IC Simplifies Analog Control Of The Totem-Pole PFC Stage
by Christophe Basso, Future Electronics, Toulouse, France, How2Power Today, Jul 15 2022
Focus:
SiC and GaN power switches made the totem-pole PFC (TPPFC) architecture practical, but
initially required an MCU to implement control. This article describes an alternative,
analog-based approach to design using onsemi’s NCP1680 controller IC. After reviewing
operation of a traditional PFC circuit, the article introduces the bridgeless PFC concept
and its issue of common-mode noise, and explains how the TPPFC addresses this problem. The
uses of GaN, SiC and superjunction silicon MOSFETs along with zero voltage switching and
synchronous rectification in the TPPFC are discussed. Onsemi’s use of borderline (aka
boundary or critical) conduction mode for control of the TPPFC switches as implemented by
the NCP1680 controller is explained including its method of overpower protection. The
control-to-output transfer function for this controller is given, and a compensation
strategy is described. The author then demonstrates how to test the transfer function of
the NCP1680-based PFC stage in SIMPLIS to verify converter performance and stability.
What you’ll learn:
- How to implement a totem-pole PFC that does not require an MCU or writing software code
- How to implement a totem-pole PFC for applications below 500 W using the NCP1680 controller IC
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