Power Factor Correction (PFC)
The environmental and economic benefits of Power Factor Correction (PFC) and harmonic current reduction have led to standard requirements (e.g. IEC1000-3-2) in most power supply designs today.
Single Cycle Control
Traditional PFC Design
Design factors such as power density, efficiency and system cost must be considered when choosing the correct version of the "Boost" topology commonlyused in SMPS PFC.
Traditionally, two types of control are mostly used - Continuous Current Mode (CCM) or Discontinuous Current Mode (DCM) - and are generally selected for the power level of the application.
In DCM, (70W to around 200-250W) the PFC MOSFET is turned on only when the inductor current has reached zero.
In CCM (upwards from 200W) the MOSFET is turned on when inductor current is still above zero and therefore all reverse recovery energy is dissipated in the MOSFET.
The PFC MOSFET operates in a 'Hard Switched' mode and so IR have developed the K-series range of 500V and 600V HEXFET® Power MOSFETs.
In CCM, the PFC diode must be extremely fast (very low trr). The new 'ETX' series of 600V ultrafast diodes has been special developed for use in CCM PFC. These parts are 8ETX06 and 15ETX06 which are available in TO-220, TO-220FP, TO-262 and D2Pak.
In DCM, the PFC diode must have a low forward voltage (VF). The new 'ETL' series of 600V diodes has been special developed for use in DCM PFC. These parts are 8ETL06 and 15ETL06 which are available in TO-220, TO=220FP, TO-262 and D2Pak.
New PFC Toplology: Single Cycle Control
Both CCM and DCM PFC circuits are a compromise of power density, complexity, system cost and/or efficiency with a long, complicated design process. A new topology called "Single Cycle Control" offers a 'No Compromise' solution with high performance, high power density, low component count and a fast, easy design process.
Single Cycle Control PFC