTBF (mean time before failure) is a basic measure of reliability for repairable electronic assemblies. It is calculated as T/N where T is the total operating time and N is the number of catastrophic failures. MTBF calculations do not reflect parametric failures where electrical or optical output decreases beyond the specified parameter. In a lighting system, parametric failures are shown by lumen and CCT maintenance plots (see page 19 Lumen Maintenance). Catastrophic failure rate over time of the RF driver follows a typical bathtub curve observed in many electronics assemblies. There are three distinct periods in the bathtub curve that describes the failure rate over time. First period is characterized by decreasing failure rate and occurs in early life due to infant mortality. This period is relatively short and the weaker units die off leaving a population of more rigorous units. To ensure that the weaker units are not released, LUXIM performs burn in and power cycling of lamp systems. In addition, LUXIM uses components that are rated for significantly higher temperature than actual use condition. The next period characterized by a low but constant failure rate where the failures are random in nature. This is the period of useful life of the RF driver where MTBF and FIT calculations apply. The last period is characterized by an increasing failure where components wear out due to physical, electronic, and thermal stresses over its lifetime. MTBF calculations are no longer valid in this period. Failure rate (failures/unit time) Burn in (infant mortality) Wear-out Useful life (random ta: lives) Lifetime MTBF Study Details In the period of useful life, the failure rate, R(t) can be computed as R(t)=e-λt whereλis =1/MTBF and t is the operating time. The probability of catastrophic failure is simply P(t) = 1- R(t). The MTBF calculations for the STA-41 RF driver are performed using MIL-STD-217 techniques. There are several factors that determine reliability including: »» Temperature of operation »» Stress levels of the components »» Time in production (learning curve) »» Quality level of the components »» Operating environment The system MTBF calculation is done using data from actual testing by component manufacturers and historical performance of the components. The following conditions were assumed: »» 85º C base plate temperature »» Learning curve of < 1 year »» COTS quality level (commercial off the shelf ) »» Ground, Fixed (not directly exposed to the outer environment) »» Typical and Maximum stress levels With these assumptions, the LEP RF Driver has an MTBF of 151,000 hours at maximum stress levels and 212,000 at typical stress levels. This corresponds to a 28% and 21% failure rate at the specified 50,000 hours. In a properly designed light fixture, 79% survival at the end of life is typical. Learning curve (years) Stress level t (hours) MTBF lambda - 1/ MTBF R(t) = exp[-lambda * t] P(t) 1 max 50000 150965 6.62E-06 0.72 0.28 1 typical 50000 212000 4.72E-06 0.79 0.21 Accelerated Testing One method of accelerating the failure mechanism of RF drivers is to power cycle the lamp system. Power cycling introduces the most stress on the RF electronics due to unfavorable load conditions, higher current spikes, and rapid thermal change. Below is the measured survival rate over time due to rapid cycling of STA-41 series lamps (10 minutes ON/15 minutes OFF). LEP drivers sustained greater than 8000 power cycles with greater than 90% survival rate. This is equivalent to more than 20 years of operation. 100% 10000 90% 9000 80% 8000 70% 7000 60% 6000 50% 5000 Survival Rate 40% 4000 Number of Starts 30% 3000 20% 2000 10% 1000 0% 0% 0 5 10 15 Equivalent Number of Years 20 25 Number of Starts Survival Rate Driver Sustainability Over Time Lamps Cycling 10 Minutes On / 15 Minutes Off Notes on Lumens Maintenance and CCT Change Lumens and CCT maintenance for the STA-41 lamp is extrapolated from measured data of the previous generation of emitter design (STA-40). STA-41 lamps are expected to perform similar or better as they use the same lamp chemistry and have an even lower wall loading (power input/inner surface are of lamp) and hence lower thermal stress that the STA-40 emitter. The lifetime of the LEP-STA-41 plasma systems are defined as the time to 70% lumen maintenance of L70. Below are some notes on the lumen maintenance testing: 1. Lumen maintenance is extrapolated from actual lamp (emitter + driver) data of 5000 hours. As data is updated every 1000 hours, LUXIM will continue to update the extrapolation. 2. Seasoning period of first 300 hours is eliminated in order to extrapolate the lumen maintenance end of life. 3. Lumens are measured in an integrating sphere following closely to IESNA LM79 standard 2π measurement geometry. 4. Test conditions are as follows: »» 30º C room temperature »» Constant current and voltage »» Emitter oriented vertical down »» Benchmarking at 1000 hour intervals Lumen Maintenance Typical Lumen Maintenance Ra=80 Typical STA 41 Lumen Maintenance 100% 90% 80% % Light Output 70% 60% 50% Lumens 40% 30% avg extrapol� 20% max extrapol� 10% min extrapol� 0% 0 10000 20000 30000 Hours of Operation 40000 50000 CCT Change Typical CCT Change Ra=80 8000 7000 CCT (Kelvins) 6000 5000 4000 3000 CCT (kelvin) 2000 1000 0 0 500 1000 1500 2000 Hours of Operation 2500 3000 3500 Field Trial Data In order to validate predictions for lumen and CCT maintenance based on life test data (pages 17 and 18), LUXIM continually monitors field trials. Field trials are the most unbiased data set that captures degradation in not only the light source but also in the optics, electronics and thermal management of the fixture. Below is the measured performance of light fixtures using STA-41-01 light source in outdoor field trials. This trial consists of 12 cobra head light fixtures on a 12 hour ON/12 hour OFF cycle. Pictures of the test site UV and IR Performance The following data represent the typical spectral emission in W/nm for the STA-41 emitter from 200 nm to 3000 nm. It is overlaid with the sun’s spectrum and with the human eye’s response to light (photopic curve). L I F I -S T A - 4 1 -0 2 S p e c t r a l D i s t r i b u t i o n 2 0 0 -3 0 0 0 n m 00.4 .4 1 STA-41-02 (W/nm) STA-41-02 (W/nm) Sunlight (normalized) Sunlight (normalized) 0.322 0 .3 00.8.8 Photopic (normalized) Photopic (normalized) 00.6.6 W/nm 0.166 0 .1 00.4.4 0.088 0 .0 00.2.2 W/nm 0.244 0 .2 00 0 2 200 00 700 70 0 11200 20 0 11700 700 22200 2 0 0 2700 2 7 0 0 W a v Wavelength e l e n g t h(nm) (n m ) Watts Percentage UV (200-400) 10.9 9% Visible (400-750) 85.6 70% NIR (750-1400) 20.7 17% SWIR (1400-3000) 5.4 4% Compliance & Performance Testing STA-41 lamps and luminaries will be subjected to the following regulatory and standardized testing. Photometric and Flux Measurement: LTL Test Report, Number 21950 Safety Light Source: UL1029 (US), EN 61347-1: 2008, EN 61347-2-9: 2001 (EU) EMC: FCC Part 18 Class A, CISPR22, EN55022 Recycling and Waste: RoHS, WEEE (EU)
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