| Abstract |
For a long time, power supply designers of the off-line converters have thought about new concepts such
as the synchronous rectification, resonant topologies and other solutions to improve the capability of
power converters. All these solutions come, after the AC rectification stage, and most often, no new
concepts and no new components have been developed for the front-end stage. The major problems, in
this part of the converter, are the low frequency harmonic currents and the inrush current due to the
charging of the bulk capacitor. The Power Factor Corrector (PFC) introduced few years ago, allows the
first problem to be improved while resistive impedance (stand-alone resistor, NTC) shorted by a power
switch (SCR, a TRIAC or a relay) allows the peak current at the start-up to be reduced. However, all these
common solutions used to limit the inrush current do not satisfy all the expectations of power supply. In
addition to the limitation of the inrush current magnitude, the perfect solution should include:
- No degradation of power efficiency in the steady state,
- No degradation of the power density of the converter,
- Compatibility with the EMC test corresponding to lightning induced surges (contribute to MTBF) [1],
- Fast response to AC line brownouts [2].
Based on the ASD™ technology [3], STMicroelectronics now proposes a new component used in a Half
Controlled Rectifiers Bridge (HCRB) configuration. The new device, called the STIL, has been designed
to satisfy the criteria listed above. This paper describes how to get the most of the STIL devices when it is
used in PFC and fly-back converters and, it highlights all the benefits of this solution in the off-line
converter design. |
