
•
2048
•
2176
•
2304
•
2432
•
2560
•
2688
•
2816
•
2944
•
3072
•
3200
•
4096
•
4224
•
4352
•
4480
•
4608
•
4736
•
4864
•
4992
•
5120
•
5248
The parameter in the NVM is a positive delta with respect to the “PFC Min Tsw Vskip”. The real value used during
the code execution is therefore
Equation 7
"PFC Max Pin Vskip" = "PFC Min Pin Vskip" + "PFC Max Pin Vskip delta "
(7)
Use
This parameter is mainly used to guarantee a fast reaction to transients, forcing the PFC to reduce the number of
valleys or to switch to the transition mode when the internal power value plus nValleys * “PFC Delta Pin Vskip” is
greater than this parameter.
The frequency based mode change measures the frequency at each half line cycle, then if the frequency is out
of the “PFC Min Tsw Vskip” or “PFC Max Tsw Vskip” values it increments or decrements the number of valleys
by one. By only relying on the frequency it would require 4 half-line cycles to change from DCM to TM, potentially
causing a dip on the Vbus.
The threshold should be kept high enough so that in the steady state the frequency dominates the mode change.
3.3.11
PFC Delta Pin Vskip
Size: 5 bits
Sets a correction factor used when switching between valley-skipping modes.
Available values are:
•
160
•
176
•
192
•
208
•
224
•
240
•
252
•
272
•
288
•
304
•
320
•
336
•
352
•
368
•
384
•
400
•
416
•
432
•
448
•
464
•
480
•
496
•
512
•
528
•
544
•
560
•
576
•
592
•
608
•
624
•
640
•
656
Use
This parameter should be approximately set to the reduction of output power determined by the addition of one
valley.
The device uses this parameter to reduce the discontinuity on the output power when changing the number of
valleys skipped.
UM3002
PFC parameters
UM3002
-
Rev 1
page 14/42