AN2439 Datasheet, PDF (1/20 Pages) STMicroelectronics – 27 W Output power ultra wide range input

AN2439
Application note
27 W Output power ultra wide range input
flyback converter
Introduction
As the telecommunications market grows, the need for suitable PSUs (Power Supply Unit)
for equipment grows as well. For products used in telecommunications, the available
voltage is either the mains voltage (from 88 V_AC to 265 V_AC) or 48 V_DC (from 36 V_DC to 72
V_DC). Power supplies that are able to manage input AC voltage in the full range of 88Vrms
to 265Vrms are quite common while ultra wide range (from 36 V_DC to 264 V_AC) power
supplies are not as common. The main advantage in using a UWR PSU is the savings in
design and qualification. Instead of designing and qualifying two PSUs, the work is done
once. Cost advantages come from bigger volume production as there is just one product
that meets a larger range of electrical specifications.
Disadvantages are the difficulties in having a high performance system in working
condition. This application note describes a UWR flayback converter that can be used to
supply a DSLM (DSL Multiplexer).
The advantage in using a flyback converter in this application is the moderate variation of
the duty cycle with the input voltage. The main drawback is the high value of the rms current
in the secondary winding, in the output diode and in the output capacitor.
June 2007
Rev 1
1/20
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