High performance & light weight LED lighting For several specialised super-car OEMs the most critical factors in lighting are performance and weight, prioritised above additional functionality and balanced with design. These type of projects need a design ethos different to the LED mainstream, but many of the rules developed may also be applied other vehicle segments as they enable : - Increased efficiency - Reduced component count and development - Lower full life cycle environmental impact
Key principles - Specify essential functions only - Use function to define the form - Minimise size and complexity - No compromise on performance
Project application McLaren P13 / 570s Specify essential functions only Yes Low beam High beam DRL and PO Direction indicator No ADB / AFS Glare free high beam Headlamp washer A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away Antoine de Saint Exupéry Low speed cornering Laser
Use function to define the form Low beam optic system is selected for efficiency only : Single glass 50mm aspheric lens Main beam uses the only optic type capable of achieving the target peak values ; direct imaging of the LED die, in a 10 LED array, 20mm imaging optic for each LED The lamp design is built around the optical elements, not vice -versa
Minimise size and complexity at every opportunity Dip and main beam mounted on a single die cast aluminium combined heatsink adjuster frame. Additional CNC processing for high precision beam alignment DRL, PO and DI functions combined in a dual function twin light pipe design, sharing a single PCB and heatsink In total 12 bespoke manufactured components Headlamp external dimensions 340 x 210 x 410
No compromise on performance benchmarks The first low beam target is to maximise efficiency, 2000lm only are available ; In-line camera based luminance measurement to characterise and PWM programme LED power. Using a look up table for a series of calibrated lamps the system can accurately define nominal 2000lm Highest efficacy light source requires low LED drive current, hyperlite module uses 12 dies in a 3 x 4 array at approx 600mA drive current. Reduced drive current offers ~ 8% increase in flux for the same thermal power over reduced LED count at maximum rated 1000mA
No compromise on performance benchmarks The second target for low beam is to create a beam pattern optimised for sports cars without bend lighting or low speed cornering function ; The optimised distribution is lower and wider then typical Xenon, with reduced peak. Total 850 lm on the road so just above 40% efficiency from LED light module to road PEAK VALUE : 40 lx (XENON TYP : 50 lx) 10 o L/R VALUE : 24 lx (XENON TYP : 15 lx) 10 o DOWN VALUE : 8 lx (XENON TYP : 2 lx) 20 o L/R VALUE : 8 lx (XENON TYP : 4 lx)
No compromise on performance benchmarks Main beam has to match benchmark of Xenon + auxiliary main beam ; In this case efficiency has to be sacrificed to achieve extreme performance from a compact system, 10 LEDs @ 900mA give a total source flux of ~ 3000lm. The imaging optic achieves peak values of 230 lx / 142,000 cd Performance v Target @ 25m Test Area Target Simulated H-V : 200lx 229lx 4 o L/R : 120lx 110lx 6 o L/R : 40lx 48lx 10 o L/R : 25lx 15lx 15 o L/R : 10lx 9lx
Project application McLaren P13 / 570s Results : - Low beam with 850 lm on the road, subjectively rated close to best in class, from 2000 source lm - High beam achieves best subjective rating in class - Headlamp weight @ 2.7kg (inc ECU) is 40% lighter than the full LED headlamps from benchmark vehicles + washer system weight saving
Other project applications - Design principles applied to the Aston Martin Vulcan race car lighting - LED rearlamp with only 2 moulded components (2K bezel / optic blades & housing) @ 1.2kg - In the drive for lightweight even outer lenses are optional!
Other project applications - Modular micro LED fog & reverse lamp - Housing combined with heatsink & electrical connector - Outer lens with B surface collimating & beam shaping optics - Visible dimensions 50 x 5mm, weight 120g
Next light weight technologies - High intensity LEDs allow reduction in size main beam and / or increased performance. Compact 200,000cd main beam should be possible - Digital dynamic bend lighting can add functionality without significant weight, and under 2000lm - Silicone optics allow complex thick section freeform shapes, increasing optical efficiency with significant weight saving over glass - Magnesium heatsink can offer 30% weight savings compared to die cast aluminium - Micro laser modules using a single diode
Thank you Mike Greenrod (BSc hons) Director of Design Wipac Ltd Project data reproduced with kind permission of :