BD7690FJ-E Datasheet, PDF (15/26 Pages) Rohm – Power Factor Correction Controller IC

BD7690FJ
2．Decision of minimum frequency fsw
The switching frequency of PFC
 _ PFC Vin ² Vo _ PFC  2 Vin
fsw 

2 Po _ PFC  L
Vo _ PFC
The frequency is minimized in the minimum input voltage. Slow frequency is effective about loss and noise. However,
inductance is large value at low frequency. In addition, it enters the audible band when frequency lowers to 20kHz or less,
and sound banging occurs. It designs the minimum frequency as 50kHz this time.
3．Calculation of the inductance
L  ^{ _ PFC Vin2}  ^{Vo _ PFC  2 Vin}
2 Po _ PFC  fsw
Vo _ PFC
Ex）Vin=AC90V, Vo_PFC=400V, Po_PFC=200W, η_PFC=0.9, fsw=50kHz
L  248.5uH  250uH
4．Calculation of the inductor current
Ipk  ^{2 Vin}  ton  ^{2 2  Po _ PFC}  6.98A
L
 _ PFC Vin
5．Calculation of the ON width
T_ON
_
MAX
[s]

2 L
V²
ACMin
P_O _ PFC
 _ PFC
ON width is short at the high AC voltage. Therefore, the ON width is decided with the minimum AC voltage.
It recommends RT setting such as the maximum ON width is just covered at the minimum AC voltage. ON width is small
when the high AC voltage. And the EO voltage range is small. EO voltage band width is the large then the ON width
setting by the RT resistance is short.
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TSZ22111 • 15 • 001
15/22
TSZ02201-0F2F0A200280-1-2
27. Mar. 2017 Rev.002