Simpler, cheaper, more efficient

Key components of LED lighting – control gear

Multi-circuiting is the key to success where highly-efficient LED lighting is concerned. This lighting standard represents the next step for the well-known control gears manufactured by inpotron/exscitron.

Following up on the great interest the first generation of control gears aroused in the market, the young company exscitron GmbH, together with its parent company inpotron Schaltnetzteile GmbH, has fulfilled its promise. As with the basic devices, the goal-oriented corporate policy has remained unchanged: optimal efficiency, high durability and an excellent cost-performance ratio. This has been achieved by the tried and tested method: simplification thanks to know-how.

Efficiency, durability, size, features and price could thus be combined in a package that has yet to be equaled. Based on this technology, the next leap in development could be tackled.

Multi-circuiting

Owing to ever increasing tolerances in the voltage flow of LEDs, parallel circuits of several cables can only be recommended in exceptional cases. The best solution, therefore, is to construct a power supply with more circuits in the first place. Most clients would also prefer the output voltage to be in the region of SELV (safety extra low voltage).

For this reason, a good solution consists of 12 LEDs in a row, in order to safely stay below 50V maximum voltage output at greater tolerances. At 700mA/LED, each circuit must produce 30W. In the high-power LED sector, established power supplies have a performance of 120W, 90W, 60W and 48W, ideally equipped with 4 circuits.

We quickly realized that none of the technologies available on the market would satisfy these requirements.

The required specifications were as follows:

• Power efficiency > 92% of complete system
• ize 3" x 6.5" (including IP65 casing)
• Lifetime of 100 000 h
• Dimmability 30-100%
• Harmonics class C for the whole dim spectrum
• No starting current inrush I²t < 0,05A²s
• 4 controlled current generators

The solution opted for could not be taken from "modern" circuit approaches as the cost of materials, efficiency, lifetime and space required for 4 separate current generators, whether boost converters or buck converters, were not acceptable. High-loss passive or linear solutions were out of the question.

Current generators with 99% power efficiency

In the end, it was our comprehensive expertise regarding inductors and the experience gained from high frequency technology that furnished the basic principles. It was necessary to translate the basic concept of splitters and combiners from megahertz and gigahertz into kilohertz. The result of this prolonged phase of work is an integrated inductor that can passively split a current generator into any number of self-balancing current generators almost without loss. In addition to compensating for the varying voltage flow of the LEDs, these current generators are also able to counterbalance defective LEDs without overriding each other. Even an absolute short circuit in one or more cables has no effect on the overall system.

Technology	Efficiency	Price	EMC	Dimming	Control	Required space
Linear regulator	--	+	++	--	+<	++
Switch regulator	+	--	-	+	-	-
Integated magnetics	++	+	++	++	++	++

After the first design phase with discreet splitters had already reached the stage where it was ready for serial production, the exscitron team focused on further optimization of this technology. The target was to develop a single integrated inductor.

Without the proactive support provided by our long standing partner in development, EPCOS, a company within the TDK-EPC Corporation, we would not have been able to achieve this goal. The specialist in electronic components agreed to manufacture prototypes of special ferrites for this application, in order to assist us with this innovative approach.

The result was an extremely flat, planar key unit that can split the required power into 4 circuits. The total power is currently a maximum of 120W.

Thanks to the cascadability of design and the thermal load capacity of this new component, a whole range of potential new special applications in systems with high-power LEDs has emerged:

• automotive industry
  … thanks to the thermal load capacity and durability under extreme conditions
• LED background lighting
  … for LCD TV, thanks to its cascadability and extremely flat design
• outdoor lighting
  … thanks to its high durability and efficiency
• indoor lighting
  … as its design lends itself to modern, extremely flat lighting systems.

Presscontact:
exscitron GmbH - Stephan Gruber - Uhlichstr. 13 - 09112 Chemnitz
Fon.: +49 3 71 / 35 58 60 10 –