AN3106 Datasheet, PDF (1/34 Pages) STMicroelectronics – The use and growing popularity of LEDS, thanks to their high efficiency

AN3106
Application note
48 V - 130 W high-efficiency converter with PFC for
LED street lighting applications
By Claudio Spini
Introduction
The use and growing popularity of LEDS, thanks to their high efficiency and very long
lifetime, are driving the innovation of different types of lamps and contributing to the
reduction of energy consumption for internal and external lighting. Streetlight applications
require that the power supply designed to power an LED lamp must have high efficiency and
at least an equivalent lifetime in order to guarantee maintenance-free operation during the
life of the LED.
This application note describes the characteristics and features of a 130 W demonstration
board (EVL130W-STRLIG), tailored to an LED power supply specification for street lighting.
The circuit is composed of two stages: a front-end PFC using the L6562AT and an LLC
resonant converter based on the L6599AT.
The strengths of this design are very high efficiency, wide input mains range (85-305 V_AC)
operation and long-term reliability.
Because reliability (MTBF - “mean time between failures”) in power supplies is typically
affected by the high failure rate of electrolytic capacitors unless using very expensive types,
this board shows a very innovative design approach. The board doesn't implement any
electrolytic capacitors, but uses instead film capacitors from EPCOS. Component de-rating
has been also carefully applied during the design phase, decreasing the stress of the
components as recommended by the MIL-HDBK-217D. The number of components, thanks
to the use of the new devices L6562AT and L6599AT has also been minimized, thus
increasing the MTBF and optimizing the total component cost. Thanks to the high efficiency
achieved, just a small heatsink for the PFC stage is needed, while the other power
components are SMT (surface mount technology) like most of the passive components, thus
decreasing the production labor cost.
The board also has protection features in case of overload, short-circuit, open loop by each
stage or input overvoltage. For this particular application, all protections in case of
intervention have an auto-restart functionality.
Figure 1. EVL130W-STRLIG: 130 W SMPS for LED street lighting applications
September 2012
Doc ID 16775 Rev 2
1/34
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