CCM PFC Boost Converter Design

8

Design Note DN 2013-01

V1.0 January 2013

(2)

→ Inductor saturation current, rectifier bridge, MOSFET and boost diode, must all be rated at > 7.5A . One

practical design would suggest 12A current ratings.

(3)

(4)

Off the shelf inductors are available and usable for a first pass design, typically with single layer windings

and a permeability droop of 30% or less [ ].

In some circumstances it may be desirable to further optimize the inductor configuration, in order to meet

requirements for high power factor over a wide line and input current range, and to optimize the inductor

size. Many of the popular PFC controllers use what is known as single cycle current loop control, which can

provide very good performance provided that the inductor remains in CCM mode operation. At low-line this is

no problem, but for operation in the high-line band (176VAC to 265VAC), the operating current will be much

lower. If an inductor is used with a nominal “stable” value of inductance, what works well at low-line results

in DCM mode operation for a significant part of the load range at high-line, and poorer power factor and

higher EMI than necessary.

Figure 4.2 Swinging Boost Inductor example optimized for CMM mode operation over wide range