
3.3.12
PFC maximum DCM power
Size: 4 bits
Sets the power threshold to switch from the DCM to the valley-skipping mode. Sets also the on-time duration of
the PFC gate drive while in the DCM mode.
Available values are:
•
1024
•
1152
•
1280
•
1408
•
1536
•
1664
•
1792
•
1920
•
2048
•
2304
•
2560
•
2816
•
3072
•
3328
•
3584
•
3840
In the DCM mode, the MOSFET on-time is calculated with the following formula
Equation 8
Ton = "PFC Maximum DCM power" ∙ 2
Vin2
(8)
3.3.13
PFC Min Tsw Vskip
Size: 5 bits
Sets the minimum switching period (i.e. the maximum switching frequency) for the valley skipping mode.
Available values are:
•
234 kHz
•
221 kHz
•
208 kHz
•
197 kHz
•
188 kHz
•
179 kHz
•
170 kHz
•
163 kHz
•
156 kHz
•
150 kHz
•
144 kHz
•
139 kHz
•
134 kHz
•
129 kHz
•
125 kHz
•
121 kHz
•
117 kHz
•
110 kHz
•
104 kHz
•
99 kHz
•
94 kHz
•
89 kHz
•
85 kHz
•
82 kHz
•
78 kHz
•
75 kHz
•
72 kHz
•
69 kHz
•
67 kHz
•
65 kHz
•
63 kHz
•
60 kHz
The period is measured at the peak of the mains sinusoidal voltage. If the measured period is lower than this
value, the system increases the number of valleys, towards DCM.
The corresponding frequency values are shown above.
Use
UM3002
PFC parameters
UM3002
-
Rev 1
page 15/42