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Reporting period: 2018-05-01 to 2020-04-30

The majority of solid state light (SSL) systems use light emitting diodes (LED) as the light source. The whole lighting system consists of the electrical part (light engine), the mechanical part (luminaire) and the optical part (reflector and lens). The light engine is the bottleneck for size, weight and cost reduction as well as reliability and energy efficiency. LEDLUM, therefore focuses on this part.
The light engine contains an LED module and a driver. The LED is responsible for the limit in energy efficacy (lm/W), but the driver is limiting factor for size, cost and reliability. To operate the LEDs from the electric grid, the driver must convert source power to LED-appropriate voltage and current levels.
LEDLUM is committed to innovations in solid-state lighting engines by
• Reducing size and weight of power electronics in the LED driver by 90%
• reducing material cost by a factor of 2
• reducing energy losses by 45 %
• increasing the expected lifetime from 5 to 10 years.
The major novel concepts developed are
• increasing switching frequency of grid-interfaced power electronics by a factor of 1000 (to 50 to 100 MHz) with state-of-the-art System in Package (SIP) integration
• which enables usage of magnetics inductors (up to 360 nH/mm2) and ultra-high-density capacitors (up to 500 nF/mm2) on silicon
• innovative unprecedented circuit design.
The methods include integrated magnetics, deep-trench silicon level capacitor design, integrated circuit level power electronics and mechanical design for optics and end user ready demonstrators.
WP1: The system architecture and requirements were described thoroughly early in the project forming a solid foundation for the work carried out on passives (WP2), semiconductors (WP3), power electronics (WP4) and driver system (WP5).
The focus was split into a development track and a research track. The focus for the development track was taking the first demonstrator from lab mock-up to a full system demonstrator. It is aimed at a high technology readiness level at an attractive material cost level. The focus for the research track was to push towards a small size and lightweight LED driver. This required WP1 to cope with several different system architectures and requirements, but all based on the solid foundation designed at the beginning of the project.
WP2: A state of the art review for sputtered soft magnetic materials has identified Co Zr Ta B (CZTB) as a promising first candidate material which shows a significant improvement over the present plated material. Consequently, CZTB was the choice of material for fabricating the generation 1 magnetic devices. Laminated films of CZTB and dielectric material were fabricated and characterised in relation to their magnetic properties. The development of a patterning process for laminated CZTB stacks was completed. Generation 1 and 2 integrated magnetic devices were fabricated using CZTB as the magnetic core material.
WP3: Process selection for full integration was narrowed down to 3 options: AMS, X-FAB and ST. Discrete (e.g. naked dies) GaN FETs are identified as a potential other solution. Furthermore, integrated custom designed GaN FETs from Fraunhofer are under investigation.
A start-up circuit for the Class-E inverters from WP4 was designed, simulated, laid out and sent for production as a tape-out in the AMS 180nm, 50 V process.
WP4: The interface between the AC/DC and DC/DC was thoroughly examined early on. The tradeoffs between various nominal voltages and the allowed low frequency ripple was discussed and a high bulk voltage was used for the first demonstrator.
The D-track managed design The focus was to improve the performance, meet the full list of specs and make it mature enough for cost and lifetime evaluations.
For the R-track it was decided to shift to a low bulk voltage, as this gave a wide range of possibilities on the AC/DC and could be an opportunity to reach the objective of 90% size reduction.
WP5: A low-voltage auxiliary power supply (LVPS) and DALI interfaces was developed and tested. This was integrated with a AC/DC and DC/DC from WP4 to build a complete LED driver.
Various PWM modulation techniques were investigated. As a result of this, a solution that simultaneously fulfilled the dimming requirements and the flicker requirements according to IEEE 1789 was found.
WP5 was responsible for the evaluation of the first complete driver, the system integration for both the D- and R-track and evaluation of the complete drivers from these.
WP6: Candidate light fittings in the 18-50W range were identified and the first prototype D-track driver was demonstrated to satisfactorily drive a wide range of these fittings. The first prototype D-track driver was modified along with a surface mount LED light engine to create a daughterboard driver on board a motherboard LED light engine; the light fitting was demonstrated.
A light fitting was developed to demonstrate the advantages of the conventional LEDLUM D-track second prototype driver size and form factor. This was a linear transparent panel with side and downlighting from an aluminium spine, doubling as the driver housing and heat sink for the LEDs and the driver. The final prototype driver was demonstrated with the prototype of this fitting.
LEDLUM aims for the world’s smallest SSL engine with lowest weight and longest expected lifetime and cheapest material cost based on novel technology and IP protected solutions. This is strengthening Europe as the center of gravity for miniaturised power electronics and expands Europe’s position in ultra high-density passive integrated components.
The results can be applied to LED systems but will also have an impact on other power conversion disciplines like chargers, household appliances, general power supplies for multimedia, power-over-ethernet and more. VHF technology is also an enabler for new services in professional lighting like indoor positioning via visible light communication and data-streaming (LiFi).
Furthermore, LEDLUM lowers failures and enhances lifetime. By using less highly chemical processed material in electrolytic capacitors and magnetic core materials it reduces WEEE and RoHS that are a burden on society. The increased lifetime leads to a reduction in electronic waste.
It has not been possible to meet the objectives of LEDLUM in full, but the performance has been pushed significantly compared to state-of-the-art on all parameters, incl. size, weight, cost, losses/efficiency and lifetime/reliability.
Traditionally Europe has strong players in the lighting industry. LEDLUM with its disruptive technological approach will strengthen the market position in the field of LED drivers and LED based luminaires for the next decade. LEDLUM covers the whole supply chain starting from passive and semiconductor components of power electronics systems, light engines to complete luminaires. Thereby a European eco-system that supports highly optimized LED system is established while creating new skilled jobs.
LEDLUM Group Picture at Karren in Dornbirn (Austria)