AN3276 Datasheet, PDF (1/22 Pages) STMicroelectronics – ST solution for efficiency improvement in PFC applications

AN3276
Application note
ST solution for efficiency improvement in PFC applications,
back current circuit (BC²)
Introduction
The challenges for modern high efficiency switching power supplies are to minimize power
losses and increase their power density without raising the cost. The goal is to reduce both
power conduction and power switching losses.
Minimization of power conduction losses is difficult to achieve without considerably affecting
the cost and power density, since more material is required (bigger active and passive
components). Unlike the conduction losses, it is easier to reduce the power switching losses
without significantly increasing the power supply cost. There are two main ways to achieve
this improvement:
■ working on the dynamic behavior of the semiconductor technologies
■ working on circuit topologies
Novel diodes using technologies such as SiC and GaN materials significantly reduce the
switching losses. However, their high price makes them not so attractive for applications
such as desktop server power supplies, solar inverters and µinverters.
The patented circuit [see Section 5: References, 1.], described in this Application note is
based on the soft switching method and meets market expectations since its
efficiency/cost/power, and density/EMI trade-offs are better than high voltage SiC Schottky
diodes.
November 2010
Doc ID 17975 Rev 1
1/22
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