LED lighting systems for automotive industry (DACIA)
Automotive industry shows in present a fierce competition (only surpassed by mobile telecommunication) and LED lighting represent a major technology to be implemented because of its pros: high added-value for luxury cars, but still cost-effective for popular cars.
LED lighting systems have a very low energy consume, life-time 25 times better than those presently used and are environmentally friendly (no pollutants: mercury, cadmium, lead etc.) strongly challenging classical lighting systems. The absence of UV emission in every LED lighting means an important added characteristic for the consumer safety.
Microelectronica has selected some types of LED-dies from OSRAM Semiconductors (Germany), CREE (USA), Nichia (Japan), Lumileds (Europe), but also from SemiLeds-Taiwan (company with very aggressive development).
LED light systems need a constant current (intensity) source. The majority of LED-dies have a specified current intensity level for which is achieved a maximum brightness without premature failure. Luminous radiation of an LED is proportional to the current flowing through it.
There are 2 ways to control luminous intensity.
One of them is controlling the current input. This can be achieved using a variable resistor or a controlled voltage source.
Another way for constant specified current is a signal with width pulse modulation (PMW) or variable frequency and fixed filling factor.
LED-die junction temperature is one of the factors that decisively contribute on the color of light. That's why the temperature must be compensated. A simple, economic efficient method is to use specific microcontroler and a NTC thermistor (Negative Temperature Coefficient) next to LED-die.
Other method is to precisely measure the direct LED voltage.
A common problem for car is little space. Lighting systems need to use all possible spaces in chairs, doors etc. Spaces for electronics are usually as little as 10x20mm or less than that, solution being the packaging in SSOP, QFN or DFN types. Environmental temperature and LED itself warming need a very careful thermal management, for all semiconductor components and the operating temperature between -40°C and 125°C.
Microelectronica has researched and designed solutions dealing with issues like electronic circuits, temperature, space, etc. and result of that is an innovative / competitive product for national / European market.
The functional model realized is a brand new product combining innovative LED lighting and other new technologies but responding to the high performances requirements and safety standards of automotive industry.
- Research on polymers/plastics dealing with mechanical strength, dimensions and lens characteristics;
- Research, design and construct LED light customized based on dimensions, luminous intensity, electric parameters (current, voltage), color;
- Research, design of electronic circuit for LED-die (temperature management, input current, control) all for the car braking system;
- The implement LED light functional system into the existent braking system of car on market;
The final innovative and functional product which was tested on the vehicle is a LED lamp considered to be a standard third stop light of the car.