Page 23 - PEN eBook October2023
P. 23
DESIGN
Optimizing DCM
PFC to Provide High
Efficiency Across Load and
Shrink Power Components
By Andrew Smith, director of technical outreach at Power Integrations
USB-PD chargers are getting smaller. Various techniques have been employed to reduce their size,
yet certain power components—specifically, the boost inductor, boost diode and integrated boost
switch—remain stubbornly space-consuming. A new IC, used in boost power-factor–correction (PFC)
topology designs, addresses this issue.
Typical boost PFC circuits fall into one of three categories, depending on how current flows in the
boost inductor during each switching cycle: discontinuous-conduction mode (DCM), critical mode (CrM,
sometimes referred to as boundary mode) and continuous-conduction mode (CCM). The basic circuit
is the same for each mode of operation: A boost inductor stores energy when a power switch is turned
on, and this is transferred to the output via a boost diode when the boost MOSFET turns off. Input
42 OCTOBER 2023 | www.powerelectronicsnews.com
